Equation-oriented formulation

[RoberAgro]

Develop an equation-oriented model formulation for centrifugal compressors.

Key elements to include:

• Conservation of mass at each station

• Conservation of rothalpy in each component

• Velocity triangle calculations

• Calculation of fluid properties with CoolProp:

  • Should we use enthalpy-entropy function calls as for the axial-turbine model?
  • Should we use pressure-enthalpy function calls only to be able to use look-up-tables easily?

• Boundary conditions:

  • Stagnation pressure/temperature at inlet
  • Inlet mass flow rate (subsonic flow without choking)
  • Exit pressure or "throttle valve" boundary conditions for cases with choking in the future

[lasseba-stf]

Hi,

I would like to discuss some approaches for modeling the vaneless diffuser space. If I remember correctly from our meeting we planned to use the conservation of angular momentum with a loss term: $$r{in}c{\theta, in} = r{out}c{\theta, out} + \Delta AM $$

Is this used in combination with a correlation for the pressure or enthalpy loss? I see Meroni presented an equation for calculating the exit static pressure: $$p{out} = p{in} + CP(p{0,in} - p{in})$$ while in the Oh and Chaowei paper use a correlation for the enthalpy loss: $$\Delta h = CpT{0,in} \left[\frac{p{out}}{p{0, out}}^{\frac{\gamma - 1}{\gamma}} - \frac{p{out}}{p{0, in}}^{\frac{\gamma - 1}{\gamma}}\right]$$

If I am not mistaken, both approaches can be used mathematically, but is one approach more appropriate than the other?