SU1520381A1 - Method of determining dust content of gaseous flow - Google Patents

Abstract

The invention relates to methods for measuring the dust content of a moving unsteady dust and gas flow by partial sampling. The aim of the invention is to improve the accuracy and reliability of dust measurement by providing isokineticity in the selection of a dust sample. The method involves suction of a dust-gas sample with a "zero" type dust extraction tube connected to the partial sampling line, measuring static pressures on the inner and outer surfaces of the tube nose and maintaining their difference at a predetermined level by changing the measured value of the aspirated dust-gas sample. According to the invention, the dependence of the static pressure on the external and internal surfaces of the nozzle of the tube on the gas flow rate in the channel under test is preliminarily determined under the condition that the isokinetic selection is expressed and the flow rate is expressed through the amount of suction gas flow on the partial extraction line. When sampling a dust-gas sample, they continuously maintain the correspondence between the obtained values of the difference in static pressures and the gas flow rate in the partial extraction line. 3 il.

Description

The invention relates to the measurement of the parameters of a moving two-phase medium, and more specifically to the measurement of the dust content of a moving unsteady dust and gas flow by a partial selection method.

The aim of the invention is to improve the accuracy and reliability of the dust measurement by ensuring isokineticity in the selection of a dust sample.

Continuous maintenance of compliance with the difference by the static pressure difference inside and outside the dust extraction tube and the gas flow rate in the partial extraction line ensures guaranteed isokineticity of the gas flow inside and outside the tube.

FIG. 1 shows the scheme of the proposed method; in fig. graph of static pressure versus suction gas consumption; in fig. 3 - pneumatic circuit for implementing the method.

To determine the dependence of the static pressure difference on the external and internal surfaces of the tube nozzle on the gas flow rate under the condition of isokineticity, the sampling tube (Fig. 1) is placed in a calibration device (for example, a wind tunnel) with a known distribution of the gas velocity in the section under study.

Taking into account the known value of the gas velocity in the tube inlet section and the inlet area, the gas flow through the tube is calculated to ensure the isokinetic selection, and the corresponding output signal value of the flow meter on the partial gas extraction line (for example, pressure drop on the diaphragm fixed by the micromanometer). At steady state of gas flow in the calibration device, using a device that provides suction and flow control (for example, an ejector with a gas valve), equalize the speed inside and outside the nozzle of the dust extraction tube, until a certain calculation is obtained for the output signal of the flow meter 3 than provide isokinetic sampling dust sample. At the same time using the micromanometer 6 fix the difference of static pressures on the outer and inner surface of the tube.

This cycle of measurements is repeated at different values of the gas velocity in the calibration tool.

The obtained dependence of the static pressure difference on the flow rate of the suction gas (or the output signal value of the flow meter on the partial extraction line) is unambiguous, i.e. each value of consumption

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Suction gas corresponds to a certain pressure difference, (Fig. 2).

Thus, in order to ensure the isokineticity conditions during the sampling of the dust sample, one should continuously maintain the correspondence between the obtained values of the difference in static pressures and the gas flow rate in the partial extraction line.

To implement this method, it is necessary to assemble a pneumatic circuit containing a zero-type series-connected dust extraction tube 1 (Fig. 3) with a micromanometer 2 connected to the measuring orifices of the static head, allonge with absolute filter 3, flow meter 4 (for example, a diaphragm), equipped with a metering device 5 (for example, a micromanometer), an integrated gas meter 6 for the volumetric flow rate and a device 7 for suctioning and adjusting the gas flow through the partial extraction line (for example, an ejector). In addition, weights are also necessary for weighing an absolute filter (e.g., analytical).

The measurement of the dust content of the gas stream is carried out as follows.

Absolute filter 3 is weighed, it is loaded into the allonge. The spout of the dust extraction tube 1 is installed at a controlled point of the flow under investigation, the dust content of which is to be determined, and by means of a device 7 that sucks gas through the partial sampling line, the readings of the instruments showing the difference of static pressures on the spout of the dust extraction tube are obtained and the output signal of the flow meter four,

The ratio of these parameters is set in the form of a graphical dependence, obtained earlier by means of calibration, carried out in strict compliance with the isokineticity of sampling. Maintaining compliance is to adjust the flow rate (i.e., the pressure drop across the flow meter) as long as the pressure drop across the flow meter; and the tube at the same time does not coincide with the specified dependence curve between these parameters.

After completion of sampling, overlap suction, remove the absolute filter and weigh it. Weighing the filter is carried out according to a known method. The processing of the results is carried out according to the generally accepted method

The application of the proposed method will significantly improve the accuracy and accuracy of measuring the dust content of the gas stream, which is especially important when testing high-performance cleaning tools, such as diesel engine diesel air purifiers, where due to the insignificance of the allowable skip factor for its sufficiently accurate determination, high accuracy of dust measurement of the gas flow passed through the air cleaner is required.

In addition, the proposed method will allow more stringent control over the compliance of air cleaners with the requirements of policy documents and, as a result, increase the service life of the units protected by the said air cleaners from contamination (and associated wear) through the air supply system.

Claims (1)

Invention Formula Method for determining the dust content of a gas stream, including suction Dust gas sample at help (And connected to the partial sampling line of a zero-type dust extraction tube, measuring static pressures on the inner and outer surfaces of the tube tip and maintaining their difference at a given level by changing the measured flow rate suctioning dust and gas samples, measuring its volume and determining the mass concentration of the fluid contained in it, characterized in that, in order to improve the accuracy and the reliability of measurements by ensuring isokineticity during the sampling of a dust sample; the dependence of the static pressure on the external and internal surfaces of the tube nozzle on the gas flow rate in the channel under investigation is determined while observing the isokinetic selection and expressing the flow rate through the amount of suction gas flow on the partial extraction line, and when collecting dust and gas samples, they continuously maintain the correspondence between the obtained values of the difference in static pressures and the consumption of hectares for in-line partial selection. Cfffombiu O.S1,0r, S No flow rate / ru 9ve.Z p-fO-fi / C