HyBlade ebm-papst: reducing fan noise

Systems that regulate air temperature are often a source of troublesome noise. In air-conditioning, cooling and heating systems alike, the most common cause is the operation of fans, which are found in all equipment of this type. This article presents solutions used in the design of ebm-papst’s HyBlade® series of fans to reduce their operating noise.

A fan is one of the basic components of all ventilation and air-conditioning equipment. It is also usually the component that affects the noise level of the entire unit. Today, because of requirements for room comfort and often the recommendations of standards, noise level has become a very important technical indicator for fans alongside performance parameters. It is of interest to both manufacturers and users of this equipment. For this reason, when improving their products, fan manufacturers focus on eliminating the noise they generate as effectively as possible. Laboratories specially equipped for this type of work make it possible to pinpoint the cause of troublesome noise more accurately and find the most effective ways to reduce it.

Axial fans

This type of research enabled ebm-papst to analyse the main sources of noise in axial fans. Measurements showed that the greatest noise is generated at two points on an axial fan blade.

These are:

• the leading edge of the blade,
• the end of the blade on the suction side, furthest from the motor.

The other parts of an axial fan blade, particularly the trailing edge, have little significance for noise generation. Special finishing, such as changing the thickness or making this part of the blade “jagged”, therefore has no effect and does not reduce the operating noise of an axial fan.

Winglets

ebm-papst was one of the first companies to introduce so-called “winglets” on its axial fans, positioning them on the blade edges furthest from the motor. This method of reducing air turbulence that causes noise is known, among other things, from aircraft design, where wings often have a similar profile. The element used significantly reduces noise emissions caused by disordered airflow. The reduction in noise level has been confirmed by tests conducted in ebm-papst laboratories.

HyBlade® fans

The developed technology using winglets has been used, among other applications, in the HyBlade® series of axial fans with plastic blades. Carefully profiling the blade sections that are the main sources of noise, together with the use of a special material, has made these some of the quietest and lightest axial fans on the market. The design of the entire fan, including how the blades are joined to the motor, has made it possible to achieve quality and strength characteristics typical of the widely used axial fans with metal blades, and in some cases even to exceed them.