| With the rapid development of China’s shipping industry,the demand for petroleum resources has been further expanded.The stricter national coastal emission regulations implemented since 2019 have made marine diesel engine energy conservation and emission reduction being a popular research direction for researchers.Finding renewable resources,studying new combustion modes and optimizing the combustion chamber of diesel engines have become effective measures to achieve diversified energy supply,energy conservation and emission reduction.Exhaust gas recirculation(EGR)can achieve low temperature combustion of diesel engines.By blending biodiesel,the low calorific value and high oxygen content of biodiesel can be used to improve low temperature combustion and effectively avoid areas with high NOx and Soot emissions.At the same time,the diesel engine parameters are optimized to improve the combustion quality.In addition,according to the viscosity characteristics of biodiesel,the combustion chamber structure is optimized and improved to improve the quality of the oil and gas mixture and achieve efficient combustion of fuel.First,CHEMKIN was used to generate n-heptane-fatty acid methyl ester-polycyclic aromatic hydrocarbon reaction mechanism,coupled with FIRE software to generate CFD model,and the model optimization and adjustment of AVL_FIRE software were carried out according to the actual specifications of the diesel engine after electronic control transformation.In the setting of initial conditions and boundary conditions,the simulation value and test value of the model are compared and adjusted until the error is less than 5%,thus establishing the diesel-biodiesel dual-fuel combustion model.Secondly,the biodiesel blending ratio and EGR rate are changed to study the matching range of the biodiesel blending ratio and EGR rate under full load conditions;the intake air pressure is adjusted to study the power and emissions of pure diesel and mixed fuels Performance impact.Under low-temperature combustion conditions,the engine combustion chamber was double-convoluted to improve the mixing and diffusion of oil and gas,and the fuel injection advance angle and nozzle hole diameter were optimized.By coupling AMEsim and AVL_FIRE software,the fuel injection pressure and regular changes due to changes in combustion chamber parameters are adjusted accordingly.Finally,the five parameters of the engine involved in the above are designed for orthogonal test and simulated,and the results are subjected to range and principal component analysis with power and emissions as the targets.Compare the corresponding results with the original machine,and bring them into the model to determine the best combination.The results show that the increase in the blending ratio of biodiesel can effectively reduce the emissions of CO and Soot,but the amount of NO production has increased significantly;the introduction of waste recycling can effectively reduce the NO emissions,but the amount of CO production has also increased accordingly.The combination of 40%biodiesel and 12.5%EGR rate can reduce the in-cylinder temperature to below 1650K.While achieving low-temperature combustion,it can effectively reduce the production of Soot and NO.Properly increasing the intake pressure can effectively improve the power and economy.Insufficient;optimization of the combustion chamber and related parameters helps to promote the mixing of oil and gas and improve the quality of combustion.The final optimization result is that,biodiesel blending ratio is 40%,EGR rate is 12.5%,intake pressure is 0.233MPa,injection hole diameter is 0.26mm,fuel injection advance angle is 22.6℃A.The mass fraction of NO is reduced 77.98%compareing to the original machine,the Soot generated quality score was lower than the original machine 98.04%,CO emission was lower than the original machine73.54%,the indicated power was 48.032kW,lower than the original machine 12.67%,under the premise of sacrificing a small amount of power,greatly improve its emissions. |
