A regenerative cooling calculation method for hydrogen peroxide bipropellant rocket engine

Abstract

The application discloses a kind of hydrogen peroxide bipropellant rocket engine regenerative cooling calculation method, belong to liquid rocket engine regenerative cooling field.For the problem that in existing regenerative cooling design, because of hydrogen peroxide thermophysical property data and decomposition characteristics are not clear, can only adopt large flow low temperature rise scheme, the application obtains the density, dynamic viscosity, specific heat and thermal conductivity of high-pressure high-concentration hydrogen peroxide using property calculation software;Based on Clapeyron-Klaus equation, calculate the decomposition temperature point under different pressure and concentration;Based on first-order reaction kinetics and fluid residence time, calculate decomposition rate;Establish regenerative cooling channel distribution parameter heat transfer calculation model, use piecewise control volume method to solve mass conservation, component mass conservation, energy conservation and momentum conservation equation simultaneously, iteratively solve to obtain the spatial distribution of temperature, component concentration, decomposition rate and pressure drop in the channel.The application can provide calculation basis for optimizing coolant flow and channel size, reducing pumping power.

Description

Technical Field

[0001] This invention belongs to the field of regenerative cooling technology for liquid rocket engines, specifically relating to a calculation method for regenerative cooling of a hydrogen peroxide bicomponent rocket engine, and more specifically to a method for predicting and evaluating regenerative cooling performance applicable to a regenerative cooling system for a bicomponent liquid rocket engine using hydrogen peroxide as an oxidant, capable of coupled calculation of the flow, heat transfer, and decomposition processes of the working fluid within the cooling channel. Background Technology

[0002] Liquid rocket engines possess advantages such as high specific impulse, variable thrust, and reusability, making them crucial in aerospace propulsion systems. Hydrogen peroxide (… Liquid rocket propellant (LPR) is a green propellant with advantages such as high density and specific impulse, strong room temperature storage capacity, non-toxicity and pollution-free properties, and single-component propellant characteristics, and is widely used in various rocket propulsion systems. The thrust chamber is a key component of a liquid rocket engine, operating at temperatures up to 3500 K. Effective cooling technologies are required to ensure its reliability under high temperature and pressure. Regenerative cooling technology has become the preferred cooling method for high-pressure, high-thrust rocket engines because it can reduce engine weight, suppress material thermal fatigue and oxidation damage, and increase engine specific impulse.

[0003] Current research on regenerative cooling in liquid rocket engines mainly focuses on enhancing heat transfer in cooling channels and reducing flow resistance within these channels. For For kerosene-fuel bicomponent rocket engines, existing research has focused on regenerative cooling design and coupled calculations of the combustion chamber and cooling channels. Currently, it is generally possible to complete the thermal protection design and verification of the cooling channels under conservative operating conditions. However, existing solutions have the following shortcomings:

[0004] I. Existing Regenerative cooling tests and designs typically limit coolant temperature rise to ensure safety, for example, by... The temperature rise along the passage is controlled within the range of approximately 20 K to 50 K; this scheme can reduce... While mitigating risks, it increases coolant flow requirements, leading to larger cooling channel sizes, increased pumping system load, more complex flow regulation, channel erosion, and reduced structural reliability.

[0005] II. Existing Regenerative cooling calculations lack sufficient understanding of the changes in thermal properties under high pressure and high concentration conditions. In particular, the data on the changes in density, dynamic viscosity, specific heat and thermal conductivity with temperature and pressure are incomplete, making it difficult to support accurate calculations of heat transfer, pressure drop and pumping power along the flow path under high temperature rise conditions.

[0006] three, The decomposition behavior is significantly affected by pressure, concentration, and temperature, with marked differences in decomposition initiation temperature and reaction rate under different operating conditions. Existing solutions often fail to couple the decomposition temperature, decomposition rate, decomposition products, and decomposition heat release with the heat transfer process in the regeneration cooling channel, making it difficult to determine the optimal decomposition parameters. The location where decomposition begins within the channel, the degree of decomposition, and its impact on local heat transfer and pressure loss;

[0007] IV. Existing information While research on regenerative cooling has yielded some numerical and experimental results, it still faces challenges in addressing specific needs. There is still a lack of research on the decomposition characteristics under regenerative cooling conditions and their impact on convective heat transfer, cumulative pressure drop and overall thermal-hydraulic performance, making it difficult to provide direct calculation basis for improving allowable temperature rise, flow margin and optimizing cooling channel size. Summary of the Invention

[0008] The purpose of this invention is to address the problems in the design of existing regenerative cooling systems for bicomponent rocket engines using hydrogen peroxide as an oxidant. These problems stem from a lack of quantitative description of the coupling relationship between the thermophysical properties of hydrogen peroxide over a wide concentration range under high pressure, decomposition initiation temperature, decomposition rate, decomposition heat release, product formation, and convective heat transfer and pressure drop within the cooling channel. This leads to conservative design methods that rely on high flow rates and low temperature rises, resulting in larger cooling channel dimensions, increased pumping power, and increased pressure drop along the cooling path. The invention proposes a regenerative cooling performance prediction method that establishes a database of hydrogen peroxide thermophysical properties and methods for calculating decomposition temperature and rate. These methods are coupled into a distributed parameter heat transfer calculation model for the regenerative cooling channel. This allows for the acquisition of performance evaluation parameters such as temperature along the cooling path, Nusselt number, cumulative decomposition rate, cumulative pressure drop, and pumping power. This provides accurate calculation basis for improving the allowable temperature rise of hydrogen peroxide, optimizing coolant flow rate and channel size, and reducing pumping power.

[0009] To achieve the above objectives, the technical solution provided by this invention is:

[0010] A calculation method for regenerative cooling of a hydrogen peroxide bicomponent rocket engine is provided, including the following steps:

[0011] Step 1: For the working fluid of hydrogen peroxide in the engine regeneration cooling channel, take hydrogen peroxide in the non-decomposition state as the research object, and use physical property calculation software to calculate the key thermal physical property parameters of hydrogen peroxide under different pressure conditions. The thermal physical property parameters include density, dynamic viscosity, specific heat and thermal conductivity. The calculation temperature range covers the temperature range that hydrogen peroxide may reach in the cooling channel, and the upper limit does not exceed the corresponding decomposition temperature point, forming a thermal physical property parameter database.

[0012] Step 2: Based on the thermophysical parameter database obtained in Step 1, and using the experimental data on the decomposition initiation temperature of hydrogen peroxide under normal pressure as a fitting sample, the decomposition initiation temperature of hydrogen peroxide at different concentrations under normal pressure is obtained. On this basis, for hydrogen peroxide of the same concentration, assuming that it is in phase equilibrium when it reaches the critical decomposition state under two different pressure conditions, the Clapeyron-Clausius equation is introduced to calculate the decomposition temperature points of hydrogen peroxide under different pressure and concentration conditions.

[0013] Step 3: Using the decomposition temperature point obtained in Step 2 as the basis for determining the decomposition start point, and based on the first-order reaction kinetics assumption and combined with the empirical correlation of the reaction rate constant, calculate the decomposition rate of hydrogen peroxide under different operating conditions; wherein, under the quasi-steady-state assumption, the reaction time is defined as the residence time required for the hydrogen peroxide fluid to flow from the decomposition start point position determined in Step 2 to any position along the cooling channel.

[0014] Step 4: Using the thermal property parameter database obtained in Step 1, the decomposition temperature points obtained in Step 2, and the decomposition rates at various locations along the cooling channel obtained in Step 3 as inputs, establish a heat transfer calculation model for the distributed parameters of the regenerative cooling channel. The channel is divided into several axial control volumes using the segmented control volume method. In each control volume, the mass conservation equation, component mass conservation equation, energy conservation equation, and momentum conservation equation are solved simultaneously to achieve the coupling of multiple physical characteristics of fluid flow, convection and conduction heat transfer, decomposition reaction, and phase change, and obtain the spatial evolution results of temperature, component concentration, decomposition rate, and pressure drop along the channel.

[0015] Furthermore, in step 3, the decomposition rate of hydrogen peroxide is calculated according to the following formula:

[0016]

[0017] In the formula, The decomposition rate of hydrogen peroxide, The reaction rate constant is... Reaction time; reaction rate constant Determined according to the following empirical correlation:

[0018]

[0019] In the formula, is a correction factor related to impurity concentration; T is the reaction temperature.

[0020] Furthermore, in step 3, the dwell time is calculated according to the following formula:

[0021]

[0022] In the formula, The axial distance from the decomposition starting point to the calculation position is... The fluid velocity within the channel; the fluid velocity within the channel Calculate using the following formula:

[0023]

[0024] In the formula, ρ is the total mass flow rate of the fluid, and ρ is the fluid density. For the number of cooling channels, The cross-sectional area of ​​a single cooling channel is given; the fluid density ρ is calculated using the following formula:

[0025]

[0026] In the formula, The density of hydrogen peroxide, The density of water, The density of oxygen. This represents the decomposition rate of hydrogen peroxide.

[0027] Furthermore, in step 4, the mass conservation equation is: the total mass flow rate of hydrogen peroxide remains constant during the flow process in the cooling channel.

[0028]

[0029] In the formula, This represents the total mass flow rate of the fluid. This represents the mass flow rate of hydrogen peroxide. The mass flow rate of water, This represents the mass flow rate of oxygen.

[0030] Furthermore, in step 4, the component mass conservation equation is:

[0031]

[0032]

[0033]

[0034] In the formula, For reaction time, is the reaction rate constant.

[0035] Furthermore, in step 4, the energy conservation equation is:

[0036]

[0037]

[0038] In the formula, For fluid specific enthalpy, Here are the position coordinates along the axial direction of the cooling channel. The heat flux density transferred to the cooling passages of the engine. The hydraulic diameter of the cooling channel. The decomposition heat release rate per unit channel length, The heat released per unit mass of hydrogen peroxide decomposition.

[0039] Furthermore, in step 4, the momentum conservation equation is specifically as follows: The total pressure drop consists of frictional pressure drop and local drag pressure drop:

[0040]

[0041] In the formula, For total pressure drop, For frictional pressure drop, This refers to the local pressure drop in the bend.

[0042] Furthermore, in step 4, the convective heat transfer coefficient is calculated using the Gnielinski correlation:

[0043]

[0044] In the formula, For Nusselt numbers, As the friction factor, The Reynolds number is... For Prandtl numbers, This is the temperature correction factor. This is the correction coefficient for the ingress effect;

[0045] For cooling channels with an inclined nozzle section, the Nusselt number is corrected according to the following formula:

[0046]

[0047]

[0048] In the formula, Here, E is the corrected Nusselt number, and E is the heat transfer enhancement correction factor caused by the channel tilting with the engine shape. The radius of curvature of the cooling channel;

[0049] The convective heat transfer coefficient of hydrogen peroxide is calculated using the following formula:

[0050]

[0051] In the formula, The convective heat transfer coefficient; is the thermal conductivity of the fluid.

[0052] Furthermore, in step 4, the cooling channels are rectangular structures, uniformly distributed along the circumference of the engine, and modeling and analysis are carried out with the flow and heat transfer within a single channel as the research object.

[0053] The advantages of this invention are:

[0054] 1. This invention establishes a database of thermophysical parameters of hydrogen peroxide covering a wide range of pressures and concentrations. By using a property calculation software system to calculate the density, dynamic viscosity, specific heat and thermal conductivity of hydrogen peroxide under different pressure conditions, it fills the gap in thermophysical data of hydrogen peroxide under high-pressure conditions and provides reliable basic data support for the precise design of regeneration cooling systems.

[0055] 2. This invention establishes a method for calculating the decomposition temperature of hydrogen peroxide under different pressure conditions based on the Clapeyron-Clausius equation, and establishes a method for calculating the decomposition rate based on the first-order reaction kinetics assumption combined with residence time. This enables quantitative determination of the location where hydrogen peroxide begins to decompose in the cooling channel, the degree of decomposition, and its evolution along the process, overcoming the shortcomings of existing technologies that rely solely on empirical safety margins due to unclear decomposition behavior.

[0056] 3. This invention constructs a heat transfer calculation model for the distributed parameters of the regenerative cooling channel by simultaneously solving the mass conservation equation, component mass conservation equation, energy conservation equation, and momentum conservation equation. It couples the hydrogen peroxide decomposition reaction kinetics, decomposition heat release, product generation, and convective heat transfer and flow pressure drop within the channel to obtain key performance parameters such as temperature field, component concentration field, decomposition rate distribution, cumulative pressure drop, and pumping power within the cooling channel, providing a complete calculation tool for the quantitative evaluation of the regenerative cooling system.

[0057] 4. This invention can provide accurate calculation basis for improving the allowable temperature rise of hydrogen peroxide, optimizing coolant flow rate and channel size, and reducing pumping power under the given engine thermal flow boundary and channel geometry parameters. It effectively overcomes the technical defects of existing conservative design schemes, such as large cooling channel size, heavy pumping system load and high pressure drop along the flow path. It is also applicable to regenerative cooling systems of hydrogen peroxide bicomponent rocket engines of different specifications and has wide engineering applicability. Attached Figure Description

[0058] The above and other features and advantages of the present invention will become more readily understood from the following description with reference to the accompanying drawings, in which:

[0059] Figure 1 The following are curves showing the changes in the thermophysical properties of hydrogen peroxide with temperature under different pressure conditions in this embodiment of the invention: density curve, dynamic viscosity curve, specific heat curve, and thermal conductivity curve.

[0060] Figure 2 These are the decomposition initiation temperature curves of hydrogen peroxide at different concentrations under normal pressure in embodiments of the present invention;

[0061] Figure 3 This is a flowchart illustrating the solution process for the heat transfer theoretical model of hydrogen peroxide regeneration cooling distribution parameters in an embodiment of the present invention.

[0062] Figure 4 This is a curve showing the temperature distribution of hydrogen peroxide along the cooling channel and the Nusselt number in an embodiment of the present invention.

[0063] Figure 5 This is the distribution curve of the final mass flow rate and cumulative decomposition rate of hydrogen peroxide outlet in the cooling channel in this embodiment of the invention;

[0064] Figure 6 The embodiments of the present invention show the cumulative pressure drop of hydrogen peroxide and the distribution curve of friction factor along the cooling channel. Detailed Implementation

[0065] The present invention will now be described in detail with reference to the accompanying drawings and exemplary embodiments thereof. It should be noted that the following detailed description of the present invention is for illustrative purposes only and is not intended to limit the scope of the invention.

[0066] This invention provides a calculation method for regenerative cooling of a hydrogen peroxide bicomponent rocket engine. Under given conditions of hydrogen peroxide solution concentration, engine thermal flux boundary, inlet pressure, and cooling channel geometry, the method uses theoretical calculations to obtain performance evaluation parameters such as the temperature along the path of the regenerative cooling system, Nusselt number, cumulative decomposition rate, cumulative pressure drop, and pumping power. This provides a calculation basis for optimizing the cooling system design, increasing the allowable temperature rise of hydrogen peroxide, optimizing coolant flow rate and channel size, and reducing pumping power.

[0067] The following reference Figures 1 to 6 The specific description of the hydrogen peroxide bicomponent rocket engine regenerative cooling calculation method as an exemplary embodiment of the present invention includes four steps: obtaining the thermophysical parameters of high-pressure, high-concentration hydrogen peroxide, calculating the hydrogen peroxide decomposition temperature point, calculating the hydrogen peroxide decomposition rate, and calculating the heat transfer of the regenerative cooling channel distribution parameters.

[0068] Step S1: Obtaining thermophysical parameters of high-pressure, high-concentration hydrogen peroxide

[0069] This step focuses on hydrogen peroxide as the working fluid in the engine's regenerative cooling channel. Taking hydrogen peroxide in its non-decomposed state as the research object, key thermophysical parameters of hydrogen peroxide under different pressure conditions are calculated using physical property calculation software.

[0070] In this embodiment, Aspen Plus is used as the software for property calculation. Aspen Plus contains a vast property database (called Aspen Properties) containing property information for thousands of chemical substances. Aspen Plus is used to perform property calculations on high-pressure hydrogen peroxide, establishing a thermal property database covering the range from 300K to the decomposition temperature. Thermal property parameters include density. (Unit is) Dynamic viscosity (Unit is) ), specific heat (Unit is) ) and thermal conductivity (Unit is) The calculated temperature range covers the temperature range that hydrogen peroxide may reach within the cooling channel, with the upper limit not exceeding the corresponding decomposition temperature, ensuring that the obtained thermophysical property data all correspond to hydrogen peroxide in its non-decomposition state. The calculated pressure range is 5–15 MPa, covering the typical operating pressure range of the rocket engine regenerative cooling channel.

[0071] Figure 1 The curves showing the changes in thermophysical properties of hydrogen peroxide with temperature under conditions of 5 MPa and 15 MPa are presented in the figure. and These are the hydrogen peroxide decomposition temperatures at 5 MPa and 15 MPa, respectively. , The curves represent the temperature variation ranges under different pressure conditions. From Figure 1 It can be seen that each thermophysical property parameter exhibits its own development trend with temperature and pressure: density and dynamic viscosity generally decrease with increasing temperature, specific heat increases with increasing temperature, and thermal conductivity shows an upward parabolic trend with temperature; except for specific heat, the properties under different pressures are not significantly different. However, there are significant differences in the decomposition temperature points. These data provide basic data support for subsequent heat transfer calculations of distributed parameters in regenerative cooling channels. If this database is not established and property data that does not consider decomposition is directly substituted into the operating condition calculations, it will lead to significant deviations in the calculation of heat transfer coefficients and pressure drops, thus affecting the accuracy of cooling channel design.

[0072] Step S2: Calculation of the decomposition temperature of hydrogen peroxide

[0073] This step uses the thermophysical parameter database obtained in step S1 as a basis to calculate the decomposition temperature of hydrogen peroxide under different pressure and concentration conditions.

[0074] First, based on atmospheric pressure ( Experimental data on the decomposition onset temperature of hydrogen peroxide at MPa were used as fitting samples to obtain different concentrations at atmospheric pressure. Decomposition onset temperature of hydrogen peroxide (in wt%) . Figure 2 The decomposition onset temperature curves of hydrogen peroxide at different concentrations under normal pressure are presented. Figure 2 It can be seen that under normal pressure, the decomposition onset temperature of hydrogen peroxide first decreases and then increases with concentration. When the concentration is below 48.75 wt%, the decomposition onset temperature decreases with increasing concentration, while when the concentration is above approximately 48.75 wt%, the decomposition onset temperature increases significantly with increasing concentration. Therefore, this embodiment uses a piecewise fitting method to describe the decomposition temperature of hydrogen peroxide at different concentrations under normal pressure, providing a data basis for subsequent calculations of the decomposition temperature of hydrogen peroxide under high pressure and multiple concentrations.

[0075] Based on this, for hydrogen peroxide of the same concentration, assuming it reaches phase equilibrium when it reaches its critical decomposition state under two different pressure conditions, the Clapeyron-Clausius equation is introduced to calculate the decomposition temperature of hydrogen peroxide under different pressures and concentrations. The Clapeyron-Clausius equation is in the form of:

[0076]

[0077] In the formula, and For two different pressures, and Two pressures respectively and The corresponding Decomposition temperature, ΔH is the molar enthalpy change, and R is the universal gas constant.

[0078] Table 1 shows the calculated decomposition temperature of hydrogen peroxide under different pressures and concentrations.

[0079] Table 1 Decomposition temperature of the solution (K)

[0080]

[0081] As shown in Table 1, at the same concentration, increased pressure leads to an increase in the decomposition temperature; conversely, at the same pressure, increased concentration also leads to an increase in the decomposition temperature. For example, for 100 wt% hydrogen peroxide, the decomposition temperature is 527.90 K at 5 MPa, but rises to 558.90 K at 15 MPa. At 5 MPa, the decomposition temperature of 40 wt% hydrogen peroxide is 361.47 K, while that of 100 wt% hydrogen peroxide is 527.90 K. This pattern implies that high pressure and high concentration conditions help suppress premature decomposition of hydrogen peroxide, but also that once the temperature reaches the decomposition point, the decomposition reaction will occur rapidly. This calculation provides a temperature criterion for subsequently determining the decomposition initiation location within the cooling channel. Only by comparing the local fluid temperature within the channel with this decomposition temperature can we accurately determine when and where hydrogen peroxide begins to decompose within the channel.

[0082] Step S3: Calculation of hydrogen peroxide decomposition rate

[0083] This step is based on the first-order reaction kinetics assumption and combined with the empirical correlation of the reaction rate constant to calculate the decomposition rate of hydrogen peroxide at any temperature; under the quasi-steady-state assumption, the reaction time is defined as the residence time required for the hydrogen peroxide fluid to flow from the decomposition initiation point along the cooling channel to any other location.

[0084] The decomposition of hydrogen peroxide is a first-order reaction. The decomposition rate is calculated using the following formula:

[0085]

[0086] In the formula, The decomposition rate of hydrogen peroxide; The reaction rate constant is expressed in units of 1000 m / s. ; This refers to the reaction time.

[0087] Reaction rate constant Determined according to the empirical correlation specified in the "Guideline for the Storage of Hydrogen Peroxide at Concentrations" published by the Peroxide Industry Group of the European Chemical Industry Council (Cefic).

[0088]

[0089] In the formula, This is a dimensionless correction factor related to impurity concentration. When the chemical purity of hydrogen peroxide is high, the impurity content is below the detection limit, and its effect on reaction kinetics is negligible, In this embodiment, The value is 1; T is the reaction temperature.

[0090] Under the quasi-steady-state assumption, reaction time The residence time is defined as the time required for hydrogen peroxide fluid to flow from the decomposition initiation point along the cooling channel to any other location. The residence time is calculated using the following formula:

[0091]

[0092] In the formula, This is the axial distance from the decomposition starting point to the calculation position, in meters. ,in This refers to the length of the cooling channel; The velocity of the fluid within the channel is expressed in m / s.

[0093] Fluid velocity within the channel Calculate using the following formula:

[0094]

[0095] In the formula, The total mass flow rate of the fluid is taken as a value in this embodiment. kg / s; ρ is the fluid density, in units of kg / s. ; This refers to the number of cooling channels; This refers to the cross-sectional area of ​​a single cooling channel.

[0096] Since hydrogen peroxide decomposes into water and oxygen, the density of the mixed fluid changes with the rate of decomposition. (Fluid density) Calculate using the following formula:

[0097]

[0098] In the formula, The density of hydrogen peroxide, The density of water, This is the density of oxygen.

[0099] Step S4: Calculation of heat transfer parameters for regeneration cooling channel distribution.

[0100] This step uses the thermal property parameter database obtained in step S1, the decomposition temperature points obtained in step S2, and the decomposition rate at each position along the cooling channel obtained in step S3 as inputs to establish a heat transfer calculation model for the distributed parameters of the regeneration cooling channel.

[0101] In this embodiment, the regenerative cooling channel includes a first bend section, a second bend section, and a straight section connected in sequence to form a continuous cooling medium flow path, and each pipe section is arranged to fit the contour of the rocket engine wall. Specifically, the first and second bend sections are both inclinedly arranged on the outer wall of the engine nozzle section to adapt to changes in the engine wall contour and achieve a smooth transition in the channel direction; both bend sections and the straight section adopt a rectangular structure with a cross-sectional dimension of [missing information]. , length is 300 mm, evenly distributed along the circumference of the engine. There are 18 cooling channels. Due to the symmetry of the channels, the flow and heat transfer within a single channel are modeled and analyzed.

[0102] Figure 3 The solution process for the heat transfer theoretical model of hydrogen peroxide regeneration cooling distributed parameters is presented. The specific process is as follows:

[0103] First, input the initial conditions such as cooling channel geometry, engine heat flux density, hydrogen peroxide inlet pressure, temperature, and concentration. Then, retrieve the working fluid properties from the thermophysical database and calculate the decomposition temperature. The hydrogen peroxide inlet temperature is set to 293.15 K, and the hydrogen peroxide inlet concentration is set to 100 wt%.

[0104] Subsequently, the cooling channel was divided into several control volumes along the axial direction using a segmented control volume method. The essence of this method is to discretize the continuous partial differential equations in space, assuming uniform material properties and flow parameters within each micro-element, thus transforming the partial differential equations into a system of algebraic equations for solution. In this embodiment, the cooling channel was divided into 2250 control volumes. Then, within each control volume, the mass conservation equation, component mass conservation equation, energy conservation equation, and momentum conservation equation were solved simultaneously to obtain local temperature, heat transfer, and pressure drop parameters. During the calculation process, the decomposition temperature point obtained in step S2 was compared with the energy conservation equation... The calculated fluid temperature along the flow path is compared to determine whether the current micro-element temperature has reached the hydrogen peroxide decomposition point. If the decomposition point has not been reached, the current calculation result is directly output and the process proceeds to the next control volume. If the decomposition point has been reached, the position where the decomposition temperature is first reached is determined as the decomposition start point. From this position, the decomposition source term is included, and the decomposition rate (reaction time is defined as the residence time of the fluid flowing from the decomposition start point along the channel to the current micro-element) and the thermophysical parameters of the mixture are calculated sequentially. The energy equation and each heat transfer and flow equation are resolved. Convergence is determined by comparing the temperatures of adjacent iteration steps. When the convergence condition is met... Output the parameters of the control volume when it is in use; otherwise, continue iterating. and They represent the first Second and third During the nth iteration, the 1st Fluid temperature value within a control volume;

[0105] Repeat the above calculations until the cooling channel outlet is reached, and finally obtain the temperature along the path, Nusselt number, hydrogen peroxide decomposition rate, pressure drop, and other heat transfer flow results.

[0106] Through the above solution process, the coupling of multiple physical characteristics of fluid flow, convection and conduction heat transfer, decomposition reaction and phase change is realized, and the spatial evolution results of temperature, component concentration, decomposition rate and pressure drop along the channel can be obtained.

[0107] The total mass flow rate of hydrogen peroxide remains constant during its flow through the cooling channel. The mass conservation equation is:

[0108]

[0109] In the formula, This represents the total mass flow rate of the fluid. The mass flow rate of hydrogen peroxide, The mass flow rate of water, This represents the mass flow rate of oxygen.

[0110] The mass conservation equations for each component are:

[0111]

[0112]

[0113]

[0114] The energy change of the fluid along the channel is determined by both external heating and internal chemical reactions, and the energy conservation equation is:

[0115]

[0116]

[0117] In the formula, Specific enthalpy is the enthalpy of a unit mass of hydrogen peroxide, expressed in J / kg. These are the position coordinates along the axial direction of the cooling channel; The heat flux density transmitted from the engine to the cooling passages, in MW / m³. 2 In this embodiment, 7.5 MW / m 2 ; The hydraulic diameter of the cooling channel is taken in this embodiment. =1.72 mm; The decomposition heat release rate per unit channel length; for The heat release per unit mass decomposition is 1.59 × 10⁻⁶ in this embodiment. 6 J / kg. This equation shows that the enthalpy increase of the fluid along the channel consists of two parts: one part is the heat transferred into the fluid by the external heat flow through the wall, and the other part is the heat released by the decomposition reaction of hydrogen peroxide. This invention reduces the heat released by the decomposition of hydrogen peroxide per unit mass. Defined as a positive value, this term is included with a positive sign in the energy equation, further increasing the fluid's specific enthalpy and temperature. This coupling relationship is the key difference between this invention and current technologies. Existing methods often do not consider the decomposition effect or ignore the heat released during decomposition, while this invention utilizes the energy conservation equation... The project directly couples the thermal effect of the decomposition reaction with the flow heat transfer process.

[0118] The total pressure drop in the cooling channel consists of frictional pressure drop and local resistance pressure drop. The momentum conservation equation is expressed in a one-dimensional engineering form by integrating along the cooling channel axis:

[0119]

[0120] in:

[0121]

[0122]

[0123]

[0124]

[0125]

[0126]

[0127] In the formula, For total pressure drop, For frictional pressure drop, The pressure drop in the bend is represented by f, where f is the friction factor. Let Reynolds number be 1. ; For the absolute roughness of the pipe wall, in this embodiment, we take... =1×10 -6 m; This refers to the bend resistance coefficient; The radius of curvature of the cooling channel is 155.36 mm in this embodiment, and the radius of curvature of the first bend is 36.21 mm.

[0128] The heat transfer of hydrogen peroxide in the channel is convective heat transfer, and the convective heat transfer coefficient is calculated using the Gnielinski correlation. The Gnielinski correlation is applicable to fully developed turbulent flow in a tube, and its form is as follows:

[0129]

[0130] In the formula, The Nusselt number is obtained directly using the Gnielinski correlation. For Prandtl numbers, ; For temperature correction coefficients, in this embodiment, we take... ; The inlet effect correction coefficient is taken in this embodiment. =1.

[0131] Because the cooling channels in the conformal engine nozzle section are arranged at an angle, the fluid flowing through the curved channels experiences centrifugal force, generating secondary flow and thus enhancing heat transfer between the wall and the fluid. Therefore, the Nusselt number in this region needs to be corrected.

[0132]

[0133]

[0134] In the formula, Here is the corrected Nusselt number, and E is the heat transfer enhancement correction factor caused by the channel tilting with the engine shape.

[0135] The convective heat transfer coefficient of hydrogen peroxide is calculated using the following formula:

[0136]

[0137] In the formula, is the convective heat transfer coefficient.

[0138] The model is solved numerically using MATLAB.

[0139] Figure 4 The distribution curves of hydrogen peroxide temperature along the cooling channel and the Nusselt number are presented. From... Figure 4 It can be seen that under both inlet pressures of 5 MPa and 15 MPa, the temperature of hydrogen peroxide gradually increases along the flow direction, indicating that the coolant continuously absorbs heat from the engine wall. Near the nozzle throat, the Nusselt number shows a significant increase, which is due to the enhanced secondary flow caused by the change in channel curvature, improving near-wall fluid mixing and convective heat transfer. Since liquids are difficult to compress, the heat transfer effect is not significantly different before their respective decomposition points. After the decomposition points, due to the small amount of decomposition, the effect on temperature and Nusselt number is also not significantly different. However, at 5 MPa, hydrogen peroxide vaporizes earlier, so the rapid increase in volume leads to an increase in flow velocity, resulting in a sharp enhancement of heat transfer, while its temperature remains constant during the evaporation process. These reasonable heat transfer characteristics indicate that the model of this invention can reflect the flow and heat transfer laws of hydrogen peroxide in the regenerative cooling channel and can be used to determine the heat transfer capacity and local heat load changes within the cooling channel.

[0140] Figure 5The final mass flow rate and cumulative decomposition rate at the outlet of the hydrogen peroxide channel within the cooling channel are given. The distribution curve of ). From Figure 5 It can be seen that hydrogen peroxide does not decompose before the decomposition initiation point; after passing the decomposition initiation point, the decomposition rate gradually increases with the increase of flow distance. The cumulative decomposition rate reflects the total amount of hydrogen peroxide decomposed from the channel inlet to the current position. Figure 5 A comparison of curves under different pressure conditions shows that increasing the inlet pressure raises the decomposition temperature and inhibits hydrogen peroxide decomposition, thus reducing the cumulative decomposition rate at the channel outlet. Figure 5 It can quantitatively determine the degree of hydrogen peroxide decomposition in the channel, thereby providing more accurate theoretical calculations for channel heat transfer, and also providing an assessment basis for thermal safety.

[0141] Figure 6 The cumulative pressure drop of hydrogen peroxide in the cooling channel is given. The distribution curves of the friction factor along the path. Figure 6 It can be seen that the cumulative pressure drop gradually increases along the flow direction, with a significant step increase at the throat and in the variable cross-section region. This is due to the increased local resistance caused by changes in channel curvature. The friction factor gradually decreases along the flow path, indicating that the viscosity of the coolant decreases after heating, thus reducing frictional resistance. The trends of cumulative pressure drop and friction factor are basically consistent under different pressures, indicating that pressure has a relatively small impact on flow resistance. Figure 6 It can quantitatively assess the pressure drop changes in the cooling channel, providing a basis for estimating the pumping power of the cooling system and optimizing the channel structure.

[0142] The above results demonstrate that the method of this invention can theoretically calculate performance evaluation parameters such as the temperature along the path, Nusselt number, cumulative decomposition rate, cumulative pressure drop, and pumping power of the regenerative cooling system, given the hydrogen peroxide solution concentration, engine heat flux boundary, inlet pressure, and cooling channel geometry. This provides accurate calculation basis for optimizing cooling system design, increasing the allowable temperature rise of hydrogen peroxide, optimizing coolant flow rate and channel size, and reducing pumping power. This method is applicable to regenerative cooling calculations under different hydrogen peroxide concentrations, inlet pressures, and engine heat flux conditions, and can provide a reliable theoretical calculation method for the design of regenerative cooling systems for hydrogen peroxide-based bicomponent rocket engines.

[0143] Finally, it should be noted that the features mentioned and / or shown in the above description of exemplary embodiments of the present invention can be combined in the same or similar manner with one or more other embodiments, combined with or substituted for corresponding features in other embodiments. These combined or substituted technical solutions should also be considered to be included within the scope of protection of the present invention.

Claims

1. A calculation method for regenerative cooling of a hydrogen peroxide bicomponent rocket engine, characterized in that, Includes the following steps: Step 1: For the working fluid of hydrogen peroxide in the engine regeneration cooling channel, taking hydrogen peroxide in a non-decomposition state as the research object, the key thermal properties of hydrogen peroxide under different pressure conditions are calculated using physical property calculation software. The thermal properties include density, dynamic viscosity, specific heat and thermal conductivity. The calculation temperature range covers the temperature range that hydrogen peroxide may reach in the cooling channel, and the upper limit does not exceed the corresponding decomposition temperature point, forming a thermal property parameter database. Step 2: Based on the thermophysical parameter database obtained in Step 1, and using the experimental data on the decomposition initiation temperature of hydrogen peroxide under normal pressure as a fitting sample, the decomposition initiation temperature of hydrogen peroxide at different concentrations under normal pressure is obtained. On this basis, for hydrogen peroxide of the same concentration, assuming that it is in phase equilibrium when it reaches the critical decomposition state under two different pressure conditions, the Clapeyron-Clausius equation is introduced to calculate the decomposition temperature points of hydrogen peroxide under different pressure and concentration conditions. Step 3: Using the decomposition temperature point obtained in Step 2 as the basis for determining the decomposition start point, and based on the first-order reaction kinetics assumption and combined with the empirical correlation of the reaction rate constant, calculate the decomposition rate of hydrogen peroxide under different operating conditions; wherein, under the quasi-steady-state assumption, the reaction time is defined as the residence time required for the hydrogen peroxide fluid to flow from the decomposition start point position determined in Step 2 to any position along the cooling channel. Step 4: Using the thermal property parameter database obtained in Step 1, the decomposition temperature points obtained in Step 2, and the decomposition rates at various locations along the cooling channel obtained in Step 3 as inputs, establish a heat transfer calculation model for the distributed parameters of the regenerative cooling channel. The channel is divided into several axial control volumes using the segmented control volume method. In each control volume, the mass conservation equation, component mass conservation equation, energy conservation equation, and momentum conservation equation are solved simultaneously to achieve the coupling of multiple physical characteristics of fluid flow, convection and conduction heat transfer, decomposition reaction, and phase change, and obtain the spatial evolution results of temperature, component concentration, decomposition rate, and pressure drop along the channel.

2. The calculation method for regenerative cooling of a hydrogen peroxide bicomponent rocket engine according to claim 1, characterized in that, In step 3, the decomposition rate of hydrogen peroxide is calculated according to the following formula: In the formula, The decomposition rate of hydrogen peroxide, The reaction rate constant is... The reaction time; the reaction rate constant Determined according to the following empirical correlation: In the formula, is a correction factor related to impurity concentration; T is the reaction temperature.

3. The calculation method for regenerative cooling of a hydrogen peroxide bicomponent rocket engine according to claim 1, characterized in that, In step 3, the dwell time is calculated according to the following formula: In the formula, The axial distance from the decomposition starting point to the calculation position is... The fluid velocity within the channel; the fluid velocity within the channel Calculate using the following formula: In the formula, ρ is the total mass flow rate of the fluid, and ρ is the fluid density. For the number of cooling channels, The cross-sectional area of ​​a single cooling channel; the fluid density ρ is calculated according to the following formula: In the formula, The density of hydrogen peroxide, The density of water, The density of oxygen. This represents the decomposition rate of hydrogen peroxide.

4. The calculation method for regenerative cooling of a hydrogen peroxide bicomponent rocket engine according to claim 1, characterized in that, In step 4, the mass conservation equation is: the total mass flow rate of hydrogen peroxide remains constant during the flow of hydrogen peroxide in the cooling channel. In the formula, This represents the total mass flow rate of the fluid. This represents the mass flow rate of hydrogen peroxide. The mass flow rate of water, This represents the mass flow rate of oxygen.

5. The calculation method for regenerative cooling of a hydrogen peroxide bicomponent rocket engine according to claim 4, characterized in that, In step 4, the component mass conservation equation is: In the formula, For reaction time, is the reaction rate constant.

6. The calculation method for regenerative cooling of a hydrogen peroxide bicomponent rocket engine according to claim 5, characterized in that, In step 4, the energy conservation equation is: In the formula, For fluid specific enthalpy, Here are the position coordinates along the axial direction of the cooling channel. The heat flux density transferred to the cooling passages of the engine. The hydraulic diameter of the cooling channel. The decomposition heat release rate per unit channel length, The heat released per unit mass of hydrogen peroxide decomposition.

7. The calculation method for regenerative cooling of a hydrogen peroxide bicomponent rocket engine according to claim 6, characterized in that, In step 4, the momentum conservation equation is specifically as follows: the total pressure drop consists of frictional pressure drop and local drag pressure drop. In the formula, For total pressure drop, For frictional pressure drop, This refers to the local pressure drop in the bend.

8. The calculation method for regenerative cooling of a hydrogen peroxide bicomponent rocket engine according to claim 6, characterized in that, In step 4, the convective heat transfer coefficient is calculated using the Gnielinski correlation: In the formula, For Nusselt numbers, As the friction factor, The Reynolds number is... For Prandtl numbers, This is the temperature correction factor. This is the correction coefficient for the ingress effect; For cooling channels with an inclined nozzle section, the Nusselt number is corrected according to the following formula: In the formula, Here, E is the corrected Nusselt number, and E is the heat transfer enhancement correction factor caused by the channel tilting with the engine shape. The radius of curvature of the cooling channel; The convective heat transfer coefficient of hydrogen peroxide is calculated using the following formula: In the formula, The convective heat transfer coefficient; is the thermal conductivity of the fluid.

9. The calculation method for regenerative cooling of a hydrogen peroxide bicomponent rocket engine according to any one of claims 1 to 8, characterized in that, In step 4, the cooling channels are rectangular structures and are evenly distributed along the circumference of the engine. The flow and heat transfer within a single channel are taken as the research object for modeling and analysis.

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