JP2010107304A - Exhaust gas dilution system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the gaseous component emitted from the inner wall when an exhaust gas is measured, with a simple a constitution, by peeling a gaseous component attached to the inner wall of an exhaust gas dilution apparatus 100. <P>SOLUTION: An exhaust gas dilution system includes: an inner pipe section 2 for forming a first flow path FP supplied with dilution air, and diluting the exhaust gas from an engine 200; an outer pipe section 3 for forming a second flow path SP provided so as to surround the inner pipe section 2, and flowing the exhaust gas from the engine 200 between the inner pipe section 2; and a gas supply section 4 provided so as to be held between the inner pipe section 2, the outer pipe section 3 and the engine 200, and selectively supplying the exhaust gas from the engine 200 to the first flow path FP or the second flow path SP. The gas supply section 4 is configured so as to flow the exhaust gas to the second flow path SP before the exhaust gas flows in the first flow path FP. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an exhaust gas dilution apparatus that dilutes exhaust gas discharged from an engine such as a diesel engine with intake air.

  In an engine, immediately after combustion of fuel, hydrocarbons (HC) and the like in PM (Prticulate Matter) are not in a particulate state and exist as gaseous components. And if exhaust gas is discharge | released and diluted to air | atmosphere, a gaseous component will be cooled and condensed, and it will grow into a particle. Therefore, in the PM measurement in the exhaust gas of the engine, an exhaust gas dilution device as shown in FIG. 2 is used.

  In this exhaust gas dilution device, the exhaust gas of the engine is led to the center of the dilution tunnel and mixed with the diluted air. At this time, the exhaust gas is diluted so as to be 52 ° C. or lower (or 42 ° C. to 52 ° C.) and sucked so that the diluted exhaust gas has a constant flow rate (by a blower provided on the downstream side of the dilution tunnel). . A part of the diluted exhaust gas is collected at a constant flow rate, and PM is collected by a filter. The mass of PM collected from the mass of the filter before and after the test is obtained, and the total emission amount of PM in the exhaust gas is obtained.

  Here, recent diesel vehicles are equipped with exhaust gas aftertreatment devices such as DPF (Diesel Particulate Filter), and the amount of PM emission is greatly reduced. On the other hand, the dilution tunnel also tests engines that do not have exhaust gas after-treatment devices such as DPF or engines with old exhaust gas regulations, so that the condensed tunnel is attached to the wall of the dilution tunnel in addition to soot particles. is doing. If so, deposits such as soot particles and gaseous components released from the inner wall at the time of exhaust gas measurement are added as background to the PM discharged from the engine, which is a problem particularly when testing an engine equipped with a DPF.

  On the other hand, the gas attached to the inner wall of the dilution tunnel is operated by operating the engine at the rated power before the test or driving the vehicle at high speed to discharge the high temperature exhaust gas and flowing the high temperature exhaust gas through the dilution tunnel. A method of peeling the components is considered (generally referred to as “baked out”).

  However, even in this bake-out process, since it is sucked by a blower provided downstream of the dilution tunnel, dilution air is supplied into the dilution tunnel and the temperature of the high-temperature exhaust gas is cooled, and the inner wall of the dilution tunnel is cooled. Cannot be sufficiently heated, and the attached gaseous components and the like cannot be peeled off.

  In addition, since exhaust gas flows in the dilution tunnel in the bake-out process, even if the gaseous components adhering to the bake-out process can be removed, the exhaust gas flowed during the bake-out process causes the dilution tunnel. There is also a problem that a gaseous component newly adheres to the inner wall.

On the other hand, in order to heat the dilution tunnel, it is conceivable to provide a separate heating device such as winding an electric heater around the dilution tunnel. However, since the dilution tunnel itself is large, the heating device for heating the dilution tunnel is also large. It is costly, and the power is large, which is not a good idea.
JP 2000-329661 A

  Therefore, the present invention has been made to solve the above-mentioned problems all at once, and, while having a simple configuration, the deposits such as gaseous components adhering to the inner wall of the exhaust gas dilution apparatus are peeled off to measure the exhaust gas. The main goal is to reduce the amount of deposits sometimes released from the inner wall.

  That is, the exhaust gas dilution apparatus according to the present invention is provided so as to surround the inner pipe portion, the inner pipe portion forming a first flow path for diluting the exhaust gas of the engine supplied with dilution air, and the inner pipe portion. An outer pipe part that forms a second flow path through which the exhaust gas of the engine flows, and an inner pipe part and an outer pipe part interposed between the engine and the exhaust gas from the engine. A gas supply section that selectively supplies the first flow path or the second flow path to the second flow path before supplying the exhaust gas to the first flow path. It is characterized by flowing exhaust gas.

  In such a case, the exhaust gas is allowed to flow through the second flow path before the exhaust gas is supplied to the first flow path, although it has a simple configuration in which a double pipe structure of the inner pipe portion and the outer pipe portion is formed. As a result, the inner pipe can be heated by the exhaust gas. As a result, the gaseous component condensed and attached to the inner wall of the inner tube portion can be vaporized and peeled off, and the soot particles attached can be peeled off. Therefore, it is possible to reduce the gaseous component released from the inner wall during exhaust gas measurement and to enable accurate and reproducible PM emission measurement.

  In order to simplify the configuration and switching of the gas supply unit, one end of the gas supply unit is connected to the engine, the other end is branched, and one of the gas supply units is connected to the inner pipe unit and connected to the first flow path. An exhaust gas supply pipe that communicates with the other pipe and communicates with the second flow path, and is connected to the second flow path, and is provided in the exhaust gas supply pipe to supply exhaust gas from the engine to the inner pipe or to the outer pipe It is desirable to provide a switching valve for switching between the two.

  In order to uniformly heat the inner tube and to uniformly remove the deposit from the inner wall, it is desirable that the inner tube portion and the outer tube portion are provided concentrically.

  When supplying the exhaust gas to the second flow path, if the dilution gas is supplied to the first flow path, the temperature of the inner tube cannot be increased. In order to solve such a problem and to sufficiently raise the temperature of the inner wall of the inner tube and sufficiently separate the deposits, when supplying the exhaust gas to the second channel, the first channel It is desirable to stop the supply of dilution air to

  If the reference measurement for obtaining the reference value for performing background correction and the exhaust gas measurement for obtaining the exhaust gas measurement value are different, the percentage of deposits released is considered to be different due to the difference in temperature. Background correction is not possible. In order to solve such a problem, when obtaining a reference value used when background correction is performed by flowing only the dilution gas into the first flow path, the amount of exhaust gas flowing through the second flow path is set to It is desirable to adjust the temperature so that it is substantially the same as the temperature in the first flow path when performing exhaust gas measurement.

  According to the present invention configured as described above, the adhering matter such as soot particles and gaseous components adhering to the inner wall of the exhaust gas dilution device is peeled off and released from the inner wall at the time of exhaust gas measurement. Kimono can be reduced. As a result, the fluctuation of the exhaust gas measurement value due to the background fluctuation can be reduced, and the reproducibility of the measurement value can be improved.

  Hereinafter, an exhaust gas dilution apparatus 100 according to the present invention will be described with reference to the drawings. FIG. 1 is an overall schematic diagram of an exhaust gas dilution apparatus 100 according to the present embodiment.

<Device configuration>
The exhaust gas dilution apparatus 100 of this embodiment is used for an exhaust gas sampling apparatus for measuring the PM mass in exhaust gas discharged from an engine 200 such as a diesel engine.

  This exhaust gas dilution apparatus 100 has a dilution tunnel having a double tube structure of an inner tube portion 2 and an outer tube portion 3, and forms a first flow path FP for diluting the exhaust gas by supplying dilution air. An inner tube portion 2 that surrounds the inner tube portion 2, and an outer tube portion 3 that forms a second flow path SP between the inner tube portion 2 and the exhaust gas of the engine 200, and the inner tube A gas supply unit 4 that is provided between the engine unit 2 and the outer tube unit 3 and the engine 200 and selectively supplies exhaust gas from the engine 200 to the inner tube unit 2 or the outer tube unit 3. ing.

  The inner pipe portion 2 is for diluting the entire amount of exhaust gas discharged from the engine 200 such as a diesel engine, and has a substantially cylindrical shape. On the upstream side, a dilution air introducing portion 5 having an air cleaning filter is formed, and on the downstream side thereof, a venturi flow meter 6 (for example, a critical flow venturi (CFV)) and a blower as a suction device are formed. 7 is connected to an exhaust pipe portion 8 provided in this order.

  Further, a connection port to which a branch pipe of a gas supply unit 4 described later is connected is provided on the upstream side of the inner pipe part 2 (near the downstream side of the introduction part 5). A gas sampling pipe 9 for sampling a part of the diluted exhaust gas is provided. This gas sampling pipe 9 is inserted and connected to the downstream side of the inner pipe part 2, one end of which opens at the center of the inner pipe part 2, and the other end is branched into two parts. 92 includes filters 10 and 11 for collecting PM contained in the sample gas.

  One branch pipe 91 constitutes a sample gas flow path for flowing a sample gas at the time of PM collection (at the time of exhaust gas measurement), and the other branch pipe 92 receives sample gas at the time of PM non-collection (at the time of reference measurement). A bypass flow path is formed for flow. In addition, suction pumps (for example, roots blower pumps) 12 and 13 whose suction capacity is variable by rotation speed control are provided at the downstream ends of the branch pipes 91 and 92, respectively.

  The suction pumps 12 and 13 are controlled by a control device (PID controller) (not shown) so that the gas flow rate passing through the filter 10 always has a constant proportional relationship with the gas flow rate in the first flow path FP. To follow. That is, a gas flow rate measured by a flow meter (not shown) provided downstream of the gas sampling pipe 9 is a gas flow rate measured by a venturi flow meter 6 provided in the exhaust pipe portion 8 connected to the inner pipe portion 2. The flow rate is controlled so as to have a constant proportional relationship.

  The outer tube portion 3 has a substantially cylindrical shape, and is provided substantially coaxially (substantially concentrically) so as to surround the outer periphery of the inner tube portion 2. That is, the distance between the inner peripheral surface of the outer tube portion 3 and the outer peripheral surface of the inner tube portion 2 is substantially the same in both the axial direction and the circumferential direction. Further, the axial end portion of the outer tube portion 3 is airtightly connected to the outer peripheral surface of the inner tube portion 2.

  A connection port (not shown) to which a branch pipe of a gas supply unit 4 to be described later is connected is provided on the upstream side of the outer tube unit 3 in order to introduce exhaust gas into the inside (second flow path SP). A discharge port 31 for discharging exhaust gas from the inside (second flow path SP) is provided on the downstream side.

  The gas supply unit 4 has a supply order switching function for switching supply of exhaust gas to the first flow path FP and supply to the second flow path SP, and one end is connected to the engine 200 and the other end branches. One branch pipe 41a is connected to the connection port of the inner pipe part 2 and communicates with the first flow path FP, and the other branch pipe 41b is connected to the connection port of the outer pipe part 3 and connected to the second flow path SP. An exhaust gas supply pipe 41 communicating with the changeover valves 42a and 42b provided in the exhaust gas supply pipe 41, for switching whether the exhaust gas from the engine 200 is supplied to the inner pipe portion 2 or the outer pipe portion 3, Is provided.

  The switching valves 42a and 42b may be configured to be switched by a manual operation by a user, or may be configured to be switched by an automatic operation by a control device (not shown).

  Therefore, the gas supply unit 4 of the present embodiment switches the switching valves 42a and 42b so that the exhaust gas flows through the second channel SP before supplying the exhaust gas to the first channel FP.

  More specifically, before the exhaust gas measurement or the reference measurement, the first flow is supplied after the exhaust gas is supplied to the second flow path SP and the deposits (gaseous components, etc.) adhering to the inner wall of the inner pipe portion 2 are peeled off. Exhaust gas is supplied to the path FP and exhaust gas measurement or reference measurement is performed. At this time, the supply of the exhaust gas to the second flow path SP may be, for example, supplying an exhaust gas with a 100% load (maximum output) at a rated rotation (drive) of the engine 200 for a predetermined time (for example, 20 minutes). That is, the supply of the exhaust gas to the second flow path SP may be performed so that the temperature and time are such that the gaseous component adhering to the inner wall of the inner pipe portion 2 is peeled off.

  Further, when supplying the exhaust gas to the second flow path SP, the supply of dilution air to the first flow path FP is stopped. That is, the drive of the blower 7 of the exhaust pipe part 8 connected to the inner pipe part 2 is stopped, and the suction in the first flow path FP is stopped. Thereby, the dilution air does not flow into the inner pipe part 2, the inner wall of the inner pipe part 2 is not cooled by the dilution air, and the inner pipe part 2 can be efficiently heated by the exhaust gas flowing through the second flow path SP. it can.

  Further, in the reference measurement in which only the dilution air is circulated in the first flow path FP to obtain the reference value used when performing background correction, the amount of exhaust gas flowing through the second flow path SP is adjusted. At this time, the temperature in the first flow path FP in the reference measurement is substantially the same as the temperature in the first flow path FP at the time of exhaust gas measurement (for example, 52 ° C. or less defined in JIS standards). Adjust the temperature. Here, the method of adjusting the amount of exhaust gas flowing through the second flow path SP is performed by adjusting the valve opening of the switching valve 42b. Thereby, background correction can be performed more accurately.

  Finally, a procedure for PM sampling of exhaust gas using the exhaust gas dilution apparatus 100 of the present embodiment will be described.

  In a state where the gas supply pipe 41 is connected to the engine 200, the inner pipe portion 2, and the outer pipe portion 3, the engine 200 is operated. Before the exhaust gas measurement and before the reference measurement, the switching valve 42a provided in the branch pipe 41a is closed, and the switching valve 42b provided in the branch pipe 41b is opened. Then, the exhaust gas from the engine 200 flows through the second flow path SP and is discharged from the discharge port 31 while heating the wall of the inner pipe portion 2. Thereby, deposits such as gaseous components and soot particles adhering to the inner wall of the inner tube portion 2 can be peeled off.

  Thereafter, the switching valves 42 a and 42 b are closed, and only the dilution air is caused to flow through the first flow path FP by the blower 7 provided in the exhaust pipe part 8 to cool the inner pipe part 2. At this time, the separated deposit is released together with the dilution air. In addition, when there is sufficient time until exhaust gas measurement or the like, after the peeled off deposits are discharged with dilution air, it may be naturally cooled without flowing dilution air.

  After the inner pipe part 2 is cooled to room temperature, for example, the switching valve 42a provided in the branch pipe 41a is opened to supply exhaust gas to the first flow path FP. At this time, dilution air is also sucked by the blower 7 to dilute the exhaust gas. The diluted exhaust gas is collected by the gas sampling pipe 9 provided in the inner pipe portion 2 and collected on the filter 10.

<Effect of this embodiment>
According to the exhaust gas dilution apparatus 100 according to the present embodiment configured as described above, a simple structure in which the double pipe structure of the inner pipe portion 2 and the outer pipe portion 3 is used and only the switching valves 42a and 42b are switched. Before the exhaust gas is supplied to the first flow path FP, the inner pipe can be heated by the exhaust gas by flowing the exhaust gas through the second flow path SP. As a result, the gaseous component condensed and attached to the inner wall of the inner tube portion can be vaporized and peeled off, and the soot particles attached can be peeled off. Therefore, it is possible to reduce the gaseous component released from the inner wall during exhaust gas measurement and to enable accurate and reproducible PM emission measurement.

<Other modified embodiments>
The present invention is not limited to the above embodiment. In the following description, the same reference numerals are given to members corresponding to the above-described embodiment.

  For example, in the above-described embodiment, the gas supply unit is configured using a branch pipe and a switching valve, but in addition, a flow in which exhaust gas is supplied by attaching and detaching using one single gas supply pipe. You may make it switch a path. In addition, a gas supply pipe connected to the introduction port of the inner pipe part and a gas supply pipe connected to the introduction port of the outer pipe part are provided, and in each process, either gas supply pipe is connected to the engine (tail pipe). You may make it connect.

  Moreover, it is not necessary to provide each switching pipe as a switching valve, and a three-way switching valve may be provided at the branch point of the gas supply pipe to switch the supply of exhaust gas.

  Furthermore, since the effect of the present invention can be achieved by heating the inner pipe portion to a temperature equal to or higher than the temperature at the time of exhaust gas measurement, even when the exhaust gas is allowed to flow through the second flow path, You may make it flow dilution air through a path. Note that the flow rate of the dilution air may be adjusted in order to adjust the temperature of the inner pipe portion when the exhaust gas flows through the second flow path.

  Moreover, although the exhaust gas dilution apparatus of the said embodiment was a whole flow dilution type, a split flow dilution type may be used.

  In addition, “flowing exhaust gas to the second flow path before supplying exhaust gas to the first flow path” means that exhaust gas is flowed to the second flow path after completion of exhaust gas measurement to flow exhaust gas to the first flow path. Including preparation for the next exhaust gas measurement. At this time, the exhaust gas is supplied to the second flow path before the exhaust gas is supplied to the first flow path in the next exhaust gas measurement.

  In addition, some or all of the above-described embodiments and modified embodiments may be combined as appropriate, and the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention. .

The schematic diagram which shows the structure of the exhaust gas dilution apparatus which concerns on one Embodiment of this invention. The schematic diagram which shows the structure of the conventional waste gas dilution apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 ... Exhaust gas dilution apparatus 200 ... Engine FP ... 1st flow path 2 ... Inner pipe part SP ... 2nd flow path 3 ... Outer pipe part 4 ... Gas supply part 41 ... Exhaust gas supply pipes 42a, 42b ... Switch valves

Claims (5)

An inner pipe that is supplied with dilution air and forms a first flow path for diluting the exhaust gas of the engine;
An outer pipe part that is provided so as to surround the inner pipe part and forms a second flow path for flowing exhaust gas of the engine between the inner pipe part,
A gas supply unit provided between the inner pipe part and the outer pipe part and the engine, and selectively supplying exhaust gas from the engine to the first flow path or the second flow path; With
An exhaust gas dilution device configured to cause the exhaust gas to flow through the second channel before supplying the exhaust gas to the first channel. The gas supply unit is
Exhaust gas supply with one end connected to the engine, the other end branched, one connected to the inner pipe and connected to the first flow path, and the other connected to the outer pipe and connected to the second flow path Tube,
An exhaust gas dilution apparatus, comprising: a switching valve that is provided in the exhaust gas supply pipe and switches whether exhaust gas from the engine is supplied to the inner pipe part or the outer pipe part.   The exhaust gas dilution device according to claim 1 or 2, wherein the inner tube portion and the outer tube portion are provided concentrically.   The exhaust gas dilution device according to claim 1, 2, or 3, wherein when supplying exhaust gas to the second flow path, supply of dilution air to the first flow path is stopped.   When obtaining a reference value for use in performing background correction by flowing only the dilution gas through the first flow path, the amount of exhaust gas flowing through the second flow path is adjusted to perform the exhaust gas measurement. The exhaust gas dilution device according to claim 1, 2, 3, or 4, wherein the temperature is adjusted so as to be substantially the same as the temperature in one flow path.