The 16th Symposium on Measuring Techniques in Transonic and Supersonic Flow in Cascades and Turbomachines 1 OPTICAL MEASUREMENT TECHNIQUES IN ENGINES: PIV AND OET

ABSTRACT The paper describes two optical techniques, which are capable of providing high frequency, non-intrusive measurements in harsh engine environments. Particle Image Velocimetry (PIV) has been used to provide an instantaneous intrarotor transonic flow mapping. Optical Emission Tomography (OET) is being developed for the study of gas turbine combustors and IC engines. Both represent novel measurement applications

Large-scale time-resolved digital particle image velocimetry (TR-DPIV) for measurement of high subsonic hot coaxial jet exhaust of a gas turbine engine

The development of a highly configurable triple digital particle image velocimetry (DPIV) system is described, which is capable of acquiring both continuous, statistically independent measurements at up to 14 Hz and time-resolved PIV data at MHz rates. The system was used at QinetiQ's Noise Test Facility (NTF) as part of the EU-funded CoJeN programme to obtain measurements from high subsonic (Mach <= 0.9), hot (similar to 500 degrees C), large (1/10th) scale coaxial jet flows at a standoff distance of similar to 1 m. High-resolution time-averaged velocity and turbulence data were obtained for complete coaxial engine exhaust plumes down to 4 m (20 jet diameters) from the nozzle exit in less than 1 h. In addition, the system allowed volumetric data to be obtained, enabling fast assessment of spatial alignment of nozzle configurations. Furthermore, novel six-frame time-series data-capture is demonstrated up to 330 kHz, used to calculate time-space correlations within the exhaust, allowing for study of spatio-temporal developments in the jet, associated with jet-noise production. The highly automated system provides synchronization triggers for simultaneous acquisition from different measurement systems (e.g. LDA) and is shown to be versatile, rugged, reliable and portable, operating remotely in a hostile environment. Data are presented for three operating conditions and two nozzle geometries, providing a database to be used to validate CFD models of coaxial jet flow

Form-finding as a modelling tool for shaping mechanical components: a feasibility case study of an axial-flow compressor blade

This paper reports on an exploratory study to assess the capability of a novel, form-finding methodology for generating optimal shapes of shell-type structures subjected to complex load regimes, using an axial-flow, compressor blade as a case study. The methodology exploits the natural principle of 'form follows force', in which the structural form is shaped according to the forces acting on it. Such forms, or objects, which are found in nature, are known to have optimal strength and stiffness characteristics for a predominant load regime. Our methodology makes use of a direct relationship between form and force, offered by the Laplace-Young equation that describes shapes of minimal surface membranes, such as soap films. Unlike structural optimisation in which the form is modified within its initially prescribed shape, form-finding literally finds the shape within prescribed boundary conditions. This is the first application of the methodology to modelling mechanical components, such as a compressor blade. The blade shapes obtained by this method correspond, in the first instance, to a minimal form and, subsequently, a minimal form subjected to a known (empirically determined) pressure profile. The behaviour of the blades is studied under a variety of loads and includes modal analysis. In view of the methodology adopted, attention is directed to structural performance. The results, compared against a 'control' blade produced by a conventional design/optimisation method are very encouraging; they indicate that the proposed methodology has the potential to improve significantly the current blade design process