Abstract
The interaction between gas turbines and airborne particles determines detrimental effects on the performance, efficiency, and reliability of the power unit. When it is possible, the interaction is reduced by the use of inlet separators and filtration systems. In an aero engine, these barriers are difficult to implement, and only bigger particles (usually greater than 10 μm) are separated from the airflow. Small units, especially those equips helicopters, are usually affected by fouling issues, especially when the aircraft is employed in harsh environments such as firefighting and rescue activities. To recover this contamination, the unit is washed after the mission by ground operations to restore the unit performance by removing the deposits. This operation occurs during a sub-idle unit operation, and the washing process has to be effective when the engine operates in this off-design condition. In this paper, the evaluation of the washing performance during a sub-idle unit operation is carried out. The compressor unit is a multistage axial compressor that equips the Allison 250-C18 engine. The washing operation was performed by water, and a sensitivity analysis is carried out to discover the capability of water droplets to remove the contaminants. The experimental analysis involves the contamination of the unit by micro-sized soot particles and a washing operation by micro-sized water droplets. These experimental results are compared to numerical simulations to discover the effects of the washing operation on a small power unit during sub-idle operating conditions. The off-design regime imposes a specific evaluation of the proper setup of the washing strategy: flow separations involve wider regions in the compressor unit, and the removal capability is strongly related to the droplet path through the stages. The results show how in the off-design washing operation, the droplet diameter has greater importance than the water flow rate for reducing the deposits over the compressor stages.
Highlights
Particle adhesion, commonly known as fouling, characterizes several issues in the numbers of machines and energy system devices as the heat exchanger, solar panels, and gas turbines [1 – 4]
The washing operation was performed by water, and a sensitivity analysis is carried out to discover the capability of water droplets to remove the contaminants
The results show how in the off-design washing operation, the droplet diameter has greater importance than the water flow rate for reducing the deposits over the compressor stages
Summary
Commonly known as fouling, characterizes several issues in the numbers of machines and energy system devices as the heat exchanger, solar panels, and gas turbines [1 – 4]. A particular harsh condition experienced by a gas turbine is related to the helicopter operation These engines usually operate in dusty conditions due to the downwash of the rotor that spreads microparticles from the ground into the environment (up to a few meters), as reported in [12]. Deposits located at the compressor section have to be removed by a washing operation usually carried out by manual operation, using a manual jet during a subidle operation regime of the engine immediately after the mission. This operation could be carried out using water or cleaner depending on the location and resource availability [14]
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