Analytical investigation of off-design performance of a transonic turbine Page: 3 of 24
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analytical method of predicting off-design turbine performance and
losses was developed and is presented in reference 2. The entire tur-
bine performance map can be predicted by this method from either the
known or estimated design-point data. In reference 3 the method was
applied to nine turbine designs, and a comparison between the predicted
and the experimental performance showed the method to be fairly reliable
in predicting off-design performance for turbines of conservative de-
sign. Reference 4 presents an analytical method of predicting off-
design turbine performance and losses similar to that of reference 2, cG
except that this method includes certain refinements in ascertaining 4
the losses and the flow conditions throughout the turbine. The method t
of reference 4 was applied to a high-speed, high-specific-mass-flow
turbine, and very close agreement was obtained between the analytically
predicted off-design performance and that obtained experimentally.
An analysis was therefore made of the transonic turbine of reference
1 by the method of analysis of reference 4. (The term "method of analy-
sis" used hereafter refers to the method of ref. 4.) In addition to the
over-all performance and a breakdown of the losses, the rotor hub in-
cidence angle, relative entrance Mach number, and reaction were also
obtained in the analytical procedure. The purpose of this report is to
present the results of the analysis and to compare them with the ex-
perimental results of the transonic turbine. The variation of the losses
obtained analytically for the transonic turbine is compared with that
previously obtained from a similar analysis of a subsonic turbine. Any
limitations encountered in the analytical procedure are also discussed.
The trends of the aforementioned rotor hub conditions for the transonic
turbine are also compared with those obtained previously for the subsonic
turbine to ascertain whether the variation of trends for the transonic
turbine differed substantially from that of the subsonic turbine.
The investigation was conducted at the NACA Lewis laboratory.
The following symbols are used in this report:
c specific heat at constant pressure, Btu/(1b)(oF)
cv specific heat at constant volume, Btu/(lb)(oF)
g acceleration due to gravity, 32.174 ft/sec2
Ah' equivalent specific work based on total state, Btu/lb
K blade effective loss parameter (ref. 4)
NACA M E54DOSX
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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/m1/3/: accessed April 18, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.