JP2018197684A - Flow rate measuring device - Google Patents

Abstract

To provide a flow rate measuring device that has high responsiveness, can measure a flow rate even pulsation or back flow exists, and can accurately measure a low flow rate.SOLUTION: A flow rate measuring device of the present embodiment includes: an inflow port of exhaust gas; a mesh filter that communicates with the inflow port, has an outlet of the exhaust gas at a position higher than an inlet thereof, and removes particles and moisture from the exhaust gas; a layer flow element that communicates with the mesh filter, has an inlet of the exhaust gas at a position higher than an outlet thereof, and causes the exhaust gas to flow in a layer flow state; a differential pressure gauge for measuring a differential pressure between an air pressure of the exhaust gas near the inlet of the layer flow element and an air pressure of the exhaust gas near the outlet of the layer flow element; and an outflow port for discharging the exhaust gas having passed through the layer flow element.SELECTED DRAWING: Figure 1

Description

  Embodiments according to the present invention relate to a flow measurement device.

  The flow rate measurement of exhaust gas from automobiles and the like has been performed in a driving test assuming actual road driving using a chassis dynamometer or an engine dynamometer in a test room. However, in actual road driving, driving conditions differ depending on driving routes, traffic conditions such as traffic jams, weather, and the like. For this reason, the flow rate measurement result in the test room is different from the actual flow rate measurement result on the road.

  Under such circumstances, the standardization of the driving test mode is being promoted worldwide. International Harmonized Light Vehicle Test Procedure (WLTP), transient test cycle (WHTC (Worldwide Harmonized Transient Cycle)), and in-vehicle use, which are tests close to actual road driving The introduction of a Real Driving Emissions (RDE) test using a portable emission measurement system (PEMS) is being considered.

  In particular, regarding the RDE test using PEMS, it is important to accurately measure the exhaust gas flow rate in actual driving so as to meet strict environmental standards. In addition, since the RDE test using PEMS is performed while actually running with PEMS on-board, it is necessary to consider the measurement environment such as weather conditions.

  In the RDE test using PEMS, the discharge amount of the specific component is calculated from the product of the concentration of the specific component of the exhaust gas and the total flow rate of the exhaust gas. In this case, it is necessary to measure the flow rate of the exhaust gas with high accuracy. In addition, it is necessary to measure the exhaust gas flow rate with high accuracy in order to obtain the dilution rate of particulate matter (PM).

Shigeru Yanagihara, laminar flow meter, internal combustion engine, Vol.7, No.77 1968.10.p 11 The Japan Society of Mechanical Engineers, technical data, fluid measurement method, p214, 4.9.2 laminar flow meter, 1985, August 25 Dynamic measurement of EGR (1st report, flow measurement) JSME Dynamics & Design Conference 2008, No.557 (2008)

JP 2007-024730 A JP 2012-127864 A

  Exhaust gas flow rate measurement in actual driving is highly accurate considering the effects of pulsating flow and reverse flow at low revolutions such as idling, sudden flow rate changes and temperature changes during acceleration, and vibration and condensed water. It is required to measure. Moreover, in order to be able to be mounted on a vehicle, it is necessary to consider the size of the PEMS itself.

  For example, a flow meter such as a Coriolis type or a Karman vortex flow meter is difficult to accurately measure the flow rate in vibration resistance, pulsation flow, or reverse flow. On the other hand, the Pitot tube type flow meter can measure the flow rate accurately even if there is a backflow or condensed water, and the structure is simple and small. For this reason, the Pitot tube type flow meter is frequently used as PEMS. However, the topy tube type flow meter has a problem that the relationship between the pressure difference of the exhaust gas and the flow rate is not linear, and in particular, the flow rate cannot be measured accurately at a low flow rate.

  The present invention has been made in view of the above problems, and is to provide a flow rate measuring device that has high responsiveness, can be measured even when there is pulsation or backflow, and can accurately measure a low flow rate. .

ΔＰは層流素子の圧力損失、Ｐは排出ガスの圧力、Ｔは排出ガスの温度、μは排出ガスの粘度、μ_２０は温度２０度における空気の粘度、Ｑは排出ガスの流量である。 The flow rate measuring apparatus according to the present embodiment includes an exhaust gas inlet, a mesh filter that communicates with the inlet and has a higher outlet than the inlet of the exhaust gas, and removes particles and moisture from the exhaust gas. The laminar flow element in which the exhaust gas inlet is positioned higher than the outlet and flowing the exhaust gas in a laminar flow state, the exhaust gas pressure near the laminar flow element inlet and the exhaust near the laminar flow element outlet A differential pressure gauge that measures a differential pressure from the gas pressure and an outlet that discharges exhaust gas that has passed through the laminar flow element are provided.
Both the mesh filter and the laminar flow element may be arranged vertically so that the exhaust gas flows in a substantially vertical direction, and may be configured in an inverted U shape together with the piping between the mesh filter and the laminar flow element.
The flow rate measuring device may further include a drain hole provided at a position lower than the inlet and the mesh filter for discharging moisture out of the flow rate measuring device.
The ratio of the sum of the opening cross-sectional areas of the thin tubes constituting the laminar flow element to the entire cross-sectional area of the laminar flow element may be 0.9 or more.
The flow rate measuring device includes four or more first gas extraction holes provided at substantially equal intervals over the circumference on the inlet side of the laminar flow element, and substantially equal intervals over the circumference on the outlet side of the laminar flow element. Four or more second gas extraction holes provided in the plurality, a plurality of first joints connecting two first gas extraction holes adjacent in the circumferential direction of the laminar flow element, and a circumferential direction of the laminar flow element A plurality of second joints connecting two adjacent second gas extraction holes, at least one third joint connecting two first joints adjacent in the circumferential direction of the laminar flow element, and a laminar flow element And at least one fourth joint that connects the two second joints adjacent in the circumferential direction, and the differential pressure gauge is configured to discharge exhaust gas in the vicinity of the inlet of the laminar flow element via the first and third joints. The pressure of the exhaust gas is measured near the outlet of the laminar flow element through the second and fourth joints. The may be measured.
The flow rate measuring device includes a first conduit from the vicinity of the inlet of the laminar flow element to the differential pressure gauge via the first and third joints, and a first conduit from the vicinity of the outlet of the laminar flow element to the differential pressure gauge via the first and third joints. You may further provide the purge gas supply part which supplies purge gas to 2 conduit | pipe.
The flow rate measuring device may further include a thermometer that measures a first temperature of the exhaust gas near the inlet of the laminar flow element and a second temperature of the exhaust gas near the outlet of the laminar flow element.
The flow rate measuring device further includes a storage unit that preliminarily stores coefficients a, b, and c derived from exhaust gases having a plurality of temperatures, and a calculation unit that calculates the flow rate Q using the coefficients a, b, and c. May be. still,

ΔP is the pressure loss of the laminar flow element, P is the pressure of the exhaust gas, T is the temperature of the exhaust gas, μ is the viscosity of the exhaust gas, μ ₂₀ is the viscosity of air at a temperature of 20 degrees, and Q is the flow rate of the exhaust gas.

The figure which shows the structural example of the laminar type flow meter 1 by this embodiment. Schematic which shows the structural example of the laminar flow element 30, the pressure pipe 60, the conduit | pipe 70, and the differential pressure gauge 80. FIG. The schematic diagram which looked at the laminar flow element 30, the pressure pipe 60, the conduit | pipe 70, and the differential pressure gauge 80 from the substantially perpendicular | vertical upper direction. The figure which shows the structural example of the laminar flow element. Schematic which shows the structural example of a flow volume calibration apparatus. Graph showing the relationship between the flow rate coefficient K ₂₀ between the measured values X. The flowchart which shows the flow volume calibration method of the laminar type flow meter 1 using the flow volume calibration apparatus. The flowchart which shows the method of measuring a flow volume using number a, b, c. Sectional drawing which shows the structural example of the drain hole 110. FIG.

  Embodiments according to the present invention will be described below with reference to the drawings. This embodiment does not limit the present invention.

  FIG. 1 is a diagram illustrating a configuration example of a laminar flow meter 1 according to the present embodiment. A laminar flow meter 1 includes an inlet 10, a mesh filter 20, a laminar flow element 30, a pressure pipe 40, a pressure gauge 50, a pressure pipe 60, a conduit 70, a differential pressure gauge 80, and a temperature sensor 90. A thermometer 100, a drain hole 110, an outlet 120, pipes 141 to 146, and a calculation unit 130.

  The laminar flow meter 1 is a laminar flow meter provided with a laminar flow element 30, and is a laminar flow exhaust gas flow meter (ExLFM (Exhaust Gas Lamina Flowmeter)). In the present embodiment, the laminar flow meter 1 is calibrated and then applied to PEMS to perform an RDE test.

  The inflow port 10 is an opening of a pipe 141 that takes in the exhaust gas E into the laminar flow meter 1. For example, the inflow port 10 is attached to a muffler of an automobile and takes in the exhaust gas E from the engine of the automobile. The exhaust gas E from the engine is accompanied by a pulsating flow and contains combustion products such as combustion gas and water vapor.

  The exhaust gas E passes through the pipe 141 and moves vertically upward and reaches the mesh filter 20. The mesh filter 20 is provided in the pipe 142 and communicates with the inflow port 10. In the mesh filter 20, the outlet 22 is higher than the inlet 21 of the exhaust gas E. For example, the mesh filter 20 has a cylindrical bowl-like shape and extends in a substantially vertical direction. The mesh filter 20 is vertically arranged in the vertical upward direction of the opening. The outer edge of the opening of the mesh filter 20 is attached to the upstream end of the pipe 143, and all the exhaust gas E moves to the pipe 143 through the mesh filter 20. The mesh filter 20 is made of, for example, a metal having excellent corrosion resistance and heat resistance, such as 316UL. The size of the mesh filter 20 is not particularly limited, but is, for example, 0.6 mm or less. Exhaust gas E that has passed through the mesh filter 20 from the inlet 21 moves vertically upward and flows from the outlet 22 to the pipe 143. As described above, when the exhaust gas E passes through the mesh filter 20, particles contained in the exhaust gas E are removed from the exhaust gas E by the mesh filter 20. The diameter of the pipe 142 is larger than the diameter of the pipe 141. Therefore, when the exhaust gas E reaches the pipe 142 from the pipe 141, the pressure of the exhaust gas decreases, and the moisture contained in the exhaust gas is likely to condense. When the exhaust gas E in such a state passes through the mesh filter 20, the moisture contained in the exhaust gas E is condensed. Condensed water once adheres to the mesh filter 20, but the mesh filter 20 is vertically arranged, so it drops vertically or along the inner walls of the pipes 141, 142, and drains below the mesh filter 20. It collects in the storage part 115 above the hole 110.

  The drain hole (capillary) 110 is provided at a position lower than the inlet 10 and the mesh filter 20, and discharges the condensed water accumulated in the reservoir 115 together with a part of the exhaust gas E to the outside of the laminar flow meter 1. The diameter of the drain hole 110 is, for example, about 1 mm. A part of the exhaust gas discharged from the drain hole 110 is set to a level that does not affect the flow rate of the exhaust gas (for example, less than 0.1% of the flow rate of the exhaust gas). At this time, particles contained in the condensed water can also be discharged from the drain hole 110 together with the condensed water and the exhaust gas.

  FIGS. 9A to 9C are cross-sectional views illustrating a configuration example of the drain hole 110. The drain hole 110 may discharge condensed water by gravity and / or a pressure difference between the inside and the outside of the pipe 141. As shown in FIG. 9A, the drain hole 110 may be a substantially straight tube.

  As shown in FIG. 9B, the drain hole 110 may be an inverted J-shaped tube. In this case, the drain hole 110 discharges condensed water when the pressure difference between the inside and the outside of the pipe 141 is larger than a predetermined value. The predetermined value of the pressure difference is determined by the height Hb from the end EDGb to the upper end. Thereby, when the exhaust gas E is discharged from the drain hole 110, it has a certain resistance. This can suppress the exhaust gas E from leaking to the outside unnecessarily.

  Furthermore, as shown in FIG. 9C, the drain hole 110 may be a J-shaped tube. Also in this case, the drain hole 110 discharges condensed water when the pressure difference between the inside and the outside of the pipe 141 is larger than a predetermined value. The predetermined value of the pressure difference is determined by the height Hc from the end EDGc to the lower end. Accordingly, like the drain hole 110 in FIG. 9B, the exhaust gas E has a certain resistance when discharged from the drain hole 110. This can suppress the exhaust gas E from leaking to the outside unnecessarily. Thus, the drain hole 110 may be a substantially straight tube, or may be a tube having a trap bent in an inverted J shape or a J shape. When it is necessary to reduce the leakage of the exhaust gas E, the drain hole 110 shown in FIG. 9B or 9C may be used.

  The exhaust gas E passes through the mesh filter 20 and the pipe 143 and moves to the pipe 144. The pipe 143 has an inverted U shape, and changes the flow direction of the exhaust gas E from the upper direction to the lower direction. The piping 144 is provided with a pressure pipe 40, and the pressure pipe 40 is provided with a pressure gauge 50. The pressure gauge 50 measures the pressure P of the exhaust gas E through the pressure pipe 40.

  The exhaust gas E moves vertically down the pipe 144 and reaches the laminar flow element 30 through the pipe 145. In addition to the laminar flow element 30, the pipe 145 is provided with a pressure pipe 60 and a temperature sensor 90.

  The laminar flow element 30 is composed of a large number of thin tubes 33 (see FIG. 4) so that the inlet 31 of the exhaust gas E is higher than the outlet 32 and the exhaust gas E flows in a laminar flow state. The laminar flow element 30 is arranged vertically and is configured to flow the exhaust gas E substantially vertically downward. Even when condensed water adheres to the laminar flow element 30, the condensed water is discharged downstream of the exhaust gas E, that is, vertically downward by flowing the exhaust gas E downward. The laminar flow element 30 is forcibly discharged together with the flow of the gas E. The mesh filter 20 and the laminar flow element 30 are configured in a substantially inverted U shape together with the pipes 142 to 145 between the mesh filter 20 and the laminar flow element 30.

  A plurality of pressure tubes 60 are provided near the inlet and the outlet of the laminar flow element 30. A differential pressure gauge 80 is connected to the pressure pipe 60. The differential pressure gauge 80 measures a differential pressure ΔP between the pressure of the exhaust gas E in the vicinity of the inlet of the laminar flow element 30 and the pressure of the exhaust gas E in the vicinity of the outlet of the laminar flow element 30 through the plurality of pressure tubes 60. The conduit 70 is provided between the pressure pipe 60 and the differential pressure gauge 80. The configurations of the pressure pipe 60, the differential pressure gauge 80, and the conduit 70 will be described later.

  A plurality of temperature sensors 90 are provided near the inlet and the outlet of the laminar flow element 30. The temperature sensor 90 in the vicinity (upper side) of the inlet of the laminar flow element 30 detects the first temperature of the exhaust gas E in the vicinity of the inlet of the laminar flow element 30. A temperature sensor 90 in the vicinity (lower side) of the outlet of the laminar flow element 30 detects the second temperature of the exhaust gas E in the vicinity of the outlet of the laminar flow element 30. A thermometer 100 is connected to the temperature sensor 90, and the thermometer 100 measures the first and second temperatures of the exhaust gas E detected by the temperature sensor 90.

  The reason why the temperature of the exhaust gas E is measured both upstream and downstream of the laminar flow element 30 is as follows. The temperature of the exhaust gas E also decreases due to heat dissipation when passing through the laminar flow element 30, and the temperature is different between upstream and downstream of the laminar flow element 30. For this reason, in either the upstream or downstream measurement, the temperature of the exhaust gas E passing through the laminar flow element 30 cannot be obtained, and an error occurs. The higher the temperature of the exhaust gas E, the greater the amount of heat release. Therefore, the temperature difference between the upstream and downstream cannot be ignored in a fluid that is at a high temperature such as exhaust gas. In order to reduce the temperature difference in this way, the temperature sensor 90 measures the vicinity of the upstream and downstream of the laminar flow element 30. Furthermore, the temperature of the exhaust gas E passing through the laminar flow element 30 may be set using an average method such as arithmetic average (arithmetic average), weighted average, harmonic average, etc. by using many temperature measurements. Thereby, the temperature of the exhaust gas E passing through the laminar flow element 30 can be accurately measured.

  The exhaust gas E is discharged from the outlet 120 of the pipe 146 when the pipe 145 moves vertically downward.

  The pipes 141 to 146 communicate with each other in a substantially sealed state from the inlet 10 to the outlet 120. The pipes 141 to 146 are made of a metal having excellent corrosion resistance and heat resistance, such as 316UL (stainless steel), for example.

  The calculation unit 130 calculates the flow rate Q of the exhaust gas E using the pressure of the exhaust gas E measured by the pressure gauge 50, the differential pressure ΔP measured by the differential pressure gauge 80, and the temperature measured by the thermometer 100. Calculate. At this time, the flow rate Q is calculated using coefficients a, b, and c stored in advance in the storage unit 135. The calculated result data may be displayed on an attached monitor (not shown) or may be output to the outside. Derivation of the coefficients a, b, and c and calculation of the flow rate Q will be described later.

  FIG. 2 is a schematic diagram illustrating a configuration example of the laminar flow element 30, the pressure pipe 60, the conduit 70, and the differential pressure gauge 80. A plurality of (for example, four) pressure tubes 60 are provided on each of the upstream side and the downstream side of the laminar flow element 30. The pressure pipe 60 provided on the upstream side of the laminar flow element 30 is 60_1, and the pressure pipe 60 provided on the downstream side of the laminar flow element 30 is 60_2. Further, the conduit 70 provided on the upstream side of the laminar flow element 30 is 70_1, and the conduit 70 provided on the downstream side of the laminar flow element 30 is 70_2. In this case, the pressure pipe 60_1 is connected to the conduit 70_1, and is connected to the differential pressure gauge 80 via the conduit 70_1. The pressure pipe 60_2 is connected to the conduit 70_2, and is connected to the differential pressure gauge 80 via the conduit 70_2.

  A purge gas supply unit PGS is connected to the conduits 70_1 and 70_2. The purge gas supply unit PGS includes a pressure adjustment unit 140 and flow rate adjustment units 150 and 160. The pressure adjusting unit 140 adjusts the overall pressure of the purge gas PG supplied from the outside. The flow rate adjustment units 150 and 160 adjust the purge gas PG having a predetermined pressure supplied from the pressure adjustment unit 140 to flow through the conduits 70_1 and 70_2 at a predetermined flow rate. At this time, the flow rate adjusting units 150 and 160 cause the purge gas PG to flow through the conduits 70_1 and 70_2 at substantially the same flow rate so as not to hinder measurement of the differential pressure. The purge gas suppresses the condensate contained in the exhaust gas E from flowing backward into the pressure pipes 60_1 and 60_2 and the conduits 70_1 and 70_2. This is because when the condensed water flows backward, the condensed water blocks the pressure pipes 60_1 and 60_2 or the conduits 70_1 and 70_2, and measurement is impossible. At the same time, the purge gas protects the pressure pipes 60_1 and 60_2, the conduits 70_1 and 70_2, and the differential pressure gauge 80 from corrosion by the exhaust gas. For this reason, the purge gas is continuously supplied from the purge gas supply unit PGS into the pipe 145 during the flow rate measurement. Thereby, it can suppress that measurement of differential pressure is interrupted. Furthermore, since the purge gas PG cools the pressure pipes 60_1 and 60_2 and the conduits 70_1 and 70_2, the heat resistance restriction of the materials of the pressure pipes 60_1 and 60_2, the conduits 70_1 and 70_2, and the differential pressure gauge 80 can be relaxed. The purge gas PG may be, for example, an inert gas such as dry air or nitrogen. The purge gas PG flows from the pressure pipes 60_1 and 60_2 to the pipe 145. However, the flow rate of the purge gas PG is very small (for example, less than 0.1%) compared to the flow rate of the exhaust gas E. Therefore, the flow rate Q of the exhaust gas E is hardly affected.

  FIG. 3 is a schematic view of the laminar flow element 30, the pressure pipe 60, the conduit 70, and the differential pressure gauge 80 as viewed from substantially vertically above. Four pressure pipes 60 </ b> _ <b> 1 serving as first gas extraction holes are arranged on the upstream side of the laminar flow element 30 at approximately equal intervals in four directions over the circumference of the pipe 145. Further, although hidden under the pressure pipe 60_1 in FIG. 3, the four pressure pipes 60_2 as the second gas extraction holes are substantially arranged in four directions over the circumference of the pipe 145 on the downstream side of the laminar flow element 30. It is arranged at equal intervals.

  For convenience, the four pressure pipes 60_1 provided on the upstream side of the laminar flow element 30 are denoted by 60_1a, 60_1b, 60_1c, and 60_1d. For convenience, the conduits 70_1 connected to the pressure pipes 60_1a, 60_1b, 60_1c, and 60_1d are referred to as 70_1a, 70_1b, 70_1c, and 70_1d, respectively.

For convenience, four pressure pipes 60_2 provided on the downstream side of the laminar flow element 30 are denoted by 60_2a, 60_2b, 60_2c, and 60_2d. For convenience, the conduits 70_2 connected to the pressure pipes 60_2a, 60_2b, 60_2c, and 60_2d are referred to as 70_2a, 70_2b, 70_2c, and 70_2d, respectively.
On the upstream side of the laminar flow element 30, the two conduits 70_1a and 70_1b adjacent to each other in the circumferential direction of the laminar flow element 30 are connected by a T-shaped joint (first joint) TC1a. That is, the two pressure pipes 60_1a and 60_1b adjacent to each other in the circumferential direction of the laminar flow element 30 are connected by the T-shaped joint TC1a via the conduits 70_1a and 70_1b. The other two conduits 70_1c and 70_1d adjacent to each other in the circumferential direction of the laminar flow element 30 are connected by a T-type joint (first joint) TC1b. That is, the other two pressure pipes 60_1c and 60_1d adjacent to each other in the circumferential direction of the laminar flow element 30 are connected by the T-shaped joint TC1b via the conduits 70_1c and 70_1d.

  Furthermore, the two conduits 70_1e and 70_1f adjacent in the circumferential direction of the laminar flow element 30 are connected by a T-shaped joint (third joint) TC1c. That is, two T-type joints TC1a and TC1b adjacent to each other in the circumferential direction of the laminar flow element 30 are connected by the T-type joint TC1c via the conduits 70_1e and 70_1f. The T-shaped joint TC1c is connected to the differential pressure gauge 80 via a conduit 70_1g.

  The configuration in which the conduits 70_1a to 70_1f are connected by the three T-shaped joints TC1a to TC1c and combined into one conduit 70_1g is called “triple T”. By adopting the triple T, the differential pressure gauge 80 can detect the average value of the atmospheric pressure obtained through the four pressure tubes 60_1a to 60_1d.

  The same applies to the downstream side of the laminar flow element 30. Two conduits 70_2a and 70_2b adjacent in the circumferential direction of the laminar flow element 30 are connected by a T-shaped joint (second joint) TC2a. That is, the two pressure pipes 60_2a and 60_2b adjacent to each other in the circumferential direction of the laminar flow element 30 are connected by the T-shaped joint TC2a via the conduits 70_2a and 70_2b. The other two conduits 70_2c and 70_2d adjacent to each other in the circumferential direction of the laminar flow element 30 are connected by a T-shaped joint (second joint) TC2b. That is, the other two pressure pipes 60_2c and 60_2d adjacent to each other in the circumferential direction of the laminar flow element 30 are connected by the T-shaped joint TC2b via the conduits 70_2c and 70_2d.

  Furthermore, the two conduits 70_2e and 70_2f adjacent in the circumferential direction of the laminar flow element 30 are connected by a T-shaped joint (fourth joint) TC2c. That is, two T-type joints TC2a and TC2b adjacent to each other in the circumferential direction of the laminar flow element 30 are connected by the T-type joint TC2c via the conduits 70_2e and 70_2f. The T-shaped joint TC2c is connected to the differential pressure gauge 80 via a conduit 70_2g.

  As described above, the “triple T” configuration in which the conduits 70_2a to 70_2f are connected by the three T-shaped joints TC2a to TC2c and combined into one conduit 70_2g also on the downstream side. Thereby, the differential pressure gauge 80 can detect the average value of the atmospheric | air pressure obtained through the four pressure pipes 60_2a-60_2d.

  With such a configuration, the differential pressure gauge 80 has an average atmospheric pressure in the four pressure pipes 60_1a to 60_1d arranged evenly on the circumference of the laminar flow element 30 on the upstream side of the laminar flow element 30, and the laminar flow element 30. A differential pressure ΔP from the average atmospheric pressure is measured in the four pressure pipes 60_2a to 60_2d that are equally arranged on the circumference of the laminar flow element 30 on the downstream side. That is, the differential pressure gauge 80 measures the average pressure of the exhaust gas E in the vicinity of the inlet of the laminar flow element 30 via the T-type joints TC1a, TC1b and TC1c, and the laminar flow element via the T-type joints TC2a, TC2b and TC2c. The average pressure of the exhaust gas E in the vicinity of 30 outlets can be measured, and the differential pressure between them can be calculated. Alternatively, the differential pressure gauge 80 is a pressure receiving unit (not shown) that directly takes the differential pressure between the average pressure of the exhaust gas E near the inlet of the laminar flow element 30 and the average pressure of the exhaust gas E near the outlet of the laminar flow element 30. It may be detected.

  The purge gas supply unit PGS includes the first conduit 70_1 from the vicinity of the inlet of the laminar flow element 30 to the differential pressure gauge 80 via the T-type joints TC1a, TC1b, and TC1c, and the T-type joint TC2a from the vicinity of the outlet of the laminar flow element 30. , Purge gas is supplied to the second conduit 70_2 to the differential pressure gauge 80 through TC2b and TC2c. At this time, the purge gas supply unit PGS may supply the purge gas to any of the first conduits 70_1a to 70_1g, and may supply the purge gas to any of the second conduits 70_2a to 70_2g.

  4A and 4B are diagrams illustrating a configuration example of the laminar flow element 30. FIG. 4A is a diagram showing a configuration of the thin tube 33, and FIG. 4B is an enlarged view of a frame C in FIG. 4A and 4B show a cross section of the laminar flow element 30 perpendicular to the direction in which the exhaust gas E flows.

  The laminar flow element 30 includes an elongated metal plate 34 that is elongated, and a metal plate 35 that is provided on the metal plate 34 and is bent in a zigzag shape or a wave shape. The thin tube 33 is configured by a substantially trapezoidal gap between the metal plate 34 and the metal plate 35. By winding the metal plate 34 having the metal plate 35 around the center O of the laminar flow element 30 shown in FIG. 3, the laminar flow element 30 having a large number of thin tubes 33 as shown in FIG. It is formed. In addition, the cross-sectional shape of the thin tube 33 is not limited to a trapezoid, and may be a circle or another polygon.

  Further, the ratio of the sum of the opening cross-sectional areas of the thin tubes 33 to the entire cross-sectional area of the laminar flow element 30 is set to 0.9 or more. As a result, the pressure loss (ΔP) can be reduced, and the adhesion of dirt can also be reduced.

  Furthermore, a heater (not shown) may be provided in the laminar flow element 30 in order to remove condensed water and contamination of the laminar flow element 30. In this case, since the temperature of the exhaust gas E also changes, it is necessary to perform temperature compensation in the derivation of coefficients a, b, and c described later and the calculation of the flow rate Q.

  Next, the derivation of the coefficients a, b, and c and the calculation of the flow rate Q will be described. In the laminar flow meter, the number of lay nozzles of the plurality of thin tubes 33 in the laminar flow element 30 as shown in FIGS. 4 (A) and 4 (B) is lower than the critical number of lay nozzles. For this reason, the narrow tube 33 makes the exhaust gas E passing through the inside thereof into a laminar flow. When the exhaust gas E is a laminar flow, the pressure drop due to the viscous resistance of the exhaust gas E in the narrow tube 33 is proportional to the fluid flow velocity (flow rate) (Hagen-Poiseuille's law).

The principle of a laminar flow meter such as a laminar flow meter is to measure a pressure loss (differential pressure) ΔP of the laminar flow element 30 and convert the differential pressure ΔP to a flow rate Q. Differential pressure [Delta] P is to pressure loss when the law of Hagen-Poiseuille is applied to laminar flow element 30 (pressure loss of the laminar flow element 30) and [Delta] P _1, of the laminar flow element 30 the inlet end and the approach section in the vicinity thereof when the pressure loss was [Delta] P ₂ in, the formula 1.

式２において、二項定理を用いて差圧ΔＰの三次項まで流量Ｑについて解くと、式３で表される。

気体の状態方程式より、Ｐを排出ガスＥの圧力、Ｔを排出ガスＥの温度、Ｒを状態定数とすると、密度ρは式４のように表される。

また、

とすると、流量Ｑは式５のように表される。

ここで、μ は排出ガスＥの実際の粘度であり、μ₂₀は標準状態（２０℃の空気）の粘度であるとすると、流量Ｑは式６のように表される。

粘度比率μ₂₀/μは、空気の場合サザランド（Sutherland）の式から式７のように表される。

さらに、

とすると、流量Ｑは、式１１のように流量係数Ｋ_２０、粘度比率μ₂₀/μおよび差圧ΔＰで表される。

式９のＸは、層流素子３０の差圧ΔＰ、層流素子３０の近傍の圧力Ｐ、層流素子３０の温度Ｔから得られる計測値である。圧力Ｐは、層流素子３０の上流または下流のいずれの圧力でもよい。μ は、温度Ｔの関数である。流量係数Ｋ_２０は、測定値Ｘの関数であり、複数の温度の排出ガスにおける測定値Ｘを、図５に示す流量校正装置２を用いて校正し、係数ａ、ｂ、ｃを導出する。 Further, the differential pressure ΔP is expressed by Equation 2 where Q is the flow rate of the exhaust gas E, d is the diameter of the narrow tube, L is the length of the narrow tube, ρ is the density of the exhaust gas E, μ is the viscosity of the exhaust gas E, ζ is the loss factor. expressed.

In Equation 2, when the flow rate Q is solved up to the cubic term of the differential pressure ΔP using the binomial theorem, it is expressed by Equation 3.

From the gas equation of state, if P is the pressure of the exhaust gas E, T is the temperature of the exhaust gas E, and R is the state constant, the density ρ is expressed as shown in Equation 4.

Also,

Then, the flow rate Q is expressed as shown in Equation 5.

Here, μ is the actual viscosity of the exhaust gas E, and μ ₂₀ is the viscosity in the standard state (20 ° C. air), the flow rate Q is expressed by Equation 6.

In the case of air, the viscosity ratio μ ₂₀ / μ is expressed as shown in Equation 7 from Sutherland's equation.

further,

Then, the flow rate Q is expressed by a flow coefficient K ₂₀ , a viscosity ratio μ ₂₀ / μ, and a differential pressure ΔP as shown in Equation 11.

X in Equation 9 is a measured value obtained from the differential pressure ΔP of the laminar flow element 30, the pressure P near the laminar flow element 30, and the temperature T of the laminar flow element 30. The pressure P may be any pressure upstream or downstream of the laminar flow element 30. μ is a function of temperature T. Flow rate coefficient K ₂₀ is a function of the measured values X, the measured values X in the exhaust gas of a plurality of temperature, calibrated using the flow calibration device 2 shown in FIG. 5, to derive coefficients a, b, c.

  FIG. 5 is a schematic diagram illustrating a configuration example of the flow rate calibration apparatus. The flow rate calibration device 2 includes a blower 210, a reference flow meter 220, and a heater 230. A laminar flow meter 1 to be calibrated is attached to the flow rate calibration device 2. The flow rate of the exhaust gas is adjusted by the blower 210, and the flow rate is measured by the reference flow meter 220. The heater 230 adjusts the exhaust gas E to a predetermined temperature, and the laminar flow meter 1 measures the flow rate of the exhaust gas E. The flow rate calibration device 2 measures the flow rate of the exhaust gas E with the laminar flow meter 1 while measuring the flow rate of the exhaust gas E with the reference flow meter 220 and changing the temperature and flow rate.

For example, FIG. 6 is a graph showing the relationship between the flow rate coefficient K ₂₀ between the measured values X. This graph, with a flow rate calibration device 2, which is a function of X and K ₂₀ obtained when changing the temperature of the exhaust gas E at 50 ° C. to 200 DEG ° C.. That is, this graph represents Expression 10. The measured values X in the exhaust gases having a plurality of temperatures are calibrated using the flow rate calibration device 2 to derive coefficients a, b, and c. The coefficients a, b, and c are eigenvalues of the flow meter 1 and are derived for each solid of the flow meter 1. Since the coefficients a, b, and c are calibrated so as to correspond to the exhaust gases having a plurality of temperatures, the flow meter 1 provides the highly accurate flow coefficient K ₂₀ and the flow rate Q even for the high temperature exhaust gas E. Can be obtained. The coefficients a, b, and c are stored in advance in the storage unit 135 of the flow meter 1 and used for calculating the flow rate Q _{EX in} the actual RDE test shown in FIG.

  FIG. 7 is a flowchart showing a flow rate calibration method of the laminar flow meter 1 using the flow rate calibration device 2. First, the exhaust gas E is caused to flow through the flow rate calibration device 2, and the temperature and flow rate are set (changed) (S10, S20). Next, the differential pressure ΔP, the atmospheric pressure P, and the temperature T are measured in the laminar flow meter 1 (S30). The number of measurements of the flow rate and temperature is counted by a counter (not shown) provided in the flow rate calibration device 2.

  Next, it is determined whether or not the number of times of flow rate measurement exceeds a predetermined value (S40). Further, it is determined whether or not the number of temperature measurements exceeds a predetermined value (S50). The determinations in steps S40 and S50 are executed by a control unit (not shown).

  If the number of measurement of the flow rate does not exceed the predetermined value (NO in S40), steps S20 to S50 are repeated.

  When the flow measurement count exceeds the predetermined value, but the temperature measurement count does not exceed the predetermined value (YES in S40, NO in S50), steps S10 to S50 are repeated.

  If the number of temperature measurements also exceeds the predetermined value (YES in S50), the flow rate and temperature measurement ends. Note that either the flow rate or the temperature measurement may be performed first or at the same time. Further, the determination of the number of measurement of the flow rate and the temperature may be performed first or may be performed simultaneously.

Next, the flow rate calibrating device 2 calculates μ / μ ₂₀ from the measured ΔP, P, T using Expression 7, and calculates X using Expression 9 (S60). Further, the flow rate calibration device 2 calculates K ₂₀ from Q, μ / μ ₂₀ and ΔP using Equation 11 with Q as a reference flow rate (S70). This gives K ₂₀ and X at a certain flow rate and a certain temperature. Once K ₂₀ and X are calculated for all measured flow rates and temperatures, the function of Equation 10 is approximately known. Thus, the coefficients a, b, and c are determined using an approximate curve calculation method such as a least square method. In order to accurately calculate the coefficients a, b, and c, the flow rate and temperature measurement points are preferably points divided by 10 or more over the flow rate measurement range, for example.

  The coefficients a, b, and c calculated in this way are stored in the storage unit 135 of the flow meter 1. Thus, the calibration of the laminar flow meter 1 by the flow rate calibration device 2 is completed.

  After calibration, the laminar flow meter 1 is actually attached to an automobile or the like, and the actual flow rate is measured. That is, the exhaust gas E from the flow rate measurement target is actually measured.

  FIG. 8 is a flowchart showing a method of measuring the flow rate using the coefficients a, b, and c obtained by the flow rate calibration method of FIG. First, the laminar flow meter 1 is attached to an automobile or the like, and the differential pressure ΔP, the atmospheric pressure P, and the temperature T of the gas E actually discharged from the automobile or the like are measured (S11).

Next, in the laminar flow meter 1, the calculation unit 130 calculates μ / μ ₂₀ and X _EX from the measured differential pressure ΔP, pressure P, and temperature T using Equation 7 and Equation 9 (S21). . X _EX indicates X of the actual exhaust gas E to be measured for flow rate.

Next, the arithmetic unit 130 calculates a coefficient K _EX from X _EX using the coefficients a, b, and c stored in the storage unit 135 (S31). K _EX indicates a coefficient K of an actual exhaust gas E to be measured.

Next, the calculation unit 130 calculates the flow rate Q _EX of the exhaust gas E from the differential pressure ΔP, μ / μ ₂₀ , and K _EX . The flow rate Q _EX is a numerical value used for the RDE test.

  As described above, the laminar flow meter 1 according to the present embodiment calculates the coefficients a, b, and c in advance using the third-order term of the differential pressure ΔP in Equation 3, and stores this. The laminar flow meter 1 measures the actual flow rate Q of the exhaust gas E using the coefficients a, b, and c.

Normally, when Equation 2 is solved up to the quadratic term of ΔP using the binomial theorem for the flow rate Q, it is expressed as Equation 12 and Equation 13.

  In a general laminar flow meter, A and B in Equation 13 are given as constants by flow rate calibration. However, the constant B has terms of density ρ and viscosity μ. Therefore, in a fluid with a high temperature such as exhaust gas or a fluid whose pressure fluctuates (pulsates), the error in the constant B increases. Therefore, when the conventional laminar flow meter is used for the RDE test as PEMS, it is difficult to obtain an accurate flow rate Q.

  On the other hand, the laminar flow meter 1 according to the present embodiment calculates the coefficients a, b, and c in advance using the third-order term of the differential pressure ΔP in Equation 3. The laminar flow meter 1 measures the actual flow rate Q of the exhaust gas E using the coefficients a, b, and c. Thereby, the highly accurate coefficients a, b, and c considering the density ρ and the viscosity μ in more detail can be calculated. Therefore, the laminar flow meter 1 can be used for the RDE test as PEMS even for a fluid having a high temperature and a large pressure fluctuation (pulsation) such as exhaust gas.

  In addition, the laminar flow meter 1 according to the present embodiment includes a mesh filter 20 at a position where the outlet 22 is higher than the inlet 21 of the exhaust gas E in the front stage of an inverted U shape. Thereby, the mesh filter 20 can remove the particles contained in the exhaust gas E from the inlet 21 and can exclude moisture (condensed water) contained in the exhaust gas E.

  Moreover, since the laminar type flow meter 1 has a drain hole 110 below the mesh filter 20, it discharges condensed water and particles accumulated in the storage unit 115 to the outside while discharging a very small amount of the exhaust gas E. I'm going.

  Further, the laminar flow meter 1 includes a laminar flow element 30 that is vertically arranged so as to flow the exhaust gas E in a substantially vertical direction, at the subsequent stage of the inverted U shape. Thus, by arranging the laminar flow element 30 vertically, even if the moisture of the exhaust gas E adheres to the laminar flow element 30 as condensed water, it is dropped from the laminar flow element 30 and discharged from the outlet 120 of the exhaust gas E. can do.

  The ratio of the sum of the opening cross-sectional areas of the thin tubes 33 to the entire cross-sectional area of the laminar flow element 30 is 0.9 or more. As a result, the pressure loss (ΔP) can be reduced, and the adhesion of dirt can also be reduced.

  Regarding the extraction of the differential pressure ΔP generated in the laminar flow element 30, the conduit 70 between the differential pressure gauge 80 and the pipe 145 is a so-called triple T connection. This triple T connection is both upstream and downstream of the laminar flow element 30. As a result, the average pressure of the differential pressure ΔP can be measured upstream and downstream of the laminar flow element 30, and clogging of the conduit 70 can be suppressed.

  Further, a purge gas supply unit PGS is connected to the conduits 70_1 and 70_2, and the purge gas PG is constantly supplied to the conduits 70_1 and 70_2 when the differential pressure is measured. The purge gas PG is a small amount that does not affect the exhaust gas E, and is supplied to the conduits 70_1 and 70_2 at an approximately equal flow rate. Thereby, it is possible to suppress the condensate contained in the exhaust gas E from flowing back to the pressure pipes 60_1, 60_2, the conduits 70_1, 70_2, and the differential pressure gauge 80 without hindering the measurement of the differential pressure. By suppressing the reverse flow of the condensed water, the pressure pipes 60_1 and 60_2, the conduits 70_1 and 70_2, and the differential pressure gauge 80 can be protected from corrosion.

  Further, the laminar flow meter 1 is not as large as the topy tube flow meter, but can be miniaturized to the extent that it can be mounted on the vehicle, and can measure the flow rate of the exhaust gas E alone. On the other hand, the laminar flow meter 1 can measure a low flow rate with higher accuracy than the topy tube flow meter.

Ｑは流量、Ｑｍは振動流の平均流量、Ｑａは振動流の振幅流量、ωは角速度、ｔは時間、ｕｍは振動流の平均流速、ｕａは、振動流の振幅流速、Ｗ０はウォーマスリィ数 (Womersley Number)、Φは位相である。 The response of the laminar flow meter to the pulsating flow is considered based on the Naviestokes equation of the incompressible fluid in the narrow tube 33. Further, assuming that the pulsating flow is a simple oscillating flow as shown in Equation 14, the Navier-Stokes equation of the incompressible fluid in the narrow tube 33 is expressed as shown in Equation 15.

Q is the flow rate, Qm is the average flow rate of the vibration flow, Qa is the amplitude flow rate of the vibration flow, ω is the angular velocity, t is the time, um is the average flow velocity of the vibration flow, ua is the amplitude flow velocity of the vibration flow, and W0 is the Warmersley number ( Womersley Number), Φ is the phase.

振動流に対してウォーマスリィ数Ｗ_０は応答性を示す指標になり、Ｗ_０＝２．５としたときの角速度ωが応答可能な周波数を示す。 In Equation 15, the Warmersley number W0 is a dimensionless number represented by the frequency and viscosity defined by Equation 14.

The Warmersley number W ₀ is an index indicating responsiveness with respect to the oscillating flow, and the angular velocity ω when W ₀ = 2.5 indicates a response frequency.

The laminar flow meter 1 can be said to have good responsiveness because the angular velocity ω is 344 rad / s (55 Hz) when W ₀ = 2.5 in air at 100 ° C.

  The laminar flow meter 1 according to the above embodiment can also be applied to the measurement of the flow rate of exhaust gas such as a chimney.

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and the equivalents thereof.

1 laminar flow meter,
10 Inlet,
20 mesh filter,
30 laminar flow elements,
40 pressure pipe,
50 pressure gauge,
60 pressure tubes,
70 conduit,
80 Differential pressure gauge,
90 temperature sensor,
100 thermometer,
110 drain hole,
120 outlet,
141-146 piping,
130 Calculation unit

Claims (8)

An exhaust gas inlet,
A mesh filter that communicates with the inlet and has a higher outlet than the inlet of the exhaust gas, and removes particles and moisture from the exhaust gas;
A laminar flow element communicating with the mesh filter, wherein the exhaust gas inlet is at a position higher than the outlet, and the exhaust gas flows in a laminar flow state;
A differential pressure gauge for measuring a differential pressure between the pressure of the exhaust gas in the vicinity of the inlet of the laminar flow element and the pressure of the exhaust gas in the vicinity of the outlet of the laminar flow element;
A flow rate measuring device comprising: an outlet for discharging the exhaust gas that has passed through the laminar flow element.   The mesh filter and the laminar flow element are both arranged vertically so as to flow the exhaust gas in a substantially vertical direction, and are configured in an inverted U shape together with a pipe between the mesh filter and the laminar flow element. The flow rate measuring device according to claim 1.   The flow rate measuring device according to claim 1, further comprising a drain hole provided at a position lower than the inflow port and the mesh filter and discharging the moisture to the outside of the flow rate measuring device.   The flow rate according to any one of claims 1 to 3, wherein a ratio of a sum of opening cross-sectional areas of the thin tubes constituting the laminar flow element to a total cross-sectional area of the laminar flow element is 0.9 or more. measuring device. Four or more first gas outlet holes provided at substantially equal intervals over the circumference on the inlet side of the laminar flow element;
Four or more second gas extraction holes provided at substantially equal intervals over the circumference on the outlet side of the laminar flow element;
A plurality of first joints connecting the two first gas extraction holes adjacent in the circumferential direction of the laminar flow element;
A plurality of second joints connecting the two second gas extraction holes adjacent in the circumferential direction of the laminar flow element;
At least one third joint connecting the two first joints adjacent to each other in the circumferential direction of the laminar flow element;
And at least one fourth joint that connects the two second joints adjacent to each other in the circumferential direction of the laminar flow element;
The differential pressure gauge measures the pressure of the exhaust gas in the vicinity of the inlet of the laminar flow element through the first and third joints, and in the vicinity of the outlet of the laminar flow element through the second and fourth joints. The flow rate measuring device according to any one of claims 1 to 4, which measures the pressure of the exhaust gas.   From the vicinity of the inlet of the laminar flow element to the differential pressure gauge via the first and third joints and from the vicinity of the outlet of the laminar flow element to the differential pressure gauge via the first and third joints The flow rate measuring device according to any one of claims 1 to 5, further comprising a purge gas supply unit configured to supply a purge gas to the second conduit.   The thermometer which further measures the 1st temperature of the said exhaust gas in the vicinity of the inlet of the said laminar flow element, and the 2nd temperature of the said exhaust gas in the vicinity of the exit of the said laminar flow element of Claim 1-6. The flow measurement device according to any one of the above. A storage unit for storing in advance the coefficients a, b, c derived by the exhaust gas having a plurality of temperatures;
An arithmetic unit that calculates the flow rate Q using the coefficients a, b, and c.

ΔP is the pressure loss of the laminar flow element, P is the pressure of the exhaust gas, T is the temperature of the exhaust gas, μ is the viscosity of the exhaust gas, μ ₂₀ is the viscosity of air at a temperature of 20 degrees, and Q is the exhaust gas The flow rate measuring device according to any one of claims 1 to 7, wherein the flow rate is the following flow rate.

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