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This paper documents a feasibility study on a waste heat recovery system for heavy-duty tr-uck engines based on an organic Rankine cycle (ORC) turbogenerator. The study addr'esses many ofthe challenges of a mobile automotive application: The system must be simple, efficient, r-elatively small, lightweight, and the working fluid must satisfy the many technical, environmental, and toxicological requirements typical of the automotive sector. The choice of a siloxane as the working fluid allows for the preliminary design of an efficient r-adial twbine, whose shaft can be lubricated by the working fluid itself. The system's heat exchangers, though mor'e voluminous than desirable, are within acceptable limits. The simulated ORC system would add approximately 9.6 kW at the design point, corresponding to a truck engine power output of 150 kW at 1500 rpm. Future work will be devoted to further system and components optimization by means of simulations, to the study of dynamic operation and coritrol, and will be followed by the design and construction of a laboratory test bench for mini-ORC systems and components.

Road traffic is a dominant source of urban air pollution. Therefore, it is necessary to quantify emission levels as accurately as possible. In this paper, an overview of methods to describe the emission behavior of road transport is presented. The various methods are emission computation methods based on real driving behavior; methods based on road stretch analysis to facilitate emission inventory development; and mileage-related emission balances. Each computational method has its own range of application. Example computations are presented to reveal the major areas of application for each method and to show how small changes in input parameters affect the results of the calculations. It is also shown that considerable errors of interpretation can arise when simple methods are applied to more complex problem areas. It is not easy to say which method is most accurate, but the more precise the description of the driving behavior and fleet composition, the more reliable the emission estimate will be.The main focus of this paper is emission models. While the origin and quality of traffic data is not discussed, it should be remembered that data such as number of vehicles and number of miles traveled are at least as important as the emission calculation model used.

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