Engine exhaust gas recirculation particle trap

Details Engine exhaust gas recirculation particle trap Engine exhaust gas recirculation particle trap

2001-02-01

2003-07-29

Denion, Thomas (Department: 3748)

Power plants

Internal combustion engine with treatment or handling of...

By sorber or mechanical separator

C060S278000, C055SDIG003

Reexamination Certificate

active

06598388

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention concerns devices for reducing pollutants discharged by an internal combustion engine. More specifically, the invention relates to such devices adaptable to diesel engines which trap particles and vapor carried by the exhaust gas discharged from the engine.
It is recognized that the production of noxious oxides of nitrogen (NO
x
) which pollute the atmosphere are undesirable. Steps are therefore typically taken to eliminate, or at least minimize, the formation of NO
x
constituents in the exhaust gas products of an internal combustion engine. The presence of NO
x
in the exhaust gas of internal combustion engines is generally understood to depend, in large part, on the temperature of combustion within the cylinders of the engine. In connection with controlling the emissions of such unwanted exhaust gas constituents from internal combustion engines, it is widely known to recirculate a portion of the exhaust gas back to the air intake portion of the engine (so-called exhaust gas recirculation or EGR). Since the recirculated exhaust gas effectively reduces the oxygen concentration of the combustion air, the flame temperature at combustion is correspondingly reduced, and since NO
x
production rate is exponentially related to flame temperature, such exhaust gas recirculation (EGR) has the effect of reducing the emission of NO
x
.
It is further known to adapt the engine with electronic sensors to evaluate and control various operational parameters of the engine. One example includes providing a differential pressure transducer across an orifice to measure mass flow rate of the exhaust gas. Using this mass flow rate measurements of the exhaust gas, exhaust gas recirculation may be controlled to optimize engine performance and decrease emission levels. These sensors are typically placed in direct contact with the intake or exhaust gas which are often hostile to the electronic sensor itself. For example, the differential pressure sensor may be placed within the exhaust system that is in direct contact with debris laden exhaust gas.
Debris mixed with the exhaust gas includes particulate emissions can cause extensive damage to engines turbochargers or superchargers. Particulate debris is abrasive and enters the engine oil causing undue wear on the piston rings, valves, and other parts of the engine. A common form of particulate matter is “soot” which is a sticky substance that can lead to carbon build-up on surfaces exposed to the soot. The soot is particularly damaging to electronic sensors such as temperature and pressure sensors. Soot build-up on the sensor causes a degradation in sensor accuracy and in some instances permanent damage.
FIG. 1
depicts a typical engine and EGR system
10
including known components for actively controlling the mass flow of the recirculated exhaust gas. An internal combustion engine
12
includes an air intake manifold
14
attached to the engine
12
and coupled to the various cylinders
16
of the engine, typically through valves (not shown). Intake manifold
14
receives intake ambient air via conduit
18
. An exhaust gas manifold
20
is attached to the engine
12
and coupled to the exhaust gas ports of the various combustion cylinders typically through valves (not shown). The exhaust manifold
20
exhaust combustion gas to the atmosphere via exhaust gas conduit
22
. The engine
12
typically includes a fan
24
which is driven by the rotary motion of the engine to cool engine coolant fluid flowing through a radiator (not shown) positioned proximate the fan
24
.
An exhaust gas recirculation line
26
is connected at one end
28
to the exhaust gas conduit
22
, and at its opposite end
30
to an EGR cooler
32
. The cooler
32
reduces the temperature of the exhaust gas in anticipation of re-entering the inlet air stream of conduit
18
. An EGR flow control valve
34
is connected at one end
36
thereof to EGR cooler
32
via conduit
38
, and at an opposite end
40
thereof to exhaust manifold
20
via conduit
42
. The valve
40
is controllable to open or close the EGR path in response to engine performance requirements.
An air intake system (not shown) provides a supply of fresh intake air through a filter (not shown) to compressor
44
of a turbocharger
46
. A first portion of the exhaust gas discharged from exhaust manifold
20
of engine
12
is supplied to intake conduit
18
through exhaust gas recirculating line
26
to combine with fresh air driven by the turbocharger compressor. A second portion of the exhaust gas flows through turbine
48
of turbocharger
46
to rotate compressor
44
. As a result, intake air exiting from compressor
44
of turbocharger
46
is compressed and heated. The compressed intake air preferably flows through an intake air cooler
50
to reduce the air temperature to a level for optimum combustion in the engine cylinders. Intake air cooler
50
may be an air-to-air type heat exchanger, however, other types of diesel engine coolers or heat exchangers may be satisfactorily used. In operation, the EGR flow control valve
34
is controlled by an engine control module
52
(ECM) in response to differential pressure sensed through a pressure sensor
54
providing a pressure signal to the ECM
52
, via signal path
56
. The ECM
52
uses the differential pressure to calculate the mass flow rate of recirculated exhaust gas through valve
34
. In response to the pressure signal, ECM
52
provides a corresponding control signal to EGR valve
34
, through control circuit
58
. Therefore, the EGR valve
34
is controlled via the ECM
52
to divert any desired amount of exhaust gas directly from the exhaust gas recirculation line
26
to intake conduit
18
.
In one attempt to decrease particulate carried by the exhaust gas, devices referred to as “baghouses” have been employed to filter solid material carried by the exhaust gas. The baghouses can be provided with a fiber bag to capture debris with little on no exhaust gas backpressure. However, once a substantial amount of particulate is captured by the bag the device would lead to a detrimental increase in exhaust gas backpressure. This backpressure can result in a build up of debris within the exhaust system causing poor engine performance and ultimately failure of the engine.
Other known devices which decrease particulate emissions carried by the exhaust gas include regeneration devices which burn away the accumulation of debris. U.S. Pat. No. 5,390,492 to Levendis discloses a regeneration device for use with a filter assembly to decrease the particulate emission in the system. The regeneration device includes a collection chamber fitted with an electric powered incinerator to burn away material accumulating in the collection chamber. Unfortunately, the device is complicated and not a viable alternative for internal combustion engines utilizing after market equipment to decrease exhaust particulate. Furthermore, regeneration devices tend to be expensive to implement and are susceptible to malfunction.
U.S. Pat. No. 5,458,664 issued to Ishii et al. discloses a particle trap provided with a metallic mesh filter, the particle trap is placed directly in the exhaust gas line and is sized to avoid significant exhaust gas backpressure. However, the filter inherently accumulates debris and decreases the flow area, and consequently, an unwarranted back pressure develops. The backpressure in the exhaust line causes degradation of engine power and permanent engine damage, after a period of time.
What is therefore needed is a device for trapping debris in the form of exhaust gas particulate and vapor to protect equipment downstream and at the same time cause only insignificant restriction of exhaust gas from the engine. Moreover, a device that is inexpensive to manufacture and includes widespread adaptability to virtually all sizes and types of engines is desirable. Preferably, such a device should be serviceable rather than warranting periodic device replacement.
SUMMARY OF THE INVENTION
These unmet needs are addressed by the

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