Multi-domain unified modeling and simulation of semi-active suspension in magnerorheological damper
In order to build high-precision and highefficient MR damper system model, a multi-domain unified modeling method was proposed. Firstly, based on the analysis of a MR damper semi-active suspension system model, various fields of MR, such as structure, magnetic field, control and mechanics, were studied to find the main influencing parameters. And then for the multi-domain coupling characteristics of MR damper, a multi-domain unified modeling of MR damper system was established based on Modelica/MWorks platform. By adjusting the main influencing parameters, the relationship diagrams between the parameters and the performances were obtained. Finally, some performance results were compared with the traditional method used Matlab/simulink modeling and the method proposed. The results show that the model based on Modelica can preferably reflect the complex relationship between the MR damper coupling among the parameters within the system, and can get a better simulation result.
Behavior of a semi-active suspension system versus a passive suspension system on an uneven road surface
The present paper intends to study the behavior of semi-active suspension systems in comparison with passive suspension systems when subjected to oscillation sources caused by the rolling surface. For this, it was nec-essary to establish the equations specific to the passive and semi-active suspension systems. For each case, the simulation schemes were developed using Matlab Simulink. For the simulation, the quarter car model was chosen. In order to verify the correctness of the model, the State Space and Transfer function models were also used. As the passive dampers have a linear dampening characteristic, we studied the semi-active systems that use magneto-rheological dampers with adjustable characteristics. In the simulation diagram we used a PID controller – proportional integrative derivative. Using two types of stimulus signals we analyzed the behavior of the semi-active suspension system with different dampening coefficients. By simulation, response signals for damper/spring displacement and damper/spring velocity were obtained. The analysis of the obtained results shows the advantages of semi-active systems in comparison with passive systems and the limitations of such systems compared to active systems. DOI: http://dx.doi.org/10.5755/j01.mech.20.1.6591
Hydrogen-rich gas production from biomass air and oxygen/steam gasification in a downdraft gasifier
Biomass gasification is an important method to obtain renewable hydrogen. However, this technology still stagnates in a laboratory scale because of its high-energy consumption. In order to get maximum hydrogen yield and decrease energy consumption, this study applies a self-heated downdraft gasifier as the reactor and uses char as the catalyst to study the characteristics of hydrogen production from biomass gasification. Air and oxygen/steam are utilized as the gasifying agents. The experimental results indicate that compared to biomass air gasification, biomass oxygen/steam gasification improves hydrogen yield depending on the volume of downdraft gasifier, and also nearly doubles the heating value of fuel gas. The maximum lower heating value of fuel gas reaches 11.11MJ/Nm3 for biomass oxygen/steam gasification. Over the ranges of operating conditions examined, the maximum hydrogen yield reaches 45.16gH2/kg biomass. For biomass oxygen/steam gasification, the content of H2 and CO reaches 63.27–72.56%, while the content of H2 and CO gets to 52.19–63.31% for biomass air gasification. The ratio of H2/CO for biomass oxygen/steam gasification reaches 0.70–0.90, which is lower than that of biomass air gasification, 1.06–1.27. The experimental and comparison results prove that biomass oxygen/steam gasification in a downdraft gasifier is an effective, relatively low energy consumption technology for hydrogen-rich gas production.