A control method for switching between open-loop mode and closed-loop mode of a fluidic pre-cooling system

Abstract

The application belongs to the technical field of aero-engines, and particularly relates to a control method for switching of open-loop and closed-loop modes of a jet pre-cooling system. The main control plan is divided into two parts: open-loop control and closed-loop control. The switching between the two controls is controlled by a bench instruction "closed-loop-open-loop mode selection" switch. The main difference between the two control modes lies in the calculation of water supply flow. In the open-loop control scheme: the calculation of water supply flow is based on the values of engine low-pressure rotor converted speed, engine inlet total pressure, engine inlet total temperature and engine inlet total temperature expected value, and open-loop water supply amount expected value is calculated by using a function relationship; in the closed-loop control scheme: the size of water supply amount is calculated in a closed loop according to the difference between the actual value of engine inlet total temperature and the expected value of engine inlet total temperature.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of aero-engines, and particularly relates to a control method for switching between open-loop and closed-loop modes of a jet pre-cooling system. BACKGROUND

[0002] In recent years, a large amount of research has been carried out on jet pre-cooling expansion envelopes of turbine engines at home and abroad, that is, a water injection pre-cooling device is installed in an inlet duct, and atomized liquid water is injected into the inlet duct, so as to reduce the engine inlet total temperature through the principle of water vaporization heat absorption, and to improve the flight speed of an aircraft without changing the geometric limit, pressure limit, temperature limit and speed limit of the turbine engine. The basic principle of using jet pre-cooling technology to increase the thrust of an engine is as follows: first, water evaporation cools the airflow in the inlet duct, so that the airflow temperature is reduced, the fan equivalent speed is increased, the air density is increased, the air flow entering the engine is increased, and the thrust is also increased; second, although the increase in engine thrust is mainly caused by the decrease in air temperature, the water vaporization into the inlet duct also increases the thrust; third, the increase in working medium humidity increases the gas constant, and the working medium heat capacity is increased, so that the engine exhaust velocity is increased, and the unit thrust is increased.

[0003] The jet pre-cooling system is used to cool high-temperature air at a high Mach number, and the main medium is water. According to the functional requirements, the jet pre-cooling control system needs to have the functions of open-loop water supply control and closed-loop water supply control.

[0004] Therefore, it is necessary to design an open-loop / closed-loop control switching method for the jet pre-cooling system.

[0005] At present, when the jet pre-cooling of an aero-engine controls water flow, there are open-loop water amount calculation methods and closed-loop water amount calculation methods, but the switching method between the open-loop and closed-loop modes is missing. If the mode is directly switched, it is easy to cause disturbance, and then the inlet total temperature is greatly changed, which affects the control effect. SUMMARY

[0006] In order to solve the above problems, the application provides a control method for switching between open-loop and closed-loop modes of a jet pre-cooling system, which comprises the following steps:

[0007] Mode 1: When the jet pre-cooling system performs open-loop water supply, open-loop water amount calculation is performed: an inlet total temperature expected value T2Dem is obtained, an open-loop water supply amount expected value WwDem_open is calculated according to the inlet total temperature expected value T2Dem and an actual value T2 of the inlet total temperature collected by a sensor and an inlet total pressure P2, and the jet pre-cooling device performs water supply in the open-loop water supply amount expected value WwDem_open.

[0008] Mode 2: When the closed-loop water supply is carried out by the jet pre-cooling system, the closed-loop water quantity is calculated: the intake total temperature expectation value T2Dem is obtained, the closed-loop water supply expectation value WwDem_closed is calculated by the PID algorithm according to the intake total temperature expectation value T2Dem and the intake total temperature actual value T2 collected by the intake total temperature sensor, and the jet pre-cooling device carries out water supply according to the closed-loop water supply expectation value WwDem_closed;

[0009] Mode 3: When the jet pre-cooling system is switched from the open-loop water supply to the closed-loop water supply,

[0010] The difference ΔT between the intake total temperature expectation value T2Dem and the intake total temperature actual value T2 is obtained, the switching time t corresponding to the time length is selected according to the size of the difference ΔT in different ranges, and the size of the closed-loop water supply expectation value WwDem_closed is corrected so that the difference between the open-loop water supply expectation value WwDem_open and the closed-loop water supply expectation value WwDem_closed and the switching time t are in a linear function relationship;

[0011] Mode 4: When the jet pre-cooling system is switched from the closed-loop water supply to the open-loop water supply, the difference ΔT between the intake total temperature expectation value T2Dem and the intake total temperature actual value T2 is obtained, the switching time t corresponding to the time length is selected according to the size of the difference ΔT in different ranges, and the size of the open-loop water supply expectation value WwDem_open is corrected so that the difference between the closed-loop water supply expectation value WwDem_closed and the open-loop water supply expectation value WwDem_open and the switching time t are in a linear function relationship.

[0012] Preferably, the specific method for calculating the open-loop water supply expectation value WwDem_open includes:

[0013] The temperature difference ΔT is obtained according to the intake total temperature expectation value T2Dem and the intake total temperature actual value T2 collected by the sensor:

[0014] Based on the corresponding relationship between the temperature difference ΔT and the water vapor table, F2 is calculated;

[0015]

[0016] Wherein, T2min is the minimum value of T2, T2max is the maximum value of T2, Lamda1 is the water vapor ratio corresponding to ΔT at T2min temperature, and Lamda2 is the water vapor ratio corresponding to ΔT at T2max temperature;

[0017] F3 is calculated according to the inlet total temperature T2 and the inlet total pressure P2:

[0018]

[0019] Wherein, P stdis a constant 101.325 KPa, T std is a constant 288.15 K;

[0020] The open-loop water supply amount expected value WwDem_open is:

[0021] WwDem_open = W 2R × F3 × F2;

[0022] Wherein, W 2R is an intermediate quantity, the value of which is determined by W 2R and the engine low-pressure compressor conversion speed

[0023] N 1r relationship table selection.

[0024] Preferably, the control principle calculation step of the PID algorithm is:

[0025] According to the PID control principle, we have:

[0026]

[0027] Wherein, k p_out is the outer loop proportional coefficient, T i_out is the outer loop integral constant, and T d_out is the outer loop differential constant;

[0028] Wherein, K d_out (k) = K p_out (k) × T d_out (k); k is the current period;

[0029] Then we have

[0030] The continuous quantity is discretized to obtain the closed-loop water amount calculation formula as follows:

[0031]

[0032] The advantages of the present application include: the jet pre-cooling system realizes smooth switching when switching between the open-loop water supply mode and the closed-loop water supply mode, and does not appear the phenomenon of large fluctuation of the total temperature at the inlet due to mode switching. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 is a preferred embodiment of the jet pre-cooling system open / closed loop mode switching control method flow chart of the present application. DETAILED DESCRIPTION

[0034] In order to make the technical solutions of the present application and the advantages thereof clearer, the technical solutions of the present application will be further clearly and completely described in detail below in conjunction with the drawings. It should be understood that the specific embodiments described herein are only partial embodiments of the present application, and are only used to explain the present application, but not to limit the present application. It should be noted that, for the purpose of description, only parts related to the present application are shown in the drawings, and other related parts can be referred to the general design. In the case of no conflict, the embodiments in the present application and the technical features in the embodiments can be combined to obtain new embodiments.

[0035] In addition, unless otherwise defined, the technical terms or scientific terms used in the present application description should be the general meanings understood by the general technical personnel in the field of the present application. The words indicating the direction or position relationship such as "upper", "lower", "left", "right", "center", "vertical", "horizontal", "inner", "outer" and the like used in the present application description are only used to indicate the relative direction or position relationship, but not to imply that the device or element must have a specific orientation, be constructed and operated in a specific orientation, and the relative position relationship may also change accordingly when the absolute position of the described object changes, therefore it cannot be understood as a limitation on the present application. The "first", "second", "third" and the like used in the present application description are only for the purpose of description, to distinguish different components, and cannot be understood as indicating or implying relative importance. The "one", "an" or "the" and the like used in the present application description should not be understood as an absolute limitation on the quantity, but should be understood as the existence of at least one. The "include" or "contain" and the like used in the present application description means that the elements or objects appearing before the word cover the elements or objects listed after the word and their equivalents, and do not exclude other elements or objects.

[0036] In addition, it should be noted that, unless otherwise defined and limited, the "installation", "connection", "connection" and the like used in the present application description should be understood in a broad sense, for example, the connection can be fixed connection, or detachable connection, or integral connection; can be mechanical connection, or electrical connection; can be directly connected, or indirectly connected through intermediate medium, or the internal communication of two elements, and the person skilled in the art can understand the specific meaning of the present application according to the specific circumstances.

[0037] The present application synchronously and real-timely calculates the open-loop mode water quantity and the closed-loop mode water quantity, and distinguishes the linear transition time according to the difference between the total import temperature and the target value to achieve the effect of smooth transition when the mode is converted.

[0038] The hypersonic aircraft turbine engine needs to use the jet pre-cooling technology to expand the envelope line to deal with the high temperature inflow problem. The success or failure of the jet pre-cooling system directly determines the engine expansion envelope line capability and is one of the core key technologies of the aerospace engine. The jet pre-cooling device and the water supply system are composed of a spray rod and a nozzle, a water supply pipeline, a controller, a water pump, a regulating valve, a sensor and other components.

[0039] The main control plan is divided into two parts: 1) open loop control, which is composed of “engine inlet total temperature expectation value calculation, open loop water quantity calculation, mode selection, water quantity servo control and jet injection function”; 2) closed loop control, which is composed of “engine inlet total temperature expectation value calculation, closed loop water quantity calculation, mode selection, water quantity servo control and jet injection function”. The switching between the two controls is controlled by the “closed loop-open loop mode selection” switch of the test bench. The main difference between the two control modes is the calculation of the water supply flow. In the open loop control scheme: the calculation of the water supply flow is based on the values of the engine low pressure rotor conversion speed, the engine inlet total pressure, the engine inlet total temperature and the engine inlet total temperature expectation value, and the open loop water quantity expectation value is calculated by using the functional relationship; in the closed loop control scheme: the size of the water supply quantity is calculated according to the difference between the actual value of the engine inlet total temperature and the expectation value of the engine inlet total temperature;

[0040] Specifically, the following modes are included:

[0041] Mode 1: When the jet pre-cooling system performs open loop water supply, open loop water quantity calculation is performed: the inlet total temperature expectation value T2Dem is obtained, and the open loop water quantity expectation value WwDem_open is calculated according to the inlet total temperature expectation value T2Dem and the actual value T2 of the inlet total temperature collected by the sensor and the inlet total pressure P2; the jet pre-cooling device performs water supply with the open loop water quantity expectation value WwDem_open;

[0042] A specific embodiment is:

[0043] Step one:

[0044] According to the difference between the T2 temperature collected by the inlet total temperature sensor and the T2 target value set in the digital electronic controller, the temperature deviation is calculated:

[0045] ΔT = T2 - T2Dem; (1)

[0046] Step two:

[0047] According to the corresponding relationship of Lamda1, Lamda2 and ΔT, when T2 is between 390K and 436K, F2 is calculated by linear interpolation:

[0048]

[0049] Table 1 Relationship table of Lamda1 and ΔT

[0050] ΔT K )]]> 0 25 50 75 100 125 150 175 200 225 250 Lamda1 0 0.0106 0.0213 0.0329 0.0459 0.0590 0.0722 0.0851 0.0983 0.1108 0.1235

[0051] Table 2 Relationship table of Lamda2 and ΔT

[0052]

[0053]

[0054] Step three:

[0055] F3 is calculated according to the total temperature T2 and the total pressure P2 of the inlet:

[0056]

[0057] P std is a constant 101.325 KPa, T std is a constant 288.15 K;

[0058] Step four:

[0059] The calculation of the open-loop water supply amount W2R is shown in Table 3:

[0060] W w Dem_open = W 2R × F3 × F2.

[0061] Table 3 Relationship table of W2R and N1r

[0062] N1r 60.44 64.75 67.37 71.97 74.82 77.7 80.97 83.57 W2R 59.93 64.02 66.53 71.12 75.24 80.25 86.43 91.62 N1r 86.21 89.25 92.24 94.24 96.24 98.22 100.19 100.5 W2R 97.15 103.65 108.99 114.09 118.31 122.26 125.47 125.91

[0063] Mode 2: When the jet pre-cooling system performs closed-loop water supply, the closed-loop water amount is calculated: the expected value of the total temperature of the inlet air T2Dem is obtained, and the expected value of the closed-loop water supply WwDem_closed is calculated through a PID algorithm according to the expected value of the total temperature of the inlet air T2Dem and the actual value of the total temperature of the inlet air T2 collected by the inlet temperature sensor; the jet pre-cooling device performs water supply at the expected value of the closed-loop water supply WwDem_closed;

[0064] One specific embodiment is: the expected value of the total temperature of the inlet of the engine, i.e., the outer ring given value T2Dem, is calculated according to the Mach number of the aircraft, and the deviation value ΔT is obtained by subtracting the actual value T2 collected by the inlet temperature sensor; the current water supply amount expected value is calculated through a PID algorithm.

[0065] According to the PID control principle:

[0066]

[0067] Wherein: k p_out , T i_out, T d_out are outer loop proportional coefficient, outer loop integral constant and outer loop differential constant respectively;

[0068]

[0069] K d_out (k) = K p_out (k) x T d_out (k) (7)

[0070]

[0071] According to formula (6), (7), formula (8) is obtained, that is, the form of Kp, Ki and Kd.

[0072] The discrete PID parameter design method is adopted, the continuous quantity is discretized, and the closed-loop water quantity calculation formula is obtained as follows:

[0073]

[0074] Mode 3: When the jet pre-cooling system is switched from open-loop water supply to closed-loop water supply,

[0075] The difference ΔT between the desired value T2Dem of the total temperature of the inlet air and the actual value T2 of the total temperature of the inlet air is obtained, according to the size of the difference ΔT, the switching time t of the corresponding duration is selected, and the size of the closed-loop water supply desired value WwDem_closed is corrected, so that the difference between the open-loop water supply desired value WwDem_open and the closed-loop water supply desired value WwDem_closed and the switching time t are in a first function relationship;

[0076] 1) Open-loop mode to closed-loop mode conversion

[0077] Let the open-loop water quantity be W w Dem_open, the closed-loop water quantity be WwDem(k), the inlet total temperature set value be T2Dem, and the actual value of the inlet total temperature be T2.

[0078] Step one:

[0079] When the conversion instruction is received, the size of ΔT = T2-T2Dem is judged and the closed-loop water quantity WwDem(k) is calculated.

[0080] Step two:

[0081] If ΔT≤5K, then the difference between the open-loop water quantity W w Dem_open and the closed-loop water quantity WwDem(k) is corrected according to a first function relationship; K is in degrees Kelvin.

[0082] If 5K≤ΔT≤10K, the difference between the open-loop water quantity W w Dem_open and the closed-loop water quantity WwDem(k) is corrected as a linear function of WwDem(k);

[0083] If ΔT≥10K, the difference between the open-loop water quantity W w Dem_open and the closed-loop water quantity WwDem(k) is corrected as a linear function of WwDem(k).

[0084] Mode 4: When the ejection pre-cooling system is switched from closed-loop water supply to open-loop water supply, the difference ΔT between the desired value T2Dem of the total temperature of the inlet air and the actual value T2 of the total temperature of the inlet air is obtained, and according to the size of the difference ΔT, a switching time t corresponding to the range is selected, and the size of the open-loop water quantity WwDem_open is corrected so that the difference between the closed-loop water quantity WwDem_closed and the open-loop water quantity WwDem_open is a linear function of the switching time t.

[0085] 2) Closed-loop mode to open-loop mode conversion

[0086] Let the open-loop water quantity be W w Dem_open, the closed-loop water quantity be WwDem(k), and the total temperature of the inlet air set value be T2Dem and the actual value of the total temperature of the inlet air be T2.

[0087] Step one:

[0088] When the conversion instruction is received, the size of ΔT=T2-T2Dem is determined and the open-loop water quantity W w Dem_open is calculated.

[0089] Step two:

[0090] If ΔT≤5K, the difference between the closed-loop water quantity WwDem(k) and the open-loop water quantity W w Dem_open is corrected as a linear function of W w Dem_open;

[0091] If 5K≤ΔT≤10K, the difference between the closed-loop water quantity WwDem(k) and the open-loop water quantity W w Dem_open is corrected as a linear function of W w Dem_open;

[0092] If ΔT≥10K, the difference between the closed-loop water quantity WwDem(k) and the open-loop water quantity W wThe difference of Dem_open is proportional to W w Dem_open is modified.

[0093] The above merely provides the specific implementation of the present application, but the protection scope of the present application is not limited thereto, any person skilled in the art can easily think of the changes or replacements within the technical range disclosed by the present application, which should be covered in the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A control method for switching between open-loop and closed-loop modes of a fluidic precooling system, characterized in that, Comprise: Mode 1: when the jet precooling system carries out open-loop water supply, open-loop water quantity calculation is carried out: the total temperature expectation value T2Dem of inlet air is obtained, and the open-loop water supply quantity expectation value WwDem_open is calculated according to the total temperature expectation value T2Dem of inlet air and the actual value T2 of total temperature of inlet air collected by a sensor and the total pressure P2 of inlet air; the jet precooling device carries out water supply with the open-loop water supply quantity expectation value WwDem_open; Mode 2: when the jet precooling system carries out closed-loop water supply, closed-loop water quantity calculation is carried out: the total temperature expectation value T2Dem of inlet air is obtained, and the closed-loop water supply expectation value WwDem_closed is calculated through PID algorithm according to the total temperature expectation value T2Dem of inlet air and the actual value T2 of total temperature of inlet air collected by an inlet total temperature sensor; Mode 3: when the jet precooling system switches from open-loop water supply to closed-loop water supply, The difference ΔT between the total temperature expectation value T2Dem of inlet air and the actual value T2 of inlet air is obtained, and the switching time t of corresponding length is selected according to the size of the difference ΔT in different ranges, and the size of the closed-loop water supply expectation value WwDem_closed is corrected so that the difference between the open-loop water supply quantity expectation value WwDem_open and the closed-loop water supply expectation value WwDem_closed is a linear function of the switching time t; specifically: If ΔT≤5K, then the water quantity W is linearly transited from the open-loop water quantity W w The difference between Dem_open and the closed-loop water quantity WwDem(k) is corrected by a linear function of WwDem(k); K is the Kelvin degree; If 5K≤ΔT≤10K, then the difference between the open-loop water amount W w The difference between Dem_open and the closed-loop water amount WwDem(k) is corrected as a linear function of WwDem(k); ΔT ≥ 10 K, then the open-loop water amount W w The difference between Dem_open and the closed-loop water amount WwDem(k) is corrected as a linear function of WwDem(k); Mode 4: when the jet precooling system switches from closed-loop water supply to open-loop water supply, the difference ΔT between the total temperature expectation value T2Dem of inlet air and the actual value T2 of inlet air is obtained, and the switching time t of corresponding length is selected according to the size of the difference ΔT in different ranges, and the size of the open-loop water supply quantity expectation value WwDem_open is corrected so that the difference between the closed-loop water supply expectation value WwDem_closed and the open-loop water supply quantity expectation value WwDem_open is a linear function of the switching time t; specifically: If ΔT≤5K, then the water demand WDem(k) is modified in a linearly interpolated manner from the closed loop water demand WwDem(k) to the open loop water demand W w Dem_open as a function of the difference between W w Dem_open; If 5K < ΔT < 10K, then linearly interpolate from the closed loop water amount WwDem(k) to the open loop water amount W w Dem_open in a manner proportional to the difference between W w Dem_open; ΔT≥ 10 K, then the open-loop water amount W w Dem_open is modified by a difference value of W w Dem_open.

2. The control method of the on / off switching of the open / close loop mode of the fluidic precooling system according to claim 1, characterized by, The specific method for calculating the open-loop water supply quantity expectation value WwDem_open comprises: The temperature difference ΔT is obtained according to the total temperature expectation value T2Dem of inlet air and the actual value T2 of total temperature of inlet air collected by a sensor: F2 is calculated based on the corresponding relationship between the temperature difference ΔT and the water vapor table; Wherein, T2min is the minimum value of T2, T2max is the maximum value of T2, Lamda1 is the water vapor ratio corresponding to ΔT at T2min temperature, and Lamda2 is the water vapor ratio corresponding to ΔT at T2max temperature; F3 is calculated according to the inlet total temperature T2 and the inlet total pressure P2: where P std is a constant 101.325 KPa, T std is a constant 288.15 K; The open-loop water supply quantity expectation value WwDem_open is: WwDem_open = W 2R xF3 x F2; wherein W 2R is an intermediate quantity, which takes a value by W 2R and the engine low-pressure compressor speed N 1r relationship table selection.

3. The control method of the on / off switching mode of the fluidic precooling system according to claim 1, characterized by, The control principle calculation steps of the PID algorithm are: According to the PID control principle, the following is obtained: wherein k p_out is an outer loop proportional coefficient, T i_out is an outer loop integral constant, T d_out is an outer loop derivative constant; wherein, K d_out (k) = K p_out (k) x T d_out (k); k is the current period; then we obtain The closed-loop water quantity calculation formula is obtained by discretizing the continuous quantity as follows:

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