pressure ratio and not to u201c flame hold u201d with fuels having lower mwi indexes as used herein a high mwi non design gas fuel has a higher mwi than design gas it should be appreciated that controlling flame holding margin 86 facilitates using non design fuels that facilitate reducing nitrous oxide nox emissions more specifically because controlling flame holding margin 86 allows using a wider variety of non design gas fuels non design gas fuels that inherently or more effectively reduce nox and co emissions when burned may be used for combustor designs for example if a non design gas fuel produces one part per million nox when burned and the design gas fuel produces five parts per million nox when burned it may be better to operate a turbine engine using non design gas fuel to reduce nox emissions moreover it should be appreciated that the design gas fuel may be heated to improve penetration improve fuel mixing to decrease nox emissions and reduce damaging dynamics it is desirable to increase the fuel flexibility of turbine engines by operating turbine engines with less expensive and more readily available alternative non design gas fuels rather than design gas fuels such alternative non design gas fuels include but are not limited to liquefied naural gas lgn syngas and process gas using alternative fuels requires providing sufficient flame holding margin in premixed fuel nozzles it should be appreciated that controlling jet penetration height produces acceptable flame holding margin for operation on a single fuel passage and extends flame holding margins fig6 is a schematic diagram showing an alternative exemplary operating window 110 for non design gas fuel in diffusion nozzle assemblies not shown diffusion nozzle assemblies mix non design gas fuel.