Continuous Spectrum of the Rotordynamic Forces on a Four Bladed Inducer

2011 ◽  
Author(s):  
Lucio Torre ◽  
Angelo Pasini ◽  
Angelo Cervone ◽  
Luca d’Agostino
Keyword(s):  
Continuous Spectrum ◽  
Experimental Technique ◽  
Cavitation Number ◽  
Flow Coefficient ◽  
Test Facility ◽  
Liquid Temperature ◽  
Qualitative And Quantitative ◽  
Experimental Campaign ◽  
The Stability ◽  
Rotordynamic Forces

The paper illustrates the 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 four-bladed, tapered-hub, variable-pitch inducer, designated as DAPAMITO4. The roles of the imposed whirl motion of the rotor, flow coefficient, cavitation number and liquid temperature have been investigated. A novel experimental technique, consisting in measuring the continuous spectra of the forces as functions of the whirl ratio, has been developed and validated. This technique gives the possibility of extracting valuable information from the experiments by clearly identifying the qualitative and quantitative behavior of the forces, and is therefore useful to catch the unlikely foreseeable complexity of the rotordynamic forces and their consequences on the stability of axial inducers.

Continuous Spectrum of the Rotordynamic Forces on a Four Bladed Inducer

2011 ◽  
Vol 133 (12) ◽  
Author(s):  
Angelo Pasini ◽  
Lucio Torre ◽  
Angelo Cervone ◽  
Luca d’Agostino
Keyword(s):  
Continuous Spectrum ◽  
Experimental Technique ◽  
Cavitation Number ◽  
Flow Coefficient ◽  
Test Facility ◽  
Liquid Temperature ◽  
Qualitative And Quantitative ◽  
Experimental Campaign ◽  
The Stability ◽  
Rotordynamic Forces

The paper illustrates the results of an experimental campaign conducted in the Cavitating Pump Rotordynamic Test Facility at ALTA S.p.A., aimed at characterizing the rotordynamic forces acting on a whirling four-bladed, tapered-hub, variable-pitch inducer, designated as DAPAMITO4. The roles of the imposed whirl motion of the rotor, flow coefficient, cavitation number and liquid temperature have been investigated. A novel experimental technique, consisting in measuring the continuous spectra of the forces as functions of the whirl ratio, has been developed and validated. This technique gives the possibility of extracting valuable information from the experiments by clearly identifying the qualitative and quantitative behavior of the forces, and is therefore useful to catch the unlikely foreseeable complexity of the rotordynamic forces and their consequences on the stability of axial inducers.

Experimental Characterization of the Rotordynamic Forces on Space Rocket Axial Inducers

2011 ◽  
Vol 133 (10) ◽  
Author(s):  
Lucio Torre ◽  
Angelo Pasini ◽  
Angelo Cervone ◽  
Luca d’Agostino
Keyword(s):  
Flow Coefficient ◽  
Test Facility ◽  
Speed Ratio ◽  
Quadratic Functional ◽  
Pump Operation ◽  
Functional Behavior ◽  
Space Rocket ◽  
The Stability ◽  
Rotordynamic Forces

The present paper illustrates the results of an experimental campaign conducted in the Cavitating Pump Rotordynamic Test Facility (CPRTF) at ALTA S.p.A. aimed at characterizing the rotordynamic forces acting on two different whirling tapered-hub, variable-pitch axial inducers. 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 destabilizing role of cavitation has been confirmed. The experimental results are consistent with previous experimental campaigns documented by the open literature, including the former data published by Caltech researchers. The observed dependence of the tangential and normal components of the rotordynamic force on the whirl-to-rotational speed ratio does not follow the quadratic functional behavior often assumed in the open literature. Rotordynamic forces of large amplitude and destabilizing nature especially occur in the presence of cavitation, potentially compromising the stability of the pump operation.

Influences of the Operating Conditions on the Rotordynamic Forces Acting on a Three-Bladed Inducer Under Forced Whirl Motion

2015 ◽  
Vol 137 (7) ◽  
Author(s):  
Dario Valentini ◽  
Giovanni Pace ◽  
Lucio Torre ◽  
Angelo Pasini ◽  
Luca d’Agostino
Keyword(s):  
Flow Rate ◽  
Excitation Frequency ◽  
Operating Conditions ◽  
Test Facility ◽  
Experimental Characterization ◽  
Liquid Temperature ◽  
The Stability ◽  
Rotordynamic Forces ◽  
Motion Flow

In 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 Cavitating Pump Rotordynamic Test Facility (CPRTF) 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, flow rate, 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.

scholarly journals Rotordynamic Forces in Cavitating Inducers

1997 ◽  
Vol 119 (4) ◽  
pp. 768-774 ◽  
Author(s):  
A. Bhattacharyya ◽  
A. J. Acosta ◽  
C. E. Brennen ◽  
T. K. Caughey
Keyword(s):  
Experimental Investigation ◽  
Axial Flow ◽  
Cavitation Number ◽  
Flow Coefficient ◽  
Quadratic Functional ◽  
Functional Behavior ◽  
Rotordynamic Forces ◽  
Frequency Ratios

This paper reports an experimental investigation of rotordynamic forces in a whirling axial flow inducer under the influence of cavitation at various flow coefficients. The results show the occurrence of large destabilizing peaks in the force tangential to the whirl orbit for positive whirl frequency ratios. The magnitude of the destabilizing forces increased with a decrease in cavitation number and flow coefficient. The rotordynamic data obtained do not exhibit quadratic functional behavior normally assumed in many rotordynamic models. Consequently, conventional generalized stiffness, damping, and inertia matrices cannot be determined for the inducer. The results demonstrate the complexity of rotordynamic forces and their consequences on stability of axial flow inducers.

Influence of a Stability Control Device on the Performance of a Cavitating Water Pump Inducer

2014 ◽  
Author(s):  
R. Lundgreen ◽  
D. Maynes ◽  
S. Gorrell ◽  
K. Oliphant
Keyword(s):  
Fluid Dynamic ◽  
Stability Control ◽  
Control Device ◽  
Design Flow ◽  
Flow Coefficient ◽  
Low Flow ◽  
Stable Operation ◽  
Dynamic Simulations ◽  
The Stability ◽  
Rotordynamic Forces

An inducer performance has been explored with and without the implementation of a stability control device. Multiphase, time-accurate computational fluid dynamic simulations have been conducted at the design flow coefficient and at two low off-design flow coefficients. At the design flow coefficient, the inducer performance was similar with and without the stability control device. At low flow coefficients, the inducer without the stability control device exhibited significant cavitation instabilities, which led to high rotordynamic forces on the inducer blades. When the stability control device was incorporated into the inducer design, nearly all of the cavitation instabilities were suppressed at low flow coefficients and the rotordynamic forces were reduced by more than an order of magnitude. Stable operation at flow coefficients far below the design value leads to a significant increase in the suction performance of the inducer, allowing pumps to operate at lower inlet pressures.

scholarly journals Environmental impact of intensive farming in sloping areas

2018 ◽  
Vol 174 ◽  
pp. 01001
Author(s):  
Giovanni Bosco ◽  
Lucia Simeoni
Keyword(s):  
Pore Water Pressure ◽  
Water Pressure ◽  
Sprinkler Irrigation ◽  
High Yield ◽  
Qualitative And Quantitative ◽  
Intensive Farming ◽  
Yield Production ◽  
Large Water ◽  
The Stability ◽  
Irrigation Runoff

The increased demand for food causes intensive farming with high yield production and large water consumption to extend significantly. Depending on soil properties, seasonal rainfall, surface drainage and water resources, hence the consumption-infiltration balance, the ground water table might be raised or depleted; soils could be saturated or remain partly saturated with negative pore pressures. As a result sloping grounds may become prone to shallow slides, as mudflows, or deep seated movements, involving large volumes of soil, especially after rupture of major watering lines or after long uncontrolled irrigations. Within this framework the paper investigates the possible effects of replacing grassland with intensive apple farming on the stability conditions of slopes. Apples require frequent watering, especially during spring and summer to meet qualitative and quantitative productive standards. Also, sprinkler irrigation is often used to protect against hail. From the precipitation, irrigation, runoff, evaporation and plant transpiration balance, the evolution of the pore water pressure distribution within an average year is calculated. Then the modified shear strength of the unsaturated-saturated soils is determined and the factor of safety against sliding is calculated.

Increasing Inducer Stability and Suction Performance With a Stability Control Device

2018 ◽  
Vol 141 (1) ◽  
Author(s):  
R. Lundgreen ◽  
D. Maynes ◽  
S. Gorrell ◽  
K. Oliphant
Keyword(s):  
Fluid Dynamic ◽  
Leading Edge ◽  
High Energy ◽  
Stability Control ◽  
Control Device ◽  
Design Flow ◽  
Flow Coefficient ◽  
Blade Tip ◽  
Rotordynamic Forces ◽  
Suction Performance

An inducer is used as the first stage of high suction performance pump. It pressurizes the fluid to delay the onset of cavitation, which can adversely affect performance in a centrifugal pump. In this paper, the performance of a water pump inducer has been explored with and without the implementation of a stability control device (SCD). This device is an inlet cover bleed system that removes high-energy fluid near the blade leading edge and reinjects it back upstream. The research was conducted by running multiphase, time-accurate computational fluid dynamic (CFD) simulations at the design flow coefficient and at low, off-design flow coefficients. The suction performance and stability for the same inducer with and without the implementation of the SCD has been explored. An improvement in stability and suction performance was observed when the SCD was implemented. Without the SCD, the inducer developed backflow at the blade tip, which led to rotating cavitation and larger rotordynamic forces. With the SCD, no significant cavitation instabilities developed, and the rotordynamic forces remained small. The lack of cavitation instabilities also allowed the inducer to operate at lower inlet pressures, increasing the suction performance of the inducer.

A Variable Viscosity Approach for the Analysis of Steady State and Dynamic Characteristics of Two-Lobe Journal Bearing With TiO2 Based Nanolubricant

2017 ◽  
Author(s):  
Ashutosh Kumar ◽  
Sashindra Kumar Kakoty
Keyword(s):  
Steady State ◽  
Dynamic Characteristics ◽  
Journal Bearing ◽  
Volume Fraction ◽  
Variable Viscosity ◽  
Flow Coefficient ◽  
Viscosity Model ◽  
Nano Lubricant ◽  
The Stability ◽  
Stiffness And Damping

Steady-state and dynamic characteristics of two-lobe journal bearing, operating on TiO2 based Nano-lubricant has been obtained. The effective viscosity is obtained by using Krieger-Dougherty viscosity model for a given volume fraction of nanoparticle in the base fluid. Various bearing performance characteristics are then obtained by solving modified Reynolds equation for variable viscosity model and couple stress model. The stiffness and damping coefficients are also determined for various values of the volume fraction of the nanoparticle in the nanofluid. Results reveal that load carrying capacity and flow coefficient increase whereas friction variable decreases without affecting the stability condition of two-lobe journal bearing operating on TiO2 based nanolubricant. On the other hand attitude angle and dynamic coefficients remains constant for all the values of volume fraction of nanoparticle.

A Study of Cavitation Flow in a Centrifugal Pump at Part Load Conditions Based on Numerical Analysis

2012 ◽  
Author(s):  
Jianping Yuan ◽  
Yanxia Fu ◽  
Shouqi Yuan
Keyword(s):  
Centrifugal Pump ◽  
Flow Rate ◽  
Suction Side ◽  
Cavitation Number ◽  
Flow Coefficient ◽  
Inlet Pipe ◽  
Part Load ◽  
Cavitation Inception ◽  
Wide Range ◽  
Load Conditions

In order to predict cavitation performance of the centrifugal pump, including cavitating structures and vapour volume at the blade suction side, as well as its relationship with the backflow in the impeller eye, a 3D numerical simulation of detailed steady and unsteady cavitating flow was applied to reproduce its inner flow fields at part load conditions (0.5Qd and 0.4Qd). The comparisons of cavitation characteristics of the current centrifugal pump at an on-design point (1.0Qd) and a high flow rate (1.2Qd) were achieved as well. In addition, Frequency analysis of pressure fluctuations at the blade passages and the inlet pipe were also obtained during cavitation for a flow coefficient of 50%. The results further show that successive blade cavitation patterns and the creeping cavitation number dropping appear for a wide range of flow rates when the inlet total pressure decreases from cavitation inception to the breakdown of the centrifugal pump, as is quite different from that when cavitation occurs at 1.0Qd or 1.2Qd. Unbalanced attached cavities on the blade suction side were also observed at 0.5Qd. Meanwhile, the unsteady behaviour of cavities attached to the blade suction side and cavitation number dropping depend on the flow rate and cavitation number. Another significant characteristic of the phenomenon is that all the domain frequencies in blade passages and inlet pipe at part load conditions are 0.048Hz∼48.285Hz, which is typically lower than the shaft rotational frequency of the model centrifugal pump.

Control of Self-Excited Oscillations in Centrifugal Blowers

2007 ◽  
Author(s):  
Saad A. Ahmed
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Critical Mass ◽  
Industrial Applications ◽  
Rotating Stall ◽  
Operating Conditions ◽  
Flow Coefficient ◽  
Flow Area ◽  
The Stability

Centrifugal compressors or blowers are widely used in many industrial applications. However, the operation of such systems is limited at low-mass flow rates by self-excited flow instabilities which could result in rotating stall or surge of the compressor. These instabilities will limit the flow range in which the compressor or the blower can operate, and will also lower their performance and efficiency. Experimental techniques were used to investigate a model of radial vaneless diffuser at stall and stall-free operating conditions. The speed of the impeller was kept constant, while the mass flow rate was reduced gradually to study the steady and unsteady operating conditions of the compressor. Additional experiments were made to investigate the effects of reducing the exit flow area on the inception of stall. The results indicate that the instability in the diffuser was successfully delayed to a lower flow coefficient when throttle rings were attached to either one or both of the diffuser walls (i.e., to reduce the diffuser exit flow area). The results also showed that an increase of the blockage ratio improves the stability of the system (i.e., the critical mass flow rate could be reduced to 50% of its value without blockage). The results indicate that the throttle rings could be an effective method to control stall in radial diffusers.

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