Design method of solid engine ignition device capable of resisting strong vibration load environment

Abstract

The invention provides a design method of a solid engine ignition device resisting a strong vibration load environment. The method comprises the steps that the explosive quantity of the ignition device is determined; an ignition device shell material is selected, and the shell thickness is calculated; determining the structure, thickness distribution and open pore distribution of the pipe body; designing an internal circuit, and giving resistance; a base and a top cover are designed according to the mechanical interface, the base is located at the head of the pipe body, and the top cover is arranged at the tail of the pipe body. The effect of gradual ablation and falling from back to front can be achieved, complete ablation is achieved within one second, and normal work of a solid engine is guaranteed. The design method disclosed by the invention has been verified by two types of engine work, and the two types of engines both work in a strong vibration load environment.

Description

Technical Field

[0001] The invention relates to the field of solid engine ignition, in particular to a design method for an ignition device tube body. Background Art

[0002] Some existing solid motor ignition devices are designed with metal tubes of equal wall thickness, so that the ignition device tube melts during the operation of the engine; some designs use non-metallic materials pasted or molded on the outer wall of the metal tube, so that the ignition device tube maintains structural integrity during the operation of the engine. However, for solid motors working under strong vibration load environments, both of the above two forms of ignition devices have safety risks:

[0003] (1) The strength of metal tubes with equal wall thickness decreases in high temperature environments. Accompanied by strong vibrations, they may break from the root of the tube. If the size of the broken tube structure is too large, it may collide with the throat liner during the process of being ejected from the nozzle throat. This will cause the throat liner to break, the internal pressure of the engine to decrease, and abnormal operation;

[0004] (2) When non-metallic materials are pasted or molded on the outer wall of the metal tube of the ignition device, high-temperature ablation will reduce the strength of the non-metallic materials. Also, accompanied by strong vibration, it may break from the root of the tube. At the same time, non-metallic materials are resistant to ablation, and their structural dimensions are large when they fly out from the nozzle throat liner. There is a very high probability that the throat liner will be damaged, resulting in abnormal engine operation. Summary of the invention

[0005] In order to overcome the shortcomings of the prior art, the present invention provides a method for designing a solid engine ignition device that can resist a strong vibration load environment. Conventional solid engine ignition devices are no longer applicable in a strong vibration load environment and can easily cause abnormal engine operation. The present invention is intended to propose a method for designing a solid engine ignition device that can resist a strong vibration load environment, thereby improving the adaptability and reliability of the ignition device in a strong vibration load environment.

[0006] The specific steps of the technical solution adopted by the present invention to solve its technical problem are as follows:

[0007] The first step is to determine the amount of ignition device powder;

[0008] According to the parameters of engine cavity volume, ignition pressure and propellant type, calculate and determine the type and mass of ignition powder; calculate the minimum ignition powder quantity;

[0009] Choose black powder and ignition powder to use together;

[0010] The second step is to select the ignition device shell material and calculate the shell thickness;

[0011] According to the use environment requirements, the ablation thin-wall rod structure is adopted and the shell thickness is calculated;

[0012] The third step is to determine the tube structure, thickness distribution, and opening distribution;

[0013] Ignition device tube structure Figure 1 As shown in the figure, after determining the minimum design wall thickness h, in order to adapt to the strong vibration environment and ensure that (1) the tube body gradually melts from the tail to the head and (2) the fragments falling off the tube body are much smaller than the throat diameter, based on the above two points, the tube body adopts a variable wall thickness design, with a larger wall thickness at the head and a smaller wall thickness at the tail. The tail wall thickness h min Greater than or equal to the minimum design wall thickness;

[0014] Determine the length L based on the amount of ignition powder and the overall volume of the ignition powder packaging bag to ensure that the internal volume can be loaded with ignition powder and ignition circuits;

[0015] The fourth step is to design the internal circuit and set the resistance;

[0016] In the ignition circuit, an insensitive ignition element is selected. To ensure ignition redundancy, a double insensitive ignition element is connected in parallel.

[0017] Step 5: Other structural designs;

[0018] The base and the top cover are designed according to the mechanical interface. The base is located at the head of the tube body, and the top cover is arranged at the tail of the tube body.

[0019] The minimum ignition charge amount m ig The calculation formula is:

[0020]

[0021] K—empirical correction coefficient;

[0022] P ig — ignition pressure;

[0023] V g —Initial free volume of the engine cavity;

[0024] ε—Relative content of solid particles in the fuel gas;

[0025] R g —gas constant;

[0026] T g —Ignition gas temperature.

[0027] When selecting black powder and ignition powder for use together, for small ignition devices, the amount of black powder used should not exceed 10g.

[0028] The ignition powder is magnesium polytetrafluoroethylene or boron-potassium nitrate.

[0029] In the second step, an aluminum alloy material with high strength, light weight and moderate melting point is selected as the material of the ignition device housing.

[0030] The shell thickness is calculated according to the following formula:

[0031]

[0032] Where h is the minimum design wall thickness, P b is the maximum expected pressure inside the ignition device, D c is the maximum diameter of the shell, which is determined according to the distance between the outer wall of the tube and the charge interface; σ h The ultimate strength of the material.

[0033] Holes are opened on the pipe body as a leakage channel for ignition gas. The holes are gradually denser from the head to the back, and the maximum cross-sectional area of ​​the fragments is less than 1 / 10 of the throat section.

[0034] In the fourth step, two low-pass filters are connected in series in the circuit according to the use requirements to ensure that the ignition circuit meets 1A1W5min without ignition.

[0035] The beneficial effect of the present invention is that the ignition device designed by the present invention can achieve the effect of gradually melting and falling from the back to the front under a strong vibration load environment, and completely melt within 1 second, ensuring the normal operation of the solid engine. The design method of the present invention has been verified by the operation of two engines, both of which operate under a strong vibration load environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 Diagram of the typical ignition device tube structure.

[0037] Figure 2 Typical ignition circuit.

[0038] Figure 3 Typical ignition device structure.

[0039] Figure 4 Cross-section of the ignition device tube.

[0040] Among them, 1-base, 2-metal tube body, 3-top cover. DETAILED DESCRIPTION

[0041] The present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0042] The first step is to determine the amount of ignition device powder;

[0043] According to the parameters of engine cavity volume, ignition pressure and propellant type, calculate and determine the type and mass of ignition powder; calculate the minimum ignition powder quantity;

[0044] Choose black powder and ignition powder to use together;

[0045] The second step is to select the ignition device shell material and calculate the shell thickness;

[0046] According to the use environment requirements, the ablation thin-wall rod structure is adopted and the shell thickness is calculated;

[0047] The third step is to determine the tube structure, thickness distribution, and opening distribution;

[0048] Ignition device tube structure Figure 1 As shown in the figure, after the minimum design wall thickness h is determined, in order to adapt to the strong vibration environment and ensure that (1) the tube body gradually melts from the tail to the head, and (2) the fragments falling off the tube body are much smaller than the throat diameter, based on the above two points, the tube body adopts a variable wall thickness design, with a larger wall thickness at the head and a smaller wall thickness at the tail, and the tail wall thickness hmin is greater than or equal to the minimum design wall thickness;

[0049] Determine the length L based on the amount of ignition powder and the overall volume of the ignition powder packaging bag to ensure that the internal volume can be loaded with ignition powder and ignition circuits;

[0050] The fourth step is to design the internal circuit and set the resistance;

[0051] In the ignition circuit, an insensitive ignition element is selected. To ensure ignition redundancy, a double insensitive ignition element is connected in parallel. According to the use requirements, two low-pass filters are connected in series in the circuit to ensure that the ignition circuit meets 1A1W5min without ignition.

[0052] Step 5: Other structural designs;

[0053] The base and the top cover are designed according to the mechanical interface. The base is located at the head of the tube body, and the top cover is arranged at the tail of the tube body.

[0054] The calculation formula of the minimum ignition charge mig is:

[0055]

[0056] K-empirical correction coefficient;

[0057] P ig - ignition pressure;

[0058] V g - Initial free volume of the engine cavity;

[0059] ε-relative content of solid particles in the fuel gas;

[0060] R g - Gas constant;

[0061] T g - ignition gas temperature;

[0062] When selecting black powder and ignition powder for use together, for small ignition devices, the amount of black powder used should not exceed 10g.

[0063] The ignition powder is magnesium polytetrafluoroethylene or boron-potassium nitrate.

[0064] In the second step, an aluminum alloy material with high strength, light weight and moderate melting point is selected as the material of the ignition device housing.

[0065] The shell thickness is calculated according to the following formula:

[0066]

[0067] Where h is the minimum design wall thickness, Pb is the maximum expected pressure inside the ignition device, and D c is the maximum diameter of the shell, which is determined according to the distance between the outer wall of the tube and the charge interface; σ h The ultimate strength of the material.

[0068] Holes are opened on the pipe body as a leakage channel for ignition gas. The holes are gradually denser from the head to the back, and the maximum cross-sectional area of ​​the fragments is less than 1 / 10 of the throat section.

[0069] The axial vibration of a certain type of rocket sled engine during operation exceeds 100g. The design process of the engine ignition device is as follows:

[0070] (1) Calculation of minimum ignition charge;

[0071] The ignition device uses magnesium polytetrafluoroethylene as the ignition powder, and the parameters for calculation are as follows:

[0072] K-empirical correction coefficient, take 0.4

[0073] P ig -Ignition pressure, take 2MPa

[0074] V g -The initial free volume of the engine cavity is 38.8L;

[0075] ε-relative content of solid particles in the fuel gas, taken as 60%;

[0076] R g -Gas constant, taken as 293.3 (J / kg·K);

[0077] T g - Ignition gas temperature, 2590K;

[0078] The minimum amount of ignition powder required is calculated to be 0.125 kg, and the final amount selected is 0.16 kg, which is used with 5 g of black powder;

[0079] (2) Calculation of the minimum wall thickness of the pipe body;

[0080] The ignition device is made of 2A12 aluminum alloy material, with an estimated maximum ignition pressure of 5MPa, a maximum inner diameter of the shell of 43.5mm, a material ultimate strength of 210MPa, a safety factor of 1, and a minimum wall thickness of 0.52mm. The final minimum wall thickness is 0.7mm and the maximum wall thickness is 2mm. Figure 4 shown.

Claims

1. A method for designing a solid rocket engine ignition device that can withstand strong vibration load environments, characterized in that The steps include: The first step is to determine the amount of ignition device powder; According to the parameters of engine cavity volume, ignition pressure and propellant type, calculate and determine the type and mass of ignition powder; calculate the minimum ignition powder quantity; Choose black powder and ignition powder to use together; The second step is to select the ignition device shell material and calculate the shell thickness; According to the use environment requirements, the ablation thin-wall rod structure is adopted and the shell thickness is calculated; The third step is to determine the tube structure, thickness distribution, and opening distribution; After determining the minimum design wall thickness h, in order to adapt to the strong vibration environment, ensure that the tube body gradually melts from the tail to the head, and the fragments falling off the tube body are much smaller than the throat diameter, the tube body adopts a variable wall thickness design, with a larger wall thickness at the head and a smaller wall thickness at the tail. The tail wall thickness h min Greater than or equal to the minimum design wall thickness; Determine the length L based on the amount of ignition powder and the overall volume of the ignition powder packaging bag to ensure that the internal volume can be loaded with ignition powder and ignition circuits; The fourth step is to design the internal circuit and set the resistance; In the ignition circuit, an insensitive ignition element is selected. To ensure ignition redundancy, a double insensitive ignition element is connected in parallel. Step 5: Other structural designs; The base and the top cover are designed according to the mechanical interface. The base is located at the head of the tube body, and the top cover is arranged at the tail of the tube body.

2. The method for designing a solid rocket engine ignition device capable of resisting a strong vibration load environment according to claim 1, characterized in that: The minimum ignition charge amount m ig The calculation formula is: K—empirical correction coefficient; P ig — ignition pressure; V g —Initial free volume of the engine cavity; ε—Relative content of solid particles in the fuel gas; R g —gas constant; T g —Ignition gas temperature.

3. The method for designing a solid rocket engine ignition device capable of resisting a strong vibration load environment according to claim 1, characterized in that: When selecting black powder and ignition powder for use together, for small ignition devices, the amount of black powder used should not exceed 10g.

4. The method for designing a solid rocket engine ignition device capable of resisting a strong vibration load environment according to claim 1, characterized in that: The ignition powder is magnesium polytetrafluoroethylene or boron-potassium nitrate.

5. The method for designing a solid rocket engine ignition device capable of resisting a strong vibration load environment according to claim 1, characterized in that: In the second step, an aluminum alloy material is selected as the material of the ignition device housing.

6. The method for designing a solid rocket engine ignition device capable of resisting a strong vibration load environment according to claim 1, characterized in that: The shell thickness is calculated according to the following formula: Where h is the minimum design wall thickness, P b is the maximum expected pressure inside the ignition device, D c is the maximum diameter of the shell, which is determined according to the distance between the outer wall of the tube and the charge interface; σ h The ultimate strength of the material.

7. The method for designing a solid rocket engine ignition device capable of resisting a strong vibration load environment according to claim 1, characterized in that: Holes are opened on the pipe body as a leakage channel for ignition gas. The holes are gradually denser from the head to the back, and the maximum cross-sectional area of ​​the fragments is less than 1 / 10 of the throat section.

8. The method for designing a solid rocket engine ignition device capable of resisting a strong vibration load environment according to claim 1, characterized in that: In the fourth step, two low-pass filters are connected in series in the circuit according to the use requirements to ensure that the ignition circuit meets 1A1W5min without ignition.

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