Research On Multi-operating Vibration Characteristics And Operating State Identification Method Of Converter Transforme

Exploration of the efficient conversion and utilization of biomass energy to open up alternative roles for biomass energy is one of the important ways to accelerate the carbon peak and realize carbon neutrality.Biodiesel and fuel ethanol,as the most important biomass liquid fuels,have become important substitutes for traditional fossil fuels due to their renewable,low-carbon,and clean characteristics.Among many forms of biomass energy utilization,complete combustion is the most direct and efficient form.At present,improvements in the combustion stability,combustion efficiency,and clear path of the derivation of fuels are urgent problems to be solved.So the combination of combustion reaction kinetics and combustion characteristic test is a necessary step to solve these problems.The combustion model for biodiesel consists of hundreds or thousands of chemical reactions.It is not practical to form a comprehensive mechanism that includes all chemical components.Therefore,the method of constructing a surrogate model was used to reproduce the combustion properties of the real fuel.The determination of the reaction path and the rate coefficient are the key and difficult points in the research of combustion reaction kinetics.The quantitative method can overcome the limitations of experimental measurements and obtain kinetic data comparable to experimental measurements.Therefore,this paper took biodiesel and biodiesel/ethanol dual fuel as the research objects and calculated the kinetic parameters of the macromolecular system in biodiesel based on the quantitative method.It explored the flame characteristics and path derivation process of fuel combustion.The results can be summarized as follows.Clarification of the intrinsic relationship between the components and physical/chemical properties of the biodiesel and dual fuel can provide a theoretical basis for the actual combustion process.Firstly,the ignition performance and low-temperature flow performance indicators of the biodiesel were tested.The kinetic model for the reaction of the chain ester branched by palmitic acid was constructed employing the integration method to realize the differential change in the spatial structure to improve the low-temperature flow performance of the biodiesel.Secondly,to solve the problems of complex components and complicated measurements of the dual fuel,relative bond length and branching degree were introduced to construct the mixed topological index（G_m）model.Then the QSPR topology prediction of the physical property parameters of the dual fuel was carried out.The results showed that the linear model could reflect the correlation among the G_m,the calorific value,and the density more accurately.The models of y=ae^-x/t+y₀and y=（a+bx）/（1+cx+dx²）were more suitable for expressing the correlation between G_m,kinematic viscosity,and the solidifying point.Finally,the QSPR topology prediction model between G_m and critical parameters was established based on the L-B mixing rule.Through internal and external verification,the feasibility of established prediction model is proved.A simplified study on the detailed combustion mechanism of the biodiesel and ethanol fuels was carried out.The result was verified by the combustion test data such as the ignition delay period,the concentration of important components,and the flame propagation speed.The kinetic parameters of the hydrogen extraction and cracking reactions between the methyl decanoate molecule and the radicals of H,OH,HO₂ and CH₃ were obtained based on the quantitative method.A high-precision method to calculate the macromolecular system requires more time and resources,and it may not achieve the goal.A hierarchical ONIOM[QCISD（T）/CBS:DTF]method was proposed to construct the reaction energy barrier for the extraction and dissociation reactions between methyl decanoate and H free radicals.Aiming at solving the problems of low-level optimal methods and selecting an active site in the ONIOM.Firstly,based on eight density functional theory methods,the geometric structures of methyl butyrate,methyl crotonate,methyl caproate and methyl heptanoate were optimized,and the bond length,bond angle and bond energy were calculated.Through the global standard absolute deviation,it is clear that M06-2X is the best optimization method.Secondly,the M06-2X method was used to visualize the global and local reactivity to determine the optimal active site position in the hierarchical ONIOM.Finally,based on the conventional transition state theory and variational transition state theory combined with Ki STel P,the reaction rate coefficient was calculated and the kinetic model for the combustion reaction of the biodiesel was constructed.The results showed that the relative error of the working conditions was reduced from less than 30%of the simplified mechanism to less than 20%and the renewal mechanism could predict the generation and consumption of component concentrations more accurately.In-depth research on the combustion kinetics and flame characteristics of the biodiesel/ethanol dual fuel was carried out.Firstly,a dual-fuel combustion kinetics with 183 components and 855 reactions was formed based on the"decoupling method".The reaction paths of the biodiesel in low-temperature and high-temperature combustion stages were analyzed by the method of the reaction rate analysis and the influence of ethanol on the dual fuel reaction paths and related reactions were studied.Secondly,a biomass atomization evaporation combustion system was built to carry out synchronous measurement experiments combined with the planar laser-induced fluorescence technology.Explore the flame height,flame front area,and OH radical distribution characteristics of biodiesel and dual fuel.A box-counting dimension-corrosion method based on a mathematical morphology was proposed and applied to the flame volatility diagnosis.The average value of the fractal dimension slope was used to reflect the flame volatility.Finally,the combustion dynamic analysis of OH in the dual fuel was carried out,and the variation law of the flame OH intensity was investigated.The results showed that with the increase of the equivalence ratio,the flame height of Jatropha biodiesel increases,and the flame front area first decreases and then increases.As the blending ratio of ethanol increases,the flame front area and OH intensity of the dual fuel show a downward trend.From the dual fuel path and OH related reaction rate,it can be seen that the OH consumed by ethanol through dehydrogenation reaction is far greater than that produced by the characterization fuel.And the consumption rate of OH is much higher than the generation rate.Therefore,the OH strength decreases with the increase of ethanol blending ratio,and the simulation and experimental results are verified.In this paper,a kinetic model of combustion reaction of biomass liquid fuel is built based on quantitative calculation,which clarifies the influence of ethanol on the reaction path of biodiesel and dual fuel,and reveal the evolution process of important intermediates in the combustion process,and carry out experimental research on combustion flame characteristics of biodiesel and dual fuel,providing theoretical and data support for the engineering combustion process.