Thermodynamics

9–111 Repeat Problem 9–110 using argon as the workingfluid.Jet-Propulsion Cycles9–112C What is propulsive power? How is it related tothrust?9–113C What is propulsive efficiency? How is it determined?9–114C Is the effect of turbine and compressor irreversibilitiesof a turbojet engine to reduce (a) the net work, (b) thethrust, or (c) the fuel consumption rate?9–115E A turbojet is flying with a velocity of 900 ft/s at analtitude of 20,000 ft, where the ambient conditions are 7 psiaand 10°F. The pressure ratio across the compressor is 13, andthe temperature at the turbine inlet is 2400 R. Assuming idealoperation for all components and constant specific heats forair at room temperature, determine (a) the pressure at the turbineexit, (b) the velocity of the exhaust gases, and (c) thepropulsive efficiency.9–116E Repeat Problem 9–115E accounting for the variationof specific heats with temperature.9–117 A turbojet aircraft is flying with a velocity of320 m/s at an altitude of 9150 m, where the ambient conditionsare 32 kPa and 32°C. The pressure ratio across thecompressor is 12, and the temperature at the turbine inlet is1400 K. Air enters the compressor at a rate of 60 kg/s, andthe jet fuel has a heating value of 42,700 kJ/kg. Assumingideal operation for all components and constant specific heatsfor air at room temperature, determine (a) the velocity of theexhaust gases, (b) the propulsive power developed, and(c) the rate of fuel consumption.9–118 Repeat Problem 9–117 using a compressor efficiencyof 80 percent and a turbine efficiency of 85 percent.9–119 Consider an aircraft powered by a turbojet enginethat has a pressure ratio of 12. The aircraft is stationary onthe ground, held in position by its brakes. The ambient air isat 27°C and 95 kPa and enters the engine at a rate of 10 kg/s.The jet fuel has a heating value of 42,700 kJ/kg, and it isburned completely at a rate of 0.2 kg/s. Neglecting the effectof the diffuser and disregarding the slight increase in mass atthe engine exit as well as the inefficiencies of engine components,determine the force that must be applied on the brakesto hold the plane stationary. Answer: 9089 N9–120 Reconsider Problem 9–119. In the problemstatement, replace the inlet mass flow rate byan inlet volume flow rate of 9.063 m 3 /s. Using EES (or other)software, investigate the effect of compressor inlet temperaturein the range of –20 to 30°C on the force that must beapplied to the brakes to hold the plane stationary. Plot thisforce as a function in compressor inlet temperature.9–121 Air at 7°C enters a turbojet engine at a rate of16 kg/s and at a velocity of 300 m/s (relative to the engine).Chapter 9 | 545Air is heated in the combustion chamber at a rate 15,000 kJ/sand it leaves the engine at 427°C. Determine the thrustproduced by this turbojet engine. (Hint: Choose the entireengine as your control volume.)Second-Law Analysis of Gas Power Cycles9–122 Determine the total exergy destruction associatedwith the Otto cycle described in Problem 9–34, assuming asource temperature of 2000 K and a sink temperature of 300K. Also, determine the exergy at the end of the power stroke.Answers: 245.12 kJ/kg, 145.2 kJ/kg9–123 Determine the total exergy destruction associatedwith the Diesel cycle described in Problem 9–47, assuming asource temperature of 2000 K and a sink temperature of 300K. Also, determine the exergy at the end of the isentropiccompression process. Answers: 292.7 kJ/kg, 348.6 kJ/kg9–124E Determine the exergy destruction associated withthe heat rejection process of the Diesel cycle described inProblem 9–49E, assuming a source temperature of 3500 Rand a sink temperature of 540 R. Also, determine the exergyat the end of the isentropic expansion process.9–125 Calculate the exergy destruction associated witheach of the processes of the Brayton cycle described in Problem9–73, assuming a source temperature of 1600 K and asink temperature of 290 K.9–126 Determine the total exergy destruction associatedwith the Brayton cycle described in Problem 9–93, assuminga source temperature of 1800 K and a sink temperature of300 K. Also, determine the exergy of the exhaust gases at theexit of the regenerator.9–127 Reconsider Problem 9–126. Using EES (orother) software, investigate the effect of varyingthe cycle pressure ratio from 6 to 14 on the total exergydestruction for the cycle and the exergy of the exhaust gasleaving the regenerator. Plot these results as functions ofpressure ratio. Discuss the results.9–128 Determine the exergy destruction associated witheach of the processes of the Brayton cycle described inProblem 9–98, assuming a source temperature of 1260 Kand a sink temperature of 300 K. Also, determine theexergy of the exhaust gases at the exit of the regenerator.Take P exhaust P 0 100 kPa.9–129 A gas-turbine power plant operates on the simpleBrayton cycle between the pressure limits of 100 and 700kPa. Air enters the compressor at 30°C at a rate of 12.6 kg/sand leaves at 260°C. A diesel fuel with a heating value of42,000 kJ/kg is burned in the combustion chamber with anair–fuel ratio of 60 and a combustion efficiency of 97 percent.Combustion gases leave the combustion chamber andenter the turbine whose isentropic efficiency is 85 percent.Treating the combustion gases as air and using constant specificheats at 500°C, determine (a) the isentropic efficiency