The combustor component is used to simulate both primary (gas generator) combustors and afterburners. Data may be specified for:

The combustion process

•Fuel type and/or composition

There is a distinction in design and off-design fuel type. This is to analyze OD effects of alternative fuels for example.

•Combustor design fuel input (Design tab sheet), specified by either

•Fuel flow Wf

•Exit temperature

•Fuel-Air Ratio

•Stator Outlet Temp SOT

For the latter 3 options, corresponding fuel flow is calculated automatically using GSP's chemical combustor model maintaining full conservation of energy. The input field corresponding to the selected input is active for input, the other 3 disabled. The Update input to DP button resets the inactive input fields to the last calculated Design point value if existing. This is convenient to directly see corresponding values and after switching input type to have the correct value for the new parameter to be used.

For the last (SOT) option, a DP equation has to be added. SOT is evaluated in an error equation (with Wf as state variable) for the iteration towards user specified SOT (iteration necessary because SOT may be affected by downstream hpt cooling flows).

•Combustion efficiency, using one of a number of different models for off-design efficiency

•User specified combustion efficiency

User defined fixed off-design combustion efficiency

•Use combustion efficiency map

Efficiency as function of combustor temperature rise and pressure ratio Delta

•Use afterburner combustion efficiency maps

Define 3 maps to determine afterburner combustion efficiency based on FAR, and corrections for Mach number and relative pressure drop:

1.	Comb. eff. vs. FAR map text file, to calculate the efficiency from reheat FAR

2.	Flow Mach nr. correction map text file, to calculate the efficiency correction for Mach value

3.	Pressure correction map text file, to calculate the correction factor for relative pressure drop

Combustor pressure loss

Different models for off-design pressure loss are modelled:

•Specified design rel. pressure loss only

User specified design pressure loss only, with off-design calculated relative pressure loss (=PR) by scaling to corrected mass flow (squared)

•User specified off-design press. loss

Use fixed user specified off-design pressure loss

•Pressure loss map

Use pressure loss map, dP = f(Wc), where Wc is based on

•Corrected entry mass flow

•Fuel mass flow

Pressure loss as result of the addition of heat and resulting increase in velocity:

•Calculate Fundamental Pressure Loss

The fundamental pressure loss is determined with the conservation of momentum and is usually used for afterburner mode only, when the effect becomes significant due to the very high temperature increase.

Emission formation

Optionally combustor exit emission values (NOx, CO, UHC indices and Smoke number) can be calculated using either one of three emission formation models:

•None

•Interpolation in ICAO table (NLR correction method)

•Semi-empirical ratio- or direct prediction method

Note that an additional option can be found in the component Multi Reactor Combustor found in the Special Gas Path Component Library inheriting from Combustor.

•Multi-reactor combustion model

Static conditions inside the burner

The combustor has a separate Burner static conditions Duct cross area for enabling calculation of averaged static conditions inside the combustor (i.e. between the inlet and exit stations). These static conditions are required if Fundamental pressure loss calculation is required or when the combustor is running in afterburner mode and the static pressure input for the afterburner efficiency map is required.

Fuel pump/compressor

The power required for compressing the fuel for injection into the combustor can be calculated using the Fuel pump.

Water injection

To lower combustor temperature for e.g. lowering NOx emisions or to increase specific power output, water or steam can be injected for both design and off-design calculation.

Afterburner specific

Design point calculation frequently does not include afterburning, hence an option on the Design tab sheet has been added to set the design afterburner fuel flow to zero (Checkbox "Zero Wf in design Calc. (afterburner)").

Output tab sheet

The combustor component inherits most of the inlet and exit parameters of the Common output parameters, and adds combustor specific output parameters (Combustion and Emissions)

ERchem is the chemical equivalence ratio. This output parameter contains the calculated chemical equivalence ratio. This is simply the quotient of the total oxygen needed for a stoichiometric mixture and the total oxygen that is present in the mixture. For the difference between the chemical equivalence ratio and the more known equivalence ratio defined by the quotient of actual fuel-air-ratio and stoichiometric fuel-air-ratio, readers are referred to NASA RP1311, Users Manual. However, a few remarks are made here: if all the positive valence atoms (C,H,..) are present in the fuel and all the negative valence atoms (O,..) in the oxidizer, the two equivalence ratios are equal. If not, they are still equal when they are one (stoichiometric mixture), and they are both smaller than one for lean mixtures and higher than one for rich mixtures. The chemical equivalence ratio can be determined for a mixture, without prior knowledge of the fuel composition, for the other equivalence ratio, the fuel composition must be known.

LHV is the Lower Heating Value. This is the heat of combustion where it is assumed that the water component of the combustion process is in vapor state at the end of the combustion.

Unburnt is the amount of fuel flow that is not burnt in the combustor.