Flow Field in the Secondary, Seal-Containing Passages of Centrifugal Pumps

1993 ◽  
Vol 115 (4) ◽  
pp. 702-709 ◽  
Author(s):  
E. A. Baskharone ◽  
S. J. Hensel
Keyword(s):  
Flow Field ◽  
Flow Model ◽  
Computational Domain ◽  
Centrifugal Pumps ◽  
Galerkin Finite Element Method ◽  
Hydraulic Pump ◽  
Galerkin Finite Element ◽  
Swirl Velocity ◽  
Through Flow ◽  
The Impact

This paper illustrates the impact of seal configuration on the through-flow leakage in centrifugal pumps with shrouded impellers. The flow model is based on the Petrov-Galerkin finite element method, and the computational domain permits the primary/secondary flow interaction at both ends of the clearance gap. The model is applied to a hydraulic pump with two different seal configurations for the purpose of comparison. The computed results show a strong dependency of the leakage flow percentage and swirl-velocity retention on the overall shape of the shroud-to-housing passage including, in particular, the seal geometry. The results are generally consistent with documented observations and measurements in similar pump stages. From a rotordynamic standpoint, the current computational model conceptually provides the centered-rotor “zeroth-order” flow field for existing perturbation models of fluid/rotor interaction. The flow model is applied to two different secondary passage configurations of a centrifugal pump, and the results used in interpreting existing rotordynamic data concerning the same passage configurations.

Effects of Fuel Staging on the Hydrodynamic Stability of Multinozzle Swirl Flows

2020 ◽  
Vol 142 (10) ◽  
Author(s):  
Saarthak Gupta ◽  
Kiran Manoharan ◽  
Santosh Hemchandra
Keyword(s):  
Heat Release ◽  
Flow Velocity ◽  
Hydrodynamic Stability ◽  
Flow Model ◽  
Base Flow ◽  
Computational Domain ◽  
Fuel Staging ◽  
Flow Oscillations ◽  
The Impact ◽  
Oscillation Characteristics

Abstract Hydrodynamic instability in lean premixed gas turbine combustors can cause coherent flow velocity oscillations. These can in turn drive heat release oscillations that when favorably coupled with combustor acoustic modes can result in combustion instability. The aim of this paper is to understand the impact of fuel staging on the characteristics of hydrodynamic modes in multinozzle combustors. We extend our recent numerical study on the hydrodynamic stability characteristics of a multinozzle combustor having three nozzles in a straight line with uniform fuel–air ratio in each nozzle, to the nonuniform fuel–air ratio case. As before, we construct the base flow model for this study by superposing contributions from individual nozzles, determined using a base flow model for a nominally axisymmetric single nozzle, at every point in the computational domain. The impact of fuel staging is captured by changing the burnt to unburnt gas density ratio parameter in the individual contribution from each nozzle. We investigate the characteristics of the most locally absolutely unstable mode for two cases. The first one is when the middle nozzle is made fuel rich when compared to the side nozzles and the second is when the side nozzles are made fuel rich relative to the middle nozzle. The impact of nonuniform fuel/air ratio on the local absolutely unstable temporal eigenvalues is seen to be small. However, significant changes in the spatial structure of the flow oscillations associated with the hydrodynamic eigenmodes are observed. In the first case, the flow oscillations with a different locally azimuthal nature on the middle nozzle when compared to the side nozzles emerge as the middle nozzle is made richer. In the second case, the oscillations on the two side nozzles are suppressed leaving the middle nozzle in a state that closely matches that of a single unconfined nozzle with the same nominal base flow velocity field. These types of internozzle variations in flow oscillation characteristics can explain the emergence of nonuniformity in heat release oscillation characteristics between individual nozzles in multinozzle combustors.

Unsteady Flow Field and Noise Generation in a Centrifugal Pump Impeller With a Vaneless Diffuser

2005 ◽  
Author(s):  
Giorgio Pavesi ◽  
Guido Ardizzon ◽  
Giovanna Cavazzini
Keyword(s):  
Flow Field ◽  
Acoustic Radiation ◽  
Wake Flow ◽  
Test Model ◽  
Centrifugal Pumps ◽  
Vaneless Diffuser ◽  
Pump Impeller ◽  
Model Flow ◽  
Return Channel ◽  
The Impact

To improve understanding of the phenomena of stall in centrifugal pumps, extensive research was conducted to investigate the impact on flow field instabilities and the noise generated in a pump equipped with a diffuser. A pump fitted with a vaneless diffuser and a return channel was used as the test model. Flow velocity was measured at the pump and at diffuser inflow to establish a link between the flow field structure and acoustic radiation. Activity was based upon the cross spectral analysis of output signals from piezoelectric transducers placed flush with the wall at the inflow and outflow of the pump, and 3D fully-viscous unsteady computations. Results showed the jet-wake flow pattern induced an unstable vortex, which influenced flow discharging from the adjacent passage and destabilised jet-wake flow in the passage. Consequently, periodic fluctuations were seen at impeller discharge which were found to be coherent from blade to blade and possessed a rich harmonic content. With the exception of the total pressure in the far field, the pressure frequency scattering by the pump was found to be consistent when compared to the experimental and analytic results.

The Effect of Rotary Arms on Corotating Disk Flow

1995 ◽  
Vol 117 (2) ◽  
pp. 259-262 ◽  
Author(s):  
John Girard ◽  
Scott Abrahamson ◽  
Kevin Uznanski
Keyword(s):  
Reynolds Number ◽  
Flow Field ◽  
Radial Flow ◽  
Disk Drives ◽  
Number Range ◽  
Reynolds Number Range ◽  
Through Flow ◽  
Dominant Feature ◽  
Flow Visualizations ◽  
The Impact

This investigation studied the impact of rotary style arms on the flow between corotating disks contained by a stationary cylindrical enclosure. Both ventilated and nonventilated hub configurations were considered. The particular geometry used represents a simplified model for common disk drives. Flow visualizations were performed over the Reynolds number range of 3.4 × 104 to 3.4 × 105. The arms were observed to dramatically alter the flow field and to produce an azimuthal pressure gradient throughout the flow field. The dominant feature of the flow between two disks was the arm wake. Moreover, an exchange of fluid across the shroud opening, which provided arm access, was observed. Arm effects became stronger as the arm tips were positioned closer to the hub. The combination of arms and radial through flow was studied over a similar Reynolds number range. In this case, the flow field remained dominated by arm effects, although some effects arising from the radial flow were observed.

scholarly journals A Time-Discontinuous Galerkin Finite Element Method for the Solution of Impact Problem of Gas-Saturated Coal

2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Jingfei Zhang ◽  
Deyong Guo ◽  
Wenhua Wu ◽  
Pan Guo
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Discontinuous Galerkin ◽  
Impact Loading ◽  
Galerkin Finite Element Method ◽  
Galerkin Finite Element ◽  
Discontinuous Galerkin Finite Element ◽  
The Impact ◽  
Impact Problem ◽  
Element Method

Based on the general Biot theory of saturated porous media, a modified time-discontinuous Galerkin finite element method (MDGFEM) is presented to simulate the structural dynamics and wave propagation problems of gas-saturated coal subjected to impact loading. Numerical results of one dimension and two dimensions show that the present MDGFEM possesses better abilities and provides much more accurate solutions than the traditional Newmark method and previous DGFEM for the impact problem. It can effectively capture the discontinuities of the wave and filter out the effects of spurious numerical oscillation induced by high-frequency impulsive load. The results can provide a technological basis for the research of the prevention of coal and gas dynamic disasters under deep mining. And the method could be useful for the further numerical research of coal-rock-gas coupling problems and coal-gas-heat coupling problems subjected to impact loading.

Numerical and Experimental Investigations on a Centrifugal Pump With and Without a Vaned Diffuser

2004 ◽  
Author(s):  
G. Pavesi ◽  
G. Ardizzon ◽  
G. Cavazzini
Keyword(s):  
Flow Field ◽  
Acoustic Radiation ◽  
Pressure Sensors ◽  
Wake Flow ◽  
Experimental Investigations ◽  
Test Model ◽  
Centrifugal Pumps ◽  
Vaned Diffuser ◽  
Return Channel ◽  
The Impact

Extensive research on centrifugal pumps was designed to investigate the impact of a diffuser on flow field instabilities and the noise generated by these instabilities. Activity was based upon a coupled use of measurements and 3D fully-viscous, unsteady computations. The test model was a seven-blade pump-turbine, used as a pump. Fitted with a vaneless diffuser, and two vaned diffusers with twenty-two adjustable, guide-diffuser vanes, and a return channel with eleven continuous vanes. Diffusers were equipped with eight pressure sensors in the adjustable guide-diffuser vanes, and nineteen pressure taps in the continuous vanes. To establish a link between the flow field structure and acoustic radiation, flow velocity was measured in the vaneless part of the diffuser. Piezoelectric transducers, placed flush with the wall, were used to measure pressure fluctuation inside the blade channels. Signal analysis was carried out in the frequency domain. Results showed the jet-wake flow pattern induced an unstable vortex, which influenced flow discharging from the adjacent passage, and destabilized jet-wake flow in the passage. This instability caused a periodic fluctuation at the discharge of the impeller. Fluctuations were found to be coherent from blade to blade, and to possess a rich harmonic content. Numerical analyses did not fully confirm these results.

Study of the Effect of Impeller Side Clearance on the Centrifugal Pump Performance Using CFD

2015 ◽  
Author(s):  
A. Farid Ayad ◽  
H. M. Abdalla ◽  
A. Abou El-Azm
Keyword(s):  
Numerical Simulation ◽  
Centrifugal Pump ◽  
Reference Frame ◽  
Internal Flow ◽  
Computational Domain ◽  
Performance Parameters ◽  
Centrifugal Pumps ◽  
Empirical Formulas ◽  
Pump Performance ◽  
The Impact

Centrifugal pumps (CP) are probably among the most often used machinery in industrial facilities as well as in common practice. Compared to other types of rotating pumps, CP yield higher efficiency. In aerospace application reducing the weight of the CP impeller has the advantage of reducing mechanical stresses and enable using the CP at high number of revolution. In order to minimize the impeller weight the requirements to study and develop the CP with semi-open impeller appears. Using this type of impeller results in clearance between the impeller blades and the casing which degrade the centrifugal pump performance. The impact of this side clearance has not been deeply investigated in open literature. The present paper is devoted to reveal more details about the impact of CP side clearance on its performance. This is done by numerically investigating the influence of the variation of the CP side clearance width (0:0.2 impeller width) on the CP performance parameters at different flow rates (0:5 Liter/s). These CP performance parameters include the pump head, efficiency, slip factor, blades loads and the internal flow structure. 3-D steady numerical simulation has been carried out using commercial software, ANSYS® CFX. The computational domain consists of four zones: inlet, side gab, impeller and volute with outlet. They are defined by means of the multi-reference frame technique. The impeller is situated in the rotating reference frame, while the inlet, side gab and outlet zones are in the fixed reference frame, and they are related to each other through the “frozen rotor” interface. The meshes of four computational domains are generated separately after performing mesh sensitivity analysis. The boundary conditions are set as total pressure at inlet and the mass flow at outlet. A no-slip condition is imposed at the wall boundary defined at the blade and casing. A turbulent, incompressible flow solver has been adapted using SST k–ω turbulent model. The numerical simulation has been compared with own experimental results and a published empirical formulas to verify the numerical solution. The CFD results show an acceptable agreement with the results of the experimental work and the empirical formulas. It has been shown that the impeller side clearance have a great regression effect on the centrifugal pump performance. An explanation to the performance regression has been proposed based on the flow field feature. Performance regression could be attributed to the drop in the pressure difference between the impeller inlet and outlet. And the redistribution of the velocity inside the impeller channel and the side clearance.

Adaptive Preliminary-Design Workflow for Aero Engine Secondary Air System Cavities With an Application Case of Windage and Heat Transfer in a Rotor-Stator Cavity With Axial Through Flow

2018 ◽  
Author(s):  
Toni Wildow ◽  
Hubert Dengg ◽  
Klaus Höschler ◽  
Jonathan Sommerfeld
Keyword(s):  
Heat Transfer ◽  
Flow Field ◽  
Design Stage ◽  
Design Parameters ◽  
Preliminary Design ◽  
Geometry Model ◽  
Through Flow ◽  
Air System ◽  
Secondary Air ◽  
The Impact

At the preliminary design stage of the engine design process, the behaviour and efficiency of different engine designs are investigated and evaluated in order to find a best matching design for a set of engine objectives and requirements. The prediction of critical part temperatures as well as the reduction of the uncertainty of these predictions is decisive to bid a competitive technology in aerospace technology. Automated workflows and Design of Experiments (DOE) are widely used to investigate large number of designs and to find an optimized solution. Nowadays, technological progress in computational power as well as new strategies for data handling and management enables the implementation of large DOEs and multi-objective optimizations in less time, which also allows the consideration of more detailed investigations in early design stages. This paper describes an approach for a preliminary-design workflow that implements adaptive modelling and evaluation methods for cavities in the secondary air system (SAS). The starting point for the workflow is a parametric geometry model defining the rotating and static components. The flow network within the SAS is automatically recognized and CFD and Thermal-FE models are automatically generated using a library of generic models. Adaptive evaluation algorithms are developed and used to predict values for structural, air system and thermal behaviour. Furthermore, these models and evaluation techniques can be implemented in a DOE to investigate the impact of design parameters on the predicted values. The findings from the automated studies can be used to enhance the boundary conditions of actual design models in later design stages. A design investigation on a rotor-stator cavity with axial through flow has been undertaken using the proposed workflow to extract windage, flow field and heat transfer information from adiabatic CFD calculations for use in thermal modelling. A DOE has been set up to conduct a sensitivity analysis of the flow field properties and to identify the impact of the design parameters. Additionally, impacts on the distribution of the flow field parameters along the rotating surface are recognized, which offers a better prediction for local effects in the thermal FE model.

Effects of Fuel Staging on the Hydrodynamic Stability of Multi Nozzle Swirl Flows

2019 ◽  
Author(s):  
Saarthak Gupta ◽  
Kiran Manoharan ◽  
Santosh Hemchandra
Keyword(s):  
Heat Release ◽  
Flow Velocity ◽  
Hydrodynamic Stability ◽  
Flow Model ◽  
Base Flow ◽  
Computational Domain ◽  
Fuel Staging ◽  
Flow Oscillations ◽  
The Impact ◽  
Oscillation Characteristics

Abstract Hydrodynamic instability in lean premixed gas turbine combustors can cause coherent flow velocity oscillations. These can in turn drive heat release oscillations that when favourably coupled with combustor acoustic modes can result in combustion instability. The aim of this paper is to understand the impact of fuel staging on the characteristics of hydrodynamic modes in multi-nozzle combustors. We extend our recent numerical study on the hydrodynamic stability characteristics of a multi-nozzle combustor having three nozzles in a straight line with uniform fuel-air ratio in each nozzle, to the non-uniform fuel-air ratio case. As before we construct the base flow model for this study by super-posing contributions from individual nozzles, determined using a base flow model for a nominally axi-symmetric single nozzle, at every point in the computational domain. The impact of fuel staging is captured by changing the burnt to unburnt gas density ratio parameter in the individual contribution from each nozzle. We investigate the characteristics of the most locally absolutely unstable mode for two cases. The first one is when the middle nozzle is made fuel rich when compared to the side nozzles and the second is when the side nozzles are made fuel rich relative to the middle nozzle. The impact of non-uniform fuel/air ratio on the local absolutely unstable temporal eigenvalues is seen to be small. However, significant changes in the spatial structure of the flow oscillations associated with the hydrodynamic eigen-modes are observed. In the first case, the flow oscillations with a different locally azimuthal nature on the middle nozzle when compared to the side nozzles emerge as the middle nozzle is made richer. In the second case, the oscillations on the two side nozzles are suppressed leaving the middle nozzle in a state that closely matches that of a single unconfined nozzle with the same nominal base flow velocity field. These types of inter-nozzle variations in flow oscillation characteristics can explain the emergence of non-uniformity in heat release oscillation characteristics between individual nozzles in multi-nozzle combustors.

RANS Based Iso-Thermal CFD Analysis of the Flow Field Created by a Radial Swirler in a Conical Nozzle

2019 ◽  
Author(s):  
Rampada Rana ◽  
Sonu Kumar ◽  
Nagalingam Muthuveerappan
Keyword(s):  
Flow Field ◽  
Maximum Flow ◽  
Field Studies ◽  
Combustion Efficiency ◽  
Computational Domain ◽  
Conical Nozzle ◽  
Ansys Fluent ◽  
Upstream Direction ◽  
Ignition Characteristics ◽  
The Impact

Abstract Improvement of specific fuel consumption and specific thrust of gas turbine engines have necessitated to have better combustion performances requirements in terms of combustion efficiency, flame stability, better ignition characteristics, lower emissions etc. Injector designs play a very pivotal role to meet the above requirements. In this paper steady state flow field studies have been carried out in a conical nozzle fitted with single swirler which is the fundamental part of a typical injector. The aspects of the flow field both inside and outside the injector have been captured by using RANS based calculations of commercial software Ansys Fluent. The computational domain extends from 500mm in the upstream direction and the exit flow of the nozzle is allowed to meet on to a domain of length more than 2000mm. The downstream domain is so chosen that the impact of the wall on to the evaluation of the flow field is found to be negligible resembling the flow field studies in open atmosphere. Realizable k-ε turbulent model and standard wall function were used with wall y+ extended from 30 onwards. The study shows a distinct feature of maximum flow velocity at the exit of the injector lip apart from the presence of regular re-circulation bubble at the exit of the injector.

Sign in / Sign up

Export Citation Format

Share Document