• 한국자동차공학회논문집
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• 제4권2호
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• pp.11-22
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• 1996

It has been generally accepted that NOx formation increases as the maximum temperature or correspondingly the maximum pressure of a combustion system increases. Recently some exceptional experimental results have been reportes that under certain circumstance NOx formation could be reduced while the maximum pressure was increasing by varying the methods of combustion for the same kind of premixed gases. Until now that kind of results have been acquired only for the case of a dual opposed prechamber. But the mechanism has not been clearly understood yet. 3D computer simulation has been tried to clarify the mechanism. Flor this purpose KIVA-Ⅱ has been modified and applied to the model combustion chamber with which the same kind of experimental works have been done by the authors. A good agreement with the experimental results was achieved with the spatial and temporal resolution which is hard th be obtained by the experimental methods. And it was observed that for the dual opposed prechamber case the time for the NOx formation, which is non-equilibrium reaction, is shorter than any other case by an appropriate mixing process in the main combustion chamber. The shorter time reduceed heat loss through the combustion chamber walls and thereby obtaines the higher maximum pressure.

• 한국추진공학회지
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• 제8권2호
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• pp.95-101
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• 2004

보론 카바이드를 함유한 고체연료 그레인을 사용하여 당량비와 공기 질량 유속에 따라 연소 효율이 어떻게 변하는가를 조사하였다. 연소 효율은 당량비의 증가 방향과 질량유속 감소 방향에 따라서 증가하였다. 높은 흡입온도가 높은 연소 효율을 보이는데 이는 확산 영역에서 큰 보론 입자들의 연소 증진 결과이다. 재순환 영역으로 주로 이루어진 짧은 그레인에서는 큰 보론 입자의 형성으로 연소 효율은 감소하고 있다. 흡입 온도에 따라 증가하는 연소 효율은 흡입온도 증가에 따라 일반적으로 열역학적 사이클의 효율이 감소하는 것과는 상반되는 방향이나 실험적 결과를 해석할 때 합당한 결과로 나타나고 있다.

• 한국해양공학회지
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• 제13권3B호
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• pp.38-46
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• 1999

Increasing stringent emissions legislation and requirement of more effective energy used for diesel engine demand the fine control of the fuel injection system. Recently, the electromagnetic fuel injection control system for diesel engine is tried to realize the optimum diesel combustion by the feel back sensing as optical signal of combustion flame. The photo detectors were made for the feed back signal of electromagnetic fuel injection control for small DI diesel engine. Their abilities to detect defining combustion events were examined. By evaluating test results, it was shown that the wider acceptable optical range design of optical probe window face, and selection of installation position and installation method of detector were important point for improving sensing ability. The detector was shown to detect start and end of diffused combustion and maximum point of flame intensity impossible for pressure sensor, and also shown that the maximum point of flame intensity was 75% of accumulated heat release point within the experimental conditions.

• 대한기계학회논문집B
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• 제29권8호
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• pp.963-970
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• 2005

The combustion instability of turbulent flames is the most important problem of the gas turbine combustor. Thus improved understanding of mechanisms of combustion instability is necessary for the design and operation of gas turbine combustors. In this study, the cause of the combustion instability in a rearward-step dump combustor was investigated with respect to the fuel flow modulation; choked fuel flow, unchoked fuel flow and fully premixed mixture flow. We observed various types of combustion instabilities with respect to the change of equivalence ratio, fuel flow conditions and fuel injection location. Particularly in the unchoked fuel flow condition, it was found that the oscillation time of combustion instability is strongly related to the convection time of the fuel and that the pressure fluctuation in a lab-scale combustor is highly related to the vortex and the equivalence ratio fluctuations due to fuel flow modulation and unmixedness of the fuel and air.

• Journal of Advanced Marine Engineering and Technology
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• 제34권2호
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• pp.243-249
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• 2010

디젤기관에 있어서 PM과 NO의 동시저감을 위한 에멀전연료의 적용은 급속도로 발전되어져왔다. 하지만, C중유 에멀젼연료의 연소계측 해석은 다른 연료에 비하여 복잡한 연소형태 때문에 어려움이 많다. 본 연구에서는 높은 압력과 온도의 정적연소실에서 에멀젼 C중유를 분사 연소시켜, 연소해석에 대한 실질적인 근거를 제시한다.

• 한국자동차공학회논문집
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• 제7권8호
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• pp.43-54
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• 1999

The effects of equivalence ratio and pressure on burnt gas temperature in premixed fuel rich propane-oxygen-inert gas combustion are investigated over the wide ranges of equivalence ration from 1.5 to 2.7 and pressure from 0.1 to 7 MPa by using a specially designed disk -type constant-voume combustion chamber, The premixtures are simultaneously ignited by eight spark plugs located on the circumference of combustion chamber with 45 degree interals. The eight converging flames compress the end gases to high pressures. The burnt gas temperature is meausured by the nmodifie dtow-colr pyrometry method. The transmissivity in the chamber center during the final stage of combustion at the hightest pressure is meausred by in situ laser extinction method. It is found that a temperature difference between the burnt gas temperature measured by mofidied and conventrational two-color method is 10 to 20 K, but the accuracy of the modified two-color methdo is higher if the local transmissivity in observed region is uniform , and the combustion at higher pressures results gas density conditions and the burnt gas temperature increases as the volume fraction of argon is increased because the specific heat of argon is lower compared to that of nitrogen with a constant equivalence ratio.

• International Journal of Automotive Technology
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• 제7권6호
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• pp.675-680
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• 2006

In the direct injected gasoline engine, atomized spray is desired to achieve efficient mixture formation needed to good engine performance because the injection process leaves little time for the evaporation of fuels. Therefore, substantial understanding of global spray structure and quantitative characteristics of spray are decisive technology to optimize combustion system of a GDI engine. The combustion and emission characteristics of gasoline-fueled stratified-charge compression ignition(SCCI) engine according to intake temperature and compression ratio was examined. The fuel was injected directly to the cylinder under the high temperature condition resulting from heating the intake port. With this injection strategy, the SCCI combustion region was expanded dramatically without any increase in NOx emissions, which were seen in the case of compression stroke injection. Injection timing during the intake temperature was found to be an important parameter that affects the SCCI region width. The mixture stratification and the fuel reformation can be utilized to reduce the required intake temperature for suitable SCCI combustion under each set of engine speed and compression ratio conditions.

• 대한기계학회논문집B
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• 제30권5호
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• pp.457-464
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• 2006

Controlled auto ignition (CAI) combustion, also known as HCCI (homogeneous charge compression ignition), offers the potential to simultaneously improve fuel economy and reduce emission. CAI-combustion was achieved in a single cylinder gasoline DI engine, with a cylinder running in a CAI mode. Standard components were used the camshafts which had been modified in order to restrict the gas exchange process. The effects of air-fuel ratio, residual EGR rate and injection timing such as early injection and late injection on the attainable CAI combustion region were investigated. The effect that injection timings on factor such as start of combustion, combustion duration and heat release rate was also investigated. From results early injection caused the mixture to ignite earlier and burn more quickly due to the exothermic reaction during the recompression and gave rise to good mixing of the fuel-air.

• 한국분무공학회지
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• 제26권2호
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• pp.57-66
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• 2021

The reactivity controlled compression ignition (RCCI) is the technology that provides two different types of fuel to the combustion chamber with the advantage of significantly reducing particulate matter and nitrogen oxides emissions. However, due to the characteristics of lean combustion, combustion efficiency is worsened. The conventional type of pistons for conventional diesel combustion (CDC) has mostly been used in the researches on RCCI. Because the pistons for CDC are optimized to enhance flow and target spray, the pistons are unsuitable for RCCI. In this study, a piston that is suitable for RCCI is designed to improve combustion efficiency. The new piston was designed by considering the factors such as squish geometry, bowl depth, and surface area. The experiment was carried out by fixing the energy supply to 0.9kJ/cycle and 1.5kJ/cycle respectively. The two pistons were quantitatively compared in terms of thermal efficiency and combustion efficiency.

• 한국추진공학회지
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• 제23권4호
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• pp.70-80
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• 2019

화염 가시화가 가능한 모델 연소실에서 형상과 리세스 길이가 다른 6종의 동축 와류형 분사기를 이용한 연소실험을 수행하였다. 실제 추진제 대신 기체메탄과 기체산소를 사용하여, 분사기 설계와 실험 조건이 화염구조와 연소 안정성에 미치는 영향을 분석하였다. 실험조건뿐 아니라 리세스 길이 및 오리피스 직경과 같은 분사기 형상은 연소 안정성에 큰 영향을 미치는 것을 알 수 있었다. 또한 연소불안정의 발생에 따라 열방출 패턴의 형상이 달라지는 것이 확인할 수 있었다.