WÄRTSILÄ WARTSILA32, Руководство по эксплуатации продукта, Страница: 59 / 254

● exhaust gas to exhaust system
●
cooling water from cylinder head to the return pipe
4.2.9 Camshaft and valve mechanism
The cams are integrated in the drop forged shaft material. The bearing journals are made in
separate pieces, which are fitted, to the camshaft pieces by flange connections. The camshaft
bearing housings are integrated in the engine block casting and are thus completely closed.
The bearings are installed and removed by means of a hydraulic tool. The camshaft covers,
one for each cylinder, seal against the engine block with a closed O-ring profile.
The valve tappets are of piston type with self-adjustment of roller against cam to give an even
distribution of the contact pressure. The valve springs make the valve mechanism dynamically
stable.
Variable Inlet valve Closure (VIC), which is available on IMO Tier 2 engines, offers flexibility to
apply early inlet valve closure at high load for lowest NOx levels, while good part-load
performance is ensured by adjusting the advance to zero at low load. The inlet valve closure
can be adjusted up to 30° crank angle.
4.2.10 Camshaft drive
The camshafts are driven by the crankshaft through a gear train.
4.2.11 Turbocharging and charge air cooling
The SPEX (Single Pipe Exhaust) turbocharging system is designed to combine the good part
load performance of a pulse charging system with the simplicity and good high load efficiency
of a constant pressure system. In order to further enhance part load performance and prevent
excessive charge air pressure at high load, all engines are equipped with a wastegate on the
exhaust side. The wastegate arrangement permits a part of the exhaust gas to discharge after
the turbine in the turbocharger at high engine load.
In addition there is a by-pass valve on main engines to increase the flow through the
turbocharger at low engine speed and low engine load. Part of the charge air is conducted
directly into the exhaust gas manifold (without passing through the engine), which increases
the speed of the turbocharger. The net effect is increased charge air pressure at low engine
speed and low engine load, despite the apparent waste of air.
All engines are provided with devices for water cleaning of the turbine and the compressor.
The cleaning is performed during operation of the engine.
In-line engines have one turbocharger and V-engines have one turbocharger per cylinder bank.
For in-line engines and 12V32, the turbocharger(s) can be placed either at the driving end or
at the free end. 16V32 and 18V32 have the turbochargers always placed at free end.
The turbocharger is supplied with inboard plain bearings, which offers easy maintenance of
the cartridge from the compressor side. The turbocharger is lubricated by engine lubricating
oil with integrated connections.
A two-stage charge air cooler is standard. Heat is absorbed with high temperature (HT) cooling
water in the first stage, while low temperature (LT) cooling water is used for the final air cooling
in the second stage. The engine has two separate cooling water circuits. The flow of LT cooling
water through the charge air cooler is controlled to maintain a constant charge air temperature.
4.2.12 Fuel injection equipment
The fuel injection equipment and system piping are located in a hotbox, providing maximum
reliability and safety when using preheated heavy fuels. The fuel oil feed pipes are mounted
directly to the injection pumps, using a specially designed connecting piece. The return pipe
is integrated in the tappet housing.
Wärtsilä 32 Product Guide - a21 - 7 September 2016 4-3
4. Description of the Engine Wärtsilä 32 Product Guide