RU2596077C2 - Slot-type injector-vortex generator and operation method thereof - Google Patents

Abstract

FIELD: energy.

SUBSTANCE: invention relates to power engineering. Slot-type injector-vortex generator installed in the channel along the direction of high-energy gas flow. Wherein said flat slot-type channel of the injector is made with a diagonal cut at the output and is installed so that the slot forms an acute angle with the direction of incoming high-energy flow. Value of slot angle is selected based on the intensity of mixing of gas flows and uniform filling of flow with injected gas. Also disclosed is a method of operation of slot-type injector.

EFFECT: invention allows to intensify processes of mixing, ignition and combustion of fuel-air mixtures in combustion chambers of ramjet engines and other installations with interconnecting piperack.

2 cl, 2 dwg

Description

The invention relates to systems for supplying gaseous, liquid, two-phase fuels to a high-temperature high-speed gas stream and is intended to intensify the processes of mixing, ignition and combustion of air-fuel mixtures in the combustion chambers of ramjet engines and in other plants with heat and mass supply.

The proposed technical solution relates to injectors for feeding and mixing high-speed gas streams installed in the mixing channel, and methods for their operation.

Known thermopower injection rack [1], placed in a gas-air high-speed hot stream. The rack has a streamlined aerodynamic profile and in the rear part contains a fuel channel, in the wall of which there are a number of elliptical nozzles for injecting fuel in a tangent to the main gas stream. The front edge of the rack is located at an angle of sweep ∠α with respect to the direction of the incoming flow. Thermal protection of the most thermally stressed element of the rack — the leading edge — is ensured by the fact that the edge is made of porous metal through which an inert gas (nitrogen) is blown through a special channel located inside the rack along the leading edge. The laminar flow of inert gas flowing from the micropores of the leading edge forms a protective jacket around the rack, which provides thermal protection for the rack structure.

The disadvantages of this solution are: the need to arrange an additional inert gas supply system, large recommended angles переднейα of the leading edge (from 45 ° to 90 °), additional losses of the kinetic energy of the main stream caused by the supply of inert gas from the leading edge. Low efficiency of mixing flows due to the satellite fuel supply, as well as the complexity of the design and manufacturing technology.

As a prototype, a pylon - auto-igniter of fuel [2], installed in the combustion chamber of a ramjet engine and having a body composed of a number of bonded plugged tubes installed obliquely, was selected. The leading edge of the pylon is located at an angle of sweep to the main stream and is cooled by a small amount of gaseous fuel injected against the stream through a series of microholes made in the frontal inclined tube of the pylon. The acute angle of sweep of the leading edge ∠α (in the range of 20-70 °) is determined by the formula

where M is the Mach number of the incident main supersonic flow.

The pylon is intended for injection and autoignition of gaseous fuel in a supersonic gas-air high-temperature flow. The injection of the main amount of fuel gas is carried out through rows of perforations in the side and rear walls - the pylon tubes. The drawback of the pylon is that it is made of perforated microtubes, which have low strength due to perforation and limited heat resistance in the stream. In addition, the operation of the pylon provides for auto-ignition and fuel combustion directly on the side surface of the tubes, which further reduces its heat resistance in the stream. The wave-like lateral surface of the pylon, in turn, along with the stimulation of autoignition causes an increased aerodynamic drag of the pylon.

The lack of effectiveness of the prototype as a self-igniter is partially compensated by the correction of the sweep angle α, a special mechanism that changes this angle in relation

where k is the adiabatic exponent, Tc is the autoignition temperature, T is the static flow temperature [3].

In the second modification, insufficient thermal strength of the prototype structure is compensated, in addition to mechanical rocking, by an additional restriction on the set of operating modes of this device in the stream in the ratio:

where P _o is the total pressure acting on the strut, P is the static pressure before the head wave, M is the Mach number, λ is the reduced velocity behind the shock, and σ is the permissible stress of the strut material [4].

Thus, the prototype in the above modifications is operable in the flow of hot gases due to mechanization and automation of movement, the complexity of the implementation of which eliminates the initially stated simplicity of design, the stability of self-ignition and mixing efficiency achieved by the initial distribution of the injection holes on the injector surface. In addition to the listed disadvantages that limit the thermal stability of the structure, the prototype and its modifications used the satellite and tangential methods of secondary gas injection, which do not allow efficient mixing of gases in short channels at supersonic speeds of the main stream.

It is known [5] that the mixing processes of supersonic gas flows are complicated due to the low energy of the velocity pulsations in comparison with the kinetic energy of the interacting flows, that is, supersonic flows are essentially laminar. The following methods have been proposed and applied as mixing methods: strong acoustic effects on the flow [6, 7], pulsating compressive deformations of the injectant jets by modulating injection into the channel boundary layer (Richmayer-Meshkov method) [8], and the method of organizing decaying large-scale eddies behind the wedge in main stream, successfully used in subsonic mixers [9]. The main objective of the applied physical processes is to exchange devices between stratified layers of a supersonic flow by generating flow intermittency effects, which initiate subsequent processes of effective mixing.

The objective of the invention is the effective mixing of gas flows, ensuring thermal strength of the injector design in the washing high-energy flow of the main gas, low aerodynamic resistance of the injector, simplicity of design.

The stated technical problem is solved by the proposed device — a slotted injector — a vortex generator installed in the mixing channel along the direction of motion of the high-energy gas stream. The flat slit channel of the injector is made with an oblique cut at the outlet and is installed in such a way that the slit cut forms an acute angle with the direction of the incident high-energy flow, while the cut-off angle is set based on considerations of the intensity of mixing of the gas flows and the uniformity of filling of the high-energy gas flow with injected gas.

The method of operation of the slotted injector - vortex generator includes a tangential injection of injected gas into the mixing channel with a high-energy gas stream. According to the method, a flow of injected gas is generated in the flat slotted channel of the injector, formed by longitudinal pairs of microvortices of an injected gas of opposite rotation (spin), while a high-energy gas stream incident at an acute angle to the oblique section of the slotted channel separates microvortices depending on the direction of rotation (spin), it captures them from the cut-off surface of the injector and directs them along the flow along the outer walls of the injector, cooling the injector, moreover, in a high-energy gas stream flowing around the region Injection, a large-scale vortex pair is formed, which involves the micro-vortices of the injectant gas in the lateral macrodisplacement, providing the effect of intermittent flows, which in turn determines the uniformity of the filling of the entire flow with the injected gas.

Achievable technical result: the formation of gas-dynamic structures of flows intensifying the spatial distribution (intermittency) and subsequent mixing of gases with high completeness, achieving a given depth of penetration of the injected gas into the main stream, efficient mixing of gases in short channels at supersonic speeds of the main stream, ensuring thermal strength of the injector design in washable high-speed gas flow, low aerodynamic drag of the injector, simplicity of design and.

In FIG. 1 shows a General view of the slit injector installed at the inlet to the mixing channel with a high-energy gas stream, and the principle of its operation; in FIG. 2 - evolution of a hydrogen cloud in a high-energy gas stream when blowing through a slotted injector.

The proposed slotted injector - vortex generator is made with an oblique cut of the leading edge, containing a narrow slotted channel inside the injector body. A general view of the injector installed at the inlet to the mixing channel and the principle of its operation are presented in FIG. 1: in the channel 1 along the direction of movement of the main stream of high-energy gas, a slit injector 2 of the secondary injecting gas with an oblique cut at the outlet is installed; cascade of microvortex bundles 3 of the injectant gas (hydrogen); macrovortices 4 of the main high-energy flow formed in the main high-energy gas flow during the flow around the injector. In FIG. 2 shows the evolution of the hydrogen cloud in a supersonic air flow, where 5 are the cross sections of the hydrogen cloud, 6 is the projection of the trailing edge of the injector, 7 is the localization of hydrogen microvortex bundles, 8 is localization at the wall of the mixing channel.

The injector is formed by two closely spaced flat walls, the distance between which varies from 0.1 to 0.7 mm. The design dimensions of the injector are selected based on the following:

- the gap width is calculated according to the criteria for the formation of a cascade of injectant microvortices in the process of gas outflow, following the provisions of the theory of gap gas flows [10];

- the height of the leading edge of the injector is selected taking into account the thickness of the boundary layer of the flowing main stream;

- the height of the trailing edge is selected based on the specified depth of penetration of the injectant, the purpose of the injector and the purpose of the mixing channel (combustion chamber, mixing chamber), based on the conditions for minimizing the mixing length of gas flows;

- the angle of inclination of the leading edge α can be chosen to be minimal according to relation (1), since flat extended walls form a structurally rigid strong channel of a minimal midsection subject to minimal thermal influence by a washer flow;

- the length of the slit along the direction of the main flow is limited only by the layout considerations of the entire mixing device according to studies [11].

A slotted vortex injector generator with an oblique cut of the leading edge is installed at the entrance to the mixing channel, through which the main stream of high-energy gas flows, with its lateral plane along the longitudinal axis of the channel. In this case, the oblique cut of the leading edge of the injector is located at a certain sweep angle (∠α) to the direction of the main high-energy gas flow. The angle value is selected according to well-known dependencies, based on the conditions of heat resistance of the injector design, minimization of the mixing length of gas flows, minimization of the loss of the total pressure of the flow and ensuring the conditions of autoignition of the mixture. In the body of the injector streamlined around the main high-energy gas stream, an extended narrow slotted channel is made, through which an injected secondary injector gas is supplied to the channel. In this case, the injectant supply regimes by mass flow rate are selected from among the characteristic modes that ensure the formation of a cascade of longitudinal microvortex bundles such as Taylor vortices. The slotted channel ends with an oblique cut of the front edge of the injector. Due to this arrangement, the injected gas flowing from the slit of the injector with an oblique cut into the main stream of hot gases enters into spin-selective interaction with the main high-energy gas stream, as a result of which it forms an external protective jacket around the injector body, thereby preventing thermal destruction of the structure washed by the main high energy gas flow.

The way the slit injector works.

At the entrance to the mixing channel 1 serves the main high-energy gas stream. At the same time, a subsonic flow of cold secondary injector gas is supplied to the injector 2 inlet. The injectant flow is subjected to mechanical stress - it is deformed by the walls inside the thin slit of the injector. Therefore, it transforms into the so-called slotted flow, consisting of a flat cascade of microvortex bundles 3. The injection gas in neighboring bundles occurs in opposite directions, in other words, the neighboring microvortices have the opposite Taylor-Couette spin. In FIG. 1, such rotation is conventionally indicated by arrows 3 with a tail part of variable thickness. The rotation is supported by the longitudinal and transverse gradients of the gas pressure existing in the oblique slit channel of the injector. After the gas flows out of the gap, the injecting gas enters into a spin-selective force interaction with the flowing supersonic flow of high-energy gas, expands and forms a deformed off-design jet, while developing in the direction of the flow of the washing main flow. At the same time, in the process of force interaction, the flat cascade of injector microvortex harnesses splits / selects into separate strands of the opposite spin, which are deployed in opposite sides of the plane of the oblique cut of the injector due to the different spin. Conventionally, the splitting of the injector cascade is indicated in FIG. 1 arrows 3 different directions. Then, the individual rotating micro-eddy harnesses of the injector are pressed by a high-energy gas flow washing onto the outer surface of the injector, forming a thermoprotective jacket. At the same time, the flowing high-energy gas stream is cut into two halves by the cylindrical edge-by-edge “off-grid structure” of the injectant gas. As a result, a pair of macrovortices 4 arises in the flowing high-energy gas stream, similar to the aerodynamics of a “cylinder placed along the stream at an angle of attack”. The resulting macrovortices 4 involve the longitudinal injectors 3 in the lateral displacement, i.e., a slit injector with an oblique cut at the outlet, installed at the channel inlet along the direction of the high-energy gas flow, so that the slit cut forms an acute angle with the direction of the oncoming high-energy flow and generates a vortex the mechanism of transition of a part of the kinetic energy of a high-energy flow to the effects of intermittency of flow structures, which then turn into turbulent pulsations, which stirred and injected flows of high molecular gases to a desired level of homogeneity.

To confirm the effectiveness of the technical solution, experiments were conducted at ITAM SB RAS. Hydrogen gas was injected into a supersonic air stream with a Mach number M = 2 through a slotted injector with an oblique cut at the outlet made of steel grade 12Kh18N9T. The braking temperature ranged from 1300-3000 K. Tests have shown that the injector has unlimited resistance and provides ignition and subsequent combustion of hydrogen over 90%, which is an indicator of the efficiency of mixing processes. The results of laser imaging of the flow in the mixing channel (to scale) are presented in FIG. 2. Positions 5 and 7. Cross sections in the form of shaded areas illustrate the efficiency of the mixing of gas flows, characterizing the dynamics of filling the cross section of the air flow with a cloud of injected hydrogen. Measurements showed that, at a length of ~ 1.8 gauge of the channel, injected hydrogen already reaches the walls of channel 8 in the transverse direction, and at a length of ~ 3.3 gauge, the air flow cross section is already filled with hydrogen by 35-40% (the spread of reducible accuracy is due to the pulsed imaging principle )

Information sources:

1. RF patent No. 2383761, IPC F02K 7/10, F01D 5/18.

2. RF patent No. 2428576, IPC F02C 7/26, F23R 3/20 - prototype.

3. RF patent No. 2444639, IPC F02C 7/26.

4. Patent for utility model of the Russian Federation No. 104971, IPC F02C 7/22.

5. Kochetkov Yu.M. Turbulence. The fundamental equation of supersonic gas dynamics is a new profiling method for LPRE nozzles. Engine No. 3 (87), 2013, p. 44.

6. Kochetkov Yu.M. Turbulence in ramjet and scramjet. Engine No. 6 (72), 2010, p. thirty.

7. UKRAINE Patent No. 86966, Method for adding a gas turbine to a turbo pump turbine pump of a solid rocket engine and an extension for further storage. IPC F02K 9/42 (2006.01) F23H 9/00.

8. Qingchun Yang, Juntao Chang, and Wen Bao. Richtmyer-Meshkov Instability Induced Mixing Enhancement in the Scramjet Combustor with a Central Strut. Advances in Mechanical Engineering Volume 2014 (2014), Article ID 614189, 7 pages, http://dx.doi.org/10.1155/2014/614189.

9. RF patent No. 2106573 C1, IPC F23D 14/62, F23D 17/00 1994.

10. Crevice seals. In the book. Seals and sealing technology. Directory. ed. A.I. Golubeva. - M.: Mechanical Engineering, 1986, p. 375-405.

11. C. Birzer, C.J. Doolan A quasi-one-dimensional model of hydrogen-fueled scramjet combustors. J. Propulsion & Power 25 (6), 1220-1225, 2009.

Claims (2)

1. A slotted vortex injector-generator installed in the mixing channel along the direction of motion of the high-energy gas stream, characterized in that the flat slit channel of the injector is made with an oblique cut at the outlet so that the slit of the slot channel forms an acute angle with the direction of the incident high-energy gas stream, In this case, the value of the cutoff angle of the slit channel of the injector is calculated from the conditions for ensuring uniformity of filling and intensity of mixing of the injected gas with the incident high-energy gas stream. 2. The method of operation of the slotted injector - vortex generator, including the tangential injection of injected gas into the mixing channel with a high-energy gas stream, characterized in that the injected gas flow structure is formed in the flat slotted channel of the injector, consisting of longitudinal pairs of microvortices of the opposite direction, while running under At an acute angle to the oblique cut of the slotted channel, the high-energy gas flow captures microvortices from the surface of the oblique cut of the injector and separates them depending on systematic way rotation and guides the flow along the outer walls of the injector, the injector cooling and forming a pair of large-scale vortex involving microwhirlwinds gas injectant into lateral makroperemescheniya providing uniform filling of the entire stream.

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