Energy Systems Engineering / Enerji Sistemleri Mühendisliği
Permanent URI for this collectionhttps://hdl.handle.net/11147/4752
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Article Citation - WoS: 8Citation - Scopus: 10Spray Analysis of Biodiesels Derived From Various Biomass Resources in a Constant Volume Spray Chamber(American Chemical Society, 2022) Ulu, Anılcan; Yıldız, Güray; Rodriguez, Alvaro Diez; Özkol, ÜnverThis research aimed to analyze the spray characteristics of various biodiesels, which have rarely been investigated in terms of spray analysis in the literature compared to fossil diesel. For this purpose, four different methyl ester-type biodiesels were produced from canola, corn, cottonseed, and sunflower oils. These feedstocks were selected due to their wide availability in Turkey and being among the significant resources for biodiesel production. Measured physical properties of biodiesel samples showed that biodiesel fuels had, on average, 1.7 to 1.9 times higher viscosities, 5.3 to 6.6% larger densities, and 37 to 39.1% higher contact angle values than the reference diesel fuel. Spray characteristics of all fuels were experimentally examined in a constant volume spray chamber under chamber pressures of 0, 5, 10, and 15 bar and injection pressures of 600, 800, and 1000 bar. All tested biodiesels performed, on average, 3 to 20% longer spray penetration lengths, 5 to 30% narrower spray cone angles, and 5-18% lesser spray areas than the reference diesel fuel under chamber pressures of 5 and 10 bar. No significant differences occurred at 15 bar ambient pressure between biodiesels and diesel. In addition, analytical and empirical predictions showed that biodiesels had around 21.2-35.1% larger SMD values and approximately 7% lower air entrainment.Article Citation - WoS: 22Citation - Scopus: 24Size Dependent Influence of Contact Line Pinning on Wetting of Nano-textured/Patterned Silica Surfaces(Royal Society of Chemistry, 2020) Özçelik, H. Gökberk; Satıroğlu, Ezgi; Barışık, MuratWetting behavior on a heterogeneous surface undergoes contact angle hysteresis as the droplet stabilized at a metastable state with a contact angle significantly different from its equilibrium value due to contact line pinning. However, there is a lack of consensus on how to calculate the influence of pinning forces. In general, the pinning effect can be characterized as (i) microscopic behavior when a droplet is pinned and the contact angle increases/decreases as the droplet volume increases/decreases and (ii) macroscopic behavior as the pinning effects decrease and ultimately, disappear with the increase of the droplet size. The current work studied both behaviors using molecular dynamics (MD) simulation with more than 300 different size water droplets on silica surfaces with three different patterns across two different wetting conditions. Results showed that the contact angle increases linearly with increasing droplet volume through the microscopic behavior, while the droplet is pinned on top of a certain number of patterns. When we normalized the droplet size with the corresponding pattern size, we observed a "wetting similarity" that linear microscopic contact angle variations over different size heterogeneities continuously line up. This shows that the pinning force remains constant and the resulting pinning effects are scalable by the size ratio between the droplet and pattern, independent of the size-scale. The slope of these microscopic linear variations decreases with an increase in the droplet size as observed through the macroscopic behavior. We further found a universal behavior in the variation of the corresponding pinning forces, independent of the wetting condition. In macroscopic behavior, pinning effects become negligible and the contact angle reaches the equilibrium value of the corresponding surface when the diameter of the free-standing droplet is approximately equal to 24 times the size of the surface structure. We found that the pinning effect is scalable with the droplet volume, not the size of the droplet base.Article Citation - WoS: 32Citation - Scopus: 37Mcdm Analysis of Wind Energy in Turkey: Decision Making Based on Environmental Impact(Springer Verlag, 2018) Değirmenci, Sinem; Bingöl, Ferhat; Sofuoğlu, Sait CemilDevelopment of new wind energy projects require complex planning process involving many social, technical, economic, environmental, political concerns, and different agents such as investors, utilities, governmental agencies, or social groups. The aim of this study is to develop a tool combining Geographic Information System (GIS) and Multi-Criteria Decision-Making (MCDM) methodologies, and its application for Turkey as a case study. A variety of constraints and criteria were identified based on a literature review and regulations gathered from variety of agencies, use of which resulted in determination of infeasible sites. Then, pairwise comparisons were carried out using analytic hierarchy process as the MCDM method to estimate relative importance of the criteria, and to visualize a suitability map with three classes. As the final stage, decision making was carried out based on environmental impact where 45.5% of the Turkish territory was found as infeasible area. Sixty percent of the remaining area are covered by the moderate suitability class, followed by the highly suitable area (20.3%) and low suitable area (19.8%). The output of this study can be used by energy planners to estimate the extent that wind energy can be developed based on public perception, administrative, and environmental aspects