Design method of variable thrust engine jet pipe profile for inhibiting thrust overshoot

Abstract

The invention discloses a design method of a variable thrust engine nozzle profile for inhibiting thrust overshoot, which comprises the following steps: step 1, establishing a relationship among a throat bolt configuration, a throat bolt position and a throat area by utilizing a search algorithm, and solving to obtain an equivalent minimum throat area; 2, calculating the estimated thrust of the engine according to the equivalent minimum throat area; 3, the position of the throat bolt is adjusted according to the difference value between the estimated thrust of the engine and the preset thrust of the engine, and profile coordinates of the engine jet pipe are designed according to the position of the throat bolt when the difference value between the estimated thrust of the engine and the preset thrust of the engine is smaller than a preset value; according to the on-demand forward design of the throat bolt molded surface of the variable-thrust engine, the design of the throat bolt molded surface can be realized according to the thrust overshoot inhibition demand; the inner ballistic performance can be adjusted according to an expected rule, for example, thrust overshoot is restrained, and the thrust dynamic adjusting rule and the steady-state rule are kept basically consistent.

Description

Technical Field

[0001] The invention belongs to the field of variable thrust engine nozzle profiles, and in particular relates to a design method for a variable thrust engine nozzle profile for suppressing thrust overshoot. Background Art

[0002] Solid rocket engines are widely used in missiles and rockets. The variable thrust engine is an advanced solid power with energy management capabilities, which helps to improve the maneuverability and combat capability of missiles. The design of the throat plug surface is related to the internal ballistic performance of the engine and restricts the improvement of control accuracy. It is a difficult and key issue in the design of the throat plug engine.

[0003] At present, research at home and abroad is all aimed at specific throat plug shapes, mainly focusing on the adjustment characteristics and performance of throat plugs with simple geometric configurations, such as cones, ellipsoids, segmented cones, etc. It is impossible to design the throat plug shape according to usage requirements, such as specific thrust adjustment rules or suppressing thrust dynamic overshoot. Summary of the invention

[0004] The purpose of the present invention is to provide a design method for a variable thrust engine nozzle profile for suppressing thrust overshoot, so as to solve the problem that the throat plug profile cannot be designed according to the actual thrust overshoot suppression requirements.

[0005] The present invention adopts the following technical solution: a design method for a variable thrust engine nozzle profile for suppressing thrust overshoot, comprising:

[0006] Step 1: Use the search algorithm to establish the relationship between the throat plug configuration, throat plug position and throat area, and solve to obtain the equivalent minimum throat area;

[0007] Step 2: Calculate the estimated thrust of the engine based on the equivalent minimum throat area;

[0008] Step 3: Adjust the position of the throat plug according to the difference between the estimated thrust of the engine and the preset thrust of the engine, and design the surface coordinates of the engine nozzle at the throat plug position when the difference between the estimated thrust of the engine and the preset thrust of the engine is less than the preset value.

[0009] Furthermore, the calculation formula for the equivalent minimum throat area in step 1 is:

[0010]

[0011] In the formula, A t is the equivalent minimum throat area; (x A ,y A ) is the coordinate of the equivalent throat position on the nozzle, (x B ,y B) is the coordinate of the equivalent laryngeal position at the laryngeal plug; (x t0 ,y t0 ) is the coordinate origin; (x t ,y t ) is the coordinate of the throat front edge.

[0012] Furthermore, the calculation method of the estimated thrust F of the engine in step 2 is:

[0013] F=C F P c A T

[0014] In the formula, C F is the thrust coefficient, P c is the combustion chamber pressure, A t is the equivalent minimum throat area.

[0015] The beneficial effects of the present invention are:

[0016] The on-demand forward design of the throat plug profile of the variable thrust engine of the present invention can realize the throat plug profile design according to the thrust overshoot suppression requirement; the internal ballistic performance can be adjusted according to the expected law, such as suppressing the thrust overshoot, so that the thrust dynamic adjustment law is basically consistent with the steady-state law;

[0017] The throat plug profile design of the present invention adopts a numerical method, and the throat plug profile is discretized and then solved. By improving the discrete point density and the accuracy of numerical calculation, a more accurate throat plug profile can be obtained. Through the optimization design of the throat plug profile, the thrust overshoot problem of the throat plug type engine can be suppressed to a certain extent. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the equivalent throat area of ​​the present invention;

[0019] Figure 2 This is a schematic diagram of the initial head profile of the laryngeal plug of the present invention;

[0020] Figure 3 This is a schematic diagram of the throat plug profile design result of the present invention;

[0021] Figure 4 A schematic diagram of the thrust dynamic adjustment results of the optimized design profile, cone and ellipsoid throat plugs of the present invention;

[0022] Figure 5 It is an overshoot enlarged schematic diagram of the thrust dynamic adjustment results of the optimized design profile, cone and ellipsoid throat plugs of the present invention. DETAILED DESCRIPTION

[0023] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0024] The present invention discloses a design method for a nozzle profile of a variable thrust engine for suppressing thrust overshoot, comprising:

[0025] Step 1: Use the search algorithm to establish the relationship between the throat plug configuration, throat plug position and throat area, and solve for the equivalent minimum throat area.

[0026] Before the laryngeal plug profile is designed as required, the initial laryngeal plug head profile can be a simple profile such as an ellipsoid or a pointed cone, such as Figure 2 As shown in the figure, during the adjustment of the throat plug position, the engine equivalent throat changes continuously due to the influence of the throat plug head profile and the nozzle inner profile. The relative position of the equivalent throat area and the nozzle inner profile and the throat plug head profile is shown in Figure 1 As shown in the figure, the engine throat area is the conical annular area formed by the straight line segment AB rotating around the x-axis, which can be expressed as:

[0027]

[0028] Among them, AC and BC are Figure 1 Center straightness length.

[0029] As the position of the throat plug is adjusted, a search algorithm is used to establish a numerical solution for the relationship between the throat plug configuration, throat plug position and throat area. The equivalent minimum throat area A is obtained by calculating the annular area of ​​the cone at different positions. t .

[0030] Among them, the calculation formula of the equivalent minimum throat area is:

[0031]

[0032] Among them, the origin of the coordinate is the front edge of the engine axis throat, x is the axial coordinate position, and y is the radial coordinate. Then, is the coordinate origin, (x t ,y t ) is the coordinate of the throat front edge; A is the equivalent throat position on the nozzle, B is the equivalent throat position at the throat plug, (x A ,y A ) is the coordinate of the equivalent throat position on the nozzle, (x B ,y B ) is the coordinate of the equivalent laryngeal position at the laryngeal plug.

[0033] Step 2: Calculate the estimated engine thrust based on the equivalent minimum throat area

[0034] Ignoring the changes in the engine combustion surface and the erosion effect, the fuel gas is regarded as a perfect gas, and the internal ballistic calculation adopts a zero-dimensional model. The burning rate meets r = aP n For a regular propellant, ignoring the effect of the throat plug on the nozzle efficiency, the thrust coefficient is calculated by the following formula:

[0035]

[0036] The combustion chamber equilibrium pressure formula is:

[0037]

[0038] The engine thrust formula is:

[0039] F=C F P c A t

[0040] In the formula, C F is the thrust coefficient, P e is the nozzle outlet pressure, Pa is the standard atmospheric pressure, P c is the combustion chamber pressure, A e is the nozzle exit area, A t is the throat area, k is the specific heat ratio of the gas, ρ P is the propellant density, C* is the propellant characteristic velocity, a is the burning rate coefficient, A b is the burning surface area and n is the pressure index.

[0041] Step 3: The position of the throat plug is adjusted according to the difference between the estimated thrust of the engine and the preset thrust of the engine, and the profile coordinates of the engine nozzle are designed based on the throat plug position when the difference between the estimated thrust of the engine and the preset thrust of the engine is less than a preset value. The preset value may be 5% of the preset thrust or 10% of the preset thrust.

[0042] The correction coefficient can be given based on experience. Generally, the correction coefficient is between 0.9 and 1.1. After point-by-point correction of the throat plug coordinates, the throat plug profile design that meets the use requirements is obtained. The result of point-by-point correction of the discrete coordinate points of the throat plug profile is as follows: Figure 3 shown.

[0043] It should be noted that the throat plug profile design is carried out using a numerical method. The throat plug profile is discretized and then solved to improve the density of discrete points and the accuracy of numerical calculation to obtain a more accurate throat plug profile. At the same time, the algorithm can be reasonably selected to accelerate convergence and carry out rapid design of the throat plug profile.

[0044] The equivalent minimum throat area solution in the present invention is used to calculate the equivalent throat area when the throat plug of a given initial profile is in different positions, such as Figure 2As shown in FIG. 1 , the initial throat plug head profile can generally be given as a simple profile such as an ellipsoid or a pointed cone. The internal ballistic performance calculation is used to calculate the steady-state internal ballistic performance corresponding to the initial profile throat plug, and obtain the relationship between the engine internal ballistic performance and the throat plug position. Further, according to the throat plug movement law, the thrust dynamic adjustment law is calculated; the overshoot evaluation and throat plug profile correction are used to compare the dynamic internal ballistic performance with the steady state, find out the performance difference points, and find the position of the equivalent throat area corresponding to the difference points on the throat plug profile one by one, and correct the profile coordinates according to the difference with the preset target value. Taking the linear change of thrust with the throat plug position as an example, the result of point-by-point correction of the discrete coordinate points of the throat plug profile is shown in FIG. Figure 4 and Figure 5 After the throat plug profile design is completed, the above steps can be repeated to check the design results.

[0045] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for designing a nozzle profile of a variable thrust engine for suppressing thrust overshoot, characterized in that: include: Step 1: Use the search algorithm to establish the relationship between the throat plug configuration, throat plug position and throat area, and solve to obtain the equivalent minimum throat area; Step 2: Calculate the estimated thrust of the engine based on the equivalent minimum throat area; Step 3: Adjust the position of the throat plug according to the difference between the estimated thrust of the engine and the preset thrust of the engine, and design the surface coordinates of the engine nozzle at the throat plug position when the difference between the estimated thrust of the engine and the preset thrust of the engine is less than the preset value.

2. The method for designing a nozzle profile of a variable thrust engine for suppressing thrust overshoot according to claim 1, characterized in that: The calculation formula for the equivalent minimum throat area in step 1 is: In the formula, A t is the equivalent minimum throat area; (x A ,y A ) is the coordinate of the equivalent throat position on the nozzle, (x B ,y B ) is the coordinate of the equivalent laryngeal position at the laryngeal plug; is the coordinate origin; (x t ,y t ) is the coordinate of the throat front edge.

3. The method for designing a nozzle profile of a variable thrust engine for suppressing thrust overshoot according to claim 2, characterized in that: The estimated thrust F of the engine in step 2 is calculated as: F=C F P c A T In the formula, C F is the thrust coefficient, P c is the combustion chamber pressure, A t is the equivalent minimum throat area.

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