Aerospace Technic and Technology

The article provides the substantiation of the rational scheme of the boost system of the aircraft diesel engine KhADI-100A to ensure its altitude from the point of view of the lowest losses of the effective engine power. A method is proposed for assessing the power loss of an aircraft diesel engine depending on the flight altitude. Three variants of the supercharging system are considered: with one free turbocharger; parallel drive compressor and free turbocharger; sequential drive compressor and free turbocharger. As a result of the computational study, it was shown that in the case of using one free turbocharger at an altitude of h > 1500 m, the normal operating process of a diesel engine cannot be realized, since in this case, the excess air ratio falls below the critical value for a diesel engine α <1.4. Even if a constant excess air ratio is maintained, the effective engine power, with one free turbocharger, decreases by about 6 ... 11 kW per 1000 m with an increase in flight altitude. In schemes with a driving compressor, the quality of the fuel-air mixture will not change with altitude, and the power losses for their drive are insignificant in comparison - within 1 ... 2 kW per 1000 m of lifting height and can be compensated by increasing the cycle fuel supply without losing the quality of the working process. As a result of the computational study, it was concluded that the most rational from the point of view of the least power consumption is the scheme with a sequential drive compressor and a free turbocharger, the power consumption for the compressor drive at an altitude of 5000 m is 1.4 kW less than in the scheme with a parallel drive compressor and is the maximum value of 8.5 kW. The use of an electrically driven compressor is proposed since in this case the unit gains control flexibility to select the optimal operating mode and the possibility of using alternative energy sources for the drive electric generator (solar batteries, accumulators, thermoelectric generators, etc.).

aircraft diesel engine; boost system; drive compressor; engine power; flight altitude

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