RU2793868C1 - Supercharged pulse jet - Google Patents

Abstract

FIELD: aviation.

SUBSTANCE: invention relates to pulse jets (PJ) and can be used as an aircraft power plant. The jet design includes a spark plug (1), a combustion chamber (2), a fuel supply pipe (3), a gas-dynamic input diode (4), an air manifold with nozzles (5), a nozzle assembly (6), a unit with inlet guide vane (7), vortex tube (8) and adjustable nozzle (9). Exhaust gases from the combustion chamber exit through a nozzle assembly into a vortex chamber with intense swirling, where atmospheric air is ejected and compressed from the peripheral zone through inlet channels and passes along the vortex chamber, splitting into cold and hot vortices, and the hot vortex exits into the atmosphere through an adjustable nozzle, and the cold one goes to the inlet to the combustion chamber through a gas-dynamic diode.

EFFECT: increased efficiency of the PJ due to a denser filling of the combustion chamber with an air-fuel mixture.

1 cl, 5 dwg

Description

The invention relates to engine building, in particular to pulse jet engines (PUVRD), and can be used as a power plant for an aircraft, can also be used as a power plant, for example, unmanned reconnaissance aircraft, flying targets, loitering ammunition.

A known method of purge pulsating air-jet engine of the German cruise missile of the Second World War V-1 (see G. B. Sinyarev, M. V. Dobrovolsky. Liquid rocket engines. - Oborongiz, 1957, pp. 19, 20). It is implemented based on the use of a valve grid at the inlet to the combustion chamber. The main advantage of the PUVRD purge method based on the use of mechanical valve grids is the high gas-dynamic resistance to combustion products trying to break through against the oncoming flow during an explosion in the combustion chamber.

The disadvantage is the resistance to fresh flow at the entrance to the combustion chamber, which leads to a low cyclic filling and, as a result, to low specific and frontal thrust at high flight speeds. But their main drawback is a small resource, no more than 60 minutes.

Known PuVRD (RF patent No. 48368, IPC F02K 7/067, publ. 10.10.2005), which includes a combustion chamber 1.5-2.0 long of its diameter, having a cylindrical shape of circular cross section with a flat or special shape of the front wall and a flat rear wall, an exhaust pipe with a diameter of 0.5 of the combustion chamber diameter, consisting of a cylindrical part and an expanding cone, with its front end associated with the rear wall of the combustion chamber, on an expanding cone, with an opening angle of 5-6 °, a cylindrical nozzle with a diameter of not more than combustion chambers, aerodynamic valves, in the form of cylindrical tubes, for preparing and supplying an air-fuel mixture to the combustion chamber, with an air intake at one end, built into the rear wall at the other end, the axes of which are parallel to the axis of the combustion chamber. The total length of the combustion chamber and the exhaust pipe with the nozzle combined is 10-12 combustion chamber diameters.

The disadvantage of the technical solution is the low amplitude of the pressure pulsations in the combustion chamber and, accordingly, the low thermodynamic efficiency (coefficient of performance) due to the low combustion rate of the air-fuel mixture.

The indisputable advantage of this type of engines is their manufacturability and low price, the disadvantage is the lack of pre-compression of air, as is done in gas turbine (GTE) or piston engines. This is the reason for the low efficiency.

The closest analogue in terms of a set of essential features is the method of supercharging internal combustion engines (RF patent No. 2756831, IPC F02B 37/00, F02B 75/10, publ. 10/06/2021), containing an air ejector with exhaust or exhaust gases and a Rank vortex tube separating mixture of gases into cold and hot vortices. A cold vortex containing a large amount of air goes to pressurize the engine, and a hot one is released into the atmosphere.

The objective of the technical solution is to equip the combustion chamber of the PuVRD with gas-dynamic pressurization using part of the energy of the exhaust gases. Pressurization of the combustion chamber will increase the efficiency of the engine.

The purpose of the claimed solution is to increase the efficiency of the PUVRD by taking part of the energy from the exhaust gases for ejection and compressing a fresh portion of air in order to more densely fill the combustion chamber with an air-fuel mixture.

The technical result is achieved due to the fact that in the PWRD containing a combustion chamber with a spark plug, a fuel supply pipe, a pipe with a gas-dynamic diode for air supply from the vortex chamber, the exhaust gases exit through the nozzle apparatus into the vortex chamber with intense swirling, where from the peripheral zone through inlet channels eject and compress atmospheric air and pass along the vortex chamber, dividing into cold and hot vortexes, the hot vortex exiting into the atmosphere through an adjustable nozzle, and the cold one goes to the combustion chamber inlet.

The gas-dynamic structure of the engine is based on the well-known gas properties:

1. Ejection consists in the fact that a flow with a higher pressure, moving at a high speed, entrains a low-pressure medium. Increasing the pressure of the ejected flow without direct mechanical energy is used in jet devices that are used in various branches of technology. The mass of the added air must be greater than the mass of the exhaust gases.

2. Vortex effect (Ranque-Hilsch Effect) - the effect of temperature separation of gas when swirling in a cylindrical or conical chamber, provided that the gas flow in the pipe passes not only straight, but also in the opposite direction. A swirling flow with a high temperature is formed at the periphery, and a cooled flow exits from the center in the opposite direction. The swirl of the flow occurs in the nozzle apparatus. The vortex tube is tuned by changing the flow section of the nozzle.

In the exhaust gases, the two main combustion products are carbon dioxide CO ₂ (13.7% by volume - one and a half times denser than air) and water vapor H ₂ O (13.1%), the rest is nitrogen, etc. Solid particles of coke, soot, water vapor, air dust and the most dense gases are separated from a strongly swirling flow, they are pressed against the pipe wall by centrifugal forces and exit into the atmosphere together with a hot whirlwind. The cold vortex along the axis of the vortex chamber goes in the opposite direction to the inlet to the combustion chamber through the gas-dynamic diode.

3. It is known from gas dynamics that the gas flow rates strongly depend on the duct profile. With the passage of a converging - confusing nozzle by gas in the forward and reverse directions, this coefficient may differ by several times. The nozzle stack creates the effect of a gas dynamic diode. In addition, the nozzles are at some distance from each other and the walls of the nozzles form a labyrinth with a pronounced inclination of the walls. Toroidal vortices are formed in the labyrinth space, which enhance the diode effect. (Machine Building Journal No. 2 2012. “Numerical Simulation of Flow in Gas-Dynamic Diodes” UDC 621.436.052). The gas-dynamic diode works like a valve, to the best of its ability preventing the passage of gas from the combustion chamber into the vortex chamber.

4. The combustion of the fuel-air mixture in the combustion chamber occurs cyclically as it is filled with a fresh charge and this charge reaches the spark plug or the hot zone of the chamber. The burning time is rather short, a huge proportion of the gas, due to its inertia, does not have time to escape. Thus, combustion or heat supply occurs at a constant volume, i.e. according to the isochoric cycle. It allows you to increase the thermal efficiency of the motor by 10 ... 15% compared to the isobaric cycle.

The claimed technical solution is characterized by the following drawings:

in fig. 1 - shows a diagram of a supercharged PUVRD;

in fig. 2 - the nozzle apparatus and the gas-dynamic diode are shown in the path for supplying a cold vortex from the vortex chamber to the combustion chamber;

in fig. 3 shows an inlet device with guide vanes.

in fig. 4 - shows the moment of purge of the combustion chamber;

in fig. 5 - shows the moment of the working stroke of the gas in the supercharged PUVRD;

The design of the engine is schematically shown in figure 1 includes a spark plug (1), a combustion chamber (2), a fuel supply pipe (3), a gas-dynamic input diode (4), an air manifold with nozzles (5), a nozzle apparatus (6 ), an inlet with guide vanes (7), a vortex tube (8) and an adjustable nozzle (9).

In FIG. 2 schematically shows a nozzle apparatus (6) and a gas-dynamic diode (4) in the path for supplying a cold vortex from the vortex chamber to the combustion chamber. The blades of the nozzle apparatus have an axial inlet and a tangential outlet, their task is to turn the exhaust gas flow at an angle close to 90 °, this will create an intense vortex. At the initial moment after the flash, the pressure drop across the nozzle apparatus (6) is supercritical, and when the gas leaves the confuser interblade path at the speed of sound, seal shocks are possible, this is for a short moment - the volume of the combustion chamber is small. The gas-dynamic diode (4) consists of a stack of nozzles located at some distance from each other, with a narrow part directed towards the combustion chamber (2). Their task is to reduce the flow of gas from the combustion chamber into the vortex chamber (8) after the flash. Part of the gas that breaks through them will slow down the start of the combustion chamber purge (2) for the next cycle, this is useful for better cleaning the combustion chamber from residual gases.

In FIG. 3 schematically shows the inlet device (7) with guide vanes. Its task is to let in air from the atmosphere and form ejected air channels directed in the direction of rotation of the vortex.

The vortex chamber (8), in the wide part of which the vortex is generated and energetically fed, begins immediately behind the nozzle apparatus (6) and the channels of the ejected air. Then it smoothly passes into the cylindrical part along which the vortex moves, dividing into hot and cold components. The vortex chamber ends with an adjustable nozzle (9). This diagram shows a nozzle with a central body movable along the axis.

A supercharged puVRD operates in two cycles: purging the combustion chamber until the fuel-air mixture ignites and the gas power stroke.

The engine is started as follows: air is supplied under pressure to the air manifold (5), which blows through the combustion chamber (2) and the fuel supply zone through the nozzles, and fuel enters the fuel system (3), a cycle of discharges occurs on the spark plug (1) . In FIG. 4 shows the moment of purging the combustion chamber (2). After starting the engine, air into the combustion chamber (2) begins to flow from the vortex chamber (8) through the gas-dynamic input diode (4), the air manifold (5) is turned off. A fresh charge displaces air or residual gases from the combustion chamber (2), when the stoichiometric composition of the fuel-air mixture reaches the spark plug (1), a "pop" occurs in the combustion chamber, the pressure rises sharply, the gas-dynamic diode (4) is locked and the gas rushes through the nozzle apparatus (6) into the vortex chamber (8). The gas starts to generate energy. In FIG. 5 shows the stroke of the gas. The pressure drop across the nozzle apparatus (6) at this moment is higher than the critical one. The velocities in the resulting vortex are close to sonic. The vortex ejects air from the air intake (7) and gives it part of its energy. The pressure rises in the vortex chamber (8). The gas that has broken through the gas-dynamic diode (4) slows down the start of the purge for the next cycle. Due to their inertia, the gas masses in the vortex motion, passing along the trailing edges of the nozzle blades (6), eject residual gases from the combustion chamber. The pressure in the combustion chamber (2) decreases, a cold vortex begins to flow from the vortex chamber (8). A fuel-air mixture is formed, the next cycle begins. Thus, the cyclical operation is ensured. Energy pumping of the vortex occurs on each cycle.

The experience of fine-tuning the Argus-Schmidt HWK 109-014 for the German V-1 projectile shows that the pressure in the combustion chamber reached 6 atmospheres, the initial pressure was atmospheric. Thus, the combustion chamber can be considered as an amplifier with a gain of 5...6. The gas pressure in the swirl chamber (8), and hence the boost pressure, determines the cross section of the adjustable nozzle (9). At the initial moment, there is no reason to expect high values of boost parameters. It can be assumed that the increase in pressure per cycle will be 0.01 atmospheres, then at a pulsation frequency of 100 Hz in a second this pressure will already be one atmosphere. In reality, the pressurization process is a chain reaction with an amplification factor in the combustion chamber. An increase in the charge of the combustion chamber entails an increase in its pressure and gas flow along the entire path: the nozzle apparatus and the vortex chamber, etc. The pressure pumping into the combustion chamber can be quite significant. Detonation of part of the fuel is possible. This will further increase the efficiency of the engine.

The engine is controlled by a change in fuel consumption and an adjustable nozzle.

Claims (1)

A pulsating air-jet engine containing a combustion chamber with a spark plug, a fuel supply tube, an inlet device and a resonant exhaust pipe, characterized in that in a PUVRD containing a combustion chamber with a spark plug, a fuel supply pipe, a pipe with a gas-dynamic diode for air supply from a vortex chambers, the exhaust gases exit through the nozzle apparatus into a vortex chamber with intense swirling, where atmospheric air is ejected and compressed from the peripheral zone through the inlet channels and pass along the vortex chamber, splitting into cold and hot vortices, and the hot vortex exits into the atmosphere through an adjustable nozzle, and the cold goes to the inlet to the combustion chamber.

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