Cross flow fan (also known as cross flow fan or cross flow fan) is a special structure of fan, whose working principle and airflow characteristics are significantly different from common axial or centrifugal fans. The following provides a detailed analysis from two aspects: working principle and airflow characteristics:
1、 Working principle of cross flow fan
Structural features
Impeller design: The core component is a long cylindrical impeller, with blades arranged in parallel along the axial direction, usually using forward multi wing blades (such as 35-60 blades), and the blade inclination matches the direction of rotation.
Airflow path: Air enters from the inlet on one side of the impeller, passes through the blade gap radially, forms a vortex inside the impeller, and is discharged from the outlet on the other side. The airflow direction is parallel to the axis of the impeller.
Guiding components: The outer shell is usually designed as a gradually expanding shape, and internal guiding plates may be installed to optimize the direction of airflow.
Working process
When the impeller rotates, the blades apply centrifugal force and lift to the air, pushing the air to move along the circumference of the impeller.
Due to the closure of both ends of the impeller, the airflow is forced to form a spiral flow inside the impeller, and finally discharged along the axial direction, forming a uniform laminar air curtain.
Driving mechanism
The aerodynamic design relying on blades (such as airfoil profiles and installation angles) generates pressure differentials, rather than solely relying on centrifugal force (such as centrifugal fans) or axial thrust (such as axial fans).
2、 Analysis of Airflow Characteristics
Airflow distribution
Uniformity: The airflow is evenly distributed along the length of the impeller, suitable for scenarios that require wide air supply (such as air conditioning vents).
Low wind speed and high air volume: The wind speed is relatively low (usually 1-5 m/s), but the air volume is large, suitable for gentle air supply.
Pressure characteristics
Low static pressure: Due to the complex airflow path and high energy loss, the static pressure is usually lower than that of centrifugal fans but higher than that of axial fans.
High dynamic pressure ratio: The outlet airflow has significant kinetic energy, making it suitable for direct blowing applications such as dryers and air curtains.
Eddy current and energy loss
Internal eddies: There are secondary flows and eddies inside the impeller, resulting in lower efficiency (usually 40-60%).
Noise characteristics: Vortex separation and blade passing frequency noise are significant, and it is necessary to reduce noise by optimizing the number and spacing of blades or using non-uniform distribution.
Unique advantages
Controllable air outlet direction: 180 ° air outlet angle adjustment can be achieved through diversion design.
Compact: The axial length can be flexibly designed, suitable for installation in narrow spaces.
3、 Comparison with Axial/Centrifugal Fans
| Characteristics | cross flow fan | Axial flow fan | Centrifugal fan |
| Airflow direction | Axial entry and exit, radial internal turning point | Pure axial direction | Radial (90 ° turning point) |
| Pressure capacity | Medium low static pressure | low static pressure | High hydrostatic pressure |
| Air volume | Large and uniform | Large but concentrated | medium |
| efficiency | Lower（40-60%） | higher（70-85%） | rising-falling（60-75%） |
| Typical applications | Air conditioning, air curtains, car ventilation | Heat dissipation and ventilation | HVAC、dust elimination |
4、 Application scenarios
Household appliances: air conditioning indoor unit, heater (using uniform air curtain to avoid direct blowing).
Industrial equipment: air curtain machine (isolating hot and cold air), drying equipment.
Automotive field: electric vehicle battery cooling, seat ventilation system.
5、 Optimization direction
Blade design: Using asymmetric airfoils or variable angle blades to reduce eddy currents.
Spiral shell optimization: Improve the inlet and outlet diversion structure to reduce turbulence losses.
Material lightweighting: For example, carbon fiber impellers increase speed and reduce inertia.
Cross flow fans achieve an irreplaceable performance balance in specific applications through their unique airflow organization, but require targeted design trade-offs between efficiency and noise.