Investigation Of Technique On Regenerative Cooled Scramjet

For scramjet applications, temperature in the combustor can easily exceed the maximum working temperature of most materials. Thermal management becomes a key technique for a successive scramjet operation. Regenerative fuel cooling has been considered to be one of the most effective and practical methods for hydrocarbon fueled scramjet applications. The design of active cool structures, flow and heat transfer to endothermic hydrocarbon fuels in coolant channels and development of actively cooled scramjet are reviewed.A one-dimensional numerical model based on semi-empirical correlations has been developed with heat and mass transfer in a cooling channel for supercritical kerosene under pyrolysis. The validation of the model, based on experimental result of heat transfer in a stainless steel tube for China No.3 kerosene is presented. Impact of different equation of characteristic numbers and mean temperature difference on the results has been studied.Wall temperatures and the fuel temperatures and pressure along the flow path were measured in experimental research of regenerative cooled scramjet. The drag coefficient,chemical heat sink and coefficient of empirical correlations are fixed. Heat transfer characteristics of regenerative cooled scramjet are investigated in the experiment. Nearly 80 percent of the coolant channels are filled with supercritical kerosene while about 60 percent of it are in thermal crack region. About 30 percent of the heat transfer rate is absorbed by kerosene through thermal crack. Furthermore, heat transfer rate between outer-wall and air, which is nearly 12.6 percent the value of that between inner-wall and combustor flow, should not be neglected. Heat transfer enhancement was found as the kerosene temperature approaching the critical temperature, but no more benefit of the fin can be found. Additional cooling can be obtained by increasing the heat sink capacity of hydrocarbon fuel through thermal cracking.The influences of coolant channels dimension and inlet boundary conditions on the cooling performance are investigated. The result is of significance to the design and manufacture of regenerative cooled channels with less thickness of wall and fin. High aspect ratio cooling channels improve heat transfer by fin effect, however, exact mechanism within channel that lead to improved performance have not been fully revealed. Besides, more channels under certain coolant mass flow rate and higher inlet pressure and temperature result in more smooth heat flux distribution along the channel.