The
structure and lean extinction of premixed liquefied petroleum
gas–air flames seated on conductive perforated plates were
examined experimentally, with focus on the effects of plate material,
thickness, and hole diameter. The lean extinction limit was determined
by gradually reducing the fuel-flow rate for a given air-flow rate,
until extinction occurred. Flame structure was quantified by mapping
the local mean temperature and species concentrations and by imaging
the average visual length of the flame plume. Pyrometer measurements
of the temperature of the upper plate surface were made to estimate
the heat transfer through the plate. It was found that the flames
stabilized on plates with higher thermal conductivity were shorter
and more stable (i.e., have lower lean extinction limits). This was
attributed to preheating of fresh reactant mixture by greater heat
transfer through the plate. Increasing the hole diameter (percentage
open area) was found to enhance flame stability by reducing the reactant
jet velocity for a given flow rate of reactant mixture. Heat transfer
through the plate deteriorated with increasing hole size. However,
the positive effect of smaller jet velocity on flame stability overpowered
the negative effect of reduced heat transfer, and the net result was
enhanced stability with larger hole sizes. Plate thickness, on the
other hand, was found to have a weak effect on flame stability and
structure. Thicker plates showed slightly better stability characteristics
because of greater heat transfer through them. Nonetheless, plate
heat transfer did not affect flame stability as significantly as jet
velocity did.
The growing importance of three-dimensional radiotherapy treatment has been associated with the active presence of advanced computational workflows that can simulate conventional x-ray films from computed tomography (CT) volumetric data to create digitally reconstructed radiographs (DRR). These simulated x-ray images are used to continuously verify the patient alignment in image-guided therapies with 2D-3D image registration. The present DRR rendering pipelines are quite limited to handle huge imaging stacks generated by recent state-of-the-art CT imaging modalities. We present a high performance x-ray rendering pipeline that is capable of generating high quality DRRs from large scale CT volumes. The pipeline is designed to harness the immense computing power of all the heterogeneous computing platforms that are connected to the system relying on OpenCL. Load-balancing optimization is also addressed to equalize the rendering load across the entire system. The performance benchmarks demonstrate the capability of our pipeline to generate high quality DRRs from relatively large CT volumes at interactive frame rates using cost-effective multi-GPU workstations. A 5122 DRR frame can be rendered from 1024 × 2048 × 2048 CT volumes at 85 frames per second.
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