Effects of Flue Gas Recirculation on NOx Emissions from Gas-Fired Utility Boilers

Gas-fired utility boilers are most common in the district heating system in the city of Belgrade. Thus, they are an important stationary source of NOx emissions, which are particularly harmful for people and environment. In this paper the effectiveness of the flue gas recirculation (FGR) system that is applied to reduce NOx emissions of the utility hot water and steam boilers in district heating plant is experimentally investigated. Two types of systems are analysed; the first with the application of flue gas recirculation fan at hot water boilers; and the second without the application of flue gas recirculation fan at steam boilers. In both cases the rate of flue gas recirculation was 10%. The results of measurements showed that applied FGR systems efficiently reduced NOx emissions from utility boilers by 20 to 50% and below the reference values defined by legislative regulations. Emissions are higher at steam boiler which is expected because of the higher flue gas temperature at boiler furnace. Since the measured values for hot water boilers are close to the reference values, it was concluded that there is a potential for further improvements by increasing the flue gas recirculation rate

Strain determination of self-adhesive resin cement using 3D digital image correlation method

Introduction/Objective. In an attempt to simplify dental procedures, a new group of resin cements, self-adhesive resin cements (SARCs), have been introduced. Performance of SARCs can widely vary. One of the main reasons of adhesion failure is polymerization shrinkage. The aim of this study was to determine, evaluate, and measure strain field of self-adhesive dual cure resin cement during polymerization in self-cure mode using 3D digital image correlation (DIC) method. Methods. The self-adhesive Maxcem Elite (Kerr, Orange, CA, USA) cement was tested in five cylindrical samples (5 mm in diameter and 2 mm in thickness) prepared by filling plastic ring-type molds. Digital images were recorded immediately after sample preparation. Results. Non-uniform strain distribution was found in resin cement with higher strain values along the periphery (up to 15%) and lower strain values in central parts (around 4%) of each sample. Conclusion. It can be concluded that DIC is a powerful tool for full-field strain measurements in material characterization. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no.TR35031 and Grant no. TR35040

Strain measurement of medical textile using 2d digital image correlation method

Medical textile plays an important role in the technical textiles sector as one of the most rapidly growing sectors in the technical textile market. The textile materials should have some adequate mechanical properties to be useful as medical textile. Tensile strength presents one of the basic mechanical properties used to describe textile specimens. Standardized tensile testing procedures on textile specimens were commonly used in the past. The aim of this paper was to measure in-plane strain field on the tensile medical textile specimen using 2D Digital Image Correlation method (2D-DIC). 2D-DIC is a non-contact optical method for accurate displacement and strain full-field measurement. In this study, two medical cotton textiles, with density 120 and 130 g/m2, were used to create three specimens for each material. Each specimen was placed in the tensile testing machine and measured until the break. During the tensile testing, camera was automatically recording full-field displacement in X and Y directions. Textile 1 and Textile 2 showed significant differences in point distance values, despite the small deviation in densities (less than 10%). Mean value of the elongation for Textile 1 is more than a double than the elongation for Textile 2, although the difference for mean value of Maximum force if negligible. Also, it has been showed that 2D-DIC can play significant role for measurement in textile mechanical properties measurement