• 한국연소학회:학술대회논문집
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• 한국연소학회 2014년도 제49회 KOSCO SYMPOSIUM 초록집
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• pp.233-234
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• 2014

Lean-rich combustion system was composed both fuel-lean and fuel-rich flame at once. Each of fuel-lean and fuel-rich combustion types to reduce Thermal $NO_x$ and obtain flame stability. This study was confirmed a stability of flame through variation of flame shape that EGR was applied and compared the emission characteristics of EGR lean-rich combustion system to normal premixed combustion system at real condition to review a utility of the system. As a result, emission index of $NO_x$ and CO generated from EGR lean-rich combustion system at global equivalence ratio is 0.85 just half level($NO_x$ 0.31 g/kg, CO 0.08g/kg) compared to the amount generated from normal premixed combustion system at equivalence ratio is 0.78.

• 한국자동차공학회논문집
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• 제22권2호
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• pp.60-66
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• 2014

A control oriented model of the Lean $NO_x$ trap (LNT) was developed to determine the timing of $NO_x$ regeneration. The LNT model consists of $NO_x$ storage and reduction model. Once $NO_x$ is stored ($NO_x$ storage model), at the right timing $NO_x$ should be released and then reduced ($NO_x$ reduction model) with reductants on the catalyst active sites, called regeneration. The $NO_x$ storage model simulates the degree of stored $NO_x$ in the LNT. It is structured by an instantaneous $NO_x$ storage efficiency and the $NO_x$ storage capacity model. The $NO_x$ storge capacity model was modeled to have a Gaussian distribution with a function of exhaust gas temperature. $NO_x$ release and reduction reactions for the $NO_x$ reduction model were modeled as Arrhenius equations. The parameter identification was optimally performed by the data of the bench flow reactor test results at space velocity 50,000/hr, 80,000/hr, and temperature of $250-500^{\circ}C$. The LNT model state, storage fraction indicates the degree of stored $NO_x$ in the LNT and thus, the timing of the regeneration can be determined based on it. For practical purpose, this model will be verified more completely by engine test data which simulate the NEDC transient mode.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집D
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• pp.66-70
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• 2001

The combustion characteristics have been investigated to develop the low $NO_{x}$ gas turbine combustor. The lean premixed combustion technology was applied to reduce the $NO_{x}$ emission. Also, the conventional combustor was designed and tested for the baseline of low $NO_{x}$ combustor performance. The test was conducted at the condition of high temperature and ambient pressure. The combustion air which has the temperature of 500K were supplied to the combustor through the air preheater. The temperature and emissions of $NO_{x}$ and CO were measured at the exit of combustor. The premixing chamber can be operated very lean condition of equivalence ratio around 0.35. The $NO_{x}$ was decreased with decreasing the equivalence ration. The CO was decreased with decreasing the equivalence ratio, but the CO was increased with decreasing the equivalence ratio below 0.45. But, at the very lean condition of equivalence ratio below 0.35 both NOx and CO were increased because of the flame unstability. The $NO_{x}$ was decreased slightly and CO was increased with increasing inlet air flowrate. This results can be used to determine the size of combustor. The low $NO_{x}$ combustor has lower values of $NO_{x}$ and CO compared with conventional one. Consequently the performance of combustor shows the possibility of the application to the gas turbine system.

• 한국자동차공학회논문집
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• 제21권6호
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• pp.64-71
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• 2013

In this study we designed a lean $NO_x$ trap (LNT) model with $GT-POWER^{TM}$ program and then the LNT model was compared to the bench flow reactor test results. This model consists of 9 kinetic reactions to represent the main steps of NO oxidation, $NO_x$ adsorption, $NO_x$ release and then its reduction. The comparison was performed on the operating conditions at the space velocity of 50,000 1/hr and 80,000 1/hr with the temperature range of $200^{\circ}C{\sim}500^{\circ}C$ with the even spaced temperature step of $50^{\circ}C$. The experimental results show that the $NO_x$ conversion efficiency was enhanced by the temperature up to $350^{\circ}C$ and then decayed at higher temperatures. The LNT model predicts the similar trend of the $NO_x$ conversion efficiency to the experimental results below $350^{\circ}C$, but overestimates above $350^{\circ}C$. This overestimation comes from the higher reduction efficiency which was obtained by the different reduction gas composition such as $C_3H_6$ in the model to replace $CH_4$, $C_2H_4$ in the bench test.

• 한국수소및신에너지학회논문집
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• 제17권1호
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• pp.75-81
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• 2006

Lean premixed combustion is a well known method for low $NO_x$ gas turbine combustor. But lean combustion is usually accompanied by flame instability. To overcome this problem, the hydrogen ($H_2$) was added to main fuel methane to increase flammable limit. In this paper, the effects of hydrogen addition on lean premixed combustion of methane ($CH_4$) were investigated numerically. Results showed that the extinction stretch rate increases and the extinction temperature constant with relatively small amount of $H_2$ addition. The flame temperature and NO emission increase with $H_2$ addition at the same stretch rate and equivalence ratio but it could increase the range of lean extinction and extinction equivalence ratio limit. Eventually, the $H_2$ addition case showed almost same or lower NO emission than no addictive $CH_4$ case in the extinction condition.

• 대한기계학회논문집B
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• 제34권3호
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• pp.283-290
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• 2010

이 연구의 목적은 NOx 저감을 위한 연료희박 재연소 기법과 산화제 다단 연소 기법의 혼합 기법의 실험적 연구를 목표로 한다. 실험용 연소로에서 재연소 연료 분율, 재연소 노즐 직경, 산소부하도 및 재연소 연료 분사 위치등을 고려한 실험을 수행 하였다. 또한, 산화제 다단 연소를 통하여 생성된 유동장이 NOx 저감에 미치는 영향을 연료희박 기법의 NOx 저감율과 비교하는 실험을 수행하였다. 실험을 통하여 연료희박 재연소와 산화제다단연소 기법의 혼합 기법이 NOx 저감에 미치는 긍정적인 효과를 관찰 하였다.

• 한국분무공학회지
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• 제26권4호
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• pp.204-211
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• 2021

Lean combustion performance of natural gas and hydrogen was compared in a spark-ignition engine. The lean combustion engine operation with natural gas was limited due to combustion instability at an excess air ratio (EAR) above 1.8. The total hydrocarbon (THC) emissions increased significantly with increasing EAR. The nitrogen oxides (NO_X) emissions were also high due to the limitation of increasing EAR. The lean combustion engine operation with hydrogen showed superior combustion stability as well as low THC and NO_X emissions, even at high EARs. However, boosting technology was required to reach the high EARs.

• 대한기계학회논문집B
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• 제32권3호
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• pp.216-223
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• 2008

Reburning is a useful technology in reducing nitric oxide through injection of a secondary hydrocarbon fuel. In this paper, an experimental study has been conducted to evaluate the effect of fuel lean reburning on $NO_X/CO$ reduction in LPG flame. Experiments were performed in flames stabilized by a co-flow swirl burner, which was mounted at the bottom of the furnace. Tests were conducted using LPG gas as the reburn fuel as well as the main fuel. The effects of reburn fuel fraction and injection location of the reburn fuel were studied when the fuel lean reburning system was applied. The paper reports data on flue gas emissions and temperature distribution in the furnace for a wide range of experimental conditions. At steady state, temperature distribution and emission formation in the furnace have been measured and compared. This paper makes clear that in order to decrease both NOx and CO concentrations in the exhaust when the fuel lean reburning system was adapted, it is important that the control of some factors such as initial equivalence ratio, reburn fuel fraction and temperature of reburn fuel injection region. Also it shows the fuel lean reburning is also effective method to reduce NOx as much as reburning.

• 한국자동차공학회논문집
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• 제24권3호
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• pp.345-351
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• 2016

This study was carried out to determine an optimal lean $NO_x$ trap (LNT) regeneration condition based on a $NO_x$ storage fraction. The LNT regeneration was performed by an in-cylinder post fuel injection method. A $NO_x$ storage fraction is defined by the ratio of current cumulated $NO_x$ amount in the LNT to the $NO_x$ storage capacity: 0 means empty and 1 fully loaded. In this study five engine operating conditions were chosen to represent the New European Driving Cycle. With various $NO_x$ storage fractions each engine operating condition, the LNT regeneration was executed and then $NO_x$ conversion efficiency, additional fuel consumption, CO and THC slip, peak catalyst temperature were measured. The results showed that there exist an optimal condition to regenerate the LNT, eg. 1500 rpm 6 bar BMEP with below 0.7 $NO_x$ storage fraction in this experimental constraint.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회B
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• pp.3452-3457
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• 2007

Experiments were carried out in an atmopheric pressure, lab-scale gas turbine combustor to see the effect of partial premixing on unstable flame structure and $NO_X$ emission characteristics. The swirl angle is 45 deg., fuel-air mixing degrees were varied 0, 50, and 100% respectively at equivalence ration ranging from 0.53 to 0.79. The evaluation of phased-locked OH chemiluminescence images were acquired with an ICCD. $NO_X$ emission characteristics were also investigated at each experimental condition. The effect of the fuel-air mixing degree on the flame structure was obtained from phase-locked $OH^*$ images. And it was obtained from local heat release characteristics that the information about the region which the combustion instability was amplified or damped. It also could be confirmed that ${\sigma}$ has greatly influence on $NO_X $emission characteristics at lean regimes. It would be expected that it could provide invaluable data for understanding the mechanism of combustion instability