In view of increasingly stringent exhaust emission legislation and fuel economy requirements there is a need for more efficient and clean combustion of the fuel in the automobile engine cylinder. Recent developments in engine technology have shown that with direct-injection stratified charge engines it is possible to achieve reduction in specific fuel consumption of around 20% or more. The benefits of this technology have been clearly demonstrated for 1.82.0 litre four-valve engines.
This proposal aims to establish the feasibility of achieving similar savings of around 20% in fuel consumption by developing and implementing direct-injection divided charge strategies in small (1.0-1.3 litre) engines. In view of the small size of the engines, it is proposed to consider three- rather than four-valve engine geometries and to investigate thoroughly, using a concurrent engineering approach, concepts akin to those applied successfully in larger engines to achieve fuel consumption reductions.
The present proposal aims to build on existing experience from earlier studies by the proposers and others and to investigate new mixture stratification strategies under various engine operating conditions in order to identify the means by which the fuel distribution in the engine cylinder can be optimised. The aim is to achieve fuel economy and acceptable emission levels through strategies involving direct injection and novel inlet port and piston head designs.
Initially CFD predictions will be carried out to identify promising stratification strategies. These will be validated against flow visualisation and LDA data to be obtained in an engine simulator rig and a motored optical engine. Subsequently the most appropriate strategies will be investigated further, utilising existing spray data. For the most promising engine design(s) cylinder head and piston prototypes will be manufactured and performance and emission testing will be performed to assess the operational characteristics.
The proposed work will utilise state-of-the-art diagnostic
tools - unobtrusive optical techniques in optical engines and engine performance analysis methods - and CFD methodology, to allow the determination of the velocity, turbulence and air/fuel distribution for a range of promising stratification strategies and the formulation of combustion optimisation guidelines for generic small engine designs. The industrial objectives of the proposed research are:
1. A more efficient use of fuel in petrol engines;
2. Development of port and piston designs and injection strategies for efficient generation of tumble and/or swirl and charge stratification in small three-valve engines;
3. Reduction of development time through validation of the concepts and designs developed by CFD and other predictive tools against detailed bechmmark experimental data on the flow characteristics and other relevant performance and operation data.
Funding SchemeCSC - Cost-sharing contracts
SS15 6EE Basildon