New approach to turbochargers for four-cylinder gasoline engines

International Journal of Engine Research

Brace

2015

Engine downsizing, which is the use of a smaller engine that provides the power of a larger engine, is now considered a mega-trend for the internal combustion engine market. It is usually achieved using one or more boosting devices including a supercharger or a turbocharger. Although supercharging is beneficial for engine's transient response, turbocharging technology is more widely adopted considering its advantages in fuel efficiency. Compared to turbocharged compression ignition engines, turbocharged spark-ignition engines tend to be more challenging with respect to the gas exchange process mainly due to their higher pumping loss, the need for throttling and the fact that spark-ignition engines demand more controllability due to the mitigation of knock, particularly with regard to minimizing trapped residuals. These challenges encourage the entire gas exchange process of turbocharged spark-ignition engines to be regarded as a complete air management system instead of just looking at the boosting system in isolation. In addition, more research emphasis should be focused on novel approaches to improve the gas exchange process of downsized turbocharged spark-ignition engines because the refinement of the conventional technologies cannot provide continuous gains indefinitely and only innovative concept may improve the engine performance to meet the fuel efficiency target and the more stringent emission regulation in the future. This article will first briefly review knowledge of the current state of the art technologies that are in production as opposed to approaches that are currently only being investigated at a research level. Next, more novel methods of the gas exchange process are introduced to identify the improved synergies between the engine and the boosting machine. The major findings to improve the gas exchange process that emerge from this review comprise four aspects (depending on the location where the novel technologies are implemented) which are as follows: charge air pressurization/de-pressurization improvement, combustion efficiency enhancement within the chamber, valve event-associated development and exhaust system optimization. Although the interaction between these technologies on different aspects of the gas exchange process was found to be highly complex, the optimization or the combination of these technologies is anticipated to further improve a downsized turbocharged spark-ignition engine's performance.

Section: Downsized Turbocharged Si Engine Only At the Research Stagementioning

confidence: 99%

Section: Gas Exchange Process Metrics and Issues On Turbocharged Si Ementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Novel approaches to improve the gas exchange process of downsized turbocharged spark-ignition engines: A review

International Journal of Engine Research

Brace

2015

“…Currently, most of the supercharged passenger car gasoline engines are fitted with a fixed-ratio positive-displacement device, among which the Volkswagen 1.4 TSI, 7 Volvo T6 8,9 and Ultraboost 1,10–13 are three examples that are using both a turbocharger and a supercharger (all are Eaton type) to provide all the necessary boost. They have all demonstrated better performance compared to a similar-size turbocharged rival.…”

Section: Introductionmentioning

confidence: 99%

“…Although supercharged engines are not as fuel-efficient as their turbocharged counterparts at the same engine operating point, in the real world supercharged vehicles due to their capability to further downsize without largely affecting the driveability and to enable a down-speeding strategy from an enhanced low-end torque response may achieve better fuel efficiency and improved driveability simultaneously. 6 Currently, most of the supercharged passenger car gasoline engines are fitted with a fixed-ratio positivedisplacement device, among which the Volkswagen 1.4 TSI, 7 Volvo T6 8,9 and Ultraboost 1,[10][11][12][13] are three examples that are using both a turbocharger and a supercharger (all are Eaton type) to provide all the necessary boost. They have all demonstrated better performance compared to a similar-size turbocharged rival.…”

Section: Introductionmentioning

confidence: 99%

Experimental analysis of the V-Charge variable drive supercharger system on a 1.0 L GTDI engine

Proceedings of the Institution of Mechanical Engineers, Part D:

et al. 2017

A compound charging system that pairs a turbocharger with a supercharger seems to be a potential trend for future passenger car gasoline engines, as the strength of both could be enhanced and the deficiencies of each could be offset. The use of a fixed-ratio positive-displacement supercharger system on a downsized turbocharged gasoline engine has already appeared on the market. Although such systems can achieve enhanced low-end torque and improved transient response, several challenges still exist. An alternative solution to the fixed-ratio positive-displacement supercharger is the V-Charge variable ratio centrifugal supercharger. This technology utilizes a Torotrak continuously variable transmission (CVT) coupled to a centrifugal compressor for near silent boosting. With a wide ratio spread of 10:1 and rapid rate of ratio change, the compressor speed can be set independently of the engine speed to provide an exact boost pressure for the required operating points, without the need to recirculate the air through a bypass valve. A clutch and an active bypass valve can also be eliminated, due to the CVT capability to down-speed, thus improving the noise vibration and harshness performance. This paper will, for the first time, present and discuss the V-Charge technology optimization and experimental validation on a 1.0 L GTDI engine to achieve a better brake specific fuel consumption and transient response over the turbo-only and the fixed-ratio positive-displacement supercharger solution. The potential for the V-Charge system to increase the low-end torque and enable a down-speeding strategy is also discussed.

Observations on and potential trends for mechanically supercharging a downsized passenger car engine:a review

Turner

Proceedings of the Institution of Mechanical Engineers, Part D:

et al. 2016

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 stateof-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.