Gas turbine exhaust temperature active cooling system based on electrically-driven gas compressor load

Abstract

The invention discloses a gas turbine exhaust temperature active cooling system based on an electrically-driven gas compressor load. According to the system, 0.7-0.8 MPa compressed air is used as a cooling air source of an air storage tank at the rear end of an electrically-driven air compressor, is fed into an exhaust mixing pipe of a cross-shaped and rotational flow guide composite structure through an exhaust cooling pipeline and an exhaust cooling adjusting valve, and is mixed with exhaust in an exhaust cooling injection pipe. The exhaust temperature is controlled to be less than or equal to 100 DEG C through inclined flow guide holes of an annular flow guide ring, induction of rotational flow of a piezoelectric ceramic actuator, self-adaptive adjustment of variable-aperture mixing holes with dense front parts and sparse rear parts and shape memory alloy, and matching with a mixed prediction-feedback control model. Waste heat is recovered through the heat pipe heat exchanger, and the energy efficiency is improved. The problem that the exhaust temperature of the micro gas turbine test bed is too high is solved, precise cooling control is achieved, and the advantages of being high in mixing efficiency, high in load adaptability, low in energy consumption and the like are achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of gas turbine cooling, and in particular to a gas turbine exhaust temperature active cooling system based on an electric drive compressor load and a method for achieving precise control of the exhaust temperature. Background Art

[0002] During the operation of the micro-turbine test bench, when the electric-driven compressor is used as the load, the high exhaust temperature of the gas turbine is a pressing issue that needs to be addressed. Excessive exhaust temperature not only damages the downstream equipment, affecting its service life and stability, but can also lead to a decrease in the operating efficiency of the entire system.

[0003] Existing gas turbine exhaust cooling systems have numerous shortcomings. Traditional cooling systems often employ simple mixing structures, such as straight mixing tubes. This results in inefficient mixing of cooling air and hot gas, leading to poor exhaust temperature control accuracy and difficulty maintaining stable exhaust temperature within the ideal range during load fluctuations. For example, within the load range of 50%-100%, the exhaust temperature of traditional systems fluctuates widely, failing to meet the requirement of ≤100°C.

[0004] Furthermore, traditional systems rely on manual adjustment, which not only increases operator workload but also prevents precise real-time adjustments based on changes in gas turbine load. At low loads (e.g., less than 30%), temperature control response times are long and cooling efficiency is poor, seriously impacting system reliability and economic efficiency.

[0005] In addition, some existing cooling systems lack adaptive adjustment capabilities in their structural design and are unable to automatically adjust the flow distribution of cooling air according to changes in load and temperature. Under high load, insufficient cooling air flow may occur, while under low load, excessive cooling air flow may occur, causing the exhaust temperature to be too low, affecting the normal operation of the gas turbine.

[0006] In summary, the existing technology lacks an exhaust cooling system that can dynamically and adaptively adjust based on gas turbine load and exhaust temperature, achieve efficient mixed cooling, precisely control exhaust temperature within a low range, and simultaneously offer high reliability and low energy consumption. Therefore, developing an active gas turbine exhaust temperature cooling system based on the load of an electric-driven compressor has important practical significance and application value. Summary of the Invention

[0007] The present invention aims to provide a gas turbine exhaust temperature active cooling system based on an electric drive compressor. By utilizing the 0.7-0.8MPa compressed air in the air storage tank behind the electric drive compressor as the cooling air source, after the gas turbine is ignited, the compressed air is supplied to the exhaust mixing pipe through the exhaust cooling pipe and the exhaust temperature regulating valve, and mixed with the exhaust gas flowing into the exhaust cooling ejector pipe from the gas turbine exhaust port, thereby controlling the exhaust temperature to below 100°C, solving the problem of excessively high exhaust temperature when the micro gas turbine test bench is loaded with an electric drive compressor, and realizing active cooling and regulation of the exhaust temperature.

[0008] 1. Device composition

[0009] The gas turbine exhaust temperature active cooling system based on an electric drive compressor of the present invention is composed of multiple functional modules, specifically including:

[0010] (1) Cooling air source module: The air storage tank at the rear end of the electric compressor can stably provide 0.7-0.8 MPa of compressed air, and is equipped with a pressure sensor to monitor the pressure in the tank in real time;

[0011] (2) Pipeline and regulation module: The air storage tank and the exhaust mixing pipe are connected through the exhaust cooling air pipeline, and an exhaust cooling regulating valve is installed on the exhaust cooling air pipeline to accurately control the flow rate of cooling air;

[0012] (3) Mixing cooling module: It consists of exhaust cooling ejector pipe and exhaust mixing pipe.

[0013] The exhaust mixing pipe adopts a "cross-shaped + swirl flow guide" composite structure, as follows:

[0014] 1. Composite flow channel design: The cross-tube of the exhaust mixing pipe is composed of a high-temperature resistant alloy tube with a cross-shaped structure. The four-end extension sections all adopt a gradually expanding trumpet shape (expansion angle of 15°-20°) to expand the coverage of the cooling air injection; an annular guide ring is added at the center of the cross, and a 45° oblique guide hole is opened on the ring wall to guide the cooling air to form a swirl mixing field. The cross-tube and the annular guide ring of the exhaust mixing pipe are integrally formed with a high-temperature resistant alloy. A piezoelectric ceramic actuator array is installed on the outside of the annular guide ring, and a pulsed airflow is injected into the oblique guide hole through a high-frequency vibration of 1-5kHz, so that it is coupled with the gas flow rate (Strouhal number St≈0.2), thereby inducing the formation of a Karman vortex street and enhancing the turbulence intensity.

[0015] 2. Variable aperture mixing hole layout: along the exhaust flow direction (axial direction), a "dense front and sparse back" aperture distribution is adopted. Dense mixing holes of Φ3-Φ5mm (hole spacing 10-15mm) are opened at the front end (exhaust inlet side), and sparse mixing holes of Φ8-Φ10mm (hole spacing 25-30mm) are opened at the rear end.

[0016] 3. Adaptive variable aperture structure: Shape memory alloy (SMA) is used to make the edge of the mixing hole. When the exhaust temperature exceeds 80°C, the alloy expands due to heat, causing the mixing hole diameter to automatically increase by 1-2mm, thereby achieving dynamic adaptive adjustment of the mixing hole diameter with temperature. For example, the dense mixing holes of Φ3-Φ5mm at the front end can be expanded to Φ4-Φ6mm at high temperatures, and the sparse mixing holes of Φ8-Φ10mm at the rear end can be expanded to Φ9-Φ11mm. At the same time, a ring-shaped heating wire array is embedded in the outer wall of the cross-tube of the exhaust mixing pipe. The PLC is used to trigger the expansion of the mixing hole diameter according to the real-time monitored exhaust temperature (50-120°C), thereby achieving adaptive adjustment of the mixing hole diameter.

[0017] Exhaust cooling ejector: It is a gradually diverging nozzle connected to the exhaust mixing pipe through a flange. Its inlet is aligned with the exhaust port of the gas turbine, and its outlet is connected to the back-end equipment to achieve sufficient mixing of the exhaust gas and compressed air.

[0018] (4) Control system: The upper control system adopts PLC and is equipped with an industrial computer. It is connected to pressure sensors, temperature sensors, flow sensors, etc. through 4-20mA signals to collect relevant data in real time, and calculate and control the opening of the exhaust temperature regulating valve according to the gas turbine load.

[0019] The control strategy of the control system is as follows:

[0020] Hybrid prediction-feedback control model: The feedforward channel calculates the initial opening V of the exhaust cooling control valve based on formula (7) P0 , the feedback channel introduces temperature deviation ΔT(=T out -100℃), the opening ΔV is dynamically corrected by the fuzzy PID algorithm (using the triangle membership function) P , the final exhaust cooling regulating valve opening V P =V P0 +K P ΔT+K i ∫ΔTdt(where K P , K i Online adjustment by the fuzzy rule base) to achieve more precise control.

[0021] Mixing efficiency monitoring module: An infrared thermal imager (sampling rate 60Hz) is placed at the outlet of the exhaust cooling ejector. The mixing unevenness index η is calculated using a temperature field reconstruction algorithm. When η exceeds a threshold, the piezoelectric ceramic actuator power or SMA aperture is automatically adjusted to ensure the mixing effect.

[0022] (5) Waste heat cascade utilization module:

[0023] Install a compact heat pipe heat exchanger at the outlet of the exhaust cooling ejector to recover the waste heat of the mixed gas (80–100°C):

[0024] 1. Primary heat exchange: preheating the gas turbine intake air (improving combustion efficiency);

[0025] 2. Secondary heat exchange: drives the absorption chiller to provide cooling for the control cabinet.

[0026] 2. Working Principle

[0027] When the gas turbine is ignited, 0.7-0.8MPa compressed air enters the exhaust mixing pipe through the exhaust cooling regulating valve, and is mixed with the exhaust gas in the exhaust cooling ejector pipe through the "cross-shaped + swirl guide" structure. Among them, the oblique guide holes of the annular guide ring make the cooling air form an axial swirl with a swirl number of 0.3-0.5, forming a three-dimensional turbulent flow field with the radial flow of the exhaust, thereby enhancing the mixing efficiency; the piezoelectric ceramic actuator induces the formation of a vortex street through high-frequency vibration. Under the condition of the same cooling air volume, the mixing efficiency is increased by 25%, thereby increasing the cooling air flow Q m,air2 The variable diameter mixing hole layout makes the front dense mixing holes at high load (P load >80%), the critical flow is opened first, and the sparse mixing hole at the rear end supplements the flow at low load, realizing adaptive flow regulation. When the exhaust temperature rises, the heating wire heats the SMA alloy to increase the diameter of the mixing hole, realizing self-optimization of the flow distribution with temperature. load When the temperature fluctuates by ±20%, the mixing uniformity is improved by 35% (the temperature standard deviation is reduced from ±5°C to ±2°C), which effectively improves the mixing effect.

[0028] The hybrid prediction-feedback control model quickly responds to load changes through feedforward prediction. The feedback channel uses fuzzy PID to correct temperature deviations in real time, improving control accuracy from ±5°C to ±1.5°C and tripling the load disturbance resistance capability. The infrared thermal imager of the mixing efficiency monitoring module monitors mixing uniformity in real time, achieving a 100% elimination rate of high-temperature hotspots and ensuring stable operation of the system.

[0029] The system establishes a mathematical model based on the energy conservation equation (1), mass conservation equation (2) and the gas injection air coefficient (0.05), and derives the mixed cooling air flow rate Q m,air2 and gas turbine load P load Functional relationship.

[0030] The flow balance of the system is shown as follows Figure 2 shown

[0031] Then, according to the energy conservation equation (1):

[0032] Q m,gas ·h gas +Q m,air1 ·hair1 +Q m,air2 ·h air2 =Q m,out ·h out (1)

[0033] According to the mass conservation equation (2):

[0034] Q m,out =Q m,gas +Q m,air1 +Q m,air2 (2)

[0035] At the same time, take the gas injection air coefficient as 0.05, then

[0036] Q m,air1 =0.05Q m,hout (3)

[0037] From the above equation, we can obtain:

[0038]

[0039] In the above formula, h gas The gas turbine exhaust temperature T gas , exhaust pressure P gas Calculate, where temperature and pressure are load P load The function is obtained by calibrating the gas turbine characteristics;

[0040] Q m,gas is the gas turbine exhaust flow rate, is the load P load function;

[0041] h air1 is the specific enthalpy of air at room temperature, unit is kJ / kg;

[0042] h air2 is the specific enthalpy of air at room temperature and pressure of 0.7 MPa, in kJ / kg;

[0043] h out It is the specific enthalpy of the mixed gas at a temperature of 50°C and a pressure of 0.101325 MPa, in kj / kg.

[0044] Then, according to equation (4) and the relationship between the enthalpy values ​​of the main parameters, the mixed cooling air flow rate Q m,air2 Only the gas turbine load P load The function is:

[0045] Q m,air2 =f(P load )(5)

[0046] Combined with the exhaust cooling control valve flow calculation formula (considering parameters such as the specific heat ratio coefficient of 1.4 and the valve pressure difference ratio coefficient of 0.75), the exhaust cooling control valve real-time K v The value determines the exhaust cooling regulating valve opening V P The upper control system controls the automatic exhaust cooling adjustment valve opening to ensure that the exhaust temperature is ≤100℃.

[0047] According to the relationship between the exhaust cooling regulating valve flow and pressure, the exhaust cooling regulating valve works in the critical flow state. According to the expansion coefficient method of the regulating valve flow, the relationship between the exhaust cooling valve flow and opening satisfies:

[0048]

[0049] Where, F γ is the specific heat ratio coefficient, take 1.4; X T K is the valve pressure difference ratio coefficient, which is 0.75; v is the flow coefficient of the valve at different openings, which is obtained from the valve flow coefficient curve and the opening. P1 is the pressure before the valve, which is the gas tank pressure, i.e. 7 bar, and ρ1 is the air density in the gas tank.

[0050] Substituting (5) into (6), we can obtain the real-time K of the valve: v The demand value can be further calculated from the flow characteristic curve of the valve to obtain the real-time exhaust cooling control valve opening V P value:

[0051]

[0052] Formula (7) is written into the upper control system, and a hybrid prediction-feedback control model is used to achieve more accurate control of the valve opening.

[0053] 3. Working Process

[0054] (1) Startup initialization phase:

[0055] The upper system initializes the exhaust cooling control valve and sets its opening to 5%. This ensures that cooling air can slowly flow into the exhaust mixing pipe when the gas turbine is ignited, avoiding impact on the system. At the same time, the SMA alloy orifice plate maintains its initial aperture and the piezoelectric ceramic actuator is in standby mode.

[0056] (2) Cooling gas supply stage:

[0057] When the gas turbine is successfully ignited, the upper control system receives the ignition signal and immediately issues a command to gradually increase the opening of the exhaust cooling regulating valve to 30%. At this time, the compressed air flows from the gas storage tank through the exhaust cooling air pipe and the exhaust cooling regulating valve into the exhaust mixing pipe, and is ejected in different areas through the variable aperture mixing holes: the cooling air flow ejected from the dense mixing holes at the front end is large, which performs preliminary cooling of the high-temperature fuel gas; the cooling air flow ejected from the sparse mixing holes at the rear end is small, which further evenly cools the fuel gas.

[0058] (3) Hierarchical mixing and swirl intensification stage:

[0059] The exhaust gas flows from the exhaust port into the exhaust cooling ejector pipe, and forms a hierarchical mixing mode of "low-speed premixing at the front end and high-speed uniform mixing at the end" with the cooling air ejected from the exhaust mixing pipe. At the same time, the annular guide ring guides the cooling air to form a swirl, forming a three-dimensional turbulent flow field with the exhaust gas, increasing the contact area and improving the mixing efficiency. When the exhaust temperature T gas At temperatures above 80°C, the heating wire begins to heat the SMA orifice. As the temperature rises, the aperture gradually expands, dynamically adjusting the flow distribution to adapt to varying temperature conditions. The piezoelectric ceramic actuator activates high-frequency vibration (e.g., 3kHz), injecting pulsed airflow into the oblique guide holes, inducing the formation of a swirling flow field, enhancing turbulence intensity, and further improving mixing efficiency.

[0060] (4) Dynamic load matching stage:

[0061] The control system collects the gas turbine load P in real time load The required cooling air flow is calculated by the energy and mass conservation equations, and the exhaust cooling control valve opening V is solved by combining the exhaust cooling control valve flow model. P , automatically adjust the opening of the exhaust cooling regulating valve to achieve dynamic matching of cooling air volume and load.

[0062] P load =80% as an example: the feedforward channel is calculated according to formula (7) to obtain V P0 =60%, if the feedback channel detects T out =102℃, then ΔT=2℃, and ΔV is calculated by fuzzy PID. P =5%, final opening V P =65%, enabling precise adjustment of the exhaust cooling control valve opening to match the current load demand. If the infrared thermal imager detects that η exceeds a threshold (e.g., 0.3), the piezoelectric ceramic actuator power is automatically increased by 15% or the SMA pore size distribution is adjusted to ensure uniform mixing.

[0063] (5) Temperature stability control:

[0064] The exhaust mixing pipe is designed to form a uniform temperature field in the exhaust cooling ejector through the above series of designs, and finally the exhaust temperature is controlled below 100℃ (at P load =50%-100%), the system enters a stable operation state.

[0065] (6) Energy efficiency optimization stage:

[0066] When the exhaust gas from the exhaust cooling ejector outlet passes through the waste heat cascade utilization module, the compact heat pipe heat exchanger recovers 80-100°C waste heat. The first stage of heat exchange is used to preheat the gas turbine intake air to improve combustion efficiency; the second stage of heat exchange is used to drive the absorption chiller to provide cooling for the control cabinet. In this way, the system's net energy consumption is reduced, the overall energy utilization rate is improved, and energy efficiency is optimized.

[0067] 4. Beneficial Effects

[0068] Cooling efficiency is significantly improved: swirl mixing and variable aperture design improve the exhaust temperature control accuracy to ±5℃, load =50%-100% range can be stable ≤100℃, which can more effectively protect the back-end equipment.

[0069] Enhanced load adaptability: The application of adaptive variable aperture and active swirl enhancement technology makes the present invention more load =No static error adjustment can be achieved within the range of 20%-100%, and good cooling effect can be maintained under different working conditions.

[0070] Improved structural reliability: The cross pipe and annular guide ring of the exhaust mixing pipe are made of high-temperature resistant alloy and are integrally formed. Finite element analysis shows that the structural stress concentration factor is reduced and the fatigue life is improved, meeting the continuous operation requirements of the test bench. The simple structure also facilitates maintenance and repair.

[0071] Energy consumption reduction: load =100%, Q m,air2 The reduction reduces the gas source energy consumption and improves the economy of the system of the present invention.

[0072] The intelligence level and maintainability are significantly improved: the realization of the online monitoring function of mixing efficiency ensures 100% elimination of high-temperature hotspots, extends the system life, reduces maintenance costs, reduces the workload of manual maintenance, and improves the intelligence level and maintainability of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0073] Figure 1 It is a schematic diagram of the composition of the present invention.

[0074] Figure 2 This is a schematic diagram of the flow balance structure of the present invention.

[0075] Figure 3 This is a schematic diagram of the exhaust mixing pipe structure of the present invention.

[0076] Figure 4 This is a schematic diagram of the layout of the variable pore size mixing holes of the present invention.

[0077] Reference numerals: 1 - turboshaft gas turbine 2 - starting air solenoid valve 3 - starting air duct 4 - electric drive compressor 5 - air storage tank 6 - exhaust cooling air duct 7 - exhaust cooling regulating valve 8 - exhaust cooling ejector 9 - exhaust mixing pipe 10 - compact heat pipe heat exchanger 901 - cross pipe of exhaust mixing pipe 902 - annular guide ring 903 - oblique guide hole 904 - dense mixing hole 905 - sparse mixing hole DETAILED DESCRIPTION

[0078] The following examples further illustrate the technical solution of the gas turbine exhaust temperature active cooling system based on the electric drive compressor load of the present invention.

[0079] 1. Implementation

[0080] (1) Device composition and connection relationship

[0081] 1. Cooling air source module

[0082] A 5m3 volume is installed at the rear end of the electric drive compressor 4. 3 The gas tank 5 uses a pressure sensor to monitor the pressure in the tank in real time, ensuring that it is maintained stably within the range of 0.7-0.8 MPa. The gas outlet of the gas tank 5 is connected to the exhaust cooling air duct 6 via a flange. The flange sealing surface adopts a concave and convex surface to ensure airtightness.

[0083] 2. Piping and regulation module

[0084] The exhaust cooling air duct 6 is constructed of 20# seamless steel pipe, Ø89mm x 4mm, with a total length of 15m. A pneumatic diaphragm exhaust cooling regulating valve 7 (model: ZJHM-16C) with a nominal diameter of DN80, a nominal pressure of 1.6MPa, and an equal percentage flow characteristic is installed on the duct. The valve is secured to the C30 concrete foundation via a bracket.

[0085] 3. Mixing cooling module

[0086] (1) Exhaust mixing pipe

[0087] 1. Composite Flow Channel Design: The exhaust mixing tube 9 utilizes a composite "cross-shaped + swirl flow guide" structure. The cross-shaped tube 901 is constructed from four 108mm x 5mm Φ Inconel 718 high-temperature alloy tubes welded together in a cross pattern. The four end extensions are machined into a gradually expanding bell-shaped design with an 18° expansion angle. An annular guide ring 902 with an inner diameter of 80mm and an outer diameter of 120mm is welded to the center of the cross-shaped tube. The ring wall is uniformly provided with 45° oblique flow guide holes 903 with an aperture diameter of 8mm and a spacing of 10mm. A piezoelectric ceramic actuator array operating at a frequency of 3kHz is mounted on the outside of the annular guide ring 902. This high-frequency vibration injects pulsed airflow into the oblique flow guide holes, inducing the formation of a Karman vortex street.

[0088] 2. Variable aperture mixing hole layout: A "dense front and sparse back" aperture distribution is adopted along the exhaust flow direction (axial direction): dense mixing holes 904 of Φ4 mm are opened within a circumferential length of 150 mm at the front end (exhaust inlet side), with a hole spacing of 12 mm; sparse mixing holes 905 of Φ9 mm are opened within a circumferential length of 150 mm at the rear end, with a hole spacing of 28 mm.

[0089] 3 Adaptive variable aperture structure: The edge of the mixing hole is made of Ti-Ni shape memory alloy, and the outer wall of the cross pipe 901 of the exhaust mixing pipe is embedded with a ring heating wire array (power density 50W / m 2 ), triggering the SMA pore expansion according to the real-time monitored exhaust temperature (50-120°C) through PLC.

[0090] (2) Exhaust cooling ejector

[0091] The exhaust cooling ejector pipe 8 is constructed of 20# seamless steel pipe, 2000mm long, and is connected to the exhaust mixing pipe 9 via a flange, with a spiral wound gasket installed between the flanges. The inlet of the exhaust cooling ejector pipe 8 is aligned with the gas turbine exhaust port, and the outlet is connected to the back-end equipment.

[0092] 4. Control system

[0093] The upper control system uses an industrial control computer and PLC, which connect to pressure sensors, temperature sensors, and flow sensors via 4-20mA current signals to collect data in real time. The PLC controls the opening of the exhaust cooling control valve 7 by outputting a 4-20mA current signal.

[0094] The control system is equipped with an infrared thermal imager (sampling rate 60 Hz), which is installed at the outlet of the exhaust cooling ejector 8 to monitor the mixing unevenness index η.

[0095] 5. Waste heat cascade utilization module

[0096] Install a compact heat pipe heat exchanger 10 (heat exchange area 10m2) at the outlet of the exhaust cooling ejector 8. 2), the first stage heat exchange is used to preheat the intake air of gas turbine 1, and the second stage heat exchange drives the lithium bromide absorption refrigerator (cooling capacity 5kW) to provide cooling for the control cabinet.

[0097] (2) Work process

[0098] 1. Start the initialization phase

[0099] Thirty minutes before ignition of gas turbine 1, the electrically driven compressor 4 is started to charge the gas storage tank 5, raising the pressure within the tank to 0.75 MPa. The upper control system initializes the exhaust cooling control valve 7, setting the opening to 5%. The SMA alloy orifice plate maintains its initial aperture, and the piezoelectric ceramic actuator is in standby mode.

[0100] 2. Cooling air supply stage

[0101] After successful ignition of gas turbine 1, the upper control system receives the ignition signal and gradually increases the opening of exhaust cooling control valve 7 to 30%. Compressed air enters exhaust mixing pipe 9 through exhaust cooling air duct 6 and exhaust cooling control valve 7. It is ejected in different regions through variable-diameter mixing holes: 4mm dense mixing holes 904 at the front end eject a large flow of cooling air for preliminary cooling of the high-temperature exhaust; 9mm sparse mixing holes 905 at the rear end eject a smaller flow of cooling air for further uniform cooling of the exhaust.

[0102] 3.Layered mixing and swirl intensification stage

[0103] The exhaust gas flows from the exhaust port of the gas turbine 1 into the exhaust cooling ejector 8 at a speed of 30 m / s and a temperature of 600°C, and forms a hierarchical mixing mode of "low-speed premixing at the front end - high-speed uniform mixing at the end" with the cooling air ejected from the exhaust mixing pipe 9 (temperature 25°C, flow rate 50 kg / h).

[0104] When the exhaust temperature T gas When the temperature is ≥80℃, the electric heating wire heats the SMA orifice plate, and the diameter of the mixing holes gradually expands as the temperature rises (for example, when the temperature reaches 100℃, the diameter of the front dense mixing holes 904 expands to Φ5mm, and the diameter of the rear dense mixing holes 905 expands to Φ10mm), dynamically adjusting the flow distribution.

[0105] The piezoelectric ceramic actuator starts high-frequency vibration (3kHz) and injects pulsed airflow into the oblique guide hole 903, inducing the formation of a swirl field, increasing the swirl number to 0.4, enhancing the turbulence intensity, and improving the mixing efficiency.

[0106] 4. Dynamic load matching stage

[0107] When the gas turbine 1 load P load =80%:

[0108] The feedforward channel calculates the initial exhaust cooling regulating valve opening V according to formula (7) P0 =60%, if the feedback channel detects T out =102℃, then ΔT=2℃, and ΔV is calculated by fuzzy PID algorithm. P =5%, final opening V P If the infrared thermal imager detects that η=0.35 (exceeding the threshold value of 0.3), the power of the piezoelectric ceramic actuator is automatically increased by 15% until η≤0.3.

[0109] 5. Temperature stabilization control stage

[0110] After the above process, the mixed airflow forms a uniform temperature field in the exhaust cooling ejector pipe 8, the exhaust temperature is controlled at 95°C, meeting the requirement of ≤100°C, and the system enters a stable operation state.

[0111] 6. Energy efficiency optimization stage

[0112] The exhaust gas at the outlet of the exhaust cooling ejector 8 is recycled through the compact heat pipe heat exchanger 10 at 80-100°C:

[0113] The first stage heat exchange preheats the inlet temperature of gas turbine 1 from 25°C to 40°C, improving the combustion efficiency by 3%.

[0114] The secondary heat exchange drives the absorption chiller to provide cooling air at 7°C for the control cabinet, and the temperature inside the control cabinet is maintained at 25±2°C.

[0115] 2. Comparative Example (1) Comparative Example 1: Traditional Gas Turbine Exhaust Cooling System

[0116] 1. Device composition

[0117] Compared to the examples, the conventional system primarily consists of a conventional air compressor (exhaust pressure 0.5 MPa), piping, a manual regulating valve, and a simple straight mixing tube. The mixing tube lacks a swirl flow guide, a variable-aperture mixing hole layout, or a backpressure compensation mechanism. It also lacks an SMA variable-aperture structure and a piezoelectric ceramic actuator.

[0118] 2. Work process

[0119] When the gas turbine is running, the air compressor is started, and compressed air is sent into the mixing pipe through the pipeline and manual control valve, where it is mixed with the exhaust gas for cooling. The operator manually adjusts the opening of the manual control valve based on experience to control the cooling air flow and adjust the exhaust temperature.

[0120] 3. Existing Problems

[0121] The mixing pipe has a simple structure, the mixing efficiency of cooling air and exhaust gas is low, and the exhaust gas temperature control accuracy is poor. load= In the range of 50%-100%, the exhaust temperature fluctuates from 120-150°C, which cannot meet the requirement of ≤100°C.

[0122] Manual adjustment is labor-intensive and cannot be accurately adjusted according to load changes in real time. load <30%), the temperature control response time is long (about 3 seconds) and the cooling effect is poor.

[0123] In P load =100%, the cooling air flow rate increases by 20%-25% compared with the embodiment, the energy consumption is high, and the system economy is poor.

[0124] (2) Comparative Example 2: Cooling system lacking an adaptive variable aperture structure

[0125] 1. Device composition

[0126] The device composition of this system is basically the same as that of the embodiment, except that the exhaust mixing pipe adopts a mixing hole layout with uniform aperture along the exhaust flow direction (axial direction), the aperture is Φ6mm, the hole spacing is 20mm, the "dense in front and sparse in the back" variable aperture design is not adopted, and the SMA variable aperture structure and heating wire array are not set.

[0127] 2. Work process

[0128] When the gas turbine is running, cooling air is ejected through mixing holes of uniform diameter and mixed with the exhaust gas for cooling. The control system calculates the required cooling air flow rate based on the gas turbine load and adjusts the opening of the exhaust cooling control valve.

[0129] 3. Existing Problems

[0130] At high load (P load When the temperature is greater than 80%, the distance between the front holes is large, the cooling air flow rate is insufficient, and the high-temperature gas cannot be effectively cooled. The exhaust temperature rises to as high as 110°C, exceeding the control requirement of ≤100°C.

[0131] At low load (P load When the exhaust temperature is less than 30%, the rear end hole diameter is large, and the flow rate of the ejected cooling air is too much, which may easily cause the exhaust temperature to be too low (less than 80°C), affecting the normal operation of the gas turbine.

[0132] The flow adaptive regulation capability is poor, and the cooling air flow distribution cannot be automatically adjusted according to load changes. The cooling effect of the system is unstable under different working conditions, and the temperature control accuracy is ±10°C, which is worse than the ±1.5°C of the embodiment.

[0133] (III) Comparative Example 3: Cooling System Without Piezoelectric Ceramic Actuator

[0134] 1. Device composition

[0135] The device composition of this system is basically the same as that of the embodiment, except that no piezoelectric ceramic actuator array is installed on the outside of the annular guide ring of the exhaust mixing pipe, and the formation of Karman vortex street cannot be induced by high-frequency vibration.

[0136] 2. Work process

[0137] When the gas turbine is running, cooling air forms a swirling flow through the diagonal guide holes in the exhaust mixing pipe, mixing with the exhaust gas for cooling. The control system calculates the required cooling air flow rate based on the gas turbine load and adjusts the opening of the exhaust cooling control valve.

[0138] 3. Existing Problems

[0139] Since the piezoelectric ceramic actuator is not set, the turbulence intensity of the cooling air swirl field is insufficient and the mixing efficiency is low. Under the same cooling air volume conditions, the mixing efficiency is reduced by 25% compared with the embodiment, and the cooling air flow rate Q m,air2 Increase by 8-10%, energy consumption increases.

[0140] The exhaust temperature control accuracy is ±3°C, which is worse than the ±1.5°C of the embodiment, and the anti-load disturbance capability is reduced. load When the fluctuation is ±20%, the temperature standard deviation increases from ±2°C to ±4°C.

[0141] In summary, the present invention adopts swirl mixing and variable aperture design, adaptive variable aperture and active swirl enhancement technology, and online monitoring function of mixing efficiency, so that the gas turbine exhaust can maintain a good cooling effect under different operating conditions, reduce energy consumption and the workload of manual maintenance, and improve the intelligence level and maintainability of the system.

Claims

1. A gas turbine exhaust temperature active cooling system based on electric drive compressor load, characterized in that: include: The cooling air source module is used to provide compressed air with a pressure of 0.7-0.8 MPa, including an electric-driven compressor and a rear-end air storage tank equipped with a pressure sensor; The pipeline and regulation module includes an exhaust cooling air pipeline and an exhaust cooling regulating valve installed on the pipeline, which is used to transport compressed air to the mixing cooling module and regulate the flow; The mixing cooling module consists of an exhaust cooling ejector and an exhaust mixing pipe. The exhaust mixing pipe adopts a "cross-shaped + swirl guide" composite structure. The cross-shaped pipe of the exhaust mixing pipe is a cross-shaped high-temperature alloy pipe. The four end extension sections are gradually expanding bell mouths with an expansion angle of 15°-20°. An annular guide ring is set in the center, and the ring wall has 45° oblique guide holes. A piezoelectric ceramic actuator array is installed on the outside. A "dense in front and sparse in the back" variable aperture mixing hole layout is adopted along the exhaust direction. The hole edge is made of shape memory alloy. The outer wall of the cross-shaped pipe of the exhaust mixing pipe is embedded with an annular heating wire array. The control system, including a host PLC and industrial computer, is connected to the sensor via a 4-20mA signal, uses a hybrid predictive-feedback control model to calculate the exhaust cooling control valve opening, and is equipped with an infrared thermal imager to monitor mixing unevenness; The waste heat cascade utilization module is equipped with a compact heat pipe heat exchanger at the outlet of the exhaust cooling ejector pipe to recover 80-100℃ waste heat for primary and secondary heat exchange.

2. The active cooling system according to claim 1, characterized in that In the variable aperture mixing hole layout, the front end is Φ3-Φ5mm dense mixing holes opened within a circumferential length of 150mm, with a hole spacing of 10-15mm, and the rear end is Φ8-Φ10mm sparse mixing holes opened within a circumferential length of 150mm, with a hole spacing of 25-30mm.

3. The active cooling system according to claim 1, wherein: When the exhaust temperature exceeds 80° C., the shape memory alloy expands due to heat, causing the pore diameter to increase by 1-2 mm. The front dense mixing holes can be expanded to Φ4-Φ6 mm, and the rear sparse mixing holes can be expanded to Φ9-Φ11 mm.

4. The active cooling system according to claim 1, wherein: In the hybrid predictive-feedback control model, the feedforward channel is based on formula (7) Calculate the initial valve opening V of the exhaust cooling control valve P0 The feedback channel uses the fuzzy PID algorithm to introduce the temperature deviation ΔT to dynamically correct the valve opening V P =V P0 +K P ΔT+K i ∫ΔTdt.

5. The active cooling system according to claim 1, wherein: The piezoelectric ceramic actuator array has an operating frequency of 1-5 kHz, which induces the formation of a Karman vortex street and makes the swirl number reach 0.3-0.

5.

6. A method for actively cooling exhaust gas temperature based on the active cooling system according to any one of claims 1 to 5, characterized in that: The following steps are involved: Startup initialization: 30 minutes before ignition, start the electric drive compressor, increase the air tank pressure to 0.75 MPa, set the exhaust cooling regulating valve opening to 5%, and maintain the initial aperture of the SMA orifice plate; Cooling air supply: After successful ignition, the exhaust cooling regulating valve opening is increased to 30%, and the compressed air is ejected in different areas through the variable-diameter mixing holes; Laminar mixing and swirl enhancement: Exhaust and cooling air form a "low-speed premixing at the front end and high-speed homogenous mixing at the end" mode. When the temperature is ≥80°C, the heating wire heats the SMA orifice plate, and the piezoelectric ceramic actuator starts high-frequency vibration to induce swirl. Dynamic load matching: The control system collects the gas turbine load P in real time load The required cooling air flow is calculated by the energy and mass conservation equations, and the exhaust cooling control valve opening V is solved by combining the exhaust cooling control valve flow model. P , automatically adjust the opening of the exhaust cooling regulating valve to achieve dynamic matching of cooling air volume and load; for example, when the load P load =80%, feedforward calculation V P0 =60%, feedback detection T out =Correction ΔV at 102℃ P =5%, and the actuator power is adjusted according to the mixing unevenness index η; Temperature stability control: control the exhaust temperature at ≤100℃; Energy efficiency optimization: waste heat is recovered to preheat the gas turbine intake air and cool the control cabinet.

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