scholarly journals Optimal Design of a Plenum Fan with Three-Dimensional Blades

2020 ◽  
Vol 10 (10) ◽  
pp. 3460
Author(s):  
Kyung Jung Lee ◽  
Il Wung Park ◽  
Ki Suk Bang ◽  
Yeong Min Kim ◽  
Young Chull Ahn
Keyword(s):  
Fluid Flow ◽  
Flow Separation ◽  
Static Pressure ◽  
Three Dimensional ◽  
Leading Edge ◽  
Original Model ◽  
Flow Friction ◽  
Static Efficiency ◽  
Curved Blade ◽  
Optimized Model

We successfully designed an optimized plenum fan with a three-dimensional, smooth, curved blade. The optimized model revealed that the static pressure in the channel had been increased uniformly and stably, and the flow separation at the leading edge was significantly reduced. According to simulations, the three-dimensional blade stabilized the fluid flow, and the flow friction was reduced by suppressing the flow separation as much as possible so that both the static pressure and the static efficiency were clearly improved in comparison with those of the original model. As a result, the static efficiency was improved by 6.3% compared with that of the original model.

scholarly journals Optimal Design of a Plenum Fan with Three-Dimensional Blades

2020 ◽  
Author(s):  
Kyung Jung Lee ◽  
Il Wung Park ◽  
Ki Suk Bang ◽  
Yeong Min Kim ◽  
Young-Chull Ahn
Keyword(s):  
Fluid Flow ◽  
Flow Separation ◽  
Static Pressure ◽  
Three Dimensional ◽  
Leading Edge ◽  
Original Model ◽  
Flow Friction ◽  
Static Efficiency ◽  
Curved Blade ◽  
Optimized Model

We successfully designed an optimized plenum fan with a three-dimensional, smooth, curved blade. The optimized model revealed that the static pressure in the channel had been increased uniformly and stably, and the flow separation at the leading edge was significantly reduced. To conclude, the three-dimensional blade stabilized the fluid flow, and the flow friction was reduced by suppressing the flow separation as much as possible so that both the static pressure and the static efficiency were clearly improved in comparison with those of the original model. The static efficiency, as a result, was improved by 6% compared with that of the original model.

Numerical Flow Analysis in a Subsonic Vaned Radial Diffuser With Leading Edge Redesign

1999 ◽  
Vol 121 (1) ◽  
pp. 119-126 ◽  
Author(s):  
E. Casartelli ◽  
A. P. Saxer ◽  
G. Gyarmathy
Keyword(s):  
Static Pressure ◽  
Flow Analysis ◽  
Three Dimensional ◽  
Pressure Rise ◽  
Leading Edge ◽  
Inverse Design ◽  
Navier Stokes ◽  
Two Dimensional ◽  
Characteristic Lines ◽  
Design Software

The flow field in a subsonic vaned radial diffuser of a single-stage centrifugal compressor is numerically investigated using a three-dimensional Navier–Stokes solver (TASCflow) and a two-dimensional analysis and inverse-design software package (MISES). The vane geometry is modified in the leading edge area (two-dimensional blade shaping) using MISES, without changing the diffuser throughflow characteristics. An analysis of the two-dimensional and three-dimensional effects of two redesigns on the flow in each of the diffuser subcomponents is performed in terms of static pressure recovery, total pressure loss production, and secondary flow reduction. The computed characteristic lines are compared with measurements, which confirm the improvement obtained by the leading edge redesign in terms of increased pressure rise and operating range.

Analysis of Flow Separation in an Annular Expansion—Contraction With Inner Cylinder Rotating

1973 ◽  
Vol 95 (4) ◽  
pp. 485-492 ◽  
Author(s):  
G. F. Dailey ◽  
G. E. Geiger
Keyword(s):  
Turbulent Flow ◽  
Numerical Solution ◽  
Steady Flow ◽  
Flow Separation ◽  
Static Pressure ◽  
Three Dimensional ◽  
Reynolds Numbers ◽  
Air Bubbles ◽  
Theoretical Computer ◽  
Laminar Separation

A three-dimensional incompressible isothermal laminar separation of a Newtonian fluid in transient and steady flow was investigated. The geometry chosen for this study was an annular expansion-contraction chamber with a rotating inner cylinder. It was found that an adaptation of a numerical solution first proposed by Fromm gave converged solutions for all Reynolds numbers in the laminar range. Theoretical computer plotted streamline patterns were superimposed on time exposure photographs of air bubbles in transparent oil. Measured static pressure differentials were compared with laminar theory. Turbulent flow was studied experimentally.

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.

Method for Providing Warning of the Onset of Buffeting, Stalling and Other Undesirable Effects of Flow Separation

1958 ◽  
Vol 62 (573) ◽  
pp. 674-676 ◽  
Author(s):  
D. W Holder ◽  
H. H. Pearcey
Keyword(s):  
Shock Wave ◽  
Recent Work ◽  
Flow Separation ◽  
Static Pressure ◽  
Separated Flow ◽  
Leading Edge ◽  
Alternative Methods ◽  
Pressure Measurements ◽  
Aircraft Wing ◽  
Trailing Edge

A Method is described for providing warning of the onset of undesirable effects produced by flow separation on an aircraft wing. It is based on static pressure measurements near the trailing edge and appears to have advantages over alternative methods.Recent work has suggested that certain effects of flow separation such as buffeting, aileron buzz and undesirable changes in loading, occur when a “ bubble ” of separated flow originating at the leading edge of a wing, or at a shock wave on its surface, first becomes sufficiently large to affect the flow at the trailing edge.

A Leading-Edge Alula-Inspired Device (LEAD) for Stall Mitigation and Lift Enhancement for Low Reynolds Number Finite Wings

2018 ◽  
Author(s):  
Mihary R. Ito ◽  
Chengfang Duan ◽  
Leonardo P. Chamorro ◽  
Aimy A. Wissa
Keyword(s):  
Aspect Ratio ◽  
Flow Separation ◽  
Three Dimensional ◽  
Leading Edge ◽  
Reynolds Numbers ◽  
Tip Vortices ◽  
Low Reynolds Numbers ◽  
Lift Enhancement ◽  
Low Reynolds ◽  
Torque Transducer

Even though Unmanned Aerial Vehicles (UAVs) operating at low Reynolds numbers are becoming common, their performance and maneuverability are still greatly limited due to aerodynamic phenomena such as stall and flow separation. Birds mitigate these limitations by adapting their wings and feather shapes during flight. Equipped with a set of small feathers, known as the alula, located near the leading edge and covering 5% to 20% of the span, bird wings can sustain the lift necessary to fly at low velocities and high angles of attack. This paper presents the effect on lift generation of different placements of a Leading-Edge Alula-inpsired Device (LEAD) along the span of a moderate aspect-ratio wing. The device is modeled after the alula on a bird, and it increases the capability of a wing to maintain higher pressure gradients by modifying the near-wall flow close to the leading-edge. It also generates tip vortices that modify the turbulence on the upper-surface of the wing, delaying flow separation. The effect of the LEAD can be compared to traditional slats or vortex generators on two-dimensional wings. For finite wings, on the other hand, the effect depends on the interaction between the LEADs tip vortices and those from the main structure. Wind tunnel experiments were conducted on a cambered wing at post-stall and deep-stall angles of attack at low Reynolds numbers of 100,000 and 135,000. To quantify the aerodynamic effect of the device, the lift generated by the wing with and without the LEAD were measured using a 6-axis force and torque transducer, and the resulting lift coefficients were compared. Results show that the location of the LEAD yielding the highest lift enhancement was 50% semi-span away from the wing root. Lift improvements of up to 32% for post stall and 37% for deep stall were obtained at this location, demonstrating that the three-dimensional effects of the LEAD are important. The lift enhancement was also more prominent on a finite moderate aspect-ratio wing (3D) than on an airfoil (2D), confirming that the LEAD is a three-dimensional device. Identifying the configurations and deployment parameters that improve lift generation the most is needed to design an adaptive LEAD that can be implemented on a UAV wing for increased mission-adaptability.

Reduction of Turbine Blade Unsteady Forces by Shape Modification of Vanes for Industrial Gas Turbines

2016 ◽  
Author(s):  
Xiying Niu ◽  
Lin Wang ◽  
Dongming Li ◽  
Qiuli Du
Keyword(s):  
Unsteady Flow ◽  
Turbine Blade ◽  
Rotor Blade ◽  
Static Pressure ◽  
Pressure Coefficient ◽  
Three Dimensional ◽  
Leading Edge ◽  
Turbine Stage ◽  
Shape Modification ◽  
Unsteady Forces

The flow in turbomachinery is inherently three-dimensional unsteady and turbulent. Unsteady factors due to the viscous wakes and potential effects of blades, affect the blade surface pressure distribution, which leads to blade vibrations by periodic pulsating flow forces. While the aerodynamic excitation frequency equals to the natural frequency of blades, critical blade vibrations are excited, which could lead to a reduction of lifetime or even a destruction of rotor blades. Although a large number of investigations about turbine unsteady flow fields and unsteady excitation forces have been carried out, these investigations do not focus on how to reduce the turbine blade unsteady forces. In this article, the turbine stators were redesigned by forward-swept and positive-leaned vanes, in order to reduce the blade excitation forces. And, the swept angles and leaned angles are determined respectively, that is, the vane is forward swept 3 degree, and positive leaned 13 degree, with the purpose of ensuring that while the hub exit flow of a vane aligns with the leading edge of one downstream rotor blade, the tip exit flow could align with the leading edge of another rotor blade that is adjacent to the above rotor blade pressure side. Comparative investigations into the turbine unsteady flow fields between the redesigned and original cases are performed by using a three-dimensional Navier-Stokes viscous solver. Emphasis is placed on how the vane modification reduces the turbine blade unsteady forces. The results indicate that the static pressure fluctuation at vane trailing edge region is reduced compared to the baseline, and high loss region inside vane passages is also reduced. Besides, blade-to-blade entropy distribution of the turbine stage shows that, the vane wake width is reduced by its shape modification, especially at 5% and 95% span. Due to these, the temporal-spatial profile of rotor blade static pressure coefficient shows that, the unsteady fluctuation of rotor blade becomes weak obviously for the redesigned case. Overall, compared to the baseline, on the condition that the mass flowrate and expansion ratio are nearly the same, the torque fluctuation is reduced from 12.78% to 6.92%, and the axial force fluctuation is reduced from 8.82% to 6.51%, which not only is good for reducing the stream exciting force, but also can make the output power more stable. And, the turbine stage time-averaged efficiency increases slightly by 0.18%. Detailed results about static pressure coefficient distributions, entropy distributions, torque and axial forces are presented and discussed in the paper.

scholarly journals Simulation and Nonlinearity Optimization of a High-Pressure Sensor

Sensors ◽  
2020 ◽  
Vol 20 (16) ◽  
pp. 4419
Author(s):  
Ting Li ◽  
Haiping Shang ◽  
Weibing Wang
Keyword(s):  
High Pressure ◽  
Pressure Sensor ◽  
Pressure Sensors ◽  
Original Model ◽  
Ansys Software ◽  
Nonlinear Error ◽  
Sensor Model ◽  
Optimized Model ◽  
Simulation Results ◽  
Better Than

A pressure sensor in the range of 0–120 MPa with a square diaphragm was designed and fabricated, which was isolated by the oil-filled package. The nonlinearity of the device without circuit compensation is better than 0.4%, and the accuracy is 0.43%. This sensor model was simulated by ANSYS software. Based on this model, we simulated the output voltage and nonlinearity when piezoresistors locations change. The simulation results showed that as the stress of the longitudinal resistor (RL) was increased compared to the transverse resistor (RT), the nonlinear error of the pressure sensor would first decrease to about 0 and then increase. The theoretical calculation and mathematical fitting were given to this phenomenon. Based on this discovery, a method for optimizing the nonlinearity of high-pressure sensors while ensuring the maximum sensitivity was proposed. In the simulation, the output of the optimized model had a significant improvement over the original model, and the nonlinear error significantly decreased from 0.106% to 0.0000713%.

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