No abstract

Industrial decanter centrifuges are used in a wide range of industries to separate mixtures of solids and liquids. One of the main elements of these devices is the feed accelerator, which accelerates the incoming mixture to the high rotational speed required for separation. A well-designed feed accelerator can increase product throughput, solids recovery, and liquid clarity, while a poorly designed accelerator can increase wear and reduce the overall efficiency of the machine. This article presents experimental and computational quantification of the performance of six feed accelerator designs that are currently used in decanter centrifuges. The experimental method allowed for the measurement of accelerator and pool speed efficiencies, and high-speed photography of the flow in the annular space between the accelerator and the rotating pool. The computational model allowed for prediction of the flow path in the annular space and the torque imparted on the fluid by the accelerator. A parametric study was conducted using the aforementioned computational model for drum and disk accelerators. It was found that several of the accelerator design parameters were critical to the overall performance, reinforcing the need for an optimised design. It was found that increasing the surface area of the port faces of the drum accelerator and increasing the discharge angle and discharge radius for the disk accelerator improved the performance of the accelerators.

The effect of dead volume on the power output and efficiency of an alpha-Stirling engine is investigated in the form of an exploratory parameter study using the third-order simulation software Sage. This paper aims at identifying the underlying mechanisms in order to better understand the resulting design implications of this phenomenon that is in clear contradiction to what can be found in the literature. It turns out that additional 'passive' dead volume that does not even take part in the heat transfer processes leads to a phase shift of the pressure, resulting in increased pV-work output, especially at lower heat source temperatures. Of even greater significance, dead volume has a positive effect on the efficiency at lower heat source temperatures by reducing the temperature swing in the heat exchangers and by bringing the gas temperatures closer to the wall temperatures of the respective heat exchangers, and thus increasing the effective temperature difference. Furthermore, to a large extent the beneficial effects of dead volume can also be achieved by changing the phase angle.