A general correction method for turbine aerodynamic performance calculation

Abstract

The purpose of the present invention is to provide a universal correction method for calculating the aerodynamic performance of a turbine, comprising the following steps: determining the key factors that affect the aerodynamic performance of the turbine when the physical properties of the working fluid in the turbine change; using a numerical calculation method to obtain the evolution law of the aerodynamic performance of the turbine under different speeds and constant pressure specific heat capacity; analyzing and fitting to obtain a universal correction formula for calculating the aerodynamic performance of the turbine. The present invention uses a similarity modeling method for theoretical analysis to determine that the key factor affecting the aerodynamic performance of the turbine is the constant pressure specific heat capacity of the working fluid, and the correction method is universal; the correction formula has a simple structure, few acquisition factors, is easy to implement, and is highly practical; the formula has high calculation accuracy and can be well applied to the calculation of aerodynamic performance of turbines of different stages.

Description

Technical Field

[0001] The invention relates to a gas turbine simulation method, in particular to a turbine aerodynamic performance calculation method. Background Art

[0002] In order to further improve the comprehensive utilization efficiency of energy and realize the cascade utilization of energy, gas turbines burning medium and low calorific value fuel gas have attracted more and more attention. Medium and low calorific value fuel gas is CH 4 , H 2 ,CO,CO 2 , H 2 O and various hydrocarbons and other gases, the composition and calorific value of the fuel gas produced by different processes will also be very different. Different utilization technologies have also been developed according to the different calorific values ​​of the fuel. Medium and low calorific value fuel gas contains a large amount of inert components, namely nitrogen and carbon dioxide, which dilutes combustible components such as hydrogen, methane and carbon monoxide. Therefore, to achieve the same turbine inlet temperature, the medium and low calorific value fuel gas has a larger fuel volume in the gas turbine combustion chamber than natural gas, which changes the component matching of the gas turbine and needs to take corresponding measures to adapt to medium and low calorific value fuels. In order to adapt to these fuels, various components of the gas turbine and some components of the bottom cycle may need to be redesigned. Due to the change in fuel composition, especially when the fuel is hydrogen-rich, it may have a greater impact on the temperature of the turbine blades, especially in the high-temperature part. The temperature of the turbine blades may be higher than that when burning natural gas. Due to different fuel sources, large differences in composition and calorific value, and various flow adjustment measures for different models of gas turbines, the research on gas turbines using natural gas and medium and low calorific value gas as fuel is mostly limited to specific models and specific fuels, and the evolution mechanism of the performance of the gas turbine itself lacks in-depth research. Summary of the invention

[0003] The object of the present invention is to provide a general correction method for calculating the aerodynamic performance of turbines which can be used for calculating the aerodynamic performance of turbines at different stages, and is particularly suitable for correcting and predicting the turbine performance when the fuel composition changes.

[0004] The object of the present invention is achieved in that:

[0005] The present invention provides a general correction method for turbine aerodynamic performance calculation, which is characterized by:

[0006] (1) Determine the key factors that affect the aerodynamic performance of the turbine when the physical properties of the working fluid in the turbine change;

[0007] (2) Use numerical calculation methods to obtain the evolution law of turbine aerodynamic performance at different speeds and constant pressure specific heat capacity;

[0008] (3) Analyze and fit the general correction formula for calculating the turbine aerodynamic performance.

[0009] The present invention may also include:

[0010] 1. In step (1), the criteria affecting the similarity of turbine aerodynamic performance obtained by determining the physical quantity method are Reynolds number Re, Euler number Eu, and Weber number We. The criteria affecting the similarity of turbine aerodynamic performance obtained by the dimensional analysis method are Mach number Ma and Reynolds number Re. The criteria obtained by the differential equation method are Stanton number Sr, Reynolds number Re, Euler number Eu, Prandtl number Pr, Eckert number Ec, and Brinkman number Br. The Re number and the Eu number are general conclusions obtained by the three methods. It is ensured that the Re number and the Eu number are equal to each other and that the basic turbine operating point corresponds. When the constant pressure specific heat capacity in the working fluid physical properties changes, the two dimensionless numbers change accordingly, thereby causing the coefficients in the energy conservation equation in the control equation to change, so that the final solution is different from the original equation. That is, it is determined that when the working fluid physical properties in the turbine change, the constant pressure specific heat capacity of the working fluid is the key factor affecting the turbine aerodynamic performance.

[0011] 2. In step (2), CFD software is used to change the turbine speed and outlet conditions respectively, and a numerical calculation method is used to obtain a complete aerodynamic performance curve of the turbine at different speeds. The aerodynamic performance curve is then converted into an aerodynamic performance curve at a reduced speed, and a polynomial fitting is performed on the data points to obtain a multi-function curve passing through the data points. On this basis, the constant-pressure specific heat capacity of the working fluid is changed, and the complete aerodynamic performance of the turbine is calculated under different constant-pressure specific heat capacity values ​​to obtain the evolution law of the turbine aerodynamic performance when the constant-pressure specific heat capacity changes at the same speed.

[0012] 3. In step (3), by comparing the evolution law of the turbine aerodynamic performance at different speeds when the working fluid constant pressure specific heat capacity changes, the turbine aerodynamic performance correction formula at different constant pressure specific heat capacities is solved; first, each group of data is fitted with a polynomial, and then the fitting coefficients are fitted again using an exponential equation to solve the correction formula; finally, the correction formula with the minimum error of the turbine aerodynamic performance under the action of different fuel components is obtained:

[0013]

[0014] Where, π is the turbine expansion ratio; C p is the specific heat capacity at constant pressure; η is the turbine efficiency; G is the equivalent flow rate; subscript 0 means the working fluid is air and its specific heat capacity at constant pressure is 1006 J / kg·K.

[0015] The advantages of the present invention are:

[0016] 1. Theoretical analysis was conducted using a similar modeling method to determine that the key factor affecting the turbine's aerodynamic performance is the constant-pressure specific heat capacity of the working fluid, and the correction method is universal;

[0017] 2. The correction formula has a simple structure, few collection factors, is easy to implement, and has strong practicality;

[0018] 3. This formula has high calculation accuracy and is well suited for the calculation of aerodynamic performance of turbines of different stages. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is a flow chart of the present invention;

[0020] Figure 2 This is a comparison chart of the numerical calculation results of turbine reduced flow-pressure ratio and the calculation results of the modified formula;

[0021] Figure 3 This is a comparison chart of the numerical calculation results of turbine reduced flow-efficiency and the calculation results of the corrected formula. DETAILED DESCRIPTION

[0022] The present invention is described in more detail below with reference to the accompanying drawings:

[0023] Combination Figure 1-3 ,according to Figure 1 The flow chart takes a 1.5-stage turbine as a research object and calculates a general correction formula for turbine aerodynamic performance.

[0024] (1) Determine the key factors that affect the aerodynamic performance of the turbine when the physical properties of the working fluid in the turbine change.

[0025] By determining the physical quantity method, it is concluded that the main criteria affecting the similarity of turbine aerodynamic performance are Reynolds number Re, Euler number Eu, and Weber number We. By dimensional analysis, it is concluded that the main criteria affecting the similarity of turbine aerodynamic performance are Mach number Ma and Reynolds number Re. The main criteria obtained by the differential equation method are Stanton number Sr, Reynolds number Re, Euler number Eu, Prandtl number Pr, Eckert number Ec, and Brinkman number Br. Among them, Re number and Eu number (Mach number Ma and Euler number Eu can be converted to each other) are the general conclusions obtained by the three methods, so it is necessary to ensure that Re number and Eu number are equal to ensure the basic turbine operating point correspondence. Observe the definition of the two dimensionless numbers, both of which are affected by the constant pressure specific heat. When the constant pressure specific heat capacity in the working fluid physical properties changes, the two dimensionless numbers will change accordingly, which leads to the change of the coefficients in the energy conservation equation in the control equation, so that the final solution is different from the original equation. That is, when the physical properties of the working fluid in the turbine change, the constant-pressure specific heat capacity of the working fluid is the key factor affecting the aerodynamic performance of the turbine.

[0026] (2) Use CFD software to calculate the turbine aerodynamic performance under different conditions.

[0027] Using CFD software, the turbine speed and outlet conditions are changed respectively, and the complete aerodynamic performance curve of the turbine at different speeds is obtained using numerical calculation methods. Then, the aerodynamic performance curve is converted into the aerodynamic performance curve at the reduced speed, and the data points are fitted with polynomials to obtain a multi-function curve passing through the data points. On this basis, the constant pressure specific heat capacity of the working fluid is changed, and the complete aerodynamic performance of the turbine is calculated under different constant pressure specific heat capacity values. The evolution law of the turbine aerodynamic performance when the constant pressure specific heat capacity changes at the same speed is obtained.

[0028] (3) Fit and verify the general correction formula for turbine aerodynamic performance when the fuel composition changes.

[0029] By comparing the evolution of turbine aerodynamic performance at different speeds when the working fluid constant pressure specific heat capacity changes, the correction formula for turbine aerodynamic performance at different constant pressure specific heat capacities is solved. First, polynomial fitting is performed on each set of data, and then the fitting coefficients are fitted again using an exponential equation to solve the correction formula. Finally, the correction formula for the minimum aerodynamic performance error of a 1.5-stage turbine under different fuel components is obtained:

[0030]

[0031] In the formula, π is the turbine expansion ratio; C p ——Specific heat capacity at constant pressure, J / (kg·K); η——Turbine efficiency; G——Equivalent flow rate, kg / s; Subscript "0"——The working fluid is air and its specific heat capacity at constant pressure is 1006J / (kg·K).

[0032] For a 1.5-stage turbine, its aerodynamic performance with air as the working fluid under the design working conditions can be converted into aerodynamic performance under different constant pressure specific heat capacity working fluid conditions through the correction formula. The correction results and numerical calculation results under each working condition meet the minimum variance requirement. For a 2.5-stage turbine, the same numerical calculation method is used to obtain the numerical calculation results of its aerodynamic performance, and the above correction formula is used to calculate its aerodynamic performance. Figure 2-Figure 3 As shown in the figure, the solid line is the aerodynamic performance curve obtained by changing the constant-pressure specific heat capacity value of the working fluid in the actual numerical calculation, and the dotted line is the performance curve when the original aerodynamic performance with air as the working fluid is corrected by the correction formula to obtain the corresponding constant-pressure specific heat capacity value. By comparing the two, it is found that for a 2.5-stage turbine, the correction formula can also be well adapted to complete the correction of the turbine aerodynamic performance when the constant-pressure specific heat capacity of the working fluid changes.

Claims

1. A general correction method for turbine aerodynamic performance calculation, Its characteristics are: (1) Determine the key factors that affect the aerodynamic performance of the turbine when the physical properties of the working fluid in the turbine change; (2) Use numerical calculation methods to obtain the evolution law of turbine aerodynamic performance at different speeds and constant pressure specific heat capacity; (3) Analyze and fit the general correction formula for turbine aerodynamic performance calculation; By comparing the evolution law of turbine aerodynamic performance at different speeds when the working fluid specific heat capacity at constant pressure changes, the correction formula for turbine aerodynamic performance at different constant pressure specific heat capacities is solved; first, polynomial fitting is performed on each group of data, and then the fitting coefficients are fitted again using an exponential equation to solve the correction formula; finally, the correction formula with the minimum error in the aerodynamic performance of the turbine under the action of different fuel components is obtained: Where, π is the turbine expansion ratio; C p is the specific heat capacity at constant pressure; η is the turbine efficiency; G is the equivalent flow rate; subscript 0 means the working fluid is air and its specific heat capacity at constant pressure is 1006 J / kg·K.

2. A general correction method for turbine aerodynamic performance calculation according to claim 1, Its characteristics are: In step (1), the criteria affecting the similarity of turbine aerodynamic performance are obtained by determining the physical quantity method, which are Reynolds number Re, Euler number Eu, and Weber number We. The criteria affecting the similarity of turbine aerodynamic performance are obtained by dimensional analysis method, which are Mach number Ma and Reynolds number Re. The criteria obtained by differential equation method are Stanton number Sr, Reynolds number Re, Euler number Eu, Prandtl number Pr, Eckert number Ec, and Brinkmann number Br. Re number and Eu number are general conclusions obtained by the three methods. It is ensured that Re number and Eu number are equal and that the turbine operating point corresponds. When the constant pressure specific heat capacity in the working fluid physical properties changes, the two dimensionless numbers change accordingly, thereby causing the coefficients in the energy conservation equation in the control equation to change, so that the final solution is different from the original equation, that is, it is determined that when the working fluid physical properties in the turbine change, the constant pressure specific heat capacity of the working fluid is the key factor affecting the aerodynamic performance of the turbine.

3. A general correction method for turbine aerodynamic performance calculation according to claim 1, Its characteristics are: In step (2), CFD software is used to change the turbine speed and outlet conditions respectively, and a numerical calculation method is used to obtain the complete aerodynamic performance curve of the turbine at different speeds. The aerodynamic performance curve is then converted into an aerodynamic performance curve at a reduced speed, and a polynomial fitting is performed on the data points to obtain a multi-function curve passing through the data points. On this basis, the constant-pressure specific heat capacity of the working fluid is changed, and the complete aerodynamic performance of the turbine is calculated under different constant-pressure specific heat capacity values ​​to obtain the evolution law of the turbine aerodynamic performance when the constant-pressure specific heat capacity changes at the same speed.

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