A drive system based on the transient startup process of an axial flow pump and its optimization method

Abstract

A drive system based on the transient startup process of an axial flow pump, which belongs to the fields of hydraulic machinery and underwater drive. The present invention includes an inlet pipe, an axial flow pump, a high-pressure flow pipe, a drive pipe, a driven object, and an outlet pipe. The present invention only relates to a single fluid medium, and during the drive process, the axial flow pump as the power source is coordinated with the entire drive system for operation and performance prediction of the drive system. At the same time, the drive system can meet different drive initial conditions. For a strong transient process with a very short drive time, by establishing the connection between the steady-state characteristics and transient characteristics of the axial flow pump, the performance of the axial flow pump can still be accurately predicted during the transient process. Considering the transient startup process of the axial flow pump during the drive process, by establishing the dynamic model of the drive process, the entire drive system is coupled to achieve an integrated design and rapid performance prediction. The present invention can be applied to the fields of underwater drive technology such as ships and underwater detectors.

Description

Technical Field

[0001] The present invention belongs to the fields of hydraulic machinery and underwater drive, and particularly relates to a drive system based on the transient start-up process of an axial flow pump and an optimization method thereof. Background Art

[0002] An object that moves under the action of underwater drive cannot strike a target at a relatively long distance during the coastal launch process due to the influence of the range. Even if the range is long, it will leave more reaction time for the target. When the object moves under the drive on a vehicle, it will be detected by radar, and the vehicle itself is also at risk of being struck. Underwater drive technology, with the characteristics of concealment and safety, is very important in modern marine technology.

[0003] The purpose of an underwater drive system is to provide initial kinetic energy for an object. Traditional underwater drive systems mostly use solid fuel, gas, high-pressure gas, etc. as power sources, and the launch speed is slow. There are also certain dangers during the manufacturing, transportation, and storage processes, and once manufactured, the performance is difficult to change again, which is not suitable for variable working condition drive situations, such as different initial drive depths. In addition, due to the uncertainty of the performance of the working medium where the drive equipment is located, it is difficult for the equipment to be driven to couple with the performance of the entire drive system, and the performance is also difficult to predict. Therefore, it is very important to summarize a complete set of design methods for an underwater drive system with fast speed, good stability, variable working conditions, and good coordination, and to achieve rapid prediction of the performance of the drive system. Summary of the Invention

[0004] Aiming at the problems of long time consumption, poor stability, difficult variable working conditions, and poor coordination in the traditional underwater drive process, a drive system based on the transient start-up process of an axial flow pump and an optimization method thereof disclosed by the present invention aims to solve the technical problems: the drive system only involves a single fluid medium, and during the drive process, the axial flow pump as the power source runs in coordination with the entire drive system and the performance prediction of the drive system. At the same time, the drive system can meet different drive initial conditions. For a strong transient process with a very short drive time, by establishing the connection between the steady-state characteristics and transient characteristics of the axial flow pump, the performance of the axial flow pump can still be accurately predicted during the transient process. By establishing the dynamic model of the drive process, the entire drive system is coupled to achieve an integrated design and rapid performance prediction. The present invention can be applied to the fields of underwater drive technology such as ships and underwater detectors.

[0005] The drive initial conditions include the drive depth.

[0006] The purpose of the present invention is achieved by the following technical solutions.

[0007] A driving system based on the transient starting process of an axial flow pump disclosed by the present invention includes an inflow pipe, an axial flow pump, a high-pressure flow pipe, a driving pipe, a driven object, and an outflow pipe.

[0008] The inflow pipe is the inlet of the fluid medium, which absorbs the fluid medium from the environment and leads it to the inlet of the axial flow pump.

[0009] The axial flow pump is the power source of the driving system and is placed between the inflow pipe and the high-pressure flow pipe. The axial flow pump is driven by a motor to rotate. The impeller rotates to do work on the fluid medium, increasing the energy of the fluid medium and providing power for the driven object.

[0010] The high-pressure flow pipe is located after the outlet of the axial flow pump and is used to transport the high-pressure fluid medium output by the axial flow pump and convey the high-pressure fluid medium into the driving pipe.

[0011] The driving pipe is located after the outlet of the high-pressure flow pipe and is used to accommodate the driven object and provide a working environment for the high-pressure fluid medium to act on the driven object.

[0012] The driven object is the target to be driven, usually a cylinder or with a cylinder as the base. The diameter of the driven object is slightly smaller than that of the driving pipe. When the fluid medium passes through the gap between the driven object and the driving pipe, due to the increase in the velocity of the fluid medium, the pressure decreases, and a pressure difference is formed before and after the driven object, causing the driven object to move.

[0013] The outflow pipe is connected to the environmental fluid domain. When the driven object disengages from the outflow pipe, the system pressure decreases, and the driving process is determined to end.

[0014] The above-mentioned inflow pipe, high-pressure flow pipe, driving pipe, and outflow pipe are all made of low-damping materials, which can reduce the flow resistance of the fluid medium, thereby reducing the energy loss during the driving process.

[0015] A working method of a driving system based on the transient starting process of an axial flow pump disclosed by the present invention is as follows:

[0016] Turn on the motor switch. The axial flow pump starts at a very high speed under the drive of the motor. The inflow pipe sucks the fluid medium to the inlet of the axial flow pump. The axial flow pump does work on the fluid medium to increase the pressure of the fluid medium and generate high-pressure fluid. The high-pressure fluid medium enters the driving pipe through the high-pressure flow pipe. The driven object in the driving pipe moves in the driving pipe under the action of the pressure difference generated by the high-pressure fluid medium until it disengages from the outflow pipe, and the driving process ends.

[0017] An optimization method of a driving system based on the transient starting process of an axial flow pump disclosed by the present invention includes the following steps:

[0018] Step 1: Define the driving target and parameters of the driven object.

[0019] According to the driving requirements of the target, the initial underwater driving depth h of the driven object, the target driving time t t , the target speed v of the driven object after driving is completed t and the rotational speed change law n(t) when the motor starts. The target speed v of the driven object t is determined according to the initial underwater driving depth h, the underwater movement resistance f of the driven object after being driven out of the cylinder s and the mass m of the driven object, that is

[0020]

[0021] Step 2: Initially select the model of the axial flow pump according to the driving requirements.

[0022] Query the external characteristic curve of the selected model of the axial flow pump. According to the queried external characteristic curve, determine the head H(n) and flow rate Q(n) of the axial flow pump at different rotational speeds. Combining with the rotational speed change law n(t) of the axial flow pump when the motor starts given in the first step, establish the first relational expression: the relationship between the flow rate, head and time of the axial flow pump during startup.

[0023] f[H(t),Q(t)]=0 (2)

[0024] Step 3: Establish the flow relationship in the drive system.

[0025] According to the continuity equation, the flow rate Q in the drive system is expressed as the sum of the flow rate Q f of the fluid medium discharged by the driven object and the flow rate Q j at the gap between the driven object and the drive pipe.

[0026] Q(t)=Q f +Q j (3)

[0027] Q f =v(t)S (4)

[0028]

[0029] where S is the cross-sectional area of the driven object, P0 is the pressure at the outlet pipe, and P1 is the pressure at the tail of the driven object, which is expressed as the pressure at the outlet of the axial flow pump minus the pressure loss generated by the combined action of the frictional loss and local loss during the flow process. The head loss generated by the combined action of the frictional loss and local loss is negligible compared with the head provided by the axial flow pump. Therefore, P1 is expressed as

[0030] P1=ρgH(t) (6)

[0031] Combining (3), (4), (5) and (6) gives

[0032]

[0033] Combining equations (3) and (7) gives the second relationship: the relationship between H(t) and v(t)

[0034] f[H(t), v(t)] = 0 (8)

[0035] Step Four: Establish a coupled dynamic model of the drive system.

[0036] Although different drive systems have different structures, their principles and the physical laws they follow are the same. Therefore, this invention only targets general situations and selects important parameters in the drive system for coupled dynamic modeling, which has universality. The universal parameters in this invention are time t, drive system flow rate Q(t), drive system head H(t), mass m of the driven object, cross-sectional area S of the driven object, movement speed v(t) of the driven object after the end of the driving process, initial underwater driving depth h of the driven object, driving acceleration displacement x(t) of the driven object, and target driving time t t 。

[0037] To achieve rapid driving, the driven object usually moves in a straight line. According to the momentum theorem:[[]]

[0038] FΔt = mΔv (9)

[0039] At t = 0, the driven object is stationary, v = 0, and Ft = mv is satisfied. And the change in impulse is equal to the change in momentum at each moment. Therefore, at each moment, the following is satisfied:[[]]

[0040] Ft = mv (10)

[0041] The resultant driving force on the driven object can be expressed as[[]]

[0042] ∑F = ΔPS - f[[]] j =(P1 - P0)S - f[[]] j =[ρgH(t) - P0]S - f[[]] j (11)

[0043] where f[[]] j is the resistance suffered by the driven object during the driving acceleration process in the drive pipe, expressed as[[]]

[0044]

[0045] where k[[]] L and C are both constant coefficients, and Ω is the wetted surface area of the driven object. Therefore, the resultant force on the driven object is expressed as[[]]

[0046]

[0047] By combining equations (10) and (13), we can obtain

[0048]

[0049] By combining equations (8) and (14), the expression of v(t) can be obtained.

[0050] According to the boundary conditions at t = 0 and t = t t moments, we have

[0051]

[0052] Therefore, the problem is transformed into an initial value problem of a nonlinear ordinary differential equation. The Euler method, Runge - Kutta method, or linear multi - step method can be used to obtain the motion speed v(t) of the driven object after the driving process ends, and successfully predict the initial motion performance provided by the driving system to the driven object.

[0053] Step Five: Verify the effectiveness of the driving system and iteratively optimize the driving system until the goal is met.

[0054] Judge whether the target speed v of the driven object is reached at the end of the driving process t . If the motion speed v(t) of the driven object after the driving process ends is greater than the target speed v of the driven object t , then the goal is achieved; if the motion speed v(t) of the driven object after the driving process ends is less than the target speed v of the driven object t , then the goal is not achieved. By changing the length L of the launch tube, the variation law n(t) of the motor speed at startup, and the type of the axial - flow pump until the goal is met.

[0055] Beneficial effects:

[0056] 1. A driving system and its optimization method based on the transient startup process of an axial - flow pump disclosed by the present invention can realize the dynamic adjustment process of the driving target underwater launch depth. By adjusting the variation law n(t) of the motor speed at startup, the head H(n) and flow rate Q(n) of the axial - flow pump at different speeds can be obtained. Through a series of calculations, the motion speed v(t) of different driven objects after the driving process ends can be finally obtained to realize the dynamic adjustment of the driving target underwater launch depth.

[0057] 2. A driving system and its optimization method based on the transient startup process of an axial - flow pump disclosed by the present invention can realize the driving and launching of a single medium. The driving process only involves a single fluid medium, which is the same as the surrounding environmental fluid medium. Compared with underwater driving methods such as gas and high - pressure gas, with the help of a single medium that is the same as the surrounding environmental fluid medium, the technical means are simple, safe, and controllable.

[0058] 3. A drive system and its optimization method based on the transient startup process of an axial flow pump disclosed by the present invention take into account the transient startup process of the axial flow pump during the driving process, and can ensure the accuracy and stability of the dynamic modeling of the driven object.

[0059] 4. A drive system and its optimization method based on the transient startup process of an axial flow pump disclosed by the present invention simplify the dynamic modeling of the driven object, couple the power source axial flow pump and the driven object in the same system, and realize the integrated modeling of the drive system, so as to be able to predict the drive performance under various operating conditions. Description of the Drawings

[0060] Figure 1 It is a flow chart of an optimization method for a drive system based on the transient startup process of an axial flow pump disclosed by the present invention;

[0061] Figure 2 It is a schematic diagram of the drive system; wherein, 1 - inlet pipe, 2 - axial flow pump, 3 - high-pressure flow pipe, 4 - driven object, 5 - drive pipe, 6 - outlet pipe.

[0062] Figure 3 It is a schematic diagram of the dynamic modeling of the driven object;

[0063] Figure 4 It is the motor speed requirement;

[0064] Figure 5 It is the speed of the driven object. Detailed Embodiments

[0065] The following are specific embodiments of the present invention, and the technical solutions of the present invention will be further described in a complete and detailed manner in combination with the accompanying drawings. This embodiment is the best embodiment based on the technical solution of the present invention, but the protection scope of the present invention is not limited to the following embodiments.

[0066] Embodiment 1:

[0067] A drive system based on the transient startup process of an axial flow pump disclosed in this embodiment is as Figure 1 shown. In this embodiment, an underwater launch unmanned aerial vehicle is the driven target, and the specific implementation steps are as follows:

[0068] Step 1: Define the drive target and parameters of the driven object.

[0069] An underwater-launched unmanned aerial vehicle is a new type of unmanned equipment with three-dimensional collaborative functions, which is equipped on an unmanned platform. The underwater-launched unmanned aerial vehicle has the ability of swarm collaboration and can be extended to a group of unmanned aerial vehicles. It has functions such as transporting materials, reconnaissance information, and performing assault tasks. The underwater unmanned platform for launching the unmanned aerial vehicle has high mobility and stealth performance, and the above performances directly determine its combat survival ability, and the strong stealth performance can reduce the probability of being discovered and hit. The driving target selected in this embodiment is a medium-sized unmanned aerial vehicle, and the working location of the unmanned platform for launching the unmanned aerial vehicle is usually in the near-surface sea area (water depth within 10m). At the same time, the unmanned platform can sail quickly on the water surface.

[0070] Based on the above background, a driving system based on the transient start-up process of an axial flow pump in this embodiment will be simulated and equipped on an unmanned platform, and the unmanned aerial vehicle will achieve a rapid driving process on the unmanned platform. The working range of the unmanned platform is the near-surface area, and the water depth is 5-10m. In the system of the present invention, the inflow pipe and the driving pipe are in the same water area, and the water depth will not affect the driving process. Therefore, the initial driving water depth of 7m with the most severe cavitation conditions of the axial flow pump is selected for design. In this embodiment, the unmanned aerial vehicle needs to be quickly driven out of the water in a short time and quickly strike, so it needs to be quickly driven within 1s, leave the driving system at a sufficient moving speed, and start immediately after leaving the water to achieve rapid strike and accurate reconnaissance. The schematic diagram of the underwater driving system in this embodiment is as Figure 2 shown, and the parameters are shown in Table 1.

[0071]

[0072] Step 2: Initially select the model of the axial flow pump according to the driving requirements.

[0073] Initially select the model of the axial flow pump according to the driving requirements. From the motor speed requirements as shown in Figure 4 shown, an axial flow pump with an impeller diameter of 0.536m and a guide vane diameter of 0.4m is initially selected. Based on the steady-state external characteristic curve database of the axial flow pump, the transient external characteristics under the starting conditions are determined. According to the system design method, a flow relationship formula and a dynamic model are established.

[0074] Step 3: With the help of the MATLAB programming software, compile the equations described in the design process into a program using a programming language and solve them to obtain the moving speed v(t) after the driving process ends as shown in Figure 5 shown.

[0075] Step 4: Verify the effectiveness of the driving system and iteratively optimize the driving system until the goal is met.

[0076] As shown in Figure 5As shown, at 0.4 s, the predicted speed of the launch object is 13 m / s, satisfying that the motion speed v(t) after the end of the driving process is greater than the target speed v of the driving object t , and the driving goal is completed.

[0077] The above specific description further details the purpose, technical solution and beneficial effects of the invention. It should be understood that the above is only a specific embodiment of the present invention and is not used to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. An optimization method for a drive system based on the transient startup process of an axial flow pump, comprising the following steps: Step 1: Define the drive objectives and parameters of the driven object; According to the driving requirements of the target, the initial underwater driving depth h of the driven object, the target driving time t t , the target speed v of the driven object after driving is completed t and the rotational speed change law n(t) when the motor starts; the target speed v of the driven object t According to the initial underwater driving depth h, the underwater movement resistance f of the driven object after being driven out of the cylinder s and the mass m of the driven object are determined, that is Step 2: Preliminary select the model of the axial flow pump according to the drive requirements; Query the external characteristic curve of the selected model of axial flow pump. According to the queried external characteristic curve, determine the head H(n) and flow rate Q(n) of the axial flow pump at different rotational speeds. Combine the rotational speed change law n(t) of the axial flow pump when the motor starts given in the first step to establish the first relationship: the relationship between the flow rate, head and time of the axial flow pump during the startup process; f[H(t),Q(t)] = 0 (2) Step 3: Establish the flow relationship in the drive system; According to the continuity equation, the flow rate Q in the drive system is expressed as the sum of the flow rate Q of the fluid medium discharged by the driven object f and the flow rate Q at the gap between the driven object and the drive pipe j ; Q(t) = Q f +Q j (3) Q f = v(t)S (4) where S is the cross-sectional area of the driven object, P0 is the pressure at the outlet pipe, P1 is the pressure at the tail of the driven object, expressed as the pressure at the outlet of the axial flow pump minus the pressure loss generated by the combined action of the frictional loss and local loss during the flow process. And the head loss generated by the combined action of the frictional loss and local loss is negligible compared with the head provided by the axial flow pump. Therefore, P1 is expressed as P1 = ρgH(t) (6) Combining (3)(4)(5)(6) gives Combining (3)(7) gives the second relationship: the relationship between H(t) and v(t) f[H(t),v(t)] = 0 (8) Step 4: Establish the coupled dynamic model of the drive system; Although different drive systems have different structures, their principles and the physical laws they follow are the same. Therefore, the present invention only targets general situations and selects important parameters in the drive system for coupled dynamics modeling, which has universality. The universal parameters in the present invention are time t, drive system flow rate Q(t), drive system head H(t), mass m of the driven object, cross-sectional area S of the driven object, movement speed v(t) of the driven object after the end of the driving process, initial underwater driving depth h of the driven object, driving acceleration displacement x(t) of the driven object, and target driving time t t ; To achieve rapid drive, the driven object usually moves in a straight line. According to the momentum theorem: FΔt = mΔv (9) At t = 0, the driven object is stationary, v = 0, and Ft = mv is satisfied. And the change in impulse at each moment is equal to the change in momentum. Therefore, at each moment, it satisfies: Ft = mv (10) The resultant driving force acting on the driving object can be expressed as ∑F = ΔPS - f j =(P1 - P0)S - f j =[ρgH(t) - P0]S - f j (11) where f j is the resistance experienced by the driven object during the driving and accelerating process in the driving tube, expressed as where k L and C are both constant coefficients, and Ω is the wetted surface area of the driven object; thus, the resultant force acting on the driven object is expressed as Combining (10)(13) gives Combining (8)(14) gives the expression of v(t); According to the boundary conditions at times \(t = 0\) and \(t=t\) t we obtain: Therefore, the problem is transformed into an initial value problem of a nonlinear ordinary differential equation. The Euler method, Runge-Kutta method or linear multi-step method can be used to find the motion speed v(t) of the driven object after the drive process ends. The predicted drive system is provided to the driven object as the initial motion performance of the driven object; Step 5: Verify the effectiveness of the drive system and iteratively optimize the drive system until the goal is met; Determine whether the target speed v of the driven object is reached at the end of the driving process t ; if the moving speed v(t) of the driven object after the driving process ends is greater than the target speed v of the driven object t , then the target is achieved; if the moving speed v(t) of the driven object after the driving process ends is less than the target speed v of the driven object t , then the target is not achieved; by changing the length L of the emission tube, changing the rotational speed change law n(t) when the motor starts, and changing the model of the axial flow pump until the target is met.

2. A drive system based on the transient start-up process of an axial flow pump, which is used to implement the optimization method of a drive system based on the transient start-up process of an axial flow pump as described in Claim 1, characterized in that: Including an inlet pipe, an axial flow pump, a high-pressure flow pipe, a drive pipe, a driven object and an outlet pipe; The inlet pipe is the inlet of the fluid medium, which absorbs the fluid medium from the environment and leads it to the inlet of the axial flow pump; The axial flow pump is the power source of the drive system, placed between the inlet pipe and the high-pressure flow pipe. The axial flow pump is driven by a motor to rotate, and the impeller rotates to do work on the fluid medium, improving the energy of the fluid medium and providing power for the driven object; The high-pressure flow pipe is located after the outlet of the axial flow pump, used to transport the high-pressure fluid medium output by the axial flow pump and transport the high-pressure fluid medium into the drive pipe; The drive pipe is located after the outlet of the high-pressure flow pipe, used to accommodate the driven object and provide the working environment for the high-pressure fluid medium to act on the driven object; The driven object is the target to be driven, usually a cylinder or based on a cylinder; The diameter of the driving object is slightly smaller than that of the driving tube. When the fluid medium passes through the gap between the driving object and the driving tube, due to the increase in the velocity of the fluid medium, the pressure decreases, and a pressure difference is formed before and after the driving object, causing the driving object to move. The outflow pipe is connected to the environmental fluid domain. When the driving object disengages from the outflow pipe, the system pressure decreases, and the driving process is determined to end.

3. The drive system based on the transient starting process of an axial flow pump according to claim 2, wherein: The inflow pipe, high-pressure flow pipe, driving tube, and outflow pipe are all made of low-damping materials, which can reduce the flow resistance of the fluid medium, thereby reducing the energy loss during the driving process.

4. A drive system based on the transient start-up process of an axial flow pump according to claim 2 or 3, characterized in that: Turn on the motor switch. The axial flow pump starts at an extremely fast speed under the drive of the motor. The inflow pipe sucks the fluid medium into the inlet of the axial flow pump. The axial flow pump does work on the fluid medium to increase the pressure of the fluid medium and generate high-pressure fluid. The high-pressure fluid medium enters the driving tube through the high-pressure flow pipe. The driving object in the driving tube moves in the driving tube under the action of the pressure difference generated by the high-pressure fluid medium until it disengages from the outflow pipe, and the driving process ends.

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