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심한섭,이태연 한국공작기계학회 2003 한국생산제조학회지 Vol.12 No.5
Air partial pressure ratio and inlet air mass flow are influenced by water vapor and gaseous fuel in mixture on Compressed Natural Gas (CNG) engines. In this paper, the effects of the water vapor and the gaseous fuel that change the air mass flow and the air-fuel ratio are studied. Effective air mass ratio is defined as the air mass flow divided by mixture mass flow, and also it is applied to the estimation of the det air mass flow and the air-fuel ratio. The presence of the gaseous fuel and the water vapor in the mixture reduces the air partial pressure and the effective air mass ratio of the CNG engines. The experimental results for the CNG engine show that estimation of the air-fuel ratio based upon the effective air mass ratio is more accurate than that of a normal mode.
공연비 변화가 MILD 연소 특성에 미치는 영향에 관한 해석적 연구
하지수(Ji Soo Ha),김태권(Tae Kwon Kim),심성훈(Sung Hoon Shim) 大韓環境工學會 2010 대한환경공학회지 Vol.32 No.6
연소과정 중에 발생하는 질소산화물을 저감하는 기술인 MILD 연소에 대하여 공연비를 변화시키면서 나타나는 연소 특성을 수치해석을 통하여 연구하였다. 작은 크기의 공기분출속도(10m/s)에서는 공기가 연소로 내 상부영역까지 침투하지 못한다. 반면에 공기분출속도가 30m/s인 경우에는 공기유동이 연료유동을 억제하고 상부영역까지 흘러간다. 이론공기량에 해당하는 공기분출속도 18m/s에서는 10m/s 보다 상대적으로 상부영역까지 침투하였다. 이러한 유동 양상으로 공기분출속도가 작은 10m/s에서는 연소반응대가 공기노즐 측에 치우쳐 나타나고 30m/s에서는 연료노즐 측에 형성되었다. 공기분출 속도 16, 18, 20m/s에서는 공기노즐과 연료노즐 중간 영역에서 연소반응대가 형성되었다. 연소로 내 최대온도와 NOx 생성은 공기분출속도가 10m/s, 30m/s인 경우 보다 이론공기량이거나 이에 가까운 16, 18, 20m/s에서 낮게 나타났다. 본 연구로부터 MILD 연소로에서 이론공기량 조건이 NOx를 저감하는 최적의 조건이라는 것을 밝혔다. A numerical analysis of reactive flow in a MILD(Moderate and Intense Low oxygen Dilution) combustor is accomplished to elucidate the characteristics of combustion phenomena in the furnace with the variation of air fuel ratio. For the smaller magnitude of air injection velocity(10m/s), the air flow could not penetrate toward upper part of furnace. On the other hand, the air flow suppresses the fuel flow for the case of air injection velocity 30m/s. The air velocity 18m/s is corresponding to the stoichiometric air flow velocity, and for that case, the air flows to relatively more upper part of the furnace when compared with the case of air injection velocity 10m/s. The reaction zone is produced with the previous flow pattern, so that the reaction zone of the air injection velocity 10m/s is biased to the air nozzle side and for the case of air injection velocity 30m/s, the reaction zone is inclined to the fuel nozzle side. For the cases with the air injection velocities 16, 18, 20m/s, the reaction zone is nearly located at the center between air nozzle and fuel nozzle. The maximum temperatures and NOx concentrations for the cases of air injection velocity 16, 18, 20m/s are lower than the cases with air injection velocity 10, 30m/s. From the present study, the stoichiometric air fuel ratio is considered as the most optimal operating condition for the NOx reduction.
LPG 엔진에서 연료조절밸브를 이용한 공연비 제어에 관한 연구
박성천 한국기계기술학회 2008 한국기계기술학회지 Vol.10 No.1
This study investigates experimentally Air-fuel ratio feedback control with a fuel valve in a LPG engine. The fueling valve is controlled by electronic control unit which is made with micro computer. Various control logics are employed and then PID control is adopter as a proper logic for own system and Air-fuel ratio feedback control by PID control was experimentally of various operation area with the stable control algorithm of PID control that was earned from the former experiment. On the process the experiment, determination experiment of each control part coefficient was the biggest variable among the whole result of experiment. We could know as a result of experiment that the lange of overshoot is bigger as the proportional control part os bigger integral control part is related with the delay time and coefficient of differential control part is related with the decrease of overshoot range from the experiment of various operation area we could also analyse consequently that direct fuel control in the fuel value makes more stable control status in rare operation and low load area.
이태연(Taeyeon Lee),심한섭(Hansub Sim) 한국공작기계학회 1999 한국공작기계학회지 Vol.8 No.5
Since LPG has a higher octane number and a lower maximum combustion temperature than gasoline, it is getting more popular for reducing emissions from the vehicle. This paper, when an LPG engine works in the range of idle, analyzed the operating range preciously and provides reducing method of emissions for the LPG engine. An electronic control unit(ECU) for the LPG engine using a feedback mixer is presented. The ECU is built by using a microcontroller MC68HC05. A PI-controller is implemented in the ECU in order to handle Air-Fuel ratio control. The experimental results exhibit that the required engine performance are satisfied at idle.
비정상상태 유동해석을 이용한 Maniverter Design Optimization에 관한 연구
소유미(Yumi So),민선기(Sunki Min),황명진(Myungjin Hwang) 한국자동차공학회 2011 한국자동차공학회 학술대회 및 전시회 Vol.2011 No.11
The catalytic converter reduces the emissions of unburned hydrocarbons, carbon monoxide and oxides of nitrogen. Overall catalytic converter efficiency is influenced by how the flow distributes across the substrate inlet face, even if the inlet gases are well mixed. Highly non-uniform substrate inlet flow may provide incomplete HC, CO, and NOx conversion because the converter chemistry only uses a portion of the available catalyst surface area. Engine operating air-fuel ratio is maintained close to stoichiometric through the use of an oxygen sensor which provides a voltage signal dependent on the oxygen concentration in the exhaust gas stream. So, it’s important to find the optimal oxygen sensor location for the AFIM (airfuel ratio imbalance monitor) system which requires the oxygen sensor to see exhaust gases from cylinder evenly. This study recognizes the dual roles of gas mixing and flow uniformity in determining HC, CO and NOx conversion in the substrate. Also, it predicts the AFIM performance for the specified oxygen sensor type and location using 3D CFD analysis. As a result, this approach is used to optimize the manifold runner and converter inlet design through the analysis.
모사 배기가스 재순환을 이용한 압축착화 엔진 성능 및 배기 특성
강민구(Mingu Kang),권석주(Seokjoo Kwon),차준표(Junepyo Cha),박성욱(Sungwook Park),이창식(Chang Sik Lee) 한국자동차공학회 2011 한국자동차공학회 학술대회 및 전시회 Vol.2011 No.11
The effects of equivalence ratio on combustion and emissions characteristics were investigated in a compression ignition engine using simulated-EGR by diesel fuel. In order to analyze the effects of simulated exhaust gas recirculation, as a diluent almost pure carbon dioxide gas was supplied to reduce oxygen concentration at a surge tank. For investigating the effects of simulated-EGR on the combustion and emissions characteristics, the combustion characteristics for the variation of equivalence ratio were measured and analyzed in a single-cylinder diesel engine with a compression ratio of 17.3 and a displacement volume of 373.3cc. With the exhaust emission characteristics, nitrogen oxides (NOX), carbon monoxide (CO) and hydrocarbon (HC) were measured by exhaust gas analyzer under the various simulated-EGR ratios. The experimental results show that maximum IMEP was measured at BTDC 5° and the IMEP was gradually reduced as advanced injection timing. NOX emissions decreased dramatically with the increase of equivalence ratio and it was almost not produced at the range from 0.8 to 1.0 of equivalence ratio.
흡입유동제어에 의한 Lean Burn Engine의 연소성능 개선에 관한 연구
박경석,최남일 慶熙大學校 1998 論文集 Vol.27 No.-
Recently reduction of automotive emission gas has become one of the most important factors affecting vehicle performance. To satisfy the reduction of emission gas and fuel consumption at a time, much interest has grown in Lean Burn engine. In order to improve Lean Burn performance, some kinds of techniques are employed such as, the method of fuel atomization, high spark energy, intensification of intake flow or stratification of air-fuel mixture. In this study, intake flow characteristics are mainly investigated to improve the combustion performance. As a first step, the conventional gasoline engine is modified into lean burn engine by controlling the fuel supply and tested for basic performance in the engine test bench. Second, through the steady flow test, Shapes of swirl control valves with comparatively high swirl and tumble ratio are selected. After the selected swirl control valves installed between intake manifold and intake port, their influences on engine and emission performance, fuel consumption and lean limit are experimentally defined.