Initial work has been completed on a fire ring (top piston ring) wear assessment in a military pattern heavy duty high speed diesel running on a range of fuel qualities. The work performed involved developing a short duration (8 hour) technique to evaluate fire ring wear as a function of fuel ignition quality.
The technique was based upon isolating Chromium sources in a Detroit Diesel Corp, (DDC) 6V92TA (two-stroke cycle, turbocharged, and after cooled) to the fire rings by component substitution in the liner kit assembly.
With the fire rings as the only major sources of chromium from engine wear components, engine oil analysis for trace chromium (by Atomic Absorption) in the 50-1500 ppb range could then be used to determine fire ring wear. This method was used to evaluate the fire ring wear associated with 30.0, 34.5, and 45.9 Cetane Number (CN) diesel fuels. The results were verified by data obtained earlier (1) from 500 hour durability runs in which the fire rings were physically weighed. The wear measurements made by the oil analysis technique correlated within 10% of the 500 hour measurements.
The wear evaluations to date have shown that diesel fuel with cetane number of 33-35 can shorten DDC 6V92TA engine life by as much as 70%.
This paper reports on fire ring wear associated with three fuel qualities, three injection types, and three injection timing set-ups. It was shown that fire ring wear rates were minimized at neutral (base) injection timing, higher injector pressures, and higher fuel ignition qualities. The most significant effect was that of fuel quality.
Combustion pressures, ignition delays, and emissions were monitored. Brake specific fuel consumptions and rates of pressure rise were measured.