• 한국연소학회지
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• 제17권2호
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• pp.24-31
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• 2012

Diesel engines exhaust much more NOx(Nitrogen Oxides) and PM(Particulate Matter) than gasoline engines, and it is not easy to reduce both NOx and PM simultaneously because of the trade-off relation between two components. This study investigated flame characteristics of the partial premixed compression ignition known as new combustion method which can reduce NOx and PM simultaneously. The investigation was performed through the analysis of the flame images taken by a high speed camera from the visible engine which is the modified single cylinder diesel engine. The results obtained through this investigation are summarized as follows; (1) The area of the luminous yellow flame was reduced due to the decrease of flame temperature and even distribution of temperature. (2) The darkish yellow flame zone caused by the shortage of the remaining oxygen after the middle stage of combustion was considerably reduced. (3) Since the ignition delay was shortened, the violent combustion did not occur and the combustion duration became shortened.

• 한국분무공학회지
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• 제6권3호
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• pp.1-7
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• 2001

In this study, quantitative measurement of nitric oxide concentration distributions visualization were investigated in the laminar $CH_4/O_2N_2$ nixed flame by Planar laser-induced fluorescence(PLIF). The NO A-X (0,0) vibrational band around 226nm was excited using a XeCl excimer-pumped dye laser. Selecting an appropriate NO transition minimizes interference from Rayleigh scattering and $O_2$ fluorescence. The measurements were taken in $CH_4/O_2N_2$ premixed flame with equivalence ratios varying from $1.0{\sim}1.6$, and a fixed flow rate of 3slpm. NO was found to produce primarily between an inner premixed and an outer nonpremixed flame front, and total NO concentration is raised when equivalence ratios increase. These results suggest that prompt NO is likely to contribute to MO formation in $CH_4/O_2N_2$ premixed flame. Furthermore, this trend was well matched with previous works.

• 한국연소학회지
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• 제21권3호
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• pp.7-15
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• 2016

The fuel in conventional liquid fuel combustor is atomized by spray method for high efficiency and low emissions. To improve the overall fuel efficiency and lower pollutant emissions in liquid fuel combustion systems, the effective spatial and temporal separation of droplet evaporation from normal spray process is needed. In this paper, the recuperation of high temperature burnt gas for fuel evaporation was proposed to develop a cylindrical premixed combustor. The recuperation process using U shaped tube is effective to evaporate the liquid fuel. The results show that the flame mode is changed into red radiation flame, blue flame and lift off flame with decreasing equivalence ratio as gas fuel combustion mode. In particular, the blue flame is found to be very stable at heating load 9.2 kW and equivalence ratio 0.731. NOx was measured blow 105 ppm ($O_2$ zero base) from equivalence ratio 0.705 to 0.835. CO which is a very important emission index in liquid fuel combustor was observed below 5 ppm ($O_2$ zero base) under the same equivalence region.

• 한국분무공학회지
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• 제29권1호
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• pp.38-44
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• 2024

This study investigates the flow characteristics of propane-air premixed flames on AC electric field using the Schlieren method. A voltage was applied to the ring electrode and the burner was grounded to form an electric field, and the applied voltage was fixed at 16 kV (V_pp). Results show that under the application of AC electric fields, flow around the flame oscillated only at frequencies below 50 Hz, and no oscillation was observed above this frequency range. Flame height oscillated with frequency in the range of 25 to 300 Hz, with frequency doubling observed in the range of 25 to 150 Hz. The flammability limit increased with frequency up to 250 Hz, but in the high-frequency range above 250 Hz, the flammability limit did not increased and converged.

• 한국분무공학회지
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• 제8권4호
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• pp.24-30
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• 2003

This paper presents the characteristics of lifted height and flame length from non-premixed jet flames in highly preheated air to investigate the detail combustion mechanism in the gas turbine or HCCI engine, etc. Special attention was paid to the effect of preheated air temperature, oxygen concentration and fuel injection flow rate on flame length and lifted hight. By using highly preheated air, stable flames were formed even in low oxygen concentration condition. The lifted height increased with decreasing preheated air temperature, where the flame length showed opposed phenomena. The flamelet model, which is thought to have very thin flamelet, is difficult to applicable to the present flame conditions which is formed In low oxygen concentration in highly preheated air.

• 한국분무공학회지
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• 제28권1호
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• pp.24-31
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• 2023

In this study, characteristics of a propane-air premixed flame sin DC electric field was investigated. The stainless steel Bunsen burner and the stainless steel ring were used as electrode, and the high voltage supply was used for applying electric field. Flammability range increased significantly when the positive voltage was applied because of extension of LBO limit, while it shrank when the negative voltage was applied. The reason for this was not much related to the burning velocity, but the induced flow around the burner by electric field. withNOx production slightly increased after positive voltage was applied in identical equivalence ratio. Nevertheless, it was advantageous to apply the positive electric field to reduce the NOx since the extension of LBO limit makes the burner possible to operate in very low equivalence ratio.

• 대한환경공학회지
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• 제31권6호
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• pp.442-448
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• 2009

예혼합 분무화염의 유적군 연소 기구를 평가하기 위하여 레이저 가시화법, MICRO (multi-color integrated Cassegrain receiving optics) 및 PDA (phase Doppler anemometer) 광학계측 시스템을 이용하여 동시 시계열 계측을 실시하였다. 또한 유적군의 군연소수를 실험적으로 산출하여 이론해석에 적용하였을 경우 실제로 관찰되는 군연소 형태와 일치하는지에 대하여 검토하였다. 유적군 단면화상에 의해 확인된 모든 유적군에 대하여 실험적으로 군연소수 $G_c$를 산출한 결과 주로 내부 군연소와 외부 군연소로 분류되었으며 이론해석과 일치하였다. 또한 실제 관찰된 군연소 형태와 그 유적군의 군연소수를 이론해석에 적용한 경우에 군연소 형태가 일치하는 경우와 일치하지 않는 경우가 있었다. 일치하지 않는 원인은 군연소수를 유적의 기하학적 배치만으로 결정한 것이나 현상의 3차원성이 측정 결과에 영향을 미친 것이라고 생각되어진다.

• 한국자동차공학회논문집
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• 제23권4호
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• pp.402-409
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• 2015

In this study a quasi-dimensional model is developed to predict the combustion process and emissions of a GDI engine under ultra-lean conditions. Combustion of a GDI engine condition is modeled as two simultaneous processes to consider significant fuel stratification. The first process is premixed flame propagation described as burning in a hemispherically propagating flame. The second is diffusion-controlled combustion modeled as mixing of multiple spray zones in the burned gas region. Mixing is an important factor in ultra-lean conditions leaving stratified mixture of developing sprays behind the propagating premixed flame. Sheet breakup and Hiroyasu models are applied to predict the velocity of a hollow cone spray. Validation is performed against measured pressures and NOx and CO emissions at different load and rpm conditions in the test engine.

• 한국분무공학회지
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• 제28권3호
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• pp.134-142
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• 2023

Electric field assisted combustion is a method that reduces instability in lean combustion. In this study investigated the effects of electrode position on propane-air flame characteristic using a ring electrode. Results showed that burning velocity was not affected by electrode position, but positive voltage expanded the flammability limit while negative voltage contracted it. The effect of voltage polarity on the flammability limit decreased as the electrode position increased. Expanding the flammability limit with a positive voltage can reduce NOx emissions.

• Journal of Mechanical Science and Technology
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• 제17권1호
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• pp.139-145
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• 2003

Diode laser sensor is conducted to measure the gas temperature in the liquid-gas 2-phase counter flow flame. C$\_$10/H/ sub 22/ and city gas were used as liquid fuel and gas fuel, respectively. Two vibrational overtones of H$_2$O were selected and measurements were carried out in the spray flame region stabilized the above gaseous premixed flame. The path-averaged temperature measurement using diode laser absorption method succeeded in the liquid fuel combustion environment regardless of droplets of wide range diameter. The path-averaged temperature measured in the post flame of liquid-gas 2-phase counter flow flame showed qualitative reliable results. The successful demonstration of time series temperature measurement in the liquid-gas 2-phase counter flow flame gave us motivation of trying to establish the effective control system in practical combustion system. These results demonstrated the ability of real-time feedback from combustor inside using the non-intrusive measurement as well as the possibility of application to practical combustion system. Failure case due to influence of spray flame was also discussed.