共查询到20条相似文献,搜索用时 93 毫秒
1.
采用最新的二甲醚(DME)化学动力学反应机理(DME氧化机理包括399个基元反应,涉及79种组分),利用LawrenceLivermore国家实验室开发的HCT软件,进行DME均质充量压燃着火过程的变参数研究。从理论上分析讨论进气温度、进气压力、燃空当量比、发动机转速对燃烧的影响。研究结果表明:DME的均质充量压燃(HCCI)燃烧过程有明显的两阶段,进气温度、进气压力、燃空当量比和发动机转速等参数的改变都会导致DME均质压缩燃烧过程的变化。 相似文献
2.
3.
为了研究HCCI发动机着火控制时刻影响因素,建立了模拟HCCI发动机燃烧的计算模型,以甲烷/丙烷混合物和正庚烷/异辛烷混合物作为燃料,考察了十六烷值、辛烷值、压缩比、燃空当量比、进气温度和压力等因素对HCCI发动机着火时刻的影响.计算结果表明:随着燃料十六烷值的减小或辛烷值的增加,相同条件下燃料的着火延迟期增加;压缩比、燃空当量比和进气温度的变化会引起燃料着火时刻的显著变化;进气压力的变化对燃料着火延迟期的影响较小;气体十六烷值越低,辛烷值越大,着火延迟期受上述参数变化影响越大.研究结果为HCCI发动机的优化设计和燃烧控制提供指导依据. 相似文献
4.
在相同条件下对二甲醚(methoxymethane,DME)、乙醇和甲烷进行均质压燃(homogeneous charge compression ignition,HCCI)燃烧的模拟,改变压缩始点的缸内温度及压力、压缩比、燃空当量比中的一个以考察其对三种燃料HCCI燃烧过程的影响.随着压缩始点温度和压力、压缩比的提高,三种燃料的着火时刻都提前;提高燃空当量比,DME的着火时刻提前,而甲烷和乙醇则相反;三种燃料低温下的主要脱氢途径都是与OH自由基发生的脱氢反应;三种燃料实现HCCI燃烧的条件不一样,模拟结果给出了大致的趋势. 相似文献
5.
二甲醚发动机燃烧特性的试验与数值模拟研究 总被引:6,自引:0,他引:6
在一台直喷式压燃发动机上开展了二甲醚燃烧与排放特性的试验与数值模拟研究。测量了二甲醚在高压燃油泵内的泄漏量及其与发动机转速之间的定量关系,并就发动机分别燃用二甲醚和柴油的运转性能进行了对比试验研究,结果表明,发动机燃用二甲醚要比燃用柴油具有更好的性能与排放水平;另从二甲醚低温着火的化学反应机理人手,开展了其自燃着火过程的数值模拟研究,进而建立了计及温度、压力和燃空当量比因素的DME滞燃期数据库;通过将该数据库与发动机循环模拟程序相耦合,对DME发动机的运转性能进行了变参数预测分析,预测结果与试验结果吻合较好。 相似文献
6.
压缩比、CO2对二甲醚均质压燃影响的数值模拟 总被引:1,自引:0,他引:1
利用化学反应动力学软件建立二甲醚均质压燃燃烧模型,研究了压缩比和进气掺入CO2对二甲醚均质燃烧的影响。结果表明:增大压缩比加快了二甲醚基元反应速率,使着火提前,燃烧压力、温度上升;进气中加入CO2可以延迟着火时刻,降低缸内压力和温度;CO2对二甲醚均质压燃高温燃烧阶段影响更大。 相似文献
7.
在一台由CA6110柴油机改造而成的单缸发动机上进行了燃烧边界条件对乙醇燃料均质压燃(HCCI)燃烧过程影响的试验研究。结果表明,在转速和进气温度一定时,随着过量空气系数的增加,着火始点推迟,燃烧持续期变长,缸内的最大燃烧压力降低,放热率降低,φ50(50%乙醇燃烧放热量所在的曲轴转角)位置推迟,燃烧效率降低;在发动机转速、进气温度和过量空气系数一定时,随着EGR率的升高,着火始点推迟,燃烧持续期延长,φ50位置推迟,放热速率降低,压力升高率变小,缸内最大燃烧压力减小,燃烧效率降低。在转速和供油量一定时,随着进气温度的升高,着火始点提前,燃烧持续期变短,压力升高率变大,缸内的最大燃烧压力变大。得到了发动机转速、过量空气系数和对应于最大指示热效率点的进气温度间的MAP图。 相似文献
8.
9.
应用多区模型预测了均质压燃(HCCI)发动机的运行范围.运行范围的边界由敲缸(由声响强度计算)、部分燃烧(由燃烧效率计算)和循环变动(由平均有效压力对进气温度的敏感度计算)确定.通过模拟一台以异辛烷为燃料的HCCI发动机发现,在不同当量比和进气温度下,计算得到的敲缸极限和循环变动极限均与试验相当吻合,从而很好地再现了HCCI发动机的运行范围.进一步研究运行范围随转速的变化,讨论了通过调节进气温度和当量比,在不同转速下HCCI发动机的最大可运行范围.最后考察了通过使用变压缩比和增压两种策略扩展HCCI发动机运行范围的潜力.结果表明:通过调节压缩比可以有效地控制着火点,在向低负荷扩展方面,使用高的进气温度和较低的压缩比显得更为有利;在向高负荷扩展方面,使用高压缩比更好;而增压有利于HCCI发动机的控制,同时增加了向高负荷扩展的范围. 相似文献
10.
采用数值模拟方法研究了第一参比燃料(PRF50)的低温重整过程及其产物对压燃式发动机燃烧和排放特性的影响。研究结果表明,PRF50燃料的低温重整区域随当量比的增加而增大,初始温度和压力的选择范围变化有限,并且PRF50燃料发生低温反应的触发界线开始向较高的初始进气温度方向移动;初始进气温度和当量比对重整过程的影响要大于初始压力的影响;PRF50燃料的低温重整产物均可使PRF50燃料均质充量压燃的燃烧相位提前,且重整产物的加入改善了发动机有害排放中一氧化碳、未燃碳氢和氮氧化物的排放,指示热效率也可提高约3.0%。 相似文献
11.
12.
13.
14.
An experimental opposed flow diffusion flame system has been developed with which polymer ignition may be carefully investigated. The effects of ignition source intensity, oxidizer flow rate, and oxidizer composition on the ignition of polyoxymethylene have been studied. Comparisons with available theoretical models have been made where possible. It is concluded that the polymer surface temperature at ignition is independent of ignition source intensity, oxidizer composition, and oxidizer flow rate; that the ignition delay time is independent of oxidizer velocity over the range of velocities for which a flat flame can be established in the opposed flow diffusion flame system; that gas phase absorption of radiation may affect the ignition process even for relatively small optical depths and low source intensities; that the ignition delay time decreases linearly with increasing oxygen concentration in mixtures for low flame stretch rates; that ignition occurs during the transition stage when the free stream oxygen mass fraction is less than the oxygen mass fraction in the solid, and for higher free stream oxygen mass fractions it appears that oxygen diffusion to the surface is enhancing the gasification rate during the transition stage and/or decreasing the period of the transition stage; and that the various processes occurring in the gas phase during the ignition event appear to result in a net liberation of energy. 相似文献
15.
本文分析了摩托车点火系统的初级回路,给出了初级能量与初级回路的各种参数的关系式,为精确控制点火能量及其可靠性提供了理论依据。 相似文献
16.
17.
Ignition of turbulent non-premixed flames 总被引:3,自引:0,他引:3
The initiation of turbulent non-premixed combustion of gaseous fuels through autoignition and through spark ignition is reviewed, motivated by the increasing relevance of these phenomena for new combustion technologies. The fundamentals of the associated turbulent-chemistry interactions are emphasized. Background information from corresponding laminar flow problems, relevant turbulent combustion modelling approaches, and the ignition of turbulent sprays are included. For both autoignition and spark ignition, examination of the reaction zones in mixture fraction space is revealing. We review experimental and numerical data on the stochastic nature of the emergence of autoignition kernels and of the creation of kernels and subsequent flame establishment following spark ignition, aiming to reveal the particular facet of the turbulence causing the stochasticity. In contrast to fully-fledged turbulent combustion where the effects of turbulence on the reaction are reasonably well-established, at least qualitatively, here the turbulence can cause trends that are not straightforward. 相似文献
18.
聚氨酯泡沫材料阴燃的点燃过程 总被引:5,自引:0,他引:5
阴燃材料的点燃系指材料在受到外热源加热后,依靠其自身异相氧化反应所放出的热量实现阴燃自维持传播的前期过程,如果导致熄灭则称不能点燃.聚氨酯泡沫材料在受到加热时,热流密度和加热时间是实现点燃的两大因素.在自然对流条件下,热流密度在1.6~6.8kw/m^2之间能实现阴燃材料的点燃.通过积分模型分析,得出了实现点燃的临界表达式.该式表明在一定的外部条件下,点燃成功表现为需要一个确定厚度的初始高温反应区(炭层).在不同热流值的实验中,实现点燃的临界炭层厚度大约为40mm,实验结果与理论分析能够较好吻合. 相似文献
19.
20.
Initiation energy requirements for condensed phase systems were determined experimentally and analytically and found to obey a diffusion-limited reaction model. A model is described for the evaluation of the threshold input energy either by computer calculations or by approximate formulas. The use of dimensionless variables greatly reduces the necessary number of computer runs and simplifies the derivation of explicit expressions. The results are useful both for parametric study and theoretical prediction. It was found that initiation is promoted by low thermal conductance, low heat capacity, small particle sizes, and high heat of reaction. This method of analysis can also assess the effects of varying the energy deposition time. The predicted data are in reasonable agreement with experimental results which were obtained using pulsed and continuous wave lasers. The theoretical model is expected to be useful in the study of reaction phenomena associated with thermite and intermetallic pyrotechnics as well as in the study of certain metallurgical processes. 相似文献