Unthrottled Engine Operation using Variable Valve Actuation: The Impact on the Flow Field, Mixing and Combustion

Stansfield, P.; Wigley, Graham; Garner, Colin P.; Patel, Rajnikant; Ladommatos, Nicos; Pitcher, Graham; Turner, J. W. G.; Nuglisch, H.; Hélie, Jérôme

doi:10.4271/2007-01-1414

Cited by 28 publications

(15 citation statements)

References 4 publications

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“…However, the combination of EIVC with homogeneous Direct Injection (DI) has also begun to warrant interest, with the potential for further fuel savings if used together with increased compression ratio. For example, workers on the "Hotfire" collaborative project recently examined such effects in both optical and thermodynamic single cylinder SI engine assemblies (19,20). During this study, greatest fuel consumption benefits could be achieved if just one of the two inlet valves was actuated.…”

Section: Introductionmentioning

confidence: 99%

Combining Unthrottled Operation with Internal EGR under Port and Central Direct Fuel Injection Conditions in a Single Cylinder SI Engine

Cairns¹,

Todd²,

Hoffman³

et al. 2009

SAE Technical Paper Series

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The Engineering Meetings Board has approved this paper for publication. It has successfully completed SAE's peer review process under the supervision of the session organizer. This process requires a minimum of three (3) reviews by industry experts. All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of SAE. ISSN 0148-7191 Positions and opinions advanced in this paper are those of the author(s) and not necessarily those of SAE. The author is solely responsible for the content of the paper. SAE ABSTRACTThis experimental work was concerned with the combination of internal EGR with an early inlet valve closure strategy for improved part-load fuel economy. The experiments were performed in a new spark-ignited thermodynamic single cylinder research engine, equipped with a mechanical fully variable valvetrain on both the inlet and exhaust. During unthrottled operation at constant engine speed and load, increasing the mass of trapped residual allowed increased valve duration and lift to be used. In turn, this enabled further small improvements in gas exchange efficiency, thermal efficiency and hence indicated fuel consumption. Such effects were quantified under both port and homogeneous central direct fuel injection conditions. Shrouding of the inlet ports as a potential method to increase in-cylinder gas velocities has also been considered.

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Section: Introductionmentioning

confidence: 99%

Combining Unthrottled Operation with Internal EGR under Port and Central Direct Fuel Injection Conditions in a Single Cylinder SI Engine

Cairns¹,

Todd²,

Hoffman³

et al. 2009

SAE Technical Paper Series

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“…Compared to throttled operations, VVL with general valve timing and opening duration could help to maintain a higher in-cylinder pressure (or lower vacuum) during the early intake stage. Only during the late intake stage, lower valve lift will make the in-cylinder pressure be similar to the case with a throttle [8]. As demonstrated by Grimaldi et al [9], the pumping loss of a non-throttled VVL configuration could be decreased approximately by 50% compared to that of throttled conditions.…”

Section: Introductionmentioning

confidence: 89%

“…Meanwhile, while reduced MVL reduces the pumping losses and improves the air-fuel mixing and flame propagation, reduced swirl-tumble interaction as a result of the poor tumble flow might also affect the air-fuel mixing behavior. It has been reported in some research on diesel engines that air-fuel Energies 2015, 8,[13778][13779][13780][13781][13782][13783][13784][13785][13786][13787][13788][13789][13790][13791][13792][13793][13794][13795] mixing is highly dependent on the interaction of swirl and tumble flows and the angle of spray [20]. Considering at least these three influences, it will be worthwhile to undertake a more detailed study in future investigations to examine the operating characteristics of GDI engines with reduced MVL.…”

Section: Introductionmentioning

confidence: 99%

Effects of Variable Valve Lift on In-Cylinder Air Motion

et al. 2015

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An investigation into in-cylinder swirl and tumble flow characteristics with reduced maximum valve lifts (MVL) is presented. The experimental work was conducted in the modified four-valve optical spark-ignition (SI) test engine with three different MVL. Particle image velocimetry (PIV) was employed for measuring in-cylinder air motion and measurement results were analyzed for examining flow field, swirl and tumble ratio variation and fluctuating kinetic energy distribution. Results of ensemble-averaged flow fields show that reduced MVL could produce strong swirl flow velocity, then resulted in very regular swirl motion in the late stage of the intake process. The strong swirl flow can maintain very well until the late compression stage. The reduction of MVL can also increase both high-frequency and low-frequency swirl flow fluctuating kinetic energy remarkably. Regarding tumble flow, results demonstrate that lower MVLs result in more horizontal intake flow velocity vectors which can be easily detected under the valve seat area. Although the result of lower MVLs show a higher tumble ratio when the piston is close to the bottom dead centre (BDC), higher MVLs substantially produce higher tumble ratios which can be confirmed when most cylinder area lies in the measuring range.

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“…Use of valve deactivation has been shown to improve stability and reduce particulate emissions at low loads and very low (2 * 3 mm) lift valves [7,8]. In order to evaluate the effects of flexible valvetrain, the engine is modified with a dual-independent cam-phaser (DICP).…”

Section: Effect Of Valve Actuation For Low-speed Low-load Casementioning

confidence: 99%

CFD Simulation and Optical Engine Diagnostics of Mixture Formation Processes in DI Gasoline Engine with Flexible Valvetrain

Zheng

Lee

Matsumoto

et al. 2012

Lecture Notes in Electrical Engineering

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The interactions of multi-hole direct injection (DI) gasoline sprays with the charge motion are investigated using computational fluid dynamics simulation and high-speed imaging of sprays inside engines. Advanced flexible valve-train, with valve-deactivation and variable valve-lift, produces very dynamic charge flow motions, with varying tumble and swirl ratios. The resultant turbulent flow interact with off-axis multiple-hole DI injections, has important implications for the engine mixing and resultant combustion performance. The effects of injection timing on the bulk flow motion and fuel-air mixing in an optical accessible engine, in terms of tumble and swirl ratios, turbulence, and fuel wall film behaviors are first discussed for the conventional baseline engine geometry. The early-and latevariable intake valve closing events are then tested in a metal engine. The effects of different valve lifts and valve deactivation on the mixing and combustion are then discussed. Using integral analyses of the simulation results, the mechanisms in reducing fuel consumption and emissions in a variable valve-actuation engine, fuelled by side-mounted multi-hole DI injectors are illustrated. The implications to the engine mixing and the resultant combustion in a metal engine are demonstrated.

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Unthrottled Engine Operation using Variable Valve Actuation: The Impact on the Flow Field, Mixing and Combustion

Cited by 28 publications

References 4 publications

Combining Unthrottled Operation with Internal EGR under Port and Central Direct Fuel Injection Conditions in a Single Cylinder SI Engine

Combining Unthrottled Operation with Internal EGR under Port and Central Direct Fuel Injection Conditions in a Single Cylinder SI Engine

Effects of Variable Valve Lift on In-Cylinder Air Motion

CFD Simulation and Optical Engine Diagnostics of Mixture Formation Processes in DI Gasoline Engine with Flexible Valvetrain

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