• 한국산업융합학회 논문집
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• 제18권4호
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• pp.197-206
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• 2015

Recently the automobile engine has been developed in achieving the high performance, fuel economy, and emission reduction. In a conventional spark ignition engine the fuel and air are mixed together in the intake system, inducted through the intake valve into the cylinder, and then compressed. Under normal operating conditions, the combustion is initiated towards the end of the compression stroke at the spark plug by an electric discharge. Following inflammation, a flame develops and propagates through this premixed fuel-air mixture. Therefore the state of mixture is very important in the combustion and emission characteristics. In this study the combustion and emission characteristics were tested and analyzed with changing the mixture composition and engine operating parameters in order to improve the combustion and performance in engine.

• 대한기계학회논문집B
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• 제22권7호
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• pp.1022-1029
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• 1998

The relation of the inlet fuel distribution, velocity, and overall equivalence ratio to the stability of a lean burning no-swirl dump combustor was examined. Premixed or partially premixed natural gas was introduced into the air stream, which flowed to the dump region through an annular inlet pipe. Inlet air was preheated upto 400 deg.C. Combustion instability was observed to occur at higher value of equivalence ratio (> 0.6) as the degree of unpremixedness was increased. Instabilities exhibited a dominant frequency of ~ 500 Hz, which corresponded to a half wave mode of combustor. CH chemiluminescence and pressure fluctuations were in-phase when combustion instabilities occurred. Acetone LIF images revealed that there was a strong fuel concentration gradient across the inlet annulus. Phase resolved OH LIF images showed that inlet fuel distribution was affected by the combustion instabilities.

• 한국수소및신에너지학회논문집
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• 제33권6호
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• pp.776-785
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• 2022

Hydrogen combustion in modern gas-turbine engine is the cutting edge technology as carbon-free energy conversion system. Flashback of hydrogen flame, however, is inevitable and critical specially for premixed hydrogen combustion. Therefore, this experimental investigation is conducted to understand flashback phenomenon in premixed hydrogen combustion. In order to investigate flashback characteristics in premixed hydrogen (H₂)/air flame, we focus on pressure conditions and nozzle shapes. In general, quenching distance reduces as pressure of combustion chamber increases, causing flashback from boundary layer near wall. The flashback regime for reference and modified candidate configurations can broadly appear with increasing combustion chamber pressure. The later one can improve flashback-resist by compensating flow velocity at wall. Also, improved wall flow velocity profile of suggested contraction nozzle prevents entire flashback but causes local flashback at nozzle exit.

• 한국연소학회지
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• 제9권4호
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• pp.35-46
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• 2004

Activation energy asymptotics (AEA) for Linan#s premixed-flame regime is revisited in this paper. First, the detailed AEA procedure for the premixed-flame regime is demonstrated, so that the practitioners of AEA could easily apply the method to their own problems. In addition, the controversies surrounding the premixed-flame regime, namely the closure controversy and fast-time instability paradox, are explained. Finally, the limitation of AEA, mainly arising from the wrong prediction of fuel leakage through the reaction zone, is examined and the Zel#dovich-Linan kinetics is introduced as an alternative to meet the needs of modern combustion analysis, where the detailed chemical structure of flame is demanded.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2007년도 제34회 KOSCO SYMPOSIUM 논문집
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• pp.7-12
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• 2007

To reveal the newly found liftoff height behavior of hydrogen jet, we have experimentally studied the stabilization mechanism of turbulent, lifted jet flames in a non-premixed condition. The objectives of the present research are to report the phenomenon of a liftoff height decreasing as increasing fuel velocity, to analyse the flame structure and behavior of the lifted jet, and to explain the mechanisms of flame stability in hydrogen turbulent non-premixed jet flames. The velocity of hydrogen was varied from 100 to 300m/s and a coaxial air velocity was fixed at 16m/s with a coflow air less than 0.1m/s. For the simultaneous measurement of velocity field and reaction zone. PIV and OH PLIF technique was used with two Nd:Yag lasers and CCD cameras. As results, it has been found that the stabilization of lifted hydrogen diffusion flames is related with a turbulent intensity, which means that combustion occurs where the local flow velocity is valanced with the turbulent flame propagation velocity.

• 한국연소학회지
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• 제14권4호
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• pp.48-53
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• 2009

This paper describes the forced flame response in a turbulent premixed gas turbine combustor. The fuel was premixed with the air upstream of a choked inlet to avoid equivalence ratio fluctuations. To impose the inlet flow velocity, a siren type modulation device was developed using an AC motor, rotating and static plates. Measurements were made of the velocity fluctuation in the nozzle using hot wire anemometry and of the heat release fluctuation in the combustor using chemiluminescence emission. The test results showed that flame length as well as geometry was strongly dependent upon modulation frequency in addition to operating conditions such as inlet velocity. Convection delay time between the velocity perturbation and heat release fluctuations was calculated using phase information of the transfer function, which agreed well with the results of flame length measurements. Also, basic characteristics of the flame nonlinear response shown in the current test conditions were introduced.

• 대한기계학회논문집B
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• 제32권12호
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• pp.970-976
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• 2008

Characteristics of methane turbulent non-premixed flame have been studied experimentally in coflow jets with initial temperature variation. The results showed that the premixed flame model and the large-scale mixing model for turbulent flame stabilization were effective for methane fuel considered initial temperature variation. Especially, the premixed flame model has been improved by considering nitrogen dilution for the liftoff height of turbulent lifted flame. In estimating blowout velocity and the liftoff height at blowout with the premixed flame model and the large-scale mixing model, the two turbulent models were excellently correlated by considering the effect of physical properties and buoyancy for the initial temperature variation.

• International Journal of Automotive Technology
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• 제6권2호
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• pp.79-85
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• 2005

This work is to investigate the surface heat flux and combustion characteristics of premixed propane mixture in a constant volume chamber. The experiment of heat flux and combustion characteristics of premixed propane mixture are performed with various equivalence ratio and initial pressure conditions. Based on the experimental results, it is found that the maximum instantaneous temperature is increased with the increase of initial pressure in the chamber. There are significant differences in the burning velocity of premixed propane mixture at different measuring points in the constant volume combustion chamber. A]so, the trends of temperature difference at each measuring points are similar to the burning velocity in the combustion chamber. It is concluded that the total heat loss during the combustion period is affected by the equivalence ratio and the initial condition of fuel-air mixture.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2017년도 제48회 춘계학술대회논문집
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• pp.612-616
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• 2017

비예혼합합화염과 예혼합화염의 화염응답특성을 속도섭동을 다양하게 변경하며 실험하였다. 연료로는 수소($H_2$)/메탄($CH_4$)을 50/50 %로 혼합한 혼합연료를 사용하였으며 산화제로는 공기를 사용하였다. OH 자발광(OH fluorescence)을 이용하여 화염이미지를 계측하였으며 PMT(Photo Multiplier Tube)를 이용하여 열 방출량을 계측하였다. 계측된 이미지는 MatLab 코드를 이용하여 수치화하였다. 예혼합화염의 결과에서는 진폭이 증가할수록 화염섭동이 증가하는 경향성을 보았으며 진폭에 따라서 화염전달 함수의 게인 값이 선형적인 거동을 하는 것을 관찰하였다. 비예혼합화염의 화염길이는 진폭이 증가할수록 짧아지는 것을 관찰하였고 게인 값은 진폭에 비선형적인 거동을 하는 것을 확인하였다.

• 한국가스학회지
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• 제24권4호
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• pp.25-31
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• 2020

산업용 혹은 발전용 가스터빈에 사용되는 이중 콘형 예혼합 연소기의 연소 특성을 이해하기 위하여 실험적 연구를 수행하였다. 노즐의 여러 연료 분사 방식에 대하여 NOx와 CO의 배출 특성, 화염 안정성 및 연소실 온도 분포에 대한 연소특성을 비교하였다. 주 연구 결과로는 연료홀 개수가 동일하고 연료 홀 직경이 감소하는 경우와 연료 홀면적이 동일하고 연료 홀 수가 감소되는 경우 연료의 연소용 공기층 침투가 커지기 때문에 NOx의 배출은 감소하지만 화염 안정성은 감소하게 된다. 그리고 동일 연료 홀 면적을 이용하는 분사방식에 있어서 연료 홀을 교차 변경하는 경우 연료의 평균 침투거리 증가로 NOx의 배출이 감소되며 연료 침투거리가 적은 연료가 화염을 안정화시키는 역할을 한다.