Abstract:
This research work is aimed at investigating the effect of variation of coolant temperatures
ranging from 45-85°C, thus effecting the heat removal rate, on the performance of an
automotive 81 engine. The specific aim of this study was to investigate the effect of
variation of cooling water temperature as well as the cooling rate on the P-t and P-V
diagrams of the engine cycle, at different speed and load conditions. A pressure transducer
connected to the combustion chamber, signal conditioning hardware and a high-speed data
acquisition device is used for recording cyclic variation of pressure. A position sensor
tracks the TDC location as a time series, from which the cylinder volume is calculated
using piston-cylinder dimensions. Performance parameters such ~s brake specific fuel
consumption rate, air-fuel ratio, temperatures of coolant, lubricating oil as well as the
engine body and emission analysis of the exhaust gases were also investigated at different
engine speed and load conditions.
Investigations revealed that increased coolant temperature reduced the heat losses and
resulted in slight improvement of specific fuel consumption. No significant change on the
pressure-volume relationship was noticed. Variation of coolant temperature in this range
did not change the combustion inside the cylinder very much, resulting in insignificant
changes in exhaust temperature and emission analysis. The detrimental effects observed
was the elevation of temperature of the engine parts and the lubricating oil. Although
multi-grade lubricating oils appeared to be coping up with the rise of temperatures
resulting in steady engine operation. Elevated body temperatures may have detrimental
effect on the operational life of various non-metallic and metallic engine parts. When the ,
coolant temperature was raised above 85°c the heat transfer and temperature rise became
unstable due to local boiling and formation of vapour locks, leading to rapid engine
overheating. This investigation may have practical implications when many automotive
engines in Bangladesh are run with faulty/inadequate cooling systems 'specially in
congested traffic jams in hot summer days.
