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).
Comparison of valve lift diagrams and gas velocity performance between the Lorraine and Goshawk engines.
| Identifier | ExFiles\Box 5a\5\ 05-page012 | |
| Date | 30th March 1927 guessed | |
| contd :- -5- The lift diagrams are given on prints Nos.1 and 2 compared with the 20 HP., also another curve is inserted which shews the difference if the 20 HP. lift was as great as the Lorraine. There is a noticeable difference - particularly so in the case of the inlet - in the initial speed of opening and latter part of closing; the Lorraine giving quicker lift and should possess the advantage of better filling of the cylinders. Plotting the valve lift against the piston dis-placement is probably a better method of comparison than plotting against crank angles, as it shews up the effective large opening area at bottom centre to take advantage of the kinetic energy of the charge (see curves 10 and 11.) GAS VELOCITY PAST VALVES. The conventional gas velocity, calculated on the average piston velocity and assuming the inlet valve to be fully open, is shewn on print 8. For the same speed the Lorraine has a velocity 29% lower than the Goshawk. It will be seen from these curves that the I.M.E.P. starts to fall after a velocity of approx. 165 ft/sec. for the Lorraine, and has not fallen apprec-iably before this velocity on the Goshawk although the maximum value occurs about 130 ft/sec. For the former gas velocity the corresponding engine speed on the Lorraine is 2750 r.p.m. while on the Goshawk it is just below 2000 r.p.m. which is probably one of the reasons why the Lorraine maintains a high volumetric efficiency up to a higher speed than the Goshawk which is shewn by the M.E.P. curves. On print 3, are given compression pressure and contd :- | ||