Method for determining actual constant-pressure combustion temperature of solid propellant through calorimetric method

Abstract

The invention discloses a method for determining the actual constant-pressure combustion temperature of a solid propellant through a calorimetric method. The method comprises the steps that the combustion efficiency of the propellant and the iteration initial value of the actual constant-pressure combustion temperature are obtained through calculation; the average value of the iteration initial value of the actual constant-pressure combustion temperature and the theoretical constant-pressure combustion temperature is calculated, and the first iteration combustion efficiency of the propellant is calculated; the mean value of the first iteration value of the actual constant-pressure combustion temperature and the theoretical constant-pressure combustion temperature is calculated, and the second iteration combustion efficiency of the propellant is obtained through calculation; taking the combustion temperature corresponding to the nth iterative combustion efficiency of the propellant as the actual constant-pressure combustion temperature until the residual error between the nth iterative combustion efficiency of the propellant and the combustion efficiency of the propellant is smaller than a preset value; the actual constant-pressure combustion temperature of the propellant is measured through a calorimetric method and a continuous iteration mode according to the actually measured pressure explosion heat value, the theoretical constant-pressure explosion heat value and the correlation between the theoretical constant-pressure combustion temperature and the actual constant-pressure combustion temperature of the given propellant.

Description

Technical Field

[0001] The present invention belongs to the field of characterization of combustion and energy properties of solid propellants, and particularly relates to a method for determining the actual constant-pressure combustion temperature of solid propellants by calorimetry. Background Art

[0002] The combustion temperature is an important parameter for characterizing the energy properties of solid propellants. It is not only the basis for the research on the combustion mechanism of propellants and the establishment of combustion models, but also a factor that must be considered in rocket engine design, thermal insulation layer protection, etc. Contact temperature measurement is mainly based on the thermocouple temperature measurement method. During the measurement process, the temperature measurement element usually needs to be placed in the test object and directly contact the object to be measured for temperature measurement. However, its temperature measurement is limited by the melting point of the thermocouple. The highest melting point tungsten-rhenium thermocouple can measure up to 2600K. Since the theoretical combustion temperature of high-energy solid propellants is generally higher than 3000K, its combustion temperature has far exceeded the temperature measurement range of thermocouples and cannot meet the measurement requirements of high-energy propellants. Optical temperature measurement requires high-precision and high-reliability calibration standards, and there are problems such as easy contamination of the optical window, high debugging requirements, complex spectral characteristics of high-temperature combustion products, and the need to rely on complex algorithms to invert the temperature field, resulting in significant error accumulation. Summary of the Invention

[0003] The purpose of the present invention is to provide a method for determining the actual constant-pressure combustion temperature of solid propellants by calorimetry. According to the positive correlation between the constant-pressure heat of explosion and the constant-pressure combustion temperature of the given propellant, the constant-pressure combustion temperature of high-energy propellants is measured by calorimetry.

[0004] The present invention adopts the following technical solutions: A method for determining the actual constant-pressure combustion temperature of solid propellants by calorimetry, including:

[0005] Step 1: Calculate the combustion efficiency and the initial iteration value of the actual constant-pressure combustion temperature of the propellant based on the measured constant-pressure heat of explosion value, the theoretical constant-pressure heat of explosion value, and the theoretical constant-pressure combustion temperature of the propellant; wherein, the measured constant-pressure heat of explosion value is obtained by calorimetry, and the theoretical constant-pressure heat of explosion value and the theoretical constant-pressure combustion temperature are obtained by calculation;

[0006] Step 2: Calculate the average value of the initial iteration value of the actual constant-pressure combustion temperature and the theoretical constant-pressure combustion temperature, use this average value as the first iteration value of the actual constant-pressure combustion temperature, and calculate the first iteration combustion efficiency of the propellant by using the calorimetry temperature measurement iteration relational expression;

[0007] Step 3: When the first iteration combustion efficiency of the propellant is less than the combustion efficiency of the propellant calculated in Step 1, calculate the average value of the first iteration value of the actual constant-pressure combustion temperature and the theoretical constant-pressure combustion temperature, use this average value as the second iteration value of the actual constant-pressure combustion temperature, and calculate the second iteration combustion efficiency of the propellant by using the calorimetry temperature measurement iteration relational expression;

[0008] Step 4: Repeat Step 3 until the residual between the combustion efficiency of the nth iteration of the propellant and the combustion efficiency of the propellant calculated in Step 1 is less than a predetermined value, and use the combustion temperature corresponding to the combustion efficiency of the nth iteration of the propellant as the actual constant-pressure combustion temperature.

[0009] Furthermore, the calculation formula for the combustion efficiency of the propellant in Step 1 is:

[0010]

[0011] In the formula, η is the combustion efficiency of the propellant; Q p_exp is the measured constant-pressure explosion heat value, kJ / kg; Q p_th is the theoretical constant-pressure explosion heat value, kJ / kg.

[0012] Furthermore, the calculation formula for the initial iteration value of the actual constant-pressure combustion temperature in Step 1 is:

[0013]

[0014] In the formula, Q p_exp is the measured constant-pressure explosion heat value, kJ / kg; Q p_th is the theoretical constant-pressure explosion heat value, kJ / kg; T p_exp0 is the initial iteration value of the actual constant-pressure combustion temperature, K; Tp_th is the theoretical constant-pressure combustion temperature, K.

[0015] Furthermore, the calorimetric temperature measurement iteration relationship in Step 3 is:

[0016]

[0017] In the formula, η i is the combustion efficiency of the ith iteration of the propellant; C p (T) is the constant-pressure heat capacity of the combustion products of the propellant; Q p_exp is the measured constant-pressure explosion heat value, kJ / kg; Q p_th is the theoretical constant-pressure explosion heat value, kJ / kg; T p_expi is the ith iteration value of the actual constant-pressure combustion temperature, K; Tp_th is the theoretical constant-pressure combustion temperature, K;

[0018] where i ≤ n.

[0019] Furthermore, the predetermined value in Step 4 is 0.0001.

[0020] Further, when repeating Step 3, when the combustion efficiency of the i-th iteration of the propellant is greater than the combustion efficiency of the propellant calculated in Step 1, the average value of the i-th iteration value and the (i - 1)-th iteration value of the actual constant-pressure combustion temperature is used as the (i + 1)-th iteration value of the actual constant-pressure combustion temperature, and the combustion efficiency of the (i + 1)-th iteration of the propellant is calculated using the calorimetry temperature measurement iteration relationship.

[0021] The beneficial effects of the present invention are as follows:

[0022] Based on the correlation between the measured constant-pressure explosion heat value, theoretical constant-pressure explosion heat value, theoretical constant-pressure combustion temperature, and actual constant-pressure combustion temperature of the given propellant, the present invention measures the actual constant-pressure combustion temperature of the propellant by calorimetry and continuous iteration;

[0023] According to the definition of explosion heat, the present invention gives the integral relationship between the heat release (explosion heat) and temperature (the constant-pressure combustion temperature drops to 298K) during the temperature reduction process of the combustion products of the propellant, and establishes a calorimetry temperature measurement iteration relationship based on the correspondence between the theoretical constant-pressure explosion heat value and the measured constant-pressure explosion heat value, and the theoretical constant-pressure combustion temperature and the actual constant-pressure combustion temperature respectively;

[0024] The present invention splits the integral relationship of the theoretical constant-pressure explosion heat value into the sum of the measured constant-pressure explosion heat value and the integral of the high-temperature section, solving the problem that the material changes and phase changes during the large temperature-span cooling process of the combustion products of the propellant cannot be continuously integrated. Since the temperature of the complex reaction during the cooling process of the high-temperature products cannot be determined, the segmented integration cannot be achieved either. At the same time, it avoids the problem that the composition of the combustion products in the low-temperature section and C p (T) cannot be determined by the minimum free energy method;

[0025] Based on the relationship that "the combustion temperature and the combustion heat release are in a proportional relationship", the present invention determines the initial iteration value of the actual constant-pressure combustion temperature. The reasonable selection of this initial iteration value improves the iteration efficiency and can significantly shorten the number of iteration steps. Based on the correlation between the measured constant-pressure explosion heat value, theoretical constant-pressure explosion heat value, theoretical constant-pressure combustion temperature, and actual constant-pressure combustion temperature of the given propellant, it quantitatively characterizes them. At the same time, during the quantitative characterization calculation process, it solves the problem that the material changes and phase changes during the large temperature span from high temperature to low temperature cannot be integrated, and at the same time avoids the problem that the composition of the combustion products in the low-temperature section and C p (T) cannot be determined by the minimum free energy method; realizing the measurement of the constant-pressure combustion temperature of high-energy propellants by calorimetry. Specific Embodiments

[0026] The present invention will be described in detail below in conjunction with specific embodiments.

[0027] The combustion products of the propellant can be regarded as a closed system, and the relationship between its constant-pressure explosion heat and constant-pressure combustion temperature is shown in Equation (1):

[0028]

[0029] In the formula, Q p is the constant-pressure explosion heat, kJ / kg; T p is the constant-pressure combustion temperature of the propellant, K; C p (T) is the constant-pressure heat capacity of the combustion products of the propellant, kJ / (kg / agent).

[0030] It can be seen from Equation (1) that if the constant-pressure heat capacity is known and the constant-pressure explosion heat is obtained through experimental tests, the actual constant-pressure temperature T p can be calculated. However, since the constant-pressure combustion temperature of the propellant is generally 2000K - 4000K, there are problems such as the material changes and phase changes during the large temperature-span cooling process of the combustion products of the propellant that cannot be continuously integrated, and the temperature of the complex reaction during the cooling process of the high-temperature products cannot be determined. Therefore, piecewise integration cannot be achieved. At the same time, the composition of the combustion products in the low-temperature section and C p (T) cannot be determined by the minimum free energy method. Therefore, it is actually impossible to solve the constant-pressure combustion temperature through Equation (1).

[0031] In order to obtain the actual constant-pressure combustion temperature, the measured constant-pressure explosion heat value corresponds to the actual constant-pressure combustion temperature, and the theoretical constant-pressure explosion heat value corresponds to the theoretical constant-pressure combustion temperature, and the basic relationship formula for temperature measurement by the calorimetric method is established:

[0032]

[0033] In the formula, Q p_exp is the measured constant-pressure explosion heat value, kJ / kg; Q p_th is the theoretical constant-pressure explosion heat value, kJ / kg; T p_th is the theoretical constant-pressure combustion temperature, K; T p_exp is the actual constant-pressure combustion temperature, K.

[0034] The piecewise integration of the theoretical constant-pressure explosion heat value in Equation (2) is as follows:

[0035]

[0036] Then Equation (2) can be written as:

[0037]

[0038] Among them, the measured constant-pressure explosion heat value Q p_exp can be obtained through calorimetric experiments, and the theoretical constant-pressure explosion heat value Q p_th and the theoretical constant-pressure combustion temperature T p_th can both be calculated and obtained.

[0039] Introduce the measured constant-pressure explosion heat value Q through formula (3). p_exp As the integration result from 298K to T p_exp Convert the final expression into a calculation form that only depends on the extremely small temperature range C in the high-temperature section p (T) as shown in formula (4), thus solving the problem that the material changes and phase transitions in the large temperature span from high temperature to low temperature cannot be integrated, and at the same time avoiding the problem that the composition of the combustion products in the low-temperature section and C p (T) cannot be calculated and determined by the minimum free energy method. Since the combustion efficiency of solid propellants is generally greater than 90%, the actual constant-pressure combustion temperature and the theoretical constant-pressure combustion temperature both belong to the high-temperature section. The composition of the constant-pressure combustion products of the propellant and C p (T) at different temperatures in this interval can be obtained through thermodynamic calculations based on the minimum free energy.

[0040] Therefore, the present invention discloses a method for determining the actual constant-pressure combustion temperature of solid propellants by calorimetry, including:

[0041] Step 1: Calculate the combustion efficiency of the propellant and the initial iteration value of the actual constant-pressure combustion temperature according to the measured constant-pressure explosion heat value, the theoretical constant-pressure explosion heat value, and the theoretical constant-pressure combustion temperature of the propellant; wherein, the measured constant-pressure explosion heat value is obtained by calorimetry, and the theoretical constant-pressure explosion heat value and the theoretical constant-pressure combustion temperature are obtained by calculation.

[0042] Among them, the calculation formula for the combustion efficiency of the propellant in Step 1 is:

[0043]

[0044] In the formula, η is the combustion efficiency of the propellant; Q p_exp is the measured constant-pressure explosion heat value, kJ / kg; Q p_th is the theoretical constant-pressure explosion heat value, kJ / kg.

[0045] In order to iteratively solve the actual constant-pressure combustion temperature of the propellant and, according to the proportional relationship between the constant-pressure explosion heat and the constant-pressure combustion temperature of the propellant, set the initial iteration value T p_exp0 of the actual constant-pressure combustion temperature, as shown in formula (6). Therefore, the calculation formula for the initial iteration value of the actual constant-pressure combustion temperature in Step 1 is:

[0046]

[0047] In the formula, Q p_exp is the measured constant-pressure explosion heat value, kJ / kg; Q p_th is the theoretical constant-pressure explosion heat value, kJ / kg; T p_exp0is the initial iteration value of the actual constant-pressure combustion temperature, in K; Tp_th is the theoretical constant-pressure combustion temperature, in K.

[0048] Since Equation (6) does not consider the phenomenon that the constant-pressure heat capacity of the combustion products increases with the increase of the combustion temperature compared with Equation (2), so for T p_exp0 there is T p_exp0 < T p_exp < T p_th .

[0049] Step 2: Calculate the average value of the initial iteration value of the actual constant-pressure combustion temperature and the theoretical constant-pressure combustion temperature, use this average value as the first iteration value of the actual constant-pressure combustion temperature, and calculate the first iteration combustion efficiency of the propellant by using the calorimetric temperature measurement iteration relation formula (8).

[0050] Step 2 is specifically: Use the bisection method to obtain the first iteration value T p_exp1 :

[0051]

[0052] First, substitute T p_exp1 into the calorimetric temperature measurement iteration relation formula (8) to start the iteration. The calorimetric temperature measurement iteration relation formula is:

[0053]

[0054] In the formula, η i is the i-th iteration combustion efficiency of the propellant; C p (T) is the constant-pressure heat capacity of the propellant combustion products; Q p_exp is the measured constant-pressure explosion heat value, in kJ / kg; Q p_th is the theoretical constant-pressure explosion heat value, in kJ / kg; T p_expi is the i-th iteration value of the actual constant-pressure combustion temperature, in K; Tp_th is the theoretical constant-pressure combustion temperature, in K; i ≤ n.

[0055] Through thermodynamic calculations, the constant-pressure heat capacity C p (T) of the gas at different temperatures can be obtained, so as to fit the change of C p (T) with the temperature. Since T p_exp1 and T p_th are both known, the change of the constant-pressure heat capacity C p (T) with the temperature can be effectively fitted within a determined temperature range to obtain the combustion efficiency η 1 .

[0056] Step 3: When the first iteration combustion efficiency of the propellant is less than the combustion efficiency of the propellant calculated in Step 1, calculate the mean value of the first iteration value of the actual constant pressure combustion temperature and the theoretical constant pressure combustion temperature, use this mean value as the second iteration value of the actual constant pressure combustion temperature, and calculate the second iteration combustion efficiency of the propellant by using the calorimetric temperature measurement iteration relational expression.

[0057] Step 4: Repeat Step 3 until the residual between the nth iteration combustion efficiency of the propellant and the combustion efficiency of the propellant calculated in Step 1 is less than the predetermined value, and use the combustion temperature corresponding to the nth iteration combustion efficiency of the propellant as the actual constant pressure combustion temperature. Wherein, the predetermined value in Step 4 is 0.0001.

[0058] Specifically, Step 4 is as follows: When repeating Step 3, when the ith iteration combustion efficiency of the propellant is greater than the combustion efficiency of the propellant calculated in Step 1, use the mean value of the ith iteration value and the (i - 1)th iteration value of the actual constant pressure combustion temperature as the (i + 1)th iteration value of the actual constant pressure combustion temperature, and calculate the (i + 1)th iteration combustion efficiency of the propellant by using the calorimetric temperature measurement iteration relational expression.

[0059] That is, when η 1 > η, there is:

[0060]

[0061] When η 1 < η, there is:

[0062]

[0063] When η 1＝ = η, there is:

[0064] T p_exp = T p_exp1 (11)

[0066] Substitute T p_exp2 into Equation (8) to calculate the combustion efficiency η 2 , and use Equation (12) to calculate the combustion efficiency residual.

[0067] E = |η 2 - η| (12)

[0068] Compare η 2 with η, and perform the next iteration calculation according to the magnitude relationship between η 2 and η using Equation (9) or Equation (10).

[0069] Set the residual limit E to 0.0001, and repeatedly iterate to obtain the exact solution T p_expn .

[0070] Example

[0071] In this example, the classic double-base propellant SQ-2 and the common composite propellant NEPE were selected. According to Method 701.2 "Constant Temperature Method for Heat of Explosion and Heat of Combustion" in GJB770B-2024, a constant temperature oxygen bomb calorimeter was used to measure the measured constant pressure explosion heat value of the propellant. In order to obtain the test results of the actual constant pressure combustion temperature, a pressure sensor was installed on the oxygen bomb of the calorimeter, and the pressure sensor could realize the synchronous acquisition of the temperature data in the inner cylinder and the pressure data in the oxygen bomb.

[0072] The volume of this oxygen bomb was calibrated in accordance with the verification regulation of the standard metal measuring vessel JJG259-2005. Distilled water and ethanol with a density of 0.789 g / cm 3 were used for calibration three times, and the effective volume V of the oxygen bomb was obtained as 0.287 L.

[0073] (P 2 -P 1 )V = n 2 RT 2 -n 1 RT 1 (13)

[0074] Wherein, P 2 is the pressure in the oxygen bomb during the stable section of the calorimetry experiment, Pa; P 1 is the pressure in the oxygen bomb before ignition in the calorimetry experiment, Pa; n 2 is the amount of gaseous substances during the stable section of the calorimetry experiment, mol; n 1 is the amount of gaseous substances before ignition in the calorimetry experiment, mol; T 2 is the gas temperature during the stable section of the calorimetry experiment, K; T 2 is the gas temperature before ignition in the calorimetry experiment, K.

[0075] During the calorimetry experiment, the amount of propellant used was m grams, and the number of moles of the generated stable section gas was n 2 -n 1 . Therefore, the amount of substance n g of the gaseous products at the end state of the explosion heat of 1 kg of propellant can be obtained by Equation (14).

[0076]

[0077] According to the relationship formula (15) between the constant pressure explosion heat and the constant volume explosion heat, the constant pressure explosion heat of the propellant can be obtained:

[0078] Q p = Q v -n g RT (15)

[0079] Wherein, Qp and Q v are the isobaric heat of explosion and isochoric heat of explosion of the propellant, kJ / kg; R is the molar gas constant, with a value of 8.314 J / mol / K; T is the temperature at the steady state of the isochoric heat of explosion and isobaric heat of explosion, K; n g is the amount of substance of the gaseous products in the steady state of the heat of explosion of 1 kg of propellant, mol.

[0080] The actually measured isochoric heat of explosion Q v_exp of the SQ-2 propellant is 3431.1 ± 21.5 kJ / kg, and the actually measured isobaric heat of explosion Q p_exp is 3344.2 kJ / kg. The actually measured isochoric heat of explosion Q v_exp of the NEPE propellant is 7098.0 ± 53.1 kJ / kg, and the actually measured isobaric heat of explosion Q p_exp is 7012.6 kJ / kg

[0081] Through theoretical calculation, it can be obtained that the theoretical isobaric combustion temperature of the SQ-2 propellant is 2236.14 K, the theoretical isobaric heat of explosion value is 3427.4 kJ / kg, and the combustion efficiency η of the propellant is 97.58%. From Equation (6), the initial iteration value T p_exp0 of the actual isobaric combustion temperature can be obtained as 2189.3 ± 14.5 K, and through continuous iteration, the final iteration value T p_expn of the actual isobaric combustion temperature is obtained as 2198.5 ± 14.6 K. The isobaric combustion temperature of the SQ-2 propellant measured by the calorimetric method is 2198.5 K, with a difference of 37.6 K from the theoretical isobaric combustion temperature.

[0082] Similarly, through theoretical calculation, it can be obtained that the theoretical isobaric combustion temperature of the NEPE propellant is 3742.7 K, the theoretical isobaric heat of explosion value is 7319.6 kJ / kg, and the combustion efficiency η of the propellant is 95.81%. From Equation (6), the initial iteration value T p_exp0 of the actual isobaric combustion temperature can be obtained as 3595.0 ± 28.2 K, and through continuous iteration, the final iteration value T p_expn of the actual isobaric combustion temperature is obtained as 3610.2 ± 28.3 K. The actually measured isobaric combustion temperature of the NEPE propellant by the calorimetric method is 3610.2 K, with a difference of 132.5 K from the theoretical isobaric combustion temperature.

[0083] Table 1 shows the measurement results of the heat of explosion and temperature of the NEPE propellant and SQ-2 propellant by the calorimetric method

[0084]

[0085]

[0086] As can be seen from Table 1, the initial iteration value T p_exp0Compared with the iterative final value T p_expn The differences are 15.2K and 9.2K respectively. The difference between the two is small, which proves that the iterative initial value is close to the iterative final value and can significantly shorten the number of iterative steps.

[0087] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for determining the actual constant pressure combustion temperature of a solid propellant by calorimetry, characterized in that: include: Step 1: According to the actual measured detonation heat value, theoretical constant-pressure detonation heat value and theoretical constant-pressure combustion temperature of the propellant, the iterative initial value of the combustion efficiency of the propellant and the actual constant-pressure combustion temperature is calculated; wherein the actual measured detonation heat value is obtained by calorimetry, and the theoretical constant-pressure detonation heat value and theoretical constant-pressure combustion temperature are obtained by calculation; Step 2: Calculate the average of the iterative initial value of the actual constant-pressure combustion temperature and the theoretical constant-pressure combustion temperature, use the average as the first iterative value of the actual constant-pressure combustion temperature, and use the calorimetric temperature measurement iterative relationship to calculate the first iterative combustion efficiency of the propellant; Step 3: When the first iteration combustion efficiency of the propellant is less than the combustion efficiency of the propellant calculated in step 1, the average of the first iteration value of the actual constant-pressure combustion temperature and the theoretical constant-pressure combustion temperature is calculated, and the average is used as the second iteration value of the actual constant-pressure combustion temperature. The second iteration combustion efficiency of the propellant is calculated using the calorimetric temperature measurement iteration relationship; Step 4: Repeat step 3 until the residual difference between the n-th iterative combustion efficiency of the propellant and the combustion efficiency of the propellant calculated in step 1 is less than a predetermined value, and the combustion temperature corresponding to the n-th iterative combustion efficiency of the propellant is used as the actual constant-pressure combustion temperature.

2. The method for determining the actual constant pressure combustion temperature of solid propellant by calorimetry according to claim 1, characterized in that: The calculation formula for the combustion efficiency of the propellant in step 1 is: Where η is the combustion efficiency of the propellant; Q p_exp To measure the detonation heat value, kJ / kg; Q p_th It is the theoretical constant pressure explosion heat value, kJ / kg.

3. The method for determining the actual constant pressure combustion temperature of solid propellant by calorimetry according to claim 1, characterized in that: The calculation formula for the iterative initial value of the actual constant pressure combustion temperature in step 1 is: In the formula, Q p_exp To measure the detonation heat value, kJ / kg; Q p_th is the theoretical constant pressure explosion heat value, kJ / kg; T p_exp0 is the iterative initial value of the actual constant-pressure combustion temperature, K; Tp_th is the theoretical constant-pressure combustion temperature, K.

4. The method for determining the actual constant pressure combustion temperature of solid propellant by calorimetry according to claim 1, characterized in that: The calorimetric temperature measurement iteration relationship in step 3 is: Where η i is the i-th iteration combustion efficiency of the propellant; C p (T) is the constant-pressure heat capacity of the propellant combustion products; Q p_exp To measure the detonation heat value, kJ / kg; Q p_th is the theoretical constant pressure explosion heat value, kJ / kg; T p_expi is the i-th iteration value of the actual constant pressure combustion temperature, K; Tp_th is the theoretical constant pressure combustion temperature, K; Among them, i≤n.

5. The method for determining the actual constant pressure combustion temperature of solid propellant by calorimetry according to claim 1, characterized in that: The predetermined value in step 4 is 0.0001.

6. The method for determining the actual constant pressure combustion temperature of solid propellant by calorimetry according to claim 1, characterized in that: When step 3 is repeated, when the i-th iterative combustion efficiency of the propellant is greater than the combustion efficiency of the propellant calculated in step 1, the average of the i-th iterative value and the i-1-th iterative value of the actual constant-pressure combustion temperature is used as the i+1-th iterative value of the actual constant-pressure combustion temperature, and the i+1-th iterative combustion efficiency of the propellant is calculated using the calorimetric temperature measurement iterative relationship.

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