Effects of anodic oxidation for combustion chamber on heat transfer of the piston in an aero-engine

The effects of an anodic oxidation coating on piston temperature distribution and thermal stress are investigated by establishing an inverse heat conduction problem in the form of an optimization problem in an aero-engine. A thermal analysis is carried out for both coated and uncoated pistons at 2100 rpm under 50 and 100% of full load. Specially manufactured metal plugs (templugs) were installed in both kinds of pistons to measure the temperature of every survey station. The effect of the secondary motion of the piston and piston ring on the lubrication oil film was taken into consideration in determining the heat transfer coefficient. There was reasonable agreement between the numerical method and experimental measurement, shown with an error analysis using a third-order polynomial fit technique. Research results showed that the maximum temperature of the anodic oxidation coated piston head increased to 298.5 degrees C and 309.6 degrees C under 50 and 100% of full load, respectively. In addition, there was a temperature reduction in the skirt for the coated piston in contrast to the temperature for the uncoated pistons under 50 and 100% of full load. The temperature distribution and thermal stress in the pin boss were then analyzed. The results indicated an increase of maximum temperature; however, the maximum thermal stress decreased for the anodic oxidation coated piston in the pin boss. Furthermore, a 200-h durability test was performed, proving the thermal load of the piston with anodic oxidation coating would not damage the piston. Also, the effect of the anodic oxidation coating technique on aero-engine emissions was investigated. The anodic oxidation coating for the aero-engine combustion chamber slightly improved CO and HC under 50 and 100% of full load.