58 research outputs found
Perceived Noise Analysis for Offset Jets Applied to Commercial Supersonic Aircraft
A systems analysis was performed with experimental jet noise data, engine/aircraft performance codes and aircraft noise prediction codes to assess takeoff noise levels and mission range for conceptual supersonic commercial aircraft. A parametric study was done to identify viable engine cycles that meet NASA's N+2 goals for noise and performance. Model scale data from offset jets were used as input to the aircraft noise prediction code to determine the expected sound levels for the lateral certification point where jet noise dominates over all other noise sources. The noise predictions were used to determine the optimal orientation of the offset nozzles to minimize the noise at the lateral microphone location. An alternative takeoff procedure called "programmed lapse rate" was evaluated for noise reduction benefits. Results show there are two types of engines that provide acceptable mission range performance; one is a conventional mixed-flow turbofan and the other is a three-stream variable-cycle engine. Separate flow offset nozzles reduce the noise directed toward the thicker side of the outer flow stream, but have less benefit as the core nozzle pressure ratio is reduced. At the systems level for a three-engine N+2 aircraft with full throttle takeoff, there is a 1.4 EPNdB margin to Chapter 3 noise regulations predicted for the lateral certification point (assuming jet noise dominates). With a 10% reduction in thrust just after clearing the runway, the margin increases to 5.5 EPNdB. Margins to Chapter 4 and Chapter 14 levels will depend on the cumulative split between the three certification points, but it appears that low specific thrust engines with a 10% reduction in thrust (programmed lapse rate) can come close to meeting Chapter 14 noise levels. Further noise reduction is possible with engine oversizing and derated takeoff, but more detailed mission studies are needed to investigate the range impacts as well as the practical limits for safety and takeoff regulations
Adição de gesso agrĂcola em trĂŞs tipos de cama de aviário na fixação de nitrogĂŞnio e no desempenho de frango de corte
Desempenho de frangos de corte oriundos de matrizes de corte submetidas a dietas contendo aflatoxinas e glucomananos esterificados como adsorvente
Reduction of toxic effects of aflatoxin B1 by using baker yeast (Saccharomyces cerevisiae) in growing broiler chicks diets
Method of administration affects the ability of bacteriophage to prevent colibacillosis in 1-day-old broiler chickens
Evaluation of the Influence of Bacteriophage Titer on the Treatment of Colibacillosis in Broiler Chickens
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