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With the aim of accomplishing pollutant emissions policies, EGR-cooler has acquired an important role inside the whole EGR system in diesel engines. This paper presents a methodology to design and size EGR-coolers based on the integration of fluid-dynamic tools (CFD), specifically developed codes, experimental tools and a knowledge bank with previous experiences. Each different geometry of EGR-coolers (cooler family) requires an initial study through CFD, which allows the characterization of different thermo-fluid-dynamic variables. After that, correlations, related to heat exchange and pressure drop for the cooler family, are obtained from the CFD results and implemented in a fast-running one-dimensional code. This code lets size EGR-coolers with specific design characteristics and performance requirements of this family. An experimental tool carries out efficiency and pressure drop tests on EGR-cooler prototypes in order to validate the theoretical results.

In this paper, a parameter to quantify the cyclic variability in first stages of combustion is presented, as an evolution of the parameter proposed by Hill and Kapil. This parameter relates the mean time necessary for the initial flame to reach the periphery of a turbulence eddy structure moving from the flame kernel position. This parameter is used in combination with quasi-dimensional models in order to predict and analyze small-scale turbulence contribution to cyclic variations. The cyclic dispersion parameter could be introduced in the predictive models as a delay in the combustion beginning. The parameter is compared with the experimental standard deviations in mass burned fraction at spark time obtained from others researchers works and own experimental data. A satisfying agreement between predictions and measurements is achieved.