Abstract
In this paper, a theoretical model is proposed to investigate the centrifugal fans' transient behaviour in response to sudden imposed changes in pressure or flow rate. We are especially interested in the dissipative or creative energy transient behaviour of the fans located in actual aeraulic networks.The model is based on the global modelisation of the motor and resistant torques (due to pressure and viscosity actions on the blades) which are present on the rotor and by their coupling with its inertia.The model is then validated by experimental measurements which show its validity. In the case of the tested fan, the instantaneous characteristics (in particular the flow rate and rotation speed) have been correctly predicted by the model, with regard to time as well as amplitudes, provided the flow is not reversed.
Highlights
The theoretical determination of the transient behaviour of fans subjected to instantaneous variations in high static pressure or flow rate is quite difficult due to the fan’s constant time, related to the inertia of its rotor, which is usually greater than the constant establishment time of the change of pressure or flow rate
Prior to any numerical simulation of the fan’s transient behaviour, the model was first verified for its static characteristics
By using this model, we can calculate the static characteristics of the fan which are compared to experimental data points
Summary
The theoretical determination of the transient behaviour of fans subjected to instantaneous variations in high static pressure or flow rate is quite difficult due to the fan’s constant time, related to the inertia of its rotor, which is usually greater than the constant establishment time of the change of pressure or flow rate. The instantaneous effects of variations of mean flow rate on the fan, considering its inertia, are given from the application of the fundamental dynamic relation applied to the rotating system: The resistant torque depends on the instantaneous flow rate
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