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Effect of Mixture Condition on Combustion of Fuel〜Air Inhomogeneous Mixture in a Constant-Volume Vessel

混合条件对定容容器内燃料〜空气不均匀混合物燃烧的影响

基本信息

批准号：
10650212
负责人：
TOMITA Eiji
金额：
$ 2.24万
依托单位：
OKAYAMA UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1998
资助国家：
日本
起止时间：
1998 至 1999
项目状态：
已结题

项目摘要

Recently direct injection stratified charge spark-ignition engines have appeared in the commercial market. The thermal efficiency of these engines increased enormously around light duty of the driving. The combustion in these engines is probably due to the flame propagation under concentration gradient of the fuel from rich or stoichiometric to lean mixture, however, precise mechanism has not been revealed yet. Research of such propagation has been hardly done. Therefore, the purpose of this study is to investigate the combustion without turbulence fundamentally. The vessel of 25mm in diameter and 200mm in length was used. Propane was supplied from near the lower side of the vessel during a certain period. After that, the fuel of propane diffuses gradually to the upward direction and forms gradient of fuel concentration. At first, the change of the fuel concentration field along the vessel was confirmed with laser induced fluorescence (LIF) without combustion. Second, the mixture was ignited by a spark at the bottom of the vessel and the flame development was observed by high-speed Schlieren photographs. The initial and main stages of the combustion and the maximum of the pressure were analyzed from the pressure history in the vessel. The effects of the fuel concentration near the spark plug and fuel concentration field in the vessel were discussed. In homogeneous mixtures, the flames have the tendency of changing to the tulip flame in the middle of the vessel. However, in stratified concentration field, the tendency becomes weaker and the flame quenches on the way of the development due to the existence of the lean mixture before the end of the vessel. And radical species of CH, OH and C2 from the flame were detected with a monochrometer by changing the wavelength. In the near future, the observation of the quenching of the flame will be needed in detail and the relation between the flame and the Lewis number or diffusion coefficient will be discussed.

最近，直接喷射分层充气火花点火发动机已经出现在商业市场上。这些发动机的热效率大大增加了轻负荷的驾驶。这些发动机中的燃烧可能是由于燃料从浓混合气或化学计量混合气到稀混合气的浓度梯度下的火焰传播造成的，但精确的机理尚未揭示。这种传播的研究几乎没有做过。因此，本研究的目的是从根本上研究无湍流燃烧。血管直径25mm，长200mm。在一定时间内，丙烷从容器下侧附近供应。之后，丙烷燃料逐渐向上扩散，形成燃料浓度梯度。首先，在没有燃烧的情况下，用激光诱导荧光（LIF）确认了燃料浓度场沿着容器的变化。第二，混合物被点燃的火花在底部的容器和火焰的发展是由高速纹影照片观察。根据压力历程分析了燃烧的初始阶段、主要阶段和压力峰值。讨论了火花塞附近燃油浓度场和容器内燃油浓度场的影响。在均匀混合物中，火焰在容器中部有向郁金香火焰转变的趋势。而在分层浓度场中，由于容器端部前稀薄混合气的存在，这种趋势减弱，火焰在发展过程中熄灭。用单色仪通过改变波长检测火焰中CH、OH和C2自由基物种。在不久的将来，需要详细观察火焰的熄灭，并讨论火焰与刘易斯数或扩散系数之间的关系。