Thrust oscillation control method for end-combustion grain solid rocket engine

Abstract

The invention discloses a thrust oscillation control method for an end-combustion grain solid rocket engine, which comprises the following steps of: determining an overall index of the engine, and setting an acceptable range of the overall index; solid rocket engine design parameters are determined according to the overall indexes, and the end combustion grain structure size and propellant combustion speed data are preliminarily determined; based on the design parameters, a thrust model of the solid rocket engine is constructed; establishing a thrust oscillation influence model of the solid rocket engine on the basis of the expression of the thrust coefficient in combination with a balance pressure formula of the solid rocket engine, and determining key factors influencing thrust oscillation through the thrust oscillation influence model; the values of the key factors are combined with the thrust oscillation influence model for solving, and the fluctuation range of thrust oscillation is obtained; whether the overall indexes meet the range requirements of the corresponding overall indexes or not in the fluctuation range of thrust oscillation is judged; if the requirements are met, the value of the key factor is reserved as an actual design value.

Description

Technical Field

[0001] The present invention belongs to the technical field of solid rocket engine design, and particularly relates to a method for controlling thrust oscillation of a grain-end burning solid rocket engine. Background Art

[0002] With the development of unmanned general aircraft towards long-range precision strike, it is generally required that solid rocket engines need to meet the requirements of stable flight with small thrust for a long time. And the long-time small-thrust flight usually adopts the scheme of a grain-end burning solid rocket engine with a low burning rate. This type of engine is widely used in the power device for long-time flight of aircraft due to its advantages such as simple shape, easy manufacturing, high loading coefficient, excellent mechanical properties, and the ability to work for a long time. The low burning rate grain-end burning grain has a small thrust due to its small combustion area, and the amplitude of the thrust oscillation caused by the design, processing, and manufacturing processes is relatively large compared with the small thrust generated by itself, often resulting in relatively severe thrust oscillation during its flight process, thus bringing great difficulties to flight control. Therefore, thrust oscillation is a difficult point worthy of key attention.

[0003] Traditional methods for thrust oscillation mainly rely on the engineering experience of designers. Designers with insufficient experience often adopt comprehensive management of multiple factors, which leads to difficulties in managing some non-critical factors, consuming a large amount of manpower and material resources but still being difficult to meet the requirements. Summary of the Invention

[0004] Aiming at the problem of thrust oscillation of a grain-end burning solid rocket engine, the present invention proposes a method for controlling thrust oscillation of a grain-end burning solid rocket engine, which helps designers quickly locate the key factors affecting thrust oscillation and take targeted measures to make the thrust oscillation adjustable and controllable, reducing problems such as the high cost caused by the heavy dependence on engineering experience and comprehensive management in the existing thrust oscillation methods.

[0005] To achieve the above tasks, the present invention adopts the following technical solutions:

[0006] A method for controlling thrust oscillation of a grain-end burning solid rocket engine, comprising:

[0007] Determine the overall engine indicators and set the range of acceptable overall indicators;

[0008] Determine the design parameters of the solid rocket engine according to the overall indicators, and initially determine the structural dimensions of the grain-end burning grain and the propellant burning rate data;

[0009] Based on the design parameters, construct a thrust model of the solid rocket engine; based on the expression of the thrust coefficient and combined with the equilibrium pressure formula of the solid rocket engine, establish a thrust oscillation influence model of the solid rocket engine, and determine the key factors affecting thrust oscillation through the thrust oscillation influence model;

[0010] According to the initially determined structural dimensions of the end-burning grain and the burning rate of the propellant, values are taken for the key factors; the values of the key factors are combined with the thrust oscillation influence model for solution to obtain the fluctuation range of the thrust oscillation; it is judged whether the overall indicators all meet the range requirements of the corresponding overall indicators under the fluctuation range of the thrust oscillation; if the requirements are met, the values of the key factors are retained as the actual design values.

[0011] Furthermore, if the range requirements of the corresponding overall indicators are not met, then:

[0012] Determine the optimization direction of each key factor, optimize the values of the key factors by formulating a design plan, and then calculate the fluctuation range of the thrust oscillation again and judge whether the overall indicators meet the range requirements of the corresponding overall indicators; repeat this process until the requirements are met and then end.

[0013] Furthermore, the key factors affecting the thrust oscillation are determined through the thrust oscillation influence model, specifically:

[0014] Take the throat area A t , the pressure exponent n, and the deviation of the propellant burning rate as the key factors affecting the thrust oscillation.

[0015] Furthermore, the determination of the optimization direction of each key factor is specifically:

[0016] Control the range of the deviation of the propellant burning rate, reduce the pressure exponent n, and reduce the throat area A t from ablative changes during the working process.

[0017] Furthermore, the optimization of the values of the key factors by formulating a design plan includes:

[0018] According to the existing process and processing difficulty, the structural dimensions of the end-burning grain and the propellant burning rate data are adjusted twice to adjust the range of the deviation of the propellant burning rate and reduce the pressure exponent; at the same time, the ablative resistance performance data of the throat liner is adjusted to reduce the ablative changes of the throat area during the working process.

[0019] Furthermore, the determination of the overall engine indicators and the setting of the acceptable range of the overall indicators include:

[0020] Referring to the past engineering trial production experience and process difficulty, negotiate with the overall design department to determine the overall engine indicators, and determine the acceptable range of the overall indicators in combination with the processing technology and production difficulty; where the overall indicators include the median value of the thrust design and the amplitude of the thrust oscillation.

[0021] Furthermore, the thrust oscillation influence model of the solid rocket engine is as follows:

[0022]

[0023] Among them, F is the engine thrust, and C F is the thrust coefficient, n is the pressure exponent, and c * is the characteristic velocity of the propellant, a is the burning rate coefficient of the propellant, and ρ p is the propellant density, s b is the burning surface of the grain, and A t is the throat area.

[0024] Furthermore, the specific process of constructing the thrust oscillation influence model of the solid rocket engine is as follows:

[0025] First, construct the thrust model as follows:

[0026] F = C F ·P c ·A t (1)

[0027] Among them, C F is the thrust coefficient, and its calculation formula is as follows:

[0028]

[0029] In the above formula, k is the specific heat ratio of the propellant gas, P e is the nozzle exit pressure, A e is the nozzle exit cross-sectional area, P a is the atmospheric pressure; Γ is a function of the specific heat of the gas, and specifically as follows:

[0030]

[0031] Taking the logarithm of both ends of the above thrust model formula (1) and differentiating, we can get:

[0032]

[0033] According to the solid rocket engine equilibrium pressure formula:

[0034]

[0035] Among them, c * is the characteristic velocity of the propellant, a is the burning rate coefficient of the propellant, and ρ p is the propellant density, s b is the burning surface of the grain, and n is the pressure exponent;

[0036] Taking the logarithm of both sides of the solid rocket engine equilibrium pressure formula and differentiating, we can get:

[0037]

[0038] Combining formula (4) and (6) gives the thrust oscillation influence model.

[0039] A terminal device includes a processor, a memory, and a computer program stored in the memory; when the processor executes the computer program, the thrust oscillation control method for the end-burning grain solid rocket engine is implemented.

[0040] A computer-readable storage medium stores a computer program; when the computer program is executed by a processor, the thrust oscillation control method for the end-burning grain solid rocket engine is implemented.

[0041] Compared with the prior art, the present invention has the following technical features:

[0042] 1. Provide a thrust oscillation control method for an end-burning grain solid rocket engine, which is simple and fast, can quickly locate the key factors affecting the thrust oscillation of the end-burning grain solid rocket engine, can effectively guide the design of the end-burning grain solid rocket engine, and meets the needs of engineering practical applications.

[0043] 2. Applying the thrust oscillation control method of the end-burning charge solid rocket engine of the present invention can help designers carry out thrust oscillation control targeted, avoiding the high cost problem caused by the traditional thrust oscillation control relying heavily on the engineering experience of designers and being unable to grasp the key factors and only being able to carry out comprehensive treatment of multiple factors. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 It is a schematic flow chart of the method of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0045] In the actual production process, the end-burning grain is usually formed by die casting. Its external dimensions are guaranteed by the die and the process. However, due to the assembly deviation of the die and the fluctuation of the process parameters, the dimensions of the end-burning grain vary; at the same time, due to the adjustment of the propellant formula and the fluctuation of the process parameters for different batches of grains, there are deviations in the burning rate and mechanical properties of the end-burning grains; in addition, there are also dimensional deviations in the processing of engine structural parts, especially the nozzle throat liner; these factors will all cause fluctuations in the engine thrust. Therefore, by analyzing these influencing factors above, determining the key influencing factors and adopting effective measures to control the thrust oscillation amplitude in combination with the actual production is of great significance for reducing the flight control difficulty of unmanned general aircraft and improving the strike accuracy of the aircraft.

[0046] A thrust oscillation control method for an end-burning grain solid rocket engine proposed by the present invention includes the following steps:

[0047] Step 1: Referring to the previous engineering trial production experience and process difficulty, consult with the overall design department to determine the overall engine indicators, and combine with the processing technology, production difficulty, etc. to determine the acceptable range of the overall indicators; where the overall indicators include the median thrust design and the thrust oscillation amplitude.

[0048] Step 2: Determine the design parameters of the solid rocket engine according to the overall indicators; preliminarily determine the structural dimensions of the end-burning grain and performance data such as the propellant burning rate, etc.; in one embodiment of the present invention, the design parameters include the design pressure P c , the engine thrust F, and the throat area A t .

[0049] Step 3: Based on the design parameters, construct a thrust model of the solid rocket engine; based on the expression of the thrust coefficient and combined with the solid rocket engine equilibrium pressure formula, construct a thrust oscillation influence model of the solid rocket engine, and determine the key factors affecting the thrust oscillation through the thrust oscillation influence model.

[0050] Among them, the thrust model is as follows:

[0051] F = C F ·P c ·A t (1)

[0052] Among them, C F is the thrust coefficient, and its calculation formula is as follows:

[0053]

[0054] In the above formula, k is the specific heat ratio of the propellant gas, P e is the nozzle exit pressure, A e is the nozzle exit cross-sectional area, P a is the atmospheric pressure; Γ is a function of the specific heat of the gas, specifically as follows:

[0055]

[0056] Taking the logarithm of both ends of the above thrust model formula (1) and taking the derivative, we can get:

[0057]

[0058] According to the solid rocket engine equilibrium pressure formula:

[0059]

[0060] Among them, c * is the characteristic velocity of the propellant, a is the burning rate coefficient of the propellant, ρ p is the propellant density, s bis the burning surface of the grain, and n is the pressure exponent.

[0061] Taking the logarithm of both sides of the equilibrium pressure formula of the solid rocket motor and differentiating, we can obtain:

[0062]

[0063] Combining formula (4) and (6), the thrust oscillation influence model can be obtained as follows:

[0064]

[0065] Determine the key factors affecting the thrust oscillation through the thrust oscillation model, specifically:

[0066] In the above formula (7), considering the thrust coefficient C F and the characteristic velocity c * are mainly related to the propellant formulation and usually have little deviation; while the propellant density ρ p and the burning surface of the grain s b can be accurately controlled through the process and the variation range is also relatively small; at the same time, although the throat area A t can ensure the size through processing, during the operation of the solid rocket motor, the nozzle throat liner is eroded by high-temperature and high-pressure gas particles, and the influence of the change of the throat area on the thrust oscillation of the engine cannot be ignored. In addition, the pressure exponent n has a greater influence on both the engine thrust F and the burning rate. If the pressure exponent n can be appropriately reduced through process and formulation debugging, the amplitude of the thrust oscillation will be greatly reduced; the burning rate of the propellant directly affects the thrust characteristics of the engine, so it is necessary to strictly control the deviation of the propellant burning rate.

[0067] Therefore, the throat area A t the pressure exponent n, and the deviation of the propellant burning rate are taken as the key factors affecting the thrust oscillation.

[0068] Step 4: According to the initially determined end-burning grain structure size and the propellant burning rate, assign values to the key factors; combine the values of the key factors with the thrust oscillation influence model for solution to obtain the fluctuation range of the thrust oscillation; judge whether the overall indicators all meet the range requirements of the corresponding overall indicators under the fluctuation range of the thrust oscillation, that is, whether the median value of the thrust design is within the acceptable median value range and whether the amplitude of the thrust oscillation is within the acceptable oscillation amplitude range; if the requirements are met, retain the optimized values of the key factors.

[0069] If the corresponding overall indicator range requirements are not met, then:

[0070] Determine the optimization direction of each key factor, optimize the values of the key factors by formulating a design plan, then calculate the fluctuation range of the thrust oscillation again and judge whether the overall index meets the range requirements of the corresponding overall index; repeat this optimization process until the requirements are met and then end. Specifically:

[0071] In the design and production process of the end-burning grain solid rocket engine, in order to control the engine thrust oscillation, the propellant burning rate deviation, the throat area A t and the pressure exponent n should be focused on; strictly control the range of the propellant burning rate deviation, reasonably reduce the pressure exponent n, and reduce the throat area A t The ablation change during the working process can effectively reduce the amplitude of the engine thrust oscillation and improve the interior ballistic stability of the engine.

[0072] Therefore, according to the existing process and processing difficulty, the structural dimensions of the end-burning grain, the performance data such as the propellant burning rate, etc. are adjusted twice to adjust the range of the propellant burning rate deviation and reduce the pressure exponent; at the same time, the ablation resistance performance data of the throat liner is adjusted to reduce the throat area A t The ablation change during the working process.

[0073] The control method provided by the present invention can be applied to the design guidance of the long-duration small-thrust solid rocket engine. The invention can quickly locate the key influencing factors of the thrust oscillation, and can guide the designers to take relevant measures or carry out special key technology research and development targeted, so as to realize the adjustable and controllable amplitude of the thrust oscillation, effectively reduce the trial-and-error cost brought by the comprehensive treatment, ensure the interior ballistic stability of the small-thrust engine during long-duration operation, and greatly improve the accuracy of the unmanned general aircraft.

[0074] The above embodiments are only used to illustrate the technical solutions of the present application, and are not intended to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application, and should all be included in the protection scope of the present application.

Claims

1. A method for controlling the thrust oscillation of a solid rocket motor with an end-burning grain, characterized in that, Including: Determine the overall engine indicators and set the range of acceptable overall indicators; Determine the design parameters of the solid rocket engine according to the overall indicators, and preliminarily determine the structural dimensions of the end-burning grain and the propellant burning rate data; Based on the design parameters, construct a thrust model of the solid rocket engine; based on the expression of the thrust coefficient and combined with the equilibrium pressure formula of the solid rocket engine, establish a thrust oscillation influence model of the solid rocket engine, and determine the key factors affecting thrust oscillation through the thrust oscillation influence model; According to the preliminarily determined structural dimensions of the end-burning grain and the propellant burning rate, assign values to the key factors; combine the values of the key factors with the thrust oscillation influence model for solution to obtain the fluctuation range of thrust oscillation; judge whether the overall indicators all meet the corresponding range requirements of the overall indicators under the fluctuation range of thrust oscillation; if the requirements are met, retain the values of the key factors as the actual design values.

2. The thrust oscillation control method for the end-burning grain solid rocket motor according to claim 1, wherein If the corresponding range requirements of the overall indicators are not met, then: Determine the optimization direction of each key factor, optimize the values of the key factors by formulating a design plan, and then calculate the fluctuation range of thrust oscillation again and judge whether the overall indicators meet the corresponding range requirements of the overall indicators; repeat this process until the requirements are met and then end.

3. The thrust oscillation control method for a end-burning grain solid rocket motor according to claim 1, wherein Determine the key factors affecting thrust oscillation through the thrust oscillation influence model, specifically: Take the throat area A t , the pressure index n, and the deviation of the propellant burning rate as the key factors affecting the thrust oscillation.

4. The thrust oscillation control method for a end-burning grain solid rocket motor according to claim 2, wherein The specific method for determining the optimization direction of each key factor is: Control the range of propellant burning rate deviation, reduce the pressure exponent n, and decrease the throat area A t Ablation changes during operation.

5. The thrust oscillation control method of the end-burning grain solid rocket motor according to claim 2, characterized in that The optimization of the values of the key factors by formulating a design plan includes: Secondarily adjust the structural dimensions of the end-burning grain and the propellant burning rate data according to the existing process and processing difficulty, so as to adjust the range of the propellant burning rate deviation and reduce the pressure exponent; at the same time, adjust the throat liner ablation resistance performance data to reduce the ablation change of the throat area during operation.

6. The thrust oscillation control method for a end-burning grain solid rocket motor according to claim 1, characterized in that, The determination of the overall engine indicators and the setting of the range of acceptable overall indicators include: Refer to the previous engineering trial production experience and process difficulty, negotiate with the overall design department to determine the overall engine indicators, and combine the processing technology and production difficulty to determine the range of acceptable overall indicators; wherein the overall indicators include the median value of thrust design and the amplitude of thrust oscillation.

7. The thrust oscillation control method for a end-burning grain solid rocket motor according to claim 1, characterized in that, The thrust oscillation influence model of the solid rocket engine is as follows: Among them, F is the engine thrust, C F is the thrust coefficient, n is the pressure exponent, c * is the characteristic velocity of the propellant, a is the burning rate coefficient of the propellant, ρ p is the propellant density, s b is the burning surface of the grain, A t is the throat area.

8. The thrust oscillation control method for the end-burning grain solid rocket motor according to claim 7, wherein The specific process of constructing the thrust oscillation influence model of the solid rocket engine is: First, construct a thrust model as follows: F = C F ·P c ·A t (1) Among them, C F is the thrust coefficient, and its calculation formula is as follows: In the above formula, k is the specific heat ratio of the propellant gas, P e is the nozzle exit pressure, A e is the nozzle exit cross-sectional area, P a is the atmospheric pressure; Γ is a function of the specific heat of the gas, specifically as follows: Take the logarithm of both ends of the above thrust model formula (1) and take the derivative to obtain: According to the equilibrium pressure formula of the solid rocket engine: Among them, c * is the characteristic velocity of the propellant, a is the burning rate coefficient of the propellant, ρ p is the propellant density, s b is the burning surface of the grain, and n is the pressure exponent; Take the logarithm of both sides of the equilibrium pressure formula of the solid rocket engine and take the derivative to obtain: Combine formula (4) and (6) to obtain the thrust oscillation influence model.

9. A terminal device, comprising a processor, a memory, and a computer program stored in the memory; characterized in that, When the processor executes the computer program, it realizes the thrust oscillation control method of the end-burning grain solid rocket engine according to any one of claims 1 to 8.

10. A computer-readable storage medium storing a computer program therein; characterized in that, When the computer program is executed by the processor, it realizes the thrust oscillation control method of the end-burning grain solid rocket engine according to any one of claims 1 to 8.

Images