Gas separation: processes – With control responsive to sensed condition – Temperature sensed
Reexamination Certificate
1999-04-29
2001-01-23
Spitzer, Robert H. (Department: 1724)
Gas separation: processes
With control responsive to sensed condition
Temperature sensed
C095S018000, C095S283000, C055S282300, C055SDIG001, C055SDIG003
Reexamination Certificate
active
06176896
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the field of particle filters and more particularly to the determination of their fouling.
These filtering elements are generally situated in the exhaust lines of internal-combustion engines, and they are intended to collect and/or to remove certain particles contained in the gas flow so that the exhaust line discharges a gas stripped from said particles downstream, i.e. into the atmosphere.
Fouling thus appears to be a major problem for particle filters, and various methods and/or devices have already been developed with the constant objective of regenerating the filter.
BACKGROUND OF THE INVENTION
It may consist, according to a well-known concept, in periodically burning the soot deposits.
This combustion sometimes occurs naturally when the temperature of the gases reaches by itself the level required for initiating oxidation of the particles. However, medium operating conditions generally lead to temperatures that are too low to spontaneously ignite combustion of the particles. This thus leads to clogging of the filter, which is a serious disadvantage for the engine efficiency and eventually imperils the operation thereof. Complete regeneration of the filter then has to be performed artificially and arbitrarily.
Many techniques have been developed to that end. They can be based on changes in the running of the engine: intake throttling, exhaust throttling, advanced injection lag, or connected with an energy supply in the exhaust gases or in the filter (electric resistor, burner, microwave . . . ). It is then necessary to control these various devices by means of an external control managed by a computer. Most often, the criterion taken into account for triggering regeneration is the back pressure in the exhaust line.
In order to facilitate regeneration of particle filters, a different and complementary approach of chemical nature consists in adding to the fuel an organometallic additive for example, that is thereafter found in the soot deposit, which generally leads to a decrease in the ignition temperature and therefore to an increase in the regeneration frequency.
Examples of the most commonly used additives are copper, iron, cerium, sodium . . . Studies show that, in the presence of such additives, partial regenerations can occur spontaneously for relatively low exhaust gas temperatures (~200° C.).
However, for certain types of pipe, problems linked with the back pressure can remain, so that an exterior energy supply can be necessary, such as for example electric heating.
As regards energy consumption, most well-known systems using electric heating of the filter include global heating of the filtering element. This leads to a high energy consumption that is more or less controlled. Generally, the electric power required for triggering total regeneration of the filter is high and often hardly compatible with the electric resources on board the vehicle. Patent EP-B1-0,485,179 illustrates a system based on this principle.
French patent application EN.96/13,855 filed in the name of the applicant describes a concept allowing to adapt the electric power and the energy distribution in the filter to all the operating conditions of the vehicle. This concept consists in dividing the filtering unit into several zones, in equipping each of said zones with a resistor and, after detecting the global fouling of the filtering unit, in selectively activating one or more resistors. Valves are furthermore associated with the resistors in order to increase or to attenuate the effect of the resistors.
This regeneration modulation is however based on a general and global fouling evaluation.
Besides, the regeneration conditions can depend to a large extent on the state of fouling of the filter. In general, electric heating allows no flexible action according to the fouling of the filter.
The present invention allows this technology to be improved by furthermore achieving a local fouling evaluation.
SUMMARY OF THE INVENTION
More specifically, according to the invention, the local permeability of a particle filter and therefore the fouling thereof are evaluated, then regeneration is activated and modulated accordingly.
Furthermore, these various actions can be performed in real time, in a precise and reliable way.
The flow of gas to be scrubbed flows past the particle filter that consists of several juxtaposed zones through which the flow of gas to be scrubbed can also flow from one end to the other.
The object of the invention thus is a process for evaluating the local permeability of a particle filter consisting in:
measuring the temperature of said flow upstream from said filter,
measuring the temperature in at least one of said zones forming the filter,
evaluating the thermal inertia of at least one of said zones via relative measurement of the temperature or of the local resistance to said temperature upstream from the filter,
deducing therefrom the local permeability of the filter, and
locally regenerating said filter.
The process according to the invention further consists in locally regenerating at least one of said zones when said permeability is above a certain threshold value.
More precisely, local regeneration consists in local heating.
According to an embodiment of the invention, the process can consist in installing several resistors in several zones of the filter and one resistor upstream from the filter, in measuring each resistor at predetermined time intervals and in evaluating the relative resistance of each zone so as to deduce the local permeability of each zone.
Furthermore, the process according to the invention can consist in installing at least one valve upstream from at least one zone of the filter and in independently modulating the opening according to the desired local regeneration.
According to the invention, the measurement of each local resistor (Ri) itself is used to modulate the opening of each associated valve.
Besides, the measurement of each local resistor (Ri) can be stored separately in order to determine a clogging or a breakage of said resistor.
Without departing from the scope of the invention, the most fouled zones are regenerated first.
In addition, the process according to the invention can consist in injecting hydrocarbons locally and independently into at least one of said zones of the filter.
The present invention also relates to a device intended for local permeability evaluation and local regeneration of a particle filter consisting of several juxtaposed zones and through which a flow of gas to be scrubbed passes, comprising a means for evaluating the thermal inertia of at least one zone of the filter, associated with a means for measuring the temperature upstream from and at various points in the filter, and a means intended for local regeneration of the filter, cooperating with the means intended for evaluation of the local permeability of the filter.
More precisely, the means intended for local regeneration of the filter consists of at least one resistive element placed in a zone of said filter.
According to an embodiment of the invention, the means for evaluating the thermal inertia consists of a temperature detector placed in the gaseous flow upstream from the filter and of at least one temperature detector locally installed in at least one zone of the filter.
Without departing from the scope of the invention, the means for evaluating the thermal inertia comprises a resistive element placed in the gaseous flow upstream from said filter, associated with at least one resistive element installed in a zone of said filter.
Furthermore, the device according to the invention can comprise at least one valve situated upstream from a zone of the filter, associated with the local regeneration of said filter.
Advantageously, it further comprises a means intended for local injection of hydrocarbons into at least one of said zones of the filter, associated with the local regeneration of said filter.
According to the invention, the local permeability evaluation device can also comprise a means for de
Bourry Bruno
Dementhon Jean-Baptiste
Martin Brigitte
Antonelli Terry Stout & Kraus LLP
Institut Francais du Pe'trole
Spitzer Robert H.
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