Pressure-swirl atomizers are widely used in various combustion applications including aircraft jet engines. Spray characteristics, such as drop-size and velocity distribution have a principal influence on the combustion process. A number of studies have dealt with single-point laser diagnostic techniques, such as Phase-Doppler Anemometry, for spray measurements. An alternative approach is the use of a whole-field method - Particle Image Velocimetry (PIV). This contribution deals with investigation of spray characteristics of a spill-return pressure-swirl atomizer for a small-sized jet engine by means of PIV. The nozzle was operated on a cold test bench at atmospheric pressure and room temperature. Measurements were carried out in an axial section of the spray cone with various single-camera and stereoscopic PIV configurations. Results of out measurements provide a quantitative visualization of the spray flow fields in regimes based on the engine operating conditions. Comparison of velocity profiles obtained from the individual PIV configurations is presented and discussed. The pressure-swirl spray is recognised as an optically harsh environment for PIV due to large particle size range, high diameter-velocity correlations, strong velocity gradients and large velocity differences within an image, large variations in ‘seeding‘ concentration and out-of-plane particle movement. The PIV results comprise new findings to the complex 3D character of velocity field in the pressure-swirl sprays. and Obsahuje seznam literatury
Spatial navigation comprises a widely-studied complex of animal behaviors. Its study offers many methodological advantages over other approaches, enabling assessment of a variety of experimental questions and the possibility to compare the results across different species. Spatial navigation in laboratory animals is often considered a model of higher human cognitive functions including declarative memory. Almost fifteen years ago, a novel dry-arena task for rodents was designed in our laboratory, originally named the place avoidance task, and later a modification of this approach was established and called active place avoidance task. It employs a continuously rotating arena, upon which animals are trained to avoid a stable sector defined according to room-frame coordina tes. This review describes the development of the place avoidance tasks, evaluates the cognitive processes associated with performance and explores the application of place avoidance in the testing of spatial learning after neuropharmacological, lesion and other experimental manipulations., A. Stuchlík ... [et al.]., and Obsahuje bibliografii a bibliografické odkazy