A method for studying gas turbine starting laws

Abstract

The present invention relates to a method for studying gas turbine starting laws, comprising the following steps: S1, determining the gas turbine starting requirements based on the overall structure of the gas turbine and the unit installation structure; S2, calculating the gas turbine compressor characteristics, turbine characteristics, combustion chamber starting calculations, and overall performance; obtaining compressor characteristic maps, turbine characteristic maps, flow distribution at each intake position, maximum exhaust temperature limits, and maximum operating limits; S3, determining the starting motor requirements; S4, calculating the compressor transient operating curve and starting characteristic curve during the starting process based on the compressor and turbine characteristic calculation results; S5, calculating the equivalent relationship between the gas turbine speed and the natural gas intake amount based on the transient operating curve and starting characteristic curve; S6, verifying and correcting the equivalent relationship in S5 through test runs. This starting law enables smooth gas turbine starting and provides a basis for natural gas control of the gas turbine.

Description

Technical Field

[0001] The present invention relates to a gas turbine design technology, in particular to a method for studying the starting law of a gas turbine. Background Art

[0002] Distributed energy uses gas turbines to generate electricity and provide combined cooling, heating, and power. Gas turbines use natural gas to power the system, offering high economic and environmental benefits and growing widespread adoption. 1.5MW-class gas turbines, such as the DR15, hold great promise for future application. During gas turbine startup, an external power source drives the compressor until the turbine can independently generate sufficient mechanical power to maintain unit operation. During the initial startup phase, an external starter (such as an electric motor) is required to drive the compressor. Once the external starter drives the compressor to a certain speed, air is drawn in and compressed, then mixed with fuel and burned in the combustion chamber. The high-temperature, high-pressure gas generated during this process flows into the turbine, rotating it and generating work, which in turn drives the compressor. Once the mechanical power generated by the turbine exceeds the required power by the compressor, the external starter can be disconnected from the gas turbine, allowing the gas turbine to maintain operation on its own. This process marks the transition of gas turbines from relying on external power to achieving self-sustaining operation. In addition, the gas turbine startup process involves multiple key steps and parameter controls, such as pre-start inspection and preparation, cold run, purge, ignition, and speed increase. These steps ensure that the gas turbine can safely and reliably reach high-speed operation from a standstill.

[0003] During startup, the natural gas intake of a gas turbine is proportional to its speed. The higher the speed and the greater the power, the greater the natural gas intake required. Low natural gas intake can cause the speed to fall below the required level, leading to a sudden shutdown. Excessive intake can lead to exhaust overheating. Therefore, it is necessary to understand the gas turbine startup pattern based on the factors and parameters influencing gas turbine startup, determine the relationship between natural gas intake and speed, and control the natural gas intake accordingly to ensure proper startup. Currently, there is no established method for studying startup patterns.

[0004] The invention patent with publication number CN118088324A discloses a method for controlling the fuel flow of a gas turbine, and discloses a curve between the compressor outlet pressure CDP and the fuel upper limit ACU. It is a summary of the rules of gas turbine operation, but it does not disclose the relationship between the speed and the gas turbine flow at startup, nor does it disclose a research method for this relationship. Summary of the Invention

[0005] The present invention provides a method for studying the starting law of a gas turbine, which is used to solve the technical problems existing in the prior art.

[0006] A method for studying a gas turbine starting law, wherein the starting law is the corresponding relationship between the speed and the amount of gas entering the gas turbine during starting, so as to enable stable ignition and smooth starting of the gas turbine, the method comprising the following steps:

[0007] S1. Determine the gas turbine starting requirements based on the overall structure of the gas turbine and the unit installation structure; the starting requirements include fuel system requirements and starting restrictions;

[0008] S2. Calculating the gas turbine's compressor characteristics, turbine characteristics, combustor startup, and overall performance; the compressor characteristics calculation is used to obtain a compressor characteristics map, the turbine characteristics calculation is used to obtain a turbine characteristics map, the combustor startup calculation is used to obtain flow distribution at each intake position, and the overall performance calculation is used to obtain a maximum exhaust temperature limit and a maximum operating limit;

[0009] S3. Determine the starting motor requirements;

[0010] S4. Calculating the compressor transient operating curve and starting characteristic curve during the startup process based on the calculation results of the compressor and turbine characteristics;

[0011] S5. Calculating the equivalent relationship between the gas turbine speed and the amount of natural gas entering the engine based on the transient operating curve and the starting characteristic curve;

[0012] S6. Test run to verify and revise the equivalent relationship described in S5.

[0013] Furthermore, the fuel system requirements in step S1 include natural gas dosage range requirements, metering accuracy requirements, full-stroke operation time of the regulating valve, fuel cut-off time upon power failure or receiving a stop signal, and natural gas intake pressure.

[0014] Furthermore, the starting restrictions in step S1 include the time limit for starting acceleration to 5000 r / min, the time from successful ignition to 4000 r / min, the time for accelerating from 14000 r / min to 25900 r / min, the overspeed, and the overtemperature.

[0015] Furthermore, the calculation domain of the compressor characteristic calculation includes the centrifugal impeller, radial diffuser, and axial diffuser. The characteristic maps of the compressor at 20%, 40%, and 40% of the rated speed are first calculated, and then the full speed characteristic map is calculated.

[0016] Furthermore, in step S2, the turbine characteristics are calculated using three-dimensional CFX characteristics, and steady calculations are performed on different expansion ratios at 70%, 80%, 90%, 100%, and 110% of the rated speed for all design points to form a characteristic map.

[0017] Furthermore, in the step S2, the combustion chamber calculation is to perform aerodynamic performance calculation on the flame tube to obtain the flow distribution of each intake position, and perform velocity field analysis and pressure field analysis on each position of the combustion chamber to obtain the ignition position.

[0018] Furthermore, in the step S4, the conditions for calculating the transient operating curve and the starting characteristic curve of the compressor are: the gas turbine's rotational inertia constant, nozzle diameter, nozzle area, starting motor power, and rated speed.

[0019] Furthermore, in step S5, based on the transient operating curve and starting characteristic curve of the compressor obtained in step S4, the air flow rate under each speed condition is calculated, the combustion amount of natural gas under the air flow rate is calculated, and the natural gas intake amount corresponding to each speed is determined.

[0020] Furthermore, the ignition position should be determined at a location where the airflow is concentrated and the flow rate is slow.

[0021] Furthermore, the proportion of the natural gas after the air and the natural gas are mixed is no more than 2.5%.

[0022] Furthermore, the ignition nozzle extends 3 mm beyond the current stabilizer plate.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] By calculating compressor and gas turbine characteristics, combustion chamber aerodynamics, and overall gas turbine performance, this method determines performance parameters such as air flow and air-compression ratio corresponding to the design point rated speed, as well as indicators such as ignition position, temperature limits, and operating restrictions. Based on the natural gas combustion volume that can be met by the air flow, the allowable natural gas mixture ratio, and various factors such as the impact of turbine performance on the compressor, the natural gas supply corresponding to each speed is calculated. This establishes a proportional relationship between gas turbine speed and natural gas supply during startup. Through test runs, the parameters and ignition position are verified and modified, resulting in a startup law. This law provides a basis for starting gas turbines with natural gas and establishing a natural gas supply control system. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Compare the calculated flow paths of gas turbines with those in engineering drawings;

[0026] Figure 2 is the computational domain model of the compressor;

[0027] Figure 3 Compressor low speed characteristic diagram;

[0028] Figure 4 Schematic diagram of the combustion chamber calculation domain;

[0029] Figure 5 Compressor component characteristic diagram;

[0030] Figure 6 Turbine component characteristic diagrams;

[0031] Figure 7 Compressor transient operating line during natural gas fuel startup;

[0032] Figure 8 Natural gas fueled gas engine starting characteristics - speed / time variation relationship diagram;

[0033] Figure 9 Natural gas fueled engine starting characteristics - fuel consumption characteristics diagram;

[0034] Figure 10 Natural gas fueled gas engine starting characteristics - turbine exhaust temperature diagram;

[0035] Figure 11 Starting characteristics of natural gas fueled combustion engines - the relationship between fuel flow rate and turbine exhaust temperature as a function of speed;

[0036] Figure 12 Cold transfer curve diagram. DETAILED DESCRIPTION

[0037] In order to clearly illustrate the technical features of the application scheme of the present invention, the present invention is described in detail below through specific implementation methods and in conjunction with the accompanying drawings.

[0038] In the following description, many specific details are set forth to facilitate a full understanding of the present application. However, the present application may also be implemented in other ways different from those described herein. Therefore, the scope of protection of the present application is not limited to the specific embodiments disclosed below.

[0039] In addition, in the description of the present application, it should be understood that the terms "center", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first" and "second" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, features defined as "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present application, "multiple" means two or more, unless otherwise clearly and specifically defined.

[0040] In this application, unless otherwise expressly specified or limited, terms such as "installed," "connected," "connect," and "fixed" should be understood in a broad sense. For example, they may refer to fixed connection, detachable connection, or integration; mechanical connection, electrical connection, or communication; direct connection or indirect connection through an intermediate medium; and internal communication between two components or interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in this application based on specific circumstances.

[0041] In this application, unless otherwise expressly specified and limited, a first feature "above" or "below" a second feature may be that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. In the description of this specification, reference terms such as "one embodiment", "some embodiments", "example", "specific example", or "some examples" mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in an appropriate manner in any one or more embodiments or examples.

[0042] Example 1

[0043] This example uses a 1.5MW single-rotor gas turbine as an example to specifically illustrate a method for studying the starting law of a gas turbine, which is used to study the relationship between the starting speed of the gas turbine and the natural gas supply. The specific method is as follows:

[0044] S1. Determine the gas turbine starting requirements based on the overall structure of the gas turbine and the unit installation structure; the starting requirements include fuel system requirements and starting restrictions.

[0045] The gas turbine is a single-rotor gas turbine engine, which consists of six major components: reducer, air intake device, compressor, combustion chamber, turbine and exhaust section, as well as seven major systems to ensure the normal operation of the gas turbine: control system, fuel system, lubricating oil system, air system, ignition system, starting system, cleaning system. The direction of rotation of the gas generator rotor is counterclockwise (viewed against the exhaust direction).

[0046] The functional requirements of the gas turbine are as follows:

[0047] The rated power is 1500kW, the gas generator rotor speed is 27245 rpm, and the gearbox output speed is 1500 rpm. Using natural gas as fuel, the gas turbine can perform cold start, start-up, normal shutdown, and emergency stop functions. During startup, key parameters such as natural gas flow, speed, and exhaust temperature are monitored and controlled for protection. The gas turbine also features protection against abnormal conditions such as overspeed, overtemperature, flameout, and vibration.

[0048] During the startup process of the gas turbine, the fuel system requirements are shown in Table 1 Fuel System Requirements.

[0049] Table 1 Fuel system requirements

[0050]

[0051]

[0052] Safety limits are imposed on relevant parameters during the gas turbine startup process, and alarm values ​​and shutdown values ​​are determined, as shown in Table 2 below: Startup Limitation Parameters.

[0053] Table 2 Starting limit parameters

[0054]

[0055] S2. Calculate the gas turbine compressor characteristics, turbine characteristics, combustion chamber startup, and overall performance; the compressor characteristics calculation obtains a compressor characteristics map, the turbine characteristics calculation obtains a turbine characteristics map, the combustion chamber startup calculation is used to obtain the flow distribution at each intake position, and the overall performance calculation is used to obtain the maximum exhaust temperature limit and the maximum operating limit.

[0056] (1) Compressor characteristics calculation

[0057] Calculation domain model: The basic flow channel used for calculation was extracted from the gas turbine UG model. The casing flow channel corresponding to the centrifugal impeller tip and the flow channel at the chamfer of each component were adjusted. The casing flow channel corresponding to the centrifugal impeller tip was obtained by offsetting the centrifugal impeller tip flow channel outward by 0.25mm. The flow channel at the interface of each component was smoothed. Figure 1 As shown in the figure, the flow path in the engineering drawing is compared with the calculated flow path. Except for the centrifugal impeller casing flow path, the two are basically the same in other locations. The calculation model includes the inlet guide vanes, centrifugal impeller, and radial diffuser. Each row of blades is calculated using a single channel. The calculation domain is shown in the attached figure. Figure 2 shown.

[0058] Meshing: CFD calculations were performed using the numerical simulation software ANSYS CFX17.2, and the computational mesh was generated using IGG-AutoGrid5. The first mesh layer had a thickness of 0.003 mm, meeting the requirements of the k-Epsilon turbulence model. The computational domain included the centrifugal impeller, radial diffuser, and axial diffuser, totaling three rows of blades. The mesh element number distribution is shown in Table 3 below: Computational Mesh Settings.

[0059] Table 3 Computational grid settings

[0060] name Number of blades First layer grid size Number of grid nodes centrifugal impeller 13 3×10-5m 270,000 radial diffuser 19 3×10-5m 84,000 Axial diffuser 76 3×10-5m 78,000

[0061] Calculation settings:

[0062] Turbulence model: The calculation adopts the k-Epsilon turbulence model and checks the viscous work term.

[0063] Numerical calculation format: Use a calculation format with second-order accuracy.

[0064] Interface treatment between blade rows: Two adjacent blade rows adopt the "Stage (Mixing-Plane)" mixing surface method.

[0065] Boundary conditions: inlet total pressure and total temperature are 101325Pa and 288.15K respectively, with uniform axial air inlet; the static pressure at the outlet section is given and varies with different working points.

[0066] Tip clearance setting: The tip of the centrifugal impeller is set with a tip clearance of 0.25mm.

[0067] Calculation results: Since the gas turbine ignites at 20%-40% of the rated speed, there are problems such as greater ignition difficulty at this low speed and greater gas flow error. In view of the low speed characteristics of the gas turbine during startup, the software calculates the characteristic maps of 20%, 30% and 40% of the rated speed of the compressor, as shown in the attached figure. Figure 3 Based on the low speed characteristics, the full speed characteristics diagram is further calculated and obtained on the software.

[0068] (2) Turbine characteristics calculation

[0069] The turbine characteristics are calculated using three-dimensional CFX characteristics. According to the "Three-dimensional Viscous Aerodynamic CFX Calculation Specification for Aviation Gas Turbine Engine Turbines" (Q / 8SFGF40.1031-2010), steady calculations are performed for different expansion ratios of 70%, 80%, 90%, 100%, and 110% of the rated speed for all design points, and finally the characteristic curves are formed.

[0070] (3) Combustion chamber aerodynamic calculation

[0071] Calculation domain model: This calculation only calculates the aerodynamic performance of the combustion chamber flame tube, and removes the guide structure. All air film holes, nozzle internal structure, and carbon deposition groove structure are retained. Figure 4 shown.

[0072] Other simplifications include retaining the nozzle structure but performing equivalent throttling on its internal structure; deleting the welding gaps and rounding the sharp corners; and not including deflector cooling holes.

[0073] Meshing strategy: ANSYS Mesh 19.2 was used for meshing. The combustion chamber is large, so a mixed mesh of tetrahedrons and hexahedrons was used to minimize the total number of meshes, thus reducing computational time and conserving computing resources.

[0074] All structures, including the nozzle structure, carbon deposition grooves, vortex finder structure, heat shield holes, flame tube film holes, main combustion holes, mixing holes, and inserted nozzle structure, were independently segmented. Considering the majority of the fluid domain for structured meshing, the entire fluid domain was ultimately divided into 1044 blocks, forming a single part. The final meshing results are shown below. The total number of meshes is approximately 17.1 million, and the maximum distortion is 0.95.

[0075] Calculation results and analysis:

[0076] Flow distribution, based on Fluent calculation, the flow distribution of each intake position under each calculation state is statistically calculated, as shown in the flow distribution table in Table 4 below.

[0077] Table 4 Flow distribution

[0078]

[0079]

[0080] Velocity field analysis, through software simulation, reveals that because the main combustion holes and mixing holes are evenly distributed around the circumference, the high-temperature air jets converge toward the center of the combustion chamber, resulting in higher air velocities in the center of the combustion chamber outlet. Velocities at the guide vane outlet are particularly high, reaching 220 m / s, while those in other areas range from 100 to 180 m / s.

[0081] The pressure field analysis shows that except for the main combustion hole, mixing hole jet, and vortex finder outlet, the total pressure distribution inside the flame tube is relatively low; the total pressure inside the flame tube is significantly lower than the total pressure in the external channel; the pressure loss of the guide vane is mainly at the turning point; according to calculations, the total pressure loss of the combustion chamber is about 2.83%, and the total pressure loss of the guide vane is about 0.21%.

[0082] Analysis of the temperature field shows that the high-temperature airflow converges toward the center of the combustion chamber, following the jet direction of the main burner and dilution holes. This results in a higher temperature at the center of the combustion chamber. Natural gas fuel is primarily distributed along the centerline of the flame tube, with some remaining even up to the flame tube exit. This results in higher temperatures within the flame tube and at the center of the exit. Natural gas is also distributed within the atomizing air path, indicating backflow of the natural gas fuel. The highest temperature is found at the center of the combustion chamber outlet section. The average outlet temperature is 1314K, with a maximum of 2114K. The average temperature at the deflector outlet is 1312K, with a maximum of 1712K, primarily distributed on the upper annulus of the outlet. The calculated OTDF at the deflector outlet is 0.567.

[0083] (4) Overall performance calculation

[0084] The software GasTurb was used to establish a performance matching model for the gas turbine. The parameters of each section at different speeds and intake conditions were calculated. The overall performance parameters of natural gas fuel at the design point are shown in Table 5 below: Table of natural gas fuel parameters for each section at the design point.

[0085] Table 5 Natural gas fuel parameters for each section at design point

[0086]

[0087] Based on the above calculation results of compressor and turbine characteristics, the full speed characteristics of the compressor and turbine (20%--110% of the rated speed) are simulated in ANSYS. The calculation results are as shown in the attached figure. Figure 5 The full speed characteristic spectrum of the gas turbine compressor components shown in the figure and the attached Figure 5 The full speed characteristic map of the turbine components is shown.

[0088] S3. Determine the requirements for the starter motor. The gas turbine starter motor has the following technical requirements:

[0089] Type: three-phase asynchronous variable frequency motor;

[0090] Rotation direction: clockwise (facing the starter motor mounting base);

[0091] Transmission mode: driven by gear box transmission mechanism;

[0092] Rated power: 45kW

[0093] Number of poles: 2P;

[0094] Power supply voltage: 380VAC;

[0095] Rated frequency: 50Hz;

[0096] Rated speed: 3000r / min (corresponding to gas turbine speed 12048r / min);

[0097] Maximum allowable speed: 3600r / min;

[0098] Maximum torque: 286N·m;

[0099] S4. Calculating the compressor transient operating curve and starting characteristic curve during the startup process based on the calculation results of the compressor and turbine characteristics;

[0100] The gas turbine's moment of inertia is 3.555 kg·m 2 (including the turbine rotor, gearbox and generator); the nozzle is a circular surface with a diameter of 414mm and a nozzle area of ​​0.1346m2; the starting motor power is 45kW and the rated speed is 3000r / min. Based on the above conditions, the transient working curve of the compressor during the starting process (0-25900r / min) of the turbine is simulated in ANSYS and calculated (see the attached figure). Figure 7 ) and starting characteristic curve (see attached Figure 8-11 ).

[0101] S5. Calculating the equivalent relationship between the gas turbine speed and the amount of natural gas entering the engine based on the transient operating curve and the starting characteristic curve;

[0102] Based on the characteristic curve in S4, the air flow rate at each speed can be obtained, and the amount of natural gas that can be burned at this air flow rate and the natural gas's performance can be calculated. Taking into account the impact of turbine component manufacturing on the power provided by the compressor, the natural gas demand corresponding to each speed during startup can be obtained, and the gas turbine intake flow can be controlled according to the demand. The natural gas flow rate corresponding to each speed is shown in Table 6 below:

[0103] Table 6 Natural gas flow rate corresponding to each speed

[0104]

[0105]

[0106] S6. Test run to verify and revise the equivalent relationship described in S5.

[0107] Start the gas turbine for test verification. The gas turbine starting procedure is as follows:

[0108] (1) Start the auxiliary lubricating oil pump and check that the lubricating oil pressure is normal (≥0.022MPa).

[0109] (2) 0s, press the start button, the starter motor is powered on, and the vibration parking detection is turned on.

[0110] (3) Within 25 seconds after starting, the speed increases to 5000r / min.

[0111] (4) Cold run at (5500±55) r / min for 480 s.

[0112] (5) After the 180s countdown for cold start, the high-energy igniter ignites for 5s, and the natural gas regulating valve opens according to the natural gas flow rate corresponding to 5500r / min.

[0113] (6) The high-energy igniter continues to ignite for 8 seconds, the gas fuel quick shut-off valve opens, the vent valve closes, and gas begins to be supplied to the nozzle.

[0114] (7) After the ignition is successful, judging by the exhaust temperature rise within 8 seconds, the high-energy igniter is powered off and the engine speed is increased.

[0115] (8) Within 60 seconds after ignition, the speed increases to 14,000 r / min and the starter motor is powered off and disengaged.

[0116] (9) From 14000 r / min, the speed increases to 25900 r / min (about 95% of the rated speed) within 40 seconds.

[0117] (10) When the speed reaches 20,000 r / min, the auxiliary lubricating oil pump is powered off.

[0118] (11) When the speed reaches 25900 r / min, the engine enters the slow running state and runs stably at 25900 r / min, and the start-up is completed.

[0119] Based on the flow rate parameters in the speed-to-natural gas demand relationship obtained in step S5, the natural gas supply at each gas turbine speed is controlled. The gas turbine is started according to the aforementioned startup procedure to verify whether the gas turbine starts normally and whether the natural gas supply matches the gas turbine operation. Any issues discovered during the verification are corrected to obtain a final speed-to-natural gas demand relationship. This relationship constitutes the gas turbine startup pattern disclosed in this embodiment.

[0120] Example 2

[0121] This embodiment provides a method for studying the starting law of a gas turbine, and more particularly relates to a method for verifying the speed and air flow rate during the starting of a gas turbine, as described below.

[0122] The method for studying the starting law of the gas turbine is the same as that of Example 1. In the test run verification step S6, the following steps are performed: Before the starting test, the cold start function of the gas turbine is tested. The speed is increased to 5500r / min within the specified time and the engine is operated stably for 40s. During the cold start process, the engine operates stably and the relevant parameters are normal. The cold start curve of the engine is shown in the attached figure. Figure 12 shown.

[0123] After the successful cold start function test, Unit 001 underwent a start-up test, with ignition and engine speed increase according to the gas supply pattern in Table 6. After ignition, the exhaust temperature did not rise, indicating ignition failure. Preliminary analysis indicated that the ignition nozzle needed to be repositioned, extending beyond the flow stabilizer plate and positioned in a location with concentrated airflow and slower velocity. Simultaneously, the natural gas flow rate was adjusted for the first time, increasing the flow rate for each engine speed by 20 kg / h over the original flow rate.

[0124] The start-up test was carried out again according to the adjusted flow rate. The gas turbine was able to ignite successfully, and the exhaust temperature rose to 114°C, but the unit had an explosion sound and the gas turbine was shut down urgently. After inspection, it was found that the connecting bolts of the transfer section outside the unit casing were detached, and the transfer section near the casing was slightly deformed by the impact. Analysis showed that the modified natural gas flow was unreasonable, resulting in the ratio of natural gas and air accumulated in the pipeline reaching an explosive concentration before the ignition was successful. When the gas turbine was successfully ignited, the natural gas in the pipeline was ignited, causing an explosion, causing damage to the unit's transfer section. The subsequent improvement plan modified the unit's exhaust pipe to reduce the space for natural gas accumulation; the gas supply flow was recalculated according to the natural gas flow at the head of the gas turbine combustion chamber, and the ratio of natural gas and air after mixing should not exceed 2.5%. After the unit's transfer section was rectified, the natural gas flow corresponding to the gas turbine speed (5500~7500)r / min was adjusted for the second time.

[0125] Based on the second flow adjustment, the test run was continued. The test included starting at 8,000 to 9,500 r / min, motor disengagement at 14,000 r / min, overspeed protection at 18,000 r / min, speed increase at 23,800 r / min, and operation at a maximum speed of 26,000 r / min. Finally, stable operation was achieved at 25,900 r / min during slow running. Adjustments were made to the flow mismatch at each stage, ultimately forming the relationship between the starting speed and flow demand for the gas turbine in this embodiment, as shown in Table 7 below:

[0126] Table 7 Correspondence between engine speed and natural gas flow rate when starting successfully

[0127]

[0128]

[0129] Through the test run verification method of this embodiment, the gas turbine can achieve normal cold start, start-up and other functions, and the law of the relationship between the rotation speed and the natural gas supply amount is studied for the start-up of this type of gas turbine.

[0130] Example 3

[0131] This embodiment discloses a method for studying the starting law of a gas turbine. The difference from Example 2 is that in this embodiment, the top of the electric nozzle is extended about 3 mm beyond the flow stabilizer, the gas turbine ignites successfully, the exhaust temperature rises, and the ignition is stable at the installation position of the electric nozzle in this embodiment.

[0132] Obviously, the above-described embodiments of the present invention are merely examples for the purpose of clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. A person skilled in the art would be able to make other variations or modifications based on the above description. It is not necessary and impossible to enumerate all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the claims of the present invention.

Claims

1. A method for studying the starting law of a gas turbine, characterized in that: The steps include: S1. Determine the gas turbine starting requirements based on the overall structure of the gas turbine and the unit installation structure; the starting requirements include fuel system requirements and starting restrictions; S2. Calculating the gas turbine's compressor characteristics, turbine characteristics, combustor startup, and overall performance; the compressor characteristics calculation is used to obtain a compressor characteristics map, the turbine characteristics calculation is used to obtain a turbine characteristics map, the combustor startup calculation is used to obtain flow distribution at each intake position, and the overall performance calculation is used to obtain a maximum exhaust temperature limit and a maximum operating limit; S3. Determine the starting motor requirements; S4. Calculating the compressor transient operating curve and starting characteristic curve during the startup process based on the calculation results of the compressor and turbine characteristics; S5. Calculating the equivalent relationship between the gas turbine speed and the amount of natural gas entering the engine based on the transient operating curve and the starting characteristic curve; S6. Test run to verify and revise the equivalent relationship described in S5.

2. A method for studying the starting law of a gas turbine according to claim 1, characterized in that: The fuel system requirements in step S1 include natural gas dosage range requirements, metering accuracy requirements, full-stroke operation time of the regulating valve, fuel cut-off time when power is off or a stop signal is received, and natural gas intake pressure.

3. The method for studying the starting law of a gas turbine according to claim 1, characterized in that: The starting restrictions in step S1 include the time limit for starting acceleration to 5000r / min, the time from successful ignition to 4000r / min, the time for accelerating from 14000r / min to 25900r / min, the overspeed speed, and the overtemperature.

4. A method for studying the starting law of a gas turbine according to claim 1, characterized in that: In step S2, the compressor characteristics are calculated using CFD, first obtaining characteristic maps at 20%, 40%, and 40% of the rated speed of the compressor, and then obtaining a full-speed characteristic map. The turbine characteristics are calculated using three-dimensional CFX characteristics, performing steady-state calculations for different expansion ratios at all design points of 70%, 80%, 90%, 100%, and 110% of the rated speed to form a characteristic map.

5. The method for studying the starting law of a gas turbine according to claim 1, characterized in that: In the step S2, the combustion chamber startup calculation is to perform aerodynamic performance calculation on the flame tube to obtain the flow distribution of each intake position, and perform velocity field analysis and pressure field analysis on each position of the combustion chamber to obtain the ignition position.

6. The method for studying the starting law of a gas turbine according to claim 1, characterized in that: In step S4, the conditions for calculating the transient operating curve and the starting characteristic curve of the compressor are: the gas turbine's rotational inertia constant, nozzle diameter, nozzle area, starting motor power, and rated speed.

7. The method for studying the starting law of a gas turbine according to claim 1, characterized in that: In step S5, based on the compressor transient operating curve and starting characteristic curve obtained in step S4, the air flow rate under each speed condition is calculated, the combustion amount of natural gas under the air flow rate is calculated, and the natural gas intake amount corresponding to each speed is determined.

8. A method for studying the starting law of a gas turbine according to claim 5, characterized in that: The ignition position is set at a position where the airflow is concentrated and the flow speed is slow.

9. A method for studying the starting law of a gas turbine according to claim 7, characterized in that: The amount of natural gas entering must meet the following requirements: the ratio of air and natural gas after mixing is no higher than 2.5%.

10. A method for studying gas turbine startup laws according to claim 8, characterized in that: An ignition nozzle is arranged at a position where the airflow is concentrated and the flow velocity is slow, and the ignition nozzle extends 3 mm beyond the flow stabilizing plate.

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