Numerical Characterization of the Inlet Flow for Eleven Radial Turbomachines

2010 ◽  
Author(s):  
Nathan O. Packard ◽  
David Japikse ◽  
R. Daniel Maynes ◽  
Steven E. Gorrell
Keyword(s):  
Flow Field ◽  
Static Pressure ◽  
Model Development ◽  
Leading Edge ◽  
Inlet Flow ◽  
Numerical Characterization ◽  
Study Results ◽  
High Gradients ◽  
Computational Fluid Dynamics Cfd

Successful modeling of a turbomachine stage requires attention to many details, including a realistic understanding of the inlet flow field. Various levels of modeling, from 1-D to 3-D viscous, plus various levels of measurement, from a simple inlet shroud pressure tap to complex inlet surveys, are considered in design and development work. In this study, a careful review is made of measurement and calculation options for inlet modeling. Historical practice places a static pressure tap on the shroud just upstream of the impeller leading edge for experimental characterization of centrifugal turbomachines. Previously developed statistics based meanline models rely in part on this measured data. However, the location of the tap may be vulnerable to high gradients which would decrease the dependability of the developed models. Computational Fluid Dynamics (CFD) and Multi-Stream Tube (MST) analyses were performed to test the appropriateness of the historically placed static pressure tap location and to characterize the inlet flow of typical radial flow turbomachines. Eleven ConceptsNREC machines were chosen for investigation to provide a wide variety of inlet geometric and flow conditions. The results derived from the CFD and MST analyses suggest that the historically placed static pressure tap location is an inappropriate anchor point for model development. While the focus of this work is not intended to reveal why the inlet behaves as it does, it does reveal that for a wide variety of inlet configurations and impeller sizes, the presumed inlet tap location should no longer be used in experimental work. Steep gradients in the static pressure indicate that a relatively minor movement of the static pressure tap would significantly alter the experimental measurements and generate noise in statistical modeling. While large variations in the pressure field are apparent near the impeller leading edge for all machines considered, the study results show that the flow field is uniform and very predictable when well upstream of the impeller leading edge. A point approximately 3 blade heights upstream from the impeller leading edge appears to be a sound location to anchor 1-D meanline model development, as well as for future experimental investigation.

Non-Uniform Two-Phase Flow of Supercritical Carbon Dioxide Centrifugal Compressor

2020 ◽  
Author(s):  
Wenrui Bao ◽  
Ce Yang ◽  
Li Fu ◽  
Changmao Yang ◽  
Lucheng Ji
Keyword(s):  
Carbon Dioxide ◽  
Supercritical Carbon Dioxide ◽  
Flow Field ◽  
Centrifugal Compressor ◽  
Static Pressure ◽  
Leading Edge ◽  
Phase Region ◽  
Tip Clearance ◽  
Two Phase ◽  
Supercritical Carbon

Abstract An asymmetric structure of volute in a supercritical carbon dioxide centrifugal compressor induces a non-uniform circumferential distribution of the upstream flow field, which inevitably affects the formation of a two-phase region of carbon dioxide in an impeller. In this work, unsteady simulations for centrifugal compressors were conducted. First, the influence of low static strip induced by low static pressure near volute tongue on the impeller flow field was presented. Then, the non-uniform flow field distribution in the impeller passages and flow characteristics of the passages at the impeller inlet were obtained. Finally, the two-phase regions in the impeller were presented. The results demonstrate that for a centrifugal compressor with volute, the two-phase region appears not only on the suction surface of the leading edge of the blade, but also in some impeller passages, on the pressure surface of the blade near the leading edge, and in the leading edge and mid-chord of tip clearance, under the design conditions. The low static pressure strip induced by the volute leads to a high-speed region in the impeller passages where the temperature and pressure of supercritical carbon dioxide fall below the critical point and carbon dioxide enters the two-phase region. Meanwhile, the static pressure on the blade surface is distorted under the influence of a high-speed region in the passages, resulting in the formation of a two-phase region at the tip clearance. The flow distortion of passages at the impeller inlet results in the appearance of two-phase regions on the both sides of leading edge of the blade. The dryness on the suction side of the blade leading edge and the leading edge of the tip clearance is lower, which indicated that the proportion of liquid-phase carbon dioxide is higher in these two-phase regions.

scholarly journals Interpreting Aerodynamics of a Transonic Impeller from Static Pressure Measurements

2018 ◽  
Vol 2018 ◽  
pp. 1-9
Author(s):  
Fangyuan Lou ◽  
John Charles Fabian ◽  
Nicole Leanne Key
Keyword(s):  
Flow Field ◽  
High Speed ◽  
Static Pressure ◽  
Pressure Ratio ◽  
Leading Edge ◽  
Pressure Measurements ◽  
High Loss ◽  
Supersonic Inlet ◽  
Mach Numbers ◽  
Inlet Conditions

This paper investigates the aerodynamics of a transonic impeller using static pressure measurements. The impeller is a high-speed, high-pressure-ratio wheel used in small gas turbine engines. The experiment was conducted on the single stage centrifugal compressor facility in the compressor research laboratory at Purdue University. Data were acquired from choke to near-surge at four different corrected speeds (Nc) from 80% to 100% design speed, which covers both subsonic and supersonic inlet conditions. Details of the impeller flow field are discussed using data acquired from both steady and time-resolved static pressure measurements along the impeller shroud. The flow field is compared at different loading conditions, from subsonic to supersonic inlet conditions. The impeller performance was strongly dependent on the inducer, where the majority of relative diffusion occurs. The inducer diffuses flow more efficiently for inlet tip relative Mach numbers close to unity, and the performance diminishes at other Mach numbers. Shock waves emerging upstream of the impeller leading edge were observed from 90% to 100% corrected speed, and they move towards the impeller trailing edge as the inlet tip relative Mach number increases. There is no shock wave present in the inducer at 80% corrected speed. However, a high-loss region near the inducer throat was observed at 80% corrected speed resulting in a lower impeller efficiency at subsonic inlet conditions.

NUMERICAL CHARACTERIZATION OF THE FLOW FIELD IN A FOUR-GENERATION AIRWAY

2008 ◽  
Vol 08 (01) ◽  
pp. 55-74 ◽  
Author(s):  
T. C. LAI ◽  
Y. S. MORSI ◽  
M. SINGH
Keyword(s):  
Reynolds Numbers ◽  
Bronchial Tree ◽  
Secondary Flows ◽  
Fourth Generation ◽  
Numerical Characterization ◽  
Wide Range ◽  
Symmetrical Model ◽  
Computational Fluid Dynamics Cfd ◽  
Insight Into

In this paper, various aspects of respiratory airflow generated from the branching network of tubes that make up the tracheal-bronchial tree are numerically analyzed using the computational fluid dynamics (CFD) package CFX. The model used is a four-generation airway that is geometrically similar to Weibel's symmetrical model. In the present analysis, two different models (in-plane and off-plane) are examined for a wide range of Reynolds numbers that correspond to human breathing conditions. The findings indicate that the secondary flow patterns generated become more significant as the flow passes from the trachea to the fourth-generation airway. Moreover, comparison between in-plane and off-plane models shows that the skewed velocity profiles and secondary flows for the in-plane model are more prominent than those for the off-plane one. In general, the model developed in this study is capable of providing an overall insight into the effect of fluid flow in multiple generations of the human upper respiratory airways.

A Study of the Flow Field Associated with a Steadily-Rolling Slender Delta Wing

1964 ◽  
Vol 68 (638) ◽  
pp. 106-110 ◽  
Author(s):  
J. K. Harvey
Keyword(s):  
Flow Field ◽  
Static Pressure ◽  
Delta Wing ◽  
Angle Of Attack ◽  
Leading Edge ◽  
Rolling Moment ◽  
Air Stream ◽  
Total Head ◽  
Theoretical Predictions ◽  
Attached Flow

SummaryIn this paper an experiment is described in which a detailed study was made of the flow field associated with a slender sharp-edged delta wing which was rolling steadily at zero angle of attack to an air stream. The investigation was made by performing two pressure surveys: first , one of the static pressure acting on the wing’s surface and second by measuring the total-head distribution in the neighbourhood of the wing. From the former the local rolling-moment coefficients, Clp, are evaluated and these are compared with the predictions for attached flow, thus assessing the contributions to the forces acting on the wing which arise as a consequence of the leading-edge separations. The second set of surveys is used to construct a picture of the flow-field details and this is compared with that known to occur on a similar wing when it is set at an angle of attack to the airstream. One interesting finding is that the secondary separation which appears to cause the discrepancy between the theoretical predictions and the measurements made on slender wings at incidence, is absent in this configuration and thus it is concluded that these data could be used for a more meaningful test of the theory.

scholarly journals Numerical and experimental investigation of the pressure fluctuation in a mixed-flow pump under low flow conditions

2019 ◽  
Vol 234 (1) ◽  
pp. 46-57 ◽  
Author(s):  
Xi Shen ◽  
Desheng Zhang ◽  
Bin Xu ◽  
Ruijie Zhao ◽  
Yongxin Jin ◽  
...  
Keyword(s):  
Flow Field ◽  
Flow Rate ◽  
Flow Separation ◽  
Pressure Fluctuation ◽  
Static Pressure ◽  
Leading Edge ◽  
Low Flow ◽  
Flow Conditions ◽  
Mixed Flow ◽  
Flow Pump

In this paper, the large eddy simulation is utilized to simulate the flow field in a mixed-flow pump based on the standard Smagorinsky subgrid scale model, which is combined with the experiments to investigate pressure fluctuations under low flow conditions. The experimental results indicated that the amplitude of fluctuation at the impeller inlet is the highest, and increases with the reduction of the flow rate. The main frequencies of pressure fluctuation at the impeller inlet, impeller outlet, and vane inlet are blades passing frequency, while the main frequency at the vane outlet changes with the flow rate. The results of the simulation showed that the axial plane velocity at impeller inlet undergoes little change under 0.8 Qopt. In case of 0.4 Qopt, however, the flow field at impeller inlet becomes complicated with the axial plane velocity changing significantly. The flow separation is generated at the leading edge of the suction surface at t* = 0.0416 under 0.4 Qopt, which is caused by the increase of the incidence angle and the influence of the tip leakage flow. When the impeller rotates from t* = 0.0416 to t* = 0.1249, the flow separation intensified and the swirling strength of the separation vortex is gradually increased, leading to the reduction of the static pressure, the rise of adverse pressure gradient, and the generation of backflow. The static pressure at the leading edge of the impeller recovers gradually until the backflow is reached. In addition, the flow separation is the main reason for the intensification of the pressure fluctuation.

Design, Fabrication and Characterization of a Mechanical Micropump

2015 ◽  
Author(s):  
Bin Duan ◽  
Tinghui Guo ◽  
Minqing Luo ◽  
Xiaobing Luo
Keyword(s):  
Flow Field ◽  
Flow Rate ◽  
Pressure Head ◽  
Tip Clearance ◽  
Average Deviation ◽  
Blade Tip ◽  
Computational Fluid Dynamics Cfd ◽  
Inlet Angle ◽  
Blade Tip Clearance

In this paper, a centrifugal micropump was designed, fabricated and characterized. The proposed micropump is able to provide a 1.4L/min flow rate and a 75KPa pressure head at 24000 rpm with an oversize of 46mm wide and 69mm long. The hydrodynamic components were designed based on partial emission pump. Meanwhile, the geometric profiles of both impeller and volute were simplified for manufacturing. A computational fluid dynamics (CFD) analysis was performed to predict the effects of blade inlet angle and vane number on hydraulic performance. Experiments were conducted at 4 different rotational speeds to validate the numerical results. The results showed that the numerical simulation has a high accuracy to predict the micropump flow field with the overall average deviation less than 3%. As expected, the micropump prototype performed obvious partial emission pump features. In terms of the external characteristic, the pressure head at a given rotational speed decreased little with flow rate increasing. While, in the flow field, complex secondary flow was significant in the impeller passage, due to the joint action of the blade tip clearance leakage and axial vortex. Regression analysis and statistical evaluation showed that the flow nondimensional coefficients at different rotational speeds correlated well, indicating that classical similarity rules was still applicable to this micropump.

Experimental and Numerical Characterization of an Electrically Propelled Vehicles Battery Casing Including Battery Module

2014 ◽  
Vol 6 (4) ◽  
Author(s):  
Johan Anderson ◽  
Johan Sjöström ◽  
Petra Andersson ◽  
Francine Amon ◽  
Joakim Albrektsson
Keyword(s):  
Heat Transfer ◽  
Transfer Coefficients ◽  
Power Train ◽  
Fire Model ◽  
Heat Transfer Coefficients ◽  
Fire Resistance Test ◽  
Numerical Characterization ◽  
Computational Fluid Dynamics Cfd ◽  
Battery Module

This paper demonstrates the possibility to predict a battery system's performance in a fire resistance test according to the new amendment of United Nations Regulation No. 100 “Uniform Provisions Concerning the Approval of Vehicles with Regard to Specific Requirements for the Electric Power Train” (R100) based on careful measurements of the physical properties of the casing material, as well as modeling of the battery modules and computer simulations. The methodology of the work consists of estimating the heat transfer coefficients by using a gasoline pool fire model in the computational fluid dynamics (CFD) software FireDynamicsSimulator (FDS), followed by finite-element (FE) calculations of the temperatures in the battery

scholarly journals Reconstructing Compressor Non-Uniform Circumferential Flow Field From Spatially Undersampled Data: Part 2 — Practical Application for Experiments

2020 ◽  
Author(s):  
Fangyuan Lou ◽  
Douglas R. Matthews ◽  
Nicholas J. Kormanik ◽  
Nicole L. Key
Keyword(s):  
Flow Field ◽  
Total Pressure ◽  
High Speed ◽  
Static Pressure ◽  
Pressure Field ◽  
Leading Edge ◽  
Pressure Profile ◽  
Sampled Data ◽  
Mean Values ◽  
Novel Method

Abstract In the previous part of the paper, a novel method to reconstruct the compressor non-uniform circumferential flow field using spatially under-sampled data points is developed. In this part of the paper, the method is applied to two compressor research articles to further demonstrate the potential of the novel method in resolving the important flow features associated with these circumferential non-uniformities. In the first experiment, the static pressure field at the leading edge of a vaned diffuser in a high-speed centrifugal compressor is reconstructed using pressure readings from nine static pressure taps placed on the hub of the diffuser. The magnitude and phase information for the first three dominant wavelets are characterized. Additionally, the method shows significant advantages over the traditional averaging methods for calculating repeatable mean values of the static pressure. While using the multi-wavelet approximation method, the errors in the mean static pressure with one dropout measurement are 70% less than the pitchwise-averaging method. In the second experiment, the full-annulus total pressure field downstream of Stator 2 in a three-stage axial compressor is reconstructed from a small segment of data representing 20% coverage of the annulus. Results show very good agreement between the reconstructed total pressure profile and the experiment at a variety of spanwise locations from near hub to near shroud. The features associated with blade-row interactions accounting for passage-to-passage variations are resolved in the reconstructed total pressure profile.

Development of the Unsteady Flow on a Turbine Rotor Platform Downstream of a Rim Seal

2004 ◽  
Author(s):  
Kirk D. Gallier ◽  
Patrick B. Lawless ◽  
Sanford Fleeter
Keyword(s):  
Flow Field ◽  
Unsteady Flow ◽  
Leading Edge ◽  
Turbine Rotor ◽  
Secondary Flows ◽  
Thermal Design ◽  
Flow Rates ◽  
Image Velocimetry ◽  
Downstream Flow

In high temperature turbines, air from disk cavities is forced through the vane-rotor seal to prevent hot gas ingress into these cavities. This emergent seal air can play a significant role in the formation of secondary flows which emanate from the hub region near the rotor blade leading edge. The formation of these structures is also dependent on the inherently unsteady flow field driven by the vane-rotor interaction. As these secondary flows play an important role in both blade performance and heat transfer, the physics that governs them is of significant interest in turbine aero and thermal design. This work investigates and characterizes the aerodynamic signature of the interaction between an emergent seal flow and the hub flow approaching the downstream rotor including the effects of vane-rotor interaction. This is accomplished by means of an experimental investigation performed on the first stage of the Purdue Research Turbine using Particle Image Velocimetry (PIV). The flow field is interrogated in the near-hub region of the intra-stage space, downstream of the first vane row. Purge air is introduced through a planar seal at two different flow rates which characterize typical high and low boundaries for the range of dimensionless seal flow rates encountered in practice. Two-dimensional (radial and axial) velocity data from four measurement planes spaced from vane pressure side to mid-passage are acquired. These data are phase-locked to rotor position. The ensemble-averaged vorticity data from each of ten rotor positions provide a characterization of the effect of the rotor potential field on the emergent seal flow. Vane wake affects on purge strength and downstream flow development are captured at each of two seal flow rates.

Transonic Axial Compressors With Total Pressure Inlet Flow Field Distortions

2014 ◽  
Author(s):  
Andreas Lesser ◽  
Reinhard Niehuis
Keyword(s):  
Flow Field ◽  
Total Pressure ◽  
Static Pressure ◽  
Phenomenological Approach ◽  
Numerical Results ◽  
Tip Clearance ◽  
Compressor Stage ◽  
Inlet Flow ◽  
Inflow Velocity ◽  
Upstream Flow

Non-uniform inlet flow has come back into focus of research during the last years due to the need of increasing the operational range of airborne engines. Higher climbing rates for lower noise pollution at airports as well as boundary layer ingesting inlet designs lead to the demand of inlet distortion resistant engines and compressors, in particular. To fulfill this design task, a deep understanding of the dominant flow physics of the distortion transport through the compressor as well as the influence of the compressor on the upstream flow field is needed. This paper starts with the transport of a circumferential total pressure distortion through a compressor stage. Using numerical results, previously validated by experimental data, a phenomenological approach for the transport is presented. The most important finding is the essential role of the different propagation speeds of the static pressure distortion and the inflow velocity distortion and its decoupling. A static pressure and an inflow velocity distortion are present for all kinds of total pressure distortions caused by the upstream flow field redistribution of the compressor. This decoupling causes not only a significant circumferential increase of the distorted sector but also a strong variation of the distortion magnitude downstream of the compressor stage. All relevant phenomena are present in the phenomenological approach as well as in the numerical and the referred experimental results. Inlet distortions result in a decrease of stability margin [1],[2]. The crucial area for the stability of most modern transonic compressors is the tip region; therefore, the tip region was under particular investigation. The numerical results show that the flow field in the distorted area is shifted toward the stall line. The shock system and the tip clearance vortex behave similar to the results near stall with uniform inflow. No local stall can be observed, although the local operating points within the distorted sector travel beyond the stall line of the compressor map with uniform inflow. Finally, a new analytical approach for the critical distortion angle is presented. The main finding is the circumferential extent has to be big enough to separate the zones of decoupled distortion quantities.

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