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The increasing request of vehicles fuelled by Compressed Natural Gas (CNG) requires that the safety issues related to this kind of fuel should be analyzed more and more thoroughly. So far, the minimum requirement for a CNG tank is to set up a Pressure Relief Device (PRD) triggered by temperature. This work aims to develop a procedure able to perform thoroughly tank behavior analyses, in presence of fire, in order to reduce the number of expensive experimental tests and to improve the design criteria of tank safety devices. The procedure consists in the solution of the unsteady solid-fluid conjugate heat transfer problem, by means of numerical simulations, in order to evaluate the transient behavior of both the temperature field inside the solid walls of the tank and the thermo-fluid-dynamic field of the compressed gas inside it, when it is exposed to a heating source. Moreover, the melting process of the fusible plug, inside the PRD, is simulated.

A simulation code of an innovative electro-injector for Diesel engines is presented with the preliminary analysis carried out using the code. The simulation code is based on the concentrated volume method. The energy and continuity conservation equations and dynamic equations are used for the movable parts of the system under friction. The one dimensional code simulated the propagation in the feeding pump and the control of the electro-injector. The program uses the method of characteristics to solve conservation equations, simulating the propagation in the pipe between the two chambers. To go deeply into the study of the electro-injector, main routine tests were carried out checking the exact value of diesel fuel parameters and the fuel energy losses with stationary and instationary flows. A comparison with different experimental results obtained by different types of electroinjectors, running at real conditions, has been made with good agreement.