1,720,996 research outputs found
Influences of the operating conditions on the rotordynamic forces acting on a three-bladed inducer under forced whirl motion
No full textIn the present paper the results from an extensive experimental characterization of the rotordynamic forces acting on a whirling three-bladed, tapered-hub, variable-pitch inducer are presented. The campaign has been conducted in the CPRTF (Cavitating Pump Rotordynamic Test Facility) at ALTA S.p.A.. The forces acting on the impeller have been measured by means of a rotating dynamometer mounted just behind the inducer. The roles of the rotor whirl motion, flowrate, cavitating condition and liquid temperature have been investigated. The analysis has been conducted by means of the classical rotordynamic approach together with a recent experimental technique, consisting in measuring the rotordynamic forces continuous behavior (spectra) as functions of the whirl excitation frequency. This technique allows for evaluating information from experiments more rapidly and accurately with regards to previous methods. Therefore, it is useful to better capture the complexity of the rotordynamic forces and assess their consequences on the stability of axial inducers
PulCheR – Pulsed Chemical Rocket with Green High Performance Propellants: First Year Project Overview
Full text linkPulCheR (Pulsed Chemical Rocket with Green High Performance Propellants) is a research project co-funded by the European Union Seventh Framework Programme (FP7/2007-2013) under grant agreement n°313271. The project officially started as of January 1st, 2013, and is mainly aimed at demonstrating the feasibility of a pulsed propulsion system in which the propellants are fed in the combustion chamber at low pressure and the thrust is generated by means of high frequency pulses, reproducing the defence mechanism of a notable insect: the bombardier beetle. The feasibility of this new propulsion concept will be investigated at breadboard level in both mono and bipropellant configurations through the design, realization and testing of a platform of the overall propulsion system including all its main components. As an added value, the new propulsion concept will be investigated using green propellants. The present paper aims at introducing the project, its structure, its main objectives and at presenting an overview of the activities performed in the first year of the project and its current status
Analysis of Flow Instabilities on a Three-Bladed Axial Inducer in Fixed and Rotating Frames
No full textThe paper describes the results of recent experiments carried out in the Cavitating Pump Rotordynamic Test Facility for the dynamic characterization of cavitation-induced flow instabilities as simultaneously observed in the stationary and rotating frames of a high-head, three-bladed axial inducer with tapered hub and variable pitch. The flow instabilities occurring in the eye and inside the blading of the inducer have been detected, identified, and monitored by means of the spectral analysis of the pressure measurements simultaneously performed in the stationary and rotating frames by multiple transducers mounted on the casing near the inducer eye and on the inducer hub along the blade channels. An interaction between the unstable flows in the pump inlet and in the blade channels during cavitating regime has been detected. The interaction is between a low frequency axial phenomenon, which cyclically fills and empties each blade channel with cavitation, and a rotating phenomenon detected in the inducer eye
Dynamics of the Blade Channel of an Inducer Under Cavitation-Induced Instabilities
No full textA high-head three-bladed inducer has been equipped with pressure taps on the hub along the blade channels with the aim of more closely investigating the dynamics of cavitation-induced instabilities developing in the impeller flow. Spectral analysis of the pressure signals obtained from two sets of transducers mounted both in the stationary and rotating frames has allowed to characterize the nature, intensity, and interactions of the main flow instabilities detected in the experiments: subsynchronous rotating cavitation (RC), cavitation surge (CS), and a high-order axial surge oscillation. A dynamic model of the unsteady flow in the blade channels has been developed based on experimental data and on suitable descriptions of the mean flow and the oscillations of the cavitating volume. The model has been used for estimating at the inducer operating conditions of interest the intensity of the flow oscillations associated with the occurrence of the CS mode generated by RC in the inducer inlet
Pumping and Suction Performance of a Whirling Inducer
Full text linkThe experimental characterization of the rotordynamic fluid forces acting on a whirling inducer and the analysis of their influence on its pumping and suction performance are presented and discussed as functions of the operational conditions. The paper illustrates the first application of the novel approach recently developed at Alta for the simultaneous measurement of the relevant experimental data, demonstrating its remarkable versatility and effectiveness
Experimental Characterization of Rotordynamic Forces Acting on Space Turbopumps
Full text linkThe experimental characterization of the rotordynamic fluid forces acting on a whirling inducer and the analysis of their influence on its pumping and suction performance are presented and discussed as functions of the operational conditions. The paper illustrates the first application of the novel approach recently developed at Alta for the simultaneous measurement of the relevant experimental data, demonstrating its remarkable versatility and effectiveness
A Reduced Order Model for Preliminary Design and Performance Prediction of Radial Turbopumps
Full text linkA reduced order model for preliminary design and noncavitating performance prediction of radial turbopumps is illustrated. The model expresses the 3D incompressible, inviscid, irrotational flow through helical blades with slow axial variations of the pitch and backsweep by superposing a 2D cross-sectional axial vorticity correction to a fully-guided flow with axisymmetric stagnation velocity in the meridional plane. Application of the relevant governing equations yields a set of constraints for the axial evolution of the blade pitch and backsweep that allows for the closed form definition of the impeller geometry and flowfield in terms of a reduced number of controlling parameters. In turn, mass and momentum conservation are used to account for the mixing of the flow leaving the impeller and its coupling with 2D reduced order models of the flow in the diffuser (if any) and the volute, thus generating the information necessary for completing the geometric definition of the ..
Stationary Propulsive Performance of a Green Monopropellant Demonstrator for the PulCheR Project
No full textIn the framework of the PulCheR project, an experimental test campaign on a 20 N monopropellant thruster prototype has been carried out with the aim of assessing the capability of a new Pt/Al2O3 catalytic system of effectively decomposing 98% concentration hydrogen peroxide and the attainable propulsive performance in steady state conditions. The catalysts have been able to decompose up to 1 liter of 98% H2O2 with very good efficiencies (ηc* > 95% and ηΔT ≥ 90%) and without any pellets breakage or catalytic degradation. The thrust profile has been particularly smooth and the experimental specific impulse measured at sea level with the matched conical nozzle has been 130 s that corresponds to an extrapolated vacuum specific impulse for a high expansion area ratio bell-contoured nozzle higher than 185 s. The present experimental results represent useful reference data for the future assessment of the propulsive performance of the new propulsion concept proposed in the PulCheR project
Rotordynamic Forces on a Three Bladed Inducer under Forced Whirl Motion Operating at Different Conditions
Full text linkThe paper illustrates the main results of an experimental campaign conducted in the CPRTF (Cavitating Pump Rotordynamic Test Facility) at ALTA S.p.A., aimed at characterizing the rotordynamic forces acting on a whirling three-bladed, tapered-hub, variable-pitch inducer, named DAPROT3. The forces acting on the impeller have been measured by means of a rotating dynamometer mounted just behind the inducer. The roles of the imposed whirl motion of the rotor, flow coefficient, cavitation number and liquid temperature have been investigated. The results have been obtained by means of a recent experimental technique, consisting in measuring the continuous spectra of the rotordynamic forces as functions of the whirl excitation frequency. This technique allows for extrapolating valuable information from the experiments by more accurately and rapidly characterizing the spectral behavior of these forces than can be obtained from a limited number of point experiments conducted at constant whirl frequency. Therefore, it is useful to better capture the complexity of the rotordynamic forces and assess their consequences on the stability of axial inducers
Cavitating Pump Rotordynamic Test Facility at ALTA S.p.A.: Upgraded Capabilities of a Unique Test Rig
Full text linkThe paper illustrates the upgrades recently introduced in Alta’s Cavitating Pump Rotordynamic Test Facility in order to extend its experimental capabilities, with special reference to the addition of an auxiliary pump for testing of turbopump inducers over a wider range of flow coefficients, and the set-up of an original apparatus specifically designed for the characterization of the dynamic transfer matrices of cavitating inducers and turbopumps. Examples are presented of the improved capabilities of the facility
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