High speed diesel engines are difficult to start in cold
conditions (at subzero temperature) because the cylinder head and
cylinder block absorbs heat of compression and thus preventing
ignition due to the high surface to volume ratio. Also the coolant
and the engine oil become viscous at subzero temperature and make
the condition unfavorable for starting. Combustion optimization
along with the help of a heating aid can make these engines to
start quickly without any engine misbehavior.
Cold startability is the ability of an engine to start within a
specified time and continue to run without any malfunctioning.
Combustion instability will lead to the misfiring of the engine
unless it is calibrated properly. The European countries are
subjected to a minimum temperature of -20°C to -25°C. So the
intention of this work is to optimize the cold startability of
Mahindra's Multi-Purpose Vehicle (MPV) up to -25°C which is to
be sold in European countries.
For this purpose, experiments were conducted on this MPV having
a 2.2L common rail direct injection diesel engine. In order to
enhance the startability, individual glow plugs have been used in
each cylinder. The vehicle had been prepared and put in a cold
chamber where the ambient temperature can be brought down to -30°C.
The temperature had been varied from 10°C to -25°C in steps of
5°C.
At each temperature, the startability was checked and optimized
to get the best results in terms of startability, stability in idle
and smoke behavior. The possibility of introducing the multiple
injections has also been studied. The combustion optimization with
the help of starting aid helped the engine to start very quickly
even at -25°C.