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Feasibility study of operating two-stroke Miller cycles on a four-stroke platform through variable valve train.

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posted on 25.01.2016 by Lucas D Pugnali, Rui Chen
A 2-stroke combustion cycle has higher power output densities compared to a 4-stroke cycle counterpart. The modern down-sized 4-stroke engine design can greatly benefit from this attribute of the 2-stroke cycle. By using appropriate variable valvetrain, boosting, and direct fuel injection systems, both cycles can be feasibly implemented on the same engine platform. In this research study, two valve strategies for achieving a two-stroke cycle in a four-stroke engine have been studied. The first strategy is based on balanced compression and expansion strokes, while the gas exchange is done through two different strokes. The second approach is a novel 2-stroke combustion strategy - here referred to as 2-stroke Miller - which maintains the expansion as achieved in a 4-stroke cycle but suppresses the gas exchange into the compression stroke. The first 2-stroke cycle generated a torque increment of 63% at 1000 rpm on a supercharged 4-stroke engine without increasing the maximum cylinder pressures. The second 2-stroke strategy - which uses the Miller cycle concept - generated a torque increase of 51.5% at 1000 rpm and higher thermal efficiencies than the first valve strategy. The 2-stroke Miller cycle has been proposed as a means of transitioning from 4 to 2-stroke with progressive torque delivery and without requiring a throttled intake. The 2-stroke cycle appears to be a potential solution to overcome some of the difficulties faced by downsized gasoline engines during high load operations. In particular this cycle will be beneficial in a condition where the engine is already operating at peak cylinder pressures and additional torque output is not easily achievable.

History

School

  • Aeronautical, Automotive, Chemical and Materials Engineering

Department

  • Aeronautical and Automotive Engineering

Published in

JSAE/SAE 2015 Powertrains, Fuels & Lubricants International Meeting

Volume

SAE 2015-01-1974 / JSAE 20159333

Citation

PUGNALI, L.D. and CHEN, R., 2015. Feasibility study of operating two-stroke Miller cycles on a four-stroke platform through variable valve train. SAE Technical Paper 2015-01-1974.

Publisher

© SAE International

Version

AM (Accepted Manuscript)

Publisher statement

This work is made available according to the conditions of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0) licence. Full details of this licence are available at: https://creativecommons.org/licenses/by-nc-nd/4.0/

Publication date

2015

Notes

This paper was also presented at JSAE/SAE 2015 Powertrains, Fuels & Lubricants International Meeting, Kyoto, Japan, SAE 2015-01-1974 / JSAE 20159333. The paper is in closed access until 1st March 2016.

Language

en

Location

Kyoto, Japan

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