Experimental investigation on energy utilization and performance improvement of diesel engines with rare-earth hexaaluminate thermal barrier coatings

Enhancing energy efficiency and reducing pollutant emissions are critical objectives in the development of modern marine diesel engines. This study experimentally investigates the effects of LaMgAl11O19 (LMA) rare-earth hexaaluminate high infrared radiation thermal barrier coatings and conventional 8YSZ coatings on a six-cylinder diesel engine, with emphasis on combustion behavior, fuel economy, energy utilization, and emission characteristics. Engine tests were conducted under four representative propulsion load conditions following the propeller characteristic curve. Cylinder pressure, apparent heat release rate, BSFC, BTE, full engine heat balance, and exhaust emissions were systematically analyzed. The results show that both coatings effectively reduce wall heat losses and improve in-cylinder combustion. The 8YSZ coating primarily enhances conductive insulation and exhibits better performance at low load, whereas the LMA coating introduces a radiative thermal regulation effect and demonstrates superior performance at medium and high loads. At 75 % load, the LMA-coated piston achieves the lowest BSFC of 206.06 g·kWh−1 and the highest BTE of 41.3 %, corresponding to a relative efficiency improvement of 1.3 % compared with the baseline engine. Heat balance analysis reveals that coolant heat loss is reduced by up to 2.21 %, accompanied by an increased proportion of effective power. Emission results indicate reduced CO, HC, and soot emissions due to enhanced oxidation, while NOx shows a slight increase associated with higher combustion temperatures. Overall, the LMA coating enables a more balanced redistribution of in-cylinder thermal energy through synergistic conductive and radiative insulation, highlighting its potential as an advanced thermal management technology for improving energy utilization efficiency in high performance marine diesel engines.