Hybrid gas supercharger anti-surge control method

Abstract

The application belongs to the technical field of superchargers, and particularly discloses a mixed gas supercharger anti-surge control method, which comprises a transverse correction step and a longitudinal correction step; the transverse correction step comprises the following steps: calculating a preliminary change ratio of density according to a total molecular weight; calculating a final change ratio of density according to pressure; and obtaining a transverse correction number according to the types and quantities of mixed gases. The longitudinal correction step comprises the following steps: calculating a pressure ratio change value curve; and calculating a longitudinal correction curve. A user can perform operation according to an original performance curve and new gas components to generate a new anti-surge line, so that the anti-surge line of the unit is more accurate, the unit can save energy and protect the operation safety of the unit. The performance curve does not need to be recalculated by the design manufacturer and then provided to the control system manufacturer to change the anti-surge line, which is convenient, fast and highly practical.

Description

Technical Field

[0001] This invention belongs to the field of booster technology, and particularly relates to a method for anti-surge control of a mixed gas booster. Background Technology

[0002] Mixed gas compressors consist of multiple gas components. Initially, users can only provide theoretical gas composition. Due to factors such as process matching and adjustments, it's difficult to ensure the gas composition matches the design specifications on-site. Surge is a characteristic of centrifugal compressors. When the flow rate through the impeller is less than the unit's minimum allowable flow rate, surge occurs, resulting in significant noise and increased unit vibration, potentially causing direct damage. The primary prevention method is to calculate the anti-surge line based on the owner-provided medium composition and inlet / outlet conditions. When the unit approaches surge, the anti-surge valve is opened to increase the flow rate into the impeller, ensuring safe operation.

[0003] When the actual gas composition differs significantly from the theoretical gas composition, the anti-surge curve will inevitably deviate. For example... Figure 3 As shown, the horizontal axis of the anti-surge line represents flow rate, and the vertical axis represents pressure ratio. Deviations will result in two possible outcomes: First, if the calculated anti-surge line is to the right of the actual anti-surge line (blue line in the diagram), and the unit cannot operate to the right of the anti-surge line due to its limitation, resulting in a lower flow rate, the unit will operate at a higher power than actually required, wasting energy. Second, if the calculated anti-surge line is to the left of the actual surge (green line in the diagram), the unit will begin to surge when the flow rate reaches the green design anti-surge line. Since the calculated anti-surge line has not been reached, the unit's anti-surge protection line will not function. This will cause increased unit vibration, potentially triggering high vibration protection and shutdown, or even more seriously, damage to the unit and a major safety accident.

[0004] If the unit needs to modify the anti-surge line, the design manufacturer needs to recalculate and modify it based on the existing gas composition. If the gas composition changes again later, it will need to be readjusted again, which is very cumbersome and not very practical. Summary of the Invention

[0005] The purpose of this invention is to provide a method for anti-surge control of a mixed gas booster compressor. By inputting new gas components from the field, a new anti-surge line is generated, which does not require the manufacturer to reprogram and modify the code, making it quick and convenient.

[0006] To achieve the above objectives, the technical solution of the present invention is: a method for anti-surge control of a mixed gas booster compressor, comprising:

[0007] Lateral correction steps: include the following steps:

[0008] The initial density change ratio is calculated based on the total molecular weight: the original gas components of the unit are A1, A2...An, n≥2, the molecular weights of each gas component are M1, M2...Mn, and the proportions of each gas component are X1, X2...Xn. The total molecular weight M under the original gas components of the unit is M1*X1+M2*X2...+Mn*Xn; the density of the original gas of the unit is ρ; the original surge line under the original gas components of the unit is a quadratic function: y=ax 2 +bx+c; After the composition change, the existing gas components of the unit are B1, B2...Bm, where m≥2, and the molecular weight of each gas component is M. ’ 1. M ’ 2……M ’ m, the proportions of each gas component are Y1, Y2...Ym, and the total molecular weight M of the existing gas composition of the unit. ’ For M ’ 1*Y1+M ’ 2*Y2……+M ’ m*Ym; The density of the existing gas in the unit is ρ ’ The initial change in density is M. ’ / M;

[0009] The final change ratio of density is calculated based on pressure: the final change ratio of density ρ ’ / ρ is (M ’ / M)*(P1 / 100), where P1 is the actual intake pressure in kPa;

[0010] The transverse correction number is obtained based on the type and quantity of the mixed gas: the final new transverse coordinate x after the surge line shift. ’ For ε*((M) ’ / M)*(P1 / 100))*x, where x is the abscissa of the original surge line, ε is the correction factor, which is related to the type and quantity of the mixed gas and is calculated based on the gas composition at the beginning of the design. The translated performance curve y1=ax ’2 +bx ’ +c=(ε*(M ’ / M)*(P1 / 100))) 2 *ax 2 +(ε*((M ’ / M)*(P1 / 100)))*bx+c;

[0011] Vertical correction steps:

[0012] Calculate the pressure ratio change curve: Select multiple change values ​​within the range of molecular weight variation, and calculate the corresponding pressure ratio change based on these values. The pressure ratio changes are p1, p2, ..., pj, where j ≥ 2. Fit a quadratic curve using the j pressure change values: y2 = a1x1 2 +b1x1+c1;

[0013] Calculate the longitudinal correction curve: y ’ =y1*y2.

[0014] Furthermore, the range of molecular weight variation is ±20%.

[0015] Furthermore, five change values ​​were selected within the range of molecular weight variation: -20%, -10%, 0%, 10%, and 20%.

[0016] Furthermore, a new surge line is obtained based on the lateral correction number and the longitudinal correction curve, and the corresponding anti-surge line is obtained based on the surge line.

[0017] The beneficial effects of this technical solution are as follows: users can perform calculations based on the original performance curves and the new gas composition to generate new anti-surge curves, making the anti-surge curves of the unit more accurate, enabling the unit to save energy and protect its safe operation. This eliminates the need for the design manufacturer to recalculate the performance curves and then submit them to the control system manufacturer to modify the anti-surge curves, making it convenient, quick, and highly practical. Attached Figure Description

[0018] Figure 1 This is a flowchart of the anti-surge control method for a mixed gas booster compressor according to the present invention;

[0019] Figure 2 A diagram showing the relationship between surge lines and surge lines;

[0020] Figure 3 The curve of the anti-surge line in the background technology is shown. Detailed Implementation

[0021] The following detailed description illustrates the specific implementation method:

[0022] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] like Figure 2As shown in the diagram, the green dots represent the unit's operating control points, the red line on the left is the calculated surge line, and the yellow line is the corresponding anti-surge line. The anti-surge line is calculated based on the red surge line according to certain rules to prevent the operating point from suddenly crossing the red line and causing surge. With the anti-surge return valve open, the closer the operating point is to the anti-surge line, the more energy-efficient the unit. When the unit's composition changes, the red surge line will change. However, since the surge line is calculated based on design conditions during the design phase, any changes require recalculation based on actual conditions and reprogramming by the control system personnel, which is very cumbersome. Therefore, in actual use, this line is fixed. This situation necessitates increasing the yellow anti-surge margin to avoid surge, but the specific amount to move is difficult to determine for different units. The required distance must be determined through continuous trial and error, which can easily lead to surge or high energy consumption. Each change in composition after user industrial adjustments requires adjustment, which is difficult to implement in practice.

[0024] This technical solution allows for automatic lateral and longitudinal correction of the surge curve after a new gas composition is input. Lateral correction primarily addresses the density change caused by the change in gas molecular weight due to compositional variations. Since the surge curve of a centrifugal compressor is mainly affected by the inlet volumetric flow rate, the density change can be calculated from the molecular weight variation, thus enabling lateral correction. Longitudinal correction is necessary because changes in gas composition affect the compressor's compression performance; therefore, longitudinal performance correction is also required to obtain a new performance curve.

[0025] The basic implementation examples are as follows: Figure 1 The following steps are shown: Anti-surge control method for a mixed gas booster compressor:

[0026] S1: Lateral correction steps, including the following steps:

[0027] S11: Preliminary density change ratio calculated based on total molecular weight: The original gas components of the unit are A1, A2...An, n≥2, the molecular weights of each gas component are M1, M2...Mn, and the proportions of each gas component are X1, X2...Xn. The total molecular weight M under the original gas components of the unit is M1*X1+M2*X2...+Mn*Xn; the density of the original gas of the unit is ρ; the original surge line under the original gas components of the unit is a quadratic function: y=ax 2 +bx+c; After the composition change, the existing gas components of the unit are B1, B2...Bm, where m≥2, and the molecular weight of each gas component is M. ’ 1. M ’ 2……M ’ m, the proportions of each gas component are Y1, Y2...Ym, and the total molecular weight M of the existing gas composition of the unit. ’ For M’ 1*Y1+M ’ 2*Y2……+M ’ m*Ym; The density of the existing gas in the unit is ρ ’ The initial change in density is M. ’ / M.

[0028] S12: Calculate the final density change ratio based on pressure: Since density is also highly correlated with pressure, a correction should be made for pressure. The final density change ratio ρ ’ / ρ is (M ’ / M)*(P1 / 100), where P1 is the actual intake pressure, and the unit of P1 is kPa.

[0029] S13: Obtain the transverse correction number based on the type and quantity of the mixed gas: Due to the different original gas compositions, the actual density change does not perfectly match the above formula, requiring the introduction of a correction coefficient ε. The final result is the new transverse coordinate x after the surge line shift. ’ For ε*((M) ’ / M)*(P1 / 100))*x, where x is the abscissa of the original surge line, ε is the correction factor, which is related to the type and quantity of the mixed gas and is calculated based on the gas composition at the beginning of the design; the translated performance curve y1=ax ’2 +bx ’ +c=(ε*(M ’ / M)*(P1 / 100))) 2 *ax 2 +(ε*((M ’ / M)*(P1 / 100)))*bx+c.

[0030] S ’ 1: The longitudinal correction process includes the following steps:

[0031] S ’ 11: Calculate the pressure ratio change curve: Based on the normal conditions of the unit, the molecular weight change is generally within ±20%. Select -20%, -10%, 0%, 10%, and 20%, and calculate the corresponding pressure ratio change based on the change value. The pressure ratio changes are p1, p2, ..., pj, where j ≥ 2. Fit a quadratic curve to the j pressure change values: y2 = a1x1 2 +b1x1+c1.

[0032] S ’ 12: Calculate the longitudinal correction curve: y ’ =y1*y2.

[0033] S2: Obtain a new surge line based on the lateral correction number and the longitudinal correction curve, and obtain the corresponding anti-surge line based on the surge line.

[0034] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0035] The above descriptions are merely embodiments of the present invention. Commonly known structures and characteristics are not described in detail here. Those skilled in the art are aware of all common technical knowledge in the field prior to the application date or priority date, are aware of all existing technologies in that field, and have the ability to apply conventional experimental methods prior to that date. Those skilled in the art can, under the guidance of this application, improve and implement this solution in combination with their own capabilities. Some typical known structures or methods should not be obstacles for those skilled in the art to implement this application. It should be noted that those skilled in the art can make several modifications and improvements without departing from the structure of the present invention. These should also be considered within the scope of protection of the present invention, and will not affect the effectiveness of the implementation of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A surge control method for a mixed gas booster compressor, characterized in that: include Lateral correction steps: include the following steps: The initial density change ratio is calculated based on the total molecular weight: the original gas components of the unit are A1, A2...An, n≥2, the molecular weights of each gas component are M1, M2...Mn, and the proportions of each gas component are X1, X2...Xn. The total molecular weight M under the original gas components of the unit is M1*X1+M2*X2...+Mn*Xn; the density of the original gas of the unit is ρ; the original surge line under the original gas components of the unit is a quadratic function: y=ax 2 +bx+c; After the composition change, the existing gas components of the unit are B1, B2...Bm, where m≥2, and the molecular weight of each gas component is M. ’ 1. M ’ 2……M ’ m, the proportions of each gas component are Y1, Y2...Ym, and the total molecular weight M of the existing gas composition of the unit. ’ For M ’ 1*Y1+M ’ 2*Y2……+M ’ m*Ym; The density of the existing gas in the unit is ρ ’ The initial change in density is M. ’ / M; The final change ratio of density is calculated based on pressure: the final change ratio of density ρ ’ / ρ is (M ’ / M)*(P1 / 100), where P1 is the actual intake pressure in kPa; The transverse correction number is obtained based on the type and quantity of the mixed gas: the final new transverse coordinate x after the surge line shift is obtained. ’ For ε*((M) ’ / M)*(P1 / 100))*x, where x is the abscissa of the original surge line, ε is the correction factor, which is related to the type and quantity of the mixed gas and is calculated based on the gas composition at the beginning of the design. The translated performance curve y1=ax ’2 +bx ’ +c=(ε*(M ’ / M)*(P1 / 100))) 2 *ax 2 +(ε*((M ’ / M)*(P1 / 100)))*bx+c; Vertical correction steps: Calculate the pressure ratio change curve: Select multiple change values ​​within the range of molecular weight variation, and calculate the corresponding pressure ratio change based on these values. The pressure ratio changes are p1, p2, ..., pj, where j ≥ 2. Fit a quadratic curve using the j pressure change values: y2 = a1x1 2 +b1x1+c1; Calculate the longitudinal correction curve: y ’ =y1*y2.

2. The anti-surge control method for a mixed gas booster compressor according to claim 1, characterized in that: The range of molecular weight variation is ±20%.

3. The anti-surge control method for a mixed gas booster compressor according to claim 2, characterized in that: Five values ​​were selected within the range of molecular weight variation: -20%, -10%, 0%, 10%, and 20%.

4. The anti-surge control method for a mixed gas booster compressor according to claim 1, characterized in that: A new surge line is obtained based on the lateral correction number and the longitudinal correction curve, and the corresponding anti-surge line is obtained based on the surge line.

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