Investigation of turbines suitable for use in a turbojet engine with high compressor ratio and low compressor-tip speed 5: experimental performance of two-stage turbine with downstream stator Page: 3 of 46
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2 NAA ERM E5516
engine operating conditions were investigated (ref. i). Studies were
made to determine the turbine velocity diagrams for the turbine re-
quirements imposed by engine operation with constant exhaust-nozzle
area (re-2) and engine operation-at constant design rotative speed
(ref. 3). The turbine design requirements for engine operation at con-
stant design rotative speed were more critical than those for engine
operation with constant exhaust-nozzle area, and it was necessary to
incorporate a downstream stator behind a two-stage turbine in order to
obtain reasonable velocity diagrams. These velocity diagrams had high-
er Mach numbers, greater turning within blade rows, and lower static-
pressure drops across some of the blade rows than those used in con-
ventional turbine designs. Less critical turbine aerodynamic designs
could, of course, have been obtained with a three-stage turbine or by
increasing the design rotative speed, as discussed in reference 4.
Although the two-stage turbine design for engine operation with
constant exhaust-nozzle area and the two-stage turbine design with a
downstream stator for engine operation at constant design rotative speed
were critical, reasonably good turbine performance appeared to be feas-
ible. In order to obtain the performance of such a turbine design, the
two-stage turbine with a downstream stator was fabricated and investi-
gated as a component with cold-air turbine-inlet conditions. The pur-
pose of this report, then, is to (1) present the over-all performance
of this turbine and (2) evaluate the downstream stator in terms of tur-
bine over-all performance.
The turbine was operated at a constant inlet total (stagnation)
pressure of 35 inches of mercury absolute and an inlet total temperature
of 7000 R. Over-all turbine performance characteristics were obtained
over a range of pressure ratios and speeds. These performance results
are presented in terms of brake internal efficiency, equivalent work
output, equivalent weight flow, and equivalent rotor speed. The ef-
fectiveness of the downstream stator in recovering the energy of the
second rotor-exit tangential velocity over a range of turbine operating
conditions is presented. A brief description of the method used to de-
sign the blade profiles is included. Also presented herein are the
choking characteristics of the turbine obtained from the interstage
The following symbols are used in this report:
A annular area, sq ft
c specific heat at constant pressure, Btu/(lb)(0R)
E enthalpy drop (based on measured torque), Btu/lb
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Davison, Elmer H.; Petrash, Donald A. & Schum, Harold J. Investigation of turbines suitable for use in a turbojet engine with high compressor ratio and low compressor-tip speed 5: experimental performance of two-stage turbine with downstream stator, report, October 21, 1951; (digital.library.unt.edu/ark:/67531/metadc62101/m1/3/: accessed January 19, 2019), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.