Mario Amelio

The Separation Between Turbulence and Mean Flow in ICE LDV Data: The Complementary Point-of-View of Different Investigation Tools

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.

A One-Dimensional Numerical Model for Calculating the Efficiency of Pumps as Turbines for Implementation in Micro-Hydro Power Plants

Increasing interest in renewable energy sources makes attractive the exploitation of many small power hydraulic resources (micro-hydro – less than 100 kW). However, the high cost of hydraulic turbines hinders the actual realization of micro-hydro plants. An alternative cheaper solution could be to replace the turbine with a reverse-mode centrifugal pump, developing therefore a pump as turbine (PAT) system. Unfortunately, although a wide number of centrifugal pumps are commercially available for micro-hydro engineering plant, manufacturers do not provide information regarding the performance of centrifugal pumps in turbine mode. In this paper, a simple method based on a one-dimensional numerical code is presented for deriving the turbine efficiency of commercially available centrifugal pumps. The code estimates a sizing of the component using information such as impeller diameter, specific speed, head and flow rate at pump BEP, machine overall dimension which are provided in manufacturer catalogues, to deduce geometrical parameters of the machine, calculating the losses and thus determining PAT performances. The method was validated by a comparison of the predicted characteristic curves with some experimental measurements available on PATs working in a range of specific speed (Head in meters and flow rate in m3 /s) from 9 to 65. The numerical code calculations effectively predicted the measured efficiency of PATs. At BEP, the efficiency was estimated with a relative error of ±10% which is a value much lower than one obtained by using the available in literature correlations. A prediction within this error range is generally accepted for this kind of application.Copyright

Using a Statistical-Numerical Procedure for the Selection of Pumps running as Turbines to be applied in Water Pipelines: Study Cases

A combined method using statistical and numerical models has been developed by the authors for selecting a pump running as turbine to be applied in micro-hydro plants. The data of the hydrological site chosen for the installation (head and capacity) allow the calculation of two conversion factors which identify the pump to use successfully as turbine in that place. Then, a one-dimensional model, starting from data available on the pumps manufacturers catalogues, reconstructs a virtual geometry of the pump running as turbine, and calculates the performances curves, head vs. capacity, efficiency vs. capacity, useful for identifying the operating point. Two study cases are presented to apply the proposed methodology, concerning the feasibility of the installation of a pump running as turbine in the purifier water plants of Casali and Sersale, located at 1,000 m above sea level (Calabria, South Italy).The assessment of the annual energy yield gives a confirmation of the effectiveness and convenience of using pumps running as turbines.