• Journal of the Korean Society of Propulsion Engineers
• /
• v.18 no.6
• /
• pp.11-18
• /
• 2014

The combustion flowfield at the near-injector region of a 50 N scale $N_2O/C_2H_5OH$ thruster was visualized using shadowgraph technique. The explosive ignition was occurred at the design spray condition, and the expanding combustion gas quenched the flame immediately. Approximately after 83 ms from the initial ignition, the propellant spray was re-ignited, and the flame was stabilized after 23 ms elapsed. In the increased oxidizer flow rate condition, the transient pressure at the moment of ignition was smoother than explosive ignition, and the blow down phenomenon was not appeared in the same operating sequence. In addition, the flame was stabilized within 17 ms, and it is caused by improved propellants mixing before ignition.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.22 no.2
• /
• pp.96-107
• /
• 2018

Flow analysis using computational fluid dynamics was conducted to investigate the effect of the igniter flame caused by the gap between the igniter and the propellant grain in a solid rocket motor. Two propellant grain types were assumed; namely cylinder type (1 mm, 3 mm, and 5 mm gap) and the slot type. The slot type had two igniter hole locations. One was located at the small gap of the propellant grain, and the other one was located at the large gap. In the case of the cylinder type, the pressure in the igniter zone was higher with a thinner gap. Additionally, in the case of the cylinder type, the pressure difference between the igniter installed zone and the free volume was also higher as the gap became lower. The cylinder types were affected by the gap distance, but the slot types were not. Moreover, the results of the slot types were similar to the 5-mm gap case of the cylinder type.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.23 no.3
• /
• pp.1-8
• /
• 2019

In this study, Arc plasma was employed for the thermal decomposition of nitrous oxide($N_2O$). Conventional ignition systems such as torch, spark, and catalyst systems, have disadvantages in that they are not reliable and do not provide rapid responses. Therefore, this study suggests the plasma application of plasma to overcome the problems of conventional ignition methods. A gas temperature and combustion experiment was carried out to investigate the feasibility to a novel igniter. The gas temperature was measured around $960^{\circ}C$ at 1 g/s, 0.7 A at the nearest wall. In addition, a combustion test was successfully conducted in 3.1 sec after the plasma discharge was initiated with a main flow rate of 10 g/s. The energy consumption for ignition was 1,780 J(574 W).

• Fire Science and Engineering
• /
• v.27 no.6
• /
• pp.50-56
• /
• 2013

The radiation effects on the auto-ignition and extinction characteristics of a non-premixed fuel-air counterflow field were numerically investigated. A detailed reaction mechanism of GRI-v3.0 was used for the calculation of chemical reactions and the optically-thin radiation model was adopted in the simulations. The flame-controlling continuation method was also used in the simulation to predict the auto-ignition point and extinction limits precisely. As a result, it was found that the maximum H radical concentration, $(Y_H)_{max}$, rather than the maximum temperature was suitable to understand the ignition and extinction behaviors. S-, C- and O-curves, which were well known from the previous theory, were identified by investigating the $(Y_H)_{max}$. The radiative heat loss fraction ($f_r$) and spatially-integrated heat release rate (IHRR) were introduced to grasp each extinction mechanism. It was also found that the $f_r$ was the highest at the radiative extinction limit. At the flame stretch extinction limit, the flame was extinguished due to the conductive heat loss which attributed to the high strain rate although the heat release rate was the highest. The radiation affected on the radiative extinction limit and auto-ignition point considerably, however the effect on the flame stretch extinction limit was negligible. A stable flame regime defined by the region between each extinction limit became wide with increasing the fuel temperature.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.35 no.5
• /
• pp.451-457
• /
• 2011

The main objective of this study is to investigate the variation in the ignition characteristics of coals as a function of moisture content in a laminar flow reactor (LFR) equipped with a fuel moisture micro-supplier designed by the Pusan Clean Coal Center. The volatile ignition position and time were observed experimentally when a pulverized coal with moisture was fed into the LFR under burning conditions similar to those at the exit of the pulverizer and real boiler. The reaction-zone temperature along the centerline of the reactor was measured with a $70-{\mu}m$, R-type thermocouple. For different moisture contents, the volatile ignition position was determined based on an average of 15 to 20 images captured by a CCD camera using a proprietary image-processing technique. The reaction zone decreased proportionally as a function of the moisture content. As the moisture content increased, the volatile ignition positions were 2.92, 3.36, 3.96, and 4.65 mm corresponding to ignition times of 1.46, 1.68, 2.00, and 2.33 ms, respectively. These results indicate that the ignition position and time increased exponentially. We also calculated the ignition-delay time derived from the adiabatic thermal explosion. It showed a trend that was similar to that of the experimental data.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
• /
• 2000.04a
• /
• pp.165-174
• /
• 2000

새로운 에너지원으로 개발된 오리멀젼의 국내 활용에 관한 기술적인 특성을 파악하기 위하여 연료 특성과 연소에 대한 실험적인 연구를 수행하였다. 연료저장을 위한 최적온도는 6$0^{\circ}C$이었으며 온도가 낮으면 점화특성이 불량하고 너무 상승하는 경우에는 계면분리 현상이 보였다. 연소를 위해 필요한 연소실온도는 $600^{\circ}C$ 이상이 요구되었고 수분의 비등폭발에 의해 2차 연소가 특징적으로 관찰되었다. 오리멀젼 연소시 배기가스중 오염물질 농도는 과잉공기비에 SO$_2$ 가 1700-2200ppm , NOx 100-150ppm 으로 측정되었다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2004.10a
• /
• pp.43-46
• /
• 2004

This work is experimental study about a nozzle part in the aerodynamic igniter using only compressible gas. In study, constructions of the aerodynamic igniter using a supersonic nozzle and an aerospike nozzle have been introduced, and experimental results(mainly max. heating temperature characteristics) have been presented. Using of the supersonic nozzle leads to faster and higher temperature in same mass flow, and the aerospike nozzle works in wide variable range of pressure.

• 한국연소학회:학술대회논문집
• /
• 2012.11a
• /
• pp.153-156
• /
• 2012

Direct numerical simulations (DNSs) of ignition of lean primary reference fuel (PRF)/air mixtures under homogeneous charge compression ignition (HCCI) conditions are performed using 116-species reduced chemistry. The influence of variations in the initial temperature field, imposed by changing the variance of temperature, and the fuel composition on ignition of lean PRF/air mixtures is studied using the displacement speed analysis.

• Journal of the korean Society of Automotive Engineers
• /
• v.12 no.1
• /
• pp.6-9
• /
• 1990

본 고에서는 녹킹현상과 녹킹 발생의 결과, 그리고 녹킹과 연료와의 관계등에 대해 개략적으로 설명하려 한다. 녹킹 발생 유무는 흡입공기상태, 스로틀 열림정도, 연소실 형상, 스파크 점화시기, 화염 전파속도 및 연료의 자연 발화 특성에 관계되며 화염 전파속도와 end-gas에 있는 연로의 반응속도와의 경쟁이라 볼수 있다. 연료의 녹킹 발생에 대한 저항성을 나탄내는 척도가 옥탄가이며 옥탄가가 높을 수록 자연 발화하기 어려우므로 녹킹이 잘 일어나지 않는다.

• Journal of Energy Engineering
• /
• v.18 no.3
• /
• pp.163-168
• /
• 2009

This paper describes the homogeneous charge compression ignition (HCCI) engine for a new concept. HCCI engines are being considered as a future alternative for diesel and gasoline engines. HCCI engines have the potential for high indicated thermal efficiency under part load and very low NOx emissions. The objective of this paper is to clear the effects of exhaust gas recirculation (EGR) rate on the HCCI. For this purpose, a 4-cylinder, compression ignition engine was converted into a HCCI engine This work has been run with propane and butane fuels at a constant speed.