• 동력기계공학회지
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• 제7권4호
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• pp.12-18
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• 2003

Various measures have been tried to reduce the NOx emission from diesel engine, but with partial success because the mechanisms of NOx and PM formations appear to have trade-off relation between each other. Therefore it has been known to be difficult to reduce NOx emission and PM emission simultaneously. Two stage combustion method i,e. a combustion process which has rich combustion stage and lean combustion stage one by one, has been developed successfully to reduce NOx formation in the continuous combustion chambers such as in the boilers. But until yet it is not successful to apply the same method in intermittent combustion chamber like in the diesel engine cylinder, as it was, only several research works were carried out. In this study, devised was a uniquely shaped combustion chamber with reformed piston crown intended to keep fuel-rich condition during early stage of combustion and fuel-lean condition during next stage. It was found that the NOx emission decreased significantly at various conditions of operation with the two stage combustion type engines of PR20 type, but other values such as smoke, CO and specific fuel consumption deteriorated as usual.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2006년 제4회 한국유체공학학술대회 논문집
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• pp.569-572
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• 2006

In present study, the influence of changing combustor pressure on flame stabilization and nitrogen oxide (NOX) emission in the swirl flame with secondary fuel injection was investigated. The combustor pressure was controlled by suction at combustor exit. Pressure index ($P^*=Pabs/Patm$), where Pabs and Patm indicated the absolute pressure and atmosphere pressure, was controlled in the range of 0.7~1.15 for each equivalence ratio conditions. It could be observed that flame stable region became narrower with decreasing equivalence ratio and pressure index. In this combustion system, stable flames were formed until $P^*=\;0.7$. Emission index decreased with decreasing pressure index for overall equivalence ratio conditions and NOx reduction rates were almost identical for $P^*<1$ regardless of equivalence ratio though EINOx values showed different level with change of equivalence ratio for $P^*{\geq}1$. It is also observed that EINOx decreased with increasing secondary fuel injection ratio. Emission index of nitric oxide was controllable by adjusting the changing combustor pressure and injecting secondary fuel and this NOx reduction technology is applicable to industrial furnaces and air conditioning system.

• 대한기계학회논문집B
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• 제33권11호
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• pp.849-857
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• 2009

The experimental study was performed to investigate the effects of partial premixing, varying the equivalence ratio, mixing degree, swirl intensity, mixing length on the characteristics of flame structure and NOx emission. Experiments were conducted in a dump combustor at 1 bar using methane as fuel. Inlet air temperature was 570K. OH chemiluminescence images were acquired with an ICCD camera. As a result of the experimental investigation of characteristics of flame and NOx emission in partial premixed combustor, we can conclude the results as below. With the increase of swirl number, The flame length decreases and the flame width increases and it helps flame stabilization. It means that lean flammability limit is extended. With the increase of mixing of fuel-air length ratio, Flame goes to be stabilized and NOx emission and $OH^{\ast}$ intensity decrease. Through the comparison of preceding results, It is possible that the exhausted NOx emission from a gas turbine combustor will be able to predict through the $OH^{\ast}$ intensity.

• Journal of Advanced Marine Engineering and Technology
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• 제32권7호
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• pp.1080-1088
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• 2008

This paper addresses some concerns faced by the shipping industry nowadays. Initially, the environmental issues were resolved and stricter regulations are now being implemented with regards to the exhaust gas, specifically nitrogen oxides (NOx) and sulfur oxides (SOx), emitted from ships. Secondly, with the increasing and unstable cost of fuel oils in the world market, it has become almost a necessity to explore on a new alternative fuel. Hence, this study was conducted. An experiment was carried-out on a fishing survey vessel with the main engine (M/E) and generator engine (G/E) operated on expensive marine gas oil (MGO). During the experiment, two pre-refinery systems were installed and different fuel oil samples were employed for the M/E and the G/E. Furthermore, the NOx emission and soot concentration were monitored and verified. The results confirmed the compatibility of some fuel oil types to the engines and meeting the emission standards. MDO, MF15 and Bunker A can be used in place of MGO for the engines(M/E, G/E).

• 한국연소학회:학술대회논문집
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• 한국연소학회 2002년도 제24회 KOSCO SYMPOSIUM 논문집
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• pp.185-191
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• 2002

The influence of N2 addition on soot formation, flame temperature and NOx emissions is investigated experimentally with methane fuel co-flow diffusion flames. The motivation of the present investigation is the differences in NOx reduction reported between fuel-side and oxidizer-side introduction of N2. To determine the influence of dilution alone, fuel was diluted with nitrogen while keeping the adiabatic flame temperature fixed by changing the temperature of the reactants. And to see the thermal effect only, air was supplied at different temperature without N2 addition. N2 addition into fuel side suppressed the soot formation than the case of oxidizer-side, while flame temperature enhanced the soot formation almost linearly. These results reveals the relative influences of the thermal, concentration effects of N2 additives on soot formation In accordance with experimental study, numerical simulation using CHEMKIN code was carried out to compare the temperature results with those acquired by CARS measurement, and we could find that there is good agreement between those results. Emission test revealed that NOx emissions were affected by not only flame temperature but also N2 addition.

• 한국자동차공학회논문집
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• 제22권7호
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• pp.8-15
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• 2014

In order to satisfy stringent future emission regulation in diesel engines, systematic approaches to mitigate the harmful exhaust emissions were developed, such as engine hardware, fuel injection equipment, engine control, and after-treatment system. In this study, to improve the nano-particle and NOx emissions from a state-of-the-arts diesel engine, effect of various EGR and fuel injection pressure with combustion analysis were evaluated. Size-resolved nano-particle and NOx emissions showed trade-off characteristics with various EGR rate and increment of fuel injection pressure.

• Advances in aircraft and spacecraft science
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• 제9권6호
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• pp.537-551
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• 2022

The rapid decrease of fossil fuel resources and increase of environmental pollution caused by aviation industries have become a severe issue which leads to an increase in the greenhouse effect. The use of biofuel becomes an option to alleviate issues related to unrenewable resources. This study presents a computational simulation of the biofuel combustion characteristics of various alternative fuels in an annular combustion chamber designed for training aircraft. The biofuels used in this study are Sorghum Oil Methyl Ester (SOME), Spirulina Platensis Algae (SPA) and Camelina Hydrotreated Esters and Fatty Acids (CHEFA). Meanwhile, Jet-A is used as a baseline fuel. The fuel properties and combustion characteristics are being investigated and analysed. The results are presented in terms of temperature and pressure profiles in addition to the formation of NOx and soot generated from the combustion chamber. Results obtained show that CHEFA fuel is the most recommended biofuel among all four tested fuels as it is being found that it burns with 37.6% lower temperature, 15.2% lower pressure, 89.5% lower NOx emission and 8.1% lower soot emission compared with the baseline fuel in same combustion chamber geometry with same initial parameters.

• 한국자동차공학회논문집
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• 제16권4호
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• pp.75-80
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• 2008

Biodiesel fuel(BDF) can be effectively used as an alternative fuel in diesel engine. However, BDF may affect the performance and exhaust emissions in diesel engine because it has different physical and chemical properties from diesel fuel such as viscosity, compressibility and so on. To investigate the effect of injection timing on the characteristics of performance and exhaust emissions with BDF in IDI diesel engine, it was applied the BDF derived from soybean oil in this study. The engine was operated at seven different injection timings from TDC to BTDC $12^{\circ}CA$ and six loads at a single engine speed of 1500rpm. When the fuel injection timing was retarded, better results were showed, which may confirm the advantages of BDF. The simultaneous reduction of smoke and NOx was achieved at some fixed fuel injection timings of an IDI diesel engine.

• 에너지공학
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• 제12권4호
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• pp.320-327
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• 2003

IGCC용 가스터빈 연소기의 중발열량 가스 연료 대체성 및 호환성 검토를 위한 전산유체역학적 연구를 수행하였다. 연소기 전산해석 방법은 기존의 상용 CFD코드의 해석체계에 중발열량 가스연료의 화학반응 모델 및 fuel NOx 모델등을 추가적으로 결합하여 구성하였다. 본 해석방법을 이용하여, 천연가스와 IGCC 용 대체가스(석탄가스, 중잔사유 가스) 연소시의 연소기 내부 유동속도, 화학종, 온도 분포들과 화염 형상 및 거동을 비교하였고, 더 나아가 NOx 생성특성과 터빈과의 matching 조건도 분석하였다. 이러한 전산해석결과들을 바탕으로, 본 연구는 중발열량 가스를 대체연료로 사용하는 IGCC용 가스터빈 연소기의 설계 개선 및 재설계 방향을 제시하였다.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2005년도 제25회 추계학술대회논문집
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• pp.437-444
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• 2005

본 연구는 연료-공기 혼합정도가 불안정 화염 구조와 NOx 배출 특성에 미치는 영향을 조사하기 위해 대기압, 모형 가스 터빈 연소기에서 실험을 수행하였다. 선회각은 $45^{\circ}$이며, 연료-공기 혼합정도는 당량비 0.53에서 0.79 범위에서 0, 50, 100%로 변화시켰다. 화염구조를 파악하기 위해, 당량비 0.79에서 ICCD를 사용하여 위상 동기화된 OH 자발광 이미지를 취득하였다. NOx 배출은 각 상기 실험조건에서 NOx 분석기를 이용하여 취득하였다. 위상에 대한 $OH^*$ 이미지를 취득함으로써 연료-공기 혼합정도가 화염의 구조에 미치는 영향을 확인할 수 있었다. 또한 국소 열방출의 특성을 통해, 연료-공기 혼합정도에 따른 연소불안정이 발생하거나 소멸되는 영역에 대한 정보를 얻을 수 있었으며, 혼합정도에 따른 NOx 농도를 측정함으로써 희박 연소 영역에서는 $\sigma$가 커질수록 NOx 발생이 적음을 확인할 수 있었다. 이런 결과들은 연소불안정 현상의 메카니즘을 이해하는데 중요한 기초자료로 사용될 것으로 기대된다.