| With the rapid development of edible mushroom industry in China,the research on the harmless treatment of the mushroom residue is becoming more and more important.The transformation of edible mushroom residues into renewable energy through anaerobic fermentation technology is an effective way to extend the edible mushroom industry chain,increase the production value of edible mushroom and realize the multi-polar recycling of agricultural resources.The flow field model of the anaerobic fermentation reactor with Agaricus bisporus residue was established by using computational fluid dynamics(CFD)method,and the simulation results of different turbulence models were evaluated by verifying the power quotient and flow quotient of the flow field inside the reactor with the experimental results,and the most suitable model of the anaerobic fermentation reactor with Agaricus bisporus residue was obtained.The main findings are as follows:(1)The anaerobic fermentation gas production test was conducted to determine the optimal fermentation conditions and boundary condition parameters for the comprehensive evaluation of the gas production quality and gas production rate of Agaricus bisporus residue.The test showed that the optimal conditions for the anaerobic fermentation of Agaricus bisporus residue were: the inoculum concentration was 50 % and the fermentation temperature was 50 ℃,which could be used as the boundary condition parameter settings for the numerical simulation.Based on the gas production test,the geometric model of the reactor structure was designed based on the characteristics of the residue and the test results;the parameters of the CFD solver were determined;the boundary conditions and initial conditions were set;the model mesh was divided;and the anaerobic fermentation reactor model of Agaricus bisporus residue was finally established.In order to assess whether the model is reliable,the irrelevance of its mesh model is analyzed.The study shows that the reactor model can meet the requirements of prediction accuracy and mesh quality when mesh number is set as 875067.(2)The accuracy of the prediction results of three types of turbulence models,namely the achievable 6)- model,the standard 6)- model and the Reynolds stress model,for different solvers were compared and analyzed,and the discretization method and numerical solution method were determined.It is found that in the continuous stirred tank reactor(CSTR),the standard 6)- model of the first-order windward discretization scheme and the multiple reference system method can be used when the accuracy needs are low and the computation time is fast;with some accuracy guaranteed and the computation time is appropriate,the achievable 6)- model can be used in the second-order windward discretization format with the multiple reference system method,but when the problem requires higher accuracy,the Reynolds stress model with a combination of the second-order windward discretization format and the sliding grid method is better.(3)The optimal discretization scheme,numerical solution method and turbulence model parameters were used to numerically simulate the CSTR of Agaricus bisporus residues,to obtain a visual flow field cloud inside the reactor and to verify the accuracy of the axial velocity prediction results by conducting reactor tests under appropriate conditions.It was shown that the achievable 6)- model was the closest to the experimental values and the error value was within the allowed range.Therefore,it is proposed that the achievable 6)- model can be used as a model for predicting the internal flow field of the reactor when the turbulence model is adopted and the grid is divided using a multiple reference system approach and in a first-order windward discretized format.On the basis of this modeling scheme, = 60 rpm is chosen for the mixing effect and microbial growth,and the mixing effect between the fermentation material and the fermentation broth is 80 %,which results in a time of approximately 95 s based on the numerical calculation of the model proposed in this study. |
