Stratified Scavenging In 2-cycle Engines

ME433 Combustion Engine SystemsProject Presentation

Presented by: Eric Henderson

July 31, 2013

Overview

•Introduction•Stratified Scavenging Concept•Stratified Scavenging Methods

▫Air-Head Method▫Stratified Charge Injection▫Compressed Air Assisted Injection▫Multi-Layer Stratified Method

•Concluding Thoughts•Questions

Introduction

What is scavenging?

Scavenging consequencesHigh HC emissionsPoor fuel economy

Stratified Scavenging Concept

Large concentration of emissions at beginning of scavenging process

Reduce short-circuiting by providing a barrier of air between incoming charge and exhaust gases

Stratified Scavenging Methods

Air-Head Method

Fundamental method

Provides a cushion of air on top of the charge

Air is short-circuited instead of charge

Stratified Scavenging Methods

Stratified Charge Injection

Multiple ports required

Provides a curtain of air or lean charge between the rich charge and exhaust gases

Stratified Scavenging Methods

Compressed Air Assisted Injection (CAAI)

Uses motion of piston and dynamics of engine gases

Pressure pulse created in injection tube used to inject charge

Lean mixture layer between charge and exhaust gases

Stratified Scavenging Methods

Multi-Layer Stratification (MuLS)

Combines advantages of other methods

Layers consist of air, lean charge, and rich charge

Concluding Thoughts

Significant reduction in HC emissions achieved

Fuel economy (BSFC) improved

Challenges to overcomeProper fuel-air ratiosMaintain power while reducing

emissionsMaintain sufficient lubrication

References

McElligott, S., Douglas, R., Kenny, R. G., “An Assessment of a Stratified Scavenging Process Applied to a Loop Scavenged Two-Stroke Engine,” SAE Technical Paper Series , Small Engine Technology Conference and Exposition, Madison, Wisconsin, September 28-30, 1999.

Mavinahally, N., Veerathappa, J., Rajgiri, S., and Mavinahalli, V., "Multi-Layer Stratified (MuLS) Two-Stroke Engine," SAE Technical Paper Series, 2012-32-0119, 2012.

Golsborough, S. S., Blarigan, P., V., “Optimizing the scavenging system for a two-stroke cycle, free piston engine for high efficiency and low emissions: A computational approach,“ SAE Technical Paper Series, 2003-01-0001, 2003, pp. 1-20.

Yoshida, Y., Uenoyama, K., Kawahara, Y., Kudo, K., “Development of stratified scavenging two-stroke cycle engine for emission reduction,” SAE Technical Paper Series, 1999-01-3269, 1999, pp. 1278-1285.

Zahn, W., Rosskamp, H., Raffenberg, M., Klimmek, A., “Analysis of a stratified charging concept for high-performance two-stroke engines,” SAE Technical Paper Series, SAE 2000 World Congress, March 6-9, 2000.

Kobayashi, B., Sawada, T., Zama, R., Ogura, N., Wada, S., “Investigation of port design for small air-head stratified scavenging two-stroke cycle engine,” Society of Automotive Engineers of Japan, 2005-32-0012, 2012.

Hill, B.W., “Stratified-charging applied to two-stroke engine,” Automotive Engineering, Vol. 91, Issue 9, 1983, pp. 55-56.

Questions?