CN111981510A

CN111981510A - Lobe mixer capable of generating swirling jet flow

Info

Publication number: CN111981510A
Application number: CN202010757370.5A
Authority: CN
Inventors: 文清兰; 于小兵; 尹璐
Original assignee: AECC Guiyang Engine Design Research Institute
Current assignee: AECC Guiyang Engine Design Research Institute
Priority date: 2020-07-31
Filing date: 2020-07-31
Publication date: 2020-11-24

Abstract

The invention discloses a lobe mixer capable of generating a swirling jet flow, wherein the crest line of a lobe of the mixer forms a certain angle with the axis of an engine. According to the invention, the airflow angle before mixing of culvert airflow is changed by utilizing the deflection angle of the wave flap in the lobe mixer, so that swirling flow is generated after the culvert airflow flows through the lobe, the mixing of the culvert airflow and the culvert airflow is enhanced, no additional connecting structure is generated, and the structure is simple; the mixer can be applied to a medium bypass ratio afterburner or a medium bypass ratio mixed exhaust device, and can achieve the purposes of small mixing loss and high mixing heat efficiency.

Description

Lobe mixer capable of generating swirling jet flow

Technical Field

The invention belongs to the structure design technology of forced mixers of afterburners of aircraft engines, and relates to a lobe mixer with a deflection angle and capable of generating swirling jet flow.

Background

The lobe mixer is one of main components of an afterburner and a mixed exhaust device with a medium-low bypass ratio, and has the main function of mixing two air flows in different states, namely an internal bypass and an external bypass, so that the speed, the temperature and the pressure gradient along the rear path of the mixer are gradually reduced, and a flow field tends to be in a relatively uniform state. The principle is that through the appearance design of the mixer lobe, large-scale flow direction vortex and orthogonal vortex are induced between inner culvert airflow and outer culvert airflow, and meanwhile, the airflow contact area is increased, so that the forced mixing effect is achieved. In a mixed exhaust system of an engine with a medium-small bypass ratio, high-energy content gas and low-energy content gas are mixed with each other through a mixer, so that the output thrust of the aircraft engine is improved, the fuel consumption rate is reduced, and the requirement for fully utilizing the exhaust energy is met. In the afterburner of the turbofan engine with the medium-small bypass ratio, on one hand, the temperature of the afterburner culvert area can be increased through the lobe mixer, so that the fuel atomization of the outer culvert is promoted, on the other hand, the oxygen content of the inner culvert area is increased, and favorable conditions are created for organizing high-efficiency combustion of the afterburner, so that the combustion efficiency is improved.

Therefore, the lobe mixer is an important part influencing the combustion efficiency of the afterburner and the propelling efficiency of the engine. The design indexes of the lobe mixer mainly include mixing thermal efficiency and mixing loss, namely the mixer is required to achieve higher mixing thermal efficiency with smaller mixing loss within a certain size range. At present, the design of a lobe mixer mainly adjusts characteristic parameters such as width, height and expansion angle of a lobe, and in order to realize higher mixing thermal efficiency, the problems that the connection structure of the lobe mixer tends to be complex, the weight and the mixing loss are increased and the like are brought.

Disclosure of Invention

The purpose of the invention is: the lobe mixer capable of generating the swirling jet flow is provided, so that the lobe mixer generates the swirling jet flow in a bypass manner, the purposes of greatly improving the mixing heat efficiency, reducing the mixing loss, having a simple structure and avoiding weight increase of lobes under the same design parameters are achieved, and the performance requirements of a small and medium bypass ratio afterburner/mixed exhaust device are met.

The technical solution of the invention is as follows:

a lobed mixer capable of producing a swirling jet has lobes with their crests angled with respect to the engine axis. The design enables the outer culvert airflow to generate a swirling jet flow with a certain airflow angle after flowing through the mixer, and the mixing of the inner culvert and the outer culvert mixing boundary of the mixer is enhanced by the aerodynamic action. The design can achieve the purpose of enhancing mixing only by changing the deflection angle of the lobe of the mixer, does not generate an additional connecting structure, and has the characteristics of small mixing loss, no weight increase, simple structure and shortened mixing section length.

Preferably, the ridges of the lobes are parallel.

Preferably, the ridge line of the lobe forms an angle of between 10 ° and 30 ° with the engine axis. Within this angular range, the mixing efficiency of the lobe mixer is relatively high and the mixing losses are small.

Preferably, the lobe mixer has a height of not less than 120 mm. The design requirement enables the lobe to have a transition section with a certain distance along the axial direction, the on-way loss of airflow is reduced, and meanwhile, the machining stress is reduced during lobe forming.

Preferably, the lobe mixer is composed of an annular fixed surface positioned on the bottom surface and lobes which are uniformly distributed along the circumferential direction of the fixed surface and extend along the ridge line direction, the side edges of every two adjacent lobes are connected to form a wave shape, and the junction is in smooth transition.

Preferably, the ratio of the distance between every two adjacent troughs and the distance between the peaks and the troughs of the wave-shaped projection of the lobe top surface on the horizontal plane is 1-1.6. This design requirement allows the lobes to operate at relatively low stress levels without adding excessive stiffening structures.

Preferably, the lobed mixer is applied to a medium bypass afterburner or a medium bypass hybrid exhaust. The lobe mixer has stronger drainage effect on the airflow of the outer culvert close to the edge of the mixer in the afterburner with medium culvert ratio, so that the mixing of the airflow of the inner culvert and the airflow of the outer culvert behind the mixer is enhanced, and the airflow direction of the main flow after mixing is not influenced.

Preferably, the lobe mixer is formed by stamping.

Preferably, when the lobe ridges are oriented at the same angle as the included airflow, the mixing action is relatively stronger than for an oppositely oriented structure.

The invention has the advantages that: according to the invention, the airflow angle before mixing of culvert airflow is changed by utilizing the deflection angle of the wave flap in the lobe mixer, so that swirling flow is generated after the culvert airflow flows through the lobe, the mixing of the culvert airflow and the culvert airflow is enhanced, no additional connecting structure is generated, and the structure is simple; the mixer can be applied to a medium bypass ratio afterburner or a medium bypass ratio mixed exhaust device, and can achieve the purposes of small mixing loss and high mixing heat efficiency.

Drawings

FIG. 1 is a schematic diagram of a forced mixing afterburner structure.

Figure 2 is an isometric view of a lobed mixer of the present invention that can generate swirling jets.

Figure 3 is a side view of a lobe mixer of the present invention that can produce a swirling jet.

Figure 4 is a schematic diagram of mixer lobe length and section n characteristic parameters.

Fig. 5 and 6 are schematic diagrams of lobe deflection angles of the lobe mixer.

In the figure: the device comprises a central cone 1, a lobe mixer 2, a boosting fuel oil main pipe 3, a stabilizer 4, a heat shield 5, a cylinder outer wall 6 and a rectifying support plate 7.

Detailed Description

The following describes embodiments of the present invention with reference to the drawings.

As shown in figure 1, the prior forced mixing afterburner comprises a central cone 1, a lobe mixer 2, an afterburner fuel manifold 3, a stabilizer 4, a heat shield 5, a cylinder outer wall 6 and a rectifying support plate 7. The lobe mixer enables the inner culvert high-temperature gas behind the support plate to be mixed with the outer culvert low-temperature gas, and then oil injection is carried out after the stabilizer for combustion, so that the enthalpy value of the gas is further improved, and the thrust of the engine is improved. For the afterburner with medium-small bypass ratio, the oxygen content of the culvert gas is low, the temperature is high, the oxygen content of the culvert gas is high, but the temperature is low, the lobe mixer enables the temperature of the culvert behind the mixer to be increased, the oxygen content of the culvert is increased, and the afterburning efficiency is improved.

Generally the lobes of the lobe mixer are evenly distributed circumferentially and the lobe ridgelines are parallel to the engine axis, i.e. the bypass airflow passing through the lobe mixer generates almost no tangential velocity. The lobe mixer mainly achieves the purpose of improving the heat mixing efficiency by adjusting the lobe characteristic parameters, and can bring the problems of weight increment, complex reinforcing structure, increased mixing loss and the like.

The lobe mixer capable of generating swirling jet flow consists of an annular fixing surface and lobes, wherein the annular fixing surface is located on the bottom surface of the lobe mixer, the lobes are evenly distributed along the circumferential direction of the fixing surface and extend along the ridge line direction, the side edges of every two adjacent lobes are connected to form a wave shape, and the junction is in smooth transition. The ridges of the lobes are at an angle to the engine axis. The ridges of each lobe are parallel. The included angle between the crest line of the lobe and the axis of the engine is 10-30 degrees. The lobe mixer has a height of not less than 120 mm.

The ratio of the distance between every two adjacent wave troughs to the distance between the wave crests and the wave troughs of the wave projection of the lobe top surface on the horizontal plane is 1-1.6. The lobe mixer is applied to a medium bypass ratio afterburner or a medium bypass ratio mixed exhaust device. The lobe mixer is formed by stamping. When the lobe ridge is oriented at the same angle as the included airflow, the mixing action is relatively stronger than for the oppositely oriented structure.

The lobe crest line of the lobe mixer and the axis of the engine form a certain angle, so that airflow of the bypass airflow after passing through the lobe generates airflow angles within a certain range, and the flow of the bypass airflow after passing through the lobe is towards the vortex to enhance the mixing of the bypass airflow and the bypass airflow under the action of the airflow angles, so that the purposes of small mixing loss and high mixing heat efficiency are achieved.

The lobe mixer is designed by the following steps:

(1) determining the size of a fixed surface through the size of a turbine support outlet interface, determining the number of lobes through a stabilizer layout, and determining the height L of the mixer through the axial length limit of the mixer;

(2) the projection of the lobe top surface on the horizontal plane is wave-shaped, and the wave crest size of the wave is designed

And trough size

The fillet size R2 of the lobe and the transition fillet R1 size of two adjacent lobes;

(3) and designing the deflection angle of the ridge line of the lobe relative to the axis of the engine according to the direction and the size of the prerotation angle of the connotation inlet. The deflection angle design relative to the axis of the engine has two deflection angles, the deflection angle between the first ridge line and the axis of the engine is alpha, the deflection angle between the second ridge line and the axis of the engine is beta, and the direction of a preselected angle of the connotative air flow can be considered for selection, as shown in fig. 5 and 6;

(4) modeling afterburner with lobe mixer by UG, Spaceclaim and other modeling software;

(5) calculating a flow field of the lobe mixer according to the boundary conditions of the known afterburner working conditions, and performing simulation calculation optimization through CFD software to obtain the mixing heat efficiency and total pressure loss of the lobe mixer;

(6) and adjusting the deflection angle direction and the deflection angle of the lobe according to the simulation calculation result, and then carrying out iterative calculation until the design index of the lobe mixer meets the requirement.

The above-mentioned embodiments are merely illustrative of the technical ideas and features of the present invention, and the purpose thereof is to enable those skilled in the art to understand the contents of the present invention and to implement the same, and not to limit the scope of the present invention, and all equivalent changes or modifications made according to the spirit of the present invention should be covered by the scope of the present invention. The techniques, shapes, and configurations not described in detail in the present invention are all known techniques.

Claims

1. A lobed mixer producing a swirling jet, characterised in that the lobe of the mixer has its crest at an angle to the engine axis.

2. The lobed mixer of claim 1, in which the ridges of the lobes are parallel.

3. The lobed mixer for generating swirling jets of claim 1, wherein the lobe has its crest at an angle of 10 ° to 30 ° to the engine axis.

4. The lobe mixer of claim 1, wherein the lobe mixer is not less than 120mm high.

5. The lobe mixer according to any one of claims 1 to 4, wherein the lobe mixer is composed of an annular fixing surface on the bottom and lobes which are uniformly distributed along the circumference of the fixing surface and extend along the ridge line direction, the side edges of every two adjacent lobes are connected to form a wave shape, and the junctions are smooth.

6. The lobe mixer capable of generating swirling flow of claim 5, wherein the ratio of the distance between every two adjacent troughs and the distance between the peaks and the troughs of the wave projection of the lobe top surface in the horizontal plane is 1-1.6.

7. The lobed mixer of claim 5, wherein the lobed mixer is used in medium bypass afterburner or medium bypass hybrid exhaust.

8. The lobe mixer capable of generating swirling flow of claim 5, wherein the lobe mixer is formed by stamping.

9. The lobed mixer of claim 5, in which the lobe crest is oriented in the same direction as the included flow angle.