Download or read book Flow Independent Fuel Injection for More Consistent Liquid Combustion Using Pintile Injectors written by Charles Clark and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Liquid jet in crossflow systems are often used as lightweight and efficient mechanisms of atomizing fuel prior to entertainment in the flame holder and combustion, making them integral components of liquid fueled engines. Unfortunately, such systems are susceptible to deviations in both trajectory and breakup rate, depending primarily on the Weber number and momentum flux ratio of the injected jet. In these studies, the effects of solid obstructions, called pintiles, on the variability of liquid jet in cross flow trajectory and breakup are investigated. Initial investigations looked at the impacts of broad geometric parameters on flow independence, using Mie scatter imaging and phase Doppler particle analysis. The results of that investigation yielded an optimal overarching geometry for pintiles. This knowledge was then refined by looking at specific face characteristics of the obstructions, primarily investigating face angle and concavity. Spray characteristics were spatially resolved using LIF/Mie particle sizing techniques, revealing that modest convex surfaces yielded the most consistent breakup characteristics across space, while simultaneously improving the average breakup distance of the liquid jet. Finally, this progression of pintile characteristics is investigated on the effects pintiles have on overarching flame properties, using C2*/CH* chemiluminescence ratios to determine spatially resolved equivalence ratio distributions across a wide range of Weber numbers and momentum flux ratios encompassing breakup regimes from the enhanced capillary modes through to shear breakup modes. Results from these studies demonstrate significant improvement of combustion properties from the introduction of the pintiles.

Download or read book Development and Characterization of Flow Independent Fuel Injectors written by Michael Kwara and published by . This book was released on 2021 with total page 15 pages. Available in PDF, EPUB and Kindle. Book excerpt: Jet-in-crossflow is an interaction between a fuel jet and air crossflow commonly found in jet engines. The crossflow is used to break up or atomize the fuel jet for downstream combustion. This interaction between fluids while at low speeds, is predictable, varies greatly at higher speeds. This investigation seeks to (1) create a mechanism for jet-in-crossflow, using mechanical pintles, that is independent of velocity to help increase the predictability and reliability of jet engines and (2) identify key design parameters that will lead to flow independence. Parameters investigated in this experiment include pintle height, angle, and percent of pintle coverage into the jet orifice. Pintles that covered 100 percent of the jet showed a strong deviation from the traditional interaction with no pintle. Relationships were also found between the angle, height, and penetration depth although none as ubiquitous as the jet coverage.

Download or read book Fundamentals of Medium Heavy Duty Diesel Engines written by Gus Wright and published by Jones & Bartlett Publishers. This book was released on 2015-12-16 with total page 1407 pages. Available in PDF, EPUB and Kindle. Book excerpt: Based on the 2014 National Automotive Technicians Education Foundation (NATEF) Medium/Heavy Truck Tasks Lists and ASE Certification Test Series for truck and bus specialists, Fundamentals of Medium/Heavy Duty Diesel Engines is designed to address these and other international training standards. The text offers comprehensive coverage of every NATEF task with clarity and precision in a concise format that ensures student comprehension and encourages critical thinking. Fundamentals of Medium-Heavy Duty Diesel Engines describes safe and effective diagnostic, repair, and maintenance procedures for today’s medium and heavy vehicle diesel engines.

Download or read book LES of Atomization and Cavitation for Fuel Injectors written by Aqeel Ahmed and published by . This book was released on 2019 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis presents Large Eddy Simulation (LES) of fuel injection, atomization and cavitation inside the fuel injector for applications related to internal combustion engines. For atomization modeling, Eulerian Lagrangian Spray Atomization (ELSA) model is used. The model solves for volume fraction of liquid fuel as well as liquid-gas interface surface density to describe the complete atomization process. In this thesis, flow inside the injector is also considered for subsequent study of atomization. The study presents the application of ELSA model to a typical diesel injector, both in the context of RANS and LES. The model is validated with the help of experimental data available from Engine Combustion Network (ECN). The ELSA model which is normally designed for diffused (unresolved) interfaces, where the exact location of the liquid-gas interface is not considered, is extended to work with Volume of Fluid (VOF) type formulation of two phase flow, where interface is explicitly resolved. The coupling is achieved with the help of Interface Resolution Quality (IRQ) criteria, that takes into account both the interface curvature and modeled amount of interface surface. ELSA model is developed first considering both phases as incompressible, the extension to compressible phase is also briefly studied in this thesis, resulting in compressible ELSA formulation that takes into account varying density in each phase. In collaboration with Imperial College London, the Probability Density Function (PDF) formulation with Stochastic Fields is also explored to study atomization. In modern fuel injection systems, quite oftenthe local pressure inside the injector falls below the vapor saturation pressure of the fuel, resulting in cavitation. Cavitation effects the external flow and spray formulation. Thus, a procedure is required to study the phase change as well as jet formulation using a single and consistent numerical setup. A method is developed in this thesis that couples the phase change inside the injector to the external jet atomization. This is achieved using the volume of fluid formulation where the interface is considered between liquid and gas; gas consists of both the vapor and non condensible ambient air.

Download or read book Modeling and Control of Combustion Instability Using Fuel Injection written by J. P. Hathout and published by . This book was released on 2001 with total page 13 pages. Available in PDF, EPUB and Kindle. Book excerpt: Active control using periodic fuel injection has the potential of suppressing combustion instability without radically changing the engine design or sacrificing performance. In this paper. we carry out a study of optimal model-based control of combustion instability using fuel injection. The model developed is physically based and includes the acoustics. The heat-release dynamics their coupling and the injection dynamics. A heat-release model with fluctuations in the flame surface area as well as in the equivalence ratio is derived. We show that area fluctuations coupled with the velocity fluctuations drive longitudinal modes to resonance caused by phase-lag dynamics. while equivalence ratio fluctuations can destabilize both longitudinal and bulk modes caused by time-delay dynamics, similar to experimental observations. The dynamics of propositional and two-position (on-off) fuel injectors are included in the model. Using the overall model two different control designs are proposed. The first is an LQG/LTR controller where the time-delay effect is ignored and the second is a Posi-Cast controller which explicitly accounts for the delay. Injection at (i) the burning zone and (ii) further upstream is considered. The characteristics of fuel injectors including bandwidth, authority (pulsed-fuel flow rate). and whether it applies a proportional or a two-position (on-off) injection are discussed. We show that increasing authority and bandwidth result in improved performance. Injection at (ii) compared to (i) results in a trade-off between improved mixing and increased time-delay We also note that propositional injection is more successful than on-off injection since the former can modulate both amplitude and phase of the control fuel.

Download or read book Fundamentals of Fuel Injection and Emission in Two Stroke Engines written by Wadysaw Mitianiec and published by Nova Science Publishers. This book was released on 2018 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The main goal of the book is the presentation of the last theoretical and experimental works concerning fuel injection systems, mainly in small power two-stroke engines as well as in marine engines. This book includes thirteen chapters devoted to the processes of fuel injection and the combustion that takes place in a stratified charge within the cylinders of two-stroke engines. In the first two chapters, the division into different injection systems in two-stroke engines and each injection system is briefly described. Various theoretical and practical solutions of fueling system designs are described. In Chapter Three, mathematical models, the spatial movement of gas in the cylinder and the combustion chamber are introduced, taking into account the turbulence of the charge. Chapter Four relates to the behavior of fuel injected into the gaseous medium, including evaporation processes, disintegration and processes occurring while the fuel drops connect with the wall. The next section describes the zero-dimensional model of fuel injection in two-stroke engines along with examples of numerical calculations. The sixth chapter is devoted to CFD multi-dimensional models of movement and evaporation of the fuel in a closed gaseous medium, occurring also in other engine types. Chapter Seven describes a two-zone model of the combustion process and the effect of the geometry of the combustion chamber on the flame propagation with a simplified verification model of combustion. Chapter Eight compares the propagation phase of gas and liquid fuels concerning direct fuel injection as well as the direct fuel injection from the cylinder head and the thermodynamic parameters of the charge. The formation of the components during the combustion process in the direct fuel injection two-stroke engine was obtained by numerical calculations and results are discussed in Chapter Nine. Chapter Ten describes the parameters of the two-stroke engine with a direct fuel injection carried out at the Cracow University of Technology. Additionally, the chapter presents CFD simulations of fuel propagation and combustion processes, taking into account the formation of toxic components and exhaust gas emission. The processes of two direct rich mixture injection systems FAST and RMIS developed in CUT are presented in Chapter Eleven. Miscellaneous problems of direct fuel injection, such as characteristics of fuel injectors, problems of direct gaseous fuel injection, and the application of fuelling systems in outboard engines and snowmobile vehicles are presented in Chapter Twelve. A comparison of working parameters in two- and four stroke engines is also mapped out. The last chapters contain the final conclusions and remarks concerning fuel injection and emission of exhaust gases in small two-stroke engines. This book is a comprehensive monograph on fuel injection. The author presents a series of theoretical and design information from his own experience and on the basis of the works of other authors. The main text intends to direct fuel injection with respect to gas motion in the combustion chamber and influence the injection parameters for exhaust emission. The book presents its own theoretical work and experimental tests concerning a two-stroke gasoline engine with electrically controlled direct fuel injection. The book describes the processes of a general nature also occurring in other types of engines and presents a comparison of different injection systems on working parameters and gas emission. The book contains 294 images, 290 equations and 16 tables obtained from the CFD simulation and experimental works.

Download or read book Photographic Characterization of Spark ignition Engine Fuel Injectors written by and published by . This book was released on 1978 with total page 34 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Design of a Liquid Fuel Injector for Alternative Fuel Studies in an Atmospheric Model Gas Turbine Combustor written by John Ernest Stevenson and published by . This book was released on 2011 with total page 54 pages. Available in PDF, EPUB and Kindle. Book excerpt: A new liquid-fuel injector was designed for use in the atmospheric-pressure, model gas turbine combustor in Bucknell University's Combustion Research Laboratory during alternative fuel testing. The current liquid-fuel injector requires a higher-than-desired pressure drop and volumetric flow rate to provide proper atomization of liquid fuels. An air-blast atomizer type of fuel injector was chosen and an experiment utilizing water as the working fluid was performed on a variable-geometry prototype. Visualization of the spray pattern was achieved through photography and the pressure drop was measured as a function of the required operating parameters. Experimental correlations were used to estimate droplet sizes over flow conditions similar to that which would be experienced in the actual combustor. The results of this experiment were used to select the desired geometric parameters for the proposed final injector design and a CAD model was generated. Eventually, the new injector will be fabricated and tested to provide final validation of the design prior to use in the combustion test apparatus.

Download or read book Computational and Experimental Study of Geometry Modifications Inside a Flow blurring Injector written by Nathan James Vardaman and published by . This book was released on 2018 with total page 274 pages. Available in PDF, EPUB and Kindle. Book excerpt: Liquid fuel atomization is widely used for combustion in many applications. With the strong emphasis on emissions regulations coupled with the ever increasing drive to improve energy efficiency, all aspects of combustion are being thoroughly researched. One key way to achieve the above goals is further improvement in the liquid fuel atomization process. Better atomization improves mixing of fuel and air, thus results in lower emissions, whereas improved liquid fuel injector designs can improve energy efficiency. The flow-blurring (FB) atomization technique, developed recently and investigated at the University of Alabama, has shown promise in both these areas. Previous research has shown that the FB injector produces smaller droplets and a more desirable droplet distribution than the commercial air-blast injector. In addition, the FB injector is able to successfully atomize a wider range of fuels, and it is much less susceptible to the change in surface tension or viscosity of the liquid fuel. In this study, a computational fluid dynamics (CFD) model is created to mimic the mixing of the fuel and air inside the injector, and thus, understand the underlying physics of the FB atomization process. The 2D model is assumed to be asymmetric and incompressible, and it uses the mixture model for the two-phase flow. A transient solution is found and analyzed revealing a recirculation zone, due to a stagnation point near the exit, is formed within the fuel tube of the injector. The recirculation zone is responsible for the mixing of fuel and air and the formation of bubbles. Prior experimental research conclusions are compared with the model as various operating conditions are implored for verification of the models accuracy. Finally, the model is utilized by simulating and studying the effect of geometric modifications within the wall gap of the FB injector. An inner-slant wall gap provides promising results compared to the original geometry. The geometry modifications are then implemented in an actual injector tested in an atmospheric burner. Emissions measurements, thermal imaging of the combustor surface, and OH* chemiluminescence imaging of the flame are used to first verify proper operation of the combustor and then to characterize the flame structure. Several operating conditions are altered and the influence of these changes is studied. OH* chemiluminescence images reveal the flame is stable and a better distribution of OH* signals represents improved atomization. Finally, the geometric modifications to the injector are tested to determine the performance improvements with respect to the baseline design. Experimental results of the different geometries indicate the injector with inner-slant seems to improve the atomization process. The inner-slant injector has lower emissions for a range of ALR values and a lower pressure drop though the injector compared to the original geometry.

Download or read book CHARACTERIZATION OF THE POST INJECTION BEHAVIOR OF GASOLINE DIRECT INJECTION FUEL INJECTORS written by and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract : The characteristics of gasoline sprayed directly into combustion chambers are of critical importance to engine out emissions and combustion system development. The optimization of the spray characteristics to match the in-cylinder flow field, chamber geometry, and spark location are vital tasks during the development of an engine combustion strategy. Furthermore, the presence of liquid fuel during combustion in Spark-Ignition (SI) engines causes increased hydrocarbon (HC) emissions [1]. Euro 6, LEVIII, and US Tier 3 emissions regulations reduce the allowable particulate mass significantly from the previous standards. LEVIII standards reduce the acceptable particulate emission to 1 mg/mile [2]. A good Direct Injection Spark Ignited (DISI) strategy vaporizes the correct amount of fuel at the proper point in the engine cycle with the proper in-cylinder air flow for optimal power output with minimal emissions. The opening and closing phases of DISI injectors is crucial to this task as the spray produces larger droplets during both theses phases. This work focuses on the results from a novel method to investigate fuel behavior upon closing of the fuel injector. A Design of Experiments (DOE) was used to determine the effect of pressure, temperature, and pulse-width of the fuel spray after the closing event. Experiments determined that the primary source of controlling the droplet size and the mass post injector closing for a given injector was the temperature. It was found that the end of injection behavior is a highly dynamic, complex event including, but not limited to, effects from the injector design, deposit concentration, and fuel type.

Download or read book High Speed Flow Simulation in Fuel Injector Nozzles written by Sukanta Rakshit and published by . This book was released on 2012 with total page 94 pages. Available in PDF, EPUB and Kindle. Book excerpt: Atomization of fuel is essential in controlling combustion inside a direct injection engine. Controlling combustion helps in reducing emissions and boosting efficiency. Cavitation is one of the factors that significantly affect the nature of spray in a combustion chamber. Typical fuel injector nozzles are small and operate at a very high pressure, which limit the study of internal nozzle behavior. The time and length scales further limit the experimental study of a fuel injector nozzle. Simulating cavitation in a fuel injector will help in understanding the phenomenon and will assist in further development. The construction of any simulation of cavitating injector nozzles begins with the fundamental assumptions of which phenomena will be included and which will be neglected. To date, there has been no consensus about whether it is acceptable to assume that small, high-speed cavitating nozzles are in thermal or inertial equilibrium. This diversity of opinions leads to a variety of modeling approaches. If one assumes that the nozzle is in thermal equilibrium, then there is presumably no significant delay in bubble growth or collapse due to heat transfer. Heat transfer is infinitely fast and inertial effects limit phase change. The assumption of inertial equilibrium means that the two phases have negligible slip velocity. Alternatively, on the sub-grid scale level, one may also consider the possibility of small bubbles whose size responds to changes in pressure. Schmidt et al. developed a two dimensional transient homogeneous equilibrium model which was intended for simulating a small, high speed nozzle flows. The HEM uses the assumption of thermal equilibrium to simulate cavitation. It assumes the two-phase flow inside a nozzle in homogeneous mixture of vapor and liquid. This work presents the simulation of high-speed nozzle, using the HEM for cavitation, in a multidimensional and parallel framework. The model is extended to simulate the non-linear effects of the pure phase in the flow and the numerical approach is modified to achieve stable result in multidimensional framework. Two-dimensional validations have been presented with simulation of a venturi nozzle, a sharp nozzle and a throttle from Winklhofer et al. Three-dimensional validations have been presented with simulation of 'spray A' and 'spray H' injectors from the Engine Combustion Network. The simulated results show that equilibrium assumptions are sufficient to predict the mass flow rate and cavitation incidence in small, high-speed nozzle flows.

Download or read book Swirl Stabilized Injector Flow and Combustion Dynamics for Liquid Propellants at Supercritical Conditions written by and published by . This book was released on 2007 with total page 84 pages. Available in PDF, EPUB and Kindle. Book excerpt: An integrated modeling and simulation program has been conducted to substantially improve the fundamental knowledge of supercritical combustion of liquid propellants under conditions representative of contemporary rocket engines. Both shear and swirl co-axial injectors were considered. The formulation was based on the complete conservation equations in three dimensions. in addition, general-fluid thermodynamics and transport theories were incorporated to allow for a unified treatment of fluid properties over the entire range of thermodynamic states. Turbulence closure was achieved by means of the large-eddy-simulation (LES) technique. Special attention was given to the fluid behavior in the two-phase and transcritical regimes in which rapid property variations occur. Various underlying physiochemical mechanisms associated with co-axial injector dynamics were studied in detail. These included flow evolution, flame stabilization and spreading, heat transfer, and acoustic response. The effects of design attributes and operating conditions on injector characteristics were assessed. Results have not only enhanced the basic understanding of the subject problem, but also provided a quantitative basis for identifying and prioritizing the key design parameters and flow variables that exert dominant influences on the injector behavior in different environments.

Download or read book Combined PIV PLIF Measurements in a High swirl Fuel Injector Flowfield written by Liangta Cheng and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Current lean-premixed fuel injector designs have shown great potential in terms of reducing emissions of pollutants, but such designs are susceptible to combustion instabilities in which aerodynamic instability plays a major role and also has an effect on mixing of air and fuel. In comparison to prototype testing with combustors running in operating conditions, computational approaches such as Large Eddy Simulations (LES) offer a much more cost-effective alternative in the design stage. However, computational models employed by LES require validation by experimental data. This is one of the main motivations behind the present experimental study. Combined particle image velocimetry (PIV) and planar laser induced fluorescence (PLIF) instrumentation allowed simultaneous measurements of velocity vector and a conserved scalar introduced into the fuel stream. The results show that the inner swirl shear layer features two pairs of vortices, which draw high concentration fuel mixture from the central jet into the swirl stream and causes it to rotate in their wakes. Such periodic entrainment also occurs with the characteristic frequencies of the vortices. This has clear implications for temporal variations in fuel/air ratio in a combusting flow; these bursts of mixing, and hence heat release, could be a possible cause of mixing-induced pressure oscillation in combusting tests. For the first time in such a flow, all 3 components of the turbulent scalar flux were available for validation of LES-based predictions. A careful assessment of experimental errors, particularly the error associated with spatial filtering, was carried out. Comparison of LES predictions with experimental data showed very good agreement for both 1st and 2nd moment statistics, as well as spectra and scalar pdfs. It is particularly noteworthy that comparison between LES computed and measured scalar fluxes was very good; this represents successful validation of the simple (constant Schmidt number) SGS model used for this complex and practically important fuel injector flow. In addition to providing benchmark data for the validation of LES predictions, a new experimental technique has been developed that is capable of providing spatially resolved residence time data. Residence times of combustors have commonly been used to help understand NOx emissions and can also contribute to combustion instabilities. Both the time mean velocity and turbulence fields are important to the residence time, but determining the residence time via analysis of a measured velocity field is difficult due to the inherent unsteadiness and the three dimensional nature of a high-Re swirling flow. A more direct approach to measure residence time is reported here that examines the dynamic response of fuel concentration to a sudden cutoff in the fuel injection. Residence time measurement was mainly taken using a time-resolved PLIF technique, but a second camera for PIV was added to check that the step change does not alter the velocity field and the spectral content of the coherent structures. Characteristic timescales evaluated from the measurements are referred to as convection and half-life times: The former describes the time delay from a fuel injector exit reference point to a downstream point of interest, and the latter describes the rate of decay once the effect of the reduced scalar concentration at the injection source has been transported to the point of interest. Residence time is often defined as the time taken for a conserved scalar to reduce to half its initial value after injection is stopped: this is equivalent to the sum of the convection time and the half-life values. The technique was applied to a high-swirl fuel injector typical of that found in combustor applications. Two test cases have been studied: with central jet (with-jet) and without central jet (no-jet). It was found that the relatively unstable central recirculation zone of the no-jet case resulted in increased transport of fuel into the central region that is dominated by a precessing vortex core, where long half-life times are also found. Based on this, it was inferred that the no-jet case may be more prone to NOx production. The technique is described here for a single-phase isothermal flow field, but with consideration, it could be extended to studying reacting flows to provide more insight into important mixing phenomena and relevant timescales.

Download or read book Fundamentals of Fuel Injection and Emission in Two stroke Engines written by Władysław Mitianiec and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Characterization of the Effects of Ducted Fuel Injection in a Compression Ignition Engine written by Christopher William Nilsen and published by . This book was released on 2020 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Ducted fuel injection (DFI) has been proposed as a strategy to enhance the fuel/charge-gas mixing within the combustion chamber of a direct-injection mixing-controlled compression-ignition engine. The concept involves injecting each fuel spray through a small tube within the combustion chamber to facilitate the creation of a leaner mixture in the autoignition zone, relative to a conventional free-spray configuration (i.e., a fuel spray that is not surrounded by a duct). This dissertation investigates the effects of ducted fuel injection on engine-out emissions and efficiency with two-orifice and four-orifice injector tips across a wide range of conditions. A numerical study contributes to the understanding of the fluid flow effects of DFI. The experiments in chapter two use a two-orifice fuel injector to test two duct configurations relative to conventional diesel combustion. The result is that DFI is confirmed to be effective at curtailing engine-out soot emissions. It also breaks the tradeoff between emissions of soot and nitrogen oxides (NO[subscript x]) by simultaneously attenuating soot and NO[subscript x] with increasing dilution. The third chapter expands on the second by comparing ducted fuel injection to conventional diesel combustion over a wide range of operating conditions and at higher loads (up to 8.7 bar gross indicated mean effective pressure) with a four-orifice fuel injector. This chapter is achieved through sweeps of intake-oxygen mole-fraction, injection duration, intake pressure, start of combustion timing, fuel-injection pressure, and intake temperature. Ducted fuel injection is shown to curtail engine-out soot emissions at all tested conditions. Under certain conditions, ducted fuel injection can attenuate engine-out soot by over a factor of 100. In addition to producing significantly lower engine-out soot emissions, ducted fuel injection enables the engine to be operated at low-NO[subscript x] conditions that are not feasible with conventional diesel combustion due to high soot emissions. The fourth chapter explores 1.1 bar IMEP[subscript g] (low load) conditions and 10 bar IMEP[subscript g] (higher-load) conditions with the same four-orifice fuel injector as in chapter three. DFI and CDC are directly compared at each operating point in the study. At the idle condition, the intake dilution was swept to elucidate the soot and NO[subscript x] performance of DFI in this new load range. This expands the range of conditions over which DFI has been shown to attenuate soot formation. It also shows that DFI enables low-NO[subscript x], low-load operation that is not achievable with CDC due to excessive soot formation at high dilution levels. The fifth chapter uses a numerical model to develop the understanding of the fluid flow effects of DFI. This enabled studies of entrainment and mixing that would have been much more challenging to do in an experiment. This showed that DFI enhances charge gas entrainment before the duct and blocks entrainment inside of the duct. Mixing is enhanced by the duct, which resulted in lower peak equivalence ratios at the end of the duct.

Download or read book Modeling Injection and Ignition in Direct Injection Natural Gas Engines written by Xu Jr Cheng and published by . This book was released on with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Investigation of Atomization Mechanisms and Flame Structure of a Twin fluid Injector for Different Liquid Fuels written by Lulin Jiang and published by . This book was released on 2014 with total page 207 pages. Available in PDF, EPUB and Kindle. Book excerpt: Diminishing fossil fuel resources, ever-increasing energy cost, and the mounting concerns for environmental emissions have precipitated worldwide research on alternative fuels. Biodiesel, a popular renewable energy source, is produced from the transesterification process of source oils such as vegetable oil (VO) requiring processing cost and energy input. However, highly viscous glycerol produced as the waste byproduct also decreases the economically viability of biodiesel. Previous studies show that without fuel preheating or hardware modification, high viscosity fuels such as VO and glycerol cannot be burnt cleanly with the application of the typical air blast (AB) injector due to the high viscosity. However, extremely low emissions of diesel, kerosene, biodiesel, straight VO and glycerol flames at the combustor exit are reported using a novel flow blurring (FB) injector. The PDPA measurements in the FB sprays at least 1.0 cm downstream of the injector exit quantitatively show the superior fuel-flexibility and atomization capability of the FB injector as compared to the AB atomizer. This study seeks to gain insight into the detailed flame structure of both conventional and alternative fuels atomized by the FB injector. The atomization mechanism in the FB injector near field is also investigated using a high speed imaging technique and particle image velocimetry (PIV) to explore the FB spray characteristics in the near field of the injector. First, the combustion of diesel, biodiesel and straight vegetable oil (VO) using a Flow Blurring (FB) injector is investigated. Measurements of gas temperature and CO and NOx concentrations at various axial and radial locations of the combustor are acquired using custom-designed thermocouple and gas sampling probes. Heat loss rate through the combustor is estimated from wall temperatures measured by an infra-red camera. A simple droplet model is used to predict fuel vaporization behaviour in the dark-region near the injector exit. Results show that the FB injector produced low-emission clean blue flames indicating mainly premixed combustion for all three fuels. Matching profiles of heat loss rate and product gas temperature show that the combustion efficiency is fuel independent. Next, a fuel-flexible dual-fuel combustor to simultaneously burn methane and/or straight glycerol without preheating either glycerol or air is investigated by utilizing a FB liquid fuel injector. Product gas temperature, NOX and CO emissions at multiple locations inside the combustor are measured to quantitatively assess the flame structure, related to liquid atomization, droplet evaporation, and fuel-air mixing in the near field. The impact of fuel mix and air to liquid mass ratio (ALR) on combustion performance is investigated. Pure glycerol flame is also investigated to demonstrate the fuel flexibility and ease of switching between gas and liquid fuels in the present system. Results show that the methane combustion can assist glycerol vaporization to results in its rapid oxidation. In spite of the differences in the flame structure, profiles of product gas temperature and emissions at the combustor exit reveal that complete and mainly lean premixed combustion with low emissions is achieved for all of the test cases indicating excellent fuel flexibility of the present combustor using the FB injector. Next, high-speed visualization and time-resolved Particle Image Velocimetry (PIV) techniques are employed to investigate the FB spray in the near field of the injector to delineate the underlying mechanisms of atomization. Experiments are performed using water as the liquid and air as the atomizing gas. Flow visualization at the injector exit focused on field of view with the dimension of 2.3 mm x 1.4 mm, spatial resolution of 7.16 æm per pixel, exposure time of 1 æs, and image acquisition rate of 100 k frames per second (fps). Image sequence illustrates mostly fine droplets indicating that primary breakup by FB atomization occurs within the injector. Few larger droplets appearing at the injector periphery undergo secondary breakup by Rayleigh-Taylor instabilities. Time-resolved PIV technique is applied to quantify the droplet dynamics in the injector near field. Plots of instantaneous, mean, and root-mean-square droplet velocities are presented to reveal the secondary breakup process. Results show that the secondary atomization process to produce fine and stable spray is complete within a short distance of about 5.0 mm from the injector exit. These superior characteristics of the FB injector are desirable to achieve clean combustion of different fuels in practical systems. The impact of ALR shows that the increase in ALR improves both primary FB atomization and secondary atomization in the near field. Next, glycerol atomization in the near field of the FB injector is investigated in detail. Time-resolved PIV with exposure time of 1 ms and laser pulse rate of 15 kHz is utilized to probe the glycerol spray at spatial resolution of 16.83 æm per pixel. PIV results describe the droplet dynamics in terms of the instantaneous, mean, and root-mean-square (RMS) velocities, and space-time analysis and probability distribution profiles of the axial velocity. In addition, high-speed imaging (75 kHz) coupled with backside lighting is applied to reveal the glycerol breakup process at spatial resolution of 7.16 æm per pixel and exposure time of 1 æs. Results show that the primary breakup by FB atomization or bubble explosion within the injector results in a combination of slow-moving streaks and fast-moving droplets at the injector exit. Then, the secondary breakup by Rayleigh-Taylor instability occurs at farther downstream locations where the high-velocity atomizing air stretches the streaks into thin streaks that disintegrate into smaller streaks, and subsequently, into fine droplets. Thus, within a short distance downstream of the injector exit (