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to-air ratio fvert a=0.034 . The take-off gross thrust is F_(g)=34,000 Ibs (151.23 kN) at a flight speed of V_(t-0)=200kts(102m/s) For a choked nozzle that is, an exit Mach number M_(7)=1 and a turbine exit temperature (TET) T_(t,7)=1580F(860^circ C) find: (a) the effective exhaust velocity, (b)the net
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Profesyonel · 6 yıl öğretmeniUzman doğrulaması
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To solve this problem, we need to use the given information and apply the appropriate formulas to find the effective exhaust velocity and the net thrust.<br /><br />Given information:<br />- Take-off gross thrust: $F_g = 34,000$ lbs (151.23 kN)<br />- Flight speed: $V_{t-0} = 200$ knots (102 m/s)<br />- Exit Mach number: $M_7 = 1$<br />- Turbine exit temperature: $T_{t,7} = 1580^\circ F$ (860°C)<br /><br />(a) Effective exhaust velocity:<br /><br />The effective exhaust velocity ($v_{eff}$) can be calculated using the following formula:<br /><br />$v_{eff} = \sqrt{\frac{2 \cdot \gamma \cdot R \cdot T_{t,7}}{M_7^2}}$<br /><br />Where:<br />- $\gamma$ is the specific heat ratio (for air, $\gamma \approx 1.4$)<br />- $R$ is the specific gas constant (for air, $R \approx 287$ J/(kg·K))<br />- $T_{t,7}$ is the turbine exit temperature in Kelvin<br />- $M_7$ is the exit Mach number<br /><br />Substituting the values:<br /><br />$v_{eff} = \sqrt{\frac{2 \cdot 1.4 \cdot 287 \cdot (860 + 273.15)}{1^2}}$<br /><br />$v_{eff} \approx 1,000$ m/s<br /><br />(b) Net thrust:<br /><br />The net thrust ($F_{net}$) can be calculated using the following formula:<br /><br />$F_{net} = \dot{m} \cdot (v_{eff} - v_{t-0})$<br /><br />Where:<br />- $\dot{m}$ is the mass flow rate of the exhaust gases<br />- $v_{eff}$ is the effective exhaust velocity<br />- $v_{t-0}$ is the flight speed<br /><br />To find the mass flow rate ($\dot{m}$), we can use the following formula:<br /><br />$\dot{m} = \frac{F_g}{v_{t-0}}$<br /><br />Substituting the values:<br /><br />$\dot{m} = \frac{34,000}{102} \approx 333.33$ kg/s<br /><br />Now, we can calculate the net thrust:<br /><br />$F_{net} = 333.33 \cdot (1,000 - 102) \approx 327,830$ N or 32.78 kN<br /><br />Therefore, the effective exhaust velocity is approximately 1,000 m/s, and the net thrust is approximately 32.78 kN.
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