Turbine-Driven Character With Variable Area Diffuser

摘要

1,160,201. Centrifugal compressors. CATERPILLAR TRACTOR CO. Feb. 1, 1968, No. 5144/68. Heading F1C. In a turbine-driven charger comprising spaced annular substantially parallel walls defining a diffuser area surrounding the rotor, at least one of the walls is supported for movement towards and away from the other, means mounted in the diffuser area and responsive to velocity of air passing through the diffuser being provided to adjust the position of the movable wall and thereby vary the cross-sectional area of the diffuser. Fig. 1 shows a charger for an I. C. engine, comprising an exhaust-gas turbine 11 driving a centrifugal compressor 12. An annular wall 24 is supported by an annular bellows 28 so as to be movable axially relative to a fixed annular wall 23 to vary the width of the diffuser passage 22. When the speed of the I. C. engine is low and the velocity of air passing through the diffuser passage 22 is consequently low, the resiliency of the bellows 28 tends to hold the wall 24 in a position in which the width of the diffuser passage 22 is a minimum. This prevents compressor surge at low engine speeds. At higher engine speeds the velocity of the air passing around aerofoils 30, Figs. 1, 2 and 3, is high enough to produce a sufficiently low pressure area downstream of each aerofoil to cause withdrawal of air from the interior of the bellows 28 via passages 29. The resultant partial collapse of the bellows 28 causes the wall 24 to recede from the wall 23 to increase the width of the diffuser passage 22.