Consider a 3-bladed propeller, D = 2.5 m with a Clark-Y airfoil whose characteristics are described in NACA TR-640 (see Propellers folder on Canvas). (Watch for number of blades! Use Figs. 9-11). The propeller is mounted on a single engine airplane cruising at 134 m/s (~300 mph) in air that has a density of 0.909 kg/m' and temperature of 269 K and the propeller is spinning at 30 rps. Calculate the flight Mach number and the Mach number of the propeller blade tip. What blade pitch setting (blade angle at 0.75R) would give the best propeller efficiency, and what is the propeller efficiency at this setting. Estimate the thrust generated by the propeller. If the mechanical efficiency of the transmission from engine to propeller is 0.95, what is the engine power required to drive the propeller for flight at this speed. If the transmission cooling fluid has a density of 885 kg/m, average specific heat of 2100 J/kg-K, and a maximum permitted temperature rise of 100 K, calculate the required flow rate of cooling fluid (L/min) required to maintain the transmission at constant temperature. ./8 ./6 ./4N .12 45 Blade angle of 0.75R 40 .10) 35 C .08 30 25 20 .06 .04) .02 0 2 1.4 2.4 2.6 2.8 .8 10 L2 26 1.8 20 2.2 VnD FIGURE 2-Thrust-coefficient curves for propeller 5808-4, Clark Y section, 3 blades. 7 MA 10 25 [27 Te 151 30: 20 25 .6 102 2.0 25 4.5 -5 4203 11.0 -15 Blode angle of 0.75R Line of moximum efficiency for .5 3.5 1.0 25 20 2.5 3.0 C FIQUEX 10.--Design chart for propeller 5818-8, Clark Y section, 3 blades. CHARACTERISTICS OF FULL-SCALE PROPELLERS HAVING 2, 3, AND 4 BLADES 55 .38 .36 X 165 16 34 .321 155 x15 .30 28 A.12 .26 jo G! .241 .221 Las 09 C .20 ./8 os! ./6 04 . .12 .10) 02 .00 207 .06 .041 .02) HO 0 2 20125 4541 Blade angle of 0.15 R 1.0 L2 1.4 1.6 1.8 20 22 24 26 28 30 326 VnD FIRE 11 Porte-coefficient cares for propeller 580-6, Clact T section, 3 blades. 3.8 Consider a 3-bladed propeller, D = 2.5 m with a Clark-Y airfoil whose characteristics are described in NACA TR-640 (see Propellers folder on Canvas). (Watch for number of blades! Use Figs. 9-11). The propeller is mounted on a single engine airplane cruising at 134 m/s (~300 mph) in air that has a density of 0.909 kg/m' and temperature of 269 K and the propeller is spinning at 30 rps. Calculate the flight Mach number and the Mach number of the propeller blade tip. What blade pitch setting (blade angle at 0.75R) would give the best propeller efficiency, and what is the propeller efficiency at this setting. Estimate the thrust generated by the propeller. If the mechanical efficiency of the transmission from engine to propeller is 0.95, what is the engine power required to drive the propeller for flight at this speed. If the transmission cooling fluid has a density of 885 kg/m, average specific heat of 2100 J/kg-K, and a maximum permitted temperature rise of 100 K, calculate the required flow rate of cooling fluid (L/min) required to maintain the transmission at constant temperature. ./8 ./6 ./4N .12 45 Blade angle of 0.75R 40 .10) 35 C .08 30 25 20 .06 .04) .02 0 2 1.4 2.4 2.6 2.8 .8 10 L2 26 1.8 20 2.2 VnD FIGURE 2-Thrust-coefficient curves for propeller 5808-4, Clark Y section, 3 blades. 7 MA 10 25 [27 Te 151 30: 20 25 .6 102 2.0 25 4.5 -5 4203 11.0 -15 Blode angle of 0.75R Line of moximum efficiency for .5 3.5 1.0 25 20 2.5 3.0 C FIQUEX 10.--Design chart for propeller 5818-8, Clark Y section, 3 blades. CHARACTERISTICS OF FULL-SCALE PROPELLERS HAVING 2, 3, AND 4 BLADES 55 .38 .36 X 165 16 34 .321 155 x15 .30 28 A.12 .26 jo G! .241 .221 Las 09 C .20 ./8 os! ./6 04 . .12 .10) 02 .00 207 .06 .041 .02) HO 0 2 20125 4541 Blade angle of 0.15 R 1.0 L2 1.4 1.6 1.8 20 22 24 26 28 30 326 VnD FIRE 11 Porte-coefficient cares for propeller 580-6, Clact T section, 3 blades. 3.8