What is a consequence of operating a turbine engine with a "rich" fuel mixture?

Operating a turbine engine with a "rich" fuel mixture, which means there is more fuel relative to the amount of air, leads to a negative impact on efficiency and emissions. When the fuel mixture is rich, it implies that there is not enough air to completely combust the fuel, resulting in incomplete combustion. This can produce higher levels of unburned hydrocarbons and carbon monoxide in the exhaust, negatively affecting emissions.

Additionally, a rich mixture can lead to lower overall efficiency, as the engine is not utilizing the available fuel efficiently due to the lack of sufficient oxygen for proper combustion. The fuel wastage not only impacts the engine's thermal efficiency but may also result in additional deposits and fouling in the engine components over time. Consequently, while there may be some benefits under specific circumstances, the overall effects of a rich fuel mixture on a turbine engine are predominantly adverse in terms of efficiency and emissions.