The efficiency of a pitot intake inclined to the air stream

Abstract

In an earlier report on intake ducting for supersonic flight, the efficiency of a 'pitot' type intake was discussed and shown to have a marked effect on the performance of gas turbine engines. The present report is supplementary in that it describes the effect of inclining the pitot intake to the main air stream direction in the transonic Mach number range 0.7 to 1.5, an effect which is at present incalculable. Curves are presented showing the influence of inclination on intake adiabatic efficiency and air mass flow into the intake. These experimental results are then illustrated by application to the performance of a typical turbine engine and a propulsive duct in sonic and supersonic flight. At a flight Mach number of 1.5, it is found that, for both turbine engine and propulsive duct, an inclination of 5 deg reduces the net thrust by roughly 2 per cent compared with the normal flight thrust. For inclinations greater than 5 deg, however, thrust falls off more rapidly, and at 10 deg inclination, it is reduced by roughly 6.5 per cent for the turbine engine and 7.5 for the propulsive duct.