Performance of Single-Stage Turbine of Mark 25 Torpedo Power Plant with Two Special Nozzles 1 - Efficiency with 0.45-inch Rotor Blades Page: 4 of 16
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NACA RM SE90G20a 3
Nozzle K (fig. 2) has eight ports fabricated by drilling and
reaming. The circular passages have a throat diameter of 0.156 inch
and an outlet-plane diameter of 0.168 inch, making the measured
expansion ratio approximately 1.16. The passages were equally
spaced over a section of the rotor periphery to also form an arc of
gas admission of approximately 90. The angle of intangency is 6
and the inlet-air angle to the turbine rotor is 120,
Characteristics of nozzles J and K and the nozzles previously
investigated (references 1 and 3) are presented in the following
table:
Nozzle Number Port- Cross- Total Measured
of inlet sectional measured expansion
ports configuration shape throat ratio
area
(sq in.)
A 9 Rounded Rectangular 0.183 1.47
E 9 Rounded Circular .193 1.00
H 9 Sharp-edged Rectangular .226 1.12
1 9 Sharp-edged Rectangular .217 1.20
J 9 Sharp-edged Rectangular .191 1.11
K 8 Sharp-edged Circular .153 1. 16
Apparatus. - The standard Mark 25 aerial-torpedo power plant
is a two-stage counterrotating impulse turbine. For this investi-
gation, the unit was modified to operate as a single-stage turbine
by the procedure outlined in reference 4. A schematic drawing of
the nozzle and the turbine-wheel assembly is shown in figure 3. A
special 0.45-inch blade described in reference 3 was used in this
investigation. The inlet-air angle and the outlet angle are the
same as those of the standard first-stage rotor. The ratio of blade-
passage area to nozzle-throat area with the 0.45-inch blades was
approximately 1.13 times as great as that of the standard blades.
The apparatus and the instrumentation are the same as those
described in reference 1. The precision of the observed measurements
is estimated to be within the following limits:
Air flow, percent. . . . . . . . . . . . . ...... . . 1,50
Torque, foot-pounds. ...................... 0.15
Dynamometer speed, rpn .............. . . . . . +5
Inlet-gas pressure, percent. . . . . . . . ........ 0.50
Inlet-gas temperature, percent . . . . . . . ........ 0.25
Pressure, inches mercury . . . . . . . ...... . . . . . 0.05
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Schum, Harold J. & Whitney, Warren J. Performance of Single-Stage Turbine of Mark 25 Torpedo Power Plant with Two Special Nozzles 1 - Efficiency with 0.45-inch Rotor Blades, report, August 23, 1949; (https://digital.library.unt.edu/ark:/67531/metadc65236/m1/4/: accessed April 18, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.