Off-Design Performance of Turbojet Engine for Sub-Scale Supersonic Unmanned Plane

Abstract

The preliminary analysis is conducted for a turbojet engine of the Supersonic Unmanned Plane with a single spool, a convergence nozzle, a pitot intake and an afterburner. The error matrix method is employed, in which the compression ratio at the compressor, turbine inlet temperature and turbine expansion ratio are selected as independent variables for turbojet operation, then evaluated the three error vector components. The error vector is composed of the flow rate balance at compressor and turbine inlets, the compressor-turbine power balance, and pressure-mass flow rate balance at nozzle throat. To obtain solutions, the norm of error vector must be reduced to very small value by Newton iterative procedure. In the present study, compressor inlet diameter, turbine inlet temperature (TIT) limit are 0.14m, 1273K, respectively. The present engine models are operational along the constant flight dynamic pressure path of 50 kPa in transonic region ( Mach 0.9 to 1.3 ) The present study is focused on the effects of compression ratio and air flow rate at compressor on thrust level and the feasibility to break the sound barrier. For the feasibility study, the aerodynamic configuration of aircraft is proposed and its aerodynamic characteristic is also evaluated. Then, the possibility to break the sound barrier is discussed by comparing the thrust to the drag.