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INSTITUTE OF TECHNOLOGY
THE EFFECT OF MIXTURE QUALITY ON THE
EXHAUST GAS EMISSIONS OF A PETROL ENGINE
BY
ADVANCED SCHOOL OF AUTOMOBILE ENGINEERING
THE EFFECT OF MIXTURE QUALITY ON THE EXHAUST GAS EMISSIONS OF A PETROL ENGINE
A report to the Science Research Council (Contract Ref. B/SR/4670)
by
N. R. Beale. B. Sc. . D. Au. E. and
D. Hodgetts. B. S c . B. Sc. (Eng), M. I. Mech. E. SUMMARY:
Reported here is the first part of an investigation, supported by the Science Research Council, into the effects of mixture quality and mixture p r e -paration in the induction tract of a petrol engine on the mass rate of emissions of carbon monoxide, carbon dioxide, nitric oxide and hydrocarbons in the
exhaust gas.
Mixture quality or the method of supplying the fuel to the induction tract is shown to be relatively unimportant at steady loads and speeds when the loads and speeds are high. At low speeds and part throttle, particularly at idling, a well prepared fully evaporated or finely divided fuel-air mixture will allow operation at mixtures which are weaker than those with a hetrogeneous mixture. The rate of mass flow of hydrocarbons is not affected greatly but the carbon monoxide level is reduced significantly at the weaker mixtures.
An anomaly in the levels of carbon monoxide and carbon dioxide. similar to that reported by three other laboratories, is discussed in detail. No adequate explanation can yet be offered but the problem is receiving further attention.
1. INTRODUCTION 1 2. ENGINE INSTALLATION 1
2, 1 B a s i c data and modifications to the engine 2. 2 Coolant c i r c u i t
2. 3 F u e l s y s t e m s 2 . 4 Ignition s y s t e m 2. 5 Induction s y s t e m 2.6 E x h a u s t s y s t e m
2. 7 Additional equipment to aid t e s t i n g of the engine 3. O P T I C A L EQUIPMENT FOR THE OBSERVATION OF
MIXTURE BEHAVIOUR 4 4. EXHAUST GAS ANALYSIS - GENERAL COMMENTS 4
5. I N F R A - R E D GAS ANALYSIS EQUIPMENT 5
6. S A F E T Y PRECAUTIONS 6 7. ENGINE T E S T CONDITIONS 6 8. COMMENTS ON MIXTURE CONDITIONS 7
9. ENGINE T E S T RESULTS AND COMMENTS 8 9. 1 R e p e a t a b i l i t y and significance of r e s u l t s
9. 2 Idling t e s t r e s u l t s
9. 3 F u l l load Eind p a r t load t e s t r e s u l t s
10. GENERAL DISCUSSION OF RESULTS AND PROGRAM OF
WORK 9 Table 1 11 11. CONCLUSIONS 14 R E F E R E N C E S 15 APPENDICES 1 to 4 ILLUSTRATIONS
1 INTRODUCTION
1. 1 An investigation into the effect of mixture quality on exhaust gas emissions began, with the support of the Science Research Council, early in the year 1968. At that time it was well known that a major reduction of the emissions of carbon monoxide and unburnt hydrocrabons of an untreated engine could be obtained by supplying the engine with a fuel-air mixture wherein the fuel is finely divided or completely evaporated. Experimental evidence suggested that the improvement was mainly due to better distribution of the fuel, that is, the engine is provided with a mixture strength that is consistent from cycle to cycle and from cylinder to cylinder. Less obvious at that time, was the influence and importance of mixture quality - a term to describe the homogenity of the dispersion of the fuel.in the air and the physical state of the fuel - when the effects of distribution are insignificant.
1. 2 Investigations by Jones and Gagliardi (Ref. 1). Nonnenmann. (Ref.2), and other unpublished work suggested that for a given air-fuel ratio, the effects of nnixture quality were mainly to extend the range of combustible mixture in the weak region where carbon monoxide is at a very low level. The results of Nonnenmann suggest also that mixture quality can influence the levels of carbon monoxide with rich naixtures. There was little evidence in the literature of the effect of mixture quality on the emissions of the oxides of nitrogen and almost a complete absence of tests at idling conditions.
1. 3 Although it was recognised that mixture quality may have only a secondary effect, the importance of such effects cannot be ignored when legislation requirements are very stringent. For this reason the work of this report was undertaken in order to give more comprehensive information on the fundamental effects of mixture quality in the induction tract of an engine. At the request of the Science Research Council, the main attention was given to the emission of carbon monoxide and the oxides of nitrogen with less attention to unburnt hydrocarbons.
2. ENGINE INSTALLATION
2. 1 Basic data and modifications to the engine
2. 1. 1 All tests were made on a four cylinder, water-cooled 1978 cc engine with a Heron combustion chamber, a bore and stroke of 85. 6 mm and a compression ratio of 9. 0 to 1. The engine was converted to single cylinder operation by removal of the pistons and connecting rods of cylinders 1. 2 and 3, and the appropriate cam followers of the valve gear. A cylinder head with separate induction and exhaust ports was fitted to allow the use of simple single exhaust and induction pipes without branching or pockets.
2, 2 Coolant circuit
2. 2. 1 Modification of the engine coolant circuit was made in order to obtain a rapid warm-up and stable coolant temperatures. The circuit is shown diagrammatically. Fig. 1. To improve the water circulation passed the firing cylinder No. 4, the main water outlet is re-sited at the r e a r of the cylinder head. A by-pass of the thermostat at the outlet can be diverted, if
required, to a heat exchanger in the induction system (see paragraph 2. 5). The engine circuit and coolant header tank. Fig. 1, are in a closed loop. The coolant temperature is controlled by a manual valve or by a thermostat that drains hot water from the header tank. A ball valve introduces a similar quantity of relatively cold water from the main laboratory system which is also a closed circuit. Untreated water was used for coolant throughout the engine tests. 2. 3 Fuel systems
2 . 3 . 1 Two fuel systems were used. F i g . 2. Normal carburation was provided by an Amal 376 carburettor with a variable main jet and needle to allow the control and adjustment of the air-fuel ratio while the engine is running. The alternative system is based upon a Simms-Marvel-Schebler petrol injection pump with manual control.
2. 3. 2 In each case the fuel is gravity fed from the main tank to a float chamber. From the float chamber it flows to a glass burette and on to the r e s e r v o i r of the primary pump of the fuel injection equipment or through an electric lift pump to the carburettor according to the system in use.
_2 2. 3. 3 Fuel is supplied to the injection pump at a pressure of 50 Ibf. in gauge, approximately, from the primary pump. Bleedback from the three injectors not in use (four injectors when carburation is used) is returned to the r e s e r v o i r of the primary pump. The injection pump was driven at half engine speed at the original mounting for the distributor. Timing of the injection could be altered easily by turning the pump on its mounting but it was normally set to commence nominally at top dead centre of the piston and the beginning of the induction stroke. The characteristics of the pump, given in Appendix 1, are such that the injection period and timing varies with the setting of the controls or the quantity injected.
2. 3. 4. Pure normal iso-octane fuel was used throughout the tests. 2. 4 Ignition system
2. 4. 1 A conventional simple coil and contact breaker were used to provide the high voltage spark. To avoid undue electrical interference from unwanted sparks, the contact breaker cam was made by grinding off all but one of the cam lobes of the standard distributor. Subsequently, it was found to be necessary to reform part of the cam profile in araldite in order to avoid excessive heat dis-sipation in the coil when the contact points were closed for too long a time at slow engine speeds. The contact breaker was driven from the front end of the overhead camshaft.
2. 4. 2 A manual adjustment of the ignition timing was provided by swivelling the body of the contact breaker. A stroboscope triggered by the electrical pulses of the ignition low tension circuit and shown on a graduated scale on the flywheel and a fixed pointer on the engine block, was used to indicate and set the timing of the ignition.
2. 5 Induction system
2. 5. 1 The system used for all but the preliminary tests is illustrated by Fig. 3. Included in the simple induction pipe is an engine oil cooler which was adapted for the transfer of heat from the engine coolant to the inducted air or
m i x t u r e . At a l l t i m e s the a i r o r m i x t u r e t e n d s t o b e agitated o r mixed d u r i n g i t s p a s s a g e t h r o u g h the heat e x c h a n g e r . The s u p p l y of engine coolant could be cut off when no c h a r g e heating w a s r e q u i r e d .
2. 5. 2 T h e c a r b u r e t t o r s t a y s in position and p r o v i d e s the t h r o t t l e valve when o p e r a t i n g with fuel injection. P r e l i m i n a r y e x p e r i m e n t s w e r e c a r r i e d out to a s s e s s the effects of p r e s s u r e w a v e s in the induction s y s t e m and r e v e r s e flow t h r o u g h the c a r b u r e t t o r . E x p e r i m e n t a l and t h e o r e t i c a l w o r k
with s i d e b r a n c h e s and v a r i o u s pipe lengths showed t h a t the p r e s s u r e conditions in the p o r t could be influenced r e a d i l y but the p r o b l e m of flow r e v e r s a l in the c a r b u r e t t o r w a s not r e s o l v e d . Eventually the d e c i s i o n w a s t h a t the induction pipe should be m a d e s i m p l e and that it should be extended a t l e a s t ten inches before the c a r b u r e t t o r in o r d e r t o avoid a l o s s of fuel during flow r e v e r s a l s . The o v e r a l l pipe length is s u c h t h a t the engine is r e c e i v i n g the o p t i m u m r a m effect a t c r a n k s h a f t s p e e d s of about 1900 to 2000 r . p . m . . t h a t i s . about the u p p e r s p e e d r a n g e of the t e s t s r e p o r t e d h e r e .
2. 5. 3 G e n e r a l l y , the c r o s s s e c t i o n of the induction pipe i s c i r c u l a r and about 1. 25 inch d i a m e t e r . F o r a length of about eight i n c h e s , h o w e v e r , flat w a l l s w e r e built into the s i d e s of the pipe to allow a v i s u a l i n s p e c t i o n of the m i x t u r e quality d o w n s t r e a m of the h e a t e x c h a n g e r . N e a r to the induction p o r t two s m a l l windows w e r e fitted so t h a t light could be t r a n s m i t t e d a c r o s s the t r a c t for photographic o b s e r v a t i o n of the m i x t u r e motion.
2. 6 E x h a u s t s y s t e m
2. 6. 1 A s i m p l e pipe f r o m the e x h a u s t p o r t e n t e r s an e x p a n s i o n and mixing c h a m b e r about fifteen i n c h e s d o w n s t r e a m of the e x h a u s t valve . The c a p a c i t y of the c h a m b e r is about 10, 000 cubic c e n t i m e t r e s o r twenty t i m e s the c a p a c i t y of the c y l i n d e r . Tappings for the e x h a u s t g a s a n a l y s i s w e r e n o r m a l l y t a k e n d o w n s t r e a m of the mixing c h a m b e r but tappings w e r e a v a i l a b l e a l s o f r o m u p s t r e a m of the c h a m b e r and f r o m the c h a m b e r itself.
2, 7 Additional equipment to aid t e s t i n g of the engine
2 . 7 . 1 S e v e r a l d e v i c e s have been fitted o r t h e y a r e a v a i l a b l e for long-t e r m e x p e r i m e n long-t s on long-the engine. Allong-though long-t h e s e d e v i c e s have nolong-t a l l been u s e d for the work r e p o r t e d h e r e they a r e included for c o m p l e t e n e s s . They a r e l i s t e d a s f o l l o w s :
1) l o n i s a t i o n g a p s , a m p l i f i e r s , t i m i n g g a t e s and punch o r p r i n t out e q u i p m e n t for the d e t e c t i o n and m e a s u r e m e n t of flame t r a v e l t i m e s . 2) P i e z o - e l e c t r i c p r e s s u r e t r a n s d u c e r s and a m p l i f i e r s for the
indication of p r e s s u r e v a r i a t i o n s in the induction t r a c t .
3) An e x t e r n a l l y t r i g g e r e d s t r o b o s c o p e for a "slow m o t i o n " v i s u a l e x a m i n a t i o n of the i n j e c t o r s p r a y c h a r a c t e r i s t i c s .
4) An a c c u r a t e l y s l o t t e d d i s c , p h o t o - e l e c t r i c c e l l and e l e c t r o n i c t i m i n g unit which c a n be u s e d for a c c u r a t e t i m i n g of the engine e v e n t s in c r a n k s h a f t d e g r e e s .
5) A m a g n e t i c p i c k - u p is fitted a t the c a m s h a f t for the t r i g g e r i n g of a s t r o b o s c o p e o r o s c i l l o s c o p e .
6) A v a r i a b l e lift intake valve has been d e s i g n e d , built and fitted to the e n g i n e . T h i s device will be d e s c r i b e d in d e t a i l in a l a t e r r e p o r t when engine t e s t s now in p r o g r e s s a r e c o m p l e t e . 7) T h e b a l a n c e weights of the A v e r y weighing m a c h i n e of the
E n g l i s h E l e c t r i c b r a k e d y n a m o m e t e r , u s e d throughout the t e s t s . w e r e r e d u c e d in o r d e r to i n c r e a s e the b r a k e load s e n s i t i v i t y by a f a c t o r of about ten. T h i s modification has been v e r y useful for light load t e s t s of the s i n g l e c y l i n d e r .
3. O P T I C A L EQUIPMENT FOR THE OBSERVATION OF MIXTURE BEHAVIOUR
3. 1 I l l u s t r a t e d by F i g . 4 is the optical and r e c o r d i n g s y s t e m s e t up for the photographic o b s e r v a t i o n of the m i x t u r e quality and motion in the induction t r a c t . The s y s t e m i s s i m i l a r in p r i n c i p l e to that r e p o r t e d in the N. E . L. R e p o r t 331.
3. 2 The windows in the induction t r a c t , d e s c r i b e d briefly in p a r a g r a p h 2. 5. 3, a r e r e c e s s e d t o avoid, o r a t l e a s t , to r e d u c e the deposition of fuel d r o p l e t s on the s u r f a c e s . Two b r a s s t u b e s , which c a r r y the windows, a r e bonded into opposite s i d e s of the induction t r a c t and p r o j e c t into the t r a c t for a s h o r t d i s t a n c e on e i t h e r s i d e . The i n t e r n a l p r o j e c t i o n and the s h a r p r i m s of the tube w e r e d e s i g n e d to p r e v e n t l a r g e q u a n t i t i e s of fuel, which often r u n s along the w a l l s of the induction t r a c t , from s t r e a m i n g a c r o s s the o p t i c a l path and so o b s c u r i n g the liquid p a r t i c l e s in the a i r flow.
3. 2 Continuous and s t r o b o s c o p i c light s o u r c e s a r e a v a i l a b l e but. up to now. r e s u l t s have been obtained with the continuous s o u r c e only. The light b e a m i s focussed a t the nodal point of a high s p e e d cine c a m e r a and the c a m e r a focussed on a s u i t a b l e plane n e a r the c e n t r e of the induction t r a c t . T h e p a s s a g e of light t h r o u g h a d r o p l e t and the s c a t t e r i n g of light f r o m the p e r i p h e r y of a d r o p l e t g i v e s a s h a r p i m a g e on the photographic film. A F a s t e x c a m e r a w a s u s e d a t s p e e d s up to about 5000 f r a m e s / s e c .
4. EXHAUST GAS ANALYSIS - GENERAL COMMENTS
4. 1 T h e d e t e c t i o n and r e c o r d i n g of the c o n c e n t r a t i o n s of c a r b o n m o n o x i d e , c a r b o n dioxide, oxides of n i t r o g e n and h y d r o c a r b o n s a s equivalent hexane w e r e obtained with a f o u r - c h a n n e l G r u b b - P a r s o n s i n f r a - r e d g a s
a n a l y s e r . B e c a u s e a l l the t e s t i n g h a s been at s t e a d y engine loads and s p e e d s a c h a n n e l for high c o n c e n t r a t i o n s of h y d r o c a r b o n s h a s not been n e c e s s a r y . F o r the p u r p o s e of e s t i m a t i n g the a i r - f u e l r a t i o the oxygen content of the e x h a u s t w a s m o n i t o r e d with a S e r v o m e x OA 150 p a r a m a g n e t i c a n a l y s e r . 4. 2 During the p r e l i m i n a r y e x p e r i m e n t s a flame ionisation d e t e c t o r w a s u s e d for an a s s e s s m e n t of the t o t a l h y d r o c a r b o n e m i s s i o n s . Before the work began it w a s thought d e s i r a b l e to a n a l y s e the h y d r o c a r b o n e m i s s i o n s by a g a s c h r o n n a t o g r a p h in o r d e r to e s t a b l i s h the r e a c t i v i t y index of factor a c c o r d i n g to the c o m p o s i t i o n of the h y d r o c a r b o n s in the e x h a u s t . N e i t h e r the flame i o n i s a t i o n d e t e c t o r n o r the gas c h r o m o t o g r a p h , a P e r k i n s E l m e r F l l , h a s been u s e d e x t e n s i v e l y . The r e s u l t s of the flame i o n i s a t i o n d e t e c t o r tended to v a r y in a s i m i l a r m a n n e r to the l e v e l s r e c o r d e d a s equivalent h e x a n e . Since a p u r e h y d r o c a r b o n fuel w a s u s e d t h r o u g h o u t the t e s t s and t h e r e w a s m o r e
Interest in comparative levels from one test to another, the flame ionisation measurements were not taken during the main programme of t e s t s . The dicision to not use the chromatograph was influenced mainly by the modification and development necessary for complete separation of hydrocarbons and the excessive tinae required to analyse a sample but also by the secondary
importance of hydrocarbons that was suggested by the sponsors of the project. 4. 3 Although the flame ionisation detector was not used for the main s e r i e s of t e s t s , the development of the detector for the measurement of total hydrocarbons may be of interest to other investigators in this field.
4.4 The P e r k i n - E l m e r F l l chromatograph with a flame ionisation detector was adapted for this purpose. The fifty metre capillary column, for the separation of hydrocarbons, was removed and replaced by a 3 inch length of capillary tube. For the purpose of establishing the optimum flame conditions, the relation between flow r a t e , as measured with a soap bubble flowmeter, and the inlet p r e s s u r e for the hydrogen and air paths were established and plotted. Graph 1. With these figures available the inlet p r e s s u r e s for good flame conditions were set according to the manufacturers recommendation of about 400 ml. air per minute and 30 to 35 ml. hydrogen per minute.
4, 5 Experiments were then followed to optimise the gas sampling system with the following objectives in
view:-a) a rapid response;
b) no separation of hydrocarbons;
and c) a sharp peak. Because the sample volume and flow rate is constant the hydrocarbon concentration could be read directly as a peak height.
d) Adequate electrical output without the need for high amplification; and e) maintenance of good flame stability.
4.6 To achieve these objectives various sample loop volumes, connecting capillary diameters and c a r r i e r gas flow rates were tried. Suitable values were found to be:
Sample loop 5cc.
Capillary diameter 0. 010 inch
C a r r i e r gas flow rate 60 ml. nitrogen per minute
A calibration curve, which is almost linear, is given as Graph 2. The amplifier sensitivity can be altered if required for the measurement of higher or lower concentrations.
5. INFRA-RED GAS ANALYSIS EQUIPMENT
5. 1 For carbon monoxide, carbon dioxide and hydrocarbons the system supplied by the manufacturers was found to be adequate providing that a regular calibration procedure was adopted. However, the sensitivity or c r o s s response of the n i t r i c oxide detector to water vapour was considerable. A high and e r r a t i c response was found to be due to variations of the temperature of the water bath and the small size of condenser tubes which were normally
immersed in the bath of ice/water.
5. 2 The problem was solved inexpensively by the installation of a refrigeration unit (extraction rate 700 B. t. u. per hour). A thermostatically controlled water/antifreeze mixture is continuously circul.ited through the standard water bath, as provided by the manufacturer, and an auxiliary bath with a much larger water trap in the exhaust gas samplt line, see Fig. 5.
5.3 To establish the possible e r r o r due to 'hunting' of the thermostat and, consequently, small variations in the temperature oi the antifreeze mixture, measurements were made of the response of the nitric oxide channel to air plus water vapour at various mixture temperatures. Saturated air at ambient temperature was drawn into the analyser through the condenser coils for each test. The r es ul ts , plotted as Graph 3, show that the water bath temperature is very significant.
5. 4 It was found that the thermostat was capable «f maintaining the antifreeze mixture at temperatures between 0 C and 2. 5 C . Reference to Graph 3 suggests that the response to water vapour will be the equivalent of about |I45 + 30 ppm. of nitric oxide. A figure of 145 ppm was subtracted subsequently from all observed readings of the nitric oxide concentration .
6. SAFETY PRECAUTIONS
Care was taken to reduce the risk and consequences of an
accidental escape of toxic nitric oxide gases into the laboratory. Stainless steel regulators were used to avoid corrosive deterioration when nitric oxide was used for calibration purposes. All the analyser oullets were vented to atmosphere outside the laboratory. Other precautions included the
installation of a powerful fume extraction fan, an emergency exit from the laboratory, and breathing and resuscitation equipment.
7. ENGINE TEST CONDITIONS
7. 1 All the tests described in this report were at steady speeds and loads. Three methods of mixture production were
employed:-a) petrol injection with a 60 cone of fuel sprayed directly towards the inlet valve - that i s , position 1 on Fig. 3.
b) petrol injection upstream of the heat exchanger and close to the carburettor - position 2 on Fig. 3.
c) a carburetted mixture upstream of the heat exchanger.
For each method of mixture production the engine was tested at two temperature conditions, that is, at an ambient temperature of about 24 C or with the charge heated to about 60 C. In practice it was found that there was very little difference in the emission levels for methods b) and c). Since considerable difficulty was experienced in setting the carburettor accurately at part load conditions it was convenient to base the comparison of mixture quality on methods a) and b) only for most test conditions.
7. 2 Engine loads and speeds were selected to be representative of those thought to be important in a driving cycle. These
were:-a) idling at a crankshaft speed of about 800 r. p. m.
b) full load (W.O. T. , wide open throttle), 60 Ibf. in"^ and 30 Ibf. i n ' ^ brake mean effective p r e s s u r e s at engine speeds of 1500 and 2200 r. p. m.
7. 3 For each load and speed and method of mixture production the mixture strength of the engine was varied in increments from a very rich setting to the leanest limits of engine operation without a serious misfire. Ignition timing was set at the minimum advance for the best torque (M. B. T.) at each load and speed. To maintain a constant b. m. e. p. it was, of course, necessary to adjust the throttle position according to the mixture strength. For this reason and to conform to current practice the emission results are given in t e r m s of mass per unit time and not in terms of concentration.
The Spindt (Ref. 3) equation was used to calculate the mixture strength according to the level of the exhaust emissions, see Appendix 2, and the m a s s emission rates were calculated according to the equations given in Appendix 3. In each case the level of total hydrocarbon emissions was assumed to be twice that measured as equivalent hexane. A simple Fortran IV program, included as Appendix 4, was used to reduce the experimental data.
8. COMMENTS ON MIXTURE CONDITIONS
8. 1 Although visual observation was not possible, when the fuel is injected onto the back of the valve the residence time of the fuel in the port is so short that the mixture must be very hetrogeneous with a considerable amount of wall flow in the ports and on the surfaces of the valve, Some indication of these conditions can be seen in the shadow photographs. Fig. 6a and Fig. 6b, taken downstream of a valve under steady state conditions in a cold flow rig. An extreme condition at low velocities of flow is illustrated by Fig. 6b. It is unlikely that the mixture quality will be affected greatly under these conditions by the temperature of the charge air.
8. 2 With injection or carburation upstream of the heat exchanger, without heating the charge, the increased surface a r e a and flow disturbance was sufficient to give a cold relatively well mixed charge which showed a slight wetting of the glass walls of the induction tract. Heating the charge to about 60 c , was sufficient to give complete evaporation with no wetting of the walls.
8. 3 As with all previous experiments on mixture quality the description of the mixture lacks precision. A quantitative description in t e r m s of the percentage of fuel flowing on the wall, the percentage of the fuel evaporated and the mean droplet size in the main air flow would be very difficult to achieve and, with hindsight, hardly justified by the practical significance of the values. Preliminary results with the optical system described under Section 3 suggest that much could be learned about the qualitative behaviour of the mixture in an induction pipe by cine photography.
8. 4 With a continuous light source the films lack quality and definition. Nevertheless, the images of small droplets at relatively low speeds can be seen clearly. Fig. 7. Small high speed droplets cannot be distinguished separately but the general pattern of the mixture motion, acceleration. deceleration and flow r e v e r s a l s , can be observed. At times in the cycle.
individual droplets can be seen to be travelling away from the inlet valve and subsequently to reverse their direction back towards the cylinder. 8. 5 Individual frames show the droplets to be elongated in the direction of flow. This distortion is partly due to the relatively long exposure time of the camera even at its maximum speed. Better definition may be obtained by synchronising an intermittent spark source of light with the rotating prism of the camera so that the exposure time is reduced by a factor of about one hundred. Time did not permit further development of this technique since the results were unlikely to add
significantly to the prime objective of the investigation.
9. ENGINE TEST RESULTS AND COMMENTS 9. 1 Repeatability and significance of results.
All investigators of engine exhaust emission have experienced difficulty as a consequence of a lack of repeatability which can be very significant at steady loads and speeds when the levels are low and the changes to be observed are small. Graph 4 gives an indication of the variation of the recorded mass emissions for a particular engine load and speed on three separate occasions when the differences in the ambient temperature, barometric p r e s s u r e , and ambient humidity were insignificant. To reduce the effects of the lack of repeatability as much as possible comparisons between the various methods of mixture production were made for a particular load and speed during one continuous run of the engine. The results taken for a particular run of the engine were plotted on the same graph. This should mean that small differences between curves on the same graph will be more significant than small differences from one graph to another.
9. 2 Idling test results
9.2.1 A s e r i e s of tests run at 800 r. p. m. and "no-load" are
illustrated graphically by Graphs 5 to 10; Graphs 5 to 8 give the mass rate of emission for four ignition timings of 10° B. T. D. C. , 5° B. T. D. C. . T . D . C . and 5 A. T . D . C . Comparisons of the two extreme ignition timings, for a particular method of fuel supply, are given in terms of the mass rate of emissions. Graph 9, and the concentrations by volume. Graph 10.
9. 2. 2 It is well known that a retarded ignition timing is effective for the reduction of hydrocarbons. The gain, which appears to be independent of mixture quality, is illustrated by Graphs 9 and 10. According to Graph 9, the mass rate of emissions of nitric oxide is greater when the ignition is retarded. In comparison to other modes of a driving cycle, however, it is clear that the mass rate of omissions of the oxides of nitrogen are negligible during idling.
9. 2. 3 Clearly, with reference to Graphs 5 to 8. the main effects of the various methods of fuel preparation in the induction tract during idling is the extent to which lean mixtures can be utilised. With fuel injected upstream, of the heat exchanger and well upstream of the inlet valve, position 2 on Fig. 3. low levels of carbon monoxide can be obtained by running the engine with a
stoichiometric or slightly weaker mixture. At this position for injection the residence time or the mechanical mixing of the induction tract was sufficient to give a mixture quality that was not improved significantly by heating the charge. Injection at the back of the valve, whether the charge was heated or not, requires the mixture to be rich. This causes a substantial increase of carbon monoxide in comparison with that when injection is well upstream. The observed effects of mixture quality on the oxides of nitrogen was not significant for these tests since the observed differences are within the limits of experimental e r r o r , that is, the cross response to water vapour etc.
9. 3 Full load and part load test results
9 . 3 . 1 The results for engine speeds of 1500 r. p. m. and 2200 r. p. m. are illustrated by Graphs 11 to 18 and Graphs 19 to 24 respectively. In all cases the mass rate of emissions follow the known trends with mixture strength; the nitric oxide showing a maxima at mixture strengths between about 15. 5 and
17.5 to 1, or equivalence ratio between about 0.95 and 0.85; where the hydrocarbon levels tend to be a minima and the mass emissions of carbon monoxide are low. In general, the mass emissions of nitric oxide increase with speed and load and the maxima tend towards weaker mixtures as the speed and load increases.
9. 3. 2 Also expected was an increase in the emissions of nitric oxide when the charge is preheated. This increase was observed at the higher engine speed but the full load results at 1500 r . p . m . , Graphs 12 and 13, in particular, show the opposite trend. An explanation could be that the con-centrations are higher with a heated charge but at this speed the reduction in charge density and charge mass flow, as indicated also by the reduction in b. m. e. p . , is sufficient to cause a net reduction in the mass emissions. On the basis of equal power, the difference is quite insignificant.
9 . 3 . 3 Graphs 11 to 24 indicate clearly that the various methods of mixture production had little or no effect on the mass rate of emissions of carbon monoxide, hydrocarbons and the oxides of nitrogen when the engine is operating at steady loads and speeds. This finding has been reported elsewhere (Ref. 4). The small differences that were observed are relatively insignificant compared with variations due to instrument e r r o r s and the problems of good repeatability.
10 GENERAL DISCUSSION OF RESULTS AND PROGRAMME OF WORK 10. 1 According to the results and comments given in paragrapy 9. 3. 3. it could be the interpretation that the mixture quality in the induction pipe, when the engine is running at steady speeds and loads, is of little or no significance as far as combustion and the exhaust emissions of a petrol engine are
con-cerned. Results of a previous investigation (Ref. 5) at the A . S . A . E . , however, give a clear indication that extreme conditions of mixture quality will result in considerable differences in the level of exhaust gas emissions. To understand
the differences between one investigation and another a description based upon observations and a little imagination, can be offered for the means by which a fuel-air mixture is prepared before the s t a r t of combustion in the cylinder.
10. 2 Irrespective of the method used for the introduction of fuel to the induction tract it is quite evident from shadow photographs downstream of the valve (Ref. 6) that the flow through the valve induces considerable turbulence in the mixture. The mixture m.otion can be very effective in the production of a good quality homogeneous mixture as a consequence of the mixing process and the break-down and evaporation of fuel ligaments leaving the surface of the valve. The preparation of the mixture by the valve is most effective when the p r e s s u r e drop a c r o s s the valve or the rate of gas flow is high and much less effective when the pressure drop and rate of flow is low at low engine speeds and part throttle operation.
10. 3 Mixture preparation in the induction tract will most likely depend upon the mixture motion and turbulence, the temperature of the mixture and the walls of the tract, the pressure of the mixture, the relative 'humidity' in t e r m s of the fuel vapour present and that required for saturation, residence time in the duct, wetted surface area and the degree of initial atomisation of that fuel that is not deposited on the wall during its passage down the tract. A homogeneous and well evaporated mixture is more likely to be produced when the mixture motion and turbulence is great, the temperature of the mixture and walls of the tract is high, the residence time of the fuel in the tract is long, the wetted area of the tract is large, the mixture pressure is low and the fuel is finely divided and well dispersed in the air stream. 10. 4 The relative importance of mixture preparation by the valve and by the condition in the induction tract are suggested by the results given in this report. At the relatively high speeds of 1500 r . p . m . and 2200 r . p . m . and at the higher loads, the valve effect is predominant. At the idling condition the valve is less effective and conditions in the induction tract are more significant. It is clear that a good mixture, which can be produced without the necessity to heat the charge, is effective in extending the weak range of burnable mixtures. The minimum mass rate of hydrocarbon emissions does not seem to be greatly affected by mixture quality, but
Graphs 3 and 8 tend to show the lowest levels with a long residence time and a good quality mixture. This trend is seen in Table 1, the results of an investigation (ref. 5) at the A . S . A . E . on the single cylinder of a six cylinder water-cooled engine of 2550 cc capacity with a wedge combustion chamber in the head and a compression ratio of 8. 3 to 1. The figures for 'idling', that is, closed throttle at 600 r, p. m. , show clearly that the residence time is generally the most important factor but good atomisation of the fuel becomes essential with short residence times, that is, when the fuel is supplied near to the valve. There is a severe penalty in terms of carbon monoxide levels
for poorly formed mixtures at idling and closed throttle conditions at any speed.
10.5 A very 'coarse'mixture represented in the extreme by dripping fuel on the back of the valve, is undesirable even when the preparation by the valve becomes more significant, see Table 1. A drip feed will obviously be
modified considerably if the residence time is increased or the motion of the mixture is increased. As acknowledged by Dodd and Wisdom, the drip feeds
600 R . P . M . F u l l T h r o t t l e C l o s e d T h r o t t l e 1200 R . P . M . F u l l T h r o t t l e C l o s e d T h r o t t l e F u e l injection t o w a r d s back of v a l v e ( 7 " u p s t r e a n i of valve) F u e l injection into induction
t r a c t ( 1 3 " u p s t r e a m of valve) D r i p feed (7" u p s t r e a n a of valve) D r i p feed ( 1 3 " u p s t r e a m of valve) D r i p feed onto back of valve
( l " u p s t r e a m of valve) 570 ( 2 . 0 ) 650 ( 2 . 8 ) 370 (4. 7) 350 ( 4 . 0 ) 1200 ( 1 . 2 ) 900 ( 7 . 0 ) 680 (1.4) 600 (1.6) 450 (1.5) 1430 (5.4) 320 (1.4) 330 ( 3 . 2 ) 440 (4. 9) 430 ( 6 . 0 ) 700 ( 7 . 2 ) 170 (1.0) 100 (0.3) 640 (4. 1) 330 (3.0) 1500 (6.0) N o t e s : 1) The f i g u r e s given a r e m i n i m u m l ^ d r o c a r b o n c o n c e n t r a t i o n s in p. p. m . a s nneasured with
a flame i o n i s a t i o n d e t e c t o r
2) In b r a c k e t s a r e the p e r c e n t a g e c o n c e n t r a t i o n s of c a r b o n monoxide by volume
3) C l o s e d t h r o t t l e w a s s e t to give a ' m e a n ' manifold p r e s s u r e of 10. 5 inch of m e r c u r y v a c u u m in e a c h c a s e
4) Ignition t i m i n g w a s fixed at 4 B. T . D . C . 5) I s o - o c t a n e w a s u s e d for all t e s t s
6) R e p e a t a b i l i t y w a s l e s s s a t i s f a c t o r y than for the e x p e r i m e n t a l r e s u l t s plotted on G r a p h s 4 to 24.
used in their tests will be conditioned appreciably by a throttle plate downstream of the feed and, in one case, the fitting of a planum chamber between the fuel supply and inlet valve. With practical methods of fuel supply, preparation by the valve at 'high' engine speeds and loads is such that the degree at atomisation is relatively unimportant when transient operation of the engine and manifold distribution is not significant.
10. 6 Once transient operation of the engine is required the quality of the mixture is almost certainly decided by the need to accelerate or
decelerate the fuel and air together. A fully evaporated mixture or a short residence time is indicated by common sense and practical experience. A short residence time is obtained by fuel injection on to the back of the valve but some means of improving the mixture in the cylinder is desirable at idling and slow speed closed throttle conditions.
10. 7 Plotting the nitric oxide levels as a mass rate (gm. per hour) indicates clearly that these are much greater at high loads and speeds. Although the concentrations may be reduced by retarded ignition, exhaust gas re-circulation e t c . , the increased throttle required to restore the engine power may largely offset the gain. The most practical means for reducing the nitric oxide level would seem to be the use of a rich mixture allied with an efficient oxidation of hydrocarbons and carbon monoxide in the exhaust pipe at wide throttles and high speeds. Weak mixtures could be used at part and closed throttle.
10. 8 It is possible that a greater turbulence in the cylinder at part load conditions, particularly at low speed, would be effective in giving a better mixture at the time of ignition, a faster flame speed and a reduction of the thickness of the quenched hydrocarbons at the surfaces of the combustion chamber. Work now in progress and the second part of the investigation are concerned with the improvements obtained by throttling with a variable lift valve, the device mentioned previously under item 6 of paragraph 2.1.1. 10. 9 An important factor in an emissions experiment is the degree of repeatability. Variations of the order of 100% have been noted in other investigations. Although significant compared with the small changes being observed, the reliability and repeatability of the tests reported in this
investigation were more reasonable. The most likely explanation is that the use of a pure single hydrocarbon fuel, without additives, gave stable running conditions of the engine. When examined after several hours of running, the deposits in the combustion chamber were very light and easily removed with a dry cloth. The usual precautions of regular calibration of the exhaust gas analyser were taken. As described previously, particular care was taken to avoid non-representative exhaust samples and the cross response to water vapour. Nevertheless, the measured concentrations of carbon monoxide and carbon dioxide show anomalies which defy an adequate explanation in terms of engine and fuel characteristics. Similar anomalies have been reported by at least two other laboratories working independently.
10. 10 Graphs 26 and 27 illustrate that the measured concentrations of carbon monoxide with rich mixtures fall into a broad band when plotted against mixture strength. The results tend to correlate in two main groups; part load at 2200 r . p . m . and all other loads at 1500 r . p . m . and 2200 r . p . m . Results at idling tend to fall between the two. It can be seen on graph 26
that the part load results at 2200 r . p . m . compare closely with the levels expected with the assumption of a water-gas reaction equilibrium at 3000 R . The lower levels of carbon monoxide at 1500 r . p . m . and full throttle, 2200 r. p. m. graph 27, would correlate fairly well with an equilibrium conaposition at about 2400°R.
10. 11 The differences in the engine operating conditions would not appear to justify the suggestion that the cycle conditions were very different. For example, part load conditions at 2200 r . p . m . correlate at a high level of carbon monoxide whereas part load at 1500 r . p . m . correlate better at a low level. In general the results appear to be more dependent on load and speed than on the method of fuel supply to the engine. An exception to this
generalisation is that the lowest levels of carbon monoxide were obtained at 1500 r.p.m.. and 30 b. m. e.p. with fuel injection on to the back of the valve. This is in agreement with Nonnenman (Ref. 2) who observed a shift which was apparently dependent upon the method of fuel supply. He attributes the shift to lower cycle temperatures as indicated by the temperatures of the sparking plug. The differences that he measured at a particular mixture strength are far greater than those reported here and it is most unlikely that they can be explained by a change of equilibrium composition or kinetic reaction r a t e s according to temperature changes only.
10. 12 The levels of carbon dioxide, plotted on Graphs 28 and 29 do not help to explain or clarify the situation. It is shown that no results at rich mixtures, with the possible exception of part load at 2200 r . p . m . , correlate well with an equilibrium composition. An anomaly occurs in the weak region also but again the part load results at 2200 r. p. m. correlate more nearly with a composition that assumes that the dry products of combustion a r e carbon dioxide, oxygen, argon and nitrogen only. All the results at other loads and speeds a r e low by more than one percent of carbon dioxide.
Similar discrepancies have been reported (Ref. 4) by Dodd, at M.I. R . A . , and Wisdom, at E. R.A. Limited.
10. 13 Various possibilities for the apparent discrepancy have been considered. Clearly, the presence of hydrocarbons, nitric oxide e t c . , in the exhaust emissions would account for a discrepancy in the carbon monoxide and carbon dioxide levels but the difference would be much smaller than those observed. Dilution by leakage of air into the exhaust or exhaust sampling system can be discounted since the oxygen level. Graphs 28 and 29, is no g r e a t e r than would be expected when account is taken of the small fraction that is present at all mixture strengths. Plotting the sum of the carbon monoxide and dioxide concentrations. Graph 25, tends to suggest dilution or an e r r o r in the estimation of the effective mixture strength but the dioxide levels alone. Graphs 28 and 29, show clearly that a shift of the results towards weak mixtures is not acceptable. A careful check of the gas valves of the infra-red gas analyser has eliminated the possibility of dilution by nitrogen which is used as a purge gas for the instrument.
10, 14 It is important that the results of emissions experiments should be understood fundamentally. Further thought and experiment will be given to this anomaly in future work. The practical significance of the comparisons of the methods of fuel preparation reported here and elsewhere a r e unlikely to be affected but until an adequate answer is found the absolute values of the
concentrations measured cannot be accepted with complete confidence.
11 CONCLUSIONS
11. 1 Normal methods of fuel supply and mixture production have no significant effect on the mass rate of emissions of carbon monoxide, carbon dioxide and nitric oxide at engine speeds and loads other than idling. This observation is in agreement with the finding of other workers in this field. Extremes of mixture quality have an undoubted effect but a poor mixture may be improved considerably by the residence time in the induction tract and by its turbulent passage into the cylinder.
11.2 At low engine speeds and part throttle operation, particularly when idling, the preparation of the mixture by its flow through the valve may be inadequate. At conditions such as these the method of mixture preparation affects the lean limits of combustion. Lower carbon monoxide levels can be obtained by improving the mixture quality so that the engine will run at weaker mixtures.
11. 3 Mixture improvement and better combustion are likely to be obtained by increasing the turbulence in the combustion chamber. Work in progress, employing a variable lift valve, is expected to add to the knowledge of this factor,
11.4 An improvement of the mixture in the induction pipe can be obtained, if necessary, by physical means. A large wetted surface area and a small flow disturbance is sufficient to give a relatively dry mixture without heat. 11. 5 The mass rate of emissions of nitric oxide increases considerably with load and speed. According to the tests reported here, the maximum rate for a given load and speed occurs at weaker mixtures as the load and speed i n c r e a s e s . Heating the inducted mixture to 60 C increased the con-centrations of nitric oxide but did not significantly affect the mass rate of
flow per horsepower. Retarding the ignition at idling reduces the concentrations of nitric oxide but the mass rate of flow may increase. The low mass rates of flow at idling, however, are insignificant compared with those at other operating conditions.
11.6 The general repeatability of the results, a problem in most
emission experiments, was reasonable. This was mainly attributed to the use of a pure hydrocarbon fuel and the absence of deposits in the combustion chamber. Particular care was taken to reduce the cross response of the infra-red gas analyser to water vapour.
11, 7 A cine photographic technique has been successfully employed for the observation of mixture behaviour in an induction tract,
11.8 A satisfactory explanation cannot be offered yet for the low levels of carbon monoxide and carbon dioxide at many loads and speeds of the engine. Similarly, low levels of carbon dioxide have been reported by at least two other laboratories working independently. A third has reported differences in the carbon monoxide levels that lack an adequate explanation. Further attention will be given to this anomaly in future work.
R E F E R E N C E S
Vehicle e x h a u s t e m i s s i o n e x p e r i m e n t s using a p r e - m i x e d and p r e - h e a t e d a i r fuel c h a r g e M i d - Y e a r Meeting, Chicago, I l l i n o i s , May, 1967. S.A. E. P a p e r 670485.
The influence of e x t e r n a l m i x t u r e f o r m a t i o n on the p e r f o r m a n c e of the f o u r - s t r o k e p e t r o l engine. A. T . Z . , N o v e m b e r , 1966. M . I . R . A . T r a n s l a t i o n No. 2 2 / 6 7 .
A i r - f u e l r a t i o s from e x h a u s t g a s a n a l y s i s
M i d - Y e a r Meeting, Chicago, I l l i n o i s , May, 1965. S. A. E . P a p e r 650507.
Effect of m i x t u r e quality on e x h a u s t e m i s s i o n s f r o m s i n g l e - c y l i n d e r engines
P a p e r 17 of the Institution of M e c h a n i c a l E n g i n e e r s S y m p o s i u m "Motor Vehicle Air Pollution C o n t r o l " London 25-26th N o v e m b e r , 1968.
5. BLURTON-JONES, T. J. M i x t u r e quality effects on e x h a u s t e m i s s i o n s A . S . A . E . T h e s i s , O c t o b e r 1967.
6. B E A L E , N. R. A study of fuel a t o m i s a t i o n in the induction t r a c t of a fuel injection s p a r k ignition engine
A . S . A . E . T h e s i s , May 1965. 1. JONES, J. H. and GAGLIARDI, J. C. 2. NONNENMANN, M. 3. SPINDT, R . S . 4. DODD, A. E . and WISDOM. J . W .
INJECTION PUMP CHARACTERISTICS
The injection pump used throughout the tests is of the distributor type with a single reciprocating and rotating plunger.
Fuel delivery is controlled by restricting the movement of a spring loaded shuttle which connects with the pumping chamber. The injection commences once the initial plunger movement has displaced the shuttle to its stop, so that for a given speed the end of injection remains fairly constant, but the commencement, and hence the injection period, varies with control position.
The characteristics of the system were investigated by stroboscopic observation of the injector spray for various speeds and control settings, the results are plotted on Graph 30. The timing was set so that the mean point of injection commencement was approximately at T. D. C. (beginning of induction stroke), but it can be seen that for extreme conditions this varies between 29° B. T . D . C . and 23° A. T . D . C .
A i r / f u e l r a t i o s w e r e c a l c u l a t e d f r o m e x h a u s t a n a l y s i s using a method developed by Spindt (S. A. E . 650507)
The b a s i c equation for the c o m p u t a t i o n i s :
-•p A / F r a t i o = F^^ [ 1 1 . 4 9 2 F c ( ^ ^ R ^ ^ ' ^ 5 I R ' ^ ^ w h e r e R ^ - 2 Q = \ ^ - 2
(^co^^co^)
F , = fraction b u r n e d " '^ (^CO ^ ^ C O / ^HC)and F = fraction c a r b o n in fuel
c P_, = volume p e r c e n t a g e CO in e x h a u s t P = volume p e r c e n t a g e CO in e x h a u s t PO = volunae p e r c e n t a g e 0 in e x h a u s t P = p e r c e n t c a r b o n in h y d r o c a r b o n s on a p e r c a r b o n b a s i s HC ppm H_(FID) x 6 ^ _ ppm H_(NDIR) x 12 , . = '^ C OR C [ (approx. ) 4 4 10 10 T h e a c c u r a c y of this m e t h o d is independent of the amount of w a t e r v a p o u r in the a n a l y s e d g a s , and the a c c u r a c y i s only slightly affected by i n s t r u m e n t e r r o r s ; the method does however r e q u i r e the f r a c t i o n c a r b o n to be known. Since a p u r e h y d r o c a r b o n fuel of known c o m p o s i t i o n w a s used throughout the t e s t s , the method w a s s u i t a b l e . F o r fuels of u n c e r t a i n c o m p o s i t i o n a f u r t h e r method employing a c a r b o n / h y d r o g e n b a l a n c e , is a v a i l a b l e , although this method r e q u i r e s an e s t i m a t e of the w a t e r v a p o u r content of the s a m p l e , and i s affected to a g r e a t e r extent by i n s t r u m e n t e r r o r .
CALCULATION OF MASS EMISSION RATES An engine p r o d u c e s M g r a m - m o l e s of e x h a u s t g a s p e r h o u r . After cooling o r d r y i n g to r e m o v e w a t e r v a p o u r t h i s r e d u c e s to M g r a m - m o l e s / h o u r . The m o l e s of c a r b o n c o n s t i t u e n t / h o u r a r e : -C 0 2 % X Mg -CO% x M^ -CgH^^% x M^ 100 100 100 ^ 2
Moles c a r b o n / h r f r o m e x h a u s t = -z— (Co % + CO% + 6 C H %) 1 2 . 0 1 X M g r a m s c a r b o n / h r = -— ( 0 0 ^ % + CO% + 6 CgH^^%) Now fuel c o n s u m p t i o n ( m e a s u r e d ) i s X g m / h o u r . , • , C a r b o n intake of engine i s F x X = Y g m / h r w h e r e F i s f r a c t i o n c a r b o n in fuel by weight. 100 Y hence M 2 " 12. 01(C0 % + C0% + 6 CgH^^%) T h i s i s the g r a m - m o l e s of d r i e d (auialysed) e x h a u s t / h r . hence m a s s e m i s s i o n s :-CO g m / h r = ^^° x M^ x 2 8 . 0 1 C^H, ^ g m / h r = "-^6^14^° x M^ x 86. 178 ^ ^^ 100 2 NO g m / h r = ^ ^ x M x 3 0 . 0 0 8 100 2 Atomic Weights :-12, 01 = Atomic weight of c a r b o n 28. 01 = Mol weight CO
86. 178 = Mol weight of Hexane 30. 008 = Mol weight NO
61 62 FN#«UFC.VXFAF 21 T 63 L I S T ( L P ) 6'. SI;Nn rO (EO.PROGRAM F I L F . S T O R F ) 65 Pi(0GRAM(C1ÜB) 66 I M P i l J 1 = C R 0 6 ? niJTPUT2 = LPÜ 6f> F-ID 69 M'\STtR EXHAUST GAS A N A L Y S I S /O OIPFNSION S ( 1 0 ) 71 DATA X I / 4 l i n A T A / , X 2 / A H * * * C / . X 3 / 4 H * * * Z / 72 CAI I OATF ( O A T E I ) 7 3 C A L I T I M E ( T I M F1 ) 74 W R I T F ( 2 , 1 0 0 ) , ( D A T E 1 , T I M F 1 ) 75 1 0 0 F ) R M A T ( 1 H 1 / / / / 2 0 X , 2 9 H N . B F A L F H X H A U S T G A S A N A L Y S I S 1 0 X , 6 H 0 A T F AK, 76 1 2 X , 6 H T 1 M E A a , / / / / / / ) ?7 101 R t A O d . 1 0 2 ) ( S ( J ) . J=1 . 1 0 ) 7P 1 0 2 F O P H A T ( I O A H ) 79 C\l. L C0MP,i(S(1 ) . X 5 . J ) 80 U (.1-1)0.111 ,0 81 C.i\[[ r O M P ; i ( S ( 1 ) . X I . J ) Ö2 I f ( . 1 - 1 ) 1 0 1 , 0 , 1 0 1 83 1 0 3 R F A D d , 1 0 2 ) ( S ( J ) , J = 1 , 1 0 ) Ö4 CALL C ( ) M P » ( S ( 1 ) . X 2 , J ) 85 I F ( . I - 1 ) 0 , 1 0 S . O 86 w l < ^ r Ê ( ^ . 1 o A ) ( 5 ( J ) , J = i . 1 0 ) 87 1 0 4 F O R M A T ( 1 0 X , 1 0 A r t ) »P G!) TO 1 0 3 89 1 0 5 W ; < I T E ( 2 , 1 1 3 ) 90 1 1 3 F O R M A T ( 4 X , 4 H B r i e P , 6 X , 3 H S F C , 6 X . 3 H I G N . 4 X , 3 H X C 0 . 6 X . 4 H y . C n 2 . 5 X , J H X 0 2 . 4 X . 9 1 2 5 H P P M N O , 3 X , 5 H P P M H C , 3 X . 5 H P P M H C , 4 X , 5 H C 0 G / H . 4 X . 5 H H C G / H , 4 X . 5 H N O G / H , 6 X . 9 2 3 3 I I A / F ) 9 3 W R I T E ( 2 . 1 I A ) 9 4 1 1 4 F ) R ' ' ' A T ( 6 3 X . 6 H ( N D I R ) . 2 X , 5 H ( F I D ) ) 9 5 RF:An( 1 , 10(>) ( F C , DENSF , S P F E I ) ) 9 6 1 0 6 F ) P M A T ( O F r ) . O ) 9 / 1 0 7 R I - A U d , 1 0 6 ) ( B L O A O , T I 6 N , CO, 0 0 2 , 0 2 , PPMNO.PPMHCN, PPMHCF, F U F L T ) 9 f l F ( C O 2 ) O , 1 01 , O 9 9 C 1 0 0 C O t l P U T F UMFP L13/SQ I N 1 0 1 r 1 0 2 u i r p = a . 7 * i u o A D 1 0 3 C
1 0 4 C C'IMPUTE FIIFI CONSUMPTION GM/HR 1 0 5 C 106 F U C I C 0 N = 1 2 7 H 0 0 . 0 * n E N S F / F U F L T 1 0 / C 10« C C ) M P U r E FUEL C O N S U M P T I O N L B / H R 10'J C 1 1 0 F'IEL 1 1 = F U t l C O N * 2 . 2 0 4 6 2 E - 3 1 1 1 r 1 1 ? C C U M P U T E U R A K E H O R S E P U I J F R 1 1 3 C 1 1 4 R ' IP = H L O A I) » S P E E D / 3 O O O . O 1 1 5 C 1 1 6 C C O M P I I f E S P E C I F I C F U F L C O N S U M P T I O N L B / B H P . H R
1 2 1 122 1 2 3 124 125 126 1 2 7 12P 129 130 1 3 1 13? 133 134 135 136 137 138 1 3 9 140 141 142 143 144 145 146 1 4 / M>>< 149 1 5 0 1 5 1 15? 1 5 3 154 155 1 5 6 1 5 / 15e ^5Q 160 1 6 1 162 1 6 5 164 165 C C C r c c c c c c c c c c c c 1 0 8 1 0 9 1 1 0 1 1 1 1 1 2 I F ( P P - 1 H C F ) 0 , 1 0 8 , 1 0 8 P'lC = P P M I I C N * 2 . 0 E - 4 G>) TO 1 0 9 P,)C = P P M H C F * 1 . ( ) E - 4 S U M C = C 0 + C o 2 + 6 . 0 * P H C G ! i n L E X = F C * 1 0 0 . 0 * F U E l C O N / d 2 . 0 1 * S U M C ) C ' I M P U T E CO MASS E M I S S I O N G M / H R C o G P H = C O * 0 . ? 8 0 1 * G M O L g X C I M P U r E MC MASS E M I S S I O N G M / H R H C G p H = P H C * 0 . 8 6 1 7 8 * GMO L E X C I M P U T E NO MASS E M I S S I O N G M / H R G P H N O = P P M N 0 * 1 , 0 E - 4 * 0 . 3 0 0 0 8 + G M O L F X F C 1 = 1 1 , 4 ' ^ 2 * F C F C 2 = 1 2 0 . U * ( 1 . 0 - F C ) S ' ) M C 2 = C0 + C 0 ? C )i'.Cl>2 = C 0 / C O 2 COMPUTE F R A C T I O N BURNED F'H = S U M C 2 / S U M C C O t l P U T E A I R / F U E l R A T I O A K P = F : < * ( F C 1 * ( C 0 2 + O . S * C O + 0 2 ) / S U M C 2 * - F C 2 / ( 3 . 5 + C O R C 0 2 ) ) i J i U T E ( 2 , 1 1 0 ) ( n H E P . S F C . T I G N , C O , C O 2 . O 2 , P P M N O , P P M H C N , P P M M C F , C O G P H , H C G 4 P H . G P H N 0 , A F R ) F O R M A r ( F 9 . 2 . F 9 , 5 , F > } . 0 , F « . ? , F 9 . 2 , F l K 2 , F 9 . 0 , F H . 0 , F 8 . ( ) , F 1 0 . 2 , F 9 . ? . F 9 . 5 2 , F l o . 3 ) G ) TO 1 0 7 C A L I T I M E ( T I M E D M R I r F ( 2 , 1 1 2 ) ( i ) A T E 1 , T P - 1 E 1 ) F 0 R M A r ( / / / / / 1 0 X , 1 7 H E N D OF JOB DATE A 8 , 2 X . 6 H T T M F A « , / 1 H 1 ) S r 0 P E.ID F 1 M I S '( F I i» X F A E ,'M) I S C t ( . 0 « C 1 0 r t 2 0 1
i SAMPLE DATA INPUT
4 5 6
7 OATA
8 RUN 17 1500 F/L INJ POS 2 HEAT 19/11/69 9 ***C 10 0.842 0.6919 1500.0 11 14.15 16.0 8.4 8.4 0.25 225.0 440.0 -1.0 44.5 12 14.2 14.0 6.0 9.9 0.2 475.0 3S5.0 -1.0 48.6 13 1 4 . 2 1 1 . 0 3 . 4 1 1 . 5 5 0 . 2 1 3 2 5 . 0 $ 1 0 . 0 - 1 . 0 5 2 . 9 14 1 3 . 8 1 1 . 0 0 . 2 2 1 3 . 3 0 . 5 4 1 5 0 . 0 2 6 0 . 0 - 1 . 0 5 7 . 5 15 12.5 20.0 0.1 11.45 3.3 4950.0 255,0 -1.0 66.6 16 10.6 36.0 0,08 9.3 6.5 2270.0 315.0 -1.0 78.9 17 10,0 37.0 0.08 8.95 7.0 980.0 335.0 -1.0 79.8 18 8.9 40.0 0.08 8.4 7.9 175.0 400.0 -1.0 83.5 19 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 20 DATA
21 RUN 18 1500 F/L INJ POS 1 HEAT 19/11/69 22 ***C 23 0.842 0.6919 1500.0 24 14.1 15.0 9,3 8.2 0.2 200.0 445.0 -1.0 43.4 25 14.5 14.0 5.9 10.0 0.15 460.0 360.0 -1.0 48.2 26 14,7 12.0 3.25 11.75 0.2 1400.0 315.0 -1.0 52.1 27 14.3 12.0 Ü.55 13.1 0.5 3850.0 275.0 -1.0 56.1 28 13.0 24.0 0.1 11.65 3.0 5400.0 275.0 -1.0 64.6 29 10.7 32.0 0.1 9.2 6.5 1850.0 320.0 -1.0 78.0 30 10.05 38.0 0.1 Ö.95 7.2 1500.0 330.0 -1,0 79.6 31 8.8 40.0 0.11 8.2 8.2 420.0 455.0 -1.0 83.8 32 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 33 DATA
34 BUN 19 1500 1/2 I INJ POS 2 HEAT 19/11/69 35 ***C 36 0.842 3.6919 1500.0 37 6.9 22.0 7,5 9.1 0.2 260.0 465.0 -1.0 74.7 38 6.9 24.0 6,25 9.7 0.2 360.0 450.0 -1.0 76.8 39 6.9 27.0 4.5 10.75 0.25 770.0 410.0 -1.0 83.2 40 6.9 28.0 1.35 12.6 0.35 2325.0 350.0 -1.0 91.4 41 6.9 42.0 0.12 9.9 5.5 1600.0 315,0 -1.0 100.5 42 6.9 40.0 0.1 9,1 6.6 420.0 550.0 -1,0 93.2 43 0,0 0,0 0,0 0.0 0.0 0.0 0.0 0.0 0.0 44 DATA
45 RUN 20 1500 1/2 L INJ POS 1 HEAT 19/11/69 46 ***C 47 0.842 0.6919 1500.0 48 6.9 21.0 7.5 9.15 0.2 260.0 460.Ü -1.0 75.2 49 6.9 27.0 6.25 9.83 0.2 400.0 450.0 -1.0 79.3 50 6.9 25.0 4.7 10.7 0.2 630.0 390.0 -1.0 82.9 51 6.9 26.0 2.1 12.15 0.25 1670.0 350.0 -1.0 90.5 52 6.9 42.0 0.13 10.3 4.6 2450.0 295.0 -1.0 102.8 53 6.9 40.0 0.12 8.7 7.7 530.0 415.0 -1.0 96.0 54 0,0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 55 ***Z
BMEP 1 2 3 . 1 0 1 2 3 . 5 4 1 2 3 . 5 4 1 2 0 . 0 6 1 0 8 . 7 5 9 2 . 2 2 8 7 . 0 0 7 7 . 4 3 BMEP 1 2 2 . 6 7 1 2 6 . 1 5 1 2 7 . 8 9 1 2 4 . 4 1 1 1 3 . 1 0 9 3 . 0 9 8 7 . 4 3 7 6 . 5 6 BMEP 6 0 . 0 3 6 0 . Ö 3 6 0 . 0 3 6 0 . 0 3 6 0 . 0 3 6 0 . 0 3 BMEP 6 0 . 0 3 6 0 . 0 3 6 0 . 0 3 6 0 . 0 3 6 0 . 0 3 6 0 . 0 5 RUN 1 7 1 5 0 0 SFC 0 . 6 1 9 0 . 5 6 5 0 . 5 1 9 Ü . 4 9 1 0 . 4 6 8 0 . 4 6 6 0 . 4 8 9 0 . 5 2 5 RUN 1 8 1 5 0 0 SFC 0 . 6 5 7 0 . 5 5 8 . 0 . 5 0 9 U . 4 8 6 0 . 4 6 4 0 . 4 6 7 0 . 4 8 7 0 . 5 2 9 RUN 1 9 1 5 0 0 SFC 0 . 7 5 6 0 . 7 5 6 0 . 6 7 9 0 . 6 1 8 0 . 5 6 2 0 . 6 0 6 RUN 2 0 1 5 0 0 SFC 0 . 7 5 1 0 . 7 1 3 0 . 6 8 2 0 . 6 2 4 0 . 5 5 0 0 . 5 8 9 F / L I N J POS 2 IGN 1 6 . 1 4 . 1 1 . 1 1 . 2 0 . 5 6 . 5 7 . 4 0 . XCO 8 . 4 0 6 . 0 0 3 . 4 0 0 . 2 2 0 . 1 0 0 . 0 8 0 . 0 8 0 . 0 8 F / L I N J PCS 1 I 6 N 1 5 . 1 4 , 1 2 . 1 2 . 2 4 . 5 2 . 5 8 . 4 0 . 1 / 2 L I G N 2 2 . 2 4 . i7. 2 8 . 4 2 . 4 0 . 1 / 2 L IGN 2 1 . 27. 2 5 . 2 6 . 4 2 . 4 0 . %C0 9 . 3 0 5 . 9 0 3 . 2 5 0 . 5 5 0 . 1 0 0 . 1 0 0 . 1 0 0 . 1 1 I N J POS %tQ 7 . 5 0 6 . 2 5 4 . 5 0 1 . 3 5 0 . 1 2 0 . 1 0 I N J PCS XCO 7 . 5 0 6 . 2 5 4 . 7 0 2 . 1 0 0 . 1 5 0 . 1 2
SAMPLE: OUTPUT
HEAT 1 9 / 1 1 / 6 9 X C 0 2 8 . 4 0 9 . 9 0 1 1 . 5 5 1 3 . 3 0 1 1 . 4 5 9 . 5 0 8 . 9 5 8 . 4 0 5£02 0 . 2 5 0 . 2 0 0 . 2 0 0 . 5 0 5 . 5 0 6 . 5 0 7 . 0 0 7 . 9 0 HEAT 1 9 / 1 1 / 6 9 X C 0 2 8 . 2 0 1 0 . 0 0 1 1 . 7 5 1 3 . 1 0 1 1 . 6 5 9 . 2 0 8 . 9 5 8 . 2 0 X 0 2 0 . 2 0 0 . 1 5 0 . 2 0 0 . 5 0 5 . 0 0 6 . 5 0 7 . 2 0 8 . 2 0 2 HEAT 1 9 / 1 1 / 6 9 X C 0 2 9 . 1 0 9 . 7 0 1 U . 7 5 1 2 . 6 0 9 . 9 0 9 . 1 0 X 0 2 0 . 2 0 0 . 2 0 0 . 2 5 0 . 3 5 5 . 5 0 6 . 6 0 1 HEAT 1 9 / 1 1 / 6 9 X C 0 2 9 . 1 5 9 . 8 5 1 0 . 7 0 1 2 . 1 5 1 0 . 3 0 8 . 7 0 X 0 2 0 . 2 0 0 . 2 0 0 . 2 0 0 . 2 5 4 . 6 0 7 . 7 0 PPMNO 2 2 5 . 4 7 5 . 1 5 2 5 . 4 1 5 0 . 4 9 5 0 . 2 2 7 0 . 9 8 0 . 1 7 5 . PPMNO 2 0 0 . 4 6 0 . 1 4 0 0 . 5 8 5 0 . 5 4 0 0 . 1 8 5 0 . 1 5 0 0 . 4 2 0 . PPMNO 2 6 0 . 5 6 0 . 7 7 0 . 2 5 2 5 . 1 6 0 0 . 4 2 0 . PPMNO 2 6 0 . 4 0 0 . 6 5 0 . 1 6 7 0 . 2 4 5 0 . 5 5 0 . PPHHC ( N D I R ) 4 4 0 . 5 5 5 . 5 1 0 . 2 6 0 . 2 5 5 . 3 1 5 . 5 3 5 . 4 0 0 . PPMHC ( N D I R ) 4 4 5 . 5 6 0 . 5 1 5 . 2 7 5 . 2 7 5 . 5 2 0 . 5 5 0 . 4 5 5 . PPMHC ( N D I R ) 4 6 5 . 4 5 0 . 4 1 0 . 3 5 0 . 3 1 5 . 5 5 0 . PPMHC ( N D I R ) 4 6 0 . 4 5 0 . 5 9 0 . 5 5 0 . 2 9 5 . 4 1 5 . ---: PPMHC ( F I D ) - 1 . - 1 . " - 1 . * 1 • • . " 1 • 1 . -" 1 • ~ 1 • PPMHC ( F I D ) - 1 ; - 1 , - 1 . - 1 . - 1 . - 1 . - 1 . - 1 . PPMHC ( F I D ) - 1 . - 1 . - 1 . - 1 . - 1 . - 1 . PPMHC ( F I D ) - 1 . - 1 . - 1 . - 1 . - 1 . - 1 . ---^ ..-COG/H " .' 1 8 9 1 . 5 9 1 5 1 5 . 0 8 7 2 8 . 5 9 - 4 8 . 0 5 2 1 . 9 9 - 1 8 . 0 4 • 1 8 . 4 6 1 8 . 5 7 C O G / H 2 0 6 3 . 2 8 1 5 0 1 . 4 5 7 0 4 . 5 7 1 2 1 . 7 7 2 2 . 2 5 2 2 . 9 9 2 5 . 0 9 2 5 . 7 4 C O G / H 1 0 1 6 . 0 9 8 5 6 . 9 5 5 9 6 . 6 0 1 7 8 . 4 8 1 9 . 9 4 1 9 . 3 7 COG/H 1 0 0 6 . 7 5 8 2 5 . 4 4 6 2 0 . 4 1 2 7 4 . 6 6 2 0 . 3 6 2 5 . 2 9 .-- ^ -H C 6 / -H . 6 0 . 9 7 4 7 . 8 1 4 0 . 8 7 5 4 . 9 3 5 4 . 5 1 4 3 . 7 2 4 7 . 5 6 5 7 . 1 3 H C 6 / H 6 0 . 7 5 4 8 . 8 6 4 2 . 0 1 3 7 . 4 7 3 7 . 6 5 4 5 . 2 7 4 6 . 8 9 6 5 . 5 1 HCG/H 3 8 . 7 6 3 7 . 9 7 5 5 . 4 5 2 8 . 4 7 5 2 . 2 1 4 1 . 7 1 HCG/H 3 8 . 0 0 5 6 . 4 8 5 1 . 6 8 2 8 . 1 7 2 8 . 4 5 4 9 . 5 7 .. -;.^. =.:_. NOG/H .-5 . 4 3 1 1 . 1 4 3 0 . 4 1 9 7 . 0 7 1 1 6 . 6 2 5 4 . 8 5 2 4 . 2 2 4 . 3 5 : N O G / H 4 . 7 5 1 0 . 8 7 3 2 . 5 1 9 1 . 3 2 1 2 8 . 7 3 4 5 . 5 6 5 7 . 1 1 1 0 . 5 5 NOG/H 5 . 7 7 5 . 2 9 1 0 . 9 4 5 2 . 9 5 2 8 . 4 8 8 . 7 1 NOG/H 3 . 7 4 5 . 6 5 8 . 9 1 2 3 . 4 0 41 . 1 1 1 1 . 0 2 .:^ .._:...:. -.l-^J :-A / F •f 1 1 . 2 6 1 1 2 . 2 6 1 1 3 . 3 7 0 1 5 . 0 0 1 1 7 . 5 4 3 2 0 . 9 0 2 2 1 . 5 7 7 : 2 2 . 7 5 9 A / F 1 0 . 9 7 2 1 2 . 2 7 4 1 5 . 4 3 9 1 4 . 8 3 0 1 7 . 0 3 1 2 0 . 9 2 4 2 1 . 7 6 8 2 3 . 0 4 3 */•= 1 1 . 6 0 2 ' 1 2 . 0 6 8 1 2 . 8 3 2 1 4 . 2 7 7 1 9 . 5 8 9 2 1 . 0 0 7 A / F 1 1 . 6 1 7 1 2 . 0 9 4 1 2 . 7 5 1 1 3 . 8 8 6 1 8 . 6 4 8 2 2 . 2 0 0 ...F i g . F i g . F i g . F i g . F i g . F i g . F i g . 1 2 3 4 5 6a & 7 G r a p h 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 Engine coolant c i r c u i t F u e l s y s t e m s Induction s y s t e m Optical and r e c o r d i n g s y s t e m W a t e r bath coolant flow c i r c u i t
Shadow photographs d o w n s t r e a m of a valve in a f l o w - r i g D r o p l e t s in niotion - from cine film
F l a m e d e t e c t o r g a s flow v p r e s s u r e Flam.e d e t e c t o r c a l i b r a t i o n c u r v e . C r o s s r e s p o n s e of n i t r i c oxide a n a l y s e r to w a t e r v a p o u r R e p e a t a b i l i t y a t 1500 r . p . m . full load r . p . m . r . p. m . r . p. m . r . p. m . r , p, m . r . p, m, r . p . m . M a s s e m i s s i o n s 800 M a s s e m i s s i o n s 800 M a s s e m i s s i o n s 800 M a s s e m i s s i o n s 800 M a s s e m i s s i o n s 800 V o l u m e t r i c c o n c e n t r a t i o n s 800 M a s s e m i s s i o n s 1500 r . p . m . M a s s e m i s s i o n s M a s s e m i s s i o n s h e a t e d c h a r g e M a s s e m i s s i o n s 1500 r . p . m injection M a s s e m i s s i o n s M a s s e m i s s i o n s heated c h a r g e M a s s e m i s s i o n s M a s s e n a i s s i o n s h e a t e d c h a r g e M a s s e m i s s i o n s M a s s e m i s s i o n s h e a t e d c h a r g e M a s s e m i s s i o n s M a s s e m i s s i o n s heated c h a r g e M a s s e m i s s i o n s 2200 r . p . m . M a s s e m i s s i o n s 2200 r . p . m . h e a t e d c h a r g e C a r b o n monoxide % + C a r b o n monoxide % v 1500 1500 1500 1500 1500 1500 2200 2200 2200 2200 2200 2200
(no load) ignition 10 B. T. D. C. (no load) ignition 5 B. T . D . C . (no load) ignition T. D. C. (no load) ignition 5° A. T. D. C. (no load) i n j e c t o r position 2
r . p. m . (no load) i n j e c t o r position 2 full load) c a r b u r a t i o n and injection full load) i n j e c t o r positions 1 & 2 full load) i n j e c t o r positions 1 & 2 60 b. m . e . p . ) c a r b u r a t i o n and r . p . r . p . m . m . m . m . m . m . na. m . 60 60 30 30 b. m . e. p. ) i n j e c t o r positions 1 & 2 b . m . e . p . ) i n j e c t o r p o s i t i o n s 1 & 2 b. m . b. ra. p. ) i n j e c t o r p o s i t i o n s 1 & 2 p. ) i n j e c t o r positions 1 & 2 full load) injector position 1 & 2 full load) i n j e c t o r p o s i t i o n s 1 & 2 (60 b. m . e. p. ) i n j e c t o r p o s i t i o n s 1 & 2 (60 b. m . e . p . ) i n j e c t o r p o s i t i o n s 1 & 2 (30 b. m . e. p.) i n j e c t o r p o s i t i o n s 1 & 2 (30 b . m . e. p.) i n j e c t o r p o s i t i o n s 1 & 2 C a r b o n dioxide % v a i r - f u e l r a t i o a i r - f u e l r a t i o at idle and 2200 r . p. m . p a r t load C a r b o n monoxide % v a i r - f u e l r a t i o at 1500 r . p . m . and 2200 r . p . m . full load
C a r b o n dioxide % and Oxygen % v a i r - f u e l r a t i o at 2200 r . p. m . p a r t load
C a r b o n dioxide % and Oxygen % v a i r - f u e l r a t i o at i d l e , 1500 r . p . m . and 2200 r . p . m . full load
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FIG. 1 ENGINE COOLING CIRCUIT
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FIG. 6 SHADOW PHOTOGRAPHS DOWNSTREAM OF AN INLET VALVE
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(a) at a high air velocity
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