In gas-turbine applications, the desired temperatures are in the range 1100- 1400 °C. Conventional catalysts such as supported metals or transition metal oxides are not resistant to the severe operating condition of such systems. Hence, novel materials have to be developed to serve as both catalyst materials and substrate materials. These new materials should be able to withstand temperatures of 1100-1400 °C in atmospheres containing steam and oxygen, and for continuous operation for at least one year, if not more. Ideal properties for a high-temperature combustion catalyst are given below. This is a list of issues to be improved or problems yet to be solved.
1. Ignition of the fuel-air mixture at compressor outlet temperature, i.e. 350- 400 °C and velocities of 1-25 m·s-1.
2. Stable combustion up to 1400 °C.
3. Withstand extreme thermal shock up to 1000 °C·s-1.
4. Stable performance for at least one year.
As previously reported, no single material is available for these specifications. The constraint regarding the high thermal stability requirement has been partially solved by design system engineering approaches.
Necessity is the mother of invention. When material science and catalysis cannot meet the above demands, systems engineering has been called in for a rescue operation as follows:
1. Combine materials know-how and systems engineering
2. Create a functional system for gas turbines
3. Apply combustion engineering to circumvent material limitations.