Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7148
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Article Citation - WoS: 9Citation - Scopus: 10Experimental Studies of Autoignition and Soot Formation of Diesel Surrogate Fuels(SAGE Publications Inc., 2013) Diez, Alvaro; Crookes, Roy J.; Lovas, TereseComputational simulation has undergone vast development for internal-combustion engine research as a time- and costsaving tool. Yet combustion simulation for conventional hydrocarbon petroleum fuels faces difficult challenges since such fuels have very complex compositions, consisting of many different molecular species, for which data are sparse. The use of surrogate fuels for combustion simulation could provide a solution to this problem. In this investigation, n-heptane and mixtures of n-heptane and toluene were studied within a broad range of potential surrogate diesel fuels, and the ignition delay and soot formation trends were compared with those of diesel fuel. Ignition delays show good agreement with those for diesel fuel and it was also possible to replicate partially the soot formation behaviour for certain engine conditions. Further investigation is needed to find a surrogate fuel that closely matches over the range of operating conditions of a diesel engine.Article Citation - WoS: 32Citation - Scopus: 44Optical Characterization of Diesel and Water Emulsion Fuel Injection Sprays Using Shadowgraphy(Elsevier Ltd., 2016) Emberson, D. R.; Ihracska, B.; Imran, S.; Diez, AlvaroDiesel fuel and water emulsions have been shown to reduce emissions of NOx and PM from compression ignition engines. There is a lack of work examining the influence of emulsification on the sprays formed during injection. This work examines the spray cone angle and tip penetration of Diesel fuel and water emulsions, containing 10% and 20% water (by mass). All experiments were conducted under non-reacting, non-vaporizing conditions in a constant volume pressure chamber filled with nitrogen. A focused shadowgraph system, with high speed photography, coupled with a research, high current LED system was used. Differences in the spray cone angle suggest the emulsification did have an effect for the injections at a pressure of 500 bar. Emulsification had no discernible effect on the spray tip penetration. Spray tip penetration showed agreement with previous trends in terms of proportionality to time after start of injection however agreement with models found in the literature was not consistent.Article Citation - WoS: 9Citation - Scopus: 10Hydraulic Characterization of Diesel and Water Emulsions Using Momentum Flux(Elsevier Ltd., 2015) Emberson, D. R.; Ihracska, B.; Imran, S.; Diez, Alvaro; Lancaster, M.; Korakianitis, T.Diesel and water emulsions have the potential to be used in compression ignition engines to control the emissions of NOx and PM. Very little is known about the influence emulsification will have on the fuel sprays formed during injection. This paper outlines the measurement of the momentum flux of injection sprays of Diesel fuel and Diesel fuel emulsions containing 10% and 20% water, with the goal of hydraulically characterizing the sprays and identifying the influence emulsification may have on them. The momentum flux, mass flow, instantaneous mass flow, discharge coefficient, injection velocity, momentum coefficient and momentum efficiency have been examined. The injections were carried out in a high pressure chamber filled with nitrogen. The measured momentum flux is observed to increase with increasing injection pressure in a linear form. Increasing the ambient density in the chamber resulted in a decrease in the measured momentum flux. The emulsified fuel sprays had a very similar momentum flux as the neat Diesel fuel sprays. The total mass of emulsified fuel injected was less than for neat Diesel at corresponding condition. The instantaneous mass flow rate was determined using a normalized form of the momentum flux measurement and the independently measured total mass injected. The emulsions tended to have a lower discharge coefficient and there is no evidence that the nozzle is cavitating at these conditions. The emulsified fuels have tended to have a higher injection velocity than the neat Diesel fuel sprays. The momentum efficiency is introduced, which uses the instantaneous mass measurement and the theoretical velocity of the spray. The emulsified fuels have a larger momentum efficiency, a result of their high injection velocity compared with the neat Diesel fuel.Article Citation - WoS: 36Citation - Scopus: 44Assessment of Elliptic Flame Front Propagation Characteristics of Iso-Octane, Gasoline, M85 and E85 in an Optical Engine(Elsevier Ltd., 2014) Ihracska, Balazs; Korakianitis, Theodosios P.; Ruiz, Paula; Emberson, David Robert; Crookes, Roy James; Diez, Alvaro; Wen, DongshengPremixed fuel-air flame propagation is investigated in a single-cylinder, spark-ignited, four-stroke optical test engine using high-speed imaging. Circles and ellipses are fitted onto image projections of visible light emitted by the flames. The images are subsequently analysed to statistically evaluate: flame area; flame speed; centroid; perimeter; and various flame-shape descriptors. Results are presented for gasoline, isooctane, E85 and M85. The experiments were conducted at stoichiometric conditions for each fuel, at two engine speeds of 1200. rpm (rpm) and 1500. rpm, which are at 40% and 50% of rated engine speed. Furthermore, different fuel and speed sets were investigated under two compression ratios (CR: 5.00 and 8.14). Statistical tools were used to analyse the large number of data obtained, and it was found that flame speed distribution showed agreement with the normal distribution. Comparison of results assuming spherical and non-isotropic propagation of flames indicate non-isotropic flame propagation should be considered for the description of in-cylinder processes with higher accuracy. The high temporal resolution of the sequence of images allowed observation of the spark-ignition delay process. The results indicate that gasoline and isooctane have somewhat similar flame propagation behaviour. Additional differences between these fuels and E85 and M85 were also recorded and identified.Article Citation - WoS: 93Citation - Scopus: 6Natural Gas Fueled Compression Ignition Engine Performance and Emissions Maps With Diesel and Rme Pilot Fuels(Elsevier Ltd, 2014) Imran, Shahid Mohammed; Emberson, David Robert; Díez, Alvaro; Wen, Dongsheng; Crookes, Roy James; Korakianitis, Theodosios P.When natural gas is port/manifold injected into a compression ignition engine, the mixture of air and the natural gas is compressed during the compression stroke of the engine. Due to the difference in the values of specific heat capacity ratio between air and natural gas, the temperature and pressure at the time of pilot fuel injection are different when compared to a case where only air is compressed. Also, the presence of natural gas affects the peak in-cylinder (adiabatic flame) temperature. This significantly affects the performance as well as emissions characteristics of natural gas based dual fueling in CI engine. Natural gas has been extensively tested in a single cylinder compression ignition engine to obtain performance and emissions maps.Two pilot fuels, diesel and RME, have been used to pilot natural gas combustion. The performance of the two liquid fuels used as pilots has also been assessed and compared. Tests were conducted at 48 different operating conditions (six different speeds and eight different power output conditions for each speed) for single fueling cases. Both the diesel and RME based single fueling cases were used as baselines to compare the natural gas based dual fueling where data was collected at 36 operating conditions (six different speeds and six different power output conditions for each speed). Performance and emissions characteristics were mapped on speed vs brake power plots. The thermal efficiency values of the natural gas dual fueling were lower when compared to the respective pilot fuel based single fueling apart from the highest powers. The effect of engine speed on volumetric efficiency in case of the natural gas based dual fueling was significantly different from what was observed with the single fueling. Contours of specific NO<inf>X</inf> for diesel and RME based single fueling differ significantly when these fuels were used to pilot natural gas combustion. For both of the single fueling cases, maximum specific NO<inf>X</inf> were centered at the intersection of medium speeds and medium powers and they decrease in all directions from this region of maximum values. On the other hand, an opposite trend was observed with dual fueling cases where minimum specific NO<inf>X</inf> were observed at the center of the map and they increase in all direction from this region of minimum NO<inf>X</inf>. RME piloted specific NO<inf>X</inf> at the highest speeds were the only exception to this trend. Higher specific HC and lower specific CO<inf>2</inf> emissions were observed in case of natural gas based dual fueling. The emissions were measured in g/MJ of engine power. © 2021 Elsevier B.V., All rights reserved.