Showing papers on "Axial compressor published in 2018"
TL;DR: In this article, the authors present an investigation on different methods for the calculation of the angle of attack and the underlying induced velocity on wind turbine blades using data obtained from three-dimensional Computational Fluid Dynamics (CFD).
53 citations
TL;DR: The code is the first application of a physically correct Godunov solver to three-dimensional rotating stall and surge modelling and ensures the accurate calculation of inter-cell fluxes unlike in typical modern CFD codes in which the non-linear convective terms are linearised.
43 citations
TL;DR: In this paper, the authors describe the experimental effort to characterize the flow fields of various interior subchannels in a 61-pin wire-wrapped hexagonal fuel bundle prototypical for a sodium fast reactor.
42 citations
TL;DR: In this paper, the influence of squealer width and height on the aerothermal performance of a shroudless high pressure turbine blade was investigated using a computational approach for an axial turbine blade depicting an E 3 "Energy Efficient Engine" design.
40 citations
TL;DR: It is shown that the impeller is incapable to maintain constant efficiency at surge operating conditions due to the extreme alteration of the incidence angle, which induces unsteady flow momentum transfer downstream, which is reflected as compression wave at the compressor outlet traveling toward the impellers.
Abstract: Flow instabilities such as Rotating Stall and Surge limit the operating range of centrifugal compressors at low mass-flow rates. Employing compressible Large Eddy Simulations (LES), their generation mechanisms are exposed. Toward low mass-flow rate operating conditions, flow reversal over the blade tips (generated by the back pressure) causes an inflection point of the inlet flow profile. There, a shear-layer induces vortical structures circulating at the compressor inlet. Traces of these flow structures are observed until far downstream in the radial diffuser. The tip leakage flow exhibits angular momentum imparted by the impeller, which deteriorates the incidence angles at the blade tips through an over imposed swirling component to the incoming flow. We show that the impeller is incapable to maintain constant efficiency at surge operating conditions due to the extreme alteration of the incidence angle. This induces unsteady flow momentum transfer downstream, which is reflected as compression wave at the compressor outlet traveling toward the impeller. There, the pressure oscillations govern the tip leakage flow and hence, the incidence angles at the impeller. When these individual self-exited processes occurs in-phase, a surge limit-cycle establishes.
37 citations
TL;DR: In this paper, the effect of leading edge modifications via fillet shapes near vane/blade-endwall juncture in a transonic environment within the highly loaded high pressure turbine stage was investigated.
30 citations
TL;DR: In this paper, a novel design for the axial flow blood pump is proposed, based on the bearingless permanent magnet (PM) motor concept, with the design of the impeller, the rotor, and the stator explained.
Abstract: In this paper, a novel design for the axial flow blood pump is proposed, based on the bearingless permanent magnet (PM) motor concept. The design of the impeller, the rotor, and the stator is explained. The axial length of the impeller is optimized based on the finite-element analysis (FEA), and because of reduced axial length of the rotor, only one radial active magnetic bearing is used, whose functionality is embedded in the same stator, which is used for generating motor torque. A novel design of the rotor and the stator is proposed for measuring the radial position of the rotor using four linear Hall effect sensors. This sensor assembly can measure the radial position of the rotor with good accuracy. The angular position of the rotor is measured with two Hall effect sensors. The 3-D FEA of the complete system is performed, and suspension forces, stiffness, and torques are evaluated under various control conditions. The control strategy for the bearingless PM motor based on the Hall effect position sensors is explained. The experimental setup is built in order to guide the process of design. The experimental results of the system are evaluated under different operating conditions and compared with FEA results.
29 citations
TL;DR: In this paper, the authors investigate the consequences of flow-induced bending on the vortex-induced dynamics of slender cantilever cylinders, by means of numerical simulations, and find that the primary consequence of flowinduced bending is the inhibition of single mode lock-in, replaced by a multi-frequency response of the structure, and the reduction of the vibration amplitude, as a result of the broadening of the wake excitation spectrum and of the localization of the energy transfer due to the variations induced in the normal flow profile.
27 citations
TL;DR: In this paper, a three-dimensional, multi-passage unsteady numerical study was conducted to enhance the understanding of unstairedy flow phenomena in the tip region of a transonic axial compressor rotor, and two different inlet conditions were applied to demonstrate the effect of the inlet condition on the rotor tip region.
26 citations
TL;DR: In this article, the performance characteristics of a rotor that is typically used for small unmanned aircraft were analyzed in a series of wind-tunnel experiments and the results were presented in terms of thrust, power, and roll moment coefficients under different rotor rotational speeds for a T-motor 18x6.1.
Abstract: The performance characteristics of a rotor that is typically used for small unmanned aircraft were analyzed in a series of wind-tunnel experiments. Wind-tunnel measurements were conducted with the rotor at various inflow angles in order to investigate the effects on the rotor performance of partially or fully edgewise flow as they are typically encountered with small multirotor vehicles. Rotor tests were also performed under static and fully axial flow conditions in order to investigate the aerodynamic performance during hover as well as vertical climb and descent. The wind-tunnel data were corrected to account for the interference of wind-tunnel walls with the rotor wake and the blockage due to the presence of the rotor test stand in the wind-tunnel test section. The results are presented in terms of thrust, power, and roll moment coefficients under different rotor rotational speeds for a T-motor 18x6.1. Additionally, the measured thrust and power coefficients of Master Airscrew Electric 11x7 are compared with available propeller data under static and axial flow conditions for verification purposes. It is shown that the rotor performance characteristics are strongly affected by the freestream advance ratio and the freestream inflow angles. For example, at inflow angles that are typical for multirotor vehicles between about 15° and 0° with respect to the rotor disc, thrust coefficients stay constant or grow with increasing advance ratio, whereas power coefficients remain relatively constant with changing advance ratio.
26 citations
TL;DR: In this paper, the effect of grooved surfaces in the entrance region of annular flows on local heat transfer was studied and a correlation for the local Nusselt number was proposed as a function of the effective Reynolds number, the groove aspect ratio and the local axial position from 270 experimental data.
TL;DR: In this article, a 2D particle image velocimetry (PIV) system was used to characterize the velocity and the mean flow structure in the near wake of an axial flow hydrokinetic turbine in quiescent flow conditions.
TL;DR: In this article, the effect of groove type casing treatment on the aerodynamic performance of a linear turbine cascade was investigated using the computational approach for a single-stage axial turbine blade.
TL;DR: In this article, the impact of abnormal blade installation angle on the inducement mechanism of rotating stall to achieve the active control of rotating stalls in an axial fan was studied based on throttle value function and SST k-ω turbulence model.
Abstract: It is of great value to study the impact of abnormal blade installation angle on the inducement mechanism of rotating stall to achieve the active control of rotating stall in an axial fan. Based on throttle value function and SST k-ω turbulence model, numerical simulations of the unsteady flow process in stall condition of an axial flow fan with adjustable vanes were carried out, and the influence mechanism of abnormal stagger angle of a single blade in the second stage rotor on induced position and type of stall inception and evolution process of rotating stall were analyzed. The results show that compared with synchronous adjustment of blade angle, the blade with abnormal stagger angle will cause the increase of flow rate at the beginning of stall and make the fan fall into an unstable condition in advance. The existence of blade with abnormal angle does not cause the change of the induced position and type of stall inception and the inducement mechanism of rotating stall, which are the same as the axial fan with normal blade angle. Moreover, the single blade with abnormal deviation angle has important impacts on the 3D unsteady evolution process from stall inception to stall cell formation in two rotors.
TL;DR: In this paper, the impact of the circumferential grooves casing treatment over the rear rotor (R2) in a counter-rotating axial flow compressor has been investigated based on numerical simulations.
TL;DR: In this paper, the fluid dynamics properties of the flow field in the narrow gaps between the rigid rods and the dynamics of the vibrations of the flexible rods are studied by means of numerical simulations.
TL;DR: In this paper, the authors studied the impact of tip clearance on the flow structure of tip leakage flow of axial flow fans with winglet and confirmed the existence of an optimal tip clearance which results in the maximum efficiency for an axial Flow fan with a shroud height measuring 30% of the axial chord length.
Abstract: This study is concerned with the improvement in efficiency of axial flow fans that are being used in numerous fields including outdoor units of air conditioners. The tip leakage flow occurring between a blade tip and shroud is one of the major losses in the axial flow fan. A well-known method used to control such tip leakage flow is locating winglet on the suction side of blade tips. Only a few articles have studied the impact of tip clearance on the flow structure of tip leakage flow of axial flow fans with winglet. In this study, the flow structure occurring on the blade tip due to the location of a winglet was analyzed. We confirm the existence of an optimal tip clearance which results in the maximum efficiency for an axial flow fan with a shroud height measuring 30% of the axial chord length.
TL;DR: Zha et al. as discussed by the authors used an Unsteady Reynolds-Averaged Navier-Stokes (URANS) solver for a full-annulus configurat ion o capture its non-synchronous vibration (NSV) flow excitation.
Abstract: A high speed 1-1/2 axial compressor stage is simulated in thi s paper using an Unsteady Reynolds-Averaged Navier-Stokes (URANS) solver for a full-annulus configurat ion o capture its non-synchronous vibration (NSV) flow excitation. The simulation presented in this paper assu mes rigid blades. A 3rd order WENO scheme for the inviscid flux and a 2nd order central differencing for the viscous terms are used to resolve nonlinear interaction between blades and fluid flow. A fully conservative rotor /s ator sliding boundary condition is employed with multiple-processor capability for rotor/stator interfac e information exchange for parallel computing. The sliding BC accurately captures unsteady wake propagation between t h rotor and stator blades while conserving fluxes across the rotor/stator interfaces. The predicted dominan t frequencies using the blade tip response signals are not harmonic to the engine order, which is the NSV excitation. Th e simulation is based on a rotor blade with a 1.1% tip-chord clearance. Comparison to previous 1/7th annulus simulations show previous time-shifted phase-lag BCs are accurate. The NSV excitation frequency of the full annul us simulation is for the most part 3.3% lower than experimental and matches with the 1/7th annulus simulation , although some blades displayed slightly different NSV excitation frequencies. The full annulus simulation confir ms that the instability of tornado vortices in the vicinity of the rotor tip due to the strong interaction of incoming flow , tip vortex and tip leakage flow is the main cause of the NSV excitation. This instability is present in all bla des of the rotor annulus. While the time-shifted phase lag BCs can accurately capture the frequency of NSV excitati on, phenomena related to flow separation with lower frequencies, including dual-vortex systems within blade p assages, are not captured by the 1/7th annulus simulation, but are found in the full-annulus simulation. Nomenclature e total energy per unit mass L∞ blade chord at hub NB number of blade ND number of nodal diameter p static pressure Ro Rossby number, ΩL∞ U∞ r radius T period for one nodal diameter Ph.D. Student †Ph.D., Currently an engineer at Honeywell ‡Professor. 1 D ow nl oa de d by G ec he ng Z ha o n Ju ne 6 , 2 01 4 | h ttp :// ar c. ai aa .o rg | D O I: 1 0. 25 14 /6 .2 01 407 90 52nd Aerospace Sciences Meeting 13-17 January 2014, National Harbor, Maryland AIAA 2014-0790 Copyright © 2014 by GeCheng Zha. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. AIAA SciTech
TL;DR: In this article, the authors developed a fluid-structure interaction methodology to investigate numerically the onset of hydroelastic instability of flat-shell-type fuel elements under axial flow conditions.
25 Jun 2018
TL;DR: In this article, four acoustic treatment concepts were incorporated into the bottoms of the circumferential grooves and found to provide an additional 1 to 2dB sound power level reduction under 2 kHz.
Abstract: NASA is continuing to develop over-the-rotor acoustic liners for turbofan applications. A series of low Technology Readiness Level experiments were conducted to better understand the acoustic and aerodynamic effects of these acoustic liners. The final experiment included the evaluation of four acoustic casing treatment concepts and two baseline configurations in an internal flow axial compressor facility with a 1.5 pressure-ratio high-bypass turbofan rotor. An inlet in-duct array was utilized to extract sound power levels propagating forward from the turbofan rotor. The effect of a circumferentially grooved relative to a hardwall fan case was found to reduce the in-duct sound power level by about 1.5dB for frequencies less than 2kHz while increasing noise from 4 to 8kHz by as much as 7.5dB at low fan speeds. The four acoustic treatment concepts were incorporated into the bottoms of the circumferential grooves and found to provide an additional 1 to 2dB sound power level reduction under 2kHz. The sound power level reduction was found to be even greater, 2.5 to 3.5dB, when evaluating the reduction on rotor alone duct modes (co-rotating modes). The acoustic treatments also appeared to reduce multiple pure tone noise at transonic fan speeds. Depending on the acoustic treatment concept, the high-frequency noise created by the circumferential grooves was reduced by 1.5 to 5 dB. The total noise reduction from acoustic treatments embedded into the bottoms of circumferential grooves relative to a hardwall baseline was found to be 2.5 to 3.5dB sound power level. The sound power level reduction for rotor alone (co-rotating) modes was found to be 3.5 to 4.5dB. These results show the potential for significant turbofan noise reduction by incorporating acoustic treatments over-the-rotor.
TL;DR: In this article, a series of supercritical CO2 compressors with different parameters were designed for 100 MWe, 10 MWe and 1 MWe scale power systems, and all compressors were generated and analyzed with internal MATLAB programs coupled with the NIST this articlePROP database.
Abstract: The compressor is a key component in the supercritical carbon dioxide (SCO2) Brayton cycle. In this paper, the authors designed a series of supercritical CO2 compressors with different parameters. These compressors are designed for 100 MWe, 10 MWe and 1 MWe scale power systems, respectively. For the 100 MWe SCO2 Brayton cycle, an axial compressor has been designed by the Smith chart to test whether an axial compressor is suitable for the SCO2 Brayton cycle. Using a specific speed and a specific diameter, the remaining two compressors were designed as centrifugal compressors with different pressure ratios to examine whether models used for air in the past are applicable to SCO2. All compressors were generated and analyzed with internal MATLAB programs coupled with the NIST REFPROP database. Finally, the design results are all checked by numerical simulations due to the lack of reliable experimental data. Research has found that in order to meet the de Haller stall criterion, axial compressors require a considerable number of stages, which introduces many additional problems. Thus, a centrifugal compressor is more suitable for the SCO2 Brayton cycle, even for a 100 MWe scale system. For the performance prediction model of a centrifugal compressor, the stall predictions are compared with steady numerical calculation, which indicates that past stall criteria may also be suitable for SCO2 compressors, but more validations are needed. However, the accuracy of original loss models is found to be inadequate, particularly for lower flow and higher pressure ratio cases. Deviations may be attributed to the underestimation of clearance loss according to the result of steady simulation. A modified model is adopted which can improve the precision to a certain extent, but more general and reasonable loss models are needed to improve design accuracy in the future.
TL;DR: In this paper, the impact of the casing groove on tip leakage flow (TLF), the blade tip unloading effect, redirection effect and the compound effect of suction-injection are investigated in the rear rotor of a low-speed axial flow compressors with numerical simulations.
TL;DR: In this article, a full nonlinear model is presented for the dynamics of a cantilevered cylinder, terminated by an ogival free end, and subjected to confined, inverted axial flow.
TL;DR: In this article, the effects of wake strengths and reduced frequency on the unsteady boundary layer development on a low-speed axial compressor were investigated using particle image velocimetry.
Abstract: This paper examines the transition process in a boundary layer on a rotor blade under the impingement of an inlet guide vane wake. The effects of wake strengths and the reduced frequency on the unsteady boundary layer development on a low-speed axial compressor were investigated using particle image velocimetry. The measurements were carried out at two reduced frequencies (fr = fIGVS0/U2i, fr = 1.35, and fr = 0.675) with the Reynolds number, based on the blade chord and the isentropic inlet velocity, being 97 500. At fr = 1.35, the flow separated at the trailing edge when the wake strength was weak. However, the separation was almost totally suppressed as the wake strength increased. For the stronger wake, both the wake’s high turbulence and the negative jet behavior of the wake dominated the interaction between the unsteady wake and the separated boundary layer on the suction surface of the airfoil. The boundary layer displacement thickened first due to the negative jet effect. Then, as the disturbances ...
18 Oct 2018
TL;DR: This work focuses on the interaction between throughflow and blade-to-blade design and the transition to 3D CFD, and a design strategy is presented that is based on a versatile airfoil family.
Abstract: The basic tool set to design multi-stage axial compressors consists of fast codes for throughflow and blade-to-blade analysis. Detailed blade row design is conducted with 3D CFD, mainly to control the end wall flow.
This work focuses on the interaction between throughflow and blade-to-blade design and the transition to 3D CFD. A design strategy is presented that is based on a versatile airfoil family. The new class of airfoils is generated by optimizing a large number of airfoil shapes for varying design requirements. Each airfoil geometry satisfies the need for a wide working range as well as low losses. Based on this data, machine learning is applied to estimate optimal airfoil shape and performance. The performance prediction is incorporated into the throughflow code. Based on a throughflow design, the airfoils can be stacked automatically to generate 3D blades. On this basis, a 3D CFD setup can be derived.
This strategy is applied to study upgrade options for a 15-stage stationary gas turbine compressor test rig. At first, the behavior of the new airfoils is studied in detail. Afterwards, the design is optimized for mass flow rate as well as efficiency. Selected configurations from the Pareto-front are evaluated with 3D CFD.
TL;DR: In this paper, wall effects on cross and axial flow and heat transfer of a multi-lobe particle in a packed bed were investigated numerically, where the finite element method was used for solving partial equations.
TL;DR: In this article, the effect of a swept airfoil design on the aerodynamic instabilities of transonic axial flow compressors based on global stability analysis was investigated, and an approach aimed at predicting the instabilities was proposed.
Abstract: This paper investigates the effect of a swept airfoil design on the aerodynamic instabilities of transonic axial-flow compressors based on global stability analysis. An approach aimed at predicting...
TL;DR: In this paper, the authors investigated the effect of the angle of the slot angle on the entropy generation features around the turbine blade and the aerodynamics noise emission from the turbine airfoil during the normal operation.
TL;DR: In this article, the performance of a single-stage transonic axial flow compressor with non-uniform/asymmetric rotor tip clearance is discussed, and the role of the tip leakage vortex on the stall dynamics of the compressor is elucidated.