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).
Napier sleeve valve engine performance results and future development plans.
| Identifier | ExFiles\Box 179b\4\ img069 | |
| Date | 20th April 1933 | |
| -3- Ha/ML.1/MJ.20.4.33. Cont'd.{John DeLooze - Company Secretary} Napier Sleeve Valve Engine Results. Ricardo showed me some performance curves taken last month from the single cylinder unit. Unsupercharged, the engine gave a B.M.E.P. of 105 lbs/sq.in. at 2500 R.P.M. with 0.4 lbs/BHP/Hr. specific consumption. At higher R.P.M.'s. the consumption rose rapidly. The above figures are uncorrected. With a boost pressure of 8 lbs./sq.in. gauge, boost temp. 60°C. and a maximum pressure of 950 lbs/sq.in. the B.M.E.P. was 152 lbs/sq.in. at 2500 R.P.M. specific consumption 0.4 lbs/BHP/Hr. The above figures make no allowance for the power required to drive the blower. If 10 lbs/sq.in. is the power absorbed in driving the blower the effective B.M.E.P. is then 142 lbs/sq.in. and the specific consumption 0.43 lbs/BHP/Hr. Since the consumption of the engine is better unsupercharged than supercharged it is proposed to connect the blower to the engine by means of a clutch. For getting off the ground the engine would be supercharged and for cruising the supercharger would be disconnected. It is an unfortunate property of the 'pot' form of head that it does not perform equally well supercharged and unsupercharged; it must be developed to suit one condition for the best results and herein lies the difficulty with the Napier Sleeve Valve Unit. When visiting the Air Ministry I was shown in confidence Napiers' proposals for a 12 cylinder supercharged sleeve valve engine built up from the above unit. It is to run at 2500 R.P.M. and develope 180 lbs/sq.in. B.M.E.P. with a specific consumption of 0.39 lbs/BHP/Hr. (nett). The estimated specific weight is 1.75 lbs/BHP. VISIT TO MR. TREDIS AT AIR MINISTRY. The programme of four-stroke work was discussed and the following was agreed upon :- Side Injection. That a Scintilla Injection pump be tested with the open type nozzles as the Bosch pump has proved unsuitable. The best number, size, and direction of nozzle holes to be found by using open type nozzles and Scintilla pump before experimenting with differential type injectors as these latter are more difficult to make and cannot be relied upon to give satisfactory results | ||