Propeller erosion test by Soft Surface Method - Using stencil ink proposed by the cavitation committee of the 14th ITTC

PAPERS

OF

SHIP RESEARCH INSTITUTE

Propeller Erosion Test by Soft Surface Method

using Stencil Ink proposed by the Cavitation Committee of the 14th

ITTC-By

Yuzo KUROBE and Yukio TAKEL

March 1980

Ship Research Institute

Tokyo, Japan

tW4

Lab.

V.

Scheepsbouwkun

ARCH1E

Technische

Hogeschool

Deift

PROPELLER EROSION TEST BY SOFT SURFACE METHOD

using Stencil Ink proposed by the Cavitation Coniniittee

of the 14th

ITTC-By

Yuzo KUROBE and Yukio TAKEl CONTENTS

Introduction

Standard procedure of the paint coating method Experiments and results

3-1. Repeatability on extent of flaked paint

3-2. Effect of rotational speed of propeller

3-3. Effect of exposure time

3-4. Effect of cavitation number

3-5. Effect of cavitation type Closing remarks

References

ABSRACT

Reliability of a soft surface technique using the Roller system stencil ink is discussed. Furthermore, from the results of experiments, it is shown that this paint coating method is useful to estimate the relative intensity

of cloud cavitation on propeller blades.

1. INTRODUCTION

In many cavitation tunnels, paint coating methods have been adopted

in order to predict cavitation erosion on a propeller blade.1 In reference 2), the standard test procedure of the paint coating method using the stencil

ink is proposed and it is said that this method is useful to estimate

cavita-tion erosion. Reliability of this method, however, is not examined

sufficient-ly. In this report, repeatability on extent of flaked paint and effect of various factors were investigated in using this method. And then the pos-sibility to measure the relative intensity of cloud cavitation which causes

cavitation erosion is discussed.

2. STANDARD PROCEDURE OF THE PAINT COATING METHOD The standard procedure is as follows;

Bibliotheek van de

Afdeng Scheepcbou'- en Scelpvaartkunde

Techii e

-ch:'oI, Deift

DOCUMENT,\TE

Papers of Ship Research Institute, No. 59 (March 1980)

Composition of paint*: Roller system stencil ink, S-1 (black) and

ethyl alcohol (99.5% in purity). The mixture ratio: 1 by i Coating: Dipping the propeller model into the paint bath for 3 or

4 minutes and then drawing it up (thickness of the coated paint

may be 8--10 micron)

Drying: Drying naturally in the room

The propeller models painted by the above mentioned procedure are usually tested for 30 minutes under a cavitating condition.

3. EXPERIMENTS ANI) RESULTS

The experiments were carried out in the No. 1 working section of the

large cavitation tunnel of the Ship Research Institute. The principal

partic-ulars of the propeller models are shown in Table 1. M.P. No. A and M.P. No. B were designed at J=0.68, K=0.200 and J0.40, K7=0.197 respec-tively. These propeller models are coated with blue coloured alumite.

Table 1. Principal particulars of the model propellers

The wake distribution reproduced by wire mesh screens is shown in Fig. 1. The test conditions are shown in Table 2.

The nomenclatures are defined as follows;

K.;

thrust coefficient, K7 = T/-tpn2D4

cavitation number based on rotational speed of a propeller an = (P, e) ¡ -i-p(nD)2

V (mean) ; mean velocity in a propeller disk Np; rotational speed of a propeller

P,; pressure at the shaft centre of a propeller air contents ratio

Drying time; drying time of the paint coating on a propeller blade

Humidity; relative humidity measured by wet and dry bulbs

The kind of thinner and the mixture ratio are different from the ITTCCavitation Committee's proposal. The detail is indicated in Ref. 2.

M. P. No. A B

Diameter (m) 0.250 0.239

Pitch Ratio 1.000 0.679

Expanded Area Ratio 0.800 0.610

Number of Blades 6 5

O

300 360

O dq.

3-1 Repeatability on extent of flaked paint

On the propeller model, M.P. No. A, the repeatability tests were carried

out under the condition 1-(1) to (5) shown in Table 2. The sketches of the cavitation patterns on the No. i blade are shown in Fig. 2. 8 is the angular position of the No. i blade. The cloud cavitation occurred near the trailing

edge of 0.8-0.9 radius at O65E85. In each test condition, the most

intense cloud cavitation appeared at about 70 degrees, and then it became intermittent. 3 K Table 2. Test

lv

_(mean) (m/s) (rps) conditions Drying time (Hr) M. P. No. T. No. PO (mmHg) 0.253 1.60 2.7 19.0 152 0.4 43 (2) 0.250 1.60 2.7 19.0 152 0.4 19 (3) 0.255 1.60 2.7 19.0 153 0.5 19 (4) 0.253 1.60 2.7 19.0 153 0.3 19 (5) 0.259 1.63 2.7 19.0 154 0.5 19 A 2-(1) C _{0.253 1.60 2.4 16.7 121 0.5 19} (2) C 0.253 1.60 2.4 16.7 123 0.3 43 3 4 C z 0.255_0.255 1.60_{1.60 2.7}3. 0 21.6_19.0 194₁₅₃ 0.5_0.5 19₆₇ 5 0.255 1.70 2.7 19.0 162 0.5 19 6 0.255 1.80 2.7 19.0 172 0.5 19 7 0.200 1.75 2.5 29.9 349 0.5 19 8 0.200 1.50 2.5 29.9 301 0.5 19 9 C 0.200 1.25 2.5 29.9 252 0.5 19 B 10 0.198 1.42 2.7 32.8 341 0.4 19 C «-11 Z 0.238 1.54 1.7 29.4 300 0.4 19 1.0 rl M.NaA 0.912 r0 B Q954 0.760 0.795 0.624 0.653 C o 0.504 0.527 240 0 60 20 180 TOP BOTTOM

Fig. 1. Wake distribution

Humidity (%) 73 67 83 60 63 67 61 75 60 60 65 90 90 90 90 90

Schematic representation of cavitation patterns

Q

Q00 Q

Sheet cavitation.

Thicker formation often merging into tip vortex. Thick tip vortex.

Thin tip vortex.

Bubble cavitation,free bubbles are generated.

Spots of sheet cavitation close to bubble cavitation. Cloud cavitation

Line indicating the limit when the extension of cavitation is varying.

Fig. 2. Sketch of cavitation patterns (T. No. 1)

The patterns of flaked paint on the No. i blade after 30 minutes ex-pcsure time are shown in Photos. 1-(i) to (7). The positions where the paint was flaked off are nearly the same among the blades and theposition agrees well with the position where the cloud cavitation was observed. But there are a little difference among the patterns of flaked paint on each blade.

The degree of flaked paint is classified roughly as follows;

Grade A: The number of spots of flaked paint is very few.

Grade B: The number of spots of flaked paint is more than A and

they look like pockmark.

Grade C: The number of spots of flaked paint is more than B and they are crowded, but it is not like D, i.e. there are no over-lapped spots of flaked paint. The area where the spots of flaked

paint exist is larger than B.

Grade D: There are overlapped spots of flaked paint. The area

where the spots of flaked paint exist is nearly the same as in C.

Grade E: Large flaked off-area by overlapping of the spots of

flaked paint are. The area where the spots of flaked paint exist

is larger than D.

4;

i

--

5

The classification of pattern of flaked paint on the blades is shown in

Table 3. Table 3 shows that repeatability on extent of flaked paint is almost

good. It is found that the degree of flaked paint on the No. 6 blade is rela-tively lower comparing with the other blades. The wash-back of the No. 6 blade is larger by 0.1 mm than that of others. However the cause of rela-tively small flaked paint on the No. 6 blade cannot be explained only by the

larger wash-back.

This difference also appeared in the results of T.

No. 2, 3 and 4.

T. N. I-4; 5) T. No. 1-5 (6) T. No. 1-(l)

(enlarged) Table 3. Degree of flaked paint (T. No. 1)

T. No. B. No. 1-Cl) l-(2) i-(3) 1-(4) 1-(5) 4 30 min. i D D C E C _C: 2 D D C E C C 3 D D D E C C 4 D D D E D C 5 D D D E C D 6 B B B C B B

(7) T. No. 1-(1)

Photo. 1. (1)-.-(7) Comparison of patterns of flaked paint (repeatability) Except T. No. 1- (4), the tests have been carried out under the condi-tion that the air contents ratio are 0.4'0.5. In case of T. No. 1- (4), the test was carried out under the condition that the air contents ratio is 0.3. It is

found that the degree of flaked paint in T. No. 1-(4) is higher than that in other tests as shown in Photo. 1-(4).

3-2. Effect of rotational speed of propeller

To investigate the effect of rotational speed of the propeller, the tests

were carried out at the three kinds of rotational speeds under the same condition of KT and an. In the tests (T. No.2, 1 and 3). The Reynolds'

numbers, Rn, are 4.2x10, 4.7x10" and 5.4x 10 respectively, and the aver-age inflow velocities to the blade element at 0.8 radius are 10.6 m/s, 12.1 rn/s and 13.8 m s respectively. The change of cavitation pattern according

to the angular position and the occurrence of cloud cavitation are similar in

all the conditions. Photographs of cloud cavitation at 70 degrees on the No. 1 blade are shown in Photos. 2-(1), (2) and (3).

The patterns of flaked paint on the No. i blade under the conditions, T. No. 1-(1), T. No. 2-(1) and T. No.3, are shown in Photos. 3(1) to 3-(4). Photo. 3-(2) shows the pattern of flaked paint in T. No. 1-(1) which seems to be a representative in T. No. 1 series. The positions of flaked paints are

(hj T. No. 2 (2) T. No. i (3) T. No. 3

(n =16.7 rps) (n=19.0 rpS( (n =21.6 rps) corresponding to 0=70- in Fig. 2

Photo. 2. (1)(3) Cavitation patterns (0=70)

the same in all the conditions, but the classifications of pattern of flaked paint are different each other. The classifications in T. No. 2 are B, D in

the T. No. i and E in the T. No. 3 respectively. According to the above results, it can be said that an increase of rotational speed of propeller makes the energy of collapsing bubbles of cloud cavitation large. Therefore,

rela-tive intensity of cloud cavitation can be distinguished in some degree in using the paint coating method adopted here.

3.3 Effect of exposure time

The time dependency of flaked paint pattern was investigated under the test condition T. No. 4. After 6 minutes, 16 minutes, 30 minutes and

55 minutes in total exposure time, the patterns were examined. The pat-terns of the blade No. i are shown in Photos. 4-(1) to (4). The classifica-tion of flaked paint changes from A to C' (C' means the classificaclassifica-tion be-tween C and D). It seems that over 30 minutes in total exposure time, the change of the degree of flaked paint is small.

3-4. Effect of cavitation number

T. No. 1, 5 and 6 were conducted to investigate the relationship between

cloud cavitation and flaked patterns. As shown in Table 2, the rotational

speed of propeller and the velocity were the same in all the conditions, and

only pressure of the tunnel was changed.

The difference of cavitation patterns between T. No. 5 (an=1.7) and T. No. i (crn=1.6) is not noticed visually. But the position of flaked paint is slightly different between them (Photo. 5 and Photo. 1- (7)). Averaged

classification of flaked paint in T. No. i is D, and C in T. No. 5.

In case of T. No.6 (n=l.8), the cloud cavitation occurred

intermit-tently near the 0.9 radius of the blades. The classification of flaked paint in this condition is A (Photo. 6).

(1) T. No. 2-(1) (2) T. No. 1-(1)

(4) T. No. 3

Photo. 3. (1).(4) Comparison of patterns of flaked paint

(effect of inflow velocity)

3-5. Effect of cavitation type

Using the another propeller mode), M.P. No. B, the paint tests were carried out in uniform flow under sheet cavitation condition (T. No. 7), sheet and spot cavitation condition (T. No. 8) and super cavitation condi-tion (T. No. 9). Any flaked paint was not observed on the blades of the

(4) 56 min.

Photo. 5

Pattern of flaked paint

(cn= 1. 7)

(2) 16 min.

Photo. 6

Pattern of flaked paint

(en = 1.8)

9

(3) 30 min.

Photo. 4. (1).(4) Comparison of patterns of flaked paint (effect of exposure time)

Photo. 7

Cavitation pattern at 67

(T. No. 10)

propeller after 90 minutes in total exposure time. It may be said that the

cavitation related to erosion does not occur in uniform flow.

lo

out (T. No. 10 and 11) using M.P. No. B. The test method is the same as that of M.P. No. A. The change of cavitation patterns due to angular posi-tions of a blade are shown in Fig. 3, and the cloud cavitation is shown in

Photo. 7. The pressure distributions calculated by the lifting surface theory are shown in Fig. 4. The numbers in degree means the angular

position of the blade.

0.0

Fig. 3. Sketch of cavitation patterns (T. No. 10)

300 _R/R00.80 W*=12.lnh/s

L.E.

T.No. i (1.P.No.A)

a_w*=0.25

Fig. 4 Calculated pressure distributioìs

-e

6

4P .! 1pI.

-7

---/

e -7 e=57

-e=62

I

\-0.0 0.5 1.0 i I I

L.E. c/co T.E.

T.No. 10 (M.P.No.B) R/R0=0.92 W*=i9.7m/s 17 Cp

-0.5

0.0 Cp

-0.5-li

As shown in Fig. 3 and Photo. 7, the cloud cavitation occurred visually,

but any flaked paint is not observed. From the results of T. No. 10 and II, it can be said that the estimations of the intensity of cloud cavitation and

of the collapsing position of bubbles are very difficult only by means of the observation of cavitation. The estimation of erosion, however, can be easily

possible in using the paint coating method.

4. CLOSING REMARKS

From the experimental results mentioned above, we obtain informa-tions as follows;

The information of the position where the intense cloud cavitation occurs.

If we carry out the paint tests in which the condition of paint

coating, air contents in the water, total exposure time and inflow velocity to the blade element are the same in each a test, we can get considerably the information of relative intensity of cloud cavitation as the degree of

flaked paint.

REFERENCES

Appendix B, Cavitation Committee, the 15th ITTC. 1978.

Kadoi, H., and Sasajima, T., "Cavitation Erosion Prediction Using a Soft Sur-face' ", International Shipbuilding Progress, Vol. 25, No. 28, 1978.

Koyama, K., "A Numerical Method for Propeller Lifting Surface Theory in Non-uniform Flow and Its Application", Journal of the Society of Naval Architects of

PAPERS OF SHIP RESEARCH INSTITUTE

No. i Model Tests on Four-Bladed Controllable-Pitch Propellers, by Atsuo Yazaki, March 1964.

No. 2 Experimental Research on the Application of High Tensile Steel to Ship

Struc-tures, by Hitoshi Nagasawa, Noritaka Ando and Yoshio Akita, March 1964.

No. 3 Increase of Sliding Resistance of Gravity Walls by Use of Projecting Keys under

the Bases, by Matsuhei Ichihara and Reisaku moue, June 1964.

No. 4 An Expression for the Neutron Blackness of a Fuel Rod after Long Irradiation,

by Hisao Yamakoshi, August 1964.

No. 5 On the Winds and Waves on the Nothern North Pacific Ocean and South Ad-jacent Seas of Japan as the Environmental Condition for the Ship, by Yasufumi Yamanouchi. Sanae Unoki and Taro Kanda. March 1965.

No. 6 A code and Some Results of a Numerical Integration Method of the Photon

Transport Equation is Slab Geometry, by Iwao Kataoka and Kiyoshi Takeuchi,

March 1965.

No. 7 On the Fast Fission Factor for a Lattice System, by Hisao Yamakoshi, June

1965.

No. 8 The Nondestructive Testing of Brazed Joints, by Akira Kannö, November 1965.

No. 9 Brittle Fracture Strength of Thick Steel Plates for Reactor Pressure Vessels, by

Hiroshi Kihara and Kazuo Ikeda. January 1966.

No. 10 Studies and Considerations on the Effects of Heaving and Listing upon Thermo-Hydraulic Performance and Critical Heat Flux of Water Cooled Marine Reactors,

by Naotsugu Isshiki, March 1966.

No. il An Experimental Investigation into the Unsteady Cavitation of Marine Propel-lers, by Tatsuo Ito, March 1966.

No. 12 Cavitation Tests in Non-Uniform Flow on Screw Propellers of the

Atomic-Power-ed Oceanographic and Tender ShipComparison Tests on Screw Propellers De-signed by Theoretical and Conventional Methods, by Tatsuo Ito, Hajime Takahashi and Hiroyuki Kadoi. March 1966.

No. 13 A Study on Tanker Life Boats, by Takeshi Eto. Fukutaro Yamazaki and Osamu Nagata, March 1966.

No. 14 A Proposa] on Evaluation of Brittle Clack Initiation and Arresting Temperatures

and Their Application to Design of Welded Structures, by Hiroshi Kihara and

Kazuo Ikeda. April 1966.

No. 15 Ultrasonic Absorption and Relaxation Times in Water Vapor and Heavy Water Vapor, by Yahei Fujji. June 1966.

No. 16 Further Model Tests on Four-Bladed Controllable-Pitch Propellers, by Atsuo

Yazaki and Nobuo Sugai, August 1966.

Supplement No. i

Design Charts for the Propulsive Performances of High Speed Cargo Liners with CB=

0.575, by Koichi Yokoo. Yoshio Ichihara, Kiyoshi Tsuchida and Isamu Saito, August

1966.

No. 17 Roughness of Hull Surface and Its Effect on Skin Friction, by Koichi Yokoo, Akihiro Ogawa. Hideo Sasajima, Teiichi Terao and Michio Nakato, September

1966.

No. 18 Experiniets on a Series 60. CB=0.70 Ship Model in Oblique Regular Waves,

by Yasufumi Yamanouchi and Sadao Ando, October 1966.

No. 19 Measurement of Dead Load in Steel Structure by Magnetostriction Effect, by Junji Iwayanagi, Akio Yoshinaga and Tokuharu Yoshii, May 1967.

No. 20 Acoustic Response of a Rectangular Receiver to a Rectangular Source, by

14

No. 21 Linearized Theory of Cavity Flow Past a Hydrofoil of Arbitrary Shape, by

Tatsuro Hanaoka, June 1967.

No. 22 Investigation into a Nove Gas-Turbine Cycle with an Equi-Pressure Air Heater, by KOsa Miwa, September 1967.

No. 23 Measuring Method for the Spray Characteristics of a Fuel Atomizer at Various

Conditions of the Ambient Gas, by Kiyoshi Neya, September 1967.

No. 24 A Proposal on Criteria for Prevention of Welded Structures from Brittle Frac-ture, by Kazuo Ikeda and Hiroshi Kihara, December 1967.

No. 25 The Deep Notch Test and Brittle Fracture Initiation, by Kazuo Ikeda, Yoshio Akita and Hiroshi Kihara, December 1967.

No. 26 Collected Papers Contributed to the 11th International Towing Tank Conference, January 1968.

No. 27 Effect of Ambient Air Pressure on the Spray Characteristics of Swirl Atomizers,

by Kiyoshi Neya and Seishirö Sato, February 1968.

No. 28 Open Water Test Series of Modified AU-Type Four- and Five-Bladed Propeller

Models of Large Area Ratio, by Atsuo Yazaki, Hiroshi Sugano, Michio Takahashj and Junzo Minakata, March 1968.

No. 29 The MENE Neutron Transport Code, by Kiyoshi Takeuchi, November 1968. No. 30 Brittle Fracture Strength of Welded Joint, by Kazuo Ikeda and Hiroshi Kihara,

March 1969.

No. 31 Some Aspects of the Correlations between the Wire Type Penetrameter Sensi-tivity, by Akira Kanno, July 1969.

No. 32 Experimental Studies on and Considerations of the Supercharged Once-through

Marine Boiler, by Naotsugu Isshiki and Hiroya Tamaki, January 1970.

Supplement No. 2

Statistical Diagrams on the Wind and Waves on the North Pacific Ocean, by Yasufumi Yamanouchi and Akihiro Ogawa, March 1970.

No. 33 Collected Papers Contributed to the 12th International Towing Tank Conference,

March 1970.

No. 34 Heat Transfer through a Horizontal Water Layer, by Shinobu Tokuda, February

1971.

No. 35 A New Method of C.O.D. MeasurementBrittle Fracture Initiation Character-istics of Deep Notch Test by Means of Electrostatic Capacitance Method, by Kazuo Ikeda, Shigeru Kitamura and Hiroshi Maenaka, March 1971.

No. 36 Elasto-Plastic Stress Analysis of Discs (The ist Report: in Steady State of Thermal and Centrifugal Loadings), by Shigeyasu Amada, July 1971.

No. 37 Multigroup Neutron Transport with Anisotropic Scattering, by Tomio Yoshimura.

August 1971.

No. 38 Primary Neutron Damage State in Ferritic Steels and Correlation of V-Notch Transition Temperature Increase with Frenkel Defect Density with Neutron

Ir-radiation, by Michiyoshi Nomaguchi, March 1972.

No. 39 Further Studies of Cracking Behavior in Multipass Fillet Weld, by Takuya Kobayashi, Kazumi Nishikawa and Hiroshi Tamura. March 1972.

No. 40 A Magnetic Method for the Determination of Residual Stress, by Seiichi Abuku,

May 1972.

No. 41 An Investigation of Effect of Surface Roughness on Forced-Convection Surface

Boiling Heat Transfer, by Masanobu Nomura and Herman Merte, Jr., December

1972.

NO. 42 PALLAS-PL, SP A One Dimensional Transport Code, by Kiyoshi Takeuchi,

February 1973.

No. 43 Unsteady Heat Transfer from a Cylinder, by Shinobu Tokuda, March 1973. No. 44 On Propeller Vibratory Foces of the Container shipCorrelation between Ship

Takahashi, March 1973.

No. 45 Life Distribution and Design Curve in Low Cycle Fatigue, by Kunihiro lida and Hajime moue, July 1973.

No. 46 Elasto-Plastic Stress Analysis of Rotating Discs (2nd Report: Discs subjected to Transient Thermal and Constant Centrifugal Loading), by Shigeyasu Amada and Akimasa Machida, July 1973.

No. 47 PALLAS-2DCY, A Two-Dimensional Transport Code, by Kiyoshi Takeuchi, November 1973.

No. 48 On the Irregular Frequencies in the Theory of Oscillating Bodies in a Free

Surface, by Shigeo Ohmatsu, January 1975.

No. 49 Fast Neutron Streaming through a Cylindrical Air Duct in Water, by Tohimasa Miura, Akio Yamaji, Kiyoshi Takeuchi and Takayoshi Fuse, Septembe: 1976.

No. 50 A Consideration on the Extraordinary Response of the Automatic Steer Lng

Sys-tem for Ship Model in Quartering Seas, by Takeshi Fuwa, November 1976. No. 51 On the Effect of the Forward Velocity on the Roll Damping Moment, by Iwao

Watanabe, February 1977.

No. 52 The Added Mass Coefficient of a Cylinder Oscillating in Shallow Water in the Limit K-0 and K-.co, by Makoto Kan, May 1977.

No. 53 Wave Generation and Absorption by Means of Completely Submerged Horizontal

Circular Cylinder Moving in a Circular OrbitFundamental Study on Wave Energy Extraction, by Takeshi Fuwa, October 1978.

No. 54 Wave-power Absorption by Asymmetric Bodies, by Makoto Kan, February 1979. No. 55 Measurement of Pressures on a Blade of a Propeller Model, by Yukio Takei.

Koichi Koyama and Yuzo Kurobe, March 1979.

No. 56 Experimental Studies on the Stability of Inflatable Life Raft, by Osamu Nagata.

Masayuki Tsuchiya and Osamu Miyata, March 1979.

No. 57 PALLA5-2DCY-FC, A Calculational Method and Radiation Transport Code in

Two-Dimensional (R, Z) Geometry, by Kiyoshi Takeuchi, July 1979.

No. 58 Transverse Pressure Difference between Adjacent Subchannels in a Square Pitch Nuclear Fuel Rod Bundle, by KOki Okuxnura. November 1979.

In addition to the above-mentioned reports, the Ship Research Institute has another

series of reports, entitled "Report of Ship Research Institute". The "Report" is published in Japanese with English abstracts and issued six times a year.