Abstract:
An aspect encompasses an engine system wherein a turbocharger is coupled to an internal combustion engine to receive exhaust from the engine and to provide compressed air for combustion to the engine. The turbocharger is driven to generate the compressed air by the exhaust from the engine. An expander/generator is coupled to the turbocharger to receive at least a portion of the compressed air and generate electricity by expanding the compressed air.

Description:
REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application claims the benefit, under 35 U.S.C. §119, of U.S. Provisional Patent Application No. 61/323,644, filed Apr. 13, 2010 and entitled “Waste Exhaust Energy Recovery from an Engine,” the entirety of which is hereby incorporated by reference. 
     
    
     BACKGROUND 
       [0002]    A turbocharger is a device, driven off the combustion exhaust of an internal combustion engine, that boosts the pressure and throughput of combustion air into the engine. The turbocharger has a compressor, typically a centrifugal compressor, for compressing the combustion air. The compressor resides on a common shaft with a turbine, typically a radial or axial turbine, for receiving the combustion exhaust and driving the compressor via the common shaft.  FIG. 1  shows a typical turbocharged engine arrangement having a reciprocating internal combustion engine  12  with an exhaust manifold  14  and a turbocharger  16  coupled to receive exhaust from the manifold  14 . The exhaust passes through the turbine stage of the turbocharger  16  and out an exhaust conduit  18 . A wastegate valve  20  upstream of the turbocharger  16  can be selectively operated (e.g., by an Engine Control Unit) to partially bypass the turbocharger  16 , directing some of the exhaust directly into the exhaust conduit  18 . The exhaust that passes through the turbine stage of the turbocharger  16  drives the compressor stage to compress ambient air received at the turbocharger  16  and output the compressed air through an intake conduit  22  into the intake of the engine  12 . The compressed air and fuel are combusted in the engine  12  to produce kinetic energy, typically in the form of rotating movement of an output shaft. 
       SUMMARY 
       [0003]    The concepts described herein are directed to generating electricity from waste exhaust energy. In certain instances, an expander/generator recovers exhaust energy that would otherwise be wasted, i.e. exhaust energy bypassed via wastegate valve or exhaust energy used to generate compressed air ultimately vented via the blow-off valve, in the form of excess compressed air and expands the excess compressed air to generate electricity. 
         [0004]    An aspect encompasses an engine system wherein a turbocharger is coupled to an internal combustion engine to receive exhaust from the engine and to provide compressed air for combustion to the engine. The turbocharger is driven to generate the compressed air by the exhaust from the engine. An expander/generator is coupled to the turbocharger to receive at least a portion of the compressed air and generate electricity by expanding the compressed air. 
         [0005]    An aspect encompasses a method where, with a turbocharger, excess compressed air beyond the operating requirements of an internal combustion engine is generated. This excess compressed air is expanded to generate electricity. 
         [0006]    An aspect encompasses a method performed on an internal combustion engine having a turbocharger coupled to the engine to receive exhaust from the engine, be driven to generate compressed air by the exhaust from the engine and to provide compressed air for combustion to the engine. In the method an expander/generator is coupled between the turbocharger and the engine to receive at least a portion of the compressed air and generate electricity by expanding the received compressed air. 
         [0007]    The details of one or more implementations are set forth in the accompanying drawings and the description below. Features, objects, and advantages will be apparent from the description and drawings, and from the claims. 
     
    
     
       DESCRIPTION OF DRAWINGS 
         [0008]      FIG. 1  is a schematic flow diagram of a prior art internal combustion engine system having a turbocharger. 
           [0009]      FIG. 2  is a schematic flow diagram of an internal combustion engine system having a turbocharger and being configured for waste exhaust energy recovery in accordance with the concepts described herein. 
           [0010]      FIG. 3  is a one quarter side cross-sectional view of an example expander/generator that could be used in an internal combustion engine system configured for waste exhaust energy recovery. 
           [0011]      FIG. 4  is a side view of an example expander/generator and electronics package in accordance with the concepts described herein. 
       
    
    
       [0012]    Like reference symbols in the various drawings indicate like elements. 
       DETAILED DESCRIPTION 
       [0013]      FIG. 2  shows an exemplary engine system configured for waste exhaust energy recovery. The system  10  includes a reciprocating internal combustion engine  12  of the type that has one or more pistons that reciprocate in one or more cylinders. In other instances, the engine  12  could be another type of engine. For example, the engine  12  could be a non-piston and/or non-turbine type engine, such as a Wankel rotary engine and/or other type of engine. 
         [0014]    A turbocharger  16  is coupled to receive combustion exhaust from combustion of fuel and air within the internal combustion engine  12  via the engine&#39;s exhaust manifold  14 . The exhaust passes through the turbine stage of the turbocharger  16  and out an exhaust conduit  18 . The exhaust that passes through the turbine stage of the turbocharger  16  drives the compressor stage to compress ambient air received at the turbocharger  16  and output the compressed air through an intake conduit  22  into the intake of the engine  12 . The compressed air and fuel are combusted in the engine  12  to produce kinetic energy, typically in the form of rotating movement of an output shaft. Although  FIG. 2  shows a configuration without a wastegate valve, in certain instances, a wastegate valve can be provided, as in  FIG. 1 , upstream of the turbocharger  16  and selectively operated (e.g., by an Engine Control Unit) to partially bypass the turbocharger  16  and direct some of the exhaust directly into the exhaust conduit  18 . 
         [0015]    The engine system includes an expander/generator  26  coupled to the intake conduit  22  to receive compressed air and direct the compressed air through the expander/generator  26  away from the engine  12 . In certain instances, the expander/generator  26  is a turbine (radial and/or otherwise) coupled to an electric generator having a rotor and a stator. The turbine is coupled either directly on a common shaft with the rotor (such that the turbine and rotor rotate at the same speed) or through a gear train (to increase or decrease the ratio of turbine rotations to rotor rotations). Compressed air from the intake conduit  22  is expanded through the turbine of the expander/generator  26 , thus causing the turbine to rotate the rotor and operate the generator to produce electricity. The air exiting the expander/generator  26  is vented to the atmosphere and/or, as described below, used for another purpose. A blow-off valve  24  can be included between the intake conduit  22  and expander  26  to selectably control, or restrict, the amount of air provided to the expander/generator  26  and/or bypass the expander/generator  26  completely. 
         [0016]    An intercooler  28  (air to air and/or air to liquid) can be provided in the intake conduit  22  to cool the compressed air prior to entry into the engine  12 . The expander/generator  26  can receive compressed air from either upstream or downstream of the intercooler  28 . However, when upstream as shown in  FIG. 2 , the air provided to the expander/generator  26  will be hotter than were the air provided to the expander/generator  26  from downstream of the intercooler  28 . In certain instances, the hotter air is less prone to condensation. In one example system, the compressed air before the intercooler is about 200° C., and after the intercooler is about 50° C. The air at 200° C. after expansion is expected to be 80-50° C. and less prone to condensation than if air at 50° C. were expanded to a much lower temperature. 
         [0017]    Typically, the turbocharger  16  will produce more compressed air than the engine requires during certain operating conditions. For example, in certain instances, when the turbocharger  16  is sized to obtain the necessary pressure and flow at low operating speeds and/or loads on the engine, it produces excess pressure and flow at higher operating speeds and/or loads. In a system without the expander/generator  26 , this excess compressed air would be reduced or eliminated by-passing a portion of the engine&#39;s exhaust from the turbocharger via a wastegate valve (i.e., to reduce the amount of compressed air generated by the turbocharger) or venting the generated compressed air from the intake conduit  22  via a blow-off or recirculation valve. However, in the present system, all or substantially all of the excess compressed air is provided to the expander/generator  26  and utilized to generate electricity. The turbocharger can thus be operated at full capacity (i.e., without venting exhaust with a wastegate valve) over the engine&#39;s  12  operating range, because any excess compressed air beyond the engine&#39;s requirements can be directed to the expander/generator  26 . In harnessing the excess compressed air, the expander/generator  26  recovers exhaust energy that would otherwise be wasted, i.e. exhaust energy bypassed via wastegate valve or exhaust energy used to generate compressed air ultimately vented via the blow-off or recirculation valve. In certain instances, the turbocharger  16  can be configured to produce more compressed air than the engine requires during additional and/or all operating conditions of the engine, including steady state or near steady state operations in a desired operating range, to produce more electricity than if the turbocharger  26  were conventionally sized. In instances where the engine  12  is driving a relatively constant speed load (e.g., driving a generator, pump, ship&#39;s propulsion and/or other load), the amount of excess air available can be readily controlled to be relatively constant and drive the expander/generator  26  to produce a relatively constant amount of power. 
         [0018]    In certain instances, the blow-off valve  24  is a pressure actuated valve configured to vent compressed air in the intake conduit  22  in response to a pressure in the intake conduit  22  exceeding a specified pressure (e.g., a pressure over atmospheric, a pressure over the pressure downstream of the engine&#39;s throttle and/or another pressure). In certain instances, the blow-off valve  24  is controlled to supply an amount of compressed air to the expander/generator  26  based on the compressed air requirements of the engine  12 . For example, an Engine Control Unit (ECU)  38  that is coupled to the engine  12  to control aspects of the engine  12 , such as the amount of fuel supplied to the engine, ignition timing, and/or other aspects, can also be coupled to the blow-off valve  24  to adjust the blow-off valve  24  to vary the amount of compressed air supplied to the expander/generator  26  based on the compressed air requirements of the engine  12 . In certain instances, the ECU can be configured to ensure that the engine&#39;s  12  compressed air requirements are met and any excess compressed air is supplied to the expander/generator  26 . 
         [0019]      FIG. 3  shows an example expander/generator  100  that can be used as expander generator  26 . Excess compressed air from the turbocharger enters the expander/generator  100  through an inlet conduit  105 , for example, coupled to intake conduit  22  and/or blow-off valve  24 , and thereafter expands through the turbine stage (including turbine wheel  120 ). The expanded air is then directed, through the generator stage (including stator  162  and rotor  140 ) to an outlet conduit  109 . In certain instances, the expanded air can cool the stator  162  and rotor  140  by passing through the air gap between the stator  162  and rotor  140  and/or by passing through passages around the exterior of the stator  162 . In certain instances, the expanded air can be the primary or only cooling system for the stator  162  and rotor  140 . 
         [0020]    The expander/generator  100  can include bearings  115  and  145  arranged to rotationally support the turbine wheel  120  and rotor  140 . In certain instances, one or more of the bearings  115  or  145  can include ball bearings, needle bearings, active and/or passive magnetic bearings, journal bearings, and/or other type of bearings. For example, the first and second bearings  115  and  145  can be magnetic bearings similar to those described in U.S. Pat. No. 6,727,617 assigned to Calnetix Inc. 
         [0021]    In certain instances, the rotor  140  can be a permanent magnet rotor, having rare earth and/or other permanent magnets retained by a non-magnetic, non-conductive sleeve. Rotation of the rotor  140  within the stator  162  generates electric power. 
         [0022]    Referring back to  FIG. 2 , the electric power generated by the expander/generator  26  can be transmitted to a generator electronics package  30  arranged outside of the expander/generator  26  to process the electric power before outputting for use. In certain instances, the electronics package  30  can be coupled to a utility power grid or an AC or DC bus for providing electric power to a load or loads for use. The electric power generated by the expander/generator  26  may be of a certain phase, frequency, voltage and be AC or DC, depending on the configuration of the generator and the operating speed of the expander/generator  26 . The electronics package  30  reconfigures the phase, frequency, and/or voltage of the electric power to a desired phase, frequency, and/or voltage, for example, to match the power carried on the grid or bus or other specified characteristics. In certain instances the electronics package includes an inverter and/or rectifier for converting power output from the expander/generator  26  from AC to DC or DC to AC depending on the configuration of the expander/generator  26  and the desired output. In certain instances, the electronics package  30  can also include electronics for controlling active magnetic bearings of the expander/generator  26 . 
         [0023]    In certain instances, the generator electronics package  30  may be used to output 3-phase 60 Hz AC power output at a voltage of about 400 VAC to about 480 VAC, preferably about 460 VAC. In certain instances, the generator electronics package may be used to output a DC voltage of about 12 V to about 270 V, including selected outputs of 12 V, 125 V, 250 V, and 270 V. Other settings, including other phases, frequencies, and voltages, AC or DC are within the concepts described herein. The expander/generator apparatus  100  can be used to generate power in a “stand alone” system in which the electrical power is generated for use in an isolated network (e.g., to power an isolated machine or facility) or in a “grid tie” system in which the power output is linked or synchronized with a power grid network (e.g., to transfer the generated electrical power to the power grid). An example expander/generator similar to expander/generator  100  is described in more detail in U.S. Pat. No. 7,638,892. 
         [0024]    The air exhausted from the expander/generator  26  can be used in cooling the generator electronics package  30 .  FIG. 2  shows the expander/generator  26  and the electronics package  30  arranged in a common housing  32  with air exhausted from the expander/generator  26  supplied into the generator electronics package  30 .  FIG. 4  shows the expander/generator  26  and the electronics package  30  arranged in sequential housings (expander/generator housing  34 , electronics package housing  36 ). In  FIG. 4  the housings  34 ,  36  are provided with flanges at their ends to facilitate coupling the expander/generator  26  and electronics package  30  in-line in a piping; however, in other instances the housings  34 ,  36  can be differently configured. 
         [0025]    The waste exhaust energy recovery concepts described herein can be readily retrofitted to an existing internal combustion engine  12  installation. In certain instances, since the expander/generator  26  can be configured as a separate stand-alone device, as contrasted to systems integrated with the turbocharger, it is not necessary to replace and/or reconfigure the turbocharger and/or existing wastegate valve system to incorporate the expander/generator  26  and its electronics package  30  into an existing engine system. Furthermore, as a stand-alone device, no additional ancillary systems are needed. Therefore, retrofitting the expander/generator  26  and its electronics package  30  into an existing engine system can be done by simply coupling the expander/generator  26  to the intake conduit  22 , between the turbocharger  16  and the engine  12 . A blow-off valve  24  can be provided between the expander/generator  26  and the intake conduit  22  to regulate flow to the expander/generator  26 . If configured in the same housing, the expander/generator  26  and electronics package  30  can be pre-coupled so that the outlet of the expander/generator  26  is directed to cool the electronics package  30 . Alternately, the electronics package  30  can be coupled to the outlet of the expander/generator  26  as in  FIG. 4 . 
         [0026]    The concepts described herein can be applied to multiple different engine applications. For example, the expander/generator can be installed on ship board engines, including those used for ship propulsion. The expander/generator can be installed on stationary engines, such as those used to run compressors, pumps, and other equipment. The expander/generator can be installed on road going and off-road vehicle engines, as well as locomotive engines. Still further example applications exist. 
         [0027]    A number of implementations have been described. Nevertheless, it will be understood that various modifications may be made. Accordingly, other implementations are within the scope of the following claims.