Effect of Section Thickness and Trailing-Edge Radius on the Performance of NACA 65-Series Compressor Blades in Cascade at Low Speeds Page: 3 of 68

                                
2                                 -     L               NACA RM L51J16
and angle of attack to produce a desired turning angle, the inlet angle
of the flow and the solidity of the blades being known. In aircraft
axial-flow compressors, blade sections of maximum thickness other than
the average value of 10 percent are used for most of the blade length.
Information is desired to indicate the changes in performance to be
expected if the section maximum thickness is varied from 10 percent
chord in order to apply the data and design charts of reference 1 to the
actual case. Therefore, the test program of reference 1 was extended
to include tests of blade sections of one camber with maximum thickness
varied from 6 percent to 15 percent of the blade chord at three
combinations of inlet angle and solidity. Two of the combinations
selected .  = 450, a = 1.5  and 0 = 600, a = 1.0   are considered to be
typical of usual axial-flow compressor conditions. The third combination
0 = 600, a = 1.5 was studied because the section thickness was expected
to produce more pronounced effects at this high-inlet-angle, high-solidity
condition, thus aiding in establishing trends.
As a further practical consideration, current mass-production
blade-construction methods require greater thickness in the region
near the blade trailing edge than is provided by the basic thickness
shape used for the tests of reference 1. It is desirable to know the
penalty, if any, which is being paid for ease of construction in order
to determine if there is any need for development of improved construction
methods. In view of this, the NACA 65-(12)10 blade section was tested
at two combinations of inlet angle and solidity with the trailing
region thickened to 2 and 4 percent chord.
SYMBOLS
c          blade chord, feet
cd         section drag coefficient
cZ         section lift coefficient
CIo        camber, expressed as design lift coefficient of isolated
airfoil
cw         wake-momentum-difference coefficient
L/D        lift-drag ratio
P          total pressure, pounds per square foot
p          static pressure, pounds per square foot