An adjustable air inlet passage experimental device and a design method thereof

Abstract

The application discloses an air inlet channel experimental device capable of adjusting air exhaust flow and a design method thereof. By appropriately simplifying a high supersonic air inlet channel with a large internal contraction ratio, the length of the air inlet channel can be significantly reduced under the condition that the effect is similar, and a sliding air exhaust flow adjusting device is applied in the air inlet channel to continuously adjust the air exhaust flow. The air inlet channel experimental device provided by the application has the advantages of small size, simple structure, high reliability and small influence of aerodynamic force, can be used for high supersonic air inlet channel experiments in a wind tunnel with small size and low Mach number, and realizes flow control in multiple motion modes and multiple speeds, thereby providing a reliable experimental device for realizing wide speed range flight in a large internal contraction ratio fixed geometry air inlet channel.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of hypersonic inlet aerodynamic experiment, and particularly relates to an adjustable air discharge flow inlet experiment device and a design method thereof. BACKGROUND

[0002] As an important pressurization system of a hypersonic vehicle, an inlet mainly reduces the speed of the oncoming high-speed airflow through a shock wave system to increase the pressure, and at the same time, undertakes important tasks such as meeting the flow demand of an engine and reasonably organizing the flow of a forebody. Research shows that improving the compression capacity of the inlet is of great significance to improving the working efficiency of the propulsion system and reducing the weight of the propulsion system. However, the improvement of the compression capacity of the inlet mainly depends on the increase of the contraction ratio in the inlet, which brings two problems. First, the inlet is difficult to start at a low Mach number, which will limit the wide-speed flight capability of the vehicle. Second, the inlet has a prominent shock wave / boundary layer interference phenomenon, which causes the flow channel of the inlet to be congested and brings local high-temperature heat flow, high-pressure pulsation and the like.

[0003] Therefore, in view of the series of adverse effects of high compression on the inlet, a plurality of slots or holes are usually arranged in the inner contraction section, and the excess flow or low-energy fluid is driven out of the inlet by using the high pressure of the compressed airflow, so as to achieve the effects of expanding the stable working boundary of the inlet and effectively suppressing separation. This method is simple and reliable in structure and has very obvious effect, and is widely used in various inlets as a common flow control method of the inlet. However, since the discharged is usually high-pressure gas after compression of the inlet, the air discharge resistance is large, and the discharge flow at the flight limit state is usually more than 10% of the total captured flow, which further worsens the problem of insufficient thrust of the propulsion system. Therefore, the aerodynamic thrust and resistance of the vehicle must be considered on the premise of meeting the smooth working demand of the inlet as much as possible.

[0004] In order to solve this problem, the method of adjusting the air discharge flow is usually adopted, so that the air discharge flow of the inlet at a low Mach number is large, the aerodynamic performance is good, the air discharge flow is reduced at a cruising state, and the thrust is large. In the meanwhile, limited by the size of the wind tunnel, the long forebody of the hypersonic vehicle brings great difficulty to the experiment, and the space for arranging the flow adjusting device is more cramped due to the simplification of the inlet, which not only makes it impossible to truly simulate the flight state, but also makes the space for arranging the flow adjusting device more cramped. The high temperature and strong aerodynamic force of the high-speed airflow in the experiment also have high requirements for the reliability of the actuating mechanism. If continuous stepless adjustment of the flow adjusting device is required, it is also one of the difficulties.

[0005] Therefore, a new technical solution is needed to solve the above technical problems. SUMMARY

[0006] The application aims to provide an air inlet duct experimental device with adjustable air discharge flow and a design method thereof.

[0007] The technical scheme is as follows: an air inlet duct experimental device with adjustable air discharge flow, characterized in that it comprises an air inlet duct system and an adjusting system.

[0008] The air inlet duct system comprises a compression surface, a lip cover above the compression surface, side plates on both sides of the compression surface, and the lip cover, the compression surface and the side plates form an air inlet duct inner channel.

[0009] The adjusting system comprises a sliding plate, a driving device connected to the sliding plate, a sliding block connected to the sliding plate and a slide rail for the forward and backward movement of the sliding block.

[0010] Further, the front section of the compression surface is an isosceles pentagon, the longer base of the isosceles pentagon is the compression surface front edge, the shorter base connects the air inlet duct inner channel, the front section of the compression surface is straight, the compression surface gradually curves after entering the inner channel, and the compression surface is straight again after the throat.

[0011] Further, the front section of the compression surface is provided with a sawtooth transition strip with the same width as the compression surface front edge near the front edge position, so that the boundary layer is transitioned and thickened.

[0012] Further, the slide rail has two parallel slide rails extending from front to back, and the sliding blocks are distributed on the two slide rails.

[0013] Further, the air discharge groove is located at the compression surface from the air inlet duct inner channel inlet to the throat.

[0014] Further, several of the air release slots are grouped, the width of the air release slots in each group is equal to the interval between the slots, and the interval between the groups is greater than one air release slot width.

[0015] Further, the outlet area of the air release cavity is equal to the sum of the areas of all the air release slots in the corresponding group.

[0016] Further, the side plates are connected to both sides of the compression plate, and optical glass is arranged in the side plates.

[0017] Further, the driving device is connected to the sliding plate to drive the sliding plate to move back and forth along the sliding rails on both sides by means of the sliding blocks.

[0018] A design method of an air intake experimental device with adjustable air release flow, comprising the following steps:

[0019] Step 1: determining the air intake aerodynamic performance index requirement, designing the air intake configuration accordingly, and obtaining the compression surface deflection angle δ1 and the lip deflection angle δ2;

[0020] Step 2: based on the air intake configuration obtained in step 1, cutting the last stage compression surface to the isolation section part, rotating the compression surface deflection angle δ1 by an angle to make the front end of the compression surface horizontal, and obtaining a simplified air intake configuration, the internal contraction ratio of which is

[0021] ICR = H in / H throat

[0022] Wherein, ICR is the internal contraction ratio, H in is the air intake inlet height, H throat is the air intake throat height, and the internal contraction ratio of the simplified air intake configuration is greater than 2.5;

[0023] Step 3: based on the simplified air intake configuration obtained in step 2, the front end of the compression surface is an isosceles pentagon, the longer bottom side is the model leading edge, and the length of the longer bottom side is greater than the air intake inlet width;

[0024] Step 4: arranging a sawtooth transition strip at the front end of the compression surface, the length of which is equivalent to the model leading edge, and the rear end of the transition strip is away from the air intake inlet by L d ≥ 100 mm;

[0025] Step 5: the sawtooth protruding plane of the transition strip is in the shape of an isosceles right triangle;

[0026] Step 6: based on the simplified air intake configuration obtained in step 5, the air flow deflection angle δ3 is calculated according to the compression surface deflection angle δ1 and the lip deflection angle δ2, and δ3 = δ1 + δ2.

[0027]

[0028] ​According to the shock wave angle β calculation formula of oblique shock wave

[0029]

[0030] Obtaining the oblique shock wave incident position, wherein M1 is the Mach number of the incoming flow, and arranging a plurality of air bleed grooves in front and back of the incident position as a center;

[0031] Step 7, in order to avoid air leakage, a plurality of air bleed grooves on the compression surface are divided into a group, the width of the air bleed grooves in each group is equal to the interval between the grooves, and the interval between the groups is greater than one air bleed groove width;

[0032] Step 8, the air bleed cavities are vertically recessed from the lower bottom surface of the air bleed grooves according to the grouping, each air bleed cavity corresponds to a group of air bleed grooves, the outlet area of the air bleed cavity is equal to the sum of the areas of all air bleed grooves in the corresponding group, and the outlets of the air bleed cavities are in the same plane;

[0033] Step 9, the sliding plate is placed close to the air bleed cavity, the sliding plate has a plurality of openings and baffles, and the movement of the sliding plate in front and back makes the openings and / or baffles be located below the air bleed cavity outlet to change the bleed area of the air bleed cavity outlet;

[0034] Step 10, the driving device is placed in the central part of the support, and drives the sliding plate to move forward and backward along the slide rails on both sides by means of the sliding blocks;

[0035] Step 11, the side plate, bottom plate and support are designed according to the actual space and installation requirements of the wind tunnel.

[0036] Beneficial effects: the air inlet experimental device provided by the application can adjust the air bleed flow, has small size, simple structure, strong reliability, small influence of aerodynamic force, can perform hypersonic air inlet experiment in a wind tunnel with small size and low Mach number, can control the flow of multiple motion modes and multiple speeds, has certain universality, provides a reliable device for wide-speed-range flight experiment of a large internal contraction ratio fixed-geometry air inlet, and has the advantages of small size, simple structure, strong reliability, small influence of aerodynamic force, and the like.

[0037] The design method of the air inlet experimental device provided by the application can significantly reduce the length of the air inlet under the condition of similar effect by reasonably simplifying a large internal contraction ratio hypersonic air inlet, and can continuously adjust the air bleed flow by using a sliding air bleed flow adjusting device. BRIEF DESCRIPTION OF DRAWINGS

[0038] Figure 1 It is a schematic diagram of the external three-dimensional structure of the air inlet of the application;

[0039] Figure 2 It is a simplified schematic diagram of the air inlet of the application;

[0040] Figure 3is a schematic view of the cross section of the inlet passage of the present application;

[0041] Figure 4 is a top view of the inlet passage of the present application;

[0042] Figure 5 is the inlet Mach number distribution when the incoming flow Mach number is 3.8 in the embodiment of the present application;

[0043] Figure 6 is the Mach number cloud picture when the incoming flow Mach number is 3.8 in the embodiment of the present application. DETAILED DESCRIPTION

[0044] The present application will be further illustrated in combination with the accompanying drawings and specific implementation methods.

[0045] The present application discloses an experimental device for an inlet passage with adjustable bleed flow and a design method thereof. The detailed implementation steps of the embodiment designed by the method of the present application are described below.

[0046] Please combine Figure 1 The present application provides an experimental device for an inlet passage with adjustable bleed flow, which comprises a driving device 1, a compression surface 2, inlet passage side plates 3 symmetrically arranged on both sides of the compression surface, a lip cover 4 located above the inlet passage side wall, a bleed cavity 5 located below the compression surface, a sliding plate 6 located below the bleed cavity, supports 7 located on both sides of the sliding plate, a bottom plate 8 located below the supports, and supports 9 at the four corners of the bottom plate.

[0047] The compression surface 2, the air inlet channel side plate 3 and the lip cover 4 jointly constitute an air inlet channel; the front end of the compression surface 2 is an isosceles pentagon, the longer base thereof is the front edge of the compression surface 2, and the shorter base connects the air inlet channel, which is straight in this section, gradually curved after entering the inner channel, and straight again after the throat. The compression surface 2 is provided with a sawtooth transition strip 21 with the same width as the front edge at a position close to the front edge of the front end of the compression surface 2, so as to make the boundary layer transition and thicken. In addition to the sawtooth transition strip, there is no obvious protrusion on the compression surface 2. A plurality of air release grooves 22 are formed in the compression surface 2 at the inlet of the air inlet channel to the throat, and there are 5 groups of 6 grooves. Optical glass 31 is arranged in the air inlet channel side plate 3, so as to facilitate observation of the flow in the inner channel. The lip cover 4 covers the air inlet channel side plate 3, forming a channel penetrating front and back. The air release cavity 5 is located below the compression surface 2 and is divided into 5 air release cavities separated from each other and corresponding to the 5 groups of air release grooves, and the outlet of the air release cavity is located on the same horizontal plane. The driving device 1 is placed above the front side beam of the support 7, connected with the sliding plate 6 and drives the sliding plate 6 to move forward and backward relative to the air release cavity 5, so as to control the air release flow of the air inlet channel. The connecting blocks 61 are fixed on the two sides of the sliding plate 6 by bolts and are respectively fixed on the four sliding blocks 72, so as to provide support for the sliding plate 6. The sliding blocks 72 are distributed on the two slide rails 71, and the slide rails 71 are fixed on the two sides of the support 7. The support 7 is connected and fixed with the support 9 at the four corners of the bottom plate 8.

[0048] Please refer to Figures 2 to 4 , according to the original high supersonic speed large internal contraction ratio fixed geometry air inlet channel configuration, the last stage compression surface to the isolation section is intercepted, and the compression surface is rotated by an angle δ1 to become horizontal, wherein δ1 is the deflection angle of the last stage compression surface of the original large internal contraction ratio air inlet channel. The air inlet channel inlet height H in and the throat height H throat are obtained, and the calculated internal contraction ratio ICR of the air inlet channel should be greater than 2.5. On the basis of the obtained simplified air inlet channel configuration, the front end of the compression surface is designed as an isosceles pentagon, the longer base thereof is the model front edge, the length L fore of the front edge is greater than the air inlet channel inlet width L in , and the other shorter base connects the air inlet. At the same time, a sawtooth transition strip is arranged at the front end of the compression surface, the length of which is equivalent to the model front edge, and the distance L d from the rear end of the transition strip to the air inlet is greater than or equal to 100 mm. The transition strip has sawteeth protruding from the plane of the compression surface, and the sawteeth are designed as isosceles right triangles, that is, θ = 90° and L zig = L zagBased on this, the airflow deflection angle δ3, obtained by adding the compression surface deflection angle δ1 and the lip deflection angle δ2, is used to calculate the shock wave angle β of the oblique shock wave, thus determining the incident position of the oblique shock wave. Several venting channels are arranged in the region between the inlet and throat of the air intake before and after the incident position of the oblique shock wave, grouped into sets of 3 to 6 channels. The width L of each venting channel in each group... gap Spacing L between the groove bleed Equal, the interval L between groups ’ gap It needs to be larger than the width L of the venting groove. bleed The venting chambers are vertically recessed from the bottom surface of the venting slots. Each venting chamber corresponds to a set of venting slots, which are spaced apart from each other, and the bottom surfaces of the venting chamber outlets remain on the same horizontal plane. A rectangular sliding plate is placed horizontally against the bottom surface of the venting chamber outlet. The sliding plate has several openings in the middle, each corresponding to a venting chamber outlet and being the same size and shape. The sliding plate is driven by a drive device, moving back and forth along slide rails on both sides using a slider. The drive device is located in the middle of the front crossbeam of the support plate. Furthermore, the base plate and support structure are designed according to the actual space of the wind tunnel and installation requirements.

[0049] Meanwhile, an embodiment of a design method with specific parameters for obtaining and verifying the simplified experimental device structure of the aforementioned air intake is provided, as detailed below:

[0050] The goal is to design a simplified experimental model of a hypersonic inlet with a high internal contraction ratio and an original design Mach number of 6.0. The simplified model has an incoming flow Mach number of approximately 3.8. The detailed implementation steps of the simplified experimental device and design method for the high internal contraction ratio inlet with adjustable venting flow are described.

[0051] Step 1, Combining Figure 2 As shown, based on the design flight state of the hypersonic vehicle and the corresponding aerodynamic performance requirements of the inlet, the original hypersonic large internal contraction ratio fixed geometry inlet is designed with a design Mach number of 6.0 and a flight angle of attack of 4°. A three-stage compression layout is adopted, with the last stage compression surface deflection angle δ1 = 13.5°. To reduce flight drag, a horizontal lip is adopted, i.e., the lip deflection angle δ2 = 0°.

[0052] Step 2, Combining Figure 3 As shown, the section from the last stage compression surface to the isolation section is cut off, and the entire section is rotated clockwise by 13.5° until the front end of the compression surface is horizontal, resulting in a simplified intake configuration. During this process, the intake profile remains unchanged. In this embodiment, the intake inlet height H... in =30mm, intake throat height H throat =10mm, then its internal shrinkage ratio (ICR) is 3.0, which is greater than the required 2.5;

[0053] Step 3, combination Figure 4 As shown in the figure, the front end of the compression surface is an isosceles pentagon, and in this embodiment, the longer base is the model front edge length L fore = 140 mm, the inlet width L in = 80 mm;

[0054] Step 4, the zigzag transition strip is arranged at the front end of the compression surface, and the length is also 140 mm, and the rear end of the transition strip is 100 mm away from the inlet L d ;

[0055] Step 5, the zigzag protruding plane of the transition strip is an isosceles triangle, the top angle θ = 90°, and the two legs L zig = L zag = 5.65 mm;

[0056] Step 6, combination Figure 3 and Figure 4 As shown in the figure, the airflow deflection angle δ3 = 13.5° is the sum of the compression surface deflection angle δ1 = 13.5° and the lip deflection angle δ2 = 0°, and the shock wave angle relationship formula of the oblique shock wave is further obtained

[0057]

[0058] Where M1 is the Mach number of the incoming flow, and in this embodiment, the incoming flow Mach number M1 = 3.8, so the shock wave angle β of the lip oblique shock wave is 26.325°, and the oblique shock wave incidence point is about 208 mm away from the model front edge, and the bleed slot is arranged on both sides of the position;

[0059] Step 7, in this embodiment, 6 bleed slots are taken as a group, and a total of 5 groups are divided, the bleed slot width and the interval between the slots L gap = L bleed = 2 mm, the interval between the groups L ’ gap = 2L bleed = 4 mm, and the bleed slot length is 76 mm;

[0060] Step 8, according to the grouping of the bleed slots, there are 5 vertical downward bleed cavities, and the outlets of the 5 bleed cavities are in the same horizontal plane, and the area A bleed-out = 12 × 76 mm = 912 mm 2 = A bleed-in ;

[0061] Step 9, the sliding plate is rectangular, and 5 openings are arranged in the middle, which are completely the same in shape and size with the bleed cavity outlet, and are placed horizontally close to the lower bottom surface of the bleed cavity outlet, and the openings correspond to the bleed cavity outlets one by one;

[0062] Step 10, the driving device is placed in the front center of the support, used to drive the sliding plate to move forward and backward along the slide rails on both sides by the sliding block;

[0063] Step 11, according to the actual space of the wind tunnel, four supporting columns are arranged at four corners in the embodiment, and the supporting columns are fixed on the rectangular bottom plate through bolts, and the bottom plate is fixed with the wind tunnel.

[0064] The adjustable air release flow large internal contraction ratio inlet passage simplified experimental device can be obtained through the above steps 1 to 11.

[0065] According to the present application, the performance of the adjustable air release flow large internal contraction ratio inlet passage simplified experimental device is verified by numerical simulation method when the incoming flow Mach number M0 is 3.8. Figure 5 The figure shows the inlet Mach number distribution of the embodiment of the present application. As can be seen from the figure, the boundary layer generated by the simplified experimental device is turbulent and the thickness δ is about 3.6mm, the main flow is uniform, and the Mach number distribution is almost a straight line, which shows that the inlet flow quality of the device is good. Figure 6 The figure shows the Mach number distribution cloud chart of the embodiment of the present application. It can be seen that the shock wave system in the inner channel is complete and clear, and the main flow and air release flow structure is obvious. When the air release outlet is fully open, the air release flow is maximum, and the lip shock wave incidence point does not produce obvious separation (A area); when the air release outlet is reduced, the air release flow is greatly reduced, and the lip shock wave incidence point appears obvious large scale separation (B area), and the flow structure in the inner channel becomes very complex. This shows that the device can effectively control the air release flow of the inlet passage, and at the same time, the performance of the inlet passage can be improved by adjusting the air release flow.

[0066] In addition, the specific implementation methods and ways of the present application are many, and the above description is only the preferred embodiment of the present application. It should be pointed out that for ordinary skilled in the art, without departing from the principle of the present application, some improvements and decorations can be made, and these improvements and decorations should be considered as the protection scope of the present application.

Claims

1. A method for designing an adjustable bleed flow rate inlet duct experimental device, characterized in that: the inlet duct experimental device comprises an inlet duct system and an adjustment system; the inlet duct system comprises a compression surface, a lip cover above the compression surface, and side plates on both sides of the compression surface, and the lip cover, the compression surface, and the side plates form an inlet duct inner passage; a plurality of independent bleed cavities are arranged below the compression surface from front to back; a bleed slot is arranged on the compression surface to connect the bleed cavities and the inlet duct inner passage; and a bleed cavity outlet is arranged at the bottom of each bleed cavity; the adjustment system comprises a sliding plate, a driving device connected to the sliding plate, a sliding block connected to the sliding plate, and a slide rail for the front and back movement of the sliding block; the sliding plate is arranged close to the bleed cavity outlet; the sliding plate is provided with a plurality of openings and baffles between adjacent openings; the driving device drives the sliding plate to move forward and backward, so that the openings and / or baffles of the sliding plate are located below the bleed cavity outlet to change the discharge area of the bleed cavity outlet; and the design method comprises the following steps: step 1, determining the inlet duct aerodynamic performance index requirement, designing the configuration of the inlet duct according to the requirement, and obtaining a compression surface deflection angle δ1 and a lip cover deflection angle δ2; step 2, based on the inlet duct configuration obtained in step 1, the last stage compression surface to the isolation section part is intercepted, the compression surface front end is rotated by an angle of the compression surface deflection angle δ1 to be horizontal, and a simplified inlet duct configuration is obtained, and the inlet duct configuration has an inner contraction ratio of step 3, based on the simplified inlet duct configuration obtained in step 2, the compression surface front end is an isosceles pentagon, a longer bottom side is a model leading edge, and the length of the longer bottom side is greater than the inlet width of the inlet duct; step 5, the sawtooth protruding plane of the transition zone is in the shape of an isosceles right triangle; step 6, based on the simplified inlet duct configuration obtained in step 5, a flow deflection angle δ3 is calculated according to the compression surface deflection angle δ1 and the lip cover deflection angle δ2, and the flow deflection angle δ3 has δ3 = δ1 + δ2; the incident position of the oblique shock wave is obtained according to the shock wave angle β of the oblique shock wave calculation formula, wherein M1 is the Mach number of the incoming flow, and a plurality of bleed slots are arranged in front of and behind the incident position; step 7, in order to avoid air leakage, a plurality of bleed slots on the compression surface are divided into a group, the width of the bleed slots in each group is equal to the interval between the slots, and the interval between the groups is greater than the width of one bleed slot; step 8, the bleed cavities are vertically recessed from the bottom surface of the bleed slots according to the grouping, each bleed cavity corresponds to a group of bleed slots, the bleed cavity outlet area is equal to the sum of the areas of all bleed slots in the corresponding group, and the bleed cavity outlets are in the same plane; step 9, the sliding plate is arranged close to the bleed cavity, the sliding plate is provided with a plurality of openings and baffles, and the front and back movement of the sliding plate makes the openings and / or baffles located below the bleed cavity outlet to change the discharge area of the bleed cavity outlet; step 10, the driving device is arranged in the central part of the front of the support, and drives the sliding plate to move forward and backward along the slide rails on both sides by means of the sliding block; and step 11, the side plates, the bottom plate, and the support are designed according to the actual space and installation requirements of the wind tunnel. ​ ​ ​ ​ ​ ​ ICR=H in / H throat where ICR is the internal contraction ratio, H in is the inlet height of the inlet passage, H throat is the throat height of the inlet passage, and the internal contraction ratio of the simplified inlet passage configuration is greater than 2.5; ​ Step 4, serrated trip strip is arranged at the front end of the compression surface, the length is equivalent to the model leading edge, the rear end of the trip strip is away from the inlet of the inlet L d ≥ 100 mm; ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2. The method of designing an air intake experiment apparatus according to claim 1, wherein The front end of the compression surface is an isosceles pentagon, the longer base of which is the front edge of the compression surface, and the shorter base connects the inner passage of the inlet channel; the front end of the compression surface is straight, the compression surface is gradually curved after entering the inner passage, and becomes straight again after the throat.

3. The method of designing an air intake experiment apparatus according to claim 2, wherein The front end of the compression surface is provided with a serrated transition strip with the same width as the front edge of the compression surface.

4. The method of designing an air intake experiment apparatus according to claim 3, wherein The slide rails are parallel to each other and extend from front to back, and the slide blocks are distributed on the two slide rails and located at the bottom of the two sides of the slide plate.

5. The method of designing an air intake experiment apparatus according to claim 4, wherein The air release grooves are located at the inlet of the inner passage of the compression surface to the throat.

6. The method of designing an air intake experiment apparatus according to claim 5, wherein A plurality of the air release grooves are divided into a group, the width of the air release grooves in each group is equal to the interval between the grooves, the interval between the groups is greater than one air release groove width, and one group of air release grooves corresponds to one air release cavity.

7. The method of designing an air intake experiment apparatus according to claim 6, wherein The outlet area of the air release cavity is equal to the sum of the areas of all the air release grooves in a corresponding group.

8. The method of designing an air intake port experiment apparatus according to claim 7, wherein The side plates are connected to the two sides of the compression plate, and optical glass is arranged in the side plates.

9. The method of designing an air intake port experiment apparatus according to claim 8, wherein, The driving device is connected to the slide plate to drive the slide plate to move back and forth along the slide rails on the two sides by means of the slide blocks.

Images