Internal Combustion Engine Aftertreatment Heating Loop

Abstract

An engine with an SCR catalyst aftertreatment system includes a turbocharger exhaust duct in fluid communication with the turbocharger outlet and a heating loop segment including an inlet and an outlet. The inlet and the outlet are in fluid communication with the exhaust duct, and the inlet extracts a portion of exhaust gases from the exhaust duct. The engine further includes an exhaust pressure driven air amplifier, an electric preheater, a fuel injector, an oxidation catalyst, a urea injector, and a temperature sensor on the heating loop segment.

Claims

1. An engine with an SCR catalyst aftertreatment system comprising: a turbocharger exhaust duct in fluid communication with the turbocharger outlet; a heating loop segment including an inlet and an outlet, wherein the inlet and the outlet are in fluid communication with the exhaust duct, wherein the inlet extracts a portion of exhaust gases from the exhaust duct; an exhaust pressure driven air amplifier on the heating loop segment; an electric preheater on the heating loop segment; a fuel injector on the heating loop segment; an oxidation catalyst on the heating loop segment; a urea injector on the heating loop segment; and a temperature sensor on the heating loop segment.

2. The engine of claim 1, further comprising a compressed air amplifier on the heatling loop segment.

3. An engine with an oxidation catalyst aftertreatment system comprising: an exhaust duct in fluid communication with the engine outlet; a heating loop segment including an inlet and an outlet, wherein the inlet and the outlet are in fluid communication with the exhaust duct, wherein the inlet extracts a portion of exhaust gases from the exhaust duct; a compressed air amplifier on the heating loop segment; a fuel injector on the heating loop segment; an oxidation catalyst on the heating loop segment; and a temperature sensor on the heating loop segment.

4. The engine of claim 3, further comprising a burner system on the heating loop segment.

5. The engine of claim 4, further comprising an electric preheater on the heating loop segment.

6. The engine of claim 3, further comprising electric preheater on the heating loop segment.

7. The engine of claim 3, wherein the engine is a natural gas engine.

8. The engine of claim 3, wherein the fuel injector comprises an air amplifier.

9. An engine with an oxidation catalyst aftertreatment system comprising: an exhaust duct in fluid communication with the engine outlet; a heating loop segment including an inlet and an outlet, wherein the inlet and the outlet are in fluid communication with the exhaust duct, wherein the inlet extracts a portion of exhaust gases from the exhaust duct; a compressed air amplifier on the heating loop segment; a fuel injector on the heating loop segment; an oxidation catalyst on the heating loop segment; a urea injector on the heating loop segment; and a temperature sensor on the heating loop segment.

10. The engine of claim 9, further comprising a burner system on the heating loop segment.

11. The engine of claim 10, further comprising an electric preheater on the heating loop segment.

12. The engine of claim 9, further comprising electric preheater on the heating loop segment.

13. The engine of claim 9, wherein the engine is a natural gas engine.

14. The engine of claim 9, wherein the fuel injector comprises an air amplifier.

Description

DESCRIPTION OF THE DRAWINGS

[0025] FIG. 1 is a side view of a turbocharged engine with an aftertreatment system including a heating loop.

[0026] FIG. 2 is a side view of a normally aspirated engine with an aftertreatment system including a heating loop.

[0027] FIG. 3 is a preferred embodiment for a turbocharged diesel engine with an SCR aftertreatment system.

[0028] FIG. 4 is a block diagram of a control system with its sensors and valves.

DETAILED DESCRIPTION

[0029] To facilitate an understanding of the present disclosure, a number of terms and phrases are defined below:

[0030] Blended Aftertreatment System (BATS): As described in U.S. Pat. No. 9,752,481, incorporated herein by reference, a BATS system reduces the NOx emissions from the mixed exhaust of two engines in a single larger SCR assembly using only one UREA injection point into the exhaust of the smaller engine.

[0031] Gaseous Fuel: The predominant gaseous fuel used in internal combustion engines is natural gas consisting mostly of methane, but with minor modifications these engines could consume any gaseous fuel including but not limited to propane, natural gas and hydrogen. In this document the term natural gas and gaseous fuel are used interchangeably.

[0032] Hydrocarbon (HC): Emissions resulting from incomplete combustion of fuel and engine lube oil.

[0033] Main Charge: The air fuel mixture in the main combustion chamber space between the piston top and the cylinder head. If an opposed piston engine, this would be the space between the opposed piston faces.

[0034] Particulate Matter (PM): Particulate matter is a criteria pollution emitted from many sources. In this document we will commonly refer to it simply as PM. It could include both diesel soot PM that is considered toxic in California or the type of PM created by the consumption and combustion of lube oil from an engine. While still considered PM as a criteria emission, the PM from lube oil consumption is considered less toxic than diesel soot.

[0035] Reductant: In active NOx reductions systems like a Selective Catalytic Reduction (SCR) system, a reductant is mixed with the hot exhaust gases and is chemically processed by the catalyst system along with the exhaust gasses to reduce NOx emissions to N2 and water. Diesel Exhaust Fluid (DEF) is currently the most common reductant for SCR systems in mobile applications. DEF is actually a mixture of 32.5% UREA and 67.5% water. Once injected into the engine the DEF is first vaporized, and then the UREA crystals are decomposed into ammonia and CO2 molecules. It is the ammonia particles that the SCR catalyst uses to reduce NOx into N2 and water. SCR systems can be used on heat engines burning any kind of fuel so the DEF term can be misleading, in Germany DEF falls under the trademark AdBlue. DEF is also frequently called UREA for short. In some instances ammonia gas is extracted from some other system and injected directly into the exhaust flow as a gas before the exhaust and ammonia mixture reaches the SCR catalysts. Throughout this document the reductant injected into any aftertreatment device that actively reduces NOx will typically be referred to as UREA. In addition the term SCR will be used to identify any active NOx reduction system that uses a reductant.

[0036] FIG. 1 is a side view of a turbocharged medium speed engine with a heating loop. Exhaust Manifold 3 is on top of engine 1 and routes pressurized exhaust gases into turbocharger 2. Main exhaust duct 4 routes the exhaust gases from turbocharger 2 into aftertreatement 5. After the exhaust gases are treated in aftertreatment 5 they exit the engine system through main exhaust outlet 20. Aftertreatment 5 may contain OC substrates, SCR substrates or a combination of both. If an aftertreatment 5 system contains both types of substrates it is controlled in the same manner as a system with only SCR substrates.

[0037] Heating loop inlet 6 extracts a portion of exhaust gases from main exhaust duct 4 and directs it through heater loop 7. Once the portion of exhaust gases have been processed through all the devices along heater loop piping 7 they are then injected back into the main exhaust duct 4 through heater loop exit 8. Air amplifier EP 10 will be fed pressurized exhaust gas sourced from exhaust manifold 3 to assist drawing more exhaust gas into heater loop piping 7. Air Amplifier CA 11 is driven by compressed air from an external source somewhere in the vehicle. This could be supplied by an engine driven air compressor that supplies air to the air brake system. If the vehicle doesn't already have an air compressor is could be supplied by the compressor in turbo 3, although this would be less efficient as turbo 3 boost pressure is likely that of the air brake system and will require 4 times as much air mass to be as effective and all of this air will need to be heated by adding more heat energy into the heating loop 7. Electric preheater 12 is used to increase the temperature of the portion of exhaust gases to a point that the OC 15 will light off and burn the fuel and lean exhaust gas mixture. Electric preheater 12 would typically only be used with a fuel other than methane that has a lower ignition temperature, diesel fuel would be the most appropriate fuel for use with electric preheater 12. Fuel injector 13 is used to inject fuel into the heating loop 7. This is most likely the same fuel used to power engine 1, it could be a liquid hydrocarbon fuel such as diesel or any gaseous fuel. In the case of pressurized gaseous fuels, fuel injector 13 may also act as an air amplifier that is powered by the pressurized gaseous fuel. Fuel burner 14 is used typically for gaseous fuels like methane that have very high ignition temperatures that are not reasonable for use of an electric preheater 12. Fuel burner 14 will likely incorporate a flame holder and ignition system to start combustion. OC 15 is where flameless combustion will occur once the heating loop 7 is at operating temperature. Temperature sensor 16 is the parameter that a control system will monitor to determine the system status and determine when to inject fuel, how much fuel to inject and when to transition from fuel burner 14 to OC 15 to catalytically burn the injected fuel at the highest efficiency at lowest emissions. Gaseous fuel can be injected at any time, but diesel fuel should only be injected after the portion of exhaust gas flow has been preheated by electric preheater 12 to a threshold temperature that will cause light off of OC 15. After light off, the temperature sensor 16 will monitor the exit temperature of OC 15 and that temperature will be used to determine if more or less fuel should be injected by fuel injector 13 to achieve the target temperature in the heating loop 7.

[0038] For an aftertreatment 5 unit that only has an OC substrate, the temperature sensor 16 will be the last device that heating loop 7 is equipped with and the now heated portion of exhaust gases would be then injected through heating loop exit 8 back into the main exhaust duct 4.

[0039] For an aftertreatment 5 unit that does have an SCR substrate, additional components will be added to heating loop 7. UREA injector 17 is used to inject UREA into heating loop 7. Temperature sensor 19 will be used to measure the temperature of the portion of exhaust gas that was first heated and then cooled by injecting UREA into it. With an SCR function temperature sensor 19 becomes the parameter that is used to determine fuel flow through fuel injector 13 to maintain a target temperature at the exit of heating loop 7. In some embodiments, if a temperature sensor 19 is installed, the temperature sensor 16 after OC 15 can be eliminated.

[0040] Recent research has indicated that decomposition of UREA is assisted by being passed through a catalyst at high temperature. In a conventional SCR system, when the air and UREA mixture gets to the SCR substrates, the UREA is typically only 50% of the way through the decomposition process and the remaining decomposition to ammonia occurs as the exhaust gas and decomposing UREA move along the flow length of the substrate. This lowers the overall effectiveness of the substrate. If all of the UREA had been decomposed to ammonia before the exhaust gases started passing through the SCR substrate, it would have a higher NOx reduction efficiency and would be able to operate at lower temperatures. OC 18 is used to increase the amount of decomposition of the mixture of UREA and heated exhaust gases before they exit the heating loop 7 on their way to the SCR substrates inside of aftertreatment 5.

[0041] FIG. 2 is a side view of a normally aspirated medium speed engine with a heating loop. FIG. 2 has all the same components and functionality as FIG. 1 except that turbo main exhaust duct 4 connects exhaust manifold 3 directly to aftertreatment 5 and turbo 3 and the exhaust pressure driven air amplifier EP 10 have been deleted. Because air amplifier EP 10 has been deleted, the compressed air driven air amplifier CA 11 may have to provide more motive force to induce enough exhaust gas flow through heating loop 7

[0042] FIG. 3 is the preferred embodiment of a medium speed turbocharged diesel engine with and SCR aftertreatment system and simplified heating loop. Exhaust Manifold 3 is on top of engine 1 and routes pressurized exhaust gases into turbocharger 2. Main exhaust duct 4 routes the exhaust gases from turbocharger 2 into aftertreatement 5. After the exhaust gases are treated in aftertreatment 5 they exit the engine system through main exhaust outlet 20.

[0043] Heating loop inlet 6 extracts a portion of exhaust gases from main exhaust duct 4 and directs it through heater loop 7. Once the portion of exhaust gases have been processed through all the devices along heater loop piping 7 they are then injected back into the main exhaust duct 4 through heater loop exit 8. Air amplifier EP 10 will be fed pressurized exhaust gas sourced from exhaust manifold 3 to assist drawing more exhaust gas into heater loop piping 7. Electric preheater 12 is used to increase the temperature of the portion of exhaust gases to a point that the OC 15 will light off and burn the diesel fuel and lean exhaust gas mixture. Fuel injector 13 is used to inject diesel fuel into the heating loop 7. OC 15 is where flameless combustion will occur once the heating loop 7 is at operating temperature. Temperature sensor 19 is the parameter that a control system will monitor to determine the system status and determine when to inject fuel and how much fuel to inject. Diesel fuel should only be injected after the portion of exhaust gas flow has been preheated by electric preheater 12 to a threshold temperature that will cause light off of OC 15. After light off temperature sensor 19 will monitor the exit temperature of OC 15 and that temperature will be used to determine if more or less fuel should be injected by fuel injector 13 to achieve the target temperature in the heating loop 7. Once OC 15 is at temperature and catalytically combusting the injected fuel, electric preheater 12 can be turned down or off.

[0044] After temperature sensor 19 has determined that the heating loop 7 temperature is hot enough, UREA injector 17 is used to inject UREA into heating loop 7. As more UREA is injected through injector 17, temperature sensor 19 will detect a dropping temperature in heating loop 7 and the control system will command more fuel be injected through injector 13 to bring the heating loop exhaust gas exit temperature back up to its target temperature.

[0045] FIG. 4 is a bock diagram of a simplified control system for a heating loop 7. Controller unit 30 is electrically connected to various sensors and control valves. Temp sensor 31 will read the exhaust exit temperature from heating loop 7 and depending on its control mode with control the amount of fuel flowing through injector 3. This fuel flow can be controlled by valve 32 which could be an on or off solenoid valve that is modulated to control the flow rate of fuel to injector 13 or this control valve 32 could be an integral part of injector 13. Control solenoide 33 will control the flow of electricity to electric preheater 12 if the system is so equipped. This electric current flow could be controlled by several different electrical devices ranging from a simple switch to a PWM controlled transistor module.

[0046] Control valve 34 regulates the supply of compressed air to an air amplifier CA 11 if the system is so equipped. It may be a simple on off valve with one setting, it can also be PWM controlled to linearly regulate flow.

[0047] Control valve 35 will control UREA flow to UREA injector 17. This could be a solenoid valve that modulates flow or a pumping system of some sort that provides a metered amount of UREA.

[0048] Controller 30 may have its own table of engine operating parameters, but it most likely will be in communication with a master controller that will send it engine load information and updated operating parameters such as heating loop 7 target exhaust temperature. Any of these control valves or solenoids could be physically integrated into control 30 without changing its functionality. Controller unit 30 itself could be integrated into another controller that controls other devices and even the entire engine system or vehicle.

[0049] It should be noted that various changes and modifications to the presently preferred embodiments described herein will be apparent to those skilled in the art. Such changes and modifications may be made without departing from the spirit and scope of the present invention and without diminishing its attendant advantages.