RU2444639C1 - Self-ignition of fuel mix in ramjet engine - Google Patents

Abstract

FIELD: engines and pumps.

SUBSTANCE: post is made up of aerodynamic-profile body with lateral cylindrical surface and furnished with injectors arranged on front and rear edges to communicate with fuel feed channels. Said post is mounted on chamber walls to turn thereon. Proposed method consists in feeding fuel in chamber via said injectors in post front and rear edges. Chilled-down fuel is fed via front edge injectors. Fuel is mixed with air for obtained mix to be heated to self-ignition temperature in collision of mix with post front edge due to compression in shock wave. Fuel mix is ignited and directed along said post to chamber inlet. Main portion of fuel is fed into airflow via post rear edge injectors. Said fuel is mixed with air and heated products of combustion of fuel forced into combustion chamber via injectors of post front edge for resultant mix to be ignited. Ignited fuel is fed into combustion chamber.

EFFECT: self-ignition of fuel fed into ramjet operated at Mach of 4 to 10.

4 cl, 5 dwg

Description

The invention relates to systems for supplying and igniting liquid and / or gaseous fuels into the combustion chambers of multimode supersonic ramjet engines, operating in a wide range of Mach numbers, for example, from 4 to 10.

A serious problem in the development of methods for burning fuels in the design of power plants, where a high-speed high-temperature air-gas flow is realized, is the choice of fuel supply and ignition systems.

An equally serious problem is ensuring the operability of fuel lines that are under conditions of heat and power exposure to high-speed high-temperature air flow.

A known method of ignition of a fuel mixture used in jet engines and rocket engines. The method consists in preliminarily forming a fire torch in the engine combustion chamber by means of an igniter placed in the chamber. Fuel components are fed into the chamber and ignited by a fire torch (Theory of jet engines. Workflow and characteristics. / Ed. By Acad. Stechkin BS M .: Gosoborongiz, 1958. P. 105). The disadvantage of this method is that when implementing it requires an additional device for the formation of a torch. This complicates the design of the combustion chamber and reduces the reliability. The sensitivity of the flare igniter to the composition of the fuel mixture can lead to failure in operation.

Known aerodynamic flame stabilizer for afterburner combustion chambers of the WFD of the company MTU (German patent No. 2329346, F02K 3/10, 03/08/73), which provides a stable combustion process and minimal hydraulic flow loss in the chamber. The contours of the flame stabilizer are an aerodynamic profile, on both surfaces of which there are nozzle openings through which the finished air-fuel mixture is supplied into the air stream under pressure.

Inside the stabilizer body are a mixing chamber with a nozzle device — a tube — and one or more air cavities. The air needed to prepare the air-fuel mixture enters the air cavities, from where it enters the mixing chamber through openings located on its outer wall. Fuel is also injected into the chamber. A homogeneous air-fuel mixture from the chamber is injected into the external stream. The ignition of the fuel-air jets is carried out by a spark plug placed at the end of the recirculation zone.

The disadvantage of this type of stabilizer is the complexity of its protection from high-density heat fluxes acting on the stabilizer from high-speed air flow, due to which there is no protection of the most heat-stressed place - the front edge of the stabilizer. In addition, it is not possible to compensate for the thermal deformation of the stabilizer design, which, with strong heating, can cause its destruction. The use of a spark plug to ignite the fuel mixture creates constructive additional complexity and unreliability in operation.

Closest to the claimed technical solution is a flame stabilizer for ramjet (US patent No. 3913319, F02C 7/22, 10.21.75). The stabilizer consists of front and rear well streamlined axisymmetric bodies connected by a cylindrical niche of smaller diameter. The stabilizer is attached to the wall of the combustion chamber using a streamlined rack. Fuel is piped to the nozzles at the leading edge, injected against the air stream and mixed with it. The resulting fuel mixture ignites in the recirculation zone in the niche. The recirculation zone is fed by mass transfer between the incoming flow of the fuel mixture and the vortex flow in the niche. The stabilizer creates ignition of the fuel mixture without additional sources of ignition, but does not ensure the safety of the leading edge in all modes of heat exposure to the air flow.

The basis of this invention is the solution of the following tasks:

- providing auto-ignition of the fuel mixture fed into the combustion chamber of a ramjet engine operating in a wide range of Mach numbers (from about 4 to 10);

- stabilization and increase the reliability of ignition of the fuel mixture;

- uniformity of atomization and ignition of the fuel when it is fed into the combustion chamber;

- creation of a rack for supplying fuel to the ramjet combustion chamber, operable under conditions of thermal and power impact on it of an incoming high-speed air flow.

The tasks are solved in that in the proposed method of auto-ignition of the fuel mixture, the combustion chamber of a ramjet engine contains a rack for supplying fuel. The stand is made in the form of a body of an aerodynamic profile with leading and trailing edges, fixed on one side inside on the wall of the chamber through a support, damped on the other side, and oriented by the profile along the path of the chamber. In addition, the rack is equipped with one channel for supplying fuel and fuel nozzles in communication with the channel located on the leading edge. Moreover, the method consists in the fact that the high-temperature high-speed air stream is supplied to the combustion chamber, the front edge of the strut is blown with air stream, which causes local braking and heating of the air stream. Fuel is supplied through the nozzles against the air stream and mixed with it, the fuel mixture in the stream is heated and ignited.

What is new in the invention is the use of a strut, which is further provided with a second fuel supply channel located at the rear of the strut and fuel nozzles in communication with the channel located along the trailing edge. The stand has a lateral cylindrical surface and is mounted on the wall of the combustion chamber through a support with the possibility of rotation along the path of the chamber. The ignition of the fuel mixture is carried out by the fact that in the air flow the rack in the place of fastening on the wall is installed obliquely to the axis of the chamber path at a sweep angle χ, depending on the engine operation mode, moreover, the discrete value of the sweep angle χ for a specific engine operation mode is determined by the ratio

,

,

where T ^* _s is the auto-ignition temperature of the air-fuel mixture;

T is the static temperature of the air flow;

Mn is the Mach number of the air flow running onto the rack;

K is the adiabatic index of air.

Through the channels and nozzles of the rack, fuel is supplied to the combustion chamber, while the channel and nozzles of the leading edge supply refrigerated fuel. In the combustion chamber, fuel is mixed with air, and upon impact of the fuel mixture in the air flow with the front edge of the strut, due to compression in the shock wave, the mixture is heated to the level of auto-ignition temperature of the fuel. The fuel mixture is ignited, the burning fuel mixture and the combustion products are directed from the front edge of the rack along its side surfaces to the rear edge and further into the chamber. The main part of the fuel is fed into the air stream through the second channel and the nozzles of the trailing edge of the rack, they are sprayed and mixed with the combustion products of the fuel, which are directed downstream of the front edge of the rack. Ignite the fuel mixture of the main part of the fuel and stabilize the process of burning it with the heated combustion products of the fuel supplied to the air stream from the front edge of the rack. The combustion products of the fuel mixture are sent to the combustion chamber.

With this method of auto-ignition of the fuel mixture in the combustion chamber of a ramjet:

- additional supply of the rack with a second fuel supply channel located at the rear of the rack, and fuel nozzles communicating with the channel located along the rear edge of the rack, provides the main part of the fuel to be burned in the prepared stabilized air flow;

- the implementation of the rack with a lateral cylindrical surface provides a simplified design;

- installation of the stand on the wall of the combustion chamber through a support with the possibility of rotation along the path of the chamber and securing the stand on the wall of the chamber obliquely at an angle of sweep χ to the axis of the path, depending on the operating mode according to a given ratio of parameters, ensures air flow braking on the front edge of the rack in a shock wave with by sliding, heating and auto-ignition of the fuel mixture with a decrease in heat flux to the front edge of the rack, as well as a decrease in the heat and power effects of the air flow on the rack;

- supply of refrigerated fuel to the combustion chamber through the channel and nozzles of the leading edge together with the tilt of the rack to the axis of the combustion chamber provides an additional reduction in heat fluxes to the front edge of the rack and its minimum heating;

- the direction of the burning fuel mixture and combustion products from the front edge of the rack along its side surfaces to the rear edge and further into the chamber ignites the main part of the fuel;

- the supply of the main part of the fuel through the second channel and nozzles of the trailing edge of the rack ensures its contact with the burning air-fuel mixture and its subsequent ignition;

- the continuity of heating of the flow of air flowing onto the rack, miscible with fuel, ensures the stability of the ignition of the fuel, and the direct contact of the heated air with the fuel creates the reliability of its ignition;

- one-sided mounting of the rack on the wall of the chamber eliminates the power load on the rack from thermal deformation.

The development of the set of essential features of the invention for particular cases is given below.

On the side surfaces of the strut, fuel nozzles can be made communicating with the second fuel supply channel, which increases the fuel supply in the cross section of the air flow. This ensures a uniform fuel supply in the cross section of the combustion chamber and the reliability of ignition of the fuel mixture.

The strut may have symmetrical longitudinal niches on the outer side surfaces, where in the niches they form a recirculation of a part of the incoming flow of the fuel mixture and vortex combustion zones of this mixture, and through this, due to mass transfer, additional combustion stabilization of the main part of the fuel mixture flow is carried out.

In the niches, fuel nozzles can be made, which are connected to the second channel for supplying fuel to the rack, where fuel is fed into the niche through the nozzles and intensifies the stabilization of combustion of the oncoming flow of the fuel mixture.

Thus, the objectives of the invention are solved:

- provided auto-ignition of the fuel mixture fed into the combustion chamber of a ramjet engine operating in a wide range of Mach numbers (from about 4 to 10);

- provided stabilization and increased reliability of ignition of the fuel mixture in the combustion chamber of the ramjet;

- uniformity of atomization and ignition of the fuel when it is supplied to the combustion chamber is ensured;

- A rack for supplying fuel to the ramjet combustion chamber was created, operable under the conditions of thermal and power impact of the incoming high-speed air flow on it.

The present invention is illustrated by the following description of the structure of the rack and the method of its operation with reference to the illustrations presented in figures 1-5, where

figure 1 schematically shows the path of the combustion chamber ramjet with installed in it with the possibility of rotation on the wall of the rack;

figure 2 is a cross section aa of the rack in figure 1;

figure 3 is a cross section aa in figure 1 for a variant with additional fuel nozzles on the side surfaces of the rack;

figure 4 is a cross section aa in figure 1 for an embodiment of the longitudinal niches on the outer side surfaces of the rack;

figure 5 is a cross section aa in figure 1 for a variant with additional fuel nozzles made in niches on the outer side surfaces of the rack.

The method of auto-ignition of the fuel mixture (see figure 1) in the combustion chamber 1 of a ramjet engine is carried out using a rack 2 for supplying fuel. Stand 2 is made (see Fig. 2) in the form of an oval-shaped aerodynamic profile body with front 3 and rear 4 edges, has a cylindrical side surface 5 and is oriented by a profile along the path of combustion chamber 1. Stand 2 is fixed on one side inside on the chamber wall 6 combustion 1 through the support 7 with the possibility of rotation along the path of the chamber and is drowned from the other side. The rack 2 is equipped (see Fig. 2) with one fuel supply channel 8 communicating with the fuel nozzles 9 located on the leading edge 3 and a second fuel supply channel 10, which is located at the rear of the rack 2 and communicates with the fuel nozzles 11 located on the trailing edge 4. On the side surfaces 5 of the strut 2 (see FIG. 3), fuel nozzles 12 can be made in communication with the second channel 10. The strut 2 (see FIG. 4) may have symmetrical longitudinal niches on the outer lateral surfaces 5 13, and in niches 13 can be performed (see figure 5) fuel nozzles 14 communicating with the second channel 10. It should be noted that the discrete value of the sweep angle χ of the tilt of the rack 2 to the axis of the path of the chamber 2 is set in the range from 30 to 90 degrees.

The method of auto-ignition of the fuel mixture in the combustion chamber 1 of a ramjet engine is as follows. When working in the combustion chamber 1 of the engine direct (see figure 1) a high-speed high-temperature air flow that runs on the front edge 3 of the rack 2. At the front edge 3, the temperature of the incoming supersonic air flow, due to compression in the shock wave, is raised above the temperature self-ignition of the air-fuel mixture. Through channel 8 (see FIGS. 2-5), coolant is supplied to the rack 2, which is cooled from the inside by the front edge 3 of the rack 2 and through the fuel nozzles 9 is fed into the combustion chamber 1 against the air flow, where it is mixed with it. When the fuel mixture in the air stream collides with the leading edge 3 of the strut 2, due to compression in the shock wave, the mixture is heated to the level of auto-ignition temperature of the fuel, the fuel mixture that burns the fuel mixture is ignited, and its combustion products in the air stream are directed from the leading edge 3 struts 2 along its lateral surfaces 5 to the trailing edge 4 and further into the combustion chamber 1. The necessary increase in the temperature of the fuel mixture due to its compression in the shock wave at the front edge 3 at the lowest possible heat the flow in the rack 2 is provided by installing the rack 2 at an angle of sweep χ at a predetermined ratio.

The main part of the fuel (see figure 2-5) is fed into the air stream through the channel 10 and the nozzle 11 of the trailing edge 4 of the rack 2. Spray and mix this fuel with the products of combustion of fuel, which are directed downstream from the front edge 3 of the rack 2, ignite the fuel mixture of the main part of the fuel in the recirculation zone behind the trailing edge 4 of the rack 2 and stabilize the process of burning it with the heated combustion products of the fuel supplied to the air stream from the front edge 3 of the rack 2. The ignited main part of the fuel is sent to the combustion chamber 1. From the side surfaces 5 of the rack 2 (see FIG. 3) through the nozzles 12 communicating with the second channel 10, it is possible to supply fuel across the path of the combustion chamber 1. When performing on the outer side surfaces 5 of the rack 2 symmetrical longitudinal niches 13 (see FIG. 4) incomplete combustion products formed at the leading edge 3 have an additional stabilization zone 13, the possibility of ignition and combustion. Adding fuel to niches 13 through nozzles 14 (see FIG. 5) intensifies the process of burning unburned fuel mixture.

To confirm the effectiveness of the technical solution, experimental studies were carried out of the ignition of the fuel mixture in the ramjet combustion chamber when fuel was supplied from the front edge of the pylon against the air flow. During the tests, the temperature and braking pressure of the incoming flow were varied within 1400-1850 K and 15-25 bar, respectively. The test results showed the stability of ignition and subsequent combustion of the fuel mixture.

Claims (4)

1. The method of auto-ignition of the fuel mixture in the combustion chamber of a ramjet engine containing a strut for supplying fuel, made in the form of an aerodynamic profile body with leading and trailing edges, where the strut is mounted internally on the wall of the chamber through a support on one side, and is muffled on the other hand and the profile is oriented along the chamber path, in addition, the rack is equipped with one fuel supply channel and fuel nozzles in communication with the channel located on the leading edge, the method being in that air high-temperature high-speed flow is supplied to the combustion chamber, air blows the front edge of the strut, which causes local braking and heating of the air flow, fuel is supplied through the nozzles against the air flow and mixed with it, the fuel mixture is heated and ignited in the flow, different the fact that they use a rack, which is additionally equipped with a second fuel supply channel located at the rear of the rack, and fuel nozzles in communication with the channel located along the rear the edge of the rack, and the rack has a lateral cylindrical surface and is mounted on the wall of the combustion chamber through a support with the possibility of rotation along the path of the chamber, where the ignition of the fuel mixture is carried out by the fact that in the air flow the rack in the place of fastening on the wall is mounted obliquely to the axis of the chamber path sweep χ, depending on the engine operating mode, moreover, the discrete value of the sweep angle χ for a particular engine operation mode is determined by the ratio

where T ^* _s is the auto-ignition temperature of the air-fuel mixture;
T is the static temperature of the air flow;
Mn is the Mach number of the air flow running onto the rack;
K is the adiabatic exponent of air,
fuel is supplied through the channels and nozzles of the rack to the combustion chamber, while coolant is supplied through the channel and nozzles of the leading edge, fuel is mixed in the combustion chamber with air, and when the fuel mixture collides in the air flow with the front edge of the rack, they are heated in the shock wave by compression the mixture to the level of auto-ignition temperature of the fuel, ignite the fuel mixture, the burning fuel mixture and the combustion products are sent from the front edge of the rack along its side surfaces to the rear edge and then to measure, the main part of the fuel is fed into the air stream through the second channel and nozzles of the trailing edge of the rack, spray and mix this fuel with the combustion products of the fuel, which are directed downstream of the front edge of the rack, ignite the fuel mixture of the main part of the fuel and stabilize the process of burning with heated products the combustion of fuel supplied to the air stream from the front edge of the rack, the combustion products of the mixture of the main fuel are sent to the combustion chamber. 2. The method of auto-ignition of the fuel mixture according to claim 1, characterized in that on the side surfaces of the struts fuel nozzles are connected to the second fuel supply channel and supply, ignite and burn fuel in the cross section of the combustion chamber. 3. The method of auto-ignition of the fuel mixture according to claim 1, characterized in that in the strut on the outer side surfaces symmetrical longitudinal niches are performed, vortex combustion zones are formed in the niches and the combustion of the free flow of the fuel mixture is stabilized. 4. The method of auto-ignition of the fuel mixture according to claim 3, characterized in that the fuel nozzles are carried out in the niches, the nozzles are connected to the second channel for supplying fuel to the rack, the fuel is fed into the niche and the combustion stabilization of the oncoming fuel mixture is intensified.

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