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열충격 하중 하에서의 엔진 배기매니폴드의 역학적 거동에 관한 연구
최복록(Boklok Choi),김원섭(Wonseop Kim),이경우(Kyungwoo Lee),장훈(Hoon Chang) 한국자동차공학회 2009 한국자동차공학회 학술대회 및 전시회 Vol.2009 No.11
In this study, we investigated the thermally induced fatigue behaviors and gas sealing mechanism of the exhaust manifold under thermo-mechanical cyclic loads. At first, full engine model was considered to identify the critical locations and their results were compared to failure areas of the engine bench test. And the equivalent system model was proposed based on the mechanical behaviors of the full engine model. The weak areas of both FE models show a good agreement with the experimental crack locations. As a result, a simplified modelling methodology was verified to estimate the thermo-mechanical behaviors of the exhaust manifold under thermal shock test condition.
CFD/FEM 에 의한 엔진 배기 매니폴드의 열피로 특성 해석
최복록(Boklok Choi),박재인(Jaein Park),장훈(Hoon Chang),박관흠(Kwanhum Park) 한국자동차공학회 2002 한국자동차공학회 춘 추계 학술대회 논문집 Vol.2002 No.5_3
This paper presents a numerical method for the engine exhaust manifold subject to severe cyclic thermomechanical loading. The analyses based on the geometry of the exhaust manifold, temperature dependent material properties as well as nonlinear stress-strain relationship, proper boundary conditions, and temperature distribution data equivalent to the thermal cycles. As a result of nonlinear thermal stress analysis, compressive plastic deformations occurred during heating process since the thermal expansion of the manifold was restricted by less expanded inlet flange and cylinder head. And, tensile stress remained when the manifold was cooled down to the ambient temperature. From these repetitions of heating and cooling, we can obtain the stress-strain hysteresis loop in a critical zone. The estimated plastic strain range was often used as the crack initiation criteria. This method was applied to assess the characteristics of the low cycle thermal futigue for the "A" engine exhaust manifold. The results show a good agreement between numerical analysis and experimental results.
1.4리터급 가솔린 엔진용 터보차저의 기계마찰손실 이론계산 및 시험적 분석
이인범(Inbeom Lee),김구성(Kusung Kim),김정배(Jungbae Kim),최복록(Boklok Choi) 한국자동차공학회 2017 한국자동차공학회 부문종합 학술대회 Vol.2017 No.5
Most turbochargers are supported by two oil lubricated journal bearings and a thrust bearing. This is a main cause of the mechanical friction losses which strongly influence on the mechanical efficiency of the turbocharger. In this paper, theoretical and experimental methods were used to identify the mechanical friction losses of the torbo rotor. The Petroff’s equation was used for numerical calculating the mechanical friction losses in theoretical method. The calorimetric measurement technique was used in experimental method. In order to know the mechanical friction losses of two radial journal bearings without a thrust bearing, the experimental measurement was proceeded in the range which has no axial thrust loads. The turbocharger for a 1.4L gasoline engine was used to measure and calculate the mechanical friction losses and the SAE 10W-30 grade engine oil was used for lubricating the Bearings. In the results of this paper, it was identified that the magnitude of mechanical friction losses due to the oil lubricated bearings. Through the comparison of theoretical result and experimental result, that was verified.