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Indexed by:会议论文

Date of Publication:2021-02-02

Volume:2

Page Number:1120-1126

Abstract:Regenerative cooling technology has been commonly used to cool liquid rocket engines. Prior to fuel injection and burning, the hydrocarbon fuel would be circulated in mini cooling channels surrounding the combustor chamber in order to cooling the engine. Regenerative cooling process commonly occurs at a high pressure above the critical point of the fuel, thus convective heat transfer at supercritical pressures comes about. Up to now, numerical and experimental works mainly focus on the steady-state heat transfer process at supercritical pressures, and very few studies have been conducted under unsteady-state. Heat transfer at a stepwise change in surface heat flux and a steady fluid flow rate is one of the simplest cases of unsteady heat transfer. But even in this case the underlying mechanisms are still not fully understood. Since the transient phenomena in engine cooling channels might influence the stability of fuel injection and subsequent combustion process, detailed numerical studies on transient heat transfer processes at supercritical pressures are needed to be carried out in order to look deeper into the thermophysical and transport mechanisms. In this paper, a numerical study has been conducted to investigate transient responding behaviours of fluid flow and heat transfer of n-decane at a supercritical pressure and temperature below 800 K, at which point the pyrolysis process can be neglected. The extended corresponding states method is applied for accurately calculating strong variations of the thermophysical properties of n-decane, including fluid density, constant-pressure heat capacity, and viscosity. A steady-state cold flow is instantly enforced with a constant surface heat flux to activate the transient heat transfer process. The effects of two key influential parameters on transient responses are examined in detail. Results indicate that inlet boundary condition and unheated entry section length of cooling tube can strongly affect the pressure oscillations. The pressure oscillation under the velocity inlet condition has stronger magnitude but weaker frequency and longer response time than the case under the stagnation condition; the oscillation magnitude marginally increases but the oscillation frequency sharply decreases as the entry section length increases. © 2017 International Astronautical Federation IAF. All rights reserved.