Author
Ujjwal K. Saha
Other affiliations: Indian Institute of Technology Bombay
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.
Topics: Diesel engine, Diesel fuel, Rotor (electric), Turbine, Wind tunnel
Papers published on a yearly basis
Papers
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TL;DR: In this article, the fluid flow over a Savonius wind turbine rotor has been analyzed by using a multi-physics simulation program, which accounts for fully flow simulation, the effect of rotation on flowfield in, around and far behind the turbine rotor.
Abstract: The fluid flow over a Savonius wind turbine rotor has been analyzed by using a multi-physics simulation program. The analysis accounts for fully flow simulation, the effect of rotation on flowfield in, around and far behind the turbine rotor. The aim of this investigation is to study the evolution of fluid contours and the velocity circulation. The flow distribution at various rotor tip speed ratios was studied at an air velocity of 10 m/s. Results obtained from the investigation have been discussed and analyzed.
7 citations
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TL;DR: In this article, a single-cylinder, direct-injection, variable-compression-ratio diesel engine is modified into a dual-fuel diesel engine by incorporating a venturi gas mixer at the inlet manifold.
Abstract: Biogas has great potential as a clean alternative fuel for dual-fuel diesel engines. The present work is aimed at investigating the operating parameters such as compression ratio (CR) and injection timing (IT) for a dual-fuel diesel engine run on biogas and rice-bran biodiesel. The motivation behind this investigation is to obtain a diesel equivalent performance together with a reduction in emission. To achieve this, a single-cylinder, direct-injection, variable-compression-ratio diesel engine is modified into a dual-fuel diesel engine by incorporating a venturi gas mixer at the inlet manifold. A set of combinations composed of CRs of 17, 17.5, and 18 and ITs of 23°, 26°, 29°, and 32° before top dead center (BTDC) at different loading conditions are considered. The combination of IT=32° BTDC and CR=18 is found to produce a maximum brake thermal efficiency of 25.88% and a liquid fuel replacement of 82.75% at 100% load. On average, there is a reduction of carbon monoxide as well as hydrocarbon emiss...
7 citations
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TL;DR: In this paper , the authors present some of the critical aspects of wind power development, current statistics, potential, and challenges, and provide some essential recommendations for wind energy development, market value addition, tariff regulation, grid connectivity, research and development, and future scope of offshore wind farms in India.
Abstract: A country of billion people, India has witnessed a sharp increase in its economic activities in the past few decades, fulfilling the needs of its ever-growing population, which has come at the expense of a considerable sum of energy and carbon emission. With rising global concern on climate change and India's commitment toward reducing carbon emission, the country is gradually shifting towards harnessing energy through renewable energy (RE), and in recent times, the electricity generation via RE covers about 20%. The road towards RE comes with many challenges, especially when most of its economic activities heavily rely on conventional energy sources. The article highlights the ever-increasing energy requirements of India and the contributions that the RE is making. Being the most contributor among all the RE in India, wind energy has a significant role. This paper presents some of the critical aspects of wind power development, current statistics, potential, and challenges. There upon, it provides some essential recommendations for wind power development, market value addition, tariff regulation, grid connectivity, research and development, and future scope of offshore wind farms in India.
7 citations
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TL;DR: In this paper, a modified σ-transformation was used to solve 2D and 3D nonlinear liquid sloshing problems in vertically excited containers with a grid independence study.
Abstract: In this paper, various aspects of the 2D and 3D nonlinear liquid sloshing problems in vertically excited containers have been studied numerically along with the help of a modified σ-transformation. Based on this new numerical algorithm, a numerical study on a regularly and randomly excited container in vertical direction was conducted utilizing four different cases: The first case was performed utilizing a 2D container with regular excitations. The next case examined a regularly excited 3D container with two different initial conditions for the liquid free surface, and finally, 3D container with random excitation in the vertical direction. A grid independence study was performed along with a series of validation tests. An iteration error estimation method was used to stop the iterative solver (used for solving the discretized governing equations in the computational domain) upon reaching steady state of results at each time step. In the present case, this method was found to produce quite accurate results and to be more time efficient as compared to other conventional stopping procedures for iterative solvers. The results were validated with benchmark results. The wave elevation time history, phase plane diagram and surface plots represent the wave nonlinearity during its motion.
7 citations
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TL;DR: In this paper, the authors evaluated the performance of a biogas with jatropha bio-diesel as an ignition source in a compression ignition diesel engine at six different loads under dual fuel mode.
Abstract: The objective of this work is to review state of art practices and potential in diesel engines using greener fuels. Biogas with jatropha bio-diesel as ignition source was tested in a compression ignition diesel engine at six different loads under dual fuel mode. With a simple modification, the base engine was qualified to a dual fuel operation. For all the loads evaluated, dual fuel mode achieved a possible bio-diesel substitution of about 65%. In addition, it consumed lesser friction power as compared to the diesel mode during the operation. There were reductions in thermal efficiency, cylinder peak pressure and combustion noise under the dual fuel operation than the diesel mode due to lower burning velocity of biogas together with a longer pilot delay. However, this operation registered extremely lower NOx levels at all loads along-with reduced CO emissions at medium and higher loads. While significant increases in hydrocarbon emissions were observed.
7 citations
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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
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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
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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
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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