Single-shaft turbofan engine

Abstract

A single-shaft turbofan engine comprises a convergent duct for initial acceleration of an airflow, a fan having a blade profile adapted for operation at supersonic airflow speeds, a starter-generator built into the central part of the fan impeller and being based on a brushless DC machine, a multi-stage axial compressor for compressing the airflow of the engine core, an annular combustion chamber, and a turbine having an active blade profile and one or several impellers. The fan, the starter-generator, the axial compressor and the turbine are mounted on a single shaft with no reduction gearing. The parameters of the blades, the fan, the compressor and the turbine are optimized in such a way as to eliminate the need to gear down the impellers. The technical solution can be used in engines with a bypass ratio of up to 8. The invention makes it possible to improve the weight and size characteristics of turbofan engines while maintaining good efficiency.

Description

[0001] Single-shaft turbofan engine

[0002] The invention relates to turbojet dual-circuit fan engines. Its application is most effective in low-power turbojet dual-circuit fan engines with a thrust of 1000 to 5000 N.

[0003] A single-shaft, single-circuit engine (Kurt Schreckling, Model turbines 2005 Traplet Publications Ltd) of low power is known. The engine includes a centrifugal compressor and a turbine with one working wheel mounted on one shaft. The engine is distinguished by a simple compact design. A removable starter is used to start the engine. The engine served as a prototype for most low-power engines used as a power plant for ultra-light, unmanned aerial vehicles, and aircraft models.

[0004] The disadvantage of the known design is the low efficiency of the power plant, low reliability and long pre-launch preparation of the engine.

[0005] A low-power single-shaft gas turbine engine is known (invention certificate 165039 USSR). The engine is made with a centrifugal compressor and a centripetal turbine mounted on one shaft. The starter is connected via a single-stage gear transmission and a freewheel clutch.

[0006] The disadvantage of the known design is the low efficiency of the power plant due to the use of a single-stage centrifugal compressor and a single-stage centripetal turbine, and the use of a starter installed through a freewheel clutch and gear transmission reduces the reliability of the engine.

[0007] A single-shaft dual-circuit turbojet engine is known (patent RU 2674172 C1) and is accepted as the closest analogue based on a number of features. The engine comprises a compressor, a turbine, a main continuous-detonation combustion chamber with fuel supply channels, fuel injectors and a detonation initiator, a gas-dynamic damper, a nozzle apparatus and a turbine. In the engine's post-turbine cavity there are four continuous-detonation combustion chambers in the form of closed annular sectors, the inlet of each of which is connected to the air duct of the outer circuit. The inlet of the main combustion chamber is connected to the air duct of the inner circuit. The bypass ratio of the engine is equal to or greater than one. An electric machine connected to a battery pack is located on the engine shaft. A ring piezoelectric generator consisting of two parts separated by a buffer is also connected to the battery pack.Around the inner surfaces of the main and after-turbine combustion chambers, annular cooling jackets with permeable matrix injectors and fuel injector units are installed. To cool the outer surfaces of the four after-turbine combustion chambers in places that come into contact with the hot gas flow leaving the turbine, an annular cooling cavity with matrix injectors and a fuel injector unit is installed. The invention is aimed at increasing the thermodynamic efficiency of the engine, thrust, reducing the weight and size characteristics, and expanding the range of thrust vector variation.

[0008] The disadvantages of the known design include its complexity and, as a consequence, its low reliability, non-stationarity of the detonation combustion process, leading to the occurrence of vibration processes in the design and a low operational life, low durability of the piezoelectric elements used as an electric power generator, the need to use additional gas-dynamic dampers worsens the mass and size characteristics of the engine.

[0009] The purpose of the present invention is to develop a maximally compact, easy-to-manufacture design of a low-thrust, dual-circuit turbojet engine from 1000 to 5000 N, suitable for large-scale production, for use in ultra-light aircraft and structurally similar products.

[0010] The stated objective is achieved by optimizing the fan impellers, axial compressor, turbine and starter-generator design so that their operating speeds coincide for their installation on one rotor shaft without the need to use upshifting or downshifting gears. To solve the stated objective, a confuser is installed at the entrance to the engine impeller, which allows for a reduction in the outer diameter of the fan impeller, thereby reducing the peripheral speed of the fan blade edge. The blade shape is selected in such a way as to ensure its operability not only at subsonic speeds, but also at supersonic speeds.A multi-stage axial compressor is installed in the internal circuit of the engine, the use of an axial compressor design compared to a centrifugal version allows to reduce the diameter of the engine design and avoid the need to use a large flow straightener, the so-called "snail", the consequence of this solution is the ability to increase the bypass ratio of the engine with fairly compact dimensions up to 8. A brushless DC electric machine is used as a starter-generator, the use of high-energy magnets in such types of electric machines allows to obtain good specific power, and the high efficiency of such machines leads to the absence of the need to use complex and large cooling systems. A brushless DC machine does not have a contact unit and is characterized by a long service life. The rotor of the starter-generator is fixedly attached to the shaft of the turbojet engine.The turbine impeller is made with active-type blades; the operating speed of turbines with active-type blades is lower than the operating speed of similar reactive or active-reactive turbines. The use of active-type blades makes it possible to reduce the operating speed of the turbine to acceptable values ​​and install it on the same shaft with the fan impeller without using reduction systems. The use of active-type blades on the turbine leads to some efficiency losses, but makes it possible to operate at lower peripheral speeds; in this case, the unused portion of the internal energy of the fuel combustion products is converted into useful work in the engine nozzle block. The essence of the invention is explained by a drawing of a longitudinal section of the engine, see Fig. 1. Position 1 marks the confuser of the air flow acceleration supplied to the fan impeller pos. 2. The fan impeller is put on the rotor pos. 3 of the starter-generator. The stator of which is fixedly secured to the bracket pos.5 of the inner engine circuit. The rotor is mounted on the hollow shaft of the engine pos. 6. The working wheels of the compressor stages pos. 7 with intermediate air flow rectifiers pos. 8 are installed sequentially on the shaft. The shaft passes through the combustion chamber of the annular type engine pos. 9 isolated from its working zone by the inner casing pos. 10. The working wheel of the turbine pos. 11 is installed at the end of the shaft. Combustion products are fed to the working wheel through the guide vane pos. 12, then the flow of combustion products passes through the flow rectifier 13 and enters the nozzle block of the inner circuit pos. 14 with the central body pos. 15. The air flow pumped by the fan into the outer engine circuit pos. 16 passes through the nozzle block of the outer circuit pos. 17.The proposed technical solution will make the engine design as compact as possible, maintain a relatively high engine efficiency while maximally simplifying the design and ensuring its high reliability, which is especially critical for low-thrust engines. The absence of complex technological design units will ensure the possibility of rapid organization of serial production of such engines.

Claims

5 Invention formula A single-shaft turbojet dual-circuit fan engine comprising a confuser, a fan with a supersonic blade profile, a brushless DC electric starter-generator built into the central portion of the fan, a multi-stage axial compressor of the inner circuit, a combustion chamber and a turbine with one or more stages with an active blade profile, characterized in that, in order to ensure the compactness of the design, the fan supplying air to two circuits, the starter-generator, the axial compressor and the turbine stages are mounted on a single shaft without the use of gearboxes.

Images