Emissions control

Details Emissions control Emissions control

2002-08-22

2004-10-05

Denion, Thomas (Department: 3748)

Power plants

Internal combustion engine with treatment or handling of...

By means producing a chemical reaction of a component of the...

C060S274000, C060S290000, C060S298000, C060S310000

Reexamination Certificate

active

06799422

ABSTRACT:

TECHNICAL FIELD
This invention relates to controlling emissions from internal combustion engines, such as from fixed-speed engines driving electrical generators and the like.
BACKGROUND
Reducing combustion engine exhaust emissions is a continual object of research and development, driven both by awareness of environmental effects and increased government regulation. Some of the most effective and cost-efficient emissions controls involve the use of downstream chemical catalysts that further oxygenate incompletely combusted compounds. Sometimes exhaust is directed sequentially through multiple catalyst beds. It is generally understood that higher catalyst temperatures provide more effective emissions control. Much exhaust catalysis development has been focused on developing catalytic converters for automotive applications, in which engine speed varies substantially with vehicle speed and gear selection.
In several other applications, such as in powering fixed-frequency electrical generators, engine speed is held as constant as possible during use, even while generator and engine loads fluctuate. Some engine-generator sets are designed for installation on board moving vehicles, either on land or in water.
Marine generators are subjected to specific regulations, both for emissions and for safety concerns. For example, exposed engine surface temperatures (including exhaust system surface temperatures) must be kept low to avoid increased risk of fire hazard. Seawater is injected into many marine engine exhaust flows so as to cool exiting exhaust gases, and seawater is also frequently circulated through exhaust system components so as to maintain low surface temperatures.
Further improvements in exhaust emissions controls for constant speed engine applications are desired, particularly improvements suitable for marine use.
SUMMARY
Many aspects of the invention feature methods of controlling emissions from a fixed-speed internal combustion engine.
In one aspect, the method includes governing engine speed with respect to a selected constant speed; flowing exhaust from the engine through an exhaust system, the exhaust flowing through, in order, a first catalyst, an inter-catalyst space, and a second catalyst; injecting oxygen-laden gas (such as atmospheric air) into the exhaust in the inter-catalyst space, such that the exhaust and the oxygen-laden gas both flow through the second catalyst; and controlling a rate of oxygen-laden gas injection as a function of a variable that changes with engine load.
In some cases, controlling the gas injection rate includes electronically monitoring the variable that varies with engine load. For example, the rate of gas injection may be selected from a specific series of discrete rates as a function of the monitored variable. In some applications the gas injection rate is controlled by an electronic controller with memory configured to store a predetermined table of variable values and associated gas injection rates.
In some preferred embodiments, the engine is driving an electrical generator. In some such embodiments, the monitored variable is generator output current.
In some other embodiments, the monitored variable is engine driveshaft torque or exhaust manifold pressure.
Preferably, the injection rate is increased when engine load increases, and decreased when engine load decreases.
Controlling the gas injection rate includes, in some embodiments, varying operating speed of an air pump motivating the oxygen-laden gas into the inter-catalyst space. In some other embodiments, it includes modulating a valve operably disposed between a source of pressurized oxygen-laden gas and the inter-catalyst space. The valve may be a dump valve, for example, modulated to dump a variable proportion of an incoming flow of gas to atmosphere.
In some instances, water (such as seawater) is injected into the exhaust downstream of the second catalyst. This may be water employed to cool the exhaust housing about the catalysts. For example, the first and second catalysts may both be disposed within a water-jacketed housing, with cooling water flowing through the housing is injected into the exhaust downstream of the second catalyst. In some cases, the first catalyst is disposed within a water-jacketed exhaust manifold and the second catalyst is disposed within a water-jacketed exhaust elbow secured to an outlet of the manifold, with cooling water flowing from the manifold into the elbow before mixing with the exhaust. This arrangement is particularly useful to marine applications with tight exhaust surface temperature requirements and available seawater.
According to another aspect, the method includes governing engine speed to maintain a desired generator output frequency over a range of operating loads; flowing exhaust from the engine through an exhaust system, the exhaust flowing through, in order, a first catalyst, an inter-catalyst space, and a second catalyst; determining approximate engine load; injecting air into the exhaust in the inter-catalyst space at a rate selected according to the determined approximate engine load; and injecting seawater into the exhaust downstream of the second catalyst.
In many preferred embodiments, approximate engine load is determined by monitoring generator output, and wherein in the rate of air injection is selected according to the monitored generator output. The monitored generator output can be, for example, generator current.
In some cases, approximate engine load is determined by monitoring engine exhaust manifold pressure, the rate of air injection being selected according to the monitored manifold pressure.
The first and second catalysts are both preferably disposed within a water-jacketed housing, that may be hydraulically connected to a source of seawater. In some cases cooling water flowing through the housing is injected into the exhaust downstream of the second catalyst.
According to another aspect, the method includes governing engine speed with respect to a selected constant speed; flowing exhaust from the engine through an exhaust system, the exhaust flowing through, in order, a first catalyst, an inter-catalyst space, and a second catalyst; injecting oxygen-laden gas (such as atmospheric air) into the exhaust in the inter-catalyst space, such that the exhaust and the oxygen-laden gas both flow through the second catalyst; and controlling a rate of oxygen-laden gas injection as a function of temperature within the inter-catalyst space.
In a preferred configuration, controlling the gas injection rate includes electronically monitoring inter-catalyst space temperature, and may also include selecting the rate of gas injection from a specific series of discrete rates as a function of inter-catalyst space temperature.
In some cases, the engine is driving an electrical generator.
The gas injection rate is preferably increased when inter-catalyst space temperature increases.
Controlling the gas injection rate may include varying operating speed of an air pump motivating the oxygen-laden gas into the inter-catalyst space, or modulating a valve operably disposed between a source of pressurized oxygen-laden gas and the inter-catalyst space, for example.
In some applications, water (such as seawater) is injected into the exhaust downstream of the second catalyst.
As discussed above, the first and second catalysts are both preferably disposed within a water-jacketed housing for some applications. Cooling water flowing through the housing may be injected into the exhaust downstream of the second catalyst. In one configuration, the first catalyst is disposed within a water-jacketed exhaust manifold, and the second catalyst is disposed within a water-jacketed exhaust elbow secured to an outlet of the manifold, with cooling water flowing from the manifold into the elbow before mixing with the exhaust.
According to yet another aspect, the method includes governing engine speed with respect to a selected constant speed; flowing exhaust from the engine through an exhaust system, the exhaust flowing through, in order, a first catalyst,

Affiliated with

Also associated with

Rating

Emissions control does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Emissions control, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Emissions control will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3331023