The first foundation principle is a very effective stratified gas arrangement promoted by using the piston, during the compression stroke, to force air to spin around the periphery of an external cylindrical combustion chamber with a strong forward bias towards the far end of the chamber where the spark plug is situated. This type of motion is called Helical Swirl and is similar to the geometry of a screw thread. It has the effect of stacking layers of rotating gas so that air delivered early in the compression stroke is situated near the spark plug end of the combustion chamber and remains in this location throughout the compression stroke.

The external chamber is connected to the engine’s cylinder by a generous orifice (see diagrams below) that is large enough to minimise the pumping losses associated with this gas transfer. The orifice forces air to emerge as a powerful jet as it enters the combustion chamber. The velocity, density and temperature of the air in the jet all increase during the compression stroke. A GDI fuel injector, shown as the Economy Injector, delivers gasoline, or other volatile liquid fuels, directly into the air jet emerging from the orifice.

The second foundation principle is the injection of the fuel directly into the air jet to ensure rapid vaporisation.

Fuel delivered early on in the compression stroke finds its way to the spark plug end and remains there, as an ignitable mixture, ensuring spark ignition, even when air with no fuel follows after the fuel injection stops. The formation of a stratified charge keeps the fuel/air mixture separate from air with no fuel in this way, while ensuring a very rapid vaporisation of injected fuel. This allows MUSIC to operate completely unthrottled from idling to full load.




Side View





Top View



The third foundation principle ensures control over local mixture strength in the combustion chamber.

This is achieved by controlling the timing of the beginning of the fuel injection process.

This unique capability ensures exact control over local mixture strength by the formation of a pre-vaporised stoiciometric air/fuel mixture situated near the spark plug irrespective of engine speed or load and it enables the ignition of lean mixtures which are formed later on during the fuel injection process. It makes use of the fact that the air mass flow through the orifice varies considerably during the compression stroke, increasing towards the end of the stroke. Hence the GDI fuel injector, which can deliver at a constant rate, can form a stoiciometric (or chemically correct) mixture if it injects fuel at the crank angle position when the air mass flow rate through the orifice is some 14.5 times greater than the fuel mass flow rate through the injector. Such a mixture, called the Primary Mixture, will be stratified near the spark plug and will readily ignite when the spark is energised. If fuel injection continues for a longer duration after the formation of the Primary Mixture a lean fuel/air mixture will be formed but this will be ignited by the flame produced by the adjacent Primary Mixture described above. The timing of fuel injection start, needed to form the Primary Mixture, is advanced with engine speed to ensure that a stoiciometric mixture is formed, now at an earlier crank-angle position, as the air mass flow rate in the orifice increases with engine speed.

To achieve high loads MUSIC needs to deliver fuel to the air jet until the end of the compression stroke when the air mass flow is very rapid and time is short. A second fuel injector, shown as the Power Injector, is used for this with a larger fuel flow rate capacity. The Power Injector injects axially into the air jet when the air is hot and dense, so enabling rapid vaporisation over the available short time period. The Power Injector can also deliver some fuel to the air contained in the bump clearance above the piston at top dead centre at the end of the compression stroke. It may be possible to incorporate the functions of the two injectors into one complex injector but the cost and complexity of such an injector may exceed the cost of two simple solenoid injectors that are currently mass-produced.

The thermal efficiency advantage of MUSIC is derived from its ability to burn an overall lean air fuel mixture smoothly from some 140:1 at idling to 14.5:1 at full load. It is this capability that makes the diesel engine more efficient than the petrol engine at part load. MUSIC also has an advantage over diesel engines since the heat loss by radiation from the combustion chamber surfaces is more than halved at part load due to the smaller surface area of the MUSIC chamber.
MUSIC can incorporate a simple variable compression ratio system (VCR) by simply moving the end wall of its combustion chamber so as to increase the compression ratio at part load, further increasing the fuel economy under these conditions. MUSIC can be turbocharged in a similar manner to diesel engines.

Exhaust emissions from MUSIC benefit from the fact the NOx is virtually absent under lean burn conditions and only appears under heavy loads when the exhaust temperature is high and capable of lighting up catalytic converters. Moreover, with excess oxygen at part load and without any fuel trapped in crevices around the piston, complete combustion is assured minimising hydrocarbon and carbon monoxide emissions at lower part loads encountered in urban driving. Generally speaking, the larger engines stand to benefit from MUSIC more than smaller engines since they operate at lower part loads when driven in urban environments.

Music is a cylinder head conversion and can be fitted to existing crankcases. It involves no moving parts, other than the VCR version if used, and has no need for new unproven technologies for its implementation. Since it shares the same thermodynamic advantage enjoyed by the diesel engine it should at least offer the same thermal efficiency as the diesel if not better.




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Part of the latest seminar Music Gasoline Engine, held on 15.02.2008 at Coventry University