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1 KIGAS Vol. 12, No. 4, December, 2008 (Journal of the Korean Institute of Gas) l x CNG» v m s w ½ Á y w» œw ( , , k) Numerical Analysis for Temperature Distribution and Thermal Stresses in a Turbocharged Large CNG Engine Piston Yang Sul Kim Su Chul An Department of Mechano-Informatics & Design Engineering Hongik University (Received 30. September. 2008, Revised 10. December. 2008, Accepted 10. December. 2008) 6»m ƒ v m w 3 ww k s x dwš,» w m mw v m w w» wš w. w þƒ l v m w e w sƒw» w þƒ y v m s s š x w. v m š j ùkûš, v m j w w. Abstract The purpose of this paper is to establish a standard finite element analysis model of a piston by carrying out three dimensional modeling of a series six-cylindered CNG engine's piston to forecast temperature distribution at stationary state and the following thermal stress and variation, and cross checking it with existing analysis. Also, in order to evaluate the affects of the cooling system to the piston s heat load, the paper analyzed piston's temperature and thermal stress distribution according to the cooling water temperature changes and the following variations. As a result, the maximum temperature was found at the center of the crown in the piston and the maximum thermal stress occurred from the lower part of the piston. Key words : finite element method, CNG engine, temperature distribution, thermal stress and deformation, heat transfer coefficient I. š» wd ƒš. p, x»»ƒ w»» w. x wƒ w w» w wù ƒ (CNG) wù.» w w š, p x ƒ (CNG) w»ƒ w d w. e :kimys@hongik.ac.kr Fig Dimensional FE-model of a piston. 58

2 l x CNG» v m s w ü x ww ƒ (CNG) y w w, v w t v m w y w [5,7]. Fig. 1 v m 3 ww k s x dwš,» w m mw v m w w» wš w [6,9]. w g ADINA(Automatic Dynamic Incremental Nonlinear Analysis, R&D, Inc., 1999) w s w w. II. v m w 2.1. v m v m y, š v m fp w p ww» w v m d x w w. ù» w x l l[1] v m y wš y Ì w z š x [2] w z w w. w w x w w v m ƒ Fig. 2. Table 1. Material properties of aluminum alloy. Elastic modulus, E [GPa] Poisson s ratio, ν 0.33 Density, ρ [kg/m 3 ] Coef. of thermal exp, β [1/K] Table 2. Maximum and minimum temperatures in the piston ( o C). Tc Min. temperature Max. temperature Difference Fig. 2. Thermal circuit method of resulted boundary conditions of the piston. Fig. 3. Temperature distribution of the piston. 59 w ƒ wz 12«4y

3 ½ Á 2.2. v m w w w 3 v m w s w ww. w x CNG» v m ( w ) e(300 o C) Table 1 [4,10]. v m s w k þƒ v m þƒ l v m w e w sƒw» w þƒ y v m s w w š w. w þƒ ƒ» 80 o C» 10 o C, 20 o C j û ù ƒ w w. þƒ w s Fig. 3 ùkü. Table 2 þƒ ƒ v m š ƒ, š w ùkû. w, Fig. 3 š j sw š, fp w w. III. v m w v m w. w w w w w w ww. Fig. 4 v m Stress Strain ùkü. j w MPa w š, p p (Thrust side) mmƒ w. IV v m s v m ü s w xk s v m (Bowl) ùkù x» ew. Fig. 5 š x[3] d w ƒ e w w mw w. e ƒ ù, w š w x w w š w Fig. 4. Thermal stress and strain distribution of a piston. Fig. 5. Comparison with temperature results of the piston for analysis and experiment. KIGAS Vol. 12, No. 4, December,

4 터보과급 대형 CNG기관 피스톤의 온도분포와 열응력 해석 Fig. 6. Position temperature distribution of the piston. 적 만족한 결과를 도출하였다. 피스톤의 각 부위별 온도 분포는 Fig. 6과 같다. 피스톤의 열응력분포 열전달 해석을 통해 구한 각 절점에서의 온도를 입 한국가스학회지 제12권 제4호 2008년 12월

5 ½ Á Table 3. Summary of results thermal stress of the piston. Tc ( o C) Max. stress (MPa) Max. displacement (mm) s w. s Fig. 4 j w š w. w, v m þƒ l v m w e w sƒw» w þƒ y v m s w w. Table 3 þƒ ƒ v m û ùkû. þƒ ƒ v m û þƒ ƒ v m š (Temperature gradient)ƒ» q. VI. CNG v m w s w ww. v m ƒ e w v m s w š, w s w v m w w. (1) v m j v m fp ƒ w w ùkþš, š j ùkû. (2) v m s wù v m j w w š, v m vy w., v m» j w w š ƒ v m ƒ š q. (3) x v m j ó w j v m w w w j, x ƒ š q. 2008w y w w w. š x [1] Li, K.S. Study on Heat Transfer and Thermal Behavior Characteristics of a Naturally Aspirated Diesel Engine, w w, (1997) [2] Li, C.H. Piston Thermal Deformation and Friction Considerations, SAE , (1982) [3], l v m w w, w œwz, 2(9), 92-98, (2001) [4],, x, x, ü» v m w w w w, w» wz, 12(3), , (1988) [5] Overbye, E.A. Unsteady Heat Transfer in Engines, SAE Translation, 69(461), , (1961) [6] Bertodo, R. and T.J. Carter, Stress Analysis of Diesel- Engine Cylinder Heads, Journal of Strain Analysis, 6(1), (1971) [7] Pattas, K. Thermische Belastung des Zylinderkopfes von Hochleistungs Dieselmotoren, MTZ, 35(10), , (1974) [8] Garro, A. and V. Vullo, Some Consideration on the Evaluation of Thermal Stress in Combustion Engine, SAE , (1978) [9] Hohenberg, G.F. Advanced Approaches for Heat Transfer Calculations, SAE , (1979) [10] Assanis, D.N. and E. Badillo, Transient Heat Conduction in Low-Heat Rejection Engine Combustion Chambers, SAE , , (1987) KIGAS Vol. 12, No. 4, December,

14.531~539(08-037).fm

14.531~539(08-037).fm G Journal of the Korea Concrete Institute Vol. 20, No. 4, pp. 531~539, August, 2008 š x y w m š gj p { sƒ z 1) * 1) w w Evaluation of Flexural Strength for Normal and High Strength Concrete with Hooked