Aircraft jet engines operating at high altitudes in ice crystal clouds can experience operational problems and/or damage resulting from accretion of ingested ice crystals within the compressor. It is believed the ice crystals partially melt, allowing them to stick to internal components. A method for modelling such mixedphase accretion is required to de-risk new engine designs, modify existing designs with such icing issues and define critical operating points for scrutiny in proposed ice crystal certification tests. This paper presents preliminary results for a modelling approach which treats the accretion process as strictly a sticking phenomenon, largely ignoring heat transfer, phase change, runback and other location-dependent effects commonly used in the analysis of supercooled water icing. Ice-on-ice growth is described by a sticking efficiency, defined as the fraction of the mixed-phase impinging mass flux which remains on the surface (i.e. sticks). Experimental results are presented for 3 test articles tested in a small mixed-phase icing tunnel located in an altitude chamber (Research Altitude Test Facility or RATFac) at the National Research Council of Canada. These results show that the sticking efficiency is highly correlated with the ratio of liquid water content (LWC) to total water content (TWC) in the freestream, reaching a maximum value of 0.4-0.5 at melt (LWC/TWC) ratios in the approximate range 10-20%, as measured with a multi-element probe. It is shown that sticking efficiencies are largely independent of TWC, Mach number (M) and particle size at normal incidence (i.e. at the stagnation point) at these melt ratios, at least in the limited ranges of these variables investigated, but are strongly dependent on these parameters at oblique impingement angles. It is also shown that accretions can grow to a very large size at an almost constant rate at high levels of TWC. The experimental results are used to develop an erosion-based semi-empirical accretion model which at least partially explains this super-growth phenomenon and predicts most of the experimental results with acceptable fidelity. The model predicts that the almost unlimited growth observed in the experiments is possible at lower Mach numbers (e.g. 0.25) for TWC levels exceeding ~10g/m 3 , when the sticking efficiency remains finite at all particle impingement angles. The model also predicts that such growth is unlikely for higher Mach numbers (e.g. 0.4), at least for the 45μ (MVD) particles to which the model is applied. Smaller particles will likely extend the Mach number range over which the sticking efficiency remains finite. Nomenclature a, b = TWC-dependent coefficients in relation for t & a f = coefficient in expression for flux reduction factor f A,B = constants dependent on mechanical, physical properties of eroded material and erodent particles D = diameter D xx = particle diameter below which the cumulative particle volume is xx% of the total particle volume DSD = droplet size distribution E = erosion function (of γ) f = eros...

Experimental and computational results are presented from cascade testing on the nozzle blading of a high pressure ratio single stage turbine. Testing on this blading in 1986 showed surprising evidence of a redistribution of the downstream total temperature field. The nozzle midspan section has subsequently been tested in a large scale low aspect ratio planar cascade, having a continuous room-temperature inlet flow, to obtain more detailed information over the subsonic and transonic speed ranges. The blades had a blunt trailing edge which caused strong von Ka´rma´n vortex shedding throughout the subsonic range. This was shown to result in Eckert-Weise effect temperature redistribution. The first time-resolved measurements of this effect were measured in this cascade. Unusual vortex configurations were also observed at transonic speeds. The purpose of the current observations was to obtain reliable time-averaged measurements of flow through the cascade, which is proving to be an excellent vehicle for validating CFD predictions. A three-hole finger probe was traversed at the inlet and outlet of the cascade to evaluate the aerodynamic performance. Mach number and base pressure distributions, together with schlieren and surface oil-flow visualization, aided understanding of flow and loss behavior. Two-dimensional numerical simulations were performed over the speed range. The results assisted understanding of the influence of Mach number on losses and flow structures, specifically the shock configurations and base pressures. Comparisons of numerical results and experimental measurements of the flow-field showed good agreement.

This paper presents a numerical and experimental assessment of a plasma actuation concept for controlling corner stall separation in a highly loaded compressor cascade. CFD simulations were first carried out to assess actuator effectiveness and determine the best actuation parameters. Subsequently, experiments were performed to demonstrate the concept and confirmed the CFD tool validity at a Reynolds number of 1.5 × 105. Finally, the validated CFD tool was used to simulate the concept at higher velocities, beyond the experimental capability of existing plasma actuators. These results were used to obtain a preliminary scaling law that would allow approximation of the plasma actuation requirements at realistic operating conditions. Several configurations were examined, but the most effective setup was found to be when plasma actuators were mounted upstream of the separation point on both the suction surface and the endwall. Most of the improvement in total pressure loss stemmed from the suction surface actuator. Comparison with experimental data showed that the CFD simulations could capture the flow features and the effect of plasma actuation reasonably well. Simulations at higher flow velocities indicated that the required plasma actuator strength scales approximately with the square of the Reynolds number.

Experiments were conducted on the flow through a transonic turbine cascade. Secondary flows and a wide range of vortex types were encountered, including horseshoe vortices, shock-induced passage vortices, and streamwise vortices on the suction surface. In the separation region on the suction surface, a large rollup of passage vorticity occurred. The blunt leading edge gave rise to strong horseshoe vortices and secondary flows. The suction surface had a strong convex curvature over the forward portion and was quite flat further downstream. Surface flow visualization was performed and this convex surface displayed coherent streamwise vorticity. At subsonic speeds, strong von Kármán vortex shedding resulted in a substantial base pressure deficit. For these conditions, time-resolved measurements were made of the Eckert-Weise energy separation in the blade wake. At transonic speeds, exotic shedding modes were observed. These phenomena all occurred in experiments on the flow around one particular turbine nozzle vane in a linear cascade.

This paper presents a critical development to a prototype sensor that is capable of measuring total air temperature and humidity in a mixed-phase environment, consisting of liquid water droplets and ice crystals. The sensor has fast and stable measurement response under particularly challenging mixed-phase conditions. Total temperature and humidity levels measured with the probe are in good agreement with the results of analytical energy and moisture balances. NomenclatureC p = Specific heat capacity E = Energy h = Enthalpy IWC = Ice-water concentration (ice flow rate/total volume airflow) ICD = Inter compressor duct LWC = Liquid water content (mass of water/volume of air) ̇ = Mass flow Ma = Freestream Mach number MVD = Median volume diameter P = Static pressure = Vapor pressure of water P 0 = Stagnation pressure PSI = Pound per square inch RH = Relative humidity SH = Specific humidity (also known as mixing ratio) TAT = Total air temperature T = Static air temperature T wb = Wet bulb temperature T 0 = Stagnation temperature Subscripts a = Air m = At the spray mast t = In the test section v = Vapor w = Water wbs = Wet bulb temperature at static conditions 1 = Prior to water flow initiation 2 = Following water flow initiation and sensor stabilization