8
Matching
8.1
Matching Procedure
The matching procedure of a turbocharger with VTA differs from that for a
turbocharger without VTA as follows:
TIP
Compare also with the Project Guide “TCA Turbochargers”.
8.2
Adjusting the Charging Air Pressure
If the VTA is used, this naturally dispenses with the need to exchange a noz-
zle ring. Furthermore, the charge pressure is infinitely adjustable.
Matching generally involves checking a complete VTA motion and control
program rather than a single fixed component.
Examples of such motion programs include:
▪
Diesel engine: closing the VTA towards partial load
▪
Gas-powered engine: opening the VTA towards partial load
▪
Keeping the charge air pressure constant in varying ambient conditions
▪
Transient motion programs to improve the transient response, e.g.
reduction of soot emissions in the case of load applications.
See also the chapter
Adjustable turbine nozzle ring (VTA)
VTA range of applications.
When creating the motion program, it must be ensured that all VTA positions
required for this program are within the lower and upper limits of the flow
cross section. These limit values are determined by the mechanical limits of
the adjusting mechanism and the permissible stress on the turbine blades.
Moreover, the following limits resulting from the application must also be
complied with in the program:
▪
It must be ensured that an excessively high charge air pressure does not
result in the maximum ignition pressure being exceeded, particularly in
the load range of 85%-100%.
▪
The cycle limit values for the NO
X
emissions must be complied with.
▪
In the case of gas-powered engines, the permissible
λ
window between
the knocking range and the instability range must be taken into consider-
ation.
IMPORTANT! During matching, it is important to check that all aforemen-
tioned operating points are within the possible operating range even in the
case of unfavorable ambient conditions (compressor intake temperature,
ambient pressure, charge air temperature, fuel composition and exhaust gas
back-pressure).
If the corresponding conditions cannot be set during matching (e.g. maxi-
mum temperatures for gas-powered engines, minimum temperatures for die-
sel engines), a check must be carried out using ISO correction factors or
process calculation.
Motion program
8 Matching
8.2 Adjusting the Charging Air Pressure
2013-12-04 - de
8
MAN Diesel & Turbo
30 (38)
EN-US
