NACA-TN-1695

Abstract

A study has been made to evaluate the effect of pressure recovery on the performance of a typical jet engine and of a typical jet-propelled fighter airplane. It was found that the pressure-recovery efficiency of an airplane air-induction system is best represented by ram-recovery ratio, which is the ratio of the impact pressure recovered to the impact pressure available. The effect of ram-recovery ratio on the net thrust and on the specific fuel consumption of a turbo jet engine was calculated for various speeds and for altitudes from sea level to 40,000 feet. The resulting changes in maximum speed, range, and climbing performance of the airplane are indicated. <br>For an airplane flying 650 miles per hour at sea level, an increase in ram-recovery ratio from 0.70 to 0.90 will result in an 18.9-percent increase in net thrust and a 9.5-percent decrease in specific fuel consumption. From these and other similar effects indicated in the performance analysis, it would appear that the attainment of high ram recovery should be given major consideration. The analysis shows further that ram recovery will become of greater importance in obtaining optimum performance as airplanes are developed which have higher drag-divergence Mach numbers and which utilize more powerful jet engines.