The fuel switching is achieved by using two pressurized circuits,
one for diesel and one for the alternative fuel. These circuits are
separated by a four-way valve that controls which fuel is recirculated
and which fuel is supplied to the atomizer. In both circuits,
the pressure is controlled by setting a needle valve in a bypass line.
The pressure level is chosen such, that the thermal input after
switching is similar and therefore the rotational speed of the
MMGT is hardly influenced. Besides the fuel pressure, also the temperature
is adjusted before switching to minimize the risk on a
blowoff. The alternative fuel, which is a viscous biofuel in this
research, is preheated in the tank and then further heated by two
cartridge heaters in the fuel line