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Fluids with a high proportion of dissolved air lead to an increased air release in hydraulic components. Looking at the fluid flow in a piston pump, the resulting multiphase flow may affect its metering performance. To improve effects caused by cavitation, it is necessary to detect and analyze all critical flow areas in detail. This paper presents investigations of the multiphase flow in an electromagnetically driven dosing pump. This type of pump is suitable for metering any kind of liquid in motor vehicles in a very precise manner. Using high speed camera equipment and transparent components for the displacement chamber, the presented experimental work gives a comprehensive insight into the most relevant cavitation effects in the pump. In addition, the pressure inside the displacement chamber is measured with the help of a miniature pressure sensor. By combination of measuring data and visual recordings, cavitation phenomena can be determined precisely, so that a profound understanding of the flow behavior in the pump is achieved.

Uncontrolled magnetically driven dosing pumps cause noise when the armature reaches the mechanical end stops. The reason for this is the impulse of the armature, which depends on the armature speed. A speed reduction before reaching the end stops could reduce the noise level. This requires a special modification of the time-dependent armature motion using variable energy supply. In order to control the armature motion independently from various inputs such as supply voltage, outlet pressure and liquid properties, the position has to be known. Sensorless position estimation is used, since it offers the determination of the armature position without modifying the simple pump design. The estimation is based on the evaluation of electrical values. In order to show feasibility of position estimation in dosing pumps considering different control strategies, simulation based preliminary investigations are performed and validated with experimental results. For this purpose, a co-simulation of controller, electrical and mechanical system simulation and magnetic FEM simulation is used.

Modelling of activated sludge processes is a commonly used technique to design and optimize wastewater treatment processes. Since wastewater and activated sludge is characterized by chemical oxygen demand (COD) measurements, units of state variables describing organic matter are expressed as equivalent amounts of COD. However, current procedures for measuring it have several drawbacks, including the production of hazardous wastes, so the utility of other variables for characterizing the organic load in modelling, such as total organic carbon (TOC), warrant re-evaluation. Other advantages of TOC over COD are that it provides matrix-independent analytical results and it can be readily measured online. Proposals for TOC-based models were made in the 1990s, but they seem to have sunk into obscurity. To re-assess the value of TOC for this purpose, we have recalculated the EAWAG module for Bio-P removal coupled to the Activated Sludge Model No. 3 on a TOC basis, and tested it against data acquired in batch experiments with four single carbon sources (acetate, glucose, citrate and casein). The batch test-based calibrations showed a good match with experimental data, following modifications of the model to account for the anaerobic volumes and retention times applied in the tests.