Ejecting system for sand prevention device and design method

Abstract

The invention belongs to the technical field of aircraft design, and relates to an ejection system for a sand prevention device and a design method. The method comprises the steps that firstly, the arrangement positions and the number n of ejectors of an ejection system are determined; 2, the sand dust amount Qi needing to be ejected by each ejector is calculated; the total injection coefficient psi of all the injectors is calculated, and the main flow qi needing to be reached by each injector is calculated; 3, the diameter d0 of the air entraining pipe is calculated; fourthly, according to the main flow qi and the total ejection coefficient psi of each ejector, the structural size of the ejector is designed, the structural size of a nozzle of the ejector and the structural size of a mixing pipe of the ejector are included, the ejection coefficient psi i of each ejector is obtained through fluid simulation, i = 1, 2... n, and the structural size parameters of the ejector are adjusted till delta = psi i-psi is larger than or equal to 0; 5, modeling simulation is conducted on the whole injection system, the structural size of the ejector is adjusted preferentially, and if the requirement cannot be met, the n value is iterated till the overall requirement is met.

Description

Technical Field

[0001] This invention belongs to the field of aircraft design technology, and relates to an ejector system and design method for a sand-proof device. Background Technology

[0002] When helicopters operate near the ground, they easily stir up sand and dust, which can be ingested by the engine, damaging components within the engine intake, such as compressor blade wear and bearing seizure, posing a significant threat to the helicopter's safe operation. Therefore, in environments frequently exposed to sand and dust, installing a sand filter can reduce the impact of sand and dust on the engine. Multi-tube sand filters are a common type of sand filter, widely used in helicopter intake protection due to their high separation efficiency, lack of moving parts, strong adaptability, and ease of maintenance. The sand filter's bleed air system uses an ejector system at the outlet of the bleed channel to eject sand and dust using the high-pressure gas from the engine's P3 bleed port. The ejector system is widely used in sand filters due to its simple structure and convenient maintenance.

[0003] The ejector system used in sand control devices is a mechanical device that utilizes high-temperature, high-pressure engine P3 bleed air to draw in sand-laden gas separated from the sand control device. By thoroughly mixing two fluids at different pressures in a mixing tube, the sand-laden gas is then exhausted outside the sand control device, thus achieving sand and dust separation. The use of engine P3 bleed air in the ejector system results in engine power loss. To minimize this loss, the amount of P3 bleed air used in the ejector system must be as small as possible, while still meeting the ejection capacity requirements to ensure effective sand and dust separation. The core components of the ejector system are the ejector nozzle and the mixing tube. Their structural parameters significantly affect the ejection efficiency. Furthermore, the ejector gas must form a relatively uniform ejection flow field at the outlet of the sand control device to ensure that all sand-laden gas in the sand discharge channel is completely expelled from the device. Existing research mainly analyzes the impact of single structural parameters on the performance of individual ejectors, with limited research on the ejector system itself used in sand control devices. Summary of the Invention

[0004] Purpose of the invention: This invention provides an ejector system and design method for a sand control device. By uniformly distributing the P3 air volume through a gas distribution device, a supersonic fluid is formed in each ejector, enhancing the ejection capability. At the same time, the design of the ejector nozzle and mixing tube structure parameters is optimized to improve the mixing efficiency and further enhance the ejection capability of the ejector system.

[0005] To address the aforementioned technical issues, this application provides... A design method for an ejector system for a sand control device, comprising the following steps: Step 1: Determine the location and number n of the ejectors in the ejection system; First, determine the overall configuration and basic layout of the ejector system, which will also serve as the input value for solving the diameter d0 of the air intake tube.

[0006] Step 2: Calculate the amount of sand and dust Q to be ejected by each ejector. i Calculate the total ejection coefficient ψ of all ejectors as the initial value for each ejector, and calculate the main flux q that each ejector needs to achieve. i ; The ejection performance of each ejector is initially determined and used as input for the structural parameter design in step four.

[0007] Step 3: Calculate the diameter d0 of the air intake tube; As input values ​​for subsequent system modeling and simulation.

[0008] Step 4: Based on the main flow rate q of each ejector i Given the total ejection coefficient ψ, the structural dimensions of the ejector are designed, including the dimensions of the ejector nozzle and the ejector mixing tube. The ejection coefficient ψ of each ejector is obtained through fluid simulation. i For i=1,2……n, adjust the ejector structure dimensions until Δ=ψ i -ψ≥0; The structural dimensions of each ejector are obtained and used as input values ​​for system modeling and simulation.

[0009] Step 5: Model and simulate the entire ejector system, adjust the structural dimensions of the ejector, and if the requirements cannot be met, iterate the value of n until the overall requirements are met.

[0010] Furthermore, in step one, the number of ejectors is calculated as follows: The initial value is according to Take the integer part; Furthermore, in step two, the amount of sand and dust to be ejected by each ejector is Q. i =Q m *(1-φ)*m.

[0011] Q m The air intake volume of a single vortex tube in the sand control device; φ represents the vortex tube separation efficiency; m is the number of vortex tubes covering each ejector.

[0012] Furthermore, in step two, the total entrainment coefficient ψ = ∑Q i / q0 q0 is the bleed air flow limit value at the engine P3 bleed air inlet; The required flow rate q for each ejector i =Q i ×ψ.

[0013] Furthermore, in step three, the calculation process for the airway diameter d0 is as follows: Calculate the total length L0 of the straight section of the ventilator and the equivalent length L of the bend. t ; Equivalent total length of system piping L = L0 + L t ; The pressure P0 at the engine P3 bleed air inlet and the pressure P at the ejector system outlet c Using the pipeline flow rate and pressure drop formula ΔP=P0-P c =450*q0^1.85*L / (d0^5*P) Calculate the system voltage drop; ΔP is solved by iteratively changing d0 until ΔP < 0.1; d0 is the diameter of the required venting pipe.

[0014] Furthermore, in step four, the ejector nozzle structure dimensions include: nozzle throat diameter D1, nozzle inlet diameter D3, nozzle outlet diameter D2, distance from nozzle inlet to throat L1, and distance from nozzle throat to outlet L2. The dimensions of the air purging mixing tube include throat diameter d1, inlet diameter d3, outlet diameter d2, distance from inlet to throat l1, and distance from throat to outlet l2; Initial value of ejector nozzle throat diameter D 1i0 =1.13× f p Let f be the area of ​​the nozzle throat. p =q i *a p / (k0*π p *p p ); a p The critical velocity of air flowing in the ejector; k0 is the adiabatic index of air; π p The air insulation index factor; p p This refers to the pressure at the nozzle inlet.

[0015] Initial value of ejector nozzle outlet diameter D 2i0 =1.13× f p1 Let f be the export area, initially set to f. p1 =f p / q ps ; q ps The coefficient is initially set between 0.65 and 0.7.

[0016] Initial value of nozzle inlet diameter D 3i=k×D 1i0 Where k≥5, initially k=5; Initial value L of the distance from the ejector inlet to the throat 1i =(D 2i0 -D 1i0 ) / (2×tan(δ / 2)), where δ is the nozzle expansion angle; Initial value of mixing pipe inlet diameter d 1i =5×D 1i0 ; Initial value of the distance from the throat to the outlet of the mixing pipe l 2i =5×d i1 Distance from entrance to throat l 1i ≥L 1i ; Initial value of mixing pipe outlet diameter d 2i =d 3i +2*l 2i *tan(β). β is the expansion angle of the mixing tube.

[0017] Furthermore, in step five, the main flux q of each ejector is calculated through modeling and simulation. i and the entrainment coefficient ψ i ; Calculate Δ1=|∑q i -q0| / q0; Calculate Δ 2i =ψ i -ψ; If Δ1>5% or any Δ 2i ≥0, adjust the ejector nozzle and mixing tube dimensions; Until the overall requirement Δ1 < 5% and all Δ 2i <0.1.

[0018] A sand-control device ejector system, comprising: The initiator assembly is connected at one end to the engine compressor and at the other end to the gas distributor; The gas distributor is a straight pipe with an inlet connected to an ejector assembly and n evenly distributed outlets, each outlet connected to an ejector. The ejector includes a nozzle and a mixing tube, with the nozzle connected to the outlet of the gas distributor; The positioning device is a long plate with n through holes evenly distributed therein, and n ejector mixing tubes are fixed in the through holes.

[0019] Furthermore, it is characterized by: Nozzle throat diameter , where ρ is the air density; c is the local speed of sound; Nozzle inlet diameter D 3i 5≤D 3i / D1i ≤7; Nozzle outlet diameter D 2i 1 <D 2i / D 1i ≤1.5; Distance L from nozzle inlet to throat 1i L 1i / D 1i ≥10; Distance L from nozzle throat to nozzle outlet 2i 5≤L 2i / D 1i ≤10.

[0020] Furthermore, the ratio d between the diameter of the ejector mixing tube throat and the nozzle throat 1i / D 1i ≥8; Mixing pipe outlet diameter d 2i ,1<d 2i / d 1i <5; Mixing pipe inlet diameter d 3i d 3i / d 1i >1.2; Distance from mixing tube inlet to throat l 1i , l 1i / d 1i >0.7; Distance from nozzle throat to nozzle outlet l 2i 5 <l 2i / d 1i <8.

[0021] In summary, the beneficial effects of the present invention are as follows: 1) Calculation speed: The performance calculation method of this application can obtain the local optimal solution and the global optimal solution of the ejector system relatively quickly, and can accurately control the ejection performance of each ejector, thereby controlling the ability of each ejector to eject sand and dust.

[0022] 2) High ejection efficiency: The ejection system of this application is designed with 6 ejectors. The optimal value of the system is obtained by using performance calculation method. The ejection effect can reach more than 10 as verified by simulation test.

[0023] 3) Low power loss: Since the ejector system uses engine P3 bleed air as the power source for sand removal by the sand control device, the larger the engine P3 bleed air volume, the greater the engine power loss. The P3 bleed air volume used in this ejector system is no more than 15 g / s, which is only 0.83% of the engine flow rate, and its impact on engine power is almost negligible. Attached Figure Description

[0024] Figure 1 A flowchart illustrating the design method of an ejector system for a sand control device.

[0025] Figure 2 This is a schematic diagram of an ejector system for a sand control device.

[0026] Figure 3 This is a schematic diagram of a gas distributor and an ejector.

[0027] Figure 4 This is a schematic diagram of a single ejector.

[0028] Figure 5 This is a schematic diagram of the nozzle and mixing tube.

[0029] Figure 6 This is a schematic diagram of a sand control device. Detailed Implementation

[0030] A design method for an ejector system for a sand control device is disclosed, and an ejector system for a sand control device is designed based on this method. The ejector system of this application includes an air intake pipe assembly 1, a gas distributor 2, an ejector 3, and a positioning device 4. The power source of the ejector system 3 is high-temperature, high-pressure gas from an engine compressor. One end of the air intake pipe assembly 1 is connected to the engine compressor, introducing the high-temperature, high-pressure gas from the engine compressor into the air intake pipe assembly 1. The other end is connected to the gas distributor 2 through a pipe joint, guiding the high-temperature, high-pressure gas into the gas distributor 2, where the gas flow is distributed. The distributed gas flows into different ejectors, thereby controlling the ejection capacity of a single ejector.

[0031] The first part, the steps of the method for calculating the performance of the ejector system provided in this application, include: Step 1: Based on the arrangement of the vortex tubes and sand discharge channels of the sand control device, preliminarily determine the location and number n of the ejectors in the ejector system. The initial value is according to Take the integer part; Step Two: To ensure that the sand and dust separated from the sandproof panel can be removed from the machine body, the ejector system typically includes multiple ejectors. Based on the ejector positions and the number of vortex tubes around the air intake, a preliminary calculation is made of the amount of sand and dust Q that each ejector needs to eject. i (i=1,2……n), Q i =Q m *(1-φ)*m(Q m φ represents the air intake volume of a single vortex tube in the sand control device; φ represents the vortex tube separation efficiency; m represents the number of vortex tubes surrounding each ejector. Based on the bleed air flow rate q0 at the engine's P3 bleed air inlet, the total ejection coefficient ψ = ∑Q is calculated. i / q0, confirms the required main flux q for each ejector. i =Qi ×ψ(i=1,2……n; Step 3: Based on the bleed air flow rate q0 at the engine P3 bleed air interface, calculate the diameter d0 of bleed air pipe 1 using the flow resistance calculation method.

[0032] In detail, calculating the vent pipe diameter requires the total straight pipe length L0 of the system and the equivalent length L of the system bends. t The equivalent total length of the system piping L = L0 + L t The pressure P0 at the engine P3 bleed air inlet and the pressure P at the ejector system outlet. c (P) c (Generally atmospheric pressure), using the pipeline flow rate and pressure drop formula ΔP=P0-P c The system pressure drop is calculated as 450*q0^1.85*L / (d0^5*P). ΔP is solved by iteratively changing d0 until ΔP < 0.1. d0 is then the diameter of the required venting pipe 1.

[0033] Step 4: Based on the main flow rate q of each ejector i Given the ejector coefficient ψ, the structural dimensions of the ejector are designed, including the dimensions of the ejector nozzle and the ejector mixing tube. The performance ψ of each ejector is obtained through fluid simulation. 4i (i=1,2……n), if the design requirements are not met, adjust the ejector structural parameters until Δ=ψ 4i -ψ≥0; In detail, the ejector nozzle structure dimensions include nozzle throat diameter D1, nozzle inlet diameter D3, nozzle outlet diameter D2, and distance from nozzle inlet to throat L1; the air evacuator mixing tube dimensions include throat diameter d1, inlet diameter d3, outlet diameter d2, distance from inlet to throat l1, and distance from throat to outlet l2.

[0034] In detail, the initial value D of the ejector nozzle throat. 1i0 =1.13× f p Let f be the area of ​​the nozzle throat. p =q i *a p / (k0*π p *p p ); a p The critical velocity of air flowing in the ejector; k0 is the adiabatic index of air; π p The air insulation index factor; p p This refers to the pressure at the nozzle inlet.

[0035] In detail, the initial value D of the ejector nozzle outlet diameter. 2i0 =1.13× f p1 Let f be the export area, initially set to f. p1 =f p / q ps ; q ps The coefficient is initially set between 0.65 and 0.7.

[0036] In detail, the initial value of the nozzle inlet diameter D 3i =k×D 1i0 , where k≥5, initially k=5.

[0037] In detail, the initial value L of the distance from the ejector inlet to the throat. 1i =(D 2i0 -D 1i0 ) / (2×tan(δ / 2)), where δ is the nozzle expansion angle.

[0038] In detail, the initial value of the mixing pipe inlet diameter d 1i =5×D 1i0 ; In detail, the initial value of the distance l from the throat to the outlet of the mixing pipe. 2i =5×d i1 Distance from entrance to throat l 1i ≥L 1i .

[0039] In detail, the initial value of the outlet diameter d of the mixing pipe. 2i =d 3i +2*l 2i *tan(β). β is the expansion angle of the mixing tube.

[0040] Step 5: Overall Simulation Verification of the Ejector System. Input the number of ejectors (n), the diameter of the bleed pipe (d0), and the pipe length (L) into the overall ejector system model. Use 3D fluid simulation software to simulate and calculate the main flow rate (q) of each ejector. i Meanwhile, compare Δ1=|∑q i -q0| / q0 and Δ 2i =ψ 5i -ψ, such as Δ1>5% or any Δ 2i ≥0, adjust the ejector nozzle and mixing tube dimensions until Δ1 < 5% and all Δ 2i <0.1.

[0041] In summary, this application provides a method for calculating the performance of an ejector system. Utilizing the principle of resistance distribution and flow resistance calculation, it proceeds from calculating the performance of a single ejector, to simulation verification, iteratively calculating the entire ejector system, and finally obtaining the structural parameters of the ejector system. This performance calculation method, by moving from local optima to system optima, can quickly find the optimal values ​​and obtain a system solution in the design of ejector systems with multiple parameters and objectives. Compared to the previous method of iteratively calculating the ejector structural parameters, the performance calculation method of this application can obtain the local and global optimal solutions of the ejector system more quickly, and can accurately control the ejection performance of each ejector, thereby controlling the ability of each ejector location to eject sand and dust. (Appendix) Figure 1 This is a flowchart of the performance calculation.

[0042] The second part describes the design of an ejection system based on the performance calculation method of this application: Based on the actual sand control device layout, the ejector system designed in this application consists of 6 ejectors (3-1, 3-2, 3-3, 3-4, 3-5, 3-6). Each ejector consists of a nozzle a and a mixing tube b. The high-temperature and high-pressure gas distributed by the gas distributor flows into the nozzle. The gas is accelerated in the nozzle to form supersonic gas. After the high-speed gas is ejected, it is rapidly mixed in the mixing tube and simultaneously ejects the sand-dust-containing gas inside the sand control device, which is then discharged outside the sand control device.

[0043] In detail, the design values ​​for the ejector nozzle throat diameter and the mixing tube throat diameter should ensure d 1i / D 1i ≥8, ensuring sufficient diffusion space for the accelerated supersonic gas and reducing the impact of wall effects; In detail, the nozzle inlet diameter D 3i 5≤D 3i / D 1i ≤7; Nozzle outlet diameter D 2i 1 <D 2i / D 1i ≤1.5; Distance L from nozzle inlet to throat 1i L 1i / D 1i ≥10; Distance L from nozzle throat to nozzle outlet 2i 5≤L 2i / D 1i ≤10.

[0044] In detail, the outlet diameter d of the mixing pipe 2i ,1<d 2i / d 1i <5; Mixing pipe inlet diameter d 3i d 3i / d 1i>1.2; Distance from mixing tube inlet to throat l 1i , l 1i / d 1i >0.7; Distance from nozzle throat to nozzle outlet l 2i 5 <l 2i / d 1i <8.

[0045] Example: 1. For example, a certain type of sand control device, Figure 6 Assume that each ejector has the same ejection capacity. The engine has a flow rate limit q. 0= 15g / s, following step one, n=6.8, rounded down, n=6.

[0046] 2. The sand and dust separated by approximately 60 vortex tubes in the sand control device needs to pass through each separator. The air intake of a single vortex tube is 4 g / s, and the sand and dust separation efficiency is 94%. The amount of sand and dust to be ejected by each ejector is Q. i =14.4, the total entrainment coefficient ψ==∑Q i / q0=5.76, the required main flux q for each ejector i =Q i / ψ=2.5.

[0047] 3. The equivalent total length of the system piping L = L0 + L t =2.5, the pressure at the engine P3 bleed air inlet P0 = 6.5 bar, the outlet pressure P c =1 bar, iterate d0, and find d0=4.5.

[0048] 4. Satisfies Δ=ψ 4i When -ψ≥0, the nozzle throat diameter D1=2.8mm, the nozzle outlet diameter D2=3.5mm, and the mixing tube throat diameter d1=15mm. Other parameters are calculated iteratively according to the given formulas.

[0049] 5. Simulation modeling and iterative solution of final parameters.

Claims

1. A design method for an ejector system for a sand control device, characterized in that: The steps are as follows: Step 1: Determine the location and number n of the ejectors in the ejection system; Step 2: Calculate the amount of sand and dust Q to be ejected by each ejector. i Calculate the total ejection coefficient ψ of all ejectors as the initial value for each ejector, and calculate the main flux q that each ejector needs to achieve. i ; Step 3: Calculate the diameter d0 of the air intake tube; Step 4: Based on the main flow rate q of each ejector i Given the total ejection coefficient ψ, the structural dimensions of the ejector are designed, including the dimensions of the ejector nozzle and the ejector mixing tube. The ejection coefficient ψ of each ejector is obtained through fluid simulation. i For i = 1, 2, ..., n, adjust the ejector structural dimensions until Δ = ψ i -ψ≥0; Step 5: Model and simulate the entire ejector system, and adjust the structural dimensions of each ejector. If the requirements cannot be met, iterate the value of n until the overall requirements are met.

2. The method according to claim 1, characterized in that: In step one, the number of ejectors is calculated as follows: Initial value according to Take the integer part; q0 is the bleed air flow limit value at the engine P3 bleed air inlet; ρ is the air density; c is the local speed of sound.

3. The method according to claim 2, characterized in that: In step two, the amount of sand and dust to be ejected by each ejector is Q. i =Q m *(1-φ)*m. Q m The air intake volume of a single vortex tube in the sand control device; φ represents the vortex tube separation efficiency; m is the number of vortex tubes covering each ejector.

4. The method according to claim 3, characterized in that: In step two, the total entrainment coefficient ψ = ∑Q i / q0 q0 is the bleed air flow limit value at the engine P3 bleed air inlet; The required flow rate q for each ejector i =Q i *ψ.

5. The method according to claim 4, characterized in that: In step three, the calculation process for the diameter d0 of the airway is as follows: Calculate the total length L0 of the straight section of the ventilator and the equivalent length L of the bend. t ; The equivalent total length of the system piping L = L0 + L t ; The pressure P0 at the engine P3 bleed air inlet and the pressure P at the ejector system outlet c Using the pipeline flow rate and pressure drop formula ΔP=P0-P c =450*q0^1.85*L / (d0^5*P) Calculate the system voltage drop; ΔP is solved by iteratively changing d0 until ΔP < 0.1; d0 is the diameter of the required venting pipe.

6. The method according to claim 5, characterized in that: In step four, the ejector nozzle structural dimensions include: nozzle throat diameter D1, nozzle inlet diameter D3, nozzle outlet diameter D2, distance from nozzle inlet to throat L1, and distance from nozzle throat to outlet L2. The dimensions of the air purging mixing tube include throat diameter d1, inlet diameter d3, outlet diameter d2, distance from inlet to throat l1, and distance from throat to outlet l2; Initial value of ejector nozzle throat diameter f p Let f be the area of ​​the nozzle throat. p =q i *a p / (k0*π p *p p ); a p The critical velocity of air flowing in the ejector; k0 is the adiabatic index of air; π p The air insulation index factor; p p This refers to the pressure at the nozzle inlet. Initial value of ejector nozzle outlet diameter f p1 Let f be the export area, initially set to f. p1 =f p / q ps ; q ps The coefficient is initially set between 0.65 and 0.

7. Initial value of nozzle inlet diameter D 3i =k×D 1i0 Where k≥5, initially k=5; Initial value L of the distance from the ejector inlet to the throat 1i =(D 2i0 -D 1i0 ) / (2×tan(δ / 2)), where δ is the nozzle expansion angle; Initial value of mixing pipe inlet diameter d 1i =5*D 1i0 ; Initial value of the distance from the throat to the outlet of the mixing pipe l 2i =5×d i1 Distance from entrance to throat l 1i ≥L 1i ; Initial value of mixing pipe outlet diameter d 2i =d 3i +2*l 2i *tan(β). β is the expansion angle of the mixing tube.

7. The method according to claim 6, characterized in that: In step five, the main flow rate q of each ejector is calculated through modeling and simulation. i and the entrainment coefficient ψ i ; Calculate Δ1=|∑q i -q0| / q0; calculationD 2i =ψ i -ψ; If Δ1>5% or any Δ 2i ≥0, adjust the ejector nozzle and mixing tube dimensions; Until the overall requirement Δ1 < 5% and all Δ 2i <0.

1.

8. A sand-control device ejector system, designed based on the method of any one of claims 1-7, characterized in that: The ejection system includes: The bleed air assembly is connected to the engine compressor at one end and to the gas distributor at the other end. The gas distributor is a straight pipe with an inlet connected to an ejector assembly and n evenly distributed outlets, each outlet connected to an ejector. The ejector includes a nozzle and a mixing tube, with the nozzle connected to the outlet of the gas distributor; The positioning device is a long plate with n through holes evenly distributed therein, and n ejector mixing tubes are fixed in the through holes.

9. The system according to claim 8, characterized in that: Nozzle throat diameter Where ρ is the air density; c is the local speed of sound; Nozzle inlet diameter D 3i 5≤D 3i / D 1i ≤7; Nozzle outlet diameter D 2i 1 <D 2i / D 1i ≤1.5; Distance L from nozzle inlet to throat 1i L 1i / D 1i ≥10; Distance L from nozzle throat to nozzle outlet 2i 5≤L 2i / D 1i ≤10.

10. The system according to claim 9, characterized in that: The ratio d of the diameter of the ejector mixing tube throat to the diameter of the nozzle throat 1i / D 1i ≥8; Mixing pipe outlet diameter d 2i ,1<d 2i / d 1i <5; Mixing pipe inlet diameter d 3i d 3i / d 1i >1.2; Distance from mixing tube inlet to throat l 1i , l 1i / d 1i >0.7; Distance from nozzle throat to nozzle outlet l 2i 5 <l 2i / d 1i <8.

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