Turbochargers include various components to handle flow of fluids such as exhaust gas. For example, some turbochargers may include a wastegate to divert exhaust gas flow around the turbocharger and/or a mechanical shaft to control tuning of a turbine of the turbocharger. These components may pass through one or more walls of the turbine housing, creating potential leak paths for leakage of exhaust gas out of the turbocharger. Conventional seals may not be suitable to prevent leakage of exhaust gas from around the mechanical shafts, as the shafts are associated with the turbine at areas of very high exhaust pressure and temperature. Hence, conventional seals may not be able to withstand these extreme conditions.
One example approach for managing flow of leaked exhaust gas is shown in U.S. Pat. No. 9,103,271 and includes capturing leaked exhaust gas through a port intersecting with a pair of bushings around a wastegate valve shaft and directing the captured leaked exhaust gas from the port to an engine crankcase, thereby preventing the leaked exhaust gas from escaping to atmosphere.
The inventors herein recognize that in the above-described approach, the leaked exhaust gas may be routed to the crankcase even in conditions when emission parameters and pressure parameters along an exhaust pipe are conducive for flowing leaked exhaust through one or more emission control devices to atmosphere, thereby increasing the crankcase pressure. The engine crankcase is designed to operate at relatively low pressure and abnormally high crankcase pressure nay result in oil leaks. To manage the exhaust leaks associated with movable portions in contact with exhaust gas flow more efficiently, the inventors herein provide an exhaust gas leakage management system and a method for operating the exhaust gas leakage management system based on engine operating parameters.
In one example, an exhaust gas leakage management system may include a port disposed to capture a leaked exhaust gas from an insertion region of an exhaust gas flow component, a first passage at a bifurcation of the port, the first passage fluidically connecting the port to an engine crankcase, a second passage at the bifurcation of the port, the second passage fluidically connecting the port to a downstream portion of an exhaust pipe, and a three-way valve at the bifurcation of the port, the three-way valve regulating flow of the leaked exhaust gas through the port to the first passage and to the second passage. The insertion region may be along a movable shaft inserted into a turbine.
An example method for managing the flow of leaked exhaust gas may include, responsive to a first condition, positioning a three-way valve in a first position to flow leaked exhaust gas from a port through a first passage to an engine crankcase, the port capturing the leaked exhaust gas from an insertion portion of a moveable shaft, the three-way valve positioned at a bifurcation of the port, and responsive to a second condition, positioning the three way valve in a second position to flow leaked exhaust gas from the port through a second passage to a downstream portion of an exhaust pipe.
In this way, the leaked exhaust gas from the area around the movable shaft associated with the turbine housing may be managed by directing the leaked exhaust gas to flow to the crankcase of the engine or by directing the leaked exhaust to flow to the downstream exhaust pipe, depending on pressure and emission level parameters. The above described exhaust leakage management system may prevent degradation of emissions due to the leaked exhaust gas escaping to atmosphere and may ensure that the engine crankcase handles some of the leaked exhaust gas, while maintaining the crankcase pressure within a desired range for efficient crankcase operation.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.