CN202582624U

CN202582624U - Thermal gas flowmeter for mine

Info

Publication number: CN202582624U
Application number: CN 201220232054
Authority: CN
Inventors: 叶寒生; 顾宇
Original assignee: HEFEI COMATE INTELLIGENT SENSOR TECHNOLOGY Co Ltd
Current assignee: HEFEI COMATE INTELLIGENT SENSOR TECHNOLOGY Co Ltd
Priority date: 2012-05-22
Filing date: 2012-05-22
Publication date: 2012-12-05
Anticipated expiration: 2022-05-22

Abstract

The utility model discloses a thermal gas flowmeter for a mine, which is characterized in that two groups of built-in probes, namely a thermal flow sensor and a water spray correction sensor, are arranged in a sensor supporting rod; the thermal flow sensor comprises a heating platinum resistor R11 and an unheated platinum resistor R12; the heating platinum resistor R11 is provided with a constant power heating control circuit; the water spray correction sensor comprises a heating platinum resistor R21 and an unheated platinum resistor R22; and the heating platinum resistor R21 is provided with a constant temperature difference heating control circuit. The flow of gas-liquid two-phase mixed flow containing lots of water spray can be accurately measured.

Description

Mining thermal gas flowmeter

Technical field

The utility model relates to flow sensor, more specifically says so to be applied in the Minepit environment, and gas flow in the measuring channel, and can revise the thermal gas flowmeter of the measuring error that high concentration steam contained in the gas introduced automatically.

Background technology

Thermal gas flowmeter is based on the thermal diffusion principle and the flow instrument designed and developed, promptly utilizes gas stream to cross the principle that heat that thermal objects takes away and flow rate of fluid be proportionate relationship and designs.The sensing element that thermal flowmeter is commonly used is a RTD, and the resistance of RTD changes with self temperature variation.Typical thermal diffusion type flowmeter adopts two RTDs, and one for the resistance that tests the speed is heated, and another is used as temperature detecting resistance and is not heated.Out-of-date as air flow stream, obtain the flow velocity of air-flow with respect to the change in resistance amount of temperature detecting resistance through the detection resistance that tests the speed.The physical property of heat dissipation and fluid media (medium) of resistance of testing the speed in the thermal flowmeter is closely related.

Characteristics such as thermal gas flowmeter is low owing to its measurement lower limit, range ratio is wide are particularly suitable for large pipeline, and the gasmetry applied environment of low flow velocity is like the gas pumping in the mine.But in mine, gas pumping is unavoidably introduced in pipeline has water smoke, and the variation of temperature, pressure also can make fluid produce dewfall in addition, and the existence of these water smokes and dewfall phenomenon makes traditional thermal flowmeter to be measured accurately.

Summary of the invention

The utility model is for avoiding above-mentioned existing in prior technology weak point, a kind of mining thermal gas flowmeter being provided, so that can measure the flow of the gas-liquid two-phase flow that contains a large amount of water smokes comparatively exactly.

The utility model adopts following technical scheme for the technical solution problem:

The design feature of the mining thermal gas flowmeter of the utility model is: two groups of built-in probes are set on the sensor support bar, are respectively thermal flow rate sensor and water smoke correction sensor; Said thermal flow rate sensor includes heating RTD R11 and does not heat RTD R12; For said heating RTD R11 is provided with permanent power heating control circuit; Said water smoke correction sensor comprises to be had heating RTD R21 and not to heat RTD R22; For said heating RTD R21 is provided with the constant difference heating control circuit.

Medium heats RTD R11 and does not heat temperature difference maximum between the RTD R12 when static state, and along with the mobile temperature difference of medium reduces; In actual measurement, the temperature substantially constant of heating RTD R12, along with the difference of flow velocity, the temperature that does not heat RTD R11 has corresponding variation, as sensor, temperature variation is converted to the change in resistance of resistance with RTD.Can obtain the flow value of not compensated through the difference that relatively heats RTD R11 and do not heat the resistance of RTD R12.

Hold when constant when the rational quality guarantee of dielectric object, the difference between current of flowing through heating RTD R21 and not heating RTD R22 is a steady state value.When water smoke disturbs, revise with the flow velocity error that the variable quantity of heating current is introduced water smoke, thus the flow speed value that obtains revising.

Compared with present technology, the utility model can be measured the flow of the gas-liquid two-phase flow that contains a large amount of water smokes comparatively exactly.

Description of drawings

Fig. 1 is the utility model structural representation;

Fig. 2 is the utility model metering circuit block scheme;

Fig. 3 is permanent power type of heating schematic diagram;

Fig. 4 is a constant difference type of heating schematic diagram;

Fig. 5 is the metering system operational flow diagram that realizes flow metering with the utility model;

Gas flow curve map when sneaking into a large amount of water smoke during Fig. 6 not compensated in the gas;

Fig. 7 contains the flow curve figure of the gas-liquid two-phase flow of a large amount of water smokes after over-compensation.

Embodiment

Referring to Fig. 1, the structure setting of mining thermal gas flowmeter is in the present embodiment: two groups of built-in probes are set in thermal flowmeter, are respectively thermal flow rate sensor and water smoke correction sensor; Said thermal flow rate sensor includes heating RTD R11 and does not heat RTD R12; For said heating RTD R11 is provided with permanent power heating control circuit; Said water smoke correction sensor comprises to be had heating RTD R21 and not to heat RTD R22; For said heating RTD R21 is provided with the constant difference heating control circuit.

In the practical implementation, water smoke correction sensor is arranged on the back side of support bar, to avoid receiving the influence of media flow.

Fig. 2 is a measuring principle block scheme in the present embodiment; The change in resistance of thermal flow rate sensor and water smoke correction sensor converts voltage to through the advance signal pre-process circuit; And through signal amplify and filtering after send into the A/D change-over circuit and convert aanalogvoltage to digital quantity, by digital processing unit this digital quantity is carried out computing and obtains flow value and be presented on the LCD.The user can come the instrument operational factor is provided with through keyboard, also can select to check parameters such as flow velocity through keyboard.The RS485 interface is used for carrying out communication with host computer, can give industrial computer with data upload such as flow velocity, flows, also can receive, handle the order that level controlling system is sent.4～20mA interface is used for output current signal, with the lower limit and the upper limit of indication flow or flow velocity.Frequency Output Interface Circuit is used for exporting the frequency signal corresponding with flow, satisfies the frequency pulse of 200 ~ 1000Hz of mining communication standard according to range ratio output.

Fig. 3 is permanent power type of heating schematic diagram, and the temperature of resistance R c is constant among the figure, and along with the difference of flow velocity, the temperature of resistance R w has corresponding variation, and RTD can convert temperature variation to the change in resistance of resistance.And the current value that flows through RTD is known, therefore can obtain the magnitude of voltage of resistance.

Fig. 4 is a constant difference type of heating schematic diagram.The constant difference heating is to heat a RTD Rw earlier, makes it exceed a stationary temperature than the RTD Rc that does not heat.Along with flowing of medium, heated RTD is owing to heat transmission is reduced temperature, and the electric current (perhaps voltage) of negative-feedback circuit meeting control heater keeps the temperature difference constant.Obtain the changing value of water smoke concentration through the variable quantity of measuring electric current (voltage).

Fig. 5 is the metering system operational flow diagram that realizes flow metering with the utility model, after system powers on operation, carries out following steps according to the sequential of setting:

Step 1: system initialization is also accomplished self check, the heating of popping one's head in after self check is errorless;

Step 2: read the A/D conversion value, obtain the voltage V1 and the V2 of the corresponding output of thermal flow rate sensor and water smoke correction sensor respectively, judge according to the output voltage V 2 of water smoke correction sensor whether gas has sneaked into water smoke in the tested pipeline, and definite behavior pattern;

Step 3: according to behavior pattern decision flow rate calculation method.If pattern 1 is then carried out the flow correction computing according to V1 and V2, the flow value that is compensated; If pattern 2 is then directly carried out the flow computing according to V1.

Step 4: on LCD, show the flow rate value, send 4～20mA signal and RS485 signal and give host computer that the pulse signal of 200 ~ 1000Hz of mining communication standard is satisfied in output; Accomplish and detect i.e. shutdown.

Gas flow curve map when Fig. 6 sneaks into a large amount of water smoke when the thermal flowmeter not compensated in the gas.Flowmeter work is reliably before the T0, and when T0 sneaked into water smoke in the gas constantly, serious saltus step had appearred in curve, and measuring error is considerably beyond the practical application accuracy requirement, and flowmeter can't accurately be measured.

Fig. 7 is for containing the flow curve figure of the gas-liquid two-phase flow of a large amount of water smokes after compensating with the utility model.Can find out that on scheming at T0 constantly, though there are a large amount of water smokes to sneak into medium, revise owing to add, measuring error obviously reduces and, can reflect actual gas phase flow in the reasonable scope.

In the practical implementation, the measured value correction is to accomplish through the calibration of specialty.Need take the clean, dry air during calibration and contain the water smoke air to carry out verification.The water smoke concentration that air is sneaked into is set at 10%, 30%, 50%, 80%, 100%.When carrying out calibration to contain the water smoke air, the thermal flow rate sensor output voltage is V ₁, water smoke correction sensor output voltage is V ₂When carrying out calibration with the clean, dry air, the thermal flow rate sensor output voltage is V ' ₁, water smoke correction sensor output voltage is V ' ₂(reference voltage value).At each flow velocity point, can obtain five groups of (V ₁, V' ₁, V ₂, V ' ₂) data.The actual flow value is only by V ' ₁Calculate V' when water smoke is arranged ₁With V ₁, V ₂, V ' ₂There is certain relation.Adopt least square method to come match V ' ₁=f (V ₁, V ₂-V ' ₂) function expression.After demarcating completion, carry out flow correction according to this expression formula during flowmeter in-situ work and calculate, obtain actual flow value comparatively accurately.

Claims

1. mining thermal gas flowmeter, it is characterized in that: two groups of built-in probes are set on the sensor support bar, are respectively thermal flow rate sensor and water smoke correction sensor; Said thermal flow rate sensor includes heating RTD R11 and does not heat RTD R12; For said heating RTD R11 is provided with permanent power heating control circuit; Said water smoke correction sensor comprises to be had heating RTD R21 and not to heat RTD R22; For said heating RTD R21 is provided with the constant difference heating control circuit.

2. mining thermal gas flowmeter according to claim 1 is characterized in that: said water smoke correction sensor is arranged on the back side of support bar.