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Electrical power and efficiency are decisive factors to minimise payoff time of cogeneration units and thus increase their profitability. In the case of (small-scale) cogeneration engines, low-NOx operation and high engine efficiency are frequently achieved through lean burn operation. Whereas higher diluted mixture enables future emission standards to be met, it reduces engine power. It further leads to poor combustion phasing, reducing engine efficiency. In this work, an engine concept that improves the trade-off between engine efficiency, NOx emissions and engine power, was investigated numerically. It combines individual measures such as lean burn operation, overexpanded cycle as well as a power- and efficiency-optimised intake system. Miller and Atkinson valve timings were examined using a detailed 1D model (AVL BOOST). Indicated specific fuel consumption (ISFC) was improved while maintaining effective compression ratio constant.

A study of the internal flow in the most used nozzle types in Diesel engines (microSAC and valve covered orifice VCO) was carried out in order to compare injection characteristics and understand the differences between them. To determine these differences, several experimental installations will be used, such as the injection rate test rig, steady flow test rig and spray momentum test rig, to obtain a full hydrodynamic characterization. With the help of the silicone methodology and a microscope, it is possible to determine the needle tip geometry (seat). As the geometrical characterization of the components in both nozzles was known, it was possible to carry out a CFD analysis at several needle lifts and thus observe the behavior of the internal flow in the nozzle seats and be able to compare both nozzles

The objective of the work is to learn about the internal structure of transient evaporative Diesel sprays. A simple atomization model of a non-stationary evaporative spray, described in [1], is used in this paper to study the effects of the operating variables and atomization parameters, of the primary and secondary models, on the Diesel sprays characteristics. The model is a phenomenological and DDM one, and is realized in a PC with C programming language. There are several sub-models included: A primary atomization model of the jet liquid vein based on the jet interface instabilities caused by the aerodynamic action, including an intact length model. A secondary atomization model of droplets break-up based on the Taylor analogy. A droplet evaporation model including the heat-up and the stationary periods, as well as the natural and forced convection effects.

A comparison between conventional and bio-derived fuel spray characteristics is described in this paper. Radial distributions of drop size, axial and radial velocity components were measured using a Phase-Doppler Anemometer (PDA). A digital visualization system including a CCD camera was used to estimate the spray tip penetration. Fuel was injected through a single hole diesel injector into a test section at ambient pressure. An empirical expression was found to estimate the spray tip penetration at ambient conditions.

An experimental procedure to determine the two components of the crankshaft force on the bearing cap is presented in this work. The method is based on the use of two load cells, one in each bearing cap bolt. A system to calibrate the force transference from the bearing cap to the load cells has been used. This system allows the calculation of the two components of the crankshaft forces as a function of the load cells signals. Some experiments have been done with this system, and the results of a firing and motored engine have been compared in order to know the influence of combustion and inertia forces on the crankshaft load in the bearing cap. The results are compared with a model for the dynamics of the piston-connecting rod-crankshaft system.