| A thrust model has been derived and tested for a Pratt & Whitney JT15D-1B turbofan engine. The method has been found to be an accurate model for static thrust and, without loss of generality, should be suitable for forward flight. This method is based upon momentum theory and only requires the measurement the hot exhaust total pressure and the cold exhaust total pressure. After an aircraft static thrust test was conducted, Newton's method was used to identify the values of the engine section efficiencies (inlet, hot exhaust, and cold bypass exhaust). The model was compared to both a thrust prediction program supplied by P&WC and the actual total measured thrust obtained from the aircraft ground static test. The thrust model provided results which were within 5% of the measured static thrust at low power settings and within 1% at higher settings. It was found that the engine section efficiencies varied linearly with respect to power setting, but were not dependent on ambient temperatures. The efficiencies at low power settings were approximately 6% lower than that of typical cruise conditions. |
