• 대한기계학회논문집B
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• 제24권5호
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• pp.660-667
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• 2000

In order to investigate the exhaust structure and secondary oxidation of unburned hydrocarbon (HC) in the exhaust port, concentrations of individual HC species were measured in exhaust process, the degree of oxidation were obtained. Using a solenoid-driven fast sampling system on single-cylinder research engine fueled with 94% propane, the profiles of unburned hydrocarbons (HCs) and non-fuel HCs with a propane fueled engine were obtained from several locations in the exhaust port during the exhaust process. The sampled gases were analyzed using a gas chromatography of HC species with 4 or lesser carbon atoms. The change of total HC concentration and HC fractions of major components through the exhaust port were discussed. The results showed that non-uniform distribution of HC concentration existed around the exhaust valve and changed with time, and that the exhaust gas exhibited nearly uniform concentration profile at port exit, which was due to mixing and oxidation. Also it could be known that bulk gas with relatively high HC concentration came out through the bottom of the exhaust valve. To estimate the mass-based degree of HC oxidation in the exhaust port from measured HC concentrations, a 3-zone diagnostic cycle simulation and plug flow modeling were used. The degree of oxidation ranged between 26 % and 36 % corresponding to the engine operation conditions.

• 한국자동차공학회논문집
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• 제8권2호
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• pp.33-40
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• 2000

In order to investigate the exhaust structure and secondary oxidation of unburned hydrocarbon (HC) in the exhaust port, a numerical simulation was performed with 3-dimensional flow model and oxidation mechanism optimized for port oxidation. To predict the exhaust and oxidation process with consideration of flow, mixing, and temperature, 3-dimensional flow model and HC oxidation model were used with a commercial computational program, STAR-CD. The flow model were with moving grid for valve motion, which could predict the change of flow field with respect to valve lift. Optimization was performed to predict the HC oxidation with temperature range of 1200~1500K, low HC and oxygen concentration, existence of intermediate species, as typical in port oxidation. The constructed model could predict the port oxidation process with oxidation degree of 14~48% according to the engine operation conditions.

• Journal of Advanced Marine Engineering and Technology
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• 제22권1호
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• pp.77-84
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• 1998

Based on experimental analysis, the characteristics of pulsating pressure wave propagation is clarified by testing of 4-stroke gasoline engine. The pulsating pressure wave in exhaust system is generated by pulsating gas flow due to working of exhaust valve. The pulsating pressure wave is closely concerned to the loss of engine power according to back pressure and exhaust noise. It is difficult to exactly calculate pulsating pressure wave propagation in exhaust system because of nonlinear effect. Therefore, in the first step for solving these problems, this paper contains experimental model and analysis method which are applied two-port network analysis. Also, it shows coherence function, frequency response function, back pressure, and gradient of temperature in exhaust system.

• 대한기계학회논문집
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• 제13권3호
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• pp.500-507
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• 1989

본 논문에서는 흡배기 변동압을 실측하여 이것을 계산의 입력수치로 사용 하는 전산프로그램을 개발하여 간단하면서도 정확한 사이클 시뮬레이션이 가능하도록 하여 체적효율을 예측하였다.

• International Journal of Automotive Technology
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• 제8권4호
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• pp.403-411
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• 2007

This article describes a methodology based on experiments and 1D modeling work related to the exhaust system analysis of a small two-stroke engine. The primary goal of this work was to understand how the design criteria of a compact exhaust system influenced the exhaust port pressure, since its evolution controls not only engine performance but also exhaust emissions. On the experimental side, a fully instrumented 50cc two-stroke engine was used to check the behavior of three different exhaust systems. A problem related to instantaneous pressure measurements in unsteady, hot flow was detected and solved during the study. To build the 1D model of the three exhaust systems, experimental information on the steady flow and the impulse test rigs was obtained under controlled conditions in specific facilities. Accurate comparisons between measured and calculated exhaust port instantaneous pressures were obtained from the following different exhaust system configurations: a straight duct, a tapered pipe and the three compact exhaust systems. The last step in the method used this model to analyze the pressure waves inside the exhaust system and detect the influence of the geometric parameters. The results should lead to improvements in the design process of complex compact exhaust systems in two-stroke engines.

• 한국자동차공학회논문집
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• 제4권4호
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• pp.18-26
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• 1996

Based on experimental analysis, the characteristics of pulsating pressure wave propagation is clarified by testing of 4-stroke gasoline engine. The pulsating pressure wave in exhaust system is generated by pulsating gas flow due to working of exhaust valve. The pulsating pressure wave is closely concerned to the loss of engine power according to back pressure and exhaust noise. It is difficult to exactly calculate pulsating pressure wave propagation in exhaust system because of nonlinear effect. Therefore, in the first step for solving these problems, this paper contains experimental model and analysis method which are applied two-port network analysis. Also, it shows coherence function, frequency response function, back pressure, and gradient of temperature in exhaust system.

• 한국화재소방학회논문지
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• 제30권2호
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• pp.68-74
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• 2016

도로터널에 적용하는 반횡류환기방식은 터널의 전연장에 걸쳐서 단위길이당 풍량이 균일하게 될 수 있도록 포트의 개도 조정이 필수적이다. 그러나 현재 국내에서 운영중인 터널의 경우에는 설계시 이에 대한 고려가 적절히 이루어지지 못하고 있는 실정이다. 이에 본 연구에서는 개도계산을 위한 프로그램을 개발하고 반횡류환기방식의 터널에서 포트의 운영방안을 제시하였다. 연구결과, 포트의 개도는 급기방식의 덕트에서는 환기소측에서 덕트의 말단(bulk head)쪽으로 갈수록 증가하였다가 감소하는 경향을 가지며, 최소 개도는 56% 정도로 나타나고 있다. 또한 배기방식에서는 환기소측이 15% 정도로 가장 작고 bulk head 쪽으로 갈수록 증가하는 경향을 보이고 있다. 화재시 300 m 구간의 배연풍량을 검토한 결과, 포트사이즈를 조정하지 않는 경우와 급기방식으로 포트사이즈을 조정한 경우에는 터널중앙부의 배연량이 각각 8.1%와 12.5%로 터널중앙부의 배연풍량이 저조한 것으로 나타났다. 따라서 반횡류환기방식의 터널에서는 평상시 환기효율이 저하하더라도 배연시 균일한 풍량을 얻을 수 있도록 포트의 개도를 설정하여 운영하는 것이 반드시 필요한 것으로 판단된다.

• 한국자동차공학회논문집
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• 제14권2호
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• pp.166-173
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• 2006

This study investigates a heavy duty diesel engine with swept vol. 12.6L, 4cycle-OHC type to verify the effects of the performance and exhaust gas emission according to the variable specifications of both swirl ratio and flow coefficient in inlet port, combustion bowl and fuel injection system. To meet the high BMEP and stringent exhaust emission standard, a turbocharger with wastegate and an intercooler were installed in the engine. Helical port, major design parameters for combustion chamber and electronic fuel injection pump with 1,000bar were reviewed and applied. Confirmation tests were also performed to meet the target value, $NO_x$ 5.0g/kWh and PM 0.1g/kWh of Euro3 exhaust emission legislation. The results of this study show that not only is it effective to use a relatively bigger bowl size for controlling rapid burning condition due to the decreased in-bowl swirl, but also to use a concave cam with double injection rates to decrease $NO_x$.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 1996년도 춘계학술대회 논문집
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• pp.72-78
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• 1996

Based on experimental analysis, the characteristics of pulsating pressure wave propagation is clarified by testing of 4-stroke gasoline engine. The pulsating pressure wave in exhaust system is generated gyulsating gas flow due the working of exhaust valve. The pulsating pressure wave is closely concerned to the loss of engine power according to back pressure and exhaust noise. It is difficult to exactly calculate pulsating pressure wave nonlinear effect. Therefore, in the first step for solving these problems, this paper contains experimental model and analysis method which are applied two-port network analysis. Also, it shows coherence function, frequency response function. back pressure, and gradient of temperature in exhaust system.

• 한국자동차공학회논문집
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• 제14권3호
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• pp.35-43
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• 2006

A four-stroke four-cylinder turbocharged diesel engine can be fitted with various types exhaust system. In this paper, the impacts of exhaust system design on scavenging performance and wave action characteristic during valve overlap are investigated by using one-dimensional gas dynamic code. This work shows that a huge reflected exhaust pressure waves which reaches the exhaust port during valve overlap period is crucial design factor which determines quality and quantity of the fresh charge. Hence pressure wave that reaches the exhaust port of the cylinder during the valve overlap sequence should be weakened for good scavenging performance. This paper describes advantages and disadvantages of the various exhaust systems applied to a turbocharged and intercooled 4-cylinder diesel engine system in terms of scavenging efficiency and engine performance. To verify the computational results, experimental comparison has also performed.