ccp.Point
ccp.Point#
- class ccp.Point(suc=None, disch=None, disch_p=None, flow_v=None, flow_m=None, speed=None, head=None, eff=None, power=None, power_shaft=None, power_losses=None, torque=None, phi=None, psi=None, volume_ratio=None, pressure_ratio=None, disch_T=None, b=<Quantity(0.005, 'meter')>, D=<Quantity(0.5, 'meter')>, surface_roughness=<Quantity(3.175e-06, 'meter')>, casing_area=None, casing_temperature=None, ambient_temperature=None, convection_constant=<Quantity(13.6, 'watt / kelvin / meter ** 2')>, polytropic_method=None)#
A performance point. A point in the compressor map that can be defined in different ways.
- Parameters
- speedpint.Quantity, float
Speed in rad/s.
- flow_v or flow_mpint.Quantity, float
Volumetric (m³/s) or mass (kg/s) flow.
- suc, dischccp.State, ccp.State
Suction and discharge states for the point.
- suc, disch_p, effccp.State, float, float
Suction state, discharge pressure and polytropic efficiency.
- suc, head, effccp.State, float, float
Suction state, polytropic head and polytropic efficiency.
- suc, head, powerccp.State, pint.Quantity or float, pint.Quantity or float
Suction state, polytropic head (J/kg) and gas power (Watt).
- suc, head, power_shaft, power_lossesccp.State, pint.Quantity or float, pint.Quantity or float, pint.Quantity or float
Suction state, polytropic head (J/kg), shaft power (Watt) and power losses (Watt).
- suc, eff, volume_ratioccp.State, float, float
Suction state, polytropic efficiency and volume ratio.
- suc, pres_ratio, disch_Tccp.State, float, pint.Quantity or float
Suction state, pressure ration and discharge temperature.
- bfloat, pint.Quantity
Impeller width at the outer blade diameter (m).
- Dfloat, pint.Quantity
Impeller outer diameter (m).
- power_shaftfloat, pint.Quantity
Shaft power (Watt), optional.
- power_lossesfloat, pint.Quant
Mechanical power losses (Watt), optional.
- torquefloat, pint.Quantity
load torque (N.m), optional. (N.m), optional.
- surface_roughnesspint.Quantity, optional
Gas passage mean surface roughness (m). Used in the reynolds correction calculation. Default value is 3.048e-6 m.
- casing_areapint.Quantity, optional
Compressor case area used to calculate case heat loss (m²).
- casing_temperaturepint.Quantity, optional
Compressor case temperature used to calculate case heat loss (degK).
- ambient_temperaturepint.Quantity, optional
Ambient temperature used to calculate case heat loss (degK).
- convection_constantpint.Quantity, optional
Heat transfer (convection) constant (W / m²degK). Default value is 13.6.
- polytropic_methodstr, optional
Polytropic method used for head and efficiency calculation. Options are: “mallen_saveille”, “sandberg_colby”, “schultz” and “huntington”. The default is “schultz”. The default value can be changed in a global level with: ccp.config.POLYTROPIC_METHOD = “<desired value>”
- Returns
- Pointccp.Point
A point in the compressor map.
- Attributes
- succcp.State
A ccp.State object. For more information on attributes and methods available see:
ccp.State- dischccp.State
A ccp.State object. For more information on attributes and methods available see:
ccp.State- flow_vpint.Quantity
Volumetric flow (m³/s).
- flow_mpint.Quantity
Mass flow (kg/s)
- speedpint.Quantity
Speed (rad/s).
- headpint.Quantity
Polytropic head (J/kg).
- effpint.Quantity
Polytropic efficiency (dimensionless).
- powerpint.Quantity
Power (Watt).
- power_shaftpint.Quantity
Shaft power (Watt) which includes bearing and seal losses.
- power_lossespint.Quantity
Mechanical power losses (Watt) which includes bearing and seal.
- torquepint.Quantity
Load torque (N*m) at coupling which includes bearing and seal losses.
- phipint.Quantity
Volume flow coefficient (dimensionless).
- psipint.Quantity
Polytropic head coefficient (dimensionless).
- volume_ratiopint.Quantity
Volume ratio - suc.v() / disch.v() (dimensionless).
- bfloat, pint.Quantity
Impeller width at the outer blade diameter (m).
- Dfloat, pint.Quantity
Impeller outer diameter (m).
- casing_areapint.Quantity
Compressor case area used to calculate case heat loss (m²).
- casing_temperaturepint.Quantity
Compressor case temperature used to calculate case heat loss (degK).
- ambient_temperaturepint.Quantity
Ambient temperature used to calculate case heat loss (degK).
- convection_constantpint.Quantity
Heat transfer (convection) constant (W / m²degK).
- reynoldspint.Quantity
Reynolds number (dimensionless).
- machpint.Quantity
Mach number (dimensionless).
- phi_ratiofloat
Ratio between phi for this point and the original point from which it was converted from.
- psi_ratiofloat
Ratio between psi for this point and the original point from which it was converted from.
- reynolds_ratiofloat
Ratio between Reynolds for this point and the original point from which it was converted from.
- mach_difffloat
Difference between Mach for this point and the original point from which it was converted from.
- volume_ratio_ratiofloat
Ratio between volume_ratio for this point and the original point from which it was converted from.
- polytropic_methodstr
Polytropic method used for head and efficiency calculation.
Methods
- __init__(suc=None, disch=None, disch_p=None, flow_v=None, flow_m=None, speed=None, head=None, eff=None, power=None, power_shaft=None, power_losses=None, torque=None, phi=None, psi=None, volume_ratio=None, pressure_ratio=None, disch_T=None, b=<Quantity(0.005, 'meter')>, D=<Quantity(0.5, 'meter')>, surface_roughness=<Quantity(3.175e-06, 'meter')>, casing_area=None, casing_temperature=None, ambient_temperature=None, convection_constant=<Quantity(13.6, 'watt / kelvin / meter ** 2')>, polytropic_method=None)#
- classmethod convert_from(original_point, suc=None, find='speed', speed=None, reynolds_correction=False, **kwargs)#
Convert point from an original point.
The procedure to convert a point considering that the volume ratio will be the same, follows the following steps: 1. Assume that eff_converted = eff_original and psi_converted = psi_original 2. Assume that volume ratio will be the same to keep similarity 3. Calculate discharge volume based on suction state and volume ratio 4. Calculate discharge state using newton method to find the discharge pressure. Criterion for convergence is the polytropic efficiency. 5. Calculate head based on the new discharge state 6. Calculate speed based on head and psi
This procedure is followed whe we have find=”speed”.
- Parameters
- original_pointccp.Point
Original point from which the desired point will be converted.
- findstr, optional
If the calculation will find a new speed keeping constant volume ratio, or a new volume ratio for the desired speed. Options are “speed” or “volume_ratio”, default is “speed”.
- speedfloat, pint.Quantity, optional
Desired speed. If find=”speed”, this should be None.
- reynolds_correctionbool, optional
If reynolds correction should be applied during the conversion. If True the ASME PTC 10 reynolds correction is applied
- The user must provide 3 of the 4 available arguments. The argument which is not
- provided will be calculated.
- classmethod load(file_name)#
Load point from toml file.
- mach_limits(mmsp=None)#
Calculate Mach lower and upper limits.
- Parameters
- mmspfloat, optional
Mach number specified. Default value is the point Mach number.
- Returns
- limitsdict
Dict with keys: ‘lower’, ‘upper’ and ‘within_limits’.
- plot_mach(fig=None, **kwargs)#
Plot allowable Mach range and point.
This will plot the allowable Mach range and the point according to the PTC criteria.
- Parameters
- figplotly.Figure
Plotly figure.
- Returns
- figplotly.Figure
Plotly figure.
- plot_reynolds(fig=None, **kwargs)#
Plot allowable Reynolds range and point.
This will plot the allowable Mach range and the point according to the PTC criteria.
- Parameters
- figplotly.Figure
Plotly figure.
- Returns
- figplotly.Figure
Plotly figure.
- plot_similarity(fig=None, **kwargs)#
Plot similarity results.
Plots the similarity results showing the Mach and Reynolds plots with their respective limits and also a table summarizing the results comparing the current (converted) point to the original point.
- Parameters
- figplotly.Figure
Plotly figure.
- Returns
- figplotly.Figure
Plotly figure.
- reynolds_limits(remsp=None)#
Calculate Reynolds lower and upper limits.
- Parameters
- remspfloat, optional
Reynolds number specified. Default value is the point reynolds number.
- Returns
- limitsdict
Dict with keys: ‘lower’, ‘upper’ and ‘within_range’.
- save(file_name)#
Save point to toml file.
- similarity_table(fig=None, **kwargs)#
Plot similarity table.
This table show the values for the non dimensional numbers (Mach, Reynolds and Volume ratio) and their calculated relations with respect to the original points used in the conversion (in the formulas, ‘c’ means converted points and ‘o’ means original point).
If values are within limits, relation cells are colored in green, otherwise they are colored in red.