Fuel supply in microjet engines typically makes use of fuel vaporizers. These have a simple design however, their operation involves complicated physics including the disintegration of liquid jet under co-flowing air, impingement of liquid jet on hot wall, formation and motion of liquid film, droplet splashing and fuel evaporation occurring over different two-phase flow regimes. The objective of the presented study is to investigate these processes and develop physical models to evaluate the fuel evaporation rate. The work involved a coupled analytical – experimental study of the disintegration of liquid jet, the impingement process and the heat transfer between combustion gases and a the two phase flow within a tube exposed to these gases. A major effort was invested to develop the experimental setup for these studies that included a swirl stabilized kerosene fueled combustor with a crossing metal tube in which fuel and air were supplied under conditions complying with the flow in a typical vaporizer. The vaporization rate was measured by deducting the collected fuel at the exit of the tube from the inlet flow rate after its separation from the flowing gaseous phase (air & fuel vapor). The main result indicated that the evaporation is very sensitive to the inlet fuel to air mass flow ratio. Hence, by modifying the fuel to air mass flow ratio, one can control the vaporizer performance and improve the combustion efficiency and the global engine performance.
On the operation of a microjet engine’s vaporizer under steady-state conditions
Fuel supply in microjet engines typically makes use of fuel vaporizers. These have a simple design however, their operation involves complicated physics including the disintegration of liquid jet under co-flowing air, impingement of liquid jet on hot wall, formation and motion of liquid film, droplet splashing and fuel evaporation occurring over different two-phase flow regimes. The objective of the presented study is to investigate these processes and develop physical models to evaluate the fuel evaporation rate. The work involved a coupled analytical – experimental study of the disintegration of liquid jet, the impingement process and the heat transfer between combustion gases and a the two phase flow within a tube exposed to these gases. A major effort was invested to develop the experimental setup for these studies that included a swirl stabilized kerosene fueled combustor with a crossing metal tube in which fuel and air were supplied under conditions complying with the flow in a typical vaporizer. The vaporization rate was measured by deducting the collected fuel at the exit of the tube from the inlet flow rate after its separation from the flowing gaseous phase (air & fuel vapor). The main result indicated that the evaporation is very sensitive to the inlet fuel to air mass flow ratio. Hence, by modifying the fuel to air mass flow ratio, one can control the vaporizer performance and improve the combustion efficiency and the global engine performance.
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