Nilotpal Banerjee

Bond graph modeling of a railway truck on curved track

Abstract Rail vehicles become unstable beyond a critical speed because of speed dependant creep forces at the rail-wheel contact surface. There is a constant demand for improved rail vehicle model for design of high-speed vehicles, and track. Works available in the literature are based on models of trucks with various simplifying assumptions such as reduced degree of freedom, small displacements and without kinematic nonlinearities and inclination of the contact surface. In this paper an integrated bond graph model of a truck is developed for the first time without the aforementioned assumptions. It is found that truck dynamical behavior is significantly different from those found in the literature in some cases.

Bond Graph Modeling of Rail Wheelset on Curved Track

This paper presents a bond graph model of a free rail wheelset rolling on fleXible curved track, considering siX degrees of freedom without linearity approXimations. Modeling of engineering systems through bond graphs is based on eXchange of power amongst the basic elements of a system and several energy domains can be represented in a unified manner. In this paper, the modeling approach is based on creating subsystem bond graph models or capsules representing various analytical aspects of wheelset dynamics. The model is finally converted to a wheelset capsule, which can be further used for the development of truck and carbody models with suspension elements. The model can accommodate any creep force formulation for the rail—wheel contact forces. In this work, both Kalkers linear theory and heuristic modification based on non-linear formulation by Vermeulen and Johnson are used separately in a comparative study. Both these formulations allow the creep forces to be modeled by a non-linear bond graph R elements acted upon by the corresponding slip velocities between the wheel and track. Kinematic analysis of the wheelset is carried out to determine velocities of the contact points. The bond graph is created using software SYMBOLS 2000 and simulated for a set of parameter values.

Modelling of a free rail wheelset using non-linear creep force

This paper presents a bond graph model of a free railway wheelset rolling on flexible curved track. A module-based approach is used here. A model of a wheelset considering six degrees of freedom without linearity approximation is created using subsystem models called capsules. Capsules represent various analytical aspects of wheelset dynamics. Different subsystem models are combined to develop a complete bond graph model of a wheelset for simulation on a rigid railway track. For the rail-wheel contact forces (creep forces), a heuristic non-linear formulation is used, which can also be used with slight modification as a linear model for comparative study. Kinematic analysis of the wheelset is done to find out velocities of the contact points on the wheelset. The bond graph is created on the bond graph software SYMBOLS 2000 and simulated for a set of parameter values.

A Heuristic Approach to Design Discrete Fractional Order Integrators without Using s-to-z Transform

In this paper, a heuristic optimization technique called Harmony Search Algorithm (HSA) is efficiently employed to design Infinite Impulse Response (IIR) Discrete Fractional Order Integrators (DFOIs). Unlike the methods reported in the literature, no discretization (s-to-z transform) operator is necessary to obtain the DFOIs by using the proposed approach. To investigate the design efficiency, the HSA-based DFOIs have been evaluated against the designs based on Real coded Genetic Algorithm (RGA), Particle Swarm Optimization (PSO), and Differential Evolution (DE) using different frequency response error metrics. The reliability in the performance of the proposed DFOIs are extensively investigated by conducting various statistical tests. Comparison of fitness convergence demonstrates that HSA achieves the near global optimal solution in the least number of iterations. Thus, HSA exhibits superior computational efficiency in solving this multimodal optimization problem. The proposed DFOIs also outperform the reported designs.

Aero-Structure Interaction for Mechanical Integration of HP Compressor Blades in a Gas Engine Rotor

Aero-structure interaction during turbomachinery blade design has become an important area of research due to its critical applications in aero engines, land based gas turbines. Studies reveal that a small mistuning leads to stress build up through mode localization under operating conditions. This paper deals with a case study of Aero-structure interaction for a free standing HP blade of a gas turbine. Assuming 100 % fixity at blade root, the study involves critical parametric evaluations involved in achieving Mechanical Integrity in airfoil design and blade platform design. Mechanical Integrity involves stress checks, frequency margins, Campbell diagram, gross yield stress and so on, for design and off-design conditions for a given stage efficiency of 72 % in an Ideal HP compressor of a gas turbine engine.

A LabVIEW-Based Data Acquisition System in a Quarter Car Test Rig to Optimize Vehicle Suspension System

Suspension design is always been a challenging task for automobile designers in view of multiple input parameters, complex objectives, and disturbances which are stochastic in nature. The conflicting nature of ride comfort (RC) and road holding (RH) compels a judicial compromise between these two. In the present work, full factorial design of experiment (DoE) has been used successfully for the purpose of multi-objective optimization of RC and RH with input variables spring stiffness (K), damping coefficient (C), sprung mass (M), and speed. For experiments with combination of various input variables, a quarter car test rig is developed with proper data acquisition system by NI-hardware and Laboratory Virtual Instrumentation Engineering Workbench (LabVIEW) to collect real-time data. A regression model of RC and RH with R 2 value 95.98 and 95.78 %, respectively, can be effectively used to evaluate optimal settings of various input parameters using response optimization with a high desirability value.

Microstructure and Mechanical Properties of Friction Stir Welded Joints of Dissimilar AA6061-T6 and AA7075-T6 Aluminium Alloys

Dissimilar friction stir welding was carried out between AA6061-T6 and AA7075-T6 aluminum alloys. The effect of tool rotational speed and welding speed, on microstructure and mechanical properties were analysed in detail and presented. The tool rotational speed, welding speed, axial load and shoulder diameter to pin diameter (D/d ratio) were the parameters taken into consideration for the study. It was concluded that the tensile strength and hardness value gradually increased with the increase in tool rotational speed and decreased with the further increase in tool rotational speed. The microstructural analysis was carried out for the high strength specimen at various zones. Fine grain size and proper material mixing were observed in the stir zone. Fractographic image of the fractured surface for the high strength joint was presented and discussed. The joint fabricated with tool rotational speed 1000 RPM, welding speed 25 mm/min, axial load 6 kN and D/d ratio 3 exhibited superior mechanical properties when compared to all other joints.

Integrated Drying and Partial Coal Gasification for Low NOX Pulverized Coal Fired Boiler

Coal bound moisture is a key issue in pulverized coal fired power generation. Coal being hygroscopic, accumulates considerable surface moisture with seasonal variations. A few varieties of coals are having unusually high inherent as well as surface moisture that affects the pulverizer performance and results lower thermal efficiency of the plant. A proper coal drying is essential for effective pulverization and pneumatic conveyance of coal to furnace. But, the drying capacity is limited by available hot airflow and temperature of hot primary air. Even, use of high-grade coal for blending would not provide the entire useful heat value due to moisture, when used for matching power plant design coal parameters. Besides, the inefficient mining, transportation, stacking and associated coal fleet management deteriorates the “as fired” coal quality affecting cost while purchased on “total moisture and gross heat value” basis. Partial devolatilisation of coal in a controlled heating process, prior combustion in fuel-rich environment ensures better in-furnace flame stability and less residual carbon in product of combustion. It improves the opportunity of a lower flame zone temperature, delivering better control over thermal NOx formation from fuel bound nitrogen. The pulverized coal fired power plants use coal feeders in either gravimetric or volumetric mode of feeding that needs correction for moisture in coal which changes the coal throughput requirement. In this paper an integrated coal drying and partial coal gasification system model is discussed to improve the useful heat value for pulverized coal combustion of high moisture typical power coals so that related improvement in coal throughput can be carried out by application of suitable coal drying mechanism like Partial Flue Gas Recirculation through Pulverizer (PFGR© ) for mitigating the coal throughput demand with optimizing available pulverizing capacity along NOx control opportunity without derating steam generation capacity of the boiler.Copyright