Investigation On Compound Cooling Characteristics In Curved Section Of Reverse-flow Combustion Chamber

With the modern aero-engine performance improving, the temperature and pressure in combustion chamber gradually increase, on one hand, the air in chamber used for combustion is more and more, which leads to the air in chamber used for cooling is less and less, on the other hand, because of the air temperature and pressure from the air compressor is increasing, so the temperature of cooling air is also increasing, this is not propitious to the chamber cooling, so whether the flame tube wall can be cooled effectively has already been a pivotal technology for the high temperature hoist combustion chamber of the high-powered aero-engine.Compound cooling is an highly efficient cooling method, it combines the convective heat transfer and film cooling between the high temperature wall and cooling air, which exert their superiority, so it makes the cooling effect much better than the single film cooling. Now the compound cooling is widely used in the cooling of flame tube wall in the large-scale turbine fan engine, for the reverse-flow combustion chamber in the turbine shaft engine, the total amount of air is much less than the large-scale turbine fan engine, especially the air used for cooling is much more less. With the power-weight ratio of the turbine shaft engine improving, the traditional single film cooling is far from enough for the future high temperature hoist combustion chamber cooling, so searching new compound cooling technology is necessary for the cooling of reverse-flow combustion chamber. Based on this, different cooling configurations in curved section of reverse-flow combustion chamber have been designed in this paper, these include impingement + reversed convection(with pin fin or not)+film cooling configuration, impingement + effusion cooling configuration and so on, the cooling efficiency and discharge coefficient have been studied numerically and experimentally, the analysis of the effects of blowing ratio and configuration parameter on the cooling efficiency and discharge coefficient have been showed, Results show that:(1)For configuration of impingement + reversed convection(with pin fin or not)+film cooling in curved section, the efficiency of compound cooling increases with the increase of the blowing ratio at the same wall position; The efficiency of impingement pin fin+reversed convection+film cooling in curved section with pin fins is better than that without pin fins, especially when the blowing ratio is small; The number of rows of pin fins and arrangement of pin fins have little effect on cooling efficiency; At the same blowing ratio, impingement distance has little impact on cooling efficiency in this paper's parameter, at the same wall position, cooling efficiency grows bigger as impingement distance is reduced. (2)For configuration of investigate impingement + effusion cooling configuration in curved section, the efficiency of compound cooling and discharge coefficient increase with the increase of the blowing ratio,especially the increment is bigger when the blowing ratio is small; The inclination angle has important effects on the efficiency of compound cooling, generally speaking, reducing the inclination angle can increase the cooling efficiency and discharge coefficient; For given streamwise space ratio,the shorter the cross space ratio is ,the higher the efficiency of compound cooling and discharge coefficient is ,for given abeam space ratio,with the streamwise space ratio increasing,the cooling efficiency and discharge coefficient increase. Through matching the experimental data obtain the efficiency of compound cooling and flow coefficient of correlation criteria.