Thermal management of fuel in advanced aeroengine in view of chemical recuperation

The working process of an advanced aeroengine such as scramjet with endothermic hydrocarbon fuel cooling is a chemical recuperative cycle and the heat sink utilization of fuel, which is directly related with the recuperation effectiveness, is the primary issue for thermal management of advanced aeroengines. In the chemical recuperation, the increase in chemical recuperation effectiveness improves both the performances of the fuel cooling system and the combustion system. And the influencing factors on the recuperation effectiveness are complex, including the operating and design parameters. So, in order to study the thermal management of fuel in view of chemical recuperation, one, two and three dimensional models of flow and heat transfer process in a single cooling channel of endothermic hydrocarbon fuel cooled scramjet in terms of endothermic reaction are respectively developed, which are validated by corresponding experimental data. Based on one dimensional model, different methods are put forwarded to control the utilization level of fuel heat sink and thus the chemical recuperation effectiveness. And effective residence time of fuel during fuel cooling process is defined to distinguish global method and local method. The control of fuel mass flow rate or the height of cooling channel can be regarded as a global method, while the control of operating pressure in the cooling process can be considered as a local method. Analytical results indicate that the control methods can effectively improve the chemical recuperation effectiveness. However, the efficiency of the global method is limited by the allowable wall temperature. In contrast, the local method can be used not only to control the chemical recuperation effectiveness, but also to improve the heat transfer and pressure drop performance of fuel. Based on the two and three dimensional models, it is found that the conclusions that come from the one dimensional model can be modified and extended. The results of two or three dimensional models show that the nonuniformity of the fuel velocity and temperature on the channel cross section, which is not considered in the one dimensional model, has great effects on the chemical recuperation effectiveness. The calculation results of the three dimensional model with asymmetric heated rectangular cooling channel show that the width of the channel has great effects on the chemical recuperation effectiveness because of the secondary flow in the cooling channel, which is different from the results got from the one dimensional model.