Pranjal Sarmah

The use of a simulation software allows us to perform studies of complicated systems whose analytic solution is not known or whose experiment cannot be performed in actual system. A simulated model has to be prepared describing the interaction between elements of the system. After preparing the model random number generation takes place. Simulated model is run with the help of random numbers. Simulation basical- ly involves conducting experiments on the model of the system. With the help of simulation software like ARENA, AUTOCAST, SIMPY, ELMER etc. simulation becomes a vital tool for solving complex problems.

Abstract This article investigates the effect of powder metallurgy processing parameters on multi-responses: mass density and hardness of Al2O3/Cu composite based on Taguchi method coupled with Grey relational analysis. Based on Taguchi’s L18 orthogonal array, the experimental trial runs were conducted with four controllable powder processing parameters: milling time, compaction pressure, sintering temperature and holding time. The Grey relational analysis (GRA) was performed to find the optimal powder processing condition with Grey relational grade (GRG) as a measure of performance index. Analysis of variance (ANOVA), 3D surface plots and contour plots were used to express the most influential parameter that affects mass density and hardness of Al2O3/Cu composite. Confirmation tests were conducted to make sure the validity of test results. The scanning electron microscope (SEM) images show the presence of Al2O3 particle in the composite. The Energy Dispersive X-Ray (EDX) spectrum indicates the presence of chemical elements: Cu, Al, O in the composite. The results show that the optimal powder metallurgy parameter combination is A2B3C3D1. The mean Grey relational coefficient (GRC) analysis shows that the mass density was more easily influenced by factors considered compare to hardness. The mean GRG result shows that the compaction pressure has the strongest correlation to responses. The result of 3D surface plots, contour plots and ANOVA indicate that the compaction pressure has most influential parameter that affect GRG. The % contribution of parameters shows that the % contribution of compaction pressure is significant (80.22%) compare to other main effects and interaction effects. The confirmation tests revealed that the performance characteristic of Al2O3/Cu composite was improved by GRA based Taguchi technique. The Monte Carlo simulated model summery show that based on Taguchi L18 Orthogonal Array design, one can easily find the reality of what will be happening in a process. Therefore, optimization of processes parameter could be simplified by using the Grey-based Taguchi method.

Abstract This paper presents the erosive wear of MWCNTs/MnO2 nanocomposite. The nanocomposites with 5, 10 and 15 wt% of MWCNTs were fabricated using cost effective powder metallurgy technique. The mass density analysis shows that the green and sintered mass density of the nanocomposites increases with addition of MWCNTs from 5wt% to 10wt% and then decreases from 10wt% to 15wt%. The decrease in density from 10wt% to 15wt% may be due to agglomeration of MWCNTs in the nanocomposites. The erosive wear test was done by self designed erosive wear tester. The erosive wear test indicates that 10 wt% MWCNTs/MnO2 nanocomposite exhibits higher erosive wear resistance as compared to 5 and 15 wt% MWCNTs/MnO2 nanocomposite. The field emission scanning electrone microscope (FESEM) surface morphology of fractured surface shows that the nanocomposites were brittle fractured during erosion process. The erosive wear of the nanocomposite depends highly on its mass density, hardness and dispersion of multiwalled carbon nanotube in H2SO4(aq) solution.

Abstract Inverse analysis is an efficient method to estimate parameters that characterizes a given system. It offers lot of flexibility at the designer’s hand in selecting the most suitable combination of parameters satisfying a given set of objective functions. In this study, inverse analysis of a solid oxide fuel cell (SOFC)–gas turbine (GT)–steam turbine (ST) combined cycle (CC) power system is performed. The system’s net power, efficiencies (energy and exergy) and the total irreversibility at compressor pressure ratio (CPR) 6 and 14 are considered as objective functions for the inverse problem. A differential evolution (DE) based inverse algorithm is used for simultaneously estimating six operating parameters of the plant. It was seen that the inverse technique was very effective in estimating the operating parameters of a hybrid SOFC–GT–ST plant correctly within the prescribed lower and upper bound of the parameters. Multiple combinations of parameters are obtained from the study and all these combinations of parameters satisfy the given single objective function/set of objective functions. Any objective function value be set and then operating parameters be determined accordingly using the inverse method. The results offer plenty of scope for selection of suitable operating parameters for the plant.

Abstract In this article, a thermodynamic model is developed for analyzing the energetic and exergetic performance of a solid oxide fuel cell (SOFC) integrated combined power system with triple pressure reheat cycle in the bottoming steam turbine (ST) plant. A temperature difference range of 15–20 °C is considered between flue gas and steam at superheater inlet in the high and intermediate pressure stages of the heat recovery steam generator (HRSG). Also, a temperature difference of 20 °C is maintained at the pinch point between flue gas and saturated water in the low pressure stage of the HRSG. Detail performance variation is provided as a function of compressor pressure ratio (CPR) showing that the system’s power and efficiency increase while total irreversibility decreases at higher CPR. Further, thermodynamic modeling is done for two other systems with dual pressure reheat and single pressure ST cycles for performance comparison amongst all, under identical conditions. The comparative study shows that the system with single pressure ST cycle performs better compared to the others; the highest power is obtained from this system with minimum total irreversibility. It is recommended that the system with single pressure ST cycle would be the most appropriate as it is simple with less number of components and minimum total cost.

ABSTRACT This article provides the energy and exergy based performance analysis of a solid oxide fuel cell (SOFC) – gas turbine (GT) – steam turbine (ST) combined cycle power plant. The system utilizes the GT exhaust heat for fuel and air preheating subsequently in a fuel recuperator (FR) and an air recuperator (AR) before finally producing steam in a heat recovery steam generator (HRSG) coupled with the ST cycle. It considers 30% external reforming in a pre-reformer (PR) by steam extracted from the bottoming ST plant. The study considers the effect of additional fuel burning in the combustion chamber (CC) as a means for increasing the net GT and ST power output. A detailed parametric analysis based on variation of compressor pressure ratio (CPR), fuel flow rate (FFR), air flow rate (AFR), current density, single level boiler pressure and ST inlet temperature (STIT) is also provided. Results indicate improved system performance at higher CPR. The optimum single level boiler pressure is found to be 40 bar with 50% additional fuel burning. Burning of additional fuel improves the GT and ST power output, however with reduction in the plant’s overall efficiency. Further comparison of performance with a similar other system where the AR is placed head of the FR indicates slightly better performance of the proposed system with FR ahead of AR (FRAOAR).