Patent Publication Number: US-2010115944-A1

Title: Boost assist device energy conservation using windmilling

Description:
This application claims the benefit of U.S. Provisional Application No. 60/891,765 filed Feb. 27, 2007. 
    
    
     TECHNICAL FIELD 
     The field to which the disclosure generally relates includes engine systems including a boost assist device. 
     BACKGROUND 
     Several technologies are emerging to improve fuel economy, emissions and performance of internal combustion engine powered vehicles. One of these technologies involves the addition of air boost assist devices. Examples of these boost assist devices include hydraulically driven devices, electrically driven devices, belt driven devices and pneumatically driven devices. These devices may be driven directly from the engine, such as with a belt or via a hydraulic pump (which may be driven by the engine), or via an alternator (which is driven by the engine). Alternatively, a boost assist device may be driven by stored energy such as in an accumulator or a set of batteries. In any case, the economical usage of energy (especially stored energy) is of primary importance due to sizing considerations, fuel economy considerations and performance considerations. 
     One of the factors that can have a significant impact on the efficient use of energy with these types of devices is the initial speed up of the boost assist device. This initial speedup can consume a significant amount of energy due to the need to overcome the inertia of the device and/or because the efficiency of the boost assist device at low speeds is often very poor. 
     SUMMARY OF EXEMPLARY EMBODIMENTS OF THE INVENTION 
     One embodiment of the invention includes windmilling a boost assist device by passing intake air through the boost assist device during operating modes where the device is not required to be operated (i.e., is not being actively powered). The windmilling effect will cause the boost assist device to rotate due to the windmilling effects of the air. This windmilling effect would normally not achieve full boosting device operating speeds, but will normally be sufficient to allow the boost assist device to avoid high energy usage during any initial speed up phase of operation when the boost assist device is called upon to be actively powered. In one embodiment of the invention the windmilling conserves energy used to drive the boost assist device. 
     Another embodiment of the invention includes increasing the windmilling effect and the speed of the rotating boost assist device by positioning an intake air swirl device at an inlet of the boost assist device. 
     Other exemplary embodiments of the invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while disclosing exemplary embodiments of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Exemplary embodiments of the invention will become more fully understood from the detailed description and the accompanying drawings, wherein: 
         FIG. 1  is a schematic diagram of an engine system according to one embodiment of the invention. 
         FIG. 2  is a logical flow chart illustrating a method of operating an engine system according to one embodiment of the invention. 
         FIG. 3  is a chart illustrating the change over time of engine speed, boost assist device speed, energy input to the boost assist device, and bypass valve position in an engine system operated without windmilling the boost assist device. 
         FIG. 4  is a chart illustrating the change over time of engine speed, boost assist device speed, energy input to the boost assist device, and bypass valve position in an engine system operated by windmilling the boost assist device according to one embodiment of the invention. 
         FIG. 5  is a chart illustrating the change over time of engine speed, boost assist device speed, energy input to the boost assist device, and bypass valve position in a system operated by selectively windmilling the boost assist device during selective operating regions of an engine system according to one embodiment of the invention. 
         FIG. 6  illustrates a boost assist device according to one embodiment of the invention. 
         FIG. 7  is a perspective view of an intake air swirl device suitable for positioning in an inlet of a boost assist device to increase windmilling effect and rotation of the boost assist device according to one embodiment. 
         FIG. 8  is another view of the intake air swirl device of  FIG. 7 . 
         FIG. 9  illustrates a portion of an engine system according to one embodiment of the invention. 
         FIG. 10  illustrates a portion of an engine system according to another embodiment of the invention. 
         FIG. 11  illustrates another embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     The following descriptions of the embodiments are merely exemplary in nature and are in no way intended to limit the invention, its application, or uses. 
     One embodiment of the invention includes windmilling a boost assist device by passing intake air through the boost assist device during operating modes where the device is not required to be operated (i.e., is not being actively powered). Doing this will cause the boost assist device to rotate due to the windmilling effects of the air. This windmilling effect normally may not achieve full boost assist device operating speeds, but will normally be sufficient to allow the boost assist device to avoid high energy usage during an initial speed up phase of operation when the boost assist device is called upon to be actively powered. In one embodiment of the invention the windmilling conserves energy used to drive the boost assist device. 
     Reducing the energy usage during initiation of an active power operating mode reduces the total energy usage of the boost assist device. This leads to the ability to reduce the size of the boost assist device (smaller energy storage, smaller drive system). It also helps improve energy efficiency and thus fuel economy. It can also help to improve system performance because the boost assist device achieves its target speed quicker. 
     Because the added restriction of a boost assist device in an inlet line to an engine can, under certain conditions, have a negative effect on engine operation, this operating mode may be utilized when the net effect on the overall engine system is positive. For example, when the engine is operating at full power, it may be desirable to not windmill the boost assist device as this may lead to an excessive restriction in the inlet line to the engine. In addition, the boost assist device would not need to be activated as the engine is transitioning out of this full engine power mode, so the initial state of the boost assist device is not critical (and hence windmilling to speed it up is unnecessary). 
     Referring now to  FIG. 1 , one embodiment includes an engine system  10  which may include one or more components as described hereafter. The engine system  10  may be used in a vehicle, such as an automobile or truck. In one embodiment, the engine system  10  may include an engine  12  such as, but not limited to, a diesel, gasoline or other combustible fuel engine. An air intake system  14  may include components and devices located upstream of the engine  12 . For example, the air intake system  14  may include plumbing connected to the engine  12  at one end and the plumbing may include an open end  18 . As used herein, the term plumbing includes any suitable conduit, tubes, hoses, passages, or the like. An optional air filter or cleaner  28  may be provided in the air intake system  14  at or near the open end  18  thereof. 
     An exhaust system  16  may be connected to the engine  12  to exhaust combustion gases out an open end  20  thereof. Optionally, a turbocharger  22  may be provided including a turbine  24  constructed and arranged to be turned by exhaust gas flowing through the plumbing of the exhaust system  16 . The turbocharger  22  may include a compressor  26  operatively connected to the turbine  24  for turning the compressor  26  to deliver compressed air through the intake system  14  plumbing to the engine  12 . 
     The air intake system  14  may include an air intake line  30  including a first segment  30 ′ which may extend from the open end  18  of the air intake system  14  plumbing to the turbocharger compressor  26 . A boost assist device  32  may be provided in the first segment  30 ′ and may be constructed and arranged to assist the turbocharger compressor  26  by selectively delivering compressed air through the air intake system  14  to the compressor  26  and to the engine  12 . The boost assist device  32  may include a drive mechanism  36  to receive any suitable drive power, and a compressor  34  coupled to and driven by the drive mechanism  36 . 
     A bypass line  42  may be provided to provide bypass air through a path bypassing the boost assist device  32 . In one embodiment of the invention, the bypass line  42  may be connected to the air intake line  30  at a first point  44  and at a second point  46 . 
     A valve  48 , such as a bypass valve, may be provided, preferably in the bypass line  42 , and may be constructed and arranged to fully or partially open and/or close to allow, prevent, or meter the flow of air through the bypass line  42 . As used herein the term close includes fully closed, and/or partly closed such that the valve  48  is also partly open. Likewise, the term open includes fully open, and/or partly open such that the valve is also partly closed. When the valve  48  is closed, air is forced to pass through the boost assist device  32  thereby windmilling the boost assist device  32 . 
     In an alternative embodiment, the valve  48  may be a 3-way valve positioned at the first point  44  or the second point  46 . When positioned at the first point  44 , the valve  48  is constructed and arranged to have one inlet port and two outlet ports. In this location, the valve  48  may be operated to allow flow through the bypass line  42  to the engine  12  and/or through the boost assist device  32 , or to close both outlet ports to stop flow though the bypass line  42  and through the boost assist device  32 , for example, to brake the engine  12 . When the 3-way valve  48  is positioned at the second point  46  the valve  48  has two inlets and one outlet, and functions similarly. 
     The engine system  10  may also include a controller system  50  constructed and arranged to control the valve  48  to fully open one or more of the inlet and outlet ports of the valve  48 , fully close any one or more inlet and outlet ports or to partially open or close any one or more of the inlet and outlet ports. The controller system  50  may be the same as or separate from the controller used to control the engine  12 . In one embodiment of the invention, the controller system  50  may control the valve  48  in response to a variety of input signals or data collected from sensors and like devices such as, but not limited to, an engine speed sensor  52 , an accelerator pedal position sensor  54 , a turbocharger component speed sensor  56 , and/or an exhaust sensor  58 . The controller system  50  may include any suitable processing device(s) for executing computer readable instructions or the like, and any suitable memory device(s) coupled to the processing device(s) for storing data and computer readable instructions. For example, engine speed data may be collected over time and stored in the memory device and later used to determine whether to windmill the boost assist device  32 . The valve  48  may be controlled based on information regarding the current engine speed and/or the engine speed that was recently collected in the past. Illustrative examples of using such signals and/or data to control the valve  48  will be provided hereafter. The controller system  50  may control the valve  48  based on information obtained representative of the engine load which may be directly measured or calculated or estimated from the fuel being commanded to the fuel injectors from the engine controller, from the throttle position, boost or MAP sensors, or the turbocharger compressor speed or from any of a variety of actuator command signals (e.g., fueling, VTG, etc.) 
     Optionally, a swirl device  96  may be provided at or near the inlet of the boost assist device  32  as will be described in detail hereafter. The swirl device  96  swirls air entering the boost assist device  32  to enhance windmilling. 
     The engine system  10  may also include an energy conversion device  38  for example for converting mechanical energy from the engine  12  to electrical energy, hydraulic energy, pneumatic energy, etc. Suitable energy routing devices  40  may be provided, such as valves, switches, and the like. Also, energy storage devices  39  such as batteries, accumulators, or the like may be provided. 
     Referring now to  FIG. 9 , in another embodiment of the invention the bypass line  42  may have an end  18 ′ open to the atmosphere to provide an air path from the open end  18 ′ through the bypass line  42  to the turbocharger compressor  26  or engine  12 . Preferably the end  18 ′ that is open to the atmosphere is connected to the same or a different air filter as the end  18 . A 3-way valve  48  may have a first inlet port (not shown) connected to the bypass line  42  and one outlet port connected by plumbing to the turbocharger compressor  26  or engine  12 . The 3-way valve  48  also includes a second inlet port (not shown) connected to the first segment  30 . 
     The valve  48  may be controlled in any suitable manner. For example, the valve  48  may be controlled so that the second inlet port (connected to the bypass line  42 ) may be open at times when the windmilling effect would have a negative effect on the engine  12 , for example, when the engine  12  is at high load and speed and the first inlet port may be fully open. Also, the valve  48  may be controlled so that the first inlet port (connected to the first segment  30 ′ including the boost assist device  32 ) may be may be fully closed and the second inlet port (connected to the bypass line  42 ) fully open to enhance the windmilling effect on the boost assist device  32  for example when the engine  12  is at idle. The valve  48  may be controlled to partially open either or both of the first and second inlet ports. The valve  48  may also be controlled to close both inlet ports to brake the engine if desired. 
     Referring now to  FIG. 10 , in a further embodiment of the invention, the bypass line  42  may have an end  18 ′ open to the atmosphere to provide an air path from the open end  18 ′ through the bypass line  42  to the turbocharger compressor  26  or engine  12 . A valve  48  may be provided in the bypass line  42  to permit or prevent air from flowing therethrough. A first segment  30 ′ is provided and is separate from the bypass line  42 . A boost assist device  32  may be provided in the first segment  30 . The first segment  30 ′ is connected to the turbocharger compressor  26  or engine  12  at one end and open to the atmosphere at another end  18 . A valve  48 ′ is provided in the first segment  30 . 
     The valves  48 ,  48 ′ may be controlled in any suitable manner. 
     For example, the valve  48 ′ may be open and the other valve  48  closed, when windmilling is desired, for example when the engine  12  is at idle. Also, the valve  48 ′ may be closed, and the other valve  48  open, when windmilling is not desired, for example when the engine  12  is at high load or speed or when the engine  12  is transitioning from a higher speed to a lower speed. Furthermore, both valves  48  and  48 ′ may also be controlled to close to brake (or stop) the engine  12  if desired, or to partially open to more freely control windmilling. 
     In yet another embodiment shown in  FIG. 11 , the first segment  30 ′ and the bypass line  42  may be defined by a common conduit with a divider therebetween, the boost assist device  32  in the first segment, and a flap valve  200  at an upstream or downstream end of the divider. In operation, the flap valve can be moved to at least two positions: a full boost position  204  to block airflow through the bypass line  42  and, thus, force all airflow through the boost assist device  32 ; and a partial boost or partial bypass position  206  to meter airflow through both the bypass line  42  and the boost assist device  32 . Unlike the embodiments with a three-way valve, however, the flap valve  200  does not block all airflow to brake the engine  12 . 
       FIG. 2  is a logic flow chart  60  illustrating a simplified algorithm that may be used to control the engine system  10  to selectively provide the windmilling operation according to one embodiment of the invention. The algorithm may be stored in suitable memory within the controller system  50  and may be executed by any suitable processor therein. The algorithm describes an approach where during modes of active boost assist, no windmilling is done. When not actively driving the boost assist device  32 , the algorithm decides if the cost of windmilling (i.e., the added inlet restriction) would be worth the potential benefit of having a spinning booster. If so, then the bypass valve  48  is closed and windmilling of the boost assist device is accomplished. Note that alternatively, one could provide a more continuous control of the bypass valve position. For example, under conditions where windmilling would be very beneficial (e.g., under operating conditions where boost assist is likely to be needed in the near future (near idle)) and the cost of windmilling is small or even negative (e.g., during in-gear braking) then the bypass valve  48  may be fully closed. Under conditions where boost assist is not likely to be needed in the near future (e.g. operating at high engine speed already) and the engine  12  would be impacted negatively by windmilling (e.g. at high load) then the bypass valve  48  may be fully opened. In intermediate situations where windmilling is only somewhat likely and there are only small negative impacts on the engine  12 , then the valve  48  may be set to some partially closed position which would provide some windmilling but at a reduced impact on the engine operation. 
     Referring now specifically to the flow chart  60  shown in  FIG. 2 , a method according to one embodiment may include a start point  62 . A first step  64  may include determining whether active boost assist is required. If yes, a second step  66  may include driving the boost assist device  32  by supplying energy to the drive mechanism  36  of the boost assist device  32  to drive the boost assist device compressor  34 . The energy supplied may be mechanical, electrical, pneumatic and/or hydraulic. Optionally, a third step  68  may include closing or substantially closing the valve  48  so that intake air flows substantially only through the boost assist device  32 . If boost assist is not required, a fourth step  72  is to not supply energy to the boost assist device  32 . A fifth step  74  is determining whether windmilling the boost assist device  32  is worth the potential negative effect on the engine  12 . If yes, a sixth step includes windmilling the boost assist device  32  by closing or substantially closing the valve  48  in the bypass line  42 . If not, a seventh step  80  includes opening the valve  48  in the bypass line  42 . Thereafter the method be repeated and may end at step  70 . 
       FIG. 3  is a chart illustrating the change over time of engine speed  82 , boost assist device speed  88 , energy input  86  to the boost assist device, and bypass valve position  84  in the engine system  10  operated without windmilling the boost assist device  32 .  FIG. 3  is an example plot showing boost assist device rotational speed during engine operation using a standard non-windmilling approach. Engine speed  82  and active energy input  86  to the booster is also shown. As can be seen, a large amount of energy is used to start the boost assist device  32  spinning from 0 RPM. The boost speed comes up relatively slowly due to the inefficiency at low speeds and the engine speed increases relatively slowly due to the lower boost available to it. 
       FIG. 4  is a chart illustrating the change over time of engine speed  82 , boost assist device speed  88 , energy input  86  to the boost assist device, and bypass valve position  84  in the engine system  10  operated by windmilling the boost assist device  32  according to one embodiment of the invention.  FIG. 4  shows a similar area of engine operation as in  FIG. 3  but wherein windmilling of the boost assist device  32  is utilized according to one embodiment of the invention. When the valve  48  is in a position that causes all or a percentage of the intake air to pass through the boost assist device  32  (fully closed or partially closed (as is the case in the figure)) during the initial non-energized portion of operation (1-9 seconds) the boost assist device speed is non-zero. When energy is applied directly to the boost assist device  32 , a smaller amount of energy is required. Also, the boost assist device  32  accelerates more quickly due to the better efficiency. Finally, the engine speed increases more quickly due to the faster availability of more air. 
     The example plot of  FIG. 4  is illustrative of some efficiency gains and some response performance gains. Of course in practice, the engine system  10  may be tuned to gain maximum performance (e.g. still use large initial energy, but spin the boost assist device  32  faster) or it may be tuned for maximum efficiency (e.g. input much less energy so that the baseline engine response is achieved but with much less energy), or again, some compromise of the two. 
       FIG. 5  is a chart illustrating the change over time of engine speed  82 , boost assist device speed  88 , energy input  86  to the boost assist device, and bypass valve position  84  in the engine system  10  operated by selectively windmilling the boost assist device during selective operating regions of the engine  12  according to one embodiment of the invention.  FIG. 5  shows an operating mode where, initially, direct power to the boost assist device  32  is turned off and then the valve  48  is fully open. As noted previously, this may be a situation in which the added restriction of the boost assist device  32  in the inlet air stream is overly detrimental to the efficient operation of the engine  12 . It may also be a situation in which the engine  12  is in an operating region which has no direct path to another operating region where active operation of the boost assist device  32  is required. The engine  12  will need to first pass through another operating region where the boost assist device  32  can then be windmilled, before it will be required to be actively driven. For example, the engine  12  may be operating at high load and speed, wherein boost assist may not be needed. The engine  12  will need to go through a deceleration period before driving of the boost assist device  32  is required again. So, as long as the engine  12  remains at high load and speed, the valve  48  can remain open. As the engine  12  decelerates, the valve  48  may begin to close in preparation of the next active boosting event. 
     Referring now to  FIG. 6 , an exemplary boost assist device  32  useful in embodiments of the invention may include a compressor housing  90 , housing inlet  92 , air compression wheel with associated blades  100  for compressing air, and the drive mechanism  36 . Examples of this boost assist device  32  include hydraulically driven systems, electrically driven systems, belt driven systems and pneumatically driven systems. Such devices may be driven directly from the engine  12 , such as with a belt or via a hydraulic pump (which may be driven by the engine), or via an alternator (which is driven by the engine). Alternatively, the boost assist device  32  may be driven by stored energy such as in an accumulator or a set of batteries. 
     Referring now to  FIGS. 7-8 , the windmilling effect may be enhanced and the speed of the rotating boost assist device  32  may be increased by positioning an intake air swirl device  96  at, in, or near the inlet  92  of the boost assist device  32 . In this embodiment of the invention, the swirl device  96  includes a plurality of blades  98  constructed and arranged to direct the intake air in a direction, which increases compressor speed such as by directed passage of air over compressor vanes. For example, the swirl device  96  may direct intake air toward the outer wall of the inlet port  92  and toward the housing wall. However, the invention is not limited to the specific embodiment shown in  FIGS. 7-8 . Any type of swirl device that enhances the windmilling effect and increases the speed of the rotation of the boost assist device  32  may be used. 
     The above description of embodiments of the invention is merely exemplary in nature and, thus, variations thereof are not to be regarded as a departure from the spirit and scope of the invention.