Paper 11: Origins of Rotary Positive Displacement Blower Noise

Abstract

Rotary positive displacement blowers (Roots type) are widely used for two-stroke cycle diesel engines. The inlet noise varies from about 100 to 150 dB over its operating range and thus, even with the predominant source of noise from the engine, very little of the delivery noise is emitted.

An investigation into the origins of the inlet noise was carried out by the author on a number of commercially available blowers of different design and size, ranging from 0mD03 ft³ /rev swept volume to 3 ft³ /rev swept volume.

A detailed study of the origins of the noise was made on a small two-lobe experimental blower. The two end casings were fitted into circular locating grooves cut in the end plates. These side casings could be removed or their position varied.