Heat Transfer Characteristics of Liquid Film Formed on a Superheated Wall during Pulsed Injection of Liquid Jet

Abstract

The liquid film cooling technique was employed in bipropellant thrusters to protect the thrust chamber from high-temperature combustion gases. Heat soak-back from the throat to the face plate occurs in the interval between each pulse firing event. A liquid jet would be injected onto the superheated wall in pulse firing operation. To gain experimental knowledge for contributing to effective cooling and hazard prevention of thrusters, pulsed cooling tests of the metal plate, in which a liquid jet was intermittently injected onto the superheated surface, were conducted. The liquid film behavior was captured by a high-speed camera, and the transient change in wall temperature was measured by an infra-red camera simultaneously. In the pulsed cooling tests, the coolant liquid jet was injected three times with different duty cycles and flow rates under constant total injection quantity. The removed heat by the liquid film in the pulsed cooling test was compared with that in the continuous cooling test. Results showed that the cooling performance decreased with the decrease of the duty cycle because the longer interval contributed to the temperature rise of the metal plate.