Application Functional principle Effect
2-stroke diesel engine
▪ Scavenge air pressure at partial
load is increased by closing the
VTA:
▪ At partial load either
Economy Mode (Mode 1.)
Increased ignition pressure for reduction
of SFOC
3)
Reduced fuel consumption
(NOx increased) or
Emission Mode (Mode 2.)
Ignition pressure is kept constant by
ignition retard.
▪ Compensation of ambient tem-
perature influences on scavenge
pressure
▪ Closing on acceleration
▪ Compensation of extracted gas
flows (e.g. for power turbine
applications, see “Power tur-
bine” line)
▪
Plants with EGR
4)
:
Scavenge air pressure kept con-
stant when EGR rate is modified
3) Specific fuel oil consumption
4) Exhaust gas recirculation
Reduced NOx emissions
(Fuel consumption slightly higher than
Mode 1.).
In conjunction with a variable injection
system and appropriate optimization, the
VTA enables reduced consumption and
flexible changing between Mode 1. and
Mode 2.
▪ Slight increase in consumption at
full load
▪ Shifting of auxiliary blower
switch-off point towards lower
outputs
▪ Elimination of a bypass for scav-
enge pressure compensation at
extremely low intake tempera-
tures
(“Arctic conditions”)
▪ Improved load application behav-
ior
▪ Additional improvement of partial
load performance by shifting the
maximum efficiency towards a
lower engine load
▪ Exhaust gas temperatures at
partial load reduced
NOTE!
In the dedicated “Economy Mode”
(Mode 1.), the VTA rating must be
adapted to the NOx limit values.
Table 1: VTA range of applications on 2-stroke diesel engine
2013-12-04 - de
1 Adjustable turbine nozzle ring (VTA)
1.1 Range of applications
MAN Diesel & Turbo
1
EN-US
5 (38)
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