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Ujjwal K. Saha

Bio: Ujjwal K. Saha is an academic researcher from Indian Institute of Technology Guwahati. The author has contributed to research in topics: Diesel engine & Diesel fuel. The author has an hindex of 28, co-authored 120 publications receiving 3565 citations. Previous affiliations of Ujjwal K. Saha include Indian Institute of Technology Bombay.


Papers
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Proceedings ArticleDOI
18 Sep 2014
TL;DR: In this paper, an attempt has been made to improve the efficiency of a Savonius-style vertical axis wind turbine under concentrated and oriented jets through installation of deflectors at different positions ahead of the turbine.
Abstract: With the rapid growth of renewable energy sector, vertical axis wind turbines are finding their applications in the small-scale distributed wind energy system, particularly in rural areas. These turbines are simple in construction and easy to install with comparatively lower cost. However, the efficiency of these turbines is not competitive to that of horizontal axis wind turbines. In this paper, an attempt has been made to improve the efficiency of a Savonius-style vertical axis wind turbine under concentrated and oriented jets through installation of deflectors at different positions ahead of the turbine. The aim is to make the major portion of the flow to be incident on the concave part of the blades. Experiments are conducted in a low speed wind tunnel with an open test section facility. For all the experiments, the wind speed in the tunnel is kept constant at 6.2 m/s. The mechanical loads are varied to analyze the performance of the turbine at various tip speed ratios. In each case, both power and torque coefficients are calculated in order to estimate the performance indices of the turbine. Moreover, a suitable operating range of this turbine is specified. The present investigation demonstrates that with the installation of deflectors, the performance of the Savonius-style wind turbines can be sufficiently improved under concentrated and oriented jets. The peak power coefficient of 0.32 is achieved with an optimized position of the deflectors in front of both the advancing and returning blades.Copyright © 2014 by ASME

3 citations

Journal ArticleDOI
TL;DR: In this article, the authors conducted low speed cascade studies of compressor blading in a cascade wind tunnel to document the high flow deflection capability of some known single blade rows and some tandem blade rows.
Abstract: Low speed cascade studies of compressor blading have been conducted in a cascade wind tunnel to document the high flow deflection capability of some known single blade rows and some tandem blade rows. The study aimed at qualitative comparison through well known blade design parameters via Diffusion Factor (DF) and Loss Factor (LF). The tested blade profiles are composed of controlled diffusion airfoil (CDA) having aspect ratio 1.5 in either case. CDA 43 with 43° camber for single bladed cascade and two tandem cascades, viz. CDA 21-43 with two different cambers of 21° and 43°, and CDA 21-21 with two identical 21° camber airfoils have been used. Both the cascades have been tested at 26° stagger angle with varying solidity and angle of incidence. Potential of tandem bladed cascade is observed at high solidity in the negative incidence range. Nomenclature c, s blade chord, blade pitch β ι, ß2 inlet and outlet blade angles σ solidity (c/s) θ blade camber (βι ß2) ζ setting or stagger angle Viae local velocity VmaxF maximum local velocity on front blade VmaxR maximum local velocity on rear blade pi inlet static pressure Pqi, Pq2 inlet and outlet total pressures pi density of air αϊ, a2 inlet and outlet flow angles δ deviation angle (012 β2) ε deflection angle (αϊ (X2) i incidence angle (αϊ βι) Fi, V2 inlet and outlet flow velocities Vmax maximum local velocity Δ Fe tangential velocity component Dioc local diffusion factor 1 2 q\ inlet dynamic pressure (—piFj ) Cp Coefficient of Pressure ω loss coefficient Abbreviations AVDR Axial Velocity Density Ratio DCA Double Circular Arc FADEC Full Authority Digital Electronic Control MCA Multiple Circular Arc CDA Controlled Diffusion Airfoil DF Diffusion Factor LF Loss Factor

3 citations

Journal ArticleDOI
TL;DR: In this paper , the authors give a conspectus of various wind turbine wake models that have evolved over the years and then recommend some conceptual wind farm designs of assorted configurations, and then give a summary of wind farm performance.
Abstract: Of late, the design and development of large and small wind farms are gaining importance to meet the growing energy demand. In this aspect, several wind turbine wake models have been proposed over the years, some of which are the legacy of Jensen, Larsen, Lissaman, Frandsen, and Ainslie wake models. Despite their robustness, the analytical formulations of these models are widely explored as research tools for estimating the performance of wind farms. However, because of several limitations and assumptions like top-hat shape, Gaussian profile, axisymmetric, negligible atmospheric boundary layer effect, and others, these models often overestimate the flow characteristics. In view of this, there is always a scope for developing better correlations to predict the performance of wind farms more accurately. This article gives a conspectus of various wind turbine wake models that have evolved over the years and then recommends some conceptual wind farm designs of assorted configurations.

3 citations


Cited by
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Journal ArticleDOI
TL;DR: In this paper, the importance of urban physics related to the grand societal challenges is described, after which the spatial and temporal scales in urban physics and the associated model categories are outlined.

627 citations

Journal ArticleDOI
TL;DR: In this article, a dual-fuel engine with high-cetane fuel and natural gas injection is used to provide a source of ignition for the charge of a spark-ignition (SI) engine.

595 citations

Journal ArticleDOI
TL;DR: In this paper, the authors provide a perspective on the past, present and future of Computational Wind Engineering (CWE) and provide a more detailed view on CFD simulation of pedestrian-level wind conditions around buildings.

570 citations

01 Jan 2002
TL;DR: In this article, the aerodynamic design and performance of VAWTs based on the Darrieus concept is discussed, as well as future trends in design and the inherent socioeconomic and environmental friendly aspects of wind energy as an alternate source of energy.
Abstract: Wind energy is the fastest growing alternate source of energy in the world since its purely economic potential is complemented by its great positive environmental impact. The wind turbine, whether it may be a Horizontal-Axis Wind Turbine (HAWT) or a Vertical-Axis Wind Turbine (VAWT), offers a practical way to convert the wind energy into electrical or mechanical energy. Although this book focuses on the aerodynamic design and performance of VAWTs based on the Darrieus concept, it also discusses the comparison between HAWTs and VAWTs, future trends in design and the inherent socio-economic and environmental friendly aspects of wind energy as an alternate source of energy.

549 citations

Journal ArticleDOI
TL;DR: An attempt has been made to review the applications of fuzzy logic based models in renewable energy systems namely solar, wind, bio-energy, micro-grid and hybrid applications and indicates that fuzzy based models provide realistic estimates.
Abstract: In recent years, with the advent of globalization, the world is witnessing a steep rise in its energy consumption. The world is transforming itself into an industrial and knowledge society from an agricultural one which in turn makes the growth, energy intensive resulting in emissions. Energy modeling and energy planning is vital for the future economic prosperity and environmental security. Soft computing techniques such as fuzzy logic, neural networks, genetic algorithms are being adopted in energy modeling to precisely map the energy systems. In this paper, an attempt has been made to review the applications of fuzzy logic based models in renewable energy systems namely solar, wind, bio-energy, micro-grid and hybrid applications. It is found that fuzzy based models are extensively used in recent years for site assessment, for installing of photovoltaic/wind farms, power point tracking in solar photovoltaic/wind, optimization among conflicting criteria. The review indicates that fuzzy based models provide realistic estimates.

411 citations