Experimental study on effects of injection strategies on improving thermal efficiency and reducing emissions by coal-to-liquid/ammonia dual-fuel engine

Under "dual carbon" goals, the use of CTL to ignite NH3 has a significant potential to alleviate the ignition challenge of NH3 and improve the clean utilization of coal. An experimental study is conducted to explore the mechanism by which the CTL injection strategies improve BTE and reduce emissions from dual-fuel engines. The results indicate that, under multiple injection strategies, the CE of NH3 increases with an increase of the pre-injection angle. Furthermore, the use of the pre-injection strategies enhances BTE, reaching a maximum of 40.38 %. As the pre-injection angle and pre-injection rate increases, the cylinder temperature increases and PM emissions decrease; However, this leads to an increase in NOx emissions, peaking at 11.89 g/kW·h, which decreases to 6.69 g/kW·h with the addition of 15 % AEF. Compared to CTL, the use of dual fuel results in increased PM emissions from the engine, and with the increase in AEF, the CO and THC emissions from the engine also rise. When AEF increases from 5 % to 15 %, unburned ammonia emissions increase by 211.4 %. According to the comprehensive evaluation, the engine performance is the best when the AEF is 5 %, the pre-injection rate is 10 % and the pre-injection angle is 5°CA.