TECHNOLOGY OF COMPOSITE MATERIAL FORAERODYNAMICS – INNOVATION AT ZIEHL-ABEGG
How technology of composite materials helps fans to run quietly, convey large volumes of air and consume little energy in the process
Until the turn of the millennium, impellers, blades and nozzles were mainly made of steel and aluminium. Today, composite material components dominate here at ZIEHL-ABEGG – and the trend is rising, accounting for 80 % of the fans supplied. These enable the implementation of a particularly optimised, aerodynamic design as well as functional integration in a lightweight construction, where previously elaborately welded, riveted or screwed components were used, which were also much heavier as metal components. One example of this is the ZAplus fan series, in which the motor mount and the guide wheel are integrated into the plastic nozzle. The air technology specialists at ZIEHL-ABEGG have now created an innovative second generation ZAplus, which is even more efficient and quieter, and made it ready for series production. The fact that this was only possible thanks to interdisciplinary collaboration between various specialists is demonstrated below.
Interdisciplinary interaction plays a major role
The support struts of the ZAplus nozzle have very different functions and must be optimised with regard to these functions.
The main functions are
- Maximising the efficiency of the fan, which means minimising the electrical energy required for an operating point
- Generating the lowest possible noise during fan operation
- Static function (strength) during transport and operation
- Reliable and optimum injection moulding process: the component is filled by the struts; the distortion when the component cools depends largely on the strut geometry
- Influencing the vibration behaviour during operation
This shows that the design of the ZAplus nozzle with the guide struts is a task to be solved jointly by the various specialists in close coordination with each other. One technology that opens up such possibilities is simulation methods. They make it possible for all specialist disciplines such as aerodynamics, aeroacoustics, strength design, vibration design or injection moulding process design in particular to evaluate a preliminary design (virtual prototype) with regard to its suitability and quality in a comparatively short time and to iteratively optimise various designs in a relatively short time.
With the help of 3D printed prototypes in the ZIEHL-ABEGG test laboratory, the data obtained with the simulations can be validated on the corresponding test benches, as the simulation can be associated with uncertainties.
Flow simulation and acoustic simulation
Air performance and efficiency on the one hand and acoustic values on the other can be calculated based on a CAD model of a design, i.e. a virtual prototype, using various special simulation programmes. The simulation calculations are complex to carry out, as a corresponding computational mesh often has to be created for the geometry files. The actual calculations require a great deal of computing time and are carried out at ZIEHL-ABEGG on specially equipped large computers with hundreds of processors. As a result of the flow simulations (CFD simulations), the air performance (volume flow and pressure increase) as well as power consumption and efficiency can be calculated. The acoustic simulations make it possible to predict the sound power of virtual prototypes. In addition, a wide range of detailed information can be extracted or visualised from the simulation results, enabling targeted optimisation steps to be taken. The following three figures show examples of visualisations. On the left you can see the outflow behaviour based on the streamlines, in the middle you can see the strike lines on the blade surfaces and can recognise possible detachments and on the right a pressure distribution on the surfaces of the ZAplus unit is shown.
The simulation results shown are from the finalised ZAplus Next Generation, the optimum variant. The main innovation is the guide vane, which is divided into two different areas. The inner area primarily serves the goal of maximising efficiency by avoiding any efficiency-reducing hub backflow. The outer area is optimised for the significantly more critical acoustics. A small number of slender blades have been realised, which are far away from the impeller and very strongly ‘sickled’.
Simulation of injection moulding process and warpage
A crucial step in the development process is injection moulding simulation with the Cadmould software from Simcon, which has been in use at ZIEHL-ABEGG since 2020. This technology is extremely important, as all new developments of composite material components are simulated in-house. This minimises distortion and ensures the correct function and dimensional accuracy of the components. Long glass fibre-reinforced PP, PA6 or PA66 and short glass fibre-reinforced PA6 are predominantly used.
The simulations include filling behaviour, holding pressure, warpage calculation and fibre orientation. The result of the fibre orientation is mapped to FEM calculation models and thus the strength and deformation calculation is determined much more precisely, taking into account the orientations (anisotropy). Using Cadmould, DOE (Design of Experiment) studies can be carried out to optimise injection parameters and determine their influence on certain parameters. This enables developers to create the optimum conditions for production.
Warpage of the impeller blade angle
Distortion of the flange with ZAplus
Bind seams of impeller
Component strength and vibration behaviour
The strength and vibration behaviour can be calculated using FEM simulation programs. For fibre-reinforced compoite material components, the existing fibre orientation, which is known from the injection moulding simulation, is a prerequisite, as this influences strength and vibration behaviour.
The intermediate ring in the trailing edge of the new ZAplus allows aerodynamicists and aeroacousticians to have a different number of wings on the inside and outside. At the same time, it is a highly stiffening element and makes it possible to fulfil strength and vibration requirements. The intermediate ring gives the new ZAplus a very high degree of rigidity, even with the incredibly small number of six outer, highly inclined strut wings.
Fibre orientation with ZAplus
Efficient production and sustainable manufacturing
The new ZAplus fans are produced in the company’s own injection moulding facilities, which have been in operation since 2017. This decision to produce large parts in-house significantly reduces the company’s ecological footprint, as unnecessary transport is avoided. The production halls are equipped exclusively with machines that use state-of-the-art hot runner technology to minimise material consumption and increase efficiency.
With the energy transition and advancing digitalisation, the company sees positive prospects for the future: ‘The energy transition and digitalisation with the associated increase in data centres is a great advantage, as these industries cannot do without efficient air technology.