EFFECT OF AN AXIALLY TILTED VARIABLE STATOR VANE PLATFORM ON PENNY CAVITY AND MAIN FLOW

2021 ◽  
pp. 1-20
Author(s):  
Johannes Janssen ◽  
Daniel Pohl ◽  
Peter Jeschke ◽  
Alexander Halcoussis ◽  
Rainer Hain ◽  
...  
Keyword(s):  
Wind Tunnel ◽  
Flow Region ◽  
Cavity Flow ◽  
Main Flow ◽  
Pressure Probe ◽  
Stator Vane ◽  
Cfd Analyses ◽  
Annular Cascade ◽  
The Impact ◽  
Variable Stator

Abstract This paper presents the impact of an axially tilted variable stator vane platform on penny cavity flow and passage flow, with the aid of both optical and pneumatic measurements in an annular cascade wind tunnel as well as steady CFD analyses. Variable stator vanes in axial compressors require a clearance from the endwalls. This means that penny cavities around the vane platform are inevitable. Production and assembly deviations can result in a vane platform which is tilted about the circumferential axis.. Penny cavity and main flow in geometries with and without platform tilting were compared in an annular cascade wind tunnel. Detailed particle image velocimetry measurements were conducted inside the penny cavity and in the vane passage. Steady pressure and velocity data was obtained by two-dimensional multi-hole pressure probe traverses in the inflow and the outflow. Furthermore, pneumatic measurements were carried out using pressure taps inside the penny cavity. Additionally, oil flow visualization was conducted on the airfoil, hub, and penny cavity surfaces. Steady CFD simulations have been benchmarked against experimental data. The results show that tilting the vane platform reduces the penny cavity leakage mass flow. By decreasing penny cavity leakage, platform tilting also affects the passage flow where it leads to a reduced turbulence level and total pressure loss in the leakage flow region. In summary, the paper demonstrates the influence of penny platform tilting on cavity flow and passage flow and provides new insights into the mechanisms of penny cavity-associated losses.

Effect of an Axially Tilted Variable Stator Vane Platform on Penny Cavity and Main Flow

2021 ◽  
Author(s):  
Johannes Janssen ◽  
Daniel Pohl ◽  
Peter Jeschke ◽  
Alexander Halcoussis ◽  
Rainer Hain ◽  
...  
Keyword(s):  
Wind Tunnel ◽  
Flow Region ◽  
Cavity Flow ◽  
Main Flow ◽  
Pressure Probe ◽  
Stator Vane ◽  
Cfd Analyses ◽  
Annular Cascade ◽  
The Impact ◽  
Variable Stator

Abstract This paper presents the impact of an axially tilted variable stator vane platform on penny cavity flow and passage flow, with the aid of both optical and pneumatic measurements in an annular cascade wind tunnel as well as steady CFD analyses. Variable stator vanes (VSVs) in axial compressors require a clearance from the endwalls. This means that penny cavities around the vane platform are inevitable. Production and assembly deviations can result in a vane platform which is tilted about the circumferential axis. Due to this deformation, backward facing steps occur on the platform edge. Penny cavity and main flow in geometries with and without platform tilting were compared in an annular cascade wind tunnel, which comprises a single row of 30 VSVs. Detailed particle image velocimetry (PIV) measurements were conducted inside the penny cavity and in the vane passage. Steady pressure and velocity data was obtained by two-dimensional multi-hole pressure probe traverses in the inflow and the outflow. Furthermore, pneumatic measurements were carried out using pressure taps inside the penny cavity. Additionally, oil flow visualization was conducted on the airfoil, hub, and penny cavity surfaces. Steady CFD simulations with boundary conditions, according to the measurements, have been benchmarked against experimental data. The results show that tilting the VSV platform reduces the mass flow into and out of the penny cavity. By decreasing penny cavity leakage, platform tilting also affects the passage flow where it leads to a reduced turbulence level and total pressure loss in the leakage flow region. In summary, the paper demonstrates the influence of penny platform tilting on cavity flow and passage flow and provides new insights into the mechanisms of penny cavity-associated losses.

scholarly journals Variable Stator Vane Penny Gap Aerodynamic Measurements and Numerical Analysis in an Annular Cascade Wind Tunnel

2020 ◽  
Vol 11 (2) ◽  
pp. 44-55
Author(s):  
Daniel Pohl ◽  
Johannes Janssen ◽  
Peter Jeschke ◽  
Alexander Halcoussis ◽  
Hannes Wolf
Keyword(s):  
Numerical Analysis ◽  
Wind Tunnel ◽  
Stator Vane ◽  
Annular Cascade ◽  
Variable Stator

Wind Tunnel Test of a Rotorcraft with Lift Compounding

2021 ◽  
Vol 66 (1) ◽  
pp. 1-16
Author(s):  
Andŕe Bauknecht ◽  
Xing Wang ◽  
Jan-Arun Faust ◽  
Inderjit Chopra
Keyword(s):  
Wind Tunnel ◽  
Flow Field ◽  
Reverse Flow ◽  
Lift Coefficient ◽  
Wind Tunnel Test ◽  
Flow Region ◽  
Field Analysis ◽  
Rolling Moment ◽  
The Impact ◽  
Side Flow

Rotorcraft flight speed is limited by compressibility effects on the advancing blade side and decreasing lift potential on the retreating blade side. It may thus be beneficial to employ a hingeless rotor to generate additional lift with the advancing blade and compensate the resulting rolling moment with a fixed wing on the retreating blade side. This concept is a form of "lift compounding" that appears to show enormous potential. The present paper presents results of a wind tunnel test with a slowed, hingeless rotor and single fixed wing on the retreating blade side. Based on rotor test stand data and flow field measurements, the impact of operational and rotor parameters on system performance and aerodynamics is examined, mutual interaction effects between rotor and fixed wing are analyzed, and dominant flow structures are characterized in the reverse flow region on the retreating blade side. Flow field analysis reveals a reverse flow entrance vortex that freely convects through the reverse flow region and rivals the blade tip vortices in strength. Contrary to previous beliefs, this vortex originates from upstream of the reverse flow region and only its detachment from the rotor blade is related to entering this region. The combination of finite rolling moment trim and aft shaft tilt significantly increases rotor lift coefficient and corresponding peak lift-to-drag ratio of the compound rotorcraft. Results are compared with predictions from a comprehensive rotor analysis that is expanded to cover the main effects of the added fixed wing and is able to reproduce general performance trends of the rotorcraft. The present study highlights that adding a single fixed wing and hingeless rotor to a high-speed rotorcraft could significantly improve its performance.

Bluff body aerodynamics of the Thies Laser Precipitation Monitor investigated using CFD and wind tunnel measurements

2020 ◽  
Author(s):  
Mattia Stagnaro ◽  
Enrico Chinchella ◽  
Arianna Cauteruccio ◽  
Luca Giovanni Lanza
Keyword(s):  
Particle Size ◽  
Wind Tunnel ◽  
Bluff Body ◽  
Stokes Equations ◽  
Flow Direction ◽  
Atmospheric Precipitation ◽  
Pressure Probe ◽  
Fall Velocity ◽  
Local Flow ◽  
The Impact

<p>Optical disdrometers are among the non-catching type instruments used to measure liquid and solid precipitation. The increasing use of such instruments in operational observations is due to their capability to provide additional information than the precipitation rate alone, like e.g. the particle size distribution and the fall velocity of hydrometeors. Furthermore, they are well suited to operate in unattended, automatic weather stations. Having no collector to catch the approaching hydrometeors, their outer shape strongly depends on the measuring principle exploited. The impact of wind on the measurement is therefore different from the typical undercatch that is expected from more traditional catching type precipitation gauges. In general, they are not axisymmetric and base the identification and classification of hydrometeors on the coupling of particle size and fall velocity characteristics, which can be affected by the wind and by the airflow deformation and turbulence produced by their bluff-body aerodynamic response. The focus of this work is the Thies Laser Precipitation Monitor (LPM), which uses an optical sensor to detect the obstruction of an infrared laser beam caused by the crossing hydrometeors. The reduction in the sensor output voltage is proportional to the drop dimension, while the duration of the reduction is proportional to the drop falling speed. This instrument presents a very complex and not axisymmetric outer shape that makes it difficult to qualitatively predict the flow pattern and requires to consider multiple wind directions and wind speeds. The airflow field was obtained with a Computational Fluid Dynamics (CFD) approach, by numerically solving the Reynolds Averaged Navier-Stokes equations with the k-ω SST turbulence closure model. Results are validated through local flow velocity measurements obtained in the DICCA wind tunnel. The Thies LPM® was placed in the measuring chamber of the wind tunnel (1.7 x 1.35 x 8.8 m) on to a rotating plate and the airflow velocity was sampled at multiple positions around the instrument. The measurements were obtained using a traversing system equipped with a “Cobra” multi hole pressure probe, that provides the three velocity components of the local flow. Different orientation angles of the gauge with respect to the incoming flow direction were tested. Based on the simulations and wind tunnel tests performed, the less impacting configuration of the instrument relative to the main wind direction is obtained. The information can be useful to design effective solutions to minimise the impact of wind and turbulence on the measurements (e.g. windshields) and to derive suitable correction curves to improve the measurement accuracy. This work is funded as part of the activities of the EURAMET – Normative project “INCIPIT – Calibration and Accuracy of Non-Catching Instruments to measure liquid/solid atmospheric precipitation”.</p>

scholarly journals A Mathematical Model for Swallowing of Concentrated Fluids in Oesophagus

2011 ◽  
Vol 8 (3-4) ◽  
pp. 309-321 ◽  
Author(s):  
S. K. Pandey ◽  
Dharmendra Tripathi
Keyword(s):  
Mathematical Model ◽  
Flow Rate ◽  
Plug Flow ◽  
Flow Region ◽  
Mechanical Efficiency ◽  
Casson Fluid ◽  
Local Pressure ◽  
Integral Number ◽  
Tomato Puree ◽  
The Impact

This model investigates particularly the impact of an integral and a non-integral number of waves on the swallowing of food stuff such as jelly, tomato puree, soup, concentrated fruits juices and honey transported peristaltically through the oesophagus. The fluid is considered as a Casson fluid. Emphasis is on the study of the dependence of local pressure distribution on space and time. Mechanical efficiency, reflux limit and trapping are also discussed. The effect of Casson fluid vis-à-vis Newtonian fluid is investigated analytically and numerically too. The result is physically interpreted as that the oesophagus makes more efforts to swallow fluids with higher concentration. It is observed that the pressure is uniformly distributed when an integral number of waves is there in the oesophagus; but it is non-uniform when a non-integral number of waves is present therein. It is further observed that as the plug flow region widens, the pressure difference increases, which indicates that the averaged flow rate will reduce for a Casson fluid. It is also concluded that Casson fluids are more prone to reflux.

A numerical approach for the assessment of crosswind effects on barrier-protected trains running on bridges

2021 ◽  
Author(s):  
Giuseppe Porpiglia ◽  
Paolo Schito ◽  
Tommaso Argentini ◽  
Alberto Zasso
Keyword(s):  
Wind Tunnel ◽  
Velocity Profile ◽  
Wind Velocity ◽  
Aerodynamic Force ◽  
Numerical Approach ◽  
Aerodynamic Performance ◽  
Vehicle Speed ◽  
Initial Condition ◽  
Cfd Analyses ◽  
Moving Train

<p>This paper introduces a new methodology to assess the influence of a windscreen on the crosswind performance of trains running on a bridge. Considering the difficulties encountered in both carrying out wind tunnel tests that consider the vehicle speed or complete CFD analyses, a simplified CFD approach is here discussed. Instead of simulating simultaneously the windscreen plus the moving train, the numerical problem is split into two parts: firstly, a simulation of the windshield alone is used to extract the perturbed velocity profile at the railway location; secondly, this profile used as an inlet condition for the wind velocity acting on an isolated train. The method is validated against a complete train plus windshield simulation in terms of pressure distribution and aerodynamic force coefficients on the train, and flow streamlines. This approach opens to the possibility of evaluating the aerodynamic performance of a vehicle on bridges considering bridge and vehicle as separated. Wind velocity profiles measured on the bridge during a wind tunnel campaign could be used as the initial condition for numerical simulations on vehicles.</p>

Wind Tunnel Test on a Slowed Mach-Scaled Hingeless Rotor with Lift Compounding

2021 ◽  
Author(s):  
Shashank Maurya ◽  
Xing Wang ◽  
Inderjit Chopra
Keyword(s):  
Wind Tunnel ◽  
Reverse Flow ◽  
Wind Tunnel Test ◽  
Bending Moment ◽  
Flow Region ◽  
Dynamic Stall ◽  
Rolling Moment ◽  
Slowing Down ◽  
Slowed Rotor ◽  
Compressibility Effects

A single main rotor helicopter's maximum forward speed is limited due to the compressibility effects on the advancing side and reverse flow and dynamic stall on the retreating side. Compound helicopters can address these issues with a slowed rotor and lift compounding. There is a scarcity of test data on compound helicopters, and the present research focuses on a systematic wind tunnel test on lift compounding. Slowing down the rotor increases the advance ratio and, hence, the reverse flow region, which does not produce much lift. The lift is augmented with a wing on the retreating side. A hingeless rotor hub helps to balance the rolling moment with lift offset. Wind tunnel tests were carried out on this configuration up to advance ratios of 0.7 at two different wing incidence angles. Rotor performance, controls, blade structural loads, and hub vibratory loads were measured and compared with in-house comprehensive analysis, UMARC. A comparison between different wing incidences at constant total lift provided many insights into the lift compounding. It increased the vehicle efficiency and reduced peak-to-peak lag bending moment and in-plane 4/rev hub vibratory loads. The only trade-off was steady rotor hub loads and rolling moment at the wing root carried by the fuselage.

Surface Roughness Impact on Secondary Flow and Losses in a Turbine Exhaust Casing

2018 ◽  
Author(s):  
Isak Jonsson ◽  
Valery Chernoray ◽  
Borja Rojo
Keyword(s):  
Surface Roughness ◽  
Secondary Flow ◽  
Suction Side ◽  
Pressure Probe ◽  
Time Resolved ◽  
Pressure Distributions ◽  
Turbulence Decay ◽  
Inlet Swirl ◽  
High Level ◽  
The Impact

This paper experimentally addresses the impact of surface roughness on losses and secondary flow in a Turbine Rear Structure (TRS). Experiments were performed in the Chalmers LPT-OGV facility, at an engine representative Reynolds number with a realistic shrouded rotating low-pressure turbine (LPT). Outlet Guide Vanes (OGV) were manufactured to achieve three different surface roughnesses tested at two Reynolds numbers, Re = 235000 and Re = 465000. The experiments were performed at on-design inlet swirl conditions. The inlet and outlet flow of the TRS were measured in 2D planes with a 5-hole probe and 7-hole probe accordingly. The static pressure distributions on the OGVs were measured and boundary layer studies were performed at the OGV midspan on the suction side with a time-resolved total pressure probe. Turbulence decay was measured within the TRS with a single hot-wire. The results showed a surprisingly significant increase in the losses for the high level of surface roughness (25–30 Ra) of the OGVs and Re = 465000. The increased losses were primary revealed as a result of the flow separation on the OGV suction side near the hub. The loss increase was seen but was less substantial for the intermediate roughness case (4–8 Ra). Experimental results presented in this work provide support for the further development of more advanced TRS and data for the validation of new CFD prediction methods for TRS.

Interaction of Shroud Leakage Flow and Main Flow in a Three-Stage LP Turbine

2003 ◽  
Vol 127 (4) ◽  
pp. 649-658 ◽  
Author(s):  
Jochen Gier ◽  
Bertram Stubert ◽  
Bernard Brouillet ◽  
Laurent de Vito
Keyword(s):  
Main Flow ◽  
Secondary Flows ◽  
Test Facility ◽  
Navier Stokes ◽  
Leakage Flow ◽  
Jet Engines ◽  
Flow Interactions ◽  
Lp Turbine ◽  
The Impact ◽  
The Ideal

Endwall losses significantly contribute to the overall losses in modern turbomachinery, especially when aerodynamic airfoil load and pressure ratios are increased. In turbines with shrouded airfoils a large portion of these losses are generated by the leakage flow across the shroud clearance. Generally the related losses can be grouped into losses of the leakage flow itself and losses caused by the interaction with the main flow in subsequent airfoil rows. In order to reduce the impact of the leakage flow and shroud design related losses a thorough understanding of the leakage losses and especially of the losses connected to enhancing secondary flows and other main flow interactions has to be understood. Therefore, a three stage LP turbine typical for jet engines is being investigated. For the three-stage test turbine 3D Navier-Stokes computations are performed simulating the turbine including the entire shroud cavity geometry in comparison with computations in the ideal flow path. Numerical results compare favorably against measurements carried out at the high altitude test facility at Stuttgart University. The differences of the simulations with and without shroud cavities are analyzed for several points of operation and a very detailed quantitative loss breakdown is presented.

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