Researches On In-tube Convection Heat Transfer Of Supercritical Pressure Hydrocarbon Fuel Under Rotating Condition

Advances in the cooling of turbine blades have important implications for improving the engine's pre-turbine inlet temperature.The regenerative cooling technology of the engine means that the supercritical pressure hydrocarbon fuel as a coolant absorbs heat by convection heat transfer while preheating before entering the combustion chamber.This technology can also be used for the cooling of rotating turbine blades using hydrocarbon fuel and has a higher cooling efficiency than gas,which is largely used at present.In this dissertation,the convective heat transfer and flow of n-decane under supercritical pressure in the rotating U-duct were studied by theoretical analysis,experimental research and numerical simulation.This work presents an experimental investigation of the study on heat transfer and pressure drop of the supercritical pressure n-decane in a 2 mm diameter U pipe under the conditions of different rotation speed,mass flow rate,pressure and heat flux.The heat transfer at the trailing edge of the centrifugal section was the strongest,the leading edge was weakest,and the two sides were similar.The heat transfer of outer side in the horizontal section was the strongest,while the inner side was the weakest.The distribution centripetal section due to the mixing effect of the turning section was very small.The section average convective heat transfer coefficient increased with the increase of rotating speed,and the section average convective heat transfer coefficient of 1500r/min was about 2~3 times that of the static condition.The phenomenon of oscillation was observed in the thermocouple section near the exit of the horizontal section which was caused by return flow and great changes of properties.The heat transfer coefficient in the centrifugal and horizontal sections increaseed with the increase of the mass flow rate,and decreased in the centripetal section.The effects of flow acceleration and buoyancy on heat transfer were analyzed.The expression of a dimensionless criterion for the buoyancy force under rotating conditions considering gravity buoyancy and centrifugal buoyancy was proposed.The convective heat transfer from low speed to high speed in different sections was studied,and the mechanism of the heat transfer deterioration at low speeds was performed.The criteria for the deterioration and recovery of heat transfer by buoyancy was given.New local Nusselt number correlations for the heat transfer of n-decane at supercritical pressures under rotating condition were proposed.The pressure drop of supercritical pressure n-decane in rotating U-duct was investigated by experimental mesurements and theoretical analyses.The experiment found that the rotation resulted in the centrifugal force potential and increased the frictional pressure drop.A new friction coefficient ratio correlation was proposed and used for prediction of rotating pressure drop.The numerical simulation of convective heat transfer of supercritical pressure n-decane under rotating conditions was studied,and the reliability of the model was validated by the experimental data.The mechanism of the heat transfer in different sections was given by analyzing the flow field details such as velocity distribution and turbulent kinetic energy distribution.