JPH07218399A - Constant volume diluting type sampling - Google Patents

Abstract

PURPOSE:To improve the stability of a flow rate and to achieve the compact size of an apparatus and space saving by receiving temperature/pressure data into a controller for controlling the flow rate of a blower, performing the correcting operation of the flow rate all the time, and performing the feedback control of the number of rotation of the blower so that the flow rate after the correction agrees with the preset flow rate. CONSTITUTION:As a flow-rate detecting sensor, a vortex flow meter 35 is used. As a pressure detector, a differential-pressure transmitter 37 is used. The pressure in the pipe is measured based on the pressure difference between the inside of the pipe and atmosphere. A temperature detector 39 measures the temperature in the pipe. The respective measured values are inputted into an adjust controller 43 through converters 41, 41a and 41b. The flow rate is corrected by using a correcting expression, and the flow rate under the standard state is obtained. Then, the operating function in the controller 43 is used, and the rotation of a blower 55 is controlled through an inverter 23 based on the deviation with respect to the preset flow rate. The controller 43 can set the flow rate with a button switch 45. With the real-control being performed, the total amount of the mixed gas during the measurement can be read out with an integrating flowmeter 49 through a converter 47.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas flow rate measuring device, and more particularly to a constant volume dilution type sampling device for measuring and controlling the emission mass of harmful components generated during engine test operation of an automobile.

[0002]

2. Description of the Related Art Conventionally, a constant volume dilution type sampling device (Constant Volume) has been used as a device for measuring the emission mass of harmful components in exhaust gas emitted from an automobile engine.
Sampler and below called CVS).

A conventional CVS device sucks a gas, which is a mixture of exhaust gas discharged from a tail pipe of an automobile and clean air, at a constant flow rate. With the conventional CVS system, this suction system allows the constant capacity pump system (Posi
tive Displacement Pump-constant Volume Sampler (hereinafter referred to as PDP method) and the Critical Venturi method (Critical Flow Venturi-Constant Volume Sampler) shown in FIG.
(Hereinafter referred to as CFV method).

As shown in FIG. 2, the PDP system is used in an automobile 1.
The exhaust gas of is mixed uniformly with the dilution air introduced through the filter 5 in the mixer 3, and the mixed gas dedusted by the cyclone 7 is controlled to a constant temperature by the heat exchanger 9,
It is sucked into the metering pump 21. Part of this mixed gas is
It is collected in the collection bag 13 by the sample collection pump 11,
It is supplied to the analyzer 19. Reference numerals 15 and 17 are an air collection pump and a collection bag for measuring the concentration of harmful components in the diluted air.

The Roots blower 21 of the metering pump is rotatably driven by a synchronous motor 25 driven by an inverter 23, and a temperature detector and a detector 27 for detecting pressure are used to display a temperature and pressure on a display 31 and a loop blower during a test period. The accumulated rotation number of 21 is displayed.

As shown in FIG. 3, the CFV system is used in an automobile 1
The exhaust gas is mixed with the dilution air in the mixer 3, dust is removed in the cyclone 7, and the quantitative flow rate of the mixed gas is secured by the critical flow venturi 33. Part of the mixed gas is sampled by the sample collection pump 11 into the collection bag 13 and supplied to the analyzer 19. The temperature detector 27a and the pressure detector 29 calculate the instantaneous flow rate and the total integrated flow rate and display them on the displays 49 and 53.

[0007]

By the way, in the CVS device, the stability of the mixed gas and the accuracy of detection and measurement influence the accuracy of the measurement of harmful components in the exhaust gas. However, in the PDP method, a large-sized roots blower 21 must be used, and there is a differential pressure at the inlet and outlet of the roots blower 21 and a flow rate characteristic (ΔP-ΔV (V: capacity)), which is used for setting and detecting the flow rate. Will cause an error in the case of.

[0008] This is because the capacity per one rotation of the roots proofer 21, that is, the flow rate changes due to the pressure difference between the inlet and outlet of the PDP system, and therefore, in actual use, it is necessary to frequently perform flow rate correction. In addition, it is necessary to regularly verify the flow characteristics. Further, since the suction gas temperature of the roots proofer 21 also has a flow rate characteristic (ΔT-ΔV) for the same reason, the heat exchanger 9 is installed to keep the suction gas at a constant temperature as shown in FIG. It is necessary, and the size of the device becomes large, and at the same time, it takes time to manage it.

The CFV system is a Venturi type which utilizes the property that the flow rate becomes constant when the gas has a sonic velocity.
The flow rate change is extremely small and it can be used stably for a long time, so it has the advantage of being able to guarantee highly accurate measurement results, but care must be taken when maintaining and handling the venturi 33.
The venturi 33 must be replaced when changing the dilution ratio or when changing the dilution capacity according to the displacement of the test engine. Further, there is a defect that the Venturi 33 per unit is also expensive. Both the PDP method and the CFV method require a large-scale device and are expensive.

In order to improve the above-mentioned problems, an object of the present invention is to incorporate temperature / pressure data into a controller for controlling the flow rate of a proofer, always perform a correction calculation of the flow rate, and then to perform the flow rate after the correction. Feedback control of the rotation speed of the blower ensures that the flow rate always matches the set flow rate, and the flow rate is automatically corrected, the stability of the flow rate is improved, and the structure is downsized and space is saved. That is to provide a constant volume dilution type sampling device.

[0011]

In order to achieve the above object, the present invention provides a constant volume dilution type sampling device for measuring the emission amount of harmful components in exhaust gas. A flow rate sensor that detects the volumetric flow rate of the mixed gas, and a pressure sensor that detects the internal pressure at the measurement point,
A temperature sensor for detecting an internal temperature, and a controller for controlling the rotation speed of the blower by inputting detection signals of the flow rate sensor, the pressure sensor and the temperature sensor to correct the pressure and temperature of the mixed gas. This is a constant volume dilution type sampling device.

[0012]

By adopting the constant volume dilution type sampling device of the present invention, a flow rate sensor for detecting the volumetric flow rate of the mixed gas of exhaust gas and diluted air is provided, and a pressure sensor for detecting the internal pressure at the measurement point is provided. A temperature sensor that detects the internal temperature is provided, and the pressure and temperature of the mixed gas are corrected by using the detection signals of the flow rate sensor, the pressure sensor, and the temperature sensor as input, and a constant flow rate correction calculation is performed. By providing a controller for controlling the rotation speed of the blower, the flow rate is automatically corrected, the stability of the flow rate is improved, and the structure is downsized and space is saved.

[0013]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 is a schematic block diagram of an embodiment of the present invention. In the figure, a vortex flowmeter 35 is adopted as a flow rate detecting sensor. This vortex flowmeter 35 inserts a columnar member (vortex generator) into the flow in the pipe to generate a Karman vortex,
The pressure change caused by the generation of this vortex is measured as a change in stress.

In the present embodiment, a differential pressure transmitter 37 is used as the pressure detector used for correcting the flow rate, and the internal pressure of the pipe is measured by measuring the differential pressure between the inside of the pipe and the atmosphere. The temperature detector 39 measures the in-tube temperature by converting the temperature into the resistance value of the resistance temperature detector.

The above-mentioned flow rate and pressure are converted into the output of the vortex flowmeter 35 and the pressure transmitter 37 via the converters 41 and 41a and input to the controller 43, and the temperature is converted into the resistance value of the temperature detector 39. Input to the controller 43 via the instrument 41b.

At this time, the controller 43 corrects the flow rate by the following equations (1) and (2).

[Equation 1] PQ / T = P1 Q1 / T1 (1) where P: Design pressure P1: Measured pressure Q: Design flow rate Q1: Measured flow rate T: Design temperature T1: Measured temperature Therefore, Q = (T / P ・ P1 / T1) ・ Q1 ＝ (P1 / P ・ T ・ T1) ・ Q1 ………… (2) where P 1 / P: Pressure correction coefficient T / T 1: Temperature correction coefficient or more The flow rate value in the standard state is obtained by the controller 43 by the calculation of

Therefore, the deviation between the flow rate in the standard state and the preset flow rate can be obtained. Based on that deviation,
The proportional / integral / derivative (PID) calculation function inside the controller 43 outputs the flow rate control value to the blower 45 (rotation speed control via the inverter 23).

The controller 43 sets the maximum set flow rate to 15
The flow rate can be set with the button switch 45 at about m3 / min, and control is performed in real time, and the output of the corrected flow rate value to the integration counter is started by the operation switch of the control panel or the command from the host computer.・
The control for switching the stop timing is performed. This makes it possible to obtain the total amount of the mixed gas being measured in the integrated flow meter 49 via the converter 47 while controlling the flow rate to be constant.

The control panel also has a display 53 for displaying instantaneous data.
Is provided, and the converters 41, 4 are connected by the changeover switch 51.
1a, 41b output signals s1, s2, s3 and controller 43 output signal s4 are switched to display instantaneously the flow rate before correction, pressure, temperature and flow rate after correction on the display 53. is there.

The present invention is not limited to the above-described embodiment, but by making appropriate design changes, other aspects such as pressure and It is also possible to omit one or both of the temperature sensors.

[0022]

As is apparent from the above description, the constant volume dilution type sampling device of the present invention is provided with a flow rate sensor for detecting the volumetric flow rate of the mixed gas of exhaust gas and diluted air, and the measuring point. A pressure sensor for detecting the internal pressure at, a temperature sensor for detecting the internal temperature are provided, and a constant flow rate correction for correcting the pressure and temperature of the mixed gas by inputting the detection signals of the flow rate sensor, the pressure sensor and the temperature sensor By providing a controller that calculates and controls the rotation speed of the blower with the corrected flow rate, the problems of the conventional technology are effectively solved, the flow rate is automatically corrected, and the stability of the flow rate is improved. Moreover, because the structure is miniaturized and it becomes a space-saving constant volume dilution type sampling device,
Sampling equipment that was conventional equipment for exhaust gas testing or equipment for research and development does not require advanced handling technology,
The present invention has the effect of becoming a general-purpose sampling device that can be widely applied to vehicle inspection factories.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of a conventional PDP system.

FIG. 3 is a schematic configuration diagram of a conventional CFV system.

[Explanation of symbols]

 19 Analysis device 21 Roots blower 23 Inverter 35 Vortex flowmeter 41, 41a, 41b Converter 43 Controller

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Teruhiko Inoue 4-30-3 Yoyogi, Shibuya-ku, Tokyo Fuji Electric Techno Engineering Co., Ltd.

Claims (1)

[Claims] 1. A constant volume dilution type sampling device for measuring the discharge amount of harmful components in exhaust gas, and a flow rate sensor for detecting a volume flow rate of a mixed gas of the exhaust gas and diluted air, and a measuring point A pressure sensor for detecting pressure,
The temperature sensor that detects the internal temperature, and the detection signals of the flow rate sensor, pressure sensor, and temperature sensor are input to correct the pressure and temperature of the mixed gas, and constantly perform flow rate correction calculation to rotate the blower at the corrected flow rate. A constant volume dilution type sampling device comprising a controller for controlling the number.