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Exhaust gas purifying apparatus

a technology of exhaust gas purification and purification apparatus, which is applied in the direction of machine/engine, exhaust treatment electric control, separation process, etc., can solve the problems of large amount of pm accumulated in the dpf, unstable plasma generation, and large load on the engine, so as to improve the trapping effect of pm

Inactive Publication Date: 2005-02-24
TOYOTA JIDOSHA KK
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

The present invention is an exhaust gas purifying apparatus that includes a PM purifying reactor, a detecting device for measuring the amount of PM accumulated in the reactor, a power supply for the reactor, and a controlling device for controlling the power supply based on signals from the detecting device. The apparatus uses plasma to burn PM and detects the amount of accumulated PM by measuring the pressure loss across the reactor. The apparatus can save energy by controlling the power supply based on the amount of accumulated PM rather than the engine speed. The detecting device can determine the amount of PM accumulated in the reactor by measuring the differential pressure across it. The PM purifying reactor comprises electrodes and an insulative honeycomb structure with cell passages where PM is deposited and burned out. The electrodes generate an electric field that improves trapping of PM and the PM is burned with the use of plasma and an electrical current that passes through it. The technical effects of the invention include improved purification efficiency, reduced energy consumption, and improved control of PM accumulation.

Problems solved by technology

However, the DPF is plugged by the trapped PM as time goes by and increases the differential pressure across the DPF and this causes a larger load on the engine.
However, even though the DPF has a higher temperature, a large amount of PM may be accumulated in the DPF due to the change of combustion conditions in the engine.
Once such a large amount of PM is accumulated in DPF, the accumulated PM makes the generation of plasma unstable and lowers the PM oxidation ability, and therefore, PM is further accumulated in the DPF.
This becomes a vicious cycle.
A large amount of heat is generated, if the large amount of accumulated PM is burned out at once to remove.
The large amount of heat shortens the life of the DPF, and may break the DPF.
However, changes in the combustion conditions in the engine are not always pradictable.
Therefore, in some cases, plasma generation controlled on the basis of engine speed, etc. may be not enough in order to properly remove PM.

Method used

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Examples

Experimental program
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Effect test

example 1

[0050] A PM purifying reactor was provided as shown in FIG. 3. That is, in this reactor, around the circumference surface of a straight-flow type cordierite honeycomb structure (diameter: 30 mm and length: 50 mm, cell density: 200 cells / square inch, porosity: 65%, and average pore size: 25 μm (micro meters)), a stainless steel mesh (width: 40 mm, SUS 304, 300 mesh) was surrounded to be an outer electrode. On the center axis of the honeycomb structure, a center electrode (bar electrode) having needle electrodes was fixed.

example 2

[0051] The exhaust gas purifying apparatus of this example was the same as that of the example 1, except that a wall-flow type cordierite honeycomb structure (cell density: 300 cells / square inch, porosity: 65%, and average pore size: 25 μm) was used in place of the straight-flow type cordierite honeycomb of the example 1.

[0052] Performance Evaluation: PM trapping

[0053] Each of the reactors of the examples 1 and 2 was surrounded by an alumina mat and inserted in a quartz tube having an inner diameter of 37 mm (milli-meters). The center electrode was electrically connected to an electric power supply, and the outer electrode was grounded. To the exhaust gas purifying apparatus, a part of the exhaust gas (100 L / minute) from a direct-injection system diesel engine having a displacement volume of 2400 cc was pumped, and a voltage of 4 kV (input electric power of about 3 W) was applied. The contents of the PM in the exhaust gas were determined at the upstream and downstream of the appar...

example 3

[0057] A PM purifying reactor was provided as shown in FIG. 4. That is, straight-flow type cordierite honeycomb structures in rectangular parallelepiped form (cell density: 200 cells / square inch, porosity: 65%, average pore size: 25 am, height: 15 cells, width: 5 cells, and length: 50 mm) are sandwiched with stainless steel mesh electrodes (SUS 304, height of 24 mm, length of 45 mm, and 300 or 30 mesh).

[0058] In the experiment, the exhaust gas passes through the reactors in a direction indicated by an arrow 100 in FIG. 4. The mesh electrodes are alternatively connected to an electric power supply and to the ground. The electrodes connected to the electric power supply are anodes, and the grounded electrodes are cathodes.

[0059] Performance Evaluation: PM Trapping

[0060] A PM trapping rate was determined as in examples 1 and 2, except that the reactor of the example 3 was surrounded by an alumina mat and inserted in an acrylic tube having a profile of 34×48 mm, and that a DC electri...

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Abstract

The present invention relates to an exhaust gas purifying apparatus comprising; a plasma-assist PM purifying reactor; a detecting device for detecting an amount of PM accumulated in the PM purifying reactor; a power supply for the PM purifying reactor; and a controlling device for controlling the power supply on the basis of signals from the detecting device. The controlling device controls the power supply to start supplying the electric power to the PM purifying reactor, or to increase the amount of electric power which is supplied to the PM purifying reactor, when the amount of accumulated PM detected by the detecting device exceeds a predetermined amount.

Description

BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to an apparatus for purifying an exhaust gas emitted from an internal combustion engine and, in particular, to an apparatus for purifying PM (particulate matter) emitted from a diesel engine. [0003] 2. Description of Related Art [0004] Diesel engines are usually used for motor vehicles, and particularly, for large motor vehicles. The diesel engine must now have a decreased emission of nitrogen oxide (NOx), carbon monooxide (CO) and hydrocarbon (HC) as well as PM. Therefore, it is desired to develop not only the technique which decreases the amount of generated PM by improving engine itself or optimizing combustion condition thereof, etc., but also the technique which purifies the PM in the exhaust gas. [0005] It is possible to trap the PM in the exhaust gas by the use of a so-called diesel particulate filter (DPF). However, the DPF is plugged by the trapped PM as time goes by and increa...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): H05H1/24B01D46/42B01J19/08F01N3/02F01N3/027F01N9/00
CPCF01N3/0275F01N2240/28F01N9/002
Inventor KAKINOHANA, MASARUTSUCHIYA, JIRO
Owner TOYOTA JIDOSHA KK
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