Hydraulic manifolds are used to realize compact circuit layout, but may introduce a high pressure drop in the system. Their design is in fact oriented more toward achieving minimum size and weight than to reducing pressure losses. This work studies the pressure losses in hydraulic manifolds using different methods: Computational Fluid Dynamic (CFD) analysis; semi-empirical formulation derived from the scientific literature, when available; and experimental characterization. The purpose is to obtain the pressure losses when the channels' connections within the manifold are not ascribable to the few classic cases studied in the literature, in particular for 90 • bends (elbows) with expansion/contraction and offset intersection of channels. Moreover, since CFD analysis is used to predict pressure losses, general considerations of the manifold design may be outlined and this will help the design process in the optimization of flow passages. The main results obtained show how CFD analysis overestimates the experimental results; nevertheless, the numerical analysis represents the correct trends of the pressure losses.

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In order to comply with current emissions regulations, a detailed analysis of the combustion and emission formation processes in the Diesel engines accounting for the effect of the main operating parameters is required. The present study is based both on 0D and 3D numerical simulations by compiling 0D chemical kinetics calculations for Diesel oil surrogate combustion and emission (soot, NOx) formation mechanisms to construct a φ-T (equivalence ratio - temperature) parametric map. In this map, the regions of emissions formation are depicted defining a possible optimal path between the regions by placing on the same map the engine operation conditions represented by the computational cells, whose parameters (equivalence ratio and temperature) are calculated by means of 3D engine modelling. Unlike previous approaches based on static parametric φ-T maps to analyze different combustion regimes and emission formations in Diesel engines, the present paper focuses on a construction of dynamic φ-T maps, in which the pressures and the elapsed times were taken in compliance with those calculated in the 3D engine simulations. The 0D chemical kinetics calculations have been performed by the SENKIN code of the Chemkin-2 library. In-cylinder conditions represented by computational cells with known φ and T are predicted using KIVA-3V code. When cells are plotted on the map, they identify the trajectories helping to navigate between the emissions regions by varying hardware and injection parameters. Sub-models of the KIVA-3V, rel. 2 code has been modified including spray atomization, droplet collision and evaporation, accounting for multi-component fuel vapor coupled with the improved versions of the chemistry/turbulence interaction model and new formulation of the combustion kinetics for the diesel oil surrogate (consisting in 70 species participating in 310 reactions). Simulations were performed for the HSDI 1.300 Fiat Diesel engine at optimized engine operating conditions and pilot injections. Finally, numerical results are compared with the experimental data on in-cylinder pressure, Rate of Heat Release, RoHR, and selected species distributions.

This study investigated dual-fuel operation with a light duty Diesel engine with Natural gas over a wide engine load range. Natural gas was hereby injected into the intake duct, while Diesel was injected directly into the cylinder. At low loads, high fuel shares are critical in terms of combustion stability and emissions of unburnt hydrocarbons. Dual-fuel combustion has the advantage of providing diesel-like efficiency with Natural gas as the primary fuel, providing potential increases in efficiency of 50% while reducing emissions. Typically a small liquid fuel pilot is injected into a lean mixture of air and a more volatile fuel that is less inclined to auto-ignite. Often it is difficult to simulate the separate chemical effects of the two fuels. In present study we are using non premixed type of combustion model for better mixing and penetration of fuel and air so the complete combustion is achieved and emission is reduced by a great amount as compare to premixed method. NOx emission is reduced as compare to previous base research. Fluent accurately tracks flame propagation, which is critical for dual-fuel cases where the injection and auto-ignition of the liquid pilot fuel serves to initiate the flame propagation. In Fluent the simulation can simultaneously consider both auto-ignition and flame-propagation modes of combustion progress. Fluent fluid flow allows investigations of fuel or additive composition effects, impacts on liquid pilot amount and timing, and NOx reduction techniques such as EGR, etc.

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