Research on the combustion characteristics of ethanol-blended fuel in high-altitude non-road diesel engine TCD (turbocharger charge air cooling diesel particle filter) combustion systems under multi-operating conditions

• Under 100%, 75%, and 50% load conditions, the performance of the TCD combustion system is optimal when E5 is blended. Under a 25% load condition, the combustion stability is better when no ethanol (E0) is mixed in. As the load decreases from 100% to 25%, both the TCD and the optimal ethanol blending mass ratio of the ω system show a nonlinear attenuation trend. Unlike the ω system, the 100% load TCD has the best performance when ω is blended with E10. • Ethanol has the dual characteristics of high oxygen content but low calorific value. Under different load conditions, the differences in the excess air coefficient (φ a ) result in changes in the dominant factors. Specifically, φ a is relatively small at 100%, 75%, and 50% loads, allowing the oxygen-rich characteristics of ethanol to play a significant role. When the load is 25%, φ a is relatively large and there is sufficient oxygen in the cylinder. At this time, the low calorific value characteristic of ethanol becomes the main influencing factor. • For the TCD combustion system of non-road diesel engines on high altitudes, only one ethanol blending strategy can be selected in practical applications. Comprehensively considering the performance requirements of different load conditions, a matching strategy is proposed to adjust the ethanol mass blending ratio for medium and large load conditions (100%, 75%, and 50%), aiming to achieve optimal comprehensive performance under multiple load conditions. • The point where the combustion performance of TCD increases the most compared to the original ω system does not necessarily occur at the optimal matching ethanol blending ratio. With the increase in load, the proportion of ethanol blending in which the combustion performance of TCD improves the fastest exhibits a nonlinear decreasing trend. In plateau oxygen-deficient environments, diesel engines face issues such as low combustion efficiency and high emissions. Enhancing in-cylinder "fuel-air-chamber" matching and utilizing clean alternative fuels are effective solutions. This study investigates the impact of ethanol blending on diesel engine performance using a wall-guided flow TCD combustion system and AVL Fire simulation. It analyzes the optimal ethanol blending rules and mechanisms under different loads (100%, 75%, 50%, 25%), proposes a multi-condition cooperative optimization strategy for TCD ethanol blending, and reveals the performance advantages of TCD over the original ω combustion system. Key findings include: 1) The lowest indicated specific fuel consumption (ISFC) for TCD is achieved with E0, E5, E5, and E5 at 25%–100% load, measuring 253.95, 225.10, 239.89, and 241.49 g/kW·h, respectively. Optimal ethanol blending ratios for both TCD and ω decrease nonlinearly as load decreases, though ω performs best with E10 at 100% load. 2) Ethanol’s high oxygen content dominates at 50%–100% load (smaller φ a ), while its low calorific value predominates at 25% load (larger φ a ). 3) A practical TCD optimization strategy is proposed, adjusting ethanol blending ratios at medium and high loads (100%, 75%, 50%) for coordinated multi-condition performance improvement. 4) Compared to the original engine, TCD with E10, E10, E5, and E5 at 25%–100% load reduces ISFC by 0.94–11.98 g/kW·h, with the most significant combustion improvement occurring at non-optimal ethanol ratios and showing nonlinear attenuation as load increases.