Pressure pulsations in volumetric compressor manifolds are one of the most important problems occurring in the compressor installations. They cause noise and vibrations, which may result in installation failures. In 2005 DOE USA (Advanced Reciprocating Compression Technology (ARCT), 2005, Final Report SwRI® Project No. 18.11052, DOE Award No. DE-FC26-04NT42269) published a report where pressure pulsations attenuation is named as one of the three most important problems in compressor plants design and operation. Three main approaches of modeling acoustic wave can be named here: one dimensional pipeline modeling with real domain solution and finite difference methods, Helmholtz theory based acoustic model, where complex Fourier transform is used, or finally full computational fluid dynamics (CFD) multidimensional approach. All of them have limited capabilities. With one dimensional model no real geometry of an oil separator or a damper can be introduced. In the Helmholtz approach apart from the length limit of a pipe, complex geometry requires transmission properties of the element. CFD is the most accurate but very time consuming in both computational time and data preparation for the CFD software. In the present paper, one of the coupling methods is shown with the introduction of transmittance characteristics. The resulting simulation using generalized Helmholtz model shows much better agreement with the experimental results than for the classic Helmholtz modeling.

Drying and sanitising equipment has been very common in industrial plants since the pandemic. These are devices that consume significant amounts of energy. The best solution is to use a drying chamber equipped with a heat pump, which allows partial recovery of the energy. In the design of the drying chamber, the drying time is important, which depends both on the parameters of the heat pump itself, and the geometry and airflow of the drying chamber. The geometry and airflow supply should be arranged to ensure a uniform distribution of velocity throughout the drying area. For this purpose, the use of CFD simulations has been proposed. A model was developed in ANSYS/FLUENT where all model parameters, including the optimal mesh density, turbulence models, etc., were determined. The model was verified on the experimental results of the basic design of the chamber. Then an innovative design was proposed that was modelled and optimised in terms of the distribution of the inlet’s perforation. The final design was made, and, at the same time, the simulation’s results were verified by measuring the velocity of airflow in the new design. Together with the optimisation of the heat pump, this made it possible to reduce the drying time by 50%, with a simultaneous reduction in the energy consumed.

Vibration and noise caused by pressure pulsations in the volumetric compressor manifolds are one of the most important problems in the volumetric compressor's operation. For pressure pulsation attenuation, different types of mufflers are applied using a design based on the Helmholtz resonator approach. This design is not effective for variable revolution speed compressors and in this case other pressure pulsations attenuation methods are required. Nowadays, due to the increasing application of variable speed compressors new design methods are developed. 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 well known that a nozzle can attenuate pressure pulsations, however, it increases the compressor power at the same time. The main criterion for the nozzle selection is the highest possible attenuation of pressure pulsations coupled with the lowest possible effect on the compressor pumping power. In some cases 25-30% of the pressure damping is good enough to reach the standard requirements. The method applying CFD impulse flow simulations has been developed for the estimation of the nozzle influence on pressure pulsations for all frequencies. The FLUENT/ANSYS software has been used for the simulation. The CFD simulation requires a lot of effort for proper selection of the boundary conditions, solution methods, turbulence models, discretization methods, mesh design etc. The results are in some cases surprisingly different between different methods. In this paper the flow simulations for the nozzle flow with the connecting pipe using impulse function as a mass inflow excitation is shown. In this investigation project various models and methods have been compared and results in 2D and recalculated into 0D time only dependent functions are presented