For the production of oxide nanoparticles at a commercial scale, flame spray processes are frequently used where mostly oxygen is fed to the flame if high combustion temperatures and thus small primary particle sizes are desired. To improve the understanding of these complex processes in situ, noninvasive optical measurement techniques were applied to characterize the extremely turbulent and unsteady combustion field at those positions where the particles are formed from precursor containing organic solvent droplets. This particle-forming regime was identified by laser-induced breakdown detection. The gas phase temperatures in the surrounding of droplets and particles were measured with O(2)-based pure rotational coherent anti-Stokes Raman scattering (CARS). Pure rotational CARS measurements benefit from a polarization filtering technique that is essential in particle and droplet environments for acquiring CARS spectra suitable for temperature fitting. Due to different signal disturbing processes only the minority of the collected signals could be used for temperature evaluation. The selection of these suitable signals is one of the major problems to be solved for a reliable evaluation process. Applying these filtering and signal selection steps temperature measurements have successfully been conducted. Time-resolved, single-pulse measurements exhibit temperatures between near-room and combustion temperatures due to the strongly fluctuating and flickering behavior of the particle-generating flame. The mean flame temperatures determined from the single-pulse data are decreasing with increasing particle concentrations. They indicate the dissipation of large amounts of energy from the surrounding gas phase in the presence of particles.
Pressure attenuators, especially side branch bladder-type accumulators, for suppression of pressure pulsations in industrial fluid applications are not suitable for higher-pressure pulsation frequencies, e.g., with centrifugal pumps. Accumulators of the flow-through-type promise a faster response time and thus a wider application range. The damping performance of a flow-through pressure accumulator with respect to fluid pressure pulsations and the resulting structure-borne noise was investigated. The influence of varying pulsation frequencies, damper precharge pressure, and damping effect throughout the piping system was evaluated. Experiments were performed in an industrial-scale closed-loop test facility, with both pressure pulsations and piping vibrations in the focus. The damper, characterized by means of high-speed video analysis, proved to be capable of damping effectively the pressure pulsations and piping vibrations induced by a centrifugal pump.
The design of reciprocating pumps for the chemical industry requires a detailed knowledge of the apparent phenomena such as undesirable pipe pulsation and harmful cavitation. Since the detailed understanding of the entire mechanism is rather limited, emphasis will be put on the verification of a fluid-dynamic cavitation model for reciprocating positive displacement pumps. This model was established by means of particle image velocimetry (PIV) measurements carried out at a repetition rate of 2 kHz. The PIV results indicate that the fluid-dynamic cavitation model corresponds with the physical reality. While common practice dictates that cavitation should be prevented at all times, the proposed model offers a great opportunity for manufacturers to predict a limit for the extent of occurring cavitation.Cavitation is one of the main causes of damage to piping elements and hydraulic machinery. Cavitation itself is the process of nucleation in a liquid when the pressure falls below saturated vapor pressure. Due to different generation and growth mechanisms, depending on the pressure level, the classification of cavitation types is deemed to be useful. Therefore, cavita-
In industrial plants, centrifugal pumps are frequently operated in parallel configuration, not least for redundancy and operational reliability reasons. However, regarding the resulting pressure pulsations and energy consumption, this operation mode has so far not been in the focus of scientific studies. The object of the present article is to clarify the effect of parallel operation with respect to the observable pressure pulsations. Measurements were carried out with two identical centrifugal pumps operating in parallel mode in an industrial‐scale closed‐loop piping system. The results suggest that, regarding both the resulting pressure pulsations and the operating point of each pump, this operation mode is quite sensitive to smallest rotational speed deviations as they may occur due to different motor slip. The results indicate furthermore that, for minimum pressure pulsations, equal power consumptions of the two pumps are crucial, but not necessarily equal rotational speeds.
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