Calculation method for characteristic velocity efficiency of solid propellant

Abstract

The invention relates to a method for calculating the characteristic velocity efficiency of a solid propellant, which comprises the following steps of: firstly, carrying out multi-component quantitative analysis on a pretreatment product consisting of active aluminum, aluminum nitride and aluminum oxide after a combustion product of a target solid propellant is pretreated to determine the contents of the three components; then calculating the actual combustion efficiency of the active aluminum based on the contents of the three components, and then substituting the actual combustion efficiency into a fitting relational expression of the actual combustion efficiency of the active aluminum and the characteristic velocity efficiency of the target solid propellant to calculate the characteristic velocity efficiency of the target solid propellant. According to the method, complete engine test run is not needed, errors caused by nozzle deformation and combustion chamber pressure sensor signal distortion to characteristic speed efficiency calculation are avoided, the calculation precision is high, the required multi-component quantitative analysis experiment can be at the laboratory level, the cost is low, and the complexity is low.

Description

Technical Field

[0001] The present invention relates to the technical field of solid propellant combustion performance evaluation, and particularly to a calculation method for the characteristic velocity efficiency of solid propellants. Background Art

[0002] Aluminum powder is usually used as the main energy-providing fuel in solid propellants for engines. Adding aluminum powder can increase the density and specific impulse of solid propellants and suppress high-frequency unstable combustion. The combustion products of solid propellants consist of active aluminum, aluminum nitride, aluminum oxide, and unburned carbon.

[0003] Characteristic velocity is the core parameter for measuring the energy release and combustion efficiency of solid propellants, directly affecting the specific impulse and thrust performance of engines. Characteristic velocity efficiency usually refers to the ratio of the actual characteristic velocity of a solid propellant to the maximum value of the theoretical characteristic velocity, which can represent the combustion adequacy of the solid propellant in an engine. Determining the combustion adequacy of solid propellants can provide reference support for the formulation research and development of propellants. Therefore, it is necessary to calculate the characteristic velocity efficiency of solid propellants.

[0004] The traditional calculation method for the characteristic velocity efficiency of solid propellants is to calculate the percentage of the actual characteristic velocity of the solid propellant obtained by measuring through ground tests of engines and the theoretical value calculated based on thermodynamic models such as the NASACEA software. However, to obtain the actual characteristic velocity through ground tests of engines, a complete solid engine test run is first required to determine the throat area of the engine, determine its average mass flow rate based on the propellant loading and working time, and collect the combustion chamber pressure in real time through a dynamic pressure sensor, calibrate the sensor and eliminate high-frequency noise, and then back-calculate the characteristic velocity through the pressure-flow relationship. The method of obtaining the actual characteristic velocity of solid propellants through ground tests of engines is costly, the process is complex, and the thermal expansion of the nozzle throat at high temperatures will cause additional flow errors. In addition, the pressure-flow relationship used to back-calculate the characteristic velocity is based on the one-dimensional uniform flow assumption, while there are temperature gradients, component stratifications, and local unburned areas in the actual combustion chamber, resulting in the measured value of the combustion chamber pressure only representing the spatial average pressure and being unable to reflect the details of the real flow field. Combustion chamber pressure pulsations will cause sensor signal distortion. Especially in high-frequency oscillation conditions, the dynamic pressure measurement error may exceed 5%, resulting in a large error in the back-calculated characteristic velocity, thereby increasing the cost, complexity, and calculation error of the traditional calculation method for the characteristic velocity efficiency of solid propellants. Summary of the Invention

[0005] Based on this, it is necessary to provide a calculation method for the characteristic velocity efficiency of solid propellants, which has the characteristics of low cost, low complexity, and small error, in view of the above technical problems.

[0006] The present invention provides a calculation method for the characteristic velocity efficiency of solid propellants, comprising the following steps:

[0007] Pre-treat the combustion products of the target solid propellant to obtain a pre-treated product composed of three components: active aluminum, aluminum nitride, and aluminum oxide;

[0008] Determine the contents of the three components of active aluminum, aluminum nitride, and aluminum oxide in the pre-treated product;

[0009] Calculate the actual combustion efficiency of active aluminum through the difference in the enthalpies of formation of aluminum nitride and aluminum oxide;

[0010] Establish a fitting relationship between the actual combustion efficiency of active aluminum and the characteristic velocity efficiency of the target solid propellant. The fitting relationship between the actual combustion efficiency of active aluminum and the characteristic velocity efficiency of the target solid propellant is a linear fitting relationship, a polynomial fitting relationship, or a Gaussian fitting relationship;

[0011] Substitute the actual combustion efficiency of active aluminum into the fitting relationship between the actual combustion efficiency of active aluminum and the characteristic velocity efficiency of the target solid propellant to obtain the characteristic velocity efficiency of the target solid propellant.

[0012] In one embodiment, the calculation formula for calculating the actual combustion efficiency of active aluminum through the difference in the enthalpies of formation of aluminum nitride and aluminum oxide is:

[0013]

[0014] In the formula, η Al represents the actual combustion efficiency of active aluminum, represents the enthalpy of formation of aluminum oxide, ΔH AlN represents the enthalpy of formation of aluminum nitride, m Al represents the content of active aluminum in the pre-treated product, m AlN represents the content of aluminum nitride in the pre-treated product, represents the content of aluminum oxide in the pre-treated product.

[0015] In one embodiment, the linear fitting relationship between the actual combustion efficiency of active aluminum and the characteristic velocity efficiency of the target solid propellant is:

[0016]

[0017] In the formula, represents the characteristic velocity efficiency of the target solid propellant, a1 = 0.83027 ± 2.32026e-4, b1 = 0.17804 ± 4.01781E-4;

[0018] The polynomial fitting relationship between the actual combustion efficiency of active aluminum and the characteristic velocity efficiency of the target solid propellant is:

[0019]

[0020] Where, a2=0.8221±1.01148E-4, b2=0.22715±3.97107E-4, c2=-0.04911±3.59256E-4;

[0021] The Gaussian fitting relationship between the actual combustion efficiency of activated aluminum and the characteristic velocity efficiency of the target solid propellant is:

[0022]

[0023] Where, y0 = -0.2309 ± 0.42291, x c =1.91952±0.11454, w=6.03593±1.35994, A=9.75332±5.45642.

[0024] In one embodiment, pre-treating the combustion products of the target solid propellant comprises the following steps:

[0025] The combustion products of the target solid propellant are fully ground;

[0026] The combustion products of the fully ground target solid propellant are dried at 75-85° C. for 48-72 hours.

[0027] In one embodiment, determining the content of activated aluminum in the pretreated product comprises the following steps:

[0028] Weigh 0.002-0.02 g of the pretreated product into a 500 mL ground-mouth conical flask, add 30-40 mL of 0.825 mol / L ferric sulfate and 10 mL of 10% dilute sulfuric acid, and boil for 35-45 min to obtain a solid-liquid mixture;

[0029] After the solid-liquid mixture has cooled to room temperature, transfer it to a 250 mL conical flask and add 10-20 mL of a 4:1 phosphorus-sulfuric acid mixture to decolorize the solution.

[0030] Add 0.5-1 mL of sodium diphenylamine sulfonate solution as an indicator and titrate the solid-liquid mixture with 1 / 120 mol / L potassium dichromate solution, recording the volume of potassium dichromate solution consumed.

[0031] The content of active aluminum in the pretreatment product is calculated based on the volume of potassium dichromate solution consumed. The calculation formula is:

[0032]

[0033] Wherein, c represents the concentration of the potassium dichromate standard solution, with the unit of mol / L, V represents the volume of the titrated potassium dichromate solution, with the unit of mL, and m s represents the mass of the pretreatment product placed in a 500 mL ground conical flask, with the unit of g.

[0034] In one of the embodiments, determining the content of aluminum nitride in the pretreatment product includes the following steps:

[0035] Weigh 0.5 - 2 g of the pretreatment product, and determine the content of nitrogen element in the pretreatment product through an inorganic nitrogen analyzer;

[0036] Calculate the content of aluminum nitride according to the conservation of nitrogen element, and the calculation formula is:

[0037]

[0038] Wherein, w(N) represents the content of nitrogen element in the pretreatment product, 41.04 is the molar mass of aluminum nitride, with the unit of g / mol, and 14.01 is the molar mass of nitrogen atom, with the unit of g / mol.

[0039] In one of the embodiments, calculate the content of aluminum oxide in the pretreatment product by the subtraction method, and the calculation formula is

[0040] The beneficial effects of the present invention are as follows: The method of the present invention establishes a fitting relationship between the actual combustion efficiency of active aluminum and the characteristic velocity efficiency of the target solid propellant. This method first conducts multi-component quantitative analysis on the pretreatment product composed of three components, namely active aluminum, aluminum nitride, and aluminum oxide, after the combustion products of the target solid propellant are pretreated to determine the content of the three components. Then, based on the content of the three components, calculate the actual combustion efficiency of active aluminum. Next, substitute the actual combustion efficiency into the fitting relationship between the actual combustion efficiency of active aluminum and the characteristic velocity efficiency of the target solid propellant to calculate the characteristic velocity efficiency of the target solid propellant. The method of the present invention does not require a complete engine test run, avoids the errors brought to the calculation of the characteristic velocity efficiency by the nozzle deformation and the distortion of the combustion chamber pressure sensor signal, has a high calculation accuracy, and the required multi-component quantitative analysis experiment can be at the laboratory level, with low cost and low complexity. Description of the Drawings

[0041] Figure 1 It is a flow schematic diagram of a calculation method for the characteristic velocity efficiency of a solid propellant provided in the embodiment of the present invention;

[0042] Figure 2 It is a schematic diagram of the fitting curve of different fitting relationships;

[0043] Figure 3Schematic diagram of the process for preprocessing the combustion products of the target solid propellant provided in the embodiments of the present invention;

[0044] Figure 4 Schematic diagram of the process for measuring the content of active aluminum in the preprocessed product provided in the embodiments of the present invention;

[0045] Figure 5 Schematic diagram of the process for measuring the content of aluminum nitride in the preprocessed product provided in the embodiments of the present invention. Detailed implementation manners

[0046] Currently, the calculation method for the characteristic velocity efficiency of solid propellants is to calculate the percentage of the actual characteristic velocity C of the solid propellant obtained by measuring through ground tests of the engine * to the theoretical value calculated based on thermodynamic models such as the NASA CEA software.

[0047] The specific calculation formula is:

[0048]

[0049] where the actual C * measures the average mass flow rate of the engine nozzle throat area and the pressure in the combustion chamber through ground tests of the engine, and then calculates the characteristic velocity through the following formula;

[0050]

[0051] In the formula, A t is the nozzle throat area, P c is the combustion chamber pressure, C * is the characteristic velocity, represents the average mass flow rate of the engine nozzle throat area.

[0052] However, there are temperature gradients, component stratifications, and local unburned areas in the actual combustion chamber, resulting in the measured value of the combustion chamber pressure only representing the spatial average pressure and being unable to reflect the details of the real flow field. Combustion chamber pressure pulsations can cause sensor signal distortion. Especially in high-frequency oscillation conditions, the dynamic pressure measurement error may exceed 5%, that is, the error of P c exceeds 5%. In addition, heat transfer on the combustion chamber wall may cause thermal expansion of the nozzle throat area at high temperatures, that is, the finally measured A t has an error, ultimately resulting in a large error in the calculated actual characteristic velocity C * with a large error.

[0053] In the combustion of aluminum-based solid propellants, the main energy-providing fuel is aluminum powder. The combustion of aluminum powder determines the energy performance of the engine. Therefore, the combustion efficiency of aluminum powder can represent the energy release characteristics of the propellant. Based on this, the present invention proposes a calculation method for the characteristic velocity efficiency of solid propellants. The multi-component quantitative analysis method is used to determine the contents of three products in the pretreatment product composed of active aluminum, aluminum nitride, and aluminum oxide after the combustion products of the target solid propellant are pretreated. Then, the actual combustion efficiency of active aluminum is calculated based on the contents of the three components. Next, the actual combustion efficiency is substituted into the fitting relationship between the actual combustion efficiency of active aluminum and the characteristic velocity efficiency of the target solid propellant to calculate the characteristic velocity efficiency of the target solid propellant. In this method, multi-component quantitative analysis can be completed in the laboratory, and other steps are all calculation steps. The whole process has low cost and low complexity. In addition, this method does not require a complete engine test run experiment, avoiding errors in the calculation of the characteristic velocity efficiency caused by nozzle deformation and signal distortion of the combustion chamber pressure sensor, and has high calculation accuracy.

[0054] In order to make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0055] In one embodiment, the calculation method for the characteristic velocity efficiency of solid propellants includes the following steps:

[0056] S101. Pretreat the combustion products of the target solid propellant to obtain a pretreatment product composed of three components: active aluminum, aluminum nitride, and aluminum oxide.

[0057] The combustion products of solid propellants are composed of active aluminum, aluminum nitride, aluminum oxide, and unburned carbon. The purpose of pretreatment is to remove the residual carbon in the combustion products of the target solid propellant.

[0058] S102. Measure the contents of three components: active aluminum, aluminum nitride, and aluminum oxide in the pretreatment product.

[0059] Specifically, in this embodiment, multi-component quantitative analysis is used to determine the contents of the three components.

[0060] S103. Calculate the actual combustion efficiency of active aluminum through the enthalpy of formation difference between aluminum nitride and aluminum oxide.

[0061] Among them, the calculation formula for calculating the actual combustion efficiency of active aluminum through the enthalpy of formation difference between aluminum nitride and aluminum oxide is:

[0062]

[0063] In the formula, η Al represents the actual combustion efficiency of active aluminum. Denotes the enthalpy of formation of alumina, ΔH AlN Denotes the enthalpy of formation of aluminum nitride, m Al Denotes the content of active aluminum in the pretreated product, m AlN Denotes the content of aluminum nitride in the pretreated product Denotes the content of alumina in the pretreated product

[0064] Specifically, when aluminum completely burns to form Al2O3 (α-phase), the energy release efficiency is 100%. The standard enthalpy of formation of the α-phase Al2O3 crystal form is -1675.7 kJ / mol, and the standard enthalpy of formation of AlN, ΔH AlN is -317.6 kJ / mol

[0065] S104. Establish a fitting relationship between the actual combustion efficiency of active aluminum and the characteristic velocity efficiency of the target solid propellant. The fitting relationship between the actual combustion efficiency of active aluminum and the characteristic velocity efficiency of the target solid propellant is a linear fitting relationship, a polynomial fitting relationship, or a Gaussian fitting relationship

[0066] Among them, the linear fitting relationship between the actual combustion efficiency of active aluminum and the characteristic velocity efficiency of the target solid propellant is

[0067]

[0068] In the formula Denotes the characteristic velocity efficiency of the target solid propellant, a1 = 0.83027 ± 2.32026e-4, b1 = 0.17804 ± 4.01781E-4

[0069] The polynomial fitting relationship between the actual combustion efficiency of active aluminum and the characteristic velocity efficiency of the target solid propellant is

[0070]

[0071] In the formula, a2 = 0.8221 ± 1.01148E-4, b2 = 0.22715 ± 3.97107E-4, c2 = -0.04911 ± 3.59256E-4

[0072] The Gaussian fitting relationship between the actual combustion efficiency of active aluminum and the characteristic velocity efficiency of the target solid propellant is

[0073]

[0074] In the formula, y0 = -0.2309 ± 0.42291, x c= 1.91952 ± 0.11454, w = 6.03593 ± 1.35994, A = 9.75332 ± 5.45642.

[0075] Specifically, through the open-source thermodynamics software NASA CEA, the composition of the initial formulation of the solid propellant and the operating conditions are input, and the characteristic velocity C of this formulation is calculated. * This result is the ideal situation obtained when the aluminum powder in the formulation is completely burned, that is, the combustion efficiency is 100%. The characteristic velocity C obtained at this aluminum content in the formulation * is used as the theoretical characteristic velocity when this formulation is completely burned. At this time

[0076] On this basis, the aluminum content in the formulation calculated by the open-source thermodynamics software NASACEA is reduced, and the content of Al2O3 is increased. Since Al2O3 does not participate in subsequent chemical reactions, it can be considered that part of the energy release of aluminum is reduced. At this time, the combustion efficiency is η Ali , and the characteristic velocity calculated again is the actual characteristic velocity at this combustion efficiency (η Ali ). At this time According to this method, the C values at different aluminum powder contents of a group of propellant formulations are calculated. * A set of data for fitting the combustion efficiency η Al and the characteristic velocity efficiency C * is obtained. Then, different fitting methods are used to fit the data for fitting the combustion efficiency η Al and the characteristic velocity efficiency C * to obtain three different fitting relationships between the actual combustion efficiency of active aluminum and the characteristic velocity efficiency of the target solid propellant.

[0077] The R values of the three fitting relationships are calculated respectively. 2 R 2 represents the proportion of the variation of the dependent variable that can be explained by the independent variable, reflecting the explanatory ability of the fitting relationship to the data. The closer it is to 1, the better the model fitting and the higher the calculation accuracy. Among them, the R value of the linear fitting relationship between the actual combustion efficiency of active aluminum and the characteristic velocity efficiency of the target solid propellant is 2 = 0.9949, the R value of the polynomial fitting relationship between the actual combustion efficiency of active aluminum and the characteristic velocity efficiency of the target solid propellant is 2 = 1, and the R value of the Gaussian fitting relationship between the actual combustion efficiency of active aluminum and the characteristic velocity efficiency of the target solid propellant is 2 = 0.9999.

[0078] As Figure 2 shown, Figure 2are the fitting curves of different fitting relationships, where the polynomial fitting curve coincides with the Gaussian fitting curve. Combining each fitting relationship, Figure 2 and the R of each fitting relationship 2 It can be seen that the linear fitting relationship is the simplest, with a fast calculation speed but slightly lower accuracy, and can be used for a quick and rough estimation of the characteristic velocity efficiency of the target solid propellant. The polynomial fitting relationship and the Guass fitting relationship, although having a higher calculation complexity compared to the linear fitting, have high accuracy and can be used for high-precision prediction of the characteristic velocity efficiency.

[0079] S105. Substitute the actual combustion efficiency of the active aluminum into the fitting relationship between the actual combustion efficiency of the active aluminum and the characteristic velocity efficiency of the target solid propellant to obtain the characteristic velocity efficiency of the target solid propellant.

[0080] The calculation method for the characteristic velocity efficiency of the solid propellant in this embodiment does not require a complete engine test run throughout the process, avoiding errors in the calculation of the characteristic velocity efficiency caused by nozzle deformation and signal distortion of the combustion chamber pressure sensor, and has high calculation accuracy.

[0081] In one embodiment, the combustion products of the target solid propellant are pretreated, including the following steps:

[0082] S301. Grind the combustion products of the target solid propellant sufficiently.

[0083] Specifically, the combustion products of the target solid propellant can be placed in a grinder and continuously ground for at least 5 minutes.

[0084] S302. Dry the sufficiently ground combustion products of the target solid propellant at 75 - 85 °C for 48 - 72 hours.

[0085] The function of drying is to completely oxidize the residual carbon in the combustion products of the target solid propellant into CO2 and remove it, so that the pretreated product consists only of three components: active aluminum, aluminum nitride, and aluminum oxide.

[0086] In one embodiment, determining the content of active aluminum in the pretreated product includes the following steps:

[0087] S401. Weigh 0.002 - 0.02 g of the pretreated product and place it in a 500 mL ground glass conical flask, add 30 - 40 mL of ferric sulfate with a concentration of 0.825 mol / L and 10 mL of 10% dilute sulfuric acid, and heat and boil for 35 - 45 minutes to obtain a solid-liquid mixture.

[0088] During the dissolution process of the pretreated product, the active metal aluminum reacts with ferric sulfate in an acidic environment to generate Al 3+ and Fe 2+, alumina and aluminum nitride do not participate in the reaction. The ionic reaction equation for the reaction of active metal aluminum with ferric sulfate in an acidic environment is

[0089] 2Al + 3Fe 3+ = 2Al 3+ + 3Fe 2+ ;

[0090] S402. After the solid-liquid mixture is cooled to room temperature, transfer it to a 250 mL conical flask, and add 10 - 20 mL of a phosphorus-sulfuric acid mixture with a ratio of 4:1 to fade the solution.

[0091] It should be noted that when transferring the solid-liquid mixture to a 250 mL conical flask, the inner wall of the 500 mL ground-glass conical flask needs to be washed with distilled water more than three times to prevent the residual solution on the inner wall from affecting the titration accuracy.

[0092] S403. Add 0.5 - 1 mL of sodium diphenylamine sulfonate solution as an indicator, and titrate the solid-liquid mixture with 1 / 120 mol / L potassium dichromate solution, and record the volume of the potassium dichromate solution consumed.

[0093] Among them, during the titration process, dichromate ions will react with ferrous ions to generate ferric ions and chromic ions. The specific ionic reaction equation is:

[0094] 6Fe 2+ + Cr2O7 2- + 14H + = 6Fe 3+ + 2Cr 3+ + 7H2O;

[0095] After the titration is completed, the solid-liquid mixture turns purple. When the potassium dichromate standard solution is titrated to the stoichiometric point, the indicator sodium diphenylamine sulfonate is oxidized by slightly excessive K2Cr2O7, and the solution shows a purplish red color, indicating the arrival of the titration end point.

[0096] S404. Calculate the content of active aluminum in the pretreatment product based on the volume of the potassium dichromate solution consumed. The calculation formula is:

[0097]

[0098] In the formula, c represents the concentration of the potassium dichromate standard solution, with the unit of mol / L, V represents the volume of the titrated potassium dichromate solution, with the unit of mL, and m s represents the mass of the pretreatment product placed in the 500 mL ground-glass conical flask, with the unit of g.

[0099] In one embodiment, measuring the content of aluminum nitride in the pretreatment product includes the following steps:

[0100] S501. Determine the nitrogen element content in the pretreated product by using an inorganic nitrogen analyzer. In this step, weigh 0.4 - 1 g of the pretreated product for nitrogen element content determination by the inorganic nitrogen analyzer.

[0101] S502. Calculate the content of aluminum nitride according to nitrogen element conservation. The calculation formula is:

[0102]

[0103] In the formula, w(N) represents the nitrogen element content in the pretreated product, 41.04 is the molar mass of aluminum nitride, with the unit of g / mol, and 14.01 is the molar mass of nitrogen atom, with the unit of g / mol.

[0104] In one embodiment, calculate the content of aluminum oxide in the pretreated product by the subtraction method. The calculation formula is

[0105] In a specific embodiment, when pretreating the combustion product of a solid propellant with an aluminum powder mass fraction of 16%, dry the well - ground combustion product of the target solid propellant at 80 °C for 48 h. When determining the content of active aluminum in the pretreated product, weigh 0.01 g of the pretreated product and place it into a 500 mL ground - glass conical flask, add 35 mL of ferric sulfate with a concentration of 0.825 mol / L and 10 mL of 10% dilute sulfuric acid, heat and boil for 40 min to obtain a solid - liquid mixture; after the solid - liquid mixture cools to room temperature, transfer it to a 250 mL conical flask, add 15 mL of a phosphorus - sulfur mixed acid with a ratio of 4:1 to fade the solution; add 1 mL of sodium diphenylamine sulfonate solution as an indicator, and titrate the solid - liquid mixture with 1 / 120 mol / L potassium dichromate solution, and record the volume of potassium dichromate solution consumed.

[0106] Finally, the combustion efficiency of the solid propellant with an aluminum powder mass fraction of 16% calculated by the calculation formula for calculating the actual combustion efficiency of active aluminum through the difference in formation enthalpy between aluminum nitride and aluminum oxide is 88.89%. Substitute it into the polynomial fitting relationship between the actual combustion efficiency of active aluminum and the characteristic velocity efficiency of the target solid propellant, and the characteristic velocity efficiency of the solid propellant with an aluminum powder mass fraction of 16% can be calculated to be 0.991.

[0107] The quantitative analysis of each component of the method of the present invention can be completed in the laboratory, and other steps are all calculation steps. The whole process has low cost and low complexity.

[0108] In a specific embodiment, when preprocessing the combustion products of the target solid propellant, the combustion products of the target solid propellant after sufficient grinding are dried at 75 °C for 36 h. When determining the content of active aluminum in the preprocessed product, 0.002 g of the preprocessed product is weighed and placed into a 500 mL ground conical flask, 30 mL of ferric sulfate with a concentration of 0.825 mol / L and 8 mL of 10% dilute sulfuric acid are added, and the mixture is heated and boiled for 35 min to obtain a solid-liquid mixture; after the solid-liquid mixture is cooled to room temperature, it is transferred to a 250 mL conical flask, 10 mL of a phosphorus-sulfur mixed acid with a ratio of 4:1 is added to fade the solution; 0.5 mL of sodium diphenylamine sulfonate solution is added as an indicator, and a 1 / 120 mol / L potassium dichromate solution is used to titrate the solid-liquid mixture, and the volume of the potassium dichromate solution consumed is recorded. The quantitative analysis of each component of the method of the present invention can be completed in the laboratory, and other steps are all calculation steps. The whole process has low cost and low complexity.

[0109] In a specific embodiment, when preprocessing the combustion products of the target solid propellant, the combustion products of the target solid propellant after sufficient grinding are dried at 85 °C for 72 h. When determining the content of active aluminum in the preprocessed product, 0.02 g of the preprocessed product is weighed and placed into a 500 mL ground conical flask, 40 mL of ferric sulfate with a concentration of 0.825 mol / L and 12 mL of 10% dilute sulfuric acid are added, and the mixture is heated and boiled for 45 min to obtain a solid-liquid mixture; after the solid-liquid mixture is cooled to room temperature, it is transferred to a 250 mL conical flask, 20 mL of a phosphorus-sulfur mixed acid with a ratio of 4:1 is added to fade the solution; 1 mL of sodium diphenylamine sulfonate solution is added as an indicator, and a 1 / 120 mol / L potassium dichromate solution is used to titrate the solid-liquid mixture, and the volume of the potassium dichromate solution consumed is recorded. The quantitative analysis of each component of the method of the present invention can be completed in the laboratory, and other steps are all calculation steps. The whole process has low cost and low complexity.

[0110] The above embodiments only represent several implementation manners of the present invention. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the patent of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the appended claims.

Claims

1. A calculation method for the characteristic velocity efficiency of solid propellants, characterized in that, It includes the following steps: Pre-treat the combustion products of the target solid propellant to obtain a pre-treated product composed of three components: active aluminum, aluminum nitride, and aluminum oxide; Determine the contents of the three components of active aluminum, aluminum nitride, and aluminum oxide in the pre-treated product; Calculate the actual combustion efficiency of active aluminum through the enthalpy of formation difference between aluminum nitride and aluminum oxide; Establish a fitting relationship between the actual combustion efficiency of active aluminum and the characteristic velocity efficiency of the target solid propellant. The fitting relationship between the actual combustion efficiency of active aluminum and the characteristic velocity efficiency of the target solid propellant is a linear fitting relationship, a polynomial fitting relationship, or a Gaussian fitting relationship; Substitute the actual combustion efficiency of active aluminum into the fitting relationship between the actual combustion efficiency of active aluminum and the characteristic velocity efficiency of the target solid propellant to obtain the characteristic velocity efficiency of the target solid propellant.

2. The calculation method for the characteristic velocity efficiency of solid propellant according to claim 1, wherein The calculation formula for calculating the actual combustion efficiency of active aluminum through the enthalpy of formation difference between aluminum nitride and aluminum oxide is: where η Al represents the actual combustion efficiency of reactive aluminum, represents the enthalpy of formation of aluminum oxide, ΔH AlN represents the enthalpy of formation of aluminum nitride, m Al represents the content of reactive aluminum in the pretreated product, m AlN represents the content of aluminum nitride in the pretreated product, represents the content of aluminum oxide in the pretreated product.

3. The calculation method for the characteristic velocity efficiency of solid propellants according to claim 2, characterized in that, The linear fitting relationship between the actual combustion efficiency of active aluminum and the characteristic velocity efficiency of the target solid propellant is: In the formula, represents the characteristic velocity efficiency of the target solid propellant, a1 = 0.83027 ± 2.32026e-4, b1 = 0.17804 ± 4.01781E-4; The polynomial fitting relationship between the actual combustion efficiency of active aluminum and the characteristic velocity efficiency of the target solid propellant is: In the formula, a2 = 0.8221 ± 1.01148E-4, b2 = 0.22715 ± 3.97107E-4, c2 = -0.04911 ± 3.59256E-4; The Gaussian fitting relationship between the actual combustion efficiency of active aluminum and the characteristic velocity efficiency of the target solid propellant is: where y0 = -0.2309 ± 0.42291, x c = 1.91952 ± 0.11454, w = 6.03593 ± 1.35994, A = 9.75332 ± 5.45642.

4. The calculation method for the characteristic velocity efficiency of solid propellants according to claim 3, wherein Pre-treat the combustion products of the target solid propellant, including the following steps: Fully grind the combustion products of the target solid propellant; Dry the fully ground combustion products of the target solid propellant at 75 - 85 °C for 48 - 72 h.

5. The calculation method for the characteristic velocity efficiency of solid propellants according to claim 4, characterized in that, Determining the content of active aluminum in the pre-treated product includes the following steps: Weigh 0.002 - 0.02 g of the pre-treated product and place it into a 500 mL ground glass conical flask, add 30 - 40 mL of ferric sulfate with a concentration of 0.825 mol / L and 8 - 12 mL of 10% dilute sulfuric acid, heat and boil for 35 - 45 min to obtain a solid-liquid mixture; After the solid-liquid mixture cools to room temperature, transfer it to a 250 mL conical flask, add 10 - 20 mL of a phosphorus-sulfur mixed acid with a ratio of 4:1 to fade the solution; Add 0.5 - 1 mL of sodium diphenylamine sulfonate solution as an indicator, and titrate the solid-liquid mixture with 1 / 120 mol / L potassium dichromate solution, record the volume of potassium dichromate solution consumed; Calculate the content of active aluminum in the pre-treated product based on the volume of potassium dichromate solution consumed. The calculation formula is: Wherein, c represents the concentration of the potassium dichromate standard solution, with the unit of mol / L, V represents the volume of the titrated potassium dichromate solution, with the unit of mL, and m s represents the mass of the pretreatment product placed in a 500 mL ground glass conical flask, with the unit of g.

6. The calculation method for the characteristic velocity efficiency of solid propellants according to claim 4, characterized in that, Determining the content of aluminum nitride in the pre-treated product includes the following steps: Weigh 0.5 - 2 g of the pre-treated product and determine the nitrogen element content in the pre-treated product through an inorganic nitrogen analyzer; Calculate the content of aluminum nitride according to nitrogen element conservation. The calculation formula is: In the formula, w(N) represents the nitrogen element content in the pre-treated product, 41.04 is the molar mass of aluminum nitride, with the unit g / mol, and 14.01 is the molar mass of nitrogen atoms, with the unit g / mol.

7. The calculation method for the characteristic velocity efficiency of solid propellants according to claim 4, characterized in that, Calculate the content of aluminum oxide in the pre-treated product by subtraction. The calculation formula is

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