Primary Stream Research Articles

Experimental studies on a rectangular ejector with air

Experimental studies have been conducted to depict the flow patterns in a small rectangular ejector by using schlieren flow visualisation technique. A transparent ejector is designed, fabricated, and operated using air as working fluid. Geometry of the ejector is in form of two-dimensional extrusion with two suction inlets: one on top and other at bottom of the convergent-divergent nozzle. Ejector performance has been analysed by measuring the mass flow rates at primary and secondary inlets. The results of flow visualisation studies have been compared with those obtained using numerical computations. Variation of entrainment ratio with change in primary stream pressure has been presented. Moreover, the shock wave patterns in constant area mixing chamber and diffuser for set of inlet and outlet conditions have been visualised and presented.

Study of a full scale oxy-fuel cement rotary kiln

Oxy-fuel combustion has been shown to be an attractive technology to be implemented in cement production with CO2 capture from a process point of view. Due to the market situations and future perspectives it is necessary that the technology can be retrofitted into existing plants. As part of the H2020 EU project CEMCAP, the study presented here investigates the retrofitting of oxy-fuel combustion technology on a typical full-scale cement rotary kiln of 3000 ton/year clinker capacity. The flame generated by a commercial burner has been modelled by CFD with a seven steps combustion reaction model, the k-omega SST turbulence model, and the discrete ordinates radiation model with the Weighted Sum Grey Gas model. The burner is composed of an annular outlet where coal is fed and nozzles from which angled high velocity jets generate a swirling motion for flame stabilization and mixing purposes. As in all rotary cement kilns, a high temperature low velocity secondary oxidizer stream coming from the clinker cooler flows coaxially to the burner in the kiln for heat efficiency purposes. A flame developing in air has been used as a reference case and several oxy-fuel flames have been characterized and compared. The oxy-fuel inlet parameters that are varied in the study are the oxidizer composition and flow rates in both the primary and secondary streams. The work presented is part of an optimization procedure based on iterative interaction with the process modelling of the whole cement plant with full oxy-fuel capture (not presented in this article). With retrofit application in mind, the objective was to reproduce a heat radiation profile to the clinker equivalent to that obtained in the air reference case. The optimized oxy-fuel case is characterized by a primary burner oxidizer of lower flow rate, but with higher oxygen concentration of up to 52.1% to generate the necessary heat in the near burner region.

Experimental investigation of jet noise from a high BPR dual-stream jet in a static model-scale test

The noise characteristics of a dual-stream jet of bypass ratios greater than 10 were investigated in response to area ratio, nozzle-operating conditions, installation effect, and chevron effect. The key conclusions were as follows. (1) The area ratio impacted the noise by up to 3 dB at aft angles and at mid-frequency for heated conditions. (2) The spectral variation due to the change of primary stream parameters was constant at low Strouhal numbers and diminished at high Strouhal numbers. (3) The impact of the secondary stream pressure was described by the scaling law of single-stream jets for unheated conditions. The flow parameters of other jets were required to describe the spectra of Strouhal numbers between 0.2 and 2.0, based on the secondary jet for heated conditions. (4) The installed jet noise was quantified for various wing configurations and was more pronounced at forward angles. (5) The chevron nozzle reduced overall noise by up to 4 dB, though it became less attractive when installed. The quantified information is expected to improve the estimation of noise from a dual-stream jet of high bypass ratios.

The impact of country image and destination image on US tourists’ travel intention

Abstract Over the past decades there has been a sustained interest in country image and destination image constructs in two primary streams of literature, including international marketing and tourism. However, limited research in tourism has investigated the differences and interaction between these two constructs and their impacts on intention to visit. The current study addresses this gap by developing and testing a theoretical model that examines the relationships among the country and destination image of Cuba, a country that has continuous political conflicts with the US, and Americans’ intention to visit Cuba as a tourism destination. In addition, the moderating role of destination familiarity on the proposed relationships is examined. Structural equation modeling (SEM) is utilized to test the proposed model using data collected from 353 US residents. The results demonstrate that country image has a positive impact on destination image, and both country image and destination image positively influence intention to visit. A significant moderating effect of destination familiarity is also found on the relationships between country image and destination image, and destination image and intention to visit. This research provides valuable theoretical and practical implications for academics and practitioners in the field of destination marketing and management.

Influence on CO and PM Emissions of an Innovative Burner Pot for Pellet Stoves: An Experimental Study

In this study, an extensive set of experiments has been performed to investigate how the emissions of carbon monoxide (CO) and particulate matter (PM) from wood pellet combustion are correlated with the different layout of air inlets in the two burner pots of pellet stoves. In particular, emissions generated using a “traditional” burner pot are compared with those produced with an innovative one. Tests were carried out on four pellet stoves (8–11 kW burning power). Tests show that CO emissions can be reduced close to zero using the innovative burner pot. PM emissions are also reduced, but not as much as those of CO. This phenomenon is explained assuming that CO reduction implies a reduction of the organic part of PM, but not of the inorganic matter. Experiments also show an apparent dependence of PM release on the time from ignition for both burner pot models: PM emissions increase and the color of PM deposited on filters varies over a wide range. It is argued that this effect is due to ash accumulation on the bottom of the burner pot and to its interaction with the primary air stream that flows over it.

Phantasying, How to Get Out of Oneself and Yet to Remain Within

Assuming the importance of Alfred Schutz’s “protosociology” in social theory as a given, the paper tries to explore its philosophical core, treating Schutz’s sociophenomenology as an answer to the most fundamental questions of phenomenology, such as evidence and phenomenological reduction. It analyses Schutz’s point of departure – the problematization of Max Weber’s concept of the meaning of social action and its deepening by means of Henri Bergson’s and Edmund Husserl’s notion of time – and tries to unravel the double structure of consciousness (first in Brentano and Husserl, then in Schutz), revealing increasingly its complex temporal character. Brentano’s and Husserl’s double intentionality, seeming to offer a kind of “decent realism” in modern philosophical context, in Schutz turns out to be marked by the profound pastness of reflexive consciousness, reaching the primary stream experience only by means of primary and secondary acts of remembrance, re-effectuated intersubjectively in acts of phantasying about future (modo futuri exacti), thus constituting the very core of meaning, with its reference to external objects. It appears that only analysing this mode of phantasying in reference to its motives that we can solve the conundrum of realism in its modern shape.

High recovered pressure gain generator assembly in deuterium fluoride lasers

The gain generator assembly is the core component which influences the recovered pressure of high energy deuterium fluoride(DF) chemical laser. The recovered pressure of DF laser exhaust gas using traditional gain generator assembly is about 6.7 kPa. A compact type of TRIP gain generator assembly was designed, with breakthroughs on the key techniques of running with high cavity pressure, primary stream curtain and restraining regurgitant stream of the laser cavity boundary wall. The recovered pressure of the DF laser was increased obviously. The test results show that the recovered pressure of the laser exhaust gas and the power flux were both increased effectively with the increase of the mass flow rate in the range of 1.3~3.3 gs-1cm-2. When the mass flow rate was 3.3 gs-1cm-2, the DF laser could operate efficiently at 26.7 kPa background pressure (air pressure of 10 km altitude).

Bryolithochemical studies in the search for and evaluation of gold-silver mineralization based on stream sediments (northeastern Russia)

The first bryolithochemical studies have been carried out within the Dukat ore field (Balygychan-Sugoi trough, northeastern Russia), in its northeast (Dukat Au-Ag deposit, Chaika site) and on its eastern flank (Au-Ag ore occurrence, Piritovyi site). Sampling was made along primary water streams draining Au-Ag ore zones, because the headstreams localized in the permafrost zone are poor in alluvial sediments or lack them, whereas the stream banks and beds are overgrown with aquatic and semiaquatic mosses. We examined samples of moss cushions with loose sediments (fine silt suspension and sand-silt material). The study has shown that moss cushions are an effective natural trap extracting finely dispersed, ultradisperse, and colloid-dispersed particles, including ore ones, from water stream suspension. The contents of major elements indicating Au-Ag mineralization (Au, Ag, Hg, Sb, As, Pb, and Zn) in the bryolithochemical and lithochemical samples were compared. The highest contents of these elements have been revealed in the bryolithochemical samples. Scintillation analysis shows a predominance of finely dispersed Au and Ag particles. The chemical composition of lithoparticles and probable species of elements indicating mineralization were studied by energy-dispersive X-ray microanalysis. It has been concluded that the bryolithochemical stream sediments are an integral part of the lithochemical ones and can also be effectively used to reveal geochemical anomalies and identify the corresponding ores. It is shown that the bryolithochemical sediment streams bear important information about the chemical composition of primary ores, as they have the same major indicator elements (Au, Ag, Hg, Sb, As, Pb, and Zn) and nearly the same mineral composition (finely dispersed gold and silver, electrum, silver sulfosalts, and simple sulfides). The proposed bryolithochemical research is promising not only for northeastern Russia but also for other areas with similar landscapes, primarily areas where lithochemical and bryolithochemical stream sediments form in the northern subarctic and arctic environments.

The human factor in supply chain forecasting: A systematic review

Demand forecasts are the lifeblood of supply chains. Academic literature and common industry practices indicate that demand forecasts are often subject to human interventions. Judgmental forecasting or judgmental forecast adjustments can cause both positive and negative repercussions to the rest of the supply chain. This paper provides the first systematic literature review of judgmental forecasting and adjustments focusing on key features that impact various decisions in supply chains. A carefully assembled and shortlisted literature pool is analyzed for systematic mapping of the published works using bibliometric tools. The primary sub streams of research within the broader scope of the field are synthesized from a rigorous keyword cluster analysis and a thorough discussion is presented. Our review concludes by encapsulating the key learnings from four decades of academic research in judgmental forecasting and suggests future research avenues to expand our understanding of the role of humans in demand forecasting and supply chain decision-making.

99Tc immobilization from off-gas waste streams using nickel-doped iron spinel.

Technetium-99 (99Tc) incorporation within stable spinel phases is a novel method for 99Tc removal and immobilization from waste streams. In this study, transformation of Ni-doped Fe(OH)2(s) to spinel minerals, e.g. trevorite (NiFe2O4), is explored as a method for removing 99Tc from Hanford Waste Treatment and Immobilization Plant (WTP) primary off-gas waste stream simulant. The Fe(OH)2(s) transformation process was found to reduce 99Tc(VII) to 99Tc(IV) and incorporate reduced Tc(VI) into the produced spinel simultaneously. Nickel doping was applied in the mineral transformation to inhibit potential reoxidation of 99Tc(IV). Solid phase characterization by XRD and XANES confirmed the formation of nickel substituted ferric-spinel, and suggest incorporation of 99Tc(IV) in the final spinel. Furthermore, in the primary off-gas stream, which contains both redox-sensitive contaminants Cr(VI) and 99Tc(VII), results from solution analysis and solid digestion indicate that nearly 100% Cr and over 80% 99Tc can be simultaneously removed by adding Fe(OH)2(s) to solution with a solid to solution ratio of 5 g/L under near neutral and alkaline conditions. The 99Tc removal approach developed herein provides an alternative treatment method to eliminate the proposed recycle process of the off-gas waste stream, which ultimately can reduce WTP mission cost and operation time.

On the Leakage, Torque, and Dynamic Force Coefficients of Air in Oil (Wet) Annular Seal: A Computational Fluid Dynamics Analysis Anchored to Test Data

Subsea pumps and compressors must withstand multiphase flows whose gas volume fraction (GVF) or liquid volume fraction (LVF) varies over a wide range. Gas or liquid content as a dispersed phase in the primary stream affects the leakage, drag torque, and dynamic forced performance of secondary flow components, namely seals, thus affecting the process efficiency and mechanical reliability of pumping/compressing systems, in particular during transient events with sudden changes in gas (or liquid) content. This paper, complementing a parallel experimental program, presents a computational fluid dynamics (CFD) analysis to predict the leakage, drag power, and dynamic force coefficients of a smooth surface, uniform clearance annular seal supplied with air in oil mixture whose inlet GVF varies discretely from 0.0 to 0.9, i.e., from a pure liquid stream to a nearly all-gas content mixture. The test seal has uniform radial clearance Cr = 0.203 mm, diameter D = 127 mm, and length L = 0.36 D. The tests were conducted with an inlet pressure/exit pressure ratio equal to 2.5 and a rotor surface speed of 23.3 m/s (3.5 krpm), similar to conditions in a pump neck wear ring seal. The CFD two-phase flow model, first to be anchored to test data, uses an Euler–Euler formulation and delivers information on the precise evolution of the GVF and the gas and liquid streams' velocity fields. Recreating the test data, the CFD seal mass leakage and drag power decrease steadily as the GVF increases. A multiple-frequency shaft whirl orbit method aids in the calculation of seal reaction force components, and from which dynamic force coefficients, frequency-dependent, follow. For operation with a pure liquid, the CFD results and test data produce a constant cross-coupled stiffness, damping, and added mass coefficients, while also verifying predictive formulas typical of a laminar flow. The injection of air in the oil stream, small or large in gas volume, immediately produces force coefficients that are frequency-dependent; in particular the direct dynamic stiffness which hardens with excitation frequency. The effect is most remarkable for small GVFs, as low as 0.2. The seal test direct damping and cross-coupled dynamic stiffness continuously drop with an increase in GVF. CFD predictions, along with results from a bulk-flow model (BFM), reproduce the test force coefficients with great fidelity. Incidentally, early engineering practice points out to air injection as a remedy to cure persistent (self-excited) vibration problems in vertical pumps, submersible and large size hydraulic. Presently, the model predictions, supported by the test data, demonstrate that even a small content of gas in the liquid stream significantly raises the seal direct stiffness, thus displacing the system critical speed away to safety. The sound speed of a gas in liquid mixture is a small fraction of those speeds for either the pure oil or the gas, hence amplifying the fluid compressibility that produces the stiffness hardening. The CFD model and a dedicated test rig, predictions and test data complementing each other, enable engineered seals for extreme applications.

Integrated Hydrological and Geophysical Characterisation of Surface and Subsurface Water Contamination at Abandoned Metal Mines

The mining and processing of metal ores in the UK has left a legacy of environmental degradation, and abandoned metal mines still pose a significant threat to terrestrial and fluvial environments. Flow gauging, water quality and geophysics were combined in an integrated assessment of surface and subsurface hydrological contamination at Esgair Mwyn, an abandoned mine in Ceredigion, Wales. Heavy metals discharged from the site are polluting downstream watercourses, leading to widespread Environmental Quality Standards (EQS) compliance failures. Through salt water dilution gauging and water quality sampling, a daily efflux of 876 g of heavy metals was calculated, with contaminant mobilisation occurring mainly in two primary surface streams draining an exposed tailings heap. Electrical resistivity tomography subsurface imaging found a seepage plane within the tailings lagoon wall, whilst the main tailings heap became increasingly saturated with depth. A large adjacent field also had a high potential to convey pollutants in solution, yet its morphological characteristics have limited transmission, as the area acts as a passive treatment type system. With remediation of already polluted water both difficult and expensive, this approach provides a cost-effective way to identify the origins and pathways of contaminants, informing mitigation strategies focussed on containment. Esgair Mwyn is not an isolated case, as abandoned metal mines release at least 860 t of heavy metals annually into UK water bodies. These techniques could reduce or prevent abandoned metal mine hydrological pollution for decades to come, and enable associated UK water bodies to comply with future water quality standards.

Analysis and Isolation of Potential Artemisinin Precursors from Waste Streams of Artemisia Annua Extraction.

High-performance liquid chromatography, liquid chromatography–mass spectrometry, and gas chromatography–mass spectrometry methods were developed to analyze the process waste streams of Artemisia Annua extraction. Results from these methods suggested that the final waste from the extraction process could serve as a source of dihydroartemisinic acid (DHAA) that could be converted to additional artemisinin. Two additional impurities were isolated and identified in the waste material as well as in A. annua leaf samples. That these impurities also appear as side-products in chemical transformations of DHAA to artemisinin supports the conclusion that the in vivo transformation proceeds as nonspecific oxidations. These impurities do not appear in isolated artemisinin. A simple, high-yielding procedure for recovery of DHAA from the primary waste stream was developed.

Improving competing voices segregation for hearing impaired listeners using a low-latency deep neural network algorithm.

Hearing aid users are challenged in listening situations with noise and especially speech-on-speech situations with two or more competing voices. Specifically, the task of attending to and segregating two competing voices is particularly hard, unlike for normal-hearing listeners, as shown in a small sub-experiment. In the main experiment, the competing voices benefit of a deep neural network (DNN) based stream segregation enhancement algorithm was tested on hearing-impaired listeners. A mixture of two voices was separated using a DNN and presented to the two ears as individual streams and tested for word score. Compared to the unseparated mixture, there was a 13%-point benefit from the separation, while attending to both voices. If only one output was selected as in a traditional target-masker scenario, a larger benefit of 37%-points was found. The results agreed well with objective metrics and show that for hearing-impaired listeners, DNNs have a large potential for improving stream segregation and speech intelligibility in difficult scenarios with two equally important targets without any prior selection of a primary target stream. An even higher benefit can be obtained if the user can select the preferred target via remote control.

Performance evaluation and parametric studies on variable nozzle ejector using R134A

Computational fluid dynamics of variable nozzle ejector has been studied to determine the optimum nozzle exit position for reliable ejector cooling cycle operations. The flow rates of primary and secondary stream were varied to obtain the optimum entrainment ratio under different ranges of operating conditions.The refrigerant R134a was chosen based on the merit of its environmental and performance characteristics, the refrigerant was chosen because currently is used widely in air conditioning system. It was found that the computational fluid dynamics showed that the optimum positioning of nozzle exit position, which was based on the parameters such as pressure inlet variation the temperature inlet. The results obtained after the optimization of the results showed that the optimum nozzle exit position was found at 3 mm from the mixing chamber inlet when the operating conditions pressure inlet, secondary pressure inlet, primary temperature inlet and outlet pressure were at (18bar,6bar,373K,and5.6bar) respectively. Similarly, the range of entrainment ratio was varied between 0.24−1.283 at a constant area ratio, and at varied operating conditions.

Pitot and static pressure measurement and CFD simulation of a co-flowing steam jet

Condensation in the primary nozzle of a steam ejector changes the steam jet properties during the nozzle expansion process and affects the mixing rate of the primary and secondary streams and thus the performance of steam ejectors. Only limited experimental data is available for the mixing of wet steam jets at conditions relevant to steam ejectors. The present work provides static and pitot pressure measurements within a wet supersonic steam jet which mixes with a low pressure co-flowing secondary stream. High pressure steam was delivered to the primary nozzle at a stagnation pressure and temperature of 270 kPa and 406 K, respectively. The primary nozzle throat diameter was 3.2 mm and its exit diameter was 13.6 mm. Pitot and static pressure measurements were obtained on the mixing jet centreline from the nozzle exit to a downstream location of 185 mm in the mixing chamber. Radial profiles of pitot and static pressure were also measured at positions of 5, 20, 35, 85, 135 and 185 mm downstream of the nozzle exit. With the mixing chamber pressure maintained at approximately 1.3 kPa, the mixing jet was in an under-expanded condition. CFD simulations with a non-equilibrium wet steam model also demonstrate the under-expanded jet structure. The pitot pressure profiles at the furthest locations downstream (135 and 185 mm) show reasonable agreement between experiments and simulations in terms of the spreading of the jet due to turbulent mixing. However, there are significant differences between the experimental and simulated pitot and static pressures profiles in the transverse and axial directions. Contributions to these differences are likely to arise because the simulated static pressures in the under-expanded wet steam jet core are lower than the triple point for water (0.61 kPa), so potential exists for liquid-solid and vapour-solid phase transitions that are not currently modelled in the simulations.

Experimental performances of a two-phase R134a ejector

This paper presents an experimental study of a liquid–vapour ejector operated under various conditions encountered in refrigeration and other cooling processes with R134a as the working fluid. Ejector performance in terms of entrainment ratio and pressure lift were investigated by imposing the pressure at the inlets and outlet of the ejector over ranges corresponding to intended applications. The primary stream subcooling level varied over a range of values in order to evaluate its impact on overall ejector operation. This range was sufficiently wide to include application cases such as found in some industrial processes with moderate to relatively high subcooling levels in comparison to those found in conventional refrigeration. Pressure sensors inside the mixing chamber allowed monitoring the pressure variation inside the ejector. Two-phase ejector entrainment ratio was found to strongly depend on the primary subcooling, especially below 20 °C values. The resulting performance curves show that the tested ejector works in off-design mode. Suction strength at the secondary inlet depended very much on the expansion of the secondary stream in the mixing chamber. The largest expansion recorded in the secondary flow hardly exceeded 25 kPa.

A compatible configuration strategy for burner streams in a 200 MWe tangentially fired oxy-fuel combustion boiler

The configurations of burner streams under oxy-fuel combustion are highly affected by its increased initial oxygen level. In this study, an air combustion and oxy-fuel combustion compatible configuration strategy for burner streams is proposed for a 200 MWe tangentially fired boiler, by aid of numerical simulation. Firstly, to achieve a momentum of primary and secondary streams that is similar to that of air combustion, the tertiary stream is switched-off in oxy-fuel combustion. In addition, the opposing tangential primary stream technology is suggested to reduce the gas temperature deviation in the upper furnace, which affects the quality of the steam and the safe operation of the boiler. For the present study, the appropriate opposing tangential angle is 5°–7° relative to the original primary stream design, and the ratio of opposing tangential momentum flow moment should be controlled at the low limit of 0.8 to decrease gas temperature deviation. To achieve a supported flame by the secondary stream, the momentum of the bottom secondary stream in oxy-fuel combustion should not be less than that in air combustion. The study illustrates for the first time that, the key design features of tangentially fired burners under oxy-fuel combustion. Although there are significant changes in the oxidant volume, oxidant composition, and chemical reaction under oxy-fuel combustion conditions, the design criteria of oxy-fuel tangentially fired boiler, in terms of momentum of the primary stream, momentum of the bottom secondary stream, and momentum ratio and momentum flow moment ratio of the secondary stream to primary stream, are consistent with those under air combustion.

Preliminary assessment of some physico-chemical parameters of Hanyin Danmani stream, Kaduna State, Nigeria

Preliminary determination of physico-chemical properties of Hayin Danmani stream, Igabi Local Government Area of Kaduna State, Nigeria was conducted in order to determine some physic-chemical parameters concentrations. Two different sampling stations were selected and samples were collected twice a month for three months, Nov 2015-Jan 216, along the course of Hayin Danmani stream. The mean values of pH (7.5±5.6), electrical conductivity (EC143±27.92 μs/cm), total dissolved solids (TDS 1515±54 mg/L) and turbidity (85±74.5 NTU were found to be higher than the recommended limit of World Health Organization (WHO) and Federal Environmental Protection (FEPA) with the exception of dissolved oxygen (DO, 6.5±3.4 mg/L), biochemical demand (BOD, 3±1.06 mg/L) and temperature, which were found to be in lower concentrations and within the recommended limits of FEPA and WHO respectively. The analysis of variance showed no significant difference in the months of November to January (p>0.05). The study revealed that Hayin Danmani Stream was polluted and the receiving river, the primary important streams, ponds and rivers need to be well monitored against all forms of contaminations and thus the impairment of water quality and other important aquatic organisms.Keywords: Water quality, evaluation, pollution, Hanyin Danmani Stream

Performance improvement of underwater jet pump by optimal arrangement of primary jet stream

Performance improvement of underwater jet pump by optimal arrangement of primary jet stream