Combustion instability sustained by unsteady vortex combustion

The determination of an internal feedback mechanism which leads to combustion instability inside a small scale laboratory combustor is presented in this paper. During combustion instability, the experimental findings show that a large vortical structure is formed at an acoustic resonant mode of the system. The subsequent unsteady burning, within the vortex as it is convected downstream, feeds energy into the acoustic field and sustains the large resonant oscillations. These vortices are formed when the acoustic velocity fluctuation at the flameholder is a large fraction of the mean flow velocity. The propagation of these vortices is not a strong function of the mean flow speed and appears to be dependent upon the frequency of the instability. Continued existence of large vortical structures which characterize unstable operation depends upon the fuel-air ratio, system acoustics, and fuel type

Sharing the 620-790 MHz band allocated to terrestrial television with an audio-bandwidth social service satellite system

A study was carried out to identify the optimum uplink and downlink frequencies for audio-bandwidth channels for use by a satellite system distributing social services. The study considered functional-user-need models for five types of social services and identified a general baseline system that is appropriate for most of them. Technical aspects and costs of this system and of the frequency bands that it might use were reviewed, leading to the identification of the 620-790 MHz band as a perferred candidate for both uplink and downlink transmissions for nonmobile applications. The study also led to some ideas as to how to configure the satellite system

Everything Under the Sun: A Guide to Siting Solar in the Lone Star State

Encouraging energy production using renewable resources is a widely recognized public policy that is promoted by both the federal and state governments in the U.S., and with recent technological advances, renewable-electricity generation is rapidly becoming economically viable. The Energy Information Administration (EIA) forecasts that electricity production from all renewable sources will increase 72% between 2013 and 2040, with the renewable share of total U.S. electricity generation growing from 13% to 18%.1 The future of solar power is especially bright with a projected growth rate of 6.8% per year between 2013 and 2040. If this projection holds true, solar power will far outpace the growth of other renewables. Combined with the Investment Tax Credit (ITC) introduced in 2006, rapid improvements in photovoltaic (PV) solar panel efficiency and dramatic reductions in PV costs are driving a veritable solar boom in the U.S. In fact, the Solar Energy Industries Association (SEIA) reports a 73% decrease in the cost of installing solar since the implementation of the ITC, and anticipates an additional 20,000 Megawatts (MW) of solar generation capacity will come online in the next two years, doubling current U.S. solar capacity. Likewise, the EIA projects that solar power will account for nearly half of the total 109,000MW of renewable-generation-capacity that is expected to be added to the U.S. electricity grid by 2040.The Kay Bailey Hutchison Center for Energy, Law, and Busines