Investigation of micro gas turbine system configurations for compact lightweight applications based on reversible bladeless Tesla machinery

Globally, the demand for low-emission, cost-effective, low-noise, lightweight and compact devices is rapidly increasing. In order to meet such market demands on a small scale, microgas turbines (MGTs) could play a crucial role. However, there are many challenges with MGT compatibility with internal combustion engines (e.g., low efficiency, fuel flexibility, light weight-compactness). As part of this study, the focus is on the component basis, where the study examines the Tesla or bladeless turbomachinery in both a compressor and expander configuration. Since little data is available on Tesla compressors/pumps, this study focuses primarily on the bladeless compressor, which is also analyzed as an expander due to its reversibility. The activity started from a 3-kW air Tesla expander prototype available at the University of Genoa. It is examined in compressor mode using a 3D CFD approach and its results are compared to experimental results. The CFD and experiments show good agreement for the pressure, with an error of less than 3% at zero flow condition. Despite the CFD analysis predicting a static efficiency of around 42% (without losses), the experiment did not meet that prediction due to significant leakage flows and other losses. Moreover, using LMS Test Lab software, the acoustic behavior of the Tesla compressor has been analyzed at different speeds and distances, and several aspects are compared with conventional or bladed technologies (same tip speed, same mass flow rate, and same pressure). It has been demonstrated that Tesla technologies are substantially quieter than bladed technologies. To improve Tesla compressor performance, a 3D numerical analysis has been carried out for the rotor only and coupled rotor-stator and volute configurations. The disk gap is optimized by relying on Ekman and Reynolds numbers. Based on the numerical analysis, the disk gap should be 3 times the thickness of the boundary layer with the best Reynolds number 9-11 and Ekman number 1.5-1.65. Moreover, numerical analysis has been performed for 2, 2.5, 3 and 4 diameter ratios in order to optimize the rotor diameter ratio. Higher diameter ratios indicate better performance than lower diameter ratios. Based on a CFD analysis, it has been predicted that at low mass flow rates, greater than 95 % efficiency can be achieved with the optimal disk gap and diameter ratio. In this case, the outlet flow angle would be around 89.9 degree, however, in practice, maintaining almost a tangential flow angle is difficult. In order to improve the performance of Tesla compressors, several stators have been studied. The stator outlet and inlet ratio between 2 and 4 is optimal for stator/diffuser performance. With an optimal rotor and eight stators, CFD analysis predicts a total stator efficiency of >53%; however, with a low number of stators, this efficiency will be somewhat improved. As part of an effort to enhance the performance of the Tesla compressor, a (stator-less) volute design has also been numerically analyzed, which shows better performance in terms of pressure ratio and efficiency than the stator configuration. Compared to a stator configuration, the total to static efficiency is estimated to increase by 3 to 5%. A new reversible Tesla prototype model has been developed using an optimized rotor (optimal disk gap and diameter ratio) and volute configuration for 22 krpm. CFD predicted total to static efficiency of 58% in compressor mode and 66% in expander mode without consideration of system losses. For this new reversible machine, leakage and end wall losses are also analyzed under a variety of conditions, including different end wall gaps and different exit radial clearances (with and without sealing systems). The implementation of the sealing system has resulted in a reduction in leakage, but the amount varies in accordance with the clearance of the radial exit. The end wall power loss varies with end wall gap, but usually ranges between 50 W-60 W for 22 krpm design speed, while power is around 600 W. During this dissertation writing, experimental work on a reversible bladeless machine is in progress. Preliminary results show the pressure ratio is 1.24 and the isentropic efficiency is 31%. Comparing these results with CFD simulations at closed valve conditions shows good agreement in terms of pressure ratio with < 3% error. It is observed that leakage occurs during the first test which passes through the narrow radial clearance of 0.3 mm. As a result of this preliminary investigation, some modifications have been made to the test-rig in order to ensure that good results are achieved with the least amount of leakage. An in-depth study of the reversible Tesla machine (compressor and expander) has shown that such technologies possess several attractive features (reversibility, low noise level, cost effective and operate with any kind of fluid), but are difficult to implement as Tesla envisioned (higher efficiency). Under ideal design conditions, however, such technologies could potentially achieve > 50% efficiency. The use of such technologies can be beneficial in areas where conventional technologies are not practical or less efficient

A software architecture for autonomous maintenance scheduling: Scenarios for UK and European Rail

A new era of automation in rail has begun offering developments in the operation and maintenance of industry standard systems. This article documents the development of an architecture and range of scenarios for an autonomous system for rail maintenance planning and scheduling. The Unified Modelling Language (UML) has been utilized to visualize and validate the design of the prototype. A model for information exchange between prototype components and related maintenance planning systems is proposed in this article. Putting forward an architecture and set of usage mode scenarios for the proposed system, this article outlines and validates a viable platform for autonomous planning and scheduling in rail

Variations in atmospheric Carbon Dioxide and its association with rainfall and vegetation over India

In this paper we have studied variability and growth rate of surface observed atmospheric Carbon Dioxide (CO2) concentrations over Cape Rama, west coast of India and its association with rainfall and vegetation over this region. Cape Rama is a maritime site which experiences a seasonal reversal wind pattern receiving air masses having marine (continental) signatures during summer (winter) monsoon season. This study reveals that summer monsoon (JJAS) precipitation and monthly values of atmospheric CO2 concentration during the season are well correlated. Negative correlations are seen with CO2 concentrations of concurrent months of the season as well as subsequent months. However the magnitudes of correlation coefficients are decreased till hot pre-monsoon season (MAM). Annual cycle and interannual variability show negative relationship between CO2 concentration and vegetation over the region. CO2 concentration shows increasing trend and NDVI shows decreasing trend. However, the magnitude of increasing trend of CO2 concentration is higher. Amplitude of decreasing phase of vegetation is higher than the amplitude of increasing phase. Though the results show certain link between CO2 and climate variability, further examination with dense and longer data may be needed to confirm the result

Electron transport in atomic-scale devices

Ph.DDOCTOR OF PHILOSOPH

Atmospheric CO2 source and sink patterns over the Indian region

In this paper we examine CO2 emission hot spots and sink regions over India as identified from global model simulations during the period 2000–2009. CO2 emission hot spots overlap with locations of densely clustered thermal power plants, coal mines and other industrial and urban centres; CO2 sink regions coincide with the locations of dense forest. Fossil fuel CO2 emissions are compared with two bottom-up inventories: the Regional Emission inventories in ASia (REAS v1.11; 2000–2009) and the Emission Database for Global Atmospheric Research (EDGAR v4.2) (2000–2009). Estimated fossil fuel emissions over the hot spot region are  ∼  500–950 gC m−2 yr−1 as obtained from the global model simulation, EDGAR v4.2 and REAS v1.11 emission inventory. Simulated total fluxes show increasing trends, from 1.39 ± 1.01 % yr−1 (19.8 ± 1.9 TgC yr−1) to 6.7 ± 0.54 % yr−1 (97 ± 12 TgC yr−1) over the hot spot regions and decreasing trends of −0.95 ± 1.51 % yr−1 (−1 ± 2 TgC yr−1) to −5.7 ± 2.89 % yr−1 (−2.3 ± 2 TgC yr−1) over the sink regions. Model-simulated terrestrial ecosystem fluxes show decreasing trends (increasing CO2 uptake) over the sink regions. Decreasing trends in terrestrial ecosystem fluxes imply that forest cover is increasing, which is consistent with India State of Forest Report (2009). Fossil fuel emissions show statistically significant increasing trends in all the data sets considered in this study. Estimated trend in simulated total fluxes over the Indian region is  ∼  4.72 ± 2.25 % yr−1 (25.6 TgC yr−1) which is slightly higher than global growth rate  ∼  3.1 % yr−1 during 2000–2010

A questionnaire-based comparison of conventional teaching methods to computer assisted learning in experimental pharmacology for undergraduate medical students

Background: Computer Assisted Learning (CAL) for teaching experimental pharmacology is now widely accepted as alternative to animal experiments. The objective of this study was to compare the performance of undergraduate medical students by conventional teaching methods (lecture and discussion) and CAL.Methods: This was a questionnaire based observational study involving 109 MBBS students of fifth semester. The students were taught experimental pharmacology practical by both conventional methods (lecture with discussion) and computer assisted learning (CAL). Questionnaire and their filled responses by these students were taken at the end of lecture-discussion (pre-CAL) and after the CAL experiments (post-CAL), covering the same topics of experimental pharmacology. Pre-CAL and post-CAL data were assessed statistically.Results: In the pre-CAL session, only 53.39%, 47.56%, 53.39% and 49.5% of the students were having the scores above 40% in the rabbit eye, DRC and potentiation, frog heart and dog BP experiment respectively, which was increased to 77.44%, 75.48%, 75.47% and 75.48% of the students respectively in the post-CAL assessment. A statistically significant difference (p <0.05) in the performance was observed among the students in the pre-CAL and post-CAL assessment.Conclusions: CAL is a good alternative to animal experimentation. Lecture with discussion, followed by CAL experiments on the same topics, enhanced the performance of students as shown by improvement in post-CAL scores

Productivity improvement of a computer hardware supply chain.

Abstract Purpose -To determine the key reverse logistics variables, which the top management should focus so as to improve the productivity and performance of computer hardware supply chains. Design/methodology/approach -In this paper, an interpretive structural modeling (ISM) based approach has been employed to model the reverse logistics variables typically found in computer hardware supply chains. These variables have been categorized under &quot;enablers&quot; and &quot;results&quot;. The enablers are the variables that help boost the reverse logistics variables, while results variables are the outcome of good reverse logistics practices. Findings -A key finding of this modeling is that environmental concern is the primary cause of the initiation of reverse logistics practices in computer hardware supply chains. For better results, top management should focus on improving the high driving power enabler variables such as regulations, environmental concerns, top management commitment, recapturing value from used products, resource reduction, etc. Originality/value -In this research, an interpretation of reverse logistics variables in terms of their driving and dependence powers has been carried out. Those variables possessing higher driving power in the ISM need to be taken care on a priority basis because there are a few other dependent variables being affected by them. Variables emerging with high dependence contribute to productivity and performance of green supply chain

Temperature measurement of cold atoms using transient absorption of a resonant probe through an optical nanofibre

Optical nanofibres are ultrathin optical fibres with a waist diameter typically less than the wavelength of light being guided through them. Cold atoms can couple to the evanescent field of the nanofibre-guided modes and such systems are emerging as promising technologies for the development of atom-photon hybrid quantum devices. Atoms within the evanescent field region of an optical nanofibre can be probed by sending near or on-resonant light through the fibre; however, the probe light can detrimentally affect the properties of the atoms. In this paper, we report on the modification of the local temperature of laser-cooled 87Rb atoms in a magneto-optical trap centred around an optical nanofibre when near-resonant probe light propagates through it. A transient absorption technique has been used to measure the temperature of the affected atoms and temperature variations from 160 μk to 850 μk, for a probe power ranging from 0 to 50 nW, have been observed. This effect could have implications in relation to using optical nanofibres for probing and manipulating cold or ultracold atoms

FORMULATION AND CHARACTERIZATION OF FLOATING TABLET DOSAGE FORM OF DUAL DELIVERY OF DRUG CURCUMIN AND BERBERINE HYDROCHLORIDE USING SIMULTANEOUS ESTIMATION BY UV SPECTROSCOPY

Objective: The present study was aimed to develop a combinational floating tablet of curcumin and berberine HCl utilizing synthetic polymers synthetic HPMC K-15M and evaluate its various characteristics. Methods: The formulations were developed by the process of wet granulation and evaluated for drug content, content uniformity, floating lag time, total floating time, in vitro buoyancy studies, and in vitro drug release profile. A simultaneous estimation method for curcumin and berberine was developed using U. V spectroscopy. Results: The results clearly indicated that the tablets produced were having acceptable physical parameters. The absence of any drug/polymer/excipient interactions was confirmed using infrared spectroscopy. It was found that the drug content of was in between 96.22 to 99.45 % in all the formulations. Because of their low densities, in vitro floatability tests showed that most of the tablets floated for more than 8 h. The in vitro release studies confirmed the sustained release of more than 80 percent of drug contained within a period of 8 h. In vitro buoyancy was good in all three batches (F1-F3). The overall floating time for the F2 formulation was 24 h. After one month of storage at 40 °C and 75 percent RH, the F2 formulation showed no noticeable change in physical as well as pharmaceutical performance characteristics. Conclusion: Floating tablets of curcumin and berberine was successfully developed and had passed on various pharmaceutical parameters

Resource Allocation and Mode Selection in 5G Networks Based on Energy Efficient Game Theory Approach

With the advent of next-generation cellular networks, energy efficiency is becoming increasingly important. To tackle this issue, this paper investigates energy efficiency in D2D-enabled heterogeneous cellular networks. Boosting the longterm energy efficiency of wireless 5G communication networks is being explored through mode selection and resource allocation. The study proposed a three-stage process for energy-efficient mode selection and resource allocation. The process starts with cellular users who switch to D2D emitting a beacon and cellular users within close proximity reacting to it. A proposed auction mechanism will be enacted inside the group in the second state ( in this paper, the group size will be four). Next, each cellular user was classified according to SINR values, distance, and battery life, so that they could dynamically transition between standard cellular mode and D2D mode. For stage three, direct-hop hybrid D2D communication, we developed a TAMM double auction game model that efficiently splits resources. To identify the true bidders in our game model, we compute the median and mode values of the ASK and BID values received by both seller and buyer cellular users. A simulation study shows that the proposed method is energy-efficient in a heterogeneous network enabled by D2D