The six-cylinder 6S46MC-C low-speed, two-stroke engine employing a TCA 55 turbocharger
equipped with variable turbine
area (VTA) technology is shown
here undergoing shop tests.
Variable Turbine Area
Technology for MAN
Diesel Turbos
The turbocharger business unit of
MAN Diesel reported on the test process for its new variable turbine area
(VTA) technology for turbines that will
be developed for all turbocharger models in the TCR radial series and in the
TCA axial series. The new technology,
which will allow variable output to the
turbochargers, is currently under test
on a medium-bore, two-stroke low-speed engine for a marine application.
As MAN Diesel recently announced,
its two-stroke engine production is
going to be shifted to licensees only,
and in this case shop tests have been
completed on a six-cylinder 6S46MC-
C engine built by Man Diesel’s Croatian
licensee Brodosplit. The engine is soon
going to be installed aboard a 70 000
ton shallow-draught tanker under construction at the Brodosplit shipyard for
the Stena Concordia Maritime shipping
line. The propulsion system will feature
two twin 6S46MC-C engines with
mechanically controlled fuel injection
and exhaust-valve actuation, running
on heavy fuel oil — the one unit featuring VTA technology, and a second one
with conventional turbocharger.
Dr. Alexander Rippl, head of turbocharger development at MAN Diesel,
explained that the new technology will
offer customers better engine performance and lower fuel consumption, at the
same time helping meet future emission
regulations.
“Using our VTA system, we can more
precisely match the volume of charge-air
to the quantity of injected fuel at all
points on an engine’s load profile,” said
Rippl. “The result is reduced specific fuel
consumption in combination with
reduced HC and CO emissions and
improved dynamic behavior of the
engine-turbocharger system.”
The VTA system consists of a nozzle
ring, equipped with adjustable vanes.
By adjusting vanes pitch, the pressure
of the exhaust gases can be regulated
and the compressor output optimized
at all points on the engine’s performance map. Each vane has a lever, directly connected to a control ring. The control ring is actuated by an electric positional motor with integrated reduction
gear, a development that was an integral part of MAN Diesel’s VTA solution.
The company added that the adjustable vanes are manufactured in
heat- and erosion-resistant alloy steel.
This careful selection of fits and materials will ensure operation under all
conditions without sticking, especially
in applications where engines burn
heavy fuel oil.
The new nozzle ring of the VTA system replaces the fixed-vane nozzle
rings fitted in the standard TCA turbochargers, to assure retrofitting option for the VTA technology on conventional MAN Diesel turbochargers
already in the field.
The control of vane position is fully
electronic and the manufacturer confirmed that it can offer control packages
precisely tailored to a specific application, including both mechanically con-
