| Energy is the basis for human beings to survive and engage in social activities in modern society.Most of our motor vehicle powertrains are fuelled by petrol and diesel.The exhaust fumes emitted by these vehicles can cause enormous damage to the environment.While the lack of domestic charging stations leads that pure electric vehicles cannot be effectively charged in the sparsely populated highlands and mountainous areas.In this context,research on power systems that do not use conventional fuels is of great importance.Based on the biomass energy comprehensive conversion module and demonstration system project,a biomass gasification system is developed in this research.This system,paired with Stirling generator sets,can enable vehicles to perform long-distance driving tasks in areas where conventional energy sources are difficult to obtain.By comparing the advantages and disadvantages of domestic and foreign biomass gasifiers,an experimental prototype of downdraft gasifier was designed and several experiments were carried out.In order to improve the problem of large fluctuations in the composition of the gas produced during the operation of the gasifier,the overall structure of the gasifier is improved.Combined with the technical indicators to be completed by the project,this project complete the structural design of the biomass gasifier in the power system.The most distinctive feature of the gasifier is the gas supply unit installed on it.Aiming at the problems of partial burning,burn-through and large vortex in the gas supply unit during gasifier operating process,the numerical simulation method of computational fluid dynamics is used to simulate the gas supply structure of the gasifier,helping to build velocity clouds and particle trajectory maps inside the gas supply unit.According to the simulation results,the reasons for the problems of the gasifier during operation are analyzed.Based on the thesis,the gas supply structure of the gasifier is rationally optimized.The flow field simulation results of the optimized air supply structure show that the air flow of each air outlet of the structure is uniform.In addition,there is no large vortex inside the gas supply unit.The gasification experiment research is carried out on the biomass gasification demonstration system.The effects of factors such as air equivalence ratio and secondary air intake rate on the composition and calorific value of the output gas are explored.The gasification experiment results show that: when the secondary air intake rate is 0%and the equivalence ratio increases from 0.2 to 0.3,the calorific value of the output gas first increases from 4.78MJ/m~3 to 5.01 MJ/m~3 and then drops to 4.90MJ/m~3;The equivalence ratio is fixed at 0.25,the secondary air intake rate increases from 0% to10%,and the gas calorific value increases from 5.01MJ/m~3 to 5.25MJ/m~3.At the end of the experiment,the heating experiment of low melting point alloy is also carried out.The experimental results verify that the small gasification system designed in this paper has reached the preset technical indicators.This paper uses ASPEN PLUS software to build a biomass gasification simulation model.The effects of gasification pressure,material moisture content and oxygen equivalence ratio on gasification characteristics are investigated by simulation,the results of which indicates that: high gasification pressure is helpful to produce biomass gas with high methane content;gasification is not suitable for feedstocks with too high a moisture content;the use of oxygen as a gasification agent contributes to the production of high calorific value gas.Finally,by designing a three-factor orthogonal test and analyzing the test results,the following rules are obtained: the oxygen equivalence ratio has the highest influence on the calorific value and gas yield;the material moisture content has the greatest influence on the gasification efficiency;gasification pressure has the least effect on the three gasification indexes. |
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