Search Results

A study has been undertaken on a boosted single cylinder research engine with direct injection of hydrogen. In order to reduce NOx emissions and tendency to knock, efforts have been made to reduce the temperatures and rate of heat release during combustion. Lean boosted operation, stoichiometric operation with exhaust gas recirculation, and water injection using a dual fluid direct injector were investigated and NOx emissions, thermal efficiency, and combustion stability were compared. Conclusions are developed for specific power optimisation and NOx management which may be applied for hydrogen fuelling of small general purpose through to heavy duty engines.

Ethanol shows promise as a renewable automotive fuel. However the widespread adoption of ethanol as a fuel rather than gasoline diluent is hindered by several issues including cost. The current study evaluates the comparative performance for ethanol and gasoline fuels in a multi-cylinder turbo-charged direct injection SI engine. In particular the study investigates the potential for high specific output with ethanol, an enabler for highly efficient and more market tenable powertrain solutions. Data indicate that the operation of a turbo-charged spray guide DI engine on pure ethanol can efficiently achieve very high specific output with some update to engine design. The ethanol direct injection or EDI approach shows overall significant potential for aggressive engine downsizing for a dedicated or dual-fuel solution.

The paper describes the principal features of Omnivore, a spark-ignition-based research engine designed to investigate the possibility of true wide-range HCCI operation on a variety of fossil and renewable liquid fuels. The engine project is part-funded jointly by the United Kingdom's Department for the Environment, Food and Rural Affairs (DEFRA) and the Department of the Environment of Northern Ireland (DoENI). The engineering team includes Lotus Engineering, Jaguar Cars, Orbital Corporation and Queen's University Belfast. The research engine so far constructed is of a typical automotive cylinder capacity and operates on an externally-scavenged version of the two-port Day 2-stroke cycle, utilising both a variable charge trapping mechanism to control both trapped charge and residual concentration and a wide-range variable compression ratio (VCR) mechanism in the cylinder head.

Ethanol as a renewable fuel is employed in either the hydrated or anhydrous states. The production of anhydrous ethanol requires an additional and costly processing step, and is less advantageous with regard to Life Cycle Inventory. The use of hydrated ethanol may then be preferred for high blend and pure fuels, and future engine technologies designed for ethanol may need to accommodate either form. In the current study a spark ignited ethanol direct injection (EDI) turbocharged engine, proposed for efficient delivery of high specific output, is evaluated for performance at high load with anhydrous and hydrated ethanol as fuel. Test data show the EDI engine may be operated at high load on either fuel with the same output and efficiency. The key differences arising from fuel water content are reduced burn rate requiring advance in ignition timing, a decrease in engine emissions of NOx and increase of HC, and higher potential for increase of compression ratio and output.

In the current study a single cylinder Spark Ignited engine has been operated in Controlled Auto Ignition mode with centrally mounted spray guided direct injection, employing negative valve overlap to achieve the conditions required for auto-ignition. The injector is a type known in the market and utilises air at elevated pressure to assist preparation of the fuel and delivery of the fuel spray into the combustion chamber. Operation of the injector enables a high degree of control for fuel and air delivery, particularly with regard to stratification of fuel, temperature, air and turbulence within the chamber. Engine test data show that variation in injection parameters at a fixed engine condition yields high authority over the CAI combustion process. A range of combustion phasing is achieved from 355 to 375 degrees ATDC for the timing of 50% Mass Fraction Burned, whilst the range of maximum pressure rise rate is 70 to 450 kPa / degree.