A new concept for squirrel-cage fan inlet

1998 ◽  
Vol 212 (5) ◽  
pp. 343-349 ◽  
Author(s):  
N Montazerin ◽  
A Damangir ◽  
S Mirian
Keyword(s):  
Laser Doppler Anemometry ◽  
Separated Flow ◽  
Rotor Blades ◽  
Manufacturing Cost ◽  
Flow Area ◽  
Squirrel Cage ◽  
Standard Characteristic ◽  
Measured Flow ◽  
Major Loss ◽  
Conceptual Study

The squirrel-cage fan with a newly introduced outward inlet lip is studied experimentally. Previous research has demonstrated the importance of inlet flow control on the general flow field and vortex generation of such fans. The bell-mouth inlet, which is the common industrial and academic practice, has drawbacks that result in flow separation and turbulence enhancement. The adapted experimental approach is a conceptual study. It is a combination of standard characteristic measurements and detailed laser Doppler anemometry. The measured flow pattern inside the volute demonstrates that the separated flow behind the inlet lip, which for an ordinary inward lip occupies a large part of the rotor blades, disappears. This is promising since removing this separated flow diminishes a major loss-making region in this fan and adds to the effective flow area. It also reduces noise and gives uniform blade loading. The results also show an improvement in performance in comparison with that of a fan with an ordinary inward inlet lip. This modification is industrially feasible with no extra manufacturing cost and therefore can represent a substantial advance over the current practice.

scholarly journals The Influence of an Upstream Pylon on Open Rotor Aerodynamics at Angle of Attack

2019 ◽  
Vol 141 (2) ◽  
Author(s):  
Nishad G. Sohoni ◽  
Cesare A. Hall ◽  
Anthony B. Parry
Keyword(s):  
Potential Field ◽  
Angle Of Attack ◽  
Separated Flow ◽  
Rotor Blades ◽  
Tip Vortex ◽  
Rotor Wake ◽  
Rotor Aerodynamics ◽  
Open Rotor ◽  
Urans Cfd ◽  
Work Done

The aerodynamic impact of installing a horizontal pylon in front of a contra-rotating open rotor engine, at take-off, was studied. The unsteady interactions of the pylon's wake and potential field with the rotor blades were predicted by full-annulus URANS CFD calculations at 0 deg and 12 deg angle of attack (AoA). Two pylon configurations were studied: one where the front rotor blades move down behind the pylon (DBP), and one where they move up behind the pylon (UBP). When operating at 12 deg AoA, the UBP orientation was shown to reduce the rear rotor tip vortex sizes and separated flow regions, whereas the front rotor wake and vortex sizes were increased. In contrast, the DBP orientation was found to reduce the incidence variations onto the front rotor, leading to smaller wakes and vortices. The engine flow was also time-averaged, and the variation in work done on average midspan streamlines was shown to depend strongly on variation in incidence, along with a smaller contribution related to change of radius.

Some Aspects of the Aerodynamics of Gurney Flaps on a Double-Element Wing

2000 ◽  
Vol 123 (1) ◽  
pp. 99-104 ◽  
Author(s):  
David Jeffrey ◽  
Xin Zhang ◽  
David W. Hurst
Keyword(s):  
Laser Doppler Anemometry ◽  
Separated Flow ◽  
Surface Flow ◽  
Wake Flow ◽  
Single Element ◽  
Suction Surface ◽  
Gurney Flaps ◽  
Gurney Flap ◽  
Flow Features ◽  
Flap Deflection

Gurney flaps of different heights have been fitted to a generic double-element wing, and the effects at two typical flap angles have been observed using force and pressure measurements, and by performing flow surveys using Laser Doppler Anemometry. At a low flap setting angle of 20 deg the suction-surface flow remains attached to the trailing edge of the flap, and vortex flow features and perturbation velocities are all similar to those observed when Gurney flaps are fitted to single element wings. At a high flap deflection of 50 deg there is an extensive region of separated flow over the flap, yet the Gurney flap still alters the flow structure. The measurements suggest that the wake flow behind the Gurney flap consists of a von Karman vortex street of alternately shed vortices. The effects of the Gurney flap on the lift, zero-lift drag, and pressure distributions are reported, and the differences between the trends observed for single-element wings are discussed.

Experimental Study of Entrance Effects on Laminar Gas Flow Through Silicon Orifices

2005 ◽  
Author(s):  
Aaron J. Knobloch ◽  
Joell R. Hibshman ◽  
George Wu ◽  
Rich Saia
Keyword(s):  
Flow Rate ◽  
Gas Flow ◽  
Flow Area ◽  
Fully Developed Flow ◽  
Flow Rates ◽  
Flow Models ◽  
Entry Length ◽  
Orifice Flow ◽  
Measured Flow ◽  
Flow Through

This study summarizes a fundamental investigation of flow through an array of silicon micromachined rectangular slots. The purpose of the study is to evaluate the effect of entrance pressure, flow area, orifice thickness, slot length, and slot width of the orifice on flow rate. These orifices were fabricated using a simple frontside through wafer DRIE process on a 385 μm thick wafer and wafer bonding to create thicker orifices. The dies were then packaged as part of a TO8 can and flow tested. To complement the results of this experimental work, two simple flow models were developed to predict the effect of geometrical and entrance conditions on the flow rate. These models were based on macroscale assumptions that were not necessarily true in the case of thin orifices. One relationship was based on Pouiselle flow which assumes fully developed flow conditions. Calculation of the entry length required for fully developed flow indicate that in the low Reynolds Number regime (32-550) evaluated, the entry flow development requires 2-8 times the thickness of the thickest orifices used for this study. Therefore, calculations of orifice flow based on a Pouiselle model are an overestimate of the actual measured flow rates. Another model examined typical orifice relationships using head loss at the entrance and exit of the slots did not accurately capture the particular flow rates since it overestimated the expansion or constriction losses. A series of experiments where the pressure was varied between 75 and 1000 Pa were performed. A comparison of the Pouiselle flow solution with experimental results was made which showed that the Pouiselle flow model overpredicts the flow rates and more specifically, the effect of width on the flow rates. The results of these tests were used to develop a transfer function which describes the dependence of flow rate on orifice width, thickness, length, and inlet pressure.

scholarly journals Experimental Measurement Benchmark for Compressible Fluidic Unsteady Jet

Actuators ◽  
2018 ◽  
Vol 7 (3) ◽  
pp. 58
Author(s):  
Pablo Fernandez ◽  
Jerome Delva ◽  
Celestin Ott ◽  
Philipp Maier ◽  
Quentin Gallas
Keyword(s):  
Extreme Values ◽  
Laser Doppler Anemometry ◽  
Measurement Techniques ◽  
Synthetic Jet ◽  
Velocity Measurements ◽  
Worst Case ◽  
Synthetic Jet Actuator ◽  
Cold Wire ◽  
Measured Flow ◽  
Unsteady Jet

A benchmark of different measurement techniques is presented to characterize the dynamic response of a synthetic jet actuator working in compressible regime. The setup involves a piston-based synthetic jet, as well as the benchmarked measurements are hot-wire, cold-wire, Laser Doppler Anemometry, pressure transducer, and Schlieren visualization. Measured flow temperatures range from 20 °C to 150 °C, pressure ranges from 0.5 atm to 4 atm, and velocity are up to 300 m/s. The extreme values of these ranges are reached in an oscillating fashion at a frequency ranging from 30 to 100 Hz. The measurements are pointing out the limitation of cold-wire measurements, due to its high thermic inertia. The results show consistency in the velocity measurements, within 10% in the worst case, between all measurement techniques and the errors are traced back to the calibration ranges, whose sensitivity is also studied.

Performance Evaluation of Prototype Microchannel Evaporators for the Residential Air-Conditioning Application

2005 ◽  
Author(s):  
Honggi Cho ◽  
Keumnam Cho
Keyword(s):  
Air Conditioning ◽  
Flow Distribution ◽  
Cooling Capacity ◽  
Parallel Flow ◽  
Manufacturing Cost ◽  
Flow Area ◽  
Pressure Drops ◽  
Wet Condition ◽  
Flow Heat ◽  
Residential Air Conditioning

The present study was aimed to evaluate the performance of prototype microchannel evaporators for the residential air-conditioning application using R-22 refrigerant under wet condition. Eight prototype evaporators were manufactured and tested using psychrometric calorimeter test facilities. Each evaporator consisted of two or three parallel flow heat exchangers connected with return pipes. The parallel flow heat exchanger had 41 parallel microchannel tubes that brazed into the inlet and outlet headers. The tube had 8 rectangular ports with the hydraulic diameter of 1.3 mm. The louvered fin had louver angle of 27°, louver pitch of 1.4 mm and flow depth of 18.8 mm. It was found that the flow area ratio had a great effect on the cooling capacity of the microchannel evaporator from experimental results of prototypes 4, 5 and 6, and there was an appropriate range for cooling capacity. The flow distribution characteristics were slightly affected by the pressure drop resulting from the configuration of the refrigerant flow at the exit of the evaporator like merging manifold, which means that it could be possible to reduce the manufacturing cost of the microchannel evaporator. Both refrigerant and air-side pressure drops for the best prototype evaporator were 28.6 kPa and 2.53 mmAq, respectively, which could be affordable for the residential air-conditioning application.

Turbulent Flow in a Rotating Two Pass Smooth Channel

1999 ◽  
Vol 121 (4) ◽  
pp. 725-734 ◽  
Author(s):  
Shou-Shing Hsieh ◽  
Ping-Ju Chen ◽  
Hsiang-Jung Chin
Keyword(s):  
Flow Field ◽  
Cross Section ◽  
Flow Separation ◽  
Laser Doppler Anemometry ◽  
Centrifugal Forces ◽  
Mean Velocity ◽  
Axis Of Rotation ◽  
Smooth Channel ◽  
Measured Flow ◽  
Turbulent Air Flow

Laser-Doppler anemometry has been applied to approximately 2-D turbulent air flow in a rotating 2 pass channel of square cross section. The axis of rotation is normal to the axis of the duct, and the flow is radially outward/inward. The duct is of finite length and the walls are isothermal. Smooth channels are experimentally conducted with rotational speeds of 100, 200, and 300 rpm with ReH = 5000 and 10,000. The main features of the flow, flow separation and mean velocity as well as turbulent intensity at particular location along the downstream are presented. The measured flow field is found to be quite complex, consisting of secondary cross-stream and radially outward flows due to the Coriolis effects and centrifugal forces.

Periodical Unsteady Flow Within a Rotor Blade Row of an Axial Compressor: Part I — Flow Field at Midspan

2007 ◽  
Author(s):  
Ronald Mailach ◽  
Ingolf Lehmann ◽  
Konrad Vogeler
Keyword(s):  
Flow Field ◽  
Unsteady Flow ◽  
Pressure Distribution ◽  
Rotor Blade ◽  
Laser Doppler Anemometry ◽  
Pressure Sensors ◽  
Stability Limit ◽  
Rotor Blades ◽  
Experimental Investigations ◽  
Blade Row

In this two-part paper results of the periodical unsteady flow field within the third rotor blade row of the four-stage Dresden Low-Speed Research Compressor are presented. The main part of the experimental investigations was performed using Laser-Doppler-Anemometry. Results of the flow field at several spanwise positions between midspan and rotor blade tip will be discussed. In addition time-resolving pressure sensors at midspan of the rotor blades provide information about the unsteady profile pressure distribution. In part I of the paper the flow field at midspan of the rotor blade row will be discussed. Different aspects of the blade row interaction process are considered for the design point and an operating point near the stability limit. The periodical unsteady blade-to-blade velocity field is dominated by the incoming stator wakes, while the potential effect of the stator blades is of minor influence. The inherent vortex structures and the negative jet effect, which is coupled to the wake appearance, are clearly resolved. Furthermore the time-resolved profile pressure distribution of the rotor blades is discussed. Although the negative jet effect within the rotor blade passage is very pronounced the rotor blade pressure distribution is nearly independent from the convectively propagating chopped stator wakes.

Rotating Instabilities in an Axial Compressor Originating From the Fluctuating Blade Tip Vortex

2000 ◽  
Author(s):  
R. Mailach ◽  
I. Lehmann ◽  
K. Vogeler
Keyword(s):  
Rotor Blade ◽  
Laser Doppler Anemometry ◽  
Stability Limit ◽  
Rotor Blades ◽  
Tip Clearance ◽  
Tip Vortex ◽  
Experimental Investigations ◽  
Flow Phenomenon ◽  
Low Speed ◽  
Blade Tip

Rotating instabilities (RI) have been observed in axial flow fans, centrifugal compressors as well as in low-speed and high-speed axial compressors. They are responsible for the excitation of high amplitude rotor blade vibrations and noise generation. This flow phenomenon moves relative to the rotor blades and causes periodic vortex separations at the blade tips and an axial reversed flow through the tip clearance of the rotor blades. The paper describes experimental investigations of RI in the Dresden Low-Speed Research Compressor (LSRC). The objective is to show that the fluctuation of the blade tip vortex is responsible for the origination of this flow phenomenon. RI have been found at operating points near the stability limit of the compressor with relatively large tip clearance of the rotor blades. The application of time-resolving sensors in both fixed and rotating frame of reference enables a detailed description of the circumferential structure and the spatial development of this unsteady flow phenomenon, which is limited to the blade tip region. Laser-Doppler-Anemometry (LDA) within the rotor blade passages and within the tip clearance as well as unsteady pressure measurements on the rotor blades show the structure of the blade tip vortex. It will be shown that the periodical interaction of the blade tip vortex of one blade with the flow at the adjacent blade is responsible for the generation of a rotating structure with high mode orders, termed as rotating instability (RI).

Aerodynamic Investigation on the Excitation of a Laminar Separation Bubble by Secondary Jets

2014 ◽  
Author(s):  
Samson AnnapuReddy ◽  
S. Sarkar
Keyword(s):  
Shear Layer ◽  
Laser Doppler Anemometry ◽  
Separation Bubble ◽  
Sudden Change ◽  
Separated Flow ◽  
Leading Edge ◽  
Constant Thickness ◽  
Laminar Separation ◽  
Separated Shear Layer ◽  
Transition Criteria

Aerodynamic interactions of a separated shear layer from the semi-circular leading edge of a constant thickness aerofoil model with jets ejecting in the vicinity of reattachment from a row of discrete holes at an angle of 30° in the streamwise direction are elucidated. Experiments are carried out for two Reynolds numbers (ReD) 25000 and 55000 (based on the leading-edge diameter) and two velocity ratios (V.R) 0.5 and 1. The time-averaged velocity and turbulence quantities are measured using Laser-Doppler Anemometry (LDA) at different streamwise locations along the centre line of the jet, while the instantaneous flow filed is obtained using Particle Image Velocimetry (PIV). Measurements reveal that the flow undergoes separation at the blending point of semi-circle and flat plate owing to sudden change in geometry. It is observed that in the absence of the jet, the separated shear layer undergoes transition with formation Kelvin-Helmholtz (K-H) rolls and a significant growth of Reynolds stress in the second-half of the bubble is evident. With injection, the separation bubble length in the upstream of jet has decreased with increased growth rate of velocity fluctuations. However, the characteristics of the flow in the separated region remains almost unchanged and the transition criteria even follows the universal intermittency characteristics of Dhawan and Narasimha [35]. The instantaneous results elucidate that K-H rolls from the separated shear layer interact with the injected jet resulting in its oscillation. In the downstream of injection, the presence of the jet is felt with enhanced turbulence activities in the outer layer, particularly for high V.R. Further, the onset and end of transition of the separated flow are compared with correlations available in the literature.

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