A New Cavitating Pump Rotordynamic Test Facility

The present paper illustrates the operational characteristics of the CPRTF (Cavitating Pump Rotordynamic Test Facility), an experimental apparatus specifically designed for the measurement of rotordynamic fluid forces acting on turbopump impellers in fluid dynamic and inertial/thermal cavitation similarity conditions. The realization of the CPRTF is currently in progress under ASI (Agenzia Spaziale Italiana) funding and consists in the upgrade of the CPTF (Cavitating Pump Test Facility), already available at Centrospazio, Consorzio Pisa Ricerche, Pisa, Italy. The experimental apparatus, operating in water, will be capable of carrying out the measurement of the steady and unsteady forces exerted by the flow on the impellers of cavitating/noncavitating turbopumps. More generally, the facility is designed as a flexible, versatile and inexpensive apparatus that can be readily be adapted to carry out detailed experimental investigations on practically any kind of fluid dynamic phenomena relevant to high performance turbopumps. The main operational requirements, development choices and design trade-offs that led to the final configuration of the facility are illustrated and its performance in testing of cavitating/noncavitating turbopumps under fluid dynamic and thermal cavitation similarity are discussed. Experimental results from a number of turbopump configurations and operational conditions are presented to illustrate the present capabilities of the facility

Optimal Third-Harmonic Current Injection for an Asymmetrical Nine-phase PMSM with Non-Sinusoidal back-EMF

The paper investigates an optimal strategy to exploit the third harmonic current injection for the torque enhancement in a nine-phase permanent magnet synchronous machine (PMSM). The machine is with asymmetrical winding configuration and has a single isolated neutral point. The optimization follows the minimization of the average power losses for a given reference torque or, equivalently, the maximization of the developed torque for a given current RMS. It is shown that, in contrast to the situation for a symmetrical configuration, the optimal ratio between the fundamental and the third harmonic components does not correspond to the ratio between the corresponding back-EMF components. It is demonstrated that this is due to the fact that the phase currents have to sum to zero; consequently, the third harmonic current injection in different three-phase sets has to be different with regard to the magnitude and phase shift. The strategy is introduced using an entirely analytical approach and its effectiveness has been successfully validated through numerical simulations

Cavitation Experiments on Turbopump Inducers and Hydrofoils at Alta/Centrospazio: Overview and Future Activities

The aim of the present paper is to provide some highlights about the most interesting experimental activities carried out during the years 2000-2004 through the CPRTF (Cavitating Pump Rotordynamic Test Facility) at Centrospazio/Alta S.p.A. After a brief description of the facility, the experimental activities carried out on a NACA 0015 hydrofoil for the characterization of the pressure coefficient on the suction side and evaluation the cavity length and oscillations are presented. Then, the results obtained to characterize the performance and the cavitation instabilities on three different axial inducers are showed: in particular, a commercial three-bladed inducer, the four-bladed inducer installed in the LOX turbopump of the Ariane Vulcain MK1 rocket engine and the “FAST2”, a twobladed one manufactured by Avio S.p.A. using the criteria followed for the VINCI180 LOX inducer. The ..

A New Cavitation Test Facility at Centrospazio

The present paper illustrates the result of the trade-offs between operational requirements and practical limitations leading the final design of the CPTF (Cavitating Pump Test Facility), the CPRTF (Cavitating Pump Rotordynamic Test Facility) and the related TCT (Thermal Cavitation Tunnel). The CPTF is an experimental apparatus specifically designed for the performance analysis of turbopumps in fluid dynamic and inertial/thermal cavitation similarity conditions. The apparatus, operating in water up to 90°C, is capable of controlling the pump’s operational conditions and carrying out the measurement of the steady and/or unsteady flow parameters (pressure, velocity, temperature) at the inlet and discharge of full-scale cavitating/noncavitating turbopumps for space propulsion applications. More generally, the CPTF is designed as a flexible, versatile and inexpensive facility that can be readily be adapted to carry out detailed experimental investigations on practically any kind of fluid dynamic phenomena relevant to high performance turbopumps. The CPRTF is currently being completed under ASI (Agenzia Spaziale Italiana) funding and consists in an upgraded version of the CPTF capable of carrying out the measurement of the steady and unsteady rotodynamic forces exerted by the flow on whirling impellers of cavitating/noncavitating turbopumps using an especially designed rotating dynamometer. To this purpose the CPRTF can operate the pump under forced whirl conditions on a circular orbit with assigned eccentricity and angular speed. The TCT is a small-scale water tunnel that can be installed on the suction line of the CPTF, with the specific capability of running tests under thermal cavitation similarity conditions. The main operational requirements and development choices that led to the final configurations of the CPTF, CPRTF and TCT are illustrated and their performance in testing cavitating/noncavitating turbopumps and hydrofoils under fluid dynamic and thermal cavitation similarity are illustrated. Experimental results are presented to document the present capabilities of the facility in a number of typical configurations and operational conditions

Thermal Cavitation Experiments on a NACA 0015 Hydrofoil

The present paper illustrates the main results of an experimental campaign conducted in the Thermal Cavitation Tunnel of the CPRTF (Cavitating Pump Rotordynamic Test Facility) at Centrospazio. Experiments were carried out on a NACA 0015 hydrofoil at various incidence angles, cavitation numbers and freestream temperatures, in order to investigate the characteristics of cavitation instabilities and the impact of thermal cavitation effects. Measured cavity length, surface pressure coefficients and unsteady pressure spectra are in good agreement with the data available in the open literature and suggest the existence of a strong correlation between the onset of the various forms of cavitation and instabilities, the thermal cavitation effects, and the effects induced by the presence of the walls of the tunnel. Further analytical investigations will be carried out in order to provide a better interpretation of the above results

Experimental Activities on Liquid Propellant Turbopumps at Centrospazio

The present paper reviews recent experimental activities at Centrospazio on cavitation in liquid propellant turbopumps. These activities have been carried out in a dedicated, low-cost, versatile and easily instrumentable test facility, designed in 1996 under ESA (European Space Agency) funding and later refined and realized in 1999-2000 under a 1998/99 Fundamental Research contract by ASI (Italian Space Agency). The first part of the paper describes the characteristics and performance of the three alternative configurations of the facility: the CPTF (Cavitating Pump Test Facility), for general experimentation on cavitating/non-cavitating turbopumps under fluid dynamic and thermal cavitation similarity; the CPRTF (Cavitating Pump Rotordynamic Test Facility), capable of investigating rotordynamic fluid forces under forced vibration experiments on turbopump rotors of adjustable eccentricity and sub-synchronous or super-synchronous whirl speeds; and the TCT (Thermal Cavitation Tunnel), specifically designed for the investigation of 2D or 3D cavitating flows over test bodies in thermal cavitation similarity conditions. The second part of the paper presents some recent results of cavitation tests on helical inducers and hydrofoils. Future activities in this field at Centrospazio are illustrated

Optimal Third-Harmonic Current Injection for Asymmetrical Multiphase Permanent Magnet Synchronous Machines

This article proposes a modeling approach and an optimization strategy to exploit a third-harmonic current injection for the torque enhancement in multiphase isotropic permanent magnet synchronous machines with nonsinusoidal back electromotive forces. The modeling approach is based on a proper vector space decomposition and on the associated rotational transformation, aimed to properly select a set of stator current space vectors to be controlled. It is presented for a generic (i.e., asymmetrical, with an arbitrary angular shift) winding configuration. The injection strategy is related to the choice of a constant synchronous current set aimed at minimizing the average stator winding losses for a given reference torque by using the first and the third spatial harmonics of the air-gap flux density. The optimal solution has been found analytically and has been developed in detail for a selected set of asymmetrical winding configurations. Both the numerical and experimental results are in good agreement with the theoretical analysis

Experimental Characterization of the Cavitation Instabilities in the Avio “FAST2” Inducer

The present paper illustrates the main results of an experimental campaign conducted using the CPRTF (Cavitating Pump Rotordynamic Test Facility) at Alta S.p.A. The tests were carried out on the FAST2 inducer, a two-bladed axial pump designed and manufactured by Avio S.p.A. using the criteria followed for VINCI180 inducer. The transparent inlet section of the facility was instrumented by several piezoelectric pressure transducers located at three axial stations: inducer inlet, outlet and at the middle of the axial chord of the blades. For each axial station at least two transducers were mounted at a given angular spacing, in order to cross-correlate their signals for coherence and phase analysis. The most interesting detected instabilities were: a cavitation auto-oscillation at about 5÷12 Hz, a high order cavitation surge having a frequency of about 4.4W and a rotating stall at about 0.31W. Some experiments were carried out under forced vibration cond..

Optimal Third-Harmonic Current Injection for Asymmetrical Multiphase PMSMs

The paper proposes a modelling approach and an optimization strategy to exploit a third harmonic current injection for the torque enhancement in multiphase isotropic PMSMs with non-sinusoidal back-EMFs. The modelling approach is based on a proper vector space decomposition and on the associated rotational transformation, aimed to properly select a set of stator current space vectors to be controlled. It is presented for a generic (i.e. asymmetrical, with an arbitrary angular shift) winding configuration. The injection strategy is related to the choice of a constant synchronous current set, aimed at minimizing the average stator winding losses for a given reference torque by using the 1st and the 3rd spatial harmonics of the air-gap flux density. The optimal solution has been found analytically and has been developed in detail for a selected set of asymmetrical winding configurations. Both the numerical and experimental results are in good agreement with the theoretical analysis

Cognitive conflicts in major depression : Between desired change and personal coherence

This is an open access article under the terms of the Creative Commons Attribution-NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposesThe notion of intrapsychic conflict has been present in psychopathology for more than a century within different theoretical orientations. However, internal conflicts have not received enough empirical attention, nor has their importance in depression been fully elaborated. This study is based on the notion of cognitive conflict, understood as implicative dilemma (ID), and on a new way of identifying these conflicts by means of the Repertory Grid Technique. Our aim was to explore the relevance of cognitive conflicts among depressive patientsPeer reviewedFinal Published versio