Was ist Selftracking? Eine Autoethnografie des vermessenen Selbst

Was ist eigentlich Selftracking? Dieser Frage nachspürend, autoethnografisch und nahkörperlich forschend, zeichnet Nikola Plohr Erfahrungen mit der technologisierten Selbstvermessung nach. Dabei verschränken sich medienwissenschaftliche, körper- und sportsoziologische Perspektiven mit Tagebucheinträgen und Beobachtungen aus der Bewegung heraus. Wer sich schon immer gefragt hat, was die Faszination des Selftrackings ausmacht, findet hier Antworten, Kritik und neue Fragen, die sich zwischen Theorie und Alltagserfahrung bewegen

Two-dimensional Cascade Investigation of the Maximum Exit Tangential Velocity Component and Other Flow Conditions at the Exit of Several Turbine Blade Designs at Supercritical Pressure Ratios

The nature of the flow at the exit of a row of turbine blades for the range of conditions represented by four different blade configurations was evaluated by the conservation-of-momentum principle using static-pressure surveys and by analysis of Schlieren photographs of the flow. It was found that for blades of the type investigated, the maximum exit tangential-velocity component is a function of the blade geometry only and can be accurately predicted by the method of characteristics. A maximum value of exit velocity coefficient is obtained at a pressure ratio immediately below that required for maximum blade loading followed by a sharp drop after maximum blade loading occurs

Investigation of the Effects of Low Reynolds Number Operation on the Performance of a Single-Stage Turbine with a Downstream Stator

High-altitude turbojet performance is adversely affected by the effects of low air density. This performance loss is evaluated as a Reynolds number effect, which represents the increased significance of high fluid viscous forces in relation to dynamic fluid forces as the Reynolds number is decreased. An analytical and experimental investigation of the effects of low Reynolds number operation on a single-stage, high-work-output turbine with a downstream stator was carried out at Reynolds numbers of 182,500, 39,600, and 23,000, based on average rotor-design flow conditions. At low Reynolds numbers and turbulent flow conditions, increased viscous losses caused decreased effective flow area, and thus decreased weight flow, torque, and over-all efficiency at a given equivalent speed and pressure ratio. Decreasing the Reynolds number from 182,500 to 23,000 at design equivalent speed resulted in a 5.00-point loss in peak over-all turbine efficiency for both theory and experiment. The choking equivalent weight flow decreased 2.30 percent for these conditions. Limiting loading work output was reached at design equivalent speed for all three Reynolds numbers. The value of limiting loading work output at design speed decreased 4.00 percent as Reynolds number was decreased from 182,500 to 23,000. A theoretical performance-prediction method using basic boundary-layer relations gave good agreement with experimental results over most of the performance range at a given Reynolds number if the experimental and analytical design operating conditions were carefully matched at the highest Reynolds number with regard to design performance parameters. High viscous losses in the inlet stator and rotor prevented the attainment of design equivalent work output at the lowest Reynolds number of 23,000

Selfie-Technologie

Für diesen Beitrag ist leider kein Abstract verfügbar. ----------

Experimental Test of the Influence of Propulsion Efficiency on Contrail Formation

According to a previously established thermodynamic theory, contrails are expected to form at a threshold temperature that increases with the overall efficiency of the aircraft propulsion. As a consequence, aircraft with modern engines, with higher overall efficiency, cause contrails over a larger range of cruise altitudes. To validate this theory, an experiment was performed in which contrail formation was observed behind two different fourengine jet aircraft with different engines flying wing by wing. Photographs document the existence of an altitude range in which the aircraft with high engine efficiency causes contrails whereas the other aircraft with lower engine efficiency causes none. For overall efficiencies of 0.23 and 0.31 and an ambient temperature lapse rate of 12 K km-1, the observed altitude difference is 80 m. This value would be larger (200m) in a standard atmosphere with smaller temperature lapse rate (6.5K km-1). In a standard atmosphere, an increase of overall efficiency from 0.3 to 0.5, which may be reached for future aircraft, would cause contrails at about 700 m lower altitude