Flow calculation and calibration method for non-pressure-difference constant jet water supply system

Abstract

A flow calculation and calibration method of a non-pressure-difference constant jet water supply system, the non-pressure-difference constant jet water supply system comprising: a water pump, a metering valve connected at the outlet of the water pump, and a nozzle installed at the outlet of the metering valve. Since there is no pressure difference maintaining mechanism, the water supply volume is related to the position of the metering valve and also related to the pressure difference before and after the metering valve. The flow control needs to consider two dimensions of the valve pressure difference and the valve displacement, and the flow control and calibration work is extremely tedious. A simplified flow calibration method is established, including: starting the water pump; selecting multiple points as metering valve position expected values within the full range of the metering valve, and controlling the nozzle based on the selected multiple metering valve position expected values by the controller; measuring the metering valve inlet and outlet pressure difference and the metering valve water flow corresponding to each metering valve position expected value respectively; converting the metering valve water flow into the water flow under the standard pressure difference, and obtaining the corresponding relationship between the metering valve position expected value and the water flow under the standard pressure difference and establishing a calibration line.

Description

Technical Field

[0001] This application belongs to the field of aero-engine technology, and specifically relates to a method for calculating and calibrating the flow rate of a non-differential constant jet water supply system. Background Technology

[0002] In recent years, a great deal of research has been carried out both domestically and internationally on jet precooling expansion lines for turbine engines. This involves installing a water spray precooling device in the intake manifold, injecting atomized liquid water into the intake manifold, and reducing the total temperature of the engine inlet through water evaporation and heat absorption.

[0003] The jet precooling engine is based on a mature aero-turbine engine. It sprays water onto the turbine engine, and the original geometric, pressure, temperature and speed limitations of the turbine engine remain unchanged.

[0004] The basic principle of increasing thrust by using jet precooling technology in an engine is as follows: First, water evaporation cools the airflow in the intake manifold, lowering the airflow temperature, increasing the fan's conversion speed, increasing density, and increasing the airflow into the engine, which also increases thrust. Second, although the increase in engine thrust is mainly caused by the decrease in air temperature, the vaporization of water injected into the intake manifold also increases thrust additionally. Third, the increased moisture content of the working fluid, the increased gas constant, the increased heat capacity of the working fluid, the increased exhaust velocity of the engine, and the increased thrust per unit area.

[0005] In traditional constant differential pressure fuel systems, there is a one-to-one correspondence between the metering valve displacement and fuel flow rate. Therefore, in a constant differential pressure fuel system, fuel flow control can be transformed into metering valve position control through a "metering valve position and fuel flow calibration line." Fuel flow control is actually achieved through the metering valve position.

[0006] Currently, the jet precooling water supply control system is a completely new development, adapted to the development requirements of water supply systems. The design employs a non-differential pressure maintaining metering scheme. Based on the flow characteristics of the slide valve, it is known that the position of the metering valve is not the sole factor determining the water flow rate. When controlling the water supply flow according to the plan, the water flow rate can be calculated using the pressure before and after the metering valve, as well as the valve position. To achieve better water supply flow control accuracy, the relationship between the water supply flow rate and the pressure before, after, and at the metering valve needs to be calibrated before the water supply system officially begins operation.

[0007] Disadvantages of existing technology:

[0008] 1) The water flow rate Qw is related to both the displacement Lw of the metering valve and the pressure difference Pw of the metering valve. It is a two-dimensional function, which makes the calibration complex.

[0009] 2) The calibration method is complex and uses two-dimensional function calculations. Therefore, the algorithm designed for closed-loop control of water flow is highly complex, which places higher performance demands on the digital electronic controller.

[0010] 3) Before the test run, flow rate calibration is required. It's difficult to maintain a constant pressure difference at the test site. In the control system, this two-dimensional difference will increase the computational load and complexity, and the calibration time for the two-dimensional parameters will increase exponentially. This increases the non-experimental time spent on the test bench for the engine water supply system, affecting the development progress and economic benefits.

[0011] Therefore, under the premise that the accuracy is acceptable, the calibration work of non-differential constant water supply control system needs to be simplified. Summary of the Invention

[0012] To address the aforementioned issues, this application provides a flow rate calibration method for a non-differential constant jet water supply system, characterized in that the non-differential constant jet water supply system comprises: a water pump, a metering valve connected to the outlet of the water pump, and a nozzle installed at the outlet of the metering valve.

[0013] The controller calculates the desired displacement of the metering valve based on the airflow temperature in the intake duct and the desired cooling effect. Based on this desired displacement and the displacement sensor used to measure and control the metering valve position, the controller performs closed-loop control of the nozzle flow rate.

[0014] The flow rate calibration method includes:

[0015] Turn on the water pump;

[0016] Multiple points are selected as expected values ​​for the position of the metering valve within its full range. The controller performs closed-loop control of the metering valve position based on these selected expected values.

[0017] Measure the pressure difference between the inlet and outlet of each metering valve and the water flow rate of each metering valve when the position of each metering valve is stable at the expected value;

[0018] Convert the water flow measured at each metering valve position into water flow Q under standard pressure difference. d And obtain the expected value L of the metering valve position. w The correspondence between -Dem and water flow rate under standard differential pressure was established, and a calibration line was set.

[0019] Preferably, the formula for converting the flow rate of the metering valve into the flow rate under standard differential pressure is as follows:

[0020] Q d =Q / sqrt(ΔP)

[0021] Q dQ is the water flow rate under standard pressure difference, Q is the water flow rate of the metering valve, and ΔP is the pressure difference between the inlet and outlet of the metering valve.

[0022] Preferably, the method for obtaining the pressure difference at the inlet and outlet of the metering valve is as follows:

[0023] Pressure sensors are installed at both the outlet and inlet of the metering valve to obtain the water pressure P at the inlet of the metering valve. jq And the water pressure P at the outlet of the metering valve jh Then the pressure difference between the inlet and outlet of the metering valve ΔP = P jq -P jh .

[0024] A method for calculating the flow rate of a non-differential pressure constant jet water supply system includes:

[0025] Calculate the expected water flow rate Q under standard pressure difference based on the expected water supply rate Q_Dem. d _Dem;

[0026] Based on the calibration line of the flow calibration method for the non-differential pressure constant jet water supply system according to any one of claims 1-3, the expected value L of the metering valve position is determined. w -Dem;

[0027] Adjust L in each cycle w The size of _Dem is determined, and the position of the metering valve is controlled in a closed loop.

[0028] Preferably, it includes:

[0029] Expected water flow rate Q under standard pressure differential d The formula for calculating _Dem is:

[0030] Q d _Dem = Q_Dem / sqrt(ΔP);

[0031] Wherein, ΔP is the pressure difference between the inlet and outlet of the metering valve.

[0032] The advantages of this application include: the jet precooling control system is a completely new, pre-developed system, and the non-differential pressure constant metering system lacks calibration guidance methods. This patent proposes a bench calibration method for the water supply control system of such a non-differential pressure constant metering system. It provides a calibration method and usage method for a one-dimensional interpolation table, enabling the water supply system to control the water flow rate based on the position of the water supply metering valve, meeting development requirements. Furthermore, this method is relatively simple, adaptable to situations with limited bench testing resources and development timelines, and saves costs. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the water supply control principle of a metering valve according to a preferred embodiment of this application. Detailed Implementation

[0034] 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.

[0035] 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.

[0036] 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.

[0037] The jet precooling zoned water supply system, for each zone, has the following structural principle: Figure 1 As shown, the non-differential constant jet water supply system includes: a water pump, a metering valve connected to the outlet of the water pump, and a nozzle installed at the outlet of the metering valve.

[0038] The controller calculates the expected value of the metering valve displacement based on the airflow temperature in the intake duct and the desired cooling effect. Based on the expected value of the metering valve displacement and the displacement sensor that measures and controls the position of the metering valve, the controller performs closed-loop control of the metering valve displacement.

[0039] The metering valve has a slide valve structure; therefore, the water flow rate through the metering valve can be calculated using the following formula.

[0040] Q = C d *A*sqrt(ΔP / ρ) (1)

[0041] Where A is the area of ​​the metering valve orifice, and L is the displacement of the metering valve. w It is a one-to-one correspondence; C d ρ is the flow coefficient, ρ is the fluid density, and ΔP is the pressure difference before and after the metering valve, ΔP = P jq -P jh P jq and P jh like Figure 1 These represent the pressure before the metering valve and the pressure after the metering valve, respectively.

[0042] When the water supply system is operating, the water flow rate is controlled based on the engine inlet temperature T2. When demand is high, a higher water supply is desired; however, due to operating conditions P... jq -P jh Since it is a non-controllable variable, the pressure difference ΔP changes during actual operation. Therefore, the displacement L of the same metering valve will also change. w The corresponding water supply volume may vary significantly, so ΔP needs to be introduced for calculation.

[0043] Assume that C in the water supply calculation formula d The changes in ρ are small and within the specified precision control range.

[0044] Simplified calibration method:

[0045] 1) The water pump operates, providing sufficient pressure to the water supply system;

[0046] 2) Manually set the desired value L of the metering valve position. w -Dem, take at least 12 points across the entire range;

[0047] 3) The controller implements closed-loop control of the metering valve position, and performs closed-loop stable control at 12 points respectively;

[0048] 4)L w For each point in -Dem, when the closed-loop control is stable, record P. jq and P jh Size, record ΔP;

[0049] 5) The water supply volume Q is measured using a flow meter;

[0050] 6) Repeat steps 3)-5) until all 12 points have completed closed-loop control.

[0051] The above method yields a 12*3 data table, as shown in the table below.

[0052] Table 1 Calibration Data Recording Table

[0053] <![CDATA[L w -Dem]]> <![CDATA[L w _1]]> <![CDATA[L w _2]]> <![CDATA[L w _3]]> <![CDATA[L w _4]]> … <![CDATA[L w _10]]> <![CDATA[L w _11]]> <![CDATA[L w _12]]> ΔP ΔP_1 ΔP_2 ΔP_3 ΔP_4 … ΔP_10 ΔP_11 ΔP_12 Q Q_1 Q_2 Q_3 Q_4 … Q_10 Q_11 Q_12

[0054] The data in the table are the raw data. During the calibration process, while keeping the pump speed and nozzle back pressure constant, ΔP decreases as the flow rate increases during the test.

[0055] 7) Calculate the flow rate Q shown in Table 1 into the standard differential pressure using the following formula. d ;

[0056] Q d =Q / sqrt(ΔP) (2)

[0057] The data shown in the table below can then be obtained.

[0058] Table 2. Flow rate calibration lines under equivalent standard pressure difference.

[0059] <![CDATA[L w -Dem]]> <![CDATA[L w _1]]> <![CDATA[L w _2]]> <![CDATA[L w _3]]> <![CDATA[L w _4]]> … <![CDATA[L w _10]]> <![CDATA[L w _11]]> <![CDATA[L w _12]]> <![CDATA[Q d ]]> <![CDATA[Q d _1]]> <![CDATA[Q d _2]]> <![CDATA[Q d _3]]> <![CDATA[Q d _4]]> … <![CDATA[Q d _10]]> <![CDATA[Q d _11]]> <![CDATA[Q d _12]]>

[0060] Table 2 shows the final calibration lines obtained. These calibration lines are then written into the water supply control system. During water flow control, the desired water supply flow can be obtained using the following control method.

[0061] Based on the expected water supply value Q_Dem, Q is calculated using the following formula. d _Dem,

[0062] Q d _Dem=Q_Dem / sqrt(ΔP) (3)

[0063] According to Q, via the calibration line d _Dem, perform linear interpolation on Table 2 to determine L w -Dem

[0064] Adjust L in each cycle w The size of _Dem is determined, and closed-loop control of the metering valve position is performed.

[0065] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for calculating the flow rate of a non-differential constant pressure jet water supply system, the non-differential constant pressure jet water supply system comprising: A water pump, a metering valve connected to the outlet of the water pump, and a nozzle installed at the outlet of the metering valve; The controller calculates the expected value of the metering valve displacement based on the airflow temperature in the intake duct and the desired cooling effect. Based on the expected value of the metering valve displacement and the displacement sensor that measures and controls the position of the metering valve, the controller performs closed-loop control of the nozzle flow rate. The characteristic feature is that the flow calculation method includes: Calculate the expected water flow rate Q under standard pressure difference based on the expected water supply rate Q_Dem. d _Dem; The calibration line for determining the expected value L of the metering valve position is based on the calibration method for a non-differential pressure constant jet water supply system. w -Dem; Adjust L in each cycle w The size of _Dem is determined, and the position of the metering valve is controlled in a closed loop. Expected water flow rate Q under standard pressure differential d The formula for calculating _Dem is: Q d _Dem = Q_Dem / sqrt(ΔP); Wherein, ΔP is the pressure difference between the inlet and outlet of the metering valve; The flow rate calibration method for the non-differential pressure constant jet water supply system includes: Turn on the water pump; Multiple points are selected as expected values ​​for the position of the metering valve within its full range. The controller performs closed-loop control of the metering valve position based on these selected expected values. Measure the pressure difference between the inlet and outlet of each metering valve and the water flow rate of each metering valve when the position of each metering valve is stable at the expected value; Convert the water flow rate measured at each metering valve position into the water flow rate Q under standard pressure difference. d And obtain the expected value L of the metering valve position. w -Dem and water flow rate Q under standard pressure difference d The corresponding relationship was established and calibration lines were set.

2. The flow rate calculation method for a non-differential constant jet water supply system as described in claim 1, characterized in that, The method for obtaining the pressure difference at the inlet and outlet of the metering valve is as follows: Pressure sensors are installed at both the outlet and inlet of the metering valve to obtain the water pressure P at the inlet of the metering valve. jq And the water pressure P at the outlet of the metering valve jh Then the pressure difference between the inlet and outlet of the metering valve ΔP = P jq -P jh .

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