As an inexpensive and low carbon fuel, the combustion of natural gas reduces fuel cost and generates less carbon dioxide emissions than diesel and gasoline. Natural gas is also a clean fuel that generates less particulate matter emissions than diesel during combustion. Replacing diesel by natural gas in internal combustion engines is of great interest for industries. Dual fuel combustion is an efficient way to apply natural gas in internal combustion engines.
An issue that to a certain extent offsets the advantage of lower carbon dioxide emissions in natural gas–diesel dual fuel engines is the higher methane emissions and low engine efficiency at low load conditions. In order to seek strategies to improve the performance of dual fuel engines at low load conditions, an experimental investigation was conducted to investigate the effect of diesel injection split on combustion and emissions performance of a heavy duty natural gas–diesel dual fuel engine at a low load. The operating conditions, such as engine speed, load, intake temperature and pressure, were well controlled during the experiment. The effects of diesel injection split ratio and timings were investigated. The engine efficiency and emissions data, including particulate matter, nitric oxides, carbon monoxide and methane were measured and analyzed. The results show that diesel injection split significantly reduced the peak pressure rise rate. As a result, diesel injection split enabled the engine to operate at a more optimal condition at which engine efficiency and methane emissions could be significantly improved compared to single diesel injection.