A natural gas based staged fuel supply system and starting method

Abstract

This invention discloses a staged fuel supply system and starting method based on natural gas, specifically relating to the field of gas turbine technology. The system includes a fuel supply shut-off valve, a fuel filter, an online fuel composition monitoring unit, a metering system, an electric heater, and parallel standby and main fuel branches. The gas turbine electronic controller calculates the fuel activity coefficient based on the fuel composition and presets the ignition flow rate and heating temperature. The starting method includes dry-running, ignition, acceleration, and target state stages: during the ignition stage, the fuel supply pattern is corrected according to the fuel activity coefficient; during the acceleration stage, the main fuel rate is reduced based on vibration spectrum feedforward control; and a backfire treatment is included. This invention can adapt to fuel composition, actively suppress backfire, and improve ignition reliability, operational safety, and component lifespan.

Description

Technical Field

[0001] This invention relates to the field of gas turbine technology, and more specifically, to a staged fuel supply system based on natural gas and a starting method. Background Technology

[0002] Gas turbines are an important power plant with wide applications in distributed power generation, mechanical drive and aviation propulsion. For micro gas turbines that use natural gas or hydrogen as fuel, the fuel supply system is a key component for reliable start-up and stable operation.

[0003] During the start-up process of a gas turbine, the airflow velocity, pressure, and temperature in the combustion chamber are low, resulting in poor fuel-air mixing conditions. Conventional fuel supply systems typically use a single metering device and a single path, which leads to insufficient metering accuracy under low flow conditions during the start-up phase. This makes it difficult to form a suitable mixture concentration field for ignition, often resulting in ignition difficulties, unstable flame propagation, or even deflagration or flameout.

[0004] To address the aforementioned issues, some existing technologies have proposed a staged fuel supply scheme. This involves setting up a standby fuel path and a main fuel path, establishing a standby flame first during the startup phase, and then igniting the main flame. However, the control logic of most existing staged supply systems is based on a preset open-loop plan, which cannot be dynamically corrected according to real-time fluctuations in fuel composition (such as the hydrogen blending ratio of natural gas). Furthermore, for hydrogen or highly hydrogen-blended fuels, the flame propagation speed is fast and the ignition energy is low. Existing technologies lack proactive means to suppress the risk of backfire, posing safety hazards during startup and under low-load conditions.

[0005] In addition, existing start-up control methods mostly use feedback regulation of engine speed or exhaust temperature. When combustion oscillation or backfire tends to occur, the feedback control has a lag and is difficult to intervene in time, which may lead to damage to the combustion chamber or compressor.

[0006] Therefore, how to achieve highly reliable start-up and active safety control of gas turbines under conditions of fluctuating fuel composition and highly reactive fuel is a technical problem that urgently needs to be solved in this field. In view of this, the present invention provides a staged fuel supply system and start-up method based on natural gas. Summary of the Invention

[0007] In order to overcome the above-mentioned defects of the prior art, embodiments of the present invention provide a staged fuel supply system and starting method based on natural gas to solve the problems mentioned in the background art.

[0008] To achieve the above objectives, the present invention provides the following technical solution:

[0009] On one hand, the present invention provides a staged fuel supply system based on natural gas, comprising:

[0010] The fuel supply pipeline, and the fuel gas supply shut-off valve, fuel filter, fuel component online monitoring unit, metering system, fuel gas pressure regulating servo valve, electric heater, and the standby fuel branch and main fuel branch arranged in parallel along the fuel flow direction;

[0011] The duty fuel branch is equipped with a duty fuel gas flow regulating servo valve, which is connected to the duty nozzle located at the head of the combustion chamber.

[0012] The main fuel branch is equipped with a swirler fuel gas flow regulating servo valve, which is connected to a two-stage radial swirler.

[0013] The system also includes a gas turbine electronic controller, which is connected to the fuel component online monitoring unit, metering system, fuel gas pressure regulating servo valve, electric heater, shift fuel gas flow regulating servo valve, cyclone fuel gas flow regulating servo valve, as well as speed sensor, exhaust temperature sensor, compressor inlet total temperature sensor, compressor inlet total pressure sensor, and vibration sensor installed on the gas turbine body.

[0014] The gas turbine electronic controller integrates a dynamic adaptive preset controller, which is used to calculate the fuel activity coefficient based on the fuel component signal detected by the fuel component online monitoring unit, and to preset the fuel flow reference value and the target temperature of the electric heater in the ignition stage before starting based on the fuel activity coefficient.

[0015] It also includes a gas fuel venting solenoid valve, which is installed between the electric heater and the duty fuel branch and the main fuel branch, and is used to vent residual fuel in the pipeline when the system is shut down.

[0016] Preferably, the fuel composition online monitoring unit is used to detect the hydrogen volume percentage and calorific value in the fuel in real time, and send the detection results to the gas turbine electronic controller;

[0017] The fuel activity coefficient is expressed as:

[0018]

[0019] in, , The preset weighting coefficients are used, and the standard natural gas calorific value is the preset baseline calorific value.

[0020] Preferably, the target temperature of the electric heater is dynamically adjusted by the gas turbine electronic controller according to the fuel activity coefficient. When the fuel activity coefficient is higher than a preset threshold, the target temperature is reduced, and when the fuel activity coefficient is lower than the preset threshold, the target temperature is increased.

[0021] On the other hand, the present invention also provides a staged fuel supply start-up method based on natural gas, applied to the above-mentioned system, comprising the following stages:

[0022] Dry drive stage: The gas turbine rotor is driven by an electric starter only, without fuel supply or ignition;

[0023] Ignition stage: After reaching the ignition speed, the reference value of ignition fuel flow and the target temperature of electric heater are preset and corrected according to the fuel activity coefficient, and the standby fuel is supplied according to the corrected ignition fuel supply law to form the standby flame.

[0024] Start-up and acceleration phase: After the standby flame is established stably, standby fuel and main fuel are supplied simultaneously according to the acceleration closed-loop control law, and the vibration signal of the vibration sensor is monitored in real time. When the amplitude of the vibration signal spectrum exceeds the safety threshold at the preset combustion acoustic mode frequency, the gas turbine electronic controller performs feedforward control and instantly reduces the main fuel supply rate.

[0025] Target state stage: After the engine speed reaches the end speed of the start-up acceleration stage, the fuel supply is adjusted according to the flexible speed control law until the target speed is reached.

[0026] Preferably, the ignition fuel supply pattern during the ignition stage is as follows:

[0027]

[0028] in, For ignition fuel flow rate, This is the basic quantity of ignition fuel flow. This is the correction for the total temperature at the compressor inlet. This is the correction for the total pressure at the compressor inlet. This is the total exhaust temperature correction amount. This refers to the total temperature at the compressor inlet. This is the total pressure at the compressor inlet. This refers to the total exhaust temperature.

[0029] Preferably, during the start-up acceleration phase, the acceleration closed-loop control law is expressed as follows:

[0030]

[0031] in, For the gas turbine rotor acceleration, This shows the relationship between acceleration and rotational speed. , , These are the compressor inlet total temperature correction, compressor inlet total pressure correction, and exhaust total temperature correction, respectively.

[0032] Preferably, the feedforward control specifically includes: when the amplitude of the vibration signal spectrum detected by the vibration sensor exceeds the safety threshold in the preset combustion acoustic mode frequency band, the gas turbine electronic controller directly sends a command to the swirler fuel gas flow regulating servo valve to reduce the opening, without waiting for feedback signals of speed or exhaust temperature.

[0033] Preferably, a warm-up phase is provided between the start-up acceleration phase and the target state phase. During the warm-up phase, the gas turbine electronic controller shuts off the ignition device and controls the fuel supply according to the minimum fuel flow limit law, so that the gas turbine is kept at the warm-up speed.

[0034] Preferably, the method further includes a backfire treatment step: when the amplitude of the vibration signal spectrum or the fluctuation rate of the exhaust temperature detected by the vibration sensor exceeds the preset safety limit, the gas turbine electronic controller determines that it is a backfire event, immediately cuts off the fuel supply of the main fuel branch, and maintains the fuel supply of the standby fuel branch, so that the gas turbine enters a degraded operation state.

[0035] Preferably, the flexible speed control law is as follows:

[0036]

[0037]

[0038] in The relative speed of the gas turbine. It is a constant. For speed increments, This is the speed increment coefficient. To control the number of cycles.

[0039] The technical effects and advantages of this invention are as follows:

[0040] 1. This invention sets up an online fuel composition monitoring unit to detect the hydrogen volume percentage and calorific value in the fuel in real time, and introduces the fuel activity coefficient (FAC) to dynamically preset and correct the ignition fuel flow reference value and the electric heater target temperature. When the fuel activity is high, the heating temperature is automatically reduced to suppress the risk of backfire, and when the fuel activity is low, the heating temperature is increased to improve atomization and ignition performance. This adaptively adapts to a wide range of composition changes from pure natural gas to fuels with high hydrogen blending ratios, effectively solving the problems of difficult ignition, unstable flame, or even flameout in traditional staged supply systems under fluctuating fuel composition conditions. The ignition success rate and combustion stability are significantly improved.

[0041] 2. This invention introduces a feedforward control strategy based on vibration sensor spectrum analysis during the start-up and acceleration phase. When the amplitude of the vibration signal spectrum at the preset combustion acoustic mode frequency exceeds the safety threshold, the gas turbine electronic controller directly sends a command to the swirler fuel gas flow regulating servo valve to reduce the opening. It can actively intervene within milliseconds of combustion oscillation or backfire tendency, instantly reducing the main fuel supply rate. At the same time, this invention also has a backfire treatment step. When the vibration spectrum amplitude or exhaust temperature fluctuation rate exceeds the safety limit, the main fuel branch is immediately cut off and the standby fuel branch is maintained, so that the gas turbine enters a degraded operation state, thereby minimizing the risk of backfire damage. It is especially suitable for the safe application of highly reactive fuels such as hydrogen.

[0042] 3. This invention incorporates a warm-up phase and a flexible speed control mechanism during startup. During the warm-up phase, the ignition device is shut off, and fuel supply is controlled according to the minimum fuel flow limit, keeping the gas turbine at a warm-up speed to uniformly heat hot-end components such as the turbine and combustion chamber, reducing thermal stress concentration. The flexible speed control mechanism uses a linear incremental method to adjust the speed, avoiding mechanical shocks caused by sudden speed changes. At the same time, the on-duty flame maintenance mechanism under degraded operation prevents damage to the compressor and combustion chamber from sudden backfire events, significantly reducing the impact load during gas turbine startup and under abnormal operating conditions, and effectively extending the maintenance cycle and service life of hot-end components. Attached Figure Description

[0043] Figure 1 This is a diagram of the overall system framework of the present invention.

[0044] Figure 2 This is a flowchart of the method stages of the present invention.

[0045] The attached diagram is labeled as follows: 1. Fuel supply shut-off valve; 2. Fuel filter; 3. Metering system; 4-5. Fuel gas pressure regulating servo valve; 6. Gas fuel venting solenoid valve; 7. Electric heater; 8-9. Cyclone fuel gas flow regulating servo valve; 10-11. Standby fuel gas flow regulating servo valve; 12. Standby nozzle; 13. Two-stage radial cyclone; 14-15. Gas turbine electronic controller. Detailed Implementation

[0046] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0047] Example 1

[0048] As attached Figure 1As shown, the present invention provides a graded fuel supply system based on natural gas, including a fuel supply pipeline, and a fuel gas supply shut-off valve 1, a fuel filter 2, a fuel component online monitoring unit, a metering system 3, a fuel gas pressure regulating servo valve 4-5, an electric heater 7 arranged sequentially along the fuel flow direction, as well as a duty fuel branch and a main fuel branch arranged in parallel.

[0049] The standby fuel branch is equipped with a standby fuel gas flow regulating servo valve 10-11, which is connected to the standby nozzle 12 located at the head of the combustion chamber. The main fuel branch is equipped with a swirler fuel gas flow regulating servo valve 8-9, which is connected to a two-stage radial swirler 13.

[0050] The system also includes a gas turbine electronic controller 14-15, which is connected to the fuel component online monitoring unit, metering system 3, fuel gas pressure regulating servo valve 4-5, electric heater 7, shift fuel gas flow regulating servo valve 10-11, cyclone fuel gas flow regulating servo valve 8-9, as well as the speed sensor, exhaust temperature sensor, compressor inlet total temperature sensor, compressor inlet total pressure sensor, and vibration sensor installed on the gas turbine body.

[0051] The gas turbine electronic controller 14-15 integrates a dynamic adaptive preset controller, which is used to calculate the fuel activity coefficient based on the fuel component signal detected by the fuel component online monitoring unit, and preset the fuel flow reference value and the target temperature of the electric heater 7 in the ignition stage before starting based on the fuel activity coefficient.

[0052] It also includes a gas fuel venting solenoid valve 6, which is located between the electric heater 7 and the duty fuel branch and the main fuel branch, and is used to vent the residual fuel in the pipeline when the system is shut down.

[0053] In this embodiment, the fuel composition online monitoring unit is used to detect the hydrogen volume percentage and calorific value in the fuel in real time, and send the detection results to the gas turbine electronic controller 14-15;

[0054] The gas turbine electronic controller 14-15 calculates the fuel activity coefficient according to the received hydrogen volume percentage and calorific value using the following formula. :

[0055]

[0056] in, , The standard natural gas calorific value is a preset weighting coefficient, and the standard natural gas calorific value is a preset benchmark calorific value. Through this fuel activity coefficient, the system can quantitatively characterize the current combustion activity of the fuel, providing a basis for the dynamic adjustment of subsequent control parameters.

[0057] In this embodiment, the target temperature of the electric heater 7 is dynamically adjusted by the gas turbine electronic controller 14-15 according to the fuel activity coefficient. Specifically, when the fuel activity coefficient is higher than the preset threshold, it indicates that the fuel activity is high, such as a large proportion of hydrogen blending. At this time, the target temperature of the electric heater 7 is reduced to reduce the risk of backfire. When the fuel activity coefficient is lower than the preset threshold, it indicates that the fuel activity is low, such as high purity of natural gas or low calorific value. At this time, the target temperature of the electric heater 7 is increased to improve the fuel atomization and ignition performance.

[0058] Example 2

[0059] As attached Figure 2 As shown, the present invention also provides a staged fuel supply start-up method based on natural gas, applied to the above-mentioned staged fuel supply system based on natural gas, including a dry-running stage, an ignition stage, a start-up acceleration stage, and a target state stage.

[0060] During the dry-running stage, the gas turbine rotor is driven by only the electric starter, without fuel supply or ignition. This stage is used to establish the initial speed and create conditions for subsequent ignition.

[0061] After reaching the ignition speed, the gas turbine electronic controller 14-15 makes a preset correction to the ignition fuel flow reference value and the target temperature of the electric heater 7 according to the fuel activity coefficient, and supplies the standby fuel according to the corrected ignition fuel supply law to form the standby flame.

[0062] The ignition fuel supply pattern during the ignition phase is as follows:

[0063]

[0064] in, For ignition fuel flow rate, This is the basic quantity of ignition fuel flow. This is the correction for the total temperature at the compressor inlet. This is the correction for the total pressure at the compressor inlet. This is the total exhaust temperature correction amount. This refers to the total temperature at the compressor inlet. This is the total pressure at the compressor inlet. Total exhaust temperature;

[0065] This principle scales the entire mixture based on the fuel activity coefficient, while also adjusting for ambient temperature, pressure, and exhaust temperature to ensure that a suitable ignition mixture concentration can be achieved under different operating conditions.

[0066] After the standby flame is established stably, the gas turbine electronic controller 14-15 supplies standby fuel and main fuel simultaneously according to the acceleration closed-loop control law, and monitors the vibration signal of the vibration sensor in real time. When the amplitude of the vibration signal exceeds the safety threshold at the preset combustion acoustic mode frequency, the gas turbine electronic controller 14-15 performs feedforward control and instantly reduces the main fuel supply rate.

[0067] The acceleration closed-loop control law is as follows:

[0068]

[0069] in, For the gas turbine rotor acceleration, This shows the relationship between acceleration and rotational speed. , , These are the compressor inlet total temperature correction, compressor inlet total pressure correction, and exhaust total temperature correction, respectively.

[0070] Specifically, the feedforward control is as follows: when the amplitude of the vibration signal spectrum detected by the vibration sensor exceeds the safety threshold in the preset combustion acoustic mode frequency band, the gas turbine electronic controller 14-15 directly sends a command to the cyclone fuel gas flow regulating servo valve 8-9 to reduce the opening, without waiting for the speed or exhaust temperature feedback signal. This feedforward control can intervene at the initial stage of combustion oscillation or backfire tendency, which significantly improves the operational safety.

[0071] Between the start-up acceleration phase and the target state phase, there is also a warm-up phase. During the warm-up phase, the gas turbine electronic controller 14-15 shuts off the ignition device and controls the fuel supply according to the minimum fuel flow limit law, so that the gas turbine is kept at the warm-up speed to evenly heat the hot end components and reduce thermal stress impact.

[0072] After the engine speed reaches the end speed of the starting acceleration phase, the gas turbine electronic controller 14-15 adjusts the fuel supply according to the flexible speed control law until the target speed is reached.

[0073] The flexible speed control principle is as follows:

[0074]

[0075]

[0076] in The relative speed of the gas turbine. It is a constant. For speed increments, This is the speed increment coefficient. To control the number of cycles;

[0077] Through this flexible control law, the rotational speed increases smoothly in a linear increment, avoiding mechanical and thermal shocks caused by sudden changes in rotational speed.

[0078] The starting fuel supply method of the present invention also includes a backfire treatment step. When the amplitude of the vibration signal spectrum or the fluctuation rate of the exhaust temperature detected by the vibration sensor exceeds the preset safety limit, the gas turbine electronic controller 14-15 determines that a backfire event has occurred, immediately cuts off the fuel supply of the main fuel branch, and maintains the fuel supply of the standby fuel branch, so that the gas turbine enters a degraded operation state. This degraded operation state can prevent backfire from damaging the compressor and combustion chamber, while keeping the gas turbine operating in a safe state, which is convenient for subsequent handling by the operator.

[0079] The parameters in the aforementioned starting fuel supply pattern and control logic are configured through the FLASH parameter table in the control application software within the gas turbine electronic controller 14-15. The FLASH parameters support online and offline modification, as well as local and remote modification. Permitted start-related parameters include: cold start time, purging time, ignition speed, initial fuel supply speed, flame detector current threshold, ignition exhaust temperature criterion value, unignition time allowable value, ignition phase end speed, electric starter disengagement speed, warm-up speed, warm-up time, start-up acceleration phase end speed, and target speed. Parameter modification employs dual password verification; modification is only permitted after both passwords are correct. After modification, confirmation and saving are required, and the system automatically generates a new version number to ensure the security and traceability of parameter configuration.

[0080] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A staged fuel supply system based on natural gas, characterized in that: include: The fuel supply pipeline, and the fuel gas supply shut-off valve (1), fuel filter (2), fuel component online monitoring unit, metering system (3), fuel gas pressure regulating servo valve (4-5), electric heater (7) arranged in sequence along the fuel flow direction, as well as the duty fuel branch and the main fuel branch arranged in parallel; The duty fuel branch is equipped with a duty fuel gas flow regulating servo valve (10-11) and is connected to the duty nozzle (12) located at the head of the combustion chamber. The main fuel branch is equipped with a swirler fuel gas flow regulating servo valve (8-9) and is connected to a two-stage radial swirler (13). The system also includes a gas turbine electronic controller (14-15), which is connected to the fuel component online monitoring unit, the metering system (3), the fuel gas pressure regulating servo valve (4-5), the electric heater (7), the duty fuel gas flow regulating servo valve (10-11), the cyclone fuel gas flow regulating servo valve (8-9), and the speed sensor, exhaust temperature sensor, compressor inlet total temperature sensor, compressor inlet total pressure sensor, and vibration sensor installed on the gas turbine body. The gas turbine electronic controller (14-15) integrates a dynamic adaptive preset controller, which is used to calculate the fuel activity coefficient based on the fuel component signal detected by the fuel component online monitoring unit, and to preset the fuel flow reference value and the target temperature of the electric heater (7) in the ignition stage before starting based on the fuel activity coefficient. It also includes a gas fuel venting solenoid valve (6), which is located between the electric heater (7) and the duty fuel branch and the main fuel branch, and is used to vent the residual fuel in the pipeline when the system is shut down.

2. The staged fuel supply system based on natural gas according to claim 1, characterized in that: The fuel composition online monitoring unit is used to detect the hydrogen volume percentage and calorific value in the fuel in real time, and send the detection results to the gas turbine electronic controller (14-15). The fuel activity coefficient is expressed as: in, , The preset weighting coefficients are used, and the standard natural gas calorific value is the preset baseline calorific value.

3. The staged fuel supply system based on natural gas according to claim 1, characterized in that: The target temperature of the electric heater (7) is dynamically adjusted by the gas turbine electronic controller (14-15) according to the fuel activity coefficient. When the fuel activity coefficient is higher than the preset threshold, the target temperature is reduced, and when the fuel activity coefficient is lower than the preset threshold, the target temperature is increased.

4. A staged fuel supply start-up method based on natural gas, applied to the system described in any one of claims 1-3, characterized in that: Includes the following stages: Dry drive stage: The gas turbine rotor is driven by an electric starter only, without fuel supply or ignition; Ignition stage: After reaching the ignition speed, the reference value of ignition fuel flow rate and the target temperature of electric heater (7) are preset and corrected according to the fuel activity coefficient, and the duty fuel is supplied according to the corrected ignition fuel supply law to form the duty flame; Start-up acceleration phase: After the standby flame is established stably, standby fuel and main fuel are supplied simultaneously according to the acceleration closed-loop control law, and the vibration signal of the vibration sensor is monitored in real time. When the amplitude of the vibration signal spectrum exceeds the safety threshold at the preset combustion acoustic mode frequency, the gas turbine electronic controller (14-15) performs feedforward control to instantly reduce the main fuel supply rate. Target state stage: After the engine speed reaches the end speed of the start-up acceleration stage, the fuel supply is adjusted according to the flexible speed control law until the target speed is reached.

5. The staged fuel supply start-up method based on natural gas according to claim 4, characterized in that: The ignition fuel supply pattern during the ignition phase is as follows: in, For ignition fuel flow rate, This is the basic quantity of ignition fuel flow. This is the correction for the total temperature at the compressor inlet. This is the correction for the total pressure at the compressor inlet. This is the total exhaust temperature correction amount. This refers to the total temperature at the compressor inlet. This is the total pressure at the compressor inlet. This refers to the total exhaust temperature.

6. The staged fuel supply start-up method based on natural gas according to claim 4, characterized in that: During the start-up acceleration phase, the acceleration closed-loop control law is expressed as follows: in, For the gas turbine rotor acceleration, This shows the relationship between acceleration and rotational speed. , , These are the compressor inlet total temperature correction, compressor inlet total pressure correction, and exhaust total temperature correction, respectively.

7. The staged fuel supply start-up method based on natural gas according to claim 4, characterized in that: The feedforward control specifically includes: when the amplitude of the vibration signal spectrum detected by the vibration sensor exceeds the safety threshold in the preset combustion acoustic mode frequency band, the gas turbine electronic controller (14-15) directly sends a command to the cyclone fuel gas flow regulating servo valve (8-9) to reduce the opening, without waiting for the speed or exhaust temperature feedback signal.

8. The staged fuel supply start-up method based on natural gas according to claim 4, characterized in that: Between the start-up acceleration phase and the target state phase, there is also a warm-up phase. During the warm-up phase, the gas turbine electronic controller (14-15) shuts off the ignition device and controls the fuel supply according to the minimum fuel flow limit law, so that the gas turbine is kept at the warm-up speed.

9. The staged fuel supply start-up method based on natural gas according to claim 4, characterized in that: It also includes a backfire handling step: when the amplitude of the vibration signal spectrum or the fluctuation rate of the exhaust temperature detected by the vibration sensor exceeds the preset safety limit, the gas turbine electronic controller (14-15) judges it as a backfire event, immediately cuts off the fuel supply of the main fuel branch, and maintains the fuel supply of the standby fuel branch, so that the gas turbine enters a degraded operation state.

10. The staged fuel supply start-up method based on natural gas according to claim 4, characterized in that: The flexible speed control law is as follows: in The relative speed of the gas turbine. It is a constant. For speed increments, This is the speed increment coefficient. To control the number of cycles.

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