Numerical And Experimental Study Of Heat Transfer Characteristics And Oxidation Deposition Of Aviation Kerosene At Supercritical Pressure

The cooled cooling air(CCA)will play a crucial role in the development of aero-engine in the future.The improvement in heat transfer and thermal stability of fuel is the critical concern for CCA cooling technology.Firstly,based on the previous researches of surrogate models and component analysis of RP-3,a four-species surrogate was proposed.The numerical results for thermo-physical properties are in good agreement with the experimental data,especially in the prediction of critical temperature.The model provides a good basis for the heat sink experiment and simulation.Secondly,the main influencing factors on the heat transfer of aviation kerosene were studied.The various heat-transfer experiments,including pressure,temperature,inlet mass flow rate and the flow structures have been conducted respectively.The results indicate that under supercritical pressure condition,the substantial changes in physical properties of the fuel affect heat transfer characteristics significantly.The influence of pressure on the heat transfer process mainly depends on the change of thermal physical properties,especially around the value of critical pressure.The Reynolds number depended on the inlet mass flow rate affects the flow conditions.Therefore,heat transfer enhancement in a spiral tube is induced by turbulent flow and secondary flow.Considering the variation in physical properties,entrance effect and the boundary layer effect,three empirical heat transfer correlations of aviation kerosene RP-3 was developed based on the measured data in the straight tube,s-shaped pipe,and spiral pipe structures,respectively.Thirdly,the effects of temperature,entrance effect,dissolved oxygen concentration,residence time,strengthening convective heat transfer,secondary flow and temperature gradient on the oxidation deposition were investigated experimentally.The heat transfer,coke distribution and morphology were analyzed.The results prove that the entrance effect,inducing high amount of deposits,which is interpreted by the temperature gradient and the boundary layer.In comparison with the air-saturated fuel,the high-dissolved-oxygen fuel experiences a sharp rise in deposits,while the deoxygenated fuel has the lowest deposition quantity.The impacts of Reynolds number on the deposition mainly depend on the thickness of sublayer where the deposition precursors are formed.The secondary flows in the bend section promote the heat transfer,resulting in a sharp decline in wall temperature and deposition.A large amount of deposits are corresponding to the sharp temperature gradients.The rank of influencing oxidation deposition is listed as temperature>dissolved oxygen concentration>temperature gradient>flow condition.Finally,a pseudo-detailed chemical kinetic and global deposition mechanism of supercritical pressure aviation kerosene RP-3 was developed with the consideration of the temperature gradient.The numerical model incorporating convective heat transfer and oxidation deposition reaction for supercritical pressure aviation kerosene RP-3 was conducted and validated by the experimental data of different dissolved oxygen concentration.The results demonstrate that the model performs well in the prediction of the total amount of deposition,oxygen consumption and the deposition distribution along the axis in the normal oxygen case.