CN118564313A - A sharp curved special-shaped exhaust diffuser with a pneumatic nozzle on the outlet surface - Google Patents

Abstract

The invention discloses a sharp-bending special-shaped exhaust diffuser with a pneumatic nozzle on an outlet surface, which comprises a diffuser inlet section, a diffuser outlet section and a bending section connected between the diffuser inlet section and the diffuser outlet section; a partition plate is arranged in the diffuser outlet section to divide the diffuser outlet section into a first outlet section and a second outlet section which are mutually independent. According to the invention, the pneumatic nozzle is additionally arranged at the outlet of the exhaust diffuser, so that on one hand, the circulation capacity of the exhaust diffuser is not weakened (namely, the performance of the exhaust diffuser is not influenced), on the other hand, the gas flow at the sharp bend of the exhaust diffuser is enhanced, the adverse effect caused by the fact that part of high-temperature gas flows backwards into an engine compartment is avoided, the gas mobility at the sharp bend of the sharp bend special-shaped exhaust diffuser is improved to a great extent, and the gas flow velocity at the sharp bend is greatly improved.

Description

Sharp bending special-shaped exhaust diffuser with pneumatic nozzle on outlet surface

Technical Field

The invention relates to the field of engine and aircraft design, in particular to a sharp-bending special-shaped exhaust diffuser.

Background

The high power-to-weight ratio is one of the key technical indexes pursued by the new generation of turboshaft engines, and in order to improve the power-to-weight ratio, the comprehensive performance of core components such as a compressor, a combustion chamber, a turbine and the like of the turboshaft engine is comprehensively improved, and meanwhile, the performance improvement of an exhaust pipe which is a downstream component of a free turbine is also required to be paid attention. The turboshaft engine exhaust pipe is different from the turbojet engine exhaust pipe, the inner surface of the channel is a subsonic diffuser, and the purpose of the turboshaft engine exhaust pipe is to reduce the pressure of the outlet of the free turbine, convert the enthalpy passing through the free turbine into shaft power as much as possible, and obviously, the diffusing capability of the turboshaft engine exhaust pipe is obviously influenced by the output shaft power of the free turbine. It is generally considered that the maximum continuous power loss of the engine is 0.5 to 1.0% per 1% of the total pressure of the exhaust system. In addition, in the integrated design process of the helicopter, the exhaust diffuser also bears the function of injecting ventilation cooling air flow in the engine cabin, the injection capacity can be directly related to the temperature in the engine cabin, the temperature of engine lubricating oil and the temperature of the surface of an accessory related to the outside of the engine, and the malfunction of an engine related sensor can be caused under severe conditions, so that the engine is out of control. Helicopter engineers may not be aware of the specificity of the diffusion flow (and even the possible separation of the air streams) within the exhaust pipe of the turboshaft engine, resulting in a significant loss of shaft output power from the turboshaft engine.

For the turboshaft engine with a rear output shaft, the power output shaft of the engine needs to pass through the middle of the exhaust diffuser, the flow path inside the exhaust diffuser is of a special-shaped irregular surface, and the exhaust direction is lateral exhaust, so that the exhaust pipe of the turboshaft engine is designed into a bent special-shaped exhaust diffuser. In recent years, helicopter flight platforms have increasingly severely constrained the overall dimensions of the engine, and the axial length of the exhaust diffuser needs to be as short as possible. In this context, the exhaust pipe of the turboshaft engine for the rear output shaft is often designed as a sharp bend profiled exhaust diffuser. This type of exhaust diffuser creates a large flow separation area at the inner flow path flow bend due to the short axial distance. The existence of the separation area not only can cause the non-uniformity of an exhaust outlet flow field, but also can reduce the injection capacity of the exhaust diffuser on the air flow in the engine compartment, thereby causing the high temperature of the local position compartment in the engine compartment; in the working environment integrated with the helicopter, part of high-temperature fuel gas can be caused to flow backwards into the engine cabin, so that the working temperature of accessories at the local position of the engine is increased sharply, and the related sensor can be caused to be out of order in severe cases. This adds somewhat to the complexity of the flow control scheme because the flow of gas completes the deflection of the flow direction in the axially short space. At present, no research on control of the flow phenomenon of the type is seen at home.

Therefore, the development of the simple and effective flow control structure for the separation area at the sharp bend can improve the flow speed of the airflow at the near wall of the sharp bend without sacrificing the flow capacity of the exhaust diffuser, and the high-temperature fuel gas is prevented from flowing backwards into the engine compartment.

Disclosure of Invention

The invention aims to: the invention provides a sharp-bending special-shaped exhaust diffuser with a pneumatic nozzle on an outlet surface, and aims to improve the flow speed at a sharp bend on the premise of not influencing the performance of the exhaust diffuser so as to enhance the jet capacity of air flow at the sharp bend and avoid high-temperature fuel gas from flowing backwards into an engine cabin.

The technical scheme is as follows: in order to achieve the above purpose, the present invention adopts the following technical scheme:

A sharp-bending special-shaped exhaust diffuser with a pneumatic nozzle on an outlet surface comprises a diffuser inlet section, a diffuser outlet section and a bending section connected between the diffuser inlet section and the diffuser outlet section; the diffuser outlet section is provided with a partition plate to divide the diffuser outlet section into a first outlet section and a second outlet section which are mutually independent, the inlet of the first outlet section and the inlet of the second outlet section are communicated with the bending section, and the outlet area of the first outlet section is smaller than the outlet area of the second outlet section; the inlet area of the first outlet section is larger than the outlet area of the first outlet section such that the interior of the first outlet section gradually constricts from its inlet to its outlet.

Further, the central axis of the inlet section of the diffuser is perpendicular to the central axis of the outlet section of the diffuser.

Further, the partition plate extends outwards and obliquely from the inside of the outlet section of the diffuser, and the included angle theta between the axis of the longitudinal section of the partition plate extending and the central axis of the outlet section of the diffuser is 10 degrees.

Further, the first outlet section is the aerodynamic nozzle area of the sharp bend profiled exhaust diffuser.

Further, the longitudinal section of the partition plate is a wing profile, one end of the wing profile is a sharp point end, and the other end of the wing profile is an arc end; the arc end is positioned at a deeper position of the outlet section of the diffuser, the sharp point end is close to the outlet position of the outlet section of the diffuser, and the sharp point end is positioned at an inner position of the outlet section of the diffuser.

Further, the distance l1=0.018×d between the tip end of the airfoil surface and the outlet cross-section; the distance l2=7l1 of the circular arc end of the airfoil profile from the outlet cross section, d is the sharp curve profiled exhaust diffuser inlet diameter.

Further, the outlet area s2=0.037×3.14× (D/2) of the first outlet section.

Further, the inside of the sharp curved special-shaped exhaust diffuser is provided with a curved special-shaped flow passage which is shaped like a pipe.

The beneficial effects are that: according to the invention, the guide plate is added on the outlet surface of the sharp-bent special-shaped exhaust diffuser and is combined with the sharp-bent wall surface to form the pneumatic nozzle, so that the airflow velocity at the sharp-bent position is obviously improved after the airflow flows through the pneumatic nozzle, on the other hand, the adverse effect caused by re-inhalation of high-temperature fuel gas is avoided, the flow characteristic at the sharp-bent position is improved to a greater extent, and the flow field distortion of the outlet is reduced. Meanwhile, the invention does not influence the whole flow characteristic of the exhaust diffuser and has the advantages of simple structural design and obvious control effect.

Drawings

FIG. 1 is a schematic view of an exhaust diffuser meridian plane configuration of the present invention;

FIG. 2 is a front view of the present invention in a tight curve profiled exhaust diffuser;

FIG. 3 is a top view of the tight curve profiled exhaust diffuser of the present invention;

FIG. 4 is a prior art radial velocity profile cloud of a prototype, sharp curve, profiled exhaust diffuser;

FIG. 5 is a meridional velocity profile cloud of a tight curve profiled exhaust diffuser of the present invention.

Detailed Description

The invention will now be described in further detail with reference to the drawings and to specific examples.

Referring to fig. 1 to 3, the present invention discloses a sharp curved special-shaped exhaust diffuser with a aerodynamic jet group at an outlet, which comprises a diffuser inlet section 10, a diffuser outlet section 20, and a curved section 30 connected between the diffuser inlet section 10 and the diffuser outlet section 20. Wherein the inside of the curved section 30 is shorter than the front curved surface 2, and the outside of the curved section 30 is longer than the rear curved surface 4. The diffuser outlet section 20 is provided with a partition 21 to divide the diffuser outlet section into a first outlet section 22 and a second outlet section 23 which are independent of each other. The inlet of the first outlet section 22 and the inlet of the second outlet section 23 are both in communication with the curved section 30. And the outlet area of the first outlet section 22 is smaller than the outlet area 23 of the second outlet section 23. The inlet area S1 of the first outlet section 22 is larger than the outlet area S2 of the first outlet section such that the interior of the first outlet section gradually constricts from its inlet to its outlet. Specifically, the baffle extends from the inside of the outlet section of the diffuser in an outward inclined manner, and the vertical section axis of the baffle extending and the central axis of the outlet section of the diffuser form a direct included angle theta of 10 degrees. The first outlet section 22 is the aerodynamic nozzle area of the sharp bend profiled exhaust diffuser. The pneumatic nozzle is integrally contracted from the inlet to the rear. The pneumatic nozzle is arranged to improve the flow velocity of the near-wall area at the sharp-bending wall to resist the local strong reverse pressure gradient, thereby effectively inhibiting the generation of a separation area at the near-wall area, optimizing the flow field quality and improving the ejection capacity of the airflow at the sharp-bending wall.

In the present embodiment, the longitudinal section of the partition plate 21 is an airfoil surface, and one end of the airfoil surface is a tip end and the other end is a circular arc end; the arc end is located at a deeper position of the diffuser outlet section 20, and is separated from the outlet section by a distance l2=7xl1; the sharp point end is near the exit location of the diffuser exit section 20, but the sharp point end is located inward of the exit of the diffuser exit section 20, at a distance l1=0.018×d from the exit cross-section. The separator 21 should be arranged such that the outlet area s2=0.037×3.14×d/2 (D/2) of the first outlet section.

Wherein the design of the diaphragm airfoil is referred to in the related art. The pneumatic nozzle is arranged to improve the flow velocity of the near-wall area at the sharp-bending wall to resist the local strong reverse pressure gradient, thereby effectively inhibiting the generation of a separation area at the near-wall area, optimizing the flow field quality and improving the ejection capacity of the airflow at the sharp-bending wall.

Application instance

The proposal is as follows:

A standard prototype sharp bending special-shaped exhaust diffuser and a sharp bending special-shaped exhaust diffuser with a pneumatic nozzle on the outlet face are designed, the total inlet pressure is 110kPa, the total temperature is 830K, the outlet back pressure of the exhaust diffuser is 101kPa, and the ambient temperature is 288.15K. The inlet diameter phiD of the sharp bending special-shaped exhaust diffuser=205 mm, the area shrinkage ratio of the channel in the pneumatic nozzle is 1.18, the included angle theta between the baffle plate and the sharp bending curved surface is 10 degrees, L1=3.7mm, L2=25.9 mm. And comparing and analyzing the standard prototype sharp-bending special-shaped exhaust diffuser and the sharp-bending special-shaped exhaust diffuser with the pneumatic nozzle at the outlet through three-dimensional numerical simulation.

As shown in fig. 4, in the prototype, the exhaust diffuser has a larger separation area at the front curved surface, and the flow velocity is low near the wall of the front curved surface, so that it can be judged that the position has very weak injection capacity against surrounding air flow. And it can be speculated that there may be a risk of high temperature gas being sucked in by the power pod under the helicopter platform.

As shown in FIG. 5, the sharp curved profiled exhaust diffuser with pneumatic nozzles on the outlet face has a greatly improved flow velocity near the front sharp curved surface because of the greatly improved flow velocity near the wall face where the ability of the airflow to resist local strong back pressure gradients is significantly enhanced. The separation zone at the near wall is substantially absent and the separation zone at the front curved wall is greatly improved. Furthermore, it can be seen from the figure that the low total pressure area of the outlet face of the exhaust diffuser is significantly reduced compared to the prototype solution.

As shown in Table 1, the aerodynamic performance of the sharp curved special-shaped exhaust diffuser with the pneumatic nozzle on the outlet surface is greatly improved at the sharp curved surface compared with that of the standard prototype exhaust diffuser, wherein the circulation capacity of the whole exhaust diffuser is not reduced, but slightly improved; the flow near the sharp curve is turned into positive flow and there is a considerable increase in flow velocity.

Table 1 comparison of aerodynamic performance of prototype exhaust diffusers and diffusers with pneumatic nozzles at the outlets of the present invention

The present invention has been described in terms of the preferred embodiments thereof, and it should be understood by those skilled in the art that various modifications can be made without departing from the principles of the invention, and such modifications should also be considered as being within the scope of the invention.

Claims (8)

1. An emergency curved special-shaped exhaust diffuser with a pneumatic nozzle on an outlet surface, which is characterized in that: the device comprises a diffuser inlet section, a diffuser outlet section and a bending section connected between the diffuser inlet section and the diffuser outlet section; the diffuser outlet section is provided with a partition plate to divide the diffuser outlet section into a first outlet section and a second outlet section which are mutually independent, the inlet of the first outlet section and the inlet of the second outlet section are communicated with the bending section, and the outlet area of the first outlet section is smaller than the outlet area of the second outlet section; the inlet area of the first outlet section is larger than the outlet area of the first outlet section such that the interior of the first outlet section gradually constricts from its inlet to its outlet.

2. The tight curve profiled exhaust diffuser of claim 1, wherein: the central axis of the diffuser inlet section is perpendicular to the central axis of the diffuser outlet section.

3. The tight curve profiled exhaust diffuser according to claim 1 or 2, characterized in that: the baffle extends outwards and obliquely from the inside of the outlet section of the diffuser, and the direct included angle theta between the axis of the longitudinal section of the baffle extending and the central axis of the outlet section of the diffuser is 10 degrees.

4. A tight curve profiled exhaust diffuser as claimed in claim 3, wherein: the first outlet section is the aerodynamic nozzle area of the sharp bend profiled exhaust diffuser.

5. A tight curve profiled exhaust diffuser as claimed in claim 3, wherein: the longitudinal section of the partition plate is an airfoil surface, one end of the airfoil surface is a sharp point end, and the other end of the airfoil surface is an arc end; the arc end is positioned at a deeper position of the outlet section of the diffuser, the sharp point end is close to the outlet position of the outlet section of the diffuser, and the sharp point end is positioned at an inner position of the outlet section of the diffuser.

6. The tight curve profiled exhaust diffuser of claim 5, wherein: the tip end of the airfoil profile is at a distance l1=0.018×d from the outlet cross-section; the distance l2=7l1 of the circular arc end of the airfoil profile from the outlet cross section, d is the sharp curve profiled exhaust diffuser inlet diameter.

7. The tight curve profiled exhaust diffuser of claim 1, wherein: the outlet area of the first outlet section s2=0.037×3.14× (D/2) ×d/2.

8. The tight curve profiled exhaust diffuser of claim 5, wherein: the inside of the sharp bending special-shaped exhaust diffuser is provided with a bending special-shaped flow passage which is similar to a pipe shape.