Chemical processes often exhibit nonlinear dynamics and tend to generate complex state trajectories, which present challenging operational problems due to complexities such as output multiplicity, oscillation, and even chaos. For this reason, a complete knowledge of the static and dynamic nature of these behaviors is required to understand, to operate, to control, and to optimize continuous stirred tank reactors (CSTRs). Through nonlinear analysis, the possibility of output multiplicity, self-sustained oscillation, and torus dynamics are studied in this paper. Specifically, output multiplicity is investigated in a case-by-case basis, and related operation and control strategies are discussed. Bifurcation analysis to identify different dynamic behaviors of a CSTR is also implemented, where operational parameters are identified to obtain self-oscillatory dynamics and possible unsteady-state operation strategy through designing the CSTR as self-sustained periodic. Finally, a discussion on codimension-1 bifurcations of limits cycles is also provided for the exploration of periodic forcing on self-oscillators. Through this synergistic study on the CSTRs, possible output multiplicity, oscillatory, and chaotic dynamics facilitates the implementation of novel operation/control strategies for the process industry.
As a new type of waste heat conversion machine, the roots power machine can convert low-quality waste heat resources that are difficult to use into mechanical energy. In order to study the influence of tip clearance and radial clearance on the roots power machine, experimental studies were conducted with the roots power machine having different combination of tip and radial clearances and their influence on the performance of the roots power machine was examined. A parametric study was undertaken using CFD to find the sensitivity of these clearances in influencing the performance of roots power machine in the range of 0.2-0.5 mm. From the analysis, it was inferred that radial clearance was sensitive for clearance range of 0.25-0.5 mm and tip clearance in the range of 0.2-0.25 mm. Reduction in clearance from 0.5 mm to 0.2 mm caused an increase of 10.368 and 11.423 % in mechanical and volumetric efficiency respectively.
Roots power machine has obvious advantages in low and medium temperature
waste heat recovery. The existing roots power machine has the problem of
internal flow field disturbance, which seriously affects the power
generation efficiency of the power machine. In order to solve the problem of
disturbance of the internal flow field of roots power machine, the
traditional involute rotor roots power machine is improved, and the roots
power machine based on negative displacement involute rotor is proposed. The
structure model and turbulence model of roots power machine are constructed,
and the internal flow field simulation of roots power machine is realized by
computational fluid dynamics. The pressure contour and torque change of
roots power machine before and after improvement are compared, and the
experimental research on the improved structure is carried out. The results
show that the intensity of flow field disturbance in the modified involute
rotor roots power machine decreases, and the working performance of the
roots power machine improves, which provides a reference for the structural
improvement and performance optimization of roots power machine.
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