Performance characteristics of a two-stroke low speed engine applying ammonia/diesel dual direct injection strategy

• NH 3 /Diesel dual direct injection strategies were investigated on a two-stroke engine. • The combustion modes and phase of liquid phase ammonia spray was regulated by JCCI. • Ammonia combustion duration was shortened by dual-direct injection strategy. • The mode of dual fuel could achieve higher ITE than that of the pure diesel mode. • Soot, CO and thermal type NOx were suppressed effectively under the dual fuel mode. Ammonia has been attracting widely interests among the world because of the property of carbon-free energy resource. As the alternative and renewable fuel of internal combustion engine, its application is expected to comply with the GHG (greenhouse gas) reducing goal of traditional power equipment. However, the defects of low combustion efficiency, high pollutant emissions and poor power performance are restricting the promotion of ammonia fuel. Experimental validation and evaluation of Ammonia/Diesel dual direct injection mode of two-stroke low speed engine were conducted in the current study based on the concept of diesel Jet Controlled Compression Ignition (JCCI). The engine performance and emission characteristics were discussed under the cases of various ammonia injection quantity, timing and different diesel injection timing conditions. It reveals that the injection timing of diesel, which is responsible for the ignition of liquid phase ammonia spray, can regulate the engine combustion phase precisely. The combustion duration of ammonia is accelerated by the ignition of high energy diesel flame, which results in the improvement of indicated thermal efficiency (ITE). Moreover, the worrying fuel type NOx emission, which is mainly produced by the ammonia combustion, is reduced by the reasonable arrangement of injection timings of diesel and ammonia.