Classification of Impeller Types

I. By Structural Design

1. Closed Impeller

Structure: Enclosed by front and rear shrouds, with vanes between them.

Features: High efficiency, good hydraulic performance, and suitable for clear liquids.

Applications: Centrifugal pumps for clean water, chemical fluids, and oil.

2. Semi-Closed Impeller

Structure: Only has a rear shroud (or no shroud), with vanes exposed on one side.

Features: Balances efficiency and solids-handling capability, less prone to clogging.

Applications: Pumps for slightly contaminated liquids (e.g., sewage, slurries with small particles).

3. Open Impeller

Structure: No shrouds, vanes directly attached to the hub.

Features: High tolerance for solids and debris, but lower efficiency.

Applications: Slurry pumps, dredge pumps, and pumps for highly viscous or particle-laden media.

II. By Fluid Flow Direction

1. Radial Flow Impeller

Flow Path: Fluid enters axially and exits radially (perpendicular to the shaft).

Features: High head generation, suitable for high-pressure applications.

Examples: Centrifugal pumps in water supply, chemical processing.

2. Axial Flow Impeller

Flow Path: Fluid moves parallel to the shaft (axial direction) through the impeller.

Features: High flow rate, low head; efficient for large-volume, low-pressure systems.

Examples: Axial flow pumps in irrigation, cooling towers, ship propulsion.

3. Mixed Flow Impeller

Flow Path: Combines radial and axial components, with fluid exiting at an angle.

Features: Balances flow rate and head, suitable for medium-pressure applications.

Examples: Mixed flow pumps in water treatment plants, drainage systems.

III. By Application and Pump Type

1. Centrifugal Pump Impellers

Design: Radial or mixed flow, closed/semi-closed/open structures.

Applications: Water circulation, chemical process pumps, and oil pipelines.

2. Axial Flow Pump Impellers

Design: Propeller-like, with airfoil-shaped vanes.

Applications: Flood control pumps, marine propulsion systems, and HVAC cooling.

3. Reciprocating Pump Impellers

Note: Strictly speaking, reciprocating pumps use pistons, but some hybrid designs may adopt impeller-like components.

4. Specialized Impellers

Vortex Impeller: Creates a vortex flow, ideal for highly viscous fluids or solids with fibers.

Multi-Stage Impeller: Used in multi-stage pumps to achieve high heads (e.g., boiler feed pumps).

Magnetic Drive Impeller: Seamlessly integrated with magnetic couplings for leak-free applications.

IV. By Vane Configuration

1. Straight Vane Impeller

Features: Simple design, easy to manufacture, suitable for low-speed applications.

Applications: Basic water pumps, low-head systems.

2. Curved Vane Impeller

Features: Optimized for fluid dynamics, reduces turbulence and improves efficiency.

Applications: High-performance centrifugal pumps, turbochargers.

3. Pitched Vane Impeller

Features: Vanes angled to control flow direction, common in axial/mixed flow designs.

Applications: Circulating pumps, agitators, and marine propellers.

V. Key Selection Factors

Medium Characteristics:

Clear liquids: Closed impellers for high efficiency.

Solids/viscous fluids: Open/semi-closed impellers to prevent clogging.

Flow and Head Requirements:

High head: Radial flow (centrifugal) impellers.

High flow: Axial flow impellers.

Operational Conditions:

High speed: Curved vane or aerodynamic designs to reduce noise and vibration.