Since the needle displacement exerts a fundamental influence in the operation of a Common Rail Diesel injection equipment, an accurate measurement of the instantaneous position of the control piston is crucial for a more thorough analysis of the behavior of the injectors, in particular when multiple injections are employed. Moreover, the development of a cheap instrumentation would allow to enlarge the Diesel engine on-board equipment with an instrumentation for the diagnosis of the injector operation. Eddy current sensors have been traditionally used in lab activities to measure the position of the needle inside the injector; apart from its high cost, the scientific literature clearly shows their inadequacy, given the presence of electromagnetic disturbance: the current pulse which controls the opening of the injector nozzles generates electromagnetic fields which strongly affect the acquisition of data. Many attempts have been made either to solve the interference occurring during the measures or to propose a displacement transducer whose operation is not influenced by electromagnetic interference. The sensor that will be proposed in this paper (Patent filing October 2012, under submission for PCT extension) follows the latter line: it is an optical transducer which joins the simple and very cheap construction with the employment of a reliable physical principle for measuring the needle lift. The paper provide all technical and scientific details of the operation of the proposed sensor, as well as a wide proposition of experimental applications aiming at assessing its capability of detecting also multiple injections.

A simplified one dimensional model for the performance estimation of vaneless radial diffusers is presented. The starting point of such a model is that angular momentum losses occurring in vaneless diffusers are usually neglected in the most common turbomachinery textbooks: it is assumed that the angular momentum is conserved inside a vaneless diffuser, although a non-isentropic pressure transformation is considered at the same time. This means that fluid-dynamic losses are taken into account only for what concerns pressure recovery, whereas the evaluation of the outlet tangential velocity incoherently follows an ideal behavior. Several attempts were presented in the past in order to consider the loss of angular momentum, mainly solving a full set of differential equations based on the various developments of the initial work by Stanitz. However, such formulations are significantly more complex and are based on two empirical or calibration coefficients (skin friction coefficient and dissipation or turbulent mixing loss coefficient) which need to be properly assessed. In the present paper, a 1D model for diffuser losses computation is derived considering a single loss coefficient and without the need of solving a set of differential equations. The model has been validated against massive industrial experimental campaigns, in which several diffuser geometries and operating conditions have been considered. The obtained results confirm the reliability ofthe proposed approach, able to predict the diffuser performance with negligible drop of accuracy in comparison with more sophisticated techniques. Both preliminary industrial designs and experimental evaluations of the diffusers may benefit from the proposed model.

Designing and manufacturing high-efficiency heat exchangers is usually considered a limiting factor in the development of gas turbines employing either heat recovery Joule-Brayton cycles or external combustion. In this work, an innovative heat exchanger is proposed, modeled, and partially tested to validate the developed numerical model employed for its design. The heat exchanger is based on an intermediate medium (aluminum oxide Al(2)O(3)) flowing in countercurrent through an hot stream of gas. In this process, heat can be absorbed from the hot gas, temporarily stored, and then similarly released in a second pipe, where a cold stream is warmed up. A flow of alumina particles with very small diameter (of the order of hundreds of microns) can be employed to enhance the heat transfer. Experimental tests demonstrate that simple one-dimensional steady equations, also neglecting conduction in the particles, can be effectively employed to simulate the flow in the vertical part of the pipe, namely, to compute the pipe length required to achieve a prescribed heat exchange. On the other side, full three-dimensional computational fluid dynamics simulations have been performed to demonstrate that a more thorough gas flow and particle displacement analysis is needed to avoid a bad distribution of alumina particles and, thus, to achieve high thermal efficiency. [DOI: 10.1115/1.4002157]

This paper aims to explore the opportunities of scaling up an ultrasound technique applied to virgin olive oil extraction plants. Many encouraging results have been demonstrated the goodness of the idea to perform an ultrasound treatment on olive paste, transforming the current malaxing batch process in a real continuous process. The social, economic, and environmental consequences of an innovative process are an integral part of the cost and benefit analysis. Also if the benefits of the employment of an energy saving technology cannot always be estimated easily, examining the SWOT analysis it is clear that this innovation can be successful because the benefits are major than the costs. The SWOT analysis confirms the applicability of this innovative technology to a full scale plants, and some hypothesis about the design of a new device which should overcome traditional malaxer have been proposed.

The present paper proposes a very simple one dimensional (1-D) model that accounts for the energy loss caused by the fluid dynamic losses occurring in the vaneless diffusers of centrifugal compressors and pumps. Usually, the present techniques to design turbomachines (pumps, compressors and turbines) emphasize numerical methods and their use is relatively complex because several parameters need to be chosen and a lot of time is required to perform the calculation. For this reason, it is relevant to perform an accurate preliminary design to simplify the numerical computation phase and to choose a very good initial geometry to be used for accelerating and improving the search for the definitive geometry. However, today 1-D modeling is based on the classical theory that assumes that the angular momentum is conserved inside a vaneless diffuser, although the flow evolution is considered as non-isentropic. This means that fluid-dynamic losses are taken into account only for what concerns pressure recovery, whereas the evaluation of the outlet tangential velocity incoherently follows an ideal behavior. Starting from such considerations, a new conservation law for the angular momentum is analytically derived, which incorporates the same fluid-dynamic losses modeled by the thermodynamic transformation law that is employed for correlating pressure recovery with enthalpy increase. Similar arguments hold for incompressible flows. Detailed and very accurate three-dimensional flow simulations are employed to analyze if the new model is capable of predicting the outlet tangential velocity more accurately than the classical theory. Results provided for both compressible (centrifugal compressors) and incompressible (centrifugal pumps) flows and for different inlet velocity profiles show a significant accuracy improvement of the new conservation law in the prediction of the outlet flow conditions when compared with the classical theory, thus demonstrating that the proposed model can be employed in the preliminary design of vaneless diffusers (i.e., in the estimation of the outlet diameter) more effectively than the classical ideal theory. Furthermore, the model is validated against industrial experimental campaigns. Even further experimental data, reported in a previous paper by the same authors, confirm the reliability of the employed approach.

Although Ozone Depleting Substances (ODS) were banned with the Montreal Protocol in 1987, current refrigeration plants can not be considered sustainable for the environment. ODS have been in fact substituted by gases with high Global Warming Potential (GWP). Among many alternatives, inverse Joule Brayton air cycle had been already implemented and tested for refrigeration purposes. In the open cycles described in the available literature, the operating fluid (air) is firstly compressed by a bootstrap (volumetric) compressor and then processed by a second (centrifugal) compressor and cooled; then, it is expanded in a turbine which drives the centrifugal compressor and discharges a cold flow which can be used (directly or indirectly) for refrigeration purposes. In this work, an inverse Joule Brayton air cycle has been studied with the employment of turbocharger units. Experimental tests have been performed in order to reproduce the state-of-the-art with a small automotive turbocharger unit. Measurements show Coefficient Of Performance (COP) smaller than unit together with minimum turbine exit temperature equal to -10°C. This is due to low components efficiency: the analysis of turbine and turbocompressor maps highlights a non-optimal coupling between them. Secondly, basing on these considerations, two new air cycle layouts are proposed and analyzed. Calculations performed by means of a thermodynamic model show that higher COP and lower cycle minimum temperature can be achieved with the proposed new cycles by means of better turbine and turbocompressor matching and bigger turbocharger units with higher components efficiency.

An innovative heat exchange device has been recently proposed, which employs an intermediate solid medium to transfer heat from a gas flow at low pressure and high temperature to another gas flow at higher pressure but lower temperature, with negligible pressure losses. In this paper, a key component of this innovative heat exchanger is analyzed in deep, namely the pressurization device responsible for the particles transit between the two separate environments. The operation of the proposed pressurization system is described in detail and then modeled as a zero-dimensional time-dependent system to analyze the influence of the related mass and energy losses onto the heat exchanger efficiency. An experimental test rig reproducing the pressurization tank has been also set up: the data collected at different operating conditions confirmed the reliability of the analytical model and the negligible energy losses occurring in the pressurization process.""" AMORUSO Vitantonio"

Nowadays, the development of new power plants capable of effectively using non-conventional energy sources is strongly desirable in order to obtain a significant reduction in costs of energy. In this regard, this paper proposes a new small scale (about 100 kW) combined cycle plant which can be fired externally by any kind of biomass. Particularly, the research activity presented here is concerned with the preliminary design of this innovative plant, which will be built, by means of a project funded by “Apulia Region”, at the LabZero Research Centre of Polytechnic University of Bari in the south of Italy. The goal of the paper is to demonstrate the effectiveness of the plant in terms of energy efficiency and availability and reliability of its components. The plant is mainly composed of a centrifugal compressor and a centripetal turbine of an automotive turbocharger, with the working fluid (clean air) being heated in a high temperature heat exchanger (HTHE) by using hot flue gases produced in an external combustion chamber burning biomass. The clean hot air expands in the turbine and then feeds the combustion chamber, where biomass is burned. In order to increase the efficiency, the flue gases exiting the HTHE are delivered into a heat recovery steam generator to generate water steam which can finally expand through a rotary actuator. Two configurations, employing an open Rankine cycle and a close one respectively, are analysed, and the use of biomass is compared with methane.

This paper evaluates the effects of cavitation upon the performance of a hydraulic, proportional, directly-operated, directional valve by means of thorough experimental and numerical investigations. The experimental campaign is performed to estimate how cavitation changes the performance curves of the valve; in particular, the experimental equipment assembled to control the cavitation phenomenon inside the proportional valve is described, and the influence of cavitation on the flow rate and the flow coefficient as a function of the spool position is assessed. In addition, a full three-dimensional mixture model of the flow field within the valve is developed to accurately predict cavitation within the flow path for several spool positions. The accuracy of the numerical model is proven by previous experiences and by comparing the numerical results with the experimental data. After their validation, the numerical predictions are employed to analyse the characteristics of cavitation that cannot be experimentally evaluated, such as the volume of vapour, and to identify the zones where cavitation occurs. The numerical simulations are finally employed to predict how the variation in cavitation intensity influences the driving forces required to move the sliding spool and to calculate the minimum cavitation number for which the effects of cavitation are negligible.

The aim of this paper is to propose an effective technique which employs a proportionalintegral Fuzzy logic controller for the thrust regulation of small scale turbojet engines, capable of ensuring high performance in terms of response speed, precision and stability. Fuzzy rules have been chosen by logical deduction and some specific parameters of the closed loop control have been optimized using a numerical simulator, so as to achieve rapidity and stability of response, as well as absence of overshoots. The proposed Fuzzy logic controller has been tested on the Pegasus MK3 microturbine: the high response speed and precision of the proposed thrust control, revealed by the simulations, have been confirmed by several experimental tests with step response. Its stability has been demonstrated by means of the frequency response analysis of the system. The proposed thrust control technique has general validity and can be applied to any small-scale turbojet engine, as well as to microturbines for electricity production, provided that thrust being substituted with the net mechanical power.

Purpose – The purpose of this paper is to present a full 3D Computational Fluid Dynamics (CFD) analysis of the flow field through hydraulic directional proportional valves, in order to accurately predict the flow forces acting on the spool and to overcome the limitations of two-dimensional (2D) and simplified three-dimensional (3D) models. Design/methodology/approach – A full 3D CAD representation is proposed as a general approach to reproduce the geometry of an existing valve in full detail; then, unstructured computational grids, which identify peculiar positions of the spool travel, are generated by means of the mesh generation tool Gambit. The computational grids are imported into the commercial CFD code Fluent, where the flow equations are solved assuming that the flow is steady and incompressible. To validate the proposed computational procedure, the predicted flow rates and flow forces are compared with the corresponding experimental data. Findings – The superposition between numerical and experimental curves demonstrates that the proposed full 3D numerical analysis is more effective than the simplified 3D flow model that was previously proposed by the same authors. Practical implications – The presented full 3D fluid dynamic analysis can be employed for the fluid-dynamic design optimization of the sliding spool and, more generally, of the internal profiles of the valve, with the objective of reducing the flow forces and thus the required control force. Originality/value – The paper proposes a new computational strategy that is capable of recognizing all 3D geometrical details of a hydraulic directional proportional valve and that provides a significant improvement with respect to 2D and partially 3D approaches.

This paper proposes the design of an innovative high temperature gas-to-gas heat exchanger based on solid particles as intermediate medium, with application inmediumand large scale externally fired combined power plants fed by alternative and dirty fuels, such as biomass and coal. An optimization procedure, performed by means of a genetic algorithm combined with computational fluid dynamics (CFD) analysis, is employed for the design of the heat exchanger: the goal is the minimization of its size for an assigned heat exchanger efficiency.Two cases, corresponding to efficiencies equal to 80% and 90%, are considered.Thescientific and technical difficulties for the realization of the heat exchanger are also faced up; in particular, this work focuses on the development both of a pressurization device, which is needed to move the solid particles within the heat exchanger, and of a pneumatic conveyor, which is required to deliver back the particles from the bottom to the top of the plant in order to realize a continuous operation mode. An analytical approach and a thorough experimental campaign are proposed to analyze the proposed systems and to evaluate the associated energy losses.

This article proposes an effective methodology for the fluid-dynamic design optimization of the sliding spool of a hydraulic proportional directional valve: the goal is the minimization of the flow force at a prescribed flow rate, so as to reduce the required opening force while keeping the operation features unchanged. A full three-dimensional model of the flow field within the valve is employed to accurately predict the flow force acting on the spool. A theoretical analysis, based on both the axial momentum equation and flow simulations, is conducted to define the design parameters, which need to be properly selected in order to reduce the flow force without significantly affecting the flow rate. A genetic algorithm, coupled with a computational fluid dynamics flow solver, is employed to minimize the flow force acting on the valve spool at the maximum opening. A comparison with a typical single-objective optimization algorithm is performed to evaluate performance and effectiveness of the employed genetic algorithm. The optimized spool develops a maximum flow force which is smaller than that produced by the commercially available valve, mainly due to some major modifications occurring in the discharge section. Reducing the flow force and thus the electromagnetic force exerted by the solenoid actuators allows the operational range of direct (single-stage) driven valves to be enlarged.

The optical system allows the detection of the opening and then the control and diagnostics of injectors of any type, with any type of petrol and supply, as well as other mechanical moving parts drowned in a fluid. This system includes: - a measuring environment with an almost watertight chamber, - a fixed body, such as the body (8) of an injector, having at least two coaxial holes (3) of any geometry, - movable body, such as a control piston (7), having at least one through hole (4) of any geometry, - at least one diode (1) for the emission of an infrared or other light frequency beam placed in one of said coaxial holes (3) drilled on the fixed body, - at least one photoreceiver transistor (2) for receiving said beam, positioned frontally to said diode, and placed in the second of said coaxial holes (3) formed on the fixed body, - an electronic circuit for the transmission and reception of the light signal. The diode (1) emits an infrared or other light frequency beam which, passing through the coaxial holes (3) on the fixed body and the through hole (4) on the movable body, reaches the photoreceiver (2) that produces an indicative voltage derived from the intensity of the received light signal which is due to the displacement of the movable body with respect to the fixed body, said voltage being proportional to the percentage of juxtaposition between said through holes of the fixed body and said through hole of the movable body.