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).
Technical review and comparison of Junkers, Fowler, and Blackstone engines.
| Identifier | WestWitteringFiles\W\September1931-November1931\ Scan091 | |
| Date | 18th November 1931 | |
| -2- He/CHP.1/MJ.18.11.31.Cont'd.{John DeLooze - Company Secretary} allowed in this engine, but assume it is between 800 and 900 lbs/sq.in. JUNKERS. This engine, exhibited on the Gilford Motor Company's stand, is almost identical with the Junkers C.I. aero engine. It is a six cylinder unit functioning on the two-stroke cycle and having two opposed pistons in each cylinder. Two crankshafts are used, coupled at one end by a train of four gears. The inlet ports are uncovered by the upper pistons and the exhausts by the lower, air at 7 lbs/sq.in. pressure being utilized to scavenge the cylinder. Junkers injection equipment is fitted, the injection pressure being 6000 lbs/sq.in. The bore is 2.750" and the stroke of each piston 4.140". The engine developed 120 BHP. at its maximum speed of 2000 RPM., the BMEP. being :- 80.7 lbs/sq.in. at 2000 RPM. 82.2 lbs/sq.in. at 1800 RPM. 101.0 lbs/sq.in. at 1000 RPM. A maximum BMEP. of 106.0 lbs/sq.in. is claimed (presumably at 1000 RPM). Consumption for medium loads is .400 lbs/BHP/Hr., but figures for full power were not available. FOWLER. This engine is unique for its "cavity-piston", which is a modification of the "Acro" principle. When the pistons is at the top of the compression stroke, most of the air is contained in a cavity within the piston, which communicates with the outside of the piston by three small holes in the piston top. The injected fuel is sprayed across the top of the piston and thus meets the air as it issues from the cavity. This system, is of course, unsuitable for high speed working owing to the late combustion. At the maximum speed of 1600 RPM. a BMEP. of 66.0 lbs/sq.in. is attained, the consumption being .515 lbs/BHP/Hr. The maximum BMEP. of 78lbs/sq.in (.446 lbs/BHP/Hr) is obtained at 1100 RPM. BLACKSTONE. This engine employs the "spring injection" method of introducing the fuel into the cylinder. This comprises of pumping a measured quantity of fuel into a small cylinder against the pressure of a spring acting on a piston. The injection valve is then opened, when the said piston is forced forward and thus injecting the fuel. The six cylinder (4.625" x 6.0") unit developes 79.0 lbs/sq.in. BMEP. at 1000 RPM: the maximum engine speed being 1800 RPM. | ||