Staggered power cabin backflow blocking device and design method thereof

Abstract

The invention provides a staggered power cabin backflow blocking device and a design method thereof, and belongs to the technical field of helicopter aerodynamics and pneumatic design, the device comprises an engine main spray pipe, an exhaust spray pipe, an inner flow resistance plate and an outer flow resistance plate, and the inner flow resistance plate and the outer flow resistance plate are located in an injection gap formed by the engine main spray pipe and the exhaust spray pipe; one end of the inner spoiler is fixed to the outer side wall of the engine main spray pipe, one end of the outer spoiler is fixed to the inner side wall of the exhaust spray pipe, the outer spoiler is close to an exhaust outlet, the gap between the outer spoiler and the inner spoiler is 3-5 mm, and the outer spoiler and the inner spoiler have an overlapping area in the height direction. Through the staggered arrangement mode of the inner spoiler and the outer spoiler, the pressure at the ejection gap of the helicopter engine compartment is enhanced, the ablation problem caused by the fact that high-temperature tail gas exhausted by an engine flows back into the engine compartment is avoided, a main spray pipe or an exhaust spray pipe does not need to be directly replaced, the cost is reduced, and the production period is shortened.

Description

Technical Field

[0001] The invention belongs to the technical field of helicopter aerodynamics and aerodynamic design, and in particular relates to a staggered power cabin backflow blocking device and a design method thereof. Background Art

[0002] Most modern helicopters use an "ejection-type" power cabin ventilation and heat dissipation system design, which uses the excess kinetic energy of the engine's high-temperature exhaust gas to form a local low-pressure area at the engine cabin ejection gap, bringing the hot air in the power cabin to the outside atmosphere. The cold air in the outside environment then enters the power cabin through specially designed vents, thereby achieving the purpose of power cabin ventilation and heat dissipation. This heat dissipation mode requires a corresponding special ejection gap design to be realized. The ejection gap is the structural gap between the engine's main nozzle and the exhaust nozzle (also known as the mixing tube), and is a key part that affects the power cabin's heat dissipation capacity. Since the exhaust nozzle's structural design is similar to a cantilever beam structure, as the service life increases, the exhaust nozzle will gradually deform under the influence of gravity, and the deformation will inevitably lead to changes in the ejection gap. Once the change exceeds the tolerance range, it is very easy to cause the engine exhaust to flow back into the power cabin through the ejection gap, causing the temperature in the power cabin to be too high, affecting the engine's working condition, and even causing a fire.

[0003] In the related art, the solution to the above-mentioned power compartment backflow ablation problem is generally to check the installation status and structural deformation degree of the main nozzle and the exhaust nozzle. Once it is found that the injection gap exceeds the allowable range of the design tolerance, the main nozzle or the exhaust nozzle will be directly replaced. This method is costly and has a long production cycle. Summary of the invention

[0004] In order to solve the technical problem in the related art that when the ejection gap exceeds the design tolerance range, the main nozzle or the exhaust nozzle is directly replaced, which is costly and has a long production cycle, the present invention provides a staggered power compartment backflow blocking device and a design method thereof, which can prevent the high-temperature exhaust gas discharged by the engine from backflowing into the power compartment and causing ablation problems, without directly replacing the main nozzle or the exhaust nozzle, thereby reducing costs and shortening the production cycle; the technical solution is as follows:

[0005] In a first aspect, a staggered power compartment backflow blocking device is provided, comprising: an engine main nozzle 1, an exhaust nozzle 2, an inner spoiler 3, and an outer spoiler 4,

[0006] The inner spoiler 3 and the outer spoiler 4 are located in the ejection gap 5 formed by the engine main nozzle 1 and the exhaust nozzle 2. One end of the inner spoiler 3 is fixed on the outer side wall of the engine main nozzle 1, and one end of the outer spoiler 4 is fixed on the inner side wall of the exhaust nozzle 2. The outer spoiler 4 is close to the exhaust outlet. The gap between the outer spoiler 4 and the inner spoiler 3 is 3 to 5 mm, and there is an overlapping area between the outer spoiler 4 and the inner spoiler 3 in the height direction.

[0007] Optionally, the cross section of the inner spoiler 3 is rectangular.

[0008] Optionally, the inner spoiler 3 is mounted on the outer wall of the main nozzle 1 by riveting or welding, and the inner spoiler 3 and the main nozzle 1 partially form an inverted "T" shape.

[0009] Optionally, the cross section of the outer spoiler 4 is rectangular.

[0010] Optionally, the outer spoiler 4 is mounted on the inner wall of the exhaust nozzle 2 by riveting or welding, and the outer spoiler 4 and the exhaust nozzle 2 partially form a "T" shape.

[0011] Optionally, the distance between the inner spoiler 3 and the main nozzle outlet cross-section perimeter 9 is 50 mm to 70 mm, and the outer spoiler 4 is offset by 5 mm to 10 mm along the main nozzle axis 8 away from the engine based on the installation position of the inner spoiler 3 .

[0012] Optionally, the height of the inner spoiler 3 and the outer spoiler 4 is 60% to 80% of the height of the ejection gap 5 , and the length of the inner spoiler 3 and the outer spoiler 4 is 15% to 25% of the main nozzle outlet cross-section circumference 9 .

[0013] In a second aspect, a method for designing a staggered power compartment backflow blocking device is provided, which is used to design any device described in the first aspect, and the method comprises:

[0014] Step S1: Calculate and analyze the flow field in the helicopter power cabin with ablation problem under typical working conditions, reproduce the fault state, and determine the starting position of the reflow zone;

[0015] Step S2: Preliminarily design the geometric dimensions and installation position of the spoiler according to the starting position of the reflow zone and the size of the ejector gap determined in step S1;

[0016] Step S3: verify whether the spoiler designed in step S2 meets the design requirements;

[0017] Step S4: If the analysis result of step S3 does not meet the design requirements, re-execute step S1; if it meets the design requirements, the design process ends.

[0018] The present invention enhances the pressure at the ejection gap of the helicopter power compartment by arranging the inner and outer spoilers in a staggered manner, thereby blocking the high-temperature exhaust gas of the engine from flowing back into the power compartment, and preventing the high-temperature exhaust gas discharged from the engine from flowing back into the power compartment and causing ablation problems. Therefore, there is no need to directly replace the main nozzle or the exhaust nozzle, which reduces costs and shortens the production cycle. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1A schematic diagram of the structure of a staggered power compartment backflow blocking device provided by an embodiment of the present invention;

[0020] Figure 2 A schematic diagram of an ejection gap provided in an embodiment of the present invention;

[0021] Figure 3 A schematic diagram of the geometric dimensions of a spoiler provided in an embodiment of the present invention;

[0022] Figure 4 A schematic diagram of a spoiler layout provided in an embodiment of the present invention;

[0023] Figure 5 A flow chart of a design method for a staggered power compartment backflow blocking device provided in an embodiment of the present invention.

[0024] Among them, 1-engine main nozzle, 2-exhaust nozzle, 3-inner spoiler, 4-outer spoiler, 5-injection gap, 8-main nozzle axis, 9-main nozzle outlet cross-section circumference. DETAILED DESCRIPTION

[0025] The present application is further described in detail below through specific implementation methods and drawings.

[0026] An embodiment of the present invention provides a backflow blocking device, which reduces or even prevents the backflow of engine exhaust gas into the power compartment by arranging inner and outer spoilers in a staggered manner, thereby solving the problem of overheating of the power compartment.

[0027] In the embodiment of the present invention, a pair of spoilers are added inside the exhaust nozzle and outside the main nozzle, such as Figure 1 and Figure 2 As shown, the interlaced, non-airtight spoilers are used to block the high-temperature exhaust gas from flowing back into the power compartment, so that the secondary flow generated by the exhaust injection can be smoothly discharged to the outside of the power compartment, solving the engineering problem without changing the original structural design.

[0028] The embodiment of the present invention provides a staggered power compartment backflow blocking device, such as Figure 1 As shown, it includes: an engine main nozzle 1, an exhaust nozzle 2, an inner spoiler 3, and an outer spoiler 4,

[0029] The inner spoiler 3 and the outer spoiler 4 are located in the ejection gap 5 formed by the engine main nozzle 1 and the exhaust nozzle 2. One end of the inner spoiler 3 is fixed on the outer side wall of the engine main nozzle 1, and one end of the outer spoiler 4 is fixed on the inner side wall of the exhaust nozzle 2. The outer spoiler 4 is close to the exhaust outlet, and the gap between the outer spoiler 4 and the inner spoiler 3 is 3-5 mm. The length of the outer spoiler 4 and the inner spoiler 3 overlap in the height direction.

[0030] In one embodiment, the cross-section of the inner spoiler 3 may be rectangular or sector-shaped.

[0031] The inner spoiler 3 can be installed on the outer wall of the main nozzle 1 by riveting or welding; the inner spoiler 3 and the main nozzle 1 can also be integrated by 3D printing technology and installed along the perimeter 9 of the main nozzle outlet section, such as Figure 4 shown.

[0032] See also Figure 1 The inner spoiler 3 and the main nozzle 1 are partially in an inverted "T" shape.

[0033] In one embodiment, the cross-section of the outer spoiler 4 may be rectangular or fan-shaped.

[0034] The outer spoiler 4 can be installed on the inner wall of the exhaust nozzle 2 by riveting or welding; the outer spoiler 4 and the main nozzle 2 can also be integrated by 3D printing technology and installed along the perimeter 9 of the main nozzle outlet section, such as Figure 4 shown.

[0035] See also Figure 1 The outer spoiler 4 and the exhaust nozzle 2 are partially in a "T" shape.

[0036] In one embodiment, see Figure 4 and Figure 1 The distance D between the inner spoiler 3 and the main nozzle outlet cross-sectional circumference 9 is about 50 mm to 70 mm.

[0037] See also Figure 4 The outer spoiler 4 is offset by d away from the engine along the main nozzle axis 8 based on the installation position of the inner spoiler 3, and d is 5mm to 10mm.

[0038] See also Figure 1 The inner spoiler 3 and the outer spoiler 4 are arranged alternately and interspersed, and the two spoiler portions are highly overlapped with each other.

[0039] See also Figure 3 The inner spoiler 3 and the outer spoiler 4 have the same height H and the same length c.

[0040] The height of the inner spoiler 3 and the outer spoiler 4 is about 60% to 80% of the height of the ejection gap 5, and the length of the inner spoiler 3 and the outer spoiler 4 is about 15% to 25% of the main nozzle outlet cross-sectional circumference 9. Figure 4 shown.

[0041] The working principle of the staggered power compartment backflow blocking device provided in an embodiment of the present invention is: the stagnation pressure on the power compartment backflow path is increased by two staggered baffles, and the stagnation pressure in front of the blocking device is maximized. The flow velocity of the power compartment backflow continuously decreases in the process of flowing to the blocking device until it is close to 0. Therefore, the backflow stops flowing when it reaches the position of the baffle and will not enter the interior of the power compartment.

[0042] The embodiment of the present invention provides a design method for a staggered power compartment backflow blocking device, such as Figure 5 As shown, the method comprises the following steps:

[0043] Step S1: A numerical simulation method is used to calculate and analyze the flow field in the helicopter power cabin with ablation problems under typical working conditions to reproduce the fault state; and combined with the flow field characteristics in the power cabin under common working conditions such as helicopter cruising flight, hovering in ground effect, hovering without ground effect, near-ground maneuvering, take-off, and landing, the distribution law of the ejected secondary flow, temperature distribution, the starting position of the recirculation zone, etc. are comprehensively analyzed to determine a starting position of the recirculation zone covering all the above working conditions.

[0044] Step S2: Based on the starting position of the reflow zone and the size of the ejection gap determined in step S1, the geometric dimensions and installation position of the spoiler are preliminarily designed, and based on the principle of minimizing the change amount and weight, the preliminary blocking device scheme is iteratively designed in terms of structural strength, stiffness, etc., and then the blocking device structural design scheme is determined to ensure that the spoiler size is minimized.

[0045] Step S3: Verify whether the spoiler designed in step S2 meets the design requirements: According to the aerodynamic shape of the structural design scheme determined in step S2, a high-precision fluid mechanics simulation calculation model is established, and the model is used to verify whether the spoiler designed in step S2 meets the requirements. The calculation model includes a viscous grid, the height of the first layer of the viscous grid is not greater than 1‰ of the ejection gap, the number of layers is not less than 30, and the growth ratio is not greater than 1.2.

[0046] After the calculation model is established, the simulation calculation is started. The return flow path and the position of the ablation area in the power compartment are analyzed based on the simulation calculation results. If the return flow enters the power compartment and ablation occurs, the height or length of the spoiler is appropriately increased according to the return flow path, and the installation position is fine-tuned if necessary. If there is no return flow entering the power compartment, the height or length of the spoiler is appropriately reduced according to the return flow path to reduce design redundancy.

[0047] By analyzing the improvement degree, reflux path and distribution range of the power compartment reflux ablation problem, it is judged whether the design requirements of the power compartment ventilation and cooling system are met based on the analysis results.

[0048] Step S4: If the verification result of step S3 does not meet the design requirements, restart step S1; if it meets the design requirements, the design process ends.

[0049] Both numerical simulation and helicopter flight tests show that the present invention can avoid problems such as ablation caused by backflow into the power compartment, and has a simple manufacturing process, short time consumption, low cost, and is easy to install in the field.

[0050] The above only expresses the implementation methods of the present application, and the description is relatively specific and detailed, but it cannot be understood as limiting the scope of the patent. It should be pointed out that for ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the present application, which all belong to the protection scope of the present application. In addition, the parts that are not detailed in this application are all conventional technologies.

Claims

1. A staggered power compartment backflow blocking device, characterized in that: include: The engine main nozzle, exhaust nozzle, inner spoiler, and outer spoiler, The inner spoiler and the outer spoiler are located in the ejection gap formed by the main nozzle and the exhaust nozzle of the engine; one end of the inner spoiler is fixed on the outer wall of the main nozzle of the engine, and one end of the outer spoiler is fixed on the inner wall of the exhaust nozzle, and the outer spoiler is close to the exhaust outlet, and the gap between the outer spoiler and the inner spoiler is 3 to 5 mm, and there is an overlapping area between the outer spoiler and the inner spoiler in the height direction.

2. The device according to claim 1, characterized in that The cross section of the inner spoiler is rectangular.

3. The device according to claim 1, characterized in that The inner spoiler is installed on the outer side wall of the main nozzle by riveting or welding, and the inner spoiler and the main nozzle are partially in an inverted "T" shape.

4. The device according to claim 1, characterized in that The cross section of the outer spoiler is rectangular.

5. The device according to claim 1, characterized in that The outer spoiler is installed on the inner wall of the exhaust nozzle by riveting or welding, and the outer spoiler and the exhaust nozzle are partially in a "T" shape.

6. The device according to claim 1, characterized in that The distance between the inner spoiler and the circumference of the main nozzle outlet cross section is 50 mm to 70 mm, and the outer spoiler is offset by 5 mm to 10 mm along the main nozzle axis away from the engine based on the installation position of the inner spoiler.

7. The device according to claim 1, characterized in that The height of the inner spoiler and the outer spoiler is 60% to 80% of the height of the ejection gap; the length of the inner spoiler and the outer spoiler is 15% to 25% of the circumference of the main nozzle outlet cross section.

8. A design method for a staggered power compartment backflow blocking device, characterized in that: For designing the device according to any one of claims 1 to 7, the method comprises: Step S1: Calculate and analyze the flow field in the helicopter power cabin with ablation problems under typical working conditions, reproduce the fault state, and determine the starting position of the reflow zone; Step S2: Preliminarily design the geometric dimensions and installation position of the spoiler according to the starting position of the reflow zone and the size of the ejector gap determined in step S1; Step S3: verify whether the spoiler designed in step S2 meets the design requirements; Step S4: If the verification result of step S3 does not meet the design requirements, step S1 is executed again; if the design requirements are met, the design process ends.

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