# Shutdown Analysis

## Description

## Shutdown Analysis Inputs

UIName (.flo label) | Description |
---|---|

Start Shutdown (sec) (SHUT_TIME) |
Time in the mission when the shutdown logic starts being used. All mission times after SHUT_TIME (for example, mission time > SHUT_TIME) uses the shutdown logic. |

Minimum HTC Option (HTC_MIN_OPT) |
Option for using the minimum HTC during the analysis. All
calculated Heat Transfer Coefficients (HTC)are compared to
HTC_MIN, according to one of the following options. 0: Not used - never use HTC_MIN (default). 1: Always used - always use HTC_MIN. 2: Use after Shutdown Time – only use HTC_MIN when mission time > SHUT_TIME. |

Minimum HTC (HTC_MIN) |
All calculated HTC’s are compared to HTC_MIN. If the calculated HTC is less than HTC_MIN, HTC_MIN replaces the calculated HTC. |

Pressure Scaling Option (PRESS_OPT) |
Option to determine how chamber reference pressures are
calculated when mission time > SHUT_TIME. 0: Use Cycle Parameters. 1: Use Boundary Chambers. |

Low Pressure Cycle Parameter (PRESS_LO) |
If PRESS_OPT = 0, low chamber reference pressure is extracted from this cycle parameter. |

High Pressure Cycle Parameter (PRESS_HI) |
If PRESS_OPT = 0, high chamber reference pressure is extracted from this cycle parameter. |

Low Pressure Chamber (PRESS_LO) |
If PRESS_OPT = 1, low chamber reference pressure is extracted from this chamber. |

High Pressure Chamber (PRESS_HI) |
If PRESS_OPT = 1, high chamber reference pressure is extracted from this chamber. |

Flow/Thermal Coupling Limit
Option (CPL_PCT_OPT) |
Option to determine when the coupling limit percentage
(CPL_PCT) is used to stop exchanging data between the flow and
thermal solvers. 0: Not used - never use CPL_PCT (default). 1: Always used - always use CPL_PCT. 2: Use after Shutdown Time - only use CPL_PCT when mission time > SHUT_TIME. |

Stop Coupling after % Max Iteration (CPL_PCT) |
The percent of the maximum iterations to stop exchanging data between the flow and thermal solvers. This may improve convergence for some models. Do not make this value too small since it may lead to less accurate results. Recommended value is > 80%. |

Minimum Mass Flow Rate (FLOW_MIN) |
A minimum flow rate for elements when mission time > SHUT_TIME. |

## Shutdown Analysis Calculations

- Element Flow Rates
- The flow rate for most elements is kept at a constant percentage core flow rate throughout the transient when mission time > SHUT_TIME. The core flow rate is usually the flow through the core of the gas turbine, but it can be any flow rate in the mission. The core flow rate is specified in the Reference Conditions window.
- Chamber Pressures
- After SHUT_TIME, the flow rates are no longer calculated in the usual way, so the internal (non-boundary) chamber pressures are also no longer calculate in the usual way. After SHUT_TIME, the chamber pressure is based on a linear interpolation between a high and low pressure.
- Heat Transfer Coefficients
- After SHUT_TIME, the HTCs are calculated the same as before SHUT_TIME, but the HTCs can get very low if flow rates get very low. A minimum HTC can be assigned to increase the HTC to a reasonable value that may account for free convection, machine vibration, and so on. The minimum HTC can also be used for all times of a steady state or transient solution by setting HTC_MIN_OPT=”Always Used”.
- Flow/Thermal Coupling Limit
- Only use the coupling limit if the model is having convergence problems and a “Relaxation Factor on Thermal-Fluid Coupling” < 1.0 is not helping. For most analysis types, the thermal solver is not called after a (CPL_PCT) percentage of the flow solver iterations is completed. For the Quasi Steady Flow + Transient Thermal, the flow solver is not called after a (CPL_PCT) percentage of the thermal solver iterations is completed. This limit can be used for all times of a steady state or transient solution by setting CPL_PCT_OPT=”Always Used”.