The Combustion Noise And Combustion Simulation In A Biogas Diesel Dual-Fuel Engine

During recent years the use of gaseous fuel in internal combustion engine is becoming an important research aspect for the improvement of fuel consumption and reduction of emission. The dual fuel engine modified from diesel engine with pilot diesel fuel ignition is widely used due to its high efficiency and low emissions. Biogas produced by gasification oven from biomass materials is a kind of good alternative fuel for the engines. It is becoming a most important resource to solve the shortage of energy and reduce the second pollution from the burning of biomass materials. The biogas is used more and more widely in engine. The current situation on development and technical strategy of dual fuel engine are briefly discussed. The development and the current situation of biomass energy and the evolvement of combustion model of compression ignition dual fuel engine are summarized. The dual fuel engine is discussed by theory and experiment on the basis research of predecessors. Scientific foundation for the utilizing and development trend of biomass energy sources is introduced.A biogas—diesel dual fuel engine ignited by the pilot diesel fuel has been modified from a single cylinder, direct injection diesel engine. The dual fuel engine can operate by normal diesel fuel (no gas was added) or dual fuel. The characteristics map of fuel consumption, combustion parameters and specific emissions of diesel engine and dual-fuel engine are analysed. The effects of parameters such as load, engine speed and fuel supply advance angle on combustion process are analysed. The results show that compared with diesel engine, the ignition timing of dual fuel engine is delayed.The maximum combustion pressure and maximum combustion pressure rise are lower and their corresponding phases are delayed except at low speed and high load conditions. The after combustion period is longer. The NO_x emission of dual fuel engine compared to the diesel engine decrease remarkably, but the HC and CO emission increase obviously.The combustion noise of the biogas diesel dual-fuel engine is comprehensively evaluated in time region and frequency region. The total combustion sound pressure level is caculated. The data of dual fuel engine are compared with those of diesel engine. The effect of the different fuel supply advance angle and load and speed on the combustion process are studied. The results show that the combustion noise is larger with the increasing of load. The combustion noise is larger with the increasing of fuel supply advance angle. The combustion noise of diesel engine is larger than that of dual fuel engine.According to the combustion characteristics of dual-fuel engine, a new multi-zone combustion and heat release model has been developed to calculate the combustion heat release rate based on the measured cylinder pressure. This new model is applied to the biogas-diesel dual fuel engine and compared with the conventional diesel calculation model. The research results show that the peak heat release rate of dual fuel engine is larger than that of the diesel engine. However the total combustion period is delayed. Compared with the conventional calculation model, the new model agrees well with the experimental results.On the basis of experimental data and theory analysis, a universal combustion model was developed to predict the performance of the dual fuel engine. The new model is based on the fractal nature of turbulent flames, including ignition delay model, fuel spray and air entrainment model, flame propagation model, combustion chemical reaction model, heat transfer model and the NO_x emission model. This new model is applied to the biogas-diesel dual fuel engine to predict the characteristics of the engine. The simulation results show that the model has good precision compared with the experimental data.