Mixing Capability Research Articles

Monitoring of friction stir welding for dissimilar Al 6063 alloy to polypropylene using sensor signals

The present work addresses the feasibility of friction stir butt welding of dissimilar Al6063 to polypropylene for cylindrical and threaded tool pin profile at different tool positions like tool offsetting and slotted edge–based base plate design as bridle joint to improve the weld quality. The new slotted edge–based design using threaded tool pin profile was found to be highly efficient. This work was further extended with the interaction effect of tool rotational speed and traverse speed. The major objective was to investigate the variation of axial force and torque due to the parametric variation, especially to find the correlation with weld quality characteristics. The mean and standard deviation of axial force and torque indicated the formability and material mixing capability during welding which in turn found to be highly correlated to weld bead uniformity. The joint behavior due to tensile load and bonding mechanism in weld stirred zone have been studied using stress-strain diagram and scanning electron micrographs, respectively. The weld joint interface was found to be the weakest zone rather than weld stirred zone due to the presence of carbon reach phases as per micro-hardness variation through the weld centerline along with energy dispersive spectroscopy analysis. The maximum joint efficiency was found to be 23.33% at 700-rpm tool rotation and traverse speed of 30 mm/min using threaded pin in slotted edge–based design.

Empirical scaling analysis of supersonic jet control using steady fluidic injection

Following our previous work [Kumar et al., “Fluidic injectors for supersonic jet control,” Phys. Fluids 30(12), 126101 (2018)], we experimentally investigate the effect of fluidic injection on the mixing enhancement of a Mach 2.0 jet. The mass flow rate ratio Cm of the injectors to that of the main jet and the expansion ratio pe/pa (where pe and pa are the nozzle exit and atmospheric pressures, respectively) to understand the mixing capability at design and off-design conditions are examined in detail. Extensive Pitot pressure measurements are performed along the jet centerline, and the jet stream has been visualized using the shadowgraph technique in the orthogonal planes of the manipulated jet. The mixing capability of the manipulated jet quantified based on the reduction in supersonic core length ΔLc* exhibits a strong dependence on Cm and pe/pa. Empirical scaling analysis of the jet control reveals that the relationship ΔLc* = f1(Cm, pe, pa, D, d) may be reduced to ΔLc* = f2(ξ), where f1 and f2 are different functions and the scaling factor ξ = MRpe/pa(Dd)1.3, where MR is the momentum ratio of the injector to the main jet, D and d are the nozzle exit diameter and the injector exit diameter, respectively. The scaling parameter ΔLc* = f2(ξ) provides important insights into the jet control physics.

Rapid mixing of colliding picoliter liquid droplets delivered through-space from piezoelectric-actuated pipettes characterized by time-resolved fluorescence monitoring.

Rapid mixing of aqueous solutions is a crucial first step to study the kinetics of fast biochemical reactions with high temporal resolution. Remarkable progress toward this goal has been made through the development of advanced stopped-flow mixing techniques resulting in reduced dead times, and thereby extending reaction monitoring capabilities to numerous biochemical systems. Concurrently, piezoelectric actuators for through-space liquid droplet sample delivery have also been applied in several experimental systems, providing discrete picoliter sample volume delivery and precision sample deposition onto a surface, free of confinement within microfluidic devices, tubing, or other physical constraints. Here, we characterize the inertial mixing kinetics of two aqueous droplets (130 pl) produced by piezoelectric-actuated pipettes, following droplet collision in free space and deposition on a surface in a proof of principle experiment. A time-resolved fluorescence system was developed to monitor the mixing and fluorescence quenching of 5-carboxytetramethylrhodamine (5-Tamra) and N-Bromosuccinimide, which we show to occur in less than 10 ms. In this respect, this methodology is unique in that it offers millisecond mixing capabilities for very small quantities of discrete sample volumes. Furthermore, the use of discrete droplets for sample delivery and mixing in free space provides potential advantages, including the elimination of the requirement for a physical construction as with microfluidic systems, and thereby makes possible and extends the experimental capabilities of many systems.

The dose of physical activity to minimise functional decline in older general medical patients receiving 24-hr acute care: A systematic scoping review.

To identify evidence for a recommended and feasible activity dose to minimise functional decline in older hospitalised general medical patients. Quality 24-hr care of older patients involves balancing activity to minimise functional decline, with rest to aid recovery. However, there is limited guidance regarding an optimal type and dose of activity to minimise functional decline in hospitalised elders receiving acute medical care. A systematic search and scoping review of the literature were conducted following Joanna Briggs methodological guidance. The results were reported in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) Statement. Study bias was determined using the Joanna Briggs Institute Critical Appraisal Tools. Fifteen primary studies of variable design, rigour and potential for bias were included. Study contexts were general medical wards (n=11, 73.3%), Acute care of the elderly unit (n=3, 20%) and a nursing unit (n=1, 6.7%) located in tertiary referral acute hospitals. Most participants were aged 75-84years (n=10, 66%), had variable medical diagnoses and samples were either physically capable (n=4, 26.7%) of limited physical capability (n=1, 6.7%) or of mixed capability to mobilise independently (n=10, 66.7%). Walking at least twice a day for approximately 20min in total appeared to be associated with less functional decline in older patients of variable physical capabilities, and the overall efficacy of twice-daily exercise to reduce functional decline was supported. The evidence tentatively supported walking for hospitalised elders, irrespective of physical capability, and based on one RCT, suggested likely benefits of graduated exercise in dependent elders. Insufficient evidence limits prescription of optimal doses of physical activity to minimise functional decline. This review could provide evidence for nurses to promote function in older patients by specifying a dose of physical activity to be undertaken in hospital.

Numerical study on the turbulent mixing in channel with Large Eddy Simulation (LES) using spectral element method

Turbulent mixing is an important thermal hydraulic phenomenon in the reactor core rod bundles and it leads to strong momentum and energy transfer among adjacent subchannels in fuel assembly. Generally, turbulent mixing coefficient is usually referred to describe turbulent effect, which commonly sets to a constant or calculated utilizing Reynolds number dependent fitting correlations based on experimental data.In this paper, a high-scalable and high-performance spectral element method combining with high passed filtered Large Eddy Simulation (LES) model has been proposed to simulate the turbulent flow through parallel wall channel and square channel with a cylindrical rod for single-phase flow. In the parallel wall channel case, mesh sensitivity analysis and model validation were accomplished by comparing the simulation data with DNS references utilizing key parameters such as velocity profile and stresses in the near wall region. Meanwhile, for the square channel with a cylindrical rod case, instantaneous lateral velocity monitored in the gap center has been compared with the experimental data with different Reynolds numbers and geometric conditions. From the simulation approach, both the absolute oscillation amplitude and the oscillation frequency increase with the pitch diameter ratio. Finally, the simulation results of turbulent mixing coefficient dependent on Reynolds number were validated with both experimental and theoretic references to demonstrate the feasibility of spectral element method combining with LES model. The root mean square (RMS) value of lateral fluctuating velocity was adopted to reflect the effective mixing capability, predicting the turbulent mixing phenomena with a reasonable degree of accuracy from the specific calculation strategy. Fast Fourier Transform (FFT) also performed and got an agreement with reference data.

Three-dimensional flow model development for thermal mixing and stratification modeling in reactor system transients analyses

Mixing, thermal-stratification, and mass transport phenomena in large pools or enclosures play major roles for the safety of reactor systems. Depending on the fidelity requirement and computational resources, various modeling methods, from the 0-D perfect mixing model to 3-D Computational Fluid Dynamics (CFD) models, are available. Each is associated with its own advantages and shortcomings. It is very desirable to develop an advanced and efficient thermal mixing and stratification modeling capability embedded in a modern system analysis code to improve the accuracy of reactor safety analyses and to reduce modeling uncertainties.An advanced system analysis tool, SAM, is being developed at Argonne National Laboratory for advanced non-LWR reactor safety analysis. While SAM is being developed as a system-level modeling and simulation tool, a reduced-order three-dimensional module is under development to model the multi-dimensional flow and thermal mixing and stratification in large enclosures of reactor systems. This paper provides an overview of the three-dimensional finite element flow model in SAM, including the governing equations, stabilization scheme, and solution methods. Additionally, several verification and validation tests are presented, including lid-driven cavity flow, natural convection inside a cavity, laminar flow in a channel of parallel plates. Based on the comparisons with the analytical solutions and experimental results, it is demonstrated that the developed 3-D fluid model can perform very well for a wide range of flow problems.

Quantitative visualization of fluid mixing in slug flow for arbitrary wall-shaped microchannel using Shannon entropy

Micro-reactors based on slug flow are among the most promising developments for improving the efficiencies of chemical reactions and unit operations in chemical engineering. Quantitative understanding of the local and global fluid dynamics and their effects on fluid mixing is required for designing effective slug flow micro-reactors. This paper proposes a new method for quantitative two-dimensional assessment of fluid mixing in slug flow. Pixel-wise calculation of local entropy inside a slug is discussed. The proposed method is based on two-phase simulation using the volume of fraction (VOF) algorithm and is thus applicable to the flow pattern in arbitrary wall-shaped micro-reactors. The method consists of three steps. (1) Flow analysis using two-phase VOF algorithm: A series of two-dimensional velocity fields inside the slug along time is obtained for a certain duration. (2) Backward particle tracking from the target image to the initial image: The slug in the initial image is divided into small regions, and each region is assigned a different label. Accumulation of backward particle tracking results reveals a two-dimensional distribution of labels in the target image. (3) Pixel-wise calculation of entropy on the obtained distribution of labels: The resulting image is a quantitative two-dimensional mixing pattern inside the slug. The proposed method was applied to three types of microchannels with different bumps on the walls. The results could quantitatively distinguish the differences in fluid mixing capability among the systems.

Oxygen lancing methods for industrial processes

Oxygen is often used in industrial combustion processes to improve emissions, reduce fuel cost and/or increase production. As opposed to simply enriching combustion air with oxygen, oxygen lancing is utilized when targeting the oxygen to a specific part of the combustion process is beneficial.This work compares 2 methods of lancing oxygen into a process, the first comprising a sonic velocity jet of ambient temperature (“cold”) oxygen and the second an oxygen jet heated to temperatures exceeding 1500 °C (“hot oxygen”). The hot oxygen jet is accelerated to a velocity 2–4 times higher than is possible with comparable cold oxygen jets. Simple jet theory is used in conjunction with detailed kinetic simulations to investigate differences in lance reactivity and effectiveness. A range of conditions is investigated, including oxygen preheat temperature, ambient gas conditions and turndown capability. In all cases, hot oxygen lancing provides better mixing capability than cold oxygen lances. In addition, the increased reactivity of hot oxygen proves more effective than cold oxygen when reacting with ambient gases.A real world comparison of cold and hot oxygen lancing into a cement kiln for CO emission reduction is also presented. In practice, a non-optimized hot oxygen lance reduces CO emissions from the flue gas by more than 25% over a fully optimized cold oxygen lance.

Simultaneous Pumping and Mixing of Biological Fluids in a Double-Array Electrothermal Microfluidic Device

Transport and mixing of minute amounts of biological fluids are significantly important in lab-on-a-chip devices. It has been shown that the electrothermal technique is a suitable candidate for applications involving high-conductivity biofluids, such as blood, saliva, and urine. Here, we introduce a double-array AC electrothermal (ACET) device consisting of two opposing microelectrode arrays, which can be used for simultaneous mixing and pumping. First, in a 2D simulation, an optimum electrode-pair configuration capable of achieving fast transverse mixing at a microfluidic channel cross-section is identified by comparing different electrode geometries. The results show that by adjusting the applied voltage pattern and position of the asymmetrical microelectrodes in the two arrays, due to the resultant circular flow streamlines, the time it takes for the analytes to be convected across the channel cross-section is reduced by 95% compared to a diffusion-only-based transport regime, and by 80% compared to a conventional two-layer ACET device. Using a 3D simulation, the fluid transport (pumping and mixing) capabilities of such an electrode pair placed at different angles longitudinally relative to the channel was studied. It was found that an asymmetrical electrode configuration placed at an angle in the range of can significantly increase transversal mixing efficiency while generating strong longitudinal net flow. These findings are of interest for lab-on-a-chip applications, especially for biosensors and immunoassays, where mixing analyte solutions while simultaneously moving them through a microchannel can greatly enhance the sensing efficiency.

Thermal hydraulic performance of micro-channel heat sink with composite metal foam-solid fin design

<p indent="0mm">Three-dimensional (3D) interconnect technology promises significant performance advantages for the next generation of high speed and multi-functional electronic devices, however, the large-scale integration of electronic circuit and vertical stacking of multi-functional dice have been demonstrated to result in substantially increased waste-heat generation rates and localized hotspots. Efficient thermal management solutions are imperative to ensure the operating temperature of components below a reasonable level. Among various cooling techniques, metal foam heat sink has been identified as a promising alternative for electronic cooling, because of the large specific surface area, high effective thermal conductivity and intensive fluid mixing capability that foam material provided. In this study, a novel micro-channel heat sink with combined metal foam-solid fin, namely combined fin heat sink (CFHS), was established for electronics cooling. Numerical simulations based on Brinkman-Darcy extended momentum equation and local thermal non-equilibrium energy equations were carried out to investigate the fluid flow and heat transfer characteristics. To simplify the computations, a single channel was used as the computational domain with a dimension of 20 mm×2.4 mm× <sc>6 mm.</sc> The constant heat flux of <sc>100 W/cm²</sc> was supplied at the bottom wall to simulate the high-powered electronic device. Metal foam and fin were made of high thermal conductivity copper, and pure water was used as the working coolant. It was assumed that the metal foam was fully saturated with fluid in laminar flow state and the thermal resistance between the metal foam and fin was neglected. Effects of combined fin configuration on the flow and heat transfer performances were studied to determine the optimal porosity and dimensionless metal foam layer thickness for designing the CFHS. The thermal performance of the novel heat sink was compared to that of the conventional heat sink, and the total thermal resistance was analyzed based on the simplified thermal resistance network. The results indicate that the CFHS is more favorable in promoting thermal performance that the average Nusselt number of CFHS is 2.53 times higher than that of the conventional heat sink, while accompanied by the high pressure drop as a penalty. The flow resistance and specific area are two conflicting parameters that affect the thermal and hydraulic performances of the CFHS, our results show that there exists a critical dimensionless metal foam thickness and optimal porosity, which are 0.9 and 0.3, respectively. Compared with the conventional heat sink, the total thermal resistance of CFHS is significantly reduced by 56%, and the thermal performance factor of CFHS performs 1.32 times higher. The presented CFHS thus provides a feasible solution for thermal management of electronic devices with high-powered density.

Fluidic injectors for supersonic jet control

An experimental investigation on the mixing capability of a Mach 2.0 jet manipulated based on a convergent injector (CI) and convergent-divergent injector (CDI) is reported in this paper. The injector parameters that influence the core length of the manipulated jet (Lc*), such as the mass flow rate ratio Cm of the minijets to the main jet and the expansion ratio pe/pa (where pe and pa are the nozzle exit and atmospheric pressures, respectively), are examined in detail. The experimental diagnostics include the detailed Pitot pressure measurement along the jet centerline and the shadowgraph visualizations captured in the orthogonal planes of the manipulated jet. Various flow structures have been identified based on the shadowgraph visualization, such as categories I and II corresponding to the off-design and design conditions of the primary jet, respectively. The core length of the manipulated jet exhibits a strong dependence on Cm, pe/pa, and the type of injection (CI or CDI). The jet mixing quantified based on ΔLc* (where ΔLc* is the percentage reduction in core length of the manipulated jet with respect to the natural jet) is maximum at the design condition than the off-design condition implying that the jet manipulation is highly efficient at the design condition.

Numerical analysis of mixing in block‐head mixing screws

The research reported here used 3D non‐Newtonian flow simulations to investigate the pumping and mixing capability of block‐head mixers. Block‐head mixers are distributive mixing screws that are widely used to homogenize the polymer melt and eliminate thermal gradients. The polymer‐processing industry employs a variety of block‐head mixers, with little consensus on design and distribution of screw flights and mixing blocks. This analysis addresses this issue based on a computational design study in which the influence of three geometrical parameters was examined: (1) the number of flights at a mixing block, (2) the number of blocks along the screw, and (3) the stagger angle between the blocks. To examine the flow behavior of the mixing screws, the pressure consumption and energy dissipation is evaluated. Distributive mixing is analyzed using residence time distribution functions, kinematic stretching parameters, and the scale of segregation. Dispersive mixing is assessed by means of the mixing index and the shear stress. The results of this design study increase the understanding of block‐head mixers and contribute to the design and optimization of such geometries. The findings can further be applied to mixing screws of similar geometry, including pin‐type and knob mixers. POLYM. ENG. SCI., 59:E88–E104, 2019. © 2018 The Authors. Polymer Engineering &amp; Science published by Wiley Periodicals, Inc. on behalf of Society of Plastics Engineers.

Challenges of friction reduction of engine plain bearings – Tackling the problem with novel bearing materials

Abstract This study specifically focuses on the friction properties of bearing materials. By means of laboratory test rigs using ring on disc and bearing segment systems extensive investigations under mixed friction conditions and start stop operation were carried out in this area. One the one hand, commonly used bearing products including bimetal and trimetal bearings with various coatings are studied resulting in elucidation of the underlying mechanisms of the friction performance. On the other hand, based on the conclusions thereof, novel bearing coatings are introduced and are verified regarding friction performance. The results emphasize the changing behaviour of the friction characteristics of bearing materials. Furthermore, the outstanding mixed friction capabilities of the herein proposed novel bearing coatings are documented.

A strategy for large-scale scalar advection in large eddy simulations that use the linear eddy sub-grid mixing model

PurposeThe purpose of this numerical work is to present and test a new approach for large-scale scalar advection (splicing) in large eddy simulations (LES) that use the linear eddy sub-grid mixing model (LEM) called the LES-LEM.Design/methodology/approachThe new splicing strategy is based on an ordered flux of spliced LEM segments. The principle is that low-flux segments have less momentum than high-flux segments and, therefore, are displaced less than high-flux segments. This strategy affects the order of both inflowing and outflowing LEM segments of an LES cell. The new splicing approach is implemented in a pressure-based fluid solver and tested by simulation of passive scalar transport in a co-flowing turbulent rectangular jet, instead of combustion simulation, to perform an isolated investigation of splicing. Comparison of the new splicing with a previous splicing approach is also done.FindingsThe simulation results show that the velocity statistics and passive scalar mixing are correctly predicted using the new splicing approach for the LES-LEM. It is argued that modeling of large-scale advection in the LES-LEM via splicing is reasonable, and the new splicing approach potentially captures the physics better than the old approach. The standard LES sub-grid mixing models do not represent turbulent mixing in a proper way because they do not adequately represent molecular diffusion processes and counter gradient effects. Scalar mixing in turbulent flow consists of two different processes, i.e. turbulent mixing that increases the interface between unmixed species and molecular diffusion. It is crucial to model these two processes individually at their respective time scales. The LEM explicitly includes both of these processes and has been used successfully as a sub-grid scalar mixing model (McMurtry et al., 1992; Sone and Menon, 2003). Here, the turbulent mixing capabilities of the LES-LEM with a modified splicing treatment are examined.Originality/valueThe splicing strategy proposed for the LES-LEM is original and has not been investigated before. Also, it is the first LES-LEM implementation using unstructured grids.

Biofluid pumping and mixing by an AC electrothermal micropump embedded with a spiral microelectrode pair in a cylindrical microchannel.

In this paper, we numerically investigated a multifunctional AC electrothermal (ACET) micropump embedded with an asymmetric spiral microelectrode pair in a cylindrical microchannel for simultaneous pumping and mixing in high-conductivity fluids, which makes the pump useful for biofluid applications. When an AC signal was applied to the asymmetric spiral electrode pair, the vortices induced on the electrode surfaces with centerlines along the corresponding spiral electrode length exhibit a spiral distribution, and the net flow in the cylindrical microchannel is generated by the ACET effect. The vorticity field distribution can explain the mechanism of simultaneous pumping and mixing. Because the vorticity field is inclined against the microchannel direction, vortices on top of the spiral electrodes can affect the ACET flow in the following two aspects at the same time: one is pumping the flow in the microchannel direction, and the other is mixing the samples by stirring the flow. We also determined that the geometric ratios of the electrode width to the gap or slant angle of the spiral electrodes can feasibly be used to control the relative strength of the pumping and mixing capabilities, and we achieved an optimal design that gives both desirable pumping and mixing efficiencies. This study shows that the spiral ACET micropump design can rapidly drive the high-conductivity fluids and efficiently mix samples simultaneously. The numerical simulation of the spiral ACET micropump is of significant importance for practical, chemical and biological applications, and feasible fabrication techiniques should be experimentally investigated in future studies.

A self-optimizing reactor

Chemistry Chemists spend a great deal of time tweaking the conditions of known reactions. Small changes to temperature and concentration can have a big influence over product yield. Bedard et al. present a flow-based reaction platform that carries out this laborious task automatically. By using feedback from integrated analytics, the system converges on optimal conditions that can then be applied with high precision afterward. A series of modules with heating, cooling, mixing, and photochemical capabilities could be configured for a broad range of reactions. These include homogeneous and heterogeneous palladium-catalyzed cross-coupling, reductive amination, and the generation of sensitive intermediates under an inert atmosphere. Science , this issue p. [1220][1] [1]: /lookup/doi/10.1126/science.aat0650

Reconfigurable system for automated optimization of diverse chemical reactions.

Chemical synthesis generally requires labor-intensive, sometimes tedious trial-and-error optimization of reaction conditions. Here, we describe a plug-and-play, continuous-flow chemical synthesis system that mitigates this challenge with an integrated combination of hardware, software, and analytics. The system software controls the user-selected reagents and unit operations (reactors and separators), processes reaction analytics (high-performance liquid chromatography, mass spectrometry, vibrational spectroscopy), and conducts automated optimizations. The capabilities of this system are demonstrated in high-yielding implementations of C-C and C-N cross-coupling, olefination, reductive amination, nucleophilic aromatic substitution (SNAr), photoredox catalysis, and a multistep sequence. The graphical user interface enables users to initiate optimizations, monitor progress remotely, and analyze results. Subsequent users of an optimized procedure need only download an electronic file, comparable to a smartphone application, to implement the protocol on their own apparatus.

Experimental and numerical analysis of Y-shaped split and recombination micro-mixer with different mixing units

Three representative types of Y-shaped split and recombination three-dimensional passive micromixers are analyzed for mixing efficiency both experimentally and by numerical simulation. These designs are important because of simple fabrication and better mixing ability. The flow and mixing capability of these mixers are numerically investigated for Reynolds number, in the range of 0.5–100. Mixing index and pressure drop of each micro-mixer design are evaluated in COMSOL 5.2a. All Proposed designs mixing index line graph and images are clearly showing that mixing is much improved as compared to straight mixer YSSAR. It is due to chaotic advection and Dean Flow effect in YCSAR, YRCSAR, and YRSAR that transverse flow mechanism enhance the mixing index. The mixing index of YRCSAR, having both circular and rhombus mixing units is 99% at Reynolds number 100 superior in mixing performance as compared other proposed micro-mixers. Mixers chips are fabricated from borosilicate glass and liquid silicone elastomer material. Red and yellow dye was used for evaluating the mixing performance experimentally. Simulation and experimental images of analyzed micro-mixers as well as the line plots, both shows that with an increase in Reynolds number mixing index increases. As a result of the increase in Reynolds number, there is an increase in the chaotic advection and Dean Flow effect, which creates rotations and vortices and hence improve the mixing index. There is a little difference in experimental and simulation results values but the overall trends are consistent in both cases.

The Microbial Community of a Terrestrial Anoxic Inter-Tidal Zone: A Model for Laboratory-Based Studies of Potentially Habitable Ancient Lacustrine Systems on Mars.

Evidence indicates that Gale crater on Mars harboured a fluvio-lacustrine environment that was subjected to physio-chemical variations such as changes in redox conditions and evaporation with salinity changes, over time. Microbial communities from terrestrial environmental analogues sites are important for studying such potential habitability environments on early Mars, especially in laboratory-based simulation experiments. Traditionally, such studies have predominantly focused on microorganisms from extreme terrestrial environments. These are applicable to a range of Martian environments; however, they lack relevance to the lacustrine systems. In this study, we characterise an anoxic inter-tidal zone as a terrestrial analogue for the Gale crater lake system according to its chemical and physical properties, and its microbiological community. The sub-surface inter-tidal environment of the River Dee estuary, United Kingdom (53°21′15.40″ N, 3°10′24.95″ W) was selected and compared with available data from Early Hesperian-time Gale crater, and temperature, redox, and pH were similar. Compared to subsurface ‘groundwater’-type fluids invoked for the Gale subsurface, salinity was higher at the River Dee site, which are more comparable to increases in salinity that likely occurred as the Gale crater lake evolved. Similarities in clay abundance indicated similar access to, specifically, the bio-essential elements Mg, Fe and K. The River Dee microbial community consisted of taxa that were known to have members that could utilise chemolithoautotrophic and chemoorganoheterotrophic metabolism and such a mixed metabolic capability would potentially have been feasible on Mars. Microorganisms isolated from the site were able to grow under environment conditions that, based on mineralogical data, were similar to that of the Gale crater’s aqueous environment at Yellowknife Bay. Thus, the results from this study suggest that the microbial community from an anoxic inter-tidal zone is a plausible terrestrial analogue for studying habitability of fluvio-lacustrine systems on early Mars, using laboratory-based simulation experiments.

Experimental study on non-vaporizing spray characteristics of biodiesel-blended gasoline fuel in a constant volume chamber

Detailed investigation of the spray phenomenology of liquid fuel injection is the primary step to understand better and predict the physical characteristics involved in fuel spray and atomization process. This study focuses on non-vaporizing transient spray characteristics of neat gasoline and biodiesel addition (10%, 20% and 40% by volume) to gasoline in three different ratios under low load and different injection pressure conditions. Different ambient gas densities and injection pressures were tested, which ranged from 10 to 20 kg/m3 and 40 to 120 MPa respectively, with a fuel temperature of 323 K. A z-type shadowgraph was utilized as an optical method to capture the highly transient spray development at 40000 frames per second and a modified image processing algorithm was implemented to determine the spray characteristics. The image processing results revealed that an increase in injection pressure significantly accelerates the spray development process while penetration length increases with the increment of biodiesel fraction. Differences in penetration lengths were much significant under lower injection pressure; however, a further increase in injection pressure diminishes the differences in tip penetration. The spray cone angle was increased for higher gasoline content which promotes a larger spray width and as a consequence, neat gasoline exhibited a larger spray area and volume. However, after a certain period of injection start, spray area and volume of neat gasoline and 10% biodiesel-blended gasoline were surpassed by 20% and 40% biodiesel-blended gasoline. In contrast, a decrease in droplet size was observed according to breakup regimes under high injection pressure and low ambient density. These results imply that the higher biodiesel blending fraction has poor air-fuel mixing capability compared to neat gasoline, and the risk of liquid impingement on the cylinder wall becomes higher if the blended-gasoline contains higher biodiesel percentage.