Roberto Lensi

Influence of Mixture Formation on Injection and Combustion Characteristics in a Compact GDI Engine

The spray characteristics are determining factors for the quality of mixture formation respectively for the combustion, when applying GDI. Their variation with load and speed is a basic criterion for the adaptability of an injection system type to an engine with known requirements. CFD models of the fluid flow dynamics, mixture formation and combustion are a determining condition for such adaptation. The paper presents the development results of a GDI four-stroke, four-valve, single cylinder engine. The pressure pulse injection system involved in this application is analyzed and presented from the fluid-dynamic behavior up to the obtained injection spray characteristics. The mixture formation and combustion processes are simulated for different load and speed values, respectively for favorable combinations of parameters, such as the injection system configuration, the opening pressure of the applied mechanical injector and the injection duration. Particular aspects of the combustion when using GDI, such as non-homogeneity of the mixture structure, super position of mixture formation and combustion and the influence of additional spark sources form an object of analysis. The results of numerical simulation are compared with the experimental results. Complete paper available under: http://www.sae.org/servlets/productDetail?PROD_TYP= PAPER&PROD_CD=2002-01-0997

Lumped Parameters Modeling of an Incinerator With Heat Recovery for Energy Production

This work shows the modeling of an incineration plant with energy recovery which operates in the vicinity of Pisa, Italy. The plant analysed was built formerly as an incineration plant and was recently refurbished with a heat recovery steam generator to drive a condensing steam turbine. In the foresight of an enlargement of the plant capacity, the Technical Office of the Company asked the Energetica Department of University of Pisa for an analysis of the recovery capability. The Technical Office and the Energetica Department decided to create a lumped parameter model in order to simulate the temperature behavior of the combustion products. This model was created inside Matlab/Simulink environment. The followed procedure led to the reproduction of the system interested by the cycle in steady state conditions in order to obtain a model simple enough but at the same time rigorous of the real behavior of steam cicle. After the description of the plant modeling, model calibration and validation is shown, by means of the comparison between the measured and simulated values of temperatures and mass flows in several load conditions. The model developed is currently used by the Technical Office of the Company for further developments of the plant.Copyright