Water Ramjet Supercharging Water Inlet System

Abstract

The present invention discloses a partially air-intake single-stage axial-flow impulse turbine, comprising an aircraft shell, an end of the aircraft shell connected to a cavitator, a booster pump fixedly connected inside the aircraft shell, the booster pump coaxially connected to a turbine, the turbine connected to a gas generator through a gas pipeline a, the gas generator connected to one end of the cavitating shell close to the cavitator through a gas channel b, an input end of the booster pump connected to a water inlet pipeline extending to the outside of the cavitating shell, an output end of the booster pump connected to a combustion chamber through a liquid pipeline, a metal charge reacting with water to generate combustion gas is contained in the combustion chamber, and the combustion chamber is fixedly connected to one end of the aircraft shell away from the cavitator; a configuration scheme of a booster water inlet system of a micro-turbine + mixed flow pump is proposed, and the booster water inlet system is driven by high-temperature combustion gas generated by a combustion gas generator in a supercavitating aircraft ventilation system, so as to increase the water inlet pressure, enable water to enter the combustion chamber and enable the engine to start working, thereby solving the problem that a water ramjet engine cannot be started at a low speed.

Description

Technical Field

[0001] The present invention belongs to the technical field of metal fuel water ramjet engines, and particularly relates to a pressurized water inlet system for a water ramjet engine. Background Art

[0002] A metal fuel water ramjet engine is a jet propulsion device that relies on the reaction of active metals such as aluminum and magnesium with water as fuel. It has characteristics such as high energy density and simple structure. It is the most ideal propeller for supercavitating torpedoes and, together with the supercavitation drag reduction technology, becomes an important technical support for the development of underwater high-speed vehicles. However, at lower speeds, the water in the external flow field cannot rush into the combustion chamber due to too low total pressure, resulting in the inability of the water ramjet engine to operate. This shortcoming restricts the engineering application of the water ramjet engine and limits its working performance. In order to give full play to the advantages of the water ramjet engine, it is urgent to solve the startup problem under low-speed conditions.

[0003] Currently, water ramjet engines are mainly applied to high-speed underwater weapons such as supercavitating vehicles. The cruising speed of a supercavitating vehicle is as high as 100 m / s, the total incoming flow pressure reaches 5 MPa, and the water flow can spontaneously rush into the combustion chamber. The prerequisite for the startup of a water ramjet engine is that there is continuous water entering the combustion chamber. Generally, the pressure in the combustion chamber of a water ramjet engine is about 2.5 MPa. Considering the pressure loss at the inlet, the stagnation pressure can continuously press the external seawater into the combustion chamber when the ship speed reaches about 90 m / s. To solve the startup problem of the water ramjet engine, a propulsion method combining a water ramjet engine and a solid rocket is generally adopted. First, thrust is generated by burning a solid propellant column to increase the speed of the vehicle until the startup conditions of the water ramjet engine are reached. In the acceleration section, supercavitation has not yet formed, and the drag coefficient of the vehicle is very large. The required thrust is much greater than the resistance received. A large amount of energy is consumed in this stage, and the energy density of the solid rocket engine is less than 25% of that of the water ramjet engine. A large amount of space has to be reserved to store the solid propellant column when designing the engine. Therefore, the carrying amount of metal fuel can only be reduced in a limited space, which limits the improvement of the range. The configuration scheme of the water ramjet engine is as Figure 1 shown. Summary of the Invention

[0004] The object of the present invention is to drive a mixed-flow pump by a micro partial-intake turbine to increase the total water inlet pressure of the water ramjet engine, and solve the problem that the water ramjet engine cannot start at low speeds.

[0005] The technical solution adopted by the present invention is a water ramjet pressurized water inlet system, which includes a vehicle shell. The end of the vehicle shell is connected to a cavitator. A pressurized pump is fixedly connected inside the vehicle shell. The pressurized pump is coaxially connected to a turbine. The turbine is connected to a gas generator through gas pipeline a. The gas generator is connected to one end of the vehicle shell close to the cavitator through gas passage b. The input end of the pressurized pump is connected to a water inlet pipeline extending outside the cavitation shell. The output end of the pressurized pump is connected to a combustion chamber through a liquid pipeline. There is a metal charge in the combustion chamber that reacts with water to generate gas. The combustion chamber is fixedly connected to the end of the vehicle shell away from the cavitator.

[0006] The features of the present invention also lie in:

[0007] The end of the combustion chamber is connected to a tail nozzle, and the tail nozzle extends outside the vehicle shell.

[0008] The turbine is an impulse partial admission turbine.

[0009] The impulse partial admission turbine includes a nozzle and a cascade. The nozzle is aligned with the cascade at an inclination angle to the cascade.

[0010] The nozzle includes a middle section whose cross-section is divided into a divergent section, a throat, and a convergent section that are connected in sequence according to the shape. The divergent section is close to and aligned with the cascade. The convergent section is designed using the Soviet V-notch formula, and the throat is transitioned with a rounded corner. The divergent section is conical.

[0011] The design process of the nozzle parameters is as follows:

[0012] Regarding the thermodynamic process of the gas in the turbine as an isentropic expansion process, the isentropic specific enthalpy drop of the working fluid in the turbine is:

[0013] (1)

[0014] In the formula, is the pressure ratio of the turbine, .

[0015] Assuming the efficiency of the turbine is , taking the nozzle flow loss coefficient , the mass flow rate of the working fluid is obtained as:

[0016] (2)

[0017] Then the nozzle throat area is:

[0018] (3)

[0019] The diameter of the throat is expressed as:

[0020] (4)

[0021] The effective outlet diameter of the nozzle is:

[0022] (5)

[0023] Wherein, is the velocity loss coefficient, and the outlet velocity is:

[0024] (6)

[0025] Wherein, is the enthalpy drop in the nozzle. Taking the reaction degree of the turbine as 0.05, then:

[0026] (7)

[0027] The minimum outlet diameter of the nozzle and the partial admission degree of the turbine are respectively:

[0028] (8)

[0029] (9)

[0030] The parameter design method of the cascade is:

[0031] The cascade includes multiple blades. When the mean diameter of the turbine D and the rotational speed n are known, the linear velocity of the blade u is expressed as:

[0032] (10)

[0033] The relative velocity of the gas working medium at the inlet of the turbine blade and the blade installation angle are respectively calculated from the velocity triangle and expressed as:

[0034] (11)

[0035] (12)

[0036] The relative velocity at the outlet of the blade is calculated according to the empirical formula and is:

[0037] (13)

[0038] The blade height ; the blade width ; the cascade pitch ; the edge thickness of the blade ; the number of blades ; Radius of the pressure surface arc ; Radius of the suction surface .

[0039] The design method of the impeller parameters of the booster pump is as follows:

[0040] Given the design parameters of the booster pump under the rated working conditions: flow rate Q , head H , rotational speed n , and the main design parameters of the impeller include the inlet diameter D j , outlet diameter D 2. Outlet width b 2. Solve the impeller parameters in the following three parts:

[0041] (1) Design of the impeller inlet diameter parameter:

[0042] The impeller inlet diameter D j is related to the impeller inlet velocity. Increasing the inlet velocity will reduce the cavitation resistance performance and hydraulic efficiency of the pump. The impeller inlet velocity V 0 is determined by the velocity coefficient method:

[0043] (21)

[0044] In the formula, K V0 is the impeller inlet velocity coefficient, expressed as:

[0045] (22)

[0046] In the formula, n s is the specific speed, calculated by the following formula:

[0047] (23)

[0048] Calculate the effective diameter D 0 of the impeller:

[0049] (24)

[0050] is the shaft diameter, and the impeller inlet diameter is:

[0051] (25);

[0052] (2) The design method of the impeller outlet diameter parameter is as follows:

[0053] The impeller outlet diameter D2 is affected by the shape of the flow and head curve and the hydraulic efficiency, and is expressed as:

[0054] (26)

[0055] In the formula, is the outlet peripheral speed:

[0056] (27)

[0057] In the formula, is the peripheral speed coefficient of the outlet diameter, calculated using the following formula:

[0058] (28);

[0059] (3) The impeller outlet width parameter design method is:

[0060] Impeller outlet width b 2Affected by the head curve, the impeller outlet width calculation formula is:

[0061] (29)

[0062] In the formula, is the average displacement coefficient at the impeller outlet, and the axial velocity at the impeller outlet is:

[0063] (30).

[0064] The turbine blade torque is equal to the boost pump impeller torque.

[0065] The beneficial effects of the present invention are:

[0066] The water ramjet engine boost water inlet system of the present invention proposes a boost water inlet system configuration scheme of a micro-turbine + mixed flow pump, and utilizes the high-temperature combustion gas generated by the gas generator in the supercavitation vehicle ventilation system to drive the boost water inlet system, which can effectively increase the water inlet pressure; the water ramjet engine boost water inlet system of the present invention relies on the boost system to increase the incoming flow pressure to the combustion chamber pressure, so that water can enter the combustion chamber and start the engine to work, thereby solving the problem that the water ramjet engine cannot be started at a low speed. BRIEF DESCRIPTION OF THE DRAWINGS

[0067] Figure 1 It is a schematic diagram of the structure of an existing water ramjet engine;

[0068] Figure 2 It is a schematic diagram of the structure of the water ramjet engine pressurization water inlet system of the present invention;

[0069] Figure 3 It is a schematic diagram of the nozzle and blade structure of the impulse partial intake turbine of the present invention;

[0070] Figure 4 It is a partial inlet turbine basin grid division diagram;

[0071] Figure 5 It is a schematic diagram of the 3D model of the booster pump and the grid division result;

[0072] Figure 6 It is a schematic diagram of the Mach number distribution of the nozzle;

[0073] Figure 7 It is a schematic diagram of the Mach distribution at half height of the moving blade cascade;

[0074] Figure 8 It is a contour map of the static pressure distribution of the booster pump;

[0075] Figure 9 It is a contour map of the velocity vector distribution of the booster pump;

[0076] Figure 10 It is a performance curve diagram of the booster pump.

[0077] In the figure, 1. Vehicle shell, 2. Cavitator, 3. Booster pump, 4. Turbine, 5. Inlet pipe, 6. Combustion chamber, 7. Metal charge, 8. Gas generator, 9. Tail nozzle, 10. Cavitation. Specific implementation mode

[0078] The present invention will be described in detail below in conjunction with the accompanying drawings and specific implementation modes.

[0079] Due to the particularity of the supercavitating vehicle, it must be fully considered during the system configuration. First, the space of the supercavitating vehicle is cramped, and the booster system must be small enough. Second, the gas consumption of the micro turbine is very small, far lower than the ventilation flow rate, and the requirement for working efficiency is not strict. In addition, when the booster system starts, the vehicle has a certain speed, and the higher total incoming pressure makes the pump have a large device cavitation margin, and the cavitation problem is not prominent. Finally, a speed reducer is usually added between the turbo pump power device and the booster device, but in order to save space and reduce the system complexity, the booster system is connected without a speed reducer. On this basis, the present invention proposes a water ramjet engine booster inlet system.

[0080] The water ramjet engine booster inlet system of the present invention, as Figure 2As shown in the figure, it includes a vehicle hull 1. One end of the vehicle hull 1 is connected to a cavitator 2. The outer shapes of the vehicle hull 1 and the cavitator 2 are the same as the appearance shape of a common water-ramjet engine pressurized water inlet system. A booster pump 3 is fixedly connected inside the vehicle hull 1. The booster pump 3 is coaxially connected to a turbine 4. The booster pump 3 can provide the power for the turbine 4 to rotate. The turbine 4 is connected to a gas generator 8 through a gas pipeline a. The gas generator 8 is connected to one end of the vehicle hull 1 close to the cavitator 2 through a gas channel b and extends to the outside of the vehicle hull 1. The gas generated by the gas generator 8 is responsible for driving the turbine 4 and ventilating the cavitation bubbles 10 formed outside the vehicle hull 1 by the cavitator 2. The input end of the booster pump 3 is connected to a water inlet pipeline 5 extending to the outside of the vehicle hull 1. The output end of the booster pump 3 is connected to a combustion chamber 6 through a liquid pipeline. The pressure in the water inlet pipeline 5 is increased by the booster pump 3, and then water enters the combustion chamber 6 under high pressure. There is a metal charge 7 in the combustion chamber 6 that reacts with water to generate gas. The combustion chamber 6 is fixedly connected to the end of the vehicle hull 1 far from the cavitator 2. The metal charge 7 is a metal fuel. First, the vehicle is started by a solid charge column to provide thrust for the vehicle. When it accelerates to a certain stage, water reacts with the metal charge to generate gas, and the metal fuel in the combustion chamber 6 burns to provide thrust for the vehicle.

[0081] One end of the combustion chamber 6 is connected to a tail nozzle 9. The tail nozzle 9 extends to the outside of the vehicle hull 1 and can eject the high-temperature gas generated by combustion in the combustion chamber 6, thereby pushing the vehicle.

[0082] The turbine 4 is an impulse partial admission turbine. The impulse partial admission turbine includes a nozzle, a moving blade row, a shaft, an exhaust pipe, and a casing. There is a very small gap between the nozzle and the moving blade row.

[0083] As Figure 3 shown, the nozzles in the impulse partial admission turbine are aligned with the blade row at an inclination angle In the figure, β is the blade setting angle; is the nozzle divergence angle; S is the blade edge thickness; t is the blade row pitch; B is the blade width; is the nozzle exit diameter; is the nozzle throat diameter.

[0084] The design parameters of the turbine under the known rated operating conditions are: rated power , combustion chamber temperature , combustion chamber pressure , ambient back pressure , turbine speed n , turbine mean diameter D , isentropic exponent k , specific heat capacity at constant pressure , gas constant R , number of nozzles Z . The present invention parametrically designs an impulse turbine according to the following three steps.

[0085] The nozzle includes an intermediate section that is divided into a divergent section, a throat, and a convergent section that are connected in sequence according to the shape. The divergent section is close to and aligned with the cascade. The convergent section is designed using the Soviet Vyshnegradskii formula, and the throat is transitioned with a fillet. The divergent section is conical.

[0086] The process of nozzle parameter design is as follows:

[0087] Regarding the thermodynamic process of the gas in the turbine as an isentropic expansion process, the isentropic specific enthalpy drop of the working fluid in the turbine is:

[0088] (1)

[0089] In the formula, is the pressure ratio of the turbine, .

[0090] Assuming the efficiency of the turbine is , taking the nozzle flow loss coefficient , the mass flow rate of the working fluid is obtained as:

[0091] (2)

[0092] Then the nozzle throat area is:

[0093] (3)

[0094] The diameter of the throat is expressed as:

[0095] (4)

[0096] The effective exit diameter of the nozzle is:

[0097] (5)

[0098] In the formula, is the velocity loss coefficient, and the exit velocity is:

[0099] (6)

[0100] In the formula, is the enthalpy drop in the nozzle. Taking the degree of reaction of the turbine as 0.05, then:

[0101] (7)

[0102] The minimum exit diameter of the nozzle and the partial admission degree of the turbine are respectively:

[0103] (8)

[0104] (9).

[0105] The parameter design method of the cascade is as follows:

[0106] The cascade includes multiple blades. Given the mean diameter of the turbine D and the rotational speed n the linear velocity of the blade is obtained u which is expressed as:

[0107] (10)

[0108] The relative velocity of the gas working medium at the inlet of the turbine blade and the blade installation angle are calculated from the velocity triangle and are respectively expressed as:

[0109] (11)

[0110] (12)

[0111] The relative velocity at the outlet of the blade is calculated according to the empirical formula which is:

[0112] (13)

[0113] Blade height ; Blade width ; Cascade pitch ; Blade edge thickness ; Number of blades ; Pressure surface arc radius ; Suction surface radius .

[0114] The process of calculating the performance parameters of the turbine is as follows:

[0115] The unit circumferential power of the turbine is:

[0116] (14)

[0117] The disk friction loss of the turbine is:

[0118] (15)

[0119] In the formula, is the density of the gas at the outlet of the turbine ​

[0120] (16)

[0121] The partial admission efficiency of the turbine is:

[0122] (17)

[0123] The leakage efficiency of the turbine is approximately:

[0124] (18)

[0125] In the formula, is the radial clearance. Then the internal efficiency of the turbine can be calculated as:

[0126] (19)

[0127] Substitute this efficiency value back into the first step and perform iterative calculations until the difference between the two is small enough.

[0128] To verify the above design method, referring to the 2 kW-class turbine of the ARL laboratory, the design specifications are shown in Table 1. The working fluid gas constant is 404 kJ / (kg·K), the isentropic exponent is 1.29, the velocity coefficient is taken as 0.93, and the flow coefficient is 0.98. Solving the turbine structure parameters according to the design specifications, it is found that the maximum deviation does not exceed 5%, and the results are shown in Table 2.

[0129] Table 1

[0130]

[0131] Table 2

[0132]

[0133] Establish a three-dimensional flow field model of the turbine for comparison, conduct numerical simulation and compare with the experimental results. The simulation process uses a steady compressible density-based three-dimensional solver, and the Spalart-Allmaras turbulence model and the implicit ROD-FDS second-order algorithm, which are more suitable for the low Reynolds number transonic turbine flow field, are used for solving. Set the nozzle inlet as the pressure inlet and the domain outlet as the pressure outlet. Set interfaces at the interfaces such as the nozzle and the axial clearance, the cascade inlet and the axial clearance, and the connection between the cascade outlet and the rear domain. Use the MRF model and set the rotational speed of the cascade domain to 435,000 rpm.

[0134] In terms of grid division, ICEM-CFD software is used to divide structured grids. In order not to affect the flow state of the cascade by the rear cavity basin, the rear cavity basin is taken as 5 times the blade width. The placement angle of adjacent nozzles is 25°, and the axial clearance between the nozzle and the cascade assembly is 1 mm. The nozzle is divided using the cooper grid type, and the turbine basin is divided using hexahedral grids. Boundary layers are added to the nozzle and the cascade, and the near-wall grids are optimized based on the requirements of the Spalart-Allmaras turbulence model for the y+ value to simulate turbulence more accurately. The final overall grid division is as shown in Figure 4 shown below:

[0135] To facilitate the comparison with the three-dimensional flow field model of the turbine, the internal efficiency calculation formula is given:

[0136] (20)

[0137] In the formula: T is the output torque of the torque turbine, is the angular velocity of the turbine rotation.

[0138] Considering that there is no data on the tip clearance in the three-dimensional flow field model of the turbine, simulation models with tip clearances of 0.05 mm and 0.1 mm are established for verification. As can be seen from Table 3, the tip clearance has a greater impact on the internal efficiency of the turbine. Among them, the simulation results when the tip clearance is 0.05 mm are almost the same as the experiment.

[0139] Table 3

[0140]

[0141] Parameter design is carried out for the turbine of the pressurized water inlet system, and simulation calculations are carried out on the design results. Given that the pressurization requirement of the booster pump is 1.95 Mpa and the flow rate Q is 10 kg / s, it can be known that the head H is 195 m. Assuming that the pump design point efficiency is 70%, the power of the turbine can be estimated to be about 27 kw from Equation . Taking the mean diameter of the turbine as 100 mm, the nozzle skew angle as 15°, and the nozzle divergence angle as 8°, the final turbine design results are shown in Table 4.

[0142] Table 4

[0143]

[0144] The simulation calculation results are shown in Table 5. The deviation of the power from the design value is 3.7%, and the result is on the small side. The main reason for the difference is that the simulation algorithm used cannot accurately calculate the micro low Reynolds number turbine.

[0145] Table 5

[0146]

[0147] To avoid increasing the system complexity, the turbine and the booster pump are directly connected coaxially. Therefore, when designing the booster pump, it is necessary to ensure that the flow rate and head meet the requirements at the rated speed, and the torque of the booster pump must also match the torque of the turbine.

[0148] The design method of the impeller parameters of the booster pump is as follows:

[0149] Given the design parameters of the booster pump under rated conditions: flow rate Q , head H , speed n , the main design parameters of the impeller include the inlet diameter D j , outlet diameter D 2, outlet width b 2. The impeller parameter solution is completed according to the following three parts:

[0150] 1. Design of the impeller inlet diameter parameter:

[0151] The impeller inlet diameter D j is related to the impeller inlet velocity. Increasing the inlet velocity will reduce the cavitation resistance performance and hydraulic efficiency of the pump. The impeller inlet velocity V 0 is determined by the velocity coefficient method:

[0152] (21)

[0153] In the formula, K V0 is the impeller inlet velocity coefficient, expressed as:

[0154] (22)

[0155] In the formula, n s is the specific speed, calculated by the following formula:

[0156] (23)

[0157] Calculate the effective diameter D 0 of the impeller:

[0158] (24)

[0159] is the shaft diameter, and the impeller inlet diameter is:

[0160] (25);

[0161] 2. The impeller outlet diameter parameter design method is:

[0162] Impeller outlet diameter D 2 is affected by the shape of the flow and head curve and the hydraulic efficiency, and is expressed as:

[0163] (26)

[0164] In the formula, is the outlet peripheral speed:

[0165] (27)

[0166] In the formula, is the peripheral speed coefficient of the outlet diameter, calculated using the following formula:

[0167] (28);

[0168] 3. The impeller outlet width parameter design method is:

[0169] Impeller outlet width b 2Affected by the head curve, the impeller outlet width calculation formula is:

[0170] (29)

[0171] In the formula, is the average displacement coefficient at the impeller outlet, and the axial velocity at the impeller outlet is:

[0172] (30).

[0173] The blade torque of the turbine 4 is equal to the impeller torque of the boost pump 3 .

[0174] For the numerical modeling and verification of the booster pump using the above booster pump parameter design method:

[0175] The simulation process uses a steady incompressible pressure-based three-dimensional solver, and the turbulence model is the standard k- , the fluid is liquid water, and the wall boundary is set to a no-slip adiabatic boundary condition. The solution format of the convection term is set to a high-order solution format, the solution format of the turbulence numerical term is set to a second-order format, and the residual convergence accuracy is In order to simulate the working process of the booster pump more realistically, the inlet and outlet boundary conditions are pressure inlet and pressure outlet. The flow domain includes a rotating part and a stationary part. An interface is set at the interface between the impeller and the pressure chamber. The MRF model is used to process the booster pump flow field with the rotating impeller as the reference system, and the steady-state method is used to calculate the unsteady-state problem.

[0176] In terms of grid division, due to the extremely large distortion of the impeller profile and the difficulty in handling the grid transition at the tongue of the volute chamber, sharp corners and fine local structures are ignored during the modeling process on the premise of not affecting the flow field. The structure is divided in the way of multi-block topology. The impeller computational domain model is divided into 6 periodic models symmetric about the origin, making the grid distribution from the impeller inlet to the outlet regular, with smooth transition, and the flow domain around the blades is encrypted to ensure the accuracy of the flow near the blades during CFD calculation. The 3D model of the booster pump and the grid division results are as Figure 5 shown:

[0177] The preliminary design simulation results are shown in Table 7. The pressurization value meets the requirements, but the torque and flow rate are both on the low side, with relative deviations of 20.1% and 26% respectively. The reason for the deviation is that the conventional design theory is not applicable to the design of the micro-booster pump.

[0178] Table 7

[0179]

[0180] The mismatch between the torque of the booster pump and the torque of the turbine will cause the rotational speed to change, thus making the entire booster system deviate from the design point and the efficiency decrease. To make the flow rate meet the design requirements and match the torque of the booster pump with the torque of the turbine, it is necessary to iteratively correct the main parameters of the booster pump based on theory combined with numerical calculation. Considering the effect of the axial vortex in the impeller passage, after making some reasonable assumptions, Stodala proved that:

[0181] (31)

[0182] In the formula, w is the angular velocity of the impeller rotation, is the blade setting angle at the impeller outlet. According to formula (31), the flow rate is positively correlated with the impeller outlet diameter. When changing the outlet diameter, the inlet diameter should be changed accordingly to ensure good cavitation performance. After increasing the impeller size, the increase in the pump power will lead to an increase in torque. Therefore, this method can achieve the purpose of increasing the pump flow rate and torque. Without changing other parameters, through repeated iteration, it is found that increasing D j to 23.7 mm and increasing D 2 to 23.5 mm, the relative deviation of the modified simulation result from the target value does not exceed 3.2%. The results are shown in Table 8.

[0183] Table 8

[0184]

[0185] Analysis of the turbine flow field:

[0186] The flow field characteristics of the supersonic nozzle have a crucial impact on the work capacity of the turbine. From Figure 6 it can be seen that the gas working medium continuously expands in the nozzle, and the internal energy is converted into kinetic energy, resulting in a gradual increase in the Mach number. Since the nozzle in this invention has a greater viscous loss during the flow of the working medium than the conventional nozzle, the sonic point in the nozzle moves backward to downstream of the throat. At the same time, the thickness of the nozzle wall gradually increases and extends to points A and B, resulting in a decrease in the Mach number at points A and B. In addition, the nozzle exit velocity can be calculated from Equation (6) to be 3.06 Ma, while the numerical calculation result is approximately 3.1 Ma, indicating that the numerical calculation result is reliable and the nozzle design is reasonable.

[0187] From Figure 7 it can be seen that the high-speed airflow enters the cascade from the nozzle and further expands at the axial clearance and the inlet of the cascade flow passage. The Mach number of the airflow increases to about 3.4 in the leftmost flow passage. Thereafter, the high-speed working medium acts on the pressure surface of the cascade, converting the kinetic energy into the mechanical energy of the cascade rotation. The Mach number drops sharply to generate a shock wave, increasing the thickness of the suction surface boundary layer and gradually extending it until separation occurs in the middle of the cascade. The Mach number decreases to 0.9 at the cascade exit, and the ratio of the Mach numbers at the inlet and outlet is about 0.26, that is, the leftmost cascade can convert about 70% of the kinetic energy of the working medium into the mechanical energy of the cascade rotation, and the work capacity of the cascade is strong. Moreover, the turbine efficiency reaches 57.8%, and the deviation between the simulation power and the design power is 3.7%, and the turbine meets the design requirements.

[0188] The static pressure distribution and absolute velocity vector distribution of the booster pump are as Figure 8 , Figure 9 shown. From Figure 8 it can be seen that due to the work done by the blades on the water, the static pressure value gradually increases in a hierarchical manner. Among them, the pressure gradient is obvious in the flow passage, the pressure near the blade pressure surface is greater than that on the suction surface, and the pressure basically tends to be consistent at the blade exit, showing an obvious non-axisymmetric characteristic. In the water pressurizing chamber, the reduction of the flow velocity causes the static pressure to continuously increase and reach the maximum at the exit. From Figure 9 it can be seen that when the fluid flows into the impeller, the flow velocity gradually increases along the direction of increasing radius, and when it flows out of the impeller and enters the water pressurizing chamber, the flow velocity gradually decreases and tends to be uniform at the exit. The streamline distribution of the impeller and the water pressurizing chamber is smooth and reasonable, without disorder, and no vortices or secondary recirculation occur. Moreover, the low-speed fluid accounts for the majority in the volute, indicating that the booster pump can effectively convert the kinetic energy of the fluid into pressure energy.

[0189] From Figure 10It can be seen that the variation trends of the head and efficiency of the booster pump with the flow rate are consistent with the theory; the head of the booster pump decreases with the increase of the flow rate, and there is no hump. The efficiency first increases and then decreases with the increase of the flow rate, which conforms to the characteristics of the performance curve of the booster pump. And the maximum deviation between the numerical calculation result and the target value under the design condition does not exceed 3.2%, indicating that the numerical simulation can accurately predict the performance of the booster pump. Through the performance prediction and analysis of the booster pump under different conditions, it can be seen that: in the engine start-up and acceleration stage, that is, under the small flow rate condition, the booster pump maintains an efficiency of more than 75%, and there is no phenomenon of instability that is prone to occur in general water pumps under small flow rates, and it can increase the inlet water pressure by at least 3.1 Mpa, so that water continuously surges into the combustion chamber. In the engine cruise stage, that is, under the design flow rate condition, the booster pump can increase the inlet water pressure by 2.0 Mpa with an efficiency of 74.5%, providing sufficient thrust for the engine in the cruise state and reducing the start-up speed of the water ramjet engine to 63 m / s. And the booster pump can maintain efficient operation in each state. Therefore, the booster pump can ensure the stable operation of the water ramjet engine in terms of boosting ability and efficiency.

[0190] To sum up, the design methods of the turbine and the booster pump and their simulation results are reliable. The comprehensive efficiency of the boosting system reaches 43.2%, and all indicators meet the design requirements.

[0191] In order to solve the problem of low-speed start of the water ramjet engine, the present invention proposes a configuration scheme and a design method for the boosting water inlet system, establishes a flow field simulation model of the boosting water inlet system, verifies the design method through simulation calculation, and obtains the working performance of the boosting water inlet system.

[0192] By the above method, the boosting water inlet system of the water ramjet engine of the present invention has the following characteristics:

[0193] (1) A configuration scheme of the boosting water inlet system of a micro-turbine + mixed-flow pump is proposed, and the high-temperature gas generated by the gas generator in the ventilation system of the supercavitating vehicle is used to drive the boosting water inlet system, which can effectively increase the inlet water pressure.

[0194] (2) A modified design method for the micro-turbine and the high-speed mixed-flow pump is proposed, and a simulation calculation model of the boosting water inlet system is established. The deviation between the simulation result of the boosting system and the target value is less than 3.2%.

[0195] (3) The performance of the boosting water inlet system is analyzed, and it is found that the system can increase the inlet water pressure by 2.0 MPa and reduce the start-up speed of a certain water ramjet engine from 90 m / s to 63 m / s.

Claims

1. Water ramjet supercharging water inlet system, characterized in that, It includes an aircraft hull (1), with a cavitator (2) connected to the end of the aircraft hull (1). A booster pump (3) is fixedly connected inside the aircraft hull (1), and the booster pump (3) is coaxially connected to a turbine (4). The turbine (4) is connected to a gas generator (8) through a gas pipeline a. The gas generator (8) is connected to one end of the aircraft hull (1) near the cavitator (2) through a gas passage b and extends outside the aircraft hull (1). The gas generated by the gas generator (8) is responsible for driving the turbine (4) and forms cavitation bubbles (10) outside the aircraft hull (1) after passing through the cavitator (2). The input end of the booster pump (3) is connected to a water inlet pipeline (5) that extends outside the aircraft hull (1), and the output end of the booster pump (3) is connected to a combustion chamber (6) through a liquid pipeline. The booster pump (3) is used to increase the pressure in the water inlet pipeline (5) so that water enters the combustion chamber (6) under high pressure. There is a metal charge (7) in the combustion chamber (6) that reacts with water to generate gas. The combustion chamber (6) is fixedly connected to the end of the aircraft hull (1) away from the cavitator (2), solving the problem that the water ramjet cannot start at low speeds; The end of the combustion chamber (6) is connected to a tail nozzle (9), and the tail nozzle (9) extends outside the aircraft hull (1); The turbine (4) is an impulse partial admission turbine.

2. The water ramjet supercharging water inlet system according to claim 1, wherein The impulse partial admission turbine includes a nozzle and a cascade, and the nozzle is aligned with the cascade at an inclination angle ​ 3. The water ramjet supercharging water inlet system according to claim 2, wherein, The nozzle includes a middle section whose cross-section is divided into a divergent section, a throat, and a convergent section that are sequentially connected according to the shape. The divergent section is close to and aligned with the cascade. The convergent section is designed using the Soviet Vey formula. The throat is transitioned with a rounded corner, and the divergent section is conical.

4. The water ramjet supercharging water inlet system according to claim 1, wherein, The cascade moment of the turbine (4) is equal to the impeller moment of the booster pump (3).

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