Inlet Turbulence and Off-Design Incidence Response of High Efficiency, Turbine OGV Profiles

2019 ◽  
Author(s):  
Benigno J. Lazaro ◽  
Ezequiel Gonzalez ◽  
Jorge Parra ◽  
David Cadrecha Robles
Keyword(s):  
High Efficiency ◽  
Guide Vane ◽  
Reynolds Numbers ◽  
Cfd Simulations ◽  
Pressure Distributions ◽  
Flow Response ◽  
Wide Range ◽  
Background Turbulence ◽  
Current Design ◽  
And Performance

Abstract In spite of advances in CFD prediction tools, the current design of outlet guide vane (OGV) stages for flow recovery downstream from low pressure turbines (LPT) still has to face significant flow entrance uncertainties. To ensure proper response of modern, high efficiency OGV’s, the sensitivity in the aerodynamic response of the vanes to both different levels of inlet turbulence and off-design incidence must be analyzed. To that end, a systematic experimental investigation of a current design LPT OGV airfoil has been undertaken in a low-speed linear cascade. Wall pressure distributions as well as high-resolution total pressure drop and LDV measurements have been used to determine the flow response. The experimental facility includes different boundary suction strategies for proper control of flow periodicity and endwall effects at significant off-design incidences. In addition, different inlet grids to promote an entrance flow having controlled isotropic background turbulence are included. The experimental flow response of the OGV airfoil is presented for a wide range of Reynolds numbers and different values of the inlet flow incidence and turbulence properties. Both at design and off-design incidences, different flow regimes and performance degradation mechanisms are discussed. In addition, the effect of inlet turbulence at close to design incidence is discussed, with the experimental evidence suggesting that its effect can be described by defining a properly scaled Reynolds number. The ability of CFD simulations based on currently available RANS transition models to describe the flow in high efficiency turbine OGV airfoils is finally explored.

Mechanical Design and Testing of a 2.5 MW sCO2 Compressor Loop

2021 ◽  
Author(s):  
Stefan D. Cich ◽  
J. Jeffrey Moore ◽  
Chris Kulhanek ◽  
Meera Day Towler ◽  
Jason Mortzheim
Keyword(s):  
High Efficiency ◽  
Mechanical Design ◽  
Guide Vane ◽  
Operating Conditions ◽  
Inlet Guide Vane ◽  
Inlet Temperature ◽  
Design Changes ◽  
Wide Range ◽  
Inlet Conditions ◽  
Design And Testing

Abstract An enabling technology for a successful deployment of the sCO2 close-loop recompression Brayton cycle is the development of a compressor that can maintain high efficiency for a wide range of inlet conditions due to large variation in properties of CO2 operating near its dome. One solution is to develop an internal actuated variable Inlet Guide Vane (IGV) system that can maintain high efficiency in the main and re-compressor with varying inlet temperature. A compressor for this system has recently been manufactured and tested at various operating conditions to determine its compression efficiency. This compressor was developed with funding from the US DOE Apollo program and industry partners. This paper will focus on the design and testing of the main compressor operating near the CO2 dome. It will look at design challenges that went into some of the decisions for rotor and case construction and how that can affect the mechanical and aerodynamic performance of the compressor. This paper will also go into results from testing at the various operating conditions and how the change in density of CO2 affected rotordynamics and overall performance of the machine. Results will be compared to expected performance and how design changes were implanted to properly counter challenges during testing.

Aerodynamic Investigations of a Variable Inlet Guide Vane With Symmetric Profile

2014 ◽  
Author(s):  
David Händel ◽  
Reinhard Niehuis ◽  
Uwe Rockstroh
Keyword(s):  
Boundary Layer ◽  
High Speed ◽  
Guide Vane ◽  
Reynolds Numbers ◽  
Boundary Layer Transition ◽  
Inlet Guide Vane ◽  
Experimental Investigations ◽  
Wide Range ◽  
Variable Inlet Guide Vane ◽  
Symmetric Profile

In order to determine the aerodynamic behavior of a Variable Inlet Guide Vane as used in multishaft compressors, extensive experimental investigations with a 2D linear cascade have been conducted. All the experiments were performed at the High-Speed Cascade Wind Tunnel at the Institute of Jet Propulsion. They covered a wide range of Reynolds numbers and stagger angles as they occur in realistic turbomachines. Within this work at first the observed basic flow phenomena (loss development, overturning) will be explained. For the present special case of a symmetric profile and a constant decreasing chord length along the vane height, statements about different spanwise position can be made by investigating different Reynolds numbers. The focus of this paper is on the outflow of the VIGV along the vane height. Results for an open flow separation on the suction side are presented, too. Stall condition can be delayed by boundary layer control. This is done using a wire to trigger an early boundary layer transition. The outcomes of the trip wire measurement are finally discussed. The objective of this work is to evaluate the influence of the stagger angle and Reynolds number on the total pressure losses and the deviation angle. The results of the work presented here, gives a better insight of the efficient use of a VIGV.

Multiobjective optimization of a tubular pump to improve the applicable operating head and hydraulic performance

2020 ◽  
pp. 095440622094711
Author(s):  
Wenlong Zhao ◽  
Jian Zhang ◽  
Xiaodong Yu ◽  
Daqing Zhou ◽  
Melih Calamak
Keyword(s):  
High Efficiency ◽  
Guide Vane ◽  
Optimization Method ◽  
Critical Parameters ◽  
Long Distance ◽  
Blade Thickness ◽  
Weighted Matrix ◽  
Wide Range ◽  
Shaft Power ◽  
Water Conveyance

Tubular pumps are widely used in irrigation and water conveyance projects. However, the operating head of most of these pumps is low, and only a few studies have focused on the design of an efficient tubular pump with a head more than 5 m, which is common in long-distance water supply projects. This work aims to improve the operating head and efficiency of tubular pumps while maintaining a low shaft power. The multi-objective orthogonal optimization method was used to determine the critical parameters of the tubular pump, i.e., blade number, airfoil, blade thickness and guide vane distance, and nine design schemes were selected. Next, by using computational fluid dynamics (CFD), a 3D model of the tubular pumps under different schemes was established, and the results were compared. Subsequently, the range method and weighted matrix method were utilized to find the optimized scheme. In addition, an experimental investigation was performed to verify the simulation and the performance of the designed tubular pump. The results indicated that the optimized scheme improved the operating head to 6.9 m with higher efficiency of 84.2% and a lower shaft power of 27.7 kW. The modeling results were in agreement with the experimental measurements, and the designed tubular pump had a wide range of high-efficiency zones.

scholarly journals Numerical Study of Pump-Turbine Instabilities Under Pumping Mode Off-Design Conditions

2015 ◽  
Author(s):  
Uroš Ješe ◽  
Regiane Fortes-Patella ◽  
Matevž Dular
Keyword(s):  
Power Plants ◽  
Numerical Study ◽  
Guide Vane ◽  
Characteristic Curve ◽  
Rotating Stall ◽  
Electrical Network ◽  
Pump Turbine ◽  
Wide Range ◽  
Pumping Mode ◽  
And Performance

Pumped storage power plants, using reversible pump-turbines, are a great solution to maintain the stability of an electrical network. The continuous operating area of reversible pump-turbines machines is usually delimited by cavitation or a hydraulic instability called hump phenomena at part load. If the machine operates under these off-design conditions, it might be exposed to vibrations and performance losses. The paper focuses on the numerical analysis of the pumping mode regime and pays special attention to the prediction of the hump shaped characteristic curve and associated rotating stall. The investigations were made on a high head pump-turbine design (nq=27) at model scale for four different guide vane opening angles and a wide range of flow rates. Numerical simulations were performed and analyzed in LEGI and were compared to the global experimental data, provided by Alstom Hydro.

scholarly journals FEASIBILITY OF BACKFIRE CONTROL AND PERFORMANCE USING CHANGES OF VALVE OVERLAP PERIOD FOR A HYDROGEN-FUELED ENGINE WITH EXTERNAL MIXTURE

2009 ◽  
Vol 12 (14) ◽  
pp. 77-85
Author(s):  
Cong Thanh Huynh ◽  
Kang Joon-Kyoung ◽  
Noh Ki-Cholo ◽  
Lee Jong-Tai ◽  
Mai Xuan Pham
Keyword(s):  
High Efficiency ◽  
Engine Performance ◽  
Continuous Variable ◽  
Variable Valve Timing ◽  
Valve Timing ◽  
Performance Loss ◽  
Wide Range ◽  
And Performance ◽  
Variable Valve ◽  
Valve Overlap

The development of a hydrogen-fueled engine using an external mixture (e.g., using port injection) with high efficiency and high power is dependent on the control of backfire. This work has developed a method to control backfire by reducing the valve overlap period. For this goal, a single-cylinder hydrogen-fueled research engine with a mechanical continuous variable valve timing (MCVVT) system was developed. This facility provides a wide range of valve overlap periods that can be continuously and independently varied during firing operation. In experiments, the behavior of backfire occurrence and engine performance are determined as functions of the valve overlap period for fuel-air equivalence ratios between 0.25 and 1.2. The results showed that the research engine with the MCVVT system has similar performance to a conventional engine, and is especially effective in controlling the valve overlap period. The obtained results demonstrate that decreasing the valve overlap period may be one of the methods for controlling backfire in a H engine. Also, a method for compensating performance loss due to shortened valve overlap period is recommended.

scholarly journals Development of a low head tidal turbine

2018 ◽  
Vol 1 (2 (Nov)) ◽  
pp. 81-90
Author(s):  
S. Hötzl ◽  
T. Schechtl ◽  
P. Rutschmann ◽  
W. Knapp
Keyword(s):  
High Efficiency ◽  
Guide Vane ◽  
Net Energy ◽  
Transient Effects ◽  
Cfd Simulations ◽  
Design And Optimization ◽  
Runner Blade ◽  
Tidal Turbine ◽  
Low Head ◽  
Four Quadrant

Recent research has shown that four-quadrant turbines are required to achieve maximum net energy production in a tidal barrage plant. These turbines can generate electricity in both flow directions and are capable of pumping. An innovative turbine concept is being reviewed in the course of the Eurostars research project Safe*Coast. This project proposes to install a turbine in a reversible cylinder in order to allow for fourquadrant operation. To evaluate the feasibility of the concept, the authors designed a compact low head axial tidal turbine with the aid of CFD simulations. This paper presents the methods used in the design and optimization process of the turbine. It also describes numerically obtained turbine characteristics, and cavitation limits. The most critical requirements of the turbine include high efficiency in turbine and pumping mode and safe cavitation properties. By computing steady state CFD simulations of the turbine stage, an extensive set of geometries was analyzed. The authors optimized the turbine performance by adjusting the meridional section, as well as runner blade and guide vane profiles and angles along with other related parameters. Transient simulations of the whole setup, including the inlet and draft tube geometries, were performed in order to study transient effects. The final design after optimization is a three bladed axial turbine with adjustable guide vanes and a rim generator. The turbine’s symmetrical inlet and outlet geometry and its relative compactness permit its integration in a reversible cylinder. The simulation results are very positive and indicate that all the relevant design criteria are satisfied. As a result, the project will continue into a new phase in which a model of the turbine will be built for physical testing in order to verify the results and to conduct further investigations.

Blood Flow and Mixing Analysis in Split-and-Recombine Micromixer With Offset Fluid Inlets

2018 ◽  
Author(s):  
Afzal Husain ◽  
Farhan A. Khan ◽  
Nabeel Z. Al-Rawahi ◽  
Abdus Samad
Keyword(s):  
Blood Flow ◽  
Numerical Model ◽  
Parametric Analysis ◽  
Three Dimensional ◽  
Reynolds Numbers ◽  
Fluid Models ◽  
Mixing Index ◽  
Blood Flows ◽  
Wide Range ◽  
And Performance

In this study, a variant of 3D split-and-recombine micromixer is proposed for enhanced micromixing. The mixing analysis was carried out for water and blood flows through the three-dimensional numerical model. The blood flow was modeled using several non-Newtonian fluid models existed in the literature and performance was compared for mixing index. Further, the performance of the proposed micromixer was compared with several other designs of micromixers available in the open literature for a wide range of Reynolds numbers covering diffusion, transient, and advection-dominated flow regimes. Finally, Carreau-Yasuda model was used to carry out parametric analysis of the proposed micromixer for mixing index.

scholarly journals A review of processing strategies to generate melt-blown nano/microfiber mats for high-efficiency filtration applications

2021 ◽  
pp. 152808372110194
Author(s):  
Yahya Kara ◽  
Kolos Molnár
Keyword(s):  
High Efficiency ◽  
Processing Parameters ◽  
Filtration Efficiency ◽  
Melt Blowing ◽  
Nonwoven Fabrics ◽  
High Particle ◽  
Processing Strategies ◽  
Wide Range ◽  
Recent Developments ◽  
And Performance

Protective masks – worn properly - have become the key to wither away the COVID-19 pandemic. Nowadays, the vast majority of these masks are made of nonwoven fabrics. High-quality products have mainly melt-blown filtering layers of nano/microfiber. Melt blowing produces very fine synthetic nonwovens from a wide range of polymers and allows a fair control of the fiber structure and morphology that makes it ideal for filtration purposes. Melt blowing has a high throughput, and the low price of the filter makes these products widely available for civil use. Although melt-blown fiber applications were rapidly growing in the last three decades, we still have limited knowledge on the processing parameters. In this regard, we detailed the melt blowing parameters to obtain a filter media with high particle capturing efficiency and a low-pressure drop. We summarized the melt-blown fiber mat characteristics with specific attention to the pore size, the porosity, the fiber diameter, the fiber packing density and the air permeability desired for highly efficient filtration. Even though we cannot estimate the future social effects and the trauma caused by the current pandemic, and protective masks might remain a part of everyday life for a long while. That also implies that near-future investments in wider manufacturing capacities seem inevitable. This paper also aims to facilitate masks' production with improved filtration efficiency by reviewing the recent developments in melt blowing, the related applications, the effects of processing parameters on the structure and performance of the nonwoven products focusing on the filtration efficiency via knowledge.

scholarly journals Experiments and Performance Evaluation of a Transonic Axial Flow Turbine With Variable Nozzle

1986 ◽  
Author(s):  
Toshiyuki Takagi
Keyword(s):  
Performance Evaluation ◽  
Surface Pressure ◽  
Axial Flow ◽  
Prediction Method ◽  
Pressure Distributions ◽  
Wide Range ◽  
Overall Performance ◽  
Transonic Turbine ◽  
Loss Systems ◽  
And Performance

To examine extensively the overall performance of a single-stage transonic turbine under high-loading conditions, aerodynamic experiments were conducted over a wide range of stage pressure ratios up to 4.16. The measured performance is estimated by means of a mean-line prediction method with two loss systems and is discussed with radial variations and surface pressure distributions. The results show that airflow characteristics, loss systems and choking Mach numbers play an important role in evaluating the performance when choking occurs at either row.

scholarly journals Mixing Performance of a Cost-effective Split-and-Recombine 3D Micromixer Fabricated by Xurographic Method

Micromachines ◽  
2019 ◽  
Vol 10 (11) ◽  
pp. 786 ◽  
Author(s):  
Ramezan Ali Taheri ◽  
Vahabodin Goodarzi ◽  
Abdollah Allahverdi
Keyword(s):  
High Efficiency ◽  
Molecular Diffusion ◽  
Low Cost ◽  
Three Dimensional ◽  
Cost Effective ◽  
Reynolds Numbers ◽  
Mixing Performance ◽  
Wide Range ◽  
Fluid Layers ◽  
Passive Micromixer

This paper presents experimental and numerical investigations of a novel passive micromixer based on the lamination of fluid layers. Lamination-based mixers benefit from increasing the contact surface between two fluid phases by enhancing molecular diffusion to achieve a faster mixing. Novel three-dimensional split and recombine (SAR) structures are proposed to generate fluid laminations. Numerical simulations were conducted to model the mixer performance. Furthermore, experiments were conducted using dyes to observe fluid laminations and evaluate the proposed mixer’s characteristics. Mixing quality was experimentally obtained by means of image-based mixing index (MI) measurement. The multi-layer device was fabricated utilizing the Xurography method, which is a simple and low-cost method to fabricate 3D microfluidic devices. Mixing indexes of 96% and 90% were obtained at Reynolds numbers of 0.1 and 1, respectively. Moreover, the device had an MI value of 67% at a Reynolds number of 10 (flow rate of 116 µL/min for each inlet). The proposed micromixer, with its novel design and fabrication method, is expected to benefit a wide range of lab-on-a-chip applications, due to its high efficiency, low cost, high throughput and ease of fabrication.

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