An air flow detection method

Abstract

The present invention relates to the technical field of flow measurement, and particularly relates to an air flow detection method, which includes using a sonic nozzle to measure the ultimate pressure of a stagnation chamber; calculating the ultimate pressure by using a Newton cooling model algorithm to obtain a target pressure value; making a rationality judgment on the target pressure value. If it is reasonable, the target nozzle is obtained and the next step is executed. If it is unreasonable, the sonic nozzle is replaced according to the rule of nozzle size and then the first step is executed; using the target nozzle to perform recursive search in a basic table to obtain an equivalent aperture, a flow value, and a nozzle number; searching for adjacent combined nozzles of the nozzle number, and performing flow combination on the adjacent combined nozzles based on the equivalent aperture and the flow value to obtain a combined nozzle; measuring the flow of the combined nozzle by using a Newton cooling model algorithm to obtain target data; fitting the target data according to the fluid Bernoulli equation to obtain a target result, solving the problem of the long detection time of the existing detection method.

Description

Technical Field

[0001] The present invention relates to the technical field of flow measurement, and in particular to an air flow detection method. Background Art

[0002] In the production control of throttle bodies for automobiles and motorcycles, it is necessary to detect and determine the air flow rate under a specific intake pressure at a specific opening. The common detection methods are as follows:

[0003] 1. Simulate the engine's intake capacity through a vacuum pump. By connecting a high-precision flowmeter in series on the measurement airway and adjusting the adjustable throttle valve to simulate the intake pressure, the flow rate is directly measured from the flowmeter.

[0004] This method has the following problems in the air flow measurement of the throttle body:

[0005] The accuracy of the flowmeter cannot effectively cover the flow range of the throttle body. Generally, the flow range of motorcycle throttle bodies is 1 - 3000 L / Min, and the accuracy of general high-precision flowmeters is 0.05% FS. For 3000 L / Min, its minimum measurement accuracy exceeds 1 L / min, and it cannot effectively measure. It is necessary to continuously change the measurement flowmeter, and it cannot measure continuously and quickly. Similarly, due to the measurement range, the control mechanism of the adjustable throttle valve at low flow rates is also different from that at high flow rates, and separate detections are also required;

[0006] Considering these defects, only the method of using multiple detection devices can be adopted to avoid them, which has a large investment, low utilization rate, long detection time, and poor efficiency.

[0007] 2. Detect the flow rate by using a sonic nozzle array. Its theoretical basis is that the flow rate of an ideal gas flowing through a sonic nozzle under critical pressure is proportional to the pressure. After the sonic nozzle is calibrated, the flow rate can be directly calculated using a formula.

[0008] In the air flow measurement of the throttle body by this method, through a multi-stage (generally 9 - 12 stages) sonic nozzle array, the standard flow rate of each stage of the nozzle is twice that of the previous stage, forming a measurement range of 1 - 1024 times, which can alleviate the deficiencies of the first measurement method above, but there are also new problems:

[0009] Since the sonic nozzle array is discrete, only specific flow combinations can be formed, and the continuously changing flow rate cannot be accurately measured. The test result is an approximate value, resulting in the result not being at the specified measurement point and the loss of accuracy; for more accurate measurement, a larger number of sonic nozzle stages are required, and the smallest sonic nozzle is difficult to manufacture and cannot meet the accuracy measurement requirements; to combine the sonic nozzle array, continuous trial and error are required; and since the pressure in the stagnation chamber at the front end of the sonic nozzle stabilizes slowly, the detection time is increased. Summary of the Invention

[0010] The object of the present invention is to provide an air flow detection method, aiming to solve the problem of long detection time of existing detection methods.

[0011] To achieve the above object, the present invention provides an air flow detection method, including the following steps:

[0012] S1 Measure the ultimate pressure of the stagnation chamber using a sonic nozzle;

[0013] S2 Calculate the ultimate pressure using the Newton cooling model algorithm to obtain the target pressure value;

[0014] S3 Judge the rationality of the target pressure value. If it is reasonable, obtain the target nozzle and execute step S4. If it is not reasonable, replace the sonic nozzle according to the nozzle size rule and then execute step S1;

[0015] S4 Recursively search in the basic table using the target nozzle to obtain the equivalent aperture, flow value and nozzle number;

[0016] S5 Search for adjacent combined nozzles of the nozzle number, and perform flow combination on the adjacent combined nozzles based on the equivalent aperture and the flow value to obtain a combined nozzle;

[0017] S6 Measure the flow rate of the combined nozzle using the Newton cooling model algorithm to obtain target data;

[0018] S7 Fit the target data according to the fluid Bernoulli equation to obtain the target result.

[0019] Wherein, the specific manner of judging the rationality of the target pressure value. If it is reasonable, obtain the target nozzle and execute step S4. If it is not reasonable, replace the sonic nozzle according to the nozzle size rule and then execute step S1 is:

[0020] Judge whether the target pressure value is between 35 and 85. If the target pressure value is between 35 and 85, obtain the target nozzle and execute step S4. If the target pressure value is not between 35 and 85, replace the sonic nozzle according to the nozzle size rule and then execute step S1.

[0021] Wherein, the specific manner of replacing the sonic nozzle according to the nozzle size rule and then executing step S1 when the target pressure value is not between 35 and 85 is:

[0022] If the target pressure value is less than 35, increment the code number of the sonic nozzle by 1 according to the rule of nozzle size and then execute step S1. If the target pressure value is greater than 85, decrement the code number of the sonic nozzle by 1 according to the rule of nozzle size and then execute step S1.

[0023] Among them, the basic table includes a nozzle pressure aperture table, an aperture pressure flow table, and a nozzle pressure flow table.

[0024] Among them, the specific method of recursively searching for the equivalent aperture, flow value, and nozzle number using the target nozzle in the basic table is as follows:

[0025] S41 Search for the equivalent aperture using the target nozzle in the nozzle pressure aperture table.

[0026] S42 Based on the equivalent aperture, search for the flow value using the target nozzle in the aperture pressure flow table.

[0027] S43 Based on the flow value, search for the nozzle number using the target nozzle in the nozzle pressure flow table.

[0028] Among them, the number of adjacent combined nozzles is 5 types.

[0029] Among them, the number of combined nozzles is at least 5 types.

[0030] An air flow detection method of the present invention measures the limit pressure of the stagnation chamber by using a sonic nozzle; calculates the target pressure value by using the Newton cooling model algorithm for the limit pressure; makes a rationality judgment on the target pressure value. If it is reasonable, obtain the target nozzle and execute the next step. If it is unreasonable, make a replacement for the sonic nozzle according to the rule of nozzle size and then execute the first step; recursively search for the equivalent aperture, flow value, and nozzle number using the target nozzle in the basic table; search for the adjacent combined nozzles of the nozzle number, and perform flow combination on the adjacent combined nozzles based on the equivalent aperture and the flow value to obtain a combined nozzle; measure the flow of the combined nozzle by using the Newton cooling model algorithm to obtain target data; fit the target data according to the fluid Bernoulli equation to obtain a target result, which shortens the detection time and solves the problem of the long detection time of the existing detection method. Description of the Drawings

[0031] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0032] Figure 1 It is the schematic diagram of an air flow detection method provided by the present invention.

[0033] Figure 2 It is the curve graph of the Bernoulli equation of air flow.

[0034] Figure 3 It is the curve graph of the Newton cooling model.

[0035] Figure 4 It is the flow chart of an air flow detection method provided by the present invention. Detailed implementation manners

[0036] The embodiments of the present invention will be described in detail below. Examples of the embodiments are shown in the accompanying drawings, where the same or similar reference numerals indicate the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to explain the present invention and should not be construed as limiting the present invention.

[0037] Please refer to Figures 1 to 4 , the present invention provides an air flow detection method, including the following steps:

[0038] S1 Measure the ultimate pressure of the stagnation box using a sonic nozzle;

[0039] Specifically, for an unknown throttle opening state, use a specific sonic nozzle (code CVM), use the No. 4 sonic nozzle, denoted as CVM4; at this time, measure the pressure P of the stagnation box.

[0040] S2 Calculate the ultimate pressure using the Newton cooling model algorithm to obtain the target pressure value;

[0041] Specifically, use the Newton cooling model algorithm, that is:

[0042] P(t) = P + (P0 - P)e-α(t - t0)

[0043] Where, P(t): the pressure of the measurement point (stagnation box) at time t (target pressure value);

[0044] P: the ultimate pressure of the stagnation box after long-term stabilization;

[0045] P0: the pressure at time 0 (i.e., when sampling starts);

[0046] e: the natural constant;

[0047] α: the exponent, different for different flow channel (including stagnation box) forms;

[0048] t: the sampling time;

[0049] t0: That is, the initial sampling moment, which can be replaced by 0;

[0050] That is, it is assumed that the stable process is exponentially decaying. Through multi-data acquisition in the relatively short detection time domain at the initial stage, the limit of the P value is obtained through digital simulation algorithms.

[0051] S3 judges the rationality of the target pressure value. If it is reasonable, the target nozzle is obtained and step S4 is executed. If it is not reasonable, the sonic nozzle is supplemented according to the nozzle size rule and then step S1 is executed;

[0052] Specifically, it is judged whether the target pressure value is between 35 and 85. If the target pressure value is between 35 and 85, the target nozzle is obtained and step S4 is executed. If the target pressure value is not between 35 and 85, the sonic nozzle is supplemented according to the nozzle size rule and then step S1 is executed.

[0053] The specific method for supplementing the sonic nozzle according to the nozzle size rule and then executing step S1 when the target pressure value is not between 35 and 85 is as follows:

[0054] If the target pressure value is less than 35, the code number of the sonic nozzle is incremented by 1 according to the nozzle size rule and then step S1 is executed. If the target pressure value is greater than 85, the code number of the sonic nozzle is decremented by 1 according to the nozzle size rule and then step S1 is executed.

[0055] S4 uses the target nozzle to perform recursive search in the basic table to obtain the equivalent aperture, flow value, and nozzle number;

[0056] Specifically, the basic table includes a nozzle pressure aperture table, an aperture pressure flow table, and a nozzle pressure flow table.

[0057] The specific method for using the target nozzle to perform recursive search in the basic table to obtain the equivalent aperture, flow value, and nozzle number is as follows:

[0058] S41 uses the target nozzle to search in the nozzle pressure aperture table to obtain the equivalent aperture;

[0059] Specifically, search the nozzle pressure aperture table. With the current used nozzle CVM number and the measured pressure P, look up the table to obtain the approximate equivalent aperture Φ of the channel.

[0060] The nozzle pressure aperture table:

[0061]

[0062] S42 based on the equivalent aperture, uses the target nozzle to search in the aperture pressure flow table to obtain the flow value;

[0063] Specifically, following the equivalent aperture Φ and the pressure P required by the technical specifications 目标 , look up the aperture-pressure-flow rate table to obtain the approximate flow rate value G of the target to be measured.

[0064] The aperture-pressure-flow rate table:

[0065]

[0066]

[0067] S43 Based on the flow rate value, use the target nozzle to look up in the nozzle-pressure-flow rate table to obtain the nozzle number.

[0068] Specifically, according to the nozzle-pressure-flow rate table, with P 目标 and the approximate flow rate G as conditions, the nozzle number CVM = X similar to the pressure conditions required by the technical specifications can be obtained.

[0069] The nozzle-pressure-flow rate table:

[0070]

[0071] S5 Look up the adjacent combined nozzles of the nozzle number, and perform flow rate combination on the adjacent combined nozzles based on the equivalent aperture and the flow rate value to obtain the combined nozzles;

[0072] Specifically, the number of the adjacent combined nozzles is 5 types. The number of the combined nozzles is at least 5 types.

[0073] Combine 5 nozzles (adjacent combined nozzles) near the obtained nozzle number X respectively, and the combined flow rate is between 0.6 and 1.5G; since the flow rate difference of each stage of nozzles is +1 times or less 1 / 2, the approximate combination is:

[0074] The first type of combined nozzle: CVM = X; the combined flow rate is G;

[0075] The second type of combined nozzle: CVM = X, a combination of two nozzles X - 1, and the combined flow rate is 1.5G at this time;

[0076] The third type of combined nozzle: CVM = X, a combination of two nozzles X - 2, and the combined flow rate is 1.25G at this time;

[0077] The fourth type of combined nozzle: CVM = X - 1, a combination of two nozzles X - 2, and the combined flow rate is 0.75G at this time;

[0078] The fifth type of combined nozzle: CVM = X - 1, a combination of two nozzles X - 3, and the combined flow rate is 0.625G at this time; ......

[0080] To improve the accuracy, more combinations can be analogized so that the flow rates of these combinations are more evenly distributed on both sides of the target flow rate.

[0081] S6 uses the Newton cooling model algorithm to measure the flow rate of the combined nozzle and obtains the target data;

[0082] Specifically, the corresponding pressure P is quickly obtained using the Newton cooling model algorithm, and according to the sonic nozzle flow measurement formula (the flow rate is linearly proportional to the pressure), in this way, 5 approximate data (target data) are obtained; generally, these 5 data will be distributed on both sides of the target result.

[0083] S7 fits the target data according to the fluid Bernoulli equation to obtain the target result.

[0084] Specifically, according to the fluid Bernoulli equation G = K.ΔP 1 / 2 , the general passage flow rate and pressure have a parabolic relationship. The 5 measured data are fitted by a parabola (i.e., a binomial digital simulation), and the target result is calculated.

[0085] Beneficial effects:

[0086] 1. It overcomes the inherent defect that the sonic nozzle measurement method cannot accurately measure and improves the measurement accuracy.

[0087] Generally, the technical specifications usually require measuring the flow rate under the common operating conditions of the engine -35KPa ± 0.5KPa. The sonic nozzle measurement method before improvement usually can only measure an uncertain value under -33KPa to -37KPa, and the error value exceeds 2%; while through the interpolation fitting of this method, a result equivalent to that measured by a direct flowmeter can be obtained, and the error value is below 0.5%;

[0088] 2. It shortens the accurate measurement time of the undetermined flow rate and can approximately double the efficiency.

[0089] The above-disclosed is only a preferred embodiment of an air flow rate detection method of the present invention. Of course, the scope of the rights of the present invention cannot be limited thereby. Those of ordinary skill in the art can understand all or part of the processes of implementing the above embodiments, and the equivalent changes made according to the claims of the present invention still fall within the scope covered by the invention.

Claims

1. An air flow detection method, characterized in that, It includes the following steps: S1 Use a sonic nozzle to measure the ultimate pressure of the stagnation chamber; S2 Calculate the ultimate pressure using the Newton cooling model algorithm to obtain the target pressure value; S3 Judge the rationality of the target pressure value. If it is reasonable, obtain the target nozzle and execute step S4. If it is unreasonable, replace the sonic nozzle according to the nozzle size rule and then execute step S1; S4 Use the target nozzle to perform recursive search in the basic table to obtain the equivalent aperture, flow value, and nozzle number; S5 Search for adjacent combined nozzles of the nozzle number, and perform flow combination on the adjacent combined nozzles based on the equivalent aperture and the flow value to obtain the combined nozzle; S6 Use the Newton cooling model algorithm to measure the flow rate of the combined nozzle to obtain the target data; S7 Fit the target data according to the fluid Bernoulli equation to obtain the target result.

2. The air flow rate detection method according to claim 1, wherein the specific method for judging the rationality of the target pressure value. If it is reasonable, obtain the target nozzle and execute step S4. If it is unreasonable, replace the sonic nozzle according to the nozzle size rule and then execute step S1 is: Judge whether the target pressure value is between 35 and 85. If the target pressure value is between 35 and 85, obtain the target nozzle and execute step S4. If the target pressure value is not between 35 and 85, replace the sonic nozzle according to the nozzle size rule and then execute step S1.

3. The air flow rate detection method according to claim 2, wherein the specific method for replacing the sonic nozzle according to the nozzle size rule and then executing step S1 when the target pressure value is not between 35 and 85 is: If the target pressure value is less than 35, add 1 to the code number of the sonic nozzle according to the nozzle size rule and then execute step S1. If the target pressure value is greater than 85, subtract 1 from the code number of the sonic nozzle according to the nozzle size rule and then execute step S1.

4. The air flow rate detection method according to claim 3, wherein the basic table includes a nozzle pressure aperture table, an aperture pressure flow table, and a nozzle pressure flow table.

5. The air flow rate detection method according to claim 4, wherein the specific method for using the target nozzle to perform recursive search in the basic table to obtain the equivalent aperture, flow value, and nozzle number is: S41 Use the target nozzle to search in the nozzle pressure aperture table to obtain the equivalent aperture; S42 Based on the equivalent aperture, use the target nozzle to search in the aperture pressure flow table to obtain the flow value; S43 Based on the flow value, use the target nozzle to search in the nozzle pressure flow table to obtain the nozzle number.

6. The air flow rate detection method according to claim 5, wherein the number of adjacent combined nozzles is 5 types.

7. The air flow rate detection method according to claim 6, wherein the number of combined nozzles is at least 5 types.

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