• 한국자동차공학회논문집
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• 제7권5호
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• pp.66-72
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• 1999

It is necessary to discuss lightening engine parts and reducing the friction of sliding parts to improve fuel consumption and combustion stability at idling condition. Lean best torque combustion which produce maximum power at a lean air-fuel ratio is effective for the reduction of exhaust gas emission and the improvement of fuel consumption. Accordingly, this study deals with the expansion of lean combustible limitation, the combustion stability and the reduction of idle speed through the analysis of combustion characteristics on the base of the control technique of precise air-fuel ratio because it does not need to maximum power at idling condition. The idle speed is increased proportional to ISC(Idle Speed Control) duty ratio. On the other hand the idle speed decreased by lean air-fuel ratio. The COV in engine speed is stable within maximum two percent up to 17.6 mixture ratio by the control of ISC duty ratio.

• 한국분무공학회지
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• 제26권1호
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• pp.18-25
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• 2021

The objective of this study is to investigate the effect of cryogenic intake air temperature on the injected fuel droplet behavior in a compression ignition engine under the different start of energizing timing. To achieve this, the intake air temperatures were changed from -18℃ to 18℃ in steps of 9℃, and the result of fuel evaporation rate, Sauter mean diameter, and equivalence ratio distributions were compared. When the intake air temperature decreased in steps of 9℃, less fuel was evaporated by about 3.33% because the cylinder temperature was decreased. In addition, the evaporated fuel amount was increased with retarding the start of energizing timing because the cylinder temperature raised. However, the difference was decreased according to the retarded start of energizing timing because the cylinder pressure was also increased at the start of fuel injection. The equivalence ratio was reduced by 5.94% with decreasing the intake air temperature. In addition, the ignition delay was expected to longer because of the deteriorated evaporation performance and the reduced cylinder pressure by the low intake air temperature.

• 한국정보통신학회논문지
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• 제11권5호
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• pp.1013-1018
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• 2007

자동차의 연료분사에 관여하는 전자제어 센서에는 공기유량 센서, 흡기온도 센서, 대기압 센서, 냉각수 온도센서, 스로틀 포지션 센서, 모터 포지션 센서 등이 있다. 본 논문에서는 흡기온도 센서의 온도 변화와 공기와 연료의 혼합비율인 공연비에 대해 퍼지 제어 기법을 적용하여 차량의 연료 소비를 제어하는 방법을 제안하였다. 제안된 기법에서는 각각의 공기 유입량과 연료 분사량을 이용하여 공연비 수치를 구한 후, 공연비, 흡기온도, 최종 연료 보정량에 대해 설정된 퍼지 소속 함수와 퍼지 추론 규칙에 따라 차량 연료가 제어된다. 제어하는 방법을 제시하였다. 시뮬레이션을 통한 일반적인 차량의 연료 제어 방법과 비교 분석한 결과, 제안된 방법이 차량의 연료제어에 있어 효과적임을 확인하였다.

• 오토저널
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• 제13권5호
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• pp.73-80
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• 1991

Air/fuel ratio control system for gasoline engines has been analyzed to determine the control gain of the system. In this analysis the engine is modelled to be a simple time delaying element and the ramp-and-jump method is used to control air/fuel ratio. The result shows that it is necessary to measure the air flow rate accurately to enhance the control performance. And also it is shown that the control gain must be determined in some bounded region to meet the fast dynamic response and high catalyst conversion efficiency together.

• 대한기계학회논문집B
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• 제28권10호
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• pp.1147-1154
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• 2004

This paper is the third of several companion papers which compare the method of Air-Fuel ratio determination. In the previous works, Eltinge chart was expanded to arbitrary fuel composition as a reference exhaust composition. The compensation of unburned hydrocarbon in Eltinge chart and comparison of Spindt and Eltinge method were also discussed. In addition to Eltinge and Spindt's one, however, there are many methods which calculate Air-Fuel ratio from exhaust emission. Among these methods, carbon balance and oxygen balance are widely used in practice. In some applications, linear formula from statistical method is being used in the field due to its simplicity and convenience. In this paper, these various methods are evaluated and compared with Eltinge results and new linear formula is proposed for the gasoline fuel. The results show that the corrected carbon balance equation has excellent agreement with Eltinge and Spindt's one. On the other hands, the oxygen-balanced formula has a limitation according to the mixture state and AFR. For gasoline fuel, newly proposed linear equation has good compatibility with Eltinge and Spindt up to AFR 17.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2010년도 추계학술대회 초록집
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• pp.103.1-103.1
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• 2010

Recently domestic wood pellet boilers are installed in rural and forestry houses. The fuel price per lower heating value of wood pellet is about 20 % lower than that of heating oil on July 2010. In spite of lower price of wood pellet, a few user of wood pellet boiler complain expensive fuel cost. One of this reason is inaccurate or improper air-fuel ratio setting of wood pellet boiler. O2 concentration of flue gas of domestic wood pellet boiler is about 9.7 % and there are few domestic wood pellet boiler which can control air-fuel ratio automatically. We tested a domestic wood pellet boiler in changing boiler thermal output and air-fuel ratio. The nominal boiler thermal output is 25 kW (21 500 kcal/h). We measured thermal efficiency and flue gas concentrations such as CO and NOx at each boiler thermal load with various air-fuel ratio. The results show that if air flow rate is the same as full load and part load, thermal efficiency of part load of 40 % drops about 7.7 %p compared to boiler full load case.

• 한국분무공학회지
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• 제3권4호
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• pp.43-49
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• 1998

In order to clarify the effect of equivalence ratio and kinds of fule in flame structure, a numerical simulation of triple flame developed in a co-flowing methane-air and air stream was carried out by the elementary chemical reaction mechanism. The following conclusions were obtained. Equivalence ratio at which the apparent burning velocity is maximum is a little larger than that of the one-dimensional premixed flame. Apparent burning velocities are two times higher than that of the one-dimensional premixed flame for the methane-air. The flame thrusts out forward in the downstream of the boundary between mixture and air stream, and a part of the flow is bent and forks out in this protruding flame so that a triple flame is originated; this triple flame is composed of fuel rich and lean premixed flame branches and a diffusion flame branch. Near the equivalence ratio at which the burning velocity of rule-dimensional premixed flame is the largest the effect of one-dimensional premixed flame becomes large and the fuel rich premixed flame advances and becomes vertical to the flow direction.

• 대한기계학회논문집B
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• 제34권9호
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• pp.835-841
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• 2010

MEMS 가스터빈 엔진에서 연료와 공기의 혼합에 영향을 미치는 중요한 요소중 하나는 연료 분사구 형상의 설계이다. 본 연구에서는 3 개의 연료 주입부와 각 주입부에 연결된 여러 개의 분사구에 의해 연료와 공기가 혼합되는 시스템을 고려하여 분사구의 배열과 연료 공급비율의 변화에 따른 혼합 정도를 당량비를 통하여 정량적으로 해석하였다.

• 대한기계학회논문집
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• 제19권7호
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• pp.1702-1708
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• 1995

Owing to the serious problem of hydrocarbon fuel such as environmental pollution, the development of alternative fuel is very urgent. To adopt hydrogen to the internal combustion engine, a solenoid-drive type in-cylinder injection system was constructed. The injection system was installed to the single cylinder research engine, and the engine performance and the emission of citric oxide were tested upon the fuel-air equivalence ratio and the spark timing. In the case of in-cylinder injection system, hydrogen is injected after the intake valve is close, so it is possible to operate the engine without the back fire and the fall of its volumetric efficiency. In the region of the fuel-air equivalence ratio below 0.5, hydrogen and air aren't well mixed and the thermal efficiency is lowered, so the nozzle should be designed to inject hydrogen uniformly into the combustion chamber. In the region of the fuel-air equivalence ratio above 0.7,the fuel-air mixture burns very fast and the amount of citric oxide emission increases rapidly, so the spark timing should be retarded as compared with MBT.

• 오토저널
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• 제9권4호
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• pp.41-49
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• 1987

It is an experimental study to improve the characteristics of combustion and exhaust emission gas in the gasoline engine. These characteristics are influenced by the fuel droplet size. To improve these characteristics, we make the ultrasonic atomization apparatus, and compare with the commercial carburetor. The results obtained are as follows: 1. Maximum atomization quantity is obtained by the vibrator of resonancy frequency 1.65MHz in the ultrasonic atomization apparatus. 2. With ultrasonic atomization apparatus, more than 99% of atomization rate can be obtained regardless of intake air temperature, velocity, and air-fuel ratio. 3. Atomization rate of the commercial carburetor increases with the air-fuel ratio and intake air temperature. 4. Difference of atomization rate between the ultrasonic atomization apparatus and the commercial carburetor increases with decreasing air-fuel ratio. 5. Droplet size is about 1-5.mu.m at the ultrasonic atomization apparatus, and 80-150.mu.m at the commercial carburetor, which indicates the ultrasonic atomization apparatus is excellent in atomization.