RU2770512C1 - Method for determining the flow characteristics (fc) of jet flow sensors (jfs) - Google Patents

Abstract

FIELD: measuring technology.SUBSTANCE: method for determining the flow characteristics of jet flow sensors by drawing air from the atmosphere through three sensors installed in series and an exemplary micronozzle, fixing temperature, atmospheric air pressure, vacuum at the output of the first, second and third sensors, the output signal f1of the first sensor. The characteristics of the first sensor (1) are determined when two sequentially installed second (2) and third (3) sensors are connected in parallel to the first sensor, identical in characteristics to the first (1), and the third sensor (3) is installed to obtain a vacuum on the second sensor (2) equal to half of the vacuum on the first (1), at the same time: at the first stage, the air is drawn in such a way that the output signal f11of the first sensor (1) corresponds to the output signal f1of the first sensor (1) when testing the sensor with a exemplary micronozzle (4). Fix the output signals f11, f21of the first (1) and second sensor (2), the vacuum at the output of the first ΔR11and the second ΔR21sensor, at the second stage, the air broach is set so that the output signal f12of the first sensor (1) becomes equal to the output signal f21of the second sensor (2) at the previous stage, output signals f12, f22of the first and second sensors are fixed, at the Nth stage, the air broach is set so that the output signal f1Nof the first sensor (1) becomes equal to the output signal f2N-1of the second sensor (2) at the previous (N-1)-th stage, the output signals f1N, f2Nof the first and second sensor are fixed, PX ΔP1N= f (Q1N) of the sensor is determined, where ΔP1N= DR11/2(N-1)is the amount of vacuum at the output of the first sensor (1); Q1Nis the amount of flow through the first sensor corresponding to the output signal f1N.EFFECT: increase in the accuracy of determining the flow characteristics of jet flow sensors is achieved.3 cl, 2 dwg

Description

SUBSTANCE: invention relates to measuring technique and can be used in determining РХ of inkjet flow sensors.

There is a known method for determining the RH of the control channel (or the power channel, or the output channel) of the jet element, by setting the pressure at the inlet to the control channel of the jet element, measuring the air flow in the control channel and determining the RH of the control channel ΔРу=f(Qy) (or the power channel , or output channel) (see L.A. Zalmanzon “Theory of Pneumonic Elements”, Iz-vo “Nauka”, M., 1969, p. 418).

The disadvantage of this method is the low accuracy of determining RH.

There is also known a method for determining the RH of the hydraulic tract and a device for its implementation, which consists in experimentally determining the pressure loss at local resistances in the hydraulic tract by pouring it - setting the value H of a constant pressure level (where: H is the pressure drop in the hydraulic tract) and determining the flow rate environment through the hydraulic path by weighing the doses of water that have passed for a given time (see patent RU No. 2582486 C1 dated 03/04/2015)

The disadvantage of this method is the low accuracy of determining the RH at low costs - at low values of the difference H.

There is also a method for determining the calculated RH of series-connected local resistances, which consists in using the Bernoulli equation for a steady turbulent movement of a fluid with the determination of head losses at local resistances using reference literature (see I.E. Idelchik "Handbook of hydraulic resistances", M. , Mashinostroenie, 1992).

The disadvantage of this method is the low accuracy of determining the RH of local resistances at low flow rates, especially in transitional (laminar-turbulent) flow regimes in local resistances.

The closest technical solution is a “Stand for testing gas meters with an electromechanical readout device” (see patent RU No. 2873 U1, G01F 25/00, dated February 28, 1995) containing a flow sensor, the output of which is connected to the inlet of the low pressure cavity , the input - with the output channel of the counter (flowmeter), the input channel of the counter is connected to the atmosphere, and the channel at the input to the flow setter (meter output) is connected to a pressure measuring device (means for measuring the pressure drop on the counter). The method for determining the PX of the gas meter consists in measuring the air temperature at the inlet to the meter and atmospheric pressure, measuring the vacuum at the inlet to the exemplary micronozzle (OMN) (equal to the pressure difference ΔP on the meter), determining the flow rate Q passing through the meter and determining the PX (dependence ΔP = f(Q)) of the counter.

The disadvantage of this method is that it does not provide high accuracy in determining the RH SDR of the meter due to the low accuracy in determining the differences in the gas meter at low flow rates, when the differences in the meter are fractions of millimeters of water column (at present, our industry does not produce differential pressure meters capable of measuring differences with an error of 0.001 mm water column).

The technical result, which the claimed method is aimed at, is to increase the accuracy of determining the RH SDR.

To achieve the specified technical result, the method for determining the RH SDR is implemented as follows: air is drawn from the atmosphere through three SDRs and OMS installed in series, the temperature, atmospheric air pressure, vacuum at the output of the first, second and third SDRs, the output signal f _{1 of} the first SDR are recorded, determination of the RH of the first SDR when connecting in parallel to the first SDR two second and third SDRs installed in series, identical in characteristics to the first one, and the third SDR is installed to obtain a vacuum on the second SDR, equal to half the vacuum on the first one, while:

- at the first stage, the air pull is set so that the output signal f ₁₁ of the first SDR corresponds to the output signal f _{1 of} the first SDR when testing the SDR with OMS, the output signals f ₁₁ , f ₂₁ of the first and second SDRs, the discharge at the output of the first ΔР ₁₁ and the second ΔР ₂₁ SDR,

- at the second stage, the air draw is set so that the output signal f ₁₂ of the first SDR becomes equal to the output signal f ₂₁ of the second SDR at the previous stage, the output signals f ₁₂ , f ₂₂ of the first and second SDRs are fixed,

- at the N-th stage, the air draw is set so that the output signal f _{1 N} of the first SDR becomes equal to the output signal f _{2 N-1 of the} second SDR at the previous (N-1)-th stage, the output signals f _{1 N} , f ₂ are fixed _N of the first and second SDRs,

- determine РХ ΔР _{1 N} =f(Q _{1 N} ) SDR,

where ΔР _{1 Ν} =ΔР ₁₁ /2 ^(N-1) - the magnitude of the discharge at the output of the first SDR;

Q _{1 N} - the amount of flow through the first SDR corresponding to the output signal f _{1 N} .

At each subsequent (N+1)-th stage, the air draw is set such that f _{1 N+1} =K ₂₁ *f _{2 N} , that is, so that the output signal f _{1 N+1 of} the first SDR becomes equal to the output signal f _{2 N} the second SDR at the previous stage, multiplied by the correction factor K ₂₁ that takes into account deviations in the characteristics of the first and second SDRs associated with permissible deviations in their manufacture.

When constructing the PX of the first SDR, the value of the pressure drop on the first SDR, to improve the accuracy of determining the PX, is taken in stages: ΔР _{1 Ν} =ΔР ₁₁ *(ΔР ₂₁ /ΔР ₁₁ ) ^N-1 . This makes it possible to increase the accuracy of determining the RH by taking into account the non-identity of the characteristics of the second and third SDRs associated with permissible deviations in their production, when the difference in the second SDR by 0.3% or more differs from half the difference in the first SDR

Distinctive features of the claimed method for determining the RH SDR, namely, connecting in parallel to the first SDR two consecutively installed second and third SDR, identical in characteristics to the first one, and the third SDR is installed to obtain a vacuum on the second SDR, equal to half the vacuum on the first one, while:

- at the first stage, the air pull is set so that the output signal f ₁₁ of the first SDR corresponds to the output signal f _{1 of} the first SDR when testing the SDR with OMS, the output signals f ₁₁ , f ₂₁ of the first and second SDRs, the discharge at the output of the first ΔР ₁₁ and the second ΔР ₂₁ SDR,

- at the second stage, the air draw is set so that the output signal f ₁₂ of the first SDR becomes equal to the output signal f ₂₁ of the second SDR at the previous stage, the output signals f ₁₂ , f ₂₂ of the first and second SDRs are fixed,

- at the N-th stage, the air draw is set so that the output signal f _{1 N} of the first SDR becomes equal to the output signal f _{2 N-1 of the} second SDR at the previous (N-1)-th stage, the output signals f _{1 N} , f ₂ are fixed _N of the first and second SDRs,

- determine RH ΔP _1N =f(Q _{1 N} ) SDR,

where ΔP _{1 N} =ΔP ₁₁ /2 ^(N-1) - the magnitude of the discharge at the output of the first SDR;

Q _{1 N} - the amount of flow through the first SDR corresponding to the output signal f _{1 N} .

At each subsequent (N+1)-bom stage, the air draw is set so that f _{1 N+1} =K ₂₁ *f _{2 N} , that is, so that the output signal f _{1 N+1 of} the first SDR becomes equal to the output signal f _{2 N} the second RDD at the previous stage, multiplied by the correction factor K ₂₁ , taking into account deviations in the characteristics of the first and second RDDs associated with tolerances in their manufacture.

When constructing the PX of the first SDR, the value of the pressure drop on the first SDR, to improve the accuracy of determining the PX, is taken in stages: ΔР _{1 N} =ΔР ₁₁ *(ΔР ₂₁ /ΔР ₁₁ ) ^N-1 . This makes it possible to increase the accuracy of determining the RH by taking into account the non-identity of the characteristics of the second and third SDRs associated with permissible deviations in their production, when the difference in the second SDR by 0.3% or more differs from half the difference in the first SDR.

Thus, the claimed method allows to improve the accuracy of the installation and determination of the pressure drop on the first SDR without the use of pressure sensors with an error of less than 0.001 mm of water. Art., which are not produced by our industry, increases the accuracy of determining the RH SDR.

The claimed method is shown in the drawings and described below.

On FIG. 1 shows a functional diagram of the installation that implements the proposed method for determining the RH SDR at large and small (very small) discharges (drops) on the SDR, which cannot be fixed with a sufficient degree of accuracy by the available measuring instruments.

On FIG. 2 shows a functional diagram of the installation that implements the method for determining the RH SDR with sufficient discharges (drops) on the SDR.

The installations contain: the first SDR (1), the second SDR (2) and the third SDR (3), OMS (4), an adjustable valve (5), means (6), (7), (8) for fixing the output signals, the first SDR (1), second SDR (2) and third SDR (3). Means for fixing the discharge at the output (9), (10), (11), respectively, of the first SDR (1), the second SDR (2) and the third SDR (3).

In the setup in Fig. 1, which implements the method for determining the RH SDR, air from the atmosphere is pulled through the SDR (1), (2), (3) and the OMS (4). At the same time, air discharges ΔР ₁ , ΔР ₂ , ΔР ₃ at the outlet of SDR (1), (2), (3), temperature and pressure of atmospheric air, output signal f ₁ SDR (1) are fixed. Determine the flow through the OMS (4), related to atmospheric pressure:

Q ₁ \u003d K _OMC * ((Rn-ΔP ₃ ) / Rn) * sqrt (Tn / 293),

where K _OMS - OMS coefficient, determined in the metrological center, when calibrating this OMS;

Тн and Рн - temperature and pressure of atmospheric air (dependencies for the critical flow rate through the OMS are known to specialists with technical education).

Thus determine the first point on the PX ΔP ₁ =f(Q ₁ ) SDR (1). Tests are carried out with other OMS having a different critical nozzle area F _KCN and other PX points ΔP _{1 N} =f(Q _{1 N} ) SDR (1) are determined.

In the setup in Fig. 2, which implements the proposed method for determining the RH SDR, air from the atmosphere is drawn through the SDR (1) and parallel to it serially connected SDRs (2), (3). In this case, the air pull is set such that the output signal f ₁₁ SDR (1) corresponds to the output signal f ₁ SDR (1) when testing the SDR with OMS according to the scheme in Fig. one.

The output signals f ₁₁ , f ₂₁ RDD (1) and (2), the discharge ΔP ₁₁ at the output of the RDD (1) (with a high degree of accuracy equal to the discharge ΔR ₃₁ at the output of the RDD (3)), the discharge ΔR ₂₁ at the output of the RDD ( 2). If all three SDRs are identical, then the pressure drop (discharge at the outlet) on the SDR (2) with a sufficiently high degree of accuracy is equal to the pressure drop on the SDR (3) and is equal to half the pressure drop on the SDR (1) (ΔР ₂₁ \u003d 0.5 * ΔР ₁₁ ). Using the value of the output signal f ₁₁ determined at the first stage and the vacuum ΔР ₁₁ SDR (1), we determine the flow rate Q ₁₁ through the SDR (1) and determine the first point on PX ΔP ₁ =f(Q ₁ ) SDR (1).

At the second stage, the air draw is set such that the output signal f ₁₂ SDR (1) becomes equal to the output signal f ₂₁ SDR (2) at the previous stage, the output signals f _l2 , f ₂₂ SDR (1) and (2) are fixed. Having determined at the second stage the output signal f ₁₂ SDR (1), we determine the flow rate Q ₁₂ through the SDR (1). And since at the second stage a broach was set through the SDR (1) such that the signal f ₁₂ SDR (1) became equal to the output signal f ₂₁ SDR (2) at the previous stage, and since the characteristics of all SDRs are identical, then at the second stage the difference in SDR (1) is equal to the drop on the SDR (2) at the previous stage, when it was equal to half the difference ΔР ₁₁ . Therefore ΔР ₁₂ =0.5*ΔР ₁₁ .

Based on the foregoing, we determine the second point on the PX ΔР ₁ =f(Q ₁ ) SDR (1).

Further, sequentially setting the air flow such that at the N-th stage the output signal f _{1 N} SDR (1) becomes equal to the output signal f _{2 N-1} SDR (2). Fixing the output signal f _{1 N} SDR (1), we determine (from f _{1 N} ) the flow rate Q _{1 N} of air through the SDR (1) at the N-th stage, we find the next point on the RH SDR (1). Finding points on the SDR flow characteristic (1) can be carried out in the entire range of SDR operability. At the same time, we can determine points on the RH SDR with drops on the SDR significantly less than 1 mm of water. Art. In the future, SDR, with the RH determined according to the above method, can be used to control drops of less than 1 mm of water. Art.

Also, according to paragraph 2 of the formula, at each subsequent stage, using the valve (7), the output signal f _{1 N+1} RDD (1) is set equal to the output signal f _{2 N} RDD (2) at the previous stage, multiplied by the correction factor K ₂₁ taking into account the degree of non-identity of the RH SDR (when, with the same drops on the SDR (1) and (2), their output signals differ significantly) and setting f _{1 N+1} =f _{2 N} *K ₂₁ , we obtain a decrease in the drop on the SDR (1) from stage to stage exactly 2 times.

The correction factor K ₂₁ depends only on the geometrical parameters of the SDR (1) and SDR (2) and does not depend on the operating modes of the SDR.

A possible way to find the correction factor K ₂₁ : set the valve (7) pressure drop on the SDR (1) equal, for example, 100 mm of water. Art., fix the output signal SDR (1) f ₁ '. Then, by changing the valve (7) the pressure drop on the SDR, set the pressure drop on the SDR (2), equal, for example, to 50 mm of water. Art., fix the output signal f ₂ ' SDR (2) and determine the value of the correction factor K ₂₁ =f ₁ '/f ₂ '.

Such accounting for the non-identity of the consumption characteristics of the SDR (1) and (2) makes it possible to increase the accuracy of determining the RH of the SDR (1) when testing the SDR with non-identical characteristics (non-identity due to inaccuracies in the manufacture of the SDR (1) and (2)).

Also, according to paragraph 3 of the formula to take into account the non-identity of the RH SDR (2) and SDR (3) (which arose due to inaccuracies in the manufacture of SDR (2) and (3)) to take into account the non-identity of the characteristics of SDR (2) and SDR (3) , (to take into account the unequal decrease in pressure drops on the SDR (2) from the SDR (3)), as a result of which: ΔР _{2 N} ≠ ΔP _{3 N} and ΔΡ _{2 N} ≠ 0.5 * ΔР _{1 N} , when performing the stages, the real pressure decrease is taken ΔР _{1 N} at each stage (not 2 times, but in (ΔР ₁₁ /ΔР ₁₂ )).

Since at each stage the degree of pressure reduction is the same, then: ΔΡ _{1 Ν} =ΔР ₁₁ *(ΔР ₁₁ /ΔР ₁₂ ) ^Ν-1 .

Thus, by reducing the pressure drop across the SDR (1) by a factor of 2 at each stage, we obtain, with a sufficiently high degree of accuracy, the PX SDR at small drops, without using special tools for measuring small pressure drops. Additionally, the use at each stage of the dependencies f _{1 N+1} =f _{2 N} *K ₂₁ and ΔP _{1 N} =ΔP ₁₁ *(ΔP ₁₁ /ΔP ₁₂ ) ^Ν-1 allows you to improve the accuracy of determining the RH SDR.

Knowing the flow characteristics of the SDR allows you to work on expanding the operating range of the SDR by connecting in parallel to the SDR jets with flow characteristics selected identical to the SDR, which makes it possible to obtain a flow meter with a wide range of flow measurement with a high degree of accuracy.

A certain relationship between f ₁ and ΔР ₁ , and also makes it possible to use the SDR to measure small pressure drops, which at present cannot be measured using pressure measuring instruments manufactured by our industry.

Claims (10)

1. A method for determining the flow characteristics (PX) of inkjet flow sensors (SDR) by drawing air from the atmosphere through three SDRs installed in series and an exemplary micronozzle (OMS), fixing the temperature, pressure of atmospheric air, vacuum at the outlet of the first, second and third SDR, outlet signal f _{1 of} the first RDD, characterized in that the determination of the RH of the first SDR is carried out by connecting in parallel to the first SDR two successively installed second and third SDRs, identical in characteristics to the first one, and the third SDR is installed to obtain a vacuum on the second SDR equal to half the vacuum on the first one, while: - at the first stage, the air pull is set so that the output signal f ₁₁ of the first SDR corresponds to the output signal f _{1 of} the first SDR when testing the SDR with OMS, the output signals f ₁₁ , f ₂₁ of the first and second SDRs, the depression at the output of the first ΔР ₁₁ and the second ΔР ₂₁ SDR, - at the second stage, the air draw is set so that the output signal f ₁₂ of the first SDR becomes equal to the output signal f ₂₁ of the second SDR at the previous stage, the output signals f ₁₂ , f ₂₂ of the first and second SDRs are fixed, - at the N-th stage, the air draw is set so that the output signal f _1N of the first SDR becomes equal to the output signal f _{2N-1 of the} second SDR at the previous (N-1)-th stage, the output signals f _1N , f _2N of the first and second HAPPY BIRTHDAY, - determine РХ ΔР _1N = f(Q _1N ) SDR, where ΔP _1N = ΔP ₁₁ /2 ^(N-1) - the magnitude of the vacuum at the output of the first SDR; Q _1N - the amount of flow through the first SDR corresponding to the output signal f _1N . 2. The method according to claim 1, characterized in that at each subsequent (N+1)-th stage, the air draw is set such that f _1N+1 = K ₂₁ *f _2N , that is, so that the output signal f _{1N+1 of} the first SDR became equal to the output signal f _2N of the second SDR at the previous stage, multiplied by the correction factor K ₂₁ that takes into account deviations in the characteristics of the first and second SDRs associated with tolerances in their manufacture. 3. The method according to claim 1, characterized in that when constructing the PX of the first SDR, the value of the pressure drop on the first SDR, to improve the accuracy of determining the PX, is taken in stages: ΔР _1N = ΔР ₁₁ *(ΔР ₂₁ /ΔР ₁₁ ) ^N-1 .

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