CN1010504B - Mtehod for measuring flow characteristics of pneumatic element - Google Patents

Abstract

The present invention relates to a method for measuring the flow characteristic of pneumatic elements, which is suitable for the pneumatic elements with various constant diameter flow paths. An effective area S at critical and a quasi-critical pressure ratio b of a measured element based on the exhausting method under the conditions of elements connected in series with constant volumes and sound velocity. According to the hypothesis that the flow characteristic of the pneumatic element in a subsonic flow state is a quarter of ellipse, the flow characteristics of the element can be fully expressed, namely that the flow passing through the element under at any pressure difference can be obtained. The present invention has the characteristic that gas consumption and the total cost of measuring devices and meters are only one tenth of that of a method of ISO/DIS6358.

Description

Mtehod for measuring flow characteristics of pneumatic element

The present invention relates to measure the method for pneumatic component flowrate property.

Along with the development of pneumatics, people wish to have a kind of method of measuring pneumatic component flowrate property, and it can intactly obtain discharge characteristic, and promptly the flow by certain element all can be asked under any pressure reduction.Draft internation standard ISO/DIS6358(data 1) propose: " available 1/4th oval horizontal component smooth connections with curve of the relation between supposition mass rate and the pressure ratio come approximate representation." this just provides a basis for intactly expressing pneumatic component flowrate property, yet there are two major defects (data 2) in this draft standard: the one, and air consumption is too big during test, and is particularly serious concerning the heavy caliber valve.The 2nd, in the range ability of very big pressure and flow, all require the measuring accuracy that reaches higher, make cost too high.So this draft standard proposed not accepted by member state yet so far from 1979, did not become official standard, planned in October, 1988 and discussed once more.

The objective of the invention is to propose a kind of method of measuring the pneumatic component flowrate property of the constant various latus rectums of runner.It can intactly measure the discharge characteristic of pneumatic element, and reduces the cost of air consumption and reduction pick-up unit significantly.

The present invention adopts the constant volume velocity of sound exhaust of element connected in series to realize.

Its principle can be seen from Fig. 1:

If element 1 and element 2 useful area and the pseudocritical pressure under critical conditions is respectively S than (annotating data 4) ₁, b ₁And S ₂, b ₂, if with the two elements series connection, the net sectional area of connecting pipe is much larger than S ₁Or S ₂And guarantee that this series connection gas circuit still is in critical conditions, critical cross-section still is in the element 2, is respectively S and b as the synthetic useful area and the pseudocritical pressure ratio of series connection gas circuit under critical conditions, then passes through the mass rate (data 5) of series connection gas circuit under critical conditions:

$q^{*}{}_{\mathrm{m\; 12}}\mathrm{=\; 0.04042}\frac{P_1}{\sqrt{T_1}}\mathrm{S\; ①}$

In the formula: T ₁Upstream stagnation temperature (absolute temperature) for element 1.P ₁Upstream pressure (absolute pressure) for element 1.

In like manner, under critical conditions, pass through the mass rate of element 2:

$q^{*}{}_{\mathrm{<figure-callout\; id="2"\; label="m"\; filenames="86108725\_DRIMG1.png"\; state="\{\{state\}\}">m</figure-callout>\; 2}}\mathrm{=\; 0.04042}\frac{P_2}{\sqrt{T_2}}{\mathrm{<figure-callout\; id="2"\; label="S"\; filenames="86108725\_DRIMG1.png"\; state="\{\{state\}\}">S</figure-callout>}}_2②$

In the formula: T ₂Upstream stagnation temperature (absolute temperature) for element 2.P ₂Upstream pressure (absolute pressure) for element 2.

By the mass rate of element 1, propose according to ISO/DIS6358, as upstream pressure P ₁With upstream stagnation temperature T ₁Keep under the stable condition, element is the hypothesis of one 1/4th elliptic curve in the discharge characteristic of subsonic flow state, then can write out the mass rate by element 1:

$q_{\mathrm{m\; 1}}\mathrm{=\; 0.04042}\frac{P_1}{\sqrt{T_1}}{S}_1\sqrt{\mathrm{1-(}\frac{\frac{P_2}{P_1}{\mathrm{-b}}_1}{{\mathrm{1-b}}_1}{)}^2}\mathrm{\dots \dots ③}$

For insulation flow, total moisture content is constant everywhere, i.e. T ₁=T ₂

According to law of conservation of mass: q ^* _M12=q ^* _M2

1. and 2. can get by formula: (P ₂)/(P ₁)=(S)/(S ₂) ... 4.

In like manner: q ^* _M2=q _M1

2. and 3. can get by formula:

$\frac{P_2}{P_1}=\frac{b_1{\mathrm{+\; (1-b}}_1)\sqrt{{\mathrm{1+(1-2b}}_1\mathrm{)(}\frac{S_2}{S_1}{)}^2}}{{\mathrm{1+(1-b}}_1{)}^2(\frac{S_2}{S_1}{)}^2}\mathrm{\dots \dots ⑤}$

4. and 5. can get by formula:

$\frac{\mathrm{<figure-callout\; id="2"\; label="S\; S"\; filenames="86108725\_DRIMG1.png"\; state="\{\{state\}\}">S</figure-callout>}}{S_{}}=\frac{b_1{\mathrm{+\; (1-b}}_1)\sqrt{{\mathrm{1+(1-2b}}_1\mathrm{)(}\frac{S_2}{S_1}{)}^2}}{{\mathrm{1+(1-b}}_1{)}^2(\frac{S_2}{S_1}{)}^2}\mathrm{\dots \dots ⑥}$

According to formula 6., with (S ₁)/(S ₂) be parameter, can make (S)/(S ₂) and b ₁Graph of relation (Fig. 2).Curve among the figure above the dotted line represents that all element 2 is in critical conditions.

1., 2. and 4. can get by formula:

${\mathrm{<figure-callout\; id="2"\; label="S"\; filenames="86108725\_DRIMG1.png"\; state="\{\{state\}\}">S</figure-callout>}}_2=\frac{S}{b_1{\mathrm{+\; (1-b}}_1)\sqrt{\mathrm{1-(}\frac{S}{S_1}{)}^2}}\mathrm{\dots \dots ⑦}$

Or

$b_1=\frac{\frac{S}{S_2}-\sqrt{\mathrm{1-(}\frac{S}{S_1}{)}^2}}{\mathrm{1\; -}\sqrt{\mathrm{1-(}\frac{S}{S_1}{)}^2}}\mathrm{\dots \dots ⑧}$

Be that isochoric process is derived following formula (data 3) by gas in adiabatic exhaust and the container simultaneously

$\mathrm{S\; =\; 0.0261}\sqrt{\frac{\mathrm{273}}{T_{\mathrm{10}}}}\frac{V}{t}\mathrm{［\; (}\frac{P_{\mathrm{10}}}{P_{\mathrm{100}}}{)}^{\frac{1}{5}}\mathrm{-\; 1\; ］\; \dots \dots ⑨}$

Measuring method of the present invention is to realize by measurement mechanism shown in Figure 3.

The volume V of selection pressure container at first.According to the latus rectum d of detected element, by formula S=(0.5～0.6) (π)/4 d ²Estimate the S value.Then 9. and velocity of sound exhaust and adiabatic exhaust requirements: P according to formula ₁Be not less than 2.8bar(a), P ₁₀At 5.5bar(a) more than, t extrapolates and measures used capacity volume 4～6 seconds scope.

Secondly select auxiliary element according to the architectural feature of detected element, connect pipeline, synthin after the series connection of detected element, auxiliary element or detected element and auxiliary element, order is connected to and contains on the compressed-air actuated constant volume device in accordance with regulations, then according to the control mode of detected element and auxiliary element, the same with the requirement of common assay method, connect related circuit.Open air cock (8), in container, inflate, until reaching P ₁₀Setting is closed air cock (8).

When the switch of container upstream switch and measured downstream element all cuts out, in 5 minutes, keep container inner pressure to change less than 0.05bar, cause error excessive with non-leaking.

Initial temperature T in the volume V of record container, the container before the venting ₁₀, original pressure P ₁₀

Allow the instantaneous unlatching of measuring sensor, with the velocity of sound exhaust, measure deflation time t and the venting surplus pressure P that the back container inner pressure tends towards stability that finishes to atmosphere ₁

Because the derivation of method is based on adiabatic process, so deflation time can not grow, and deflation time is in 4-6 scope second.If deflation time is too short, container inner pressure P before then exitting ₁₀Treat the container pressure value of tending towards stability P with having exitted ₁Difference is too small, and at this moment less pressure measurement errors can cause the error of calculation of useful area S value under the bigger critical conditions.In order to improve precision, the relative error of all tested values will be controlled in 5/1000ths.

In order to guarantee that whole deflation course is the velocity of sound exhaust all, requires extraneous pressure P in the deflation course _aWith instantaneous pressure P in the container ₁Ratio must be less than the pseudocritical pressure of measuring sensor than b, P _aBe generally atmospheric pressure, often get 1.02bar(a), the b value is not more than 0.5.

In order to improve measuring accuracy, for (S in the element connected in series exhaust ₁)/(S ₂) ratio can further select.(S)/(S from Fig. 2 ₂) and b ₁Relation curve can see: as (S ₁)/(S ₂)=0.85～0.90 o'clock, rate of curve is big.At this moment S ₁, S ₂With the caused b of S measuring error ₁The error of calculation of value is little.When series loop is under the critical conditions, no matter b ₁How many values is, as long as there is (S)/(S ₂)＜(S ₁)/(S ₂), then critical cross-section necessarily is in the element 2, is subsonic flow in the element 1 promptly, no matter and S ₁Whether less than S ₂Otherwise,, then answer S=S if be critical cross-section in the element 1 ₁In sum, (S ₁)/(S ₂) ratio in the 0.6-1.15 scope.

Suppose in the deflation course that flow velocity is slowly over time, then in the time, can think that above-mentioned formula of deriving is 1. to 8. being suitable under the steady flow condition at dt.

Ging up by adiabatic exhaust and container inner pressure like this is that formula and the discharge characteristic of pneumatic element under the subsonic speed fluidised form that isochoric process derived is the hypothesis of one 1/4th elliptic curve, calculates the S of relevant detected element ₁With b ₁, then the complete discharge characteristic of detected element is expressed as follows:

$\frac{P_a}{P_1}{\mathrm{\le \; b}}_1$

$q^{*}{}_m\mathrm{=\; 0.04042}\frac{P_1}{\sqrt{T_1}}{S}_1\mathrm{\dots \dots ⑩}$

$\mathrm{1\ge }\frac{P_a}{P_1}{\mathrm{>b}}_1$

$q_{\mathrm{m1}}\mathrm{=\; q}{}^{*}{}_m\sqrt{\mathrm{1-(}\frac{\frac{P_a}{P_1}{\mathrm{-\; b}}_1}{{\mathrm{1-b}}_1}{)}^2}\mathrm{\dots \dots \; ⑾}$

Architectural feature according to detected element can be selected one of following method.Measure discharge characteristic:

For the detected element that switching capability is arranged.The volume V of selection pressure container at first as stated above, selecting identical or close with the detected element latus rectum a, characterisitic parameter then is that known element is an auxiliary element.With detected element, synthetic element was connected to and contains on the compressed-air actuated constant volume device after detected element and auxiliary element were connected successively, adopted above-mentioned velocity of sound degassing method, carried out parameter measurement respectively.Measure detected element respectively, detected element and auxiliary element are connected the back synthin successively at the P of front and back that exits ₁₀And P ₁, t and T ₁₀

In order to guarantee that whole deflation course is the velocity of sound exhaust all, requires extraneous pressure P in the deflation course _aWith pressure P instantaneous in the container ₁Ratio must be less than the pseudocritical pressure of measured element than b, the b value is not more than 0.5.

Ging up according to adiabatic exhaust and container inner pressure is that formula and the discharge characteristic of pneumatic element under the subsonic speed fluidised form that isochoric process derived is the hypothesis of one 1/4th elliptic curve.

From known V, T ₁₀, P ₁₀, t and P ₁, through type 9. calculate respectively detected element, detected element and the auxiliary element back synthin useful area S under critical conditions that connects successively ₁And S ₁₂

From known S ₂, S ₁And S ₁₂, 8. can extrapolate by formula:

$b_1=\frac{\frac{S_{\mathrm{12}}}{S_2}-\sqrt{\mathrm{1-(}\frac{S_{\mathrm{12}}}{S_1}{)}^2}}{\mathrm{1\; -}\sqrt{\mathrm{1-(}\frac{S_{\mathrm{12}}}{S_1}{)}^2}}\mathrm{\dots \dots ⑿}$

Like this discharge characteristic of detected element 1 can by formula 10., (11) intactly express.

For the detected element that switching capability is arranged.The volume V of selection pressure container at first as stated above, select then one with detected element of the same type, with the auxiliary element of latus rectum, synthin after respectively detected element, auxiliary element, detected element and auxiliary element being connected successively, be connected to and contain on the compressed-air actuated constant volume device, adopt above-mentioned velocity of sound degassing method, carry out parameter measurement.Measure detected element, auxiliary element, detected element and auxiliary element respectively and connect the back synthin successively at the P of front and back that exits ₁₀And P ₁, t and T ₁₀

In order to guarantee that whole deflation course is the velocity of sound exhaust all, requires extraneous pressure P in the deflation course _aWith instantaneous pressure P in the container ₁Ratio must be less than the pseudocritical pressure of measured element than b, the b value is not more than 0.5.

Ging up according to insulation exhaust and container inner pressure is that formula and the discharge characteristic of pneumatic element under the subsonic speed fluidised form that isochoric process derived is the hypothesis of one 1/4th elliptic curve.

From known V, T ₁₀, P ₁₀, t and P ₁, through type 9. calculate respectively detected element, auxiliary element, detected element and the auxiliary element back S of synthin under critical conditions that connect successively ₁, S ₂And S ₁₂

From known S ₁, S ₂And S ₁₂, calculate to such an extent that the pseudocritical pressure of detected element compares b by formula (12) ₁

Like this discharge characteristic of detected element can by formula 10., (11) intactly express.

Detected element for non-switched capabilities.The volume V of selection pressure container is selected identical or close with the detected element latus rectum, an auxiliary element that characterisitic parameter is known, that switching capability is arranged then at first as stated above.Synthin after synthin, auxiliary element and detected element after respectively detected element and auxiliary element being connected successively connected successively is connected to and contains on the compressed-air actuated constant volume device, adopts above-mentioned velocity of sound degassing method, carries out parameter measurement.The P of synthin before and after venting after measuring synthin, auxiliary element and detected element after detected element and auxiliary element are connected successively respectively and connecting successively ₁₀And P ₁, t and T ₂₀

In order to guarantee that whole deflation course is the velocity of sound exhaust all, requires extraneous pressure P in the deflation course _aWith instantaneous pressure P in the container ₁Ratio must be less than the pseudocritical pressure of measured element than b, the b value is not more than 0.5.

Ging up according to adiabatic exhaust and container inner pressure is that formula and the discharge characteristic of pneumatic element under the subsonic speed fluidised form that isochoric process derived is the hypothesis of one 1/4th elliptic curve.

From known V, T ₁₀, P ₁₀, t and P ₁, through type 9. calculate respectively synthin the net sectional area S under critical conditions of detected element and auxiliary element synthin, auxiliary element and the detected element after connecting successively after connecting successively ₁₂, S ₂₁

From known S ₂₁, b ₂, S ₂, try to achieve S by following formula ₁:

$S_1=\frac{S_{\mathrm{21}}}{{\mathrm{<figure-callout\; id="2"\; label="b"\; filenames="86108725\_DRIMG1.png"\; state="\{\{state\}\}">b</figure-callout>}}_2{\mathrm{+\; (1-b}}_2)\sqrt{\mathrm{1\; -\; (}\frac{S_{\mathrm{21}}}{S_2}{)}^2}}\mathrm{\dots \dots ⒀}$

From known S ₁, S ₂And S ₁₂, through type (12) can be regarded as to such an extent that the pseudocritical pressure of detected element compares b ₁

Like this discharge characteristic of detected element can by formula 10., (11) intactly express.

Detected element 1 for non-switched capabilities.The volume V of selection pressure container is at first as stated above selected one then with detected element 1 auxiliary element 2 of the same type, that latus rectum is identical, select a latus rectum to be twice than detected element 1 or auxiliary element 3 more than a times and that switching capability is arranged again.Synthin after synthin, detected element 1 and auxiliary element 2 after synthin, auxiliary element 2 and auxiliary element 3 after respectively detected element 1 and auxiliary element 3 being connected successively connected successively and auxiliary element 3 are connected successively, be connected to and contain on the compressed-air actuated constant volume device, adopt above-mentioned velocity of sound degassing method, carry out parameter measurement.Synthin after synthin, detected element 1 and auxiliary element 2 after recording synthin, auxiliary element 2 and auxiliary element 3 after detected element 1 and auxiliary element 3 are connected successively respectively and connecting successively and auxiliary element 3 are connected successively, the P before and after the venting ₁₀And P ₁, t and T ₁₀

In order to guarantee that whole deflation course is the velocity of sound exhaust all, requires extraneous pressure P in the deflation course _aWith instantaneous pressure P in the container ₁Ratio must be less than the pseudocritical pressure of measured element than b, the b value is not more than 0.5.

Ging up according to adiabatic exhaust and container inner pressure is that formula and the discharge characteristic of pneumatic element under the subsonic speed fluidised form that isochoric process derived is the hypothesis of one 1/4th elliptic curve.Again because the useful area of auxiliary element 3 under critical conditions is bigger about four times at useful area under the critical conditions than detected element 1 or auxiliary element 2, so if there is critical cross-section in series loop, then all be in detected element 1 or the auxiliary element 2, and can not be in the auxiliary element 3, promptly element 3 only plays on-off action.

From known V, T ₁₀, P ₁₀T and P ₁, through type 9. calculate respectively synthin after connecting successively of detected element 1, auxiliary element 2, detected element 1 and auxiliary element 2, the useful area S under critical conditions ₁, S ₂And S ₁₂

From known S ₁, S ₂And S ₁₂, the pseudocritical pressure that can try to achieve detected element 1 by formula (12) compares b ₁

Like this discharge characteristic of detected element 1 can by formula 10., (11) intactly express.

Method of the present invention is compared with prior art ISO/DIS6358, it can intactly express the discharge characteristic of pneumatic element, and air consumption only is original 1/10th, and the total cost of measurement mechanism and instrument also only is original 1/10th, and is therefore very easy to use and promote.

Below in conjunction with accompanying drawing, method of the present invention is described in detail.

Fig. 1. the element connected in series schematic diagram

Fig. 2. with (S ₁)/(S ₂) be (S)/(S of parameter ₂) by b ₁Graph of relation

Fig. 3. the measurement mechanism schematic diagram

Fig. 4. when can not selecting identical or close, that characterisitic parameter is known and the auxiliary element of latus rectum with switching capability, test philosophy figure

Among the figure: 1-element 1.2-element 2.3-element 3.

The 4-synthin of connecting.The 5-pressure vessel.

The 6-master gauge.The 7-source of the gas.The 8-air cock.

The 9-timer.

P ₁Pressure (absolute pressure) in the upstream pressure of-element 1 or the pressure vessel.

P ₂The upstream pressure of-element 2 (absolute pressure).

P _a-ambient pressure (absolute pressure).

T ₁Total moisture content (absolute temperature) in the upstream stagnation temperature of-element 1 or the pressure vessel.

T ₂The upstream stagnation temperature (absolute temperature) of-element 2.

S ₁-the useful area of element 1 under critical conditions.

S ₂-the useful area of element 2 under critical conditions.

Under critical conditions, the connect useful area of synthin of S-.

S ₁₂-under critical conditions, press the useful area of the synthin of element 1, element 2 series sequences.

S ₂₁-under critical conditions, press the useful area of the synthin of element 2, element 1 series sequence.

The pseudocritical pressure ratio of b-series connection synthin.

b ₁The pseudocritical pressure ratio of-element 1.

b ₂The pseudocritical pressure ratio of-element 2.

T ₁₀The temperature of gas in the container before the-venting.

The internal volume of V-container.

P ₁After finishing ,-venting treats the pressure when container inner pressure tends towards stability.

Utilize constant volume velocity of sound degassing method to measure the embodiment of the discharge characteristic of pneumatic element:

Example 1: measure a method that latus rectum is the discharge characteristic of pneumatic element 5 millimeters, that switching capability is arranged.

Selecting a latus rectum for use is 6mm, known its characterisitic parameter S ₂=18.10mm ², b ₂=0.50 pneumatic element is an auxiliary element.

The volume of selection pressure container at first.The S of known auxiliary element ₂=18.10mm ², select P ₁=3.50bar(a), P ₁₀=5.80bar(a), t=4.40 second, T ₁₀9.=288K extrapolates V=29.481 by formula, considers to select V=301 from practicality.

Adopt the velocity of sound degassing method to carry out parameter measurement:

Detected element is connected to contains on the compressed-air actuated constant volume device, record T ₁₀=288K, P ₁₀=6.00bar(a), t=5.85 second, P ∞=4.02bar(a), 9. can try to achieve S by formula ₁=10.86mm ²

Synthin after again detected element and auxiliary element being connected successively is connected to and contains on the compressed-air actuated constant volume device, records T ₁₀=288K, P ₁₀=7.00bar(a), t=4.32 second, P ₁=5.25bar(a), 9. can try to achieve S by formula ₁₂=10.45mm ²

According to known and S that record ₁, S ₂And S ₁₂, by formula (12) calculate b ₁=0.419.

The flowrate characteristic parameter S of detected element then ₁=10.86mm ², b ₁=0.419, and (S ₁)/(S ₂Its complete stream flow characteristic of)=10.86/18.10=0.6 is expressed as follows:

$\frac{P_a}{P_1}\mathrm{\le \; 0.419}$

$q^{*}{}_m\mathrm{=\; 0.04042}\frac{P_1}{\sqrt{T_1}}{\mathrm{\times \; 10.86\; \times 10}}^{\mathrm{-6}}\mathrm{(kg/s)}$

$\mathrm{1\ge }\frac{P_a}{P_1}\mathrm{\ge 0.419}$

$q_m\mathrm{=\; q}{}^{*}{}_m\sqrt{\mathrm{1-(}\frac{\frac{P_a}{P_1}\mathrm{-\; 0.419}}{\mathrm{1-0.419}}{)}^2}\mathrm{(kg/s)}$

It is 5mm that example 2. is measured a latus rectum, and the other method of discharge characteristic of the pneumatic element of switching capability is arranged.

Selecting a pneumatic element of the same type, that latus rectum is 5mm for use is auxiliary element.

The volume of selection pressure container at first.According to (π)/4 d of formula S=(0.5～0.6) ², coefficient selects 0.6, then S=0.6 (π)/4 d ²=11.78mm ²Select P ₁₀=6.00bar(a), P ₁=3.50bar(a), T ₁₀9.=288K t=4.50 second calculates V=18.331 by formula, considers to select V=181 from practicality.

Adopt the velocity of sound degassing method to carry out parameter measurement:

Detected element is connected to contains on the compressed-air actuated constant volume device, record T ₁₀=288K, P ₁₀=6.00bar(a), t=4.79 second, P ∞=3.50bar(a), by formula 9. calculate S ₁=10.86mm ²

Again auxiliary element is connected to and contains on the compressed-air actuated constant volume device, record T ₁₀=288K, P ₁₀=6.00bar(a), t=5.52 second, P ∞=3.50bar(a), by formula 9. calculate S ₂=9.44mm ²

Synthin after again detected element and auxiliary element being connected successively is connected to and contains on the compressed-air actuated constant volume device, records T ₁₀=288K, P ₁₀=6.00bar(a), t=4.97 second, P ∞=4.00bar(a), by formula 9. calculate S ₁₂=7.77mm ²

According to calculate S ₁, S ₂And S ₁₂, by formula (12) calculate b ₁=0.413.

The flowrate characteristic parameter S of detected element then ₁=10.86mm ², b ₁=0.413.And (S ₁)/(S ₂)=10.86/9.44=1.15, its complete stream flow characteristic is expressed as follows:

$\frac{P_a}{P_1}\mathrm{\le \; 0.413}$

$q^{*}{}_m\mathrm{=\; 0.04042}\frac{P_1}{\sqrt{T_1}}{\mathrm{\times \; 10.86\; \times 10}}^{\mathrm{-6}}\mathrm{(kg/s)}$

$\mathrm{l\; \ge }\frac{P_a}{P_1}\mathrm{\ge 0.413}$

$q_m\mathrm{=\; q}{}^{*}{}_m\sqrt{\mathrm{1-(}\frac{\frac{P_a}{P_1}\mathrm{-\; 0.413}}{\mathrm{1-0.413}}{)}^2}\mathrm{(kg/s)}$

Example 3. is measured the method that latus rectum is the discharge characteristic of pneumatic element 25mm, non-switched capabilities.

Selecting a latus rectum for use is its characterisitic parameter S 25mm, known ₂=294mm ², b ₂=0.5 the element that switching capability is arranged is an auxiliary element.

The volume of selection pressure container at first.The S of known auxiliary element ₂=294mm ², select P ₁∞=2.80bar(a), T ₁₀=5.50bar(a), t=4.20 second, T ₁₀9.=288K extrapolates V=336.131 by formula, considers to select V=3361 from practicality.

Adopt the velocity of sound degassing method to carry out parameter measurement:

Synthin after auxiliary element and detected element connected successively is connected to and contains on the compressed-air actuated constant volume device, records T ₁₀=288K, P ₁₀=5.50bar(a), t=4.06 second, P ₁=3.30bar(a), by formula 9. calculate S ₂₁=226mm ²Again by formula (13) calculate S ₁=276mm ²

Synthin after again detected element and auxiliary element being connected successively is connected to and contains on the compressed-air actuated constant volume device, records T ₁₀=288K, P ₁₀=5.50bar(a), t=4.00 second, P ₁=3.32bar(a), by formula 9. calculate S ₁₂=227mm ²

According to calculate S ₁, S ₂And S ₁₂, by formula (12) calculate b ₁=0.471.

The flowrate characteristic parameter S of detected element then ₁=276mm ², b ₁=0.471.And (S ₁)/(S ₂)=276/294=0.939.Its complete stream flow characteristic is expressed as follows:

$\frac{P_a}{P_1}\mathrm{\le \; 0.471}$

$q^{*}{}_m\mathrm{=\; 0.04042}\frac{P_1}{\sqrt{T_1}}{\mathrm{\times \; 276\; \times 10}}^{\mathrm{-6}}\mathrm{(kg/s)}$

$\mathrm{1\ge }\frac{P_a}{P_1}\mathrm{\ge 0.471}$

$q_m\mathrm{=\; q}{}^{*}{}_m\sqrt{\mathrm{1-(}\frac{\frac{P_a}{P_1}\mathrm{-\; 0.471}}{\mathrm{1-0.471}}{)}^2}\mathrm{(kg/s)}$

Example 4. is measured the other method that latus rectum is the discharge characteristic of pneumatic element 25mm, non-switched capabilities.

Select for use one with detected element 1 of the same type, latus rectum is that the element of 25mm is an auxiliary element 2.Selecting a latus rectum again is auxiliary element 3 50mm, that switching capability is arranged, and it only plays on-off action.

The volume of at first selected pressure vessel.According to (π)/4 d of formula S=(0.5～0.6) ², coefficient selects 0.50, then S=0.50 (π)/4 d ²=245.3mm ², select P ₁₀=6.00bar(a), P ∞=3.00bar(a), T ₁₀=288K, 9. t=4.90 calculates V=318.11 by formula second, considers to select V=3201 from practicality.

Adopt the velocity of sound degassing method to carry out parameter measurement:

Synthin after detected element 1 and auxiliary element 3 connected successively is connected to and contains on the compressed-air actuated constant volume device, records T ₁₀=288K, P ₁₀=7.80bar(a), t=6 second, P ∞=3.05bar(a), by formula 9. calculate S ₁=280mm ²

Synthin after again auxiliary element 2 and auxiliary element 3 being connected successively is connected to and contains on the compressed-air actuated constant volume device, records T ₁₀=288K, P ₁₀=6bar(a), t=4.175 second, P ∞=3.10bar(a), by formula 9. calculate S ₂=275mm ²

Synthin after at last detected element 1 and auxiliary element 2 and auxiliary element 3 being connected successively is connected to and contains on the compressed-air actuated constant volume device, records T ₁₀=288K, P ₁₀=6.00bar(a), t=4.64 second, P ∞=3.33bar(a), by formula 9. calculate S ₁₂=219mm ²

According to calculate S ₁, S ₂And S ₁₂By formula (12) calculate b ₁=0.46.

The flowrate characteristic parameter S of detected element 1 then ₁=280mm ², b ₁=0.46, and (S ₁)/(S ₂)=280/275=1.02, its complete stream flow characteristic is expressed as follows:

$\frac{P_a}{P_1}\mathrm{\le \; 0.46}$

$q^{*}{}_m\mathrm{=\; 0.04042}\frac{P_1}{\sqrt{T_1}}{\mathrm{\times \; 280\; \times 10}}^{\mathrm{-6}}\mathrm{(kg/s)}$

$\mathrm{1\ge }\frac{P_a}{P_1}\mathrm{\ge 0.46}$

$q_m\mathrm{=\; q}{}^{*}{}_m\sqrt{\mathrm{1-(}\frac{\frac{P_a}{P_1}\mathrm{-\; 0.46}}{\mathrm{1-0.46}}{)}^2}\mathrm{(kg/s)}$

Annotate. the pseudocritical pressure ratio-rating curve of pneumatic element in the subsonic speed section assumed 1/4th ellipses and calculate that the critical pressure ratios of coming out call the pseudocritical pressure ratio.The actual critical pressure ratio of pneumatic element has a difference with the pseudocritical pressure ratio, should be distinguished.

Reference

1.ISO/DIS 6358.Pncumatic fluid powcr-Method of test-Det-ermination of flow-rate Characteristics of components using compressible fluids。

2. Xu Wen is bright: to the commentary of pneumatic component flowrate property draft internation standard and suggestion, " hydraulic industry " 1986 NO1.

3. Xu Wen is bright: calculate by draft internation standard and fill discharge characteristic." hydraulic pressure and pneumatic " 1985 NO3.

4. Xu Wen is bright: net sectional area " hydraulic pressure and pneumatic " 1984 NO3 of opinion pneumatic element.

5. Xu Wen is bright: the pressure flow characteristics auto of pneumatic system." building-block machine " 1986 NO6.

Claims (7)

1, being used to measure the method for pneumatic component flowrate property, is the hypothesis of one 1/4th ellipse garden curve by the discharge characteristic of pneumatic element under the subsonic speed fluidised form, and its feature comprises:

A) volume V of selection pressure container:

By formula

$\mathrm{S\; =\; 0.0261}\sqrt{\frac{\mathrm{273}}{T_{\mathrm{10}}}}\frac{V}{t}\mathrm{［\; (}\frac{P_{\mathrm{10}}}{P_{\mathrm{100}}}{)}^{\frac{1}{5}}\mathrm{-\; 1\; ］}$

Calculate P in the formula _{1 ∞}Be not less than 2.8bar (a), P ₁₀Be not less than 5.5bar (a), in second, the s value is pressed (π)/4 d of s=(0.5～0.6) to t at 4-6 ²(d is the latus rectum of detected element) estimate,

B) select auxiliary element according to the architectural feature of detected element, and with detected element and selected auxiliary element in accordance with regulations order be connected to and contain on the compressed-air actuated constant volume device;

C) determine original pressure P ₁₀, guarantee ambient pressure P _aPressure P when just venting has finished in the container ₁Ratio compare b less than the pseudocritical pressure of measured element;

D) adopt the velocity of sound degassing method, carry out parameter measurement.Measure detected element, auxiliary element and the original pressure P that connects by the synthin after the different order series connection in the constant volume device respectively ₁₀, the finish surplus pressure P of pressure level-off of venting _{1 ∞}, the initial temperature T in deflation time t and the container ₁₀

E) go up to be the formula that isochoric process derived by adiabatic exhaust and container inner pressure:

$\mathrm{S\; =\; 0.0261}\sqrt{\frac{\mathrm{273}}{T_{\mathrm{10}}}}\frac{V}{t}\mathrm{［\; (}\frac{P_{\mathrm{10}}}{P_{\mathrm{100}}}{)}^{\frac{1}{5}}\mathrm{-\; 1\; ］}$

Calculate detected element, auxiliary element, the synthin useful area S under critical conditions ₁, S ₂, S ₁₂

By the loop of two pneumatic elements series connection, when after the element formula that is under the critical conditions to be derived

$b_1=\frac{\frac{S_{\mathrm{12}}}{S_2}-\sqrt{\mathrm{1-(}\frac{S_{\mathrm{12}}}{S_1}{)}^2}}{\mathrm{1\; -}\sqrt{\mathrm{1-(}\frac{S_{\mathrm{12}}}{S_1}{)}^2}}$

Calculate the detected element pseudocritical pressure and compare b ₁

With useful area S and the pseudocritical pressure discharge characteristic of than b intactly explaining detected element of pneumatic element under critical conditions:

$\frac{P_a}{P_1}{\mathrm{\le \; b}}_1$

$q^{*}{}_m\mathrm{=\; 0.04042}\frac{P_1}{\sqrt{T_1}}{S}_1$

$\mathrm{1\ge }\frac{P_a}{P_1}{\mathrm{>b}}_1$

$q_m\mathrm{=\; q}{}^{*}{}_m\sqrt{\mathrm{1-(}\frac{\frac{P_a}{P_1}{\mathrm{-\; b}}_1}{{\mathrm{1-b}}_1}{)}^2}$

2, assay method according to claim 1, for the detected element that switching capability is arranged, its feature comprises:

A) volume V of selection pressure container;

B) select an auxiliary element identical or close with the detected element latus rectum, that characterisitic parameter is known, and the synthin after detected element, detected element and auxiliary element connected successively is connected to respectively and contains on the compressed-air actuated constant volume device;

C) determine original pressure P ₁₀, guarantee ambient pressure P _aPressure P when finishing with venting in the container ₁Ratio compare b less than the pseudocritical pressure of detected element;

D) adopt the velocity of sound degassing method, carry out parameter measurement, the original pressure P in the constant volume device that synthin connect after measuring detected element, detected element and auxiliary element respectively and connecting successively ₁₀, the finish surplus pressure P of pressure level-off of venting ₁₀₀, the initial temperature T in deflation time t and the container ₁₀;

E) by formula:

$\mathrm{S\; =\; 0.0261}\sqrt{\frac{\mathrm{273}}{T_{\mathrm{10}}}}\frac{V}{t}\mathrm{［\; (}\frac{P_{\mathrm{10}}}{P_{\mathrm{100}}}{)}^{\frac{1}{5}}\mathrm{-\; 1\; ］}$

Calculate detected element, the synthin useful area S under critical conditions ₁, S ₁₂;

By formula

$b_1=\frac{\frac{S_{\mathrm{12}}}{S_2}-\sqrt{\mathrm{1-(}\frac{S_{\mathrm{12}}}{S_1}{)}^2}}{\mathrm{1\; -}\sqrt{\mathrm{1-(}\frac{S_{\mathrm{12}}}{S_1}{)}^2}}$

Calculate the detected element pseudocritical pressure and compare b ₁;

The discharge characteristic of detected element is intactly explained by following formula:

$\frac{P_a}{P_1}{\mathrm{\le \; b}}_1$

$q^{*}{}_m\mathrm{=\; 0.04042}\frac{P_1}{\sqrt{T_1}}{S}_1$

$\mathrm{1\ge }\frac{P_a}{P_1}{\mathrm{>b}}_1$

$q_m\mathrm{=\; q}{}^{*}{}_m\sqrt{\mathrm{1-(}\frac{\frac{P_a}{P_1}{\mathrm{-\; b}}_1}{{\mathrm{1-b}}_1}{)}^2}$

3, assay method according to claim 1, for the tested unit that switching capability is arranged, its feature comprises:

A) volume V of selection pressure container;

B) of the same type, that latus rectum is identical auxiliary element with detected element of selection, and the synthin after will connecting successively respectively is connected to and contains on the compressed-air actuated constant volume device;

C) determine original pressure P ₁₀, guarantee ambient pressure P _aPressure P when just venting has finished in the container ₁Ratio compare b less than the pseudocritical pressure of detected element;

D) adopt the velocity of sound degassing method, carry out parameter measurement, the original pressure P in the constant volume device that synthin connect after measuring detected element, auxiliary element, detected element and auxiliary element respectively and connecting successively ₁₀, the finish surplus pressure P of pressure level-off of venting ₁₀₀, the initial temperature T in deflation time t and the container ₁₀;

E) by formula:

$\mathrm{S\; =\; 0.0261}\sqrt{\frac{\mathrm{273}}{T_{\mathrm{10}}}}\frac{V}{t}\mathrm{［\; (}\frac{P_{\mathrm{10}}}{P_{\mathrm{100}}}{)}^{\frac{1}{5}}\mathrm{-\; 1\; ］}$

Calculate the useful area S of synthin under critical conditions after detected element, auxiliary element, detected element and auxiliary element are connected successively ₁, S ₂, S ₁₂;

By formula

$b_1=\frac{\frac{S_{\mathrm{12}}}{S_2}-\sqrt{\mathrm{1-(}\frac{S_{\mathrm{12}}}{S_1}{)}^2}}{\mathrm{1\; -}\sqrt{\mathrm{1-(}\frac{S_{\mathrm{12}}}{S_1}{)}^2}}$

The pseudocritical pressure that calculates detected element compares b ₁;

The discharge characteristic of detected element can intactly be explained by following formula:

$\frac{P_a}{P_1}{\mathrm{\le \; b}}_1$

$q^{*}{}_m\mathrm{=\; 0.04042}\frac{P_1}{\sqrt{T_1}}{S}_1$

$\mathrm{1\ge }\frac{P_a}{P_1}{\mathrm{>b}}_1$

$q_m\mathrm{=\; q}{}^{*}{}_m\sqrt{\mathrm{1-(}\frac{\frac{P_a}{P_1}{\mathrm{-\; b}}_1}{{\mathrm{1-b}}_1}{)}^2}$

4, determined method according to claim 1, for the detected element of non-switched capabilities, its feature comprises:

A) volume V of selection pressure container;

B) select one identical or close with the detected element latus rectum, characterisitic parameter is known, and the auxiliary element of switching capability is arranged, and the synthin after respectively detected element and auxiliary element being connected successively is connected to and contains on the compressed-air actuated constant volume device;

C) determine original pressure P ₁₀, guarantee ambient pressure P _aPressure P when just venting has finished in the container ₁Ratio compare b less than the pseudocritical pressure of detected element;

D) adopt the velocity of sound degassing method, carry out parameter measurement, the original pressure P in the constant volume device that synthin connect after measuring synthin, auxiliary element and detected element after detected element and auxiliary element are connected successively respectively and connecting successively ₁₀, the finish surplus pressure P of pressure level-off of venting ₁₀₀, the initial temperature T in deflation time t and the container ₁₀;

E) by formula

$\mathrm{S\; =\; 0.0261}\sqrt{\frac{\mathrm{273}}{T_{\mathrm{10}}}}\frac{V}{t}\mathrm{［\; (}\frac{P_{\mathrm{10}}}{P_{\mathrm{100}}}{)}^{\frac{1}{5}}\mathrm{-\; 1\; ］}$

Calculate useful area S under the critical conditions of the synthin that synthin, auxiliary element and detected element that detected element and auxiliary element connect successively connect successively ₁₂And S ₂₁;

By formula

$S_1=\frac{S_{\mathrm{21}}}{b_2{\mathrm{+\; (1-b}}_2)\sqrt{\mathrm{1\; -\; (}\frac{S_{\mathrm{21}}}{S_2}{)}^2}}$

Calculate the useful area S of detected element under critical conditions ₁;

By formula:

$b_1=\frac{\frac{S_{\mathrm{12}}}{S_2}-\sqrt{\mathrm{1-(}\frac{S_{\mathrm{12}}}{S_1}{)}^2}}{\mathrm{1\; -}\sqrt{\mathrm{1-(}\frac{S_{\mathrm{12}}}{S_1}{)}^2}}$

The pseudocritical pressure that calculates detected element compares b ₁;

The discharge characteristic of detected element can intactly be explained by following formula:

$\frac{P_a}{P_1}{\mathrm{\le \; b}}_1$

$q^{*}{}_m\mathrm{=\; 0.04042}\frac{P_1}{\sqrt{T_1}}{S}_1$

$\mathrm{1\ge }\frac{P_a}{P_1}{\mathrm{>b}}_1$

$q_m\mathrm{=\; q}{}^{*}{}_m\sqrt{\mathrm{1-(}\frac{\frac{P_a}{P_1}{\mathrm{-\; b}}_1}{{\mathrm{1-b}}_1}{)}^2}$

5, assay method according to claim 1, for the detected element of non-switched capabilities, its feature comprises:

A) volume V of selection pressure container;

B) select one with detected element 1 auxiliary element 2 of the same type, that latus rectum is identical, a latus rectum is twice than detected element 1 or more than one times and auxiliary element 3 that switching capability is arranged, and the synthin after synthin, detected element 1 and auxiliary element 2 after synthin, auxiliary element 2 and the auxiliary element 3 after respectively detected element 1 and auxiliary element 3 being connected successively connected successively and auxiliary element 3 are connected successively is connected to and contains on the compressed-air actuated constant volume device;

C) determine original pressure P ₁₀, guarantee ambient pressure P _aPressure P when just venting has finished in the container ₁Ratio compare b less than the pseudocritical pressure of detected element ₁;

D) adopt the velocity of sound degassing method, carry out parameter measurement, the synthin after measuring synthin, auxiliary element 2 and auxiliary element 3 after detected element 1 and auxiliary element 3 are connected successively respectively and connecting successively.Original pressure P in the constant volume device that synthin connect after detected element 1 and auxiliary element 2 and auxiliary element 3 are connected successively ₁₀, the finish surplus pressure P of pressure level-off of venting ₁₀₀, the initial temperature T in deflation time t and the container ₁₀;

E) by formula

$\mathrm{S\; =\; 0.0261}\sqrt{\frac{\mathrm{273}}{T_{\mathrm{10}}}}\frac{V}{t}\mathrm{［\; (}\frac{P_{\mathrm{10}}}{P_{\mathrm{100}}}{)}^{\frac{1}{5}}\mathrm{-\; 1\; ］}$

The useful area S of synthin under critical conditions after synthin, detected element 1 and auxiliary element 2 after calculating synthin, auxiliary element 2 and auxiliary element 3 after detected element 1 and auxiliary element 3 are connected successively respectively and connecting successively and auxiliary element 3 are connected successively ₁, S ₂, S ₁₂;

By formula

$b_1=\frac{\frac{S_{\mathrm{12}}}{S_2}-\sqrt{\mathrm{1-(}\frac{S_{\mathrm{12}}}{S_1}{)}^2}}{\mathrm{1\; -}\sqrt{\mathrm{1-(}\frac{S_{\mathrm{12}}}{S_1}{)}^2}}$

The pseudocritical pressure that calculates detected element 1 compares b ₁;

The discharge characteristic of detected element 1 is intactly explained by following formula:

$\frac{P_a}{P_1}{\mathrm{\le \; b}}_1$

$q^{*}{}_m\mathrm{=\; 0.04042}\frac{P_1}{\sqrt{T_1}}{S}_1$

$\mathrm{1\ge }\frac{P_a}{P_1}{\mathrm{>b}}_1$

$q_m\mathrm{=\; q}{}^{*}{}_m\sqrt{\mathrm{1-(}\frac{\frac{P_a}{P_1}{\mathrm{-\; b}}_1}{{\mathrm{1-b}}_1}{)}^2}$

6, assay method according to claim 1 is characterized in that S ₁/ S ₂Ratio between 0.6-1.15.

7, measuring method according to claim 1 is characterized in that pseudocritical pressure is not more than 0.5 than the b value.

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