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).
Analysis of the effect of altitude on critical air temperature and engine boiling point.
| Identifier | ExFiles\Box 149a\2\ scan0328 | |
| Date | 10th January 1936 | |
| X.280 HS{Lord Ernest Hives - Chair}/Std.1/JH.10.1.36. Analysis of effect of altitude & critical Air Temperature Figure. The following definitions will be needed. The "critical air temperature" is defined as the sea level air temperature at which boiling will just take place under the worst level conditions. The "altitude corrected critical air temperature" is the sea level air temperature at which boiling will take place under worse conditions at a given altitude. The "critical air temperature at altitude" is the altitude air temperature at which boiling will just take place under conditions at the given altitude. The altitude corrected critical air temperature is affected by the following factors:- (1) Reduction of heat to be dissipated due to fall of I.H.P. with alterations in density pressure and temperature at altitude. (2) Reduction in cooling due to fall in density P. with altitude. Cooling varies as (PV)^.83. (3) Increase in cooling due to fall of air temperature with altitude. (4) Decrease in boiling point due to fall of pressure with altitude. These factors will now be calculated as follows:- (1) Assume engine gives H.{Arthur M. Hanbury - Head Complaints} I.H.P. at sea level at conditions under which critical temperature is measured, approx. 30 M.P.H. full throttle. Assume mechanical efficiency at this speed of 90%. Assume heat to coolant to be .47H ( borne out by test figures.) Let k = power factor at given altitude. This includes variation of induction pressure, back pressure and temperature. | ||