Experimental study on ignition and flame propagation of premixed ammonia ignited by Direct-Injected diesel in an optical rapid compression Machine
Liang Zheng, Jinhe Zhang, Li Huang, Xiaoxing Tan, Hongmei Li, Jiaying Pan, Mingzhi Feng
Abstract
Ammonia (NH 3 ) is considered as one of the most promising zero-carbon fuels for internal combustion engines. Based on diesel engine modification, The ammonia/diesel dual-fuel mode with port injection of ammonia and in-cylinder direct injection of diesel has been proven to be the most feasible strategy. In this paper, the effects of ignition and flame propagation of premixed ammonia ignited by direct-injected diesel were studied based on an optical rapid compression machine (RCM). The results show that the spray and distribution of diesel play the key role in the ignition and flame propagation of NH 3 /diesel dual fuels combustion. For total excess air ratio (λ T ) of 1.0, the ignition delay of NH 3 /diesel with high energy ratio of ammonia (ER of 95 %) was much shorter than ER of 66 % which was mainly due to the low injection pressure of diesel. Under the same injection pressure, with the large nozzle diameter of diesel injector of 0.28 mm, the ignition delay of NH 3 /diesel will be shortened significantly. When the ER is low, the combustion process presents the characteristics similar to the multi-point compression combustion. When the ER rises to 83 %, the combustion process is mainly dominated by NH 3 premixed combustion, and diesel mainly plays the role of ignition. Reducing the background pressure and temperature to 4 MPa and 887 K, respectively, NH 3 is not able to be ignited by diesel.