On the Entropy Rise in General Unducted Rotors using Momentum, Vorticity and Energy Transport

On the Entropy Rise in General Unducted Rotors using Momentum, Vorticity and Energy Transport

Bibliographic Details
Main Author: Siddappaji, Kiran
Language:English
Published: University of Cincinnati / OhioLINK 2018
Subjects:
Aerospace Materials
kinetic energy dissipation
entropy
exergy
unducted and ducted turbomachinery
MDAO
vorticity
Online Access:http://rave.ohiolink.edu/etdc/view?acc_num=ucin1535464679934565
id ndltd-OhioLink-oai-etd.ohiolink.edu-ucin1535464679934565
record_format oai_dc
collection NDLTD
language English
sources NDLTD
topic Aerospace Materials
kinetic energy dissipation
entropy
exergy
unducted and ducted turbomachinery
MDAO
vorticity
spellingShingle Aerospace Materials
kinetic energy dissipation
entropy
exergy
unducted and ducted turbomachinery
MDAO
vorticity
Siddappaji, Kiran
On the Entropy Rise in General Unducted Rotors using Momentum, Vorticity and Energy Transport
author Siddappaji, Kiran
author_facet Siddappaji, Kiran
author_sort Siddappaji, Kiran
title On the Entropy Rise in General Unducted Rotors using Momentum, Vorticity and Energy Transport
title_short On the Entropy Rise in General Unducted Rotors using Momentum, Vorticity and Energy Transport
title_full On the Entropy Rise in General Unducted Rotors using Momentum, Vorticity and Energy Transport
title_fullStr On the Entropy Rise in General Unducted Rotors using Momentum, Vorticity and Energy Transport
title_full_unstemmed On the Entropy Rise in General Unducted Rotors using Momentum, Vorticity and Energy Transport
title_sort on the entropy rise in general unducted rotors using momentum, vorticity and energy transport
publisher University of Cincinnati / OhioLINK
publishDate 2018
url http://rave.ohiolink.edu/etdc/view?acc_num=ucin1535464679934565
work_keys_str_mv AT siddappajikiran ontheentropyriseingeneralunductedrotorsusingmomentumvorticityandenergytransport
_version_ 1719454606904262656
spelling ndltd-OhioLink-oai-etd.ohiolink.edu-ucin15354646799345652021-08-03T07:08:29Z On the Entropy Rise in General Unducted Rotors using Momentum, Vorticity and Energy Transport Siddappaji, Kiran Aerospace Materials kinetic energy dissipation entropy exergy unducted and ducted turbomachinery MDAO vorticity AbstractEnergy conversion is a tightly coupled thermodynamic and fluid dynamic process which involves transport of several properties like mass, momentum, vorticity and energy. In reality, there is always some irreversibility associated in the form of entropy rise and must be accounted and minimized for improved performance of energy converters. Unducted and ducted rotors convert kinetic energy of the fluid into power and/or thrust. For the first time, this dissertation analyzes kinetic energy based loss as entropy rise in all horizontal axis unducted rotors using viscous dissipation through multi-fidelity framework developed in-house. Complex flow physics and the effect of B-spline based smooth manipulation of blade shapes are some of the highlights which reveal the inner workings of exergy destruction.A general low fidelity design analysis tool, py_BEM for all types of solo and contra-rotating horizontal axis unducted rotors is developed using blade element momentum theory with several enhancements to airfoil properties including contra-rotating configurations making it a unique tool. A unified approach makes it easier to design, analyze and optimize propellers, helicopter rotors in hover/vertical ascent, wind, tidal and hydrokinetic turbines at lower fidelity level. Linear and angular momentum, kinetic energy and power, exergy and entropy transport at this level provides a platform to understand energy conversion from a simplified flow physics with a thermodynamic perspective. Steady 3D RANS calculations are performed to understand the flow physics in high fidelity using control volume approach to investigate assumptions and document differences with rigorous domain and mesh dependency study. A general multi-fidelity multi-disciplinary design analysis and optimization framework is developed in-house for both ducted and unducted rotors.Underlying flow physics of unducted rotors is explained with regards to streamtube expansion (turbines) and contraction (propellers) in low and high fidelity. Kinetic energy conversion to viscous dissipation in case of auto-rotating helicopters and maple seed based decelerators with zero shaft power is demonstrated. All components of drag for the incompressible flow are accounted and their origin are discussed in detail to understand effects of local Reynolds number, airfoil shape and wake mixing downstream of the rotor. A new performance metric, entropy-power ratio is used for a deeper understanding of energy conversion. It is the ratio of amount of entropy created to the actual power produced indicating the quality of energy conversion. A vortex/vorticity dynamics based flow diagnosis using boundary vorticity flux techniques reveals a deeper connection between vorticity diffusion in boundary layer, smooth pressure gradient, geometry curvature, flow separation, associated drag and entropy production. The flux strength is linked to overall circulation on blade surfaces producing lift and the drag induced by lift. Swirl from rotor exit can be further utilized to extract power and/or thrust using a contra-rotating rotor behind it. The benefits and trade-offs of contra-rotation are quantified which depend on rotor parameters such as diameter ratio, axial gap between rotors and solidity, resulting in performance improvements of 2-13%. Realistic power coefficient in horizontal axis wind turbines is evaluated which lies between 0.4-0.5, much less than the Betz limit of 0.5926. Using Rothalpy arguments for all horizontal axis unducted rotors for the first time, it is explained why rotor shaft power is not the same as the product of torque and rotational speed of the rotor but has a viscous power loss term using a wind turbine case. 2018-10-29 English text University of Cincinnati / OhioLINK http://rave.ohiolink.edu/etdc/view?acc_num=ucin1535464679934565 http://rave.ohiolink.edu/etdc/view?acc_num=ucin1535464679934565 unrestricted This thesis or dissertation is protected by copyright: all rights reserved. It may not be copied or redistributed beyond the terms of applicable copyright laws.

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