A model free-fall wind tunnel test method and timing control method

Abstract

The present invention relates to the technical field of wind tunnel tests, and in particular to a model free-fall wind tunnel test method and a timing control method, wherein the timing control method comprises: determining the time length T1 from triggering a model delivery device to the model falling to the axial height of a nozzle; estimating the time length T2 from opening a pulse-type wind tunnel to establishing an effective flow field; making a judgment based on the size of T1 and T2; if T1 is greater than or equal to T2, the model delivery device is first triggered, and after a first delay t1, the pulse-type wind tunnel is then opened, and the first delay t1=T1-T2; if T1 is less than T2, the pulse-type wind tunnel is first opened, and after a second delay t2, the model delivery device is triggered; the second delay t2=T2-T1, or the second delay t2 is determined based on the actual film-breaking pressure difference obtained after opening the pulse-type wind tunnel and T1. The present invention can accurately match the model delivery control and the wind tunnel operation timing to achieve zero-stiffness support aerodynamic measurement.

Description

Technical Field

[0001] The embodiments of the present invention relate to the technical field of wind tunnel testing, and in particular to a model free-fall wind tunnel testing method and a timing control method. Background Art

[0002] Pulse wind tunnels are important equipment for conducting ground tests of hypersonic aircraft flight environments. Hypersonic aircraft aerodynamic measurements usually involve installing an aircraft model in a pulse wind tunnel, generating a flow field that meets simulation conditions through the wind tunnel to act on the model, and then measuring the aerodynamic loads on the model.

[0003] Compared with the common tail support internal balance aerodynamic measurement technology, the zero-stiffness support aerodynamic measurement technology can effectively improve the frequency response and data credibility of the aerodynamic signal measurement in the wind tunnel test. However, since the model will move during the zero-stiffness support aerodynamic measurement test, and the effective test time of the pulse wind tunnel is very short, in order to accurately achieve the measurement, the model needs to be in an ideal position in the effective flow field within the effective test time window of the wind tunnel. Therefore, how to accurately match the model launch control and the wind tunnel operation sequence has become an urgent problem to be solved. Summary of the invention

[0004] In order to achieve accurate matching of model release control and wind tunnel operation timing in a wind tunnel zero-stiffness support aerodynamic measurement test, an embodiment of the present invention provides a model free-fall wind tunnel test method and a timing control method.

[0005] In a first aspect, an embodiment of the present invention provides a timing control method for a model free-fall wind tunnel test, comprising:

[0006] The timing control method is applied to a wind tunnel test system including a pulse-type wind tunnel and a model launching device; the pulse-type wind tunnel includes a high-pressure section, a membrane cavity, a low-pressure section, a nozzle and a test chamber, an upstream membrane and a downstream membrane are respectively arranged between the membrane cavity and the high-pressure section and the low-pressure section, the outlet end of the low-pressure section is connected to the nozzle, and a third membrane is arranged at the outlet end; the model launching device is arranged on the top of the test chamber, and is used for pure release of the model to be measured;

[0007] The timing control method comprises the following steps:

[0008] Determine the time length from triggering the model delivery device to the time when the model falls to the height of the axis of the nozzle, which is recorded as the first time period T1;

[0009] Estimate the time length from the start of the pulse wind tunnel to the establishment of an effective flow field, recorded as the second period T2;

[0010] The judgment is made based on the size of the first time period T1 and the second time period T2; if the first time period T1 is greater than or equal to the second time period T2, the model launching device is triggered first, and then the pulse type wind tunnel is opened after the first delay t1, and the first delay t1=T1-T2; if the first time period T1 is less than the second time period T2, the pulse type wind tunnel is opened first, and then the model launching device is triggered after the second delay t2; the second delay t2=T2-T1, or the second delay t2 is determined based on the actual membrane rupture pressure difference obtained after opening the pulse type wind tunnel and the first time period T1.

[0011] Optionally, the estimating the time length from starting the pulse wind tunnel to establishing an effective flow field includes:

[0012] Repeat the test to determine the corresponding relationship between the membrane rupture pressure difference and the time length from opening the pulse-type wind tunnel to the establishment of an effective flow field, t=f(P); wherein P represents the membrane rupture pressure difference, and t represents the time length from opening the pulse-type wind tunnel to the establishment of an effective flow field;

[0013] Estimating the membrane breaking pressure difference P' when the pulse wind tunnel is opened;

[0014] Based on the estimated membrane rupture pressure difference P' and the determined corresponding relationship t=f(P), the time length t' from the start of the pulse wind tunnel to the establishment of an effective flow field is estimated.

[0015] Optionally, the estimating the membrane rupture pressure difference P' for opening the pulse wind tunnel includes:

[0016] If the pulse-type wind tunnel is opened by inflation rupture, then the rupture pressure corresponding to the downstream diaphragm is estimated based on the effective thickness l1 of the downstream diaphragm, and is recorded as the predicted rupture pressure Pt; if the pulse-type wind tunnel is opened by deflation rupture, then the rupture pressure corresponding to the upstream diaphragm is estimated based on the effective thickness l2 of the upstream diaphragm, and is recorded as the predicted rupture pressure Pt;

[0017] Obtaining the inflation pressure P0 of the membrane cavity before opening the pulse wind tunnel through a pressure sensor disposed in the membrane cavity;

[0018] According to the predicted membrane rupture pressure Pt and the inflation pressure P0, the membrane rupture pressure difference P'=|P0-Pt| for opening the pulse type wind tunnel is calculated.

[0019] Optionally, the second delay t2 is determined based on an actual membrane rupture pressure difference obtained after the pulse wind tunnel is turned on and the first time period T1, and comprises the following steps:

[0020] Obtaining the inflation pressure P0 of the membrane cavity before opening the pulse wind tunnel through a pressure sensor disposed in the membrane cavity;

[0021] Determine the actual membrane rupture pressure Pt real ;

[0022] According to the actual membrane rupture pressure Pt real and the inflation pressure P0 of the membrane cavity before opening the pulse wind tunnel, to determine the actual membrane rupture pressure difference Preal'=|P0-Ptreal|;

[0023] Based on the actual membrane rupture pressure P real 'And the corresponding relationship between the membrane rupture pressure difference and the time length t=f(P), calculate the actual time length from the opening of the pulse wind tunnel to the establishment of the effective flow field, which is recorded as the third period T3;

[0024] The second delay time t2 is determined based on the third time period T3 and the first time period T1.

[0025] Optionally, the second delay t2 is determined based on the third time period T3 and the first time period T1, using the following formula:

[0026] t2=T3-T1-Δt

[0027] Wherein, Δt represents the length of time from when the pulse wind tunnel is turned on to when t2 is calculated.

[0028] Optionally, the actual membrane rupture pressure Pt is determined real ,include:

[0029] The actual membrane rupture pressure Pt is measured by a pressure sensor arranged at the downstream side of the downstream membrane. real ; The pressure sensor is located at the upstream of the low-pressure section.

[0030] In the second aspect, an embodiment of the present invention further provides a model free-fall wind tunnel test method, which is implemented based on a wind tunnel test system including a pulse wind tunnel and a model launching device, and uses the model free-fall wind tunnel test timing control method described in any of the above items to match the timing of wind tunnel operation and model launching, so as to open the wind tunnel and launch the model to be measured.

[0031] Optionally, the model free-fall wind tunnel test method further comprises, before opening the wind tunnel and launching the model to be measured:

[0032] Obtaining wind tunnel flow field parameters and model entity parameters of the model to be measured; the model is embedded with an accelerometer combination and an offline data acquisition device, the accelerometer combination includes a plurality of accelerometers, and the offline data acquisition device is connected to each of the accelerometers for acquiring and storing the measurement results of the accelerometers;

[0033] Based on the wind tunnel flow field parameters and the model entity parameters, estimating the magnitude of the aerodynamic force acting on the model in the wind tunnel flow field through finite element simulation;

[0034] Calculating the attitude angle variation range of the model in the wind tunnel flow field based on the estimated magnitude of the aerodynamic force on the model in the wind tunnel flow field, the model entity parameters and the effective test time of the wind tunnel flow field;

[0035] Determine whether the attitude angle change range of the model in the wind tunnel flow field does not exceed a preset angle change threshold, and if yes, continue;

[0036] Determine the accelerometer combination parameters embedded in the model; the accelerometer combination parameters include the final measurement parameters, installation positions, measurement ranges and measurement accuracy corresponding to each of the accelerometers; the final measurement parameters include one or more of axial force, normal force, lateral force, pitch moment, yaw moment and roll moment;

[0037] After the wind tunnel is opened and the model to be measured is placed, the method further includes:

[0038] Obtaining measurement results of all the accelerometers within the effective test time;

[0039] Based on the obtained measurement results of all the accelerometers and the accelerometer combination parameters, the actual aerodynamic force exerted on the model in the wind tunnel flow field is solved.

[0040] An embodiment of the present invention provides a timing control method for a model free-fall wind tunnel test. The timing control method determines the time length from triggering a model delivery device to the model falling to the axial height of a nozzle, and estimates the time length from starting a pulse wind tunnel to establishing an effective flow field. Based on the two time lengths, it is determined whether to delay starting the pulse wind tunnel or delay triggering the model delivery device, and a specific delay is determined to achieve accurate matching of model delivery control and wind tunnel operation timing, so that the model is in an ideal position in the effective flow field within the effective test time window of the wind tunnel.

[0041] An embodiment of the present invention also provides a model free-fall wind tunnel test method, which is implemented based on a wind tunnel test system including a pulse wind tunnel and a model launching device. The above-mentioned model free-fall wind tunnel test timing control method is used to match the timing of wind tunnel operation and model launching, so as to open the wind tunnel and launch the model to be measured, and then perform a free-fall zero-stiffness support aerodynamic measurement test on the model. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0043] Figure 1 This is a step diagram of a timing control method for a model free-fall wind tunnel test provided by an embodiment of the present invention;

[0044] Figure 2 It is a schematic diagram of the diaphragm structure used in the pulse wind tunnel;

[0045] Figure 3 It is a schematic diagram of the structure of a pulse wind tunnel;

[0046] Figure 4 It is a normalized comparison result diagram of membrane rupture pressure difference and the time length from opening the pulse wind tunnel to the establishment of effective flow field;

[0047] Figure 5 It is a flow chart of a timing control method for a model free-fall wind tunnel test provided by an embodiment of the present invention;

[0048] Figure 6 It is a flow chart of another timing control method for a model free-fall wind tunnel test provided by an embodiment of the present invention.

[0049] In the figure: 1: upstream diaphragm; 2: downstream diaphragm; 3: third diaphragm. DETAILED DESCRIPTION

[0050] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0051] As mentioned above, pulse wind tunnels are important equipment for conducting ground tests of hypersonic aircraft flight environments. The aerodynamic measurement test of hypersonic aircraft usually involves installing the aircraft model in a pulse wind tunnel, generating a flow field that meets the simulation conditions through the wind tunnel to act on the model, and then measuring the aerodynamic load on the model. Compared with the common tail support internal balance aerodynamic measurement technology, the zero-stiffness support aerodynamic measurement technology can effectively improve the measurement frequency response and data credibility of the aerodynamic signal of the wind tunnel test. One zero-stiffness support aerodynamic measurement technology is to release the model to be measured purely above the inside of the wind tunnel test chamber, allowing the model to fall freely through the wind tunnel flow field. Since the model will move and the effective test time of the pulse wind tunnel is very short, in order to accurately achieve the measurement, it is necessary to put the model in an ideal position in the effective flow field within the effective test time window of the wind tunnel. Considering that it takes a certain amount of time for the model to move to the ideal position after being released, and it also takes a certain amount of time for the wind tunnel to open and establish an effective flow field, how to accurately match the model release control and wind tunnel operation sequence has become an urgent problem to be solved. In view of this, the present invention provides a timing control method for a model free-fall wind tunnel test. For a heavy model free-fall zero-stiffness support aerodynamic measurement test, the matching of model launch and wind tunnel operation is achieved through calculation and judgment, so that the model is in an ideal position in the effective flow field within the effective test time window of the wind tunnel.

[0052] The specific implementation of the above concept is described below.

[0053] Please refer to Figures 1 to 3The embodiment of the present invention provides a timing control method for a model free-fall wind tunnel test (hereinafter referred to as the timing control method), which is applied to a wind tunnel test system including a pulse-type wind tunnel and a model launching device; the pulse-type wind tunnel includes a high-pressure section, a membrane cavity, a low-pressure section, a nozzle and a test cabin, and an upstream membrane 1 and a downstream membrane 2 are respectively arranged between the membrane cavity and the high-pressure section and the low-pressure section (that is, an upstream membrane 1 is arranged between the membrane cavity and the high-pressure section, and a downstream membrane 2 is arranged between the membrane cavity and the low-pressure section), the model is connected to the high-pressure section through a membrane cavity valve, and / or the model is connected to the low-pressure section through a membrane cavity valve. The outlet end of the low-pressure section is connected to the nozzle, and a third diaphragm 3 is provided at the outlet end. The high-pressure section is filled with high-pressure driving gas, and the low-pressure section is filled with low-pressure test gas. The inflation pressure in the membrane cavity is between the high-pressure section and the low-pressure section, that is, there is a pressure difference P1 between the high-pressure section and the membrane cavity, and there is a pressure difference P2 between the membrane cavity and the low-pressure section; before the wind tunnel is opened, the test chamber is in a vacuum state. After the wind tunnel is opened, the upstream diaphragm 1, the downstream diaphragm 2 and the third diaphragm 3 are all broken (that is, the wind tunnel membrane is broken), and the test gas is injected into the test chamber through the nozzle, forming an effective flow field for the test in the test chamber. The specific structure of the pulse wind tunnel can refer to the prior art and will not be further described. The model launching device is arranged at the top of the test chamber, above the area where the effective flow field is located, and is used to release the model to be measured purely.

[0054] The timing control method comprises the following steps:

[0055] Step 100, determining the time length from triggering the model delivery device to the time when the model falls to the height of the axis of the nozzle, which is recorded as the first time period T1;

[0056] Step 102, estimating the time length from the start of the pulse wind tunnel to the establishment of an effective flow field, recorded as the second period T2;

[0057] Step 104, making a judgment based on the lengths of the first time period T1 and the second time period T2;

[0058] If the first time period T1 is greater than or equal to the second time period T2 (T1≥T2), the model launching device is triggered first, and then the pulse wind tunnel is opened after the first delay t1; the first delay t1=T1-T2;

[0059] If the first time period T1 is less than the second time period T2 (T1<T2), the pulse type wind tunnel is opened first, and then the model launching device is triggered after the second delay t2; wherein, the second delay t2=T2-T1, or, the second delay t2 is determined based on the actual membrane rupture pressure difference obtained after opening the pulse type wind tunnel and the first time period T1.

[0060] Since the effective test time is very short, the model needs to be in the ideal position of the effective flow field within the effective test time window. There is a problem of matching the model release control and the wind tunnel operation timing. If the wind tunnel breaks the membrane in advance relative to the moment when the model falls to the ideal position, the effective flow field may have ended and the model has not yet reached the ideal position area; if the membrane is broken late, the effective flow field may not have been established and the model has fallen out of the ideal position area. In order to avoid such situations and improve the success rate of the test, it is necessary to predict the time when the effective flow field is established, that is, to estimate the length of time from the opening of the pulse wind tunnel to the establishment of the effective flow field.

[0061] The timing control method provided by the present invention is applied to a wind tunnel test system including a pulse wind tunnel and a model delivery device, and the main purpose is to place the model in an ideal position in the effective flow field within the effective test time window of the wind tunnel through timing control. In step 100, the moment when the model delivery device is triggered, that is, the moment when the model delivery device receives the release instruction and starts to release the model to be measured in a pure manner, the present invention determines the first time period T1 based on the height of the axis of the model falling to the nozzle, so as to ensure that even if there is a certain error in the calculation, the model can be in the effective flow field range near the axis as expected within the effective test time. In step 102, the second time period T2 is estimated. From the start of the pulse-type wind tunnel to the establishment of an effective flow field, it can be divided into two stages. Stage one is from the start of the pulse-type wind tunnel to the completion of membrane rupture (referred to as membrane rupture time), and stage two is from the completion of membrane rupture to the establishment of an effective flow field. The time required from the completion of membrane rupture to the establishment of an effective flow field is generally relatively stable, but the time from the start of the pulse-type wind tunnel to the completion of membrane rupture is related to the actual performance of the diaphragm used (i.e., upstream diaphragm 1 and downstream diaphragm 2). Due to factors such as material uniformity and processing tolerance, there will be a certain deviation in the membrane rupture pressure difference between diaphragms of the same specification and different diaphragms, which will lead to a certain deviation in the membrane rupture time (i.e., the time required for stage one). Therefore, the estimated second time period T2 may deviate from the actual time length from the start of the pulse-type wind tunnel to the establishment of an effective flow field. In step 104, a judgment is made based on the size of the first time period T1 and the second time period T2, and the deviation between the first time period T1 and the second time period T2 is balanced by delaying the start of the wind tunnel or delaying the triggering of the model delivery device. If it is necessary to trigger the model delivery device first, and then open the pulse wind tunnel after the first delay t1, the first delay t1 can only be calculated based on the estimated second time period T2, which may not be consistent with the actual situation. In other words, there is a certain probability of failure in the test, and the model cannot be placed in the ideal position in the effective flow field within the effective test time window of the wind tunnel. If the pulse wind tunnel can be opened first, and the model delivery device can be triggered after the second delay t2, the second delay t2 can be calculated based on the estimated second time period T2, or the actual membrane rupture pressure difference can be measured after the pulse wind tunnel is opened, and determined based on the actual membrane rupture pressure difference and the first time period T1. In this way, the time length from the opening of the pulse wind tunnel to the establishment of the effective flow field can be determined more accurately, thereby increasing the probability of successful testing.

[0062] Described below Figure 1 How the various steps are performed.

[0063] For step 100, "determining the length of time from triggering the model delivery device to the model falling to the height of the axis of the nozzle" includes:

[0064] Through repeated tests, the length of time from triggering the model launching device to the time the model falls to the height of the axis of the nozzle is determined.

[0065] Furthermore, step 100 may also include:

[0066] By calculating the model falling time, the length of time from triggering the model delivery device to the model falling to the axial height of the nozzle is verified.

[0067] By adopting the above embodiment, the size of the first time period T1 can be effectively determined. By calculating the falling time of the model, the accuracy of the T1 value obtained by repeated tests can be verified. Assuming that the nozzle diameter is 2m, the ideal test position is the nozzle axis, and the time from the release of the model to the arrival at the nozzle axis position is about 450ms.

[0068] With respect to step 102, “estimating the time length from starting the pulse wind tunnel to establishing an effective flow field” includes:

[0069] Repeat the test to determine the corresponding relationship between the membrane rupture pressure difference and the time length from opening the pulse-type wind tunnel to the establishment of an effective flow field, t=f(P); wherein P represents the membrane rupture pressure difference, and t represents the time length from opening the pulse-type wind tunnel to the establishment of an effective flow field;

[0070] Estimating the membrane breaking pressure difference P' when the pulse wind tunnel is opened;

[0071] Based on the estimated membrane rupture pressure difference P' and the determined correspondence between the membrane rupture pressure difference and the time length from opening the pulse type wind tunnel to establishing an effective flow field t=f(P), the time length t'=f(P') from opening the pulse type wind tunnel to establishing an effective flow field is estimated.

[0072] Furthermore, the estimating of the membrane rupture pressure difference P' for opening the pulse wind tunnel includes:

[0073] If the pulse-type wind tunnel is opened by inflation rupture, then the rupture pressure corresponding to the downstream diaphragm is estimated based on the effective thickness l1 of the downstream diaphragm, and is recorded as the predicted rupture pressure Pt; if the pulse-type wind tunnel is opened by deflation rupture, then the rupture pressure corresponding to the upstream diaphragm is estimated based on the effective thickness l2 of the upstream diaphragm, and is recorded as the predicted rupture pressure Pt;

[0074] Obtaining the inflation pressure P0 of the membrane cavity before opening the pulse wind tunnel through a pressure sensor disposed in the membrane cavity;

[0075] According to the predicted membrane rupture pressure Pt and the inflation pressure P0, the membrane rupture pressure difference P'=|P0-Pt| for opening the pulse wind tunnel is calculated. The membrane rupture pressure difference is a positive value.

[0076] The methods of opening the pulse-type wind tunnel include inflation rupture and deflation rupture. If the method of opening the pulse-type wind tunnel is inflation rupture, opening the pulse-type wind tunnel (or triggering the pulse-type wind tunnel) means opening the membrane cavity valve (also called inflation membrane cavity valve) connecting the high-pressure section and the membrane cavity. Because the high-pressure section and the membrane cavity are separated by the upstream diaphragm 1 and there is a pressure difference between the high-pressure section and the membrane cavity, the gas will automatically flow into the membrane cavity through the membrane cavity valve and the pipeline, causing the pressure of the membrane cavity to increase, and increasing the pressure difference between the membrane cavity and the low-pressure section. At this stage, the pressure rise of the membrane cavity takes a certain amount of time. After the pressure in the membrane cavity rises to a certain level, the downstream diaphragm 2 is squeezed and broken. At this time, the membrane cavity and the low-pressure section space are integrated, the pressure of the membrane cavity space drops sharply, and the pressure difference borne by the upstream diaphragm 1 rises sharply. This stage is very short, the upstream diaphragm 1 breaks quickly, and almost at the same time, the third diaphragm 3 also breaks, completing the membrane rupture, the wind tunnel starts, and gas is injected into the test cabin from the nozzle to form a flow field. If the pulse-type wind tunnel is opened by deflation and membrane rupture, the pulse-type wind tunnel is opened and the membrane cavity valve (also called deflation membrane cavity valve) connecting the membrane cavity and the low-pressure section is opened, the gas in the membrane cavity enters the low-pressure section, and the pressure in the membrane cavity gradually decreases. It takes a certain amount of time for the pressure to drop in this stage. As the pressure in the membrane cavity decreases, the pressure difference between the high-pressure section and the membrane cavity increases, and the upstream diaphragm 1 is squeezed and ruptured. At this time, the high-pressure section and the membrane cavity space are integrated, the pressure in the membrane cavity space increases suddenly, and the pressure difference on the downstream diaphragm 2 increases suddenly. This stage is very short, and the downstream diaphragm 2 ruptures quickly. Almost at the same time, the third diaphragm 3 also ruptures, completing the membrane rupture and starting the wind tunnel.

[0077] Through a large number of tests and analytical comparisons, the present invention finds that in the inflation membrane rupture mode, the membrane rupture pressure difference corresponding to the downstream diaphragm 2 (the membrane rupture pressure difference is the membrane cavity pressure at the moment of membrane rupture minus the membrane cavity inflation pressure before the start of the test) is linearly related to the time from valve opening to flow field establishment, and in the deflation membrane rupture mode, the membrane rupture pressure difference corresponding to the upstream diaphragm 1 (the membrane rupture pressure difference is the membrane cavity inflation pressure before the start of the test minus the membrane cavity pressure at the moment of membrane rupture) is linearly related to the time from valve opening to flow field establishment. Figure 4 This is a normalized comparison of the membrane rupture pressure difference and the time length from the start of the pulse wind tunnel to the establishment of an effective flow field. Figure 4 The horizontal axis is the test round, and the vertical axis is the normalized value. Figure 4 The medium dark gray dots represent the normalized membrane rupture pressure difference, and the light gray dots represent the normalized time length from opening the pulse wind tunnel to the establishment of an effective flow field (also called the time from valve opening to flow field establishment). Due to the high overlap, the light gray dots are mainly displayed, and most of the dark gray dots are covered. Therefore, the present invention proposes to use the estimated membrane rupture pressure difference P' and the determined corresponding relationship t=f(P) to estimate the time length t' from opening the pulse wind tunnel to the establishment of an effective flow field.

[0078] The membrane rupture pressure difference depends on two parameters: the inflation pressure of the membrane cavity before opening the pulse-type wind tunnel (i.e., the final membrane cavity inflation pressure) and the membrane rupture pressure. The final membrane cavity inflation pressure can be measured and determined by a preset membrane cavity pressure sensor before opening the wind tunnel, but the accurate membrane rupture pressure can only be determined at the moment of diaphragm rupture. The membrane rupture pressure is affected by factors such as the degree of deformation of the diaphragm under the final membrane cavity inflation pressure, the effective thickness of the diaphragm, and the diaphragm processing accuracy. It is mainly related to the effective thickness of the diaphragm and is approximately proportional. That is, the greater the effective thickness of the diaphragm, the higher the membrane rupture pressure. The structure of the diaphragm (including the upstream diaphragm 1, the downstream diaphragm 2, and the third diaphragm 3) is as follows: Figure 2 As shown, in order to ensure the controllable membrane rupture pressure and uniform membrane rupture, a cross groove is opened in the middle of the diaphragm. The effective thickness of the diaphragm is the thickness corresponding to the bottom area of ​​the cross groove. For inflation membrane rupture, the downstream diaphragm 2 ruptures first, and the downstream diaphragm 2 plays a leading role. When estimating the membrane rupture pressure (that is, determining the predicted membrane rupture pressure Pt), the effective thickness of the downstream diaphragm 2 is mainly used as the basis; if it is deflation membrane rupture, then the upstream diaphragm 1 ruptures first. When estimating the membrane rupture pressure, the effective thickness of the upstream diaphragm 1 is mainly used as the basis. The specific correspondence between the effective thickness of the diaphragm and the membrane rupture pressure can be determined by repeated experiments. After determining the specific correspondence, the effective thickness of the corresponding diaphragm is obtained, and the corresponding membrane rupture pressure can be estimated.

[0079] By adopting the above embodiment, the length of time from opening the pulse-type wind tunnel to establishing an effective flow field can be estimated in combination with the actual situation of the diaphragm, so that the estimated second time period T2 is as close to the actual situation as possible, so as to accurately determine the sequence and specific delay of triggering the model launching device and opening the pulse-type wind tunnel.

[0080] With respect to step 104, "the second delay t2 is determined based on the actual membrane rupture pressure difference obtained after the pulse wind tunnel is turned on and the first time period T1", further comprising the following steps:

[0081] Obtaining the inflation pressure P0 of the membrane cavity before opening the pulse wind tunnel through a pressure sensor disposed in the membrane cavity;

[0082] Determine the actual membrane rupture pressure Pt real ;

[0083] According to the actual membrane rupture pressure Pt real and the inflation pressure P0 of the membrane cavity before opening the pulse wind tunnel, to determine the actual membrane rupture pressure difference Preal'=|P0-Ptreal|;

[0084] Based on the actual membrane rupture pressure P real' and the corresponding relationship between the membrane rupture pressure difference and the time length t = f (P), calculate the actual time length from the opening of the pulse wind tunnel to the establishment of the effective flow field, which is recorded as the third period T3; T3 = f (P real ');

[0085] The second delay time t2 is determined based on the third time period T3 and the first time period T1.

[0086] By adopting the above embodiment, the membrane rupture pressure can be measured, the membrane rupture time can be calculated at high speed, and the delay amount can be automatically set to calculate the actual time length from opening the pulse wind tunnel to the establishment of an effective flow field, thereby obtaining a more accurate delay and improving the probability of test success.

[0087] Further, the second delay t2 is determined based on the third time period T3 and the first time period T1, using the following formula:

[0088] t2=T3-T1-Δt

[0089] Wherein, Δt represents the length of time from when the pulse wind tunnel is turned on to when t2 is calculated.

[0090] The above embodiment not only takes into account the actual time length from opening the pulse wind tunnel to the establishment of an effective flow field (i.e., T3), but also takes into account the calculation time from measuring the membrane rupture pressure to obtaining the calculation result (i.e., Δt). In other words, the calculation accuracy of the delay amount can be further improved by calibrating the time required for calculation and deducting the time required for calculation. The specific value of Δt can be determined by calibration. Δt should have good repeatability and should not be too large (should be less than t2). The larger the Δt, the higher the resolution requirement for the delay device. If the first delay t1 = T1-T2 or the second delay t2 = T2-T1, the estimated second time period T2 can be used directly without considering the influence of the calculation time.

[0091] Furthermore, the actual membrane rupture pressure Pt is determined real ,include:

[0092] The actual membrane rupture pressure Pt is measured by a pressure sensor arranged at the downstream side of the downstream membrane. real ; The pressure sensor is located at the upstream of the low-pressure section.

[0093] The above embodiment obtains the actual membrane rupture pressure through actual measurement by the pressure sensor. The closer the pressure sensor is to the membrane cavity, the more accurate the measured result is, which is conducive to improving the calculation accuracy of the delay amount.

[0094] In a specific embodiment, Figure 5 and Figure 6As shown in the figure, the nozzle diameter is 2m, the ideal test position is the nozzle axis, the time from the release of the model to the arrival of the nozzle axis position is about T1 = 450ms, and the duration of the second stage from the completion of the wind tunnel film breaking to the establishment of the effective flow field is relatively stable, about 30ms. Therefore, the time length T2 from the opening of the pulse wind tunnel to the establishment of the effective flow field is estimated. If T2 is greater than 450ms, the timing control method is as follows Figure 5 As shown, the membrane breaking time T2'>420ms, when the test is triggered, the pulse wind tunnel is first turned on, and after the second delay t2, the model launching device is triggered, t2=T2-T1=(T2'+30)-450=T2'-420ms; if T2 is less than or equal to 450ms, the timing control method is as follows Figure 6 As shown, the membrane breaking time T2'≤420ms, the model launching device is triggered first, and then the pulse wind tunnel is opened after the first delay t1, and the first delay t1=T1-T2=450-(T2'+30)=420-T2'ms.

[0095] The present invention also provides a model free-fall wind tunnel test method, which is implemented based on a wind tunnel test system including a pulse wind tunnel and a model launching device, and adopts the model free-fall wind tunnel test timing control method described in any of the above embodiments to match the timing of wind tunnel operation and model launching, so as to open the wind tunnel and launch the model to be measured.

[0096] Preferably, the model free-fall wind tunnel test method is implemented based on a wind tunnel test system including an impulse wind tunnel and a model launching device, and comprises the following steps:

[0097] Obtaining wind tunnel flow field parameters and model entity parameters of the model to be measured; the model is embedded with an accelerometer combination and an offline data acquisition device, the accelerometer combination includes a plurality of accelerometers, and the offline data acquisition device is connected to each of the accelerometers for acquiring and storing the measurement results of the accelerometers;

[0098] Based on the wind tunnel flow field parameters and the model entity parameters, estimating the magnitude of the aerodynamic force acting on the model in the wind tunnel flow field through finite element simulation;

[0099] Calculating the attitude angle variation range of the model in the wind tunnel flow field based on the estimated magnitude of the aerodynamic force on the model in the wind tunnel flow field, the model entity parameters and the effective test time of the wind tunnel flow field;

[0100] Determine whether the attitude angle change range of the model in the wind tunnel flow field does not exceed a preset angle change threshold, and if yes, continue;

[0101] Determine the accelerometer combination parameters embedded in the model; the accelerometer combination parameters include the final measurement parameters, installation positions, measurement ranges and measurement accuracy corresponding to each of the accelerometers; the final measurement parameters include one or more of axial force, normal force, lateral force, pitch moment, yaw moment and roll moment;

[0102] The timing control method for the model free-fall wind tunnel test described in any one of the above embodiments is used to match the timing of the wind tunnel operation and the model placement, so as to open the wind tunnel and place the model to be measured, and allow the model to fall freely in the wind tunnel flow field;

[0103] Obtaining measurement results of all the accelerometers within the effective test time;

[0104] Based on the obtained measurement results of all the accelerometers and the accelerometer combination parameters, the actual aerodynamic force exerted on the model in the wind tunnel flow field is solved.

[0105] Considering the lack of a supporting structure, the model has a higher degree of freedom. If the model's attitude changes significantly within the effective test time, the measurement results may be distorted. Therefore, the present invention obtains the wind tunnel flow field parameters and the model entity parameters of the model to be measured, estimates the attitude angle changes that may occur in the model during the wind tunnel test, and compares them with the preset angle change threshold, so as to determine whether the current model is suitable for measuring aerodynamic forces in the zero-rigidity support form provided by the present invention, so as to obtain more accurate and reliable measurement results. The present invention uses an embedded accelerometer combination and an offline data acquisition device in the model to be measured. Through the measurement results of the accelerometer combination, the actual value of the final measurement parameter is calculated, and the corresponding measurement results can be obtained without the model moving a significant displacement. The present invention can break the frequency response limitation of the cantilever beam configuration and effectively improve the measurement frequency response. Compared with the frequency response of about 20 Hz of the tail support internal balance aerodynamic measurement technology, the frequency response of the model free-fall wind tunnel test method provided by the present invention can be improved to more than 1000 Hz. At the same time, the wind tunnel test system used for measurement has a more compact structure and higher rigidity, which can reduce the interference of difficult-to-handle low-frequency interference on the model aerodynamic measurement signal, improve data credibility, and thus more accurately measure millisecond-level instantaneous aerodynamic signals.

[0106] It should be noted that, in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0107] A person of ordinary skill in the art can understand that all or part of the steps of implementing the above method embodiments can be completed by hardware related to program instructions, and the aforementioned program can be stored in a computer-readable storage medium. When the program is executed, it executes the steps of the above method embodiments; and the aforementioned storage medium includes: ROM, RAM, magnetic disk or optical disk, etc., various media that can store program codes.

[0108] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A timing control method for a model free-fall wind tunnel test, characterized in that: The timing control method is applied to a wind tunnel test system including a pulse-type wind tunnel and a model launching device; the pulse-type wind tunnel includes a high-pressure section, a membrane cavity, a low-pressure section, a nozzle and a test chamber, an upstream membrane and a downstream membrane are respectively arranged between the membrane cavity and the high-pressure section and the low-pressure section, the outlet end of the low-pressure section is connected to the nozzle, and a third membrane is arranged at the outlet end; the model launching device is arranged on the top of the test chamber, and is used for pure release of the model to be measured; The timing control method comprises the following steps: Determine the time length from triggering the model delivery device to the time when the model falls to the height of the axis of the nozzle, which is recorded as the first time period T1; Estimate the time length from the start of the pulse wind tunnel to the establishment of an effective flow field, recorded as the second period T2; The judgment is made based on the size of the first time period T1 and the second time period T2; if the first time period T1 is greater than or equal to the second time period T2, the model launching device is triggered first, and then the pulse type wind tunnel is opened after the first delay t1, and the first delay t1=T1-T2; if the first time period T1 is less than the second time period T2, the pulse type wind tunnel is opened first, and then the model launching device is triggered after the second delay t2; the second delay t2=T2-T1, or the second delay t2 is determined based on the actual membrane rupture pressure difference obtained after opening the pulse type wind tunnel and the first time period T1.

2. The timing control method according to claim 1, characterized in that: The estimating the time length from starting the pulse wind tunnel to establishing an effective flow field comprises: Repeat the test to determine the corresponding relationship between the membrane rupture pressure difference and the time length from opening the pulse-type wind tunnel to the establishment of an effective flow field, t=f(P); wherein P represents the membrane rupture pressure difference, and t represents the time length from opening the pulse-type wind tunnel to the establishment of an effective flow field; Estimating the membrane rupture pressure difference P' when the pulse wind tunnel is opened; Based on the estimated membrane rupture pressure difference P' and the determined corresponding relationship t=f(P), the time length t' from the start of the pulse wind tunnel to the establishment of an effective flow field is estimated.

3. The timing control method according to claim 2, characterized in that: The estimating the membrane rupture pressure difference P' for opening the pulse wind tunnel comprises: If the pulse-type wind tunnel is opened by inflation rupture, then the rupture pressure corresponding to the downstream diaphragm is estimated based on the effective thickness l1 of the downstream diaphragm, and is recorded as the predicted rupture pressure Pt; if the pulse-type wind tunnel is opened by deflation rupture, then the rupture pressure corresponding to the upstream diaphragm is estimated based on the effective thickness l2 of the upstream diaphragm, and is recorded as the predicted rupture pressure Pt; Obtaining the inflation pressure P0 of the membrane cavity before opening the pulse wind tunnel through a pressure sensor disposed in the membrane cavity; According to the predicted membrane rupture pressure Pt and the inflation pressure P0, the membrane rupture pressure difference P'=|P0-Pt| for opening the pulse type wind tunnel is calculated.

4. The timing control method according to claim 2, characterized in that: The second delay t2 is determined based on the actual membrane rupture pressure difference obtained after the pulse wind tunnel is turned on and the first time period T1, and includes the following steps: Obtaining the inflation pressure P0 of the membrane cavity before opening the pulse wind tunnel through a pressure sensor disposed in the membrane cavity; Determine the actual membrane rupture pressure Pt real ; According to the actual membrane rupture pressure Pt real and the inflation pressure P0 of the membrane cavity before opening the pulse wind tunnel, to determine the actual membrane rupture pressure difference Preal'=|P0-Ptreal|; Based on the actual membrane rupture pressure P real 'And the corresponding relationship between the membrane rupture pressure difference and the time length t=f(P), calculate the actual time length from the opening of the pulse wind tunnel to the establishment of the effective flow field, which is recorded as the third period T3; The second delay time t2 is determined based on the third time period T3 and the first time period T1.

5. The timing control method according to claim 4, characterized in that: The second delay t2 is determined based on the third time period T3 and the first time period T1, using the following formula: t2=T3-T1-Δt Wherein, Δt represents the length of time from when the pulse wind tunnel is turned on to when t2 is calculated.

6. The timing control method according to claim 4, characterized in that: Determining the actual membrane rupture pressure Pt real ,include: The actual membrane rupture pressure Pt is measured by a pressure sensor arranged at the downstream side of the downstream membrane. real ; The pressure sensor is located at the upstream of the low-pressure section.

7. A model free-fall wind tunnel test method, characterized in that: Based on a wind tunnel test system including a pulse wind tunnel and a model launching device, the model free-fall wind tunnel test timing control method described in any one of claims 1 to 6 is used to match the timing of wind tunnel operation and model launching, so as to open the wind tunnel and launch the model to be measured.

8. The model free-fall wind tunnel test method according to claim 7, characterized in that: Before the wind tunnel is opened and the model to be measured is placed, the method further includes: Obtaining wind tunnel flow field parameters and model entity parameters of the model to be measured; the model is embedded with an accelerometer combination and an offline data acquisition device, the accelerometer combination includes a plurality of accelerometers, and the offline data acquisition device is connected to each of the accelerometers for acquiring and storing the measurement results of the accelerometers; Based on the wind tunnel flow field parameters and the model entity parameters, estimating the magnitude of the aerodynamic force acting on the model in the wind tunnel flow field through finite element simulation; Calculating the attitude angle variation range of the model in the wind tunnel flow field based on the estimated magnitude of the aerodynamic force on the model in the wind tunnel flow field, the model entity parameters and the effective test time of the wind tunnel flow field; Determine whether the attitude angle change range of the model in the wind tunnel flow field does not exceed a preset angle change threshold, and if yes, continue; Determine the accelerometer combination parameters embedded in the model; the accelerometer combination parameters include the final measurement parameters, installation positions, measurement ranges and measurement accuracy corresponding to each of the accelerometers; the final measurement parameters include one or more of axial force, normal force, lateral force, pitch moment, yaw moment and roll moment; After the wind tunnel is opened and the model to be measured is placed, the method further includes: Obtaining measurement results of all the accelerometers within the effective test time; Based on the obtained measurement results of all the accelerometers and the accelerometer combination parameters, the actual aerodynamic force exerted on the model in the wind tunnel flow field is solved.

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