Browse Publications Technical Papers 2007-24-0013
2007-09-16

Single-cylinder Experiments for Downsizing-Oriented SI Concepts: GDI and VVL Thermodynamic Comparison 2007-24-0013

In order to compare potential of VVL and GDI concept on a small displacement engine, tests have been made on a single-cylinder engine. Compared to multi-cylinder, single-cylinder offers good flexibility and accessibility for instrumentation but its gas dynamics non-representativeness has to be taken into account, especially for turbocharged engines. Concepts are tested on same engine basis but combustion system - chamber geometry, injection configuration, internal aerodynamics, valve train - is specifically designed for each version.
Results confirm that homogeneous stoichiometric GDI is peculiarly adapted to turbo-charged conditions: GDI engine superior knock resistance allows low-end torque improvement and higher compression ratio. In addition to cooling effect, one of the advantages of direct injection is studied: ability to scavenge residual gases without directly transferring mixture to the exhaust. Some synergies between VVL and turbo-charging are also presented in the paper.
Part load tests clearly indicate potential of VVL in reducing consumption. GDI concept has to deal with several tradeoffs in order to exploit theoretical efficiency gain coming from compression ratio increase: combustion chamber (mixture preparation / flame propagation), injection timing (mixture homogeneity / fuel impact on the piston). High pressure cycle efficiency is studied for both configurations with thermodynamic split of losses analysis.

SAE MOBILUS

Subscribers can view annotate, and download all of SAE's content. Learn More »

Access SAE MOBILUS »

Members save up to 18% off list price.
Login to see discount.
Special Offer: Download multiple Technical Papers each year? TechSelect is a cost-effective subscription option to select and download 12-100 full-text Technical Papers per year. Find more information here.
We also recommend:
TECHNICAL PAPER

Geometric Parameters of Four-Valve Cylinder Heads and Their Relationship to Combustion and Engine Full Load Performance

940205

View Details

TECHNICAL PAPER

Top Land Crevice and Piston Deflection Effects on Combustion in a High Speed Rotary Valve Engine

2008-01-3005

View Details

TECHNICAL PAPER

Quantitative Measurements of Residual and Fresh Charge Mixing in a Modern SI Engine Using Spontaneous Raman Scattering

1999-01-1106

View Details

X