Patent Publication Number: US-2018045109-A1

Title: Engine intake and exhaust flow management

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of U.S. Provisional Patent Application Ser. No. 62/116,666, filed on Feb. 16, 2015, the entirety of which is incorporated by reference herein. 
    
    
     GOVERNMENT LICENSE RIGHTS 
     This invention was made with government support under DE-EE0006844 awarded by the United States Department of Energy. The government has certain rights in the invention. 
    
    
     TECHNICAL FIELD 
     This application relates to engine systems. More specifically, the application provides a systems and methods for engine intake and exhaust flow management. 
     BACKGROUND 
     Turbocharged gasoline engines can experience knock at low engine speeds when the turbocharger is not operating in an ideal speed range. When the engine is also cold, or warming up, the knock is hard to combat because the turbocharger is not receiving the heat and mass flow necessary to spool up. A back pressure results between the engine intake and exhaust. The improper air to fuel ratio promoted by the back pressure causes the knock. Turbocharged diesel engines can experience lag and engine performance issues at lower engine speeds and during transient events when the turbocharger is not operating in an ideal speed range and high levels of EGR is being utilized. 
     One solution to correct the turbocharger challenge involves opening the exhaust valve before the compression stroke reaches bottom dead center (BDC). While this gives the exhaust more time to clear the cylinder before the next combustion cycle intakes air, the stroke reduction also reduces engine power output. Limiting boost by opening a waste gate is another commonly implemented countermeasure to address the above identified issues. However, this approach results in reduced engine power output and non-optimized engine performance/waste heat recovery. 
     SUMMARY 
     The methods and devices presented herein overcome the above disadvantages and improves the art by way of engine intake and exhaust flow management. The invention enables control of the intake and exhaust of the engine independent of the engine speed. Computer control of one or both of an intake assist device and an expander enhances engine cylinder scavenging of exhaust, reduces engine knock, improves drivability, and optimizes fuel use. 
     In one example, a power generation system is presented including a power plant having a crankshaft, an air intake system, and an exhaust outlet. The expander can include a pair of symmetric rotors in fluid communication with the exhaust outlet and a drive shaft operably connected to one of the rotors. A motor/generator coupled to the expander drive shaft can also be provided. A controller is also provided that is connected to control the power plant air intake system, the motor/generator, the controller being configured to operate the motor/generator and the air intake system such that an air intake flow into the power plant and an exhaust air flow out of the power plant are controlled independently of a rotational speed of the power plant crankshaft. 
     In one example, an engine system comprises an engine comprising an inlet manifold, an exhaust manifold, and a plurality of combustion cylinders, and each of the plurality of combustion cylinders is connected to receive air from the inlet manifold and to expel exhaust from the exhaust manifold. Intake valves regulate air flow from the inlet manifold in to a respective one of each of the plurality of combustion cylinders. Exhaust valves regulate exhaust flow from a respective one of each of the plurality of combustion cylinders in to the exhaust manifold. Pistons in each of the plurality of combustion cylinders are connected to the engine to travel in its respective cylinder from top dead center to bottom dead center to complete a combustion cycle. A variable valve timing controller is connected to the respective intake valves and to the respective exhaust valves to control the timing of each of the plurality of combustion cylinders for receiving air from the inlet manifold and to control the timing for each of the plurality of combustion cylinders for expelling exhaust to the exhaust manifold. A fuel injection system is connected to supply fuel to each of the plurality of combustion cylinders. A expander is connected to receive exhaust from the exhaust manifold. A motor/generator is connected to power the expander. An expander controller is connected to control the motor/generator connection to the expander, and the expander controller is configured to select between a passive mode, where exhaust passively moves through the expander, and an active mode, where the motor/generator powers the expander to actively draw exhaust from the exhaust manifold. Moreover, the motor/generator and associated controller allow for the expander to be operated as a compressor and/or expander in the exhaust system in addition to the previously disclosed function. 
     Additional objects and advantages will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the disclosure. The objects and advantages will also be realized and attained by means of the elements and combinations particularly pointed out in the appended claims. 
     It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the claimed invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a power generation system, which is an example in accordance with aspects of the invention. 
         FIG. 2  is a side view of the power generation system shown in  FIG. 1 . 
         FIG. 3  is a perspective view of an expander and motor/generator of the power generation system shown in  FIG. 1 . 
         FIG. 4  is a side view of the expander and motor/generator shown in  FIG. 3 . 
         FIG. 5  is a perspective view of an expander, exhaust bypass assembly, and exhaust manifold of the power generation system shown in  FIG. 1 . 
         FIG. 6  is a side view of the expander, exhaust bypass assembly, and exhaust manifold shown in  FIG. 5 . 
         FIG. 7  is a schematic of the power generation system shown in  FIG. 1  connecting an engine cylinder to controllers. 
         FIG. 8  is a schematic of a computer controller configured to operate the power generation system shown in  FIG. 1 . 
         FIG. 9  is a schematic of a modified version of the power generation system shown in  FIG. 1 , wherein an intake assist device and exhaust gas recirculation system are additionally provided. 
         FIG. 10  is a schematic of a modified version of the power generation system shown in  FIG. 9 , wherein a turbocharger is additionally provided. 
         FIG. 11  is a schematic side view of an expander usable in the power generation system shown in  FIG. 1 . 
         FIG. 12  is a schematic perspective view of the expander shown in  FIG. 11 . 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to the examples which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. Directional references such as “left” and “right” are for ease of reference to the figures. 
     Volumetric Energy Recovery Device (Expander) 
     In the disclosed systems, a volumetric energy recovery device or expander  20  is shown and described. While some details of the expander  20  are discussed in this subsection, additional structural and operational aspects can be found in Patent Cooperation Treaty (PCT) International Publication Number WO 2014/144701 and in United States Patent Application Publication US 2014/0260245, the entireties of which are incorporated herein by reference. 
     In general, the volumetric energy recovery device or expander  20  relies upon the kinetic energy and static pressure of a working fluid to rotate an output shaft  38 . The expander  20  may be an energy recovery device  20  wherein the working fluid  12 - 1  is the direct engine exhaust from the engine. In such instances, device  20  may be referred to as an expander or expander, as so presented in the following paragraphs. 
     With reference to  FIGS. 11 and 12 , it can be seen that the expander  20  has a housing  22  with a fluid inlet  24  and a fluid outlet  26  through which the working fluid  12 - 1  undergoes a pressure drop to transfer energy to the output shaft  38 . The output shaft  38  is driven by synchronously connected first and second interleaved counter-rotating rotors  30 ,  32  which are disposed in a cavity  28  of the housing  22 . Each of the rotors  30 ,  32  has lobes that are twisted or helically disposed along the length of the rotors  30 ,  32 . Upon rotation of the rotors  30 ,  32 , the lobes at least partially seal the working fluid  12 - 1  against an interior side of the housing at which point expansion of the working fluid  12 - 1  only occurs to the extent allowed by leakage which represents and inefficiency in the system. In contrast to some expanders that change the volume of the working fluid when the fluid is sealed, the volume defined between the lobes and the interior side of the housing  22  of device  20  is constant as the working fluid  12 - 1  traverses the length of the rotors  30 ,  32 . Accordingly, the expander  20  may be referred to as a “volumetric device” as the sealed or partially sealed working fluid volume does not change. 
     In the particular example shown at  FIGS. 11 and 12 , the expander  20  inlets and outlets are configured for use with a relatively low pressure working fluid, such as exhaust from an internal combustion engine or fuel cell. However, the following description is generally applicable for use with any type of a working fluid. The expander  20  includes a housing  22 . As shown in  FIG. 11 , the housing  22  includes an inlet port  24  configured to admit relatively high-pressure working fluid  12 - 1  from the heat exchanger  18  (shown in  FIG. 12 ). The housing  22  also includes an outlet port  26  configured to discharge working fluid  12 - 2  to the condenser  14  (shown in  FIG. 12 ). It is noted that the working fluid discharging from the outlet  26  is at a relatively higher pressure than the pressure of the working fluid at the condenser  14 . 
     As additionally shown in  FIG. 12 , each rotor  30 ,  32  has four lobes,  30 - 1 ,  30 - 2 ,  30 - 3 , and  30 - 4  in the case of the rotor  30 , and  32 - 1 ,  32 - 2 ,  32 - 3 , and  32 - 4  in the case of the rotor  32 . Although four lobes are shown for each rotor  30  and  32 , each of the two rotors may have any number of lobes that is equal to or greater than two, as long as the number of lobes is the same for both rotors, thereby resulting in symmetric rotors. Accordingly, when one lobe of the rotor  30 , such as the lobe  30 - 1  is leading with respect to the inlet port  24 , a lobe of the rotor  32 , such as the lobe  30 - 2 , is trailing with respect to the inlet port  24 , and, therefore with respect to a stream of the high-pressure working fluid  12 - 1 . 
     As shown, the first and second rotors  30  and  32  are fixed to respective rotor shafts, the first rotor being fixed to an output shaft  38  and the second rotor being fixed to a shaft  40 . Each of the rotor shafts  38 ,  40  is mounted for rotation on a set of bearings (not shown) about an axis X 1 , X 2 , respectively. It is noted that axes X 1  and X 2  are generally parallel to each other. The first and second rotors  30  and  32  are interleaved and continuously meshed for unitary rotation with each other. With renewed reference to  FIG. 5 , the expander  20  also includes meshed timing gears  42  and  44 , wherein the timing gear  42  is fixed for rotation with the rotor  30 , while the timing gear  44  is fixed for rotation with the rotor  32 . The timing gears  42 ,  44  are configured to retain specified position of the rotors  30 ,  32  and prevent contact between the rotors during operation of the expander  20 . 
     The output shaft  38  is rotated by the working fluid  12  as the working fluid undergoes expansion from the relatively high-pressure working fluid  12 - 1  to the relatively low-pressure working fluid  12 - 2 . As may additionally be seen in both  FIGS. 5 and 6 , the output shaft  38  extends beyond the boundary of the housing  22 . Accordingly, the output shaft  38  is configured to capture the work or power generated by the expander  20  during the expansion of the working fluid  12  that takes place in the rotor cavity  28  between the inlet port  24  and the outlet port  26  and transfer such work as output torque from the expander  20 . Although the output shaft  38  is shown as being operatively connected to the first rotor  30 , in the alternative the output shaft  38  may be operatively connected to the second rotor  32 . 
     In one aspect, the expander  20  can also be operated as a high volumetric efficiency positive displacement pump when driven by a motor/generator, such as a motor/generator  70 , as discussed in further detail below. 
     General System Architecture 
     With reference to  FIGS. 1 and 2 , a power generation system or engine system  100  is shown. The power generation system  100  can include a power plant  110 , for example an internal combustion engine or a fuel cell. In the example shown, the power plant  110  has an exhaust manifold  120  for receiving exhaust gases from the power plant  110 . An exhaust bypass assembly  130  is shown as being mounted to the exhaust manifold  120  while the expander  20  is shown as being mounted to the bypass assembly  130 . Accordingly, any fraction of exhaust from the power plant  110  can be selectively directed by the bypass assembly  130  through or around the expander  20 . The expander  20  is also shown as being coupled to the motor/generator  70  in  FIGS. 1 and 2 , wherein the output shaft  38  of the expander  20  is coupled to a drive shaft  72  of the motor/generator  70 . 
     With reference to  FIGS. 3 and 4 , the expander  20  and motor/generator  70  are shown in isolation from the power generation system  100 . As shown, the motor/generator  70  can be provided with a mounting flange  74  configured to mate against a corresponding mounting flange  27  of the expander  20 . The expander  20  and the motor/generator  70  can be secured together at the flanges  27 ,  74  via mechanical fasteners, such as bolts or screws  76 . The motor/generator  70  is also shown with ports  78  from which electrical leads can extend, for example to a battery. 
     With reference to  FIGS. 5 and 6 , the expander  20 , the exhaust bypass assembly  130 , and the exhaust manifold  120  are shown in isolation from the power generation system  100 . As shown, the exhaust manifold  120  is configured with four inlet ports  122  for receiving exhaust gases from a four cylinder engine. However, it should be understood that the any number of cylinders for the engine and corresponding ports  122  may be provided. The exhaust bypass assembly  130  is provided with a main body  132  having an inlet  133 , a first outlet  135 , and a second outlet  136 . As shown, a valve arrangement and actuator  137  is provided in the second outlet  136  to allow at least some of the exhaust gases to bypass around the expander. In an alternative configuration, the valve arrangement can be provided as a three-way valve to selectively direct exhaust air from the inlet  133  to either or both of the first and second outlets  135 ,  136  in any desired ratio between all of the exhaust gases being directed to the first outlet  135  and all of the exhaust gases being directed to the second outlet  136 . The first outlet  135  is shown as being in fluid communication with the inlet  24  of the expander  20 . The second outlet  136  can be coupled to another downstream device, such as a turbocharger, or can be more simply directed to the exhaust outlet of the power plant  110 . In the example shown, the exhaust bypass assembly  130 , the manifold  120 , and the expander  20  are provided with mounting flanges that can be mated and bolted together. Gaskets and/or seals can be provided to ensure the exhaust gases do not leak or otherwise escape as they pass from one component to the other. 
     Operational Configurations 
       FIG. 4  illustrates one cylinder  140  of the power plant  110 , when the power plant  110  is configured as a multi-cylinder engine. For example, the engine can comprise 2, 3, 4, 6, 8 or more cylinders. The cylinders  140  can be laid out in various configurations, such as in-line, V, or horizontally opposed. In the example presented, diesel combustion is shown, and so a fuel injector  142  direct injects fuel between an air intake valve  144  and an exhaust valve  146 . A piston  148  is connected to a crankshaft  150  of the power plant  110  via a connecting rod  152 . 
     Still referring to  FIG. 7 , and also to  FIG. 8 , appropriate computer control hardware, such as an on-board chip, Electrical Control Unit  200 , or dedicated variable valve timing controller  202  collects data on engine operating parameters, such as the speed of the engine crankshaft, valve location, piston location, operational status of the expander, etc. A central computing device can comprise allocation programming or multiple computing devices can send and receive data for processing. One or more processors process the data. One or more tangible memory devices store programming to execute algorithms necessary to implement a control strategy. RAM, ROM, or other memory devices can be used to store temporary data for operation on by the processor. 
     In the illustration, the variable valve timing controller  202  collects optional data from the crankshaft to determine the rotations per minute (RPMs) and rotational location of the crankshaft. Other optional data can include, for example, accelerator pedal location, throttle valve location, turbocharger speed, engine temperature, air temperature, exhaust temperature, etc. The collected data is used to determine the timing and quantity (pulse width) of fuel injection by a fuel injection controller  204 , and the timing for opening and closing the intake valve  111  and exhaust valve  112  by an intake valve controller  206  and an exhaust valve controller  208 , where provided. The data is also used to signal an expander controller  210  to power the motor/generator  70  to drive the expander  20  or to disconnect power for passive operation of the expander  20 . Additional control can be included to divert passively generated energy from the expander  20  to, for example, drive the motor/generator  70  and charge a battery  80 , augment crankshaft output, or power other system devices. 
     In one aspect, the expander  20  is coupled with the motor/generator  70  in the exhaust stream to improve engine scavenging. That is, the expander  20  is powered via the motor/generator  70  to positively displace exhaust flow, thereby scavenging exhaust out of the cylinder  140 . This reduces engine knock at low engine speeds. By assisting with exhaust exit out of the cylinder  140 , the variable valve timing controller  202  can adjust the exhaust valve timing to permit torque recovery for the full piston travel. The combustion stroke can be from top dead center TDC to bottom dead center BDC, even during low load or cold start conditions. Instead of opening the exhaust valve at time P, when the piston  148  has not travelled fully to bottom dead center BDC, the exhaust valve  146  opens at bottom dead center BDC. This operation can improve engine power output. 
     The expander  20  is able to scavenge the cylinder  140  independent of exhaust mass flow rate or engine speed, as measured at RPM sensor  216 , because the expander  20  is coupled to and independently powered by the motor/generator  70 . The expander  20  can be driven by the motor/generator  70  to impose a vacuum on the cylinder bore, which in turn reduces knock concerns and enables higher boost levels from the compressor  90 . This results in improved drivability of the vehicle and fuel efficiency improvement through down speeding and downsizing. This also enables for a change in valve timing and knock mitigation strategies. When the assisted scavenging is not needed, such as when the engine  110  is operating at peak flow, the expander  20  can passively accept exhaust flow and transmit rotational energy back to the system, for example, by charging the battery  80  or via an input pulley mounted to the shaft  38  to the system FEAD (front end accessory drive) of the engine  110 . 
     The expander  20  can also be operated at any engine speed to impose a vacuum on the cylinder  140  to remove the exhaust gasses. This gives the expander  20  a broad efficiency island to maintain expansion efficiency over a large engine operating range. This is in contrast to the operability of a turbocharger, which has a comparatively narrow operating range for peak efficiency. That is, the turbocharger is efficient for boosting the engine and for drawing exhaust in a narrow system operating range, but the expander  20  gives the system peak performance across a larger engine operating range. The expander  20  draws out the exhaust independently of the turbocharger action, the engine speed, and the engine temperature, because the expander can be linked with a motor/generator  70  that powers its positive displacement independently of these factors. 
     The fuel economy of the system is improved because the full combustion stroke is captured by the crankshaft  150 , increasing torque output. The longer stroke at low operating range augments cylinder deactivation (CDA) opportunities by permitting more torque recovery per cylinder, extending the range to deactivate the other cylinders. And, when the activated cylinder, in CDA mode, experiences a higher pressure than the deactivated cylinders, the expander  20  assists with pressure relief by drawing the exhaust out. 
     And, because the exhaust is drawn out, the boost provided by the turbocharger is more effectively taken in to the cylinder  140  for the next combustion cycle, thus improving boost. The vacuum of exhaust by the expander  20  permits a higher amount of compressed air to enter the cylinder  140  on the next intake, decreasing the scavenging burden on the intake charge, decreasing the need to open the intake and exhaust valve  144 ,  146  at the same time, further decreasing chances of knock, all while increasing torque output. The result is provision of more low end torque and better drivability. 
     Various configurations of the disclosed system are shown at  FIGS. 9 and 10 . Comparing  FIGS. 9 &amp; 10 , it is further possible to tailor the intake and the exhaust air flow by including an intake assist device  90  to provide additional air to the engine, while computer controlling the action of the expander. The intake assist device  90  is also shown at  FIG. 7  and schematically at  FIGS. 1 and 2 . Exhaust gas recirculation (EGR)  95  can be added to further reduce engine knock and to recirculate exhaust. In some examples, the expander  20  is utilized as an EGR pump to help address transient response issues with high levels of engine exhaust (i.e. a high pressure EGR strategy) or to feed back the EGR to the inlet of the intake assist device  90  (i.e. a low pressure EGR strategy). While it is possible to include a turbocharger  160 , it is also possible to eliminate the turbocharger  160  and use only an expander  20  at the outlet of the engine  110 . 
     Boost can be provided by an intake air assist device  90 , such as an electrically assisted variable speed (“EAVS”) supercharger, an electric boosting device such as a centrifugal compressor with an electric motor, or other boosting devices, such as a Roots-type, screw or scroll type supercharger, or an electrically assisted device with a planetary gear. Examples of EAVS superchargers usable in the disclosed system is shown and described at: U.S. Provisional patent application Ser. No. 11/776,834; U.S. Provisional Patent Application Ser. No. 61/776,837; U.S. Provisional Patent Application Ser. No. 62/133,038; PCT Application No. PCT/US2013/003094; and PCT Application No. PCT/US2015/11339, all of which are hereby incorporated by reference in their entireties. 
     The computer controller  200  shown at  FIG. 8  can be used for the systems shown in  FIGS. 9 &amp; 10 . An electronic control unit (ECU)  200  is an onboard computer control device comprising at least one processor  200   a  and tangible memory device  200   b . Control logic is stored in the memory  200   a  and operated on by the processor  200   b  to implement computer control. Multiple discrete modules are shown in  FIG. 8  and it is to be understood that the modules can be interconnected controllers, separate processors with affiliated storage and control logic, or the ECU  200  can comprise a central processor with allocation programming. The controllers, therefore, can be combined in to one or more processors or other communicating components such as integrated circuits. Various sensors can be utilized to collect data for processing. 
     Referring back to  FIGS. 9 &amp; 10 , the intake assist device that is controlled along with the expander to optimize engine breathing. The intake assist device  90  can be computer-controlled to provide a precision air charge, and the expander  20  can be computer-controlled to draw out the exhaust for exhaust scavenging. The ECU  200  further controls the valve timing, for independent opening and closing of the intake and exhaust valves  144 ,  146 . By controlling the intake flow and the outlet flow, it is possible to increase the compression ratio going to the cylinders  140 . This helps control transient engine performance and mitigate knock. 
     One aspect of  FIGS. 9 &amp; 10  entails the EGR  95 . The intake and exhaust control improves EGR operation by tailoring system pressure to draw and direct EGR gasses efficiently. The waste heat recovery performed by the expander  20  helps regulate exhaust pressure to enhance EGR. And, the intake assist device  90  also permits regulation of pressure and air flow to complement EGR efficiency. 
       FIG. 9  indicates along path  3  that exhaust can be directed from the engine  110  to an EGR control device  95 , such as a computer controlled EGR valve. Exhaust can be selectively let out of the system, or directed back to the intake manifold. Path  1  directs EGR gasses to the intake side of the engine  110 , for example, to the intake manifold or to a conduit connected to the outlet of the intake assist device. Path  2  directs EGR gasses to mix with fresh air and run through the intake assist device  90 . Path  4  indicates that it is possible to collect exhaust gasses after the expander  20  for recirculation by the EGR  95  in lieu of Path  3 . It is generally not practical to have all four paths in the same motive device, and so it is more likely that only paths  1  &amp;  3 ,  1  &amp;  4 ,  2  &amp;,  3 , or  2  &amp;  4  would be used, as air handling and system pressures dictate. For example, in a system with low pressure EGR gas, it is possible to direct the EGR gas for recirculation along path  2 , while a high pressure EGR gas preferably uses path  1 . But, because of the possibility to bypass air with the exhaust bypass assembly  130 , it is further possible to have a system with paths  2 ,  3  &amp;  4  or paths  1 ,  3 , &amp;  4 . 
       FIG. 10  indicates it is possible to include a turbocharger  160  for receiving exhaust along either one or both of paths  5  and  6 . Computer control of the EGR  95  directs exhaust out of the system, or along paths  1  or  2 . In lieu of a turbocharger  160 , it is also possible to use the expander  20  to draw out the exhaust, as above, and to boost the intake using a supercharger  90 . In one example, the output shaft  38  of the expander  20  is coupled to a planetary gear set which is also coupled to the motor/generator  70  and to an input shaft of the intake assist device  90 . In such an example, the intake assist device  90  can be a centrifugal compressor, wherein either or both of the expander  20  (via power generated from the exhaust gases) and the motor/generator  70  can be utilized to drive the compressor. Aspects of such a configuration are described in Patent Cooperation Publication Number WO2014/144701, the entirety of which is incorporated by reference herein. 
     The expander  20  can be sized relative to the engine  110  such that the pumping losses, or energy drain on the system, are recuperated or overcompensated for, by the torque additions from the lengthened combustion stroke. That is, the expander  20  is a relatively small device with a low energy burden on the system. The energy burden can be comparable to that of an alternator. 
     Other implementations will be apparent to those skilled in the art from consideration of the specification and practice of the examples disclosed herein. It is intended that the specification and examples be considered as exemplary only, with the true scope of the invention being indicated by the following claims.