排水下两相冲压式发动机是基于泡状两相流在Laval喷管中运动的理论开发的一种新型发动机。采用CFD数值分析的方法对水下两相冲压式发动机的工作机理进行了初步的研究。在定常流动工况下，不考虑空气的可压缩性和热交换，设来流速度和通气角度不变，得到了发动机内推力随通气参数变化的规律。通气速度为超音速的情况下，得到发动机的内推力随着通气速度的增大而增大，但是当通气速度达到一定范围时，发动机的内推力波动较大。通入单一空气时，温度对发动机内推力几乎没有影响。通入的空气体积流量不变且其中含有水蒸汽时，空气的湿度越大，发动机内推力就越小。

The underwater two-phase ramjet is one kind of the new style jet which is based on the development of the two phase bubbly flow throughout the Laval nozzle. The working mechanism of the ramjet is studied numerically by using CFD commercial software FLUENT 6.2. A steady flow, non-compressible air and non-exchanging heat are considered. When the velocity of the ship and the aeration angle is steady, and the aeration speed is supersonic, the inner thrust of the ramjet increases as the aeration speed increases. The inner thrust fluctuates in a wide range when the aeration speed increases to a very high speed. When the air is aerated only, the temperature of the air doesn’t have effect on the inner thrust almostly. While the gas aerated is composed of air and vapour, and the volume flux of the gas remains invariable, that the humidity of the gas increases causes a drop of the inner thrust of the underwater two-phase ramjet.