Man L23/30DF, Project Manual

Page: 253 / 392

Overview
MAN Diesel & Turbo four-stroke Diesel engines and
turbochargers are designed in accordance with
specifications so that optimum results, e.g. fuel
consumption and emissions performance, are
obtained through the services normally provided.
However, it is possible that specific operating situa-
tions could be managed more effectively using
additional or alternative equipment.
Equipment used to adapt the engine to specific
operating conditions or to optimise its performance
is listed in Table 1. The ideal areas of application are
also stated in this table. The purpose of table is to
provide you with an overview of the options availa-
ble and the circumstances in which they should be
used.
Equipment/Measure Propul-
sion
GenSet
Blow off charge air X X
Bypass charge air X
Charge air preheating –
via HT/LT switch-over
(2-stage charge air cooler)
X X
Control the charge air temperature
(CHATCO)
X X
Blow off exhaust gas
(Waste Gate)
X X
Accelerate turbocharger
(Jet Assist)
X X
Table 1: Equipment for optimising the operating behaviour
X = Availability
Brief description
Device for blowing off charge air
▪
Blow-off charge air pressure used for:
▪
Reduction of charge air pressure/max. pressure
at cold ambient conditions.
▪
Prevent surging at cold ambient conditions.
▪
Control of max. pressure at Part Load Opti-
mised operation.
▪
Control of exhaust gas temperature for SCR
operation.
When operating engines under full load at a low
intake temperature (≤ 5°C) there is a danger, due to
the high air density, that the charge pressure, and
therefore the ignition pressure, increases exces-
sively. In order to avoid such conditions, excess
charge air in front of or after the charge air cooler is
removed and released. In the first case, the charge
air is blown off into the engine room and in the sec-
ond case, when charge air released from the
charge air cooler is hot, the charge air is blown off
into atmosphere to prevent danger to persons and
equipment. Alternatively, this hot charge air may be
also used for inlet air preheating. This blowing off is
achieved by means of an electro-pneumatic or
spring-loaded valve.
Device for bypassing charge air
▪
Charge Air By-pass used for:
▪
For Fixed Pitch Propeller operation on part load.
▪
Increaseds charge air pressure and airflow.
▪
Decreases exhaust gas temperatures.
▪
Decreases smoke emission.
The charge air pipe is connected via a pipe with a
smaller diameter and a bypass flap to the exhaust
pipe. The flap is closed in normal operation. In the
case of propeller operation (diesel-mechanical) at
engine loads between 20% and 60% and at rated
or reduced speed, the flap is opened to direct a
part of the charge air into the exhaust pipe
upstream of the turbine. The increased air flow of
the turbine results in a higher charge air pressure of
the compressor and consequently in improved
operating behaviour of the engine. Additionally this
flap may be used to prevent turbocharger pumping.
The throttle flap is controlled by a pneumatic actua-
tor cylinder depending on the engine speed and the
filling setting of the fuel delivery pumps.
Charge air preheating – via LT - cut-out (2-stage
charge air cooler)
▪
Charge Air Preheating:
▪
For HFO low load operation (improves ignition
delay).
▪
Increases charge air temperatur (compression
temperature).
▪
Decreases smoke emission.
MAN Diesel & Turbo
3700546-9.0
Page 1 (3)
Equipment to optimize performance
B1600 0
V28/32S, L28/32S, L28/32H, L27/38S, L27/38, L23/30S, L23/30H, L21/31S,
L21/31, L16/24S, L16/24