Study On Contour Design And Heat Transfer Simulation Of Liquid Rocket Engine Nozzle

In the liquid rocket engine,the nozzle is the main component to generate thrust.The high temperature and high pressure gas expands and accelerates in the nozzle,which is discharged from the nozzle outlet and generates thrust.The nozzle of liquid rocket engine is composed of convergence section and expansion section.The flow of gas in the nozzle is directly affected by the nozzle contour and the expansion section has a bigger impact.The flow and the heat transfer characteristics of the nozzle are different due to the different contour of the nozzle expansion section the performance of the nozzle is different.In practical applications,requirements of specific impulse,mass and heat transfer should be considered comprehensively to select the proper nozzle contours.Therefore,it is of great engineering significance to study the flow and heat transfer characteristics and performance of different nozzles.In the paper,the design methods of expansion section contour of ideal contour nozzle,truncated ideal contour nozzle,compressed truncated ideal contour nozzle and thrust optimum contour nozzle were studied.Under the condition of a given length and area ratio,use MATLAB to write expansion section contour design program.Sauer's method and Kliegel's method were combined to solve the transonic region of the nozzle.The initial value line was obtained by the formula provided by Sauer's method and the velocity of the initial value line was calculated by Kliegel's method.On the basis of completing the nozzle contour design,the paper studied the flow characteristics of truncated ideal contour nozzle,compressed truncated ideal contour nozzle and thrust optimum contour nozzle through numerical simulation,calculated and compared the performance parameters of different nozzles.The nozzle length is 80%of the conical nozzle with a expansion half-angle of 15 degree.The following research results were obtained.(1)Thrust optimum contour nozzle has higher geometric efficiency,lower friction efficiency and larger mass.(2)Truncated ideal contour nozzle has lower geometric efficiency,higher friction efficiency and smaller mass.(3)The compression factor of compressed truncated ideal contour nozzle shouldn't be too small.When the compression factor reaches a certain value,specific impulse will reach the maximum value.The geometric efficiency and friction efficiency of compressed truncated ideal contour nozzle with the maximum specific impulse are between the other two nozzles and the mass is lower than that to truncated ideal contour nozzle.(4)In the case of small area ratio(?_e?2 5),specific impulse of thrust optimum contour nozzle is the highest and the maximum specific impulse of compressed truncated ideal contour nozzle is higher than that of truncated ideal contour nozzle.In the case of large area ratio(?_e?100),specific impulse of truncated ideal contour nozzle is the highest and the maximum specific impulse of compressed truncated ideal contour nozzle is close to it,while thrust optimum contour nozzle has a lower specific impulse than the other two nozzles.In addition,the influence of nozzle length on performance was studied and the result showed that it's reasonable to select the nozzle length at nearly 80%of the conical nozzle with a expansion half-angle of 15 degree.In the study of different nozzles'heat transfer characteristics,the three-dimensional numerical simulation and one-dimensional program were used to calculate the regenerative cooling heat transfer of the nozzle upper section of truncated ideal contour and compressed truncated ideal contour respectively.Numerical simulation results showed that the heat transfer per unit time of compressed truncated ideal contour nozzle is higher and it has better heat transfer effect.Hydrogen out of compressed truncated ideal contour nozzle's cooling channel has higher energy,which is good to do work.The results of one-dimensional heat transfer calculation and three-dimensional numerical simulation are compared.It was found that Bartz's formula used in one-dimensional heat transfer program had a large deviation in the heat transfer calculation of nozzles of large area ratio and the correction of constant C could not substantially improve the accuracy of the calculation.Therefore,the application of Bartz's formula in the heat transfer calculation of nozzles with large area ratio needs to be further studied in combination with experimental data.