Yazarlar
Yayınlar
- MakaleYalnız künye2017EXPERIMENTAL INVESTIGATION THE EFFECTS OF ETHANOL AND DIETHYL ETHER ADDITION INTO DIESEL FUEL ON ENGINE PERFORMANCE AND EXHAUST EMISSIONS
Sezer, Ismet
In this study, effects of ethanol and diethyl ether addition into diesel fuel on the performance and emissions of a diesel engine were experimentally investigated. A commercial diesel fuel and three different blends prepared with 15% ethanol, 15% ethanol and 2% diethyl ether and 15% ethanol and 4% diethyl ether were used in the tests. The experiments were performed at an engine speed of 1500 rpm and under various loads by using a single cylinder direct injection diesel engine. The injection, combustion, performance and emissions parameters were evaluated for baseline fuel and blends. The results show that, the injection pressure decreases for all blends, and diethyl ether addition causes a delay in the injection timing. The burnt mass fraction is lower for ethanol and diethyl ether blends during early combustion phase, while it increases for diethyl ether blends during the progressive combustion phase. Ethanol and diethyl ether blends also give the reductions in the cylinder pressure and temperature. Air excess coefficient increases the rate by 9.3-10.4%, but exhaust gas temperature decreases the rate by 4.8-5.5% when using ethanol and diethyl ether blends. Although ethanol blend causes a decrement of 1.4% in engine power, reductions in engine power are between 0.3% and 1.1% for diethyl ether blends. Both ethanol and diethyl ether blends yield increments the rate by 14.7-17.2% in brake thermal efficiency and a reduction of 8.5% in brake specific fuel consumption. The reductions were obtained the rate by 6.8-18.2% for NOx and 10.3-13.8% for CO2 emissions, when using the blended fuels. Ethanol and diethyl ether blends cause the increments the rate by 5-12.5% for HC emission, while CO emission fluctuates depending on the engine load.
- MakaleYalnız künye2015PRESSURE-DRIVEN LAMINAR PULSATING FLOW IN A PIPE: EFFECT OF THE AMPLITUDE
Aygün, Cemalettin; Aydin, Orhan
In this study, pressure-driven laminar pulsating flow in a pipe is examined numerically. Both the hydrodynamically developing flow and fully developed conditions are considered. A commercially available CFD package, FLUENT, is used in the simulations. A constant value of the time-averaged Reynolds number is considered, Re=1000. Six different values of the dimensionless frequency (F=0.01, 0.1, 1, 10, 100, 1000) and three different values of the dimensionless amplitude (A=0.1, 0.5 and 0.95) are considered. Both the hydrodynamically developing and fully developed flows are analyzed. Effects of the amplitude and frequency of the pulsating inlet velocity on the friction coefficient as well as velocity field are predicted.
- MakaleYalnız künye2013COMPARATIVE INVESTIGATION THE USE OF METHANOL AND METHYL TERTIARY BUTYL ETHER IN GASOLINE ON ENGINE PERFORMANCE, CO EMISSIONS AND FUEL COST
Sezer, Ismet; Bilgin, Atilla
This study is concerned with investigating experimentally the effects of methanol and Methyl tert-Butyl Ether (MTBE) blending to base gasoline on the performance CO emissions and fuel cost of a spark ignition (SI) engine. The fuel blends were prepared by addition 5, 10, 15, and 20 vol % of methanol and MTBE with a specified amount of base gasoline. The methanol- and MTBE-gasoline blends were designated as M5, M10, M15, M20, and MTBE5, MTBE10, MTBE15, MTBE20, respectively. Experiments were conducted under various engine speeds, spark timings (STs), and compression ratios (CRs). The engine was operated under wide-open throttle conditions. The results of the study showed that the M5 and MTBE10 blends yield the best engine performance in terms of the brake mean effective pressure (bmep), while the M20 and MTBE15 blends are the best performers in terms of brake thermal efficiency (bte). Moreover, M20 and MTBE10 blends give the minimum CO emission values. The economical analysis performed in the study is based on both the current blending fuel prices in Turkey and brake specific fuel consumption (bsfc) of the engine while using gasoline, methanol-gasoline, and MTBE-gasoline blends. It was obtained that, in contrast to the improvement of engine performance, efficiency and CO emissions, methanol and MTBE blends caused increases in fuel costs because of the expensive methanol and MTBE prices in Turkey. Uncertainty analysis was also performed in this study, and it was found that; the uncertainties in the measurement devices do not have noticeable influences on the variations of engine characteristics.
- MakaleYalnız künye2011The effect of fin pitch on heat transfer and fluid flow characteristics in the entrance region of a finned concentric passage
Kuvvet, Kemal; Yavuz, Tahir
In this study, the heat transfer and fluid flow characteristics in the unfinned and internally finned concentric passage (smooth and finned annulus) are investigated experimentally. The turbulence characteristics, mean flow, pressure drop and heat-transfer parameters in the entrance region of a concentric passage of diameter ratio 0.2 are measured. The hot-wire anemometer and the liquid-crystal technique are used for the turbulence and mean flow and the heat transfer measurements, respectively. The finned passage is designed as the fin width (W) of 2 mm, the fin height (H) of 2, 4, 6 and 8 mm and the fin pitch (P) of 20, 30 and 40 mm. Reynolds number ranges from 1.8 .104 to 1.24.105 and from 1.65.104 to 7.65.104 for flow and pressure drop and heat transfer measurements, respectively. Experiments are performed for the smooth and finned concentric passages by varying flow and fin parameters and the effects of the fin pitch are investigated. The developing of fluid flow is analyzed and the variation of turbulence intensity, friction factors, local and mean convective heat transfer coefficients in the smooth and finned concentric passages are obtained. Results obtained in the finned concentric passages are compared with the results of the smooth passage. For the average Nusselt numbers and friction factor, empirical equations are developed. As a result, it is seen that the friction factor in the finned passage increases between 3.61 and 18.05 times while the average Nusselt number augments between 1.36 and 5.23 times on the inner surface and between 1.03 and 1.80 times on the outer surface.
- MakaleYalnız künye2010Natural convection in a triangular cross section roof under daylight conditions
Küçük, Haydar; Gedikli, Hasan
The natural convection is numerically investigated in a roof of triangular cross section under constant heat flux with seven different values depending on daylight on the inclined wall, constant wall temperature on the bottom wall and adiabatic on the vertical wall boundary conditions. Continuity, momentum and energy equations are solved by using fmite volume method for laminar, two-dimensional and steady-state regime. Streamlines, isothenns, local and mean Nusselt numbers are p̧resented for AR=0.25, 0.5, 0.75 and 1.0 and Ra=103, 104, 105, 106. The amount of heat flux ranges from 163 W/m2 to 808 W/m2 depending on daylight and the Prandtl number is chosen as 0.7. It is found out that the aspect ratio and Rayleigh number highly affect the heat transfer on the bottom and inclined walls while heat flux slightly affects.