In a study of nitric oxide formation in laminar jet fl ames, the propane fuel is diluted with N2 to suppress soot formation. The nozzle fl uid is 60 percent N2 by mass. The burner has a circular port. The fuel, nitrogen, and the air are all at 300 K and 1 atm. Compare the fl ame lengths for the following two cases with the undiluted base case (m F = 5 · 10−6 kg / s). What is the physical signifi cance of your results? Discuss.

At steady state, air at 200 kpa, 325 k, and mass flow rate of 0.5 kg/s enters an insulated duct having differing inlet and exit cross-sectional areas. the inlet cross-sectional area is 6 cm2. at the duct exit, the pressure of the air is 100 kpa and the velocity is 250 m/s. neglecting potential energy effects and modeling air as an 1.008 kj/kg k, determine ideal gas with constant cp = (a) the velocity of the air at the inlet, in m/s. (b) the temperature of the air at the exit, in k. (c) the exit cross-sectional area, in cm2