• Energy Research

Abstract In order to decrease the dependency on petrol-originated energy resources, the utilization of different energy resources in internal combustion engines has been the center of interest of researchers. The main renewable alternative combustible species are ethanol, methanol, hydrogen, biodiesel, and biogas. On the other hand, appearing as a by-product during alcohol production via fermentation, the fusel oil is another alternative energy resource which can be used in internal combustion engines. Containing high alcohols, fusel oil is dark brown colored alcohol mixture, and has a strong odor. The calorific value of fusel oil close to other alternative combustible types ones and the limited number of researches on utilization of fusel oil, an alcohol derivative, in internal combustion engines constitute the base of this research. In this study, the effects of the mixture of unleaded gasoline and fusel oil on engine torque, brake specific fuel consumption and exhaust emissions in a single cylinder, spark ignition engine having port-type fuel infection system at various engine speeds and loads have been investigated. As a result of research carried out, as the amount of fusel oil in mixture increased, the improvements have been observed in engine torque at all of engine speeds and loads compared to pure unleaded gasoline. It has been determined that the brake specific fuel consumption and carbon monoxide (CO) and hydro-carbon (HC) emissions have increased while nitrogen-oxide (NO x ) emissions have decreased.

Abstract In this study, the effect of rhombic drive and crank drive mechanisms on the performance of a beta-type Stirling engine was investigated by nodal analysis. Kinematic and thermodynamic relations for both drive mechanisms were introduced and a Fortran code was written for the solution. Piston strokes, cylinder and displacer diameters, hot and cold end temperatures, regenerator volumes and heat transfer surface areas were taken equal for both engines with two different drive mechanisms. In the analysis, air was used as the working gas. Engine power and efficiency were compared for different charge pressure values, working gas mass values, heat transfer coefficients and hot end temperatures. Maximum specific engine power was 1410 W/L for the engine with rhombic drive mechanism and 1200 W/L for the engine with crank drive mechanism at 4 bars of charge pressure and 500 W/m2K heat transfer coefficient. Rhombic drive mechanism was relatively advantageous at low working gas mass values and high hot end temperatures. In comparison with the engine having rhombic drive mechanism, the relatively poor kinematic behaviour of the engine having crank drive mechanism caused lower engine efficiency and performance. Heat transfer coefficient was also predicted by using an experimental pressure trace.

Abstract Diesel engines are used widely as they have lower fuel consumption and higher thermal efficiency in transportation sector. However, the emitted high NO x , CO and soot emissions have led researchers to search different alternative fuels. At this point, diesel fuels emulsions help to reduce exhaust emissions. In this study, the effects of diesel fuel emulsions containing 5% (E5) and 10% (E10) water on engine performance an exhaust emissions has been investigated. Mono ethylene glycol was used as an auxiliary emulsifier in the preparation of the emulsion. Use of the mono ethylene glycol reduced the subsidence rate of the E5 and E10 about 34.5% and 47.1% respectively. The experiments were conducted at full load condition and at 2500, 3250 and 4000 rpm engine speeds. Engine torque and power increased according to diesel fuel between 2400 and 3600 engine speed range when emulsified fuels were used. But significant reductions were observed after that engine speed range. It was observed that the nitrogenoxide (NO x ) emission reduced 5.42% and 11.01% with using E5 and E10 fuel respectively according to diesel fuel at 2500 rpm. Also the soot emissions reduced 12.39% and 22.97% with using E5 and E10.

Çevresel kirlenmenin yol açtığı endişelerin giderek artması, içten yanmalı motorlarda daha temiz ve yenilenebilir yakıtların kullanımını arttırmıştır. Biyodizel pek çok ülkede dizel motorlarda alternatif yakıt olarak kullanılmaktadır. Bununla birlikte, dizel yakıtı ile karşılaştırıldığında biyodizelin yüksek viskozitesi ve buna bağlı olarak daha kötü atomizasyon karakteristiği kullanım alanının sınırlı kalmasına neden olmaktadır. Biyodizelin bu özelliklerinin iyileştirilebilmesi amacıyla çeşitli katkı maddeleri kullanımı üzerine araştırmalar gerçekleştirilmiştir. Bu çalışmada, karbon nanotüp katkı maddesinin, biyodizel-dizel yakıtı ile çalışan tek silindirli direkt enjeksiyonlu bir dizel motorunda performans ve emisyon karakteristiklerine etkileri incelenmiştir. Tam yükte motor hızına bağlı olarak gerçekleştirilen deneylerde, termik verim, motor gücü ve torku ile egzoz emisyonları incelenmiştir. Maksimum tork devrinde silindir içi basınç ve ısı dağılım oranı da analiz edilmiştir. Karbon nanotüp katkı maddesinin yanma başlangıcını öne aldığı ve termik verimi iyileştirdiği belirlenmiştir. Maksimum termik verim 100 ppm karbon nanotüp katkısı kullanıldığında %39,3 olarak elde edilmiştir. Karbon nanotüp katkı maddesinin CO, HC ve is emisyonlarını azalttığı ancak motor performansının iyileşmesine bağlı olarak NOx emisyonlarını arttırdığı belirlenmiştir. 100 ppm karbon nanotüp katkısının NOx emisyonlarını yaklaşık %11 arttırdığı, buna karşın CO, HC ve is emisyonları %20, %26 ve %7,9 oranında azalttığı tespit edilmiştir.

Abstract In this study, a combined thermodynamic and dynamic analysis of diesel engines has been conducted and a simulation program has been prepared for a three-cylinder conceptual engine having 3 L swept volume. The dynamic model used in the analysis consists of motion equations of pistons, connecting rods and the crankshaft. The dynamic model involves the hydrodynamic and asperity frictions as well as the gas forces and moments. The thermodynamic aspect of the analysis has been modelled by replacing the idealized thermodynamic processes with more realistic processes. In this content, the gas pressure in the cylinder during compression and expansion periods was calculated at polytrophic conditions by means of the first law of the thermodynamics which comprises the heat generation in the cylinder and the heat loss to the cylinder walls. The gas pressures in the cylinder during the intake and exhaust periods have been mathematically modeled by setting a relation between mass variation of the gas in the cylinder and pressure difference in and out of the cylinder. Pressure, temperature and mass variations in the cylinder were found to be compatible with expectations. The numerical results of the mathematical model of intake and exhaust processes have also been compared with experimental data obtained from a test engine and found to be compatible as well. Via the prepared simulation program, the performance of the engine was tested at a constant throttling condition (constant heat input) and at a constant speed. Results obtained from simulation tests were found to be compatible with physical and practical situations. At constant heat input test conducted at 1460 J/cycle heat input, the optimum torque, power and total thermal efficiency of the conceptual engine were determined as 105 N m, 25.7 kW, and 30.15% respectively while the engine speed and intake manifold pressure were 244.5 rad/s and 1.3 bar. At constant speed testing conducted at about 250 rad/s, the optimum torque, power and the effective thermal efficiency of the conceptual engine were determined as 158 N m, 39.7 kW and 34% respectively while the intake manifold pressure is 1.6 bar.

Abstract Compression ignition engines have always been attractive due to high thermal efficiency. Advanced combustion modes have been developed for internal combustion engines to reduce both harmful emissions and fuel consumption. One of these technologies is the reactivity controlled compression ignition (RCCI) mode. Mixture formation in the RCCI engine is provided by a low reactivity fuel injection (port fuel injection) during the intake stroke and stratified high reactivity fuel injection into the cylinder (direct injection) during the compression stroke. In the present study, the effect of reforming gases on RCCI combustion was investigated numerically. The RCCI experimental data were obtained from a previous study performed on a 1.9-liter GM brand gasoline engine fueled with gasoline/diesel fuels. The simulation was performed via Converge Computational Fluid Dynamics (CFD) code, and numerical results were validated with the experimental data. The maximum in-cylinder pressure was recorded as 6.84 MPa with nitrogen addition. It is reached up to 15.12 MPa in case of using hydrogen and nitrogen together. Soot production reached a maximum level of 8.5 × 10 - 3 g/kg-fuel with 72% nitrogen addition. However, soot pollutants were reduced via 4% hydrogen substitution and recorded as 2.3 × 10 - 5 g/kg-fuel. While the in-cylinder gas temperature was 1295 K with 72% nitrogen, it reached 3578.5 K with hydrogen addition.

Summary Because of some advantages such as higher theoretical thermal efficiency, lower pollutant release, working with lower noisy, working with any kind of thermal energy, and having longer life time, Stirling engines receive attentions of academic workers. The development studies related to the drive mechanism as well as the other components of Stirling engine are progressing. In the present study, a beta type Stirling engine with a rhombic-drive mechanism was manufactured and tested. Tests were performed at hot end temperatures of 600 and 800°C for five different stages of charge pressure ranging from 1 to 5 bar with 1 bar increments. Torque and power characteristics of the engine were deduced. The maximum engine torque and power were obtained as 18 Nm and 1215 W at engine speeds of 612 and 722 rpm, respectively, at 4 bar charging pressure. The cyclic work generations of the engine, which is an important parameter indicating the engine performance, were determined as 19, 27, and 25 J corresponding to 1, 3, and 5 bar charging pressures, respectively. In the experiments, the cylinder pressure variation was also measured at various charging pressures. While the charge pressure increases from 1 to 5 bar, the location of the maximum cylinder pressure ranged from 86° to 74° of crankshaft angle, which may have a bit influence on the engine performance. Copyright © 2017 John Wiley & Sons, Ltd.

Karayolu ulaştırma sektörü için emisyon regülasyonlarının giderek sıkılaşması, içten yanmalı motorlarda yeni emisyon azaltma tekniklerinin uygulanmasını zorunlu kılmaktadır. Egzoz emisyonlarının azaltılabilmesi için yanma sonrasında veya yanma sırasında birtakım önlemler alınması gerekmektedir. Düşük sıcaklık yanma çevrimleri hem düşük emisyon seviyeleri hem de yüksek enerji dönüşüm oranı sağlamaları nedeniyle popüler bir araştırma konusudur. Reaktif kontrollü sıkıştırma ile ateşlemeli (RCCI) yanma modu diğer düşük sıcaklık yanma modlarına göre yanma fazının daha kontrol edilebilir olması ve daha geniş bir çalışma aralığı sunabilmesi bakımından avantajlıdırlar. Ancak RCCI modunda motorun her çalışma şartında en yüksek verimi sağlayabilmesi için direkt enjeksiyon püskürtme başlangıcının anlık olarak kontrol edilmesi gerekir. Bu çalışmada sıkıştırma oranı 9,2 olan direkt enjeksiyonlu bir benzin motoru RCCI modda çalıştırılarak, püskürtme başlangıcı yanma fazının (KA50) anlık değişimine göre kontrol edilmiş ve farklı giriş sıcaklıkları için püskürtme avans haritası ile çalışma haritaları elde edilmiştir. En geniş çalışma aralığı 80°C giriş sıcaklığında sağlanmıştır. Minimum özgül yakıt tüketimi 232,3 g/kWh olarak ölçülmüştür. Kullanılan motorun sıkıştırma oranı çok düşük olmasına rağmen özgül yakıt tüketimi değerlerinin oldukça düşük olması yanma fazı kontrolünün başarılı olduğunun bir göstergesidir