CFD Analysis of a Unidirectional Axial Turbine for Twin Turbine Topology in OWC Plants

2013 ◽  
Author(s):  
Bruno Pereiras ◽  
Pablo Valdez ◽  
Francisco Castro ◽  
Julio C. Garrido
Keyword(s):  
Numerical Model ◽  
Flow Field ◽  
Reverse Flow ◽  
Cfd Analysis ◽  
Ocean Energy ◽  
Loss Distribution ◽  
Axial Turbine ◽  
Guide Vanes ◽  
The Core ◽  
Reverse Mode

OWC devices are widely known among researchers in ocean energy. It is well-known that the efficiency of the device is closely related to the efficiency of the Power-Take-Off (PTO) which is usually a turbine. Traditionally, self-rectifying turbines are the most widely considered for working in an OWC because unidirectional turbines require a system of valves to rectify the flow. However, another option recently proposed is the use of the “twin turbine” configuration. This paper focuses on the performance of the turbines used in this configuration. A numerical model has been developed and validated with data from the bibliography. This model has been used to analyze the flow field of the turbine when working in both performance modes: direct and reverse. Flow angles and loss distribution have been analyzed and interesting conclusions can be extracted. Once the flow field has been analyzed, changes in the turbine geometry are proposed in order to improve the efficiency of the whole system by increasing the blockage made by the turbine in reverse mode. These changes, focused on the solidity of the rotor and guide vanes, were implemented and new simulations were carried out. The results obtained are the core of this work.

scholarly journals Flow Distortion Into the Core Engine for an Installed Variable Pitch Fan in Reverse Thrust Mode

2020 ◽  
Author(s):  
David John Rajendran ◽  
Vassilios Pachidis
Keyword(s):  
Flow Field ◽  
Total Pressure ◽  
Reverse Flow ◽  
Ground Plane ◽  
Operating Conditions ◽  
Flow Distortion ◽  
Engine Operation ◽  
Variable Pitch ◽  
The Core ◽  
Reverse Thrust

Abstract The flow distortion at core engine entry for a Variable Pitch Fan (VPF) in reverse thrust mode is described from a realistic flow field obtained using an integrated airframe-engine model. The model includes the VPF, core entry splitter, complete bypass nozzle flow path wrapped in a nacelle and installed to an airframe in landing configuration through a pylon. A moving ground plane to mimic the rolling runway is included. 3D RANS solutions are generated at two combinations of VPF stagger angle and rotational speed settings for the entire aircraft landing run from 140 to 20 knots. The internal reverse thrust flow field is characterized by bypass nozzle lip separation, pylon wake and recirculation of flow turned back from the VPF. A portion of the reverse stream flow turns 180° with separation at the splitter leading edge to feed the core engine. The core engine feed flow exhibits circumferential and radial non-uniformities that depend on the reverse flow development at different landing speeds. The temporal dependence of the distorted flow features is also explored by an URANS analysis. Total pressure and swirl angle distortion descriptors, as defined by the Society of Automotive Engineers (SAE) S-16 committee, and, total pressure loss into the core engine are described for the core feed flow at different operating conditions and landing speeds. It is observed that the radial intensity of total pressure distortion is critical to core engine operation, while the circumferential intensity is within acceptable limits. Therefore, the baseline sharp splitter edge is replaced by two larger rounded splitter edges of radii, ∼0.1x and ∼0.2x times the core duct height. This was found to reduce the radial intensity of total pressure distortion to acceptable levels. The description of the installed core feed flow distortion, as described in this study, is necessary to ascertain stable core engine operation, which powers the VPF in reverse thrust mode.

CFD Analysis of Boron Distribution at Core Entrance in Case of Reverse Flow Induced From PRISE

2014 ◽  
Author(s):  
Svetlin Philipov
Keyword(s):  
Boric Acid ◽  
Input Data ◽  
Current Issue ◽  
Reverse Flow ◽  
Primary Circuit ◽  
Cfd Analysis ◽  
Reversed Flow ◽  
The Core ◽  
Loss Of Coolant ◽  
Boron Distribution

Initiating events such as primary to secondary loss of coolant (PRISE) can lead to conditions forming reversed flow from the second to the primary circuit. Current issue shows the results of a CFD analysis of the distribution of boric acid on the entrance of the core in case of such reversed flow of coolant as a result of PRISE initiation event. Analyzed accident is included in the list of design basis accidents and requires precise approach in analyzing the phenomena associated with the possibility of injection of coolant with low concentration of boric acid in the primary side. The paper emphasizes on the application of CFD to solve the problem. Analyzing the accident is done in advance with the help of system code RELAP. The input data as flow rate, concentration and temperature at the inlet of the reactor is submitted as boundary conditions in FLUENT and boric acid mixing is analyzed to the core inlet.

Influence of the Guide Vanes Solidity on the Performance of a Radial Impulse Turbine With Pitch-Controlled Guide Vanes

2011 ◽  
Author(s):  
Bruno Pereiras ◽  
Manabu Takao ◽  
Fernando Garcia ◽  
Francisco Castro
Keyword(s):  
Numerical Model ◽  
Pressure Drop ◽  
Essential Role ◽  
Experimental Tests ◽  
Energy Extraction ◽  
Ocean Energy ◽  
Impulse Turbine ◽  
Guide Vanes ◽  
Turbine Efficiency ◽  
Turbine Design

One of the most developed technologies in ocean energy is the OWC concept. In this kind of device there is a turbine which plays an essential role, it is one of the factors which determine the efficiency of the system because of its own efficiency and its coupling with the chamber. One of the main characteristics in a turbine for OWC purposes, especially impulse turbines, is to use Guide vanes to optimize the energy extraction. However, they also are the largest source of losses. Improving the Guide vanes performance could reduce the pressure drop and, thus, the efficiency increases and the damping becomes smaller. In this paper the solidity of the guide vanes is analyzed to determine the optimum one. The study has been conducted on a radial impulse turbine with pitch-controlled guide vanes to minimize the incidence losses and, therefore, analyze the effect of the solidity. Experimental tests were carried out to validate a numerical model created in FLUENT®. The numerical model has been used to analyze the same turbine design but with different solidities of the guide vanes. The results have been conclusive: there is an optimal solidity for the guide vanes, which maximize the turbine efficiency by means of improving the guide vanes performance. Moreover, it has been seen that the optimum solidity is different for the inner and outer guide vanes.

Groundwater flow simulation and its application in GaoSong ore field, China

2018 ◽  
Vol 10 (2) ◽  
pp. 276-284 ◽  
Author(s):  
Gang Chen ◽  
Shiguang Xu ◽  
Chunxue Liu ◽  
Lei Lu ◽  
Liang Guo
Keyword(s):  
Numerical Model ◽  
Flow Field ◽  
Groundwater Flow ◽  
Mine Water ◽  
Permeability Coefficient ◽  
Water Inrush ◽  
Seepage Field ◽  
Groundwater Seepage ◽  
Calculation Results ◽  
Groundwater Flow Field

Abstract Mine water inrush is one of the important factors threatening safe production in mines. The accurate understanding of the mine groundwater flow field can effectively reduce the hazards of mine water inrush. Numerical simulation is an important method to study the groundwater flow field. This paper numerically simulates the groundwater seepage field in the GaoSong ore field. In order to ensure the accuracy of the numerical model, the research team completed 3,724 field fissure measurements in the study area. The fracture measurement results were analyzed using the GEOFRAC method and the whole-area fracture network data were generated. On this basis, the rock mass permeability coefficient tensor of the aquifer in the study area was calculated. The tensor calculation results are used in the numerical model of groundwater flow. After calculation, the obtained numerical model can better represent the groundwater seepage field in the study area. In addition, we designed three different numerical models for calculation, mainly to explore the influence of the tensor assignment of permeability coefficient on the calculation results of water yield of the mine. The results showed that irrational fathom tensor assignment would cause a significant deviation in calculation results.

On the Use of an Inflatable Rubber Lip to Improve the Reverse Thrust Flow Field in a Variable Pitch Fan

2021 ◽  
Author(s):  
David John Rajendran ◽  
Vassilios Pachidis
Keyword(s):  
Flow Field ◽  
Reverse Flow ◽  
Separated Flow ◽  
Geometric Feature ◽  
Engine Operation ◽  
Design Modification ◽  
Variable Pitch ◽  
Aircraft Landing ◽  
Turn Radius ◽  
Reverse Thrust

Abstract The installed Variable Pitch Fan (VPF) reverse thrust flow field is obtained from the flow solution of an integrated airframe-engine-VPF research model for the complete reverser engagement regime during the aircraft landing run. The reverse thrust flow field indicates that the reverse flow out of the nacelle inlet is washed downstream by the freestream. Consequently, reverse flow enters the engine through the bypass nozzle from a 180° turn of the washed-down stream. This results in a region of separated flow at the nozzle lip that acts as a blockage to the reverse flow entry into the engine. To mitigate the blockage issue, a smooth guidance of the reverse flow into the engine can be achieved by using an inflatable rubber lip that would define a bell-mouth like geometric feature with a round radius at the nacelle exit. In nominal engine operation, the rubber lip would be stowed flush within the contours of the nacelle surface. The design space of the rubber lip is studied by considering different rounding radii and locations of the turn radius with respect to the nacelle trailing edge. It is observed that a rounding radius of 0.1x nacelle length is sufficient to reduce the blockage and increase the ingested reverse flow by 47% to 18% in the 140 to 40 knots landing speed range. The inflatable rubber lip represents a design modification that can improve VPF reverse thrust operation, in cases where an augmentation of reverse thrust capability is desired

CFD analysis of flow field and power consumption of in-line high shear mixers with different stator structures

2021 ◽  
Vol 98 (10) ◽  
pp. 100159
Author(s):  
Cholu Kwon ◽  
Un song Pak ◽  
Chung myong Kim ◽  
Chen ho Paek
Keyword(s):  
Flow Field ◽  
Power Consumption ◽  
High Shear ◽  
Cfd Analysis

CFD analysis of flow field in a triangular rod bundle

2010 ◽  
Vol 240 (2) ◽  
pp. 352-363 ◽  
Author(s):  
S. Tóth ◽  
A. Aszódi
Keyword(s):  
Flow Field ◽  
Cfd Analysis ◽  
Rod Bundle

On the Origin of Rotation Derived from Super Rapid Scan Satellite Imagery at the Cloud-Tops of Severe Deep Convection

2021 ◽  
Author(s):  
Jason M. Apke ◽  
John R. Mecikalski
Keyword(s):  
Quality Control ◽  
Numerical Model ◽  
Flow Field ◽  
Optical Flow ◽  
Case Studies ◽  
Model Simulation ◽  
Deep Convection ◽  
Vertical Wind Shear ◽  
Future Research ◽  
Severe Thunderstorms

AbstractSevere thunderstorms routinely exhibit adjacent maxima and minima in cloud-top vertical vorticity (CTV) downstream of overshooting tops within flow fields retrieved using sequences of fine-temporal resolution (1-min) geostationary operational environmental satellite (GOES)-R series imagery. Little is known about the origin of this so-called “CTV couplet” signature, and whether the signature is the result of flow field derivational artifacts. Thus, the CTV signature’s relevance to research and operations is currently ambiguous. Within this study, we explore the origin of near-cloud-top rotation using an idealized supercell numerical model simulation. Employing an advanced dense optical flow algorithm, image stereoscopy, and numerical model background wind approximations, the artifacts common with cloud-top flow field derivation are removed from two supercell case studies sampled by GOES-R imagers. It is demonstrated that the CTV couplet originates from tilted and converged horizontal vorticity that is baroclinically generated in the upper levels (above 10 km) immediately downstream of the overshooting top. This baroclinic generation would not be possible without a strong and sustained updraft, implying an indirect relationship to rotationally-maintained supercells. Furthermore, it is demonstrated that CTV couplets derived with optical flow algorithms originate from actual rotation within the storm anvils in the case studies explored here, though supercells with opaque above anvil cirrus plumes and strong anvil-level negative vertical wind shear may produce rotation signals as an artifact without quality control. Artifact identification and quality control is discussed further here for future research and operations use.

Ice Crystal Icing Investigation on a Honeywell Uncertified Research Engine in an Altitude Simulation Icing Facility

2020 ◽  
Author(s):  
Ashlie B. Flegel
Keyword(s):  
Particle Size ◽  
Guide Vane ◽  
Leading Edge ◽  
Inlet Guide Vane ◽  
Inlet Temperature ◽  
Ice Crystal ◽  
Guide Vanes ◽  
Inlet Guide Vanes ◽  
The Core ◽  
Break Up

Abstract A Honeywell Uncertified Research Engine was exposed to various ice crystal conditions in the NASA Glenn Propulsion Systems Laboratory. Simulations using NASA’s 1D Icing Risk Analysis tool were used to determine potential inlet conditions that could lead to ice crystal accretion along the inlet of the core flowpath and into the high pressure compressor. These conditions were simulated in the facility to develop baseline conditions. Parameters were then varied to move or change accretion characteristics. Data were acquired at altitudes varying from 5 kft to 45 kft, at nominal ice particle Median Volumetric Diameters from 20 μm to 100 μm, and total water contents of 1 g/m3 to 12 g/m3. Engine and flight parameters such as fan speed, Mach number, and inlet temperature were also varied. The engine was instrumented with total temperature and pressure probes. Static pressure taps were installed at the leading edge of the fan stator, front frame hub, the shroud of the inlet guide vane, and first two rotors. Metal temperatures were acquired for the inlet guide vane and vane stators 1–2. In-situ measurements of the particle size distribution were acquired three meters upstream of the engine forward fan flange and one meter downstream of the fan in the bypass in order to study particle break-up behavior. Cameras were installed in the engine to capture ice accretions at the leading edge of the fan stator, splitter lip, and inlet guide vane. Additional measurements acquired but not discussed in this paper include: high speed pressure transducers installed at the trailing edge of the first stage rotor and light extinction probes used to acquire particle concentrations at the fan exit stator plane and at the inlet to the core and bypass. The goal of this study was to understand the key parameters of accretion, acquire particle break-up data aft of the fan, and generate a unique icing dataset for model and tool development. The work described in this paper focuses on the effect of particle break-up. It was found that there was significant particle break-up downstream of the fan in the bypass, especially with larger initial particle sizes. The metal temperatures on the inlet guide vanes and stators show a temperature increase with increasing particle size. Accretion behavior observed was very similar at the fan stator and splitter lip across all test cases. However at the inlet guide vanes, the accretion decreased with increasing particle size.

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