Performance analysis of open cycle gas turbines

In this study, the performance of ideal open cycle gas turbine system was examined based on its thermodynamic analysis. The effects of some parameters, such as compressor inlet temperature (CIT), pressure ratio (PR) and the turbine inlet temperature (TIT), on the performance parameters of open cycle gas turbine were discussed. The turbine net power output, the thermal efficiency and the fuel consumption of the turbine were taken as the performance parameters. The values of these parameters were calculated using some basic cycle equations and variables values of thermodynamic properties. Other variables such as lower heating value, combustion efficiency and isentropic efficiencies of compressor and turbine were assumed to be constant. The result showed that the net power output and the thermal efficiency increased by a decrease in the CIT and increase in the TIT and PR values. If it is aimed to have a high net power output and the thermal efficiency for the turbine, the CIT should be chosen as low as possible and the TIT should be chosen as high as possible. Copyright © 2008 John Wiley & Sons, Ltd.     

Design of a new three-degree of freedom spherical motor for photovoltaic-tracking systems

Photovoltaic (PV) panels directly convert the solar energy to electrical energy. The amount of electrical energy converted by PV panels mainly depends on incident solar radiation. Sun tracking systems can be used to maximize energy production since they ensure keeping the photovoltaic panels perpendicular to the incoming solar radiation. Spherical motors, which have the linear and circular movement ability in three independent dimensions, can be used for precisely tracking the sun as a solution. In this study, a spherical motor controlled by a micro-controller is designed for a PV-tracking system with the ability to move on two axes. Performance of PV-tracking system over a fixed tilted one is evaluated for the climate condition of Denizli, Turkey. The designed sun tracking system is observed to be improving this performance apparently using the output voltages obtained for one day.     

Technical note An approximation to solar cell equation for determination of solar cell parameters

An approximation was applied to a solar cell equation to eliminate reverse saturation current. I–U curves obtained from the approximated equation were fitted to experimentally measured data by using the iteration technique. All instrumentation errors were taken into account in the fitting procedure. The Filling Factor (FF) and the series resistance (R_s) appeared to be important for fitting accuracy. The fitting procedure was repeated for different illuminations and solar cell temperatures.     

Developing an ecologically friendly isothermal bath to obtain a new class high-tenacity and high-modulus polypropylene fibers

A number of production methods have been developed for high-performance fibers; however, most processes use toxic solvents or generate a lot of unwanted by-products. Our research resulted in the development of a new family of high-performance polypropylene (PP) fibers by utilizing a simple, ecologically friendly bath (ECOB). Various commodity polymers can be used with ECOB melt spinning system at high throughputs and performance benefits. Our treated as-spun PP fibers had a highly oriented, but not crystalline precursor morphology with f _a up to 0.6 generating superior mechanical properties. After drawing at draw ratios of 1.49 at 120 °C, highly oriented crystalline and amorphous phases were achieved for the drawn fibers with f _c and f _a values of 0.95 and 0.87, respectively. This fine structure for ECOB-treated fibers resulted in tenacity close to 12 g/d, initial modulus higher than 150 g/d, and ultimate elongation at break of 20 %. The polymer melting point of the new fibrillar PP fibers increased by 9 °C.     

Evaluation of Natural Gas Supply Security in Turkey with Future Projection

Natural gas is one of the key energy resources for Turkey due to fact that 32% of annual primary energy supply and 45% of annual electricity production is obtained from natural gas with also common usage of residential and industrial zones. In this study, the supply security of natural gas was taken into consideration with strategic criteria of energy policy with the SWOT （strengths, weaknesses, opportunities and threats） analysis and the future projection for Turkey. It has been concluded on geopolitics criteria, domestic production and research for resources must be stimulated as high as possible and participation to abroad resources must be implemented.     

Development and characterisation of polyaniline/polyamide (PANI/PA) fabrics for electromagnetic shielding

In this study, novel conductive fabrics were developed by polymerising of aniline onto the polyamide (PA)-knitted fabrics. The fabric treatment was done by the chemical polymerisation method at 0.5, 0.8 and 1.2?M aniline concentrations. Hydrochloric acid as acidic medium and ammonium per sulphate as oxidant were employed during the polymerisation process. The polyaniline (PANI)-treated PA fabric structures were fully characterised and evaluated in terms of their electromagnetic shielding effectiveness, absorption and reflection characteristics and tensile properties. Additionally, the fabrics were examined by scanning electron microscope (SEM) for the surface morphology and Fourier transform infrared spectroscopy for the chemical functionality. The electromagnetic shielding effectiveness, absorption and reflection characteristics were determined by Network Analyzer with a frequency ranged from 15 to 3000 MHz. The electrical characteristics were measured by the two ends method. It has been concluded that the bursting strength values of the treated fabrics reduced when the amount of monomer in the concentrations decreased as compared to the untreated fabrics. It is interesting to note that 1.2 M treated fabric had the highest bursting strength values as compared to the other treated fabrics. It was also found that 0.5 M concentration of PANI-treated fabric had the lowest surface resistivity due to this it showed the highest conductivity value. Another important finding is that the 0.5 M-aniline treated fabric had the highest shielding effectiveness.     

Analyzing the effects of special washing processes on characteristics of sewing threads

In recent years, wet (washing, bleaching, etc.) and dry (abrasive, laser shaping, rodeo, etc.) operations applied on fashion denim products have become an important factor to increase the added value. However, these wet and dry processes applied to the denim products may have adverse effects on the strength of the fabric and other supplementary materials of denim products. For example, thread breakages affect the repair ratios and quality of products, which causes time and profitability losses in companies. The main objective of this study is to analyse how the types of washing affect the strength of the sewing threads that are commonly used in the production of denim trousers. In this study, 100% cotton denim fabric with a weight of 11.5 ounces and two different sewing threads were used. The fabrics are sewn as trouser legs with chain and lock stitch. Five different washes were applied to the trouser legs. The obtained data were evaluated in the R statistical program. As a result of the analyses made it is proven that the washing techniques used have an effect on the sewing threads’ tensile strength and elongation at break. The tensile strengths of lock stitch and chain stitch decrease averagely 35% and elongation at break of lock stitch decreases %22 and chain stitch decreases 29.8%.