In this paper, the first-ever measurements of the wake of a full-scale wind turbine using an instrumented uninhabited aerial vehicle (UAV) are reported. The key enabler for this novel measurement approach is the integration of fast response aerodynamic probe technology with miniaturized hardware and software for UAVs that enable autonomous UAV operation. The measurements, made to support the development of advanced wind simulation tools, are made in the near-wake (0.5D–3D, where D is rotor diameter) region of a 2 MW wind turbine that is located in a topography of complex terrain and varied vegetation. Downwind of the wind turbine, profiles of the wind speed show that there is strong three-dimensional shear in the near-wake flow. Along the centerline of the wake, the deficit in wind speed is a consequence of wakes from the rotor, nacelle, and tower. By comparison with the profiles away from the centerline, the shadowing effects of nacelle and tower diminish downstream of 2.5D. Away from the centerline, the deficit in wind speed is approximately constant ≈ 25%. However, along the centerline, the deficit is ≈ 65% near to the rotor, 0.5D–1.75D, and only decreases to ≈ 25% downstream of 2.5D.

This paper describes a recently developed miniature fast response entropy probe and its application in the turbomachinery facilities at ETH Zurich. The development of the probe is motivated by the need to more clearly document the loss generation mechanisms in the harsh environment of turbomachines. The probe is comprised of a piezoresistive sensor and a pair of thin-film gauges that measure the unsteady pressure and temperature, respectively. The unsteady relative entropy can thus be determined. The design, manufacture and calibration of the probe are first presented in detail. Its application to detail the unsteady entropy field, and associated losses, in a centrifugal compressor, axial turbine and film cooling flows are then described.

This paper reports on insights into the detailed thermodynamics of axial turbine nozzle guide vane (NGV) wakes as they interact with the rotor blades. The evidence presented is both computational and experimental. Unsteady Reynolds-averaged Navier–Stokes (RANS) simulations are used to compare the experimental observations with theoretical predictions. Output processing with both Eulerian and Lagrangian approaches is used to track the property variation of the fluid particles. The wake is found to be hot and loses heat to the surrounding fluid. The Lagrangian output processing shows that the entropy of the wake will fall due to heat loss as it passes through the rotor and this is corroborated experimentally. The experimental vehicle is a 1.5-stage shroudless turbine with modest Mach numbers of 0.5 and high response instrumentation. The entropy reduction of the wake is determined to be about four times the average entropy rise of the whole flow across the rotor. The results show that the work done by the wake fluid on the rotor is approximately 24% lower than that of the free-stream. The apparent experimental efficiency of the wake fluid is 114% but the overall efficiency of the turbine at midheight is around 95%. It is concluded that intrafluid heat transfer has a strong impact on the loss distribution even in a nominally adiabatic turbine with moderate row exit Mach numbers of 0.5.

Modern steam turbines need to operate efficiently and safely over a wide range of operating conditions. This paper presents a unique unprecedented set of time-resolved steam flowfield measurements from the exit of the last two stages of a low pressure (LP) steam turbine under various volumetric massflow conditions. The measurements were performed in the steam turbine test facility in Hitachi city in Japan. A newly developed fast response probe equipped with a heated tip to operate in wet steam flows was used. The probe tip is heated through an active control system using a miniature high-power cartridge heater developed in-house. Three different operating points, including two reduced massflow conditions, are compared and a detailed analysis of the unsteady flow structures under various blade loads and wetness mass fractions is presented. The measurements show that at the exit of the second to last stage the flow field is highly three dimensional. The measurements also show that the secondary flow structures at the tip region (shroud leakage and tip passage vortices) are the predominant sources of unsteadiness at 85% span. The high massflow operating condition exhibits the highest level of periodical total pressure fluctuation compared to the reduced massflow conditions at the inlet of the last stage. In contrast at the exit of the last stage, the reduced massflow operating condition exhibits the largest aerodynamic losses near the tip. This is due to the onset of the ventilation process at the exit of the LP steam turbine. This phenomenon results in 3 times larger levels of relative total pressure unsteadiness at 93% span, compared to the high massflow condition. This implies that at low volumetric flow conditions the blades will be subjected to higher dynamic load fluctuations at the tip region.

The quantification of aerothermal loss is carried out for streamwise and compound angled film cooling jets with and without large scale pulsation. This paper reports on the simultaneous measurements of the unsteady pressure and temperature field of streamwise and a 60 deg compound angled film cooling jet, both with a 30 deg surface angle over a flat plate with no pressure gradients. Turbine representative nondimensionals in terms of the geometry and operating conditions are studied. The main flow is heated more than the injected flow to have a temperature difference and hence a density ratio of 1.3, while the blowing ratio is maintained at 2. The entropy change, derived from pressure and temperature measurements, is calculated by using modified reference conditions to better reflect the losses in both the jet and the freestream. The effects of the periodic unsteadiness associated with rotating machinery are simulated by pulsating the jets. These effects are documented through time-resolved entropy change contours. Mass-averaged entropy and kinetic energy loss coefficients seem to be apt quantities for comparing the aerothermal performance of streamwise and compound angled injections. It is observed that the mass-averaged entropy loss of a streamwise jet doubles when it is pulsated, whereas that of a compound angled jet increases by around 50%. It may be conjectured from the measurements shown in this study that streamwise oriented jets suffer most of their entropy losses at the hole exit due to separation, whereas in compound angled jets, downstream thermal mixing between the jet and the freestream is the dominant mechanism. Downloaded From: http://turbomachinery.asmedigitalcollection.asme.org/ on 06/08/2015 Terms of Use: http://asme.org/terms Journal of Turbomachinery OCTOBER 2009, Vol. 131 / 041015-3 Downloaded From: http://turbomachinery.asmedigitalcollection.asme.org/ on 06/08/2015 Terms of Use: http://asme.org/terms Journal of Turbomachinery OCTOBER 2009, Vol. 131 / 041015-7 Downloaded From: http://turbomachinery.asmedigitalcollection.asme.org/ on 06/08/2015 Terms of Use: http://asme.org/terms Journal of Turbomachinery OCTOBER 2009, Vol. 131 / 041015-9 Downloaded From: http://turbomachinery.asmedigitalcollection.asme.org/ on 06/08/2015 Terms of Use: http://asme.org/terms 041015-10 / Vol. 131, OCTOBER 2009 Transactions of the ASME Downloaded From: http://turbomachinery.asmedigitalcollection.asme.org/ on 06/08/2015 Terms of Use: http://asme.org/terms