243 research outputs found
The effect of rotor blade thickness and surface finish on the performance of a small axial flow turbine
An experimental investigation was conducted to determine the effect of blade profile inaccuracies and surface finish on the aerodynamic performance of a 11.13 cm tip diameter turbine. The as-received cast rotor blades had a significantly thicker profile than the design intent and a fairly rough surface finish. Stage test results showed an increase of one point in efficieny by smoothing the surface finish and another three points by thinning the blade profiles to near the design profile. Most of the performance gain between the as-cast thick and the thinned rotor blades both with the same surface finish, was attributed to reduced trailing edge losses of the recontoured blades
Cold-air performance of compressor-drive turbine of Department of Energy upgraded automobile gas turbine engine. 2: Stage performance
The aerodynamic performance of the compressor-drive turbine of the DOE upgraded gas turbine engine was determined in low temperature air. The as-received cast rotor blading had a significantly thicker profile than design and a fairly rough surface finish. Because of these blading imperfections a series of stage tests with modified rotors were made. These included the as-cast rotor, a reduced-roughness rotor, and a rotor with blades thinned to near design. Significant performance changes were measured. Tests were also made to determine the effect of Reynolds number on the turbine performance. Comparisons are made between this turbine and the compressor-drive turbine of the DOE baseline gas turbine engine
Cold-air performance of compressor-drive turbine of department of energy upgraded automobile gas turbine engine. 3: Performance of redesigned turbine
The aerodynamic performance of a redesigned compressor drive turbine of the gas turbine engine is determined in air at nominal inlet conditions of 325 K and 0.8 bar absolute. The turbine is designed with a lower flow factor, higher rotor reaction and a redesigned inlet volute compared to the first turbine. Comparisons between this turbine and the originally designed turbine show about 2.3 percentage points improvement in efficiency at the same rotor tip clearance. Two versions of the same rotor are tested: (1) an as cast rotor, and (2) the same rotor with reduced surface roughness. The effect of reducing surface roughness is about one half percentage point improvement in efficiency. Tests made to determine the effect of Reynolds number on the turbine performance show no effect for the range from 100,000 to 500,000
Cold-air performance of compressor-drive turbine of Department of Energy upgraded automobile gas turbine engine. 1: Volute-manifold and stator performance
The aerodynamic performance of the inlet manifold and stator assembly of the compressor drive turbine was experimentally determined with cold air as the working fluid. The investigation included measurements of mass flow and stator-exit fluid torque as well as radial surveys of total pressure and flow angle at the stator inlet and annulus surveys of total pressure and flow angle at the stator exit. The stator-exit aftermixed flow conditions and overall stator efficiency were obtained and compared with their design values and the experimental results from three other stators. In addition, an analysis was made to determine the constituent aerodynamic losses that made up the stator kinetic energy loss
Reasons for low aerodynamic performance of 13.5-centimeter-tip-diameter aircraft engine starter turbine
The reasons for the low aerodynamic performance of a 13.5 cm tip diameter aircraft engine starter turbine were investigated. Both the stator and the stage were evaluated. Approximately 10 percent improvement in turbine efficiency was obtained when the honeycomb shroud over the rotor blade tips was filled to obtain a solid shroud surface. Efficiency improvements were obtained for three rotor configurations when the shroud was filled. It is suggested that the large loss associated with the open honeycomb shroud is due primarily to energy loss associated with gas transportation as a result of the blade to blade pressure differential at the tip section
An experimental evaluation of the performance deficit of an aircraft engine starter turbine
An experimental investigation was made to determine the reasons for the low aerodynamic performance of a 13.5 centimeter tip diameter aircraft engine starter turbine. The investigation consisted of an evaluation of both the stator and the stage. An approximate ten percent improvement in turbine efficiency was obtained when the honeycomb shroud over the rotor blade tips was filled to obtain a solid shroud surface
GRID3D-v2: An updated version of the GRID2D/3D computer program for generating grid systems in complex-shaped three-dimensional spatial domains
In order to generate good quality systems for complicated three-dimensional spatial domains, the grid-generation method used must be able to exert rather precise controls over grid-point distributions. Several techniques are presented that enhance control of grid-point distribution for a class of algebraic grid-generation methods known as the two-, four-, and six-boundary methods. These techniques include variable stretching functions from bilinear interpolation, interpolating functions based on tension splines, and normalized K-factors. The techniques developed in this study were incorporated into a new version of GRID3D called GRID3D-v2. The usefulness of GRID3D-v2 was demonstrated by using it to generate a three-dimensional grid system in the coolent passage of a radial turbine blade with serpentine channels and pin fins
Deep learning atmospheric prediction algorithm for enhanced Mars EDL guidance
Uncertainty in atmospheric density and wind is a major cause of suboptimal performance in the Entry, Descent, and Landing (EDL) guidance at Mars. We improve the robustness of current EDL guidance algorithms to uncertain dynamic environments by proposing a reliable on-board atmospheric estimation algorithm. The algorithm consists of a deep, recurrent neural network using an efficient architecture for time-series predictions, the Long Short-Term Memory (LSTM) cell. The LSTM network is trained on entry trajectories simulated with the Fully Numerical Predictor-corrector Guidance (FNPEG); in each trajectory the vehicle is subject to density and wind fields from instances of the Mars Global Reference Atmospheric Model (GRAM) 2010. Predictions of density and wind as a function of altitude expected along the trajectory are obtained from onboard acceleration measurements and state estimates. The algorithm achieves a RMS value over time for the relative density error in the order of 10 % for samples in the validation dataset, and significantly improves performance with respect to an exponential fit to the density
Retrotransposon mapping in spider monkey genomes of the family Atelidae (Platyrrhini, Primates) shows a high level of LINE-1 amplification
To investigate the distribution of LINE-1 repeat sequences, a
LINE-1 probe was Fluorescence In Situ Hybridized (FISH) on the
chromosomes of Ateles geoffroyi and Ateles fusciceps (Atelidae); a
LINE-1 probe was also mapped on Cebuella pygmaea (Cebidae)
and used as an outgroup for phylogenetic comparison. Ateles spider
monkeys have a highly rearranged genome and are an ideal model
for testing whether LINE-1 is involved in genome evolution. The
LINE-1 probe has been mapped in the two Atelidae species for the
first time, revealing a high accumulation of LINE-1 sequences
along chromosomal arms, including telomeres, and a scarcity of
LINE-1 signals at centromere positions. LINE-1 mapping in C. pygmaea (Cebidae) revealed signals at centromere positions and along
chromosome arms, which was consistent with previous published
data from other Cebidae species. In a broader sense, the results were
analyzed in light of published data on whole-chromosomal human
probes mapped in these genomes. This analysis allows us to speculate about the presence of LINE-1 sequences at the junction of
human chromosomal syntenies, as well as a possible link between
these sequences and chromosomal rearrangements
Genetic Characterization of Feline Leukemia Virus from Florida Panthers
The emergent strain of FeLV, a novel subgroup A, was probably transmitted to panthers by a domestic cat
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