Fuel injection assembly for gas turbine engine combustor

A fuel injection assembly for a gas turbine engine combustor, including at least one fuel stem, a plurality of concentrically disposed tubes positioned within each fuel stem, wherein a cooling supply flow passage, a cooling return flow passage, and a tip fuel flow passage are defined thereby, and at least one fuel tip assembly connected to each fuel stem so as to be in flow communication with the flow passages, wherein an active cooling circuit for each fuel stem and fuel tip assembly is maintained by providing all active fuel through the cooling supply flow passage and the cooling return flow passage during each stage of combustor operation. The fuel flowing through the active cooling circuit is then collected so that a predetermined portion thereof is provided to the tip fuel flow passage for injection by the fuel tip assembly

Analisis Metode Pelaksanaan Plat Precast Dengan Plat Konvensional Ditinjau Dari Waktu Dan Biaya (Studi Kasus : Markas Komando Daerah Militer Manado)

Pemilihan metode pelaksanaan suatu proyek konstruksi sangat penting karena metode pelaksanaan yang tepat dapat memberikan hasil yang maksimal terutama jika ditinjau dari segi biaya maupun waktu. Salah satu USAha yang dilakukan oleh pengelola proyek adalah mengganti cara –cara konvensional menjadi lebih modern, yaitu dengan cara penerapan beton pracetak. Tujuan penelitian ini : (1) membandingkan metode pelaksanaan pembangunan antara penggunaan sistem beton konvensional. (2) Menganalisa biaya yang diperlukan pada kedua sistem tersebut dengan perhitungan Rab. (3) Menganalisa pengaruh waktu pelaksanaan antara sistem konvensional dan Precast terhadap biaya dengan Kurva S dari kedua sistem tersebut. Dari hal-hal tersebut akan diketahui sistem pengecoran mana yang efisien dari segi waktu, biaya, peralatan, maupun faktor pendukung, serta membandingkan antara precast fabrikasi dengan precast cast in situ. Beberapa aspek tentunya berbeda, baik untuk waktu, alat maupun proses yang akan dilakukan. Hasil penelitian memperlihatkan bahwa : dengan menggunakan metode precast membutuhkan waktu pelaksanaan selama 198 hari dengan Total biaya langsungnya adalah Rp 30,352,740,000,00, sedang untuk metode konvensional membutuhkan waktu pelaksanaan selama 226 hari dengan total biaya langsung Rp 30,230,145,000,00. Perbandingan biaya adalah Rp 122,595,000,00 sedang perbandingan waktu adalah 28 hari. Dapat disimpulkan bahwa pekerjaan menggunakan sistem precast membutuhkan biaya yang lebih besar dibandingkan sistem konvensional akan tetapi dengan waktu pengerjaan yang lebih singkat. Semakin besar volume pekerjaan dengan menggunakan sistem precast, semakin murah pula harganya dibandingkan dengan metode konvensional dan waktu pelaksanaannya juga lebih cepat, apalagi dengan menggunakan sistem Precast cast in situ

Synergistic cross-scale coupling of turbulence in a tokamak plasma

For the first time, nonlinear gyrokinetic simulations spanning both the ion and electron spatio-temporal scales have been performed with realistic electron mass ratio ((m[subscript D] [over m [subscript e])[superscript 1 over 2] = 60.0), realistic geometry, and all experimental inputs, demonstrating the coexistence and synergy of ion (k[subscript θρs] ~O(1.0)) and electron-scale (k[subscript θρe] ~O(1.0)) turbulence in the core of a tokamak plasma. All multi-scale simulations utilized the GYRO code [J. Candy and R. E. Waltz, J. Comput. Phys. 186, 545 (2003)] to study the coupling of ion and electron-scale turbulence in the core (r/a = 0.6) of an Alcator C-Mod L-mode discharge shown previously to exhibit an under-prediction of the electron heat flux when using simulations only including ion-scale turbulence. Electron-scale turbulence is found to play a dominant role in setting the electron heat flux level and radially elongated (k[subscript r] ≪ k[subscript θ]) “streamers” are found to coexist with ion-scale eddies in experimental plasma conditions. Inclusion of electron-scale turbulence in these simulations is found to increase both ion and electron heat flux levels by enhancing the transport at the ion-scale while also driving electron heat flux at sub-ρ[subscript i] scales. The combined increases in the low and high-k driven electron heat flux may explain previously observed discrepancies between simulated and experimental electron heat fluxes and indicates a complex interaction of short and long wavelength turbulence.United States. Dept. of Energy. Office of Science (Contract DE-AC02-05CH11231)United States. Dept. of Energy (Contract DE-FC02-99ER54512-CMOD)United States. Dept. of Energy. Fusion Energy Postdoctoral Research Program (Oak Ridge Institute for Science and Education

Impurity transport, turbulence transitions and intrinsic rotation in Alcator C-Mod plasmas

Linear and nonlinear gyrokinetic simulations are used to probe turbulent impurity transport in intrinsically rotating tokamak plasmas. For this simulation-based study, experimental input parameters are taken from a pair of ICRF heated Alcator C-Mod discharges exhibiting a change in the sign of the normalized toroidal rotation gradient at mid-radius (i.e. a change from hollow to peaked intrinsic rotation profiles). The simulations show that there is no change in the peaking of the calcium impurity between the plasmas with peaked and hollow rotation profiles, suggesting that the impurity transport and the shape of the rotation do not always change together. Furthermore, near mid-radius, r/a = 0.5 (normalized midplane minor radius), the linear and nonlinear gyrokinetic simulations exhibit no evidence of a transition from ion temperature gradient (ITG) to trapped electron mode dominance when the intrinsic rotation profile changes from peaked to hollow. Extensive nonlinear sensitivity analysis is performed, and there is no change in the ITG critical gradient or in the stiffness of ion heat transport with the change in the intrinsic toroidal rotation profile shape, which suggests that the shape of the rotation profile is not dominated by the ITG onset in these cases.United States. Department of Energy (contract DE-FC02-99ER54512-CMOD)United States. Department of Energy (Fusion Energy Postdoctoral Research Program

Multi-scale gyrokinetic simulations: Comparison with experiment and implications for predicting turbulence and transport

To better understand the role of cross-scale coupling in experimental conditions, a series of multi-scale gyrokinetic simulations were performed on Alcator C-Mod, L-mode plasmas. These simulations, performed using all experimental inputs and realistic ion to electron mass ratio ((mi/me)1∕2 = 60.0), simultaneously capture turbulence at the ion (kθρs∼(1.0)) and electron-scales (kθρe∼(1.0)). Direct comparison with experimental heat fluxes and electron profile stiffness indicates that Electron Temperature Gradient (ETG) streamers and strong cross-scale turbulence coupling likely exist in both of the experimental conditions studied. The coupling between ion and electron-scales exists in the form of energy cascades, modification of zonal flow dynamics, and the effective shearing of ETG turbulence by long wavelength, Ion Temperature Gradient (ITG) turbulence. The tightly coupled nature of ITG and ETG turbulence in these realistic plasma conditions is shown to have significant implications for the interpretation of experimental transport and fluctuations. Initial attempts are made to develop a “rule of thumb” based on linear physics, to help predict when cross-scale coupling plays an important role and to inform future modeling of experimental discharges. The details of the simulations, comparisons with experimental measurements, and implications for both modeling and experimental interpretation are discussed.United States. Department of Energy (DE-AC02-05CH11231)United States. Department of Energy (DE-FC02-99ER54512-CMOD)United States. Department of Energy (DE-SC0006957)United States. Department of Energy (DE-FG02-06ER54871

Direct multiscale coupling of a transport code to gyrokinetic turbulence codes

Direct coupling between a transport solver and local, nonlinear gyrokinetic calculations using the multiscale gyrokinetic code TRINITY [M. Barnes, Ph.D. thesis, arxiv:0901.2868] is described. The coupling of the microscopic and macroscopic physics is done within the framework of multiscale gyrokinetic theory, of which we present the assumptions and key results. An assumption of scale separation in space and time allows for the simulation of turbulence in small regions of the space-time grid, which are embedded in a coarse grid on which the transport equations are implicitly evolved. This leads to a reduction in computational expense of several orders of magnitude, making first-principles simulations of the full fusion device volume over the confinement time feasible on current computing resources. Numerical results from TRINITY simulations are presented and compared with experimental data from JET and ASDEX Upgrade plasmas.Comment: 12 pages, 13 figures, invited paper for 2009 APS-DPP meeting, submitted to Phys. Plasma

Positioning the Arts in the Research Process: Perspectives from Higher Education

Research in the visual arts has contributed to the creation of environments that involve cross-disciplinary, multidisciplinary and interdisciplinary or transdisciplinary projects in departments within and across universities. An overview is provided of the historical context of doctoral awards in the arts with a definition of the terms practice-based, practice-led, and practice as research discussed. It articulates the challenges when acquiring explicit and exact knowledge alongside more subjective approaches that utilize tacit knowledge from artistic practice in research projects. Drawing on examples from art practice and doctoral students work, it analyzes objective, subjective, empirical, and hermeneutic paradigms, as described by Pierre Bourdieu, which can combine empirical approaches and individual understandings to re-enforce our understandings of the world

An Overview of the 13:8 Mean Motion Resonance between Venus and Earth

It is known since the seminal study of Laskar (1989) that the inner planetary system is chaotic with respect to its orbits and even escapes are not impossible, although in time scales of billions of years. The aim of this investigation is to locate the orbits of Venus and Earth in phase space, respectively to see how close their orbits are to chaotic motion which would lead to unstable orbits for the inner planets on much shorter time scales. Therefore we did numerical experiments in different dynamical models with different initial conditions -- on one hand the couple Venus-Earth was set close to different mean motion resonances (MMR), and on the other hand Venus' orbital eccentricity (or inclination) was set to values as large as e = 0.36 (i = 40deg). The couple Venus-Earth is almost exactly in the 13:8 mean motion resonance. The stronger acting 8:5 MMR inside, and the 5:3 MMR outside the 13:8 resonance are within a small shift in the Earth's semimajor axis (only 1.5 percent). Especially Mercury is strongly affected by relatively small changes in eccentricity and/or inclination of Venus in these resonances. Even escapes for the innermost planet are possible which may happen quite rapidly.Comment: 14 pages, 11 figures, submitted to CMD