Diesel particulate filter system for auxiliary power units
A system for reducing the emissions produced by an engine affixed to a body during operation and reducing noise and vibration. The present invention is particularly related to a small form factor active/passive Diesel Particulate Filter system having an exhaust backpressure sensor, a heating element, a Diesel Oxidation Catalyst, a power relay switch, a filter and an electronic control unit for controlling the heating element based on backpressure detected by the sensor.
1. A small form factor active/passive diesel particulate filter system for a diesel auxiliary power unit installed on a body having a main diesel engine, comprising:
an exhaust pipe connected to an exhaust port of the diesel auxiliary power unit for carrying an exhaust gas including a particulate matter output by the diesel auxiliary power unit, the exhaust pipe having a first internal cross-sectional surface area;
a sensor connected to the exhaust pipe for monitoring an exhaust backpressure within the exhaust pipe;
a coil assembly connected to the exhaust pipe and having a second internal cross-sectional surface area of less than 150% of the size of the first internal cross-sectional surface area for heating the exhaust gas carried by the exhaust pipe to the coil assembly and actively igniting the particulate matter;
a relay switch connected to an AC power generator of the diesel auxiliary power unit and the coil assembly for providing power to the coil assembly;
an oxidation catalyst connected to the coil assembly having a third internal cross-sectional surface area approximately equal to the second internal cross-sectional surface area for injecting NO 2 into the exhaust gas passing through the oxidation catalyst to passively ignite the particulate matter after the coil assembly stops actively igniting the particulate matter;
a filter assembly connected to the oxidation catalyst having a fourth internal cross-section surface area approximately equal to the third internal cross-sectional surface area for trapping a large percentage of the particulate matter; and
an electronic control unit connected to the sensor for receiving a first signal from the sensor representative of the exhaust backpressure within the exhaust pipe and sending a second signal to the relay switch when the first signal represents a regeneration threshold for exhaust backpressure, the second signal causing the relay switch to provide power to the coil assembly from the AC power generator.
2. The filter system of claim 1 , wherein the coil assembly includes a wire wound heating coil encased in a ceramic housing having a honeycomb-shaped passageway through which exhaust gas can pass and be heated by the wire wound heating coil.
3. The filter system of claim 1 , wherein the relay switch is normally open, and the second signal closes the relay switch for a predetermined period of time.
4. The filter system of claim 3 , wherein the predetermined period of time is based on a period of time required to heat the exhaust gas to a temperature that will cause the particulate matter to ignite.
5. The filter system of claim 1 , wherein the oxidation catalyst includes a monolith honeycomb substrate structure coated with a platinum group metal catalyst.
6. The filter system of claim 1 , wherein the filter assembly includes a honeycomb filter structure formed of silicone carbide.
7. The filter system of claim 1 , wherein the regeneration threshold is approximately 23 to 30 inches of water when the diesel auxiliary power unit is a two cylinder engine or a three cylinder engine.
8. The filter system of claim 1 , wherein the large percentage is 85 percent or greater.
9. The filter system of claim 1 , wherein the first internal cross-sectional surface area is approximately 2.40 square inches.
10. The filter system of claim 1 , wherein the electronic control unit sends a third signal to the diesel auxiliary power unit shutting down the diesel auxiliary power unit if the first signal represents a low threshold indicating a problem with the filter system.
11. The filter system of claim 1 , wherein the electronic control unit sends a third signal to the diesel auxiliary power unit shutting down the diesel auxiliary power unit if the first signal represents a high threshold indicating a problem with the filter system.