1938-01-01

Report of the Volunteer Group for Compression-Ignition Fuel Research 380121

FOLLOWING the adoption of a suitable design of engine and a tentative procedure for operating this engine, the work of the Volunteer Group has covered the investigation of other methods of measuring cetane number of Diesel fuels looking towards a simplification and improvement of reproducibility of the procedure.
Results of a second series of cooperative tests are given, using the procedure adopted in the Group's last report together with a series of tests on the same fuel using the critical-compression-ratio method with an interval timing-control device. Results of the first series do not show such good agreement, the grand average deviation on twelve samples being of the order of ±1.9. Results of the critical-compression-ratio tests show improved agreement due to better standardization.
Tests on three alternative methods based on the delay method, but using different instruments for recording the delay, are given. Results on two different full-scale engines also are presented.
It is concluded from the results of the past 18 months' work that a direct matching method on the basis of ignition delay is the best from the point of view of reproducibility and validity, even though this method will involve some sacrifice in simplicity and speed of testing. The progress of methods of instrumentation is advanced considerably, and it appears that the bouncing-pin type should be discarded in favor of a balanced-diaphragm or magnetic-pickup type.

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