From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Analysis of permissible oil temperatures, bearing conditions, and heat generation in Peregrine engines.
| Identifier | ExFiles\Box 179b\3\ img309 | |
| Date | 13th March 1933 | |
| -2- Later we hope to make an analysis of the sources of the heat at the high speed encountered. PERMISSIBLE OIL TEMPERATURES. The first Peregrine run in France was mainly driven on the oil temperature. There is no doubt that the inlet oil to the bearings was, for considerable periods, between 110 & 115°C, and on isolated occasions exceeded 120°C. The rise across the engine is, with 50 lbs/sq.in. oil pressure, about 14°C, and it may therefore be assumed that the bearings reached 130°C at least. On stripping at the completion of the 10,000 miles the big end bearings had run and were in a very poor condition. This confirms to a certain extent some tests we made on journal bearings on a rig with thermo couples inserted in the shell. We attach a print He.952 shewing the results. The second Peregrine running in France certainly has not reached such high maximum inlet to the bearings temperatures as the first, but had been run with lower oil pressure (32 lbs/sq.in.) The big ends have failed completely. Curve He.953 attached shews, from figures taken on an aircraft engine, that by dropping the oil pressure from 50 to 20 lbs/sq.in. the bearing temperature is likely to be raised 15 - 20°C. Also that at 30 lbs/sq.in. the bearing may run about 25°C hotter than the oil. These various tests, therefore, indicate that with 50 lbs/sq.in. oil pressure and whitemetal bearings we ought not to run our oil inlet to the bearings much above 100°C, or with 20 lbs/sq.in. pressure much above 85°C. HEAT GENERATED BY PUMP CIRCULATION. Queries have been raised as to the necessity for so large an oil circulation and suggestions made that this raises the temperature unduly. We think the large oil flow usefully increases the turbulence in the crankcase bottom half whilst the attached curve He.957 shews that the heat generated, even at 50 lbs/sq.in. is not more than 12 B.Th.U's at 75 M.P.H. or 4% of the total. THE EFFICIENCY OF THE PLAIN BOTTOM HALF AS AN OIL COOLER. From work on aero condensers and car radiators we | ||