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).
The formula for correcting aero engine ground B.HP for variations in atmospheric temperature and pressure.
| Identifier | ExFiles\Box 37\3\ scan 117 | |
| Date | 20th September 1917 | |
| September 20th 1917. EFC7/T20.9.17. X.3178 - CORRECTION OF AERO ENGINE GROUND B.H.P. FOR VARIATION OF ATMOSPHERIC TEMPERATURE AND PRESSURE. We assume the I.H.P. of an engine to vary as the sqaure root of the product of the atmospheric pressure and density i.e. I varies as √PD. and since P/DT is constant for all changes of atmospheric conditions (where T is the atmospheric temperature absolute) therefore D varies as P/T and I varies as √(P²/T) or as P/√T We take as our standard of reference of atmospheric state, a barometric height of 29.9" of mercury and a temperature of 16°C. (and correct our powers to this state). Let P₀ be 29.9" P the barometric reading (inches). t₀ = 16°C. T₀ = 273 + 16 = 289°C abs. t = atm. temp. (°C) - 16°C = no of degrees above 16°C. T = 289 + t (absolute temp) since I = k P/√T Contd. | ||