The acoustic emissions from supersonic jets represent an area of significant research needs; not only in the field of aero-acoustics, but in industry as well where high pressure let down processes have been known to cause acoustically induced vibrations. A common method to reduce the acoustic emissions of such processes involves dividing the single larger supersonic flow into several smaller ones. Though this is common practice, there is not yet a current model which describes the reduction of acoustic emissions from an array of smaller supersonic jets. Current research which studies supersonic jet arrays are mainly focused on the effects of screech. Though screech is important, due to its high amplitude acoustic pressure, this research focuses on the overall acoustic emissions radiated from supersonic jet arrays which can cause severe acoustic loadings. This research investigated the acoustic emissions and shock formations from several eight by eight arrays of axisymmetric jet experimentally. The array nozzle diameters investigated ranged from 1/8 inch to 1/4 inch and the spacing over diameter ratio ranged from 1.44 to 3. The net pressure ratios investigated ranged from 2 to 24. Results revealed a strong correlation between the acoustic emissions and the shock formations of the flow. Up until a critical net pressure ratio, the overall sound pressure levels were comparable to that of a single jet within an array. At net pressure ratios beyond the critical the overall sound pressure levels transitioned to higher decibel levels; equivalent to a single jet with an equivalent exit area of an entire array. Also, the characteristic acoustic frequency emitted from a nozzle array remained ultrasonic (above 20 kHz) at lower net pressure ratios and then shifted to audible levels (between 20 Hz to 20 kHz) at net pressure ratios beyond the critical. Also, before the critical net pressure ratio the shock cells from the jets within the array remained unmerged, but at net pressure ratios beyond the critical the shock cells merged and formed lattices of weak oblique shocks at first and then strong oblique shocks as the net pressure ratio continued to increase. The critical net pressure ratio was investigated by non-dimensional analysis. The non-dimensional analysis revealed that the critical net pressure ratio was a strong linear function of the spacing over diameter ratio. A linear model was derived which is able to predict the critical net pressure ratio, and in turn, predict a critical shift in the acoustic emissions of a nozzle array.

This master’s thesis deals with theme of turbocharger seals. The aims of a thesis are to compare a turbocharger seals used in PBS Turbo turbochargers and to describe a testing of a seals. Principle of turbocharging and types of turbocharger are described in fist part. Next point of the thesis is describing of a face seals and non-contacting seals. The main part of the thesis describes kinds and reasons of seals testing; also contains comparison between labyrinth seals and piston ring, comparison of seals of PBS Turbo’s turbochargers and assesses the impact of turbocharger angle on the tightness of the seal.

Oil lubrication film plays an important role in analysis of dynamic behavior of the internal gear motors and pumps. During operation, the oil film is considered as the spring and damping system. Therefore, calculation of the dynamic stiffness and damping coefficients is necessary to build the mathematical model for studying of dynamic problem. In order to calculate these coefficients, the dynamic pressure and perturbing pressure distribution must be determined firstly. In this paper, the infinitesimal perturbation method (IFP) is used to calculate the dynamic pressure distribution. Based on that the dynamic stiffness and damping coefficients can be computed. The calculation results point out that the dynamic stiffness and damping coefficients are much dependent on the eccentricity ratio.