In this study a capillary underwater discharge, that is sustained with AC (50 Hz) voltages up to 7.5 kV, is investigated. In a capillary discharge scheme, the current is, at some point along its path between two submerged electrodes, flowing through a narrow elongated bore in a dielectric material. When the current density is sufficiently high, local boiling and subsequent vapour breakdown results in the formation of a plasma within this capillary. At the same time the capillary emits an intense jet of vapour bubbles. Time-dependent electrical current, voltage and light emission curves are recorded for discharges in solutions of NaCl in distilled water and reveal different discharge regimes, depending on the conductivity and the excitation voltage, ranging from repetitive microsecond discharge pulses to a quasi-continuous discharge with a glow-like voltage-current characteristic.PACS: 52.80.Wq

In this paper, a capillary underwater discharge, that is sustained with direct current (dc) voltages up to 30 kV (20 mA), is investigated. In a capillary discharge scheme, the current is, at some point along its path between two submerged electrodes, flowing through a narrow elongated bore in a dielectric material. When the current density is sufficiently high, local boiling and subsequent vapor breakdown results in the formation of a plasma within this capillary. Spectroscopic measurements indicate that this kind of discharge is an efficient source of ultraviolet radiation (280-320 nm). Discharge images reveal that the plasma is initiated half way the capillary and that during plasma expansion, the anode and cathode plasma-liquid boundaries have markedly different velocities.Index Terms-Capillary discharge, ultraviolet (UV) emission, water.

In this paper a 'SpectraQuest' demonstrator is used to introduce misalignment in a rotating set-up. The vibrations caused by misalignment are measured by two accelerometers on the bearings and two eddy-current probes on the shaft itself. A comparison is made between the classical spectral analysis, orbitals and full spectra. Orbitals are used to explain the physical interpretation of the vibration caused by misalignment. Full spectra allow to distinguish imbalance from misalignment by looking at the forward and reversed phenomena. This analysis is done for different kinds of misalignment, couplings and combined machinery faults.

In this paper a 'SpectraQuest' demonstrator is used to introduce misalignment into a rotating machinery set-up. Depending on the coupling used in the set-up, angular and/or parallel misalignment can be brought in the rotating system. Traditionally, the data captured by accelerometers is transferred into the frequency domain in order to interpret the vibrations measured by the accelerometers. The frequency domain has proven its usefulness but even the time domain can come in handy to draw the right conclusions regarding to misalignment in a rotating set-up. Orbit plots display the integrated data captured by accelerometers, in order to display the movement of the rotating shaft. The influence of the misalignment and imbalance on these orbits will be discussed.

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