物理化学学报 >> 2019, Vol. 35 >> Issue (6): 591-597.doi: 10.3866/PKU.WHXB201806042

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煤油裂解产物/空气与煤油/空气在宽温度范围内点火延迟的对比研究

王易君,张德翔,万中军,李萍*(),张昌华   

  • 收稿日期:2018-06-21 录用日期:2018-07-27 发布日期:2018-10-31
  • 通讯作者: 李萍 E-mail:lpscun@scu.edu.cn
  • 基金资助:
    国家重点研发计划(2017YFB0202400);国家重点研发计划(2017YFB0202401)

A Comparative Study of Ignition Delay of Cracked Kerosene/Air and Kerosene/Air over a Wide Temperature Range

Yijun WANG,Dexiang ZHANG,Zhongjun WAN,Ping LI*(),Changhua ZHANG   

  • Received:2018-06-21 Accepted:2018-07-27 Published:2018-10-31
  • Contact: Ping LI E-mail:lpscun@scu.edu.cn
  • Supported by:
    The project was supported by the National Key R & D Program of China(2017YFB0202400);The project was supported by the National Key R & D Program of China(2017YFB0202401)

摘要:

煤油是一种理想的吸热性碳氢燃料,其热裂解在高速飞行器的热防护中起着重要作用。本工作利用加热激波管测量了煤油裂解产物/空气和煤油/空气的点火延时,点火温度657–1333 K,化学计量比1.0,点火压力1.01 × 105–10.10 × 105 Pa。通过对高温点火延时数据的拟合获得了两种混合物关于点火延时间和点火条件(温度和压力)的Arrhenius型关系。测量结果显示,在高温区(> 1000 K)两种混合物的点火延时很接近,并且点火延时随着温度或压力的增加而变短。但在低温区(< 1000 K),两种混合物的点火延迟特性却非常不同。煤油裂解产物的点火延时在此低温区域仍然随着温度的减小而增长,没有出现着火延迟的负温度效应;煤油的点火延迟在此温度区域却表现出明显的负温度效应。在830–1000 K温度区间,煤油裂解产物的点火延时快于煤油的;当温度低于830 K时,煤油的点火延迟时却变得比煤油裂解产物的快很多。本实验结果与机理模拟结果的比较显示,对煤油裂解产物和煤油燃烧反应机理的完善是必要的。本研究结果对了解煤油裂解产物的点火延迟特性和发展高速飞行器再生冷却技术非常有帮助。

关键词: 煤油裂解产物, 煤油, 火延迟时间, 加热激波管

Abstract:

Kerosene is an ideal endothermic hydrocarbon. Its pyrolysis plays a significant role in the thermal protection for high-speed aircraft. Before it reacts, kerosene experiences thermal decomposition in the heat exchanger and produces cracked products. Thus, to use cracked kerosene instead of pure kerosene, knowledge of their ignition properties is needed. In this study, ignition delay times of cracked kerosene/air and kerosene/air were measured in a heated shock tube at temperatures of 657–1333 K, an equivalence ratio of 1.0, and pressures of 1.01 × 105–10.10 × 105 Pa. Ignition delay time was defined as the time interval between the arrival of the reflected shock and the occurrence of the steepest rise of excited-state CH species (CH*) emission at the sidewall measurement location. Pure helium was used as the driver gas for high-temperature measurements in which test times needed to be shorter than 1.5 ms, and tailored mixtures of He/Ar were used when test times could reach up to 15 ms. Arrhenius-type formulas for the relationship between ignition delay time and ignition conditions (temperature and pressure) were obtained by correlating the measured high-temperature data of both fuels. The results reveal that the ignition delay times of both fuels are close, and an increase in the pressure or temperature causes a decrease in the ignition delay time in the high-temperature region (> 1000 K). Both fuels exhibit similar high-temperature ignition delay properties, because they have close pressure exponents (cracked kerosene: τignP-0.85; kerosene:τignP-0.83) and global activation energies (cracked kerosene: Ea = 143.37 kJ·mol-1; kerosene: Ea = 144.29 kJ·mol-1). However, in the low-temperature region (< 1000 K), ignition delay characteristics are quite different. For cracked kerosene/air, while the decrease in the temperature still results in an increase in the ignition delay time, the negative temperature coefficient (NTC) of ignition delay does not occur, and the low-temperature ignition data still can be correlated by an Arrhenius-type formula with a much smaller global activation energy compared to that at high temperatures. However, for kerosene/air, this NTC phenomenon was observed, and the Arrhenius-type formula fails to correlate its low-temperature ignition data. At temperatures ranging from 830 to 1000 K, the cracked kerosene ignites faster than the kerosene; at temperatures below 830 K, kerosene ignition delay times become much shorter than those of cracked kerosene. Surrogates for cracked kerosene and kerosene are proposed based on the H/C ratio and average molecular weight in order to simulate ignition delay times for cracked kerosene/air and kerosene/air. The simulation results are in fairly good agreement with current experimental data for the two fuels at high temperatures (> 1000 K). However, in the low-temperature NTC region, the results are in very good agreement with kerosene ignition delay data but disagree with cracked kerosene ignition delay data. The comparison between experimental data and model predictions indicates that refinement of the reaction mechanisms for cracked kerosene and kerosene is needed. These test results are helpful to understand ignition properties of cracked kerosene in developing regenerative cooling technology for high-speed aircraft.

Key words: Cracked kerosene, Kerosene, Ignition delay time, Heated shock tube

MSC2000: 

  • O643