Simulation of Regenerative Cooling System Performance for Large Expansion Ratio Rocket Motors

ABSTRACT

The paper describes the performance of the regenerative cooling system employed for large expansion ratio rocket motors (A_e/A_t ~ 100). Such motors utilize high energy propellants to produce hot gas, which are expanded through the rocket nozzle to generate high thrust. During combustion and gas expansion, the walls of the combustion chamber and the rocket nozzle are exposed to high temperature gas (about 3500 K), which can ultimately lead to structural failure. Therefore, in order to protect the hardware from thermal failure, proper cooling arrangement should be provided. In the present study, a regenerative cooling system for a cryogenic rocket motor that uses fuel (liquid hydrogen) or oxidizer (liquid oxygen) as the cooling medium is considered. The coolant is allowed to flow through the annular passage around the nozzle walls in counter- current direction, so that the heat loss from the hot gases can maintain the walls at a lower temperature. Simulations have been carried out for both constant and variable fluid properties. The influence of the thermal properties of the material and thickness of the nozzle wall on conductive heat transfer (from gas to coolant side) has also been investigated. The effect of radiative heat transfer when there is no regenerative cooling system has been analyzed. Also, heat transfer enhancement for different turbulence models has been simulated. The study has been performed by solving three dimensional Navier–Stokes equations using the finite volume discretisation technique. The flow pattern, temperature distribution, variations of wall heat flux, pressure drop in the cooling passage etc. are investigated in detail for both the cases of fuel and oxidizer employed as coolant. The numerical predictions are validated with the data available in literature.

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