Experimental Observation of Non-Ideal Nozzle Flow of Siloxane Vapor MDM

The first experimental results from the Test-Rig for Organic Vapors (TROVA) at Politecnico di Milano are reported. The facility implements an Organic Rankine Cycle (ORC) where the expansion process takes place within a straight axis convergent-divergent nozzle, which is the simplest geometry representative of an ORC turbine blade passage. In order to reduce the required input thermal power, a batch operating mode was selected for the plant. Experimental runs with air allowed to verify the throttling valve operation and the measurement techniques, which include total pressure and temperature measurements in the settling chamber, static pressure measurements along the nozzle axis. A double-passage Schlieren technique is used to visualize the flow field in the nozzle throat and divergent section and to determine the position of shock waves within the flow field. The first experimental observation of non-ideal nozzle flows are presented for the expansion of siloxane fluid MDM (C8H24O2Si3, octamethyltrisiloxane) for vapor expansion in the close proximity of the liquid-vapor saturation curve, at relatively low pressure of operation. A supersonic flow is attained within the divergent section of the nozzle, as demonstrated by the observation of an oblique shock wave at the throat section, where a 0.1 mm recessed step is located. Schlieren visualizations are limited by the occurrence of condensation along the mirror side of the nozzle. Pressure measurements are compatible with the observed flow field

Cooperative Localization Enhancement through GNSS Raw Data in Vehicular Networks

The evolution and integration of communication networks and positioning technologies are evolving at a fast pace in the framework of vehicular systems. The mutual dependency of such two capabilities can enable several new cooperative paradigms, whose adoption is however slowed down by the lack of suitable open protocols, especially related to the positioning and navigation domain. In light of this, the paper introduces a novel vehicular message type, namely the Cooperative Enhancement Message (CEM), and an associated open protocol to enable the sharing of Global Navigation Satellite Systems (GNSS) raw measurements among connected vehicles. The proposed CEM aims at extending existent approaches such as Cooperative Awareness Messages (CAM) and Collective Perception Messages (CPM) by complementing their paradigms with a cooperative enhancement of the localization accuracy, precision, and integrity proposed by state-of-the-art solutions. Besides the definition of CEMs and a related protocol, a validation of the approach is proposed through a novel simulation framework. A preliminary analysis of the network performance is presented in the case where CEM and CAM transmissions coexist and are concurrently used to support cooperative vehicle applications

Experimental observation of non-ideal expanding flows of Siloxane MDM vapor for ORC applications

Abstract Extensive experimental results characterizing the supersonic expansion of an organic vapor in non-ideal conditions are reported in this paper for the first time. The collected data also allowed the assessment of the accuracy of Computational Fluid Dynamic (CFD) tools employed to predict the non-ideal behavior of such flows, including the consistency of thermodynamic models adopted. The investigation has been carried out on the converging-diverging nozzle test section of the Test Rig for Organic VApors (TROVA), at the Laboratory of Compressible fluid-dynamics for Renewable Energy Application (CREA) of Politecnico di Milano. Supersonic nozzle flow was chosen as the simplest one of significance for organic Rankine cycle (ORC) turbine channels. The working fluid under scrutiny is Siloxane MDM, a widely employed compound for high temperature ORCs. MDM vapor expands through the TROVA nozzle at moderate non-ideal conditions in the close proximity of the vapor saturation curve. This is the region where ORC expanders typically operate, thus proving the relevance of the investigation for the ORC community. Indeed, detailed experimental data representative of typical ORC expansions were lacking in the open literature up to date. Two different nozzle geometries, featuring exit Mach number of 2.0 and 1.5 respectively, were tested, exploring a wide range of thermodynamic inlet conditions and diverse levels of non-ideality, from moderate non-ideal state, indicated by a compressibility factor Z = Pv/RT ≃ 0.80, to dilute gas conditions, Z ≥ 0.97. Maximum operating total pressure and temperature are Pt ≃ 5 bar and T T ≃ 250 °C. The nozzle flow is characterized in terms of total pressure, total temperature, static pressure at discrete locations along the nozzle axis, and schlieren imaging. In contrast to the well known case of polytropic ideal gas, the vapor expansion through the nozzle is found to be dependent on the inlet conditions, thus proving the non-ideal character of the flow. This influence is found to be consistent with the one predicted by the quasi-1D theory coupled with simple non-ideal gas models. Experimental data at the nozzle centerline are compared with those resulting from a two-dimensional viscous CFD calculation carried out using the SU2 software suite and the improved Peng Robinson Stryjek Vera (iPRSV) thermodynamic model. A very good accordance is found, demonstrating the high accuracy of the applied tools

The LuGRE project: a scientific opportunity to study GNSS signals at the Moon

The Lunar GNSS Receiver Experiment (LuGRE) is a joint NASA-Italian Space Agency (ASI) payload on the Firefly Blue Ghost Mission 1 with the goal to demonstrate GNSS-based positioning, navigation, and timing at the Moon. When launched, LuGRE will collect GPS and Galileo measurements in transit between Earth and the Moon, in lunar orbit, and on the lunar surface, and will conduct onboard and ground-based navigation experiments using the collected data. These investigations will be based on the observation of the data collected by a custom development performed by the company Qascom, based on the Qascom QN400-Space GNSS receiver. The receiver is able to provide, PVT solutions, the GNSS raw observables obtained by the real time operation, as well as snapshots of IF digital samples collected by the RF front-end at frequencies L1/E1 and L5/E5. These data will be the input for the different science investigations, that require then the development of proper analysis tools that will be the core of the ground segment during the mission. The current work done by the science team of NASA and ASI, which is supported by a research team at Politecnico di Torino, is planning the data acquisitions during the time windows dedicated to the LuGRE payload in the checkout, transit and surface mission phases

Four-year clinical outcome following randomised use of zotarolimus-eluting stents versus everolimus-eluting stents in all-comers: Insights from the DUTCH PEERS trial

Background: The DUTCH PEERS (TWENTE II) trial (clinicaltrials.gov NCT01331707) is a randomised, multicenter, single-blinded, investigator initiated all-comers trial. All coronary syndromes were permitted with no limit for lesion length, reference size, or number of lesions or diseased vessels to be treated. In total, 1811 patients were 1:1 randomised to cobalt chromium-based zotarolimuseluting stents (ZES) versus platinum chromium-based everolimus-eluting stents (EES). These durable polymer-based drug-eluting stents (DES) were developed to facilitate device deliverability and to improve stent apposition to the vessel wall. Purpose: We assessed the 4-year clinical outcome of the DUTCH PEERS trial in terms of safety and efficacy. Methods: Clinical outcome was assessed by means of follow-up data of the trial participants. The primary endpoint target vessel failure (TVF) is a composite of cardiac death, target vessel-related myocardial infarction (MI) or target vessel revascularization. Secondary endpoints included the individual components of the TVF and the incidence of definite-or-probable stent thrombosis. Endpoints were analyzed by the logrank test by comparing the time to the endpoint, using the Kaplan-Meier method. Independent contract research organizations performed the study monitoring and clinical event adjudication. Results: The 4-year clinical follow-up data were available in 1802 patients (99.5%; 4 patients were lost to follow-up and 5 withdrew consent). The ZES and EES groups showed favourable outcomes with a similar incidence of TVF (12.1% vs. 12.1%; Logrank p=0.95). The rates of the individual components of TVF were also similar for both stent arms: cardiac death (3.9% vs. 3.7%; Logrank p=0.78); target vessel-related MI (3.2% vs. 2.5%; Logrank p=0.38); and target vessel revascularization (6.8% vs. 7.5%; Logrank p=0.55), respectively. In addition, the incidence of definite-or-probable stent thrombosis was similar for patients treated with ZES versus EES (1.5% vs. 1.2%; Logrank p=0.67). Conclusion: At 4-year follow-up, ZES and EES showed similar and sustained results in terms of safety and efficacy for treating all-comer patients

High Bleeding Risk Patients Treated with Very Thin-Strut Biodegradable Polymer or Thin-Strut Durable Polymer Drug-Eluting Stents in the BIO-RESORT Trial

Purpose: Patients with high bleeding risk (HBR) who undergo percutaneous coronary intervention also have an increased risk of ischemic events and represent an overall high-risk population. The coating of durable polymer drug-eluting stents (DP-DES) may induce inflammation and delay arterial healing, which might be reduced by novel biodegradable polymer DES (BP-DES). We aimed to evaluate the safety and efficacy of treating HBR patients with very thin-strut BP-DES versus thin-strut DP-DES. Methods: Participants in BIO-RESORT (NCT01674803), an investigator-initiated multicenter, randomized all-comers trial, were treated with very thin-strut BP-DES (Synergy or Orsiro) or thin-strut DP-DES (Resolute Integrity). For the present analysis, patients were classified following HBR criteria based on previous trials. The primary endpoint was target vessel failure: a composite of cardiac death, target vessel-related myocardial infarction, or target vessel revascularization at 1 year. Results: Of all 3514 patients, 1009 (28.7%) had HBR. HBR patients were older (p < 0.001) and had more co-morbidities than non-HBR patients (p < 0.001). At 1-year follow-up, HBR patients had significantly higher rates of target vessel failure (6.7 vs. 4.2%, p = 0.003), cardiac death (1.9 vs. 0.4%, p < 0.001), and major bleeding (3.3 vs. 1.5%, p = 0.001). Of all 1009 HBR patients, 673 (66.7%) received BP-DES and 336 (33.3%) had DP-DES. The primary endpoint was met by 43/673 (6.5%) patients treated with BP-DES and 24/336 (7.3%) treated with DP-DES (HR 0.88 [95%CI 0.54–1.46], p = 0.63). There were no significant between-group differences in the most global patient-oriented clinical endpoint (9.7 vs. 10.5%, HR 0.92 [95%CI 0.61–1.39], p = 0.69) and other secondary endpoints. Conclusions: At 1-year follow-up, very thin-strut BP-DES showed similar safety and efficacy for treating HBR patients as thin-strut DP-DES