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Turbine (G)

Gas turbine in a thermodynamic cycle

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  • Turbine (G) block

Description

The Turbine (G) block models a turbine in a gas network. You can parameterize the block as a tabulated turbine map that is either a 1-D function of pressure ratio or 2-D function of pressure ratio and corrected mass flow rate. Fluid flowing from port A to port B generates torque. Port R reports shaft torque and angular velocity relative to port C, which is associated with the turbine casing.

Port VN is associated with the vane opening fraction. This value linearly scales the corrected mass flow rate but does not influence the turbine efficiency. A value of 1 corresponds to the data in the turbine map.

Turbine Map

A turbine map depicts turbine performance as a function of pressure ratio, the turbine outlet pressure to the inlet pressure, and corrected mass flow rate. Two graphs plot the isentropic efficiency and the corrected mass flow rate. In the 2D parameterization, the plots also depend on the corrected rotor speed, N. The indexing variable β does not need to be the same between the mass flow rate and efficiency tables.

Corrected Mass Flow Rate

Due to the large changes in pressure and temperature inside a turbine, the turbine map plots performance in terms of a corrected mass flow rate. The corrected mass flow rate is adjusted from the inlet mass flow rate with a corrected pressure and corrected temperature:

m˙ATATcorr=m˙corrpApcorr,

where:

  • m˙A is the mass flow rate at port A.

  • TA is the temperature at port A.

  • Tcorr is the Reference temperature for corrected flow. The data supplier specifies this value.

  • m˙corr is the corrected mass flow rate.

    When Turbine map parameterization is set to Tabulated data - Flow rate and efficiency vs. pressure ratio, this is the Corrected mass flow rate vector, mdot(pr).

    When Turbine map parameterization is set to Tabulated data - Flow rate and efficiency vs. corrected speed and pressure ratio, this is the Corrected mass flow rate table, mdot(N,beta).

  • pA is the pressure at port A.

  • pcorr is the Reference pressure for corrected flow. The data supplier specifies this value.

Shaft Torque

The shaft torque, τ, is calculated as:

τ=m˙AΔhtotalηmω,

where:

  • Δhtotal is the total change in the fluid specific enthalpy.

  • ηm is the turbine Mechanical efficiency.

  • ω is the relative shaft angular velocity, ωR - ωC.

Reversed flow, from port B to port A, is outside of the typical turbine operation mode and may not return accurate results. A threshold region when flow approaches zero ensures that no torque is generated when the flow rate is near zero or reversed.

Parameterization by Pressure Ratio

When Turbine map parameterization is set to Tabulated data - Flow rate and efficiency vs. pressure ratio, the turbine isentropic efficiency and mass flow rate are a function of the pressure ratio and do not account for any changes in the turbine rotational speed.

The last element of the Corrected mass flow rate vector, mdot(pr) and the Pressure ratio vector, pr represent the corrected mass flow rate and pressure ratio at choked flow conditions.

Default Turbine Map in the 1-D Parameterization

1D Turbine map

Parameterization by Pressure Ratio and Corrected Mass Flow Rate

When Turbine map parameterization is set to Tabulated data - Flow rate and efficiency vs. corrected speed and pressure ratio, the turbine isentropic efficiency, pressure ratio, and corrected mass flow rate are a function of the corrected speed, N, and the map index, β. The block uses linear interpolation between data points for the efficiency, pressure ratio, and corrected mass flow rate parameters.

The last column of the Corrected mass flow rate table, mdot(N,beta) and the Pressure ratio table, pr(N,beta) represent the corrected mass flow rate and pressure ratio at choked flow conditions.

Visualizing the Block Turbine Map

To visualize the block map, right-click the block and select Fluids > Plot Turbine Map.

Each time you modify the block settings, click Apply click Reload Data on the figure window.

Default Turbine Map in the 2-D Parameterization

2D Turbine map

Continuity Equations

Mass is preserved over the block:

m˙A+m˙B=0,

where m˙B is the mass flow rate at port B.

The energy balance in the block is calculated as:

ΦA+ΦBPfluid=0,

where:

  • ΦA is the energy flow rate at port A.

  • ΦB is the energy flow rate at port B.

  • Pfluid is the work done by the fluid, which is determined from the change in total fluid specific enthalpy: Pfluid=m˙AΔhtotal.

Assumptions and Limitations

  • The shaft does not rotate under reversed flow conditions. Results during reversed flows may not be accurate.

Ports

Conserving

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Fluid entry port.

Fluid exit port.

Port associated with the turbine casing.

Port associated with the turbine shaft torque and angular velocity.

Input

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Vane opening fraction. The corrected mass flow rate scales linearly with the value of VN. A fraction of 1 corresponds to the tabulated data. The isentropic efficiency is not influenced by the vane opening fraction.

Parameters

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Parameterization

Performance parameterization specification:

  • Tabulated data - Flow rate and efficiency vs. pressure ratio: Parameterize turbine isentropic efficiency and corrected mass flow rate by pressure ratio.

  • Tabulated data - Flow rate and efficiency vs. corrected speed and pressure ratio: Parameterize turbine isentropic efficiency and corrected mass flow rate by corrected speed and pressure ratio.

Minimum vane opening fraction. This value is the lower boundary to the signal at VN. It is multiplied by the elements of the XX or XX parameters to obtain the minimum corrected mass flow rate through the turbine.

Maximum vane opening. This value is the upper boundary to the signal at VN. It is multiplied by the elements of the XX or XX parameters to obtain the maximum corrected mass flow rate through the turbine.

Vector of constant shaft speeds for tabular parameterization of corrected mass flow rate and isentropic efficiency.

Dependencies

To enable this parameter, set Turbine map parameterization to Tabulated data - Flow rate and efficiency vs. corrected speed and pressure ratio.

Flow Rate Data

Vector of pressure ratio values for the tabulated parameterization of corrected mass flow rate. This vector must have the same number of elements as the Corrected mass flow rate vector, mdot(pr) parameter and all elements must be greater than 1. The last element must be the pressure ratio at choked conditions.

Dependencies

To enable this parameter, set Turbine map parameterization to Tabulated data - Flow rate and efficiency vs. pressure ratio.

Vector of corrected mass flow rate values for the tabulated parameterization of corrected mass flow rate. This vector must have the same number of elements as the Pressure ratio vector, pr parameter and all elements must be greater than 0. The last element must be the corrected mass flow rate at choked conditions.

Dependencies

To enable this parameter, set Turbine map parameterization to Tabulated data - Flow rate and efficiency vs. pressure ratio.

M-by-N matrix of turbine outlet-to-inlet pressure ratios at the specified corrected shaft speed and β value. Linear interpolation is employed between table elements. M and N are the sizes of the corresponding vectors:

  • M is the number of vector elements in the Corrected speed index vector, N parameter.

  • N is the number of β indices in the table.

The default table values are:

[1.217, 1.285, 1.323, 1.363, 1.402, 1.427, 1.495, 1.545, 1.6, 1.687, 1.747, 1.8074; 1.231, 1.302, 1.356, 1.404, 1.443, 1.473, 1.525, 1.577, 1.635, 1.709, 1.782, 1.845; 1.242, 1.328, 1.388, 1.437, 1.528, 1.617, 1.704, 1.811, 1.915, 1.979, 2.053, 2.1226; 1.244, 1.339, 1.417, 1.465, 1.528, 1.584, 1.692, 1.787, 1.899, 2, 2.075, 2.1492; 1.245, 1.34, 1.425, 1.492, 1.546, 1.684, 1.748, 1.882, 1.987, 2.084, 2.167, 2.2458; 1.251, 1.345, 1.442, 1.521, 1.596, 1.692, 1.849, 1.972, 2.1, 2.173, 2.259, 2.3424; 1.248, 1.348, 1.447, 1.516, 1.581, 1.651, 1.749, 1.839, 1.93, 2.024, 2.154, 2.242]

Dependencies

To enable this parameter, set Turbine map parameterization to Tabulated data - Flow rate and efficiency vs. corrected speed and pressure ratio.

M-by-N matrix of corrected mass flow rates at the specified corrected shaft speed and β value. Linear interpolation is employed between table elements. M and N are the sizes of the corresponding vectors:

  • M is the number of vector elements in the Constant speed index vector, N parameter.

  • N is the number of β indices in the table.

The default table values are:

[40.403, 44.417, 46.653, 47.966, 48.97, 49.544, 50.001, 50.081, 50.086, 50.095, 50.09, 50.0922; 40.044, 43.754, 46.125, 47.626, 48.513, 49.105, 49.481, 49.58, 49.597, 49.624, 49.638, 49.633; 39.941, 43.795, 46.017, 47.335, 48.795, 49.199, 49.279, 49.27, 49.248, 49.23, 49.255, 49.2428; 39.896, 43.512, 45.914, 47.061, 48.011, 48.558, 48.943, 49.042, 49.069, 49.01, 49.046, 49.0266; 39.524, 42.934, 45.686, 46.743, 47.715, 48.67, 48.777, 48.836, 48.876, 48.836, 48.845, 48.8184; 39.439, 43.01, 45.556, 46.801, 47.792, 48.388, 48.634, 48.67, 48.639, 48.647, 48.625, 48.5912; 39.502, 42.849, 45.336, 46.385, 47.312, 47.877, 48.222, 48.397, 48.459, 48.482, 48.455, 48.414] kg/s

Dependencies

To enable this parameter, set Turbine map parameterization to Tabulated data - Flow rate and efficiency vs. corrected speed and pressure ratio.

Efficiency Data

Vector of pressure ratio values for the tabulated parameterization of isentropic efficiency. This vector must have the same number of elements as the Isentropic efficiency vector, eta(pr)) parameter and all elements must be greater than 1.

Dependencies

To enable this parameter, set Turbine map parameterization to Tabulated data - Flow rate and efficiency vs. pressure ratio.

Vector of isentropic efficiency values for the tabulated parameterization of isentropic efficiency. This vector must have the same number of elements as the Pressure ratio vector, pr parameter and all elements must be greater than 0 and less than or equal to 1.

Dependencies

To enable this parameter, set Turbine map parameterization to Tabulated data - Flow rate and efficiency vs. pressure ratio.

M-by-N matrix of turbine outlet-to-inlet pressure ratios at the specified corrected shaft speed and β value. Linear interpolation is employed between table elements. M and N are the sizes of the corresponding vectors:

  • M is the number of vector elements in the Constant speed index vector, N parameter.

  • N is the number of β indices in the table.

The default table values are:

[1.224, 1.246, 1.292, 1.387, 1.457, 1.534, 1.61, 1.686, 1.743, 1.79, 1.871, 1.914; 1.237, 1.25, 1.28, 1.369, 1.459, 1.553, 1.629, 1.716, 1.799, 1.846, 1.927, 1.97; 1.241, 1.255, 1.283, 1.326, 1.401, 1.509, 1.591, 1.704, 1.806, 1.913, 1.994, 2.037; 1.25, 1.265, 1.308, 1.364, 1.456, 1.532, 1.637, 1.739, 1.851, 1.934, 2.042, 2.085; 1.281, 1.314, 1.371, 1.425, 1.498, 1.574, 1.647, 1.749, 1.878, 1.979, 2.091, 2.18; 1.252, 1.328, 1.425, 1.544, 1.642, 1.757, 1.873, 2.005, 2.1, 2.204, 2.248, 2.28; 1.382, 1.43, 1.495, 1.586, 1.688, 1.791, 1.887, 1.99, 2.079, 2.158, 2.249, 2.217]

Dependencies

To enable this parameter, set Turbine map parameterization to Tabulated data - Flow rate and efficiency vs. corrected speed and pressure ratio.

M-by-N matrix of turbine isentropic efficiencies at the specified constant shaft speed and β value. Linear interpolation is employed between table elements. M and N are the sizes of the corresponding vectors:

  • M is the number of vector elements in the Constant speed index vector, N parameter.

  • N is the number of β indices in the table.

The default table values are:

[.72, .754, .759, .739, .714, .679, .643, .603, .554, .524, .494, .48; .716, .757, .794, .819, .812, .788, .761, .728, .692, .662, .632, .618; .629, .691, .775, .831, .858, .869, .859, .842, .816, .782, .752, .738; .594, .668, .757, .804, .857, .883, .892, .893, .884, .865, .835, .821; .664, .72, .779, .823, .858, .883, .897, .905, .904, .896, .883, .868; .559, .61, .673, .741, .788, .835, .869, .895, .908, .899, .854, .751; .718, .785, .824, .855, .882, .9, .908, .906, .884, .857, .804, .701]

Dependencies

To enable this parameter, set Turbine map parameterization to Tabulated data - Flow rate and efficiency vs. corrected speed and pressure ratio.

Reference Data

Pressure at which turbine data consolidates to a corrected trend line.

Temperature at which turbine data becomes consolidated to a corrected trend line.

Efficiency of conversion from reduction in specific enthalpy to shaft torque.

Turbine inlet cross-sectional area.

Turbine outlet cross-sectional area.

References

[1] Kurzke, Joachim. "How to Get Component Maps for Aircraft Gas Turbine Performance Calculations." Volume 5: Manufacturing Materials and Metallurgy; Ceramics; Structures and Dynamics; Controls, Diagnostics and Instrumentation; Education; General, American Society of Mechanical Engineers, 1996, p. V005T16A001.

[2] Plencner, Robert M. “Plotting component maps in the Navy/NASA Engine Program (NNEP): A method and its usage.” NASA Technical Memorandum, 1989.

Introduced in R2021a