Search Results

When developing diesel fuel formulations, it is important to ensure that existing engines in the market place start and continue to run satisfactorily at low temperatures. The objective of this project, carried out jointly by Statoil and Ricardo Consulting Engineers Ltd, was to develop a test technique capable of discriminating between different fuels and to apply the technique to a range of experimental fuels tested in six diesel engines. The engines were selected to represent the technologies available in the current vehicle parc, ranging from indirect injection diesel engines used in passenger cars to highly-rated, direct injection engines found in commercial vehicles. These engines were instrumented to measure crankshaft position and speed, in-cylinder pressure and exhaust emissions. Cold start testing was carried out at -16°C and -24°C in Ricardo's cold chamber and data were recorded during the cold starts by analogue recorders and a high speed digital data logger.

This paper describes the first phase of a project to develop a medium duty engine to run on compressed natural gas (CNG) as an alternative fuel for vehicles such as school buses and medium trucks. The engine uses a lean burn, open chamber design featuring the Nebula combustion system. Mechanical air-fuel ratio control and a mapped high energy ignition system, combined with a wastegated turbocharger, will contribute to the low emissions. The CNG engine will have the maximum commonality with the existing diesel engine and will use the same production tooling wherever possible. The initial build of CNG engine is intended to avoid the expense and complication of an intercooler and catalyst. Future potential for even lower emissions and higher pressure could be achieved by the use of electronic air-fuel ratio control and the addition of intercooling and an oxidation catalyst.