AS311 Review for Section 1 PDF

AS311 Review for Section 1 Jet Propulsion Theory... For every acting force, there is an equal and opposite reacting force Newton's Third Law of Motion Newton’s Second Law of Motion Thrust equals Mass times acceleration or Thrust equals Mass times the change in velocity...

AS311 Review for Section 1 Jet Propulsion Theory... For every acting force, there is an equal and opposite reacting force Newton's Third Law of Motion Newton’s Second Law of Motion Thrust equals Mass times acceleration or Thrust equals Mass times the change in velocity or Thrust equals Mass times the change in momentum Experience 2.1 Pioneers and Early Development Orville and Wilbur Wright, Maxime Guillaume, Dr. A.A. Griffith, Hans von Ohain, Frank Whittle and Dr. Hanratty for CAD. Jet efficiency involved three key factors in development, pressure rise by the compressor, temperature of the gases as they enter the turbine and combustor efficiency. The first applications for the jet engine were military aircraft and the first requirement was speed. Dr. Hanratty with CAD. Silicon chip and titanium alloy. Aircraft: Gloster, Meteor, Me-262, Bell XP-59A, Tornado B- 45, Canberra, B-707, DC-8, etc. Turboprops, turboshafts, turbojets and turbofans Manufacturers: CFM, PW, RR, GE, and International Aero. The Jet Age 1959 to 1969. Engine failures and engine maintenance down 80% to 90%. The Concord Olympus engine weighed 7X more than Whittle’s first engine. But achieved 25X more thrust at 3X the speed and with lower specific fuel consumption. Propulsive Efficiency Page 15  F=Ma F is thrust M is the weight of the air & fuel divided by gravity a is the change in momentum of the mass Force = Thrust Forward, expressed pounds. In metrics Newtons. (4.45 Newtons = 1 lb) Mass = weight of air & fuel through the engine divided by gravity 32.2 feet per second It's accelerating at a rate of 32 feet/second, which means the velocity it's moving at, is increasing by 32 feet per second every second. acceleration = the change in momentum The velocity of the air exiting the engine. V2 or V jet The velocity of the air entering the engine. V1 or V flight We will represent the change as V2 - V1  Gross Thrust or Fg? STATIC Net Thrust or Fn? the engine has forward speed, therefore V1 has value for Ram Effect A choked nozzle (convergent) means: a perfect nozzle accelerates the exhaust gasses to the local speed of sound, no more/no less. Aj (Pj-Pam) Pam at altitude Common Conversions Knots x 1.151 = MPH MPH x.8690 = Knots MPH x 1.467 = Feet per Second (ft/sec) Knots x 1.6885 = Feet per Second (ft/sec) PSI x 2.036 = Inches of Mercury (inHg) inHg x.4912 = PSI inHg x 70.73 = Pounds per Square Foot PSI x 144 = Pounds per Square Foot (psf) Pounds per Hour / 3600 = Pounds per Second S-4 Turbofan Fn = Waf (V2 –V1) + Wac (V2 – V1) + Aj (Pj-Pam) g g  Turboprop HP is SHP Rated in Shaft Horse Power only with a Dynamometer Horsepower at shaft NOT propeller Fn = Can only be calculated inflight, Straight and Level Flight The turboprop engine was an attempt to combine in one engine the best characteristics of both the turbojet and propeller driven reciprocating engine. Turboprop engines are most efficient at speeds between 220 and 350 knots and altitudes between 18000 and 30000 feet At 375mph, one pound of thrust is equal to one horsepower Fp = Shp x 375 x 0.80 mph Back to front, reverse airflow reduced engine Navy P-3 Orion Front to back flow  King Air 200 Less than 12,500 lbs take off weight PT 6 at 850 SHP, 260 KIAS, 1369 foot pounds of torque at FL260, 80% efficiency for props What is the Fp? With a Fn of 300 lbs, what is the total thrust? Speed of Sound Changes In the rear stages of the compressor, the local speed of sound changes because of the change in temperature. As temperature increases, the speed of sound in air increases The temperature in the rear stages of the compressor may be many hundreds of degrees higher that in the front stages, the same tip speed will be a substantially lower Mach number The speed of sound in air is solely dependent on temperature change and not change in pressure  High Bypass Turbofan The max thrust for the least fuel flow The smallest acceleration to the largest mass airflow The PW1100G employs the largest bypass ratio in the history of turbofan engines. 93% bypass. And with the geared turbofan is unmatched, promising double digit fuel burn savings. The slow speed of the fan contribute to low noise, promising an enhanced passenger experience with reduced flight-related fatigue. GTF Geared Turbo Fan  Fp ? Practice 1 - SHP 1300, ALT 29.34, 80%Prop Eff 350mph IAS, Fuel Flow 1225PPH Fp ? Practice 2 - Prop Eff is 90%, 320mph IAS, 1150SHP, Altitude FL210 Practice 3 - Total Thrust ? 80% prop eff, 1400SHP, 320 KIAS, Fn is 300lbs Answers on next slide  Practice from slide 25 Practice 1 - 1300 x 375 x.80 = 390,000 divided by 350mph = 1,114 for Fp Practice 2 – 1150 x 375 x.90 = 388,125 divided by 320mph = 1,212 for Fp Practice 3 – 1400 x 375 x.80 = 420,000 divided by 320KIAS but converted to 368mph = 1,141 Fp Plus Fn of 300 lbs = 1,441 Total Thrust