where tb is the stagnation temperature ratio across the combustor(burner). The thrust is thus Cycle efficiency in terms of aerodynamic parameters nBravton=l 0-1-=1-, d lo compressor exit y Ramjet thermodynamic cycle efficiency in terms of flight Mach number, Mo For propulsion engines, the figures of merit includes more than thrust and nBravt The specific impulse, I s, measures how effectively fuel is used ri/gfms, Specific Impulse, where ni =f ri is the fuel mass flow rate To find the fuel-air ratio, f, we employ a control volume around the combustor and carry out an energy balance. Before doing this, however, it is useful to examine the way in which Isp appears In expressions for rang Muddy points What exactly is the specific impulse, Isp a measure of?(MP 2A.6) How is Isp found for rockets in space where g-0?(MP 2A.7) Why does industry use TSCP rather than Isp? Is there an advantage to this?(MP Why isnt mechanical efficiency an issue with ramets?(MP 2A. 9) How is thrust created in a ramjet?(MP 2A. 10) Why don' t we like the numbers 1 and 2 for the stations? why do we go 0-3?(MP 2A.11) For the Brayton cycle efficiency. why does T:=L2(MP 2A. 12) 2. 4.5 The Breguet Range equation See Waitz Unified Propulsion Notes, No IV(see the 16.050 Web site) Consider an aircraft in level flight, with weight W. The rate of change of the gross weight of the vehicle is equal to the fuel weight flow 2A-82A-8 where τ b is the stagnation temperature ratio across the combustor (burner). The thrust is thus: F a M b m˙ 0 = − 0( ) τ 1 Cycle efficiency in terms of aerodynamic parameters: η Brayton compressor exit T T T T T T T =− =− =− 1 11 0 0 3 0 0 , and T TT M 0 0 0 2 1 1 1 2 = + γ − , so: η γ γ Brayton M M = − + − 1 2 1 1 2 0 2 0 2 : Ramjet thermodynamic cycle efficiency in terms of flight Mach number, M0 . For propulsion engines, the figures of merit includes more than thrust and η Brayton . The specific impulse, Isp measures how effectively fuel is used: I F g F f g sp f = = m m ˙ ˙ ; Specific Impulse, where m m ˙ ˙ f = f is the fuel mass flow rate. To find the fuel-air ratio, f, we employ a control volume around the combustor and carry out an energy balance. Before doing this, however, it is useful to examine the way in which Isp appears in expressions for range. Muddy points What exactly is the specific impulse, Isp, a measure of? (MP 2A.6) How is Isp found for rockets in space where g ~ 0? (MP 2A.7) Why does industry use TSCP rather than Isp? Is there an advantage to this? (MP 2A.8) Why isn't mechanical efficiency an issue with ramjets? (MP 2A.9) How is thrust created in a ramjet? (MP 2A.10) Why don't we like the numbers 1 and 2 for the stations? Why do we go 0-3? (MP 2A.11) For the Brayton cycle efficiency, why does T 3 =T t0 ? (MP 2A.12) 2.A.5 The Breguet Range Equation [See Waitz Unified Propulsion Notes, No. IV (see the 16.050 Web site)] Consider an aircraft in level flight, with weight W. The rate of change of the gross weight of the vehicle is equal to the fuel weight flow: