CN112879949B - Backflow cover for air inlet hole in wall surface of combustion chamber of micro turbojet engine - Google Patents

Abstract

The invention discloses a backflow cover for a wall surface air inlet of a combustion chamber of a micro turbojet engine, which comprises a first backflow cover arranged on a cold side wall surface of an outer ring of the combustion chamber and a second backflow cover arranged on a hot side wall surface of the outer ring of the combustion chamber; the first backflow cover wraps the front half part of the main combustion hole along the incoming flow direction, and the second backflow cover wraps the rear half part of the main combustion hole along the incoming flow direction; when the airflow reaches the wall surface of the combustion chamber, the airflow climbs along the first backflow cover at a fixed angle and enters the main combustion hole, and part of the airflow flows along the second backflow cover in the direction opposite to the direction forming a certain angle with the incoming flow to form a backflow area. The invention can form a part of backflow zone near the main combustion zone for supplementing combustion, thereby greatly improving the problems of short combustion residence time and insufficient combustion caused by small overall size of the combustion chamber of the micro turbojet engine; meanwhile, the uniformity of combustion in the combustion chamber is improved, the overall combustion efficiency is improved, and the more excellent overall performance of the micro turbojet engine is obtained.

Description

A recirculation cover for the air inlet hole on the wall of the combustion chamber of a micro-turbojet engine

technical field

The invention belongs to the field of micro-turbojet engine combustion, and particularly relates to a return cover for an air inlet hole on a wall surface of a micro-turbojet engine combustion chamber.

Background technique

Micro-turbojet engines have the advantages of small size, small mass, and large thrust-to-weight ratio, and are widely used in military and civilian fields. In the field of aviation, small and intelligently developed UAVs play an increasingly important role in national security, real-time reconnaissance, remote surveys, disaster prevention, etc., and micro-turbojets are increasingly valued as their power source. In addition, micro-engines can also be used as power sources such as missiles and target drones, as well as auxiliary power units for large aircraft. The application market in the aviation field is very broad. At the same time, the micro-turbojet engine also has the characteristics of relatively simple structure, short research and development cycle, and low cost, and includes the core technologies of all aspects of gas turbines, so it is used as a verification platform for various new concepts and new technologies, which can quickly accumulate research and development. Experience, and related technologies are simultaneously applied to medium and large engines or transplanted into ground gas turbines for distributed energy systems, auxiliary power for military vehicles and other fields. The overall performance of the engine is limited by the performance of individual components, of which the combustion chamber is the most important high-temperature component, and the working conditions are also extremely harsh. Under the action of high temperature and high pressure combustion flame, the combustion chamber is subjected to high-intensity thermal load and thermal shock load, as well as a certain degree of mechanical vibration load. At the same time, due to the small overall size of the micro-turbojet engine, the size of the combustion chamber is correspondingly reduced, which often leads to problems such as insufficient combustion residence time and insufficient combustion sufficiency in the combustion chamber. Therefore, in order to improve the combustion efficiency of the combustion chamber and prolong the service life of the combustion chamber, thereby improving the overall performance of the micro-turbojet engine, it is necessary to reasonably optimize the problems such as insufficient combustion of the combustion chamber.

SUMMARY OF THE INVENTION

Purpose of the invention: The purpose of the present invention is to provide a micro-turbojet engine for supplementary combustion by forming a partial return flow near the main combustion zone of the combustion chamber, effectively improving the overall combustion efficiency and combustion uniformity of the combustion chamber, and thereby improving the performance of the overall turbojet engine. Recirculation cover for the air intake holes on the wall of the combustion chamber of the jet engine.

Technical solution: The present invention includes a first return hood arranged on the outer annular cooling side wall surface of the combustion chamber and a second recirculation hood arranged on the outer annular hot side wall surface of the combustion chamber; the first recirculation hood wraps the main combustion hole along the incoming flow In the first half of the direction, the second recirculation hood wraps the second half of the main combustion hole along the incoming flow direction; when the airflow reaches the wall of the combustion chamber, it climbs a fixed angle along the first recirculation hood and enters the main combustion hole, and part of the airflow flows along the second recirculation. The hood flows in the opposite direction at an angle to the incoming flow, forming a return zone.

The first return cover and the second return cover are spherical return cover, and the spherical arc surface greatly reduces the aerodynamic loss while forming the backflow supplementary combustion.

The spherical included angle _θ1 of the first return cover is in the range of 30° to 60°, the diameter of the spherical surface is the same as the diameter of the main combustion hole, and the supplementary combustion effect is best within this range.

The spherical included angle θ2 of the _second return cover ranges from 30° to 60°, the diameter of the spherical surface is the same as the diameter of the main combustion hole, and the supplementary combustion effect is best within this range.

The spherical center of the first return cover coincides with the circle center of the upper surface of the main combustion hole, the spherical center of the second return cover is coincident with the circle center of the lower surface of the main combustion hole, and the circle centers of the upper and lower surfaces of the main combustion hole are on the same central axis.

The rotation center axis of the first return cover is perpendicular to the air flow direction, and the extension direction of the spherical surface of the first return cover is the same as the airflow direction.

The rotation center axis of the second return cover is perpendicular to the flow direction of the high temperature gas, and the extension direction of the spherical surface of the second return cover is opposite to the flow direction of the high temperature gas.

Beneficial effects: Compared with the prior art, the present invention has the following beneficial effects: (1) it can form a partial return flow near the main combustion zone of the combustion chamber for supplementary combustion, effectively improving the overall combustion efficiency and combustion uniformity of the combustion chamber; (2) The spherical shape of the recirculation cover can not only form recirculation supplementary combustion, but also greatly reduce the aerodynamic loss due to its spherical arc surface, which has little effect on the overall total pressure loss of the combustion chamber; (3) The spherical diameter with the same aperture as the main combustion hole is used, and the maximum While wrapping the main combustion hole to a certain extent, the size of the return hood is also reduced, so as to avoid the influence of the excessive size on the main combustion structure.

Description of drawings

Fig. 1 is the structure diagram of the micro-turbojet engine combustion chamber to which the present invention is applied;

2 is a schematic cross-sectional view along the A-A direction of FIG. 1;

Fig. 3 is a partial enlarged view of Fig. 2;

4 is an annotated sectional view of the present invention;

Figure 5 is a vector diagram of the center section of the original model without the reflow hood of the present invention;

6 is a vector diagram of the center section of the model after arranging the reflux hood of the present invention;

Fig. 7 is the intake streamline diagram of the main combustion hole in the original model without the recirculation hood of the present invention;

Fig. 8 is the intake streamline diagram of the main combustion hole in the model after the recirculation hood of the present invention is arranged;

FIG. 9 is a comparison diagram of each main evaluation parameter of the combustion chamber after the recirculation hood of the present invention is arranged.

Detailed ways

The present invention will be further described in detail below with reference to the specific embodiments and the accompanying drawings.

As shown in FIG. 1 , for the air inlet holes on the combustion chamber wall of the micro-turbojet engine, the recirculation cover of the present invention is arranged around the main combustion holes in the second row. a hood and a second return hood arranged on the outer annular hot side wall of the combustion chamber. The first return cover wraps the first half of the main combustion hole along the incoming flow direction, and the second return cover wraps the second half of the main combustion hole along the incoming flow direction.

As shown in FIG. 2 and FIG. 3 , both the first return hood and the second return hood are spherical return hoods. In this embodiment, the central axis of rotation of the first recirculation hood is perpendicular to the air flow direction, and the extension direction of the spherical surface of the first recirculation hood is the same as the airflow direction. The rotation center axis of the second return cover is perpendicular to the flow direction of the high temperature gas, and the extension direction of the spherical surface of the second return cover is opposite to the flow direction of the high temperature gas. When the airflow reaches the wall of the combustion chamber, it first climbs a certain angle along the first recirculation hood, and after entering the main combustion hole, part of the airflow flows along the second recirculation hood and flows in the opposite direction to the incoming flow direction at a certain angle to form a recirculation zone. At the same time, the spherical center of the first return cover coincides with the circle center of the upper surface of the main combustion hole, the spherical center of the second return cover is coincident with the circle center of the lower surface of the main combustion hole, and the circle centers of the upper and lower surfaces of the main combustion hole are on the same central axis.

As shown in FIG. 4 , the spherical angle _θ1 of the first return cover ranges from 30° to 60°, the diameter of the spherical surface is the same as the aperture of the main combustion hole, and generally the diameter D is between 2 and 5 mm. The spherical included angle θ2 of the _second recirculation hood is in the range of 30° to 60°, the diameter of the spherical surface is the same as the aperture of the main combustion hole, and the general diameter D is between 2 and 5 mm. The spherical angles θ ₁ and θ ₂ of the first recirculation hood and the second recirculation hood do not have to be consistent, and can be adjusted according to different working conditions. After simulation verification, the spherical angle θ ₁ and θ ₂ are designed to be between 30° and 60°, and the effect of generating partial recirculation zone for supplementary combustion is the best. It will have a certain impact on the main combustion structure.

As shown in Figures 5 and 6, it can be clearly seen from the comparison that the spherical recirculation cover of the present invention is used around the main combustion holes in the outer ring of the micro-turbojet engine, so that the area before and after the intake of the main combustion holes in the second row can be A certain recirculation zone is generated, the combustion residence time is increased, the combustion sufficiency is improved, and the overall combustion efficiency of the combustion chamber is improved.

As shown in Figures 7 and 8, it can be clearly seen from the comparison that in the original model, the intake air enters the main combustion zone for blending and combustion, and then flows toward the downstream outlet. The angle reversely enters the main combustion area for blending combustion, and a recirculation area appears in a local area, and the streamline of the entire recirculation area gradually flows toward the downstream outlet in a spiral shape, which greatly increases the combustion residence time and further enhances the main combustion. blended combustion in the zone.

As shown in Figure 9, after the spherical recirculation cover is arranged, the overall combustion efficiency of the combustion chamber is significantly improved, from 95.2% of the original model to about 97%. The overall total pressure loss of the combustion chamber is basically unchanged, but an excessive spherical angle may have a certain impact on the total pressure loss. Compared with the original model, the OTDF at the outlet of the combustion chamber is slightly lower, from 0.42 of the original model to 0.37, indicating that the recirculation zone generated by the spherical recirculation hood model further improves the combustion sufficiency, so that the downstream outlet temperature distribution has also been improved to some extent. The overall performance of the micro-turbojet engine is also enhanced.

Claims (7)

1. The utility model provides a backward flow cover that is used for miniature turbojet engine combustion chamber wall inlet port which characterized in that: the first backflow hood is arranged on the cold side wall surface of the outer ring of the combustion chamber, and the second backflow hood is arranged on the hot side wall surface of the outer ring of the combustion chamber; the first backflow cover wraps the front half part of the main combustion hole along the incoming flow direction, and the second backflow cover wraps the rear half part of the main combustion hole along the incoming flow direction; when the airflow reaches the wall surface of the combustion chamber, the airflow climbs along the first backflow cover at a fixed angle and enters the main combustion hole, and part of the airflow flows along the second backflow cover in the direction opposite to the direction forming a certain angle with the incoming flow to form a backflow area.

2. The reverse flow cover for an intake port in a combustion chamber wall surface of a micro turbojet engine as claimed in claim 1, wherein: the first backflow cover and the second backflow cover are spherical backflow covers.

3. The reverse flow cover for an intake port in a combustion chamber wall surface of a micro turbojet engine as claimed in claim 2, wherein: spherical included angle theta of first backflow cover₁The range of the spherical surface is 30-60 degrees, and the diameter of the spherical surface is the same as the aperture of the main burning hole.

4. The reverse flow cover for an intake port in a combustion chamber wall surface of a micro turbojet engine as claimed in claim 2, wherein: spherical included angle theta of the second backflow hood₂The range of the spherical surface is 30-60 degrees, and the diameter of the spherical surface is the same as the aperture of the main burning hole.

5. The reverse flow cover for an intake port in a combustion chamber wall surface of a micro turbojet engine as claimed in claim 2, wherein: the spherical center of the first backflow cover coincides with the circle center of the upper surface of the main combustion hole, the spherical center of the second backflow cover coincides with the circle center of the lower surface of the main combustion hole, and the circle centers of the upper surface and the lower surface of the main combustion hole are located on the same central axis.

6. The reverse flow cover for an intake port in a combustion chamber wall surface of a micro turbojet engine as claimed in claim 2, wherein: the rotation central axis of the first return flow cover is vertical to the air flowing direction, and the extending direction of the spherical surface of the first return flow cover is the same as the air flowing direction.

7. The reverse flow cover for an intake port in a combustion chamber wall surface of a micro turbojet engine as claimed in claim 2, wherein: the rotation central axis of the second backflow cover is perpendicular to the flowing direction of the high-temperature fuel gas, and the extending direction of the spherical surface of the second backflow cover is opposite to the flowing direction of the high-temperature fuel gas.

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