From better injection to more efficient and cleaner diesel cars
Optimisation of fuel injection in the combustion chamber is one of the determinant factors for clean and efficient combustion of a direct injection diesel engine. This can be achieved with the aid of suitable injector nozzles design and appropriate injection strategies for improving the spatial and temporal distribution of fuel. Focusing on these objectives the Diesel - Injection for Small Engines and Low Emissions (D-ISELE) project work involved the development of suitable spray characterisation methodologies. The experimental methodologies allow measurements of spray macroscopic and microscopic characteristics for real multi-hole nozzles in order to evaluate nozzle behaviour. Existing software codes were adapted to be used for nozzles with five, six or higher number of sprays under real engine conditions using commercial diesel fuel. Based on digital photographs, correction and calibration procedures were also undertaken to ensure high accuracy in measurements. Additionally, a new masking device was developed to allow isolation of each spray. For the purposes of optical characterisation a new high-pressure nitrogen test rig was also built equipped with three windows for using different optical techniques. The technology features modularity offering increased potentialities to employ different configurations, shadowgraphy, side illumination and two hole or multi-hole nozzles. Apart from diesel injectors, visualisation of plain orifice atomisers or gasoline injectors may be also feasible. Macroscopic spray characterisation including penetration, cone angle, tip speed, hole-to-hole and shot-to-shot dispersion and microscopic characteristics, such as drop size and velocity were investigated for different nozzle layouts. The complete methodology is expected to allow the optimisation of nozzle layout for improved injections in diesel engines.
