Patent Application
20120260627
This disclosure pertains to an internal combustion engine system that provides treatment of combustion gases between first and second expansion phases of the gases.
Internal combustion engines have a power stroke defined by combustion and expansion of working gases. In motor vehicles, it is required in many geographic regions to treat the discharged working gases for reducing emissions, particularly HC, CO and NOx and particulate emissions.
Present emission reducing technology requires that the discharged working gases need to be at a certain minimum temperature in order for the catalytic after-treatment process to be effective. If conventional engines were adjusted, i.e. by varying compression ratios, fuel ratios and valve timing to run most efficiently, the discharged exhaust gases would be cooler than the required minimum temperature. Therefore, current engine designs face a tradeoff between optimizing the work extraction from the working gases and leaving enough energy in the form of heat to allow catalytic converters to effectively clean the discharged working gases.
Thus, present internal combustion engine designs, for example Diesel, Otto, Rotary, or Atkinson cycle engines when used in an automotive vehicle compromise between maximum practical expansion during the power stroke and leaving enough heat in the output gases to provide for effective catalytic after-treatment. Typically, once the hot exhaust gases are treated, they are run through a muffler, or merely discharged to the atmosphere.
What is needed is an engine design that can capture more energy from the hot exhaust gases and convert it to work output, thus increasing the efficiency of an internal combustion engine but still provide for effective emission reduction.
In accordance with an embodiment of the invention, an internal combustion engine has an engine block with a first working chamber therein. A moving member is moveably mounted in the chamber for providing an intake phase, compression phase, a combustion and first expansion phase of the working gases and a discharge phase. A second expander provides a second expansion phase of the working gases after discharge from the working chamber. An emission treatment station is interposed between the first working chamber and the second expander for treating the working gases for emission reduction. The working gases are treated after being discharged from the first working chamber but before entering the second expander for the second expansion phase.
Preferably, the emission treatment station includes a catalytic converter for treating the working gases to reduce one or more of unburned HC, CO, NOx or particulate emissions. In one embodiment, the first working chamber is a cylinder and the moving member is a reciprocating piston and the second expander is a rotary device. In another embodiment, the second expander is a reciprocating device.
In accordance with another aspect of the invention, a method of emission management for an internal combustion engine includes providing an internal combustion engine with at least one working chamber and a moving member moved by a first expansion of the working gases in the working chamber for extracting work. The working gases are then treated after being discharged from the working chamber for reducing emissions. After treatment, the working gases pass to a second expander for additional work extraction from the working gases. The working gases are then discharged from the second expander. Preferably, the working chamber is a cylinder, the moving member is a reciprocating piston moveable in the cylinder; and the treating of the working gases is at a separate emission treatment station interposed between the working chamber and the second expander.
In one embodiment, the separate emission treatment station includes a catalytic converter. In one embodiment, the second expander is a rotary device.
In accordance with another aspect of the invention, an internal combustion engine includes a first work extraction station for extracting work from combustion and expansion of the working gases. An emission treatment station is connected to the first work extraction station for treating the working gases after leaving the first extraction work station for reducing emissions. A second work extraction station is connected to the emission treatment station for receiving the working gases from the emission treatment station for a second extraction of work from the working gases.
Reference is now made to the drawing figures in which:
Referring now to
While a piston engine is shown in
The exhaust manifold 28 leads via conduit 29 to an emission treatment station 30, for example, a catalytic converter 33. The working gases are discharged from the working chamber 22 to the emission treatment station 30 at higher pressures and higher temperatures than a conventional cycle engine which enhances the effectiveness of the emission reduction process. The emission treatment station 30 may be a catalytic converter made from known ceramic materials with known porous channel structures. The emission treatment station 30 can reduce unburned HC, CO, NOx or other particulate emissions produced from the initial combustion process. The adjustable pressure range in the emission treatment station may be between 3 and 10 bar absolute.
Unlike conventional catalytic after-treatment systems, the downstream end 31 is not open to the atmosphere via a muffler or an open exhaust pipe. Instead, the downstream end 31 is connected to a conduit 32 which leads to a second expander 34 where more work is extracted from the still pressurized working gases. Further work is then extracted as much as possible. Due to the gas already having been cleaned, the final temperature of the expanded gas after the second expansion can be below temperatures where after-treatment is effective. In other words, further work can be extracted from the gas after the first expansion cycle.
The second expander 34 may be a rotary turbine type with a housing 36, vanes 38 and output shaft 40 connected to the vanes directly or through reduction gears (not shown). An air motor construction, for example a vane air motor or the Di Pietro motor are also suitable for this second expander. The output shaft 40 then can be connected to the vehicle drive train or auxiliary generator system for example. It should be also understood that while a rotary expander 34 is illustrated, other expanders such as reciprocating expanders can also be used as the second expander as shown in
After the second expansion, the working gases pass through an outlet 41 and enter an exhaust system 42 open to the atmosphere which may include an exhaust muffler and tailpipe (not shown).
By having more expansion of the working gases providing work on the second expander 34 or 46, a more efficient engine with improved fuel consumption at very low emission levels is achieved in comparison to a conventional single expansion cycle engine.
This dual expansion cycle with an intermediate emission treatment station interposed between two expansion sections can be applied to a wide variety of internal combustion engines and allow for an effective emission treatment station working at higher pressures and higher temperatures than conventional catalytic converters.
By providing a second expander, the engine provides for a very high overall expansion ratio to extract the maximum amount of energy from the working gases and thus maximizes the efficiency of the engine.
The second expander can be a separate device thus allowing the first expander to be a conventional engine modified to have a shorter power and expansion stroke.
This dual expansion phase engine according to the invention does not compromise between emission control and fuel economy. The dual expansion phase engine instead improves both emission control and fuel economy simultaneously.
Variations and modifications are possible without departing from the scope and spirit of the present invention as defined by the appended claims.
