Which factor does NOT contribute to the efficiency of a gas turbine?

The length of the intake duct does not significantly contribute to the efficiency of a gas turbine. While the design and length of the intake duct can affect airflow and pressure drops within the system, these factors are typically less critical compared to the characteristics that influence the thermodynamic cycle of the turbine itself.

In contrast, ambient air temperature plays a crucial role because higher temperatures can improve the energy content of the combustion gases, enhancing efficiency. Fuel type is also essential, as different fuels have varying combustion characteristics that can impact overall performance measures such as combustion efficiency and emissions. Turbine design is vital as well since it directly affects how effectively the gas turbine can convert thermal energy into mechanical energy.

Thus, the intake duct's length is mainly a design consideration that relates to installation and system layout rather than a direct contributor to the operational efficiency of the turbine.