Mobility and Vehicle Mechanics

19-29

Authors: ejanu Marcel , Popa Dinel, Dascălu Traian, Tabacu Ion, Pârlac Sebastian

The experimental bench has in its composure a laser equipment, a high speed recording video equipment, a measuring system for recording pressure variations and a static enclosure in which experiments are conducted. The recording of images was done using the shadowgraph technique, a source of light with xenon and a 3000 frames/s high speed camera with a resolution of 512x512 pixels. There were recorded and analyzed the next phenomenon: the variation of the flame front depending on the initial pressure, the variation of the pressure from inside the chamber depending on the initial pressure and also the shape and the way of how the flame front is propagated. The results are presented under the form of images and diagrams.

43-63

Authors: Dobrivoje Ninković, Dragan Taranović, Saša Milojević, Radivoje Pešić

Thermodynamic performance (delivery rate and power intake) and reliability of reciprocating compressors are dependent upon the valves. Since the valves open and close automatically, there is a high degree of coupling between the gas flow through the valve and the sealing element dynamics; a mismatch between the two leads inevitably to degradation of the compressor performance and/or short valve life. The latter is due to impact forces between the sealing element and other parts of the valve assembly. Therefore, matching the valves to the compressor application at hand is a complex task that calls for the use of the corresponding simulation models. Surveyed in the paper are mathematical models for the prediction of the valve performance, consisting of the sub models describing compressible gas flow through the valves, sealing element dynamics, and the interaction of the latter with the flow. Flow models based on the discharge coefficient are intrinsically not able to predict the critical flow regime with sufficient accuracy, requiring thus experimental data that are not always available. It is also suggested that other loss calculation approaches, such as the stagnation pressure loss model, should be investigated as possible alternatives to the discharge coefficient concept.