The comparative performance of Roots type aircraft engine superchargers as affected by change in impeller speed and displacement
This 1929 NASA technical report, compiled for engineers, compares Roots-type blowers used as superchargers on aircraft engines, testing how impeller speed and length change output. Its pictures are dense performance charts plotting horsepower, volumetric efficiency, impeller RPM and pressure difference against air delivered, so a designer can take from them the grid-and-curve vocabulary of technical graphs and their muted line-and-dash palette.
