Patent Publication Number: US-2017356386-A1

Title: Integrated Internal Combustion Engine And Waste Heat Recovery System Including A Selective Catalytic Reduction Unit

Description:
RELATED APPLICATION 
     This application claims benefit of priority to U.S. Provisional Patent Application No. 62/349,272, filed on Jun. 13, 2016, the entire contents of which are hereby incorporated by reference. 
    
    
     FIELD 
     A system which integrates a waste heat recovery system, a selective catalytic reduction unit and an internal combustion engine to lower pollution and reduce energy consumption. 
     BACKGROUND 
     Conventional internal combustion engines (ICE) have a limited brake thermal efficiency. The energy produced during the combustion process can only partially be converted to useful work. Most of the fuel energy is rejected as waste heat in exhaust gases from the ICE. Waste heat recovery (WHR) systems can be used to recover some or all of the waste heat from the exhaust gases to improve the thermal efficiency of the engine and/or convert it to useful energy (e.g., electrical and/or mechanical energy). 
     WHR systems for use with ICEs can be a closed or open circuit, thermodynamic system that employs a heat driven specific volume increase of a working fluid to convert heat energy into motive power. The WHR system can utilize the Rankine cycle or the Organic Rankine cycle; however, other thermodynamic cycles are used in WHR systems, including, but not limited to, the trans- or supercritical (Organic) Rankine cycle and the open or closed Brayton cycle. 
     Additionally, Selective Catalytic Reduction (SCR) units are used in automotive applications to reduce the nitrogen oxide (NO x ) emissions from exhaust streams from internal combustion engines. Exhaust streams from ICEs can include a heterogeneous mixture of gaseous emissions including carbon monoxide, unburned hydrocarbons and NO x . In SCR units, a gaseous reductant is injected into the exhaust stream from an ICE and then reacted on a catalytic surface to reduce the NO x  concentration. SCR units require a significant amount of time to allow the reductant to sufficiently react with the catalytic surface to effectively reduce the NO x  concentration. In low temperature environments, a SCR unit may not efficiently clean the exhaust stream until several minutes after an engine has been started, therefore, the SCR units require high temperatures to effectively filter NO x . 
     Therefore, it would be beneficial to integrate an internal combustion engine, a SCR unit and a WHR system to allow for the combined benefits of a lower pollution rate and a lower energy consumption rate. 
     SUMMARY 
     Provided herein is an integrated internal combustion engine and waste heat recovery system including an internal combustion engine, a system of exhaust gas conduits connected to the internal combustion engine, a first heat exchanger in fluid communication with the exhaust gas conduits, a second heat exchanger in fluid communication with the exhaust gas conduits downstream of the first heat exchanger, a selective catalytic reduction unit positioned between the first and second heat exchangers along the exhaust gas conduits, a waste heat recovery (WHR) system and a mechanical connection. The WHR system includes a system of working fluid conduits in fluid communication with the first and second heat exchangers, wherein the first heat exchanger is positioned downstream of the second heat exchanger along the working fluid conduits; an expander positioned along the working fluid conduits downstream from the first heat exchanger; a condenser positioned along the working fluid conduits downstream from the expander; and a pump positioned along the working fluid conduits downstream from the condenser and upstream from the second heat exchanger. The mechanical connection connects the internal combustion engine and the expander. The first and second heat exchangers are configured to facilitate thermal communication between the working fluid conduits and the exhaust gas conduits. The working fluid conduits include bypass conduits around the heat exchangers and the exhaust gas conduits include bypass conduits around the heat exchangers. 
     In some embodiments, the WHR system includes a pressure-increasing device positioned along the working fluid conduits between the first and second heat exchanger. In some embodiments, the WHR system includes a flash tank positioned along the working fluid conduits upstream of the first heat exchanger and downstream from the expander. In some embodiments, the WHR system includes a second expander positioned along with working fluid conduits downstream from the second heat exchanger and upstream of the first heat exchanger. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above, as well as other advantages of the present embodiments, will become readily apparent to those skilled in the art from the following detailed description when considered in the light of the accompanying drawings in which: 
         FIG. 1  is a schematic view of a preferred embodiment of an integrated internal combustion engine and waste heat recovery system; and 
         FIG. 2  is a schematic view of another embodiment of an integrated internal combustion engine and waste heat recovery system; 
         FIG. 3  is a schematic view of another embodiment of an integrated internal combustion engine and waste heat recovery system; 
         FIG. 4  is a schematic view of another embodiment of an integrated internal combustion engine and waste heat recovery system; 
         FIG. 5  is a schematic view of another embodiment of an integrated internal combustion engine and waste heat recovery system; 
         FIG. 6  is a schematic view of another embodiment of an integrated internal combustion engine and waste heat recovery system; and 
         FIG. 7  is a schematic view of another embodiment of an integrated internal combustion engine and waste heat recovery system. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     It is to be understood that the invention may assume various alternative orientations and step sequences, except where expressly specified to the contrary. It is also to be understood that the specific devices and processes illustrated in the attached drawings, and described in the following specification are simply exemplary embodiments of the inventive concepts. Hence, specific dimensions, directions or other physical characteristics relating to the embodiments disclosed are not to be considered as limiting. 
     Referring now to  FIG. 1 , a preferred embodiment of an integrated system including an internal combustion engine and waste heat recovery system (an integrated system)  110  is depicted. In one embodiment, an integrated system  110  includes an internal combustion engine (ICE)  112 , a mechanical connection  114 , a first heat exchanger  116 , a second heat exchanger  118 , a SCR unit  120  and a waste heat recovery (WHR) system  200 . 
     The WHR system  200  includes a system of working fluid conduits  210  in fluid communication with the first and second heat exchangers  116 ,  118 , an expander  212  positioned along the working fluid conduits downstream from the first heat exchanger  116 , a condenser  214  positioned along the working fluid conduits downstream from the expander  212 , a pump/compressor  216  positioned along the working fluid conduits downstream from the condenser  214  and upstream from the second heat exchanger  118 . 
     The system of working fluid conduits  210  connect the heat exchangers  118 ,  116 , the expander  212 , the condenser  214  and the pump  216 . In some embodiment, the working fluid conduits  210  circulate the working fluid through conduits to the second heat exchanger  118 , to the first heat exchanger  116 , to the expander  212 , to the condenser  214  and to the pump  216  as shown in  FIG. 1 . The system of working fluid conduits  210  can include additional components including, but not limited to, seals which prevent loss of working fluid or which prevent contaminants from entering the working fluid and valves for controlling the flow rate and pressure of the working fluid in the conduits. The working fluid can be an organic or non-organic fluid including, but not limited to, toluene, water/methanol mixture, water/ethanol mixture, water, dodecane, hexamethyldisiloxane. 
     As depicted in  FIG. 1 , the pump  216  is in fluid communication with the second heat exchanger  118  and the condenser  214 . The second heat exchanger  118  facilitates thermal communication between working fluid in working fluid conduit  218  containing the working fluid from exiting the pump  216  and a conduit of exhaust gases  306  of exiting the SCR unit  120 . The fluid conduit  218  is part of the system of working fluid conduits  210  that circulates the working fluid through the WHR system  200 . 
     The exhaust gas conduit  306  exiting the SCR unit  120  is part of a system of exhaust gas conduits  300  which transfers exhaust gases from the ICE  112 , to the first heat exchanger  116 , to the SCR unit  120 , to the second heat exchanger  118  and to an exhaust outlet. The system of exhaust gas conduits  300  can include additional components including, but not limited to, seals which prevent contaminants from entering the working fluid and valves for controlling the flow rate and pressure of the exhaust gases in the conduits. 
     In some embodiments, a filter is positioned along the system of exhaust gas conduits  300  upstream of the SCR unit  120  to remove particulates from the exhaust gases exiting the ICE before entering the SCR unit  120 . The filter can be, but is not limited to, a diesel particulate filter. In some embodiments, a filter is positioned along the exhaust gas conduits  300  before the SCR unit  120  to remove particulates from the exhaust gases in a conduit  304  exiting the first heat exchanger  116  before entering the SCR unit  120 . 
     The SCR unit  120  converts NOx in the exhaust gases exiting the ICE  112  into nitrogen and water vapor and in some cases converts urea into carbon dioxide and ammonia. The ammonia produced then reacts with the nitrous oxides to form nitrogen and water. 
     Further, as shown in  FIG. 1 , the expander  212  is in fluid communication with the condenser  214  and the first heat exchanger  116 . In some embodiments, the expander  212  is positioned along the working fluid conduit system  210  upstream of the condenser  214  and downstream of the first heat exchanger  116 . The first heat exchanger  116  facilitates thermal communication between the exhaust gases in an exhaust/outlet conduit  302  of the ICE  112  and a fluid conduit  220  containing the working fluid from the second heat exchanger  118 . 
     In one embodiment, the first heat exchanger  116  is a high temperature heat exchanger that heats and/or evaporates the working fluid while keeping the exhaust gases at a temperature required for the SCR unit  120  to effectively filter out NO x  in the exhaust gases. 
     As the working fluid passes through the heat exchangers  116 ,  118 , the working fluid is heated and, depending on the thermodynamic cycle utilized, evaporated by energy imparted to the working fluid by the exhaust gases. As a result, the working fluid leaves the first heat exchanger  116  in a gaseous state. In some embodiments, the integrated system  110  utilizes a Rankine thermodynamic cycle. The expander  212  receives the heated working fluid from the first heat exchanger  116 , extracts mechanical work that is passed via the mechanical connection  114  to the ICE  112  and releases the working fluid towards the condenser  214 . At the output of the expander  212 , the working fluid can be in a partial gaseous state and the condenser  214  reduces the working fluid specific volume prior to recirculating the working fluid back to the heat exchangers  116 ,  118  using the pump/compressor  216  that is upstream from the condenser  214 . In some embodiments, the expander  212  can be an energy conversion turbine or an axial piston engine. 
     In some embodiment, the mechanical connection  114  can be, but is not limited to a gear assembly including a speed increasing gear assembly, a speed reduction gear assembly, a planetary gear reduction assembly or a direct one-to-one gear assembly. 
     The additional mechanical work provided to the ICE  112  through the mechanical connection  114  supplements the power produced by the ICE  112 . In some embodiments, a control system can be used to control the amount of power supplied to the ICE  112 . 
     In some embodiments, a first heat exchanger bypass conduit  308  is included around the first heat exchanger  116  so that some or all of the exhaust gases in the exhaust gas conduits from the ICE  112  and/or a reductant can bypass the first heat exchanger  116 . 
     In some embodiments, a second heat exchanger bypass conduit  222  can be included around the first heat exchanger  116  so that some or all of the working fluid from the second heat exchanger  118  can bypass the first heat exchanger  116 . Bypass valves (not shown) are used to selectively open and close the bypass conduits  308 ,  222 . By controlling the valves, the first heat exchanger  116  can be bypassed if the temperature of the exhaust gases  302  would become too low for the SCR  120  to effectively remove the NO x  when passing through the first heat exchanger  116 . 
     In some embodiments, a third heat exchanger bypass conduit  310  is included around the second heat exchanger  118  so that the some or all exhaust gases exiting the SCR unit  120  in conduit  220  can bypass the second heat exchanger  118 . Additionally, in some embodiments, a fourth bypass conduit  224  is included around the second heat exchanger  118  so that some or all of the working fluid from the pump  216  can bypass the second heat exchanger  118 . 
     Bypass valves (not shown) are used to selectively open and close the bypass conduits  308 ,  222 ,  310 ,  224  to control the flow through bypass conduits  308 ,  222 ,  310 ,  224 . The bypass valves may be any suitable type of valve capable of controlling the flow of the working fluid or exhaust gases. For examples, the valves can be two-way valves. 
     In one embodiment, the heat exchangers  116 ,  118  are counter-flow heat exchangers, but other known heat exchangers including, but not limited to, cross-flow and parallel flow heat exchangers may be used. 
     In some embodiment, the integrated system  110  includes a control system (not shown) in communication with the system components including, but not limited to, the ICE  112 , mechanical connection  114 , pump/compressor  216 , expander  212 , condenser/cooler  214 , first heat exchanger  116 , second heat exchanger  118 , SCR unit  120 , bypass valves and other valves. The control system can be used to control the aspects of the system including, but not limited to, the temperature and flow rates of various streams and components of the integrated system  110 . For example, the control system can be configured to selectively open and close bypass valves around the heat exchangers  116 ,  118  to control the temperature of the inlet streams into the SCR unit  120 . 
     The control system can include a central process unit (CPU) as well as various sensors including, but not limited to, pressure, temperature and flow rate sensors. The control system can continuously send and receive signals form the components of the system and the sensors to control and monitor the operation of various components of the integrated system  110  as well as the integrated system  110  as a whole. 
     In some embodiments, the control system can include an electronic control unit that monitors the performance of the ICE  112  and other components. The control system can use predetermined control parameters registered within the CPU to control the integrated system  110 . The predetermined parameters can be based on information such as, but not limited to, the internal combustion engine speed, torque and throttle position as well as an expected pre-catalyst NOx and unburnt hydrocarbons concentration in the exhaust gases exiting the ICE from an ICE operating map. 
     Additionally, the CPU can use algorithms which factor in future road conditions and/or expected speed or road inclination data from a telematics or navigation system to estimate future heat load and pre-catalyst emissions. For example, when a negative slope in the road is detected ahead and the heat load tends to decrease below a value where the catalyst is active, the control system can raise the temperature of the SCR unit  120  in advance, e.g. by using one of the bypass conduits  308 ,  222 , to overcome a driving phase with low temperature of the exhaust gasses exiting the ICE  112 . 
     Those of skill will recognize that the control system described herein, for example, could be implemented as electronic hardware, software stored on a computer readable medium and executable by a processor, or combinations of both. The hardware or software used depends upon the particular application and design constraints imposed on the overall system. For example, the CPU can include a general purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general-purpose processor could be a microprocessor, but in the alternative, the processor could be any conventional processor, controller, microcontroller, or state machine. A processor could also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration. Software associated with such modules could reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, a hard disk, a removable disk, a CD-ROM, or any other suitable form of storage medium known in the art. An exemplary storage medium is coupled to the processor such the processor reads information from, and write information to, the storage medium. In the alternative, the storage medium could be integral to the processor. 
     In some embodiments, a reductant is added to the integrated system  110  and can be, but is not limited to, urea, ammonia or other similar fluids. The reductant is added into the exhaust gases in the conduit  302  prior to the exhaust gases entering the first heat exchanger  116  via a conduit  312 . The reductant is added prior to the first heat exchanger  116  to allow the reductant to uniformly mix with the exhaust gases from the ICE  112  prior to entry into the SCR unit  120 . In one embodiment, the reductant can be added to the exhaust gases from the ICE  112  via spraying. In some embodiment, the conduit  312  is an injection device  312  allowing the reductant to be directly injected directly in the exhaust gases as shown in  FIG. 1 ; however, the reductant can also be preheated or even premixed in some other fluid, such as hot air, to allow for improved dilution within the exhaust gases. 
     In one embodiment, the exhaust gases with the reductant diluted therein enters the SCR unit  120  via a conduit  304 . In some embodiments, the SCR unit  120  in which most of the catalytic reduction of the NO x  occurs includes a catalytic surface having a catalytic material thereon. In some embodiments, a portion of the catalytic material found in the SCR unit  120  is additionally found in at least a portion of heat exchangers  116 ,  118 . By including the catalytic material in the heat exchangers  116 ,  118 , the size of the SCR unit  120  can be reduced, thereby reducing the total cost and size of the integrated system  110 . Additionally, this configuration allows the total length of fluid conduits that the exhaust gases travel through is reduced and, thus, the friction and corresponding backpressure in the ICE  112  is reduced. 
     In one embodiment, the reductant is a urea solution that decomposes to ammonia in the exhaust gases, and is subsequently absorbed by the SCR unit  120 . The temperature of the exhaust gases and reductants entering the SCR unit  120  must be high enough so that the chemical reaction can effectively occur. Therefore, the control system can control the flow rate of the exhaust gases and working fluid in in the first heat exchanger  116  to achieve a desired set temperature for the exhaust gases in the outlet conduit  304  of the heat exchanger  116  to optimize the operation of the SCR unit  120 . 
     The exhaust gases in the conduit  306  leaving the SCR unit  120  enter the second heat exchanger  118 . In some embodiments, the second heat exchanger  118  is a low temperature heat exchanger and allows heat exchange between the exhaust gases from the SCR unit  120  and the working fluid leaving the pump  216 . The arrangement of the first and second heat exchangers  116 ,  118  in a two-stage heat exchanger configuration ensures that the working fluid reaches the maximum temperature possible as it exits the first heat exchanger  116  while maintaining the required temperature of exhaust gases in the conduit  304  entering the SCR unit  120 . The high temperature of the working fluid leaving the first heat exchanger  116  has a significant effect on the efficiency of the integrated system  110 . Therefore, the control system can control the flow rate of the exhaust gases in conduit  302  and the working fluids in conduit  220  to achieve a desired set temperature and/or pressure for the working fluid of the heat exchanger  116  to optimize the operation of WHR system  200 . 
       FIG. 2  depicts another embodiment of the integrated system  110 . In this figure, elements having the same number as those in  FIG. 1  work as described herein above, unless noted otherwise, and are described again only for clarity. 
     As shown in  FIG. 2 , in one embodiment the expander  212  is connected to a generator  128 . The generator  128  converts the mechanical energy of the expander  212  to electric energy. The electric energy can be used by other systems in the vehicle, including, but not limited to the vehicle&#39;s electric system. In some embodiments, the generator  128  is connected to an energy storage device  130  including, but not limited to, a battery. In some embodiments, the generator  128  may additionally have a mechanical connection with the ICE  112  with possible selective engagement. This connection may be used to transfer energy from the ICE  112  to the generator  128 , from the expander  212  to the ICE  112  or from the ICE  112  to the expander  212 . 
       FIG. 3  depicts another embodiment of the integrated system  110 . In this figure, elements having the same number as those in  FIGS. 1-2  work as described herein above, unless noted otherwise, and are described again only for clarity. 
     As shown in  FIG. 3 , in another embodiment, the integrated system  110  includes a pressure-increasing device  226  between the heat exchangers  116 ,  118  along the working fluid conduit system  210 . The pressure-increasing device  226  can be, but is not limited to, a pump, compressor or pressure increasing injector. The pressure-increasing device  226  allows the second heat exchanger  118  to operate at a lower pressure and still achieve the desired higher pressure of the working fluid at the outlet of the first heat exchanger  116  compared to a system without the pressure-increasing device  226 . By operating at a lower pressure, the mechanical stresses on the second heat exchanger  118  are reduced, resulting in a reduction in the weight and cost of the second heat exchanger  118 . Additionally, the pump/compressor  216  can be reduced in size to handle a working fluid at a lower pressure compared to a system without the pressure-increasing device  226 . 
     In some embodiments, where the integrated system  110  utilizes a Rankine thermodynamic cycle, the second heat exchanger  118  does not boil the working fluid and the pressure-increasing device  226  is a liquid pump, which consumes a lower amount of energy and increases the cycle efficiency as compared to a system using a pressure-increasing device in the gaseous regime. 
     In another embodiment, the working fluid leaves the first heat exchanger  116  in a liquid or partially evaporated phase. The working fluid in at least partial liquid phase, can enter the expander  212  and the expander  212  vaporizes the working fluid. In this embodiment, the expander  212  has a large volumetric expansion ratio to accommodate the at least partial liquid phase working fluid. 
       FIG. 4  depicts an additional embodiment of the integrated system  110 . In this figures elements having the same number as those in  FIGS. 1-2  work as described herein above, unless noted otherwise, and are described again only for clarity. 
     As shown in  FIG. 4 , in another embodiment, the integrated system  110  does not include a pressure-increasing device. The integrate system  110  utilizes a flash cycle to supply only vapor to the expander  212 . A flash tank  228  is in fluid communication with the first heat exchanger  116  via the working fluid conduit system and separates the working fluid into liquid and vapor phases. The liquid phase of working fluid flows from the flash tank  228  and is combined with the working fluid leaving the expander  212  before entering the condenser  214 . The vapor phase of the working fluid exits the flash tank and flows upstream to the expander  212 . The flash tank  228  can include a pressure decreasing nozzle (not shown), which causes part of the liquid contained in the fluid to vaporize. 
     In some embodiments, the liquid phase of the working fluid that remains in the flash tank  228  is fed through a pressure-reducing device  230  and is fed into the condenser  214  to ensure that any gas remaining in the liquid phase is condensed to avoid cavitation in the pump  216  downstream. 
       FIG. 5  depicts an additional embodiment of the integrated system  110 . In this figures elements having the same number as those in  FIGS. 1-2  work as described herein above, unless noted otherwise, and are described again only for clarity. 
     In some embodiments, as shown in  FIG. 5 , the integrated system  110  includes a pressure-increasing device  226  and a flash tank  228 . All or a portion of the liquid phase working fluid exiting the flash tank  228  can be combined with preheated working fluid leaving the second heat exchanger  118  before the working fluid enters the pressure-increasing device  226  and all or a portion of the liquid phase fluid exiting the flash tank  228  can be combined with working fluid exiting the pump  216 . The pressure-increasing device  226  provides a sufficient pressure difference between the flash tank  228  and the second heat exchanger  118  to ensure that the liquid phase working fluid flows toward the first heat exchanger  116 . 
       FIG. 6  depicts another embodiment of the integrated system  110 . In this figure, elements having the same number as those in  FIGS. 1-2  work as described herein above and are described again only for clarity. As shown in  FIG. 6 , the integrated system  110  utilizes a second expander  232  positioned along the system of working fluid conduits  210  between downstream of the second heat exchanger  118  and upstream of the first heat exchanger  116 . The second expander  232  is in fluid communication with the second heat exchanger  118  and the first heat exchanger  116 . The working fluid leaving the second heat exchanger  118  enters the second expander  232 . The second expander  232  receives the heated working fluid from the second heat exchanger  118 , extracts mechanical work and releases the working fluid towards the first heat exchanger  116 . The first heat exchanger  116  re-heats the working fluid. The working fluid leaving the first heat exchanger  116  is directed towards the first expander  212 . The second expander  232  can be mechanically connected to the first expander  212 . Expanders  212 ,  232  can be connected to the mechanical connection  114 . 
       FIG. 7  depicts another embodiment of the integrated system  110 . In this figure, elements having the same number as those in  FIGS. 1-2  work as described herein above and are described again only for clarity. As shown in  FIG. 7 , the integrated system  110  utilizes a second expander  232  positioned along the system of working fluid conduits  210  between downstream of the second heat exchanger  118  and upstream of the first heat exchanger  116 . The second expander  232  is in fluid communication with the second heat exchanger  118  and the first heat exchanger  116 . The working fluid leaving the second heat exchanger  118  enters the second expander  232 . The second expander  232  receives the heated working fluid from the second heat exchanger  118 , extracts mechanical work and releases the working fluid towards the first heat exchanger  116 . The first heat exchanger  116  re-heats the working fluid. The working fluid leaving the first heat exchanger  116  is directed towards the first expander  212 . The second expander  232  can be mechanically connected to the first expander  212 . Expanders  212 ,  232  can be connected to the mechanical connection  114 . Additionally, a flash tank  234  is placed in the working fluid conduit downstream from the second heat exchanger  118  and upstream from the second expander  232 . The flash tank  234  provides working fluid in vapor phase to the second expander  232  and working fluid in liquid phase to the first heat exchanger  116   
     In some embodiment, a pressure-decreasing device  236  is positioned along the working fluid conduits connecting the flash tank  234  and the first heat exchanger  116 . 
     The integrated systems  110  as described above can be included as part of a motor vehicle, in particular, but not exclusively, to a commercial vehicle. 
     Although a limited number of exemplary embodiments are described herein, those skilled in the art will readily recognize that there could be variations, changes and modifications to any of these embodiments and those variations would be within the scope of the disclosure. In accordance with the provisions of the patent statutes, the present invention has been described in what is considered to represent its preferred embodiments. However, it should be noted that the embodiments can be practiced otherwise than as specifically illustrated and described without departing from its spirit or scope.