Ajay kumar Jha

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Associate Professor Dr. Ajay Kumar Jha is the Program Coordinator of M.Sc. Engineering in Renewable Energy Engineering program at Pulchowk Campus, Institute of Engineering, Tribhuvan University, Nepal. He has completed his Ph.D in Environmental Science and Engineering from Harbin Institute of Technology, Harbin, China while Master of Science in Renewable Energy Engineering and Bachelor of Engineering in Mechanical Engineering from Pulchowk campus, Institute of Engineering, Tribhuvan University, Nepal. Dr. Jha has more than 19 years of experiences in the academic, research, industry and consulting activities related to Mechanical Engineering, Renewable Energy Engineering, Biotechnology, Biogas Technology, Agriculture, Solar PV Technology, Environmental Science, and Energy Planning. He has published more than 70 research papers in the peer-reviewed journals and conferences.

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A Case Study of Wear in a High Head Francis Turbine Due to Suspended Sediment and Secondary Flow in a Hydropower Plant of Nepal

International Journal of Fluid Machinery and Systems, 2020

The hydropower plants under Himalayan basins are mostly characterized by heavy sediment load due ... more The hydropower plants under Himalayan basins are mostly characterized by heavy sediment load due to geographical and metamorphic constraints. Run-off-river projects with limited size of the desilting basins allow suspended sediments to get carried into the turbine components causing wear due to sediment erosion. In the case of high head power plants consisting of Francis turbines, a large portion of the hydraulic energy is transformed into kinetic energy within the guide vanes. This causes various instabilities in the flow due to high acceleration and velocity. Some recent studies have shown that due to the combined effect of the secondary flow around the guide vanes and sediment carrying flow, the size of the clearance gap increases, which further aggravates the performance of the turbine. This study takes a reference of one of the power plants in Nepal containing high head Francis turbines. An in-depth analysis of the effect of the sediment in this power plant and sediment erosion in the turbine components has been performed. A CFD analysis of the guide vanes and runner blades corresponding to the same turbine has been conducted and the results are used to analyze the erosion pattern on the actual turbine. The detailed erosion analysis is made possible with a 3D scanner, such that the eroded regions can be captured and classified based on the flow behavior at those regions. Guide vanes and runner blades are found to be the predominant components affected by erosion. It has been seen that most of the erosion affected regions are originated from increasing clearance gaps between guide vane and facing plates caused due to continuous leakage flow within the two sides of the guide vanes. Keywords: Sediment erosion; high-head Francis turbine; secondary flow; Jhimruk; Nepal

Thermodynamics Analysis of Solar-Rice Husk Hybrid Power Plant

Research Journal of Applied Sciences, Engineering and Technology, 2019

The main objective of this study is to make thermodynamics analysis of different components of so... more The main objective of this study is to make thermodynamics analysis of different components of solar rice husk hybrid power plant with its modification of structure by implementing a Rice Husk Dryer between the Condensate Pre-heater and Air Pre Heater in order to feed dry rice husk to furnace and performance evaluation of power plant with respect to reduction of moisture content of rice husk using MATLAB, R2016a. The flue gas is passed to the Rice Husk Dryer, where the heat of flue gas is used to dry the rice husk before feeding to the furnace. Solar energy is limited to a 50% share in the daytime. In this research solar parabolic collector and Rice, husk feed is arranged in a parallel to produce steam. Feeding with dry rice husk in the furnace was found to reduce the heat loss due to heating moisture present in rice husk up to furnace temperature and also heat loss due to excess air supplied to the furnace for evaporating and superheating the moisture present in the rice husk. The increase in furnace efficiency, fuel efficiency, thermal efficiency and plant efficiency, reduction in specific rice husk consumption, reduction in excess air supply and decrease in rice husk consumption, etc. with respect to reduction in the moisture content of rice husk for the power plant are evaluated. The result showed that with the reduction of moisture from 10% to 90%, the power plant efficiency is to be increased by 6.97% to 64.86% for boiler pressure of 50 bar.

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Phylogenetic diversity of methanogenic archaea and kinetics of methane production at slightly acidic conditions of an anaerobic sludge

International Journal of Agriculture and Biology, 2013

Acetone–butanol–ethanol fermentation of corn stover by Clostridium species: present status and future perspectives

World Journal of Microbiology and Biotechnology, 2013

Sustainable vehicle fuel is indispensable in future due to worldwide depletion of fossil fuel res... more Sustainable vehicle fuel is indispensable in future due to worldwide depletion of fossil fuel reserve, oil price fluctuation and environmental degradation. Microbial production of butanol from renewable biomass could be one of the possible options. Renewable biomass such as corn stover has no food deficiency issues and is also cheaper in most of the agricultural based countries. Thus it can effectively solve the existing issue of substrate cost. In the last 30 years, a few of Clostridium strains have been successfully implemented for biobutanol fermentation. However, the commercial production is hindered due to their poor tolerance to butanol and inhibitors. Metabolic engineering of Clostridia strains is essential to solve above problems and ultimately enhance the solvent production. An effective and efficient pretreatment of raw material as well as optimization of fermentation condition could be another option. Furthermore, biological approaches may be useful to optimize both the host and pathways to maximize butanol production. In this context, this paper reviews the existing Clostridium strains and their ability to produce butanol particularly from corn stover. This study also highlights possible fermentation pathways and biological approaches that may be useful to optimize fermentation pathways. Moreover, challenges and future perspectives are also discussed.

Dry Anaerobic Co-digestion of Cow Dung with Pig Manure for Methane Production

Applied Biochemistry and Biotechnology, 2014

The performance of dry anaerobic digestions of cow dung, pig manure, and their mixtures into diff... more The performance of dry anaerobic digestions of cow dung, pig manure, and their mixtures into different ratios were evaluated at 35 ± 1 °C in single-stage batch reactors for 63 days. The specific methane yields were 0.33, 0.37, 0.40, 0.38, 0.36, and 0.35 LCH4/gVSr for cow dung to pig manure ratios of 1:0, 4:1, 3:2, 2:3, 1:4, and 0:1, respectively, while volatile solid (VS) and chemical oxygen demand (COD) removal efficiencies were 48.59, 50.79, 53.20, 47.73, 46.10, and 44.88 % and 55.44, 57.96, 60.32, 56.96, 53.32, and 50.86 %, respectively. The experimental results demonstrated that the co-digestions resulted in 5.10-18.01 % higher methane yields, 2.03-12.95 % greater VS removals, 2.98-12.52 % greater COD degradation and so had positive synergism. The various mixtures of pig manure with cow dung might persuade a better nutrient balance and dilution of high ammonia concentration in pig manure and therefore enhanced digester performance efficiency and higher biogas yields. The dry co-digestion of 60 % cow dung and 40 % pig manure achieved the highest methane yield and the greatest organic materials removal efficiency than other mixtures and controls.

Research on the Watershed Ecological Risk Management

Applied Mechanics and Materials, 2013

The risk management of watershed ecology is an important topic in the field of water resources ma... more The risk management of watershed ecology is an important topic in the field of water resources management. To improve the present situation of the water ecological risk management in Songhua River and Liao River watershed, based on the policy of eco-management of the important water function zone in China, and the potential risk source investigation of watershed, investigate hazard components, predict risk probability and the possible negative effects, put forward the mitigation measure on water ecological response in watershed. It is necessary to explore water ecotoxicological variation, resolve biodiversity watershed, establish a suitable ecological evaluation index system, and put forward the multi-objective of optimizing management strategies.

Ajay kumar Jha

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