http://dspace.dtu.ac.in:8080/jspui/handle/123456789/105 2026-06-12T06:11:42Z 2026-06-12T06:11:42Z MISHRA, SHOBHIT Singh, Raj Kumar (SUPERVISOR) http://dspace.dtu.ac.in:8080/jspui/handle/repository/22776 2026-06-08T05:47:49Z 2025-07-01T00:00:00Z

Title: THERMODYNAMIC PERFORMANCE AND DESIGN OF SMALL-SCALE H2O-LiBr VAPOR ABSORPTION SYSTEM FOR ROOM AIR COOLING Authors: MISHRA, SHOBHIT; Singh, Raj Kumar (SUPERVISOR) Abstract: The present study addresses the research gap in small-scale distributed trigeneration systems by investigating two novel configurations: (1) a solar power tower (SPT) driven helium Brayton cycle (HBC) integrated with a heat recovery steam generator (HRSG) and a vapor absorption cooling system (VACS), and (2) a solid oxide fuel cell-gas turbine (SOFC-GT) hybrid system coupled with a vapor absorption refrigeration system (VARS). The primary objectives of this thesis are: (i) to develop and simulate a novel SPT-HBC-HRSG-VACS trigeneration system for combined power, heating, and cooling; (ii) to perform comprehensive energy and exergy analysis of the proposed trigeneration system; (iii) to develop a SOFC-GT-VARS cogeneration system for small-scale room air conditioning; and (iv) to investigate the energy, exergy, economic, and environmental (4E) performance of the SOFC-GT-VARS system. The SPT-HBC-HRSG-VACS system exploits waste heat from a basic HBC driven by an SPT. The two subsystems, HRSG and VACS, recover waste heat for steam generation and air conditioning cooling, respectively. A comprehensive exergy and energy analysis of this proposed trigeneration system was carried out with parametric analysis using Engineering Equation Solver (EES) software. It was concluded that energy and exergy efficiency and net work output of the proposed trigeneration system were observed as 44.96%, 34.15%, and 14,562 kW respectively. The heating production through the HRSG was obtained as 8,510 kW while the cooling production by VACS was 115.10 kW. Moreover, the coefficient of performance (COP) of the VACS subsystem was observed as 0.8015. Energy and exergy efficiency of the SPT-operated basic HBC using the subsystems were improved by 58.98% and 12.92%, respectively. Parametric analysis revealed that the helium turbine inlet temperature and solar heliostat field efficiency significantly affect the trigeneration system performance. vi For the second configuration, a novel SOFC-GT-VARS system for combined cooling and power generation is developed. Thermodynamic, economic, and environmental analyses were performed on the proposed system using computational techniques. The proposed plant obtained power output, exergy efficiency, and energy efficiency of 551.29 kW, 48.03%, and 50.18%, respectively, at given operating conditions. The cooling effect of 5.275 kW (1.5 TR) was obtained from the VARS with a COP of 0.752. The total cost rate of the proposed plant was observed as 33.57 $/h, while the CO₂ emission per MWh of energy output was obtained as 394.70 kg/MWh. The research successfully fills the identified gaps in small-scale distributed trigeneration systems and provides a comprehensive framework for evaluating such systems under Indian climatic and economic conditions.

2025-07-01T00:00:00Z SINGH, PRAVEEN KUMAR GAUTAM, VIJAY (SUPERVISOR) http://dspace.dtu.ac.in:8080/jspui/handle/repository/22758 2026-06-08T05:45:07Z 2025-12-01T00:00:00Z

Title: EXPERIMENTAL AND NUMERICAL INVESTIGATIONS ON LASER FORMING OF MULTI-LAYERED CLAD SHEET METAL Authors: SINGH, PRAVEEN KUMAR; GAUTAM, VIJAY (SUPERVISOR) Abstract: The effectiveness of the laser forming process is strongly dependent on the interaction of thermal and mechanical properties inherent in a clad sheet comprising different layers having different properties. The present research examines how laser power, scanning speed, and number of passes at two distinct levels of maximum and minimum affect the bend angle in the samples of a two-ply clad sheet comprising SS430 and AA1050 layers. The clad sheet, was chosen because of its demand in precision manufacturing for performance attributes like as corrosion resistance, thermal conductivity, and mechanical strength. A central composite design was carried out to determine the correlation between the input variables and output response. Design-Expert software was employed to design the experiments, which gave 20 runs to conduct the tests. Response surface methodology was incorporated to optimize the results. The results obtained by analysis of variance were found to be in agreement with the results obtained by experiments. An optimized combination of 900 W laser power, with number of scans and velocity of 60 and 30 mm/s, respectively resulted in a maximum bend angle of 39° with a relative error of 2.14%. The effect of laser bending due to multiple scans on the clad sheet along the laser path in the thickness direction was also examined to understand the microstructure and texture evolution by electron backscattered diffraction technique. The irradiated surface is affected the most and the texture becomes poor whereas, the layer of AA1050 below the irradiated surface improved in texture. It is also observed that the residual stress in the innermost layer of SS430 is of compressive nature whereas the stress in the outermost layer of AA1050 is tensile in nature. The microhardness in the laser-irradiated zone of the SS430 layer ranges from 200 HV to a maximum of 272 HV, whereas the hardness in the AA1050 layer across the bent zone does not vary significantly.

2025-12-01T00:00:00Z KONAR, SUBHAJIT GAUTAM, VIJAY (SUPERVISOR) http://dspace.dtu.ac.in:8080/jspui/handle/repository/22755 2026-06-08T05:44:41Z 2026-03-01T00:00:00Z

Title: EXPERIMENTAL AND NUMERICAL INVESTIGATIONS ON FORMABILITY OF TAILOR WELDED BLANKS PREPARED BY FRICTION STIR WELDING PROCESS Authors: KONAR, SUBHAJIT; GAUTAM, VIJAY (SUPERVISOR) Abstract: With the advent in technology, the automotive parts makers are particularly interested in the utilization of new manufacturing concepts and modern materials. The phrase "tailor welded blank (TWB)" refers to a blank in which two or more sheets of material are welded together to form a single blank before the forming process. TWBs have considerable benefits in terms of lowering manufacturing costs, reducing vehicle weight, and enhancing part performance. Experimental and numerical investigations on the formability of longitudinally buttwelded tailor welded blank of the same thickness prepared by friction stir welding is presented in the thesis. The friction stir welding technique involves a solid-state stirring mechanism to butt weld the two blanks of aluminium alloy AA5083 and AA6082 both in annealed state. This study employs a Taguchi approach to systematically explore and optimize critical FSW parameters such as tool rotational speed and traverse speed, while keeping axial force as constant. The influence of each parameter on weld quality metrics, such as tensile properties (strength and ductility), hardness distribution, and defect formation, is assessed using an appropriate orthogonal array (L9) and signal-to-noise (S/N) ratio analysis. The Taguchi approach identifies the most significant parameters and their optimal levels with fewer experimental trials, boosting joint efficiency, increasing material flow in the stir zone, and ensuring a defect-free weld. This optimization framework offers a reliable and cost-effective way for creating different FSW joints between AA5083 and AA6082 alloys. In order to study the effect of welded region on formability, experiments are performed on tailor welded blanks with and without the annealing operation. The tensile properties of the parent sheets, welded blanks and welded region are determined by performing standard uniaxial tension tests. The formability of tailor-welded blanks was investigated by performing limiting dome height (LDH) tests vii and measuring major and minor strains along and across the weld line in deformed samples. The elastic properties, true stress-true strain and anisotropic data sets are used in the material model for the prediction of failure strains to develop forming limit plots. The predicted results from finite element analysis are validated with the experimental results obtained from limiting dome height test and are found to correlate well with experimental data. The annealing is observed to enhance the formability of the FSTWB by almost 13% in plane strain and equibiaxial stretch conditions.

2026-03-01T00:00:00Z SINGH, RANJEET KUMAR Singh, Ramesh Chandra (SUPERVISOR) http://dspace.dtu.ac.in:8080/jspui/handle/repository/22749 2026-06-08T05:37:46Z 2026-03-01T00:00:00Z

Title: FABRICATION, CHARACTERIZATIONS AND OPTIMIZATION OF FUNCTIONALLY GRADED MATERIAL FOR LEAF SPRING PLATE Authors: SINGH, RANJEET KUMAR; Singh, Ramesh Chandra (SUPERVISOR) Abstract: The present research investigates the development, characterization, modelling, and optimization of a functionally graded Al7075/B₄C composite leaf-spring plate for lightweight and high-performance automotive suspension systems. To overcome the drawbacks of conventional steel and homogeneous MMC leaf springs, such as excessive weight, poor fatigue resistance, and non-uniform stress distribution, a five- layer reinforcement gradation (16/12/8/12/16 wt% B₄C) was strategically designed to match the bending-stress profile of the leaf plate. A hybrid stir-casting and gravity die-casting approach, supported by K2TiF6 as a wetting agent, enabled uniform particle incorporation, strong interlayer metallurgical bonding, and accurate layer- wise gradation during sequential semi-solid pouring. This fabrication route proved cost-effective, scalable, and suitable for large plate-type FGM components. Detailed microstructural characterization through FESEM, EDS, and XRD confirmed the intended gradation, uniform particle dispersion, defect-free interfaces, and the absence of undesirable reaction products. Post-fabrication T6 heat treatment further enhanced matrix strengthening and particle–matrix adhesion. Mechanical and dynamic tests revealed significant improvements in hardness, tensile strength, and storage modulus in layers with higher B₄C content, while the ductile mid-layer effectively maintained impact resistance. Dynamic Mechanical Analysis demonstrated enhanced damping performance, indicating suitability for vibration- sensitive automotive environments. vi A comprehensive finite element analysis (FEA) was conducted to evaluate stress distribution, von-Mises stress variation, and deflection behaviour under realistic suspension loading conditions. The functionally graded plate exhibited reduced peak stresses, smoother stress transition across layers, and significantly lower central deflection compared with homogeneous MMC designs. Six different gradation configurations were analysed, and strong agreement between experimental and numerical results validated the modelling strategy and the mechanical behaviour of the graded system. Optimization results identified the 16/12/8/12/16 wt% B₄C configuration as the most effective design, providing an optimal balance between stiffness, ductility, stress redistribution, load-bearing capacity, damping response, and structural reliability. This configuration demonstrated the best stiffness-to-weight performance and minimal deflection, making it ideally suited for heavy-duty suspension applications. Overall, this thesis establishes a complete and integrated framework, from material selection, fabrication, and microstructural analysis to mechanical evaluation, computational modelling, and optimization-for designing functionally graded aluminium composite leaf springs. The research demonstrates that FGM architecture, combined with an economical stir-casting route, can significantly enhance the performance, durability, and energy efficiency of suspension components. The work contributes a scientifically validated and industry-ready pathway for next-generation lightweight automotive systems, supporting the broader goals of sustainable engineering, improved fuel economy, and indigenous advanced-material development.

2026-03-01T00:00:00Z