Method for calculating hydraulic efficiency of a hydraulic turbine

Abstract

The present application relates to a kind of hydraulic efficiency calculation method of water turbine, belong to the technical field of hydraulic machinery and its system.This application includes the following steps:A, determine the three-dimensional flow field region including water turbine, i.e.control body;B, perform fluid dynamics calculation, obtain the three-dimensional steady flow field distribution of each region;C, calculate the viscous dissipation power of fluid in control body;D, calculate the kinetic energy change rate of control body;E, calculate the power done by external surface force to control body;F, calculate the power done by fluid body force of control body;G, calculate the hydraulic efficiency of water turbine.The present application proposes a new kind of quantitative calculation method of hydraulic efficiency of water turbine, with universality.

Description

Technical Field

[0001] This invention relates to a method for calculating the hydraulic efficiency of a water turbine, belonging to the technical field of hydraulic machinery and its systems. Background Technology

[0002] Hydropower is a water-based power generation device that uses a water turbine to convert the kinetic energy of fluids into mechanical energy, and then into electrical energy. Due to its high energy conversion efficiency, renewability, and environmental friendliness, it is widely used in the development and utilization of hydropower. However, irreversible energy losses inevitably occur during the energy conversion process. Traditional hydraulic efficiency calculations cannot accurately account for the influence of fluid viscous dissipation work, and the comprehensive energy characteristic curves calculated based on model tests cannot accurately reflect the energy acquisition characteristics of the prototype water turbine. This leads to significant deviations in the actual output power and efficiency calculations of the prototype water turbine when it deviates from the design operating conditions, affecting the dynamic balance of the power system. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a new method for calculating the hydraulic efficiency of water turbines, so as to fill the technical gap in accurately quantifying the calculation of hydraulic efficiency of water turbines.

[0004] To achieve the above objectives, the present invention provides the following solution: a method for calculating the hydraulic efficiency of a water turbine, the specific steps of which are as follows:

[0005] Step 1: Determine the three-dimensional flow field calculation region, including the water turbine, i.e., the control volume;

[0006] Step 2: Perform fluid dynamics calculations to obtain the three-dimensional steady-state flow field distribution of the control volume;

[0007] Step 3: Calculate the viscous dissipation power E of the fluid within the control volume. S ;

[0008] Step 4: Calculate the rate of change of kinetic energy E of the control volume. K ;

[0009] Step 5: Calculate the power E exerted by the external surface forces on the control volume. P ;

[0010] Step 6: Calculate the power E generated by the fluid volume force. Z ;

[0011] Step 7: Calculate the hydraulic efficiency η of the turbine.

[0012] Specifically, in Step 1, the control body refers to the closed fluid region enclosed by the fixed wall, the flow inlet and outlet, and the surface of the impeller. The surfaces of the control body that come into contact with the outside world include the fixed wall, the flow inlet and outlet, and the rotating surface of the impeller.

[0013] Specifically, in Step 2, the fluid within the control volume is an incompressible fluid, and fluid dynamics calculations are performed to obtain the strain rate tensor S and the effective turbulent viscosity μ of the mean flow field within the control volume. eff And pressure field p.

[0014] Specifically, in Step 3, the viscous dissipation power E of the fluid in the body is controlled. S Calculate using the following formula (1)

[0015]

[0016] In the formula V represents the mass flow rate of the water turbine, and V represents the control volume.

[0017] Specifically, in Step 4, the rate of change of body kinetic energy E is controlled. K Calculate using the following formula (2)

[0018]

[0019] In the formula, V1 and V2 are the average velocities at the inlet and outlet sections of the control volume, respectively.

[0020] Specifically, in Step 5, the power E exerted by the external surface force on the control body is... P Calculate using the following formula (3)

[0021]

[0022] Here, p1 and p2 are the average static pressures at the inlet and outlet boundaries of the control volume, respectively, and ρ is the fluid density.

[0023] Specifically, in Step 6, the power E generated by the fluid volume force... Z Calculate using the following formula (4)

[0024]

[0025] Here, Z1 and Z2 are the elevations of the center points of the control volume inlet and outlet sections, respectively, and g is the local gravitational acceleration.

[0026] Specifically, in Step 7, the hydraulic efficiency η of the turbine is calculated according to formula (5).

[0027]

[0028] The beneficial effects of this invention are:

[0029] 1. This invention proposes a method for calculating the hydraulic efficiency of a water turbine, which can accurately quantify the viscous dissipation work of a prototype water turbine under different operating conditions.

[0030] 2. This invention proposes a method for calculating the hydraulic efficiency of a water turbine. It can accurately predict the hydraulic efficiency of a prototype water turbine by numerically calculating the internal flow field of the water turbine and then based on energy conservation and viscous dissipation work.

[0031] 3. This invention proposes a method for calculating the hydraulic efficiency of a water turbine, which can also accurately predict the shaft power of a prototype water turbine during any transient process, providing a useful reference for the dynamic regulation of the unit.

[0032] 4. The calculation process used in this invention has a clear physical concept, a simple calculation process, and accurate results, making it easy to grasp the comprehensive energy characteristics of the prototype turbine under steady-state operation and arbitrary transient processes. Attached Figure Description

[0033] Figure 1 This is a flowchart from the present invention;

[0034] Figure 2 This is a schematic diagram of the control body in this invention. Detailed Implementation

[0035] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0036] Example 1: As Figure 1-2 As shown, a method for calculating the hydraulic efficiency of a water turbine is described, with the following specific steps:

[0037] like Figure 2 As shown, Figure 2 This is a schematic diagram of a mixed-flow turbine, including a fixed wall, flow inlets and outlets, a runner surface, and the closed fluid region enclosed by them, i.e., the control volume. No-slip boundary conditions are applied to the fixed wall and runner surface; total pressure and velocity boundary conditions are applied at the inlet; and static pressure boundary conditions are applied at the outlet. Water is used as the flow medium, and the fluid is assumed to be incompressible and adiabatic in the calculations. The flow field calculations are performed using the shear stress transport model from the Reynolds time-averaged model.

[0038] Step 1: Determine the control entity, such as... Figure 2 As shown;

[0039] Step 2: Perform fluid dynamics calculations to obtain the three-dimensional steady-state flow field distribution of the control volume;

[0040] Step 3: Calculate the viscous dissipation power E of the fluid within the control volume. S ;

[0041] Step 4: Calculate the rate of change of kinetic energy E of the control volume. K ;

[0042] Step 5: Calculate the power E exerted by the external surface forces on the control volume. P ;

[0043] Step 6: Calculate the power E generated by the fluid volume force. Z ;

[0044] Step 7: Calculate the hydraulic efficiency η of the turbine.

[0045] Furthermore, in Step 1, the control volume refers to the closed fluid region enclosed by the fixed wall, the flow inlet and outlet, and the surface of the impeller.

[0046] Furthermore, in Step 2, the fluid within the control volume is assumed to be incompressible, and fluid dynamics calculations are performed to obtain the strain rate tensor S and the turbulent effective viscosity coefficient μ of the mean flow field within the control volume. eff And pressure field p.

[0047] Furthermore, in Step 3, the viscous dissipation power E of the fluid in the body is controlled. S Calculate using the following formula (1)

[0048]

[0049] In the formula V represents the mass flow rate of the water turbine, and V represents the control volume.

[0050] Furthermore, in Step 4, the rate of change of body kinetic energy E is controlled. K Calculate using the following formula (2)

[0051]

[0052] In the formula, V1 and V2 are the average velocities at the inlet and outlet sections of the control volume, respectively.

[0053] Furthermore, in Step 5, the power E exerted by the external surface force on the control body... P Calculate using the following formula (3)

[0054]

[0055] Here, p1 and p2 are the average static pressures at the inlet and outlet boundaries of the control volume, respectively, and ρ is the fluid density.

[0056] Furthermore, in Step 6, the power E generated by the fluid volume force... Z Calculate using the following formula (4)

[0057]

[0058] Here, Z1 and Z2 are the elevations of the center points of the control volume inlet and outlet sections, respectively, and g is the local gravitational acceleration.

[0059] Furthermore, in Step 7, the hydraulic efficiency η of the turbine is calculated according to equation (5).

[0060]

[0061] In this embodiment, under the design head (10 meters) and optimal efficiency point conditions of the water turbine, the calculated shaft power of the water turbine is 51.695 kW and the efficiency of the water turbine is 0.9399.

[0062] The specific embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above-described embodiments or operating conditions. This method can also be used to calculate hydraulic efficiency for similar hydraulic machinery, such as water pumps. Furthermore, various modifications can be made within the scope of knowledge possessed by those skilled in the art without departing from the spirit of the present invention.

Claims

1. A method for calculating the hydraulic efficiency of a water turbine, characterized in that: The specific steps are as follows: Step 1: Determine the three-dimensional flow field calculation region, including the water turbine, i.e., the control volume; Step 2: Perform fluid dynamics calculations to obtain the three-dimensional steady-state flow field distribution of the control volume; Step 3: Calculate the viscous dissipation power of the fluid within the control volume. ; Step 4: Calculate the rate of change of kinetic energy of the control volume. ; Step 5: Calculate the power exerted by the external surface forces on the control volume. ; Step 6: Calculate the power generated by the fluid volume forces. ; Step 7: Calculate the hydraulic efficiency of the turbine. ; In Step 1, the control body refers to the closed fluid region enclosed by the fixed wall, the flow inlet and outlet, and the rotating surface of the impeller. The surfaces of the control body that come into contact with the outside world include the fixed wall, the flow inlet and outlet, and the impeller surface. In Step 5, the power exerted by the external surface force on the control body Calculate using the following formula (3) （3）； Here, Represents the mass flow rate of the water turbine. and These are the average static pressures at the inlet and outlet boundaries of the control body, respectively. For fluid density; In Step 7, the hydraulic efficiency of the turbine Calculate according to formula (5) （5）。 2. The method for calculating the hydraulic efficiency of a water turbine according to claim 1, characterized in that: In Step 2, the fluid within the control volume is an incompressible fluid, and fluid dynamics calculations are performed to obtain the strain rate tensor of the average flow field within the control volume. Turbulent effective viscosity coefficient and pressure field .

3. The method for calculating the hydraulic efficiency of a water turbine according to claim 2, characterized in that: In Step 3, the viscous dissipation power of the fluid in the body is controlled. Calculate using the following formula (1) （1）； In the formula Represents the mass flow rate of the water turbine. V Represents the controlling entity.

4. The method for calculating the hydraulic efficiency of a water turbine according to claim 1, characterized in that: In Step 4, the rate of change of body kinetic energy is controlled. Calculate using the following formula (2) （2）； In the formula Represents the mass flow rate of the water turbine. and These are the average velocities at the inlet and outlet sections of the control body, respectively.

5. The method for calculating the hydraulic efficiency of a water turbine according to claim 1, characterized in that: In Step 6, the power generated by the fluid volume force Calculate using the following formula (4) （4）； Here, Represents the mass flow rate of the water turbine. and These are the elevations of the center points of the control body's inlet and outlet sections, respectively. This is the local gravitational acceleration.

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