A method for identifying aerodynamic instability in a gas turbine starting process

Abstract

The application belongs to the field of gas turbine stall identification, and is a kind of gas turbine aerodynamic instability identification method in the starting process. The gas turbine aerodynamic test of the gas turbine single rotor generator is carried out to collect the aerodynamic test data, and then the equal speed characteristic line is established as a variable to disperse the compressor working point influence curve to obtain a series of discrete working points. The starting process working line and the parking and speed reduction process working line in the discrete working line are compared. Whether the instability is judged by comparing the difference between the combustor oil-gas ratio of the aerodynamic process working line and the combustor oil-gas ratio of the parking and speed reduction process working line. The method for quickly and accurately identifying whether the compressor stalls and the degree of aerodynamic instability in the starting process by using the aerodynamic measurement parameters in the gas turbine operation process supports taking measures as soon as possible to ensure the safe operation of the gas turbine and analyzes the causes of the gas turbine failure.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of gas turbine stall recognition, and particularly relates to a method for recognizing aerodynamic instability in a gas turbine starting process. BACKGROUND

[0002] The process in which a gas turbine rapidly transits from one stable working state to another stable working state is referred to as a transition state, which includes a starting process, an accelerating process, a decelerating process, a loading process, an unloading process and the like. There are generally two forms of aerodynamic unstable working states (i.e., aerodynamic instability) of a gas turbine (generally, the compressor part is an axial flow type): compressor rotating stall and surge. The aerodynamic instability of a gas turbine may cause a significant decline in the performance of the gas turbine, or even cause a major mechanical damage to the gas turbine. Therefore, it is very important to accurately, quickly and conveniently recognize the aerodynamic instability of a gas turbine in operation, and then take measures as soon as possible to ensure the safe operation of the gas turbine.

[0003] Rotating stall is an unstable phenomenon that high-frequency oscillations of flow and outlet pressure occur when a working point of a compressor is close to a surge boundary, and is manifested as one or more stall cells propagating in the circumferential direction, resulting in non-axisymmetric pulsation of airflow. Rotating stall generally occurs in a low speed zone, and generally occurs in a starting process of a gas turbine. A time-frequency characteristic analysis method is generally used to determine whether the gas turbine is stalled and to identify whether the gas turbine is in an aerodynamic instability. Surge has obvious characteristics and is easy to identify. The present application mainly relates to the aerodynamic instability caused by rotating stall.

[0004] At present, a time-frequency characteristic analysis method is generally used to determine whether the gas turbine is stalled, but since stall is generally gradually developed from an initial stage of stall precursor to a mature stall stage, the corresponding airflow is gradually developed from normal flow to the mature stall stage of aerodynamic instability, and the pressure ratio and flow of the compressor are greatly reduced.

[0005] The corresponding relationship between the time-frequency characteristics of stall of different types of engines and the degree of aerodynamic instability of the gas turbine is complex and changeable, and generally has no clear rules. Therefore, it is difficult to quickly and accurately determine the degree of aerodynamic instability of the gas turbine. For example, it is known that many types of gas turbines have time-frequency characteristics of stall, but some types of engines are aerodynamically stable, while some types of engines are severely aerodynamically unstable, resulting in the engines being unable to work normally.

[0006] Therefore, how to quickly and accurately recognize whether the gas turbine is stalled is a problem to be solved. SUMMARY

[0007] The application aims to provide a method for recognizing aerodynamic instability in a gas turbine starting process, so as to solve the problem that the corresponding relationship between the time-frequency characteristics of stall of different types of engines and the degree of aerodynamic instability of the gas turbine is complex and changeable, and is difficult to accurately recognize.

[0008] The technical solution of this application is: a method for identifying aerodynamic instability during the start-up process of a gas turbine, comprising:

[0009] Aerodynamic tests were conducted on a single-rotor gas turbine generator, and aerodynamic test data was collected. The aerodynamic test data included the compressor inlet total temperature T. t2 Total compressor inlet pressure p t2 Total temperature T at the combustion chamber outlet t4 and the mass of air flow rate at the compressor inlet q ma ;

[0010] Set the similarity parameter T for the gas turbine inlet temperature t4 / T t2 The similarity parameter T of the gas turbine inlet temperature at different operating points was calculated and statistically analyzed using aerodynamic test data. t4 / T t2 The values ​​are used to establish the compressor operating point influence curve;

[0011] Establish isospeed characteristic lines based on aerodynamic test data. by and T t4 / T t2 As a variable, the compressor operating point influence curve is discretized to obtain a series of discrete operating points. Detailed performance parameters of each discrete operating point are calculated, where n is the gas turbine speed.

[0012] Obtain the corresponding constraints or given control laws for the compressor, and analyze the characteristic curves at various constant speeds. The upper optimization selects discrete operating points that satisfy the constraints or given control laws, and connects the corresponding discrete operating points in sequence to obtain the corresponding discrete operating lines.

[0013] By comparing the start-up process working line and the shutdown and speed reduction process working line in the discrete working lines, it is determined whether the difference between the combustion chamber oil-gas ratio of the aerodynamic process working line and the combustion chamber oil-gas ratio of the shutdown and speed reduction process working line is greater than the first threshold. If so, it is determined that when the compressor is working normally, the start-up process working line is closer to the surge boundary than the shutdown and speed reduction process working line. If not, it is determined that the gas turbine stalls and becomes aerodynamically unstable during the start-up and speed increase process.

[0014] Preferably, when the high-pressure turbine guide vane is in a critical or supercritical state, the similarity parameter T of the gas turbine inlet gas temperature is... t4 / T t2 The constant is T; when the high-pressure turbine guide vane is in a subcritical state, the similarity parameter T of the gas turbine inlet temperature is... t4 / T t2 It is a non-constant.

[0015] Preferably, the constant speed characteristic line The greater the value, the closer the working point to the surge boundary.

[0016] Preferably, each working point on the compressor working point influence curve corresponds to a unique (T t4 / T t2 , coordinate.

[0017] Preferably, the detailed performance parameters of each discrete working point are calculated by using gas turbine overall performance calculation software.

[0018] Preferably, the first threshold is obtained by gas turbine aerodynamic test and interpolation.

[0019] The gas turbine starting process aerodynamic instability identification method provided in the present application uses gas turbine running process aerodynamic measurement parameters to quickly and accurately identify whether the compressor is stalled and aerodynamically unstable and the stall degree in the starting process, supports taking measures as soon as possible to ensure the safe operation of the gas turbine and analyze the causes of the gas turbine failure. BRIEF DESCRIPTION OF DRAWINGS

[0020] In order to more clearly illustrate the technical solutions provided in the present application, the following will briefly introduce the drawings. Obviously, the drawings described below are only some embodiments of the present application.

[0021] Figure 1 It is a schematic diagram of the overall process of the present application;

[0022] Figure 2 It is a schematic diagram of the compressor steady-state working point influence curve of the present application;

[0023] Figure 3 It is a schematic diagram of the single-rotor gas generator working point discretization of the present application;

[0024] Figure 4 It is a schematic diagram of the transient state discrete working line of the present application;

[0025] Figure 5 It is a schematic diagram of the comparison between the starting working line and the parking and reducing rotation working line of the normal working process of the gas turbine of the present application;

[0026] Figure 6 It is a schematic diagram of the gas turbine starting process stall identification method of the present application. DETAILED DESCRIPTION

[0027] 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.

[0028] A method for identifying aerodynamic instability during the start-up process of a gas turbine is presented below. The principle and technical solution of the invention are illustrated using a gas turbine with a single rotor gas generator (consisting of an axial flow compressor, a combustion chamber, and a gas turbine) as an example. The invention is also applicable to single rotor core machines of other gas turbine structures.

[0029] like Figure 1 As shown, the specific design is as follows:

[0030] Step S100: Conduct a gas turbine aerodynamic test on the single-rotor gas turbine generator and collect aerodynamic test data, including the compressor inlet total temperature T. t2 Total compressor inlet pressure p t2 Total temperature T at the combustion chamber outlet t4 and the mass of air flow rate at the compressor inlet q ma wait.

[0031] Step S200: According to the aerodynamic performance principle of gas turbine, when the single rotor gas generator is working in steady state, the components restrict each other. Through the balance relationship of airflow mass flow rate, pressure balance relationship, and the equality of the physical speed of the compressor and turbine, it can be deduced that the compressor boost ratio π of the single rotor gas generator satisfies formula (1).

[0032]

[0033] In the formula:

[0034] Where σ b σ is the total pressure recovery coefficient of the combustion chamber. t The total pressure recovery coefficient, A, of the gas turbine guide vane inlet to throat section. t Let q(λ) be the critical cross-sectional area of ​​the gas turbine guide vane. t ) represents the aerodynamic function of the throat section of the gas turbine guide vane;

[0035] T t2 -Compressor inlet total temperature;

[0036] T t4 -Combustion chamber outlet total temperature;

[0037] q ma -Compressor inlet air mass flow rate;

[0038] p t2 - compressor inlet total pressure.

[0039] From equation (1) we can see that:

[0040] 1) When the high pressure turbine nozzle is in a critical or supercritical state, q(λ t ) = 1, the value of K can be considered approximately constant, in which case, when the gas turbine pre-gas temperature similarity parameter T t4 / T t2 is constant, the air flow similarity parameter through the gas turbine is directly proportional to the compressor pressure ratio π. On the compressor characteristic map, a straight line with a slope of can be drawn. Taking a series of values for the gas turbine pre-gas temperature similarity parameter T t4 / T t2 , a series of straight lines can be obtained on the compressor characteristic map, which are the compressor operating point influence curves, as shown in Figure 2 . As the value of T t4 / T t2 = const increases, the operating point moves along the constant speed characteristic line towards the surge boundary. n is the gas turbine speed.

[0041] 2) When the gas turbine is in a low speed range, the compressor pressure ratio π is low, and the gas turbine nozzle is in a subcritical state, q(λ t ) < 1, the value of K in equation (1) is no longer constant, and the compressor pressure ratio π is no longer directly proportional to the flow similarity parameter , but is a curve passing through the point π = 1 on the ordinate axis, as shown in Figure 2 .

[0042] When a single rotor gas generator is operating in a transient state, the performance parameters of the gas engine operating state change with time, there may be energy and mass accumulation and release between sections, the flow rate between sections is no longer continuous (i.e. volume effect), and there is unsteady heat exchange between the gas flow and the blades and the casing wall. In fact, when operating transiently, the volume of each component is small, and the aerodynamic and thermodynamic process parameters change much faster than the speed change, so the volume effect of these components and the unsteady heat exchange between the gas flow and the blades and the casing wall can be ignored.

[0043] It can be approximated that the flow rate at each cross-section remains continuous at any given time, and all components operate in an instantaneously stable state, i.e., the quasi-steady assumption. Ignoring component volume effects and unsteady heat exchange, the overall performance mathematical model of the single-rotor gas generator at the transient operating point is identical in all parts except for no longer satisfying the compressor and turbine power balance equations in the common operating equations at the steady-state operating point. Therefore, the transient operating point, like the steady-state operating point, also satisfies formula (1), hence any operating point on the compressor operating point influence curve of the single rotor corresponds to a unique (T) t4 / T t2 , coordinate.

[0044] The above design simplifies the compressor operating point influence curve, making subsequent processing easier.

[0045] Step S300, with parameters and T t4 / T t2 As variables, the compressor operating point influence curve is discretized to obtain a series of discrete operating points (e.g. Figure 3 Furthermore, detailed performance parameters for each discrete operating point can be calculated using gas turbine overall performance calculation software.

[0046] Step S400: Based on the constraints or given control laws of the corresponding compressor, in each... From the discrete points on the constant speed characteristic line, optimize the selection of discrete operating points that satisfy the constraints or given control law, and then select each... The corresponding discrete operating points are connected in sequence to form a discrete operating line that meets the conditions. Discrete operating lines include the starting process operating line, the transient state operating line, and the stopping and speed reduction operating line, etc.

[0047] When the engine is operating normally, the selected discrete operating point T t4 / T t2 The larger the value, the closer the transition state working line is to the surge boundary line, such as... Figure 4 China T t4 / T t2 The transition operating line 1, with a larger value, is closer to the surge boundary line than the transition operating line 2. For gas turbines with the same technical specifications and specifications, the combustion chamber air-fuel ratio and T... t4 / T t2 The basic linear positive correlation and one-to-one correspondence mean that if the gas turbine transient process has a larger oil-gas ratio, the corresponding discrete operating line will be closer to the surge boundary.

[0048] Step S500, comparing the working line of the gas turbine starting process with the working line of the parking and reducing process to identify whether the compressor is unstable: whether the difference between the combustor oil-gas ratio of the starting process working line and the combustor oil-gas ratio of the parking and reducing process working line is greater than a first threshold value, if yes, it is judged that the compressor is normally working, the starting process working line is closer to the surge boundary than the parking and reducing process working line, and the pressure ratio is higher at the same gas generator equivalent speed (for example Figure 5 ). If not, it can be judged that the gas turbine starting and reducing process is stalled and aerodynamically unstable. The first threshold value is set according to the actual type of gas turbine, which can be obtained by gas turbine aerodynamic test and interpolation.

[0049] For example, Figure 6 For a gas turbine with a single-rotor gas generator, the working lines of the starting and reducing process and the extinguishing and parking process are compared in the same test. After the gas turbine is successfully ignited aerodynamically, the combustor oil-gas ratio is higher than that in the parking process, and the pressure ratio is increased, indicating that the compressor is working normally. Then, the compressor starts to stall, the pressure ratio decreases, and the starting working line gradually decreases. When the starting working line is very close to or lower than the working line of the parking process, it can be judged that the compressor is in the mature stall stage, the gas turbine is aerodynamically unstable, and the compressor cannot work normally.

[0050] Through the above design, the method of using the aerodynamic measurement parameters of the gas turbine during operation to quickly and accurately identify whether the compressor is stalled and aerodynamically unstable during the starting process and the stall degree supports taking measures as soon as possible to ensure the safe operation of the gas turbine and analyzes the causes of the gas turbine failure.

[0051] Finally, it should be noted that the drawings of the disclosed embodiments only involve the structures involved in the disclosed embodiments, and other structures can be referred to the usual design. In the case of no conflict, the same embodiment and different embodiments of the present application can be combined with each other.

[0052] Finally, the above only describes the preferred embodiments of the present application and is not used to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A method of identifying aerodynamic instability in a gas turbine start process, characterized by, Comprising: The gas turbine aerodynamic test of the gas turbine single-rotor generator is performed, and aerodynamic test data is collected, including compressor inlet total temperature T t2 , compressor inlet total pressure p t2 , combustor outlet total temperature T t4 and compressor inlet air flow mass q ma ; Setting the gas turbine front gas temperature similar parameter T t4 / T t2 , through the aerodynamic test data calculation and statistics of different working point at the gas turbine front gas temperature similar parameter T t4 / T t2 The value of the establishment of compressor working point influence curve; The equal speed characteristic line is established according to the aerodynamic test data With And T t4 / T t2 As the variable, the compressor working point influence curve is discretized to obtain a series of discrete working points, and the detailed performance parameters of each discrete working point are calculated. The constraint condition or the given control law corresponding to the compressor is obtained, and each constant speed characteristic line is obtained The discrete working points satisfying the constraint condition or the given control law are selected by optimization, and the discrete working lines are obtained by connecting the corresponding discrete working points in sequence. Comparing the start-up process working line and the parking and turning-down process working line in the discrete working line, judging whether the difference between the combustor oil-gas ratio of the start-up process working line and the combustor oil-gas ratio of the parking and turning-down process working line is greater than a first threshold value, if yes, judging that the start-up process working line is closer to the surge boundary than the parking and turning-down process working line when the compressor is working normally; if not, judging that the gas turbine is stalled and aerodynamically unstable during the start-up and turning-up process.

2. The gas turbine start process aerodynamic instability identification method of claim 1, characterized by: When the high pressure turbine nozzle is in a critical or supercritical state, the gas turbine pre-gas temperature similarity parameter T t4 / T t2 is constant; when the high pressure turbine nozzle is in a subcritical state, the gas turbine pre-gas temperature similarity parameter T t4 / T t2 is non-constant.

3. The gas turbine start process aerodynamic instability identification method of claim 1, characterized by: The iso-speed characteristic line The greater the value of the ratio, the closer the operating point is to the surge limit.

4. The gas turbine start process aerodynamic instability identification method of claim 1, characterized by: Any working point on the compressor working point influence curve of the gas turbine single rotor generator corresponds to a unique coordinate.

5. The gas turbine start process aeromechanical instability identification method of claim 1, wherein: The detailed performance parameters of each discrete working point are calculated by using a gas turbine overall performance calculation software.

6. The gas turbine start process aerodynamic instability identification method of claim 1, characterized by: The first threshold value is obtained by gas turbine aerodynamic test and interpolation.

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