Przemysław Młynarczyk

Modelowanie przepływu przez złoże fluidyzacyjne jest zadaniem skomplikowanym, bardzo czasochłonnym oraz wymagającym dostępu do bardzo dużych mocy obliczeniowych. W niektórych jednak przypadkach modelowanie tego typu przepływu można uprościć do przepływu przez warstwę porowatą, tak jakby złoże miało postać stałą. W artykule przedstawiono porównanie przepływów bez złoża oraz ze złożem stałym w celu oszacowania wpływu na erozję warstwy wierzchniej.

Pressure pulsations in volumetric compressor manifolds are important issues in the compressor plant operation. For pressure pulsation attenuation, mufflers designed using the Helmholtz resonator approach are applied. Nowadays, the variable revolution speed compressors requires new design methods for pressure pulsation damping elements. One of the possibilities to attenuate the pressure pulsations is the introduction of specially shaped nozzles in the gas duct flow. In this paper, the impulse flow simulations conducted in FLUENT/ANSYS. The experimental validation of the simulation results is also presented.

The vibrations and noise caused by pressure pulsations are one of the major problems in volumetric compressors manifolds. There is still no easy solution for this problem. Passive damping of those pulsations is possible using specially shaped nozzle placed in place of the straight tube. Experimental analysis of the pressure pulsations damping caused by a nozzle is possible however only some arbitrary chosen nozzle shapes can be investigated. The analysis of damping of the impulse flow by the nozzle using CFD simulation is more general and gives the possibility to estimate the nozzle influence on the pulsating flow in theoretical way, so many different shapes can be investigated. In this paper examples of impulse flow damping factors for three different nozzles have been shown.

Pressure pulsations in volumetric compressor manifolds are one of the most important problems in compressor operation. These problems occur not only in huge compressor systems such as those used in natural gas piping in gas mines or national transport systems, but also in small refrigeration compressors found in domestic applications. Nowadays, systems require a new approach since in all applications, variable revolution speed compressors are introduced. Mufflers designed in a conventional way on the basis of the Helmholtz theory only have good pressure pulsation damping action within the designed frequency range. In the case of revolution speed change, the reaction of the damper designed according to the Helmholtz theory may be insufficient. Therefore, any innovative ideas for pressure attenuation is welcomed by the compressor industry. One of the possibilities to attenuate pressure pulsations over a wide range of frequencies is the introduction of specially shaped nozzles in the gas duct flow directly after the compressor outlet chamber. It is obvious that the nozzle attenuates pressure and flow pulsations due to energy dissipation, but at the same time, it also raises the requirement for the pumping power of the compressor. The estimation of nozzle pulsation attenuation may be assessed using CFD simulation. In the paper, the influence of the time step and viscous models choices have been shown. The differences between viscous and inviscid gas models have been shown.

Photonic structures and their application are one of the most intensively studied areas of modern optics. They are used in devices such as blue lasers, optical fibres or optical add-drop multiplexers. The paper describes the possibility of designing the photonic structure of the optical demultiplexer using the application written by the authors.

Pressure pulsations in volumetric compressors systems have an important influence on the compression power and reliability. This problem occurs not only in huge compressor systems, as in the natural gas piping, in gas mines or national transport systems, but also in a small refrigeration compressors in domestic applications. Nowadays, it is necessary to develop pressure pulsation damping elements which will be effective for different mass flow rate values. One of the solutions are passive damping elements in the form of various types of nozzles. In addition to the decrease of pressure pulsations value, the result is also an increase in power consumption of the compression. Therefore, shape optimization is necessary. In the article the possibility of optimizing the shape of such elements using computational simulations is discussed.

Many experimental high-energy installations, e.g. ITER (Cadarache), CERN (Geneva), SOLARIS (Krakow), require an ultra-high quality of vacuum. To meet these requirements, a vacuum void and its adjacent diagnostic systems are exposed to elevated temperatures (baking) after assembly to outgas all volatile surface contaminants. The baking temperature peaks as high as 250°C for up to 24 hours.