Fifth-Generation Compressor
The fifth-generation compressor was designed and built in three months. It was first tested in February 2006, and the data were taken in April 2006. The compressor is 12 inches long by 15 inches in diameter. It is capable of producing a pressure ratio of 6:1, while processing 205 acfm at 6,000 rpm. To date, the fastest it has operated is 3600 rpm with a flow of 129 acfm. Running without liquid or oil injection, it reached >80% energy efficiency at 2800 rpm (see plots below). This is a substantial increase in efficiency over previous generations.
Data Collection
The data shown here are results from six different measurements. A torque cell measured shaft power to the compressor. The other measurements were the inlet and outlet pressures, temperatures, and mass flow.
To ensure the accuracy of the data, the sensors were calibrated with primary standards. The flow meter was verified using a pitot tube equipped with a high-accuracy manometer. A mercury manometer was used to calibrate the pressure sensors, and a known mass suspended on a lever arm was used to calibrate the torque cell. Thermocouples were used to measure temperatures.
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This graph shows both the volumetric and energy efficiencies at the given pressure ratio (labeled PR in the graphs). The basis of comparison for the energy efficiency was an isentropic compressor. |
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This graph shows flow as a function of speed. |
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This graph shows the relationship of shaft power and torque with speed. |