counter-rotating axial flow impellers, each driven by a separate
shaft. The counter-rotating impeller configuration is well
known in marine applications for eliminating swirl at the exit of
the pump, and thereby increasing the propulsion efficiency since
swirl represents energy lost to the propulsion process. There are
no stators so the water enters at section 1
axially into impeller 1, is energized, and exits
impeller 1 at section 2. It then proceeds
directly to enter counter-rotating impeller 2 at
section 3, where the water is further energized by
impeller 2, and emerges axially at section
4. The following data is given:
Volumetric Flow Rate, Q = 25 m^3/min ;
Working Fluid: Water at STP
Impeller 1: angular velocity ω1 = 3,000
rpm, Degree of Reaction = 0.50;
Impeller 2: angular velocity ω2 = -3,000
rpm, Degree of Reaction = unknown;
Blade tip radius = 95 mm; Blade Hub Radius: 37.5 mm
Assume flow is axial at both Section 1 and Section
4.
Assume blade angles equal corresponding flow angles
Perform all calculations at the mean radius.
Find:
Blade peripheral speed at mean radius for impeller 1 (U1)
Absolute velocity and each section (V1, V2, V3, V4)
Relative velocity at each section (W1, W2, W3, W4)
Inlet and outlet blade angles on each impeller (β1, β2, on
impeller 1 and β3, β4 on impeller 2)
- A Jet Boat Water Jet Propulsion Pump Has Two Coaxial Counter Rotating Axial Flow Impellers Each Driven By A Separate Sh 1 (313.14 KiB) Viewed 27 times