Effect of Heating Device Voltage on Fuel Spray Ignition and Flame Characteristics under Aviation Propulsion System Conditions

This study investigates characteristics of ignition and flame behavior under relevant aircraft engine operating conditions. The employed operating conditions accommodate the ignition enhancement technique by setting up the combustion chamber with a hot surface probe. The amount of energy deposition by the probe was elevated by electric voltage input on the probe surface. Thereby the probe helps to heat up the neighboring air mass and the spray plume impacting on the surface. The primary purpose of this study is to reveal the predominating ignition characteristics depending on the degree of energy input applied to the probe. A heating probe model with detailed geometries and materials of each component was developed to calculate the realistic surface temperature distributions with different voltage inputs. Results obtained from the 3-dimensional CFD simulations conducted in this study display different mechanisms of ignition of the spray-air mixture and distinguishable flame development around the probe. The low voltage input case shows a relatively longer ignition delay time and results in a well-mixed fuel-air pocket far downstream of the injector and consequent spontaneous ignition. However, the elevated probe voltage input tends to shift the combustion regime to diesel-like spray combustion with a typical diffusion flame structure.