|MUSIC system schematic. Click to enlarge.|
A one-day seminar, hosted by Coventry University (UK) on 17 December 2007, will present the results of an experimental project to develop the MUSIC (Merritt Unthrottled Spark Ignition Combustion) gasoline engine to an in-vehicle demonstration stage.
The MUSIC gasoline engine promises to match or to improve on the fuel efficiency of the diesel engine at part load, providing an approximate 20% increase in fuel economy over conventional gasoline engines. MUSIC is an un-throttled, high thermal efficiency, lean-burn, spark ignition system that uses an indirect combustion chamber to produce charge stratification by means of controlled air management.
The MUSIC project has been part funded since 2006 by the UK Department of Transport under the Low Carbon Research and Development Programme, which is managed by the Energy Saving Trust. UK firm Powertrain Technologies Ltd. (PTech) is undertaking the development work, with support from Ford, BP Castrol and Coventry University. Knibb, Gormezano & Partners (KGP) is responsible for managing commercialisation of the technology.
The recently patented MUSIC engine was invented and developed by Dr. Dan Merritt while working at Coventry University.
Until now Diesel engines have given far superior fuel efficiency at part load when compared with gasoline engines but gasoline engines delivered more power for a given size. The MUSIC gasoline engine has now demonstrated part load efficiencies as good as the diesel engine but at a lower cost. For most vehicles, the greater part of operating life is spent at part load and idling.
The MUSIC technology affects only the layout of the combustion chamber in the cylinder head and does not impact the bottom end of the engine.—Dan Merritt
|Stratification by helical swirl. Red indicates stoichiometric air:fuel mixture, green indicates air only. Click to enlarge.|
Implementing MUSIC requires a modified cylinder head and a direct injection fuel system. The indirect combustion chamber features an inbuilt helical swirl that can not only run successfully at air/fuel ratios of more than 100:1 but also reduces HC and NOx emissions significantly. The developers earlier estimated that up to 80% reduction in NOx and HC is possible. Load and speed control is achieved by the precise control of injection timing and duration.
At the Stuttgart Engine Expo 2007 earlier this year, the team presented results of their work on a single-cylinder test engine, which included:
Effective ignition at air/fuel ratios of 140:1
Self sustained running at AFRs out to 105:1. (The probable limit of AFR at which useful work is done is around 85:1)
Apparent freedom from detonation (no hot spots exposed to air/fuel mixture)
Smooth idling at 700 rpm
Unthrottled start up
Very low to almost zero NOx under lean burn at AFR’s beyond 35:1
|MUSIC Single Cylinder Part Load Thermal Efficiency|
|Indicated Thermal Eff (%)||38.2||36.4||43.2||46.9||41.6|
|Volumetric Eff (%)||92.5||98.1||97.0||76.0||80.0|
|Brake Thermal Eff (%)||7.9||21.2||26.8||23.7||23.9|
The 4-cylinder prototype built for the in-vehicle demonstration is based on a Ford 2.0-liter engine.