The Research Of Heat Transfer Enhancement In Combustion Chamber By Wall Ribs For Expander Cycle Engine

In expander cycle engine,combustion chamber enhanced heat transfer technology is one of the key technologies to improve engine performance.Increasing heat transfer area is one of the most direct and effective methods in thrust chamber heat transfer enhancement technology.Hot-gas wall ribs can increase heat transfer area and at the same time,the adverse effects such as increasing the weight and size of the combustion chamber can be reduced,and it is easy to realize in techniques,therefore,it is the breakthrough direction of enhanced heat transfer technology for expander cycle engine.In this paper,a hydrogen and oxygen expander cycle engine is studied.Based on the enhanced heat transfer technology in combustion chamber,the influence of the ribbed structure of inner wall in combustion chamber on heat transfer is mainly studied.A reasonable simplified calculating model is established,and the numerical simulation of flow and heat transfer in hot-gas side of the combustion chamber is carried out by using SST k-ω model.The simulation results of ribbed structures with different structural dimensions are analyzed in details.The effects of structural dimensions such as rib height,rib width and canal width on heat transfer are studied,and then they are analyzed synthetically by orthogonal experimental method.Through the analysis of simulation results,influence factors and relationships of rib surface temperature,convection heat transfer coefficient and heat flux are obtained.Basing on the existing one-dimensional heat transfer and flow resistance calculation program of thrust chamber,the heat transfer calculation of hot-gas side rib is added according to the results of simulation,and then compared with smooth wall.At the same time.the influence of rib structure size on heat transfer and flow resistance of thrust chamber is studied and compared with CFD calculation results.The results are as follows:1.CFD numerical calculation results show that: 1)Within a certain range,wall temperature,surface heat transfer coefficient and heat flux increase with the increment of rib height.2)Wall temperature increases with the increment of rib width.Relative to rib height,the temperature change of rib top caused by the increase of rib width is relatively small.The smaller the rib width means the lager heat transfer.3)Heat flux of different ribs firstly increases and then decreases with the increase of canal width,and the max value is obtained when canal width is about 1.6mm.Not all ribbed structure bring the enhancement of heat transfer,when rib width is too large and canal width is too small contemporary,the heat transfer of ribbed wall is less than the smooth wall.4)Three kinds of the rib structure size were comprehensively analyzed,and results show that emphasis should be placed on increasing the height of ribs to increase heat transfer.2.Using the improved one-dimensional heat transfer program,calculation shows that: 1)When rib width and rib numbers are invariable,total heat transfer of thrust chamber,coolant temperature rise and pressure drop increase with the increase of rib height.2)Under circumstance of rib height and numbers unchangeable,total heat transfer,coolant temperature rise and pressure drop are all decreasing with the increase of rib width.3)With rib height and width unchanged,total heat transfer of the thrust chamber,coolant temperature rise and pressure drop are increased first and then decreased with the increase of rib numbers,and the max value is obtained when rib number is 348.The effects of three structural dimensions are analyzed synthetically by orthogonal experimental method,and the relatively better structure is that: rib height is 2.5mm,rib width is 0.6mm and rib number is 348,under these circumstances,the heat transfer is the largest and this conclusion can be used to guide the engineering practice.