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Aviation History
1947
1947 - 2006.PDF
NOVEMBER 13TH, 1947 a monthly digest of news from, the ^JfUdtol: aero-engine division T BRISTOL SLEEVE-VALVE CYLINDER SUPERIORITY CONFIRMED BY RESEARCH TESTS. Tests carried out in the Engine Research Department have repeatedly demonstrated the inherent superiority of the Bristol sleeve-valve cylinder over contem- porary poppet-valve cylinders. The following long-established characteristics are well maintained. COMBUSTION EFFICIENCY The smooth, symmetrical combustion chamber of the Bristol cylinder, with its centrally-placed sparking plugs and the controlled turbulence obtained with the sleeve-valve port action, ensure very complete burning of the fuel and oxygen. The brake thermal efficiency for a given compression ratio has been shown to be higher than in a poppet-valve cylinder of similar dimensions. DETONATION LIMITS The- Bristol cylinder also shows a superiority in detonation-limited performance, equivalent to raising the grade of fuel by several octane numbers. The practical benefit of this is to enable the compression ratio to be about 0.5 higher than is possible in a corresponding poppet-valve cylinder for a given fuel. so 40 JO BRISTOL . SLEEVE-VALVE CYLINDER / / /x y POPPET-VALVE CYLINDER 1 16O0 2000 22OO 24OO 26O0 2800 JO00 3ZQ0 ENGINE R.RM. TYPICAL POWER CURVES FDR SUPERCHARGED SINGLE CYLINDER UNITS ON 100/130 GRADE FUEL TYPfCAt FUEL CONSUMPTION LOOPS FOR. WKsswta* -«««raEB> SMKIC cnjMOEft uws <m acwiro sauce votx. m FUEL CONSUMPTION The combination of the above two characteristics results in a reduction of at least 5% in the specific fuel consumption compared with the equivalent poppet- valve unit under the same operating conditions and using the same fuel. This has been well borne out by experience with Bristol engines in service. - POWER OUTPUT ^ The Bristol cylinder gives an exceptionally good " boost response " (increase in B.M.E.P. for a given increase in boost pressure). Its characteristic power curve is steeply sloped, with very little falling-off until well beyond the maximum operational r.p.m. THE BRISTOL AEROPLANE COMPANY LIMITED BRISTOL ENGLAND
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