Troels Dyhr Pedersen.indd - Solid Mechanics

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8 Description of experimental engine setup
8.1 Engine
The engine used for the experimental work at DTU is a 0.9 L, 2 cylinder, 4 stroke DI CI
engine which is constructed for marine applications. It is a simple construction with
pushrod valve operation which makes it easy to dismantle and reassemble. The cylinder
head is a flat 2 valve design. It is naturally aspirated and does not have EGR.
The engine used for experiments at NTSEL in Tokyo was an Isuzu 4.6 L 4 cylinder truck
engine, which was modified with a common rail system developed for DME. It was
equipped with EGR and a high capacity EGR cooler. It was furthermore fitted with an
injection system for methanol for the experiment. The engine and the experimental setup
are described separately in the second paper in appendix.
8.1.1 Engine setup
The engine is coupled to an eddy current type dynamometer from Zöllner. The
dynamometer does not have motoring capability, so one of the two cylinders on the
engine was kept in DI CI operation with diesel fuel, in order to maintain the engine speed
and heat up the engine.
Figure 1: Engine stand
8.1.2 Modifications
The first modification needed to run the engine in HCCI mode was to adapt the
compression ratio to suit the fuel ignition properties. Since the compression ratio needed
to run on DME was not known initially, a solution which allowed a variable compression
volume was installed in the cylinder head. The original diesel injector hole was enlarged
to accommodate a steel cylinder, so that a piston could be used to control the
compression volume. The arrangement is shown in figures 2 and 3. By adjusting the
piston crown height a compression ratio of 14 was made, and with the adjustment piston
in bottom position, the compression ratio could be varied from 9 to 14 while the engine
was running. This modification has also been used in an HCCI engine at Lund University
[17].