CN112728584A

CN112728584A - Flame stabilizer, radial flame stabilizer and combustion chamber

Info

Publication number: CN112728584A
Application number: CN202011328240.6A
Authority: CN
Inventors: 范育新; 刘琛
Original assignee: Nanjing University of Aeronautics and Astronautics
Current assignee: Nanjing University of Aeronautics and Astronautics
Priority date: 2020-11-24
Filing date: 2020-11-24
Publication date: 2021-04-30
Anticipated expiration: 2040-11-24
Also published as: CN112728584B

Abstract

The invention discloses a flame stabilizer, a radial flame stabilizer and a combustion chamber. The stabilizer main body is provided with a periodic fluctuation profile, the periodic fluctuation profile comprises a plurality of fluctuation units distributed along the radial direction, each fluctuation unit fluctuates towards the direction far away from the stabilizer main body, the fluctuation directions of the adjacent fluctuation units are opposite, and the fluctuation height of each fluctuation unit from the front end to the rear end is gradually increased. The invention integrates mixing, oil supply and flame stabilization, can increase the residence time of fuel oil, improve the atomization and evaporation performance of the fuel oil, enhance the mixing of the fuel oil and air, improve the circumferential flame-linking capability, ensure that the combustion in the combustion chamber is more sufficient, improve the working efficiency of the combustion chamber, ensure that the outlet temperature is more uniform, and further enlarge the stable working range of the afterburner.

Description

Flame stabilizer, radial flame stabilizer and combustion chamber

Technical Field

The invention belongs to the technical field of afterburners/ramjets of turbine/ramjet combined engines and turbofan engines, and particularly relates to a flame stabilizer, a radial flame stabilizer and a combustor.

Background

As an air-breathing engine, a turbo-based combined cycle (TBCC) has the performance advantages of wide flight range, conventional take-off and landing, reusability and the like, and is considered to be the most promising power device of the hypersonic aircraft at the present stage. Due to the fact that the bypass ratio is greatly changed in the whole working range, incoming flow temperature inside a multi-mode combustion chamber of the TBCC engine is low, and local flow speed is too large. Under such flow conditions, how to achieve stable ignition, cross-fire, and reduce flow resistance losses in the un-energized state is a goal of afterburner development both currently and for some time in the future.

The flame stabilizer is used as a key part for stabilizing flame in the multi-mode combustion chamber, is most commonly used in subsonic combustion, and can be functionally divided into an on-duty stabilizer for realizing ignition and a radial stabilizer for realizing cross flame. In multi-modal combustors, V-shaped radial stabilizers are widely used because: when the stress application mode is started in the turbine mode or in the stamping mode, the good flame transmission and flame linkage capacity of the turbine is exerted to the maximum extent, and the turbine is simple in structure and convenient to apply; when the stress application mode is closed under the turbine mode, the turbine mode can be used as a mixer to strengthen the mixing of high-temperature and low-temperature air flows of an internal culvert and an external culvert, and the speed, the temperature and the pressure gradient of the two air flows are gradually leveled along a flow path.

After the ignition is successful, the rapid realization of the radial flame transmission and the circumferential flame connection behind the flame stabilizer is the basis for ensuring the efficient and stable combustion, and the problem that the flame transmission of the flame stabilizer is difficult when the multi-mode combustion chamber is wide in working range and large in change of incoming flow conditions needs to be solved at the moment.

The following problems are mainly existed in the application process of the current radial flame stabilizer: (1) the radial stabilizer mainly plays the role of radial flame transmission and circumferential flame connection with the adjacent stabilizer. In the multi-mode combustion chamber, the distance between adjacent radial stabilizers is increased along with the increase of the radial extension length, the distance is maximized near the position close to the outer wall surface, and the circumferential flame transfer distance is also maximized. Therefore, the flame behind the radial stabilizer is difficult to expand in the circumferential direction, so that the circumferential flame connection between adjacent stabilizers is difficult; (2) under the condition of high-temperature incoming flow, the fuel is easy to evaporate after being sprayed out from the nozzle hole, and on one hand, the fuel is easy to generate thermal spontaneous combustion; on the other hand, the following performance of oil drops and gas-phase fuel oil along with airflow is good, and the circumferential penetration capacity is weak, so that the fuel oil is mainly concentrated near the downstream of the nozzle; under high-speed inflow, the penetration depth of the fuel is small, the oil mist can not be diffused along the circumferential direction, the fuel is not favorably and uniformly and reasonably distributed on the whole circulation section, and the combustion efficiency is reduced; (3) when the conventional radial flame stabilizer is adopted, in order to improve the circumferential flame-linking capability, the distance between the stabilizers must be shortened. On the premise of not changing the groove width of the stabilizer, the number of the stabilizers is increased, the blocking ratio is increased, and the resistance loss is increased; in the case of keeping the plugging ratio constant, the stabilizer groove width must be reduced, which lowers the flame holding performance of the stabilizer.

The conventional design method for supplying, mixing and stabilizing oil in a space and performing other functions in a segmented way easily generates thermal spontaneous combustion in high-temperature airflow of an advanced afterburner and ablates a stabilizer; in the low-temperature high-speed airflow of the stamping combustion chamber, fuel oil is not easy to evaporate and ignite, and stable combustion is difficult. The modern afterburner and the ram combustor mostly adopt stabilizers which are integrally designed for oil supply and stabilization, and the integrally designed stabilizers have the following problems when being applied: (1) when the stabilizer with integrated oil supply and stabilization design is adopted, the penetration depth of fuel oil changes along with the changes of the incoming flow speed, the temperature and the oil supply pressure, the fuel oil is not uniformly distributed along the circumferential direction, and the propagation of flame is influenced due to the occurrence of local rich oil and local lean oil; (2) the radial flame stabilizer in the multi-mode combustion chamber works in high-temperature high-speed gas flow with extremely uneven temperature field, the temperature distribution of the integrated stabilizer is very uneven, and the thermal fatigue damage of the stabilizer can be caused by the generated thermal stress; (3) the fuel distribution of the same stabilizer is based on a partitioned partial pressure fuel supply principle, the flow of the inner ring position is small, the matched fuel flow is correspondingly reduced, if the distance between fuel injection points is ensured, the fuel supply oil pressure needs to be reduced, and fuel atomization is not facilitated; if the oil pressure of oil supply is ensured, the distance between oil injection points needs to be increased, which is not beneficial to radial flame transmission of the same stabilizer; (4) under the large working condition of the boosting/stamping combustion chamber, the integrated flame stabilizer is always in the gas flow with extremely uneven temperature field to work, and when the engine is frequently started, stopped and the working condition is switched, the gas temperature is changed rapidly. In such an operating environment, the temperature distribution of the integrated stabilizer is very uneven, and the resulting thermal stress may cause thermal fatigue failure of the stabilizer. When the stress application is started, the temperature of the incoming flow of the new generation turbine engine is greatly increased, and the integrated stabilizer is higher than the previous environment temperature. The flow is larger and the speed is higher in the stamping mode, the heat release amount after combustion is increased, the heat load of a fuel nozzle and a flame stabilizer is increased, and ablation is easy to occur.

Disclosure of Invention

The purpose of the invention is as follows: in order to solve the problems, the invention provides a flame stabilizer which integrates mixing, oil supply and flame stabilization. The invention also provides a radial flame stabilizer which is applied to an afterburner of a turbofan engine, a combustion chamber of a sub-combustion ramjet engine and a multi-mode combustion chamber of a turbofan/ramjet combined cycle engine, so that oil-gas mixing is enhanced, the circumferential flame linking capability of the flame stabilizer is improved, combustion in the combustion chamber is more sufficient, the outlet temperature is more uniform, the stable working range of the afterburner is expanded, and the working efficiency of the combustion chamber is improved.

The technical scheme is as follows: according to the flame stabilizer, the stabilizer main body is provided with the periodic fluctuation profile, the periodic fluctuation profile comprises a plurality of fluctuation units distributed along the radial direction, each fluctuation unit fluctuates towards the direction far away from the stabilizer main body, the fluctuation directions of the adjacent fluctuation units are opposite, and the fluctuation height of each fluctuation unit gradually increases from the front end to the rear end.

As a preferred structure of the present invention, the wave unit has a trapezoidal, saw-toothed or wave-shaped cross section.

The wave heights of the adjacent wave units are the same.

The invention relates to a radial flame stabilizer which comprises a front edge section, a long straight section and a stabilizer main body, wherein the long straight section is arranged at the rear end of the front edge section, and the stabilizer main body is arranged at the rear end of the long straight section.

As a preferable structure of the present invention, the long straight section is a hollow structure, a plurality of oil injection mechanisms are disposed in the long straight section, and outlets of the plurality of oil injection mechanisms are uniformly distributed on the surface of the long straight section along a radial direction.

As a preferred structure of the present invention, the leading edge section has a V-shaped structure.

The invention also provides a combustion chamber comprising the radial flame stabilizer.

Has the advantages that: (1) the invention provides a stabilizer main body with a periodic fluctuation profile as a flame stabilizing section, which enables fluid to generate flow direction vortex after passing through the flame stabilizing section, can increase the retention time of fuel oil, improve the atomization and evaporation performance of the fuel oil, strengthen the mixing of the fuel oil and air, improve the circumferential flame linking capability and enable the combustion in a combustion chamber to be more sufficient; (2) according to the invention, the flame stabilizing section is matched with the oil supply and the periodic fluctuation profile, so that the mixing of fuel oil and air can be enhanced, the circumferential diffusion capability of the fuel oil is improved, and the oil gas distribution in the combustion chamber is more uniform; (3) the flame stabilizer adopting mixing, oil supply and integrated design can improve the combustion efficiency, make the outlet temperature more uniform and enlarge the stable working range of the afterburner; (4) the flame stabilizer integrates the integration of mixing, oil supply and flame stabilization, and can finish multiple functions on one part, shorten the length of the combustion chamber, ensure that the combustion chamber has more compact structure and smaller flow loss; (5) the oil supply pipeline is arranged in the radial flame stabilizer, so that the problem that a wall oil pipeline is prone to fuel oil coking is solved. The effect of cooling the rear end wall surface of the stabilizer can be realized by using part of the fuel oil which is drawn into the flow direction vortex; (6) the stabilizer main body of the invention better solves the problem of thermal stress, and under the condition that the stabilizer is heated unevenly, the margin of thermal expansion and cold contraction of the stabilizer main body is larger.

Drawings

FIG. 1 is a schematic structural view of a flame holder according to example 1 of the present invention;

FIG. 2 is a schematic sectional view of a flame holder according to example 1 of the invention;

FIG. 3 is a schematic view of the structure of one of the radial flame holders according to embodiment 2 of the present invention;

FIG. 4 is a schematic view of the structure of one of the radial flame holders according to embodiment 2 of the present invention;

FIG. 5 is a schematic view of the structure of one of the radial flame holders according to embodiment 2 of the invention;

FIG. 6 is a schematic view showing the operating state of the radial flame stabilizer of example 2 of the invention;

FIG. 7 is a schematic view showing the structure of an oil spray hole of a radial flame holder according to embodiment 2 of the invention;

FIG. 8 is a schematic view of a radial flame holder of a prior art construction;

FIG. 9 is a schematic illustration of the specific application parameters of the undulating profile of the radial flame holder of example 2 of the present invention;

FIG. 10 is a schematic view showing the operation of the radial flame holder of example 2 of the present invention in a combustion chamber;

FIG. 11 is a cloud of flow field distributions of the structures on different X cross sections;

FIG. 12 is a cloud graph of temperature field distributions of various structures at different X-sections.

Detailed Description

Example 1: as shown in FIG. 1, a flame stabilizer according to the present invention comprises a stabilizer body 10, the stabilizer body 10 has a periodic fluctuation profile 20, the periodic fluctuation profile 20 includes a plurality of fluctuation units 201, the plurality of fluctuation units 201 are arranged along the stabilizer body 10 in a radial direction (the radial direction of the stabilizer body 10 in the present invention is the direction in which the X axis extends in FIG. 1), each fluctuation unit 201 fluctuates in a direction away from the stabilizer body 10, the direction away from the stabilizer body 10 is the direction away from the plane in which the stabilizer body 10 is located, (the plane in which the stabilizer body 10 is located is parallel to the plane formed by the X axis-Y axis in FIG. 1), the fluctuation directions of adjacent fluctuation units 201 are opposite, the fluctuation height of each fluctuation unit 201 gradually increases from the front end to the rear end (the direction in which the X axis extends, also in the present embodiment, the axial direction), and the undulation unit 201 in the periodically undulated profile 20 in the present embodiment is continuously undulated.

As an alternative of the present embodiment, the distance between the peak of each wave unit 201 and the plane on which the stabilizer body 10 is located is equal or unequal. As shown in fig. 2, the cross section (Z-Y axis forming longitudinal section) of the undulation unit 201 may have various shapes, such as a zigzag structure (structure 1) shown in (a) of fig. 2, an arcuate structure (structure 2) shown in (b) of fig. 2, or a corrugated structure (structure 3) shown in (c) of fig. 2.

As an alternative of the present embodiment, the undulation heights of the adjacent undulation units 201 are the same, that is, the distances of the tips of the undulation units sectioned by each Z-Y axis forming a longitudinal section from the plane in which the stabilizer body 10 is located are the same in the front-to-rear direction.

Example 2: as shown in fig. 3 to 5, using the stabilizer body 10 of embodiment 1, the present invention provides a radial flame stabilizer 1 including a leading edge segment 30, an elongated straight segment 40 disposed at a rear end of the leading edge segment 30, and the stabilizer body 10 as described in embodiment 1 disposed at a rear end of the elongated straight segment 40.

The leading edge section 30 in this embodiment is a V-shaped structure, and the distance between the two side surfaces of the V-shaped structure gradually increases along the front-to-back direction, the tail end of the leading edge section 30 is provided with a hollow long straight section 40, the long straight section 40 is substantially a hollow long cylinder, the two side surfaces of the long straight section 40 are provided with a plurality of oil spray holes 401, and in an optional embodiment, the oil spray holes 401 are uniformly distributed along the radial direction at intervals on the side surfaces of the long straight section. The rear end of the long straight section 40 is connected to the stabilizer body 10.

As shown in fig. 6 and 7, the airflow in this embodiment is divided into two parts after passing through the V-shaped front edge section 30, so as to reduce the flow loss, the fuel injection holes are arranged on the side surface of the long straight section 40, the airflow is mixed with the fuel through the fuel injection holes 401 arranged on the long straight section, and then the airflow passes through the stabilizer main body 10 with the periodically fluctuating profile to generate the flow vortex, so that the residence time of the fuel can be increased, the atomization and evaporation performance of the fuel can be improved, the mixing of the fuel and air can be enhanced, the circumferential flame-linking capability can be improved, and the combustion in the combustion chamber can be more sufficient.

The work flow (or the explanation of the working principle) is as follows:

as shown in FIG. 10, the gas flow direction is parallel to the X-axis, and the gas separates at the leading edge segment 30 of the radial flame holder and flows over the side of the flame holder. The long straight section 40 is hollow and provided with an oil pipe, so that fuel oil is sprayed out from two sides of the long straight section to enter the downstream for atomization and mixing. After passing through the flame stabilizer 10, the airflow generates a plurality of axial vortexes (the normal direction of each vortex is parallel to the X axis), and oil-gas mixing is enhanced through the action of the vortexes, so that fuel atomization and evaporation are facilitated.

The structure of fig. 10 is also a structural view of the application of the radial flame holder in the present embodiment to the combustion chamber, in which the radial flame holder in the present embodiment is fixed.

As shown in fig. 8, the groove width W' of the conventional radial flame stabilizer is generally in the interval of 10mm to 40mm, and is small, the flow loss of the stabilizer is small, and the flame stabilization performance is poor, while the groove width is large, the flow loss of the stabilizer is large, and the flame stabilization performance is good. As shown in fig. 9, the radial flame holder 1 in this embodiment is composed of three sections, i.e., a leading edge section 30, a long straight section 40, and a flame holding section (flame holder 10), and the radial flame holder realizes balance between reduction of flow loss and flame holding performance by providing a periodic fluctuation profile with periodically varying roughness.

The performance advantage of the radial flame stabilizer 1 is demonstrated by comparing the downstream flow field distribution and the temperature distribution of each radial flame stabilizer 1 through numerical simulation. The groove width of the radial flame holder is w', the height of the radial flame holder is H, and the groove widths of the prior art structure 1 and the prior art structure 2 are 14.14mm and 40mm, respectively. As shown in fig. 9, the groove width w' (distance from peak to trough) of the structure 1-3 in table 1 is 40mm, the width of the radial flame holder structure 1-3 is w (i.e. distance in X-axis direction), the value of w is 14.14mm, the θ angle is 90 ° (as shown in fig. 9, (a) in fig. 9 is a schematic view of the structure 1, (b) in fig. 9 is a schematic view of the structure 2, and (c) in fig. 9 is a schematic view of the structure 3), as shown in fig. 11, the value of X in the figure refers to different X sections in the calculation domain, and the blockage ratio of all the structures of the stabilizer is 0.3 in comparison with the flow field downstream of the conventional radial flame holder provided in the present embodiment. The groove widths of the conventional radial flame stabilizers are 14.14mm and 40mm respectively, the fluctuation molded surfaces of the stabilizer main body 10 of the radial flame stabilizer in the embodiment are respectively in a sawtooth shape, a bow shape and a corrugated shape, the groove width is 40mm, the height of each radial flame stabilizer is the same, as can be seen from fig. 11, compared with the conventional radial flame stabilizer, the radial flame stabilizer in the embodiment forms radially-arranged axial vortexes through the fluctuation molded surfaces, the positions of the vortexes correspond to the structures and the positions of the fluctuation units one by one, and the downstream flow fields of the conventional radial flame stabilizer with the groove width of 14.14mm and the conventional radial flame stabilizer with the groove width of 40mm in the embodiment are better mixed, the speed distribution is more uniform, and the flow loss is favorably reduced.

As shown in fig. 12, the comparison of the radial flame stabilizer with the wavy profile of the stabilizer body 10 in the zigzag, zigzag and wave forms with the temperature field downstream of the conventional radial flame stabilizer shows that the conventional radial flame stabilizer with the groove width of 14.14mm is not ignited and has no corresponding temperature distribution cloud pattern, and the temperature distribution of the flow field downstream of the conventional radial flame stabilizer is not improved with the increase of the distance, and shows the states of large temperature difference and uneven distribution. The temperature distribution of the downstream flow field of the radial flame stabilizer in the embodiment is obviously improved along with the increase of the distance, the temperature distribution is basically consistent, and the circumferential flame coupling effect of the radial flame stabilizer in the embodiment is better.

From the results of fig. 11 and 12 and the data in table 1, it can be seen that the three radial flame stabilizers provided in the present embodiment generate flow direction vortices by setting the fluctuation profile under the same width as that of the conventional radial stabilizer, thereby enhancing the flame stabilizing performance of the radial flame stabilizer; under the condition that the groove width is the same as that of a conventional radial stabilizer, the flame stabilizing performance is good through the arrangement of the wavy profile, the weight of the stabilizer is reduced, and the flow loss is reduced.

Table 1 shows the pressure loss, the OTDF (outlet temperature distribution factor) value and the RTDF (radial temperature distribution factor) value of the outlet cross section of the five stabilizers, the OTDF value and the RTDF value of the radial flame stabilizer are much lower than those of the conventional radial flame stabilizer by one order of magnitude, and the pressure loss of the corrugated radial flame stabilizer is minimal, which has a good application prospect in turbo/ramjet combined engines and turbo fan engine forced/ramjet combustors.

TABLE 1 comparison of the parameters of five stabilizers

Claims

1. A flame stabilizer is characterized by comprising a stabilizer body (10), wherein the stabilizer body (10) is provided with a periodic fluctuation profile (20), the periodic fluctuation profile (20) comprises a plurality of fluctuation units (201) distributed along a radial direction, each fluctuation unit (201) fluctuates towards a direction far away from the stabilizer body (10), the fluctuation directions of the adjacent fluctuation units (201) are opposite, and the fluctuation height of each fluctuation unit (201) gradually increases from the front end to the rear end.

2. The flame holder according to claim 1, wherein the undulation unit (201) has a trapezoidal, saw-tooth or corrugated cross-section.

3. The flame holder according to claim 1, wherein the wave heights of adjacent wave units (201) are the same.

4. A radial flame holder, comprising a leading edge segment (30), an elongated straight segment (40) arranged at the rear end of the leading edge segment (30), and a holder body (10) according to claim 1 arranged at the rear end of the elongated straight segment (40).

5. The radial flame holder as claimed in claim 4, wherein the long straight section (40) is a hollow structure, a plurality of oil injection mechanisms (3) are arranged in the long straight section (40), and outlets of the plurality of oil injection mechanisms (3) are uniformly distributed on the surface of the long straight section along the radial direction.

6. The radial flame holder of claim 4, wherein the leading edge segment (30) is a V-shaped structure.

7. A combustion chamber comprising a radial flame holder according to any of claims 4-6.