Time Dependent Effect of flow properties on addition of heat to the air flow at Compressible Subsonic Speeds

Abstract

Heat addition process is a governing phenomenon in turbojet and ramjet burners, where heat is added to the flow during the fuel-air combustion process. In the present work, an analytical study has been performed to investigate the effect of heat addition on the basic flow properties based on compressible Rayleigh flow model between the subsonic and sonic flow regime. The unsteady nature of flow properties in these regimes have been evaluated analytically by adding heat through the walls of a constant area, frictionless duct in which air flow occurs over different periods of time. Sudden variation of temperature, pressure, velocity and kinetic energy of the flow were found at flow Mach number M = 0.94. Flow velocity and kinetic energy increases until the flow approaches M = 0.94, afterwards there is a rapid increase in the flow velocity and kinetic energy until it reaches sonic conditions. Conversely, pressure decreased till the flow reaches M = 0.94, there after a sudden drop was observed. Flow enthalpy increased initially, reached maximum at flow M = 0.845 and then reduced till sonic conditions. Based on the observations, it has been concluded that the heat energy contributed to increase the kinetic energy thereby reducing the temperature of the flow.