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).
Appendix detailing the method of procedure for testing the volumetric efficiency of various cylinder heads.
| Identifier | ExFiles\Box 17\6\ Scan144 | |
| Date | 24th August 1933 guessed | |
| APPENDIX. Method of Procedure. (1) The standard method of comparing the effects of various heads on the volumetric efficiency by measuring the air taken by the engine when running was not used, owing to elaborate apparatus required and necessity for making a complete test whenever an alteration was to be made to design. Since the volumetric efficiency of an engine can only be effected by the cylinder head in so far as the latter acts as a restriction, an artificial flow of air was created through a port of the head to be tested, and the restriction to such flow was measured -the results obtained were at any rate sufficiently accurate for comparative purposes. When possible, these "theoretical" figures were reduced to a practical basis by running the cylinder heads so tested on the engine itself and comparing both the "air" curves and power curves. (2) Assumptions made and conventions etc. used. As mentioned in (1) the tests were carried out with air, being the most convenient medium. It was arranged that the velocity of the air through the ports during the tests should be approximately the same as the actual velocity if the head in question were run on the engine for which it was designed at definite speeds in the neighbourhood of its peak speeds. The question of the accuracy of estimation of such velocity does not arise, since the results are only to be used for comparative purposes - it is only necessary that the "conventional velocities" so used should be in the neighbourhood of the actual velocities. | ||