Search

The present work features post-processing methods applied to vibro-acoustic data acquired from a T100 micro gas turbine (mGT) plant coupled with different volume interposed plenums. Such experimental campaign was conducted by relying on a test bench developed at the University of Genoa for hybrid systems emulation. Nonetheless, the obtained results can be generalized to all advanced cycles in which a mGT is coupled with further external elements which cause an increase of plant overall volume size. Since in this case a 100 kW mGT was employed, the interposed vessel was placed between heat recovery system outlet and combustor inlet, such as in common cases relevant to small size plants. Post-processing techniques carried out on acoustic and vibrational measurements can make available innovative diagnostic tools and predictive solutions by relying on appropriate instability indicators which are defined basing only on microphone and accelerometer experimental data. The main results presented in this work are relevant to rotating stall and incipient surge proper identification. Such investigation has been performed to increase the knowledge about such dangerous compressor working conditions; indeed, energy systems characterized by significant interposed volumes coupled with centrifugal compressors feature issues relevant to structural damaging due to surge and rotating stall.

Tesla bladeless expanders are promising in energy harvesting and small-scale power generation applications due to their lower cost and simplicity in design. Although such expanders exhibit very high rotor efficiency (analytical total to static efficiency ~ 90%), it shows poor performance when coupled with a stator (experimental total to static efficiency ~30%) due to losses present in the stator and stator-rotor interaction. This paper presents the design and experiment of a novel, high-efficient Tesla bladeless expander concept. The concept arises from the loss phenomena in the stator-rotor interaction in conventional bladeless expanders, which are among the main causes of the low performance. This concept is believed to bring the bladeless expanders to the same performances as the traditional ones with vanes, compared to which however the bladeless machines boast greater simplicity, robustness, and the absence of performance decay as the size decreases, competing even in the contexts for traditional turbomachinery. The high-efficient bladeless expander prototype with water as a working fluid is designed and developed, representing the similitude case for a liquid butane heat pump. The available isentropic power across the throttling process in the butane case is 3.3 kW @10000 rpm. The turbine consists of 24 nozzles and 150 disks separated by 0.1 mm spacers. The turbine shaft is connected to the high-speed electric generator. The performance test on the expander is carried out at rotational speeds ranging from 3000 rpm to 6200 rpm and with differential pressure across the expander up to 14 bar. Experimental ventilation loss is characterised and its effect on the performance of the expander is discussed. The preliminary results of the expander under investigation showed satisfactory production of power with an acceptable efficiency range. It is also shown that the present concept is promising and able to address the major i.e., stator-rotor interaction which is the major source of loss in the traditional bladeless expander.

High-speed centrifugal compressors are commonly exploited to pressurize fuel cell-based hybrid energy systems. In such complex plants, because of significant interposed volumes due to fuel cells, dynamic compressor response can induce severe vibrations caused by low mass flow rates instability. In particular, surge strongly limits centrifugal compressors stable working region when moving towards low mass flow rate due to a change in system operating point. Consequently, a complete system identification is performed in order to adequately characterize compressor dynamic response for early surge detection. To this goal, a tailored experimental activity has been carried out at the Thermochemical Power Group of the University of Genoa on a vaneless diffuser compressor turbocharger used for the pressurization of an innovative solid oxide fuel cell (SOFC) emulator plant. Several post-processing methods have been performed on system vibro-acoustic responses to better predict and classify compressor status as stable or unstable. The obtained results provide original diagnostic insights for monitoring systems capable of preventing surge and other low mass flow unstable phenomena, such as rotating stall cells inception. Low mass flow rate fluid-dynamic instabilities prevention can extend compressor operating range, performance, and reliability to allow better integration with other plant components.

It is well known that bladeless or Tesla turbomachinery, which was invented by Nikola Tesla in 1913, has several distinct features, such as reversibility of operation, which includes expander as well as compressor operation, just by reversing the rotational speed, provided that the statoric channels are purposely designed. Despite their potential application to a variety of fields, such as energy harvesting, automotive, light aircraft, and food processing, especially for low volumetric flows, Tesla machines have not found yet a specific market niche. In fact, at small size, it is estimated that the Tesla machinery does not change performance significantly, while conventional bladed machines are subject to significant efficiency reduction because of mechanical tolerances, thus matching the Tesla relatively low performance. Therefore, Tesla machines can become the fluid machinery of choice for small-size applications, thanks to their competitive performance at that size, simple construction, and reversible operation. A key objective of this paper is to numerically study Tesla devices in both expander and compressor modes with air as the working fluid. As a consequence of the high losses due to rotor and stator interactions, statorless (volute) configurations are investigated here, showing superior performance in both direct and indirect modes of operation. With reference to a laboratory prototype under construction, this paper presents the numerical design results, which predict the peak isentropic efficiencies of 63.5% and 57.5%, for the expander and compressor mode of operation, respectively. Actual prototype is expected to match those performance, apart from leakage and ventilation losses, not included in the numerical analysis.

The aim of this work is to describe the design of an innovative test rig for investigating the expansion of saturated fluids in the two-phase region. The experimental test rig was thought up and built by TPG of the University of Genoa. It will be equipped by probes and some optical accesses that permit high speed video recording and laser measurements. It will be useful for the study of the quality ratio, vapour and liquid droplet thermodynamic properties and their speed.

Technology is not good or bad, neither humanizing or dehumanizing per se: what truly qualifies its meaning and impact is defined by designers and users, and by their complex interaction, thereby showing how this matter assumes deep ethical implications. The following pages assume as a premise that the purpose and the way technological tools are designed highly determines how they interact, impact and affect human users. This is remarkable in the context of a publication aimed at critically reflecting on the ethical and legal implications of the Metaverse, whose pervasive and immersive character will likely play a strong role in shaping people's lives already in the near future. After some philosophical considerations on the problematic relationship between human beings and the technique, my reflections will briefly focus on some ways in which technology may result in creating or enhancing discriminations between and among human beings, thereby negatively impacting their lives and relationships. From this conceptual platform, I will seek to show that a restorative and mediative approach can offer important conceptual and ethical standpoints for legal designers and technology developers in order to design digital technology around users, their interests and their needs rather than imposing such tools «on», or «notwithstanding», them. My final aim is to underline how this approach matches a "critical openness" towards technological innovations with the issue of ethically safeguarding the protection of their human users, without missing the point of facilitating users in their ability of consciously and successfully accessing the potentials offered by the digital world. [ABSTRACT FROM AUTHOR]