Inlet casing and suction passage structure

1. An inlet casing provided for sucking fluid into a sectional opening of fluid machinery for boosting up the fluid through rotation of an impeller mounted on a rotary shaft, comprising a suction passage arranged being orthogonal to the rotary shaft on an upstream side in a stream of the fluid directed toward the fluid machinery, and an internal passage connected to the suction passage, the internal passage being formed in a spiral shape so as to induce a swirl stream orthogonal to the rotary shaft of the fluid machinery, wherein a guide vane is provided in the vicinity of an inlet port of the internal passage to distribute flow rates in the swirl stream of the fluid in the internal passage between a swirl center side and a swirl outer peripheral side of the swirl stream, and to cause the fluid flowing from the suction passage into the internal passage to deflect into a swirling direction of the swirl stream in the internal passage.

2. An inlet casing as set forth in claim 1 , wherein an auxiliary guide vane mainly having a function capable of causing the fluid to deflect, having a configuration similar to the guide vane and arranged parallel to the latter is provided to cause.

3. An inlet casing as set forth in claim 2 , wherein the guide vane has an arcuated rectifying surface.

4. An inlet casing as set forth in claim 1 , wherein the internal passage includes a swirling part for inducing the swirl stream in the fluid, and an introduction part for introducing the swirl stream of the fluid induced by the swirling part, into the suction opening of the fluid machinery, the introduction part being provided with a bell-mouth part which is projected in the axial direction of the rotary shaft at the upstream side end of the introduction part.

5. An inlet casing provided for sucking fluid into a section opening of fluid machinery for boosting up the fluid through rotation of an impeller mounted on a rotary shaft, comprising a suction passage arranged being orthogonal to the rotary shaft on an upstream side in a stream of the fluid directed toward the fluid machinery, and an internal passage connected to the suction passage, the internal passage is formed in a spiral shape so as to induce a swirl stream orthogonal to the rotary shaft of the fluid machinery, wherein the internal passage includes a swirling part for inducing the swirl stream in the fluid, and an introduction part for introducing the swirl stream of the fluid induced by the swirling part, into the suction opening of the fluid machinery, the introduction part is provided with a bell-mouth portion which is projected in the axial direction of the rotary shaft at the upstream side end of the introduction part, the bell-mouth portion having a projecting height which is gradually decreased from the upstream side to the downstream side of a stream of the fluid in the swirling part, and a highest projecting height on the upstream side in the projecting height of the bell-mouth portion and a lowest projecting height on the downstream side in the protecting height of the bell-mouth portion have therebetween a relationship so that a ratio b c falls in a range from 1: 1.1 to 1: 1.2 where b is a passage width defined between a lower end of the bell-mouth portion and a wall surface of the internal passage in the part having the highest projecting height and c is a passage width defined between the lower end of the bell-mouth portion and the wall surface of the internal passage in the part having the lowest projecting height.

6. A fluid passage structure adapted to suck fluid into fluid machinery for boosting up the fluid through rotation of an impeller mounted on a rotary shaft, comprising a suction passage arranged being orthogonal to the rotary shaft on an upstream side in a stream of fluid directed toward the fluid machinery and an inlet casing having one end connected to the suction passage and the other end connected to the fluid machinery, the inlet casing having an internal passage connected to the suction passage, and the internal passage being formed in a spiral shape for inducing a swirl flow orthogonal to the rotary shaft of the fluid machinery, in the fluid, wherein the suction passage and the internal passage are provided so that their center lines are superposed on a first reference line which passes through the center line of the rotary shaft, passing through a heightwise center position of the suction passage or the internal passage, and is extended along the direction of the stream of the fluid directed to the fluid machinery in the suction passage, and a guide vane having a function capable of distributing flow rates in the swirl stream of the fluid in the internal passage between a swirl center side and a swirl outer peripheral side of the swirl stream, and having a function capable of causing the fluid flowing from the suction passage into the internal passage to deflect into a swirling direction of the swirl stream in the internal passage is provided in the vicinity of an inlet port of the internal passage.