Pankaj P. Gohil

Bio: Pankaj P. Gohil is an academic researcher from Sarvajanik College of Engineering and Technology. The author has contributed to research in topics: Francis turbine & Stove. The author has an hindex of 5, co-authored 11 publications receiving 144 citations. Previous affiliations of Pankaj P. Gohil include Indian Institute of Technology Roorkee.

Coalesced effect of cavitation and silt erosion in hydro turbines—A review

Abstract: Cavitation is a phenomenon which manifests itself in the pitting of the metallic surfaces of turbine parts because of the formation of cavities. However, silt erosion is caused by the dynamic action of silt flowing along with water, impacting against a solid surface. The erosion and abrasive wear not only reduce the efficiency and the life of the turbine but also cause problems in operation and maintenance, which ultimately lead to economic losses. Researchers have studied that the cavitation in silt flow is more serious than in pure water. However, the coalesced effect of silt erosion and cavitation is found to be more pronounced than their individual effects. In the present paper the studies in this field carried out by various investigators are discussed and presented. Parameters related to the combined effect of cavitation and silt erosion which are responsible for efficiency loss due to erosion as investigated by researchers have also been discussed.

Effect of temperature, suction head and flow velocity on cavitation in a Francis turbine of small hydro power plant

Abstract: Erosion due to cavitation in hydro turbines is one of the reasons for component failure that costs a lot to the hydro power plants. Inception and development of cavitation depend upon different parameters such as atmospheric pressure, suction head, velocity of flow, temperature, gas content in the liquid and operating hours of the turbine. Parameters generally considered for design of a turbine and are used to predict cavitation could be different at actual site. The cavitation in hydro turbine is predicted during model testing and correlated with specific speed. However the erosion and efficiency decay due to cavitation phenomena of turbines are too complex to stimulate which depends on other operating conditions at site. Under the present study, an attempt has been made to carry out a numerical analysis to investigate the effect of temperature, suction head and flow velocity on cavitation in a Francis turbine by using CFX code. The experimental investigation has been carried out to validate the numerical method by visualization technique. Using numerical data obtained during analysis for different considered parameters, correlations are developed for efficiency loss and cavitation rate in Francis turbine as a function of these parameters i.e., temperature, suction head and flow velocity.

Numerical Study of Cavitation in Francis Turbine of a Small Hydro Power Plant

Abstract: Cavitation is undesirable phenomena and more prone in reaction turbines. It is one of the challenges in any hydro power plant which cause vibration, degradation of performance and the damage to the hydraulic turbine components. Under the present study, an attempt has been made to carry out a numerical analysis to investigate the cavitation effect in a Francis turbine. Three dimensional numerical study approach of unsteady and SST turbulence model are considered for the numerical analysis under multiphase flow such as cavitating flow. The performance parameters and cavitating flow under different operating conditions have been predicted using commercial CFX code. Three different operating conditions under cavitation and without cavitation with part load and overload conditions of the turbine for a plant sigma factor are investigated. The results are presented in the form of efficiency, pressure fluctuation, vortex rope and vapor volume fraction. It has been observed that variation in efficiency and vapor volume fraction is found to be nominal between cavitation and without cavitation conditionsat rated discharge and rated head. Turbine efficiency loss and vapor bubbles formation towards suction side of the runner blade are found to be maximum under overload condition. However, the pressure pulsation has been found maximum under part load condition in the draft tube. The simulation results are found to be in good agreement with model test results for efficiency. The locations of cavitating zone observed wellwith the result of previous studies.

Experimental investigation of performance of conventional lpg cooking stove

Abstract: The paper works on investigation of the performance analysis of Conventional LPG cooking stove. The performance parameters are obtained by experimental method. To investigate the areas for improving performance based on the results by proper efficient burner design, produce less pollutant formation and saving losses etc. The performance of the cooking stove was studied using experimental method. The experimental method was carried out using water boiling test and emission test according to IS 4246:2002. The thermal efficiency was found nearer 66.27 % and the rate of heat generated by burner is 1.7849 KW. In the emission test, the % of volume of 2 CO was found to be 0.9 and the ppm of CO was found to be 50.

CFD: Numerical analysis and performance prediction in Francis turbine

Abstract: This paper presents a CFD based 3-D numerical simulation of steady turbulent flow in the passage of a Francis turbine. The performance parameters under different operating conditions have been analyzed using available CFX code. The five different operating conditions from part load to over load of a Francis turbine are investigated and results are presented in the form of efficiency and head loss. It has been observed that head losses are minimum and efficiency is maximum at rated discharge and rated head. An attempt has been made to compare the computed results with the available model testing results. The numerical results are found to be in good agreement with the model testing results.

Nanosecond laser micro- and nanotexturing for the design of a superhydrophobic coating robust against long-term contact with water, cavitation, and abrasion

Abstract: Existing and emerging applications of laser-driven methods make an important contribution to advancement in nanotechnological approaches for the design of superhydrophobic surfaces. In this study, we describe a superhydrophobic coating on stainless steel, designed by nanosecond IR laser treatment with subsequent chemisorption of fluorooxysilane for use in heavily loaded hydraulic systems. Coating characterization reveals extreme water repellency, chemical stability on long-term contact with water, and excellent durability of functional properties under prolonged abrasive wear and cavitation loads. The coating also demonstrates self-healing properties after mechanical damage.

A combined thermodynamic cycle used for waste heat recovery of internal combustion engine

Abstract: In this paper, we present a steady-state experiment, energy balance and exergy analysis of exhaust gas in order to improve the recovery of the waste heat of an internal combustion engine (ICE). Considering the different characteristics of the waste heat of exhaust gas, cooling water, and lubricant, a combined thermodynamic cycle for waste heat recovery of ICE is proposed. This combined thermodynamic cycle consists of two cycles: the organic Rankine cycle (ORC), for recovering the waste heat of lubricant and high-temperature exhaust gas, and the Kalina cycle, for recovering the waste heat of low-temperature cooling water. Based on Peng–Robinson (PR) equation of state (EOS), the thermodynamic parameters in the high-temperature ORC were calculated and determined via an in-house computer program. Suitable working fluids used in high-temperature ORC are proposed and the performance of this combined thermodynamic cycle is analyzed. Compared with the traditional cycle configuration, more waste heat can be recovered by the combined cycle introduced in this paper.

A review of microscopic interactions between cavitation bubbles and particles in silt-laden flow

Abstract: Erosion through synergetic effects between cavitation erosion and particle abrasion in silt-laden flow seriously affects the safe operations of hydroturbines. In this review, recent advances of cavitation inception on particles and microscopic interactions between bubbles and particles are reviewed and discussed. For cavitation inception, influences of several paramount parameters (e.g. types, sizes, shape and surface structure of particles, pressurization and memory effects) have been revealed and discussed. The interaction mechanisms between cavitation bubbles and particles are demonstrated using experimental data obtained with a single particle. Through the microscopic interactions, the particles can be accelerated by the collapsing bubbles up to 40 m/s and also be possibly split up by the cavitation, leading to deagglomeration of particle clusters.

Performance analysis of a Savonius hydrokinetic turbine having twisted blades

Abstract: In the quest for renewable energy sources, kinetic energy available in small water streams, river streams or human-made canals may provide new avenue which can be harnessed by using hydrokinetic turbines. Savonius hydrokinetic turbine is vertical axis turbine having drag based rotor and suitable for a lower flow velocity of the water stream. In order to enhance the efficiency of the turbine, this paper aims to analyze the performance of twisted blade Savonius hydrokinetic turbine. Using CFD analysis, an attempt has been made to optimize blade twist angle of Savonius hydrokinetic turbine. The simulation of a twisted Savonius hydrokinetic turbine having two blades has been carried out to investigate the performance. Commercial unsteady Reynolds-Averaged Navier-Stokes (URANS) solver in conjunction with realizable k-e turbulence model has been used for numerical analysis. Fluid flow distributions around the rotor have been analyzed and discussed. It has been found that Savonius hydrokinetic turbine having a twist angle of 12.5° yields a maximum coefficient of power as 0.39 corresponding to a TSR value of 0.9 for a given water velocity of 2 m/s.

Hamiltonian analysis of a hydro-energy generation system in the transient of sudden load increasing

Abstract: This paper addresses the Hamiltonian mathematical modeling and dynamic analysis of a hydro-energy generation system in the transient of sudden load increasing. First, six dynamic transfer coefficients of the hydro-turbine for the transient of sudden load increasing are innovatively introduced into the hydro-energy generation system. Considering the elastic water-hammer model of the penstock and third-order model of the generator, we established a dynamic mathematical model of the hydro-energy generation system in the transient of sudden load increasing. Moreover, from the point of view of the transmission and dissipation of energy of the system, we propose the hydro-energy generation system into the theory frame of the generalized Hamiltonian system. A novel Hamiltonian model of the hydro-energy generation system is established utilizing the method of orthogonal decomposition. Finally, based on the data of a real hydropower plant, numerical simulations and physical experiment are carried out, and the results indicates that the Hamiltonian system can reflect the essence of the nonlinearity of the hydro-energy generation system in the transient of sudden load increasing. More importantly, these methods and results will supply theoretical basis for designing and running a hydropower plant.