Download PDF - Voith Turbo

The core component of the mechanical/hydrodynamic
drive system is the
Voith variable-speed fan, which is available
in various versions. Its distinctive
feature is that it forms an integral unit
with a filling-controlled Föttinger coupling.
A pneumatic system is used for
filling control - and thus for control of
the fan speed - that uses the coolant
temperature of the components to be
cooled as output variable [4, 5].
The advantages of the Voith variablespeed
fan can be summarized as follows:
- The system permits a constant
coolant and component temperature
to be maintained.
-Fan speed can be varied within
certain limits and is only dependent
on diesel engine speed to a certain
extent.
- The efficiency maximum of about
90 % for the entire driveline is
reached at maximum fan speed,
i. e. when the coupling is full.
-Power consumption is matched to
the operating conditions.
- The system is self-sufficient.
- The system is considered robust,
long-lived, low-maintenance, and
vibration-resistant.
The disadvantages are:
- Lack of flexibility with regard to arrangement
in the vehicle due to the
mechanical drive.
- High cost and weight.
The hydrodynamic fan drive was therefore
replaced by the hydrostatic one.
8
3.1.2 Hydrostatic drive
The hydrostatic drive system for fans
and other auxiliary machines is considered
state-of-the-art for today’s dieselpowered
vehicles with all its hydraulic
components including electronic control.
The advantages of this system are
a high freedom of choice regarding the
arrangement of the components in the
vehicle and the favourable price of the
entire cooler group.
In principle it is possible to design a
hydrostatic drive in such a way that it is
only a hydraulic shaft without any possibility
of control. The simplest type of
control would be a pure on-off control.
Both these designs are simple and trouble-free
in respect of their operation, but
they do not come up to today’s demands
any longer and have therefore
become insignificant.
There are highly developed components
and regulating valves available
Temperature
sensors
Standby
valve
Diesel
engine
Variabledisplacement
pump
Control electronics
Control valve
Constantdisplacement
motor
Oil filter
Oil tank
Fig. 4: Voith flow system driving a cooling fan
today for variable-speed hydrostatic
drives. Several patented solutions have
emerged over the last few years both
for overall function and for control.
The use of a variable-displacement
pump that only delivers the oil flow actually
required for cooling has resulted
in a higher overall efficiency. Moreover,
the Voith flow system with variable-displacement
pump includes a stand-by
valve that guarantees availability of the
working pressure required for operation
of the pump at all drive speeds also in
the case of zero delivery (figs. 4 and
5). When the operating pressure signalled
by the control system exceeds
the stand-by pressure, the stand-by
valve opens completely and the pump
is controlled by the working pressure
of the hydrostatic system [6, 7].
The solution described here permits
power savings of about 10% on an average
compared to by-pass control. For a
diesel-hydraulic locomotive of 1,500 kW
Oil cooler
Cooling
fan