I finally figure out how to control the 2D CFD results to match the 1D results. Now I've got 0.75Mach for 2D CFD and 0.78Mach for 1D CFD. The results now make sense compared to ASME B31.1 example (velocities, pressures at points 1,2, and 3 quantities are within reasonable values). Basically, I've controlled the iterations for 2D CFD to stop just right at the point of divergence in the solution (mass and energy are balanced in the system boundaries) with mass flow rate of 12.165 kg/sec and back pressure at point 1 of 45 KPa.

Thank you all for this wonderful discussion.

Cheers!!!