scispace - formally typeset
Search or ask a question
Author

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
More filters
Proceedings ArticleDOI
25 Aug 2017
TL;DR: In this article, a NACA 0020 bladed vertical-axis turbine of solidity ratio 0.38 and aspect ratio 1.0 has been developed at an irrigation sluice having a water velocity of 1.1 m/s.
Abstract: Hydro power has always been a major source of electricity generation among different renewable energy technologies. However, due to the construction of dams, the conventional hydro energy extraction techniques cause disturbance to the ecology by diverting the natural flow of water and migrating population from their native land. Of late, energy extraction from the natural flow of water is considered as potential source of renewable power since it is clean and reliable. In view of this, the present study deals with the development and performance characterization of a vertical-axis helical-bladed hydrokinetic turbine. Considering the various design parameters, a NACA 0020 bladed vertical-axis turbine of solidity ratio 0.38 and aspect ratio 1.0 has been developed. In-situ experiments have been carried out at an irrigation sluice having a water velocity of 1.1 m/s. Further, its performance characteristics are evaluated at different mechanical loading conditions with the help of a mechanical dynamometer. It has been observed that the developed helical-bladed turbine demonstrates a peak power coefficient of 0.16 at a tip-speed ratio of 0.85. The present experimental investigation has clearly demonstrated the usefulness of the hydrokinetic turbine. It has also been logged that the average water velocity at the concerned site has a great importance on the turbine design.Copyright © 2017 by ASME

2 citations

01 Feb 2013
TL;DR: In this paper, the free surface elevation during liquid sloshing at low excitation frequency was found by using a video camera and free surface oscillations of liquid at different excitation frequencies calculated by the image processing technique.
Abstract: This paper pays attention to finding the free surface elevation during liquid sloshing at low excitation frequency. Experiments have been conducted at low frequency ratios to find the free surface elevation and the obtained results are reported here. The liquid behavior is captured by means of a video camera and the free surface oscillations of liquid at different excitation frequencies calculated by the image processing technique. The liquid height is observed by the intensity variation of the interface between the air and liquid. The location of maximum gradient has been considered as interface. The effects of excitation amplitude, frequency and liquid fill level have been studied.

2 citations

Proceedings ArticleDOI
01 Jan 2009
TL;DR: In this paper, a finite difference model was developed based on the inviscid flow equations, and a simple mapping function was used to remove the time-dependence of the free surface in the fluid domain.
Abstract: A fluid partially occupying a moving tank undergoes wave motions (sloshing). These motions generate severe hydrodynamic loads that can be dangerous for structural integrity and stability of rockets, satellites, LNG ships, trucks and even stationary petroleum containers. Free surface motions of the liquid in partially filled tanks under gravity are of practical significance particularly in marine and road transportation applications. For this reason, liquid sloshing has always been a research subject attracting great concern during the last several decades. In this paper, a fully non-linear finite difference model has been developed based on the inviscid flow equations, and a simple mapping function was used to remove the time-dependence of the free surface in the fluid domain. The time-varying fluid surface can be mapped onto a rectangular domain by the σ-transformation. This method is a simple way to simulate non-breaking waves quickly and accurately especially that has a low steepness. The fluid motion is solved in a unit square mesh in the transformed flow domain (i.e., computational domain). The fourth order central difference scheme and the Gauss–Seidel point successive over-relaxation iterative procedure are used to capture the free surface wave profiles and the free surface elevation plots of the fluid domain. Difference between the peaks and troughs of waves are discussed for the case of vertical excitation of first three natural frequency of the tank. Phase-plane diagrams are drawn to show the non-linearity of the motion of time dependent free surface. The results agree well with the previously published results.Copyright © 2009 by ASME

2 citations

Proceedings ArticleDOI
16 Dec 2020
TL;DR: In this paper, a second order sliding mode observer (SOSMO) was proposed to estimate the angular velocity/speed of the rotor of a double-fed induction generator (DFIG).
Abstract: This paper proposes a new speed estimation technique based on the second order sliding mode observer (SOSMO) to observe/estimate the angular velocity/speed of the rotor of a double-fed induction generator (DFIG). The developed observer uses the measured stator currents and voltages from the stator terminal of the DFIG. Further, the estimated rotor position/angle is obtained by integrating the rotor speed. The paper also includes the convergence and stability proof for the designed observer. Finally, the designed observer is tested on a DFIG-based hardware test setup. The experimental results show that, during different dynamic and steady-state conditions, the proposed speed observer can determine the rotational speed and angle.

1 citations

Proceedings ArticleDOI
01 Jan 2010
TL;DR: In this article, Computational Fluid Dynamics (CFD) approach is adopted to study the combustion and emission progression in a single cylinder four stroke diesel engine, operated in both diesel and dual-fuel modes.
Abstract: In this paper, Computational Fluid Dynamics (CFD) approach is adopted to study the combustion and emission progression in a single cylinder four stroke diesel engine, operated in both diesel and dual-fuel modes. The study of dual-fuel mode is performed by using synthesis gas (syngas) with 75:25 and 50:50 volumetric combinations of hydrogen and carbon monoxide, respectively. The modeling and meshing of the constant volume combustion chamber is carried out by using GAMBIT tool. The meshing of the combustion chamber is performed using tetrahedral elements and the k–e turbulence model is introduced along with non-premixed combustion modeling. The modeled hemispherical-piston-top combustion chamber is then simulated in FLUENT solver across the experimental boundary conditions at 40%, 60%, 80% and 100% of full load for both diesel and dual-fuel. The results of simulation incorporate the study of maximum combustion temperature, maximum combustion velocity and H2 O mole fraction subsequent to combustion. Further, the concentrations of emissions have also been investigated for both diesel and dual-fuel modes. The results of simulations show a good agreement with the corresponding experimental data.Copyright © 2010 by ASME

1 citations


Cited by
More filters
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