Estimation of inlet airflow non-uniformity effect on turbofan thrust

Aeronautical and Space-Rocket Engineering

Thermal engines, electric propulsion and power plants for flying vehicles


Ezrokhi Y. A.*, Khoreva E. A.**

Central Institute of Aviation Motors named after P.I. Baranov, CIAM, 2, Aviamotornaya str., Moscow, 111116, Russia



The article considers methodical approaches to developing mathematical model using “parallel compressors” method, intended for estimation of inlet flow non-uniformity effect on aircraft engine basic parameters. On the example of a two-shaft turbo-jet engine calculation at two characteristic cruise modes the results of calculated estimation, where the base value of σst and averaged value of σav stayed invariable, were presented. Parametric calculations herewith were performed for each selected relative value of the reduced pressure area.

It was demonstrated that degree of full pressure inlet non-uniformity effect on the engine thrust at the two considered modes differs significantly. Thus, if at subsonic mode this estimation could be reduced to accounting only for the effect of reduction of the averaged value of the total pressure at the inlet, while at supersonic cruise mode such reduction use might lead to considerable errors. With invariable values of pressure recovery factor at the engine entry, corresponding to the flight speed for the typical air intake, external compression σst and averaged value σav, the flow non uniformity factor Δσnu affects mainly the thrust. The degree of this parameter effect herewith depends significantly on the difference of sst and sav.

The obtained results of calculated estimations of temperature field non-uniformity at the engine inlet effect revealed that the dependence of relative thrust reduction only at the cost of relative heating was similar for the two considered modes (transonic maneuvering and supersonic flight). At the transonic mode herewith, corresponding to higher values of the reduced rotation frequency of both compressor stages, the thrust decay occurs less intensely due to relatively smaller decrease of air flow rate through the engine with reduced rotation frequency decrease due to air temperature rise at the inlet. As for the difference between the values of total thrust decay , which does characterize the effect of the input temperature field non-uniformity, with the increase of relative heating at the transonic mode it rises more intensively. It is explained by the fact that at this mode due to the less difference between air consumptions in air-gas channels of «parallel compressors» (more «dence» location of pressure downstream brunches) the speeds difference and, consequently, static pressures between the flows is much greater, than at the supersonic flight mode, which stipulates the higher losses level while these flows interaction.


total pressure and temperature non-uniformity at the engine inlet, circumferencial non-uniformity, radial non-uniformity, parallel compressors method, turbofan thrust reduction


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