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).
Page detailing formulas and examples for correcting Indicated and Brake Horsepower.
| Identifier | ExFiles\Box 37\3\ scan 119 | |
| Date | 20th September 1917 guessed | |
| Contd. -3- - = (100p / 89.9) + (50t / 289.) = 3.34 p + .173 t = % correction to I.H.P. Example. If P = 28.0" and temp.= 10°C p = 1.9 and t = - 6 % correction to I.H.P. = 6.35 - 1.04 = 5.31 so that every 100 I.H.P. corrects to 105.3 I.H.P. at standard state. To arrive at the % correction to be applied to the B.H.P:- If the B.H.P. were proportional to the I.H.P. this correction would be the same, but it is much more nearly true that the frictional loss of an engine is made up of two parts, one constant and the other proportional to the load (I.H.P.) If we take these two losses to be respectively 10% of the I.H.P. [handwritten: standard state] (at N.T.P. say) constant and 5% of the I.H.P. proportional to load; the relation between the B.H.P. and I.H.P. is B = (18 I - 200) / 17 in which relation B and I are understood to be percentages Contd. | ||