Analysis And Design On Scramjet Active Cooling System Based On Heat Transfer Enhancement

Since scramjets are used under extreme temperatures and with wide range of Mach numbers, effective thermal protection is needed to meet engine well cooled requirement, to ensure the normal working and life of the engine. It is common knowledge that since the flight Mach number becomes higher, even composite materials can't withstand the large heat load found in a Scramjet combustion chamber. Active regenerative cooling system is important in thermal protection and studied in the article. In order to improve cooling efficiency and reduce the fuel consumption, an optimized calculation scheme was developed for the imbalance of burning flow rate and coolant flow rate on scramjet engines'active cooling system. An example was present in the article to prove the program.This paper makes scientific research and in-depth discussion on thermal protection as follows:One dimension heat transfer computational model of scramjet combustor with active regenerative cooling was established based on empirical formula and actual model, and the simple computation method of active regenerative cooling was advanced. In order to evaluate the effect of active cooling, An example was given based on some scramjet model. The result showed that this method was well enough. The model can quickly work out the wall temperature distribution along the axial line and find the dangerous section of the combustor.Two dimension and three dimensions CFD model were developed to verify the conclusion of one dimension. The CFD model can analysis local flow field and temperature field, then find the rule of how to increase heat flux by heat transfer enhancement structure. Through comparative analysis, one dimension model's validity and reliability was proved.The thermal evaluation tool was applied to parametric studies on the effects of material choice (liner material and coat material) and geometry (coat thickness, fin thickness, cooling channel height and width, artificial roughness).For improve the performance of scramjet, one heat transfer enhancement method for cooling analysis was presented based on constant wall temperature principle. An optimized calculation scheme was developed for the imbalance of burning flow rate and coolant flow rate on scramjet engines'active regenerative cooling system. Basing on adding insulation coating in some high heat flux region, an optimization design model aimed at eliminate local overheating was present for cooling channel height,width and artificial roughness through two ways on constant wall temperature principle. The combustor wall temperature meets the desired objectives basically in the result.The optimization method in this article can improve fuel's cooling heat sink, save cooling fuel flow rate. This model gives a reference structure for the design of practical scramjet combustor.