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Tian Jian - One of the best experts on this subject based on the ideXlab platform.

  • Discussion on weir Flow Coefficient for broad-crest ridge-free weirs
    Advances in Science and Technology of Water Resources, 2003
    Co-Authors: Tian Jian
    Abstract:

    The broad crest ridge free weir is a common structural form of hydraulic structures. In determination of the size of sluice projects, the influence of weir Flow Coefficient should not be ignored. For convenient and precise determination of the Flow Coefficient for broad crest ridge free weirs according to the compulsive requirement of the current trade standard, a discussion is made on the adoption of the calculating formula, conforming to "the sluice design specifications" SL265 2001, to derive a suitable value of the Flow Coefficient for further calculation of the discharge capacity and determination of scale of sluice projects by a comparative analysis of data from hydraulic model tests on some completed hydraulic projects. It is concluded that the Flow Coefficient in the range of 0.36～0.375 is suitable for broad crest ridge free weirs with a rectangular conjunctive section between the upper and lower reaches of lock chambers under free outFlow conditions.

Xiao Hua Wang - One of the best experts on this subject based on the ideXlab platform.

  • Numerical Simulation of the Effect of Section Size on Averaging Pitot Tube
    Applied Mechanics and Materials, 2012
    Co-Authors: Yang Wang, Xiao Hua Wang
    Abstract:

    Averaging pitot tube has been applied in practice more often in these years. This paper set up the two-dimensional model of the bullet-shaped averaging pitot tube, numerical simulation based on CFD was used to investigate the changes of Flow Coefficient along with the Reynolds number. The geometric size of the section was changed to investigate how it influences the Flow Coefficient and differential pressure. To guarantee the accuracy of the simulation, the grid and the simulation model were investigated too.

Rathakrishnan Bhaskaran - One of the best experts on this subject based on the ideXlab platform.

  • High-Fidelity Simulations of Low-Pressure Turbines: Effect of Flow Coefficient and Reduced Frequency on Losses
    Journal of Turbomachinery-transactions of The Asme, 2016
    Co-Authors: Vittorio Michelassi, Liwei Chen, Richard Pichler, Richard D. Sandberg, Rathakrishnan Bhaskaran
    Abstract:

    Large eddy simulations validated with the aid of direct numerical simulation (DNS) are used to study the concerted action of reduced frequency and Flow Coefficient on the performance of the T106A low-pressure turbine profile. The simulations are carried out by using a discretization in space and time that allows minimizing the accuracy loss with respect to DNS. The reference Reynolds number is 100,000, while reduced frequency and Flow Coefficient cover a range wide enough to provide valid qualitative information to designers. The various configurations reveal differences in the loss generation mechanism that blends steady and unsteady boundary layer losses with unsteady wake ingestion losses. Large values of the Flow Coefficient can alter the pressure side unsteadiness and the consequent loss generation. Low values of the Flow Coefficient are associated with wake fogging and reduced unsteadiness around the blade. The reduced frequency further modulates these effects. The simulations also reveal a clear trend of losses with the wake path, discussed by conducting a loss-breakdown analysis that distinguishes boundary layer from wake distortion losses.

  • High-Fidelity Simulations of Low-Pressure Turbines: Effect of Flow Coefficient and Reduced Frequency on Losses
    Volume 2C: Turbomachinery, 2015
    Co-Authors: Vittorio Michelassi, Liwei Chen, Richard Pichler, Richard D. Sandberg, Rathakrishnan Bhaskaran
    Abstract:

    Large Eddy Simulations validated with the aid of Direct Numerical Simulation are used to study the concerted action of reduced frequency and Flow Coefficient on the performance of the T106A low-pressure-turbine profile. The simulations are carried out by using a discretization in space and time that allows minimizing the accuracy loss with respect to Direct Numerical Simulation. The reference Reynolds number is 100,000, while reduced frequency and Flow Coefficient cover a range wide enough to provide valid qualitative information to designers. The various configurations reveal differences in the loss generation mechanism that blends steady and unsteady boundary layer losses with unsteady wake ingestion losses. Large values of the Flow Coefficient can alter the pressure side unsteadiness, and the consequent loss generation. Low values of the Flow Coefficient are associated with wake fogging and reduced unsteadiness around the blade. The reduced frequency further modulates these effects. The simulations also reveal a clear trend of losses with the wake path, discussed by conducting a loss-breakdown analysis that distinguishes boundary layer from wake distortion losses.Copyright © 2015 by ASME

Zoltán S. Spakovszky - One of the best experts on this subject based on the ideXlab platform.

  • Low-Flow-Coefficient Centrifugal Compressor Design for Supercritical CO2
    Journal of Turbomachinery-transactions of The Asme, 2014
    Co-Authors: Claudio Lettieri, N. Baltadjiev, Michael Casey, Zoltán S. Spakovszky
    Abstract:

    This paper presents a design strategy for very low Flow Coefficient multistage compressors operating with supercritical CO2 for carbon capture and sequestration (CCS) and enhanced oil recovery (EOR). At Flow Coefficients less than 0.01, the stage efficiency is much reduced due to dissipation in the gas-path and more prominent leakage and windage losses. Instead of using a vaneless diffuser as is standard design practice in such applications, the current design employs a vaned diffuser to decrease the meridional velocity and to widen the gas path. The aim is to achieve a step change in performance. The impeller exit width is increased in a systematic parameter study to explore the limitations of this design strategy and to define the upper limit in efficiency gain. The design strategy is applied to a full-scale reinjection compressor currently in service. Three-dimensional, steady, supercritical CO2 computational fluid dynamics (CFD) simulations of the full stage with leakage Flows are carried out with the National Institute of Standards and Technology (NIST) real gas model. The design study suggests that a nondimensional impeller exit width parameter b2* = (b2/R)ϕ of six yields a 3.5 point increase in adiabatic efficiency relative to that of a conventional compressor design with vaneless diffuser. Furthermore, it is shown that in such stages the vaned diffuser limits the overall stability and that the onset of rotating stall is likely caused by vortex shedding near the diffuser leading edge. The inverse of the nondimensional impeller exit width parameter b2* can be interpreted as the Rossby number. The investigation shows that, for very low Flow Coefficient designs, the Coriolis accelerations dominate the relative Flow accelerations, which leads to inverted swirl angle distributions at impeller exit. Combined with the two-orders-of-magnitude higher Reynolds number for supercritical CO2, the leading edge vortex shedding occurs at lower Flow Coefficients than in air suggesting an improved stall margin.

  • Low-Flow-Coefficient Centrifugal Compressor Design for Supercritical CO2
    Volume 6C: Turbomachinery, 2013
    Co-Authors: Claudio Lettieri, N. Baltadjiev, Michael Casey, Zoltán S. Spakovszky
    Abstract:

    This paper presents a design strategy for very low Flow Coefficient multi-stage compressors operating with supercritical CO2 for Carbon Capture and Sequestration (CCS) and Enhanced Oil Recovery (EOR). At Flow Coefficients less than 0.01 the stage efficiency is much reduced due to dissipation in the gas-path and more prominent leakage and windage losses. Instead of using a vaneless diffuser as is standard design practice in such applications, the current design employs a vaned diffuser to decrease the meridional velocity and to widen the gas path. The aim is to achieve a step change in performance.The impeller exit width is increased in a systematic parameter study to explore the limitations of this design strategy and to define the upper limit in efficiency gain. The design strategy is applied to a full-scale re-injection compressor currently in service. Three-dimensional, steady, supercritical CO2 CFD simulations of the full stage with leakage Flows are carried out with the NIST real gas model. The design study suggests that a non-dimensional impeller exit width parameter b2* = (b2/R)ϕ of 6 yields a 3.5 point increase in adiabatic efficiency relative to that of a conventional compressor design with vaneless diffuser. Furthermore, it is shown that in such stages the vaned diffuser limits the overall stability and that the onset of rotating stall is likely caused by vortex shedding near the diffuser leading edge. The inverse of the non-dimensional impeller exit width parameter b2* can be interpreted as the Rossby number. The investigation shows that, for very low Flow Coefficient designs, the Coriolis accelerations dominate the relative Flow accelerations, which leads to inverted swirl angle distributions at impeller exit. Combined with the two-orders-of-magnitude higher Reynolds number for supercritical CO2, the leading edge vortex shedding occurs at lower Flow Coefficients than in air suggesting an improved stall margin.Copyright © 2013 by ASME

Ji Bao Wang - One of the best experts on this subject based on the ideXlab platform.

  • Experimental Study on Flow Coefficient of Broad-Crest Ridge-Free Weir of Gudi Hydroelectric Power Station
    Advanced Materials Research, 2011
    Co-Authors: Ji Bao Wang
    Abstract:

    The Flow Coefficient is an important factor in analyzing and computing the Flow capacity of broad-crested ridge-free weir of low head hydroelectric key position. For determine the Flow Coefficient of the broad-crested ridge-free weir of low head dam accurately, this paper study on the rule of the Flow Coefficient change base on the Gudi hydroelectric station model test. The test show in the condition of the high submergence and complex upstream and downstream Flow condition, the Flow Coefficient value that use empirical formula compute is big. The author proposes the correction formula according the empirical formula and the test result.