Flow Distributions and Discharge Coefficient Effects for Jet Array Impingement With Initial Crossflow

Abstract

Two-dimensional arrays of circular air jets impinging on a surface parallel to the jet orifice plate are considered. The jet flow, after impingement, is constrained to exit in a single direction along the channel formed by the jet orifice plate and the impingement surface. In addition to the crossflow which originates from the jets following impingement, an initial (independent) crossflow is present which approaches the array through an upstream extension of the channel. The configurations considered are intended to model the impingement cooled mid-chord region of gas turbine airfoils in cases where an initial crossflow is also present. Experimentally determined row-by-row streamwise distributions of the jet and crossflow velocities are presented for ratios of the initial crossflow rate to the total jet flow rate ranging from zero to unity. Comparisons are drawn between the measured flow distributions and a theoretical model which is presented. Effects of crossflow velocity and impingement surface proximity on jet hole discharge coefficients are also presented and discussed.

Heat transfer characteristics of high crossflow impingement channels: Effect of number of holes

“…For the evaluation of local jet mass flows, a single discharge coefficient value was considered for all the jets assuming that there is no effect of the generated crossflow according to Florschuetz and Isoda. 22 Therefore, for long orifices and L/D ¼ 2, Hu¨ning 23 correlation provided a value of C d ¼ 0.8, which is also independent from the Reynolds number range examined in this study (Lichtarowicz et al 24 ). As expected, at a given number of holes per row, the smaller is the channel width the higher is the jet variation.…”

Flow characteristics and heat transfer performances of a semi-confined impinging array of jets: effect of nozzle geometry

“…Pressure data were used to determine the flow coefficient, C D , of the jets and its variation along the flow. The flow coefficient, C D , for an individual jet was obtained using the isentropic gas dynamic laws for flow through an orifice as used by Florschuetz and Isoda [8] …”

“…Florschuetz and Isoda [8] measured the pressure drop across circular orifices of a jet array. The discharge flow coefficient, C D , was found to decrease with increasing crossflow.…”

Impingement heat transfer of staggered arrays of air jets confined in a channel

“…Existing correlations express the Nusselt number for jet impingement as a function of Re c [7,[10][11][12][13]. The exponent, c, falls in the range 0.45-0.8.…”

“…Kercher and Tabakoff [8] measured the average Nusselt number of an in-line array of confined circular air jets impinging perpendicular to a flat plate. Metzger et al [9], Florschuetz et al [10][11][12], Florschuetz and Isoda [13] and Florschuetz and Su [14] investigated the heat transfer characteristics of in-line and staggered arrays of circular air jets impinging on an isothermal plate.…”