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The nowadays two-stroke engine technique is directed toward new concepts to reduce fuel consumption and pollution. Typical features are direct injection of fuel and no lost oil lubrication: a separate scavenging system is becoming so a must. Following general consideration about different scavenging pumps, a regenerative blower solution is proposed. Regenerative blowers present in fact several advantages in comparison with other solutions like simplicity in construction and on engine fitting, no maintenance and low cost. An exhaustive experimental evaluation was carried out on a direct injection two-stroke S.I. engine with a separate scavenge, already described in a previous work by one of the authors. The results show the practical feasibility of the proposed solution. In fact, the regenerative blower is suitable to match the engine air breath demand all over its utilization range.

A transient one-dimensional model developed to simulate the thermal and conversion characteristics of adiabatic monolithic converters operating under warm-up conditions is presented. The model takes into account the gas-solid heat and mass transfer, axial heat, conduction, chemical reactions and the related heat release. The model has been used to analyze the transient response of an axisymmetric catalytic converter during a warm-up as a function of catalyst design parameters and operating conditions in order to observe their effects on the lightoff behaviour. The experimental test was carried out in two steps: the first on a sample for lightoff test and the second on two-stroke 150 cc engine with Pt/Rh metal-supported catalyst and full open-throttle condition. The simulated temperatures are close to test results. The predicted conversion efficiencies are qualitatively acceptable.