| Summary: | Approved for public release, distribution unlimited === A performance comparison between smooth-cast and rough-cast blades was conducted in a lowspeed multistage compressor. The purpose was to show that rough-cast blades can be used for initial performance tests of low-speed compressors. A baseline performance was established with smooth-cast epoxy blades and then compared to rough-cast aluminum blades. The pressure-rise coefficient versus flow coefficient and velocity triangles were used as the measure for comparison between the different blade types. The velocity triangles were constructed and compared across the span (hub-to-tip) of the secondstage. This was done by using two probes that could traverse radially along the blade and sense the flow velocity and angle relative to the compressor axis. Measurements were taken at six different locations from the hub-to-tip of the blade. The performance tests were conducted at four different throttle settings: near stall, open throttle, nominal operating point (NOP), and near the NOP. Results showed that although there were some differences between the smooth-cast and rough-cast blades, the overall performance was very similar. As a result, rough-cast blades could be used for initial performance tests or as the initial stages of a compressor in order to set up the flow for the evaluation of a new stage of smooth blades. The use of rough-cast blades in early stages would save the time and money needed to produce large numbers of high precision smooth-cast blades.
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