Flow Simulation to Determine the Effects of Shrouds on the Performance of Wind Turbines

This paper describes a flow simulation model used to determine the effects of a shroud on the performance of a wind turbine. Also, it focuses on comparing the standard type of wind turbines— upwind turbine with three blades fixed on a horizontal axis—with a new type that is called a shrouded wind turbine. In addition, the two types of turbines are compared in terms of velocities profiles, pressure distribution and power output when applying four different velocities of winds: 10, 20, 30, 40 mph. Numerical values and graphs are highlighted in order to show the main differences between the shrouded turbine and the conventional one. Finally, a conclusion and some recommendations are provided to summarize the scope of this research and give a better prediction for a future optimal design of the shrouded turbines.

Multiphase flow inside a four-strand continuous casting tundish using three types of ladle shrouds

Numerical and physical models have been built and validated to study the multiphase flow inside three ladle shrouds and a four-strand tundish.A conventional straight ladle shroud and two types of trumpet-shaped ladle shroud(TLS)have been comparatively investigated.The maximum velocity at ladle shroud outlet reduces from 1.3 to 0.5 m/s,which indicates a quieter tundish pool.It is demonstrated that the use of a TLS can also decrease the maximum surface velocity from 0.16 to 0.13 m/s,which reduces the tendency of forming tundish open eye.The flow pattern and mixing behavior are improved inside the tundish,especially in enlarging the plug volume from 6.61%to 9.04%.The difference between the near and far outlets is narrowed when the TLS is applied.A computational program was developed to calculate characteristic parameters of different ladle shroud designs,and a dimensionless index was proposed to evaluate their mass and inner volume.Plant trials have been carried out,and the results showed that TLS can reduce level fluctuation in the pouring zone,which is beneficial to promoting better protective performance from secondary contamination and heat loss during continuous casting.

Discoloration Range and Shroud Image Depth Values Cannot Be Satisfied by the Same Proton Energy

The radiative hypothesis has been revisited showing other characteristics, produced by the protons used as dyes in total disagree with the ones of the Body Image that appears on the Shroud of Turin. Our investigations highlight that for the protons to reach 3.7 cm in air, the distance that measures the range of discoloration effects, must be emitted with an energy of about 1.5 MeV using Wilson and Brobeck’s empirical formula and 1.35 MeV using Bethe’s. This last formula provides a result closer to reality. Bethe shows that the penetration depth is greater than that calculated empirically. Such a value of proton energy (1.35 MeV) makes it possible to satisfy the discoloration effects range for the Shroud but it is incompatible with a depth of penetration in linen that is only 200 nm. Moreover, using the same subatomic particles, we obtained on the colored linen a distribution of energy represented by regression but not linear. Thus, also the possible I(z) correlation, between color intensity and body-sheet distance, which should be due to the oxidizing action of protons, does not agree with that extracted from the Shroud of Turin.

Analysis of a Diffuser-Augmented,Multi-rotor Wind Turbine System

The multi-rotor approach adds a significant improvement over conventional,single rotor wind turbines by utilizing the wind side-flow that is lost by conventional turbines.The power output can be increased by as much as 26%over a conventional wind turbine of comparable size.The benefit of the addition of side flow can be easily seen when used with the multi-rotor turbines as shown in this paper.At induction factors of greater than 0.2,a multi-rotor system will begin outputting higher power than the rotors individually.Based on the results as shown in this paper,an optimal induction factor would be between 0.4 and 0.5 to get the greatest benefit of the side flow.The addition of a brimmed diffuser magnified the benefits of the side flow even more by increasing flow through and in front of the rear rotor.Depending on the rotor spacing,rotors in front of the back rotor could see the effects of the diffuser as well.Typically a rotor spacing of one meter or greater is practical depending on the size of the rotor blades.Flow simulation studies supported the benefits of a multi-rotor system and the use of side flow for rotor step sizes of greater than 4 meters.The power increase with the addition of a diffuser was supported by the flow simulation studies as well by showing significant increases in wind power and power.Additionally,according to flow trajectory animations,turbulence as a result of upstream rotating blades appeared to be dampened out because of the diffuser.

Numerical Investigation of the Fluid Flow Characteristics in the Hub Plate Crown of a Centrifugal Pump

Due to the lack of understanding in the flow mechanism of the hub plate crown, the current calculation of the disc friction loss and the axial thrust in the centrifugal pump often uses empirical formulas. Research on the flow characteristics of the hub plate crown is of practical significance. The shroud and hub cavities are respectively studied with regard to tangential and radial velocities at the four different angular positions(0°, 90°, 180°, and 270°) at the four different operational points(0.6 Qsp, 0.8 Qsp, 1.0 Qsp, and 1.2 Qsp). Results indicate that at the same operational point, the smaller the volute chamber sectional area is, the higher the tangential velocity of the fluid core zone of the shroud cavity is. Radial leakage flow from the volute to the seal ring at the same operational point appears in 0° and 90° direction;when the flow is large, the tangential and radial velocities of the shroud and hub cavities with the same radius tend to be equal with axial symmetry. The axial leakage flow through the balance holes significantly affects the radial distribution of both tangential and radial velocities of fluid flow in the hub cavity. The numerical calculation results of fluid leakage through the clearance of back sealing ring are in good agreement with the test results. Accordingly, the magnitude of leakage is closely related to the fluid pressure and velocity distribution in the hub plate crown of the centrifugal pump. The analysis of the flow characteristics in the hub plate crown of the centrifugal pump could reveal the cause of the disc friction loss from the mechanism, providing a significant guidance for improving the accuracy of calculation and balancing the axial thrust in the centrifugal pump.

Effect of perforation on flow past a conic cylinder at Re=100:vortex-shedding pattern and force history

The flow past a circular-section cylinder with a conic shroud perforated with four holes at the peak was simulated numerically at Re = 100, considering two factors, viz.the angle of attack and the diameter of the holes. The effects of the perforated conic shroud on the vortex shedding pattern in the near wake was mainly investigated, as well as the time history of the drag and lift forces. In the investigated parameter space, three flow regimes were generally identified, corresponding to weak, moderate, and strong disturbance effects.In regime I, the wake can mainly be described by alternately shedding Kármán or Kármán-like vortices. In regime II, the spanwise vortices are obviously disturbed along the span due to the appearance of additional vorticity components and their interactions with the spanwise vortices, but still shed in synchronization along the spanwise direction. In regime III,the typical Kármán vortices partially or totally disappear,and some new vortex shedding patterns appear, such as-type, obliquely shedding, and crossed spanwise vortices with opposite sign. Corresponding to these complex vortex shedding patterns in the near wake, the fluid forces no longer oscillate regularly at a single vortex shedding frequency, but rather with a lower modulation frequency and multiple amplitudes. An overview of these flow regimes is presented.

A special CAD/CAM software for electro-discharge machining of shrouded turbine blisks

In this paper, a special-purpose CAD/CAM software package, BliskCad/Cam, based on a commercial CAD/CAM software Unigraphics is developed to reduce difficulties in CNC-EDM of the shrouded turbine blisks. The software package consists of five modules such as electrode design, path searching, and machining simulation module. Functions of BliskCad/Cam include parametrical reconstruction of 3-D model of the blisk, intelligent design of complex shaped electrode, automatic generation of NC codes, search of interference-free tool path for multi-axis NC-EDM and machining simulation, etc. Experimental verification is conducted by using BliskCad/Cam and the results show that it satisfies the requirements, and can realize precision machining and reduce accessorial time remarkably.

Behaviors of fine bubbles in the shroud nozzle of ladle and tundish

Fine bubbles will create when the inert gas is introduced to the high rapidsteel stream within the shroud nozzle between ladle and tundish. The collision and attachment amongthe bubbles and fine inclusions will promote the floatation efficiency of inclusions in the tundish.The behaviors of the bubbles, such as the dispersion in shroud, coalescence and floatation intundish, are studied. The results show that the maximum sizes of the bubbles in the water and steelflow within the shroud in the length of 1.2 m are 0.70-1.44 mm and 1.53-3.16 mm respectively whenthe flow rates are 0.006-0.016 m^3/s; the terminal velocities of fine bubbles in the water andmolten steel within the tundish are 0.02-0.2 and 0.05-0.6 m/s.

Computational Fluid Dynamics Analysis of Shroud Design on Hemodynamic Performance and Blood Damage in a Centrifugal Blood Pump

Patients with extracorporeal membrane oxygenation still suffer from high rates of complication that linked to the flow field within the blood pump.So it is essential to optimise the geometry of the pump.The specification of shroud design is arguably the necessary design parameter in the centrifugal pump.However,the hemodynamic performances of the different shroud designs have not been studied extensively.In this study,ten different shroud designs were made and divided into two groups as the different covering locations(A:Covering the blade leading edge,B:Covering the blade trailing edge).In every group,six shroud designs with the covering proportions of 0,1/5,2/5,3/5,4/5,1 were made.Detailed computational fluid dynamics(CFD)analyses were performed to investigate their effects on hemodynamics and hydraulic performance at the constant flow condition(4000 rpm,5 L/min).The percentage volumes of the scalar shear stress in specific threshold(τ<1 Pa:Thrombosis,τ>9 Pa:the destruction of von Willebrand factor,τ>50 Pa:Platelet activation,τ>150 Pa:Break of red blood)were used to compare the blood damage of the different shroud designs.Also,the modified index of hemolysis(MIH)were calculated based on a Eulerian approach for different pumps.CFD simulations predicted an increase in the pump head,hydraulic efficiency,a fraction of fluid volume with scalar shear stress values above a threshold(9 Pa,50 Pa,150 Pa)and MIH with increasing shroud covering proportions from 0 to 1 in the same covering location.Also,these above results were higher in group B than group A.This means that the risks of the hemolysis,thrombosis and bleeding increased as the rise of the covering proportion and they were higher in the pump whose shroud covers the blade trailing edge.

Geometric triangular chiral hexagon complexes and clonal embryogenic body organization on the Turin Shroud crucified man image: A predictable tissue response to injury

The shroud continues to remain one of the most studied and controversial artifacts in human history. Many tests, X-ray fluorescence, reflectance, spectrometry and low energy/high-resolution X ray transmission have shown that the crucified body is not compatible with a painted image. Researchers confirm that the alleged blood is real blood. We documented the self-assembly of geometric triangular chiral hexagon complex (GTCHC) with structural organization of embryoid bodies in cancer tissues. The identification of these structures is not only limited to malignant tumors but also appears in extreme injured tissues. Our interest is to determine if we can predict and identify these patterns in the Shroud of Turin. Based on pattern recognition image was analyzed over 100 shroud images. We identified a central spectral emission line that exhibits a characteristic signature on a plot of residual electromagnetic radiation, head area narrowing and low extremities broadening, indication of decay energy changes in the velocity of the molecules in the traversal trajectory. This Electromagnetic collision event generates in the cloth stagnant blood areas with patterns identical to those identified for us in cancer damage tissues. Inflammatory cytokines activate stem cells and Notch signaling proteins in cascade of interactions to generate real clonal human embryoid template. Can we predict function from structure? These structures evoke life, regeneration, but not death. Our findings suggest the image of a crucified man on the Shroud of Turin is a real physical electromagnetic collision event in response to extreme tissue injury, with the fact that supports our previous findings in cancer tissues as real and predictable. Proteins derived from these emergent damage tissue derivate stem cells could be used to design biologic templates in regenerative medicine and develop novel strategies in cancer therapy.

Characteristics of a coherent jet enshrouded in a supersonic fuel gas

Based on a current coherent jet,this study proposes a supersonic combustion(SC)coherent jet in which the main oxygen jet is surrounded by a supersonic fuel gas.The characteristics of the proposed coherent jet are analyzed using experimental methods and numerical simulations in the high-temperature environment of electric arc furnace(EAF)steelmaking.The SC coherent jet achieved stable combustion in the EAF steelmaking environment.The simulated combustion temperature of the supersonic shrouding methane gas was 2930 K,slightly below the theoretical combustion temperature of methane–oxygen gas.The high speed and temperature of the supersonic flame effectively weakened the interaction between the main oxygen jet and the external ambient gas,inhibiting the radial expansion of the main oxygen jet and maintaining its high speed and low turbulence over a long distance.These features improved the impact capacity of the coherent jet and strengthened the stirring intensity in the EAF bath.

Design of Composite Ladle Shroud for Improving Thermal Shock Resistance

A ladle shroud is one of the functional refractories for continuous casting,which undergoes severe thermal shock by molten steel when used without pre-heating.The composite ladle shroud with an insulating liner presents excellent thermal shock resistance.Finite element simulation is an effective method to explore the maximum thermal stress for predicting the thermal shock resistance of ladle shrouds.In this paper,the influence of the lining materials and the structure of ladle shrouds on the thermal stress distribution is systematically researched.The working mechanism of the lining material on the body material is also presented.Lining materials with low thermal expansion,elastic modulus and thermal conductivity are helpful to improve the thermal shock resistance and an optimum lining thickness is suggested.The lining material can both serve as thermal resistance for the body material to buffer the thermal stress,and apply a strain load to the body material by the thermal strain to increase the stress.

Design and Analysis of a Dual Rotor Turbine with a Shroud Using Flow Simulations

This paper describes the flow simulation of a dual rotor, three-bladed wind turbine module with a shroud to determine its performance. The parameters that were evaluated are the effects of adding a second rotor, wind speed, distance between the two rotors, the size of the front rotor and the shroud. The results were obtained by using the Solid Works 2015 flow simulation program. Also, the benefits and cost issues for wind generating systems are illustrated.

延长叶轮盘、盖尺寸对离心压缩机模型级性能影响研究（英文）

CFD method was employed to analyze the effect of the wall extension of hub and shroud at the impeller outlet(rotating diffuser)in a centrifugal compressor model stage with a large mass flow coefficient.The effect of clearance leakage was considered.Results show that the extended hub and shroud increases the head coefficient and ploytropic efficiency for the centrifugal compressor stage,and the extension length is longer,the head coefficient and ploytropic efficiency is higher.When extension length is under 4.44%impeller outlet diameter(R2),the increase rate of head coefficient and polytropic efficiency is rapid.When the extension length is beyond 4.44%R2,the rate is slowed down.The uniformity at the diffuser inlet is to be improved,the total pressure loss of stationary parts decreases,and then the performance of stage is improved.The total pressure loss of stationary parts starts to reduce with the increase of mass flow coefficient when the extension length exceeds 5.56%R2 and mass flow coefficientis beyond the design value of 0.1957.

Cold Acid Postmortem Blood Most Probably Formed Pinkish-Red Heme-Madder Lake on Madder-Dyed Shroud of Turin

The Turin Shroud was extensively scientifically investigated in 1978. In its pinkish red bloodstains, normal features of human blood were found, but also seemingly anomalous ones. In the present study, hitherto unnoticed details of the data are presented, Shroud data and more modern reference data are compared, and the results of a few experiments with linen, madder dye and blood are shown. It turns out that the Shroud’s ‘anomalous’ data are strong consistent evidence that its bloodstains contain acid heme-madder lake, of which the heme derived from cold acid postmortem blood and the madder had been applied to the Shroud at manufacture. It implies that the bloodstains were formed on the Shroud before the still not reproduced body-image was. Several other ‘red-color’ hypotheses for the Shroud’s bloodstains are discussed and dismissed.

Hematite, Biotite and Cinnabar on the Face of the Turin Shroud: Microscopy and SEM-EDX Analysis

The Turin Shroud, recently accessible for hands-on scientific research, is now extensively investigated. Its pinkish red blood stains that seem anomalous ones are studied by modern techniques (notably by resolute optical microscopy and scanning electron microscopy coupled with energy dispersive X-ray). Exploration by these techniques of a blood stain located on the face permits us to discover some red-colour particles (hematite, biotite and cinnabar) of exogenous material in this stain. We finally characterize these red-colour particles and try to explain their presences in the blood stain. Globally, all these red-colour particles cannot explain all of the reddish appearance of the area under study.

A semi-analytical multi-harmonic balance method on full-3D contact model for dynamic analysis of dry friction systems

Dry friction damping structures are widely-used in aero-engines to mitigate vibration.The nonlinear nature of friction and the two-dimensional in-plane motion on the contact interface bring challenges to accurately and efficiently predict the forced response of frictionally damped structures.The state-of-the-art Multi-Harmonic Balance Method(MHBM)on quasi-3D contact model in engineering cannot precisely capture the kinematics on the friction interface although the efficiency is high.The full-3D contact model can describe the constitutive relationship of the interface in a more accurate manner;however,the efficiency and convergence are not guaranteed for large-scale models.In this paper,a semi-analytical MHBM on full-3D contact model is proposed.The original Trajectory Tracking Method(TTM)for evaluating the contact force is reformulated to make the calculation more concise and the derivation of the Analytical Jacobian Matrix(AJM)feasible.Based on the chain rule of derivation,the AJM which is the core to upgrade the performance is deduced.Through a shrouded blade finite element model,the accuracy and efficiency of the proposed method are compared with both the MHBM on full-3D contact model with numerical Jacobian matrix and the MHBM on quasi-3D contact model with AJM.The results show that the AJM improves significantly the efficiency of the MHBM on full-3D contact model.The time cost of the proposed method is in the same order of magnitude as that of the MHBM on quasi-3D contact model.We also confirm that the full-3D contact model is necessary for the dynamic analyses of shrouded blades.If one uses the quasi-3D model,the estimation relative error of damping can even reach 31.8%in some cases.In addition,the AJM also brings benefits for stability analysis.It is highly recommended that engineers use the MHBM on full-3D contact model for the dynamic analysis and design of shrouded blades.

Influence of Cavity Leakage flow on Corner Separation in a Shrouded Stator Cascade

The impacts of the cavity leakage flow on the shrouded stator aerodynamic performance were investigated by modelling the annular cascade mainstream with the seal cavity flow path based on the validated numerical method.Meanwhile,the interactions between the cavity leakage and the mainstream were also determined in the current study.The development of hub corner separation under the action of leakage was discussed and the total pressure loss coefficient as well as the entropy-based loss coefficient was employed to evaluate the performance changes at different seal clearances and cavity rotational speeds.The results show that the cavity leakage flow induces a new vortex near the blade leading edge and plays an important role in the development of passage vortex and the size of concentrated shedding vortex.By increasing the seal clearance with more cavity leakage flow rate,an increase in the pitchwise extent of the separation region under 15%span is significant and the total pressure loss in the separation core increases.In addition,with the increase of cavity rotating speed,the starting point of corner separation moves backward,reducing the size and depth of the hub corner separation.The mainstream loss reduction in combination with the entropy increase in the seal cavity causes the entropy-based loss coefficient to perform a trend of decreasing first and then increasing with the cavity speed.

Aeroelastic simulation of the first 1.5-stage aeroengine fan at rotating stall

A massive parallel aeroelastic simulation platform has been built to investigate the first1.5-stage fan of an aeroengine at rotating stall.The Computational Fluid Dynamics(CFD)solver and Computational Structural Dynamics(CSD)solver are coupled directly by non-matching mesh interfaces.The unsteady rotor/stator interaction is solved by the Sliding Mesh Interface method.The original rotor blades are shrouded by the midspan shrouds.An unshrouded fan is also created to investigate the effects of the midspan shrouds.Both the shrouded fan and unshrouded fan have stable aeroelasticity at the designed state.At rotating stall,the stalled region rotates at 30%of the rotor speed on the absolute reference frame.The energy spectrum of the rotating stalled flow is measured quantitatively.It shows that the first two order excitations are much stronger than the higher order excitations.In the flow of rotating stall,the fifth backward travelling wave mode of shrouded fan is resonated by the fifth excitation of the rotational stalled flow because the rotational speed of the stalled region coincides with the modal rotational speed,while for the unshrouded fan,the first bending mode is resonated by the second excitation of the rotational stalled flow,forming two waves in the circumference of the annulus blades.At rotating stall,the vibration of the shrouded blades is still under control but the vibration of the unshrouded blades is diverged and out of control.A novel tool,i.e.,resonance map,is proposed to predict the resonance.It provides a perspective to explain the effects of midspan shrouds at a theoretical level,and it would also be helpful in the structural design of blades.

Experimental investigation of a counter-rotating compressor with boundary layer suction

This paper presents the aspirated modification of a dual-stage counter-rotating compressor which contains inlet guide vanes（IGVs）, two counter-rotating rotors（R1, R2）, and outlet guide vanes（OGVs）.Uniform circular holes are circumferentially distributed over the rotors＇ tips on the shroud casing which are designed to remove the low-energy fluid near the shroud casing.OGVs are hollow blades with two slots designed on the suction side which can better control the flow on the suction surface through boundary layer suction.Related works about the experiments have been carried out since June 2012 and the effect of flow suction on the performance of the compressor is investigated in detail.Characteristic lines at a 70% corrected rotating speed are tested and those with higher rotating speeds will be studied in the near future.Experimental results indicate that boundary layer suction can improve the compressor characteristics and the best suction methodology varies along the operating line.At the near stall condition, suction from the R2 tip region can obviously increase the efficiency and the total pressure ratio, as well as improve the flow capacity.Isentropic efficiency can be maximally increased by 4.24% with an increase of 1.94% in massflow under a suction flow of 160 m3/h.Suction at the R1 position with a suction rate below 0.35% in a high flow situation can make the performance of the compressor better than others.Around the peak efficiency point, boundary layer suction from the slots of OGVs is the best choice in improving the efficiency, but it causes a 0.1% loss in the total pressure ratio.