Efficiency of application of direct-drive circuit for improvement of starting characteristics of gas turbine engine

Abstract

The effectiveness of measures to improve the starting characteristics of gas turbine engines (GTE) is considered. To improve the reliability of the GTE launch, it is proposed to use the so-called gearless GTE scheme, created for a “more electric aircraft”, which uses an integrated high-speed starter generator and electric drive units for fuel, oil and other life support of gas turbine engines. With the help of a nonlinear dynamic mathematical startup model, the effect of the magnitude of the given moment of inertia of the rotor on the starting characteristics of the gas turbine engine is evaluated. Change it in the direction of reduction was carried out by replacing the gearbox with attachments to one unit a high-speed starter-generator, installed coaxially with the rotor. Determination of the value of the given moment of inertia of the rotor, aggregates, bearings was carried out using the developed 3-DCAD-models. In the mathematical model of start-up, the thermal state of the oil system, the mechanical power losses for rotating aggregates, bearings, gears are taken into account. The quantitative dependence of the starting characteristics on the moment of inertia of the GTE rotor and other factors is established. For comparison of the basic APU and APU of the direct-drive circuit simulation of the start in the most stressful operating conditions P H = 101,3 kPa at low negative temperatures t H = -40 °C and under normal conditions P H = 101,3 kPa and t H = +15 °C, for “cold” and “hot” state of the engine before starting was made. The tendencies of the moment of inertia of the rotors of the executed and newly created GTE are analyzed. It is shown that the gearless APU in comparison with the basic APU due to the reduction of the moment of inertia by 9,68 % and the reduction of the oil pumped volume in the oil system has a significant improvement in the launch characteristics under ground launch conditions ( P H = 101,3 kPa).