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A comparative study to evaluate the effects of pre-chamber jet ignition for engine characteristics and emission formations at high speed
(Pergamon-Elsevier Science Ltd, 2020) Yontar, Ahmet Alper
The pre-chamber ignition technology is a good solution that can make spark-ignition engines gradually more efficient. The novelty of the study is the testing of the pre-chamber jet ignition according to detailed air-fuel mixture range and fuel injection rates by combustion chambers. The main points in using this pre-chamber jet ignition were to observe the effect of reducing fuel consumption and emission formation. The tests were carried out for 0.80-1.80 lambda ranges and the pre-chamber injection/main chamber injection mass ratio ranges. A commercial RON 98 fuel was used at two ignition modes in tests for 5000 rpm high engine speed. At the pre-chamber jet ignition usage, the in-cylinder pressure for 1.00 lambda is overall 1.78% and 19.89% higher than the 0.80 lambda and the 1.80 lambda. The brake specific fuel consumption is about 8.67% lower than the spark-plug ignition usage at 0.80-1.20 lambda range. The HC formation is overall 8.12% lower than the spark-plug usage. The NOx formation for the spark-plug ignition is approximately 53.97% higher than the pre-chamber jet ignition usage as the temperature in-cylinder is high. The pre-chamber jet ignition was led to a much shorter flame development time and better combustion stability than the spark-plug. (C) 2020 Elsevier Ltd. All rights reserved.
An experimental study on droplet-scale combustion and atomization behavior in pure ethanol, methanol, and trimethyl borate, and their blends
(Elsevier Sci Ltd, 2024) Degirmenci, Huseyin; Kucukosman, Ridvan; Yontar, Ahmet Alper
The combustion and atomization behavior of pure ethanol (EtOH), methanol (MeOH) and trimethyl borate (TMB) fuels and their blends prepared at 20 wt%, 40 wt%, 60 wt% and 80 wt% ratios were determined by processing videographs recorded with a high-speed camera and temperature data recorded with a thermal camera during droplet-scale combustion experiments performed at atmospheric pressure. EtOH and MeOH are good alternatives for transport due to their high oxygen content and relatively short carbon chains. TMB, an organoboron derivative in the liquid phase, is unique to creating a low-carbon emission and high-energy alternative fuel blend with boron, oxygen, and short carbon chains. This study focuses on the preparation of EtOH, MeOH, and TMB fuels and homogenized fuel mixtures with high energy values and the characterization of their combustion behavior. The experiments were carried out by suspending ethanol-trimethy borate (EtOHTMB) and methanol-trimethyl borate (MeOH-TMB) fuel droplets on SiC wire and igniting them with an electrode producing an arc of 1 ms duration at 20 ms intervals with 6 kV energy. The results showed that EtOH and TMB formed a homogenized fuel mixture at all mixing ratios and the largest and most homogeneous green luminescence flame envelopes (depending on boron oxidation) were formed, indicating BO2 formation in almost all fuel mixtures. On the other hand, the droplets of MeOH-TMB fuel mixtures containing 20 wt%, 40 wt%, and 60 wt% MeOH exhibited the most favorable trend to the D2-law of diameter reduction during combustion. EtOHTMB fuel droplets containing 60 wt% TMB exhibited the highest maximum flame temperature of 631 K. In this study, it has been shown that new-generation hybrid transportation fuels with no phase separation, low ignition delay times despite increased oxygen content, and high calorific value can be produced with hybrid fuel blends to be formed with TMB and alcohols. The results obtained will shed light on the literature for the solution to the problematic combustion characteristics of boron, which is tried to be used in many areas of the transportation industry.
Atomization and combustion behavior of nanofuel droplets containing perovskite-type nanoparticles
(Elsevier Ltd, 2023) Küçükosman, Rıdvan; Akçay, Aleyna; Yontar, Ahmet Alper; Ünlü, Cumhur Gökhan; Ocakoglu, Kasım
Metal and metal oxide nanoparticles (NPs) are promising agents for reducing energy consumption and pollution in applications where combustion power generation is provided. This study focuses on the production of new generation perovskite-type metal oxide NPs with enhanced catalytic activity customized for combustion and investigation of their catalytic performance for gasoline. The droplet scale combustion experiments were carried out at ambient temperature, atmospheric pressure and under normal gravity, the experimental processes were recorded with an optical system consisting of a high-speed camera and a thermal camera with a spectral range of 7.5–14 ?m, and the combustion and atomization behavior of the nanofuel droplets were characterized. Perovskite-type NPs were produced by sol-gel technique in varying stoichiometric ratios (LaMnO3, La1- XNdXMnO3, La1-XBaXMnO3, Nd1-XBaXMnO3, La0.5NdXBa0.5-XMnO3, x = 0, 0.3) to confirm their catalytic activity’s effect on gasoline droplets’ combustion behavior. Structural characterization of the obtained five different NPs was carried out by SEM and XRD techniques. Chemical analysis, surface area measurements, and spectral properties of the samples were determined by XPS, BET, and UV–Vis spectroscopy, respectively. The results showed that all perovskite-type NPs have particle size range of 25–40 nm. La0.7Nd0.3MnO3 NPs had the highest oxygen adsorption ability and La0.5Nd0.3Ba0.2MnO3 NPs had the largest surface area (393.4898 m2 /g). Perovskite type NPs tended to increase ignition delay and extinction times. The maximum flame temperature of fuel droplets loaded with La0.5Nd0.3Ba0.2MnO3 NPs was 469 ?C. This temperature was 274 ?C higher than the maximum flame temperature of the pure gasoline droplet. The outcomes demonstrated that, with the right catalyst design, perovskite-type NPs can perform better as powerful oxidizers and high energy combustion catalysts.
Combustion and secondary atomization behavior of nanofuel droplets laden with hematite, magnetite and lanthanum orthoferrites nanoparticles
(John Wiley and Sons Inc, 2023) Küçükosman, Rıdvan; Yontar, Ahmet Alper; Gökhan Ünlü, Cumhur; Ocakoğlu, Kasım
Current research concerns the droplet combustion behavior of gasoline-based nanofuel droplets containing hematite (Fe2O3), magnetite (Fe3O4) and lanthanum orthoferrites (LaFeO3, La0.5Fe1.5O3 and La0.75Fe1.25O3) perovskite type nanoparticles (NPs) at 2.5 % wt. particle loadings. The results showed that the size distribution of hematite and magnetite NPs is on the 90–100 nm scale, while the lanthanum orthoferrites NPs have a particle size distribution of 25–40 nm. The particles with the largest surface area (78,5098 m2/g) and enhanced oxygen adsorbing ability were La0.5Fe1.5O3 NPs. Droplet combustion experiments were recorded with a high speed camera and a 7.5–14 ?m spectral area thermal camera. Fe3O4 and LaFeO3 NPs high agglomerate tendency allowed only a single microexplosion event in nanofuel droplets towards the end of the experiment. Only the G/La0.5Fe1.5O3 fuel droplets trended to obey the D2-law. Nanofuel droplets containing La0.5Fe1.5O3 NPs exhibited the highest maximum flame temperature of 264 °C. The catalytic activity of lanthanum orthoferrite perovskite-type NPs during combustion was improved due to the decrease in the La ratio in the A-site and the increase in the Fe ratio in the B-site.
Combustion Behavior of Fuel Droplets with Metallic, Non-Metallic and Organo-Metallic Boron Additives
(Taylor and Francis Ltd., 2024) Küçükosman, Rıdvan; Değirmenci, Hüseyin; Yontar, Ahmet Alper; Ocakoğlu, Kasım
There is considerable interest in the utilization of fuels derived from boron materials, with their high calorific value, in various applications ranging from propellants to pyrotechnics. Conversely, their impact on the combustion behavior of conventional hydrocarbon fuels remains largely unclear. In this study, ignition, combustion, micro-explosion and simultaneous atomization behaviors of gasoline-based alternative fuels containing metallic (28–35 µm MgB2), nonmetallic (1 µm amorphous boron, 10 µm AlB12 with 86–88% and 95–97% purity) and organo-metallic boron derivatives (triethyl borate (TEB) containing C2H5 groups and trimethyl borate (TMB) containing CH3 groups) were investigated. The experiments were carried out at droplet scale and recorded using a high-speed camera and a thermal camera. The findings revealed a systematic reduction in ignition delay for each gasoline fuel enriched with boron derivatives. 2.5%AlB12/G and pure TMB droplets were the fastest extincting fuel droplets (0.9678 s and 1.245 s, respectively). The highest maximum flame temperature was recorded as 626 K and 610 K for pure TMB and 80%TEB/G, respectively. Droplet diameter regression analyses showed that the diameters of fuel droplets containing predominantly metallic and nonmetallic boron derivatives decreased in accordance with the d2-law. This study demonstrated that cost-effective and easily producible amorphous boron and organometallic boron derivatives are promising energy carriers for hydrocarbon fuels.
Combustion characteristics of gasoline fuel droplets containing boron-based particles
(Elsevier Science Inc, 2023) Kucukosman, Ridvan; Degirmenci, Huseyin; Yontar, Ahmet Alper; Ocakoglu, Kasim
Boron-based particles are dense energy carriers that are promising for a future carbon-neutral world, to store and transport abundant energy. Although it is prominent as a slurry fuel component in liquid aviation fuels, its effects on the combustion behavior of traditional hydrocarbon fuels used in public or industrial areas have not yet been clarified. In this study, combustion characteristics of gasoline-based fuel droplets containing 86-88%, and 95-97% < 1 mu m amorphous boron, 10 mu m AlB12, 28 - 35 mu m MgB2 particles and 1% oleic acid surfactant. The experimental process was recorded via a high-speed camera and a thermal camera. The results showed that the ignition delay time was reduced in all gasoline-based fuels containing boron-based particles. The fuels with the lowest extinction time were gasoline-based fuel droplets containing AlB 12 particles (similar to 1245 ms). Amorphous boron particles were transported to the flame region more than other particles and caused severe atomization phenomena. The highest maximum flame temperature for gasoline droplets at 2.5% particle load was recorded in high-purity amorphous boron particles with 537 K. At 7.5% particle load, the highest flame temperature and agglomerate temperature were observed at 513 K and 653 K, respectively, in gasoline droplets containing high-purity amorphous boron particles. In electric field tests, the shortest extinction time was detected for gasoline droplets with MgB12. Also, the addition of amorph boron particles into gasoline increase of 4.6% was seen in the flame speed. Droplet diameter regression plots show that particulate gasoline-based fuel droplets exhibit a decreasing trend, mostly following the D-2-law. It has been revealed low-cost amorphous boron derivatives can be an important energy carrier for liquid hydrocarbon fuels. (c) 2023 The Combustion Institute. Published by Elsevier Inc. All rights reserved.
Combustion Characteristics of r-GO/g-C3N4/LaFeO3 Nanohybrids Loaded Fuel Droplets
(Taylor and Francis Ltd., 2023) Küçükosman, Rıdvan; Değirmenci, Hüseyin; Sert, Buse; Yontar, Ahmet Alper; Harputlu, Ersan; Ocakoğlu, Kasım
Graphene oxide (GO), reduced graphene oxide (r-GO) and graphitic carbon nitride (g-C3N4) are two-dimensional carbon-based nanosheets that show promise in reducing emissions with their superior catalytic activity in capturing species such as NOx and CO2 thanks to their oxygen- based functional groups and active edges on their surfaces. These active surfaces also provide a scheme for the substitution of materials with high calorific value or high catalytic activity for combustion. This study focuses on the fabrication of functional nanohybrid structures customized for combustion with LaFeO3 metal oxide nanoparticles substituted on these nanosheets and their effect on the combustion behavior of gaso-line. The fabrication of r-GO/g-C3N4/LaFeO3 nanohybrid structures was carried out by a two-step hydrothermal method. The structural character-izations of the samples were confirmed by SEM and XRD analyses and their chemical states were confirmed by Raman and XPS techniques. Combustion experiments were carried out by droplet scale combustion of gasoline-based nanofuel droplets containing dilute (0.2 wt.%) and high (0.7 wt.%) concentrations of GO, r-GO, g-C3N4, g-C3N4/LaFeO3 and r-GO/g- C3N4/LaFeO3 nanoparticles. The experimental process was recorded with a high-speed camera and a thermal camera. The nanofuel droplets con-taining 0.2 wt.% g-C3N4/LaFeO3 nanohybrid structures had the highest maximum flame temperature of 519 K, and the nanofuel droplets con-taining 0.7 wt.% r-GO/g-C3N4/LaFeO3 particles had the highest maximum aggregate temperature of 1177 K. The ignition delay time decreased for all droplets with 0.2 wt.% and 0.7 wt.% particle loadings. At 0.2 wt.% concentration, g-C3N4 doped fuel droplets exhibited the lowest extinction time, while at 0.7 wt.% concentration, the lowest extinction time was measured for r-GO/g-C3N4/LaFeO3 doped fuel droplets. Fuel droplets containing g-C3N4 particles had the highest burning rate and were the fastest extinguishing fuel droplets in the electric field. In this study, it has been demonstrated that the combustion rate and energy value of hydro-carbon fuels can be increased and soot formation can be reduced at the same time with the new generation of graphene-based functional mate-rials to be created, and thus, many combustion problems can be solved simultaneously with these functional particles.
Combustion characteristics of trimethyl borate, diesel, and trimethyl borate-diesel blend droplets
(Elsevier, 2022) Yontar, Ahmet Alper; Özgüner, Ayşe Gizem; Adıgüzel, Mehmet Ali; Üstün, Deniz
In this study, droplet tests were carried out for pure and blended forms of diesel fuel, which is the traditional fuel, and trimethyl borate fuel, which is new generation fuels. In this context, the evolution of fuel droplet diameter, flame structure, and flame temperature over time was observed using a high-speed camera and a thermal camera simultaneously. Measurements were made for the addition of 20%, 40%, 60%, and 80% trimethyl borate fuel to diesel fuel in fuel blends. The curves of the time-dependent change of the dimensionless square of the droplet diameter (D/D0)2 of the fuel droplets considered in the study, in general, have been determined to comply with the D2-law. Also, as the amount of diesel rose, there were high changes in droplet distortion and high deviations from the hemispherical geometry, and also elongation in the dominant shape droplet shape changed times. While the highest flame temperature was monitored by the thermal camera in the flame formed by the trimethyl borate droplet, as the amount of diesel fuel in the mixture increased, the maximum flame temperature decreased, but the burning time of the droplet was prolonged. On the other hand, the shortest ignition delay was measured for trimethyl borate, while the longest ignition delay time was detected for diesel fuel droplet. In general, it has been observed that the addition of trimethyl borate reduces the ignition delay, shortens the extinction time, and increases the temperature during combustion compared to diesel.
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, Yahya
Compared 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.
Effects of Spinel Oxide Combustion Catalysts on the Combustion Behavior and Secondary Atomization Mechanism of Gasoline Droplets
(Taylor & Francis Inc, 2025) Kucukosman, Ridvan; Yontar, Ahmet Alper; Unlu, Cumhur Gokhan; Ocakoglu, Kasim
The catalytic activity of Mg-based spinel oxide nanoparticles (NPs) on the combustion behavior of gasoline and their effects on the atomization behavior were determined by droplet scale combustion experiments. MgFe2O4, MgCo2O4 and MgMnO3 spinel oxide NPs were produced by the sol-gel technique and doped into gasoline. The particles with the highest surface oxygen were MgCo2O4 and MgFe2O4 NPs, while the NPs with the largest surface area were MgCo2O4 NPs (517.8433 m(2)/g). The size of the flame envelope tends to shrink as the oxygen concentration of the particles rises, but an increase in their surface area tends to shorten ignition delay periods. MgFe2O4 NPs increased the flame temperature by 163 & DEG;C compared to the pure gasoline. While MgFe2O4 and MgMnO3 NPs increased the extinction time of gasoline, MgCo2O4 NPs decreased the severe time by about 75% with the violent micro-explosions they created. In this study, we focused on the production of spinel oxide agents customized for combustion with improved catalytic activity, high flammability, and different component designs, and the results showed that these particles can reduce the soot formation of conventional hydrocarbons.
Electrocombustion Characteristics of Iron Particle-Laden Methanol and Ethanol Droplets in a Direct Current Field
(Taylor & Francis Inc, 2024) Kucukosman, Ridvan; Degirmenci, Hueseyin; Yontar, Ahmet Alper
This study investigates the electrocombustion and atomization behavior of single droplets (2.5 wt.% Fe) of ethanol (EtOH) and methanol (MeOH) fuels at the droplet scale. The experiments utilize a system with two opposing plate electrodes of varying distances (200, 150, and 100 mm) and both negative (down arrow) and positive (up arrow) polarizations within a vertical direct current (DC) electric field. The results show that for EtOH and EtOH/Fe droplets, the flame envelope changes to a spherical form at (down arrow) and (up arrow) polarizations at 100 mm plate spacing, while for MeOH and MeOH/Fe droplets, the flame envelope changes to a spherical form at (down arrow) and (up arrow) polarizations at 200, 150 and 100 mm plate spacing. Increasing electric field strength reduced the micro-explosion tendency of Fe particles in the flame region and the micro-explosion intensity of Fe particles was found to be higher in ethanol droplets than in methanol. No systematic relationship could be established between the electric field effect and the presence of Fe particles. The MeOH/Fe/150(up arrow) droplet exhibited the lowest extinction time of 1050 ms. The electric field fundamentally alters the secondary atomization process of the fuel droplets. Notably, the diameter regression of all MeOH-based fuel droplets deviates significantly from a linear relationship. The investigation into the combustion behavior of pure EtOH, MeOH, and their Fe-blended counterparts within an electric field environment suggests that MeOH and MeOH/Fe fuels exhibit superior combustion characteristics. However, further research is necessary to fully elucidate these findings.
Enhancing Droplet Combustion Dynamics in Trimethyl Borate-Based Blends: Exploring Energetic Phenomena
(Taylor & Francis Inc, 2024) Yontar, Ahmet Alper; Degirmenci, Hueseyin; Kucukosman, Ridvan
Trimethyl borate (TMB) is an excellent alternative to alter the combustion of conventional fuels due to the combination of boron, stable methyl groups, and oxygen, which can improve the combustion behavior in many ways compared to alcohols and etheric hydrocarbon structures. In this research, the combustion and energetic phenomena trends of trimethyl borate blends was investigated on a droplet scale. The camera systems were used at the combustion characteristics look at how the size of the droplets, the structure of the flame, and the flame temperature changed over time. The additions of 20%, 40%, 60%, and 80% trimethyl borate fuel to gasoline were tested for their ability to burn. As the amount of TMB increased, high variations in droplet deformation and high breakups from the hemispheric geometry occurred. At this point, changes were observed in droplet shape change independent of mixing ratio. TMB droplet had the highest flame temperature of 600 K and the lowest extinction time of similar to 1270 ms. As the gasoline content of the droplets increased, the droplet flame temperature tended to decrease. Also, the shortest ignition delay time was observed for pure TMB and fuel droplets containing 40%, 60% and 80% TMB (similar to 0.714 ms). HIGHLIGHTS The highest combustion rate constant was observed in trimethyl borate. The amount of TMB raised in the blend raised high droplet deformation and breakups. The droplet deformation amplitude is at the maximum level for 8G2T. The shortest ignition delay time was noticed for the 20% gasoline 80% TMB blend. The high gasoline content in the blends caused micro-explosions were observed.
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, Emrah
A 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.
Experimental studies on combustion and atomization characteristics of aliphatic and aromatic hydrocarbons droplets
(Elsevier Sci Ltd, 2023) Kucukosman, Ridvan; Yontar, Ahmet Alper; Ocakoglu, Kasim
This study focused on how the properties of alcohols (ethanol, methanol, n-butanol), ketones (acetone), alkanes (hexane), esters (ethyl acetate), methyl benzenes (toluene), and ethers (diethyl ether) shape individual com-bustion and atomization behaviors. The experimentation conducted at the droplet scale involved suspending fuel droplets on a ceramic wire and subsequently igniting them for analysis. Experiments were recorded with a high-speed camera and a thermal camera with a spectral range of 7.5-14 & mu;m. The results showed that the flame of the oxygenated fuel droplets, unlike non-oxygenated fuels, has a high non-luminous region seen throughout the combustion process. The diameter reduction of the fuel droplets during combustion tended to obey the D2-law. Single and multicomponent fuel droplets are hemispherical for preheating (Stage I) and hemispherical in droplet disruption mode for combustion and droplet diameter decrease (Stage II). Hexane, diethyl ether, and ethyl ac-etate were the fuels that were extinguished in the shortest time among the fuels studied here with extinction times of 1.021 s, 0.925 s, and 0.885 s, respectively. Hexane, diethyl ether, acetone, and diesel droplets had the minimum ignition delay times according to the experimental conditions in this study. In terms of maximum flame temperature, ethyl acetate exhibited the highest value among oxygenated fuel droplets, reaching 155 degrees C, while toluene demonstrated the highest maximum flame temperature of 244 degrees C among all fuel types, including non-oxygenated fuels.
Exploring electric field forces and polarization influence on combustion in Fe-additive fuel droplets
(Elsevier Sci Ltd, 2024) Yontar, Ahmet Alper; Kuecuekosman, Ridvan; Degirmenci, Hueseyin
The application of electrical techniques such as electric field, polarization, and ionization in the field of combustion makes many positive developments possible. The electric field effect offers significant advantages in controlling flame stability and reducing soot formation during the combustion of fuels. Also, the conditioning effect can improve particle oxidation during combustion for hydrocarbon fuels containing metal particle inclusions with high calorific value. This study focuses on investigating the combustion and atomization behavior of Fe additive diesel fuel droplets at electric field strengths of E = 5 V/m, E = 6.7 V/m, and E = 10 V/m and in positive (up arrow) and negative (down arrow) electric field directions. The experiments were carried out by igniting a fuel droplet suspended on a ceramic wire with an arc at the center of the electric field between two conductive plates in a combustion chamber with optical apertures. The combustion processes were recorded with an optical system consisting of a high-speed camera and a thermal camera. Combustion and atomization behavior were characterized by sequential flame and droplet atomization images, respectively. The droplet shape change and flame behavior results were comparatively evaluated according to the d2 -law. Ignition delay and extinction times were determined by processing threshold technique and maximum flame temperatures were determined by processing thermal camera images. The results showed that increasing the electric field intensity in the negative electric field direction resulted in improved soot oxidation, and Fe particles burnt efficiently. Ignition delay times showed a decreasing trend with an electric field effect and an increasing trend with the addition of Fe particles. The highest maximum flame temperature and lowest extinction time were recorded as 785 K and similar to 578.34 ms for Diesel/Fe/100(1) fuel droplet, respectively and Fe particles did not exhibit microexplosion phenomena at E = 10 V/m. In this study, it has been shown that an effective oxidation can be achieved for Fe particles by increasing the mobility of ionized species in the flame zone under the effect of electric field and a homogeneous thermal field can be created in the flame zone even in fuels with particle addition at increasing electric field intensities.
Impact of ethanol, methyl tert-butyl ether and a gasoline-ethanol blend on the performance characteristics and hydrocarbon emissions of an opposed-piston engine
(Taylor & Francis Ltd, 2020) Yontar, Ahmet Alper
A prototype opposed-piston engine was tested with gasoline, ethanol, methyl tert-butyl ether (MTBE) and a gasoline-ethanol blend (E85) at full load. This is the first test of an opposed-piston engine considering engine speed, lambda, compression ratio and injection timing parameters, and comparing four fuels for the same engine. Results show that the torque for E85 is higher than for gasoline by about 3.34%. The brake specific fuel consumption (BSFC) for E85 is 30.63% higher than that of MTBE at the minimum BSFC point. The brake thermal efficiency for E85 and ethanol are overall 9.56% and 10.27% higher, respectively, than that of gasoline. At maximum torque speed, the lambda effect tests show the power for gasoline is approximately 3.26% lower than that of ethanol. The unburned fuel emission for gasoline is overall 51.51% lower than for ethanol. The compression ratio effect results show that the torque for gasoline is overall 3.03% and 1.97% less than for MTBE and E85, respectively. The hydrocarbon (HC) emission for gasoline is overall 4.94% and 3.53% higher than for ethanol and E85. The highest brake mean effective pressure areas were observed with ethanol, and the maps show high levels of HC in ethanol and E85.
Influence of acetone addition into gasoline for i-DSI engine
(Springer India, 2022) Kantaroglu, Emrah; Yontar, Ahmet Alper; Dogu, Yahya
Despite 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.
Influence of intake air temperature control on characteristics of a Homogeneous Charge Compression Ignition engine for hydrogen- enriched kerosene-dimethyl ether usage
(Pergamon-Elsevier Science Ltd, 2020) Yontar, Ahmet Alper; Zhou, Mengni; Ahmad, Saif
In this study, the high-speed of 2000 rpm and low-speed of 1000 rpm behaviors on the HCCI test engine at full load were examined experimentally by controlling the intake air temperature. The tests were carried out at 0.90 equivalence ratio for hydrogen-enriched kerosene-dimethyl ether mixture. In order to expand the usage of HCCI engines in daily life, their problems encountered at high loads and high speeds need to be solved. The main reason of these problems is the control of the start of combustion since there is no external combustion system in HCCI engines. The experimental results show that the intake air temperature directly affects engine performance and emissions. The intake air temperature control was led to shorter flame development time and better combustion stability. The in-cylinder pressure at 1000 rpm for 373 K is overall 6.82% and 4.07% higher than the 273 K and 298 K. The average heat release rate curve trends at 1000 rpm are overall 45.68% higher than 2000 rpm. The brake specific fuel consumption for 2000 rpm is about 5.29% higher than 1000 rpm. The differences between the two NO trends are 35.4% maximum and 11.03% minimum for 1000 rpm and 2000 rpm. At high engine speed, the HC formation drops linearly from 488 ppm to 339 ppm with increasing air temperature. Also, the soot formation decreased with a slope of 1.58 times higher than 1000 rpm. Overall, the increase in intake air temperature at the tests positively affected in-cylinder pressure, CO, HC and soot. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.
Influence of laser ignition on characteristics of an engine for hydrogen enriched CNG and iso-octane usage
(Pergamon-Elsevier Science Ltd, 2021) Yontar, Ahmet Alper; Wong, Victor
The study has focused on determining the laser plug effects on engine characteristics and the laser plug usage results have compared with spark plug usage. The laser ignition technique is a type of new ignition technique and an important solution that can make combustion systems more efficient. The testing of an engine with a laser plug is the novelty of the study and the tests were carried out with reference to equivalence ratio and plug power ranges. The behaviors of the engine at full load were examined so experimentally for both ignition techniques at hydrogen enriched CNG and iso-octane mixture usage. The tests were carried out for variations of 0.4-2.0 equivalence ratio and 20-120 W plug power. A mixture that 90% iso-octane and 10% HCNG in mass was used at two ignition modes in tests for 3300 rpm maximum engine torque speed. Also, the flame formation and propagation for both ignition techniques were detected via a high-speed camera. The tests have shown the laser ignition leads to more energy consumption in the rich mixture conditions and also, less energy is required in the lean conditions. The laser ignition discharge has extended the engine's lean combustion limits via a small energy input at the tests. The high-speed camera images have shown that the laser ignition reduces the Kernel flame formation and propagation time. The laser ignition technique was produced less NOx than the conventional spark ignition method. (C) 2021 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.
Injection parameters and lambda effects on diesel jet engine characteristics for JP-8, FAME and naphtha fuels
(Elsevier Sci Ltd, 2020) Yontar, Ahmet Alper
The study focused on the effects of lambda, injection duration and start of injection on the diesel jet engine characteristics and also a challenge study for alternative fuels that have similar properties. The high-speed behaviors of the diesel jet test engine at full load were examined experimentally for diesel, JP-8, FAME, and naphtha. The tests were carried out for variations of 1.0-4.0 lambda, 5 degrees-30 degrees injection duration and 4 degrees-20 degrees start of injection. The experimental results were shown comparatively that the trends of sensitivity and behavior for diesel, JP-8, FAME, and naphtha according to variations of the measurement parameters. The behavior of in-cylinder pressure curves showed that FAME was less affected by lambda change than the other fuels. The most affected fuel from the timing of injection was the naphtha for heat release rate. The injection duration variations more positively affected the brake thermal efficiency for FAME than other tested fuels. The FAME was yielded the highest brake specific fuel consumption for the lambda range. At ultra-lean condition, the ignition delay time of naphtha was about 32.27% higher than the other fuels. While the start of injection point increased from 4 degrees to 20 degrees, CO emissions were reduced by about 60% for naphtha usage. The FAME usage had the highest slope and had more sensitivity than other fuels for injection duration variations. The most affected fuel from the start of injection parameter was the diesel for NOx formation. The most extreme sensitivity to injection duration was naphtha for particulate matter formation.

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