Proceedings of the Europort Diesel Engine Symposium'91, ""MOTOR2000plus"", Part I

EUROPORT DIESEL ENGINE

SYMPOSIUM '91

14tli and ISth November 1991

PA R T ONE

Euiopoit Diesel Engine Syn^x>siiim '91 MOTOR 2000 plus

is jointly oi^ganized by:

VIV -A^ociation of Combustion Engine In^xsters

V l l l ' GVM - Group of Manufactuimof Combusticm Engines

-À

AMSTERDAM ral T W . RAI - International Exhibition Centie

ADVANCED DEVKDOFHENT METHODS FOR FUTURE HEDIUH SPEED H»5It|BS

K a r l Wojik

The main reguirement-s f o r medium speed engines with rated speeds between 4Ó0 and 1000 rpm are high s p e c i f i c performan-ces/ high economy and high r e l i a b i l i t y . As f a r as engines f o r ship a p p l i c a t i o n are concerned, heavy f u e l q u a l i f i c a t i o n i s a must. Lately, medium speed engines are confronted increasing gly with environmental demands l i k e low emissions and low noise l e v e l s .

Based on above mentioned p r o f i l e s , meditun speed engines have t o be rated with high i g n i t i o n ahd i n j e c t i o n pressures. Addi-t i o n a l l y , f r i c Addi-t i o n losses need Addi-to be minimized. R e l i a b i l i Addi-t y o f components must be assured without extended continous operating t e s t s , as the engines are large, high i n power-out-put and therefore, regarded absolutely, f u e l and energy con-sumption i s immense. A complex challenge, which may be well supported by pre-optimization with comjputational simulation methods.

Since i t s foundation by Prof. L i s t i n 1948 AVL i s dealing on a large scale not only with the development of v e h i c l e ines, but also with medium speed engines f o r locomotive eng-ines, ship propulsion and stationary generatpr sets. Con-seguently and based on AVL's experience, the advantages of modern develppment t o o l s , e s p e c i a l l y f o r l a r g e r engines,

The f i r s t phase of a t y p i c a l development process s t a r t s with engine design and the accompanying c a l c u l a t i o n s . The used aids changed remarkably i n the past years. For example, de-sigh work at AVL i s performed b a s i c a l l y with CAD. Structure optimization of the basic engine i s done by f initeelementcalcu.lation ( f i g . 1). In addition, s p e c i a l developed c a l c u l a -t i o n prograiiffi are Used which w i l l be described i n d e -t a i l lateron. The engine working process i s c a r r i e d out with the thermodynamic program PROMO, which was developed by the Ger-man Research Association FW and upgraded with AVL's modules^ For a number ôf tasks or optimizing duties we increasingly use a three-dimensional flow simulation program, which was o r i g i n a l l y developed at AVL and i s c a l l e d FIRE. The name FIRE derives from "Flows i n Reciprocating Engines". As f a r as valve c o n t r o l and valve t r a i n i s concerned, the optimization of charge-exchange i s performed by the tiiermpdynamic program PROMO and the r a t i n g of valve propulsion dynamic resp- kine-matics i s c a l c u l a t e d by s p e c i a l finiter-element-methods [ I J . Fuel i n j e c t i o n and mixture preparation are simulated by t a i -lormade hydraulic c a l c u l a t i o n programs. Fpr that work, too, the AVL FIRE-program i s p e r f e c t l y applicable, although regar-ding f u e l mixture the optimum has not been reached yet.

P i g . 2 shpws, how the crankshaft forces of the working pro-cess of c y l i n d e r s , supported by the AVL-program ^'crankshaft dynamic*^ can be entered and as a r e s u l t , the main crankshaft forces are found. The figure shows an example of a high speed gasoline engine, but of course, the same analysis may be applied on b i g metdium speed engines as w e l l . Pure mathemati-c a l l y , the mathemati-crankshaft i s r o t a t i n g l i k e i n r e a l i s t i mathemati-c operatimathemati-c on. I t i s f u l l y retained and uiKiergoes deformations which are close to r e a l i t y . The r e s u l t i n g main crankshaft forces are used i n a further AVL program "elastohydro^dynamic bearing

c a l c u l a t i o n " ' and show r e a l i s t i c a l l y the i n t e r a c t i o n between deforming bearing w a l l and o i l f i l m . Tfae c a l c u l a t i o n r e s u l t s can then be used corresponding t o f i g . 3 f o r c a l c u l a t i o n s of various model shapes f o r the e n t i r e engine arrangenent. The r e s u l t s of the s i n g l e c a l c u l a t i o n s need t o be copied t o a video tape, so t h a t the designer has the p o s s i b i l i t y t o f o l -low the deformation of the entire engine block i n s-low motion on the screen. This allows a very close look t o deformation and motion r e l a t i o n s . Worthwhile ideas f o r constructive im-provements may be gained. Structure optimizations of engine blocks i n the presented form lead t o improvements of the npise l e v e l of up t o 2 dB(A).

The thermodynamic program PROMO treats the processes i n the c y l i n d e r of course Only i n t e g r a l and shows the intake or out-l e t port one-dimensionaout-l. For more compout-lex duties or s p e c i a out-l d e t a i l l e d examinations the e n l a r g ^ e n t t o three-dimensional

flow and contostion simulation by FIRE i s advantageous.

Basic Combustion Research

The simulation of combustion processes i s a t a homogeneous combustion, as i t takes place i n today's gasoline engines, easy t o perform. I t i s more complicated a t a heterogeneous combustion l i k e i n d i e s e l engines. In the past years AVL also here could achieve remarkable progress due t o modem, optic-r e l e c t r o n i c a l measuring instrumentation, l i k e d i f f e r e n t l a s e r technique methods. F i g . 4 i l l u s t r a t e s on the l e f t side a photography o f a d i e s e l i n j e c t i o n spray a t i t s three major sequences. The dark zone i n the middle of the spray shows the almost l i q u i d spray center, while on the l e f t the cloud f o r -mation indicates evaporation zones and the l i g h t on the r i g h t s i d e points to the s t a r t of i g n i t i o n . Numerous ineasurements by l a s e r beam f i n a l l y allowed t o analyse the p r o c ^ s e s i n the

d i e s e l spray and during mixture preparation up to combustion, as i t can be seen on t h e r i g h t side of t h i s f i g u r e .

Such deep insights i n t o ntixture preparation and combustion process ease a systematic development of engines. This i s e s p e c i a l l y meaningful, as emissions are increasingly important f o r the evaluation. Such modern measuring and c a l c u -l a t i o n methods form the basis f o r furtüier improvement of mixture preparation and ccnnbustipn processes with the aûn of reduced f u e l consumptions and emissions.

P r a c t i c a l Development Results:

Consequently, a few p r a c t i c a l exanples of an e f f i c i e n t combi-nation of computer-aided simulation methods and p r a c t i c a l engine development s h a l l be presented, as applied successful-l y at AVL f o r severasuccessful-l years.

For the dominantly used quiescent combustion systems withput charge iKJtion, the f u e l ' s spray turbulence energy i s the e s s e n t i a l mixing promotor. Decreasing speeds and loads reduce both, tfae i n j e c t i o n pressure and the duration of i n j e c t i o n i f cam-driven f u e l i n j e c t i o n equipments (FIE) are tised. This diminishes the momentum exchange between f u e l and charge as i t could be seen by CFD ( c o n ^ t a t i o n a l f l u i d dynamics) calcu-l a t i o n . A s o calcu-l u t i o n t o approach i d e a calcu-l a i r u t i calcu-l i z a t i o n woucalcu-ld be tX) introduce some in-bowl s w i r l > to a c t i v a t e mixture formati-on at lower speeds and loads [2].

F i g . 5 shows AVL's t e s t r e s u l t s at rated power. Prom these t e s t r e s u l t s i t i s v a l i d to say the quiescent combustion systems o f f e r the best BSFC a t rated power. However, the p i c t u r e changes at lower speeds and loads. F i g . 6 i l l u s t r a t e s tfae benefits of an a d d i t i o n a l s w i r l at low loads and speeds. To achieve a minimum of smoke and BSFC with f i x e d spray hole

number, intake s w i r l had to he introduced increasingly t o -wards lower speeds and loads.

the flame propagation a t d i f f e r e n t compression r a t i o s - taken with AVL's endoscopic high speed combustion j^otography -confirms the t h e o r e t i c a l l y expected spray and thus, flame formation, f i g . 7. A t lower compression r a t i o but equal time the spray and thus the flame show an extended t r a v e l distance i n spray axis d i r e c t i o n . Furthermore, the flame develops i n a narrow cone with a small vertex angle whereas a t the high cqotpression r a t i o the flame plume i s highly bushy.

Injection rate shaping techniques are i n spme of high speed d i e s e l engines used t o l i m i t the i n j e c t i o n f u e l quantity within i g n i t i o n l a g . The desired objectives are to

- reduce exhaust emissions - minimize combustion noise

- improve BSFC a t constant PFP by means of advanced timing - reduce thermic and mechançicàl engine loading mainly a t

p a r t load.

Furthermore, i n j e c t i o n rate shaping techniques are used t o improve the heavy f u e l c a p a b i l i t y of a combustion system.

For medium speed d i e s e l engine application AVL decided to use the mechanical s p l i t i n j e c t i o n device (SID), f i g . 8. F i r s t measurements are taken on the f u e l t e s t r i g and compared with Gcantputer-based c a l c u l a t i o n r e s u l t s . Some of the r e s u l t s from our 18 1 s i n g l e c / l i n d e r research engine are presented i n f i g . 9. The most s i g n i f i c a n t difference between SID and con-ventional FIE can be seen a t combustion s t a r t [ 3 ] . With SID and thus, reduced f u e l discharge during i g n i t i o n l a g , the cylinder pressure develops much smoother and the i n i t i a l s p i t e o f the heat release diagram i s p r a c t i c a l l y faalfened.

Tfae engine performance data i s shown i n f i g . 10 cmd 11. Using the SID technique, combustion noise - measured by the AVL combustion noise meter [4] - i s reduced up t o 10 dB(A). An i n i t i a l l y reduced rate of f u e l discharge by means of SID improves NO - too, does not e f f e c t HC, but deteriorates smoke

X s l i g h t l y .

The process of flame propagation with SID can be studied by tfae use of AVL faigh-speed photography. The outer shape of the flame r e s u l t i n g from p i l o t i n j e c t i o n stands p r a c t i c a l l y s t i l l very close tp the nozzle t i p . The spray of the main i n j e c t i o n penetrates through the p i l o t flame and s t a r t s t o burn i n fjTont of the flame plume of the p i l o t spray i n spray axis d i r e c t i o n . This inflammation prpcess indicates that the o p t i -mara of i g n i t i o n l a g reduction f o r the main i n j e c t i o n takes place i f each xóain spray has i t s own p i l o t flame and thus i g n i t i o n kernel.

Modern Parts ProcUriänent

Even f o r parts procurement f o r prototype engines the new computer-aided metfaods brought valuable progress. Today one of the main challenges means a d r a s t i c reduction of develop-ment times to be able to launch a new product bef ore the competitor does. Here parts procurement has to bring i t s contribution. I t can be achieved due to consequent use of CAM

(computer aided manufacturing) or promising future technolo-gies a t the model shaping of casting pattern. This ;shall be shown on two examples.

F i g . 12 sfaowis on the l e f t of the CAD-screen the generated surface model of a core case f o r a s p e c i a l intake port of a d i e s e l engine tp produce an a i r intake s w i r l . CAD-data i s copied d i r e c t l y to the CNC-milling machine, so that on t h i s machine the o r i g i n a l core case aaay be cut d i r e c t l y of p l a

-s t i e -s . The end product can be -seen on the rigfat -side of the f i g u r e . F i g . 13 shows a core model of a neutral intake port which was created by stereolithography. At stereolithography a {diotopolymer i s lead by a l a s e r beam from a l i q u i d to a f i r m phase. The l a s e r beam i s also controled by CAD-data s i m i l a r l i k e the CNC-machine and builds the model l a y by l a y . The most complicated shapes of hollow bodies may be created. The stereolithograpfay machine can work around the clock wi-r tfaout e s s e n t i a l s e r v i c e personnel and therefore, gains remar-kable time savings at model shaping.

New Acoustics^ Development Methods

In acoustics developEnent of engines a reduction of the noise l e v e l i n d e c i b e l i s no longer s u f f i c i e n t . Due t o measures l i k e structure optimization^ modern engines already achieve . b a s i c a l l y low noise l e v e l s . Therefore, s ingle bothersome

noise sources come to the fore. The duty a r i s e s to f i n d these bothersome noise sources and t o eliminate tfaem as f a r as possible. AVL developed i n a three year research project ah index f o r annoyance. The core of tfais technology may be seen i n the foreground of f i g . 14. The so-called " a r t i f i c i a l head" wit^ microphones i n bpth ears i s able to take noises s i m i l a r to human beings with i t s binaural power of hearing. Extensive e l e c t r o n i c instrumentation analyse tfae various recorded n o i ^

ses and consequently, a s t a t i s t i c m t h e m a t i c a l method i n d i c a -tes the index f o r annpyance. This method i s a:h e s s e n t i a l a i d to f i n d and eliminate bothersome noise sources.

Conclusion

In g ^ e r a l , f o r engine development an extended use of compu-ter-suipported simulation programs i s e s s e n t i a l which d e l i v e r due to t h e i r permanent improvements r e s u l t s whicfa are close to r e a l i t y . I t i s intended to save complete prototype

generar-t i o n s which would lead generar-t o remarkable savings i n developmengenerar-t times. Thus> development costs could be cut down and an ear-l i e r presence on the market with the advantage against tfae competition could be achieved.

For medium speed ehgiiies the presented modem mathematic-tecfanical and a l s o experimental development t o o l s provide tfae cfaance t o save development times^ but e s p e c i a l l y development costs i n an e s s e n t i a l scale.

SS

[1] A f f e n z e l l e r J . , P f e i f f e r F., Jofaaùmi R.

Qptimizatióh of,Diesel Engine Cam and Injection Pump Drive T r a i n

CIMAC, Warschau, 1987

12] Herzog P.

Combustion Development on Medium Speed Diesel Engines Dalian/China, 1990

[3] Athenstaedt G., Noraberg J . , Herzog P.

Combustion Improvement P o t e n t i a l through the Üse of S p l i t Injection

CIMAC, Warschau, 1987

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TITLE

EXPERIENCES, LATEST DEVELOPMENTS AND FUTURE OF THE STORK-WARtSILÂ 280

NAME O f AUTHOR

Ir. R.H.M. BoTsboom

Manager Engine Performance & Testing Stork-Wärtsilä Diesel B.V.

EXPERIENCES. LATEST DEVELOPMENTS AND FUTURE OF THE STORK-WÄRTSILÄ 280

By: Ir. R.H.M. Bórsböom

Manager Engine Perfomiance & Testing Stork-Wfirtsiia Diesel B.V.

INTHODIKHION

The SW280 was iritroduced in 1982 as a medium speed diesel engine with main characteristics high reliability

capability of running on all commercially available residual fuels

next to other important design criteria like high power deiisity, which follows frotn the maximum speed of 1000 rpm, easy m^ntenance, long service interval and low' noise. The fact that o l course tow fuel consumption was atso a high priority develppment issue needs not to be mentioned. The main data of the SW280 are listed below.

Bore 280 mm Stroke 300 rrim Speed 720-1000 rprti bmep 24^4-21.0 bar Piston speed 7.2 - 1 0 m/s Output 270-325 kW/Cyl. Compression ratio 13 Cylinder nrs. 6-8^9-12-16-18

Since the introduction in 1982, in which year the first 6SW280 was sold, having logged ovcfr 45,000 hours today, approximately 2250 cylinders have been put into the market, of which some 700 operate on HFO, together having a total number of service hours of approximately 820.000. Applications can be found in areas such as propulsion, with fishery vessels as a special kind of market, power stations, auxiliary sets, offshore etc...

EXPERIENCES

Evaluation of operational results of SW280 engines in the field showed satisfying records in almost every area of the engine design. In two areas however we felt that there was room for improvement, to lift up also those areas to our high standards of pperational costs, service life of parts and service intervals. These two areas were:

Lubricating oil consumption Inlet valve wear.

To improye lub.oti consumption of the SW280 measures have been taken on both liner side as well as pistpn ring side.

Analysis of the matter of tub.oil consumption led to the following conclusions.

* In order to prevent add formation on the liner, ^ e c i a l l y at part/low load conditions, liner surface temperatures had to be elevated. Special attention was needed since the tempeiratuu'é rise at full load had to be less than the one at part/low load.

* In order to prevent boris polishing the inevitaUe carbon formation should not ^ k e place on the moving part (piston) but on the liner.

* Locsd deformations of the liner, where the engine block is supporting it, could be reduced to offer the pistpn ring pactcage a mpre undisturbed and straighter line to niove along.

* The tribo-system piston rings - liner showed some possibilities for further optimization. The measures taken from the conclusions as mentioned above have been:

* Isofôttng tubes in the cooling bores ôf the liner, that N v e characteristics causing more temperature rise at part/low load than at full load.

* Surface treatment of the upper area of the cylinder liner causing a substantial reduction of carbon formation on piston top land.

* Adaption of engine block dimensions causing the clearance between engine block and liner to be zero under operation (warm condition).

* Improvemertt of the piston ring package.

Intensive mpnitoring of a large riumber of engines after introducing the measures described in the previous section showed that after the running-in period of these engines their lub.oil consumptton became very constant and particularly low. The lub.f)jl consumption that was shown by 99% of these engines was between 0.5 and 0.7 gr/kWh.

To increase the service life of the SW280 inlet valves analysis shovyed that tyvo things had to be done: one on the inlet valve seat side and one on the side of the valve itself.

First of all the deformation of the inlet valve seats during the high pressure part of the cycle was unevenly distributed alpng the tangent and certainly not symmetrical. This causes unevenly distributed pressures and relative tnovëménts between valve and seat and thus asymmetrical wear.

To cover this side of the problem changes were put into the cylinder head design to create a better and more symmetrical support of the flame plate by the second, intermediate deck. From the side of the inlet valve the second part of the improvement was found by using valve rotators on the inlet valve. By rotating the valve, highest pressures and relative movenrrents vyill not be met by the same spots of the yalyes every cycle again. This so obtained distribution causes less overall wear.

Experiences from the field of engines having the improvemerits as discussed in the previous section are being collected at the moment. First measurements show results that should lead to substantial improvements of inlet valves service life. (See Enclosures}

LATEST DEVBLOPMBSrrS

In the continuing search for performance improvement of a dieisial engine Stork-Wärtsilä Diesel, just like any other diesel engine manufacturer, is trying tp tower fuel çprisumptipn, exhaust gas emissions, smoke figures e t c in combirtatibn with an overall perforrnapce improvement of the engine with criteria such as reliability, T B O , parts life etc..

Over the latest period of time development of the SW280 concentrated on the gas exchange of the engine (or the low priassure part of tiie engine cycle), and the fuel injection (or the combustion process).

By changing tiira valve timing, in effect exhaust opening as well as the length of the scavenging period, we managed to change the pumping losses during the low pressure part of the cycle into a positive contribution of the gas exchange.

Cycle simulation calculations^ taking into account gas dynamic phenpinena in the exhaust system^ predicted the possible improvement resulting in a fuel consumptipn reduction of 3 gr/kWh. A n extensive series of experiments confirmed these figures. During these measure-ments turbocharger si»cifications were not orüy matched to the optimized valve timing, but also optimized to each different kind of application. This last issue was made possible thanks tp improved logistics ori both engine manufacturer's side as well as on turbocharger supplier's side.

Quality of combustion in a diesel engine is for a great deal a function of the quality of the atomization of the fuel. Nozzle geometry, fuel cam shap<a, plunger size, high pressure line dimensions and injection timing are determining system parameters; fuel consumption, smoke figures, cavitation, maximum pressure in the fuel injectton system and cylinder are the performance parameters to be optimized to.

Experimental research showed that if the maximum allowable injection pressure could be increased from 1100 to 1500 bar smoke figures could be reduced substantially, together with a reduction of fuel consumption. All this without an increase in maximum allowable firing pressure, thanks tp an optimaed nozzle geometry with a smaller effective flow area.

To this nozzle, another optimum injection timing vyas found. High pressure line diameter had to be increased at the same time, to avoid cavitation in the high pressure fuel system, especially at the higher engine speeds. Fuel consumption savings went up to 2.5 gr/kWh at 1000 rpm, with a dramatic drop in the smoke figures to some 25% of the original level. To be able to operate the engine Viyith injection pressures of 1500 bar, a new injection pump has been dedgned and developed in co-operation with a fuel Injection equipment manufacturer. This new pump can npt only be operated under 1500 bar injection pressure, it also has improved characteristics regarding cavitation and HFO operation in geneiral (faûlîng, sticking etc.).

FUTURE

The future planning for the SW280 is split up in 3 stages:

* Short term; release tiie engine for operation under high temperature conditions, without derating for these ambient conditions.

* Medium term; re-design the V-engine to make it the optimum design for generator drive. * Long term; increase nominal bmep.

Short term

TTie SW280 is an engine with high power density, since Hs nominal speed (also on HFO) is 1000 rpm; the nominal bmep at 1000 rpm is rather high as well, being 21 bar.

As everybody involved in diesel engine technology knows, thermal load of an engine is very rnuch influenced by air excess ratios and combustion air temperatures at the start of the high pressure part bf the cycle. Both aire very rnuch influenced by the intake air temperature as well as the air cooler cooling water temperature. If they go up, thermal load of the engine goes up as well. If the nominal rating of an engine is high already, due to high nominal speeds and bmep's, this might be a reason fpr applying derating fpr ambient conditions to avoid getting beyong the limits of an engine.

Since maximum reliability under all operating conditions ts a main issue for Stork-Wärtsilä Diesel, until today we applied derating for ambient conditions for reasons described in the previous section.

But as technology and developments go on, it is our goal to be able to have the SW280 operate iinder high temperature conditioris vyithout derating, and without losing the slightest bit of reliability either. To find out about the overall perforrnance bf the engine when running under conditions as mentipned above and to see what wpuld be parts of the design that would need improvement first, we carried out a yery heayy duty endurance test with following characteris-tics:

20% overload

Using HFO with poor ignition quality (380 cSt; CIMAC H35) Intake air temperâtuiê 45*>C

Receiver temperature 60^C.

Inspectipn ajfter completion of the endurance test showed satisfying results of piston, piston rings and piston ring grooves. Also cylinder liner and inlet valves and seats showed a satisfying picture; fuel pump and plunger looked beautifully clean and vyithout the slightest traces of damage.

But since Stork-Wärtsilä Diesels philosophy of maximum reliability requires a 100% spotless picture as a result of Such an endurance test, we felt that on the side Pf the exhaust valves there was room for m:Tprbvement. The extreme thermal regime the engine was tested under (HFO as a fuel, 20% overload, 45*'C intake air and 60^C receiver temperature all add up to a dhrarnatic ino-ease in parts tennperatures, especially exhaust valves) showed that for these conditions in particular the exhaust valve cooling is not suffident and could do with further improvement. This is mainly an issue of importance for operation under HFO, since on one side HFO as a fuel causes an extra rise in exhaust valve temperature of some 3 0 ° C , on the other side exhaust valve temperatures get critical at lower levels running on HFO bemuse óf the preserKe of vànaûdium in the fuel.

Therefore we came to the conclusion that to meet the short term goals for HFO ^}eration exhaust valve cooling needs some improvement for MDO/gasoil operation no restrictions could be detected from the endurance t ^ .

Medium term

In the original design the V-engrne pf the SW280 series was thoi^tit to be a propulsion engine as welt. Therefore this V-type contains options and elements, incorporated in the casting as wen as in the overaO nunnber of parts, that do not have functionality for generator drive application, but only increase total costing of an engine (kW-price) and the total number of parts (maintenance and rèliability). Besides this the V-type SW280 has got a different scope of application, ever since the composition of the global range as a result from the co-operation within the Wärtsilä Diesel Group. Rnally, market research also showed t l ^ mainly generator drive has been and vvill be the application of interest for thé V-type SW280.

All reasor^ previpusly mentioned brought Us to the conclusion that it would be wise to re-design the V-engine of the SW280 tp an pptimized concept for generator drive, to be able tb serve this part of the market in the best possible way.

Long term

For the longer term Stork-Wärtsilä Diesel plans to increase the bmep-rating of the SW2&0, especiaUy in the speed range from 900 to 1000 rpm, with another 10%. This cah only be done without at the same time irrcreasing specific fuel consumption. If along with a 10% increase in bmep the maximum allowable firing pressure of the engine is increased by about 30 bar. This means a substantial increase in both mechanical and thermal loading of the engirie.

As explained before Stork-Wärtsilä Diesel is used to live up to high standards of reliability. TP ensure that reliability of the SW280 stays at that same high levti, after increasing bmep and firing pressure, an extensive process of verification of parts like cylinder head, pistpn, cormec-ting rod, bearings and crankshaft will proceed the release of thiis further uprated SW280. ThËs verification vyill be done by an accurate series of calculations, followed by a large series of tests.

As scheduled today, tiiese tests should be finished in tvvo years from now, so that the release of tills uprated SW280 is expected by the end of 1993.

C O N C L U S I O N

After completion and impl^nentation of all developmêÂit steps, described in this paper, tt is a fact that the Stork-Wârtsiïâ 280 of "tomorrow" definitely vyill be an engine with characteristics like:

Extrerhely high power density Good fuel consiurnption

: All Other benefits it already has today.

These benefits, again listed as closing remarks bf this paper, are: GotKl fuel ecoTTomy

Low hibricatir^ oil consumption Low wear rates

"Diesel Concept*

D r . - I n g . Hubert H i t z i g e r MOTOREN-WERKE MANNHEIM AG

D i e s e l Engines 2000 p l u s Amsterdam^ November 1991

T l t e l : Combustion process in r e l a t i o n t o environment: The DEUTZ MWM

" D i e s e l Concept"

L a d l e s and Gentlemen^

" D i e s e l Engines 2000 p l u s " . Let us dare to toke a glance i n t o the f u t u r e .

The populotion w i l l 1nc rease î f rom 1950 un111 today^ we have r e g i s t e r e d almost a doubling to nearly 5 b i l l i o n people. In the year 2000, i t w i l l be over 6 b i l i i o n s in 2010^ there w i l l be more than 7 b i l l i o n world Inhabitants.

Trading volume, and with It f r e i g h t t r a f f i c , w i l l grow as the population i n c r e a s e s . According to I n v e s t i g a t i o n s c a r r i e d aut by the I n s t i t u t e f o r Econom1c Po11cy and Reseorch, Kar1sruhe^ the f r e i g h t t r a f f i c by l a n d , sea and a i r . I.e. by t r u c k , t r a i n , s h i p and a i r c r a f t , w i l l have

increased by 40-50% between the yeors 1985 and 2000, and w i l l have doubled by the year 2010.

Over 80% of t h i s f r e i g h t flow i s moved by d i e s e l engines. The d i e s e l engine w i l l s u r e l y maintain t h i s s h a r e , as t h e requirement f o r prime inovers

i n c r e a s e s , s i n c e there i s no f e a s i b l e a l t e r n a t i v e to the D i e s e l , e i t h e r today or i n the foreseeable f u t u r e .

The a l t e r n a t i v e s : Gas turbines or e l e c t r i c d r i v e s are not c o m p e t i t i v e . The gas t u r b i n e Is twice as expensive to produce, and has a c o n s i d e r a b l y

higher f u e l consumption throughout the l o a d range. Figure 1 The steam t u r b i n e Is even worse.

Based oh e f f i c i e n t i y and cost chain (power s t a t i o n , d i s t r i b u t i o n network, e l e c t r i c motor), g r i d d e r i v -ed e l e c t r i c a l energy f o r e l e c t r i c locomotives^ compares very badly to the d i e s e l locomotive.

Apart from the l i m i t e d hydro e l e c t r i c power (approximately 5% of Europe's c u r r e n t energy needs), only atomic power s t a t i o n s can be considered to be environment f r i e n d l y in the "emission s e n s e " , however they have other ehvironiheht problems.

Stored e l e c t r i c a l energy and energy derived from the sun are only worth c o n s i d e r i n g f o r s m a l l , time r e s t r i c t e d power requirements, because of t h e i r a w a l l i n g l y low e f f i c i e n c y ( e l e c t r o 15%, sun 5%) and high c o s t s .

Because road t r a f f i c i s already s t r e t c h e d to i t s l i m i t s , passengers and f r e i g h t w i l l be i n c r e a s i n g -l y transported by r g -l -l and waterways. Locomotive and s h i p prime movers are a l s o dominated by d i e s e l engines.

The food supply requirements f o r the i n c r e a s i n g population w i l l a l s o not be achievable through human and animal p w e r a l o n e . Rather, t r a c t o r s and form machinery w i l l be needed, and these are

olready powered e x c l u s i v e l y by d i e s e l s , A l s o , the vegetable o l I s that a g r i c u l t u r e w i l 1 p o s s i b l y produce f o r i t s own needs ( e s p e c i a l l y In the 3rd w o r l d ) , can only be used economically In d i e s e l engines.

Why then the dispute over the d i e s e l ' s r i g h t to e x i s t ? Are not the economic f o r e c o s t s encouraging, f e a r s of the competition unwarranted, and the development p o t e n t i a l of the d i e s e l s t i l l considerable?

And the disadvantages: exhaust smoke, n o i s e and s m e l l ? F i r s t of a l l , a l l heot engines emit exhaust and noise - and where there i s l i g h t there i s

always shadow. F i g u r e 2 On the b r i g h t s i d e , the cdvantages of t h e d i e s e l

engine a r e :

economical - low f u e l consumption, maintenance f r i e n d l y

m o b i l i t y

modular matching to power requirement h i g h , ecohomlcol p a r t load c a p a c i t y

widely used and, t h e r e f o r e , f a m i l i a r , simple to operate and maintain technology

Oh the dark s i d e , the dlsadvcihtages a r e :

harmfu1 em1ss1ons - gaseous and p a r t i c u l a t e

i n t e r m i t t e n t working processes o s c i l l a t i o n s , v i b r a t i o n s , pumping losses noise emissions

cost Intensive c o n s t r u c t i o n

To keep the d i e s e l engine In p o s i t i o n , the d i s a d -vantages w i l l have to be overcome, and the advan-tages improved upon - to which end engineers are working i n t e n s i v e l y and s u c c e s s f u l l y , we a t DEUTZ MWM qs w e U j because the d r i v e f o r p e r f e c t i o n i s deep rooted i n the soul of the c r e a t i v e b e i n g ; in craftsmen, in a r t i s t s . In p h i l o s o p h e r s and a l s o i n d i e s e l e n g l n ^ r s .

With t h i s In mind, I come to the main subject o f my p r e s e n t a t i o n , where we f e e l our company has a p o s i t i v e c o n t r i b u t i o n to make: the exhaust gds problem,

This i s d e a l t with by a Research and Development Concept f o r optimised emissions reductions i n d i e s e l prime movers, s p e c i f i c a l l y p a r t i c u l a t e s and

oxides of n i t r o g e n . F i g u r e 3 Oxides of nitrogen (NOx) and p a r t i c u l a t e s (soot)

count OS the most dangerous emissions i n d i e s e l exhaust, and are t h e r e f o r e subject to the most s t r l g e n t r e g u l a t i o n s , e . g . the Clean A i r Aet

(TA L u f t ) f o r s t a t i o n a r y i n s t a l l a t i o n s , and EURO I and n l i m i t s f o r t r u c k s .

Thls r e s e a r e h , which has a sponsorship of almiost 3 m i l l i o n DM from the German M i n i s t r y f o r Research and Technology, (a s i m i l a r sum has a l s o been

invested by DEUTZ MWM), i s based upon the f a c t that oxides of n i t r o g e n and p a r t i c u l a t e s (soot) react opposlngly t o i n t e r n a l engines parameters, such qs i n j e c t i o n timing changes, changes to the compression r a t i o , i g n i t i o n d e l a y , i n j e c t i o n pressure and combustion period and intake a i r s w i r l as w e l l as combustion chamber form. These

r e l a t i o n s h i p s have been proved by us and o t h e r s . _{Figure 4} An add11 iona1 f a c t concern ing soot format1on,

which plqys a r o l e i n our c o n s i d e r a t i o n s , goes back to BoèhJakovlé. Through non-engines flame t e s t s . In 1955, he had" alreody defined the c r i t l C O 1 a i r coeff1c1ent Kr f o r soot f r e e combustion f o r coimion f u e l s ,

NOx o r i g i n a t e s from Increasing process tempera-t u r e s . For d i r e c tempera-t i n j e c tempera-t i o n d i e s e l e n g i n e s , tempera-the peak temperatures at the flame f r o n t are the s i g n i f i c a n t f a c t o r . Countermeasures include any avoidance of high peak temperatures, as with pre-chamber o p e r a t i o n o r , as we know from Mühlberg's t e s t s with a l c o h o l - d l e s e l engines i n the 1 9 5 0 ' s , by use of exhaust gas r e c i r c u l a t i o n s

(EGR).

F i g u r e 5 Figure 8

The e f f e c t of EGR i s based on the enrichment of n i t r o g e n (N2) and the p a r t i a l r e p l o c ^ e n t of the oxygen (O2) with the n o n - r e a c t i v e combustion product carbon d i o x i d e (CO2) i n the intake a i r .

Flgure 6 shows the p r i n c i p l e of o p e r a t i o n , For the some charge d i r q u a n t i t y , the oxygen content i s reduced to such a l e v e l that there i s Just enough f o r ccffnplete combustion. In t e s t e n g i n e s , the excess a i r c o e f f i c i e n t based oh oxygen content i s about 1,1 with EGR and 2,1 without EGR,

F i g u r e 6

With t h i s oxygen-lean mixture^ the burning flame has t o thread i t s way between the CO2 and NO2 molecules throughout the whole combustion chamber,

to reach the r e a c t i v e oxygen.

As a r e s u l t , a momentum and heat exchange takes p l a c e between the burning gas and the non-reoc-t a n non-reoc-t s . This In non-reoc-t u r n leads non-reoc-to a s i g n i f i c a n non-reoc-t reduc-t i o n i n reduc-the peak reduc-temperareduc-tures as compared reduc-to combustion w i t h f r e s h a i r .

As a three âtofîi g a s , CO2 has i n a d d i t i o n a s i g n i f i c a n t l y higher s p e c i f i c heat c a p a c i t y than the two atom gases; t h e r e f o r e i t absorbs an e s p e c i a l l y large q u a n t i t y o f energy from the flame, It should now be apparent why the c o l d e s t p o s s i b l e , 1 , e . c o o l e d , exhaust gas must be r e c i r c u l a t e d to achieve maximum NOx r e d u c t i o n s .

The d i f f e r e n c e s between p a r t i a l heat r e l i s e i n the combustion chamber with and without EGR can be seen q u o l l t a t l v e l y In f i g u r e 7. Without EGR, a l l of the Injected f u e l burns i n t i g h t l y confined areas of the combustion chamber, i n which, due t o the high a i r r a t i o , enough oxygen i s a v a i l a b l e f o r combustion, The combustion energy heats these gas pockets to very high peak temperatures which are

then cooled to mean combustion chamber temperature through mixing with the c o l d unused combustion a i r , C o n v e r s l y , with EGR, nearly a l l of the u n i -formly d i s t r i b u t e d oxygen has to be used f o r combust i o n , whIch resu1ts i n a cont1nuous temperature mixing p r o c e s s , without o v e r h e a t i n g . The d i f f e r e n t temperature c h a r a c t e r i s t i c i s of d e c i s i v e Importance f o r NOx f o r m a t i o n , which i n c r e a

-ses e x p o n e n t i a l l y with i n c r e a s i n g temperature. Figure 8 With the help of t h i s s i m p l i f i e d i l l u s t r a t i o n , I

hope that I have been a b l e to make the p r i n c i e s of operation of EGR understandable.

U n f o r t u n a t e l y , the t r a d e - o f f tetween NOx and soot formation I s unavoidable a l s o by EGR, Rather, the reduction of the excess a i r c o e f f i c i e n t tends to Increase i n soot formation during combustion. Exhoust gas turbocharging with charge a i r c o o l i n g o f f e r s one p o s s i b i l i t y to counter t h i s t r a d e - o f f . As you know, by t h i s method, the a i r / f u e l r a t i o can be increased without s i g n i f i c a n t l y Increasing combustion chancer peak temperatures.

Figure 9 shows the d i r e c t e f f e c t o f d i f f e r e n t pressure charging l e v e l . The upper curve a p p l i e s to the turbocharger matched f o r a production engine without EGR and with optimum t u r b i n e e f f i c i e n c y , The lower curve i s f o r the highest a c h l e v a b l e boost pressure f o r a slng1e stage system, w h i l s t accepting losses in e f f i c i e n y .

I f we drew in f i g u r e 9 the current l i m i t s f o r t h e Clean A i r Act (TA L u f t ) , - these l i m i t s were already discussed In the beginning of the 1 9 8 0 ' s , when we f i r s t s t a r t e d t h i n k i n g about the d i e s e l concept ^ , then you can envisage the dilemma of the researchers and engineers who had the t h e o r i e s , but lacked the r e l i a b l e s e l f regenera-t i n g p a r regenera-t i c l e f i l regenera-t e r s and mqnufacregenera-turable s i n g l e stage turbochargers with high pressure r a t i o s with which to put them i n t o p r a c t i c e .

On r e f l e c t i o n , i t i s understandable why, rather than challenge the fundamental problem o f the NOx/spot t r a d e - o f f , one turned to the reduction of NOx in the Otto-gas-engine through homogeneous mixture pressure c h a r g i n g . With these engines, the homogeneous mixing of f u e l and combustion a i r necessary f o r soot prevention takes place outside the engine and t h e r e f o r e Is more e a s i l y o c h i e v ^ and c o n t r o l l e d . This homogeneous mixture preparat i o n Is preparathe reason why preparathese engines hove s o o preparat -f r e e combustion.

U n f o r t u n a t e l y , i t i s a wi(3espread misconception that the use of n a t u r a l gas or gasolene alone leads to s o o t - f r e e combustion. The c l a i m t h a t n a t u r a l gas i s a c l e a n f u e l i s i n matter of f a c t , f a l s e . It has been known, at l e a s t s i n c e BoSnjakovlè, that the Kr f o r t h i s f u e l i s not

z e r o . Figure 5 A f t e r a l l , the soot needed f o r the production of

t y r e s 1st made o f methane ( n a t u r a l g a s ) . E q u a l l y , the f a c t that the Kr f o r gasolene dnd d i e s e l a r e nearly the some does not e x p l a i n why o t t o engines run s o o t - f r e e and d i e s e l engines produce

s o o t , Even c o n t i n u o u s l y operating burners ( o i l h e a t i n g . J e t e n g i n e s ) , i n which l i q u i d f u e l i s converted i n t o ù spray before combustion, can be run so that high l e v e l s of soot ore emitted from the exhaust ( s t a r t phase).

With i n c r e a s i n g experience and the c o n s o l i d a t i o n of homogeneous lean burn pressure c h a r g i n g , which i s w e l l under c o n t r o l in DEUTZ MWM engines w i t h swept volumes of up to 12 1 / c y l I n d e r , and r e l y i n g on the a v a i l a b i l i t y of usable p a r t i c l e f i l t e r s and turbocharger developments^ we have once again r e -turned to the d i e s e l concept. In order t o r e a l i s e t h i s , we have kept as c l o s e as p o s s i b l e to the homogeneous lean burn gas-engine system.

To do t h i s , only the p a r t i c l e f i l t e r PF and exhaust gas c o o l e r AK had to be i n t e g r a t e d . The t h r o t t l e v a l v e DK of the o t t o engine was more or l e s s replaced by f u e l pump governor EP of the d l e s e i engine. In the f i r s t i n s t a n c e , the t e s t s were c a r r i e d out on a s i n g l e c y l i n d e r v e r s i o n of the 234 engine t y p e , 128 mm bore, 140 mm s t r o k e , and inelüded qn e a r l y o p t i m i s o t l b n of Figure 10 0) the i n j e c t i o n system, s t a r t of I n j e c t i o n , d u r a t i o n , i n j e c t i o n ) and p i l o t Figure 11 b) the compression r a t i o , c) the combustion chamber.

F i g u r e 12 Figure 13 to meet the s p e c i f i c requirements of the exhaust

A f t e r w a r d s , the work was continued on a f u l l TBD 234 V8 engine, of which F i g u r e 14 shows a c r o s s s e c t i o n . The f i r s t step was then to i n v e s t i -gate the e f f e c t of boost pressure and c o o l i n g the r e c i r c u l a t e d exhaust gases. To t h i s end, f i x e d and v a r i a b l e geometry turbochargers from KKK were

used.

Figure 14

Figures 15 + 16 The p a r t i c l e f i l t e r system DPFS, developed by KHD/

DEUTZ MOTOR^ was a p p l i e d . This system makes use of a ceramic monolith f i l t e r element which Is thermally regenerated by a s p e c i a l DLR bumer system. The

f u n c t i o n of t h i s f i l t e r i s shown i n F i g u r e 17, the F i g u r e 17 e f f e c t i v e n e s s in combination with the 8 c y l i n d e r

234 i s shown in F i g u r e 18, F i g u r e 18 With NOx l e v e l maintained dt a constant 0.5 g/m^,

Bosch smoke l e v e l s (RW), i . e . soot c o n t e n t , can be maintained at c l o s e to 0 up to BMEP's of 18 b a r . F u r t h e r , t h i s F i g u r e shows that the unburnt hydro-carbon emissions (HC) can be kept below the l i m i t of 0.15 g/norm m' (5% O2). Above pe = 9 bar how-e v how-e r , thhow-e carbon monoxidhow-e conthow-ent (CO) how-exchow-ehow-eds thhow-e Clean A i r Act (TA L u f t ) l i m i t of 0,55 g/m^. By using an o x i d a t i o n c a t a l y s t , the CO l i m i t con be crchleved up to a BMEP of 16 bar without an NOx

Increase above 0,5 g/m' Figure 19 In order t o be oble t o achieve t h e (dynanlc

clause) p a r t i c l e l i m i t o f 0,05 g / m ' , a soot f i l t e r separation e f f i c i e n c y o f 90% i s necessary. Furthermore, the o x i d a t i o n of the sulphur oxides t o sulphates has t o be a v o i d e d , otherwise they would be measured as p a r t i c u l a t e s .

Best of a l l i s the use of low sulphur f u e l , but o x i d a t i o n c a t a l y s t s with lower sulphur o x i d a t i o n are i n development.

Summing up, the d i e s e l concept presented h e r e . Figure 10 c o n s i s t s of the f o l l o w i n g components:

c l e a n i n g of the exhaust gas by p a r t i c l e f i l t e r

c o o l i n g an amount of the cleaned exhaust gas

c o n t r o l l e d r e c i r c u l a t i o n of t h i s exhaust gas i n t o the intake a i r (up to 50% of the charge)

increase of the charge a i r pressure by turbocharger

i n t e r c o o l l n g of the charge a i r

o p t i m i s o t l o n of Internal engine parameters.

Through t h i s p r o c e s s , i t has been p o s s i b l e , f o r

the f i r s t t i m e , t o achieve the NOx l i m i t s of the Figuré 20 Clean A i r Act (TA L u f t ) , of 0.5 g/m' with a d i r e c t

i n j e c t i o n d i e s e l engine and s t i l l maintain the s i g n i f i c a n t e f f i c i e n c y b e n e f i t s over o t t o engines And th Is w 1 thout hav i ng to r e s o r t to the complication o f SCR technology with ammonia

Figure 20 f u r t h e r shows the EURO II emissions F i g u r e 20 l i m i t s which w i l l become v a l i d f o r truck engines

from 1995. The 7 g NOx/kWhr (= 2500 mg NOx/ra') l i m i t , which i s based upon a combined 13-mode t e s t over the e n t i r e load range. Is s t i l l f a r away from the 1991 Clean A i r Act (TA L u f t ) l i m i t s which hove to be complied with under f u l l load c o n d i t i o n s . And t h i s by a f a c t o r o f 2.5 compared with the 1991

l i m i t

(loop

T h i s comparison a l s o shows the great development step that have been achieved with the d i e s e l concept 1n improv1ng exhaust gas qua11ty. The technology developed on the t e s t engine w i l l be endurance t e s t e d to prove r e l i a b i l i t y , d u r a b i l i t y and r e p e a t a b i l i t y , We think that w i t h i n two or three y e a r s , we w i l l b r i n g the f i r s t " D i e s e l -concept" engines on the market,

Ladies and Gentlemen,

i n my p r e s e n t a t i o n , I hove t r i e d to report on the r e s u l t s of a research p r o j e c t that serves the general use and advancement of t h e d i e s e l engine.

I hope that I have found your I n t e r e s t . Thank you f o r your a t t e n t i o n .

380 g/kWh 340 300 260 220 180 140 Gas furbirie — — — -Diesel rtiotot 0'2 0.4 0,6 0,8 1,0 P/P„ AR 21.10.91 K M D

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Bunxlesniïnisterfum für Forschung und Technologie

Abschlußbericht Ol VQ 124 Verbrennungstechnik

Forschungs* und Entwicklungskonzept zur Schadstoffminimierung von dieselmotorisehen Antrieben, speziell der Stickoxid- und

Partikelemission

von

Dr. W.R. Dietrich W. GrundmaTin

sowie unter zeitweiser Mitarbeit von A. Schönbeck H. Hoüben Dr. W. Hühn M. Höcker R. Miebach Dr. P, Treiber Dr. H.-W. Knuth MÖTOREN-WERKE MANNHEIM ÄG Mahnheim, März 1991 Bild 0

5000 4000 3000 2000 ^ 1000 \ OK O 0 % AGR 1 0 % A6R 2 0 % AGR 27c 21 cm^ Turbinephalsquerschnitf 100 200 _{30 0 400 SOO} Staub mg/m^3(5o/^Q ) ^ ^ ^ ^ ^ • • K H D I

Trade off between NOx

. and soot formation

S so CO C^J so ^ CO fO ^

o o o o o

o

o

u

o

+

as v.^.

u u

o

a;

fi

u

c

5 "

fi o

c

— fi

< Ü

S :< ?

u

C4' ta S Ç N O C3 fa o^o^ ta 2^ + +

Je

t-o:

n-]1

2 o

CM

2 o

>5

U)

o

E

o

LJ

Oi

C

OJ

O OJ

"a

3 c

u —'

dJ

to

(/)

OJ

x :

M

OJ

1 - A 5 K 10 400 ] 300 200 100 i 0 \ Qleichgewichtskonstante i( N2-02 (N0)2 1600 1800 2000 2200 2400 2600 Te^lpe^a^u^ <K>

ài

Temperaturabhängigkeit der

Stickoxidbildunq

(Chemisches Gleichaewicnti

5000 4000-^ 3000 ^ 2000 ^ 1000 iTA-Luft 1991 0 % AGR 50 100 200 _{30 0 350 400 500} Sfaub mg/m„3

{50/^0^

Abgas

Motor

Gas

ATL Abgasturbolader

DK Drosselklappe

GLM Gasluftmischer

GV Gasventfl

LK Ladungskühler

LS Lambda-Sonde

RE Regelgerät

DleseljMïnzept

Abgas

Motor

ATL Abgasturbolader

EP Einspritzpumpe

GLM Gasluftmischer

GV Gasvieritil

AK AbgaskOhler

LK Ladungskühler

LS Lambda - Sonde

PF Partikelfilter

RE Regelgerät

M

Schad Stoff minderungsverfahren

für stat. Verbrennungsmotoren

Bild @

1-ZyL- TBD 234

Oieselkonzept

H/B = 140/128

/ n

= 1500 m

In-1

/ p = 10 bar

/

7^ iT

^1

5

1 5 F

%

Abgasrückführung

Einfluß der Einspritzung

Entwicklung

Dieselkonzept

H / B =140/128

OM = 1500 min-i

Oieselkonzept

H / B = 1 4 0 / 1 2 8

HM =1500min-i

A

Gleichdruckverbrennung

Systemverglelch FB früh

Entwicklung

Oieselkonzept

3H

200-- * "27er" Turbine mit AGR 200-- Kühlung — • " 2 1 e r " Turbine mit AGR-Kühlung

CO

n« =1500 min-1

= 14 bar

_%

Abgasrückführung

Oieselkonzept

mit /Tiridbler Turbinen-Geometrie

%

be

n^ =1500 min-1

Pme = 14 bar

m

Abgasrückführung

Si

\

S.

hi

"T

c

eu

c

Dieselkonzept

NOx 3 O . s X • — • A T L mit"21"Turbine ma

ï A ^ AGR O — - O ATL mit VTG

RegeifuktMn -Umit 0 , 6 5 ^

ir

Pz

Abgasrückführung

Einfluß der Turbinengeometrie

Entwicklung

" ' S W t S ' / o O z ) 2200 2000 1800 1600 J 1400 ] 1200 J 1000-^ 800 600 400-^ 200 J O r 0 CO-Grenzkurven in mg / ^ .a ,50/^ Qz) Imit Oxikat, 80% Konversionsrate)

{130)

/

/

/

/

(mif RuRfilter , 8 0 % Abscheidegrad)

nr 2 8 10 12 14 16 Pp bar iDEurae IMkWiM

_A

Increase of BMEP through use of