Research On The Flow Characteristics Of The Super-heated Hot Water Jet Engine

The super-heated hot water jet engine is a kind of new propeller using hot water as propellant which can generate huge thrust in a short period of time using the flashing and expansion work.When the liquid with high temperature and with high pressure in the water container flows out through the nozzle quickly,phenomena of the phase change and vapor expansion will occur.The two-phase flow spouts from the nozzle with a high speed.And the density of the two-phase flow is much larger than that of the vapor propellant.This makes the super-heated hot water jet engine have more advantages than other engine for the case of a large thrust demand during short time.There is relatively little research on super-heated hot water jet engine.The current research is mainly concerned with improving the engine thrust and finding more applications.There is no detailed research on the internal mechanism of this kind of engine.In order to make the design of the water jet engine to work at the best working point,it is necessary to deeply understand the flashing mechanism inside the engine and to find the matching relationship between relevant parameters.In this paper,a theoretical analysis and a numerical simulation were conducted to study the flow characteristics in the nozzle of the hot water jet engine.The matching relationship between relevant parameters were to be found.The main contents of the paper are given as follows:(1)Steady and unsteady one-dimensional calculation methods on flow parameters of the flashing two-phase flow in the nozzle were established.The qualitative theoretical analysis on the flow characteristics in the nozzle was made based on the mathematical model.The influences of different initial pressure and temperature on the performance of the nozzle were discussed.(2)A flash model was established based on the evaporation-condensation model.The accuracy of the model was verified.Numerical simulation of the two-phase flow in the nozzle of the water jet engine was carried out based on the flashing model.And the results of simulation were analyzed to get the characteristics of the flashing two-phase flow.The effects of the nozzle shape,initial pressure,sub-cooled degree,initial vapor volume fraction and other factors on the flow characteristics were also studied and compared with available theoretical analysis results.(3)The numerical simulation of the unsteady state process of hot water jet engine was carried out using the flashing model.And the working process was summarized and analyzed.