Method for obtaining three-gear rotating speed of variable rotating speed energy-saving air compressor

Abstract

The application provides a method for obtaining three-gear rotating speed of a variable rotating speed energy-saving air compressor, comprising the following steps: determining the total power rotating speed range and the 100% volumetric flow range of the unit during full load operation according to the limitation of the total power of the variable rotating speed energy-saving air compressor; determining the first rotating speed range corresponding to the 100% volumetric flow range according to the relationship between the volumetric flow and the rotating speed, and determining the second rotating speed range corresponding to the 70% volumetric flow range and the third rotating speed range corresponding to the 40% volumetric flow range; determining the reference rotating speed range according to the total power rotating speed range and the first rotating speed range; selecting the reference rotating speed value in the reference rotating speed range according to the set step length, obtaining the second rotating speed value in the second rotating speed range and the third rotating speed value in the third rotating speed range by making the comprehensive specific power minimum; and obtaining multiple sets of three-gear rotating speed values in cycles, and obtaining the optimal three-gear rotating speed value from the multiple sets by the bubble method. The method provided by the application can realize the fast and accurate calculation of the optimal energy efficiency rotating speed value.

Description

Technical Field

[0001] This invention relates to the field of energy-saving air compressors, and in particular to a method for obtaining three speeds in a variable speed energy-saving air compressor. Background Technology

[0002] Air compressors often account for a significant portion of factory expenses in terms of electricity consumption. Excessive power loss not only lowers factory efficiency but also leads to unnecessary energy consumption. Therefore, the market for energy-efficient air compressors has gradually emerged. For variable-speed oil-injected rotary air compressors, the unit's specific power needs to be tested at three levels and weighted to obtain comprehensive energy efficiency data. This determines the final specific power; a lower specific power means greater energy efficiency and a larger market share. Therefore, the development of energy-efficient air compressors has always been a focus of market attention.

[0003] Existing technical solutions involve extensive rough measurements of the compressor head to select three approximate speeds. Then, through trial calculations, test feedback, and further trial calculations, the speed range is continuously narrowed down to obtain the optimal three speeds. This approach requires a large amount of test data, is inefficient, has poor accuracy, relies heavily on experience for selection, and loses more potential for improving the air compressor's performance. Summary of the Invention

[0004] The main objective of this invention is to overcome the aforementioned deficiencies in the prior art and propose a method for obtaining three speeds in a variable speed energy-saving air compressor, thereby enabling rapid and accurate calculation of the optimal energy efficiency speed value of the variable speed oil-injected rotary air compressor.

[0005] The present invention adopts the following technical solution:

[0006] A method for obtaining three speeds in a variable speed energy-saving air compressor includes:

[0007] Based on the limitation of the total power of the variable speed energy-saving air compressor, determine the total power speed range and the 100% volumetric flow range of the unit when operating at full load;

[0008] Based on the relationship between volumetric flow rate and rotational speed, the first rotational speed range corresponding to the 100% volumetric flow rate range is determined, the second rotational speed range corresponding to the 70% volumetric flow rate range is determined, and the third rotational speed range corresponding to the 40% volumetric flow rate range is determined.

[0009] The reference speed range is determined based on the total power speed range and the first speed range;

[0010] Set the step size of the reference speed range, select the reference speed value in the reference speed range according to the step size, and obtain the second speed value in the corresponding second speed range and the third speed value in the third speed range by minimizing the comprehensive specific power; cyclically obtain multiple sets of three-speed values, the three-speed values ​​including the reference speed value, the second speed value and the third speed value;

[0011] The optimal three-speed values ​​are obtained from multiple sets using the bubble sort method.

[0012] Specifically, the volumetric flow rate range also includes:

[0013] When the unit operates at 70% of its full load capacity and at 100% of its full load capacity, the measured unit volumetric flow rate should not deviate from the full load unit volumetric flow rate by more than ±5%.

[0014] When the unit operates at 40% of its full load capacity, and the unit operates at 100% of its full load capacity, the deviation between the measured unit volumetric flow rate and the full load unit volumetric flow rate shall not exceed ±5%.

[0015] The comprehensive power ratio calculation is as follows:

[0016] Y = y1 * 0.25 + y2 * 0.5 + y3 * 0.25;

[0017] Where Y represents the overall specific power, and y1 represents the reference specific power at the reference speed value. y2 represents the second specific power at the second rotational speed. y3 represents the third specific power at the third rotational speed.

[0018] As can be seen from the above description of the present invention, compared with the prior art, the present invention has the following beneficial effects:

[0019] This invention provides a method for obtaining three speed settings for a variable-speed energy-saving air compressor, comprising: determining the total power speed range and the 100% volumetric flow range of the unit when operating at full load, based on the limitation of the total power of the variable-speed energy-saving air compressor; determining a first speed range corresponding to the 100% volumetric flow range, a second speed range corresponding to the 70% volumetric flow range, and a third speed range corresponding to the 40% volumetric flow range, based on the relationship between volumetric flow and speed; determining a reference speed range based on the total power speed range and the first speed range; setting a step size for the reference speed range, selecting a reference speed value within the reference speed range based on the step size, and obtaining a second speed value within the corresponding second speed range and a third speed value within the corresponding third speed range by minimizing the comprehensive specific power; iteratively obtaining multiple sets of three-speed values, wherein the three-speed values ​​include the reference speed value, the second speed value, and the third speed value; and obtaining the optimal three-speed value from multiple sets of comprehensive specific power values ​​using a bubble sort method. This invention provides a method that requires less test data, eliminates the need for repeated adjustments to the three speed settings, and enables rapid and accurate calculation of the optimal energy-efficient speed value for a variable-speed oil-injected rotary air compressor. Attached Figure Description

[0020] Figure 1 A flowchart of the method provided in an embodiment of the present invention;

[0021] Figure 2 The power-speed fitting curve provided for the embodiments of the present invention;

[0022] Figure 3 The volumetric flow rate-rotation speed fitting curve is provided for an embodiment of the present invention.

[0023] Figure 4 The power-speed fitting curve provided for an embodiment of the present invention.

[0024] Figure 5 The flowchart of the algorithm for a method to quickly obtain three speeds of an air compressor is provided in an embodiment of the present invention.

[0025] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. Detailed Implementation

[0026] The table below shows the energy efficiency testing standard for air compressors in GB 19153-2019. According to the energy efficiency testing standard for air compressors in GB 19153-2019, for the calculation of the specific power of variable speed oil-injected rotary air compressor units, it is necessary to obtain experimental data under the full load volumetric flow conditions of the unit at 100%, 70%, and 40%, and calculate the comprehensive specific power of the unit with weights of 25%, 50%, and 25%, and the deviation of the unit's volumetric flow should not be greater than ±5%. A lower specific power of the unit means that the whole machine is more energy-efficient. How to quickly and accurately obtain the corresponding speed to minimize the comprehensive specific power is the main key point of the solution of this invention.

[0027]

[0028] This scheme first obtains a small amount of displacement, power, and speed data within a large range, then uses numerical calculation tools for interpolation fitting. Based on the allowable adjustment range of three speed settings in GB19153-2019 for the specific power calculation method of variable speed energy-saving air compressors, the optimal speed is selected. Finally, the optimal unit specific power is selected using the bubble sort method. For the energy-saving prototype, its total power is required not to exceed the power of the next lower-level motor; therefore, the final total unit power must be less than the power of the next lower-level motor. Figure 1 The flowchart of the present invention specifically includes:

[0029] S101: Based on the limitation of the total power of the variable speed energy-saving air compressor, determine the total power speed range and the 100% volumetric flow range of the unit when operating at full load;

[0030] For energy-saving prototypes, the total power must not exceed the power of the next-level motor. Therefore, the final total power of the unit must be less than the power of the next-level motor. The power correspondingly affects the speed and the 100% volumetric flow range of the unit when operating at full load.

[0031] S102: Based on the relationship between volumetric flow rate and rotational speed, determine the first rotational speed range corresponding to the 100% volumetric flow rate range, similarly determine the second rotational speed range corresponding to the 70% volumetric flow rate range, and determine the third rotational speed range corresponding to the 40% volumetric flow rate range.

[0032] Specifically, the volumetric flow rate range also includes:

[0033] When the unit operates at full load, the volumetric flow rate range of 70% of the unit's volumetric flow rate is no more than ±5% when the measured volumetric flow rate is at 70% of the full load unit's volumetric flow rate.

[0034] When the unit operates at 40% of its full load capacity, the measured unit volumetric flow rate should not deviate from the full load unit volumetric flow rate by more than ±5%.

[0035] It is worth noting that the deviation of no more than ±5% is a percentage relative to the volumetric flow range. For example, when the unit operates at 70% of its volumetric flow range, the deviation is ±(70%*5%)=±3.5%; when the unit operates at 40% of its volumetric flow range, the deviation is ±(40%*5%)=2%.

[0036] S103: Determine the reference speed range based on the total power speed range and the first speed range;

[0037] S104: Set the step size of the reference speed range, select the reference speed value in the reference speed range according to the step size, obtain the second speed value in the corresponding second speed range and the third speed value in the third speed range by minimizing the comprehensive specific power; cyclically obtain multiple sets of three-speed values, the three-speed values ​​including the reference speed value, the second speed value and the third speed value;

[0038] S105: Obtain the optimal three-speed values ​​from multiple groups using the bubble method.

[0039] The comprehensive power ratio calculation is as follows:

[0040] Y = y1 * 0.25 + y2 * 0.5 + y3 * 0.25;

[0041] Where Y represents the overall specific power, and y1 represents the reference specific power at the reference speed value. y2 represents the second specific power at the second speed value. y3 represents the third specific power at the third rotational speed.

[0042] For the relationships between displacement-speed, power-speed, and specific power-speed, this embodiment of the invention employs cubic B-spline interpolation to obtain their functional relationships. The basic idea of ​​this interpolation fitting data is to use known model points (taking the displacement-speed relationship as an example, this embodiment uses speed data as the X-coordinate value of the model point and displacement data as the Y-coordinate value) to obtain the specific expression of the basis of the B-spline using mathematical methods. A tridiagonal matrix is ​​constructed using the approximation idea, and the control points are inversely calculated using the chasing method. Finally, the required curve is fitted. According to numerical experiments and error analysis, the curve constructed by this method can well meet the project requirements and is well applied in the engineering practice of simulating the optimal three speeds of an air compressor. It is worth noting that this method uses piecewise interpolation, making it relatively complicated to derive the overall functional expression; it can be obtained through mathematical calculations.

[0043] Before going into detail, it is necessary to explain the meaning of several basic parameters.

[0044] Definition of B-spline function: Given n+1 control points The equation of a p-th degree B-spline curve is defined as follows:

[0045] ;

[0046] In the formula, p-th order B-spline basis functions These are node vectors (constructed using the uniform parameter method).

[0047] For a p-th degree B-spline curve, m = n + 1 + p. The nodal vector form constructed using the uniform parameter method is as follows:

[0048] ;

[0049] Type value point ;

[0050] Node vector: ;

[0051] In this example, a cubic B-spline curve is selected as the interpolation curve. When P=3, ;

[0052] The node vector is:

[0053] ;

[0054] The basis functions are: ;

[0055] ;

[0056] + + ;

[0057] ;

[0058] In the calculation of the 3rd B-spline control points, , They are respectively at the first type value point and the last type value point Correspondingly, each internal type value point corresponds one-to-one with a node within the domain, therefore With node value One-to-one correspondence, and correspondingly, the domain of the interpolation curve is The interval where the node vector exists is Since m = n + 4, we have r = m - 6 = n - 2. At this point, the equation is determined by the interpolation conditions.

[0059] ;

[0060] As can be seen from the interpolation equations, there are currently n+1 unknowns and n-1 equations. To find the control points, two more equations need to be added. Here, non-node conditions are used, that is, the first and last value points are mapped to the parameters. and For the points on the graph, the obtained parameters should be approximated as closely as possible. .have

[0061] ;

[0062] ;

[0063] The matrix can be obtained from the above equations:

[0064] ;

[0065] in .

[0066] Further transforming the above equation into a tridiagonal matrix and solving it using the chasing method, the system of matrix equations can be reduced to the following form.

[0067] ;

[0068] in,

[0069] ;

[0070] ;

[0071] ;

[0072] The value is the result of row transformation. The control points can be obtained by using the chasing method. From the control points and basis functions, the specific expression of the cubic B-spline curve equation on each interval can be obtained.

[0073] like Figure 2 The power-speed fitting curve provided for embodiments of the present invention; as shown Figure 3 The displacement-speed fitting curve provided in the embodiments of the present invention; Figure 4 The power-speed fitting curve provided in the embodiment of the present invention; Figure 5 The flowchart of the algorithm for a method to quickly obtain three speeds of an air compressor is provided in an embodiment of the present invention.

[0074] This invention provides a method for obtaining three speeds in a variable-speed energy-saving air compressor, comprising: determining the total power speed range and the 100% volumetric flow range of the unit when operating at full load, based on the limitation of the total power of the variable-speed energy-saving air compressor; determining a first speed range corresponding to the 100% volumetric flow range, a second speed range corresponding to the 70% volumetric flow range, and a third speed range corresponding to the 40% volumetric flow range, based on the relationship between volumetric flow and speed; determining a reference speed range based on the total power speed range and the first speed range; setting a step size for the reference speed range, selecting a reference speed value within the reference speed range based on the step size, and obtaining a second speed value within the corresponding second speed range and a third speed value within the corresponding third speed range by minimizing the overall specific power; iteratively obtaining multiple sets of three-speed values, wherein the three-speed values ​​include a reference speed value, a second speed value, and a third speed value; and obtaining the optimal three-speed value from multiple sets using a bubble sort method. This invention provides a method that requires less test data, eliminates the need for repeated adjustments to three speed settings, and enables rapid and accurate calculation of the optimal energy efficiency speed for a variable speed oil-injected rotary air compressor. The adjustment range can be as low as 0.15 revolutions based on the air compressor inverter and the number of motor pole pairs. The manual calculation workload is minimal; only the original test data needs to be entered to obtain the optimal specific power speed and corresponding specific power, as well as the unit's specific power and other data.

[0075] The above are merely specific embodiments of the present invention, but the design concept of the present invention is not limited thereto. Any non-substantial modifications made to the present invention using this concept shall be considered as infringing upon the protection scope of the present invention.

Claims

1. A method for obtaining three speeds in a variable speed energy-saving air compressor, characterized in that, include: Based on the limitation of the total power of the variable speed energy-saving air compressor, the total power speed range and the 100% volumetric flow range of the unit when operating at full load are determined; wherein, the 100% volumetric flow range means that under the condition of 100% full load unit volumetric flow, the deviation between the measured unit volumetric flow and the 100% full load unit volumetric flow is no greater than ±5%; Based on the relationship between volumetric flow rate and rotational speed, a first rotational speed range corresponding to 100% volumetric flow rate is determined, a second rotational speed range corresponding to 70% volumetric flow rate is determined, and a third rotational speed range corresponding to 40% volumetric flow rate is determined. The 70% volumetric flow rate range refers to the measured volumetric flow rate of the unit operating at 70% full load, where the deviation from the measured volumetric flow rate is no greater than ±5%. The 40% volumetric flow rate range refers to the measured volumetric flow rate of the unit operating at 40% full load, where the deviation from the measured volumetric flow rate is no greater than ±5%. The reference speed range is determined based on the total power speed range and the first speed range; Set the step size of the reference speed range, select the reference speed value in the reference speed range according to the step size, and obtain the second speed value in the corresponding second speed range and the third speed value in the third speed range by minimizing the comprehensive specific power; cyclically obtain multiple sets of three-speed values, the three-speed values ​​including the reference speed value, the second speed value and the third speed value; The optimal three-speed value is obtained from multiple sets of three-speed values ​​using the bubble sort method. The specific calculation of the comprehensive power ratio is as follows: Y = y1 * 0.25 + y2 * 0.5 + y3 * 0.25; Where Y is the overall specific power, y1 is the reference specific power at the reference speed, y2 is the second specific power at the second speed, and y3 is the third specific power at the third speed.

2. The method for obtaining three speeds in a variable speed energy-saving air compressor according to claim 1, characterized in that, The speed values ​​in the reference speed range, the second speed range, and the third speed range are determined by fitting the power-speed function relationship, the volumetric flow rate function relationship, and the specific power-speed function relationship to the measured power data, volumetric flow rate data, and speed data of the variable speed energy-saving air compressor using the cubic B-spline interpolation method.

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