A control method for water flow of a combined power jet pre-cooling system

Abstract

The application belongs to the technical field of aero-engines, and particularly relates to a control method for water flow of a combined power jet pre-cooling system, which comprises open-loop control and closed-loop control. In the open-loop control, the jet pre-cooling system supplies water at a maximum flow rate at different times based on different states of the liquid. In the closed-loop control, the water flow rate is controlled accurately based on temperature. The application considers the vaporization state of water in the pipeline in front of the nozzle, adopts a corresponding control mode, and achieves the purpose of faster cooling. The application considers the influence of water supply delay when the jet pre-cooling system starts, and designs a corresponding control mode to reduce the delay time.

Description

Technical Field

[0001] This application belongs to the field of aero-engine technology, and specifically relates to a method for controlling the water flow rate of a combined power jet precooling system. Background Technology

[0002] The China Aero Engine Research Institute actively carried out research on key technologies for jet precooled engines. Using a certain type of engine as a platform, it completed the ground verification of the whole engine under ground heating of 316.7℃, verifying the technical feasibility of jet precooling to extend the envelope of the turbine engine.

[0003] In recent years, extensive research has been conducted both domestically and internationally on jet precooling expansion envelopes for turbine engines. This involves installing a water-jet precooling device in the air intake, injecting atomized liquid water into the intake, and reducing the overall engine inlet temperature through the principle of water vaporization and heat absorption. This increases the aircraft's flight speed without altering the turbine engine's geometric, pressure, temperature, and speed limitations. The basic principles of increasing thrust using jet precooling technology are as follows: First, water evaporation cools the airflow in the intake, lowering its temperature, increasing the fan's converted speed, increasing density, and increasing the airflow into the engine, thus increasing thrust. Second, although the increase in engine thrust is mainly due to the decrease in air temperature, the vaporization of water injected into the intake also contributes to the additional thrust. Third, the increased moisture content of the working fluid increases the gas constant and the working fluid's heat capacity, leading to increased engine exhaust velocity and increased thrust per unit area.

[0004] The jet precooling system is used to cool high-temperature air at high Mach numbers, with water as the primary medium. Before the jet precooling system is operational, the pipeline from the metering device to the nozzle is dry. When the combined-fuel engine is flying at high Mach numbers and the jet precooling system needs to be activated, the water just flowing from the metering device easily vaporizes due to the high inlet total temperature and low high-altitude total pressure. The latent heat of vaporization of water is qv = 2260 kJ / kg; at T = 100℃ and p = 0.01 MPa, the enthalpy of unsaturated water is h = 2687 kJ. Assuming C = 4.2 kJ / kg, and that the energy required to raise 1 kg of water from 0℃ to 100℃ is 420 kJ, while the energy required for 1 kg of water to vaporize is 2260 kJ, it is clear that the energy required to vaporize water is more than five times the energy required to raise water temperature from 0℃ to 100℃. Therefore, if the water remains in the pipeline, its latent heat of vaporization is lost, significantly reducing the cooling effect.

[0005] Currently, the jet precooling technology for cooling aero-engines mainly calculates and controls the cooling effect of liquid water, without considering the state of water that has already vaporized in the pipeline before the nozzle. Vaporized water and liquid water have different cooling effects, which will lead to a decrease in the cooling effect.

[0006] The piping from the metering device to the nozzle in a jet precooling system is typically designed to be quite long, depending on layout requirements. This design doesn't account for the impact of piping length and water flow velocity on the water supply time delay each time the jet precooling system is started. If the piping is long, the time delay from the metering device to the nozzle will affect the cooling effect.

[0007] Therefore, in order to achieve the corresponding cooling effect, it is essential to determine the state of the water and control the water volume in the jet precooling system. Summary of the Invention

[0008] To address the aforementioned problems, this application provides a method for controlling the water flow rate of a combined dynamic jet precooling system, comprising two steps: open-loop control and closed-loop control, wherein:

[0009] Step S1: Open-loop control;

[0010] The jet precooling system supplies water at maximum capacity, and the water control time specifically includes:

[0011] When the water in the pipeline before the nozzle is in a liquid state, the duration of open-loop water supply is t;

[0012] When the water in the pipeline before the nozzle is in the state of water vapor, the open-loop water supply duration is t+a;

[0013] When the water in the pipeline before the nozzle is in a gas-liquid mixed state, the open-loop water supply duration is t+b.

[0014] Where t is the time from the start of the jet precooling system to the time when the liquid water fills the pipeline before the nozzle; a is the preset compensation time when the water vapor state is open; and b is the compensation time when the gas-liquid mixture state is open.

[0015] Step S2: Closed-loop control; including:

[0016] S21 calculates the expected value of the engine inlet total temperature, T2Dem, based on the aircraft's Mach number.

[0017] S22 calculates the deviation value DeltaT2 between the inlet temperature T2 collected by the inlet total temperature sensor and the expected value T2Dem of the engine inlet total temperature.

[0018] S23 calculates the expected current water supply value WwDem based on the deviation value DeltaT2;

[0019] S24 calculates the current expected valve opening value LwDem based on the current expected water supply value WwDem and the valve opening calibration line;

[0020] S25 obtains the valve opening deviation value by subtracting the current valve opening expectation value LwDem from the opening value Lw collected by the metering valve linear displacement sensor, and calculates the water volume control current ILW based on the valve opening deviation value.

[0021] S26 controls the opening degree of the valve by controlling the current ILW of the water flow, and further controls the water flow in the pipeline before the nozzle.

[0022] Preferably, the method for judging the state of water in the pipeline before the nozzle includes:

[0023] Let the collected temperature value be T3, and let the collected pressure value be P3;

[0024] Based on the pressure value P3 and the difference between the saturation vapor line of temperature and pressure, calculate the saturation temperature Tb corresponding to P3,

[0025] When T3 > Tb, the water in the pipeline before the nozzle is in a gaseous state;

[0026] When T3 = Tb, the water in the pipeline before the nozzle is in a gas-liquid mixed state;

[0027] When T3 < Tb, the water in the pipeline before the nozzle is in a liquid state.

[0028] Preferably, a is taken as 2s and b is taken as 1s. <着

[0029] Preferably, the open-loop water supply duration t is calculated by the following formula,

[0030]

[0031] Where: L represents the pipeline length, d represents the pipeline diameter, and v represents the designed water flow velocity.

[0032] Preferably, the method for judging the state of water in the pipeline before the nozzle includes: establishing a thermodynamic parameter equation P = f(T) for water vapor in a saturated state regarding temperature and pressure;

[0033] Let the collected temperature value be T0, and let the collected pressure value be P0;

[0034] When f(T0) < P0, the water in the pipeline before the nozzle is in a gaseous state;

[0035] When f(T0) = P0, the water in the pipeline before the nozzle is in a gas-liquid mixed state;

[0036] When f(T0) < P0, the water in the pipeline before the nozzle is in a liquid state.

[0037] The advantages of this application include:

[0038] Considering the vaporization state of water in the pipeline before the nozzle, corresponding control methods are adopted to achieve the purpose of faster cooling and temperature reduction.

[0039] Considering the influence of water supply delay during the startup of the jet pre-cooling system, corresponding control methods are designed to reduce the delay time.

[0040] It can solve the problems of reduced cooling effect and delayed water supply in the initial water vaporization zone, and can also achieve precise control after filling. Attached Figure Description

[0041] Figure 1 This is a flowchart of a preferred embodiment of the method for controlling the water flow rate of a combined dynamic jet precooling system according to this application. Detailed Implementation

[0042] To make the technical solution and advantages of this application clearer, the technical solution of this application will be described in a clearer and more complete manner below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only some embodiments of this application, and are only used to explain this application, not to limit this application. It should be noted that, for ease of description, only the parts related to this application are shown in the accompanying drawings. Other related parts can be referred to the general design. In the absence of conflict, the embodiments and technical features in the embodiments of this application can be combined with each other to obtain new embodiments.

[0043] Furthermore, unless otherwise defined, the technical or scientific terms used in this application description shall have the ordinary meaning understood by one of ordinary skill in the art to which this application pertains. The terms "upper," "lower," "left," "right," "center," "vertical," "horizontal," "inner," and "outer," etc., used in this application description to indicate relative direction or positional relationship are used only to indicate relative orientation or positional relationship, and do not imply that the device or component must have a specific orientation, or be constructed and operated in a specific orientation. When the absolute position of the described object changes, its relative positional relationship may also change accordingly, and therefore should not be construed as a limitation on this application. The terms "first," "second," "third," and similar terms used in this application description are used only for descriptive purposes to distinguish different components, and should not be construed as indicating or implying relative importance. The terms "a," "one," or "the," etc., used in this application description should not be construed as an absolute limitation on quantity, but should be construed as indicating the existence of at least one. The terms "including," "comprising," etc., used in this application description mean that the element or object preceding the word covers the element or object listed after the word and its equivalents, without excluding other elements or objects.

[0044] Furthermore, it should be noted that, unless otherwise explicitly specified and limited, terms such as “installation,” “connection,” and “linkage” used in the description of this application should be interpreted broadly. For example, a connection can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; or it can be a connection within two components. Those skilled in the art can understand its specific meaning in this application according to the specific circumstances.

[0045] The problems of water vaporization and water supply delay in pipelines can be solved by adopting an open-loop-closed-loop switching control method.

[0046] illustrate:

[0047] To cope with the high-temperature incoming flow problem, hypersonic aircraft turbine engines require jet precooling technology to expand their envelope. The success or failure of the jet precooling system directly determines the engine's expansion envelope capability and is one of the core key technologies of aerospace engines. The jet precooling device and water supply system consists of components such as spray booms and nozzles, water supply pipelines, controllers, water pumps, regulating valves, and sensors.

[0048] When the water temperature before the metering device is at room temperature and the jet precooling device is in the start-up stage, and the temperature and pressure in the pipeline meet the conditions for the water to be in a gaseous state, the water supply should be increased. However, after the water has flowed for a certain period of time, the temperature in the pipeline decreases and then increases, causing the water to be in a liquid state. Moreover, the water flow rate should be greater than the rate at which the water heats up to a vapor state. Therefore, after a certain period of time, the water in the pipeline is in an unsaturated state.

[0049] Open-loop control: The valve opening is controlled according to a set flow rate, and the actual water supply is not transmitted as feedback information to the jet precooling digital electronic controller. Its disadvantage is that the actual water volume and cooling effect are unclear, resulting in poor temperature control accuracy. Its advantage is that the flow rate can be set arbitrarily and is not limited by other factors.

[0050] Closed-loop control: The valve opening is controlled according to the set flow rate. The cooling effect generated by the actual water supply is fed back to the jet precooling digital electronic controller via an inlet total temperature sensor. The controller adjusts the valve opening in real time based on the deviation to keep the water flow in a closed-loop regulation state to meet the cooling requirements. Its advantage is that the water flow is controlled through a temperature closed loop, and the water flow setpoint automatically changes with the temperature difference, resulting in precise control. Its disadvantage is that the water flow setpoint is limited by the temperature difference and cannot be directly changed; therefore, it cannot directly meet the requirement of increasing the water flow.

[0051] When the jet precooling system is started, the pipeline is in an unfilled state, and water is supplied at a large flow rate to reduce the delay time of water from the metering device to the nozzle and to reduce the impact of reduced cooling effect after water vaporization.

[0052] The specific control process includes two steps: open-loop control and closed-loop control.

[0053] Step S1: Open-loop control;

[0054] The jet precooling system supplies water at maximum capacity, and the water control time specifically includes:

[0055] When the water in the pipeline before the nozzle is in a liquid state, the duration of open-loop water supply is t;

[0056] When the water in the pipeline before the nozzle is in the state of water vapor, the open-loop water supply duration is t+a;

[0057] When the water in the pipeline before the nozzle is in a gas-liquid mixed state, the open-loop water supply duration is t+b.

[0058] Where t is the time from the start of the jet precooling system to the time when the liquid water fills the pipeline before the nozzle; a is the preset compensation time when the water vapor state is open; and b is the compensation time when the gas-liquid mixture state is open.

[0059] Step S2: Closed-loop control;

[0060] include:

[0061] S21 calculates the expected value of the engine inlet total temperature, T2Dem, based on the aircraft's Mach number.

[0062] S22 calculates the deviation value DeltaT2 between the inlet temperature T2 collected by the inlet total temperature sensor and the expected value T2Dem of the engine inlet total temperature.

[0063] S23 calculates the expected current water supply value WwDem based on the deviation value DeltaT2;

[0064] S24 calculates the current expected valve opening value LwDem based on the current expected water supply value WwDem and the valve opening calibration line;

[0065] S25 obtains the valve opening deviation value by subtracting the current valve opening expectation value LwDem from the opening value Lw collected by the metering valve linear displacement sensor, and calculates the water volume control current ILW based on the valve opening deviation value.

[0066] S26 controls the valve opening by controlling the water flow rate in the pipeline before the nozzle through the water flow control current ILW.

[0067] Preferably, the method for determining the state of the water in the pipeline before the nozzle includes:

[0068] Let the collected temperature value be T3, and the collected pressure value be P3;

[0069] Calculate the saturation temperature Tb corresponding to P3 based on the pressure value P3 and the difference between the saturation vapor line of temperature and pressure.

[0070] When T3 > Tb, the water in the pipeline before the nozzle is in gaseous state.

[0071] When T3 = Tb, the water in the pipeline before the nozzle is in gas-liquid mixed state.

[0072] When T3 < Tb, the water in the pipeline before the nozzle is in liquid state.

[0073] For example: According to the pressure sensors and temperature sensors arranged in the system, the collected pressure and temperature signals are transmitted to the jet pre-cooling digital electronic controller. The controller calculates the saturation temperature Tb according to the pressure interpolation in Table 1. By comparing the calculated saturation temperature with the actual temperature T3 in the pipeline, if T3 > Tb, it is in the water vapor state; if T3 < Tb, it is in the liquid water state; if T3 = Tb, it is in the gas-liquid coexistence state.

[0074] Table 1 P-T saturation vapor line

[0075] Pb(MPa) 0.001 0.004 0.005 0.01 0.05 0.1 0.5 1.0 5.0 22.064 Tb(°C) 6.95 28.95 32.87 45.80 81.34 99.63 151.86 179.92 263.98 373.99

[0076] In some optional implementation manners, the open-loop control includes

[0077] 1) If T3 < Tb, it is in the liquid water state

[0078] Let the maximum water supply of the single pipe of jet pre-cooling be Wmax, then the open-loop water supply, and the open-loop duration is t.

[0079] 2) If T3 > Tb, then it is in the water vapor state

[0080] The open-loop water supply, and the open-loop duration is (t + 2) s.

[0081] 3) If T3 = Tb, then it is in the gas-liquid coexistence state

[0082] The open-loop water supply, and the open-loop duration is (t + 1) s.

[0083] This application also provides a method for judging the state of the water in the pipeline before the nozzle, which includes: establishing a thermodynamic parameter equation P = f(T) for water vapor in a saturated state regarding temperature and pressure;

[0084] Let the collected temperature value be T0, and let the collected pressure value be P0;

[0085] When f(T0) < P0, the water in the pipeline before the nozzle is in gaseous state;

[0086] When f(T0) = P0, the water in the pipeline before the nozzle is in gas-liquid mixed phase;

[0087] When f(T0) < P0, the water in the pipeline before the nozzle is in the liquid phase.

[0088] As described above, it is only the specific implementation manner of this application, but the protection scope of this application is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the technical field of this application within the technical scope disclosed by this application should be covered within the protection scope of this application. Therefore, the protection scope of this application shall be subject to the protection scope of the claimed rights.

Claims

1. A control method for the water flow rate of a combined power jet pre-cooling system, characterized in that: It includes two steps of open-loop control and closed-loop control, where: Step S1: Open-loop control; The jet pre-cooling system supplies water at the maximum water supply, and the water control time specifically includes: When the state of water in the pipeline before the nozzle is liquid, the open-loop water supply duration is t; When the state of water in the pipeline before the nozzle is steam, the open-loop water supply duration is t + a; When the state of water in the pipeline before the nozzle is a gas-liquid mixture, the open-loop water supply duration is t + b; Where, t is the time from when the jet pre-cooling system is started until the pipeline before the nozzle is filled with liquid water; a is the preset compensation time in the steam state, and b is the compensation time in the gas-liquid mixture state; Step S2: Closed-loop control; including: S21 Calculate the expected value T2Dem of the total temperature at the engine inlet according to the aircraft Mach number, S22 Calculate the deviation value DeltaT2 between the inlet temperature T2 collected by the inlet total temperature sensor and the expected value T2Dem of the total temperature at the engine inlet; S23 Calculate the current expected water supply value WwDem based on the deviation value DeltaT2; S24 Calculate the current expected valve opening value LwDem based on the current expected water supply value WwDem and the valve opening calibration line; S25 Based on the valve opening deviation value obtained by subtracting the opening value Lw collected by the metering valve linear displacement sensor from the current expected valve opening value LwDem, calculate the water volume control current ILW; S26 Control the valve opening through the water volume control current ILW, and then control the water flow rate in the pipeline before the nozzle.

2. The method for controlling the water flow rate of the combined dynamic jet precooling system as described in claim 1, characterized in that, Where, The method for judging the state of water in the pipeline before the nozzle includes: Let the collected temperature value be T3, and let the collected pressure value be P3; Based on the pressure value P3 and the difference between the saturation steam line of temperature and pressure, calculate the saturation temperature Tb corresponding to P3, When T3 > Tb, the water in the pipeline before the nozzle is gaseous; When T3 = Tb, the water in the pipeline before the nozzle is a gas-liquid mixture; When T3 < Tb, the water in the pipeline before the nozzle is liquid.

3. The method for controlling the water flow rate of the combined dynamic jet precooling system as described in claim 1, characterized in that, The value of a is 2s, and the value of b is 1s.

4. The method for controlling the water flow rate of the combined dynamic jet precooling system as described in claim 1, characterized in that, The open-loop water supply duration t is calculated by the following formula, Where: L represents the pipeline length, d represents the pipeline diameter, and v represents the designed water flow velocity.

5. The method for controlling the water flow rate of the combined dynamic jet precooling system as described in claim 1, characterized in that, The method for judging the state of water in the pipeline before the nozzle includes: establishing a thermodynamic parameter equation P = f(T) for water vapor in a saturated state regarding temperature and pressure; Let the collected temperature value be T0, and let the collected pressure value be P0; When f(T0) < P0, the water in the pipeline before the nozzle is in the gas phase; When f(T0) = P0, the water in the pipeline before the nozzle is in the gas-liquid mixed phase; When f(T0) < P0, the water in the pipeline before the nozzle is in the liquid phase.

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