1991-02-01

Effects of Cooling Water Temperature on Particulate Emissions from a Small High Speed DI Diesel Engine 910740

Authors have experimented the effects of cooling water temperature on the particulate emission characteristics from a high speed DI diesel engines.
A single cylinder small high speed DI diesel engine is operated under various engine speed and load conditions. Cooling water temperature is varied from 313 K (40 °C) to 363 K (90 °C). Particulate is collected using a single stage full size dilution tunnel. Dry soot and SOF emissions are measured, as well as total particulate.
SOF increases when the cooling water temperature decreases, as well as HC increases. SOF also increases as load decreases.
This suggests that the SOF emits at the cold starting and warming up periods. This also suggests that the SOF can be reduced by increasing cooling water temperature.
IT IS IMPORTANT TO CLARIFY the effects of cooling water temperature on the particulate emission.
In the practical operation, for example, diesel engine emits a lot of white or blue smoke, which contains both SOF (soluble organic fractions) and dry soot, during warming up period.
Another problem is on the particulate testing, that the particulate emission quantity shows hysteresis with respect to the engine load, that is, the particulate concentration is higher when the load increases than when the load decreases [1]*. There have been several possible reasons for this but not clarified yet, the wall temperature history is one of the candidates for this phenomenon.
Particulate is composed of dry soot and SOF. It has not been clarified which component the water temperature affects more.
It is said there is a correlation between SOF and HC concentrations. The dominant cause of HC is wall quenching of the flame, and is affected by the cooling water temperature. This suggests that the cooling water temperature may affect the SOF and total particulate emission.
In this paper, a single cylinder engine test was carried out by changing the cooling water temperature under the various load and speed conditions. Particulates were sampled using a dilution tunnel. Results show that the lower cooling water temperature increases particulate, especially soluble organic fractions (SOF).

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