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).
Performance improvements and power loss analysis for a compression ignition engine.
| Identifier | ExFiles\Box 179\2\ img165 | |
| Date | 20th January 1932 | |
| ORIGINAL R.{Sir Henry Royce} From HS{Lord Ernest Hives - Chair}/EXP. C. to Mr. H.R. C. to Mr. K.{Mr Kilner} C. to Mr. By.{R.W. Bailey - Chief Engineer} Hs{Lord Ernest Hives - Chair}/C.F.4/HA.20. 1. 32. COMPRESSION IGNITION ENGINE. x4433. We are now in a position to report an improvement in our performance on the above unit: at 2000 R.P.M. we obtain a BMEP of 97.7 lbs/sq.in. at a specific consumption of .473 lbs/BHP/hr. (our previous figure was 94.7 lbs/sq.in. at .441 lbs/BHP/hr.) This power increase is obtained by using :- (a) A much lighter differential valve needle in the injector (weighing only one-eighth as much as the original needle.) (b) A differential ratio of .47. (c) A 25% quicker lift cam in the Bosch pump. (d) The improved element DES.1560 in the Bosch pump. In previous tests none of these four items have made any noticeable improvement to the power output. We now propose to run tests with each of these items removed, one at a time; so that any unnecessary feature may be deleted. A still quicker lift cam is also to be tried out. The differential ratio appears to be fairly critical as we have tried a valve having a ratio of .3 which causes a definite fall off in power. (We define the "differential ratio" as "the area of the valve exposed to fuel pressure when the valve is closed divided by the area exposed when the valve is open"). A recent test has confirmed our previous estimate of the amount of power we are losing in our four crankshaft bearings. For the purpose of this test we removed two of the bearings and measured the power necessary to rotate the crankshaft only. The necessary power was found to be 51% of that required when the four bearings were in position. From these tests we can say that each of our four crankshaft bearings absorbs 1.5 lbs/sq.in. BMEP. If we built a 12-cyl engine we should fit it with seven crankshaft bearings, so we may say that any one of its cylinders would be required to drive 7/12 of a bearing, whereas our present cylinder drives four bearings. Thus in a 12-cyl engine our performance would be increased by (4.0 - 7/12) x 1.5=5.125 lbs/sq. in. BMEP on the score of bearings alone, this would improve | ||