Chia-Fon Lee

Bio: Chia-Fon Lee is an academic researcher from University of Illinois at Urbana–Champaign. The author has contributed to research in topics: Combustion & Diesel fuel. The author has an hindex of 43, co-authored 250 publications receiving 7040 citations. Previous affiliations of Chia-Fon Lee include Wuhan University & Princeton University.

Experimental Investigation of Droplet Dynamics and Spray Atomization inside Thermostatic Expansion Valves

Abstract: Experimental investigation on spray atomization and droplet dynamics inside a thermostatic expansion valve (TEV) was conducted. A needle and an orifice were copied from a commercial TEV and machined to be mounted inside a chamber with optical access so that the flow inside the TEV is simulated and visualized at the same time. The break-up and atomization of the refrigerant were documented near the downstream of the orifice under different feed conditions on micro-second scale. A Phase Doppler Anemometry (PDA) system was used later to measure the size of atomized refrigerant droplets. It is found that spray impingement is inevitable and crucial to the atomization. Under steady-state operation, liquid film was seen formed on the needle plate and caused droplets splashed from plate, which will further have an effect on the droplets size. The before impact and after impact droplets were characterized by PDA system and for studying the impingement. In addition, the impact of the needle geometry inside the valve on refrigerant atomization has also been investigated. * Corresponding author: Chia-fon F. Lee

Visualization Research on Low-Temperature Ignition and Combustion Characteristics of Diesel/Gasoline Blends Under Cold-Start Conditions

Abstract: Although engines fueled with diesel/gasoline blends show excellent combustion and emission performance, its low-temperature flame development characteristics under cold-start conditions remain to be further verified. To clarify the details, experiments were conducted in an optical constant volume combustion chamber using Mie-scattering and direct photography methods at different ambient temperatures. Results show that the ignition delay of pure diesel during spray combustion shows a zero temperature coefficient (ZTC) region, and the addition of gasoline weakens the ZTC behavior until it disappears. The cool flame initiates the ignition, and the hot flame tends to far from the base of the cool flame as the gasoline content increases. In addition, the addition of gasoline to diesel increases the ratio of cool flames because the high evaporation reduces the temperature in the mixing zone, so only cool flame occurs in the G45 blends. Consequently, the total flame intensity presents an order of magnitude decrease. At lower ambient temperatures, the addition of gasoline significantly increases ignition instability. It is difficult to convert a cool flame into a hot flame due to the inhomogeneity of temperature and species field, which results in various unstable ignition phenomena, such as a short flash cool flame and intermittent cool and hot flame. Therefore, it is essential to directly target the cool flame and pay attention to the intrinsic mechanism of the evolution from the cool flame to the hot flame during the spray combustion process.

Visualization and simulation study on the impacts of conical duct geometry on the spray characteristics of ducted fuel injection

Abstract: In this work, experiment and simulation methods were employed to investigate the spray characteristics of ducted fuel injection (DFI) configured the conical duct. A cylindrical duct was used for comparison. The diameter of the small port of the conical duct is the same as the diameter of the cylindrical duct hole. The conical duct is placed in two ways, namely contracted and expanded placement. The research was conducted under injection pressure of 120 MPa, high ambient density of 65.6 kg/m3 and non-vaporizing conditions. The perspectives of spray dispersion, spray morphology and gas-fuel mixing at the duct inlet were investigated as indicators for evaluating spray performance. Results showed that the duct confinement is the main reason for the difference in spray performance. Under the duct confinement, the fuel adhering to the inner wall of the duct during the spraying process forms a film. Depending on whether the spray collides directly with the duct wall, the interaction of the spray with the duct is interpreted as direct interaction and indirect interaction. The film shows a jitter-like development under the direct interaction and develops smoothly under indirect interaction. Direct interaction is beneficial to improve spray performance, while indirect interaction is the opposite. The duct confinement changes the velocity field, Turbulent Kinetic Energy field and pressure field of the spray, which results in the difference in the spray performance of each spray method. A strong gas entrainment occurs at the duct inlet, contributing to the formation of a high quality gas-fuel mixture. For these spray performances, DFI with the conical duct does not perform as well as that of the cylindrical duct and the conical duct is better placed in contraction than in expansion.

Drop Impact Dynamics: Splashing, Spreading, Receding, Bouncing ...

Abstract: The review deals with drop impacts on thin liquid layers and dry surfaces. The impacts resulting in crown formation are referred to as splashing. Crowns and their propagation are discussed in detail, as well as some additional kindred, albeit nonsplashing, phenomena like drop spreading and deposition, receding (recoil), jetting, fingering, and rebound. The review begins with an explanation of various practical motivations feeding the interest in the fascinating phenomena of drop impact, and the above-mentioned topics are then considered in their experimental, theoretical, and computational aspects.

Review of biodiesel composition, properties, and specifications

Abstract: Biodiesel is a renewable transportation fuel consisting of fatty acid methyl esters (FAME), generally produced by transesterification of vegetable oils and animal fats. In this review, the fatty acid (FA) profiles of 12 common biodiesel feedstocks were summarized. Considerable compositional variability exists across the range of feedstocks. For example, coconut, palm and tallow contain high amounts of saturated FA; while corn, rapeseed, safflower, soy, and sunflower are dominated by unsaturated FA. Much less information is available regarding the FA profiles of algal lipids that could serve as biodiesel feedstocks. However, some algal species contain considerably higher levels of poly-unsaturated FA than is typically found in vegetable oils. Differences in chemical and physical properties among biodiesel fuels can be explained largely by the fuels’ FA profiles. Two features that are especially influential are the size distribution and the degree of unsaturation within the FA structures. For the 12 biodiesel types reviewed here, it was shown that several fuel properties – including viscosity, specific gravity, cetane number, iodine value, and low temperature performance metrics – are highly correlated with the average unsaturation of the FAME profiles. Due to opposing effects of certain FAME structural features, it is not possible to define a single composition that is optimum with respect to all important fuel properties. However, to ensure satisfactory in-use performance with respect to low temperature operability and oxidative stability, biodiesel should contain relatively low concentrations of both long-chain saturated FAME and poly-unsaturated FAME.

A comprehensive review on biodiesel as an alternative energy resource and its characteristics

Abstract: As the fossil fuels are depleting day by day, there is a need to find out an alternative fuel to fulfill the energy demand of the world. Biodiesel is one of the best available resources that have come to the forefront recently. In this paper, a detailed review has been conducted to highlight different related aspects to biodiesel industry. These aspects include, biodiesel feedstocks, extraction and production methods, properties and qualities of biodiesel, problems and potential solutions of using vegetable oil, advantages and disadvantages of biodiesel, the economical viability and finally the future of biodiesel. The literature reviewed was selective and critical. Highly rated journals in scientific indexes were the preferred choice, although other non-indexed publications, such as Scientific Research and Essays or some internal reports from highly reputed organizations such as International Energy Agency (IEA), Energy Information Administration (EIA) and British Petroleum (BP) have also been cited. Based on the overview presented, it is clear that the search for beneficial biodiesel sources should focus on feedstocks that do not compete with food crops, do not lead to land-clearing and provide greenhouse-gas reductions. These feedstocks include non-edible oils such as Jatropha curcas and Calophyllum inophyllum , and more recently microalgae and genetically engineered plants such as poplar and switchgrass have emerged to be very promising feedstocks for biodiesel production. It has been found that feedstock alone represents more than 75% of the overall biodiesel production cost. Therefore, selecting the best feedstock is vital to ensure low production cost. It has also been found that the continuity in transesterification process is another choice to minimize the production cost. Biodiesel is currently not economically feasible, and more research and technological development are needed. Thus supporting policies are important to promote biodiesel research and make their prices competitive with other conventional sources of energy. Currently, biodiesel can be more effective if used as a complement to other energy sources.

Progress in the production and application of n-butanol as a biofuel

Abstract: Butanol is a very competitive renewable biofuel for use in internal combustion engines given its many advantages. In this review, the properties of butanol are compared with the conventional gasoline, diesel fuel, and some widely used biofuels, i.e. methanol, ethanol, biodiesel. The comparison of fuel properties indicates that n-butanol has the potential to overcome the drawbacks brought by low-carbon alcohols or biodiesel. Then, the development of butanol production is reviewed and various methods for increasing fermentative butanol production are introduced in detailed, i.e. metabolic engineering of the Clostridia, advanced fermentation technique. The most costive part of the fermentation is the substrate, so methods involved in renewed substrates are also mentioned. Next, the applications of butanol as a biofuel are summarized from three aspects: (1) fundamental combustion experiments in some well-defined burning reactors; (2) a substitute for gasoline in spark ignition engine; (3) a substitute for diesel fuel in compression ignition engine. These studies demonstrate that butanol, as a potential second generation biofuel, is a better alternative for the gasoline or diesel fuel, from the viewpoints of combustion characteristics, engine performance, and exhaust emissions. However, butanol has not been intensively studied when compared to ethanol or biodiesel, for which considerable numbers of reports are available. Finally, some challenges and future research directions are outlined in the last section of this review.