柴油机压缩过程紊流场规律的研究

在直喷式柴油机气缸和燃烧室中利用热线风速仪研究了紊流场的发展变化规律;在两种不同压缩间隙情况下对压缩过程中紊流场进行测量的结果表明,只有在压缩过程的初期及中期,紊流场才可以近似地当做均匀各向同性紊流场,而在循环的其它时间内,气缸和燃烧室内的紊流场属于非均匀各向异性的;通过对气缸和燃烧室中空气运动的力、能转换的分析,导出了上止点附近燃烧室内涡流转速的估算公式,利用该公式得到的结果与试验结果相当吻合。研究和探讨了燃烧室中空气涡流和紊流强度增加的原因及其影响因素。

A STUDY OF THE VARIATION OF THE TURBULENT FLOW FIELD IN CYLINDER DURING COMPRESSION STROKE OF A D. I. DIESEL ENGINE

An investigation of the development and variation of the turbulent flow field in the cylinder and combustion chamber of a D. I. diesel engine was carried out by using the hot-wire anemometry. The measurements of the flow field were conducted throughout the compression stroke and at two different minimum clearances between the piston and cylinder head. The results show that the flow field may be considered approximately as a homogeneous and isotropical turbulent flow field only in the early and middle stages of the compression stroke. In the other partS of the cycle, however, the turbulent flow field inside the cylinder and the combustion chamber is nonhomogeneous and nonisotropic. An analysis is made of the force and energy conversion for the air motion in the cylinder and combustion chamber. A formula for predicting the swirl speed at T. D. C. in the combustion chamber is deduced. The results obtained by this formula agree quite well with the experimental results. The reasons for the increase in swirl speed and turbulence intensity inside the chamber and the factors influencing them are also studied and discussed.