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A Wake Prediction Model Based on Simplified Momentum Theorem

A technology of momentum theorem and forecasting model, applied in forecasting, data processing applications, instruments, etc., can solve the problems of reducing calculation amount, low calculation accuracy, large error, etc., and achieve the effect of improving prediction accuracy

Active Publication Date: 2021-11-12
NORTH CHINA ELECTRIC POWER UNIV (BAODING)
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

In order to reduce the amount of calculation, the current common wake research methods all make necessary assumptions on the near-field wake. For example, the brake disc theory assumes that the load is uniformly distributed along the swept surface of the wind rotor, which makes the calculation error of this method in the near-field relatively small. Large; the well-known inviscid near-field wake model assumes that the near-wake is an inviscid rotating flow, and the velocity on the cross-section of the wake area is uniformly distributed, but this model can only approximate the wind speed in the range of x<5d distribution; commonly used semi-empirical wake models are also applicable to far-field wakes, such as Jensen model, Frandsen model, Larsen model, Ishihara model, etc., and their calculation accuracy in the near-wake region is low

Method used

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  • A Wake Prediction Model Based on Simplified Momentum Theorem
  • A Wake Prediction Model Based on Simplified Momentum Theorem
  • A Wake Prediction Model Based on Simplified Momentum Theorem

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0049] Example 1: Select as figure 1 For the control volume shown, the self-similar speed loss of the LES results at different tip speed ratios and different downwind distances is as follows figure 2 shown.

[0050] An application of a near-field wake prediction model based on the simplified momentum theorem, comprising the following steps:

[0051] Step 1: Determine the reference coordinate system, take the center of the wind rotor as the coordinate origin, the rotation axis of the wind rotor is the x-axis (parallel to the incoming flow direction), the radial direction (perpendicular to the incoming flow direction) is the y-axis, and the vertical direction is the z-axis ;

[0052] Step 2: According to the incoming wind speed, compare the curve of the thrust coefficient of the unit with the wind speed to obtain the thrust coefficient C of the unit under this working condition T ;

[0053]Step 3: Determine the value range of the downstream wake boundary coefficient J by an...

Embodiment 2

[0062] Embodiment 2: The near-field wake region range calculated by the model proposed by the present invention is verified by LES data, including the maximum velocity loss in the horizontal direction and the wake region velocity loss in the vertical direction, and the results are compared with the Jensen model and the Frandsen model comparison, including the following steps:

[0063] Step 1: Table 1 shows the specific parameters of the wind tunnel experimental data (case 1) and LES results (case 2-5), including the rotor diameter d 0 , hub height z h , wind speed U at hub height hub , thrust coefficient C T , surface roughness z 0 and the ambient turbulence intensity I 0 .

[0064] Step 2: Within the value range of J, take J=1 as an example for calculation. At this time, in cases 1-5, the wake expansion coefficients k are: 0.041, 0.108, 0.0977, 0.0645 and 0.0646, respectively.

[0065] Step 3: In order to obtain the upper limit position and the lower limit position of t...

Embodiment 3

[0069] Embodiment 3: This embodiment uses the wind tunnel experimental data (case 1) and LES data (case 2-5) to verify the wake model formula (13) based on the further correction of the wake range in the near field, including the maximum velocity loss in the horizontal direction and vertical velocity loss in the wake zone, and compare the results with the Jensen model and the Frandsen model, including the following steps:

[0070] Step 1: Repeat steps 1 and 2 in Example 2.

[0071] Step 2: Substituting all input parameters into formula (13), the velocity loss at any position in the wake area calculated by the revised model is obtained, and compared with the Jensen model and the Frandsen model, as shown in Figure 5 and Figure 6 shown.

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Abstract

The invention discloses a near-field wake prediction model based on a simplified momentum theorem. The near-field wake prediction model includes the following steps: Step 1: For the near-field wake area of ​​a wind turbine, respectively use (1‑a)U ∞ and U ∞ Instead of U in the common one-dimensional momentum theorem w , to obtain two simplified one-dimensional momentum theorems; step two: assuming that the velocity loss in the wake region is Gaussian distributed along the radial direction, the maximum velocity loss in the wake region is calculated according to the two simplified one-dimensional momentum theorems in step one; Step 3: Assume that the wake expands linearly and define the wake boundary, and introduce the wake expansion coefficient k to represent the linear expansion law of the wake region; Step 4: According to the results of steps 2 to 3, obtain the upper limit position of the near-field wake region and the lower limit position, and then give the prediction range of the near-field wake boundary of the wind turbine; Step 5: Based on the results of Step 4, modify the simplified one-dimensional momentum theorem again, replacing U w To build a high-precision wind turbine wake prediction model.

Description

technical field [0001] The invention relates to the technical field of wind turbine wake calculation technology, in particular to a near-field wake prediction model based on simplified momentum theorem. Background technique [0002] The near-field wake area of ​​a wind turbine generally refers to the area where the thickness of the shear layer reaches the maximum at 2-5 rotor diameters behind the wind rotor. The flow of the wake in this area is more complicated. The component is high, the time-varying characteristic is strong, and it is significantly affected by the geometric characteristics of the wind rotor itself, and there is an obvious vortex system in the flow area. As the beginning of far-field wake calculation for wind turbines, accurate calculation of near-field wakes is of great significance for improving the prediction accuracy of wakes in the entire field. In order to reduce the amount of calculation, the current common wake research methods all make necessary a...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): G06Q10/04G06Q50/06
CPCG06Q10/04G06Q50/06
Inventor 葛铭纬武英刘永前李莉邵振州
Owner NORTH CHINA ELECTRIC POWER UNIV (BAODING)