7 research outputs found
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Western Land Managers will Need all Available Tools for Adapting to Climate Change, Including Grazing: A Critique of Beschta et al.
In a previous article, Beschta et al. (Environ
Manag 51(2):474–491, 2013) argue that grazing by large
ungulates (both native and domestic) should be eliminated
or greatly reduced on western public lands to reduce
potential climate change impacts. The authors did not
present a balanced synthesis of the scientific literature, and
their publication is more of an opinion article. Their conclusions
do not reflect the complexities associated with
herbivore grazing. Because grazing is a complex ecological process, synthesis of the scientific literature can be a
challenge. Legacy effects of uncontrolled grazing during
the homestead era further complicate analysis of current
grazing impacts. Interactions of climate change and grazing
will depend on the specific situation. For example,
increasing atmospheric COâ‚‚ and temperatures may increase
accumulation of fine fuels (primarily grasses) and thus
increase wildfire risk. Prescribed grazing by livestock is
one of the few management tools available for reducing
fine fuel accumulation. While there are certainly points on
the landscape where herbivore impacts can be identified, there are also vast grazed areas where impacts are minimal.
Broad scale reduction of domestic and wild herbivores to
help native plant communities cope with climate change
will be unnecessary because over the past 20–50 years land
managers have actively sought to bring populations of
native and domestic herbivores in balance with the potential
of vegetation and soils. To cope with a changing climate,
land managers will need access to all available
vegetation management tools, including grazing.Keywords: Grazing, Riparian areas, Public lands, Climate chang
Effect of flow velocity and temperature on minimum ignition energy in laser-induced spark ignition of gaseous fuels
Laser induced spark ignition offers the potential for greater reliability and consistency in ignition of lean air/fuel mixtures. This increased reliability is essential for the application of gas turbines as primary or secondary reserve energy sources in smart grid systems, enabling the integration of renewable energy sources whose output is prone to fluctuation over time. This work details a study into the effect of flow velocity and temperature on minimum ignition energies in laser-induced spark ignition in an atmospheric combustion test rig, representative of a sub 15 MW industrial gas turbine (Siemens Industrial Turbomachinery Ltd., Lincoln UK). Determination of the minimum ignition energies required for a range of temperatures and flow velocities is essential in determining an operating window in which laser-induced spark ignition can operate under realistic, engine-like start conditions. Ignition of a natural gas and air mixture at atmospheric pressure was conducted using a laser ignition system utilizing a Q-switched Nd:YAG laser source operating at 532 nm wavelength and 4 ns pulse length. A detailed analysis of the potential for extension of this operating window, for instance through an improvement in the lean burn limit, is presented
Lean burn limit and time to light characteristics of laser ignition in gas turbines
This work details a study of laser ignition in a low pressure combustion test rig, representative of an
industrial gas turbine (SGT-400, Siemens Industrial Turbomachinery Ltd.) and for the first time
investigates the effect of air mass flow rate on combustion characteristics at air/fuel ratios at the lean
burn limit.Boththeleanburnlimitandtimetakentolightareessentialindeterminingthesuitabilityof
a specified air/fuel ratio, especially in multi-chamber ignition applications. Through extension of the lean
burn limit and reduction of the time taken to light, the operating window for ignition with regards to the
air/fuel ratio can be increased, leading to greater reliability and repeatability of ignition. Ignition of a
natural gas and air mixture at atmospheric pressure was conducted using both a standard high energy
igniter and a laser ignition system utilizing a Q-switched Nd:YAG laser source operating at 1064 nm
wavelength. A detailed comparison of the lean burn limit and time taken to light for standard ignition
and laser ignition is presented
Effect of flow velocity and temperature on minimum ignition energy in laser-induced spark ignition of gaseous fuels
Laser induced spark ignition offers the potential for greater reliability and consistency in ignition of lean air/fuel mixtures. This increased reliability is essential for the application of gas turbines as primary or secondary reserve energy sources in smart grid systems, enabling the integration of renewable energy sources whose output is prone to fluctuation over time. This work details a study into the effect of flow velocity and temperature on minimum ignition energies in laser-induced spark ignition in an atmospheric combustion test rig, representative of a sub 15 MW industrial gas turbine (Siemens Industrial Turbomachinery Ltd., Lincoln UK). Determination of the minimum ignition energies required for a range of temperatures and flow velocities is essential in determining an operating window in which laser-induced spark ignition can operate under realistic, engine-like start conditions. Ignition of a natural gas and air mixture at atmospheric pressure was conducted using a laser ignition system utilizing a Q-switched Nd:YAG laser source operating at 532 nm wavelength and 4 ns pulse length. A detailed analysis of the potential for extension of this operating window, for instance through an improvement in the lean burn limit, is presented.</p