RU2253745C2 - Three-circuit gas-turbine engine - Google Patents

Abstract

FIELD: mechanical engineering; gas-turbine engines.

SUBSTANCE: proposed three-circuit gas-turbine engine consists of two gas-turbine engines with common intake device. One of engines is shaft-turbine engine with free turbine being additional turbine for second engine. Second engine is ejector-turbine one. Both engines have common exhaust unit. Ratio of air flow rate through compressor of shaft-turbine engine and compressor of ejector-turbine engine at takeoff is 0.15-0.3.

EFFECT: improved combustion characteristics of ejector-turbine engine at subsonic speeds of flight.

3 dwg

Description

The invention relates to aircraft engine manufacturing.

Known turbojet engines (RU 2190772, F 02 C 3/32, 2002). The disadvantage of these engines is low efficiency at subsonic flight speeds. The reason for low efficiency is the restriction on the degree of increase in air pressure by the compressor (πk ~ 4.0), imposed by a gas ejector.

Known turboshaft engines with a free turbine (Theory and calculation of jet engines. Edited by S.M.Shlyakhtenko, M .: Mechanical Engineering, 1987, p. 354, Fig. 11.4), which are widely used as turbostarter in gas turbine engines for various purposes. Turboshaft engines are highly economical at subsonic flight speeds.

Combined turbofan engines are known in which ramjet and gas turbine engines have common input and output devices (Bulletin of the Academy of Cosmonautics, No. 2, Moscow: Cosmonautics Academy, 1998, p. 105, Fig. 5).

The closest analogue to the proposed invention is a three-circuit engine described in SU 1760806, F 02 K 3 / 04,1995.

The proposed technical solution is aimed at improving the flow characteristics of turbojet engines at subsonic flight speeds.

This goal is achieved by a combination of two engines: turbojet (TRDE) and turbojet with a free turbine (TVaD). In this case, both engines have a common input and output device, and a free turbine turbine engine is kinematically connected with the turbine engine.

The essence of the invention lies in the fact that a free turbine turbine engine is an additional turbofan engine, which, by reducing the power of the turbofan engine, increases the pressure drop in the output device (at the nozzle) and, thereby, improves the traction and flow characteristics of the turbofan engine at subsonic flight speeds. In this case, the initial (under take-off) ratio of TVAD and TRDE power is set by the ratio of air flow through the TV-AD compressor and the TRDE compressor, which is 0.15-0.3 under take-off conditions.

Figure 1 shows a diagram of a three-circuit gas turbine engine;

figure 2 shows the dependence of the reduced frontal thrust on the flight speed along a typical trajectory of a hypersonic aircraft for a three-circuit gas turbine engine;

figure 3 shows the dependence of the specific fuel consumption on flight speed along a typical trajectory of a hypersonic aircraft for a three-circuit gas turbine engine.

A three-circuit gas turbine engine consists of an input device 1, an output device 2, a turbojet engine 3, a turbojet engine with a free turbine 4. The turbojet engine contains an internal channel (first circuit), inside which a compressor and the main combustion chamber are located, an external channel (second circuit), lobe a mixer connecting the external and internal channels to the mixing chamber, a turbine located behind the mixing chamber. The turboshaft engine contains a turbocharger, a free turbine. TVAD is located in the channel (third circuit) connecting the output from the input device 1 with the entrance to the output device 2. A free turbine TVAD through a gearbox is connected to the shaft of the engine.

The engine is as follows. Air through the input device 1 enters the TVAD and TRDE. The power generated by the free turbine engine is transmitted through the gearbox to the turbojet engine shaft, and hot gases leaving the turbine engine are sent to the output device 2. Hot gases coming from the turbojet engine are also sent to the output device 2. In the output device, gases from both engines mix and accelerate, creating engine traction.

The appearance of a positive effect (improvement of the flow characteristics of the turbojet engine at subsonic flight speeds) is directly related to the distribution of air flow between the high-speed engine and the engine. The specified distribution is characterized by a three-circuit coefficient t equal to the ratio of air flow through the third and first circuits, which corresponds to the ratio of air flow through the TVAD compressor and the TRDE compressor. The three-loop coefficient in take-off conditions is 0.15-0.3.

At subsonic flight speeds, the TRRE has low pressure drops at the nozzle (less critical), which leads to a significant increase in specific fuel consumption of the engine. Transferring the power of a free turbine turbine engine to the turbojet engine shaft allows reducing the pressure drop across the turbojet engine (by reducing its power) and, accordingly, increasing the pressure drop across the nozzle, which increases the specific thrust of the engine and reduces specific fuel consumption.

With an increase in the flight speed, the operation of a free turbine decreases due to a decrease in the available pressure drop, which leads to a power shortage on the turbojet engine shaft (the larger the higher t) and, as a result, to reduce the speed and air flow through the main (first and second) engine circuits . The third circuit in this case compensates for the decrease in air flow through the first two, but this, as the calculations show, is possible only up to certain values of the coefficient t, after which there is a noticeable deterioration in engine performance.

Figure 2 and figure 3 shows the speed characteristics of the three-circuit gas turbine engine, reduced to the high-speed characteristic of the turbojet engine (t = 0), for the four values of the coefficient of three-circuit in take-off conditions t _o : 0.2; 0.3; 0.4; 0.5 (index “o” corresponds to take-off conditions). It can be seen that the traction and flow characteristics at low and medium flight speeds (Mn <2) significantly increase with increasing t _o , for example, when taking off, the frontal thrust increases by more than 30%, and the specific fuel consumption decreases by more than 15%. As for the high speeds (Mn> 2), the influence of t _o on the engine performance is not so clear: if t _o <0.3, then performance degradation with respect to the engine fuel economy (t = 0) practically does not occur, but if t _o > 0.3, then already at speeds Mn> 2.5 there is a noticeable decrease in frontal thrust (figure 2) and a deterioration in engine efficiency (figure 3). This fact is explained by the fact that, at low t _{o, the} decrease in the energy flow through the main circuit (due to a decrease in the total power of the turbine gas turbine turbine compared to the turbojet turbine engine capacity: t = 0) is compensated by the supply of additional energy (hot gas) generated by the high-pressure fuel pump. At large t _o > 0.3, the decrease in turbine power is so significant that the energy flow passing through the fuel assembly does not compensate for the decrease in energy flow passing through the main (first and second) engine circuits, which leads to a deterioration in engine performance.

The minimum three-circuit degree t _o ~ 0.15 is determined from the condition for the existence of a system consisting of two engines, one of which is turbojet. The fact is that TVAD, among other things, serves as a starter for TRDE. The peculiarity of starting TRRE is that the engine speed at start-up should be at least 60% of the maximum (in conventional gas turbine engines - about 20%), which is necessary for the stable operation of the gas ejector. Ensuring such a high speed requires significant power, which determines the minimum value of the degree of three-circuit.

Claims (1)

A three-circuit gas turbine engine, consisting of two having a common input device for gas turbine engines, one of which is made turboshaft with a free turbine, which is an additional turbine of the second engine, characterized in that both engines have a common output device, the second engine is made turbo ejector, and the ratio of air flow through the turboshaft compressor and turbojet engine compressor during take-off conditions is 0.15-0.3.

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