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CN-121997394-A - Wedge-shaped grain design method for impulse method combustion test based on supercharging speed boundary

CN121997394ACN 121997394 ACN121997394 ACN 121997394ACN-121997394-A

Abstract

The invention discloses a wedge-shaped grain design method for impulse method combustion test based on a supercharging speed boundary. The method mainly solves the problem that in the impulse method experiment, when the inner hole surface-enhanced combustion tubular grain is adopted to measure the dynamic combustion speed of the solid propellant under different pressures, the high-pressure index propellant has too high pressure increasing speed in the later period of combustion, so that the combustion speed cannot respond to pressure change in time. The invention has the innovation points that (1) a mathematical relation of the size and the change rate of the area of the combustion surface and the influence of the throat diameter of the spray pipe on the pressurizing rate is established, and a design method for controlling the pressurizing process by regulating the area of the combustion surface is provided. (2) The external wedge-shaped grain is designed on the basis of the traditional tubular grain, so that the area of a combustion surface and the change rate of the combustion surface in the later period of combustion are reduced, and the supercharging rate in the later period of combustion is inhibited. (3) In the process of designing the wedge-shaped grain, the specific design flow of the wedge angle, the cylinder section meat thickness and other grain sizes of the wedge-shaped grain is given by combining the pressurizing speed, and the design flow of the wedge-shaped grain is standardized.

Inventors

  • WEI XIANGGENG
  • WANG YINGHONG
  • SHI XU
  • Cong Junhao
  • CHEN JIAN
  • HE GUOQIANG
  • LIU LINLIN
  • CHEN MAOLIN
  • YANG YUXIN

Assignees

  • 西北工业大学

Dates

Publication Date
20260508
Application Date
20251219

Claims (7)

  1. 1. The wedge-shaped grain design method for impulse method combustion test based on the supercharging speed boundary is characterized by comprising the following steps: step 1, setting an initial value of the throat diameter of a spray pipe; Step 2, according to the given minimum pressure Calculating by using a combustion chamber transient balance pressure formula to obtain an initial combustion surface Initial combustion face The corresponding pressure is lower than the lowest pressure ; Step 3, setting an initial value of the inner diameter of the wedge-shaped charge, and calculating the grain length of the wedge-shaped charge according to the initial combustion surface; Initial setting of the inner diameter of a wedge-type charge 20Mm, initial combustion face The method comprises the following steps: ; calculating grain length of wedge-shaped charge according to initial combustion surface If L <200mm, jumping to step 4; if L is 200mm or more, the inner diameter is specified Too small, the throat diameter of the spray pipe Correcting, gradually reducing the throat diameter of the spray pipe with the step length of 0.2mm, and jumping to the step 1; step 4, calculating the outer diameter of the wedge-shaped charge ; Step 5, calculating the pressurizing rate and determining the wedge angle ; Deriving a transient equilibrium pressure formula in a combustion chamber to obtain a boost rate The method comprises the following steps: ; Wherein the method comprises the steps of Is the combustion rate coefficient; is the pressure index; in order to achieve a propellant density of the propellant, For the area of the combustion surface of the propellant, Is the throat area of the spray pipe, Is a characteristic speed of the propellant; Propellant combustion surface area in combustion chamber transient balance pressure formula Expanding to obtain the pressure intensity when the combustion surface is pushed to the conical section: ; differentiating the pressure formula with time when the combustion surface is positioned on the cylindrical section to obtain a relation between the pressurizing rate of the cylindrical section and the combustion surface: ; The pressure differential of the combustion face when the combustion face is pushed to the cone segment is over time, and a relation between the pressurizing rate of the cone segment and the combustion face is obtained: ; Because the pressure continuously rises during the test, the combustion area must continuously increase, the wedge angle Satisfies the following formula: ; calculating the pressure boost rate and time curve of the tubular charge according to the relation between the cylindrical section pressure boost rate and the combustion surface to reserve a certain pressure boost rate margin, when the pressure boost rate is equal to one half of the pressure boost rate, namely When the current time t 1 is considered as the time when the combustion of the cylindrical section is finished and the combustion of the frustum section is started, the thickness of the cylindrical section at the time t 1 is determined according to the A b -t curve Determining cone section meat thickness L y according to the cylindrical section meat thickness, wherein Is a threshold value of the boost rate; Set wedge angle Is 90 °; Calculating the pressure intensity and the pressurizing rate according to the relation between the pressure intensity and the pressurizing rate of the frustum and the combustion surface when the combustion surface is pushed to the frustum section, and if the relation between the pressure intensity and the pressurizing rate of the frustum and the combustion surface simultaneously meets the requirement condition A and the requirement B, obtaining the wedge angle Meets the requirement, and if any condition of the condition A and the condition B is not met, the wedge angle Step 5 is repeated by taking 10 degrees as step length and step length of the throat diameter of the spray pipe as step length and step length of 0.2mm and calculating corresponding pressure through updated throat diameter of the spray pipe; The finally obtained wedge angle Inner diameter of Outer diameter of Length of grain Throat diameter of spray pipe Cylindrical section meat thickness The size of the final wedge-shaped medicine column is obtained.
  2. 2. The wedge grain design method for impulse method combustion test based on the supercharging speed boundary as claimed in claim 1, wherein the step of determining the critical value of the supercharging speed is: step 5-1, obtaining the combustion speed change rate of the propellant under the existence of the pressurizing rate; The combustion speed change rate is the ratio of the difference between the static pressure combustion speed and the dynamic pressure combustion speed to the response time of the dynamic pressure combustion speed, and the static pressure combustion speed of the propellant under constant pressure is The corresponding dynamic pressure burning speed is that when the pressure is changed rapidly Dynamic pressure burning speed slave Becomes as follows Is time-consuming in the process of I.e. Response time for dynamic pressure burn rate; Is the combustion rate coefficient; is the pressure intensity; The static pressure burning rate of the propellant under constant pressure is ; The corresponding dynamic pressure burning speed is that when the pressure is changed rapidly Dynamic pressure burning speed slave Becomes as follows Is time-consuming in the process of I.e. Response time for dynamic pressure burn rate; The rate of change of the combustion speed The method comprises the following steps: ; Wherein the method comprises the steps of N is the pressure index; the response hysteresis degree of the dynamic pressure burning speed to the pressure change is represented; S5-2, performing term transfer on the expression of the combustion speed change rate to obtain dynamic pressure combustion speed and a dynamic relation between the combustion speed change rate and pressure; Rate of change of combustion speed The expression of (2) is subjected to term transfer to obtain dynamic pressure burning speed and dynamic relation of burning speed change rate and pressure: The dynamic relation between the dynamic pressure burning speed, the burning speed changing speed and the pressure is a classical first-order dynamic differential equation, the dynamic relation between the dynamic pressure burning speed, the burning speed changing speed and the pressure is a first-order inertia link, when the pressure is unchanged, namely When the Viyer equation is equivalent to the dynamic pressure burning speed and the dynamic relation between the burning speed changing rate and the pressure; S5-3, determining boundary conditions of dynamic pressure burning speed and timely response pressure change; At a rate of pressurization When larger, due to Is greater than zero, so the combustion speed of the dynamic pressure and the dynamic relation between the combustion speed change rate and the pressure are obtained The dynamic pressure burn rate at which the boost rate exists is therefore less than the static pressure burn rate at steady state, and therefore appears to be when the boost rate When the dynamic pressure burning speed is larger, the dynamic pressure burning speed response is lagged; in order to ensure that the dynamic pressure burning speed timely responds to the change of the pressure, the boundary conditions for determining the dynamic pressure burning speed timely responding to the change of the pressure are as follows: when the requirement of timely responding to the pressure change boundary condition of the dynamic pressure burning speed is met, the dynamic pressure burning speed can timely respond to the pressure change, namely the dynamic relation between the Vieri formula and the dynamic pressure burning speed and the dynamic relation between the burning speed change rate and the pressure are equivalent; S5-4, deriving time by a Viyer equation according to a boundary condition that dynamic pressure burning speed timely responds to pressure change, and obtaining a boundary condition of a supercharging rate; Deriving time from the Viyer equation: The boundary conditions for bringing the result obtained by deriving the time by the Viwill formula into the dynamic pressure burning speed and responding to the change boundary conditions of the pressure in time to obtain the supercharging speed are as follows: S5-5, determining a critical value of the supercharging speed and a supercharging speed interval; the product of the change rate of the burning rate and the response time of the dynamic pressure burning rate is smaller than the dynamic pressure burning rate Is critical, i.e Calculating the critical value of the pressurizing rate to be I.e. A pressurizing rate interval for timely responding the dynamic pressure burning rate of the propellant to the pressure, and a response time of the dynamic pressure burning rate Is a key parameter for representing the dynamic response characteristic of the combustion state of the solid propellant; The smaller the value, the stronger the response capability of the propellant burning speed to the pressure change, the larger the critical value of the pressurizing rate, the burning speed response time Is a key parameter for measuring the dynamic response characteristic of the propellant; the smaller the threshold value is, the stronger the response capability of the burning speed of the propellant to the pressure change is, and the larger the threshold value of the pressurizing speed can be responded; the threshold value of the boost rate is: the minimum time interval for the combustion speed measurement based on the impulse method is 0.05s, so the combustion speed response time is required Not more than 0.005s, adopt For 0.005s as a reference value, i.e. it is believed that the propellant burn rate achieves a timely response to pressure changes within 0.005 s.
  3. 3. The method for designing a wedge-shaped grain for impulse combustion test based on a supercharging speed boundary as claimed in claim 1, wherein the nozzle throat diameter is as follows The initial value of (2) was 7mm.
  4. 4. The method for designing wedge-shaped grains for impulse combustion test based on a supercharging rate boundary as claimed in claim 1, wherein the formula of the transient equilibrium pressure of the combustion chamber is: (1) Wherein, P is pressure; In order to achieve the combustion speed, ; Is the combustion rate coefficient; is the pressure index; in order to achieve a propellant density of the propellant, For the area of the combustion surface of the propellant, Is the throat area of the spray pipe, Is a characteristic speed of the propellant.
  5. 5. The method for designing wedge-shaped grains for impulse method combustion test based on supercharging speed boundary as claimed in claim 1, wherein the outer diameter of the wedge-shaped charge is calculated The method comprises the following steps: propellant face area in transient equilibrium pressure formula in combustion chamber Expanding to obtain the pressure intensity when the combustion surface is positioned on the cylinder section: ......(2) Calculating according to a pressure formula when the combustion surface is positioned in the cylinder section to obtain a first outer diameter candidate value ; Calculating a second outside diameter candidate value The method comprises the following steps: when the pressure index n is more than 0.55, the range of the meat thickness e is more than or equal to 20mm under the premise of ensuring the burning time, and a second external diameter candidate value is obtained ; When the pressure index n < = 0.55, the wedge-shaped charge cannot meet the design requirement; external diameter of wedge-shaped charge The method comprises the following steps: Wherein To take the first outer diameter candidate and the maximum value of the first outer diameter candidate.
  6. 6. The wedge grain design method for impulse method combustion test based on the supercharging speed boundary as claimed in claim 1, wherein the condition a and the condition B are respectively: The pressure is larger than the maximum pressure required to be tested; The supercharging speed is less than 80% of the critical value of the supercharging speed.
  7. 7. A computer readable storage medium having a computer program stored therein, characterized in that the computer program, when executed by a processor, implements the wedge grain design method for impulse method combustion test based on a supercharging rate boundary according to any one of claims 1-6.

Description

Wedge-shaped grain design method for impulse method combustion test based on supercharging speed boundary Technical Field The invention belongs to the technical field of solid propellant combustion performance test, and particularly relates to a wedge-shaped grain design method for impulse method combustion test based on a supercharging rate boundary. Background The solid propellant is used as the energy source and working medium of solid rocket engine, and is the important power source of missile and rocket. The burning rate of the solid propellant is the distance of solid phase disappearance in the normal direction of the burning surface of the solid propellant in unit time, and is a key performance parameter in the process of developing the solid propellant formula and designing the solid rocket engine. The pressure is a main environmental factor influencing the burning speed of the solid propellant, and the development of the combustion characteristic research of the solid propellant in a wide pressure range is an important premise and foundation for the design of a solid rocket engine. In the impulse method for measuring the burning rate of solid propellant, it is proposed to utilize the inner hole to burn the tubular charge in the engine test, and calculate the burning rate under different pressure spans by the thrust-time curve and the pressure-time curve measured by one experiment. The method for judging the ignition synchronism of the impulse method solid propellant combustion speed test is introduced in the impulse method solid propellant combustion speed test original data validity judgment, and the impulse method is realized on the premise that combustion can instantaneously respond to pressure change. However, when the rate of pressurization is too large, combustion cannot respond instantaneously to pressure changes, and thus control of the rate of pressurization is a problem that must be considered in impulse testing. Particularly, for the propellant with high pressure index (n is more than 0.55), the self-combustion speed is higher, the combustion speed is more easily influenced by pressure due to the high self-combustion speed and the high pressure index (n is more than 0.55), and the mass of the propellant combusted in unit time in the later period of combustion is large, so that the mass of generated gas is large, and the supercharging speed is overlarge. Disclosure of Invention In order to solve the problem that in the impulse method combustion speed test, when the inner hole surface-increasing combustion tubular grain is adopted to measure the dynamic combustion speed of a solid propellant under different pressures, the high-pressure index propellant can have too high supercharging speed at the later stage of combustion, so that the combustion speed cannot respond to pressure change in time. According to the solid rocket engine principle, the transient equilibrium pressure formula in the combustion chamber is: (1) deriving a transient equilibrium pressure formula in a combustion chamber to obtain a boost rate The method comprises the following steps: (3) Wherein P is pressure; In order to achieve the combustion speed, ;Is the combustion rate coefficient; is the pressure index; in order to achieve a propellant density of the propellant, For the area of the combustion surface of the propellant,Is the throat area of the spray pipe,Is a characteristic speed of the propellant; according to the formulas (1) and (3), the pressure P and the area of the combustion surface of the propellant Positive correlation, boost rateArea of combustion surface with propellantRate of change of propellant fuel surface area over timeProportional to the area of the combustion surface of the propellantRate of change of propellant fuel surface area over timeAt a reduced boost rateIn the impulse method combustion speed test, the traditional tubular grain is carried out along with combustion, and the area of the combustion surface of the propellant is reducedThe continuous increase causes a rapid rise in pressure P. For high pressure index propellants with n >0.55, the burn rateIs extremely sensitive to pressure changes, and when the pressure changes rapidly, a phenomenon that the combustion speed response lags behind the pressure changes occurs. It follows from equation (2) that the rate of pressurization of the propellant can be limited by reducing its area size and rate of rise of the fuel. The new charge is required to have a constant surface area relative to the surface area of the tubular charge at the earlier stage of combustion, and the surface area increase rate at the later stage of combustion is reduced, thereby suppressing the rate of pressurization. The outer wedge-shaped grain is thus proposed after a geometrical adjustment on the basis of the tubular grain. The wedge-shaped grain design method for impulse method combustion test based on the supercharging speed boundary comprises the following steps: