Lean, premixed, prevaporized combustor conceptual design study

Phase 1 of the Lean Premixed-Prevaporized Comubstor Design Study is a nine month analytical study effort with no experimental or testing activities included. The program has the objective to design and analyze advanced combustor concepts with features for fuel premixing and prevaporization upstream of the combustion zone for use in future subsonic aircrafts with features for fuel premixing and prevaporization upstream of the combustion zone for use in future subsonic aircraft engines. All of the designs also embody some form of variable geometry for combustor flow modulation. The primary criterion for these designs is low oxides of nitrogen emissions at stratospheric cruise conditions. Four combustor concepts are being designed for the NASA/GE Energy Efficient Engine (EEE) envelope and cycle. Current status of the program is that the four concepts sized for the EEE were designed and are currently undergoing analysis and evaluation

Liner environment effects study

The Liner Environment Effects Study Program is aimed at establishing a broad heat transfer data base under controlled experimental conditions by quantifying the effects of the combustion system conditions on the combustor liner thermal loading and on the flame radiation characteristics. Five liner concepts spanning the spectrum of liner design technology from the very simple to the most advanced concepts are investigated. These concepts comprise an uncooled liner, a conventional film cooled liner, an impingement/film cooled liner, a laser drilled liner approaching the concept of a porous wall, and a siliconized silicon carbide ceramic liner. Effect of fuel type is covered by using fuels containing 11.8, 12.8, and 14% hydrogen. Tests at 100, 200, and 300 psia provide a basis for evaluating the effect of pressure on the heat transfer. The effects of the atomization quality and spray characteristics are examined by varying the fuel spray Sauter mean diameter and the spray angle. Additional varied parameters include reference velocity, a wide range of equivalence ratio, cooling flow rate, coolant temperature and the velocity of the coolant stream on the backside of the liner

Experimental combustor study program

Advanced combustor concepts are evaluated as a means of accommodating possible future broad specification fuels. The three advanced double annular combustor concepts consisted of (1) a concept employing high pressure drop fuel nozzles for improved atomization, (2) a concept with premixing tubes in the main stage, and (3) a concept with the pilot stage on the inside and the main stage on the sideout, which is the reverse of the other two concepts. All of the advanced concepts show promise for reduced sensitivity to fuel hydrogen content. Some hardware problems were encountered, but these problems could be quickly resolved if refinement tests were conducted. The design with the premixing main stage was selected for a parametric test because of its low NOx emissions level, carbon free dome, and very low dome temperatures which were essentially independent of fuel type. The other advanced designs also had low done temperatures. The premixing dome design liner temperatures exhibited less sensitivity to fuel type than did the base-line combustor, although more sensitivity than observed for concept 1. The inner liner hot spot and the observed smoke results for the premixing design suggest that the fuel-air mixture was not as uniform as desired

Wage Earners’ Priority in Bankruptcy: Application to Welfare Fund Payments

This paper describes a study on how cyber security experts assess the importance of three variables related to the probability of successful remote code execution attacks – presence of: (i) non-executable memory, (ii) access and (iii) exploits for High or Medium vulnerabilities as defined by the Common Vulnerability Scoring System. The rest of the relevant variables were fixed by the environment of a cyber defense exercise where the respondents participated. The questionnaire was fully completed by fifteen experts. These experts perceived access as the most important variable and availability of exploits for High vulnerabilities as more important than Medium vulnerabilities. Non-executable memory was not seen as significant, however, presumably due to lack of address space layout randomization and canaries in the network architecture of the cyber defense exercise scenario.QC 20140908</p

Evaluation of Global Wave Climate Based on the JMA/MRI-AGCM Climate Change Projection

In this study global wave climates for present and future climates are simulated with the WAM model, based on wind fields from the JMA/MRI-AGCM3.2 climate projection. The projected wave fields are analysed and compared for the two periods of 1979-2003 and 2075-2099, and climate change induced differences are identified. It is found that the wave climate is strongly dependent on latitude, with the largest waves, as well as most significant seasonal variations, located at the mid to high latitude regions. These areas are also where the climate induced changes from present to future climate are most noteworthy. The largest increases of significant wave height of approximately +5%, is experienced in the southern parts of the Indian, Pacific and Atlantic Oceans as well as in the Antarctic Ocean. The largest decreases are of the same order, and found to the northern Atlantic Ocean. In addition, a slightly smaller but widespread decrease is seen in the tropical storm affected region around Japan, in the western Pacific Ocean. In contrast to this reduction of the everyday wave climate, an evaluation of the annual maximum waves at this location indicates that the extreme wave climate might become more severe due to the projected climate change. In the central and lower parts of the mid latitude regions the projected wave climate remain fairly stable and show only minor changes between present and future climates. It is noted that the processes behind the everyday wave climate differ significantly from those causing extreme events, and that the phenomena should therefore be evaluated separately. Since this study focuses on the climate change induced effects on the wave climate under normal weather conditions, it is recommended that in future research evaluate the extremes in a more thorough manner. For that analysis using the full potential of the JMA/MRI-AGCM high-resolution wind fields output is recommended

Propagation of gauge fields in hot and dense plasmas at higher orders

Thermal field theory is indispensable for describing hot and dense systems. Yet perturbative calculations are often stymied by a host of energy scales, and tend to converge slowly. This means that precise results require the apt use of effective field theories. In this paper we refine the effective description of slowly varying gauge field known as hard thermal loops. We match this effective theory to the full theory to two-loops. Our results apply for any renormalizable model and fermion chemical potential. We also discuss how to consistently define asymptotic masses at higher orders; and how to treat spectral functions close to the lightcone. In particular, we demonstrate that the gluon mass is well-defined to next-to-leading order.Comment: 21 pages, 4 figure

Constraining minimal anomaly free U(1)\mathrm{U}(1) extensions of the Standard Model

We consider a class of minimal anomaly free $\mathrm{U}(1)$ extensions of the Standard Model with three generations of right-handed neutrinos and a complex scalar. Using electroweak precision constraints, new 13 TeV LHC data, and considering theoretical limitations such as perturbativity, we show that it is possible to constrain a wide class of models. By classifying these models with a single parameter, $\kappa$, we can put a model independent upper bound on the new $\mathrm{U}(1)$ gauge coupling $g_z$. We find that the new dilepton data puts strong bounds on the parameters, especially in the mass region $M_{Z'}\lesssim 3~ \mathrm{TeV}$.Comment: 23 pages, 4 figures. Modified model parametrization, exclusion limits with new dat