Many fuel spray characterization studies to date have been conducted in quiescent environments with single-hole fuel injectors. However, in actuality, multi-hole injectors spray into direct injection engine cylinders where significant air swirling and tumbling exist to promote fuel atomization and air-fuel mixing, which result in more efficient combustion. For this reason, researchers have begun developing correlations for fuel sprays where a jet of air acts perpendicularly to the fuel spray, also known as a cross airflow or crossflow, so as to more realistically predict fuel spray characteristics in direct injection engines. Accordingly, there is a need for a foundation of experimental data reflecting the specific conditions of fuel spray in cross airflow which can then be used for model validation and future engine design and development. In this study, fuel sprays are characterized with a commercial 8-hole fuel injector in a wind tunnel enclosure capable of cross airflows upwards of 200m/s. Particle image velocimetry was used to measure air velocities and capture pulsed spray events of biodiesel, diesel, and biodiesel-diesel blend fuels. Spray images were processed and analyzed in LaVision's DaVis and in MATLAB to calculate spray penetration length and axis deflection angle under varying cross airflow velocities, fuel injection pressures, and fuel types. Results show that strong cross airflows can decrease spray penetration by up to 44% and deflect the spray axis by up to 10.5° when compared to the same spray in a quiescent environment. Additional experiments reveal that biodiesel experiences slower spray progression when compared with diesel, resulting in shorter spray penetrations in the early phase of the spray development (up to 0.7ms after the start of injection, or ASOI). The angle between the fuel injector axis and the air jet axis plays an important role in determining the resultant spray characteristics. This angle should be considered in future correlations.

Many fuel spray characterization studies to date have been conducted in quiescent environments with single-hole fuel injectors. However, in actuality, multi-hole injectors spray into direct injection engine cylinders where significant air swirling and tumbling exist to promote fuel atomization and air-fuel mixing, which result in more efficient combustion. For this reason, researchers have begun developing correlations for fuel sprays where a jet of air acts perpendicularly to the fuel spray, also known as a cross airflow or crossflow, so as to more realistically predict fuel spray characteristics in direct injection engines. Accordingly, there is a need for a foundation of experimental data reflecting the specific conditions of fuel spray in cross airflow which can then be used for model validation and future engine design and development. In this study, fuel sprays are characterized with a commercial 8-hole fuel injector in a wind tunnel enclosure capable of cross airflows upwards of 200m/s. Particle image velocimetry was used to measure air velocities and capture pulsed spray events of biodiesel, diesel, and biodiesel-diesel blend fuels. Spray images were processed and analyzed in LaVision's DaVis and in MATLAB to calculate spray penetration length and axis deflection angle under varying cross airflow velocities, fuel injection pressures, and fuel types. Results show that strong cross airflows can decrease spray penetration by up to 44% and deflect the spray axis by up to 10.5° when compared to the same spray in a quiescent environment. Additional experiments reveal that biodiesel experiences slower spray progression when compared with diesel, resulting in shorter spray penetrations in the early phase of the spray development (up to 0.7ms after the start of injection, or ASOI). The angle between the fuel injector axis and the air jet axis plays an important role in determining the resultant spray characteristics. This angle should be considered in future correlations.

Due to the fact that cross flow fuel injection is widely used in gas turbine engines combustors, it is important to understand the mechanisms that control the spray breakup within the cross flow. In spite of a lot of work done in this field, very few studies have been carried out under conditions typical of aerospace applications. This thesis describes a series of experiments carried out to simulate these conditions in order to characterize the formation of spray within a high speed, high pressure and high temperature cross flow close to conditions typical of aerospace applications. Fuel spray characteristics were studied for Jet-A fuel injected into a crossflow (M=0.2 and M=0.35) of preheated (T=555K) air at a chamber pressure of 4 atm. It was seen that larger droplets could be found in the periphery of the spray while smaller droplets could be found closer to the injection plate. In most cases, the droplet velocities were seen to lag the incoming air flow velocity by 20-40% and a spray hat structure was created by the jet in crossflow near the injection wall most likely caused by vortex flow created around the liquid column (jet). The influence of Weber number was then studied. It was seen that shear breakup mechanism dominates at We greater than about 100. Droplets diameters were found to be in the range of 15-30 microns for higher values of We, while larger droplets (100-200 microns) were observed at Weber number of 33. The initial sharp-edged injector was then replaced by a smooth-edged injector having. Spray characteristics from the two injectors were compared. The spray produced by the smooth countersunk injector penetrated further into the test section away from the injector orifice by approximately 2mm. This injector also produced droplets with a significantly smaller mean diameter (D10). The average droplet velocities in the vertical direction deviated from the incoming air flow velocity to a lesser degree using the countersunk injector. Meanwhile, droplets from this injector had a higher average velocity in the direction of fuel injection between the core of the spray and the orifice wall.

<div>The aviation industry is continuously growing amid tight restrictions on global emission</div><div>reductions. Alternative aviation fuels have gained attention and developed to replace the</div><div>conventional petroleum-derived aviation fuels. The replacement of conventional fuels with</div><div>alternative fuels, which are composed solely of hydrocarbons (non-petroleum), can mitigate</div><div>impacts on the environment and diversify the energy supply, potentially reducing fuel costs.</div><div>To ensure the performance of alternative fuels, extensive laboratory and full-scale engine</div><div>testings are required, thereby a lengthy and expensive process. The National Jet Fuel Combustion</div><div>Program (NJFCP) proposed a plan to reduce this certification process time and</div><div>the cost dramatically by implementing a computational model in the process, which can be</div><div>replaced with some of the testings. This requires an understanding of the influence of chemical/</div><div>physical properties of alternative fuels on combustion performance. The main objective</div><div>of this work is to investigate the spray characteristics of alternative aviation fuels compared</div><div>to that of conventional aviation fuels, which have been characterized by different physical</div><div>liquid properties at different gas turbine-relevant conditions.</div><div>The experimental work focuses on the spray characteristics of standard and alternative</div><div>aviation fuels at three operating conditions such as near lean blowout (LBO), cold engine</div><div>start, and high ambient pressure conditions. The spray generated by a hybrid pressureswirl</div><div>airblast atomizer was investigated by measuring the drop size and drop velocity at</div><div>a different axial distance downstream of the injector using a phase Doppler anemometry</div><div>(PDA) measurement system. This provided an approximate trajectory of the largest droplet</div><div>as it traveled down from the injector. At LBO conditions, the trend of decreasing drop size</div><div>and increasing drop velocity with an increase in gas pressure drop was observed for both</div><div>conventional (A-2) and alternative aviation fuels (C-1, C-5, C-7, and C-8), while the effect of</div><div>fuel injection pressure on the mean drop size and drop velocity was observed to be limited.</div><div>Moreover, the high-speed shadowgraph images were also taken to investigate the effect of</div><div>the pressure drop and fuel injection pressures on the cone angles. Their effects were found</div><div>to be limited on the cone angle.</div><div><div>The spray characteristics of standard (A-2 and A-3) and alternative (C-3) fuels were</div><div>investigated at engine cold-start conditions. At such a crucial condition, sufficient atomization</div><div>needs to be maintained to operate the engine properly. The effect of fuel properties,</div><div>especially the viscosity, was investigated on spray drop size and drop velocity using both</div><div>conventional and alternative aviation fuels. The effect of fuel viscosity was found to be minimal</div><div>and dominated by the effect of the surface tension, even though it showed a weak trend</div><div>of increasing drop size with increasing surface tension. The higher swirler pressure drop</div><div>reduced the drop size and increased drop velocity due to greater inertial force of the gas for</div><div>both conventional and alternative aviation fuels at the cold start condition. However, the</div><div>effect of pressure drop was observed to be reduced at cold start condition compared to the</div><div>results from the LBO condition.</div><div>The final aspect of experimental work focuses on the effect of ambient pressures on the</div><div>spray characteristics for both conventional (A-2) and alternative (C-5) aviation fuels. Advanced</div><div>aviation technology, especially in turbomachinery, has resulted in a greater pressure</div><div>ratio in the compressor; therefore, greater pressure in combustors for better thermal efficiency.</div><div>The effect of ambient pressure on drop size, drop velocity, and spray cone angle was</div><div>investigated using the PDA system and simultaneous Planar Laser-Induced Fluorescence</div><div>(PLIF) and Mie scattering measurement. A significant reduction in mean drop size was</div><div>observed with increasing ambient pressure, up to 5 bar. However, the reduction in the mean</div><div>drop size was found to be limited with a further increase in the ambient pressure. The effect</div><div>of the pressure drop across the swirler was observed to be significant at ambient pressure of</div><div>5 bar. The spray cone angle estimation at near the swirler exit and at 25.4 mm downstream</div><div>from the swirler exit plane using instantaneous Mie images was found to be independent of</div><div>ambient pressure. However, the cone angle at measurement plane of 18 mm in the spray</div><div>was observed to increase with increasing ambient pressure due to entrainment of smaller</div><div>droplets at higher ambient pressure. Furthermore, the fuel droplet and vapor distribution in</div><div>the spray were imaged and identified by comparing instantaneous PLIF and Mie images.</div><div>Lastly, a semi-empirical model was also developed using a phenomenological three-step</div><div>approach for the atomization process of the hybrid pressure-swirl airblast atomizer. This</div><div>model includes three sub-models: pressure-swirl spray droplet formation, droplet impingement, and film formation, and aerodynamic breakup. The model predicted drop sizes as a</div><div>function of ALR, atomizing gas velocity, surface tension, density, and ligament length and</div><div>diameter and successfully demonstrated the drop size trend observed with fuel viscosity,</div><div>surface tension, pressure drop, and ambient pressure. The model provided insights into the</div><div>effect of fuel properties and engine operating parameters on the drop size. More experimental</div><div>work is required to validate the model over a wider range of operating conditions and</div><div>physical fuel properties.</div><div>Overall, this work provides valuable information to increase understanding of the spray</div><div>characteristics of conventional and alternative aviation fuels at various engine operating</div><div>conditions. This work can provide valuable data for developing an advanced computational</div><div>combustor model, ultimately expediting the certification of new alternative aviation fuels.</div></div>

Design of atomizers for gas-turbine purposes are an important ordeal. The per-formance of the atomizer directly impacts the efficiency of the gas-turbine, andconsequently, the energy extracted from the turbine. Furthermore, the design ofthe atomizer can have an impact on reducing toxic emissions. On a global scale,gas-turbines can be considered crucial for the transition to renewable energy. Forengineers, designing of atomizers are however challenging. Turbulent flow, multi-phase interaction and chemical reactions are some of the complex physics involvedwhich has to be taken into consideration when designing the atomizer. Engineerstraditionally uses experimental testing for investigation of designs, and it is still verymuch a useful methodology. However, numerical simulations and CFD have recentlygained popularity due to being a more cost-effective methodology. In this work, theprocedure for designing a prefilm atomizer involving CFD (single phase model andmulti phase model) and experimental testing is documented. The details of the twonumerical models (a single phase model and a multi phase model) has been doc-umented as well as the experimental setup. The single phase model is used for aparametric study and experimental testing is used for evaluation of designs. Themulti phase model is aimed to replicate the experimental results. The validity ofthe numerical models and the experimental setup are discussed, and possible mod-ifications of the methodology for future studies are suggested. Finally, suggestionsfor how the prefilmer should be designed is suggested.

La préoccupation de plus en plus importante ces dernières décennies, liée à l’épuisement des ressources pétrolières et au réchauffement climatique par les gaz à effet de serre a accentué l’intérêt du butanol comme carburant alternatif dans le secteur des transports grâce à ses propriétés adaptées pour le moteur à allumage par compression. Cependant, le faible rendement des procédés de production et de séparation empêche encore sa commercialisation en tant que carburant. C’est pourquoi le mélange de fermentation intermédiaire de la production de butanol, Acétone-Butanol-Ethanol(ABE), est de plus en plus considéré comme un carburant alternatif potentiel en raison de ses propriétés similaires au butanol et de ses avantages quant à son cout énergétique pour sa fabrication.Dans ce cadre, ce travail a pour objectif d’étudier l’impact des propriétés de différents mélanges d’ABE et n-dodécane en comparaison avec des mélanges d’alcools (éthanol et butanol) sur le processus de pulvérisation et de combustion et ce,pour différentes proportions en volume allant de 20% à 50%. Pour cela, une nouvelle chambre de combustion appelée"New One Shot Engine ", a été réalisée et utilisée car les conditions haute pression et haute température de "Spray-A" (60bars, 800-900 K et 22,8 kg/m³) définies par le réseau Engine Combustion network (ECN) peuvent être atteintes. Autant les phases liquides et vapeur que de combustion ont été caractérisées grâce à l’utilisation des plusieurs techniques optiques (extinction, Schlieren, chimiluminescence d’OH*) dans des conditions non réactives (Azote pur) et réactives (avec15% d'oxygène). Ces résultats expérimentaux ont non seulement permis d’étudier l’impact en oxygène moléculaire et de fournir une nouvelle base de données fiables, mais aussi d’affirmer la possibilité d’utiliser jusque 20% d’ABE en volume dans des moteurs à allumage par compression, grâce à ses caractéristiques de pulvérisation et de combustion similaires au carburant Diesel conventionnel. / The growing concern in recent decades, linked to the depletion of oil resources and global warming by greenhouse gases has increased the interest of butanol as an alternative fuel in the transport sector. However, the low yield of production and separation processes still prevents its commercialization as a fuel. Therefore, the intermediate fermentation mixture of butanol production, Acetone-Butanol-Ethanol (ABE), is increasingly considered as a potential alternative fuel because of its similar properties to butanol and its advantages in terms of the energy and cost in the separation process.The context of this work aims to study the impact of fuel properties on the spray and combustion processes of ABE mixture and alcohol fuels, blended with the diesel surrogate fuel, n-dodecane, in different volume ratio from 20% to 50%. A new combustion chamber called "New One Shot Engine," was designed and developed to reach the high-pressure and high temperatureconditions of "Spray-A" (60 bar, 800-900 K and 22.8 kg/m³) defined by the Engine Combustion Network (ECN).The macroscopic spray and combustion parameters were characterized by using the several optical techniques (extinction,Schlieren, chemiluminescence of OH*) under non-reactive (pure Nitrogen) and reactive (15% of oxygen) conditions. These experimental results not only made it possible to study the molecular oxygen impact and provide a new accurate database,but also to affirm the possibility of using ABE up to 20% by volume in compression-ignition engines, as its spray and combustion characteristics similar to conventional diesel fuel.

Vegetable oil methyl esters obtained by transesterification of vegetable oils are considered to be suitable alternative fuels for diesel engines. However, higher viscosity, surface tension and boiling temperatures of biodiesels may adversely affect spray characteristics as compared to those of diesel. Thus, spray characteristics of Jatropha Methyl Ester (JME) are studied by comparing them to those of diesel in a high-pressure chamber with optical access to simulate the actual in-cylinder conditions. Also, the effect of inner-nozzle cavitation on JME and diesel sprays is studied by utilizing two nozzles, one with sharp entry-radius and the other with larger entry-radius. Finally, spray characteristics of surrogate fuels such as n-dodecane and n-hexadecane are also studied. The first part of the work concerning precise measurements of inner-nozzle geometry revealed that one of the nozzles has a hole diameter of 190-µm and entry-radius of around 70-µm, while the other has a hole diameter of 208-µm and entry-radius of around 10-µm. Injection rate-shape and coefficient of discharge for JME and diesel flow through the two nozzles were then measured. It was observed that while the coefficients of discharge (Cd) are almost identical for JME and diesel, the nozzle with entry radius of 10-µm exhibited around 20% lower Cd than that of the entry-radius of 70-µm. This observation coupled with insight from complementary CFD simulations of inner-nozzle flow showed that the lower Cd of the nozzle with entry-radius of 10-µm could be attributed to inner-nozzle cavitation. The second part of the work involved measurement of non-evaporating spray characteristics including spray-tip penetration, spray-cone angle and droplet size measurement under realistic operating conditions using techniques such as Shadowgraphy and Particle/Droplet Imaging Analysis (PDIA). The non-evaporating spray of the fuels are studied by injecting them using a common-rail fuel injection system into the high-pressure chamber maintained at room temperature. Experimental results show that JME is associated with a slightly faster spray-tip penetration and narrow spray-cone angle indicating inferior spray atomization which is confirmed by around 5% larger droplet sizes. Slower spray-tip penetration, wider spray-cone angle and around 5% smaller droplet sizes are observed for the spray from the cavitating nozzle. Thus, the inner nozzle cavitation is observed to improve the atomization of diesel and JME sprays. The differences in spray characteristics of JME and diesel reduce as the injection pressure increases. The spray-tip penetrations of both surrogates are observed to almost match that of diesel. The third part of the work involved measurements of evaporating spray liquid length, vapour penetration and spread angle for JME, diesel and surrogates at conditions of 50 bar chamber pressure and 900 K temperature. It is observed that the JME exhibits around 16% longer liquid length than that of diesel. The liquid length of n-dodecane is significantly lower than that of diesel and liquid length of n-hexadecane is around 20% higher than that of n-dodecane mimicking the trend of JME and diesel. The liquid length of n-hexadecane is very close to that of diesel at all the three test conditions. Interestingly, the vapour penetration and spread angle for all the fuels is observed to be almost identical. As the cold spray and evaporating spray characteristics of n-hexadecane match well with those of diesel, n-hexadecane can be chosen as a pure component surrogate for diesel. Finally, an analytical model for predicting the spray vapour penetration is assessed with the experimentally-observed trends of penetration and spray spread angle. The model indicated that the effect of fuel density variation is compensated by the corresponding variation in injection velocity for a given injection pressure to result in a similar vapour penetration. Overall, the present work, in addition to studying the effect of fuel physical properties and cavitation on sprays, has generated a comprehensive experimental database on non-evaporating and evaporating sprays of biodiesel, diesel, and pure component surrogates, which would aid significantly in validation of CFD simulations.