Preliminary Results

Tests reported include baseline tests with a production chrome plated ring and gray iron liner under lubricated conditions at 25 C. These results are compared with combinations selected as the most promising, and a less promising ring, liner pair (based on engine testing experience). These combinations were tested under lubricated and unlubricated conditions at 427 C. Table II shows the five combinations reported and the test conditions under which they were run. Comparisons with Cameron Plint and actual engine test results are made.


Figures 2. 3 and 4 show baseline results with the production chrome plated top ring and gray iron liner, lubricated with mineral oil. Test temperature was 25 C and load was 19.2 lbf on the 0.27 in liner segment, or 70 lbf/in. Figure 2 shows friction coefficient as a function of crank angle over the 360 deg stroke. The average friction coefficient over the cycle shown in figure 2 was approximately 0.04. Figure 3 shows the liner sample surface profile as a function of sample length. This measurement was made with a Sheffield Surface Profilecorder, Model RLC 7. The measurements were made at 193 microinch intervals. The recessed portion of the trace, which is the length of the 1 in stroke shows the wear. Notice that the wear is greater near the dead centers and less near the center of travel. perhaps indicating a transition from boundary to EHD/mixed lubrication as the sample accelerates from rest. Figure 4 shows how the friction coefficient changed with time as the test continued. There was a substantial drop as the break-in process occurred, reaching a level of about 0.055.

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