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This paper proposes a system able to recover energy from sea waves. The system is made up essentially of a floating structure, connected to a piston pump. The pump, constrained to move vertically under the action of the waves, pushes water into a reservoir maintained at constant pressure, from which it flows in a Pelton turbine. A methodology was developed for the preliminary sizing of the proposed system. This methodology takes the height of the waves and the pressure of the reservoir as reference parameters and then provides the main geometric data of the machines. A case study developed in the present work, demonstrates the possibility of designing miniaturized components of the system, able anyway to provide acceptable energy output with contained installation costs.

Summary: The aim of this paper is to illustrate the design of a new wave energy converter, composed of a point absorber and a hydraulic system (power take off) and sized for recovering energy in calm seas from waves near the shore. The point absorber is consisting of a rectangular shaped buoy integrating a piston pump. The set buoy‐pump oscillates under the waves action and moves natural water in a closed circuit hydraulic system (power take off) composed of a piping connecting the piston pump itself, a pressurized reservoir, a hydraulic turbine and a discharge tank. The methodology adopted for designing the main constituents involves a 1D mathematical model, settled for understanding the motion of the buoy under the hypothesis of regular waves and fully developed sea, and a sizing procedure applied for the design of all the components of the hydraulic system. The project related to the Calabrian site of Cetraro (Mediterranean Sea—south Italy) led to designing a system with a 4 m large buoy, associated with a small 13 cm diameter micro Pelton turbine, so that more than 22 000 kWh could be recovered in a year. [ABSTRACT FROM AUTHOR]

LDV measurements have been taken in a disc chamber four-stroke reciprocating engine under motoring conditions. Two non-simultaneous velocity components have been recorded at three different locations on the mid-plane of the TDC clearance during the intake and compression strokes for three different speeds (600, 800, 1000 rpm). The locations are characterized by different flow conditions (near the intake valves; on the cylinder axis; near the exhaust valves). The combination of different engine speeds and different chamber locations enables one to look both at the global behavior of the flow and at the details of the turbulence time-evolution. The aim of the research is to identify the frequency which can be considered a separation between 'true' turbulence and cycle-by-cycle variation of the mean flow and to analyze the variation of such a frequency with the measuring location and with the engine speed. The analysis has been carried out by using different tools: the non-stationary velocity autocorrelation function, the power spectrum and the cycle-resolved analysis based on the frequency filter. The various approaches offer complementary perspectives of the same phenomenon, which give a clear perception of the physical meaning of the most frequently used investigation tools. The results show that the cut-off frequency increases as the engine speed increases and as the measuring point moves away from the ordered jet coming out of the intake valves. [S0742-4795(00)01204-7]

On–off valve systems, commonly used in regenerative thermal oxidizer (RTO) plants, generate, during the opening time, a mass flow rate (MFR) which is constant. On the contrary, rotary valve systems, which are increasingly adopted in RTO plants, are characterized by variable MFR profiles. In this work, the energy requirements of two RTO systems, equipped with on–off or rotary valves, were determined using a home-developed numerical code. Energy performances were evaluated by calculating the thermal efficiency and pressure drop within structured or random packed bed RTO systems, at the same mean MFR. The results demonstrated that thermal efficiency was only moderately influenced by the valve system, and is slightly lower for the RTO with on–off valve. On the other hand, the study revealed that energy requirements of all RTO systems were basically unaffected by cycle duration, allowing valve rotational velocity to be freely set to maximize for other technical requirements. On the contrary, pressure drop was greatly influenced by the valve type and increased as variability in MFR function augmented. Moreover, the type of regenerator, structured or random packed bed, affected differently the total energy requirements (basically pumping energy plus auxiliary fuel). Energy requirements of structured and random regenerators were comparable only when volatile organic compounds concentration was lower than typical values encountered in the industrial practise. In other cases, structured regenerators RTO were more competitive. Finally, structured regenerators are usually the best choice when rotating valve distribution systems are adopted. Copyright © 2007 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

A Multidimensional Performance Model of a Spark Ignition Engine Characterized by a Single Step Reaction to Equilibrium Abstract-A new multidimensional model of a spark ignition engine has been developed. The main features of this model are its two-dimensional computational scheme, the assumption of equilibrium conditions for the thermodynamical properties, and the automatic determination of the initial conditions. This approach enables the number of free parameters to be considerably reduced with respect to similar programs currently available, thus ensuring an overall increase in the reliability of the entire computational scheme. [ABSTRACT FROM PUBLISHER]