In this paper,characteristics of flow and convective heat transfer of China RP-3 kerosene in straight circular pipe were numerically studied.Navier-Stokes equations were solved using RNG k-turbulence model with low Reynolds number correction.The thermophysical and transport properties of the China RP-3 kerosene were calculated with a 10-species surrogate and the extended corresponding state method(ECS) combined with Benedict-Webb-Rubin equation.The independence of grids was first studied and the numerical results were then compared with experimental data for validation.Under flow conditions given in the paper,the results show that deterioration of convective heat transfer occurs when the wall temperature is slightly higher than the pseudo-critical temperature of kerosene for cases with wall heat flux of 1.2 and 0.8 MW/m 2.The degree of the heat transfer deterioration is weakened as the heat flux decreases.The deterioration,however,does not happen when the heat flux on the pipe wall is reduced to 0.5 MW/m 2.Based on the analysis of the near-wall turbulent properties,it is found that the heat transfer deterioration and then the enhancement are attributed partly to the change in the turbulent kinetic energy in the vicinity of pipe wall.The conventional heat transfer relations such as Sieder-Tate and Gnielinski formulas can be used for the estimation of kerosene heat convection under subcritical conditions,but they are not capable of predicting the phenomenon of heat transfer deterioration.The modified Bae-Kim formula can describe the heat transfer deterioration.In addition,the frictional drag would increase dramatically when the fuel transforms to the supercritical state.
The diffusion,viscosity and thermal conductivity coefficients of gases between two parallel solid walls have been obtained analytically based on the Green-Kubo relation under a hard-sphere model.They decrease nonlinearly as the Knudsen number defined as the ratio of the mean free path to the wall distance increases.This theoretical prediction was in good agreement by the DSMC results.
A coupling frame of speed gain and maintain was suggested to assess the flight performance of hypersonic cruise vehicles(HCV).The optimal cruise speed was obtained by analyzing the flight performance measured by the ratio of initial boost mass to generalized payload.The performance of HCVs based on rockets and air-breathing ramjets was studied and compared to that of a minimum-energy ballistic trajectory under a certain flight distance.It is concluded that rocket-based HCVs flying at the optimal speed ar...
Jing Fan~(a)) Key Laboratory of High Temperature Gas Dynamics,Institute of Mechanics,Chinese Academy of Sciences, Beijing 100190,China
The aerodynamic aspects of indirect thrust measurement by the impulse method have been studied both experimentally and numerically. The underlying basic aerodynamic principle is outlined, the phenomena in subsonic, supersonic and arc-heated jets are explored, and factors affecting the accuracy of the method are studied and discussed. Results show that the impulse method is reliable for indirect thrust measurement if certain basic requirements are met, and a simple guideline for its proper application is given.
Cheng-Kang WuHai-Xing WangXian MengXi ChenWen-Xia Pan
A modelling study is performed to compare the plasma flow and heat transfer characteristicsof low-power arc-heated thrusters (arcjets) for three different propellants: hydrogen,nitrogen and argon.The all-speed SIMPLE algorithm is employed to solve the governing equations,which take into account the effects of compressibility,Lorentz force and Joule heating,aswell as the temperature- and pressure-dependence of the gas properties.The temperature,velocityand Mach number distributions calculated within the thruster nozzle obtained with differentpropellant gases are compared for the same thruster structure,dimensions,inlet-gas stagnantpressure and arc currents.The temperature distributions in the solid region of the anode-nozzlewall are also given.It is found that the flow and energy conversion processes in the thrusternozzle show many similar features for all three propellants.For example,the propellant is heatedmainly in the near-cathode and constrictor region,with the highest plasma temperature appearingnear the cathode tip; the flow transition from the subsonic to supersonic regime occurs withinthe constrictor region; the highest axial velocity appears inside the nozzle; and most of the inputpropellant flows towards the thruster exit through the cooler gas region near the anode-nozzlewall.However,since the properties of hydrogen,nitrogen and argon,especially their molecularweights,specific enthalpies and thermal conductivities,are different,there are appreciable differencesin arcjet performance.For example,compared to the other two propellants,the hydrogenarcjet thruster shows a higher plasma temperature in the arc region,and higher axial velocitybut lower temperature at the thruster exit.Correspondingly,the hydrogen arcjet thruster has thehighest specific impulse and arc voltage for the same inlet stagnant pressure and arc current.Thepredictions of the modelling are compared favourably with available experimental results.
The flow in a low-powered arc gas heater combined with a supersonic nozzle of throat diameter less than1 mm is quite complicated and difficul to describe in quantitative detail. Experiments on arc-heated supersonic jet thrusters of monatomic gases argon and helium have been carriedoutandtheirperformancemeasured.Theflowcharacteristics are analyzed with the help of numerical simulation.Results show that the viscous effect is the most important factor causing the large difference between ideal and real performance. A large outer section of the exit flow is slowmoving. This is especially pronounced in helium, where 70 %of the exit area of the nozzle might be in subsonic flow. Friction forces can be much larger than the net thrust, reaching several times higher in helium, resulting in very low efficien cies. Other factors causing the differences between ideal and real flow include: complex flow in the throat region, electric arc extending to the nozzle expansion section, heat transfer to the inlet gas and from the hot plasma, and environmental pressure in the vacuum chamber. It is recognized that the ordinary concepts of supersonic nozzle flow must be greatly modifie when dealing with such complicated situations. The general concepts presented in this paper could be helpful in guiding the design and operation of this equipment.
