Effect of COMBUSTOR-INLET CONDITIONS on Combustion in Turbojet Engines

HIGH combustor-inlet temperatures and pressures and low inlet velocities promote combustion, study of an early Westinghouse 19B combustor shows. Altering any one of the three inlet conditions in an undesirable direction affects combustion the same as an increase in altitude. Unfavorable conditions are said to account for operational limits at altitude. As altitude increases, combustion efficiency drops and resonance develops; the maximum temperature rise obtainable and the fuel-air ratio at which it occurs decrease. The more adverse the inlet conditions, the greater their detrimental effect on combustion. In accelerating at a given altitude, there may be a range of engine speeds where operation is impossible because increased inlet velocities more than counterbalance beneficial effects of increased inlet temperatures and pressures.