Abstract:
An internal combustion engine has a first work extraction station for extracting work from combustion and expansion of working gases. An emission treatment station treats the working gases after leaving the first extraction work station for reducing emissions. A second work extraction station receives the working gases from the emission treatment station for a second extraction of work from the working gases.

Description:
TECHNICAL FIELD 
     This disclosure pertains to an internal combustion engine system that provides treatment of combustion gases between first and second expansion phases of the gases. 
     BACKGROUND OF THE INVENTION 
     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. 
     SUMMARY OF THE INVENTION 
     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. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Reference is now made to the drawing figures in which: 
         FIG. 1  is a schematic and segmented illustration of a multiple expansion phased engine with an emission treatment station interposed between the two expansion sections; 
         FIG. 2  is a schematic chart illustrating the thermal cycle of the multiple expansion phased engine shown in  FIG. 1 ; and 
         FIG. 3  is a schematic and segmented illustration similar to  FIG. 1  showing an alternate embodiment where the second expander section is also a reciprocating device. 
     
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     Referring now to  FIG. 1 , an engine  10  has a piston engine section  12 . The engine section  12  can look conventional with an engine block  14 , piston  16 , crank arm  18 , crankshaft  20  and working chamber  22  often referred to as a cylinder. Inlet and outlet valves  24  and  26  also commonly referred to as intake value  24  and exhaust value  26  allow for intake of air and exhaust or discharge of the working gases, also referred to as the combustion gases. The engine section  12  operates and functions like a conventional engine during the induction, compression and combustion phase. However, the power stroke or expansion phase is reduced compared to a conventional engine. As such, the working gases remain at higher pressures at the time when the outlet valves open and the discharge stroke commences. 
     While a piston engine is shown in  FIG. 1  as the first expander, it should be understood other engines may be used. Diesel, Otto cycle, Atkinson, Miller cycle, Brayton cycle, or split-cycle engines, for example a Scuderi cycle, can also provide the first expander section. While not all of these engines have pistons, they all have working members which function analogously to a reciprocating piston in converting expanding gas to mechanical motion. Each of these engines can be modified to have an expansion phase with a reduced expansion ratio to reserve some of the expansion for later. At the end of the first expansion process, the pressure of the working gases is still relatively higher than atmospheric pressure. Furthermore, the temperature is higher than the minimum required for effective catalytic treatment. 
     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  through opened exhaust valve  26  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.  FIG. 2  schematically shows a thermal cycle of the dual expansion phase engine and more particularly when the emission treatment occurs during the cycle. During emission treatment, the temperature of the gases may increase due to the known catalytic processes. The second expansion then takes place after the emission treatment to further decrease the pressure and temperature. 
     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  FIG. 3 , a reciprocating piston type expander  46  is illustrated where piston  48  is connected to crank arm  50  which in turn is connected to output shaft  52  that can be connected to the vehicle drive train or auxiliary system. Air control valves  54  and  56  commonly referred to as intake valve  54  and exhaust valve  56  are connected or timed with output shaft  52  for proper sequencing of opening and closing in similar fashion to the intake gate  39  and output gate  41  of the rotary turbine type second expander  34 . The working gases enter into the emission treatment station  30  through open exhaust valve  26 , and are treated in the emission treatment station  30  with the intake valve  54  closed. Exhaust valve  26  closes at the completion of the exhaust stroke of piston  16  to contain the working gases in the emission treatment station  30 . Valve  54  is then opened to allow the treated working gases to enter the second expander  34  at the beginning of the second expansion phase, i.e. the downward stroke of piston  48 . It should be noted that opening and closing timing of exhaust valve  26  is thus different than the opening and closing timing of the intake valve  54 . It should be noted that to provide for a second expansion larger than said first expansion and not a mere transfer of gases, the second piston type expander  46  is larger than the piston  16  and working chamber  22  assembly as clearly shown in  FIG. 3  i.e. the second working chamber  55  is larger than the working chamber  22  to provide a larger maximum volume than the maximum volume for the treated working gases of working chamber  22  for the untreated working gases. 
     After the second expansion, the working gases pass through the air control valve  56  or an output gate  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.