S.K. Mohapatra

An investigation into the machining characteristics of titanium using ultrasonic machining

This paper presents a review on the problems encountered in machining titanium and application of USM in machining titanium and its alloys. Experiments have been conducted to assess the effect of three factors-tool material, grit size of the abrasive slurry and power rating of ultrasonic machine on machining characteristics of titanium (ASTM Grade I) using full factorial approach for design and analysis of experiments. It has been concluded that all factors have significant effect on Material Removal Rate (MRR), Tool Wear Rate (TWR) and surface roughness of the machined surface. Two-way interactions having significant effect on MRR, TWR and surface roughness have also been identified using Minitab14 software. The levels for each factor that contribute the most to the variation in machining performance of USM of titanium have also been established. It has been concluded that titanium is fairly machinable with USM process. Moreover, the surface finish obtained is better than many of the other non-traditional processes.

Performance Characteristics of Centrifugal Slurry Pump with Multi-Sized Particulate Bottom and Fly Ash Mixtures

The present study reports on the performance characteristics of the centrifugal slurry pump with multi-sized particulate slurry of bottom ash and fly ash mixtures. The performance characteristic of the pump was experimentally evaluated at rotational speed 1450 rpm for bottom ash slurries with and without the addition of fly ash in the concentration range of 10% to 50% (by weight). Addition of fly ash in the bottom ash was varied from 10% to 30% (by weight). The pump total head, overall efficiency, and pump input power at different flow rates were evaluated. The performance characteristics results show that the value of head and the efficiency of the pump depend on the solid concentration. It was also observed that the performance parameter of the pump strongly depends on slurry properties. The addition of fine particles fly ash in the coarser particles of bottom ash slurry, leads to reduce the additional head losses in the pump. The pump performance in terms of head and efficiency improved with addition of fly ash in bottom ash slurry.

Experimental Investigation of the Effect of Flow Arrangements on the Performance of a Micro-Channel Heat Sink

Abstract An experimental study is carried out to investigate the effect of entrance and exit conditions that prevail due to different flow arrangements on the thermal performance of a copper micro-channel heat sink. Three flow arrangements—U-type, S-type, and P-type—were considered for the analysis with a test piece having inlet and outlet plenum dimensions of 10 mm × 30 mm × 2.5 mm with an array of parallel micro-channels having an individual width of 330 μm and a uniform channel depth of 2.5 mm. Performance evaluations for different flow conditions at inlet and outlet plenums were made by maintaining constant heat supply at 125 W, 225 W, and 375 W with varying Reynolds number ranging from 224 to 1,121. Nusselt number and pressure drop were computed by measuring temperature difference and pressure drop across the inlet and outlet plenum for various test combinations. Maximum heat transfer was observed for the U-type flow arrangement, followed by the P-type and S-type; maximum pressure drop was noted for the S-type flow arrangement, followed by the U-type and P-type arrangements for a constant Reynolds number. A detailed analysis of the experimental results indicate that from a pressure drop point of view, the P-type flow arrangement is preferred, whereas from the heat transfer point of view, the U-type is found to be a better option.

Properties of Glass-Fiber Hybrid Composites: A Review

ABSTRACT This paper provides a rigorous literature review in a field of glass-fiber composites. Glass-fiber composite is a type of fiber-reinforced polymer composites. Glass-fiber composite holds good properties such as low density, high strength, and easy processing, so widely used in aerospace, automotive, and construction. Fabrication of glass-fiber composite has been discussed in the present study. Combining the glass-fiber with other fibers into a single polymer matrix results in the development of hybrid glass-fiber composites. The hybridization in glass-fiber composites raised new ideas for future in the field of composites. GRAPHICAL ABSTRACT

Study of agglomeration in 3.5 MW AFBC using rice husk particles

The combustion of rice husk in fluidised bed combustors seems to be an attractive possibility for power generation in the future, keeping in view the waste disposal problems and the reduction of greenhouse gases. In commercial installations, the occurrence of agglomeration is still one of the main reasons for unscheduled outrages. In this paper, a review of agglomeration mechanism and its prevention has been made by considering the case study of a 3.5 MW rice husk-based power plant situated at Nahar Spinning Mills Ltd. (NSML), Ludhiana, Punjab, India. Proximate, SEM analysis and quantitative elementary analysis of agglomerates samples taken from plant has been done and corrective measures have been suggested. TGA of rice husk taken from the plant has also been done to correlate it with agglomeration. The agglomeration and defluidisation in 3.5 MW NSML Ludhiana using rice husk particles is caused by high potassium content in the fuel. It is not possible to measure localised temperature, which may exceed 900–1000°C, while the plant is running, which may cause agglomeration at above plant. Refreshment of bed with fresh particles and lowering bed temperature are the key measures to prevent agglomeration.

Fluidised bed combustion and gasification of rice husk and rice straw – a state of art review

Rice is cultivated in all the main regions of world. The worldwide annual rice production is 666 million tons for the year 2008. The combustion and gasification of rice husk/rice straw in fluidised bed reactors seems to be an attractive possibility of future for power generation, the solution of waste disposal problems and the reduction of greenhouse gases. In this paper, overview of fluidised bed reactors based on rice husk/rice straw and some data collected/measured from rice husk-rice straw power plant is presented. Combustion efficiency from 60% to 98%, combustion at bed temperature from to 600°C–850°C, carbon conversion efficiency up to 98% and cold gas efficiency up to 67% is reported. Gas heating value up to 6.6 MJ/m 3 and 5.5 MJ/kg is reported. Combustion intensity up to 530 kg/h/m 2 is reported. SOx and NOx emitted from fluidised bed combustors based on rice husk and rice straw are generally very less under normal operating conditions.

CFD modeling of erosion wear in pipe bend for the flow of bottom ash suspension

ABSTRACT In the present study, erosion wear behavior of slurry pipeline due to solid–liquid suspension in the pipeline has been investigated using commercial computational fluid dynamics (CFD) code FLUENT. A multiphase Euler–Lagrange model was adopted to predict the solid particle erosion wear in a 90° pipe bend for the flow of bottom ash–water suspension. A standard k–ε turbulence modeling scheme was used to simulate the flow through the pipeline. Water and bottom ash were taken as liquid and as a dispersed phase of solid–liquid mixture, respectively. A simulation study for erosion wear in a pipe bend was carried out to investigate the influence of various parameters including velocity, solid concentration, and particle size. The velocity of the bottom ash–water suspension varied from 0.5 to 2.5 m/s for solid concentrations with a range of 2.5 to 10.0% (by volume). The particle diameters of the bottom ash were 162 and 300 µm. The simulation results agree with the results of previous studies.

Head Loss Investigations Inside 90° Pipe Bend for Conveying Of Fine Coal–Water Slurry Suspension

ABSTRACT The present study investigates head loss for flow of coal–water slurry inside 90° pipe bend. The experiments were conducted with slurries of different solid concentrations, varying from 31.4 to 60.8% (by weight). Pulverized coal samples with particle sizes of less than 53 µm were used to prepare the slurry. During experimentation, average flow velocity was kept in the range of 2–5 m/s. Extensive rheological experimentation was performed to analyze the flow characteristics of coal–water slurry with and without the addition of additive namely sulfonic acid. Sulfonic acid was mixed with coal–water slurry in proportions of 1–4% (by weight) at higher concentrations (i.e., 60.8%). Coal–water slurry showed Newtonian behavior at low concentrations of 30%; above, it shows pseudoplastic behavior. The head loss across the pipe bend increases as the solid concentration of slurry increases and decreases as the proportion of an additive increases. Losses occurring in bend curves were given in terms of bend loss coefficient. The bend loss coefficient decreased as flow velocity increased and increased as solid concentration increased. The present study also highlights the role that solid concentration plays with regard to settling velocity of coal–water slurry. A trend of decreasing settling velocity was observed while the solid concentration (by weight) of the slurry was increased.

An assessment of the physical, mineral, and rheological properties of fly ash for stowing in coal mines

ABSTRACT With increasing environmental awareness, utilization of fly ash has become an attractive alternate to disposal. The objective of the present study was to investigate the physical, chemical, mineral, and rheological characteristics of fly ash for their potential utilization in stowing operation. The study was conducted with fly ash collected from the ash disposal system of Guru Govind Singh thermal power plant, Ropar, Punjab, India. From the characterization of the fly ash sample, it was found that the ash sample is enriched predominantly in silica; alumina and iron oxides fall under the category of F-type fly ash. The major mineral crystalline phase identified in the ash sample is quartz and mullite. Because of the properties of fly ash, it can be used as a stowing material in coal mines. The data obtained for critical velocity will help design a slurry pipeline system for the hydraulic stowing of fly ash slurry at any concentration and pipe size.

Leaching characteristics of bottom ash from thermal power plants

ABSTRACT The disposal of coal ash from thermal power plants in India is a challenging task. The objective of the present study was to investigate the leaching characteristics of the bottom ash disposed in ash pond of thermal power plants. A series of leaching experiments have been performed to analyze the tracing elements of metal at different liquid-to-solid ratios (L/S). L/S ratio varies from 20:1 to 80:1. From the experiment, it is observed that the elements Mn, Mg, Cr, Zn, and Cu are present in major concentrations while elements viz. Pb, Fe, Zn, and Co are present in minor concentrations. It is also observed that the leaching characteristics of the bottom ash are affected by the pH of extraction solution and L/S ratio. The minimum leachability of the solution was determined using an ASTM method, whereas the maximum leachability was determined using a TCLP method.