Analysis of the effect of additional axial stage of a compressor on characteristics of small-sized turbojet engines
Thermal engines, electric propulsion and power plants for flying vehicles
Аuthors*, **, ***, ****
Moscow Aviation Institute (National Research University), 4, Volokolamskoe shosse, Moscow, А-80, GSP-3, 125993, Russia
The article is devoted to the analysis of changes in characteristics of small-sized gas turbine engines with a two-stage axial-centrifugal compressor instead of a single-stage centrifugal compressor, and analysis of the current level of cycle parameters of small-sized gas turbine engines. The work was performed by mathematical modeling, using empirical data. Initial stage of the work revealed that even a slight improvement of modern small-sized engines cycle parameters would lead to a significant improvement in the main characteristics of the engine. Models were developed with average parameters in their class: air flow of 650 g/s, gas temperature of 1100 °K. A number of assumptions was made: the efficiency was fixed for all units, except the compressor at the operation level of design mode; generalized characteristics of high-speed turbocharges and characteristics of single-rotor single-loop single-cascade jet engine compressors were adopted as the characteristics of compressors. For a single-stage centrifugal compressor, the compression ratio in the rated mode was adopted as 4 at the level of the leading serial analogues, and for an axial-centrifugal as 5.7. Analysis of the obtained altitude-airspeed performance revealed that by employing an axial-centrifugal compressor instead of a centrifugal one we can expect improvements of the main parameters (internal thrust, specific thrust, specific fuel consumption) of the engine up to 10−15% in the entire range of airspeeds and altitudes. Particularly, in the basic modes of flight of an unmanned aerial vehicle equipped with a similar engine, i. e. cruising (M = 0.8, H = 8000 m) and take-off (M = 0, H = 0m), thrust grew by 8%, and fuel consumption reduced by 12%. This result allows concluding that it is reasonable to use a constructive scheme of a small-sized engine with a two-stage axial-centrifugal compressor while developing new engines.
Keywords:jet engine, compressor, small-sized
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