CN108426267B - Folding V-shaped blunt body standing vortex flame stabilizer - Google Patents
Folding V-shaped blunt body standing vortex flame stabilizer Download PDFInfo
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23R—GENERATING COMBUSTION PRODUCTS OF HIGH PRESSURE OR HIGH VELOCITY, e.g. GAS-TURBINE COMBUSTION CHAMBERS
- F23R3/00—Continuous combustion chambers using liquid or gaseous fuel
- F23R3/02—Continuous combustion chambers using liquid or gaseous fuel characterised by the air-flow or gas-flow configuration
- F23R3/16—Continuous combustion chambers using liquid or gaseous fuel characterised by the air-flow or gas-flow configuration with devices inside the flame tube or the combustion chamber to influence the air or gas flow
- F23R3/18—Flame stabilising means, e.g. flame holders for after-burners of jet-propulsion plants
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Abstract
The invention discloses a folding V-shaped blunt body standing vortex flame stabilizer, which belongs to the field of heat energy and power engineering and is formed by combining a plurality of groups of folding V-shaped blunt body standing vortex flame stabilizer monomers with the same or similar structures, wherein each flame stabilizer monomer comprises two wing surfaces with equal cross sections and equal span length, which are welded according to an angle alpha, or directly manufactured through superalloy additive manufacturing; the combination is radial, circumferential, or a mixture of radial and circumferential. When the device works, incoming flow carries fuel to flow through the two airfoils, the fluid forms a pair of flow-direction vortexes at the downstream of the plane V-shaped blunt body, and the incoming flow flows from the edge openings of the two airfoils to the central plane direction of the two airfoils to form vortexes distributed along the spanwise direction; the vortex of the flow direction and the vortex of the spanwise distribution form a pair of trapped vortex at the downstream, and an ignition device is arranged at the center of the trapped vortex. Flame holding is stable, the blow-out boundary is wide, and the total pressure recovery coefficient is high; the engine is easy to match with the existing model of the aeroengine, and the performance of the existing aeroengine is improved.
Description
Technical Field
The invention belongs to the field of heat energy and power engineering, and particularly relates to a folding V-shaped blunt body standing vortex flame stabilizer.
Background
The afterburner is one of important characteristics of the military aviation gas turbine engine, which is different from the civil aviation engine, and the afterburner further improves the gas temperature and gas speed sprayed out of the tail jet pipe of the engine by utilizing unburned oxygen of the main combustion chamber to organize secondary ignition combustion on the upstream of the tail jet pipe of the aviation engine, so that the thrust of the engine in a short time is greatly improved.
The afterburner can improve the thrust-weight ratio of the aircraft in a short time, comprehensively improve the maneuverability of the fighter and enlarge the flight envelope (the rise limit can be improved to 22-23 km, and the maximum flight Mach number can be improved to 2.5-3), and promote the key capacities of short-distance take-off, air-making, interception, bursting prevention, escape and the like of the fighter, the limit performances of weaponry such as the fighter, the missile and the like, and the survival and death of the fighter and the pilot can be determined in minutes or even seconds after the afterburning is started, and the bursting prevention success rate and the hit rate of the missile are determined. However, the afterburner always works near the limit working condition of the engine, the working environment is one of the most severe conditions in the hot end part of the engine, and the primary problem brought by the severe working condition to the design of the afterburner of the aeroengine is combustion instability. As in reference [1]: combustion instability simulation experiment technique; zhang Mengzheng combustion instabilities in afterburners are classified by frequency into low, medium and high frequency combustion instabilities in a form similar to an acoustic resonance type oscillation by the north-west industrial university press.
Combustion instabilities in afterburners can lead to (1) localized increased thermal loading of the combustor, causing deformation, ablation, or even complete failure of structural materials, in addition to flame oscillation quenching (extinct); (2) overload load generated by flame pulsation causes mechanical damage; (3) the performance of the engine deviates from the design point, the thrust is severely fluctuated, such as unstable combustion in the take-off stage, and serious accidents such as sudden thrust drop and death of the engine are caused; (4) and difficulty is brought to the accurate control of the tail jet pipe of the engine (especially the vector thrust jet pipe of the novel engine). Therefore, flame holders matched with the design performance and the design working condition of the engine must be reasonably designed and installed in the afterburner so as to ensure that ignition and stable combustion can be well organized under severe conditions.
The structure and layout of the flame stabilizer determine the ignition performance, flame stabilization performance, combustion efficiency and flow resistance of the afterburner, and therefore, the overall combustion performance of the flame stabilizer is improved, the resistance of the flame stabilizer is reduced, and the performance of the afterburner can be directly improved, so that the overall performance of the engine is improved.
When the prototype is developed by YF-120 in the United states, a new method of three-dimensional flow design is utilized, the problem that combustion oscillation is easy to cause when a large number of radial stabilizers are adopted in an afterburner is overcome, and an afterburner combustion stabilizing scheme which is mainly based on the radial flame stabilizers and is formed by combining a central annular V-shaped stabilizer and 12 radial stabilizers is provided; reference [2]: aero-engine structural design analysis, chen Guangzhu.
The most commonly used blunt body structure of the existing afterburner flame stabilizer of the military aircraft engine is a V-shaped blunt body, namely, the two-dimensional unit body structure of the flame stabilizer is a V-shaped structure, the two-dimensional V-shaped unit body is axially stretched into a three-dimensional flame stabilizer unit body according to actual requirements, and finally, the three-dimensional flame stabilizer unit bodies are combined into an annular flame stabilizer, a radial flame stabilizer or a combination of the annular and the radial flame stabilizer through a certain combination mode, so that the evaporative flame stabilizer actually used for forming duty flames can be regarded as a V-shaped blunt body with oil gas nozzles.
However, the V-shaped blunt body has the defects of quite definite defect, namely large total pressure loss in a non-stress state, high flame stability only controlled by the incoming flow oil gas ratio, high ignition oil gas ratio, narrow lean oil stable combustion range, poor reliability of high-altitude connection stress application, uneven wall temperature of the flame stabilizer, easiness in structural deformation and the like. One simple modification of this early stage was to use a slotted V-type (double V-type) bluff body structure, reference [3]: zhang Hongbin, wang Jigen development and application of double V-shaped flame holders [ J ]. Propulsion technology, 1994,15 (3): 38-43.) double V-shaped flame holders are substantially identical to V-shaped flame holders in major design parameters, except that the leading edge of the double V-shaped flame holder is added with a smaller V-shaped holder, and two air inlet slits of a certain width are formed in the head by telescoping of the large and small flame holders.
Compared with the V-shaped flame stabilizer, the airflow structure of the double-V-shaped flame stabilizer is changed: it consists of two streams, one stream being the main stream bypassing the main stabilizer and one stream being the pre-combustion stream bypassing the small stabilizer and flowing into the interior of the main stabilizer. The two flows respectively form a large reflux area and a small reflux area, and a narrow long large reflux area is finally formed through the interaction of the two reflux areas, the vortex core of the reflux area is arranged in the main stabilizer, the igniter is arranged in the main stabilizer and near the rear edge of the small stabilizer, the flame is the same as the V-shaped flame stabilizer by virtue of the principle of maintenance, and the unburned fuel gas is involved in the burnt area by virtue of the reflux areas, so that the duration of the combustion process is ensured.
The greatest improvement over the V-shaped flame holders is reduced blockage ratio and total pressure loss, while the improvement over other disadvantages of the V-shaped flame holders is limited, substantially closer to a head optimized evaporative flame holder. At the same time, the double V flame stabilizer increases the structural complexity and thus leads to a reduction in reliability and an increase in structural weight, which is a reversal of the overall trend of flame stabilizers. The most general, aggressive and successful attempt to date to blunt body construction flame holders is the "dune trapped vortex (BD) flame holder" invented by the university of aviation aerospace, gao Ge, beijing; reference [4]: the theory and experimental study of flame stability of the sand dune trapped vortex [ J ]. Engineering thermal physics report, 1982, V3 (1): 89-95.BD flame stabilizer works on the principle that the pressure gradient of the vortex tail area is improved by shortening or gathering the vortex tail, the streamline curvature of the vortex countercurrent turning point is reduced, the shearing speed gradient is increased, and finally, the trapped vortex structure is formed between two ox horns at the downstream of the blunt body, so that the vortex stability is obviously improved, and the ignition combustion in the area can also obtain good combustion stability due to the stability of the vortex.
From the performance aspect, the BD flame stabilizer remarkably widens the lean oil blow-out boundary of the flame stabilizer with the two-dimensional unit structure represented by the V-shaped blunt body, reduces the flow resistance by about 75 to 80 percent, and solves the flame stability problem of afterburners of military turbojet engines with a plurality of key types at the time; the significance of BD flame holders is more pronounced from a design theoretical point of view-on the one hand, BD flame holders are based on the vortex stability theory, reference [5]: research on the local stability of vortex [ J ]. Engineering thermophysics journal, 1981, V2 (4): 394-400. Truly, the design of flame stabilizer is improved from "subjective design" driven by engineering experience to "forward rational design" driven by vortex dynamics theory, which is a one-step crossover development of aircraft engine core component design methodology; on the other hand, the three-dimensional vortex structure is based on an interaction mechanism between three-dimensional vortices, and a space three-dimensional geometrical body in a flow field is utilized to actively construct a 'standing vortex' structure with strong stability, so that the three-dimensional vortex structure is a breakthrough of the design theory of the afterburner flame stabilizer based on a two-dimensional unit body structure in the past. But not admittedly, BD flame holders also have some drawbacks that limit their further development applications:
(1) The closed angle of the two ends shrinkage causes Zhou Xianglian flame to have certain difficulty, the curved surface design at the maximum groove width is not beneficial to radial flame linkage, and therefore, the flame linkage structure among all unit bodies of the BD flame stabilizer needs to be additionally increased, and the increase of structural complexity, the reduction of reliability (the flame linkage structure is not easy to cool and easy to ablate) and the increase of structural weight are brought.
(2) The excessively stable trapped vortex structure causes a smaller diffusion angle of the downstream wake shear layer, which brings adverse effects to the propagation of flame in the whole afterburner, and the problem of uneven outlet temperature distribution is easy to occur, so that a circumferential annular flame stabilizer is additionally added.
(3) The BD flame stabilizer with complex curved surface modeling and the vortex stability theory supported by the BD flame stabilizer directly bring problems in aspects of excessive design parameters, increased design difficulty and model adaptability, and limit further development and application of the BD flame stabilizer in a subsequent turbofan engine research and development stage.
(4) Unlike the V-shaped flame stabilizer structure, BD flame stabilizer has a relatively poor structural processing manufacturability formed by splicing two complex curved surfaces, and in a afterburner with high temperature, high speed and high load, the problems of uneven surface temperature distribution, reduced combustion stabilizing effect caused by deformation in appearance, failure and the like are easy to occur, which is also unacceptable for a new generation of military gas turbine engines with high requirements in terms of reliability and maintainability.
For many reasons, the theory of vortex stability of both BD flame holders and the standing vortex mechanism has not been well extended and developed over the years thereafter, and these drawbacks of BD flame holders have not been truly solved and little research work has been carried out in connection therewith, which is very unfortunate.
Disclosure of Invention
The invention provides a folding V-shaped blunt body standing vortex flame stabilizer which can be applied to a main combustion chamber and an afterburner of a military high-performance jet aeroengine, a supersonic combustion chamber of a missile (high-speed unmanned aerial vehicle) engine and other power machinery fields requiring stable combustion in high-speed airflow, and aims to solve the problems of high fuel ignition difficulty, difficulty in flame maintenance, stable combustion and the like under the condition of high-speed unsteady incoming flow; can also be used in the civil combustion device field.
The folding V-shaped blunt body standing vortex flame stabilizer is formed by combining a plurality of groups of folding V-shaped blunt body standing vortex flame stabilizer monomers with the same or similar structures, each flame stabilizer monomer comprises two wing surfaces with equal cross sections and equal span lengths, and the two wing surfaces are designed by adopting two traditional straight-edge V-shaped blunt bodies, namely, the two wing surfaces comprise two parameters of a groove width D and a vertex angle rho.
The groove width D is calculated according to the afterburner flame stability formula:
V FH is the blow-out speed; t (T) t The temperature of the incoming flow for the afterburner; p (P) sFH Blow out pressure for afterburner; k (K) st Is a stability parameter; the apex angle ρ is empirically taken.
Meanwhile, the folded V-shaped blunt body standing vortex flame stabilizer forms a sweepback angle alpha between two wing surfaces, and the angle range of the sweepback angle alpha is 60-150 degrees; the location of the trapped vortex desired to be formed is related to the size of the trapped vortex region. The two wing surfaces are welded and spliced according to an angle alpha, or are directly manufactured through high-temperature alloy additive manufacturing; the wing span length of the airfoil is L, and the value of the wing span length is 4-8 times of the slot width;
considering the convenience of processing and assembly, each flame stabilizer monomer further comprises two parameters of monomer spanwise length A and flow direction chord length d, and the flame stabilizer comprises:
the combination form of the flame stabilizer monomers is as follows: the combined outer ends of the flame stabilizer monomers are connected with the barrel of the afterburner by adopting a conventional structure according to the barrel structure of the afterburner, and the inner ends of the flame stabilizer monomers are close to the central cone of the afterburner.
The radial combination forms are divided into equal length combination or long and short combination according to the working characteristics of different aircraft engine afterburners. Equal length combination is that 12-20 equal length folding V-shaped flame stabilizer monomers are distributed in a circumference at equal intervals, and each equal length folding V-shaped flame stabilizer monomer is fixed on the circular wall of the afterburner through the end face of the airfoil;
the long-short combination comprises a long flame stabilizer monomer combination and a short flame stabilizer monomer combination which are equally spaced, wherein the length of the short flame stabilizer monomer combination is 1-2 flame stabilizer monomers welded together end to end, and the length of the long flame stabilizer monomer combination is 2-3 flame stabilizer monomers welded together end to end.
The number of the long flame stabilizer monomer combination and the short flame stabilizer monomer combination in the long flame stabilizer monomer combination and the short flame stabilizer monomer combination is determined according to the diameter of the afterburner, wherein the number of the flame stabilizer monomers selected in the long flame stabilizer monomer combination is less than or equal to 2 times of the number of the flame stabilizer monomers in the short flame stabilizer monomer combination.
The airfoil end face of each long flame stabilizer monomer combination or each short flame stabilizer monomer combination is fixed on the circular wall of the afterburner;
the circumferential combined form is formed by welding end surfaces of 8-20 flame stabilizer monomers with equal length together in an end-to-end connection mode, and the end surfaces are fixed on the circular wall of the afterburner; the number of flame stabilizer units in the circumferential combination and the size of the flame stabilizer units are determined by the design requirement of the afterburner. The circumferential combination form is connected with the afterburner cylinder body and the sudden expansion can be connected with a heat-resistant metal truss.
The radial and circumferential mixed combination comprises a circumferential flame stabilizer monomer connection form and a radial flame stabilizer monomer connection form; the circumferential connection mode is set to be 1-3 circles according to the requirement, and is arranged at the inner side of the whole combined structure and is connected with the inner side of the radial flame stabilizer monomer in a welding mode, so that the functions of maintaining the flame on duty and the like are realized.
The combination mode and the assembly principle of the flame stabilizer monomer directly adopt the original V-shaped blunt body arrangement mode or change according to actual needs.
The working principle and the working process are as follows:
when the folding V-shaped blunt body standing vortex flame stabilizer works, incoming flow rolls carry fuel to flow through two wing surfaces, as the section of the flame stabilizer is a plane V-shaped blunt body with curvature rho and height D, the fluid is inevitably separated from the plane V-shaped blunt body, and a pair of flow vortexes are formed at the downstream of the plane V-shaped blunt body, and as the folding V-shaped blunt body is provided with two symmetrical wing surfaces which are stretched at a certain sweepback angle alpha and length L and are in the same section, an overall V-shaped in three-dimensional space is formed on the orthogonal plane of the plane V-shaped blunt body, the incoming flow also flows from the edge openings of the two wing surfaces to the central plane direction of the two wing surfaces, and the vortex distributed along the spreading direction is formed;
the flow direction vortex falling off from the plane V-shaped blunt body cross section is vertical to the direction of the vortex of the spanwise distribution, and interacts with the direction of the vortex to finally form a pair of standing vortices which are stable in space and are not easy to change along with the change of the flowing condition at the downstream of the folding V-shaped blunt body flame stabilizer. The ignition device is arranged at the center of the standing vortex, so that stable combustion of flame can be ensured, and the stable combustion effect exceeding that of the traditional plane V-shaped blunt body is exerted.
The invention has the advantages that:
(1) The folding V-shaped blunt body standing vortex flame stabilizer has good adaptability to incoming flow, and can form a stable standing vortex with a space position not changed along with the incoming flow in the working condition range of Ma=0.1-1 and Re=60000-200000 by adjusting the design parameters alpha, rho and L, D of the blunt body;
(2) The folding V-shaped blunt body standing vortex flame stabilizer inherits the characteristics of good lean oil ignition characteristic and good stable combustion of the BD flame stabilizer, can finish ignition in a lean oil state, and can keep stable flame when the incoming flow working condition and the oil-gas ratio suddenly change during the ignition, and the blowing-out boundary is wide;
(3) Compared with BD flame stabilizer, the folding V-shaped blunt body vortex flame stabilizer has better flame linkage, and each monomer can be seamlessly connected in parallel to form a complete closed ring shape, so that the circumferential flame is ensured to be uniformly distributed;
(4) The folding V-shaped blunt body standing vortex flame stabilizer has good mixing property of fuel gas at the downstream of the blunt body, and can realize effective mixing of inner and outer culvert air flows in a non-stress state when a radial structure is adopted;
(5) The folding V-shaped blunt body standing vortex flame stabilizer has small flow resistance and high total pressure recovery coefficient;
(6) The folding V-shaped blunt body standing vortex flame stabilizer has a structure which is much simpler than that of a BD flame stabilizer, only two control parameters are added compared with the traditional V-shaped blunt body flame stabilizer, the flow and combustion characteristics of the folding V-shaped blunt body standing vortex flame stabilizer under different working conditions are easy to master completely, the folding V-shaped blunt body standing vortex flame stabilizer is easier to match with the existing model of an aeroengine, and the performance of the existing aeroengine is improved.
Drawings
FIG. 1 is a schematic diagram of a folded V-shaped bluff body trapped vortex flame holder according to the present invention;
FIG. 2 is a partial view of a folded V-shaped bluff body trapped vortex flame holder of the present invention;
FIG. 3 is a schematic view of the installation position of a folded V-shaped bluff body trapped vortex flame holder of the present invention;
FIG. 4 is a schematic view of a radial assembly of a folded V-shaped bluff body trapped vortex flame holder of the present invention;
FIG. 5 is a schematic view of a circumferential assembly of a folded V-shaped bluff body trapped vortex flame holder of the present invention;
FIG. 6 is a schematic view of a radial and circumferential combination of a folded V-shaped bluff body trapped vortex flame holder of the present invention.
FIG. 7 is a schematic diagram of a different sweep angle alpha trapped vortex structure of a folded V-shaped blunt body trapped vortex flame stabilizer of the present invention;
FIG. 8a is a schematic view of a conventional V-shaped bluff body flame holder having only a shedding vortex A and a separation vortex B at both ends;
FIG. 8b is a schematic view of a folded V-shaped bluff body trapped vortex flame holder of the present invention forming a pair of counter-rotating trapped vortices at the head;
fig. 9a is a schematic diagram of a trapped vortex structure obtained when the sweepback angle α=90 degrees and re=100000;
fig. 9b is a schematic diagram of the flow chart obtained when the sweepback angle α=90 degrees and re=100000 according to the present invention;
fig. 10 is a schematic diagram of the trapped vortex position obtained when the sweepback angles α and Re respectively take different values.
Detailed Description
The following describes the embodiments of the present invention in detail with reference to the accompanying drawings.
On the basis of in-depth research on the standing vortex combustion stabilizing mechanism, the invention provides the blunt body standing vortex flame stabilizer with a three-dimensional flowing folded V-shaped structure by combining the respective advantages of the sand hill standing vortex flame stabilizer and the traditional V-shaped flame stabilizer.
The folding V-shaped blunt body standing vortex flame stabilizer is formed by combining a plurality of groups of folding V-shaped blunt body standing vortex flame stabilizer monomers with the same or similar structures, wherein each flame stabilizer monomer comprises two wing surfaces with equal cross sections and equal span lengths, as shown in fig. 2, the V-shaped blunt body cross section is designed by using the design characteristics of the traditional V-shaped blunt body and comprises two parameters of a groove width D and a vertex angle rho.
The groove width D is calculated according to the afterburner flame stability formula:
V FH for blow-out speed, mach number m=0.1 to 0.35 is generally taken; t (T) t For afterburner inflow temperature, the temperature is generally T, based on the internal and external gas temperature t ＝300K～900K，P sFH To blow out pressure of afterburner, P is taken sFH ＝69kpa，K st As stability parameters, K is generally taken according to typical design conditions of domestic aero-engines st ＝5～9。
The apex angle ρ is generally 30 to 45 degrees, based on experience. Too large a value will lead to a sharp increase in the blockage ratio and flow resistance, and too small a value will be detrimental to the formation of the recirculation zone.
However, unlike conventional straight-sided V-shaped bluff bodies, the folded V-shaped bluff body trapped vortex flame stabilizer forms a backswept angle α between the two airfoils, the backswept angle α being in the range of 60 degrees to 150 degrees, depending on the desired trapped vortex position and trapped vortex region size. The two wing surfaces are formed by welding and splicing two traditional straight-side V-shaped blunt bodies according to an angle alpha, or are directly manufactured by high-temperature alloy additive manufacturing; the wing span length L of the airfoil is 4-8 times of the slot width;
reference 6: studies on the local stability of vortices [ J ]. Engineering Programme, 1981, V2 (4): 394-400; according to the vortex stability theory, since the formation of the standing vortex is the expression of flow modeling and is irrelevant to the incoming flow speed, the formation of the standing vortex is only relevant to four design parameters of the folding V-shaped blunt body standing vortex flame stabilizer, when L, D and ρ are all determined, the general rule of the parameter alpha is that when Re=40500, as shown in fig. 7, when alpha is more than 90 ℃, the larger the flowing direction length of the standing vortex is, and the narrower the spreading width is; when the angle alpha is 60 degrees and is smaller than 90 degrees, the length of the standing vortex flow direction and the span length are firstly reduced, then basically kept unchanged, and the stability is further enhanced; the flow structure is no longer significant for alpha <60 deg..
In view of convenience in processing and assembly, each flame stabilizer monomer further comprises two parameters, namely a monomer spanwise length A and a flow direction chord length d. Obviously, there are:
compared with the traditional V-shaped blunt flame stabilizer with only two parameters of groove width D and apex angle rho control, the folding V-shaped blunt standing vortex flame stabilizer is actually only increased by two parameters of span L and sweepback angle alpha.
The combination form of the flame stabilizer monomers is as follows: the combined outer ends (radial outer sides) of the flame stabilizer monomers are connected with the barrel of the afterburner by adopting conventional structures such as bolts, mortise and tenon joints, key sheaths and the like according to the barrel structure of the afterburner, and the inner ends (radial inner sides) are closely adjacent to the central cone (sudden expansion) of the afterburner.
The radial combination forms are divided into equal length combinations or multiple combinations of the equal length and the equal length according to the working characteristics of the afterburners of different aeroengines. Equal length combination, namely, 12-20 equal length folded V-shaped flame stabilizer monomers are distributed in a circumference at equal intervals, wherein equal length refers to the length of a single flame stabilizer monomer or the length formed by welding 2-3 flame stabilizer monomers end to end; each folding V-shaped flame stabilizer monomer with equal length is fixed on the circular wall of the afterburner through the end surface of the airfoil;
as shown in fig. 4, the long-short combination includes equally spaced long flame stabilizer monomer combination and short flame stabilizer monomer combination, the length of the short flame stabilizer monomer combination is 1-2 flame stabilizer monomers welded together end to end, and the length of the long flame stabilizer monomer combination is 2-3 flame stabilizer monomers welded together end to end.
The number of the long flame stabilizer monomer combination and the short flame stabilizer monomer combination in the long flame stabilizer monomer combination and the short flame stabilizer monomer combination is determined according to the diameter of the afterburner, wherein the number of the flame stabilizer monomers selected in the long flame stabilizer monomer combination is less than or equal to 2 times of the number of the flame stabilizer monomers in the short flame stabilizer monomer combination.
The airfoil end face of each long flame stabilizer monomer combination or each short flame stabilizer monomer combination is fixed on the circular wall of the afterburner;
as shown in fig. 5, the circumferential combination forms are formed by welding end surfaces together in an end-to-end connection mode by 8-20 flame stabilizer monomers with equal lengths, and the end surfaces are fixed on the circular wall of the afterburner; the number of flame stabilizer units in the circumferential combination and the size of the flame stabilizer units are determined by the design requirement of the afterburner. The circumferential combination form is connected with the afterburner cylinder body and the sudden expansion can be connected with a heat-resistant metal truss.
As shown in fig. 6, the radial and circumferential hybrid combinations are equivalent to the radial and circumferential hybrid combinations, and include both the circumferential flame stabilizer monomer connection form and the radial flame stabilizer monomer connection form; the circumferential connection mode is set to be 1-3 circles according to the requirement, and is arranged at the inner side of the whole combined structure and is connected with the inner side of the radial flame stabilizer monomer in a welding mode, so that the functions of maintaining the flame on duty and the like are realized.
The combination mode and the assembly principle of the flame stabilizer monomer are not different from the traditional V-shaped blunt body or BD-shaped blunt body, the original V-shaped blunt body arrangement mode can be directly used, and the flame stabilizer monomer can be changed according to actual needs.
The working principle and the working process are as follows:
when the folding V-shaped blunt body standing vortex flame stabilizer works, incoming flow curls and carries fuel to flow through two wing surfaces from the direction shown in figure 1, because the section of the flame stabilizer is a plane V-shaped blunt body with curvature rho and height D, the fluid is inevitably separated from the plane V-shaped blunt body, and a pair of flow-direction vortices are formed at the downstream of the plane V-shaped blunt body, as shown in figure 8a, the traditional V-shaped blunt body flame stabilizer only has a shedding vortex A and a separation vortex B at two ends, namely, ignition and combustion are realized in the vortex core low-pressure area of the flow-direction vortices.
The folding V-shaped blunt body is provided with two symmetrical wing surfaces which are stretched at a certain sweepback angle alpha, a certain length L and other cross sections, and an integral V-shaped in a three-dimensional space is formed on the orthogonal plane of the plane V-shaped blunt body, so that the incoming flow also flows from the edge openings of the two wing surfaces to the central plane directions of the two wing surfaces, and forms vortexes distributed along the spreading direction;
numerical calculation and experimental study show that as shown in fig. 8b, the flow direction vortex falling off from the plane V-shaped blunt body section is perpendicular to the direction of the vortex of the spanwise distribution, and interacts with the direction of the vortex, and finally a pair of standing vortices which are stable in space and not easy to change along with the change of the flowing condition are formed at the downstream of the folding V-shaped blunt body flame stabilizer.
The vortex core can be stably present at a specific position downstream of the blunt body, and is not changed along with the condition of the flowing, and is only related to the geometric design parameters of the blunt body. According to the characteristic, the ignition device is arranged at the center of the standing vortex, so that the ignition can be completed under extremely complex and unsteady incoming flow working conditions, the stable combustion of flame is kept, and the stable combustion effect exceeding that of the traditional plane V-shaped blunt body is exerted.
Examples:
numerical experiments were performed on a folded V-shaped bluff body trapped vortex flame holder with α=90 degrees, and when re=100000, a trapped vortex structure diagram is shown in fig. 9a, and a flow diagram is shown in fig. 9 b. Research shows that the flame can stably burn in the blunt body trapped vortex and the downstream area of the trapped vortex under the condition of higher Reynolds number, and the total pressure loss is smaller, and the combustion efficiency is very high.
As shown in fig. 10, the standing vortex position does not change with the velocity of the flow when Re takes values 30000, 40500, 50600, 60750, 70900 and 81000, respectively.
Meanwhile, when the sweepback angle alpha is 180 degrees, vortex is seen to be separated alternately on the span section of the traditional V-shaped blunt flame stabilizer; when the sweep angle α takes 150 degrees, the vortex shedding frequency decreases. When the sweepback angle alpha is 120 degrees, standing vortex is gradually formed; when the sweepback angle alpha takes 90 degrees, a complete trapped vortex is formed. When the sweepback angle alpha is 60 degrees, the trapped vortex is reduced, and the stability is enhanced.
Claims (6)
1. The folding V-shaped blunt body standing vortex flame stabilizer is characterized by being formed by combining a plurality of groups of folding V-shaped blunt body standing vortex flame stabilizer monomers with the same or similar structures, wherein each flame stabilizer monomer comprises two wing surfaces with equal cross sections and equal span lengths, the two wing surfaces adopt the design characteristics of two traditional straight-edge V-shaped blunt bodies, and the design characteristics comprise two parameters of a groove width D and a vertex angle rho;
the groove width D is calculated according to the afterburner flame stability formula:
V FH is the blow-out speed; t (T) t The temperature of the incoming flow for the afterburner; p (P) sFH Blow out pressure for afterburner; k (K) st Is a stability parameter; the vertex angle rho is empirically valued;
meanwhile, the folded V-shaped blunt body standing vortex flame stabilizer forms a sweepback angle alpha between two wing surfaces; the two wing surfaces are welded and spliced according to an angle alpha, or are directly manufactured through high-temperature alloy additive manufacturing;
the combination form of the flame stabilizer monomers is as follows: the combined outer ends of the flame stabilizer monomers are connected with the barrel of the afterburner by adopting a conventional structure according to the barrel structure of the afterburner, and the inner ends of the flame stabilizer monomers are close to the central cone of the afterburner;
the radial combination forms are divided into equal length combination or long and short combination according to the working characteristics of different aircraft engine afterburners;
the circumferential combined form is formed by welding end surfaces of 8-20 flame stabilizer monomers with equal length together in an end-to-end mode, and the end surfaces are fixed on the circular wall of the afterburner; the number of the flame stabilizer monomers in the circumferential combination and the size of the flame stabilizer monomers are determined by the design requirement of the afterburner; the circumferential combination form is connected with the afterburner cylinder body and the sudden expansion can be connected with a heat-resistant metal truss;
the radial and circumferential mixed combination comprises a circumferential flame stabilizer monomer connection form and a radial flame stabilizer monomer connection form; the circumferential connection mode is set to be 1-3 circles according to the requirement, and is arranged at the inner side of the whole combined structure and is connected with the inner side of the radial flame stabilizer monomer in a welding mode.
2. A folded V-shaped blunt body trapped vortex flame holder as in claim 1 wherein said angle of sweep α is in the range of 60 degrees to 150 degrees.
3. A folded V-shaped blunt body trapped vortex flame stabilizer as defined in claim 1 wherein the airfoil span length L has a slot width of 4 to 8 times.
4. A folded V-shaped blunt body trapped vortex flame stabilizer as recited in claim 3, wherein each of said flame stabilizer elements further comprises two parameters, element spanwise length a and flow direction chord d, as follows:
5. the folding V-shaped blunt body trapped vortex flame stabilizer of claim 1, wherein said equal length combinations are equally spaced apart 12-20 equal length folding V-shaped flame stabilizer units within a circumference, each equal length folding V-shaped flame stabilizer unit being secured to the circular wall of the afterburner by airfoil end surfaces;
the long-short combination comprises a long flame stabilizer monomer combination and a short flame stabilizer monomer combination which are equally spaced, wherein the length of the short flame stabilizer monomer combination is 1-2 flame stabilizer monomers welded together end to end, and the length of the long flame stabilizer monomer combination is 2-3 flame stabilizer monomers welded together end to end; the airfoil end face of each long flame stabilizer monomer combination or each short flame stabilizer monomer combination is fixed on the circular wall of the afterburner;
the number of the long flame stabilizer monomer combination and the short flame stabilizer monomer combination in the long flame stabilizer monomer combination and the short flame stabilizer monomer combination is determined according to the diameter of the afterburner, wherein the number of the flame stabilizer monomers selected in the long flame stabilizer monomer combination is less than or equal to 2 times of the number of the flame stabilizer monomers in the short flame stabilizer monomer combination.
6. The folding V-shaped blunt body trapped vortex flame stabilizer of claim 1, wherein the working principle and process are as follows:
when the folding V-shaped blunt body standing vortex flame stabilizer works, incoming flow takes fuel to flow through two wing surfaces, as the section of the flame stabilizer is a plane V-shaped blunt body with curvature rho and height D, fluid is inevitably separated from the plane V-shaped blunt body, a pair of flow vortex is formed at the downstream of the plane V-shaped blunt body, and as the folding V-shaped blunt body is provided with two symmetrical wing surfaces which are stretched at a certain sweepback angle alpha and a certain length L and have equal sections, an integral V-shape in a three-dimensional space is formed on the orthogonal plane of the plane V-shaped blunt body, the incoming flow also flows from the edge openings of the two wing surfaces to the central plane directions of the two wing surfaces, and the vortex distributed along the spreading direction is formed;
the flow direction vortex falling off from the plane V-shaped blunt body cross section is vertical to the direction of the vortex in the spanwise distribution, and interacts with the direction of the vortex to finally form a pair of standing vortices which are stable in space and not easy to change along with the change of the flowing condition at the downstream of the folding V-shaped blunt body flame stabilizer; the ignition device is arranged at the center of the standing vortex, so that stable combustion of flame can be ensured, and the stable combustion effect exceeding that of the traditional plane V-shaped blunt body is exerted.
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| CN110274259A (en) * | 2019-06-13 | 2019-09-24 | 中国人民解放军空军工程大学 | A kind of plasma excitation Formula V type flameholder |
| CN113701191B (en) * | 2021-09-01 | 2022-06-24 | 南昌航空大学 | Staggered flow guide middle seam type V-shaped flame stabilizer |
| CN116025926B (en) * | 2023-03-10 | 2024-07-05 | 中国航发沈阳发动机研究所 | Afterburner of aeroengine |
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