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GATE 2023 MT – Question 38

Mineral Processing and Extractive Metallurgy · Primary and secondary steelmaking · 2 marks · Multiple choice

For a supersonic oxygen jet in basic oxygen furnace steelmaking, choose the correct combination.

1. Converging–diverging nozzle

2. Diverging–converging nozzle

3. Oxygen velocity greater than sound velocity at the nozzle throat (Mach > 1)

4. Oxygen velocity equal to sound velocity at the nozzle throat (Mach = 1)

5. Exit oxygen jet pressure ≥ atmospheric pressure

6. Exit oxygen jet pressure < atmospheric pressure

  1. (1), (4), (5)
  2. (1), (3), (6)
  3. (2), (3), (5)
  4. (2), (4), (5)

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Show answer and explanation

Correct answer: (A) (1), (4), (5)

Explanation

A converging–diverging nozzle accelerates choked flow to Mach 1 at the throat and then supersonic speed in the diverging section. The listed appropriate exit-pressure condition is at least atmospheric.

Thus the correct set is **1,4,5, A**; Mach greater than 1 belongs downstream of the throat.