Method suitable for determining specific heat ratio of gas at outlet of combustion chamber of gas turbine

Abstract

The invention discloses a method suitable for determining the specific heat ratio of gas at an outlet of a combustion chamber of a gas turbine, and relates to the technical field of the specific heat ratio of gas, comprising the following steps: establishing a heat balance calculation model of the gas turbine; analyzing combustion chamber inlet and outlet boundary conditions under typical loads; analyzing the equivalence ratio of fuel to air combustion reaction under typical load; establishing a combustion chamber simplified numerical model; the specific heat ratio of combustion chamber outlet gas under the typical load is obtained through calculation; fitting a gas turbine combustion chamber outlet gas specific heat ratio change curve; and calculating to obtain the gas turbine combustion chamber outlet gas specific heat ratio. The simplified numerical model of the combustion chamber of the gas turbine established by the method can be inconsistent with a real combustion chamber model in structure and size, so that the modeling difficulty and the calculation workload of the combustion chamber can be greatly simplified; and only the equivalence ratio of the combustion chemical reaction of the fuel and the air in the simplified combustion chamber is consistent with the equivalence ratio of the combustion chemical reaction of the fuel and the air in the real combustion chamber.

Description

Technical Field

[0001] The invention relates to the technical field of gas specific heat ratio, and in particular to a method for determining the gas specific heat ratio at a gas turbine combustion chamber outlet. Background Art

[0002] The specific heat ratio, also known as the adiabatic index or specific heat ratio, refers to the ratio of the specific heat capacity of a gas under constant pressure (Cp) to the specific heat capacity under constant volume (Cv). It plays an important role in the practical application of thermodynamic theory and engineering technology. For example, in a gas turbine, the gas is first compressed by the compressor, then burned in the combustion chamber to form high-temperature and high-pressure combustion gas, and finally expanded in the turbine to do work. Compression and expansion will cause temperature changes. The specific heat ratio is an important parameter for analyzing the relationship between pressure and temperature changes during gas compression and expansion. In the process of gas turbine design and optimization, the specific heat ratio is also needed to analyze and calculate the working characteristics of the gas turbine, and then improve and optimize the gas turbine compressor, combustion chamber, turbine and other components.

[0003] The specific heat ratio of gas is closely related to the internal energy, enthalpy, constant volume heat capacity, constant pressure heat capacity and molecular freedom of gas. The high temperature and high pressure gas formed after combustion in the combustion chamber of gas turbine contains multiple gases such as carbon dioxide, nitrogen, oxygen, etc., and the volume proportion, gas temperature and gas pressure of each gas are different under different loads. The specific heat ratio of gas is directly related to the gas composition, gas temperature and gas pressure in the gas. The traditional experimental method of using gas adiabatic expansion or adiabatic compression to determine the specific heat ratio is not suitable for measuring the specific heat ratio of gas turbine gas. In the actual gas turbine cycle thermal efficiency analysis process, the average value method is still used. That is, it is generally believed that the specific heat ratio of gas in the full load condition of gas turbine is constant, about 1.33, which is different from the actual situation. It is necessary to propose a method suitable for the specific heat ratio of gas at the outlet of gas turbine combustion chamber. Summary of the invention

[0004] In view of the above-mentioned problems, the present invention is proposed.

[0005] Therefore, the technical problem solved by the present invention is: how to provide a method suitable for determining the specific heat ratio of gas at the outlet of a gas turbine combustion chamber.

[0006] To solve the above technical problems, the present invention provides the following technical solutions: a method suitable for determining the specific heat ratio of gas at the outlet of a gas turbine combustion chamber, comprising: establishing a gas turbine heat balance calculation model; analyzing the inlet and outlet boundary conditions of the combustion chamber under typical loads; analyzing the equivalence ratio of the fuel and air combustion reactions under typical loads; establishing a simplified numerical model of the combustion chamber; calculating and obtaining the specific heat ratio of the gas at the outlet of the combustion chamber under typical loads; fitting a gas turbine combustion chamber outlet gas specific heat ratio change curve; and calculating and obtaining the specific heat ratio of the gas at the outlet of the gas turbine combustion chamber.

[0007] As a preferred scheme of the method for determining the specific heat ratio of gas at the outlet of a gas turbine combustion chamber described in the present invention, wherein: the gas turbine heat balance calculation model is established for the gas turbine model used in the gas power plant using the Thermoflow power plant heat balance analysis professional software; the Thermoflow model sets the boundary parameters of the calculation model according to the historical operation data of the gas turbine, and verifies the accuracy of the calculation model using the historical operation data of the gas turbine; the verified gas turbine heat balance calculation model is used to calculate the combustion chamber inlet and outlet boundary parameters of the gas turbine from startup to full load operation.

[0008] As a preferred embodiment of the method for determining the specific heat ratio of gas at the outlet of a gas turbine combustion chamber as described in the present invention, the working load of the gas turbine generator set is in the load range of 50% to 100%, and the mass flow rate, temperature and outlet pressure parameters of the gas turbine combustion chamber inlet at typical loads of 50%, 60%, 70%, 80%, 90% and 100% are calculated.

[0009] As a preferred embodiment of the method for determining the specific heat ratio of gas at the outlet of a gas turbine combustion chamber according to the present invention, the equivalent ratio of the fuel and air combustion chemical reaction in the gas turbine combustion chamber under a typical load is calculated based on the calculated mass flow rates of air and fuel at the inlet of the combustion chamber:

[0010]

[0011] Among them, m f is the fuel mass flow rate at the inlet of the gas turbine combustion chamber; m air M is the air mass flow rate at the inlet of the gas turbine combustion chamber; air is the molecular weight of air, M ch4 is the molecular weight of methane.

[0012] As a preferred scheme of the method for determining the specific heat ratio of gas at the outlet of a gas turbine combustion chamber described in the present invention, wherein: a simplified numerical model of the combustion chamber is established, and the simplified numerical model of the combustion chamber is verified by the gas turbine heat balance calculation model; the simplified numerical model of the combustion chamber includes a fuel nozzle and a flame tube, the fuel nozzle has air and fuel inlets, and the flame tube can be a cylindrical cavity; the simplified flame tube flow cross-sectional area is divided by the flow area of ​​the real flame tube to calculate the reduction factor α of the simplified combustion chamber; the inlet boundary of the simplified numerical model of the combustion chamber is set as the air mass inlet boundary and the fuel mass inlet boundary, and the outlet boundary is set as the pressure outlet boundary.

[0013] As a preferred embodiment of the method for determining the specific heat ratio of gas at the outlet of a gas turbine combustion chamber described in the present invention, the method comprises the following steps: calculating the composition and specific heat ratio of the gas at the outlet of the combustion chamber under a typical load, comprising the following steps: using a simplified numerical model of the combustion chamber established; multiplying the mass flow rates of air and fuel at the inlet of the gas turbine combustion chamber under different loads by a scaling factor as the inlet boundary conditions of the model; calculating the equivalence ratio and comparing and verifying it with the equivalence ratio in the actual combustion chamber; setting the combustion chamber outlet pressure value under a typical load obtained by analysis as the pressure outlet boundary condition of the model; and using the simplified model to calculate the composition and specific heat ratio of the gas at the outlet of the combustion chamber under different loads when the above boundary conditions are met.

[0014] As a preferred scheme of the method for determining the specific heat ratio of gas at the outlet of a gas turbine combustion chamber described in the present invention, wherein: according to the simplified numerical model of the combustion chamber after setting the boundary conditions, the temperature, pressure and specific heat ratio and other parameters of the gas at the outlet of the combustion chamber under typical loads of 50%, 60%, 70%, 80%, 90% and 100% are calculated respectively; according to the specific heat ratio data of the gas at the outlet of the combustion chamber under the typical load obtained by calculation, with the load as the independent variable and the specific heat ratio as the dependent variable, curve fitting is performed according to the change trend of the specific heat ratio of the gas; according to the specific heat ratio calculation formula obtained by curve fitting, the specific heat ratio of the gas at the outlet of the gas turbine combustion chamber at different loads is calculated.

[0015] To further solve the above technical problems, the present invention provides the following technical solutions: A system suitable for determining the specific heat ratio of gas at the outlet of a gas turbine combustion chamber, comprising: a data acquisition module, used to collect operating parameters of the gas turbine, including atmospheric environment parameters, compressor outlet parameters, fuel and air flow rate and other data; a model building module, used to establish a gas turbine heat balance calculation model and a simplified numerical model of the combustion chamber, and verify the model; a boundary condition analysis module, used to analyze the inlet and outlet boundary conditions of the combustion chamber under typical loads, and the equivalence ratio of the fuel and air combustion reaction; a specific heat ratio calculation module, used to substitute the boundary conditions and equivalence ratio obtained by analysis into the simplified combustion chamber model, and calculate the components and specific heat ratio of the combustion chamber outlet gas under typical loads; a fitting module, used to collect the combustion chamber outlet gas specific heat ratio data calculated under different loads, and fit to obtain the change curve of the combustion chamber outlet gas specific heat ratio under different loads of the gas turbine.

[0016] A computer device comprises a memory and a processor, wherein the memory stores a computer program, and is characterized in that when the processor executes the computer program, the steps of the method for determining the specific heat ratio of gas at the outlet of a gas turbine combustion chamber are implemented as described above.

[0017] A computer-readable storage medium having a computer program stored thereon, characterized in that when the computer program is executed by a processor, the steps of the method for determining the specific heat ratio of gas at the outlet of a gas turbine combustion chamber as described above are implemented.

[0018] Beneficial effects of the present invention: The present invention can obtain the specific heat ratio of the gas at the outlet of the combustion chamber under the typical load of the gas turbine without the need for experiments, only by establishing a gas turbine heat balance calculation model and a simplified numerical model of the gas turbine combustion chamber. The simplified numerical model of the gas turbine combustion chamber established by the present invention may be inconsistent with the structure and size of the real combustion chamber model, which can greatly simplify the modeling difficulty and calculation workload of the combustion chamber. It is only necessary to ensure that the equivalent ratio of the fuel and air combustion chemical reaction in the simplified combustion chamber is consistent with the equivalent ratio of the fuel and air combustion chemical reaction in the real combustion chamber. The present invention can finally obtain a calculation formula for the specific heat ratio of the gas applicable to the typical load range of the gas turbine through segmented curve fitting, thereby improving the usability of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0020] Figure 1 It is the overall flow chart of the present invention.

[0021] Figure 2 This is a diagram showing the heat balance calculation results of the thermoflow gas turbine under 100% typical load of the present invention.

[0022] Figure 3 It is the actual structure diagram of the combustion chamber of the present invention.

[0023] Figure 4 This is a simplified numerical model diagram of the afterburner of the present invention.

[0024] Figure 5 This is a simplified temperature field distribution diagram of the combustion chamber center section of the present invention.

[0025] Figure 6 This is a diagram of the specific heat ratio of the combustion gas in the central cross section of the combustion chamber under 100% load of the present invention.

[0026] Figure 7 It is a fitting curve diagram of the specific heat ratio of the gas at the outlet of the gas turbine combustion chamber of the present invention. DETAILED DESCRIPTION

[0027] In order to make the above-mentioned purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the drawings of the specification. Obviously, the described embodiments are part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary persons in the art without creative work should fall within the scope of protection of the present invention.

[0028] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0029] Example 1

[0030] Reference Figure 1 to Figure 7 , as one embodiment of the present invention, provides a method for determining the specific heat ratio of gas at the outlet of a gas turbine combustion chamber, comprising:

[0031] 1. Establish a thermal balance calculation model for gas turbines;

[0032] 2. Analyze the combustion chamber inlet and outlet boundary conditions under typical loads;

[0033] 3. Analyze the equivalence ratio of fuel and air combustion reaction under typical load;

[0034] 4. Establish a simplified numerical model of the combustion chamber;

[0035] 5. Calculate the specific heat ratio of the combustion chamber outlet gas under typical load;

[0036] 6. Fitting the specific heat ratio curve of the gas at the outlet of the gas turbine combustion chamber;

[0037] 7. Calculate the specific heat ratio of the gas at the outlet of the gas turbine combustor.

[0038] Specifically, due to the high temperature of the gas at the outlet of the gas turbine combustion chamber, there is generally no measuring point to directly measure the pressure and temperature of the gas at the outlet of the combustion chamber. In order to obtain the boundary pressure and temperature of the inlet and outlet of the combustion chamber, the Thermoflow power plant heat balance analysis professional software is used to establish a gas turbine heat balance calculation model for the gas turbine model used in the gas power plant. The boundary parameters of the calculation model are set according to the historical operation data of the gas turbine, and the accuracy of the calculation model is verified using the historical operation data of the gas turbine. The verified gas turbine heat balance calculation model is used to calculate the inlet and outlet boundary parameters of the gas turbine from startup to full load operation. Considering that the gas turbine has high pollutant emissions when it is running at low load, the gas turbine generator set generally operates in the load range of 50% to 100%. Therefore, the above method is mainly used to calculate the boundary parameters such as the mass flow rate of air and fuel in the inlet of the gas turbine combustion chamber, the temperature and the outlet pressure of the combustion chamber under typical loads such as 50%, 60%, 70%, 80%, 90% and 100%. The typical load can be selected and determined according to the load point that the gas turbine power plant often operates.

[0039] Based on the air and fuel mass flow rates at the combustion chamber inlet calculated in step 1, the equivalent ratio of the fuel and air combustion chemical reaction in the gas turbine combustion chamber at typical loads such as 50%, 60%, 70%, 80%, 90% and 100% is calculated using formula (1):

[0040]

[0041] Where m f is the fuel mass flow rate at the inlet of the gas turbine combustion chamber; m air M is the air mass flow rate at the inlet of the gas turbine combustion chamber; air is the molecular weight of air, M ch4 is the molecular weight of methane.

[0042] The simplified numerical model of the combustion chamber is established using ANSYS commercial software, and the simplified numerical model of the combustion chamber is verified using the gas turbine heat balance calculation model established in step 1. The simplified numerical model of the combustion chamber does not need to be consistent with the shape and structure of the actual gas turbine combustion chamber. It only needs to include the fuel nozzle and the flame tube. The fuel nozzle has air and fuel inlets, and the flame tube can be a cylindrical cavity. The simplified flame tube flow cross-sectional area is divided by the flow area of ​​the actual flame tube to calculate the reduction factor α of the simplified combustion chamber. The inlet boundary of the simplified numerical model of the combustion chamber is set as the air mass inlet boundary and the fuel mass inlet boundary, and the outlet boundary is set as the pressure outlet boundary.

[0043] Using the simplified numerical model of the combustion chamber established in step 3, the mass flow rates of air and fuel at the inlet of the gas turbine combustion chamber under typical loads of 50%, 60%, 70%, 80%, 90%, and 100% obtained in step 1 are multiplied by the scale factor α of the simplified combustion chamber, and are set as the air and fuel inlet boundary parameters in the numerical model. At the same time, the equivalent ratio of the fuel and air combustion chemical reaction in the simplified combustion chamber is calculated using formula (1), and compared with the equivalent ratio of the fuel and air combustion chemical reaction in the gas turbine combustion chamber under typical load calculated in step 2 to ensure that the equivalent ratio in the simplified combustion chamber is consistent with the equivalent ratio in the real combustion chamber. The pressure outlet boundary parameter of the numerical model is set according to the combustion chamber outlet pressure value under typical load obtained in step 1.

[0044] Using the simplified numerical model of the combustion chamber established in step 3, the mass flow rates of air and fuel at the inlet of the gas turbine combustion chamber under typical loads of 50%, 60%, 70%, 80%, 90%, and 100% obtained in step 1 are multiplied by the scale factor α of the simplified combustion chamber, and are set as the air and fuel inlet boundary parameters in the numerical model. At the same time, the equivalent ratio of the fuel and air combustion chemical reaction in the simplified combustion chamber is calculated using formula (1), and compared with the equivalent ratio of the fuel and air combustion chemical reaction in the gas turbine combustion chamber under typical load calculated in step 2 to ensure that the equivalent ratio in the simplified combustion chamber is consistent with the equivalent ratio in the real combustion chamber. The pressure outlet boundary parameter of the numerical model is set according to the combustion chamber outlet pressure value under typical load obtained in step 1.

[0045] The simplified numerical model of the combustion chamber after setting the boundary conditions in step 4 is used to calculate parameters such as the temperature, pressure and specific heat ratio of the combustion chamber outlet gas under typical loads such as 50%, 60%, 70%, 80%, 90% and 100%.

[0046] Using the specific heat ratio data of the combustion chamber outlet gas under typical load calculated in step 5, with load as the independent variable and specific heat ratio as the dependent variable, curve fitting is performed according to the change trend of the gas specific heat ratio.

[0047] According to the specific heat ratio calculation formula obtained by curve fitting in step 6, the specific heat ratio of the gas at the outlet of the gas turbine combustion chamber at different loads is calculated.

[0048] In summary, the present invention can obtain the specific heat ratio of the gas at the outlet of the combustion chamber under the typical load of the gas turbine without the need for experiments, only by establishing a gas turbine heat balance calculation model and a simplified numerical model of the gas turbine combustion chamber. The simplified numerical model of the gas turbine combustion chamber established by the present invention can be inconsistent with the structure and size of the real combustion chamber model, which can greatly simplify the modeling difficulty and calculation workload of the combustion chamber. It is only necessary to ensure that the equivalent ratio of the fuel and air combustion chemical reaction in the simplified combustion chamber is consistent with the equivalent ratio of the fuel and air combustion chemical reaction in the real combustion chamber. The present invention can finally obtain a calculation formula for the specific heat ratio of the gas applicable to the typical load range of the gas turbine through segmented curve fitting, thereby improving the usability of the present invention.

[0049] Example 2

[0050] Reference Figure 1 to Figure 7 , is an embodiment of the present invention, and provides a system suitable for determining the specific heat ratio of gas at the outlet of a gas turbine combustion chamber, including: a data acquisition module, used to collect operating parameters of the gas turbine, including atmospheric environment parameters, compressor outlet parameters, fuel and air flow rate and other data; a model building module, used to establish a Thermoflow gas turbine heat balance calculation model and a simplified numerical model of the combustion chamber, and verify the model; a boundary condition analysis module, used to analyze the inlet and outlet boundary conditions of the combustion chamber under typical loads, and the equivalence ratio of the fuel and air combustion reaction; a specific heat ratio calculation module, used to substitute the boundary conditions and equivalence ratio obtained by analysis into the simplified combustion chamber model, and calculate the components and specific heat ratio of the combustion chamber outlet gas under typical loads; a fitting module, used to collect the specific heat ratio data of the combustion chamber outlet gas calculated under different loads, and fit to obtain the change curve of the specific heat ratio of the combustion chamber outlet gas under different loads of the gas turbine.

[0051] Example 3

[0052] It is an embodiment of the present invention, which is different from the previous embodiment in that:

[0053] If the functions are implemented in the form of software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art or the part of the technical solution, can be embodied in the form of a software product. The computer software product is stored in a storage medium, including several instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the methods described in each embodiment of the present invention. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), disk or optical disk, etc., which can store program codes.

[0054] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as an ordered list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by an instruction execution system, device or apparatus (such as a computer-based system, a system including a processor, or other system that can fetch instructions from an instruction execution system, device or apparatus and execute instructions), or in conjunction with such instruction execution systems, devices or apparatuses. For the purposes of this specification, "computer-readable medium" can be any device that can contain, store, communicate, propagate or transmit a program for use by an instruction execution system, device or apparatus, or in conjunction with such instruction execution systems, devices or apparatuses.

[0055] More specific examples of computer-readable media (a non-exhaustive list) include the following: an electrical connection with one or more wires (electronic device), a portable computer disk case (magnetic device), a random access memory (RAM), a read-only memory (ROM), an erasable and programmable read-only memory (EPROM or flash memory), an optical fiber device, and a portable compact disk read-only memory (CDROM). In addition, the computer-readable medium may even be a paper or other suitable medium on which the program is printed, since the program may be obtained electronically, for example, by optically scanning the paper or other medium, followed by editing, deciphering or, if necessary, processing in another suitable manner, and then stored in a computer memory.

[0056] It should be understood that the various parts of the present invention can be implemented by hardware, software, firmware or a combination thereof. In the above-mentioned embodiments, a plurality of steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented by hardware, as in another embodiment, it can be implemented by any one of the following technologies known in the art or their combination: a discrete logic circuit having a logic gate circuit for implementing a logic function for a data signal, a dedicated integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc.

[0057] Example 4

[0058] Reference Figure 2 to Figure 7 , which is an embodiment of the present invention, provides a method suitable for determining the specific heat ratio of gas at the outlet of a gas turbine combustion chamber. In order to verify the beneficial effects of the present invention, scientific demonstration is carried out through economic benefit calculation and simulation experiments.

[0059] Considering that a gas power plant uses a 9FA gas turbine, the Thermoflow power plant heat balance analysis professional software is used to establish a 9FA gas turbine heat balance calculation model. According to the historical operation data of the gas turbine, the inlet atmospheric pressure of the calculation model is set to 1.001 bar, the atmospheric temperature is 21.49 ° C, the relative humidity is 79%, and the load is set to 100%. The calculation results are shown in Figure 2 The operating data of the gas turbine in the power plant shows that the air pressure at the inlet of the combustion chamber is 15.5 bar and the temperature is 400°C. The pressure and temperature results calculated by Thermoflow are 15.46 bar and 399.8°C, respectively, which verifies the accuracy of the established gas turbine heat balance calculation model.

[0060] Considering that the regular operating load points of the gas turbine in a gas-fired power plant are 50%, 65%, 80%, 95% and 100%, the above loads are taken as typical loads, and the verified gas turbine heat balance calculation model is used to calculate the inlet and outlet boundary parameters of the combustion chamber under the above typical loads.

[0061] Among them, under 50% load, the combustion chamber inlet air temperature is 358°C, the flow rate is 341.6kg / s, the combustion chamber inlet fuel temperature is 185°C, the flow rate is 9.054kg / s, and the combustion chamber outlet pressure is 10.12bar.

[0062] At 65% load, the combustion chamber inlet air temperature is 374°C, the flow rate is 385kg / s, the combustion chamber inlet fuel temperature is 185°C, the flow rate is 10.674kg / s, and the combustion chamber outlet pressure is 11.59bar.

[0063] At 80% load, the combustion chamber inlet air temperature is 385°C, the flow rate is 436.4 kg / s, the combustion chamber inlet fuel temperature is 185°C, the flow rate is 12.168 kg / s, and the combustion chamber outlet pressure is 13.18 bar.

[0064] At 95% load, the combustion chamber inlet air temperature is 392°C, the flow rate is 490.4 kg / s, the combustion chamber inlet fuel temperature is 185°C, the flow rate is 13.608 kg / s, and the combustion chamber outlet pressure is 14.79 bar.

[0065] At 100% load, the combustion chamber inlet air temperature is 399.8°C, the flow rate is 493kg / s, the combustion chamber inlet fuel temperature is 185°C, the flow rate is 13.77kg / s, and the combustion chamber outlet pressure is 14.88bar.

[0066] Next, based on the combustion chamber inlet air and fuel mass flow rates calculated in step 1, the equivalence ratios of the fuel and air combustion chemical reactions in the gas turbine combustion chamber at typical loads of 50%, 65%, 80%, 95% and 100% are calculated to be 0.4568, 0.4779, 0.4806, 0.4783 and 0.4815, respectively.

[0067] like Figure 3 As shown in the figure, it is the real model of the combustion chamber of the 9FA gas turbine. The simplified numerical model of the combustion chamber is established using ANSYS commercial software. The simplified numerical model of the combustion chamber is as follows Figure 4 As shown in the figure, only the swirl fuel nozzle and the cylindrical flame tube are included, which is completely different from the structure and size of the real model of the 9FA gas turbine combustion chamber. The simplified flame tube flow cross-sectional area is about 0.0554m 2 The actual flame tube flow area is about 0.554m 2 Divide by, and the reduction factor of the simplified combustion chamber is calculated to be 0.1. The calculation results of the Thermoflow gas turbine heat balance model established in step 1 under 100% load are used to verify the simplified numerical model of the combustion chamber. Since the reduction factor of the simplified combustion chamber is 0.1, and the 9FA gas turbine has a total of 18 combustion chambers, the inlet air mass flow rate of a single simplified combustion chamber is set to 493 / 18*0.1=2.739kg / s, the fuel mass flow rate is 13.77 / 18*0.1=0.0765kg / s, and the combustion chamber outlet pressure is set to 14.88bar. The calculation results are shown in Figure 5 , the calculated combustion chamber outlet temperature is 1320°C, which is consistent with the 1325.8°C obtained by the Thermoflow gas turbine heat balance calculation.

[0068] Using the verified simplified numerical model of the combustion chamber in step 3, the mass flow rates of air and fuel at the inlet of the gas turbine combustion chamber under typical loads of 50%, 65%, 80%, 95%, and 100% obtained in step 1 are divided by the number of combustion chambers 18 and then multiplied by the reduction factor 0.1, and then set as the air and fuel inlet boundary parameters in the numerical model respectively. The pressure outlet boundary parameter of the numerical model is set according to the combustion chamber outlet pressure value under the typical load obtained in step 1. At the same time, the equivalent ratios of the fuel and air combustion chemical reactions in the simplified combustion chamber under typical loads of 50%, 65%, 80%, 95%, and 100% are calculated to be 0.4568, 0.4779, 0.4806, 0.4783, and 0.4815, respectively, which are consistent with the equivalent ratios of the fuel and air combustion chemical reactions in the gas turbine combustion chamber under typical loads calculated in step 2.

[0069] The simplified numerical model of the combustion chamber after setting the boundary conditions in step 4 is used to calculate the temperature, pressure and specific heat ratio of the combustion chamber outlet gas under typical loads of 50%, 65%, 80%, 95% and 100% respectively. The calculation results of the specific heat ratio of the combustion chamber center section under 100% load are shown in Figure 6 The specific heat ratios of the combustion chamber outlet gas under typical loads such as 50%, 65%, 80%, 95% and 100% are 1.33087, 1.31899, 1.28342, 1.28386 and 1.28393 respectively.

[0070] Using the specific heat ratio data of the combustion chamber outlet gas under typical load calculated in step 5, with load as the independent variable and specific heat ratio as the dependent variable, curve fitting is performed. The results are shown in Figure 7 From 50% to 80% load, the gas specific heat ratio changes greatly, and a quadratic polynomial is used for fitting. From 80% to 100% load, the gas specific heat ratio changes slightly, and a linear fit is used. The gas specific heat ratio fitting formula is:

[0071]

[0072] Wherein, γ is the gas specific heat ratio, and W is the relative load of the gas turbine.

[0073] Finally, according to the specific heat ratio calculation formula (2) obtained by curve fitting in step 6, the specific heat ratio of the gas at the outlet of the gas turbine combustor at any load in the load range of 50% to 100% can be calculated.

[0074] The high-temperature and high-pressure combustion gas formed after combustion in the gas turbine combustion chamber contains multiple gases such as carbon dioxide, nitrogen, and oxygen, and the volume proportion, gas temperature, and gas pressure of each gas are different under different loads. It is difficult to measure the specific heat ratio of the gas at the outlet of the gas turbine combustion chamber through traditional experimental methods. This scheme adopts a combination of Thermoflow heat balance calculation and ANSYS fluid numerical simulation methods. It only needs to establish a gas turbine heat balance calculation model and a simplified numerical model of the gas turbine combustion chamber to calculate the gas specific heat ratio at the outlet of the combustion chamber under the typical load of the gas turbine. Through curve segmentation fitting, the gas specific heat ratio at any load within the typical load operating range of the gas turbine can be obtained, which is beneficial to improving the thermal efficiency of the gas turbine cycle and the calculation accuracy of the work done by the gas expansion in the turbine.

[0075] Furthermore, the present invention can obtain the specific heat ratio of the gas at the outlet of the combustion chamber under the typical load of the gas turbine without the need for experiments, only by establishing a gas turbine heat balance calculation model and a simplified numerical model of the gas turbine combustion chamber. The simplified numerical model of the gas turbine combustion chamber established by the present invention can be inconsistent with the structure and size of the real combustion chamber model, which can greatly simplify the modeling difficulty and calculation workload of the combustion chamber. It is only necessary to ensure that the equivalent ratio of the fuel and air combustion chemical reaction in the simplified combustion chamber is consistent with the equivalent ratio of the fuel and air combustion chemical reaction in the real combustion chamber. The present invention can finally obtain a calculation formula for the specific heat ratio of the gas applicable to the typical load range of the gas turbine through segmented curve fitting, thereby improving the usability of the present invention.

[0076] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A method for determining the specific heat ratio of gas at the outlet of a gas turbine combustion chamber, characterized in that: include: Establish a heat balance calculation model for gas turbines; Analyze the combustion chamber inlet and outlet boundary conditions under typical loads; Analyze the equivalence ratio of fuel and air combustion reactions under typical loads; Establish a simplified numerical model of the combustion chamber; Calculate the specific heat ratio of the combustion chamber outlet gas under typical load; Fitting the change curve of specific heat ratio of gas at the outlet of gas turbine combustion chamber; The specific heat ratio of the gas at the outlet of the gas turbine combustor is calculated.

2. The method for determining the specific heat ratio of gas at the outlet of a gas turbine combustion chamber according to claim 1, characterized in that: The gas turbine heat balance calculation model is established for the gas turbine model used in the gas power plant using the Thermoflow power plant heat balance analysis professional software; The Thermoflow model sets the boundary parameters of the calculation model according to the historical operation data of the gas turbine, and verifies the accuracy of the calculation model using the historical operation data of the gas turbine; The verified gas turbine heat balance calculation model is used to calculate the inlet and outlet boundary parameters of the combustion chamber of the gas turbine from startup to full load operation.

3. The method for determining the specific heat ratio of gas at the outlet of a gas turbine combustion chamber according to claim 2, characterized in that: The working load of the gas turbine generator set is in the range of 50% to 100% load, and the gas turbine combustor inlet air and fuel mass flow, temperature and combustor outlet pressure parameters are calculated at typical loads of 50%, 60%, 70%, 80%, 90% and 100%.

4. The method for determining the specific heat ratio of gas at the outlet of a gas turbine combustion chamber according to claim 3, characterized in that: Based on the calculated air and fuel mass flow rates at the combustion chamber inlet, the equivalence ratio of the fuel and air combustion chemical reaction in the gas turbine combustion chamber under typical load is calculated: Among them, m f is the fuel mass flow rate at the inlet of the gas turbine combustion chamber; m air M is the air mass flow rate at the inlet of the gas turbine combustion chamber; air is the molecular weight of air, M ch4 is the molecular weight of methane.

5. The method for determining the specific heat ratio of gas at the outlet of a gas turbine combustion chamber according to claim 4, characterized in that: Establishing a simplified numerical model of the combustion chamber, and verifying the simplified numerical model of the combustion chamber by using the gas turbine heat balance calculation model; The simplified numerical model of the combustion chamber comprises a fuel nozzle and a flame tube, wherein the fuel nozzle has air and fuel inlets, and the flame tube may be a cylindrical cavity; Divide the simplified flame tube flow cross-sectional area by the actual flame tube flow area to calculate the reduction factor α of the simplified combustion chamber; The inlet boundaries of the simplified numerical model of the combustion chamber are set as the air mass inlet boundary and the fuel mass inlet boundary, and the outlet boundary is set as the pressure outlet boundary.

6. The method for determining the specific heat ratio of gas at the outlet of a gas turbine combustion chamber according to claim 5, characterized in that: Calculating the composition and specific heat ratio of the combustion chamber outlet gas under typical load includes the following steps: Using the established simplified numerical model of the combustion chamber; The mass flow rates of air and fuel at the inlet of the gas turbine combustor under different loads are multiplied by the scaling factor as the inlet boundary conditions of the model; Calculate the equivalence ratio and compare and verify it with the equivalence ratio in the actual combustion chamber; The combustion chamber outlet pressure value under the typical load obtained by analysis is set as the pressure outlet boundary condition of the model; Under the above boundary conditions, the simplified model is used to calculate the composition and specific heat ratio of the combustion chamber outlet gas under different loads.

7. The method for determining the specific heat ratio of gas at the outlet of a gas turbine combustion chamber according to claim 6, characterized in that: According to the simplified numerical model of the combustion chamber after setting the boundary conditions, the temperature, pressure and specific heat ratio of the combustion chamber outlet gas under the typical loads of 50%, 60%, 70%, 80%, 90% and 100% are calculated respectively; Based on the calculated specific heat ratio data of the combustion chamber outlet gas under typical load, with load as the independent variable and specific heat ratio as the dependent variable, curve fitting is performed according to the change trend of the gas specific heat ratio; According to the specific heat ratio calculation formula obtained by curve fitting, the specific heat ratio of the gas at the outlet of the gas turbine combustion chamber at different loads is calculated.

8. A system using the method for determining the specific heat ratio of gas at the outlet of a gas turbine combustion chamber as claimed in any one of claims 1 to 7, characterized in that: include: A data acquisition module, used to collect relevant data of the gas turbine; Model building module, used to build the overall three-dimensional model of the Thermoflow gas turbine and the simplified numerical model of the combustion chamber based on the collected data; Boundary condition analysis module, used to analyze the inlet and outlet boundary conditions of the combustion chamber under typical loads, as well as the equivalence ratio of fuel and air combustion reactions; The specific heat ratio calculation module is used to substitute the boundary conditions and equivalence ratio obtained by analysis into the simplified combustion chamber model to calculate the composition and specific heat ratio of the combustion chamber outlet gas under typical load; The fitting module is used to collect the combustion chamber outlet gas specific heat ratio data calculated under different loads, and to fit the change curve of the combustion chamber outlet gas specific heat ratio under different loads of the gas turbine.

9. A computer device comprising a memory and a processor, wherein the memory stores a computer program, wherein: When the processor executes the computer program, the steps of the method for determining the specific heat ratio of gas at the outlet of a gas turbine combustor according to any one of claims 1 to 7 are implemented.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the method for determining the specific heat ratio of gas at the outlet of a gas turbine combustor according to any one of claims 1 to 7 are implemented.

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