• 에너지공학
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• 제11권2호
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• pp.160-165
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• 2002

LPG 연료를 사용하는 대형 단기통엔진은 연소과정과 배기성능을 파악하기 위해서 설계.제작되었다. 실린더헤드와 피스톤 크라운은 LPG 연소를 위해서 변경되었다. 또한 플라이휠은 단기통엔진의 진동을 최소로 하기 위해서 제작되었다. 실험용 단기통엔진의 실린더내경과 행정은 각각 130mm와 140mm이다. 압축비는 피스톤 크라운 형상을 다르게 하여 8에서 9로 변경되었다. 본 연구를 위해서 제작된 단기통엔진은 1,000rpm에서 운전되었다. 본 연구의 주요 결론은 (1)제작된 엔진의 출력은 3가지 다른 압축비별로 당량비 1.0에서 최고를 나타낸다. (2) 압축비 증가에 따라서 출력이 약간 증간한다. (3) 최적 점화시기는 크랭크각으로 2에서 10까지 압축비의 증가와 함께 지각되어진다.

• 한국정밀공학회지
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• 제19권11호
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• pp.146-159
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• 2002

An efficient method to predict the convection heat transfer coefficients on the top surface of the engine piston is proposed. The method is based on the inverse method of the thermal conduction problem and uses a numerical optimization technique. In the method, the heat transfer coefficients are numerically obtained so that the difference between analyzed temperatures from the finite element method and measured temperatures is minimized. The method can be effectively used to analyze the temperature distribution of engine pistons in case when application of prescribed-temperature boundary condition is not reasonable because of insufficient number of measured temperatures. A hollow sphere problem with an analytic solution is taken as a simple example and accuracy and efficiency is demonstrated. The method is applied to a practical large liquid petroleum gas(LPG) engine piston and the heat transfer coefficients on the top surface of the piston is successfully calculated. Resulting analyzed temperature favorably coincides with measured temperature.

• Journal of Advanced Marine Engineering and Technology
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• 제28권3호
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• pp.538-550
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• 2004

The convection heat transfer coefficients on the top surface of a large liquid petroleum liquid injection(LPLi) engine piston with the oil gallery are analyzed by solving an inverse thermal conduction problem. The heat transfer coefficients are numerically found so that the difference between analyzed temperatures from the finite element method and measured temperatures is minimized. Using the resulting heat transfer coefficients as the boundary condition, temperature of a large LPLi engine piston is analyzed. With varying cooling water temperature, temperature, stress, and thermal expansion of the piston are analyzed and evaluated.

• 대한기계학회논문집B
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• 제28권1호
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• pp.59-65
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• 2004

The configuration of intake port and piston is a dominant factor of inlet air flow and mixture formation in an engine cylinder, resepectively. This study has analyzed intake port and piston characteristics for swirl flow of a heavy-duty LPG engine. As an available technology to optimize intake port, the steady flow rig test has been applied for measuring swirl ratio and mean flow coefficient. And we measured the mean velocity and turbulence intensity of swirl flow under motoring condition in transparent engine cylinder by backward scattering LDV system. From these results, the piston and cylinder head with a good evaluated swirl flow characteristics were developed and adapted fur a 11L heavy-duty engine using the liquid phase LPG injection (LPLI) system. The obtained results are expected to be a fundamental data for developing intake port and piston.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2006년도 정기 학술대회 논문집
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• pp.820-827
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• 2006

The convection heat transfer coefficients on the top surface of a large liquid petroleum liquid injection(LPLi) engine piston are analyzed by solving an inverse thermal conduction problem. The heat transfer coefficients are numerically found so that the difference between analyzed temperatures from the finite element method and measured temperatures is minimized. Using the resulting heat transfer coefficients as the boundary condition, temperature of a large LPLi engine piston is analyzed.

• 한국자동차공학회논문집
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• 제6권2호
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• pp.100-106
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• 1998

The wide open throttle performance and piston temperatures were measured by the change of fuel : gasoline and liquefied petroleum gas(LPG). Bench test method was developed and experimented to study the effect of temperature on the formation of carbon deposit. The bench test results were confirmed by measuring the piston temperature and observing the deposit production rate at an actual engine running condition. Results show that if the fuel of spark ignition engine is changed from gasoline to LPG, the output power decreases about 10% and the piston temperatures increase about 40~55$^{\circ}C$. In actual engine tests, because of this temperature increase, it was observed that the quantity of carbon deposit in the top ring groove increased in a big degree. Consuquently, it is known that the fing sticking may occur if the gasoline engine was rebuilt to LPG fuelled engine. Therefore, in order to preserve the durability of LPG fuelled engine, it is necessary to lower the piston temperature by hardware modificationor to reduce the carbon deposit by the improvement of engine oil.

• Journal of Advanced Marine Engineering and Technology
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• 제28권5호
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• pp.762-772
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• 2004

Fatigue life of a Piston for large liquid Petroleum liquid injection(LPLi) bus engines is analyzed considering effects of cooling condition parameters : temperature of cooling water, and heat transfer coefficients at oil gallery and bottom surface of piston head. Temperature of the piston is analyzed with varying cooling conditions Stresses of the piston from two load cases of pressure loading. and pressure and thermal loading are analyzed Fatigue life under repeated peak pressure and thermal cycle is analyzed by the strain-life theory. For the two load cases, required loading cycles for engine life are defined, and loading cycles to failure and partial damages are calculated. Based on the resulting accumulated fatigue usage factors, endurance of the piston is evaluated and effects of varying cooling condition Parameters are discussed.

• 한국분무공학회지
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• 제9권4호
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• pp.46-52
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• 2004

An LPG engine (KL6i) for heavy duty vehicle has been developed using liquid phase LPG injection (LPLi) system, which has regarded as one of next generation LPG fuel supply systems. For the KL6i engine, lean burn technology was introduced to minimize the thermal loading and NOx emissions due to an increase of the engine power. In this work, injection timing and piston bowl shape were investigated for the stabilization of lean burn characteristics. Experimental results reveals that fuel stratification induced by these parameters is most effective strategy to extend lean combustion limit in the LPLi system.

• 한국자동차공학회논문집
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• 제9권3호
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• pp.42-50
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• 2001

In this paper, the effects of scale formation in engine water jacket upon the thermal durability of engine itself and its component parts were studied. To understand the effect of quality of water, a full load engine endurance test for 50 hours was carried out with not-treated underground water. The followings were found through the tested engine inspection after the endurance test; 1-2 mm thick scale formation in the engine water jacket, valve seat wear, piston top land scuffing, piston pin stick, and cylinder bore scuffing in siamese area. In order to understand the causes of above test results, the heat rejection rate to coolant, the metal surface temperature of combustion chamber, and the oil and exhaust gas temperatures were measured and analyzed. The scale formed in the engine water jacket played a role as thermal insulator. The scale formed in the engine reduced the heat rejection rate to coolant and it caused to increase the metal surface temperature. The reduced heat rejection rate to coolant increased the heat rejection rate to oil and exhaust gas and increased the oil and exhaust gas temperature. Also, the reasons of valve seat wear, piston top land scuffing and cylinder bore scuffing, and piston pin stick quantitatively analyzed in this paper.