Guidance rocket inner trajectory matching parameter design method for reducing peak heat flow

Abstract

The invention discloses a guided rocket inner ballistic proportioning parameter design method for reducing peak heat flow, which puts forward design requirements on guided rocket engine inner ballistic parameters from the perspective of overall design, introduces inner ballistic curve proportioning parameters, and realizes reduction of outer ballistic peak heat flow by optimizing the proportioning parameters. The matching parameters are iterated through a double-loop optimization framework, the outer loop aims at reducing peak heat flow, the inner loop is rapidly evaluated through a ballistic optimization method, and the optimal matching parameters of the inner ballistic of the guided rocket engine are rapidly obtained. According to the method, integrated design of the inner trajectory and the outer trajectory of the guided rocket is achieved, the design dimension of the guided rocket is increased, a new scheme optimization approach is provided for overall designers, and the adaptation degree of an overall scheme and an engine scheme is improved.

Description

Technical Field

[0001] The invention belongs to the field of rocket technology, and in particular relates to a method for designing internal ballistic ratio parameters of a guided rocket for reducing peak heat flux. Background Art

[0002] In order to obtain sufficient range capability, boost-glide ammunition represented by guided rockets needs to accumulate sufficient mechanical energy in the active phase, which requires the solid rocket engine to have greater energy. Since guided rockets usually use a central side-burning charge, the engine working time does not change much under the condition of unchanged caliber, so the energy improvement of solid rocket engines is mainly reflected in the increase in thrust, that is, the guided rocket accelerates faster. Since heat flux is proportional to the high power of velocity, faster acceleration leads to a greater velocity at the same height, which will cause a sharp increase in peak heat flux.

[0003] In order to address the structural thermal risks caused by the increase in peak heat flux, conventional design methods use methods such as replacing more efficient missile thermal protection materials or using high-temperature alloys to reinforce high heat flux areas such as the head stagnation point and the leading edge of the rudder to enhance the guided rocket's tolerance to high heat flux. However, these changes have a significant impact on the missile body shape, total missile weight, and comprehensive cost, affecting the optimality of the overall solution.

[0004] It can be seen that improving the range capability of guided rockets and the thermal environment on the missile are contradictory. It is necessary to explore the overall design method that can both improve the range capability and improve the thermal environment on the missile from the mechanism. Since the solid rocket engine does not have the intermediate shutdown and flow regulation function after ignition, the speed change process of the guided rocket after launch is closely related to the internal ballistics, and the speed distribution in space determines the heat flow state of each point on the trajectory. Therefore, the acceleration characteristics of the guided rocket can be improved from the perspective of adjusting the internal ballistics, thereby affecting the external ballistic thermal environment.

[0005] Compared with structure, control, and electrical, solid rocket engines are relatively independent components in the overall design. The evaluation criteria for the performance of solid rocket engines are generally reflected in total impulse, specific impulse, and mass ratio. In actual design, the interaction with the overall design is generally only at the usage level. The overall design usually does not require the form of the guided rocket's internal ballistic curve. Summary of the invention

[0006] In order to overcome the shortcomings of the prior art, the present invention provides a method for designing the internal ballistic ratio parameters of a guided rocket that reduces the peak heat flux. From the perspective of overall design, the design requirements for the internal ballistic parameters of the guided rocket engine are proposed, and the internal ballistic curve ratio parameters are introduced. The reduction of the external ballistic peak heat flux is achieved by optimizing the ratio parameters. The ratio parameters are iterated using a dual-loop optimization framework, in which the outer loop aims to reduce the peak heat flux, and the inner loop uses a ballistic optimization method for rapid evaluation, so as to achieve rapid acquisition of the optimal ratio parameters of the internal ballistics of the guided rocket engine. The present invention realizes the integrated design of the internal and external ballistics of the guided rocket, increases the design dimension of the guided rocket, provides a new solution optimization path for the overall designer, and improves the degree of adaptation between the overall solution and the engine solution.

[0007] The technical solution adopted by the present invention to solve the technical problem is as follows:

[0008] Step 1: Modeling the internal ballistic ratio parameters to reduce the peak heat flux;

[0009] Step 1-1: Use the average thrust to evaluate the compatibility of the internal trajectory with the overall design; total , Engine operating time t s Under these conditions, the thrust P is expressed as:

[0010]

[0011] Step 1-2: Introduce the ratio parameters k1 and k2, where k1 is the total impulse ratio of the first thrust to the second thrust of the solid rocket engine; k2 is the ratio of the working time of the first thrust to the second thrust;

[0012] When k1=1 and k2=1, it corresponds to a single-chamber single-thrust engine; when the two are not equal to 1, it corresponds to a single-chamber dual-thrust engine;

[0013] The engine thrust corresponding to the ratio parameters k1 and k2 is expressed as:

[0014]

[0015] Step 1-3: The dynamic model used for the exterior ballistic calculation is as follows:

[0016]

[0017] Where: r is the current distance from the center of the earth; V is the speed of the guided rocket; θ is the local ballistic inclination; S is the range; α is the angle of attack; X is the drag, Y is the lift; g is the local gravitational acceleration; m is the mass of the whole missile; mdot is the engine flow rate per second;

[0018] Taking r, S, V, θ, m, α as state variables, the rate of change of angle of attack As the control variable, the connection between the angle of attack and the rudder angle is established by the instantaneous equilibrium assumption.

[0019] Step 2: A method for determining the internal ballistic ratio parameters of a guided rocket to reduce the peak heat flux;

[0020] Step 2-1: Use the nonlinear interior point method to establish an optimization model, where the performance indicator is the minimum peak heat flux, that is:

[0021] J=q s,max (10)

[0022] Step 2-2: The dynamic calculation of the complete external ballistics is used as the dynamic equation for optimizing the internal ballistics ratio parameters. The external ballistics is calculated using multi-constraint fixed-range trajectory optimization. The constraints of the heat flow, overload and dynamic pressure processes are set as follows:

[0023] q s ≤q max (11)

[0024]

[0025] q=0.5ρV 2 ≤q max (13)

[0026] Step 2-3: To prevent the external ballistic form from affecting the iteration results of the internal ballistic ratio parameters, the external ballistic performance index is set to minimize the total change rate of the instruction:

[0027]

[0028] Step 2-4: Use an iterative framework to determine the ratio parameters k1 and k2;

[0029] At the beginning of the iteration, the initial values ​​of k1 and k2 are given first, and the iteration starts from the single-chamber single-thrust internal ballistic form; the internal ballistics of the engine is determined according to the total impulse, working time, and charge amount provided by the engine professional; the internal ballistics is substituted into the external ballistic dynamics equation to perform multi-constraint fixed-range external ballistic calculations. After the external ballistics meets the cutoff conditions, the corresponding peak heat flux is transferred to the k1 and k2 optimization loops to determine whether the cutoff conditions are met; if they are met, the corresponding k1 and k2 values ​​are output, if not, enter the next iteration.

[0030] Preferably, the initial values ​​of k1 and k2 are set to k1=1 and k2=1.

[0031] The beneficial effects of the present invention are as follows:

[0032] Different from the passive heat protection of existing guided rockets, the method proposed in the present invention improves the acceleration characteristics of the guided rocket during the boost process from the perspective of the internal ballistics of the guided rocket engine, thereby actively reducing the peak heat flux, avoiding the large-scale use of high-value thermal protection materials, and simplifying the body design to avoid the increase in mass due to heat protection investment. By adopting this method, the integrated design of the internal and external ballistics of the guided rocket is realized, the design dimension of the guided rocket is increased, and a new solution optimization path is provided for the overall designer, which improves the degree of adaptation between the overall solution and the engine solution.

[0033] This method is simple, reliable, and has clear physical meaning. The iterative process of the guided rocket engine ratio parameters is simple. Without significantly affecting the overall plan, the method can improve the adaptability of conventional materials to the high heat flux environment brought about by the requirements of medium and long-range ranges through the change of a single discipline of the guided rocket engine, realize the active reduction of the heat load during flight, and effectively improve the energy efficiency of the solid rocket engine. This method has been verified by the design and flight of multiple guided rockets, and has good engineering reference value for improving the overall performance of guided rockets. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 is a flow chart of the method of the present invention;

[0035] Figure 2 A schematic diagram showing the comparison of heat flow curves of different ratio parameters in the embodiments of the present invention;

[0036] Figure 3 A schematic diagram showing comparison of ballistic curves of different mixing parameters according to an embodiment of the present invention;

[0037] Figure 4 A schematic diagram showing a comparison of thrust forms at the beginning and end of iterations in an embodiment of the present invention;

[0038] Figure 5 A schematic diagram showing the comparison of heat flow curves at the beginning and end of iteration in an embodiment of the present invention;

[0039] Figure 6 Schematic diagram of comparison of velocity and height curves at the beginning and end of iteration according to an embodiment of the present invention. DETAILED DESCRIPTION

[0040] The present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0041] The technical problem to be solved by the present invention is: how to influence the acceleration characteristics of the guided rocket's external ballistics through the optimization design of the internal ballistic ratio parameters of the guided rocket engine, thereby reducing the external ballistic peak heat flux of the guided rocket, improving the thermal environment on the guided rocket, reducing the heat protection cost, and improving the optimality of the overall solution.

[0042] The heat flux that an object is subjected to when flying in the atmosphere is related to the incoming flow density, structural parameters, flight speed, etc. Among them, the structural parameters are basically solidified with the aerodynamic shape, overall layout, etc., and reducing the peak heat flux requires starting with the incoming flow density and flight speed. The flight speed is related to the range requirements of the guided rocket. The maximum speed of the solid rocket engine at the moment of shutdown basically determines the range that the guided rocket can cover. Therefore, the problem of actively reducing the peak heat flux is transformed into how to reduce the environmental density of the guided rocket at that location without affecting the range capability of the guided rocket, thereby significantly reducing the peak heat flux.

[0043] Since the incoming flow density is related to the flight altitude, for guided rockets, along with the determination of the power scheme, the maximum climbing altitude that can be achieved and the maximum speed at the engine shutdown point are basically determined. Because the atmospheric density decays exponentially with the flight altitude, by limiting the maximum speed that can be achieved in the high-density area and extending the acceleration duration in the low-density area, it is possible to achieve effective utilization of energy and increase the flight altitude at the time of solid rocket engine shutdown. In the existing overall design process, usually only the engine specific impulse, total impulse, mass ratio, etc. are constrained, while there are fewer constraints on the internal ballistic form of the guided rocket engine, and the beneficial regulation of the solid rocket internal ballistics on the external ballistic acceleration process is not fully utilized.

[0044] In order to solve the above technical problems, the present invention proposes design requirements for the internal ballistic parameters of the guided rocket engine from the perspective of overall design, introduces the internal ballistic curve ratio parameters, and realizes the reduction of the external ballistic peak heat flux by optimizing the ratio parameters. The ratio parameters are iterated using a dual-loop optimization framework, in which the outer loop aims to reduce the peak heat flux, and the inner loop uses a ballistic optimization method for rapid evaluation, so as to realize the rapid acquisition of the optimal ratio parameters of the internal ballistics of the guided rocket engine.

[0045] Example:

[0046] The present invention discloses a method for designing the internal ballistic ratio parameters of a guided rocket for reducing the peak heat flux. The specific implementation process is as follows:

[0047] (1) Analysis of heat flow and its influencing factors during flight;

[0048] For ground-launched aircraft such as guided rockets, the interaction between the projectile and the dense atmosphere gradually increases during the boost phase as the flight speed gradually increases, which is mainly reflected in the changes in the force and thermal environment of the aircraft. The former is reflected in the increase in aerodynamic force and aerodynamic torque of the aircraft after the dynamic pressure increases; the latter is reflected in the gradual increase in aerodynamic heating of the projectile after the flight speed increases. Generally, the key point for the peak heat flow is near the end of the active phase.

[0049] As the range requirements of guided rockets increase, the range capability of such boost-glide vehicles, which are characterized by powered boost and unpowered gliding, is directly related to the mechanical energy obtained at the engine shutdown point. Therefore, under existing technical conditions, long-range is bound to increase the peak heat flux, and the increase in peak heat flux will force the overall designers to use high-value thermal protection materials, resulting in an increase in structural weight and missile body costs. Therefore, it is necessary to analyze the key factors affecting the peak heat flux and explore low-cost methods to reduce the peak heat flux.

[0050] Heat flux q of the missile body during atmospheric flight s The calculation formula is as follows:

[0051]

[0052] Where: q s is the heat flux at the projectile head stagnation point; R is the radius of the stagnation point at the position of interest, which is generally taken as the head stagnation point; ρ ∞ is the incoming flow density; v ∞ It is the speed at the free stream, usually the flight speed of the guided rocket.

[0053] It can be seen that the heat flux at the stagnation point of the projectile is proportional to the square root of the atmospheric density at the altitude, proportional to the 3.15th power of the flight speed, and inversely proportional to the square root of the stagnation radius. Since the increase of the stagnation radius will lead to the increase of the projectile resistance, it has a greater impact on the range capability. Generally, a suitable stagnation radius is determined by aerodynamics and structure. Therefore, reducing the peak heat flux is converted into reducing the atmospheric density and flight speed at the location where the peak heat flux occurs. The reduction in flight speed will lead to insufficient initial kinetic energy in the unpowered section, which has a greater impact on the range capability. Therefore, for guided rockets, the key to reducing the peak heat flux is to reduce the atmospheric density corresponding to the maximum speed.

[0054] The commonly used two-parameter exponential model for atmospheric density is as follows:

[0055]

[0056] Where ρ is the atmospheric density; ρ0 = 1.2250 kg / m 3 , is the atmospheric density at sea level; h s is the normalized altitude of atmospheric density corresponding to the model, which is generally 6700m; h is the actual altitude. It can be seen that the atmospheric density decays exponentially with altitude, so reducing the peak heat flux of the guided rocket can be achieved by increasing the altitude at which the solid rocket engine boost ends.

[0057] During the active phase of the guided rocket flight, the aerodynamic force on the guided rocket is a small amount relative to the thrust of the solid rocket engine. The internal ballistic form of the solid rocket engine determines the acceleration process of the guided rocket during the boost process, and ultimately determines the flight altitude and flight speed of the guided rocket at the end of the boost. Therefore, the heat flow of the external ballistics can be affected by designing the parameters of the engine's internal ballistics.

[0058] (2) Modeling of internal ballistic ratio parameters to reduce peak heat flux;

[0059] In the overall design process, the average thrust can be used to evaluate the compatibility of the internal trajectory with the overall design. total , Engine operating time t s Under these conditions, the thrust P can be expressed as:

[0060]

[0061] In order to increase the dimension of internal ballistic design, the ratio parameters k1 and k2 are introduced. Among them, k1 is the total impulse ratio of the first thrust to the second thrust of the solid rocket engine; k2 is the ratio of the working time of the first thrust to the second thrust. When k1 = 1 and k2 = 1, it corresponds to a single-chamber single-thrust engine; when the two are not equal to 1, it corresponds to a single-chamber dual-thrust engine. The engine thrust corresponding to the ratio parameters k1 and k2 can be expressed as:

[0062]

[0063] The dynamic model used for the exterior ballistics calculation is as follows:

[0064]

[0065]

[0066] In the formula: r is the current distance from the center of the earth; V is the speed of the guided rocket; θ is the local ballistic inclination; S is the range; P is the engine thrust; α is the angle of attack; X is the drag, Y is the lift; g is the local gravity acceleration; m is the total mass of the missile; mdot is the engine flow rate per second. With r, S, V, θ, m, α as state quantities, the rate of change of angle of attack is As the control variable, the connection between the angle of attack and the rudder angle is established by the instantaneous equilibrium assumption.

[0067] (3) Method for determining the internal ballistic ratio parameters of guided rockets to reduce peak heat flux;

[0068] In order to determine the values ​​of the internal ballistic ratio parameters k1 and k2, the nonlinear interior point method is used to establish an optimization model, in which the performance index is the minimum peak heat flux, that is:

[0069] J=q s,max (10)

[0070] The dynamic calculation of the complete external ballistics is used as the dynamic equation for optimizing the internal ballistics ratio parameters. The external ballistics is calculated using multi-constrained fixed-range trajectory optimization. The constraints of the heat flow, overload and dynamic pressure processes are set as follows:

[0071] q s ≤q max (11)

[0072]

[0073] q=0.5ρV 2 ≤q max (13)

[0074] In order to avoid the influence of the external ballistic form on the iteration result of the internal ballistic ratio parameters, the external ballistic performance index is set to minimize the total change rate of the instruction:

[0075]

[0076] Use Figure 1 The iterative framework shown is used to determine the ratio parameters k1 and k2. At the beginning of the iteration, the initial values ​​of k1 and k2 are given first. The iteration can be started from the single-chamber single-thrust internal ballistic form, and k1=1 and k2=1 are set; the internal ballistics of the engine is determined according to the total impulse, working time, and charge provided by the engine professional; the internal ballistics is substituted into the external ballistic dynamics equation to perform multi-constrained fixed-range external ballistic calculations. After the external ballistics meets the cutoff conditions, the corresponding peak heat flux is transferred to the k1 and k2 optimization loops to determine whether the cutoff conditions are met; if they are met, the corresponding k1 and k2 values ​​are output, and if not, the next iteration is entered.

[0077] (4) Numerical simulation;

[0078] Taking a certain type of guided rocket as an example, Figure 1 The framework establishes a dual-loop optimization model, with the single-chamber single-thrust internal ballistics as the initial iteration condition. The iterative performance index of the outer loop internal ballistics matching parameter is set to the minimum peak heat flow, and the inner loop external ballistics optimization performance index is set to the minimum instruction change rate. The heat flow and ballistic curves corresponding to different matching parameters during the iteration process are shown in the figure. Figure 2 , Figure 3 As shown. The optimal ratio parameters k1 = 1.1668, k2 = 0.2786 obtained at the end of the iteration, the corresponding internal ballistic curve and the initial iteration condition internal ballistic curve are compared. Figure 4 As shown in the figure, the external ballistic heat flow curve corresponding to the optimal ratio parameters is compared with the initial iteration conditions. Figure 5 As shown in the figure, the corresponding speed and height curves are as follows: Figure 6 The peak heat flux is reduced from 3.20MW / ㎡ to 2.06MW / ㎡, a decrease of 35.6%.

[0079] It can be seen from the calculation results of the example that the use of this method to carry out targeted design of the internal ballistic ratio parameters of the guided rocket can significantly reduce the peak heat flux at the end of the boost phase. When the ratio parameters determined by this patent are used for internal ballistic design, the external ballistics show that the maximum speed does not change much, and the altitude at the end of the active phase increases, which greatly reduces the atmospheric density at this position, and ultimately controls the peak heat flux to a smaller value. In the overall design stage, the internal ballistic ratio parameters determined according to the present invention can be used as the basis for the overall design department to require the engine department to carry out fine-grained regulation of the internal ballistics. It is a typical application of influencing the acceleration characteristics of the external ballistics through the internal ballistics. Its effect has been verified by multiple engineering projects, increasing the design options and design dimensions of the overall designers, and has important engineering application value for improving the optimality of the overall plan and improving the thermal environment on the missile.

Claims

1. A method for designing interior ballistic ratio parameters of a guided rocket to reduce peak heat flux, characterized in that: The steps include: Step 1: Modeling the internal ballistic ratio parameters to reduce the peak heat flux; Step 1-1: Use the average thrust to evaluate the compatibility of the internal trajectory with the overall design; total , Engine operating time t s Under these conditions, the thrust P is expressed as: Step 1-2: Introduce the ratio parameters k1 and k2, where k1 is the total impulse ratio of the first thrust to the second thrust of the solid rocket engine; k2 is the ratio of the working time of the first thrust to the second thrust; When k1=1 and k2=1, it corresponds to a single-chamber single-thrust engine; when the two are not equal to 1, it corresponds to a single-chamber dual-thrust engine; The engine thrust corresponding to the ratio parameters k1 and k2 is expressed as: Step 1-3: The dynamic model used for the exterior ballistic calculation is as follows: Where: r is the current distance from the center of the earth; V is the speed of the guided rocket; θ is the local ballistic inclination; S is the range; α is the angle of attack; X is the drag, Y is the lift; g is the local gravitational acceleration; m is the mass of the whole missile; mdot is the engine flow rate per second; Taking r, S, V, θ, m, α as state variables, the rate of change of angle of attack As the control variable, the connection between the angle of attack and the rudder deflection angle is established by the instantaneous equilibrium assumption; Step 2: A method for determining the internal ballistic ratio parameters of a guided rocket to reduce the peak heat flux; Step 2-1: Use the nonlinear interior point method to establish an optimization model, where the performance indicator is the minimum peak heat flux, that is: J=q s,max (10) Step 2-2: The dynamic calculation of the complete external ballistics is used as the dynamic equation for optimizing the internal ballistics ratio parameters. The external ballistics is calculated using multi-constraint fixed-range trajectory optimization. The constraints of the heat flow, overload and dynamic pressure processes are set as follows: q s ≤q max (11) q=0.5ρV 2 ≤q max (13) Step 2-3: To prevent the external ballistic form from affecting the iteration results of the internal ballistic ratio parameters, the external ballistic performance index is set to minimize the total change rate of the instruction: Step 2-4: Use an iterative framework to determine the ratio parameters k1 and k2; At the beginning of the iteration, the initial values ​​of k1 and k2 are given first, and the iteration starts from the single-chamber single-thrust internal ballistic form; the internal ballistics of the engine is determined according to the total impulse, working time, and charge amount provided by the engine professional; the internal ballistics is substituted into the external ballistic dynamics equation to perform multi-constraint fixed-range external ballistic calculations. After the external ballistics meets the cutoff conditions, the corresponding peak heat flux is transferred to the k1 and k2 optimization loops to determine whether the cutoff conditions are met; if they are met, the corresponding k1 and k2 values ​​are output, if not, enter the next iteration.

2. A method for designing interior ballistic ratio parameters of a guided rocket for reducing peak heat flux according to claim 1, characterized in that: The initial values ​​of k1 and k2 are set to k1=1 and k2=1.

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