Proceedings of the Institution of Mechanical Engineers,Part E: Journal of Process Mechanical Engineering

This paper explores some future opportunities in refrigeration for compressor designers and manufacturers. Some of the most interesting concepts are in expanders and, in particular, how to integrate them into systems, how to target suitable applications and how to convince non-technicians that this is necessary and worthwhile. In some cases, the compressor may hold the key to a problem experienced in another part of the system; at other times, the solution to a compressor design challenge may be found by making changes elsewhere.

In industrial contexts, electrical energy for compressed air represents an important share of the global electricity consumption: this figure accounts for 4–5% of the total. Among the existing compressor technologies, rotary volumetric machines proved to be more suitable than other types (dynamic, reciprocating, etc.) in terms of pressure and flow rate delivered. Even though not as widespread as screw machines, but thanks to the technological improvements made in the last two decades, sliding vane rotary compressors are characterized by premium specific energy consumptions and demonstrate an unforeseen potential in terms of energy saving due to some intrinsic features specifically related to these machines. The current research focuses on an innovative oil injection technology that is not only able to fulfill the sealing and lubrication requirements but also to cool the air during the compression phase. A comparison between the mathematical model of the new oil injection technology and the experimental p-V diagrams measured through a set of piezoelectric transducers is shown. The compression work reduction, predicted in the model and further measured at the shaft and observed in the indicator diagrams, gives a strong consistency to the injection technology.

This work focuses on high-speed visualization of the three reed valves in a scroll compressor. The visualization was performed to obtain qualitative description of the oil flow in terms of morphology and breakup and to quantify the droplet size and velocity distribution functions both for startup and cyclic operation conditions. It was observed that at startup, part of the oil film between the valve and its seat is first pushed out before the valve can start moving, after that the valve starts opening and the film is stretched so that liquid columns in organized spacing appear and are blown out by the gas originating the droplets that form a mist. During steady operation of the compressor, no oil film breakup was clearly observed at the valve–seat interface, suggesting that the oil droplets might be generated from vapor shear through the orifice since there is a recess that can hold up oil inside the orifice.

This work is devoted to the heat exchange study on rotary compressors, with external (Roots type) and internal compression, that are in demand in industries. The paper describes the implemented methods for measuring time-varying temperatures of gas and walls of the working chamber of the rotary compressors, which are investigated in conditions of the rotors motion. Results of the experiments conducted are presented. Influence of heat exchange on characteristics of rotary compressors by means of a method of mathematical simulation is established.

Rotary compressors are widely used due to their reliability, ease in operation, relative simplicity in design and high efficiency. In the present article, a method has been proposed for the analysis of the rotors’ meshing conditions in the rotary machines without rotor timing gears, taking into account the actual profile clearances. Employment of the results obtained will help to analyze and improve the rotor profiles and further to optimize the algorithm of underrating, thus improving operational characteristics of newly developed compressors.

This study presents the aerodynamic behaviours of a twin-entry radial inflow turbine under steady and transient conditions. The influence of the volute tongue is depicted by a low momentum wake propagating toward the rotor entry, but its effect does not extend beyond a circumferential position of 60°, and more total pressure loss is revealed with respect to the hub side. The transient simulations carried out at different operating conditions and Fast Fourier Transform analysis of static pressure fluctuations induced by the components’ interactions have revealed a space-time periodic behaviour which has been described by a double Fourier decomposition. The flow simulations considering the two sides subject to both non-pulsatile and pulsatile flows conditions have revealed the existing rotor and tongue potential effects and interaction effects the rotor and volute, in addition to the circumferential and spanwise flow non-uniformities at the volute exit, which are more accentuated with a pulsatile flow at inlet. The results of Fast Fourier Transform analysis of temporal pressure fluctuations at the inter-space depict an unsteady behaviour related to the pulsatile frequencies which are characterised by high amplitudes. On the other hand, the spatial pressure fluctuations for the non-pulsatile and pulsatile flows conditions seem to have the same dominant modes since Fast Fourier Transform analysis was carried out at a fixed instant.