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).
Indicator work performed on different engine exhaust systems.
| Identifier | WestWitteringFiles\L\2April1924-June1924\ Scan112 | |
| Date | 12th July 1928 | |
| R.R. 493A (40 H) (SL 42 12-7-28). J.H., D.{John DeLooze - Company Secretary} (3) Expl. No. REF: Hs{Lord Ernest Hives - Chair}/ACL/S.4.24. EXPERIMENTAL REPORT. INDICATOR WORK ON EACH SYSTEM. Light spring diagrams were taken of the exhaust and suction strokes at a speed of 2000 r.p.m. Two diagrams are given of each system - one with the cut-out closed and the other with it open. Both of the single manifolds i.e. W.W. and Derby schemes, possess the same characteristic viz. - a high 'pressure bump' on the exhaust stroke due to the interference of the exhaust from other cylinders. The diagram taken with the W.W. manifold shows that the exhaust pressure does not fall to atmospheric until the piston has moved through 15% of its induction stroke i.e. 15% of the swept volume will be exhaust gas at atmospheric pressure. With the standard exhaust system this figure will be 12.8%. Referring to the valve setting it is obvious that a certain portion of the exhaust gas is expelled into the induction pipe and drawn in again with the fresh charge. The indicated volumetric efficiency given is obtained from the diagram and is probably higher than the actual, no account being taken of the percentage and temperature of the exhaust gas in the new charge. The actual difference in power output between any of the three systems is small but the high exhaust back pressure and greater percentage of exhaust gas in the fresh charge may considerably increase the heat flow in the cylinder giving rise to valve and boiling troubles. Hs{Lord Ernest Hives - Chair}/ACL. | ||