Analytical investigation of off-design performance of a transonic turbine Page: 2 of 24
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NACA R E54D05lb
NATIONAL ADVISORY CONMI'TEE FOR AERONAUTICS
ANALYTICAL INVESTIGATION OF OFF-DESIGN PERFORMANCE OF A TRANSONIC TURBINE
By Warren J. Whitney and Warner L. Stewart
The off-design performance and a breakdown of the losses of a
transonic turbine were determined by an analytical method that was pre-
viously developed for turbines of more conservative design. The analyti-
cally obtained performance map is compared with the performance map ob-
tained from an experimental investigation of the turbine. The rotor hub
conditions of incidence angle, relative Mach number, and reaction cal-
culated from the analytical results are compared with those calculated
from experimental data.
The loss breakdown obtained for the transonic turbine did not differ
substantially from that previously obtained from a turbine of more con-
servative design, except that large stator-exit shock losses were pre-
dicted for the transonic turbine at low speeds. The trends of the rotor
hub incidence angle,. relative Mach number, and reaction calculated from
the analytical results agreed well with those calculated from the ex-
perimental data over the performance range. These trends indicate that,
compared with a turbine of more conservative design, the transonic tur-
bine operated over a much smaller range of incidence angle, a much wider
range of rotor relative Mach number, and at a considerably lower level
of reaction. Good over-all agreement was obtained between the analyti-
cally predicted performance and the experimental performance, except at 40-
percent design speed, where in the analysis the stator reached limiting
loading before the rotor choked. Since this discrepancy resulted from
errors in the simplifying assumptions used in the analysis, it is re-
garded as a limitation in the analytical method as applied to a tran-
Recent research on turbines operating with relative rotor veloc-
ities in the transonic range has made this type of design appear feasi-
ble as a jet-engine component (e.g., ref. i). It is therefore desirable
to be able to determine the off-design performance for this type of tur-
bine as well as the trends of the losses at off-design operation. An
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Whitney, Warren J. & Stewart, Warner L. Analytical investigation of off-design performance of a transonic turbine, report, May 28, 1954; (https://digital.library.unt.edu/ark:/67531/metadc64479/m1/2/: accessed April 24, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.