针对两次进水的镁基水冲压发动机,对发动机总体的燃烧室长度和一次、二次进水距离设计方法进行了研究。根据理论分析和试验测温结果,提出金属镁以熔融液滴形式进入燃烧室,镁滴燃烧为蒸气相扩散燃烧过程。采用简化的D^3/2定律计算镁滴燃烧时间,并以镁滴燃烧和雾化水滴蒸发所需时间为依据,建立了燃烧室长度和一次、二次进水距离设计方法。参照该方法对某型试验水冲压发动机构型进行了改进,两种构型发动机的地面直连试验结果表明,改进构型后的水冲压发动机性能得到较大提高,验证了该设计方法的有效性。

Magnesium-based water ramjets with two water intakes are known for their better performances than those with only one intake. This article studies the design of the combustion chamber length and water intake distance on this type of water ramjets. Theoretical anlysis and experimental temperature data indicate that magnesium enters the combustion chamber as molten droplets, and the burning process of the droplets is controlled by vapor-phase diffusion. A simplified D^3/2 law is used to calculate the droplet burning time. A method to design the combustion chamber length and water intake distance is developed on the basis of magnesium burning time and water evaporization time. The structure of a water ramjet prototype is improved with this method, and comparison tests are conducted for the two structures in a ground direct-connect testing system. An enhanced engine performance is obtained with the improved structure in the tests, which also testify the validity of the design method.