Quizwork 6

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University of Illinois, Urbana Champaign *

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312

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Aerospace Engineering

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Apr 3, 2024

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Dr. Elle Wroblewski AE 312 Spring 2024 AE 312 Quizwork 6 Due: 03/20/2024 Problem Solution Format (you will be graded on these procedures): Draw the diagram or correctly determine the diagram from provided description, add station labels. State “Given” and “Unknown” property value s that you are using or finding. As you use them in your solution, or before beginning, state your Assumptions Draw a coordinate frame indicating positive direction for vector values. In your solution describe your approach to the problem and any equations you use to solve it. As you determine your unknowns, please circle them . Use the online calculator or tables to speed up solution approaches to these problems. When uploading to Gradescope: select the pages your problems correspond to. 1. Air is flowing at a Mach number of 0.5 in a two-dimensional channel at a location where the area is 1 ft 2 . At this location the static pressure is 10 psia, and the static temperature is 500ºR. a. Calculate the mass flow rate through the channel and the stagnation pressure and temperature at this location. b. What percent reduction in area would be necessary to increase the flow Mach number to 0.75? What would the static pressure and temperature be at this location? Percent reduction: ( A A ¿ ) M = 0.5 ( A A ¿ ) M = 0.75 ( A A ¿ ) M = 0.5 × 100 c. What reduction in area would be necessary to reach a Mach number of 1.0, and what would be the corresponding static conditions? d. What would happen if the area were reduced to a value smaller than that in part (c)? 2. A converging nozzle has an exit area of 10 i n 2 . Nitrogen stored in a reservoir is to be discharged through the nozzle to an ambient pressure of 14.7 psia. Assume isentropic flow and that the reservoir temperature is 520 ° R . Determine which operating regime the nozzle is in as well as the mass flow rate through the nozzle for: a. A reservoir pressure of 20 psia b. A reservoir pressure of 40 psia c. A reservoir pressure of 100 psia 3. A Mach 2.5 air flow with a stagnation temperature of 400 K and a mass flow rate of 0.72 kg/s encounters a normal shock wave at a location with an area of 10 cm 2 . The flow then enters a diverging section whose exit area is 20 cm 2 . The flow may be assumed to be isentropic except across the normal shock wave. Find the Mach number, velocity, static pressure, stagnation pressure, static temperature, and stagnation temperature at the exit of the diverging section. 1
Dr. Elle Wroblewski AE 312 Spring 2024 (flip page for problems 4 and 5) 4. An engineer constructed the free jet flow facility shown below where air is supplied from a large tank to a short pipe of 5 cm diameter and then exits to the atmosphere. However, during experiments the engineer found that there is a slight reduction in the pipe diameter at its exit to 4.7 cm. At the operating point of interest, the pressure and temperature in the tank are 150 kPa and 300 K, respectively, and the atmospheric pressure is 100 kPa. Assume isentropic flow. a. Compare the flow conditions in the supply pipe (location 1) to those at the exit (location 2) by determining the Mach number, velocity, and static pressure at both locations. b. (1 sentence) Is the effect of the diameter reduction on Mach number significant? 5. Air flows at 500 m/s, a static pressure of 50 kPa, and a stagnation temperature of 320 K in a 10 cm diameter duct. The duct converges to a diameter of 9 cm, where the flow exhausts to an ambient pressure of 100 kPa. a. (1 sentence) Is this device a supersonic diffuser or a subsonic converging nozzle? b. Find: the Mach number, velocity, static pressure, and stagnation pressure at the exit c. Find: the mass flow rate through the system 2 P B =100 kPa P=150 kPa T=300 K 2 1 D 1 =5 cm D 2 =4.7 cm 1 2 P amb =100 kPa D 2 =9 cm D 1 =10 cm V 1 =500 m/s P 1 =50 kPa T 01 =320 K
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