Characterization of Centrifugally-Loaded Flame Migration for Ultra-Compact Combustors

The Air Force Research Laboratory (AFRL) has designed an Ultra Compact Combustor (UCC) showing viable merit for significantly reducing gas turbine combustor length making it a viable candidate for implementation as an inter-turbine burner and realization of efficiency benefits from the resulting near constant temperature cycle. This concept uses an off-axis combustor cavity and projects approximately 66% length reduction over a conventional combustor. The annular nature of the cavity creates high angular acceleration levels, on the order of 500-3500 g\u27s, resulting in strong centrifugal and buoyant forces. This unique combination works to significantly reduce the required burn time and subsequently required combustor size. However, currently tested experimental models are in the 10-20 cm diameter range while application to larger-scale commercial and military engines would require a UCC in the 50-60 cm diameter range. The Air Force Institute of Technology\u27s Combustion Optimization and Analysis Laser (COAL) laboratory was specifically designed to study the underlying UCC dynamics and investigate the feasibility of scaling the UCC to the significantly larger diameter range. Using a sectional model of AFRL\u27s annular UCC allows customization of the UCC model to investigate varying several parameters of interest associated with the UCC scaling. Several diagnostic methods were used such as Particle Image Velocimetry (PIV) for flowfield measurements, two-line Planar Laser-Induced Fluorescence (PLIF) of the hydroxyl (OH) radical for 2-D temperature profiles, single-line PLIF for qualitative flame location, and high-speed video to investigate flame migration trajectory

DETERMINATION OF THE VOCATIONAL TAXONOMY HIERARCHY FOR HIGHER VOCATIONAL SCHOOL

Taxonomy can be defined as the naming or classification of an idea or name, according to one discipline. There is a lack of regulation in the concept of vocational education. Vocational education (SMK) cannot fully use Bloom's Taxonomy. Vocational Taxonomy is centered on psychomotor theory which emphasizes aspects of physical movement. However, the purpose of this research is to determine the appropriate Vocational Taxonomy hierarchical structure for SMKN 1 Jeunib. The design of this research is qualitative research which using interview method to assess the perception of the Vocational teacher in terms of determination the Vocational Taxonomy. The sample chosen was SMKN 1 Jeunib, Bireun, Aceh, which selected 54 teachers from all departments. The result presented that the teachers believed Vocational Taxonomy is important for SMK learning and teaching. In addition, the taxonomic function is very important and assisting in teaching and learning, aiding the curriculum preparation and contributing the practical activities. Then also, the taxonomy function is important in measurement and assessment of psychomotor activities. So, the Taxonomy was recommended to related parties (SMK, Polytechnic, Vocational College, or training Institution). The research also stated that there was a need for a link between cognitive and psychomotor aspects. Finally, the students not only mastered the aspects of knowledge but also proficiency

System Integration Case Study, FAST-TRAC: Preliminary IV Deliverable #2

The full potential of IntelligentTransportation Systems (ITS) will be realized only when agencies coordinate and integrate systems across modal, institutional and jurisdictional boundaries. Integration enables the cooperation of individual ITS components. It allows the sharing of resources and information, which promises to pay great dividends in reduced costs and improved operations for customers and agencies. As a result, the U.S. Department of Transportation’s (U.S. DOT) Intelligent Transportation System (ITS) program is progressing from operational testing to system deployment with a focus on integrating various ITS technologies, as well as previously deployed systems

Near-field Development of Gas-phase Horizontal Laminar Jets with Positive and Negative Buoyancy Measured with Filtered Rayleigh Scattering

Near-field mixing characteristics of horizontally issuing jets, alternatively positively and negatively buoyant, are explored. The cross-sectional mass fraction of a buoyant horizontal jet consisting of helium flowing into ambient air is measured using a non-intrusive technique, filtered Rayleigh scattering, for Reynolds numbers ranging from 50 to 1,200, Froude numbers ranging as low as 0.71, and Schmidt numbers on the order of unity for all tests. Several corresponding experiments were carried out using carbon dioxide in place of helium in order to determine whether the direction of the buoyancy changes the characteristic shape of the jet cross-section. Consistent with the literature, mixing rates were consistently higher on the side of the jet where instability, due to density stratification, was present. At jet Froude numbers ranging between 1.5 and approximately 3, the jet cross-section takes a shape consistent with a single plume of fluid being ejected from the core in a vertical direction-upward for a jet with positive buoyancy and downward for a jet with negative buoyancy. Remarkably, for Froude numbers less than unity, the distortion of the jet is quite different in that two separate plumes emanate from each side of the jet while ejection from the center is suppressed. Both the positively and negatively buoyant jet cross-sections exhibited this trait, suggesting that the mechanism that determines the cross-sectional shape of the jet core is only mildly influenced by centripetal effects brought about by streamline curvature. The location of the jet centroid at varied streamwise locations was computed from the mass fraction data, yielding jet trajectory. Abstract © Springer-Verlag (outside the USA

A review of cavity-based trapped vortex, ultra-compact, high-g, inter-turbine combustors

Trapped vortex combustor (TVC) is different from conventional swirl-stabilized combustors. It takes advantages of a cavity to stabilize the flame. When the cavity size of a TVC is well designed, a large rotating vortex can be formed in the cavity. The vortex cannot shed out the cavity and is thus named a “locked” or “stable” vortex. One of the main challenges for TVC design is fuel injection. Typically, fuel can be injected directly into the cavity or from the diffuser upstream. Injecting from the diffuser leads to the fuel being mixed with the air before it enters the combustor. When the fuel is injected directly into the cavity, it is desirable to supply the fuel in such way that the locked vortex in the cavity is reinforced. Furthermore, the fuel-air mixing in the cavity will be promoted, as the bypass air is directly added into the cavity. Since the recirculation zone anchored in the cavity is not exposed to the main incoming flow, stable combustion is achieved, even in the presence of a high speed main flow as typically expected in Ramjets and Scramjets. A well-designed trapped vortex combustor (TVC) enables a better fuel-air mixing, a better stabilized flame, lower emission, ultra-compact and high efficient combustion to be achievable. As a promising combustion concept, intensive scientific research has been conducted on TVC in the application areas of aerospace propulsion, power generation and waste incineration. In this work, we will firstly introduce the fundamental concepts, the development and evolution history of TVCs. The combustion, aerodynamics, and aeroacoustics features of trapped vortex combustion are then described. This includes reviewing and discussing the cavity flow/aerodynamics, fuel-air injection and mixing, trapped vortex combustion, emission and combustion of alternative fuels, and aeroacoustics characteristics. The 'spin-off’ application of trapped vortex combustion concept for the design of ultra-compact and high-g combustors, inter-turbine burners, in-Situ and flameless TVC reheat combustors are then reviewed and discussed. Various practical applications of trapped vortex combustion concept in gas turbines, ramjets, scramjets and waste incinerators are discussed and summarized. Finally, the challenges and future directions of the design and implementation of TVCs are provided