Abstract

Engine downsizing is a proven approach for achieving a superior fuel efficiency. It is conventionally achieved by reducing the swept volume of the engine and by employing some means of increasing the specific output to achieve the desired installed engine power, usually in the form of an exhaust-driven turbocharger. However, because of the perceptible time needed for the turbocharger system to generate the required boost pressure, a characteristic of turbocharged engines is their degraded driveability in comparison with those of their naturally aspirated counterparts. Mechanical supercharging refers to the technology that compresses the intake air using the energy taken directly from the engine crankshaft. It is anticipated that engine downsizing which is realised either solely by a supercharger or by a combination of a supercharger and a turbocharger will enhance a vehicle's driveability without significantly compromising the fuel consumption at an engine level compared with the downsizing by turbocharging. The capability of the supercharger system to eliminate the high exhaust back pressure, to reduce the pulsation interference and to mitigate the surge issue of a turbocharged engine in a compound-charging system offsets some of the fuel consumption penalty incurred in driving the supercharger. This, combined with an optimised down-speeding strategy, can further improve the fuel efficiency performance of a downsized engine while still enhancing its driveability and performance at a vehicle level. This paper first reviews the fundamentals and the types of supercharger that are currently used, or have been used, in passenger car engines. Next, the relationships between the downsizing, the driveability and the down-speeding are introduced to identify the improved synergies between the engine and the boosting machine. Then, mass production and prototype downsized supercharged passenger car engines are briefly described, followed by a detailed review of the current state-of-the-art supercharging technologies that are in production as opposed to the approaches that are currently only being investigated at a research level. Finally, the trends for mechanically supercharging a passenger car engine are discussed, with the aim of identifying potential development directions for the future. Enhancement of the low-end torque, improvement in the transient driveability and reduction in low-load parasitic losses are the three main development directions for a supercharger system, among which the adoption of a continuously variable transmission to decouple the supercharger speed from the engine speed, improvement of the compressor isentropic and volumetric efficiency and innovation of the supercharger mechanism seem to be the potential trend for mechanically supercharging a passenger car engine.

Original languageEnglish
Pages (from-to)435-456
Number of pages22
JournalProceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering
Volume231
Issue number4
Early online date6 Apr 2016
DOIs
Publication statusPublished - 1 Mar 2017

Keywords

  • downsizing
  • engine
  • Mechanically
  • passenger car
  • supercharging

ASJC Scopus subject areas

  • Aerospace Engineering
  • Mechanical Engineering

Cite this

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title = "Observations on and potential trends for mechanically supercharging a downsized passenger car engine:a review",
abstract = "Engine downsizing is a proven approach for achieving a superior fuel efficiency. It is conventionally achieved by reducing the swept volume of the engine and by employing some means of increasing the specific output to achieve the desired installed engine power, usually in the form of an exhaust-driven turbocharger. However, because of the perceptible time needed for the turbocharger system to generate the required boost pressure, a characteristic of turbocharged engines is their degraded driveability in comparison with those of their naturally aspirated counterparts. Mechanical supercharging refers to the technology that compresses the intake air using the energy taken directly from the engine crankshaft. It is anticipated that engine downsizing which is realised either solely by a supercharger or by a combination of a supercharger and a turbocharger will enhance a vehicle's driveability without significantly compromising the fuel consumption at an engine level compared with the downsizing by turbocharging. The capability of the supercharger system to eliminate the high exhaust back pressure, to reduce the pulsation interference and to mitigate the surge issue of a turbocharged engine in a compound-charging system offsets some of the fuel consumption penalty incurred in driving the supercharger. This, combined with an optimised down-speeding strategy, can further improve the fuel efficiency performance of a downsized engine while still enhancing its driveability and performance at a vehicle level. This paper first reviews the fundamentals and the types of supercharger that are currently used, or have been used, in passenger car engines. Next, the relationships between the downsizing, the driveability and the down-speeding are introduced to identify the improved synergies between the engine and the boosting machine. Then, mass production and prototype downsized supercharged passenger car engines are briefly described, followed by a detailed review of the current state-of-the-art supercharging technologies that are in production as opposed to the approaches that are currently only being investigated at a research level. Finally, the trends for mechanically supercharging a passenger car engine are discussed, with the aim of identifying potential development directions for the future. Enhancement of the low-end torque, improvement in the transient driveability and reduction in low-load parasitic losses are the three main development directions for a supercharger system, among which the adoption of a continuously variable transmission to decouple the supercharger speed from the engine speed, improvement of the compressor isentropic and volumetric efficiency and innovation of the supercharger mechanism seem to be the potential trend for mechanically supercharging a passenger car engine.",
keywords = "downsizing, engine, Mechanically, passenger car, supercharging",
author = "Bo Hu and Turner, {James W.G.} and Sam Akehurst and Chris Brace and Colin Copeland",
year = "2017",
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AU - Turner, James W.G.

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AU - Brace, Chris

AU - Copeland, Colin

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N2 - Engine downsizing is a proven approach for achieving a superior fuel efficiency. It is conventionally achieved by reducing the swept volume of the engine and by employing some means of increasing the specific output to achieve the desired installed engine power, usually in the form of an exhaust-driven turbocharger. However, because of the perceptible time needed for the turbocharger system to generate the required boost pressure, a characteristic of turbocharged engines is their degraded driveability in comparison with those of their naturally aspirated counterparts. Mechanical supercharging refers to the technology that compresses the intake air using the energy taken directly from the engine crankshaft. It is anticipated that engine downsizing which is realised either solely by a supercharger or by a combination of a supercharger and a turbocharger will enhance a vehicle's driveability without significantly compromising the fuel consumption at an engine level compared with the downsizing by turbocharging. The capability of the supercharger system to eliminate the high exhaust back pressure, to reduce the pulsation interference and to mitigate the surge issue of a turbocharged engine in a compound-charging system offsets some of the fuel consumption penalty incurred in driving the supercharger. This, combined with an optimised down-speeding strategy, can further improve the fuel efficiency performance of a downsized engine while still enhancing its driveability and performance at a vehicle level. This paper first reviews the fundamentals and the types of supercharger that are currently used, or have been used, in passenger car engines. Next, the relationships between the downsizing, the driveability and the down-speeding are introduced to identify the improved synergies between the engine and the boosting machine. Then, mass production and prototype downsized supercharged passenger car engines are briefly described, followed by a detailed review of the current state-of-the-art supercharging technologies that are in production as opposed to the approaches that are currently only being investigated at a research level. Finally, the trends for mechanically supercharging a passenger car engine are discussed, with the aim of identifying potential development directions for the future. Enhancement of the low-end torque, improvement in the transient driveability and reduction in low-load parasitic losses are the three main development directions for a supercharger system, among which the adoption of a continuously variable transmission to decouple the supercharger speed from the engine speed, improvement of the compressor isentropic and volumetric efficiency and innovation of the supercharger mechanism seem to be the potential trend for mechanically supercharging a passenger car engine.

AB - Engine downsizing is a proven approach for achieving a superior fuel efficiency. It is conventionally achieved by reducing the swept volume of the engine and by employing some means of increasing the specific output to achieve the desired installed engine power, usually in the form of an exhaust-driven turbocharger. However, because of the perceptible time needed for the turbocharger system to generate the required boost pressure, a characteristic of turbocharged engines is their degraded driveability in comparison with those of their naturally aspirated counterparts. Mechanical supercharging refers to the technology that compresses the intake air using the energy taken directly from the engine crankshaft. It is anticipated that engine downsizing which is realised either solely by a supercharger or by a combination of a supercharger and a turbocharger will enhance a vehicle's driveability without significantly compromising the fuel consumption at an engine level compared with the downsizing by turbocharging. The capability of the supercharger system to eliminate the high exhaust back pressure, to reduce the pulsation interference and to mitigate the surge issue of a turbocharged engine in a compound-charging system offsets some of the fuel consumption penalty incurred in driving the supercharger. This, combined with an optimised down-speeding strategy, can further improve the fuel efficiency performance of a downsized engine while still enhancing its driveability and performance at a vehicle level. This paper first reviews the fundamentals and the types of supercharger that are currently used, or have been used, in passenger car engines. Next, the relationships between the downsizing, the driveability and the down-speeding are introduced to identify the improved synergies between the engine and the boosting machine. Then, mass production and prototype downsized supercharged passenger car engines are briefly described, followed by a detailed review of the current state-of-the-art supercharging technologies that are in production as opposed to the approaches that are currently only being investigated at a research level. Finally, the trends for mechanically supercharging a passenger car engine are discussed, with the aim of identifying potential development directions for the future. Enhancement of the low-end torque, improvement in the transient driveability and reduction in low-load parasitic losses are the three main development directions for a supercharger system, among which the adoption of a continuously variable transmission to decouple the supercharger speed from the engine speed, improvement of the compressor isentropic and volumetric efficiency and innovation of the supercharger mechanism seem to be the potential trend for mechanically supercharging a passenger car engine.

KW - downsizing

KW - engine

KW - Mechanically

KW - passenger car

KW - supercharging

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