JP5089340B2 - Structure of variable cross-section venturi type exhaust gas flowmeter - Google Patents

Description

The present invention relates to a technique for directly measuring an exhaust gas flow rate of an engine or the like, and relates to the structure and configuration of a practical measurement device for a gas flow rate with large fluctuations in temperature, pressure and flow velocity.

  Direct measurement of engine exhaust gas flow rate is extremely important for environmental measures, and various measuring devices have been developed. However, there are still no satisfactory results in terms of measurement range and measurement accuracy. The present invention adds a new technology to the structure of the previously disclosed variable cross-sectional area venturi type exhaust gas flow measuring device (Non-Patent Documents 1 and 2). In addition, it is possible to realize improved convenience and durability in terms of use by improving the inconvenience.

Utility Model Registration No. 3085960 JP 2003-269685 Shigeru Yanagihara, Isamu Mochizuki, Keisuke Sato, Keizo Saito, Variable cross-sectional area venturi type exhaust flow measuring device, Automobile Engineering Society of Japan 19988.5 Academic Lecture 128 Shigeru Yanagihara, et al. Variable area venturi-type exhaust gas flow meter. Technical Notes / JSAE Review 20 (1999) 259-279

  The conventional variable cross-section venturi type exhaust gas flowmeter has a measurement pipe placed horizontally, and when the measured exhaust gas flow rate is slow, high temperature exhaust gas is biased to the upper part of the pipe, causing temperature fluctuations. In addition, it is difficult to measure the average gas temperature, and the flow rate measurement accuracy may be deteriorated. In addition, a gravitational effect of a movable core or the like is received in the lateral direction of the drive shaft, and uneven wear may occur in the sliding portion of the shaft. Furthermore, since the movable core is moved in the horizontal direction, the horizontal distance from the inlet to the outlet of the measuring device becomes longer and the shape of the device becomes longer in the horizontal direction in the arrangement of the horizontal measuring pipes. There were problems such as being restricted.

としていた。ここに、Ｄｍａｘはコァーの最大径で、ｌはコァーの最大径の断面から軸方向の最大移動距離である。この形状は単純な回転放物線曲面であるが、曲面が中心軸の線となす角度が３０°以上大きくなると実際のスロート部有効断面はスロート部内周とコァー直径が形成する中心軸に直角な平面との間の環状流路断面より変化するようになる。実際にはコァー表面のごく近傍では面に沿った流れとなるので、流路断面積は放物線よりもずれることになる。コァーの移動距離に対するスロート部断面積を比例的変化にするためには回転放物線曲面から修正を必要とする課題があった。 It is most desirable in terms of cross-sectional area control that the effective flow path cross-sectional area of the variable cross-sectional area changes linearly in proportion to the moving distance of the movable core. In the conventional core, the relation of the cross-sectional diameter D (x) to the axial movement distance x is simply

I was trying. Here, Dmax is the maximum diameter of the core, and l is the maximum movement distance in the axial direction from the cross section of the maximum diameter of the core. This shape is a simple rotating parabolic curved surface, but when the angle between the curved surface and the line of the central axis increases by 30 ° or more, the actual effective section of the throat part is a plane perpendicular to the central axis formed by the inner periphery of the throat part and the core diameter. It changes from the annular channel cross section between. Actually, since the flow is along the surface in the very vicinity of the core surface, the cross-sectional area of the flow path is deviated from the parabola. In order to change the cross-sectional area of the throat portion in proportion to the movement distance of the core, there is a problem that requires correction from the parabolic curved surface.

  Since the exhaust gas temperature of the engine for which the flow rate is measured varies greatly from 100 ° C. or lower to 400 ° C. or higher depending on the operating conditions, the effective sectional area of the throat portion of the measuring portion may be affected by thermal expansion. Although this influence is considered to be mainly due to the linear thermal expansion of the drive shaft of the movable core, it is one problem to make such an influence small enough to be ignored.

  The exhaust gas temperature may reach a high temperature of 450 ° C. or higher depending on the operating conditions and the configuration of the exhaust pipe system. At such a high temperature, not only the volumetric flow rate increases, but also the heat resistance of the components of the apparatus. The problem is to be able to cool the local or the entire pipeline when the exhaust gas temperature to be introduced is particularly high.

  Exhaust gas usually contains moisture and is not condensed at a temperature higher than the dew point, but immediately after starting the engine, the exhaust pipe system including the engine is at a temperature lower than the dew point. Condensate is often discharged. Condensed water should be taken into the measurement system without delay by the measuring device and measured as exhaust gas in the vaporized state, but in actual measurement, the condensate problem is addressed by including it as an initial drain for engine start. The challenge is to make it possible.

  Usually, the exhaust gas to be measured is discharged at an angle close to horizontal and introduced into the measuring device. In the present invention, by arranging the venturi vertically or vertically, the exhaust gas flows in the vertical direction in the measurement section, and in particular by flowing upward from below, the temperature distribution is made uniform even when the exhaust gas flow rate is slow. At the same time, the drive shaft of the movable core of the variable cross-sectional area venturi type exhaust gas flowmeter is kept close to the vertical direction to reduce the lateral support force and sliding resistance applied to the shaft, and further to the horizontal as the measurement direction. The required distance in the direction can be shortened, and the arrangement is advantageous.

In many cases, the exhaust gas contains about 13% of water in a molar ratio, and the dew point is about 53 ° C. At the time of start-up, the temperature of the exhaust pipe system including the engine is lower than the dew point, so condensation occurs in moisture. This moisture is naturally a discharge component and should be included in the flow rate measurement, but handling may not always be determined. In the present invention, an appropriate heating and evaporating apparatus is disposed in the vicinity of the entrance of the apparatus so that the condensed water flowing in can be included in the exhaust gas to be measured as needed. In some cases, the drain can be discharged out of the measurement system in a timely manner.
Therefore, the structure of the variable cross-sectional area venturi type exhaust gas flowmeter according to the present invention is parallel to the axis of the venturi measurement pipe line having a pipe line that expands the flow of the pipe line through the throat portion where the flow path cross-sectional area is minimized. A movable core whose cross-sectional area changes depending on the position in the axial direction is arranged at the center of the throat, and the static pressure and absolute pressure at the inlet are measured by a venturi tube whose cross-sectional area changes depending on the position of the movable core. In a variable cross-section venturi type flow meter that measures the flow rate by measuring the temperature, static pressure in the throat, and determining the fluid density, throat flow velocity and effective throat area from the axial position of the core. The measurement pipeline was configured to be inclined with respect to the horizontal.
In the variable cross-sectional area venturi type exhaust gas flowmeter according to the present invention, the venturi measuring pipe is arranged so that the gas flow in the venturi measuring pipe is from the bottom to the top.
In addition, the structure of the variable cross-section venturi type exhaust gas flowmeter of the present invention has a movable core cross-sectional shape that can advantageously control the flow rate by linearly changing the effective cross-sectional area of the venturi throat portion with respect to the moving distance of the movable core. An annular curved surface formed by smoothly intersecting an annular conical surface formed by the normal direction of the core cross section, the venturi outer periphery and the core curved surface with respect to the axial position of the throat section of the venturi outer periphery. It has a core shape corrected from a parabolic curved surface so that the cross-sectional area is linearly changed with respect to the core movement distance.
The variable cross-sectional area venturi type exhaust gas structure according to the present invention is such that the shape of the core is such that the length of the core in the axial direction is shorter than the maximum movement distance of the core, and the core is past the throat pressure detection point plane. Is configured to reach the maximum effective throat cross-sectional area.
Further, the variable cross-sectional area venturi type exhaust gas flowmeter according to the present invention has a structure in which the position of the core is transmitted from a drive device which is arranged outside the venturi measurement pipe line and is kept at a normal temperature at the time of measurement. In some cases, the drive shaft of the movable core placed inside the measurement pipe, which may reach a high temperature of 300 ° C or more during measurement, is made of a special alloy such as amber with a very low coefficient of thermal expansion, and is used during flow rate calibration. The influence of temperature on the transmission of the core position due to the difference between the internal temperature of the measurement pipe line and the internal temperature at the actual measurement was reduced.
The variable cross-section venturi type exhaust gas flowmeter according to the present invention has a surge tube 1), 2) or a buffer device as a buffer device having a relatively small volume and a large equivalent damping volume at the inlet of the measurement pipe. A balloon buffer tube (BBT) 3) can be attached to effectively attenuate pulsation and reduce errors even in pulsating flow paths to enable highly accurate flow measurement using a Venturi tube. did.
Here, the surge tube 1) has an appropriate cross-sectional area in which gas can freely enter and exit a part of the side wall surface of an appropriate length in a gas pipeline system having a pulsation with large amplitude in pressure and flow velocity. One or more holes are provided, and a tube or bellows made of a stretchable material such as a rubber film having an appropriate volume on the outer periphery of the part and having appropriate elasticity, strength, and heat resistance is disposed. The side of the bellows etc. is expanded and contracted by the internal / external differential pressure to form a conduit that changes volume, so that it corresponds to a surge tank with a large equivalent capacity. It is a surge tube (refer to patent documents 1) which controls and eases pulsation.
In addition, the surge tube 2) has a structure in which a tube made of a stretchable material such as a rubber film with appropriate elasticity, strength, and heat resistance is disposed, and the volume of the tube changes due to expansion and contraction of the side surface of the tube due to internal / external differential pressure. In a surge tube that suppresses and alleviates pulsation of the pipeline system by volume change due to expansion and contraction of a rubber membrane, etc., both ends of a thin rubber cylindrical tube having a thickness of 0.5 mm or less are respectively O. A ring-shaped wire with a diameter of 1 mm or more and an edge that can ensure strength and airtightness is constructed, and the shaft is placed near the outer periphery of the flange that is attached at appropriate positions on both ends of the pipe while maintaining airtightness. An annular O-ring groove with an appropriate angle in the direction is provided, O-rings at the edges of both ends of the rubber thin film tube are fitted, and an O-ring in the axial direction with a clamping ring with an appropriate angled surface Tightened, and to hold the easily airtightness reliably maintain and strength to sufficiently rubber membrane is also a structure of a surge tube (see Patent Document 2).
The balloon buffer tube (BBT) 3) is provided with a side pipe having a flow area larger than the cross-sectional area of the pipe in the middle of the pipe system, branched from the pipe, and silicone rubber at the tip thereof. A flat or concave thin film elastic body made of a material that is extremely elastic and excellent in heat resistance, etc., is hermetically attached to the periphery, and thin film elasticity according to the pressure difference between the internal pressure of the side pipe and the external pressure This is a balloon buffer tube (see Japanese Patent Application No. 2006-216435) that effectively dampens the pulsation of the pressure or flow velocity of the pipeline by greatly changing the volume inside the pipeline system by expanding and contracting the body into a spherical shape.
The variable venturi type exhaust gas flowmeter according to the present invention has an actuator device including a buffer device and a drive shaft seal portion of a movable core and a measuring tube when the exhaust gas temperature reaches a high temperature of approximately 300 ° C. or higher. The outer wall of the road was forcibly cooled using a ventilation device such as an axial fan so that the temperature of each part could be maintained within an appropriate temperature range of approximately 400 ° C. or less.
In addition, the structure of the variable cross-section venturi type exhaust gas flowmeter according to the present invention is necessary in a condensate treatment apparatus provided with condensate flowing in along with exhaust gas from an inlet pipe of a measurement pipe connected to an exhaust introduction pipe. Equipped with a drain-compatible device that quickly evaporates with a heating device including preheating and adds it to the measurement system or adds it to the measurement system, or separates and stores it in the drain tank and excludes it from the measurement system. It is characterized by that.
In addition, the variable venturi exhaust gas flow meter structure of the present invention is provided with four or more wall pressure holes uniformly on the inner periphery of the same axial position of the pipe line for the static pressure of the throat section and the static pressure of the inlet. The pressure is averaged and introduced into the pressure sensor, the pressure introduction line is made as short as possible, and the line filter and line purge three-way solenoid valve are arranged and connected to the absolute pressure sensor and differential pressure sensor. In accordance with the above, the cleanliness of the pressure introduction pipe line is maintained by purging using pressurized air.

  In the present invention, the movable core of the variable cross-sectional area venturi type exhaust gas flowmeter and the shaft that supports and drives the movable core are inclined from the horizontal or arranged vertically, thereby eliminating the lateral force of the shaft due to gravity. As a result, the sliding resistance of the shaft of the movable core has been reduced, enabling smooth driving. In addition, it is possible to reduce the temperature deviation in the exhaust gas flow by tilting the measuring section from the horizontal, or by arranging it vertically or almost vertically, and by making the exhaust gas flow from bottom to top. Accurate temperature measurement is possible at the temperature measurement point, and the length of the measurement pipe line is not a restriction in the vertical arrangement, so that the horizontal length of the entire measurement apparatus can be shortened.

  In the present invention, the effective width of the annular channel is sequentially corrected according to the inclination angle by taking into account the flow along a part of the curved surface from a simple parabolic curved surface to the cross-sectional shape of the movable core forming the throat portion as a venturi tube. By designing and producing a corrected rotating curved surface, the relationship between the effective cross-sectional area of the throat and the position of the movable core can be brought closer to a linear relationship than before, and the control of the movable core has been facilitated.

  In the variable cross-section venturi type exhaust gas flow meter, the measurement temperature range is wide, so the thermal deformation of the measurement part is a problem. In the present invention, the material of the drive shaft of the movable core is a special alloy such as amber with a very small thermal expansion coefficient. Therefore, even if the flow rate measurement including the high temperature condition is performed using the flow rate coefficient based on the flow rate configuration in the vicinity of the normal temperature, it is possible to fall within a small error range with a small correction.

  The exhaust gas temperature is usually 450 ° C. or lower after the outlet of the exhaust pipe, but in some cases may exceed 500 ° C. From the aspect of volume flow rate, 350 ° C. or less is desirable, but in practice, it often exceeds 400 ° C. In particular, some components of the apparatus use silicone rubber, and although it is a structure that does not come into direct contact with high-temperature gas, it is desirable to maintain some members at 300 ° C. or less. For this purpose, in addition to using a heat shield, a means for forcibly cooling the outside including the local area with a plurality of axial fans from the outer wall of the pipe with cooling air of about room temperature was taken. An effective temperature effect was realized by forced cooling when the exhaust gas temperature was 300 ° C. or higher.

  Since the exhaust gas flowmeter of the present invention is often applied to the exhaust gas of a reciprocating engine, it is necessary to cope with the assumption that the flow of exhaust gas has pulsation. As a buffer device for effectively attenuating this pulsation, a surge tube (see Patent Documents 1 and 2) or BBT (see Japanese Patent Application No. 2006-216435) is attached to the measurement pipe entrance of the variable cross-sectional area venturi flow meter. As a result, the pulsation effect on the flow rate measurement can be completely ignored.

An example of an apparatus in which the present invention is applied to the flow measurement of automobile engine exhaust gas will be described with reference to the block diagram of FIG.
The exhaust gas flow 20 from the exhaust pipe 21 of the automobile engine 2 enters the inside of the apparatus 1 through the exhaust introduction pipe 31, and condensed water and the like are separated and introduced into the condensed water treatment apparatus 32. Exhaust gas that does not contain liquid enters the vertical measurement pipe line 10 arranged vertically via the BBT 3, and the flow is throttled to the throat part 5 having the minimum flow path cross-sectional area at the venturi contraction part 4 to increase the flow velocity. Usually, there is a movable core 7 at the center of the throat, and the flow path is annular. The inlet temperature of the venturi pipe is detected by a temperature sensor 41 such as a thermocouple, and the pressure is transferred from the pressure conduit 42 to the absolute pressure sensor 51 and the differential pressure sensor 52 by solenoid valves 46, 48 for switching purge / air and filters 47, 49. It is always connected via.

  The inner peripheral side forming the throat 5 of the Venturi tube is the outer periphery of the movable core 7, but the diameter thereof is made to change smoothly depending on the axial position, and the effective channel cross-sectional area becomes the axial movement distance. In contrast, it is designed to change linearly. Although the core cross-sectional shape is illustrated in FIG. 2, the effective cross-sectional area of the throat portion is slightly larger according to the throat position due to the influence of the flow along the inclined surface when the axial inclination of the core cross-section is larger than 30 ° C. Become. Based on the results of the experiment, a method of correcting the curved surface was attempted. In conclusion, a curved surface corrected as shown by the solid line was obtained from the simple rotating paraboloid surface shown by the dotted line in FIG. By making the curved surface of such a corrected movable core, the relationship between the core movement distance x and the effective throat cross-sectional area can be made substantially linear. The feature of the core shape that is noticeable by the correction is that the length of the core is shorter than the maximum movement distance of the core, and the core reaches the maximum effective throat cross-sectional area at a position slightly beyond the plane of the throat pressure detection point. That is.

  In the variable cross-section venturi type exhaust gas flow meter, it is extremely important to measure the static pressure at the inlet and throat, and in particular, it is necessary to measure a differential pressure of 50 Pa or less. Although it is related to the responsiveness of pressure measurement, it is extremely important to ensure the cleanliness of the pipeline including moisture. FIG. 3 illustrates a pressure measurement system used in the present apparatus. The exhaust gas may contain particulate matter, and may cause water condensation after the operation is stopped, which may obstruct the pressure conduit. The solenoid valves 46 and 48 and the filters 47 and 49 are arranged in the conduit system of the absolute pressure sensor 51 and the differential pressure sensor 52 so that the pressure conduit is purged with pressurized clean air at the start and end of measurement so that the cleanliness can always be maintained. A pressure measurement system was used. The pipe 50 is a line of pressurized air that has been regulated and cleaned.

  The moisture contained in the exhaust gas is considered to be in a vaporized state at a temperature above the dew point, but condensed water is often generated when the tube wall temperature of the flow path is low. Condensed water also flows in the exhaust pipe on the engine side at the time of start-up, so it is necessary to cope with the fact that liquid moisture is introduced into the entrance of this measuring device. FIG. 4 shows a specific configuration example of the condensed water evaporator 32. The liquid water flowing along the lower wall surface of the exhaust gas introduction pipe 31 remains on the evaporation surface 53 of the heater block of the heating evaporator 32. The evaporation surface is heated to about 150 to 200 ° C. by the heater 54 based on the signal from the temperature sensor 55, and normally the liquid water flowing in can be sufficiently vaporized. If necessary, it is discharged to the drain tank 59 via the drain pipe 56 and the electromagnetic valve 57. The outer surface of the heater block is covered with a heat insulating material 58 for heat insulation.

  An embodiment of the present invention will be described with reference to FIGS. Exhaust gas 20 discharged from the engine 2 is introduced into an exhaust introduction pipe 31 arranged substantially horizontally connected to the engine exhaust pipe 21. When there is a liquid component, a condensate treatment device 32 below is provided along the pipe wall. The gas component is introduced into the buffer device 3 (BBT) from the upper pipe line. In the buffer device 3, the pulsation of the exhaust flow is attenuated by the expansion and contraction of the silicone rubber thin film, the exhaust flow is smoothed, and enters the exhaust gas flow meter 1 disposed further upward. As shown in FIG. 4, the condensate treatment device 32 has an evaporation surface 53 having a concave lower upper surface, receives a liquid component, and immediately before the start of measurement by the heater 54, it is 150 to 200 ° C. at the beginning of operation. It is heated to the extent. This temperature control is performed from an appropriate time before the start of measurement based on a temperature sensor signal arranged at the center of the heater block. In order to avoid the accumulation of a large amount of condensed water on the evaporation surface at the time of starting or the like, it can be excluded from the measuring system from the tank 59 with the auto drain device via the drain valve 56 and the electromagnetic valve 57.

  When the exhaust gas temperature exceeds 200 ° C., for example, the axial fans 37 and 38 for cooling the buffer device (BBT) are activated, and the temperature rise of the silicone rubber film can be prevented. An axial fan 39 is disposed on the side surface of the venturi pipe, and the drive shaft 8 of the movable core passes through the pipe. The penetrating portion 13 has a shaft seal portion 14 and a cooling fin 15 is provided outside to ensure airtightness and effectively cool the shaft portion. In particular, the axial fan 36 is configured to strongly cool the actuator 16 and the through portion 13. Further, a heat shield plate 22 is arranged to reduce heat transfer from the high-temperature exhaust gas pipe.

  The measurement pipe line 10 is a vertically arranged venturi pipe that can be varied by the axial movement of the movable core 12 in which the cross-sectional area of the throat portion is arranged at the center. As shown in FIG. 3, the venturi inlet pressure is connected to the common end pipe of the solenoid valve 48 so that the average value of the four measurement holes 42 arranged on the circumference 40 can be drawn out. When energized, the open end is connected to the high pressure end of the differential pressure sensor 51 via the filter 49. At the same time, the absolute pressure at the inlet is measured by being connected to the absolute pressure sensor 52 by a pipe branched from the inlet of the differential pressure sensor 51 via a filter. The venturi throat pressure is arranged at the low pressure end of the differential pressure sensor 51 via the solenoid valve 46 and the filter 47 so that the average value can be drawn by arranging four measurement holes 43 on the circumference of the throat section like the inlet. Connected.

の径の位置にセンサ先端を配置して平均排気ガス温度を測定する。なおベンチュリ管として圧力回復を確認するためにはベンチュリ管１０の出口近くに静圧センサのための圧力測定孔４４を設けて測定することがある。さらに排気ガス試料を抽出するためにはプローブ１７をベンチュリ管の下流近傍に挿入するのが普通である。 Venturi flow calculation temperature is based on the inlet temperature, so the pipe diameter is almost the same in the pipe close to the inlet pressure measurement.

Measure the average exhaust gas temperature by placing the sensor tip at the position of the diameter of. In order to confirm pressure recovery as a venturi tube, measurement may be performed by providing a pressure measuring hole 44 for a static pressure sensor near the outlet of the venturi tube 10. Further, in order to extract the exhaust gas sample, it is usual to insert the probe 17 in the vicinity of the downstream of the venturi tube.

  The downstream side of the measurement pipe 10 is a vent pipe 18, and the exhaust gas flow is reversed in the direction and discharged from the discharge pipe 19 to the outside of the measuring device from an appropriate position. In order to reduce pressure loss, it is desirable to connect the downstream side to a pipe line with low resistance.

Industrial potential

  The exhaust gas flow meter of the present invention has a very wide measurement range as a venturi system and can be applied structurally to exhaust gas temperatures of 400 ° C or higher, especially from idling of reciprocating engines, which have a large pulsation effect, to high speed and high load operation, Since it can be applied to engines of various sizes including gasoline engines to diesel engines, the potential for use in the automobile industry is enormous. In other industries, there are many cases where flow measurement is required, and it can be widely used for gas flow measurement over a wide range, especially in flow paths with fluctuations.

The block diagram which shows arrangement | positioning of the flow path and related apparatus in embodiment of this invention. Explanatory drawing which shows the cross-sectional shape of the movable core of this invention. The system diagram of the measurement pressure conduit system in this invention. The structural example of the condensed water generator with which the entrance of the measuring apparatus of this invention is mounted | worn.

Explanation of symbols

1 Venturi type flow meter with variable cross section 2 Engine 3 Buffer device (BBT)
4 Venturi contraction section 5 Venturi / throat section 6 Venturi / expansion section 7 Movable core 8 Coar drive shaft 9 Coar position detection sensor 10 Measurement pipe 11 Coar drive shaft support bearing 12 Bearing support column 13 Coar drive shaft through section 14 Shaft seal 15 Axial seal cooling fan 16 Movable core / actuator 17 Exhaust gas sample extraction probe 18 Downstream vent pipe of measurement pipe 19 Exhaust pipe 20 Engine exhaust gas flow 21 Engine exhaust pipe 22 Heat shield plate 31 Exhaust gas introduction pipe 32 Condensed water treatment Device 33 BBT rubber film protective mesh 34 BBT silicone rubber thin film 40 Venturi inlet pressure detector 41 Venturi inlet temperature sensor 42 Venturi inlet pressure measurement hole (4 locations)
43 Venturi / throat pressure measurement holes (4 locations)
44 Venturi / enlarged part pressure recovery static pressure measurement hole 45 Average pressure conduit system 46 Three-way solenoid valve 47 Filter 48 Three-way solenoid valve 49 Filter 50 Purge airline 51 Differential pressure sensor 52 Absolute pressure sensor 53 Condensate evaporation surface 54 Heating Heater 55 Temperature sensor 56 Condensate discharge conduit 57 Solenoid valve 59 Condensate storage drain tank

Claims (5)

Smoothly squeezes the flow of the pipe, and the cross-sectional area changes smoothly to the center of the throat parallel to the axis of the venturi measuring pipe with the pipe that gradually and smoothly expands through the throat where the cross-sectional area of the flow path is minimized. A venturi pipe having a throat section flow-path cross-sectional area that varies depending on the position of the movable core, the static pressure, the absolute pressure and the temperature at the inlet section of the venturi pipe, and the static section of the throat section. In a variable cross-sectional area venturi type flow meter that measures the flow rate by measuring the pressure, measuring the fluid density , and further determining the flow rate by determining the throat flow velocity and throat effective cross-sectional area from the axial position of the core, A variable cross-section venturi that is configured in a vertical or near-vertical direction so that it can support the shaft that drives the movable core by reducing the lateral force other than the axial force. Structure of the gas-gas flow meter. The variable cross-sectional area venturi type exhaust gas flowmeter according to claim 1, wherein a surge tube or a balloon buffer tube is attached as a buffer device having a damping volume with respect to the flow pulsation at the inlet of the measurement pipe, thereby suppressing the pulsation. A variable cross-section venturi-type exhaust gas flow meter structure that is damped to enable flow measurement with a venturi tube even in pulsating flow paths. 3. The variable venturi-type exhaust gas flow meter according to claim 2, wherein when the exhaust gas temperature reaches a high temperature of approximately 300 ° C. or higher, the actuator device including the buffer device and the drive shaft seal portion of the movable core, and the outer wall of the measurement pipe The structure of a variable cross-sectional area venturi type exhaust gas flowmeter in which the temperature of each part can be maintained in an appropriate temperature range of approximately 400 ° C. or less by forcibly cooling the airflow using a ventilation device such as an axial fan. In the variable venturi-type exhaust gas flowmeter according to any one of claims 1 to 3, in the condensed water treatment apparatus provided with condensate water or the like that flows together with the exhaust gas from the inlet pipe of the measurement pipe connected to the exhaust pipe. Equipped with a condensate treatment device having a drain-compatible device such as evaporating quickly by a device and making it into a gas state and adding it to the measurement system, or separating and storing it in a drain tank and removing it outside the measurement system A variable cross-section venturi type exhaust gas flowmeter structure characterized by that. 5. The variable venturi-type exhaust gas flow meter according to claim 1, wherein the wall pressure at four or more locations is uniformly distributed on the inner periphery of the same axial position of the pipe line for static pressure at the throat portion and static pressure at the inlet. Holes are averaged to introduce pressure into the pressure sensor, and the pressure introduction line is made as short as possible, and a line filter and a line purge three-way solenoid valve are arranged to connect to the absolute pressure sensor and differential pressure sensor. The structure of the variable cross-section venturi type exhaust gas flow meter that maintains the cleanliness of the pressure introduction pipe line by purging using pressurized air as necessary.

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