Cooling 7 - Fan
In the motor car, up to, and including the middle class, electric cooling fans have asserted themselves. Over and above the middle class, and in trucks/busses, it becomes difficult to raise the necessary performance of up to 30 kw. If a belt drive is possible, the viscous cooler-fan dominates in this range.Where the installation is more difficult, the engine drives the fan through a hydraulic pump and a hydraulic motor, perhaps the pressure can also be supplied by the hydraulic power steering. Cooling surfaces are just about 1 mē in size and nowadays they require, in all cases, a controllable fan.
How it works
While the air cooling of the blowers works in the axial- as well as in the radial direction, the fans of the liquid cooling are exclusively axial blowers. The vanes are either straight (figure 2), or sickle-shaped (figure 1), perhaps also with a wind-collector (figure 4), at any rate, they are all made from synthetics. To obtain lower noise levels and perhaps a higher efficiency, the vanes are unequally distributed. They nearly always draw in- (figure 1 and 2) and more seldom exhaust the air (figure 3).
Simpler, from the controlling point of view, are probably the twin fans whose electric motors, which are mostly pulse-width modulated and no longer through pre-resistors, can reach up to the maximum at any RPMs. If only this part of the cooling system is electronically controlled, it is found in the casing of either one of the motors. It is important, in all cases, to be able to regulate the fan RPMs regardless of the engine speed, because at high engine speeds the air-flow is mostly sufficient anyhow and energy would be needlessly consumed. 09/09