Experimental investigation of the combustion characteristics and the emission characteristics of biogas–diesel dual fuel in a common-rail diesel engine

Abstract

An experimental study on biogas–diesel dual-fuel compression ignition was conducted in which biogas and diesel are used as the port-injected fuel and the directly injected fuel respectively. The effects of the total lower heating values QLHVs per cycle and the premixed ratio on the combustion characteristics and the emission characteristics are discussed in detail. The results show that, for constant QLHVs, the peak values of the heat release rate curves first decrease and then increase with increasing premixed ratio. Furthermore, the combustion phase is delayed. For a constant premixed ratio, with increasing QLHVs, the heat release rate curves change from a unimodal distribution to a bimodal distribution, and the ignition delay decreases constantly. With higher QLHVs, the nitrogen oxide emissions and the smoke emissions are relatively higher. In addition, the impacts of biogases with different components on the combustion and emissions were also researched. With increasing hydrogen, the combustion becomes increasingly concentrated, which leads to higher nitrogen oxide emissions. The proportion of carbon monoxide in the biogas has a great effect on the carbon monoxide emissions. Also, the influence of exhaust gas recirculation was also studied. With 60% exhaust gas recirculation, the nitrogen oxide emissions can be inhibited effectively.