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).
Engine tests investigating power loss, injector needle discolouration, and the performance of different injector nozzles.
| Identifier | ExFiles\Box 179b\3\ img204 | |
| Date | 4th February 1933 | |
| -14- dark brown discolouration of the injector needle in the region of the tip which was now marked in many of the tests and had not been noted in C.I.I. At this stage of the development the discolouration was thought to indicate overheating of the needle valve but subsequent experiments showed this was not so. A subsidiary test (No. 2b) was now run in which tubes 2" long and 2" dia. were fitted into the inlet ports, so as to make these approximately similar internally to C.I.I. The power was initially 97.8 lbs/sq.in. B.M.E.P. which, when allowance is made for the motoring losses, equals the performance of C.I.I. Unfortunately, after several minutes the power fell to 93.8 lbs/sq.in. On account of the power of 97.8 lbs/sq.in. having been obtained (although not held) and as cutting windows in the injector boss and fitting a copper tube weakened the cylinder it was decided to run a series of half hour tests (Nos. 2c - 2h inclusive) taking readings of power and consumption at 5 min. intervals after the engine had settled down to a steady state which was usually approached about 25 mins. after starting. The purpose of these tests was to study the falling off in power with time and the sudden power drop occasionally noted. If these tests were successful in revealing the cause of the power drop it was thought that the power of 97.8 lbs/sq.in. obtained in Test 2b. but not held (and subsequently in Tests 2h and 2j) would again be obtained and steadily held. The B.M.E.P's of Tests 2c - 2h are plotted against time from the commencement of the tests on Fig.5 together with the particulars of the nozzle used and in Fig.6 the specific consumptions are plotted. Referring to Fig.5 it will be noted that in all cases except 2c the B.M.E.P. falls off as the test proceeds and in Test 2f (New Bosch nozzle) and Test 2g (new R.R-Bosch nozzle) there is a sudden drop in power of about 6 lbs/sq.in. The best performance (Test 2h) and almost the worst (Test 2g) are both given by the same nozzle (a new Bosch) and in one case the power fell only slightly, while in the other it suffered a sudden drop. The nozzles were tested in the hand pump and no difference in their performance when cold could be detected. In Test 2h the initial power was equivalent to that of C.I.I. These tests showed that within the range of the experiments (a) a nozzle, under apparently identical conditions, might or might not give a sudden drop in power, (b) a new nozzle was as likely to give a low power as a used one and (c) Test 2c taken in conjunction with test 2b showed that fitting tubes in the inlet ports had no real affect on power. | ||