CN105651351A - Dropper type gas flow measuring device and method based on weighing principle - Google Patents

Abstract

A dropper-type gas flow measurement device and method based on the principle of weighing, the device includes an electronic scale, an oil storage tank, a dropper, a dropper bracket, an air intake valve, a fine-tuning valve, a three-way pipe and a computer, and a device for storing oil The oil storage tank is placed on the electronic scale, the lower nozzle of the dropper mounted on the dropper bracket is located below the oil level, the upper nozzle is connected with the intake valve and the fine-tuning valve through the three-way pipe, and the fine-tuning valve is connected with the measured object ; The electronic scale is connected to the computer, and the weighing data is recorded and stored by the computer, and the measurement process is timed. The method steps are: open the intake valve; adjust the fine-tuning valve so that the gas flow passing through it meets the intake requirements of the measured object; record the initial weighing reading; close the intake valve; start continuous measurement of the gas flow, and record several consecutive At the same time, record the weighing readings corresponding to each time point; when the computer determines that the measurement needs to be stopped, open the intake valve to end the measurement process; calculate the gas flow.

Description

A dropper type gas flow measurement device and method based on weighing principle

technical field

The invention belongs to the technical field of instrumentation and vacuum testing, and in particular relates to a dropper-type gas flow measuring device and method based on a weighing principle.

Background technique

Vacuum pumps have been widely used in industrial fields such as machinery, electronics, metallurgy, nuclear energy, and space simulation, as well as scientific and technological research, and play an important role in the development of modern science and technology and the construction of the national economy.

The pumping rate of the vacuum pump is usually used as its model identification, and the pumping rate is also the most critical technical index of the vacuum pump, and the measurement of the pumping rate is also a must-test item for the factory inspection and index determination of the vacuum pump. national and international standards. For example: "GB/T19955.1-2005 Vapor Flow Vacuum Performance Measurement Method Part 1: Measurement of Volume Flow Rate (Pumping Speed)" and "GB/T19956.1-2005 Volumetric Vacuum Pump Performance Measurement Method Part 1: Volume Flow Rate (pumping speed) measurement", etc. The method for measuring the pumping rate of the vacuum pump is stipulated in the above-mentioned national standard, and the basic principle of measuring the pumping rate of the vacuum pump is disclosed. Gas flow Q, and make the gas pressure in the standard test cover reach a stable balance, and then by accurately measuring the gas flow Q and gas pressure p, the pumping rate S (volume flow rate).

It can be seen that only by ensuring the accuracy of gas flow measurement can the accuracy of pumping rate be guaranteed. However, in the process of measuring the pumping rate of a vacuum pump (especially a high vacuum pump), it is inevitable to encounter the problem of measuring the small gas flow rate. At this time, the vacuum dropper type gas flow measurement device is most commonly used in the vacuum industry. And method, in the original mechanical industry standard "JB/T8472.1-1996 Performance Measurement of Vapor Flow Vacuum Pump Part 1: Determination of Pumping Rate (Volume Flow)", the dropper type gas flow measurement device is clearly recommended, and in the appendix In A, the structural composition, calculation formula and selection method of the dropper gas flow measurement device are given, and the measurement method is no longer recommended in the subsequent new national standard equivalent to the international standard.

At present, the vacuum industry also uses gas mass flowmeters as a measurement method. However, gas mass flowmeters are indirect relative measurements, and the measurement accuracy error cannot be directly estimated, and it needs to be regularly checked and calibrated by an authoritative department, which will bring extreme pressure to the user. Big inconvenience. Furthermore, the measurement result data obtained by the gas mass flowmeter cannot be published as authoritative data, and it can only be used for internal reference. Therefore, the vacuum industry is still accustomed to adopting the traditional vacuum dropper type gas flow measurement device and method.

For the traditional vacuum dropper type gas flow measurement device and method, there are still the following deficiencies in the actual application process:

① There are too many manual operations, resulting in large measurement errors;

For the measurement of each set of parameters, the surveyor needs to visually observe the liquid level in the dropper for the second time, and manually press the timer. Even if the surveyor has been trained and has good business ability, the manual operation is still a measurement error. The most important source of production.

In the Chinese patent No. ZL200910012545.3, although it is proposed to use a photoelectric liquid level switch instead of manual visual inspection to judge the time when the liquid level reaches the set height, however, due to the fact that the installation position of the liquid level switch is not suitable for adjustment Limitations, when measuring the pumping rate of the vacuum pump under different pressures, it is difficult to ensure that the measurement time interval is exactly in a high-precision state, and it is difficult to operate when changing the dropper with different diameters, and often brings new changes in the setting height of the liquid level switch error.

②It can only measure the average gas flow rate within the timing interval, and cannot reflect the instantaneous change of gas flow rate during this period;

What is calculated by the measurement formula is only the average gas flow rate in the time interval of the secondary reading, so it cannot reflect the instantaneous change of the gas flow rate in this time period. Due to the above reasons, before measuring the pumping rate at each pressure point of the vacuum pump, it needs to be maintained for a long enough time to ensure that the pressure in the standard test hood reaches a stable balance, resulting in low measurement efficiency. As for the change of gas flow caused by the decrease of gas pressure in the dropper, it can only be ignored as a principle error.

③The transparent glass dropper used has original measurement error;

First of all, the inner diameter of the glass tube for making the dropper cannot be strictly processed to ensure its dimensional consistency, and the volume indication can only be calibrated by drawing the scale line, resulting in limited reading accuracy. Secondly, when measuring the small gas flow rate, the small-diameter dropper used has serious capillary phenomenon, which has a large amount of depression for the increase of the liquid level, resulting in an error that cannot be quantitatively estimated.

Due to the above shortcomings of the traditional vacuum dropper type gas flow measurement device and method, it has brought great inconvenience to the vacuum industry. The vacuum industry urgently needs a new gas flow measurement device and method, which can be convenient, fast, accurate and reliable. The measurement of gas flow, especially the measurement of small gas flow.

Contents of the invention

Aiming at the problems existing in the prior art, the present invention provides a dropper-type gas flow measuring device and method based on the principle of weighing, whose measurement function can strictly meet the original machinery industry standard (JB/T8472.1-1996) and the new national standard And international standards (GB/T19955.1-2005/ISO/T8472.1-1996), can replace the traditional vacuum dropper gas flow measurement device and method, and effectively complete the vacuum pump pumping rate (volume flow) The measurement of performance parameters is also applicable to the measurement of small gas flow in other industries.

In order to achieve the above object, the present invention adopts the following technical solutions: a dropper-type gas flow measurement device based on the principle of weighing, including an electronic scale, an oil storage tank, a dropper, a dropper bracket, an air intake valve, a fine-tuning valve, a tee pipe and computer, the oil storage tank is placed on the electronic scale, and oil is stored in the oil storage tank; the dropper is vertically installed on the dropper bracket, and the lower end of the dropper is located below the oil level in the oil storage tank. And the pipe body of the dropper has no contact with the oil storage tank; the nozzle at the upper end of the dropper is connected with the first nozzle of the three-way pipe, and the second nozzle of the three-way pipe is connected with the air outlet of the intake valve, and the air intake The air inlet of the valve communicates with the atmosphere; the third nozzle of the three-way pipe communicates with the air inlet of the fine-tuning valve, and the air outlet of the fine-tuning valve communicates with the air inlet of the measured object; the electronic scale The signal output end is connected with the computer, and the weighing data output by the electronic scale is recorded and stored in real time through the computer, and the measurement process is timed through the computer.

The intake valve and trim valve are controlled manually or automatically. When automatic control is adopted, the opening and closing of the intake valve and the adjustment of the outlet flow of the trim valve are all controlled by a computer.

The oil storage tank has a constant cross-section in the vertical direction.

The oil storage tank is made of lightweight materials.

The dropper is made of non-transparent material, and the inner hole of the dropper is a hole of equal cross section.

A method for measuring a dropper-type gas flow rate based on a weighing principle, using the described dropper-type gas flow measurement device based on a weighing principle, comprising the following steps:

Step 1: Control the opening of the intake valve, and at the same time connect the air outlet of the fine-tuning valve with the air inlet of the measured object;

Step 2: Adjust the fine-tuning valve so that the gas flow through the fine-tuning valve meets the air intake requirements of the measured object;

Step 3: Record the weighing reading of the electronic scale at this moment through the computer, and the weighing reading is the initial weighing reading;

Step 4: Control the intake valve to close and start the continuous measurement of gas flow. During the measurement process, record several continuous time points in real time in the computer, and record the weighing readings of the electronic scales corresponding to each time point;

Step 5: When the computer determines that the measurement needs to be stopped, control the intake valve to open and end the measurement process;

Step 6: Calculate the gas flow within the timing period in the computer, the gas flow calculation formula is:

$\mathrm{<span\; class="notranslate">\; q</span>}<span\; class="notranslate">\; =</span>\frac{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; W</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; W</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&lsqb;</span>{\mathrm{<span\; class="notranslate">\; p</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}\mathrm{<span\; class="notranslate">\; a</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; \&rho;</span>}\mathrm{<span\; class="notranslate">\; g</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; a</span>}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; A</span>}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; g</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}{\mathrm{<span\; class="notranslate">\; W</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; W</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; W</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&rsqb;</span>}{\mathrm{<span\; class="notranslate">\; \&rho;</span>}\mathrm{<span\; class="notranslate">\; a</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; a</span>}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; A</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; t</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; t</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; )</span>}$

In the formula, q is the gas flow rate in the timing period, W _i is the weighing reading of the electronic scale at the beginning of the timing period, W _i+n is the weighing reading of the electronic scale at the end of the timing period, and p _a is the local atmosphere Pressure, a is the cross-sectional area of the inner hole of the dropper, ρ is the oil density, g is the local gravity acceleration, A is the difference between the cross-sectional area of the oil storage tank and the dropper body, and _V0 is the initial oil liquid in the dropper The total volume in the tube from the surface to the air inlet of the fine-tuning valve, W ₀ is the initial weighing reading of the electronic scale, t _i is the initial moment of the timing period, and t _i+n is the end moment of the timing period; among them, W _i , W In _i+n , t _i and t _i+n , i=1, 2, 3..., n=1, 2, 3...;

Step 7: When multiple measurements are required, repeat steps 2 to 6.

There are two conditions for the computer to determine that the measurement needs to be stopped:

① When the air intake requirements of the measured object are completed;

②When the height of the oil rising in the dropper reaches or exceeds the allowable height of the set oil.

It is determined by the computer that the height of the oil rising in the dropper reaches or exceeds the set allowable height of the oil, and the judgment is based on the following conditional formula:

W≤W ₀ -ρaL(1+a/A)

In the formula, W is the real-time weighing reading of the electronic scale, W ₀ is the initial weighing reading of the electronic scale, ρ is the density of the oil, a is the cross-sectional area of the inner hole of the dropper, L is the allowable height of the oil, and A is the difference between the cross-sectional area of the oil reservoir and the dropper body.

Beneficial effects of the present invention:

(1) The present invention has the automatic measurement capability of gas flow

The invention introduces the "weighing principle" into the dropper gas flow measurement for the first time, and there is no manual operation link in the measurement process, which effectively avoids the occurrence of measurement errors; when the invention is applied to the actual vacuum pump pumping speed performance measurement , The weighing reading of the electronic scale, the timing of the measurement process and the pressure reading in the standard test cover can all be automatically recorded and stored by the computer, thus enabling the present invention to have the ability to automatically measure the gas flow.

(2) The present invention possesses instantaneous flow measurement capability

Timing operation of the present invention is completed by computer completely, compared with traditional manual reading mode, has realized greatly shortening on the reading time interval; Have again, can only measure the average gas flow in very long timing interval time for traditional mode but However, the present invention can measure the gas flow in a very short interval, and the gas flow can be very close to the instantaneous flow at the time point of reading, which makes the present invention applicable to occasions where the gas flow varies with time, thereby expanding The range of application of the present invention is widened; when the present invention is applied to the measurement of the pumping speed of the vacuum pump, it can also effectively relax the harsh conditions that the pumping speed of the vacuum pump must reach a stable balance near a certain pressure point in the traditional way, greatly shortening the measurement time; Compared with the traditional manual reading method which can only obtain discrete data, the present invention can obtain continuous data, and then can draw the pumping speed curve.

(3) The present invention can adopt the dropper that non-transparent material is made

By introducing the "weighing principle", the present invention effectively expands the scope of application of the dropper manufacturing material. For the dropper that can only be made of transparent glass in the traditional way, since the present invention does not need to perform visual inspection, it only needs to be weighed. The heavy method can meet the measurement needs. Therefore, the dropper can be made of steel. Due to the material characteristics of steel, it has the ability of precision machining, which can greatly improve the machining accuracy of the inner hole of the dropper. The steel made by precision machining Dropper, the size error of the inner hole is much smaller than the traditional transparent glass dropper.

(4) The present invention can effectively avoid the capillary depression phenomenon of the ultra-fine diameter dropper

Since the dropper of the present invention has a very high precision of the inner hole size, the cross-sectional area of the inner hole of the dropper has almost no influence on the measurement accuracy. Therefore, when measuring the micro gas flow, it is not necessary to select a dropper with a too small diameter. Meet the measurement needs, thereby effectively avoiding the capillary depression phenomenon of the ultra-fine diameter dropper, thereby avoiding the measurement error caused by the capillary depression phenomenon; moreover, it is not necessary to frequently replace the dropper with different specifications and apertures due to different flow rates during measurement. Therefore, the measurement process is effectively simplified, and the labor intensity is also effectively reduced.

Description of drawings

Fig. 1 is a structural principle diagram of a dropper type gas flow measuring device based on weighing principle of the present invention;

Fig. 2 is the structural principle diagram of the automatic measurement system for the pumping speed performance of the vapor flow vacuum pump built by the present invention in the embodiment;

In the figure, 1—electronic scale, 2—oil storage tank, 3—dropper, 4—dropper bracket, 5—intake valve, 6—trimming valve, 7—tee pipe, 8—computer, 9—oil, 10—Vapor flow vacuum pump, 11—Standard test cover, 12—Foreline mechanical pump, 13—Foreline pipeline, 14—Vacuum gauge.

detailed description

The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

As shown in Figure 1, a dropper-type gas flow measurement device based on the weighing principle includes an electronic scale 1, an oil storage tank 2, a dropper 3, a dropper bracket 4, an air intake valve 5, a fine-tuning valve 6, a three-way Tube 7 and computer 8, the oil storage tank 2 is placed on the electronic scale 1, and oil liquid 9 is stored in the oil storage tank 2; the dropper 3 is vertically installed on the dropper bracket 4, and the nozzle at the lower end of the dropper 3 It is located below the liquid level of the oil liquid 9 in the oil storage tank 2, and the pipe body of the dropper 3 has no contact with the oil storage tank 2; The second mouth of pipe is connected with the air outlet of air inlet valve 5, and the air inlet of air inlet valve 5 is communicated with atmosphere; The air outlet of the valve 6 is connected with the air inlet of the measured object; the signal output end of the electronic scale 1 is connected with the computer 8, and the weighing data output by the electronic scale 1 is recorded and stored in real time through the computer 8, and through the The computer 8 times the measurement process.

The intake valve 5 and trim valve 6 are manually controlled or automatically controlled. When automatic control is used, the opening and closing of the intake valve 5 and the adjustment of the outlet flow of the trim valve 6 are all controlled by a computer 8 .

The oil storage tank 2 has a constant cross-section in the vertical direction.

In order to reduce the total bearing capacity of the electronic scale 1, the oil storage tank 2 is made of PVC plastic material.

In order to avoid the original measurement error of the transparent glass dropper, the dropper 3 is made of steel material, and the inner hole of the dropper 3 is a hole of equal cross section.

A method for measuring a dropper-type gas flow rate based on a weighing principle, using the described dropper-type gas flow measurement device based on a weighing principle, comprising the following steps:

Step 1: Control the intake valve 5 to open, and connect the air outlet of the fine-tuning valve 6 with the air inlet of the measured object at the same time;

Step 2: Adjust the fine-tuning valve 6 so that the gas flow passing through the fine-tuning valve 6 meets the air intake requirements of the measured object;

Step 3: Record the weighing reading of the electronic scale 1 at the moment through the computer 8, and the weighing reading is the initial weighing reading;

Step 4: Control the intake valve 5 to close and start the continuous measurement of the gas flow. During the measurement process, record several continuous time points in real time in the computer 8, and record the weighing readings of the electronic scale 1 corresponding to each time point ;

Step 5: When the computer 8 judges that the measurement needs to be stopped, control the intake valve 5 to open, and end the measurement process; wherein, the computer 8 judges that the measurement needs to be stopped according to the following two conditions:

① When the air intake requirements of the measured object are completed;

②When the rising height of the oil 9 in the dropper 3 reaches or exceeds the set allowable height of the oil; wherein, the computer 8 judges that the rising height of the oil 9 in the dropper 3 reaches or exceeds the set oil level. The permissible height of the liquid is determined based on the following conditional formula:

W≤W ₀ -ρaL(1+a/A)

In the formula, W is the real-time weighing reading of the electronic scale, W ₀ is the initial weighing reading of the electronic scale, ρ is the density of the oil, a is the cross-sectional area of the inner hole of the dropper, L is the allowable height of the oil, and A is the difference between the cross-sectional area of the oil storage tank and the dropper body;

Step 6: Calculate the gas flow in the timing period in the computer 8, the gas flow calculation formula is:

$\mathrm{<span\; class="notranslate">\; q</span>}<span\; class="notranslate">\; =</span>\frac{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; W</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; W</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&lsqb;</span>{\mathrm{<span\; class="notranslate">\; p</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}\mathrm{<span\; class="notranslate">\; a</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; \&rho;</span>}\mathrm{<span\; class="notranslate">\; g</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; a</span>}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; A</span>}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; g</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}{\mathrm{<span\; class="notranslate">\; W</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; W</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; W</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&rsqb;</span>}{\mathrm{<span\; class="notranslate">\; \&rho;</span>}\mathrm{<span\; class="notranslate">\; a</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; a</span>}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; A</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; t</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; t</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; )</span>}$

In the formula, q is the gas flow rate in the timing period, W _i is the weighing reading of the electronic scale at the beginning of the timing period, W _i+n is the weighing reading of the electronic scale at the end of the timing period, and p _a is the local atmosphere Pressure, a is the cross-sectional area of the inner hole of the dropper, ρ is the density of the oil, g is the local acceleration of gravity, A is the difference between the cross-sectional area of the oil storage tank and the dropper body, and _V0 is the initial oil liquid in the dropper The total volume in the tube from the surface to the air inlet of the fine-tuning valve, W ₀ is the initial weighing reading of the electronic scale, t _i is the initial moment of the timing period, and t _i+n is the end moment of the timing period; among them, W _i , W In _i+n , t _i and t _i+n , i=1, 2, 3..., n=1, 2, 3...;

Step 7: When multiple measurements are required, repeat steps 2 to 6.

The following will use the measuring device of the present invention to build an embodiment of an automatic measurement system for the pumping speed of a steam flow vacuum pump. Before the measurement system is set up, it is necessary to prepare the steam flow vacuum pump 10, the standard test cover 11, the fore-stage mechanical pump 12 and The foreline pipeline 13 is equipped with a vacuum gauge 14 on the standard test cover 11, and the structure and parameters of the above components are determined in full compliance with the national standard "GB/T19955.1-2005 Steam Flow Vacuum Performance Measurement Method Part 1: Measurement of volume flow rate (pumping speed)" shall be carried out according to the regulations. As shown in Figure 2, after the automatic measurement system for the pumping speed performance of the vapor flow vacuum pump is completed, the measurement operation can be started.

Preparatory stage before measurement: First, according to the operation method and steps specified in the national standard "GB/T19955.1-2005 Steam Flow Vacuum Performance Measurement Method Part 1: Measurement of Volume Flow Rate (Pumping Speed)", the fine-tuning valve 6 is completely Under the condition of shutting down, start the back-stage mechanical pump 12 and the vapor flow vacuum pump 10 in sequence, so that both the back-stage mechanical pump 12 and the vapor flow vacuum pump 10 reach a stable working state.

The pressure debugging stage before the measurement: first determine the inlet pressure range of the steam flow vacuum pump 10 that needs to be measured for the pumping speed, and under the condition that the intake valve 5 is opened, the fine-tuning valve 6 is controlled by the computer 8 to open, so that the gas in the standard test cover 11 The balance pressure is close to the test pressure value of each point from low to high. The specific operation steps are: corresponding to the inlet pressure set at a certain point, the computer 8 reads the actual balance pressure value in the standard test cover 11 through the vacuum gauge 14, and compares it with the set pressure. Compared with the fixed inlet pressure value, if the actual equilibrium pressure value is higher than the inlet pressure value, the computer 8 controls the fine-tuning valve 6 to reduce its valve opening, so that the gas flow through the fine-tuning valve 6 decreases, so that the standard test cover The actual balance pressure in 11 decreases; on the contrary, if the actual balance pressure value is lower than the inlet pressure value, the computer 8 controls the fine-tuning valve 6 to increase its valve opening, so that the gas flow through the fine-tuning valve 6 increases, so that the standard The actual balance pressure in the test cover 11 rises; this is repeated until the actual balance pressure in the standard test cover 11 is close to the set inlet pressure and reaches the allowable value, and finally the adjustment of the gas flow and balance pressure is completed.

Measurement stage: first record the initial weighing reading of the electronic scale 1 at the moment through the computer 8, and then control the intake valve 5 to close through the computer 8, and start the continuous measurement of the gas flow. At the time point, record the weighing reading of the electronic scale 1 corresponding to each time point, and record the pressure reading in the standard test cover 11 measured by the vacuum gauge 14, when the computer 8 judges that the measurement needs to be stopped (the judgment condition has Two: ①The deviation between the pressure reading in the standard test cover 11 measured by the vacuum gauge 14 and the set inlet pressure exceeds the allowable value; ②When the height of the oil 9 rising in the dropper 3 reaches or exceeds the set oil allowable height), control the intake valve 5 to open, and end the measurement process.

Result calculation stage: first, the gas flow q automatically calculated by the computer 8, combined with the gas pressure p measured by the vacuum gauge 14, and finally the pumping rate S of the vapor flow vacuum pump 10 can be calculated through the formula S=q/p.

Repeat the measurement phase, complete the gas flow measurement at the inlet pressure set at the remaining points, and calculate the pumping rate S of the vapor flow vacuum pump 10 at the inlet pressure set at the remaining points.

The solutions in the embodiments are not intended to limit the scope of patent protection of the present invention, and all equivalent implementations or changes that do not deviate from the present invention are included in the patent scope of this case.

Claims (8)

1. the burette type gas flow surveying instrument based on weighing principle, it is characterized in that: include electronic scale, oil storage tank, dropper, burette bracket, intake valve, reset valve, tee T and computer, described oil storage tank is positioned on electronic scale, and in oil storage tank, storage has fluid; Described dropper is vertically installed on burette bracket, and the dropper lower end mouth of pipe is arranged in below oil storage tank fluid liquid level, and dropper body is contactless with oil storage tank; The described dropper upper end mouth of pipe is connected with first mouth of pipe of tee T, and second mouth of pipe of tee T is connected with the gas outlet of intake valve, the air inlet of intake valve and atmosphere; 3rd mouth of pipe of described tee T is connected with the air inlet of reset valve, and the gas outlet of reset valve is connected with the air inlet of measurand; The signal output part of described electronic scale is connected with computer, and weighing data electronic scale exported by computer carries out real time record and storage, and by computer, measurement process is carried out timing.

2. a kind of burette type gas flow surveying instrument based on weighing principle according to claim 1, it is characterized in that: described intake valve and reset valve adopt Non-follow control or automatically control, when employing automatically controls, the open and close of intake valve, reset valve Flow-rate adjustment of giving vent to anger be controlled each through computer.

3. a kind of burette type gas flow surveying instrument based on weighing principle according to claim 1, it is characterised in that: described oil storage tank in the vertical direction is iso-cross-section.

4. a kind of burette type gas flow surveying instrument based on weighing principle according to claim 1, it is characterised in that: described oil storage tank adopts light material to make.

5. a kind of burette type gas flow surveying instrument based on weighing principle according to claim 1, it is characterised in that: described dropper adopts non-transparent material manufacture, and dropper endoporus is iso-cross-section hole.

6., based on a burette type gas flow measurement method for weighing principle, have employed the burette type gas flow surveying instrument based on weighing principle described in claim 1, it is characterised in that comprise the steps:

Step one: control inlet open, the gas outlet of reset valve is connected with the air inlet of measurand simultaneously;

Step 2: reset valve is adjusted, makes the gas flow passed through in reset valve meet the air inlet requirement of measurand;

Step 3: by the reading of weighing this moment of electronic scale under computer recording, this reading of weighing is for reading of initially weighing;

Step 4: control intake valve and close, starts the continuous measurement of gas flow, and in measurement process, some continuous print time points under real time record, record the reading of weighing of the electronic scale corresponding to each time point simultaneously in a computer;

Step 5: when computer-made decision needs to stop measuring, control inlet open, terminate this measurement process;

Step 6: calculate the gas flow in timing time section in a computer, gas flow calculates formula and is:

$q=\frac{(W_i-W_{i+n})\&lsqb;p_{a}a+\mathrm{\&rho;}g(1+a/A)V_0-g\left(2W_0-W_i-W_{i+n}\right)\&rsqb;}{\mathrm{\&rho;}a(1+a/A)(t_{i+n}-t_i)}$

In formula, q is the gas flow in timing time section, W_iFor the reading of weighing of timing time section initial time electronic scale, W_i+nFor the reading of weighing of timing time section finish time electronic scale, p_aFor local atmospheric pressure, a is the endoporus cross-sectional area of dropper, and �� is fluid density, and g is local gravitational acceleration, and A is the difference of oil storage tank and the cross-sectional area of dropper body, V₀For fluid liquid level initial in dropper to total measurement (volume) in the pipe at reset valve air inlet place, W₀For the reading of initially weighing of electronic scale, t_iFor timing time section initial time, t_i+nFor timing time section finish time; Wherein, W_i��W_i+n��t_iAnd t_i+nIn i=1,2,3, n=1,2,3;

Step 7: when needs take multiple measurements, repeats step 2 to step 6.

7. the burette type gas flow measurement method based on weighing principle according to claim 6, it is characterised in that: the condition needing to stop is measured in computer-made decision following two:

1. when the air inlet of measurand has required;

2. when the height risen in dropper when fluid meets or exceeds the fluid of setting height allowable.

8. the burette type gas flow measurement method based on weighing principle according to claim 7, it is characterised in that: the height risen in dropper by computer-made decision fluid meets or exceeds the fluid height allowable of setting, and its judgment basis is following conditional:

W��W₀-�� aL (1+a/A)

In formula, W is the reading of weighing in real time of electronic scale, W₀For the reading of initially weighing of electronic scale, �� is fluid density, and a is the endoporus cross-sectional area of dropper, and L is fluid height allowable, and A is the difference of oil storage tank and the cross-sectional area of dropper body.