Thermal performance of radially rotating trapezoidal channel with impinging jet-row

Abstract

The detailed Nusselt number distributions and Fanning friction factors of the rotating trapezoidal channel cooled by a row of six in-lined impinging jets were measured. The channel orientation relative to the rotating axis was 45 degrees and the six lateral jets issued from a plenum chamber were aimed at the centerline of the apex wall of the trapezoidal channel. The experimental conditions in terms of channel Reynolds (Re), rotation (Ro) and buoyancy (Bu) numbers were 5000–17500, 0–0.3 and 0–0.088, respectively. Also the rotational impact on the mass flow rate through each nozzle was examined. The coupled and isolated effects of Coriolis force and rotating buoyancy on the thermal performance of the rotating channel were illustrated using a selective set of test results. Due to the Coriolis-force effect on the radially outward crossflow and the impinging jets, the airflow rates issued from the jets 1–3 and 5–6 were respectively increased and decreased from the non-rotating values. With the different degrees of Ro impact on the leading, apex and trailing walls of the rotating trapezoidal channel, the Coriolis force effect on the heat transfer distribution was spatially asymmetric. The present “cavity-like” channel hub configuration significantly undermined the fluency of the spent flow to incur weak convection region adjacent to the sealed channel hub. But the Coriolis force effect considerably improved the heat convection over the channel hub region. All the Nusselt number ratios between the rotating (Nu) and non-rotating (Nu0) channels followed the general pattern of hub-to-tip decay. While the rotating buoyancy effect impaired the heat transfer performance, its impact was systematically weakened when the relative strength of Coriolis force enhanced. Two sets of empirical correlations that permitted the evaluations of the regionally averaged Nusselt number over the leading, apex and trailing walls and the overall Fanning friction factors were devised to assist the development of an internal cooling scheme of a gas turbine rotor blade.