Yigit Tascioglu

Model Testing of Francis-Type Hydraulic Turbines

Every single turbine is custom-designed specifically to meet the requirements of a hydroelectric power plant. Performance of a designed turbine is validated, to some extent, by computational fluid dynamics simulations; however, experimental testing according to International Electrotechnical Commission standards is necessary to ensure performance and reliability. Model tests are performed on similar, small-scale models at test facilities that are specifically designed for this purpose. This article features one such facility, which is capable of testing the performance and cavitation of Francis-type turbines. Test procedures, measured parameters, measuring instruments, and calibration techniques are explained in detail.

A Novel Rotary Magneto-Rheological Damper for Haptic Interfaces

Haptic interfaces require lightweight, small actuators with high force capability and low friction. In this paper, based on the structure of conventional shear mode disc and drum type MR fluid dampers, a lightweight continuous rotary MR damper working in valve mode is designed for haptic interfaces. The proposed design is compared to shear mode disc-type and drum-type designs with similar torque–to–mass ratio via computer simulations. Mathematical models for the resistant torques of both the shear mode and the valve mode are derived. Subsequently, the finite element analysis of electromagnetic circuit calculations was carried out by FEMM software to perform an optimization of the dimensions of the parts such as gap size and thickness. It is shown that the proposed continuous rotary valve mode MR damper is a fine candidate that meets the requirements of haptic interfaces.Copyright

An Eco-Improvement Methodology for Reduction of Product Embodied Energy in Discrete Manufacturing

There is an increasing awareness of global warming due to excessive greenhouse gas emissions and need to decrease the adverse effects of production on environment. It is known that greenhouse gasses are mainly originated from the fossil fuel combustion for electrical energy generation. This paper proposes an eco-improvement methodology for minimizing the product embodied energy by decreasing the electrical energy dependence of production. The methodology involves generation of STEP based process plan resulting in minimum embodied energy and simulation models enabling what-if analyses. The proposed eco-improvement methodology will be implemented in refrigerator compressor plant of Arcelik A.Ş., aiming at assessment and reduction of energy consumption in discrete manufacturing.

A Virtual Prototyping System for Additive Manufacturing Process Development

This paper describes a virtual prototyping (VP) system which is a part of an open source software package for an additive manufacturing (AM) process under development. The VP system facilitates the product development by uniting the AM process and virtual reality in order to produce digital prototypes. Moreover, it combines particle based and layer based processes by including powder-like particles as its basic material. These particles are used as color codes in the VP system. This coding enables obtaining basic building blocks in homogeneous state or in heterogeneous state by mixing with other particles. These blocks or bricks are collated side by side to obtain the heterogeneous material property all over the solid body. The thin layers obtained by these bricks are then subsequently stacked up to fabricate a virtual prototype. Construction of multiple material prototypes is possible due to selective-additive nature of this process. The effectiveness of the proposed system is demonstrated by processing a model of The Maidens Tower.

Speed control of hydraulic turbines for grid synchronization using simple adaptive add-ons

Background: Parameters of the hydroelectric power plant controllers are typically tuned at the nominal operating conditions such as nominal head and single unit operation. Water level variations in reservoir and/or tailwater, and the presence of other active units sharing the penstock are common disturbances to the nominal assumption. Methods: This article proposes two adaptive add-ons, namely gain scheduling and model reference adaptive control, to the existing speed controllers to improve grid synchronization performance when the site conditions are not nominal. The add-ons were designed and tested on a validated dynamic model of a power plant unit by using a software-in-the-loop simulation setup. An off-season scenario is simulated, in which the original controller of the unit cannot bring the turbine to synchronize with the grid due to low gross head. Then, the add-ons were implemented on-site and experiments were performed under similar conditions. The parameter sets used in gain scheduling for different operation bands are determined off-line with the help of operational experience. The model reference adaptive control add-on requires a reference model and a learning rate. A description of the turbine speed-up profile at nominal operating conditions is sufficient to be used as the reference model. The proposed piecewise linear reference model favors stability over speed in settling to the nominal speed. Results: It is experimentally shown that the proposed add-ons compensate the negative effect of head loss in grid synchronization, and perform similar to the ideal performance at the nominal head. Conclusion: Both add-ons can be implemented on the available off-the-shelf speed governor controllers. They are suitable for use in all hydroelectric power plants, especially in unmanned ones, for automatic synchronization with less waste water.

Experimental Investigation of a Magneto-Rheological Fluid Damper with Permanent Magnet for Haptic Finger Grasping

Haptic devices mimic force or torque responses of physical systems. In active devices, the synthetic responses are usually produced by DC motors, due to their wide range availability and ease of control. On the other hand, simulating rigid collisions require large motors, at the expense of size and weight, or gearboxes at the expense of transparency. Viscosity of magneto-rheological fluids (MRF) increases, up to the point of becoming a viscoelastic solid, when they are subjected to a magnetic field. Due to this property, they are used in adjustable dampers, where the damping force is controlled by varying the intensity of the magnetic field via an electromagnet. The use of MRF technology in passive or semi-active haptic devices is an attractive research area, in which, a number of damper designs have been proposed over the last decade. This paper investigates a linear MRF damper for haptic finger grasping applications. The damper incorporates an orifice area which is affected by a position controlled permanent magnet. Proximity of the permanent magnet to the orifice area manipulates the viscosity of the MRF; hence changes the reaction force of the damper.

Electro-Mechanical Control Loading System for Rotary Wing Aircraft Simulators

The focus of this paper is on the development of a high-fidelity electro-mechanical Control Loading System (CLS) for a rotary wing aircraft simulator. CLS is one of the major components of a flight simulator. It is used for providing realistic force feedback to pilots. The pilot in a real aircraft feels the forces acting on control surfaces through cockpit controls. During simulation, these forces are produced by CLS actuators. For this reason, CLS must behave exactly like the aircraft control hardware, statically and dynamically. The fidelity of the force feel simulation is a key criterion for flight simulation certification. It is also important that a CLS design is reconfigurable and modular such that it conforms easily to different simulator models and simulations of different aircrafts. The work also includes system integration of a research simulator for testing purposes. Design and selection of hardware and software components of the CLS and the simulator are presented along with the overall system architecture.Copyright

Design of a Flow Diverter Mechanism and a Nozzle for a Hydro Turbine Experimental Test Rig

Hydro turbines used in hydroelectric power plants need to be designed and tested according to the specifications of the specific power plant, mainly the head and flow rate. Their models also need to be tested according to the standards provided by International Electrical Commission (IEC) before manufacturing the actual turbines. A Hydro turbine test rig at TOBB University of Economics and Technology is currently under construction to provide standardized tests for model turbines. A typical calibration system for a flow meter has four components; nozzle, flow diverter mechanism, weighing tank and load cells. The nozzle provides the regulation of water speed and supplies water to flow as a thin-sectioned profile. The flow diverter mechanism diverts the flow either to the weighing tank or to the reservoir. The flow rate is calculated from the collected mass and total time for the process. Calculated flow rate value is compared with the digitally measured values during the experiments, since the IEC standards require a real-time calibration for the flow rate. In this study, the flow diverter mechanism and the nozzle for this test rig is designed in order to meet several internationally acceptable standards.© 2014 ASME

Design and simulation of a SCADA system using SysML and Simulink

This paper describes a methodology and a case study through which system architecture and dynamic models of related system components are gathered in order to design and simulate the SCADA system of a new hydro turbine test laboratory. System architecture model is prepared in System Modeling Language, a system modeling language based on Unified Modeling Language, while the dynamic model of the laboratory is formed in Matlab/Simulink. Some simulations are performed in order to verify the preliminary system design studies and system requirements.