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Öğe Effects of equivalence ratio and CNG addition on engine performance and emissions in a dual sequential ignition engine(Sage Publications Ltd, 2020) Yontar, Ahmet Alper; Dogu, YahyaCompared to widening usage of CNG in commercial gasoline engines, insufficient but increasing number of studies have appeared in the open literature during last decades, while engine characteristics need to be quantified in exact numbers for each specific fuel and engine. CNG usage in spark-ignition engine offers many advantages such as high specific power outputs, knock resistance, and low CO(2)emission. Engine performance and emissions are strong functions of equivalence ratio. This study focuses on determination of the effects of equivalence ratio on engine performance and emissions for a unique commercial engine for three fuels of gasoline, CNG, and gasoline-CNG mixture (90%-10%: G9C1). For this aim, the tests and the three-dimensional in-cylinder combustion computational fluid dynamics analyses were employed in quantification of engine characteristics at wide open throttle position. Equivalence ratios were defined between 0.7 and 1.4. The engine's maximum torque speed of 2800 r/min was examined. The tested commercial engine is an intelligent dual sequential ignition engine which has unique features such as diagonally positioned two spark-plugs, dual sequential ignition with variable timing and asymmetrical combustion chamber. This gasoline engine was equipped with an independent CNG port-injection system and a specific engine control unit for CNG. In addition, the engine test system has a concomitant dual fuel delivery system that supplies gas fuel into intake airline while liquid gasoline is injected behind the intake valve. Other than testing the engine, the three-dimensional in-cylinder combustion computational fluid dynamics analyses were performed in Star-CD/es-ice software for the three fuels. The CFD model was built by using renormalization group equations, k-epsilon turbulence model, and G-equation combustion model. Computational fluid dynamics analyses were run for the compression ratio of 10.8:1, equivalence ratio of 1.1, and engine's maximum torque speed of 2800 r/min. Test results show that brake torque for all fuels increases rapidly from the lean blend to the rich blend. The brake-specific fuel consumption for all fuels decreases from phi = 0.7 through the stoichiometric region and then slightly increases up to phi = 1.4. The volumetric efficiencies for three fuels have similar decreasing trend with respect to equivalence ratio. Overall, CNG addition decreases the performance values of torque, brake-specific fuel consumption, volumetric efficiency, brake thermal efficiency, while it decreases emissions of CO2, CO, HC, except NOx. Engine model results show that the maximum in-cylinder pressure is 72 bar at 722 crank angle degree (CAD), 68 bar at 730 CAD, and 60 bar at 735 CAD for gasoline, CNG, and G9C1, respectively. The cumulative heat release for gasoline is 9.09% higher than G9C1, while G9C1 is 15.71% higher than CNG. The CO(2)mass fraction for gasoline is about 22.58% lower than G9C1, while it is 40.32% higher than CNG. The maximum mass fraction value of CO is 0.21, 0.17, and 0.08 for gasoline, CNG, and G9C1, respectively. The CO for G9C1 is overall 60.04% lower than CNG and 67.45% lower than gasoline. At maximum point, HC for G9C1 is 31.43% and 71.43% higher than gasoline and CNG, respectively. CNG has the highest level of NO(x)formation. Maximum NO(x)mass fractions are 0.0098, 0.0070, and 0.0043 for CNG, G9C1, and gasoline, respectively. After the ignition, the flame development is completed at 1.07, 1.18, and 1. 28 ms for gasoline, G9C1, and CNG, respectively. Flame velocities are 28.52, 30.93, and 34.11 m/s for CNG, G9C1, and gasoline, respectively, at 2800 r/min and phi = 1.1. When the time between ignition moment and top dead center moment is considered, the increment rate of flame center temperature is 904.19, 884.10, and 861.77 K/s for CNG, gasoline, and G9C1, respectively. The highest temperature increment rate occurs for CNG.Öğe Experimental investigation of effects of single and mixed alternative fuels (gasoline, CNG, LPG, acetone, naphthalene, and boron derivatives) on a commercial i-DSI engine(Taylor & Francis Inc, 2024) Dogu, Yahya; Yontar, Ahmet Alper; Kantaroglu, EmrahA commercial i-DSI (Intelligent-Dual Sequential Ignition) engine is tested to investigate performance and emissions for single fuels and alternative fuels mixed into gasoline. The novelty of the study is the first time testing of the unconventional mixture of boron derivatives and quantification and comparison of real engine characteristics for 11 different fuels for the same commercial engine. Tested single fuels are gasoline (G100), CNG (CNG100), and LPG (LPG100). While the engine runs with gasoline, gaseous fuels are injected into the intake line at a mass rate of 10% CNG (CNG10) and 5% LPG (LPG5). The engine is also tested by adding 25-50% acetone (A25-A50) and 50% naphthalene (N50) into gasoline. Tests are also performed by mixing boron derivatives of borax-pentahydrate (BP), anhydrous-borax (AB), and boric-acid (BA) into gasoline. Tested fuels worsen engine performance compared to gasoline, except for brake specific fuel consumption (BSFC). There is a positive change in emissions for tested fuels compared to gasoline, except that NOx increases 4-5 times for CNG and LPG. One of the important findings is that, for boron-gasoline mixtures, the torque reduces by 4.0% for BP, 4.4% for AB, and 4.4% for BA. The volumetric efficiency decreases by 6.3% for BP, 7.3% for AB, and 8.5% for BA. The BSFC decreases 5.8% for BP, increases 0.4% for AB and decreases 15.2% for BA. Boron derivatives dissolved in gasoline diversely affect combustion and give some advantage in particular for BA and BP in terms of BSFC. In addition, boron-gasoline reduces the formation of HC and NOx.Öğe Influence of acetone addition into gasoline for i-DSI engine(Springer India, 2022) Kantaroglu, Emrah; Yontar, Ahmet Alper; Dogu, YahyaDespite the notable properties of acetone due to its volatility and oxygen content as a fuel additive, very few studies have been limited to small size special purpose engines. A comparative testing and 3D in-cylinder combustion CFD studies are presented for acetone-gasoline blend in an i-DSI commercial car engine as the first time. The blends contain mass ratio of acetone by 0-2-5-10-20% (G100-A2-A5-A10-A20). In testing, torque reduced 0.33% (A2), 0.66% (A5), 0.84% (A10), and 1.45% (A20) compared to gasoline. The BSFC decreased by 0.27% (A2), 0.55% (A5), 0.79% (A10), and increased 0.26% (A20). Volumetric efficiency decreased by 3.2-6.4-5.1-11.5% for A2-A5-A10-A20. The CO emission for blends is less than gasoline by 1.5% (A2), 4.0% (A5), 15.2% (A10), and 33.6% (A20). The CO2 decreased 0.8% (A2), and increased 1.3% (A5), 4.6% (A10), and 11.4% (A20). The HC reduced by 7.0% (A2), 10.1% (A5), 23.8% (A10), and 34.4% (A20). The NOx formation increased by 3.6% (A2), 4.4% (A5), 27.6% (A10), and 87.8% (A20). Acetone addition decreased torque and slightly increased BSFC. CO and HC decreased while CO2 and NOx increased with increasing acetone ratio. Acetone indeed improves the combustion while its final effect on engine performance is not found to be favorable.Öğe Investigation of ignition advance effects for CNG usage in a sequential dual ignition gasoline engine by using in-cylinder combustion cfd analysis(Gazi Univ, Fac Engineering Architecture, 2019) Yontar, Ahmet Alper; Dogu, YahyaIn this study; for a sequential dual ignition gasoline engine, the effects of ignition advance on engine characteristics and in-cylinder flame propagation have been numerically investigated for CNG usage with an in-cylinder combustion model. A CFD model for a single cylinder of the four-cylinder Honda L13A4 i-DSI engine with a sequential dual spark ignition is constructed in STAR-CD software for CNG usage by considering all components related to the combustion chamber (intake-exhaust manifold connections, intake-exhaust valves, cylinder, cylinder head, piston, spark-plugs, etc.). By using the CFD analyses for CNG usage, the optimum ignition advance is determined for the prescribed engine operating conditions of 3000-rpm engine speed, 10.8:1 compression ratio, and 1.2 air-fuel ratio. Analyzes are performed by varying the ignition advance in a wide range (60 degrees-10 degrees CAD and 55 degrees-5 degrees CAD ignition advance for the lst-2nd spark plugs, respectively). For engine operating conditions examined, it has been determined that the 30 degrees-25 degrees CAD advance value for the 1st-2nd spark plug from the top dead point is the optimum ignition advance in terms of engine performance and emission balance. For CNG, ignition advances have increased compared to gasoline. The in-cylinder flame propagation is visualized and evaluated for all investigated conditions.
