A method, program, equipment, and storage medium for thermodynamic calculation of a water ramjet engine with a wide water-fuel ratio range.

Abstract

This invention belongs to the field of thermodynamic calculation technology for water-ramjet engines, specifically relating to a method, program, equipment, and storage medium for thermodynamic calculation of water-ramjet engines with a wide water-fuel ratio range. This invention determines the engine's operating stage by comparing the total water-fuel ratio with the critical point of the water-fuel ratio, effectively performing thermodynamic calculations for the engine's operating state at different stages, and avoiding the impact of phase change problems in the combustion chamber on the thermodynamic calculations. Compared to traditional thermodynamic calculation methods for water-ramjet engines, it can solve the calculation divergence problem existing in the thermodynamic calculation of water-ramjet engines with a wide water-fuel ratio range, and more accurately reflects the engine performance characteristics at different operating stages.

Description

Technical Field

[0001] This invention belongs to the field of thermodynamic calculation technology for water ramjet engines, specifically relating to a thermodynamic calculation method, program, equipment, and storage medium for water ramjet engines with a wide water-fuel ratio range. Background Technology

[0002] Water-ramjet engines, which use water-reacting metallic fuels as fuel, are a new type of power system designed to meet the high-speed and long-range requirements of underwater hypersonic vehicles. This type of engine uses seawater as an oxidizer, reacting a high-content metallic fuel to produce high-temperature, high-pressure reaction products, which significantly improves the propellant's energy density and the engine's specific impulse. Furthermore, by introducing tertiary ramjet seawater to increase the engine's water-fuel ratio, the proportion of liquid phase in the combustion products can be increased, reducing their expansion capacity. This, in turn, lowers the nozzle velocity and increases the nozzle flow rate, facilitating the formation of a gas-liquid two-phase flow within the engine, thereby generating higher thrust through the nozzle.

[0003] Due to the introduction of seawater in the tertiary ramjet process, the calculation range of the water-fuel ratio needs to be extended to a wide range during the thermodynamic calculation of water-ramjet engines. Traditional thermodynamic calculation methods for water-ramjet engines typically utilize CEA software. However, when using CEA software for thermodynamic calculations over a wide water-fuel ratio range, calculations often show accuracy at low water-fuel ratios but divergence at high water-fuel ratios. Therefore, thermodynamic calculations for water-ramjet engines over a wide water-fuel ratio range become a significant challenge. Summary of the Invention

[0004] The purpose of this invention is to provide a thermodynamic calculation method for a water ramjet engine with a wide water-fuel ratio range, which can solve the problem of calculation divergence in the thermodynamic calculation of water ramjet engines with a wide water-fuel ratio range, thereby effectively performing thermodynamic calculations for engine operating states at different stages.

[0005] A method for thermodynamic calculation of a water-ramjet engine with a wide water-fuel ratio range includes the following steps:

[0006] Step 1: Obtain the total water-fuel ratio and sailing speed of the water ramjet engine at the current moment;

[0007] Step 2: Compare the total water-fuel ratio of the water-ramjet engine at the current moment with the critical point of the water-fuel ratio to determine the current operating stage of the water-ramjet engine;

[0008] The critical point for the water-fuel ratio includes the critical point for steam phase change and the limit point for atomization evaporation.

[0009] The working stages of the water-jet engine include the water-jet stage, the transition stage, and the gas-liquid two-phase stage.

[0010] If the total water-fuel ratio of the water-jet engine is less than the water-fuel ratio at the critical point of steam phase change at the current moment, then the water-jet engine is judged to be in the water-jet stage.

[0011] If the total water-fuel ratio of the water-ram engine is between the water-fuel ratio at the critical point of steam phase change and the water-fuel ratio at the limit point of atomization evaporation at the current moment, then the water-ram engine is judged to be in the transition phase.

[0012] If the total water-fuel ratio of the water-ram engine is greater than the water-fuel ratio at the atomization evaporation limit point at the current moment, then the water-ram engine is judged to be in the gas-liquid two-phase stage.

[0013] Step 3: Based on the current operating stage of the water ramjet engine, calculate the nozzle exit velocity of the water ramjet engine at the current moment, and then perform thermodynamic calculations on the water ramjet engine to obtain the specific impulse of the water ramjet engine at the current moment.

[0014] If the water-jet engine is in the water-jet phase, then the nozzle exit velocity v of the water-jet engine at the current moment is... e1 for:

[0015]

[0016] Among them, H c H is the enthalpy value at the combustion chamber. e This is the enthalpy value at the nozzle exit.

[0017] If the water-jet engine is in the transition phase, then the nozzle exit velocity v of the water-jet engine at the current moment is... e2 for:

[0018]

[0019] Among them, T c The combustion chamber temperature; p e p is the pressure at the nozzle exit. c The pressure inside the combustion chamber; C sl The specific heat capacity is C. g ε is the specific heat capacity of the fuel gas; ε is the mass fraction of the condensed phase; n = R g / (C g +C sl ·ε / (1-ε)), R g is the gas constant.

[0020] If the water-jet engine is in the water-jet phase or transition phase, then the specific impulse I of the water-jet engine at the current moment is... sp for:

[0021] I sp =(1+φ w )v ei -φ w U

[0022] Where, φ w The total water-fuel ratio of the water ramjet engine at the current moment; U is the current speed of the water ramjet engine; v ei Let i be the nozzle exit velocity at the current operating stage of the water jet engine, i = 1, 2;

[0023] If the water-jet engine is in the gas-liquid two-phase stage, then the nozzle exit velocity v of the water-jet engine at the current moment is... e3 for:

[0024]

[0025] Among them, K m =(m s +m l ) / m g m g Let m be the gas phase flow rate within the flow field. s m is the solid phase flow rate within the flow field. l ρ is the working fluid flow rate within the flow field; sl The density of the solid-liquid mixture is... ρ l The density of the working fluid is water; T is the temperature at the nozzle inlet section; v c The velocity of the gas-liquid two-phase flow in the combustion chamber;

[0026] When the water-ramjet engine is in the gas-liquid two-phase stage, the specific impulse I of the water-ramjet engine at the current moment is... sp for:

[0027] I sp =(1-n) ms ε s (1+φ) w )v e3 -φ f v r -φ w U

[0028] Where, n ms ε is the hysteresis loss coefficient. s The mass fraction of solid phase in the total flow rate; φ f The water-fuel ratio corresponding to the working fluid water is defined as the ratio of the mass flow rate of the working fluid water to that of the powder; v r =v g -v l , v g Let v be the gas phase velocity. l The velocity is the liquid phase velocity.

[0029] Furthermore, the method for calculating the water-fuel ratio at the critical point of steam phase change in step 2 is as follows:

[0030] Thermodynamic analysis was performed using CEA software. When liquid water appeared in the combustion products, it was marked as the critical point of steam phase change. The water-fuel ratio at the critical point of steam phase change was calculated using the total mass flow rate of fuel and the total mass flow rate of seawater introduced at the time marked as the critical point of steam phase change.

[0031] Furthermore, the method for calculating the water-fuel ratio at the atomization evaporation limit point in step 2 is as follows:

[0032]

[0033] in, φ1 is the water-fuel ratio at the limit point of atomization evaporation; φ1 is the primary water-fuel ratio, calculated based on the total mass flow rate of fuel introduced by primary combustion and the total mass flow rate of seawater. This is the second critical water-fuel ratio. m w2 The secondary influent flow rate is m. p C represents the primary combustion product flow rate. p C is the isobaric specific heat capacity of the primary combustion products. water Where L is the specific heat capacity of water at constant pressure, and T is the latent heat of vaporization. sat T is the saturation temperature of water vapor. i This refers to the temperature of the secondary water intake.

[0034] Furthermore, in step 3, if the water-jet engine is currently in the gas-liquid two-phase stage, the calculation method for the nozzle inlet section temperature T is as follows:

[0035]

[0036] Among them, T f The temperature of the working fluid, water; C s For solid phase heat capacity; C water The specific heat capacity of water at constant pressure; m v m is the mass of steam in the combustion products. w3 The working fluid is water; L is the latent heat of vaporization; n v n represents the mass fraction of the vapor phase change. T n is the temperature hysteresis coefficient for gas-solid two-phase systems. ms This is the stagnant loss coefficient.

[0037] A computer device / equipment / system includes a memory, a processor, and a computer program stored in the memory, wherein the processor executes the computer program to implement the steps of the above-described method for thermodynamic calculation of a water ramjet engine with a wide water-fuel ratio range.

[0038] A computer-readable storage medium having a computer program / instructions stored thereon, which, when executed by a processor, implements the steps of the above-described method for thermodynamic calculation of a water ramjet engine with a wide water-fuel ratio range.

[0039] A computer program product includes a computer program / instructions that, when executed by a processor, implement the steps of the above-described method for thermodynamic calculation of a water ramjet engine with a wide water-fuel ratio range.

[0040] The beneficial effects of this invention are as follows:

[0041] This invention determines the engine's operating stage by comparing the total water-fuel ratio with the critical point of the water-fuel ratio. It effectively performs thermodynamic calculations for the engine's operating state at different stages, avoiding the impact of phase change problems in the combustion chamber on the thermodynamic calculations. Compared with traditional thermodynamic calculation methods for water ramjet engines, it can solve the calculation divergence problem in the thermodynamic calculation of water ramjet engines with a wide water-fuel ratio range, and more accurately reflects the engine performance characteristics at different operating stages. Attached Figure Description

[0042] Figure 1 This is a flowchart illustrating a method for calculating the thermodynamics of a water-ramjet engine with a wide water-fuel ratio range, as described in this invention.

[0043] Figure 2 This is a detailed flowchart illustrating a method for calculating the thermodynamics of a water-ramjet engine with a wide water-fuel ratio range, as described in this invention.

[0044] Figure 3 This is a schematic diagram of the structure of a computer device provided in an embodiment of the present invention. Detailed Implementation

[0045] The present invention will now be further described with reference to the accompanying drawings.

[0046] like Figure 1-Figure 2 As shown, this invention provides a method for thermodynamic calculation of a water ramjet engine with a wide water-fuel ratio range, including:

[0047] Step 101: Obtain the total water-fuel ratio and sailing speed of the water ramjet engine at the current moment.

[0048] Step 102: Based on the water-fuel ratio critical point that exists within a wide water-fuel ratio range, compare the total water-fuel ratio of the water ramjet engine at the current moment with the water-fuel ratio critical point to obtain the working stage of the water ramjet engine at the current moment.

[0049] The critical point of water-fuel ratio includes the critical point of steam phase change and the limit point of atomization evaporation; the working stages of a water ramjet engine include the water ramjet stage, the transition stage, and the gas-liquid two-phase stage.

[0050] When the total water-fuel ratio of the water-ramjet engine is less than the water-fuel ratio at the critical point of steam phase change, the current working stage of the water-ramjet engine is defined as the water-ramjet stage.

[0051] When the total water-fuel ratio of the water-ramjet engine is between the water-fuel ratio at the critical point of steam phase change and the water-fuel ratio at the limit point of atomization evaporation, the working stage of the water-ramjet engine at the current moment is defined as the transition stage.

[0052] When the total water-fuel ratio of the water-ramjet engine is greater than the water-fuel ratio at the atomization evaporation limit point, the working stage of the water-ramjet engine at the current moment is determined to be the gas-liquid two-phase stage.

[0053] Step 103: Based on the current operating stage of the water ramjet engine, use the formula for calculating the nozzle exit velocity of the corresponding operating stage to calculate the nozzle exit velocity of the water ramjet engine at the current moment.

[0054] Step 104: Based on the total water-fuel ratio, sailing speed and nozzle exit speed of the water ramjet engine at the current moment, perform thermodynamic calculations on the water ramjet engine to obtain the specific impulse of the water ramjet engine at the current moment.

[0055] Step 105: When the water ramjet engine continues to work in the next moment, obtain the total water-fuel ratio and sailing speed of the water ramjet engine in the next moment, and replace the total water-fuel ratio and sailing speed in step 101 with the total water-fuel ratio and sailing speed of the water ramjet engine in the next moment, and return to step 101 until the water ramjet engine stops working.

[0056] The calculation process for the water-fuel ratio at the critical point of steam phase change is as follows: thermodynamic analysis is performed using CEA software. When liquid water appears in the combustion products, it is marked as the critical point of steam phase change. The total mass flow rate of fuel at the time marked as the critical point of steam phase change and the total mass flow rate of seawater introduced are used to calculate the water-fuel ratio at the critical point of steam phase change.

[0057] The formula for calculating the water-fuel ratio at the atomization evaporation limit point is as follows:

[0058]

[0059] in, φ1 is the water-fuel ratio at the limit point of atomization evaporation; φ1 is the primary water-fuel ratio, which is calculated based on the total mass flow rate of fuel introduced by primary combustion and the total mass flow rate of seawater. The second critical water-fuel ratio is determined by the formula... The calculated m w2 The secondary influent flow rate is m. p C represents the primary combustion product flow rate. p C is the isobaric specific heat capacity of the primary combustion products.water Where L is the specific heat capacity of water at constant pressure, and T is the latent heat of vaporization. c T represents the combustion chamber temperature. sat T is the saturation temperature of water vapor. i This refers to the temperature of the secondary water intake.

[0060] The specific impulse of a water-jet engine is calculated using the following formula:

[0061] I sp =(1+φ w )v ei -φ w U (2)

[0062] Among them, I sp Specific impulse of a water-jet engine; φ w The total water-fuel ratio of the water-ramjet engine at the current moment is determined based on the total fuel mass flow rate and the total seawater mass flow rate introduced at the current moment; v ei U represents the nozzle exit velocity of the water ramjet engine at the current operating stage; U represents the current speed of the water ramjet engine.

[0063] The water jet stage is characterized by the secondary water being completely vaporized by the primary combustion products, and the nozzle outlet section temperature being higher than the local saturated steam temperature, with no liquid phase water in the ejected material.

[0064] The formula for calculating the nozzle exit velocity during the water jet stage is as follows:

[0065]

[0066] Among them, v e1 H represents the velocity at the nozzle exit during the water jet phase. c H is the enthalpy value at the combustion chamber. e This is the enthalpy value at the nozzle exit, expressed in J / kg.

[0067] The transition phase is characterized by excessive secondary water intake, secondary combustion products at saturated steam temperature, partial steam liquefaction in secondary combustion products, discrete liquid phase, and ejected material mainly consisting of gas phase.

[0068] The formula for calculating the nozzle exit velocity during the transition phase is as follows:

[0069]

[0070] Among them, v e2 T is the nozzle exit velocity during the transition phase. c The temperature of the combustion chamber is expressed in Kelvin (K); p e p is the pressure at the nozzle exit. c The pressure inside the combustion chamber; C slFor condensation heat capacity, C g This refers to the specific heat capacity of the gas, measured in J / kg·K. -1 ε is the mass fraction of condensed phase; n is the dimensionless exponent, calculated according to the formula n = R. g / (C g +C sl R is calculated by ·ε / (1-ε)). g This is the gas constant, and its unit is J / kg·K⁻¹. 1 .

[0071] The gas-liquid two-phase stage is characterized by the presence of non-evaporable working fluid water in the injected seawater, with the liquid phase being regarded as a continuous phase, and the flow inside the nozzle satisfying the gas-liquid two-phase flow law.

[0072] During the gas-liquid two-phase stage, a homogeneous flow treatment method is adopted during the nozzle flow process, treating the gas-liquid two-phase flow as a uniform and continuous "pseudo-fluid" where the flow parameters of each phase in the fluid are equal. Therefore, the density ρ of the fluid inside the nozzle is... m The calculation formula is as follows:

[0073]

[0074] Taking both incompressible solid and liquid phases into account, we introduce the symbol K. m =(m s +m l ) / m g Equation (5) above simplifies to:

[0075]

[0076] In the formula:

[0077]

[0078] Where, m i V i and ρ i These represent the flow rate, volume, and density of each substance within the flow field, respectively. The subscripts g, s, l, and sl represent the gas phase, solid phase, working fluid water, and solid-liquid mixture, respectively. The unit of flow rate is kg / s, and the unit of volume is m³. 3 The unit of density is kg / m³. 3 T represents the nozzle inlet section temperature, in Kelvin; p represents the pressure inside the mixing chamber, in Pa; when converting the solid-liquid mixture density ρ... sl When the solid phase volume is ignored.

[0079] The energy equation in a gas-liquid two-phase nozzle is:

[0080]

[0081] Where v, p, and ρ represent velocity, pressure, and density, respectively, the subscript c indicates combustion chamber parameters, and the subscript e indicates nozzle exit parameters.

[0082] The change in pressure potential energy per unit mass of fluid in equation (8) above can be calculated by the following definite integral, combined with equation (6):

[0083]

[0084] Substituting equation (9) into equation (8), we obtain the nozzle exit velocity v. e3 The calculation formula is as follows:

[0085]

[0086] The nozzle inlet section temperature T can be derived from the energy conservation equation. Let the temperature of the working fluid water be T. f The combustion chamber temperature is T c The energy equation for the mixing process is as follows:

[0087]

[0088] Where, m w3 C represents the mass flow rate of the working fluid, water. g C represents the specific heat capacity of the gas. water C is the specific heat capacity of water at constant pressure. s The solid phase heat capacity; by transforming the above equation (11), the formula for calculating the nozzle inlet section temperature can be obtained as follows:

[0089]

[0090] Furthermore, the gas-liquid two-phase stage also suffers from multiphase flow losses caused by the two-phase flow effect. These multiphase flow losses include solid phase kinetic energy stagnation loss, solid phase temperature lag loss, two-phase slip velocity loss, and vapor phase change loss. Taking into account the multiphase flow losses, the formulas for calculating the nozzle inlet section temperature and the specific impulse of the gas-liquid two-phase stage are modified to obtain the modified nozzle inlet section temperature and the modified specific impulse of the gas-liquid two-phase stage.

[0091] It should be noted that the velocity lag in the gas-solid two-phase flow is considered as the solid phase kinetic energy stagnation loss. In this case, the solid phase velocity is zero due to stagnation, and all the heat is transferred to the liquid phase, resulting in the loss of thermal energy of the combustion products. Only a portion of the solid phase is ejected with the combustion gas. The formulas for calculating the nozzle inlet temperature and specific impulse after correction for solid phase kinetic energy stagnation loss are as follows:

[0092]

[0093] Among them, T ms The nozzle inlet temperature after correction for solid phase kinetic energy stagnation loss; ε is the specific impulse after correction for solid-phase kinetic energy stagnation loss; s n represents the mass fraction of the total flow rate of the solid phase; ms This is the stagnant loss coefficient.

[0094] Since the solid phase temperature hysteresis loss cannot be directly reflected in the specific impulse, it is necessary to modify the energy equation (11) to indirectly reflect the effect of temperature hysteresis on specific impulse from the perspective of temperature change. The energy equation after correction for solid phase temperature hysteresis loss is as follows:

[0095] C water m w3 (T t -T f )=(T c -T t C g m g +(T c -T s C s m s (15)

[0096] Define the temperature hysteresis coefficient of the gas-solid two-phase system as n T =(T s -T t ) / (T c -T t Combining equation (15) above, we get:

[0097]

[0098] Among them, T t T represents the nozzle inlet temperature after correction for solid phase temperature hysteresis loss. s This is the solid-state temperature, measured in Kelvin (K).

[0099] In gas-liquid two-phase flow, the difference between the actual velocities of the two phases is usually called the slip velocity, according to the formula v. r =v g -v l Calculated; where v r v is the difference between the actual velocities of the two phases. g Let v be the gas phase velocity. l The velocity is the liquid phase velocity, and the unit is m / s.

[0100] When considering the effect of two-phase slip velocity loss on specific impulse, the formula for calculating specific impulse after correction for two-phase slip velocity loss is as follows:

[0101]

[0102] Where, φ fThe water-fuel ratio corresponding to the working fluid water is defined as the ratio of the mass flow rate of the working fluid water to that of the powder.

[0103] The vapor phase change also indirectly affects the specific impulse by influencing the nozzle inlet temperature. The formula for calculating the nozzle inlet temperature after correction for vapor phase change losses is as follows:

[0104]

[0105] Among them, T v The nozzle inlet temperature is corrected for steam phase change losses; L is the steam phase change enthalpy, numerically equivalent to the latent heat of vaporization, in J / kg; m v n represents the mass of steam in the combustion products, measured in kg; v This represents the mass fraction of vapor phase change.

[0106] By combining all the multiphase flow losses and applying formulas (13)-(18), the calculation formulas for the nozzle inlet section temperature and the specific impulse in the gas-liquid two-phase stage are corrected, resulting in the following formulas for calculating the nozzle inlet section temperature and specific impulse after correction for multiphase flow losses:

[0107]

[0108] Example 1:

[0109] Select Al 0.5 Mg 0.5 Using alloys as metallic fuels, this invention provides a detailed explanation of a thermodynamic calculation method for a water-ramjet engine with a wide water-fuel ratio range, and demonstrates it through calculation examples. The specific process is as follows:

[0110] The total water-fuel ratio of the water-ram engine was set to 5, the metal fuel temperature to 298.15 K, the combustion chamber pressure to 10 bar, the sailing speed to 60 m / s, the seawater temperature to 283.15 K, and the nozzle outlet pressure to 199129 Pa.

[0111] When the total water-fuel ratio of the water-jet engine is set to 5, the corresponding combustion products are shown in Table 1:

[0112] Table 1A1 0.5 Mg 0.5 Combustion product ratio and temperature table

[0113]

[0114] In the low water-fuel ratio stage, thermodynamic calculations were performed using CEA software until liquid water appeared in the combustion products. When the water-fuel ratio was around 6.5, the combustion chamber temperature was 449.15 K, which is lower than the steam saturation temperature at the combustion pressure. At this point, liquid water appeared in the combustion chamber. The water-fuel ratio at the steam phase change point was then used to mark this point.

[0115] Let the primary water-fuel ratio φ1 = 1, and use CEA software to calculate the temperature T of the combustion products. r =2973.42K, specific heat capacity C of combustion products p = 3.3343 kJ / kg·K -1 Based on the steam parameters under different combustion pressures in Table 2, the critical flow ratio m was calculated. w2 :m p =3.328, Secondary Critical Water-Fuel Ratio Atomization evaporation limit point

[0116] Table 2. Water vapor parameters under different combustion chamber pressures.

[0117] <![CDATA[p c (bar)]]> <![CDATA[T sat (K)]]> L(kJ / kg) <![CDATA[C water (kJ / kg·K -1 )]]> 10 453.04 1812.2 4.1958 15 471.30 1750.5 4.4855 20 485.38 1693.0 4.5623

[0118] When the water-fuel ratio φ w When the value is less than 6.5, it belongs to the water-pressing stage, and CEA software is used for thermodynamic calculations in this stage.

[0119] When the water-fuel ratio is 6.5 ≤ φ w When ≤7.633, it belongs to the transition stage, with φ w Taking 7 as an example, the calculation in this stage is as follows: The combustion chamber temperature T is calculated using a self-written program based on the minimum free energy method. c =448.35K, condensation ratio in the combustion chamber ε = 0.367, specific heat capacity of fuel gas C g =2168.34 J / kg·K -1 condensation heat capacity C sl =2257.67 J / kg·K -1 The gas constant R of the gas mixture g = 532.06 J / kg·K -1 Then, according to the formula n = R g / (C g +C sl The dimensionless exponent n = 0.153 is obtained by calculating ε / (1-ε); then the velocity v at the nozzle exit during the transition phase is calculated according to formula (4). e2 =657.13m / s; The specific impulse of the transition stage is calculated to be 4837.07N·s / kg according to formula (2).

[0120] When the water-fuel ratio φw When the value is greater than 7.633, it belongs to the gas-liquid two-phase stage, with φ w Taking 17 as an example, the calculations at this stage are as follows: Using a self-written program, calculate the combustion chamber temperature T when the total water-fuel ratio of the water-jet engine is 5. c =668.47K, condensation ratio in the combustion chamber ε = 0.296, specific heat capacity of fuel gas C g =2349.46 J / kg·K -1 condensation heat capacity C sl =1155.86J / kg·K -1 The gas constant R of the gas mixture g = 546.04 J / kg·K -1 The nozzle inlet section temperature T = 357.43 K was calculated using formula (12); the nozzle outlet velocity v during the gas-liquid two-phase stage was calculated using formula (10). e3 =385.97m / s; The specific impulse of the gas-liquid two-phase stage is calculated to be 5927.39N·s / kg according to formula (2).

[0121] The above is an example of thermodynamic calculation for a water-ramjet engine with a wide water-fuel ratio range, without considering two-phase flow losses. The following example calculates the two-phase flow losses in the gas-liquid two-phase stage, still using φ... w For example, if the value is 17:

[0122] Regarding the solid-phase kinetic energy stagnation loss, parameters such as combustion chamber temperature and specific heat have been given previously, and the stagnation loss coefficient n... ms Taking 0.5, the nozzle inlet temperature T after correction for solid phase kinetic energy stagnation loss is calculated according to formula (13). ms =352.22K; The nozzle exit velocity v after correction for solid phase kinetic energy stagnation loss is calculated according to formula (10). e3 =392.96m / s; the specific impulse after correction for solid phase kinetic energy stagnation loss is calculated according to formula (14).

[0123] Regarding the solid-phase temperature hysteresis loss, parameters such as combustion chamber temperature and specific heat have been given previously, and the temperature hysteresis coefficient n... T Taking 0.5, the nozzle inlet temperature T after correction for solid phase temperature hysteresis loss is calculated according to formula (14). t =352.22K; The nozzle exit velocity v after correction for solid phase temperature hysteresis loss is calculated according to formula (10). e3 =383.16m / s; According to formula (2), the specific impulse after correction for solid phase temperature hysteresis loss is 5876.86N·s / kg.

[0124] Regarding the two-phase slip velocity loss, parameters such as combustion chamber temperature and specific heat have been given previously. The nozzle exit velocity is the velocity under ideal conditions, and the water-fuel ratio φ corresponding to the working fluid is water. f =17-5=12, sliding velocity v r Taking 5 m / s, the specific impulse after correction for two-phase slip velocity loss is calculated according to formula (17).

[0125] The vapor phase change loss is estimated using the following method: Ignoring radiation during the heat exchange process, a Newtonian cooling model is used to describe the heat exchange process:

[0126]

[0127] Where, r p ρ represents the particle radius, with units of meters (m). p Represents particle density, with units of kg / m³. 3 h p The enthalpy value representing the particle, expressed in J / kg; h c This represents the convective heat transfer coefficient between particles and airflow, with units of W / m³. 2 ·K -1 .

[0128] Let the diameter of the combustion chamber be D, and the mole fraction of vapor in the gas phase of the combustion products be X. v Then the macroscopic radius of the steam

[0129] The heat transfer coefficient h of water vapor condensation under forced convection c Approximately 5000–15000 W / m 2 ·K -1 The combustion time of aluminum-magnesium particles is taken as a reference, and the temperature integral length dt = 20ms is taken.

[0130] Let the temperature of the working fluid be T. f =283.15K, as shown in Table 2, the temperature T of the solid particles s The saturated steam temperature is set at 453.04 K, the combustion chamber diameter D = 100 mm, and the macroscopic steam radius r is calculated based on the combustion product proportions in Table 1. p = 46.91 mm. The enthalpy change dh during steam condensation in one complete flow cycle can be obtained by integrating formula (21). p =211.11~633.31kJ / kg.

[0131] Since the steam is in a superheated state before condensation, it is also necessary to calculate the enthalpy change due to cooling during the condensation process, as shown in the following formula:

[0132]

[0133] in, This represents the specific heat capacity of superheated steam. According to the steam standard, it can be found... Combining the parameters in Tables 1 and 2, we can see the enthalpy change upon cooling.

[0134] And calculate the co-current heat transfer coefficient h. c Next n v The maximum value is given by the following formula:

[0135]

[0136] dh p , Substituting the calculation result into formula (23), the mass fraction n of the steam phase change can be obtained. v =0.353~0.584.

[0137] The horizontal axis of the steam phase change intensity curve represents the water-fuel ratio, and the vertical axis represents the steam retention rate ω. v (ω v =1-n v A convex function fitting function is used to characterize the weak steam phase change intensity under low water-fuel ratio conditions, and the variation law of steam phase change intensity increasing with increasing water-fuel ratio.

[0138] A power function is used for fitting, and the fitting formula is ω. v =a(φ-5) b +c. With h c Taking 5000 as an example, the curve ω v The starting point of f(φ) is (8,1), the ending point is (35,0.647), and the anchor point is (22,0.95), used for function curve fitting. The fitted result is: a = 2.96 × 10 -6 b = 3.44, c = 1.00.

[0139] The combustion chamber temperature and other parameters have been given previously. The phase change of steam will cause changes in the parameters of the gas-phase mixture and the solid-liquid mixture. The water-fuel ratio φ is calculated based on the fitting function. w Steam retention rate ω at 17 v =0.985, therefore 98.5% of the vapor will remain in the gaseous phase, with the remainder converting into liquid water. Therefore, adjustments need to be made to the relativity and gas constant, which will not be detailed further.

[0140] The nozzle inlet temperature T after steam phase change loss correction is calculated according to formula (18). v =356.49K; The nozzle exit velocity v after correction for solid phase temperature hysteresis loss is calculated according to formula (10). e3=383.09m / s; According to formula (2), the specific impulse after correction for solid phase temperature hysteresis loss is 5875.57N·s / kg.

[0141] When considering all two-phase flow losses together, some parameters may interact with each other. An example is provided below to comprehensively consider multiphase flow losses:

[0142] (1) Take the stagnation loss coefficient n for gas-solid two-phase flow ms =0.6;

[0143] (2) Take the temperature hysteresis coefficient n of the gas-solid two-phase flow. T =0.6;

[0144] (3) Take the slip velocity v of the gas-liquid two-phase flow r =5m / s;

[0145] (4) Take the vapor phase change function as h c =5000W / m 2 ·K -1 The function for fitting the convex curve;

[0146] The nozzle inlet section temperature T after multiphase flow loss correction is calculated according to formula (19). loss =347.61K; The nozzle exit velocity v after correction for solid phase temperature hysteresis loss is calculated according to formula (10). e3 =390.03m / s; According to formula (20), the specific impulse after multiphase flow loss correction is 5525.44N·s / kg.

[0147] Example 2:

[0148] This invention provides a thermodynamic calculation method for a water-ramjet engine with a wide water-fuel ratio range, applicable to an application environment consisting of a terminal, a data storage system, and a server. The terminal communicates with the server via a network. The data storage system stores the data the server needs to process. The data storage system can be set up independently, integrated into the server, or located in the cloud or on another server. The terminal can send the current total water-fuel ratio and speed of the water-ramjet engine to the server. Upon receiving these data, the server compares the current total water-fuel ratio with the critical points within the wide water-fuel ratio range to determine the current operating stage of the water-ramjet engine. Then, using the formula for calculating the nozzle exit velocity at the corresponding operating stage, the server obtains the current nozzle exit velocity. Based on the current total water-fuel ratio, speed, and nozzle exit velocity, the server performs thermodynamic calculations on the water-ramjet engine to obtain the specific impulse at the current moment. The server can then feed back the obtained specific impulse to the terminal. In addition, in some embodiments, the thermal calculation method can also be implemented by the server or the terminal alone. For example, the terminal can directly perform thermal calculations on the total water-fuel ratio and speed of the water ramjet engine at the current moment, or the server can obtain the total water-fuel ratio and speed of the water ramjet engine at the current moment from the data storage system and perform thermal calculations.

[0149] Among them, the terminal can be, but is not limited to, various desktop computers, laptops and IoT devices, and the server can be implemented by a standalone server or a server cluster composed of multiple servers, or it can be a cloud server.

[0150] like Figure 3 As shown, this embodiment also provides a computer device, including a memory and a processor. The memory stores a computer program, and the processor executes the computer program to implement the steps in the above-described method embodiments.

[0151] This application also provides an application scenario in which the above-described thermodynamic calculation method for water ramjet engines is applied. Specifically, the thermodynamic calculation method for water ramjet engines provided in this embodiment can be applied to the performance optimization scenario of underwater vehicle engines. The engine performance optimization scenario covers the dynamic adjustment process of engine parameters during operation; the thermodynamic calculation method for water ramjet engines provided in this embodiment specifically optimizes the specific impulse performance of the engine.

[0152] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for thermodynamic calculation of a water-ramjet engine with a wide water-fuel ratio range, characterized in that, The following steps are involved: Step 1: Obtain the total water-fuel ratio and sailing speed of the water ramjet engine at the current moment; Step 2: Compare the total water-fuel ratio of the water-ramjet engine at the current moment with the critical point of the water-fuel ratio to determine the current operating stage of the water-ramjet engine; The critical point for the water-fuel ratio includes the critical point for steam phase change and the limit point for atomization evaporation. The working stages of the water-jet engine include the water-jet stage, the transition stage, and the gas-liquid two-phase stage. If the total water-fuel ratio of the water-jet engine is less than the water-fuel ratio at the critical point of steam phase change at the current moment, then the water-jet engine is judged to be in the water-jet stage. If the total water-fuel ratio of the water-ram engine is between the water-fuel ratio at the critical point of steam phase change and the water-fuel ratio at the limit point of atomization evaporation at the current moment, then the water-ram engine is judged to be in the transition phase. If the total water-fuel ratio of the water-ram engine is greater than the water-fuel ratio at the atomization evaporation limit point at the current moment, then the water-ram engine is judged to be in the gas-liquid two-phase stage. Step 3: Based on the current operating stage of the water ramjet engine, calculate the nozzle exit velocity of the water ramjet engine at the current moment, and then perform thermodynamic calculations on the water ramjet engine to obtain the specific impulse of the water ramjet engine at the current moment. If the water-jet engine is in the water-jet phase, then the nozzle exit velocity v of the water-jet engine at the current moment is... e1 for: Among them, H c H is the enthalpy value at the combustion chamber. e This is the enthalpy value at the nozzle exit. If the water-jet engine is in the transition phase, then the nozzle exit velocity v of the water-jet engine at the current moment is... e2 for: Among them, T c p represents the combustion chamber temperature. e p is the pressure at the nozzle exit. c The pressure inside the combustion chamber; C sl The specific heat capacity is C. g ε is the specific heat capacity of the fuel gas; ε is the mass fraction of the condensed phase; n = R g / (C g +C sl ·ε / (1-ε)), R g It is the gas constant; If the water-jet engine is in the water-jet phase or transition phase, then the specific impulse I of the water-jet engine at the current moment is... sp for: I sp =(1+φ w )v ei -f w U Where, φ w The total water-fuel ratio of the water ramjet engine at the current moment; U is the current speed of the water ramjet engine; v ei Let i be the nozzle exit velocity at the current operating stage of the water jet engine, i = 1, 2; If the water-jet engine is in the gas-liquid two-phase stage, then the nozzle exit velocity v of the water-jet engine at the current moment is... e3 for: Among them, K m =(m s +m l ) / m g m g Let m be the gas flow rate within the flow field. s m is the solid phase flow rate within the flow field. l ρ is the working fluid flow rate within the flow field; sl The density of the solid-liquid mixture is... ρ l The density of the working fluid is water; T is the temperature at the nozzle inlet section; v c The velocity of the gas-liquid two-phase flow in the combustion chamber; When the water-ramjet engine is in the gas-liquid two-phase stage, the specific impulse I of the water-ramjet engine at the current moment is... sp for: I sp =(1-n ms e s )(1+φ w )v e3 -f f v r -f w U Where, n ms ε is the hysteresis loss coefficient. s The mass fraction of solid phase in the total flow rate; φ f The water-fuel ratio corresponding to the working fluid water is defined as the ratio of the mass flow rate of the working fluid water to that of the powder; v r =v g -v l v g Let v be the gas phase velocity. l The velocity is the liquid phase velocity.

2. The thermodynamic calculation method for a water-ramjet engine with a wide water-fuel ratio range according to claim 1, characterized in that: The method for calculating the water-fuel ratio at the critical point of steam phase change in step 2 is as follows: Thermodynamic analysis was performed using CEA software. When liquid water appeared in the combustion products, it was marked as the critical point of steam phase change. The water-fuel ratio at the critical point of steam phase change was calculated using the total mass flow rate of fuel and the total mass flow rate of seawater introduced at the time marked as the critical point of steam phase change.

3. The thermodynamic calculation method for a water-ramjet engine with a wide water-fuel ratio range according to claim 1, characterized in that: The method for calculating the water-fuel ratio at the atomization evaporation limit point in step 2 is as follows: in, φ1 is the water-fuel ratio at the limit point of atomization evaporation; φ1 is the primary water-fuel ratio, calculated based on the total mass flow rate of fuel introduced by primary combustion and the total mass flow rate of seawater. This is the second critical water-fuel ratio. m w2 The secondary influent flow rate is m. p C represents the primary combustion product flow rate. p C is the isobaric specific heat capacity of the primary combustion products. water Where L is the specific heat capacity of water at constant pressure, and T is the latent heat of vaporization. sat T is the saturation temperature of water vapor. i This refers to the temperature of the secondary water intake.

4. The thermodynamic calculation method for a water-ramjet engine with a wide water-fuel ratio range according to claim 1, characterized in that: In step 3, if the water-jet engine is currently in the gas-liquid two-phase stage, the nozzle inlet section temperature T is calculated as follows: Among them, T f The temperature of the working fluid, water; C s For solid phase heat capacity; C water The specific heat capacity of water at constant pressure; m v m is the mass of steam in the combustion products. w3 The working fluid is water; L is the latent heat of vaporization; n v n represents the mass fraction of the vapor phase change. T n is the temperature hysteresis coefficient for gas-solid two-phase systems. ms This is the stagnant loss coefficient.

5. A computer device, comprising a memory, a processor, and a computer program stored in the memory, characterized in that: The processor executes the computer program to implement the steps of the method according to any one of claims 1 to 4.

6. A computer-readable storage medium having a computer program stored thereon, characterized in that: When executed by a processor, the computer program implements the steps of the method according to any one of claims 1 to 4.

7. A computer program product comprising computer instructions, characterized in that: When executed by a processor, the computer instructions implement the steps of the method according to any one of claims 1 to 4.

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