J. P. Solano

Novel Two-Dimensional Transient Heat Conduction Calculation in a Cooled Rotor: Ventilation Preheating—Blow-Down Flux

This contribution presents an alternative to classical data reduction techniques to measure the heat transfer using thin-film gauges. A finite-element model of the two-dimensional unsteady heat conduction equation is solved in the cross-sectional area of a metallic airfoil bounded with a polyamide sheet on which thermal sensors are deposited. This novel methodology allows capturing all 2D heat conduction effects that are irremediably neglected with the 1D data reduction technique. The application of this technique in a compression tube facility allows an exact evaluation of the initial wall heat flux into cooled rotor blades. During the spinning-up period, the rotor is spun up to nearly its nominal speed (from 0 rpm to 6200 rpm) resulting in preheating due to drag losses. The long duration of this experiment (∼450 s) and the magnitude of the wall temperature increase result in significant 2D conduction effects that are not accounted for using the 1D approach. In addition, short-duration experiments confirm the existence of 2D effects at smaller time scales (∼0.5 s), as well as the influence of the initial nonuniform temperature distribution in the rotor blade. The resulting flux with such an initial condition appears to be the superposition of the wall heat fiux at the end of the spinning up before the test and the flux due to the blow-down itself.

Adiabatic Wall Temperature Evaluation in a High Speed Turbine

Engine development requires accurate estimates of the heat loads. Estimates of the convective heat fluxes are particularly vital to assess the thermo-mechanical integrity of the turbomachinery components. This paper reports an experimental heat transfer research in a one and a half turbine stage, composed of a high-pressure turbine and a low-pressure vane. Measurements were performed in a compression tube facility at the von Karman Institute, able to reproduce engine representative Reynolds and Mach numbers. Double-layered thin film gauges were used to monitor the time-dependent temperature distribution around the airfoil. Several tests at different metal temperatures were performed to derive the adiabatic wall temperature. This research allowed quantifying the independent effects on the unsteady heat flux of the gas temperature fluctuations and boundary layer unsteadiness.

Novel 2D Transient Heat Conduction Calculation in a Cooled Rotor: Ventilation Preheating — Blowdown Flux

An alternative to classical data reduction techniques for thin film gauges in short duration facilities is presented. A finite element model of the two-dimensional unsteady heat conduction equation is solved in the cross-sectional area of a metallic airfoil bounded with a polyamide sheet, on which thermal sensors are deposited. As a result, the transient temperature field in the multilayered substrate and the experimental wall heat flux distribution are derived. The methodology allows for capuring all 2D heat conduction effects that are irremediably neglected with the 1D data reduction technique. The application of this technique in a compression tube facility allows an exact evaluation of the initial wall heat flux into cooled rotor blades. During the spinning up period, the rotor of this type of fully rotating transient facilities is spun up to nearly its nominal speed (from 0 RPM to 6200 RPM) resulting in preheating due to drag losses. The long duration of this experiment (∼450 s) and the magnitude of the wall temperature increase result in significant 2D conduction effects that are not accounted for using the 1D approach. In addition, short duration experiments confirm the existence of 2D effects at smaller time scales (∼0.5 s), as well as the influence of the initial non-uniform temperature distribution in the rotor blade. The resulting flux with such an initial condition appears to be the superposition of the wall heat flux at the end of the spinning up before the test and the flux due to the blow-down itself.Copyright

Method and Measurement of Adiabatic Wall Temperature Downstream of a High Pressure Turbine Using Thin-Film Sensors

During engine development, heat loads in the turbomachinery are analyzed based on theoretical and numerical estimates together with correlations. Accurate models of the convective fluxes are vital to assess the thermo-mechanical integrity. This paper reports an experimental heat transfer research in a 1.5 turbine stage, the researched model is a the structural vane of a multi-splittered low pressure vane located downstream of a high pressure turbine stage. This concept is envisioned for ultra-high bypass-ratio aero-engines with a swan-neck diffuser between the high-pressure turbine and the low-pressure turbine. Measurements were performed in the large compression tube facility of the von Karman Institute, at representative conditions of modern aero-engines. Double-layered thin film gauges were employed for the measurement of the time-dependent temperature distribution around the airfoil. The initial temperature of the structural vane was adjusted using a heating system. The experimental procedure has allowed the determination of the time-mean and unsteady adiabatic wall temperature. Hence this technique allows the determination of the non-dimensional Nusselt number and proper scaling of the surface temperature to engine conditions. Furthermore, the analysis of the unsteady data reveals the contribution of the temperature fluctuations to the unsteady heat fluxes.Copyright

Experimental Heat Transfer Investigation in a Multisplitter LP Vane Architecture

This paper reports the external convective heat transfer in an innovative low pressure vane with multisplitter configuration. Three small aerodynamic blades are positioned between each structural vane, providing a novel architecture for ultra-high by-pass ratio aero-engines, with increased LP vane radius and swan-neck diffuser to link the HP turbine. The measurements have been performed in the compression tube test rig of the von Karman Institute, using single layered thin film gauges. Time-averaged and time-resolved heat transfer distributions are presented for the three aerovanes and for the structural blade, at three pressure ratios tested at representative conditions of modern aeroengines, with M2,is ranging from 0.87 to 1.07 and a Reynolds number of about 106 . This facility is specially suited to control the gas-to-wall temperature ratio. Accurate time-averaged heat transfer distributions around the aerovanes are assessed, that allow characterizing the boundary layer status for each position and pressure ratio. The heat transfer distribution around the structural blade is also obtained, depicting clear transition to turbulence, as well as particular flow features on the pressure side, like separation bubbles. Unsteady data analysis reveals the destabilizing effect of the rotor left-running shock on the aerovanes boundary layer, as well as the shift of transition onset for different blade passing events.Copyright