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Near-field wake flow 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: 2018-10-09
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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  • Near-field wake flow prediction model based on simplified momentum theorem
  • Near-field wake flow prediction model based on simplified momentum theorem
  • Near-field wake flow 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 range of near-field wake area 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 area 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 th...

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 Image 6 shown.

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Abstract

The invention discloses a near-field wake flow prediction model based on the simplified momentum theorem, and the near-field wake flow prediction model comprises the following steps: 1, employing (1-a)U-infinity and U-infinity for replacing Uw in a common one-dimensional momentum theorem for a near-field wake flow region of a wind turbine generator set, and obtaining two simplified one-dimensionalmomentum theorems; 2, supposing that the speed loss of the wake flow region is in Gaussian distribution in a radial direction, and respectively calculating the maximum speed losses of the wake flow region according to the two simplified one-dimensional momentum theorems at step 1; 3, supposing the linear expansion of the wake flow, defining the wake flow boundary, and introducing a wake flow expansion coefficient k to represent the linear expansion law of the wake flow region; 4, obtaining the upper bound and bound positions of the near-field wake flow region according to the results at steps2 and 3, and giving a predicted scope of the wake flow boundary of the wind turbine generator set; 5, correcting the simplified one-dimensional momentum theorem again based on the result at step 4, and replacing Uw with (1-a / 2)U-infinity to construct a high-precision wind turbine generator set wake flow 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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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)