Patent Application
20090241515
The present disclosure relates to an exhaust gas recirculation system. More particularly, the present disclosure relates to a low pressure loop exhaust gas recirculation system that removes condensed water from the recirculated exhaust gas.
The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Exhaust systems perform several functions for a modern engine. For example, the exhaust system is expected to manage heat, reduce pollutants, control noise and sometimes filter particulate matter. Generally, these individual functions are performed by separate and distinct components. The engine exhaust system may use a set of heat exchangers to capture and dissipate heat. A separate muffler may be coupled to the exhaust outlet to control noise, while a catalytic converter assembly may be placed in the exhaust path to reduce non-particulate pollutants. Although today, the removal of particulates is generally directed to diesel engines, with the current focus on a “green” car, particulate emissions for vehicles using fuels other than diesel fuel may soon be required.
Internal combustion engines function by burning fuels (hydrocarbons) at high temperatures. In theory, the products of the combustion process are CO2 and water. It is not uncommon for incomplete combustion to occur which results in the formation of undesirable byproducts such as carbon monoxide, hydrocarbons and soot. Other reactions occurring in internal combustion engines include the oxidation on nitrogen molecules to produce nitrogen oxides and the oxidation of sulfur to form SO2 and a small percentage of SO3. Further, when the temperature decreases, the SO3 can react with H2O to form sulfuric acid. Other inorganic materials are formed as ash.
The products of these reactions result in undesirable gaseous, liquid and solid emissions from internal combustion engines. In order to improve engine emissions under medium and high load conditions, the use of a low pressure loop exhaust gas recirculation system has been developed. The low pressure loop exhaust gas recirculation system creates an exhaust gas pathway from a location downstream of a catalytic converter and/or a particulate filter to a location downstream of the intake air cleaner. This pathway typically consists of an exhaust gas recirculation cooler, an exhaust gas recirculation gas control valve and the piping necessary to connect all of these components.
Although this system provides better NOx emissions performance, when the exhaust gas in the exhaust gas recirculation cooler cools the exhaust gas, acidic water condenses into the exhaust gas recirculation flow and is directed to the internal combustion engine with the recirculated exhaust gas. Thus, the induction system and other various components of the internal combustion engine have this acidic water deposited on them. This acidic water can damage the existing components and this may cause the development engineers to change materials and designs for these components which may increase their costs, increase their weights and lower their performance inefficiencies.
The present disclosure provides a solution to this problem by providing a device which removes acidic water from the exhaust gas recirculation gas flow. By removing acidic water from the exhaust gas recirculation gas flow, the downstream induction system and other components of the internal combustion engine are not adversely affected by the acidic water and the damaging effects of the contaminant.
Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.
The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way.
The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. There is illustrated in
Internal combustion engine 12 comprises an engine block 22 defining a plurality of cylinders 24. A piston 26 is slidingly received within each cylinder 24. An intake valve 28 opens into each cylinder 24 to provide an intake charge and an exhaust valve 30 opens into each cylinder 24 to expel the products of combustion. A fuel injector 32 is disposed in each cylinder to supply the fuel for the combustion process. As is well known in the art, the motion of the piston is synchronized with the opening and closing of intake valve 28, the opening and closing of exhaust valve 30 and the supplying of fuel from fuel injector 32 such that internal combustion engine 12 runs to provide power to operate the vehicle. In diesel engines a glow plug (not shown) can be provided in each cylinder as is well known in the art and in a gasoline engine a spark plug or other means for initiating the combustion process can be disposed in each cylinder as is well known in the art.
Intake system 14 comprises an air cleaner 40 through which outside air is provided to internal combustion engine 12, a turbo-charger 42 which increases the pressure of the air being supplied to internal combustion engine 12, an intercooler 44 which cools the air being supplied to internal combustion engine 12 and a throttle valve 46 which controls the flow of intake charge to internal combustion engine 12.
HPL-EGR system 18 comprises an exhaust gas recirculation valve 50, a switching valve 52 and an exhaust gas recirculation cooler 54. HPL-EGR system 18 receives exhaust gas from exhaust system 16 immediately after the combustion process and it routes this exhaust gas back into intake system 14 downstream from throttle valve 46. Exhaust gas recirculation valve 50 controls the flow of exhaust gas through HPL-EGR system 18 based upon a control program resident in the vehicle's engine control module (not shown). Also, switching valve 52 routes the exhaust gas into exhaust gas recirculation cooler 54 or into a bypass 56 based on the control program resident in the vehicle's engine control module.
Between HPL-EGR system 18 and LPL-EGR system 20, exhaust system 16 is routed through turbo-charger 42 where the exhaust gas powers a turbine 60 which in turn powers a compressor 62 which increases the pressure of the air being supplied to internal combustion engine 12. After leaving turbine 60 of turbo-charger 42, exhaust system 16 is routed through a particulate filter 64 (for diesel applications) and it is then routed to a muffler and possibly a catalytic converter prior to being released to the atmosphere.
Referring now to
Water separator 70 receives the exhaust gas and removes water from the exhaust gas as described below. Since this water is the acidic water that can present problems with internal combustion engine 12 and intake system 14, the removal of this water reduces and/or eliminates these problems. The water collected by water separator 70 is returned to the exhaust gas flow through a drain tube or water line 76 which enters the exhaust gas flow at a position downstream of where LPL-EGR system 20 receives the exhaust gas from exhaust system 16. From water separator 70, the exhaust gas is directed through exhaust gas recirculation cooler 72 to be cooled and the exhaust gas is expelled into intake system 14. Exhaust gas recirculation valve 74 controls the flow of exhaust gas through LPL-EGR system 20 based on commands received from the program resident in the vehicle's engine control module.
Referring now to
Outlet tube 84 is disposed downstream from fixed blade turbine 82. Outlet tube 84 is smaller in diameter than inlet tube 80 and outlet tube 84 is disposed in a co-axial arrangement with inlet tube 80. Outlet tube 84 extends into inlet tube 80 a specified distance to define a collection area 90. The end of inlet tube 80 is sealingly attached to the outside of outlet tube 84. Collection area 90 defines a particle trap which prevents the acidic water from traveling further along with the exhaust gas toward intake system 14. Water return line 76 is open to collection area 90 and drains the accumulated acidic water to a position downstream from the exhaust gas inlet to LPL-EGR system 20 in exhaust system 16.
