FIRB2006_MUR “MID2R”

Study, planning, development and experimentation on direct injection motorization for low consumption and low environmental impact two-wheels vehicles, fuelled with liquid phase gasoline and with alternative fuel

• Scientific Responsible: Merola S.S.
• Participants: Tornatore C., Sementa P., Vaglieco B.M.

Area/Topic: ENERGY/TRANSPORTATION

Period: 2008-2011

Application of basic methodologies for the development of low fuel consumption and low environmental impact direct injection engines for 2-wheels vehicles fueled by gasoline and alternative fuel in gas phase.

The main objective of the project was the study of the thermo- fluid-dynamic processes that take place when liquid and/or gaseous fuel is directly injected at high-pressure into the combustion chamber. In the first phase of the research activity, an optically accessible engine with head and injection system provided by the industrial partners of the project was developed. The second phase of the project was focused on the characterization of the injection processes, mixture formation, ignition and combustion in the engine cylinder. The measurements were carried out in full load and partial load conditions.

The effects on the combustion process of a direct – high pressure – injection in the combustion chamber of liquid fuel and/or alternative gaseous fuel were evaluated. The use of a transparent engine with control of intake air temperature and pressure has assured reproducible operating conditions. This is important to release the experimental results from the variability of the initial and boundary conditions.

Specifically, different injection modes were analyzed to evaluate the effects of homogeneous and stratified charge distribution on the combustion process in terms of performance, consumption, pollutants formation and flame front propagation (normal and abnormal combustion). In particular, the application of visualization techniques based on diffusion and attenuation of UV-visible light has allowed an analysis of the morphology (macroscopic) of the spray, the distribution of liquid and vapor phase in the chamber, even in the presence of high atomization induced by high injection pressure.

Visualization techniques have been integrated with chemiluminescence measurements and natural UV-visible light emission spectroscopy. This allowed the analysis of the flame front with evaluation of the propagation velocity and flame size. Radical species characteristics of the combustion process were spatially detected for an assessment of the local A/F. The analysis of the combustion process carried out through advanced optical diagnostics has been completed by on-line measurements of engine parameters and with high temporal resolution measures of in-cylinder pressure. During the optical analysis of the pollutants formation processes, in particular carbonaceous particulate and nitrogen oxides, correlations have been realized between the investigated injection strategy and opacity and NOx values measured at the exhaust.

The optical measurements were carried out on different combustion cycles for a wide statistics, released from the problems of cycle to cycle variation. This characterization allowed building a database for the calibration of 1 and 3D – codes and model-based engine control.