Modeling In-Cylinder Water Injection in a 2-Stroke Internal Combustion Engine

AbstractIn this study, we apply Computational Fluid Dynamics (CFD) models in investigating the effect of injecting water into the combustion chamber of a 2-stroke Internal Combustion Engine (ICE). Using the commercial code, Star-CD, 3-D models for a port scavenging, in-cylinder fuel-injection; 2-Stroke engine is developed.The adapted engine's effective compression ratio (CR), crank Revolution per Minute (RPM) and fuel type are 8.5, 2000rpm and Heptane (C7H16) respectively. Two types of water mixing techniques are investigated: homogenous pre-mixing with the reactants, and direct injection around the walls of the combustion chamber. The engine's pressure, temperature, and pollutant mass fraction are estimated as a function of crank angle and injected water to fuel mass ratio, for both mixing techniques. The calculated indicated work (area under P-V diagrams) is used to estimate other engine performance indicated parameters. Results showed that although the homogenous mixing of water has an effect of reducing the combustion temperature and resulting NOx emissions, the pressure exerted on the piston is greatly diminished by this technique. However, when water vapor is injected around the chamber walls, the resulting reduction in temperature and NOx emissions has a minimum effect on the engine's P-V diagram.This is as a result of a water vapor blanket formed around the combustion zone, by the injected water vapor, which cools down the cylinder's wall with a minimum influence on the combustion process. Further analysisshowed that the water injection technique could increase the power/torque per engine size and hence, increase energy efficiency. Ultimately, the study presents the advantages of using water injection for enhancing fuel efficiency and reducing pollutant emission

3D printed microfluidic probes

In this work, we fabricate microfluidic probes (MFPs) in a single step by stereolithographic 3D printing and benchmark their performance with standard MFPs fabricated via glass or silicon micromachining. Two research teams join forces to introduce two independent designs and fabrication protocols, using different equipment. Both strategies adopted are inexpensive and simple (they only require a stereolithography printer) and are highly customizable. Flow characterization is performed by reproducing previously published microfluidic dipolar and microfluidic quadrupolar reagent delivery profiles which are compared to the expected results from numerical simulations and scaling laws. Results show that, for most MFP applications, printer resolution artifacts have negligible impact on probe operation, reagent pattern formation, and cell staining results. Thus, any research group with a moderate resolution (</=100 microm) stereolithography printer will be able to fabricate the MFPs and use them for processing cells, or generating microfluidic concentration gradients. MFP fabrication involved glass and/or silicon micromachining, or polymer micromolding, in every previously published article on the topic. We therefore believe that 3D printed MFPs is poised to democratize this technology. We contribute to initiate this trend by making our CAD files available for the readers to test our "print & probe" approach using their own stereolithographic 3D printers

Nano-carrier based drug delivery systems for sustained antimicrobial agent release from orthopaedic cementous material

Total joint replacement (TJR), such as hip and knee replacement, is a popular procedure worldwide. Prosthetic joint infections (PJI) after this procedure have been widely reported, where treatment of such infections is complex with high cost and prolonged hospital stay. In cemented arthroplasties, the use of antibiotic loaded bone cement (ALBC) is a standard practice for the prophylaxis and treatment of PJI. Recently, the development of bacterial resistance by pathogenic microorganisms against most commonly used antibiotics increased the interest in alternative approaches for antimicrobial delivery systems such as nanotechnology. This review summarizes the efforts made to improve the antimicrobial properties of PMMA bone cements using nanotechnology based antibiotic and non-antibiotic delivery systems to overcome drawbacks of ALBC in the prophylaxis and treatment of PJIs after hip and knee replacement

Numerical study of nano-biofilm stagnation flow from a nonlinear stretching/shrinking surface with variable nanofluid and bioconvection transport properties

A mathematical model is developed for stagnation point flow toward a stretching or shrinking sheet of liquid nano-biofilm containing spherical nano-particles and bioconvecting gyrotactic micro-organisms. Variable transport properties of the liquid (viscosity, thermal conductivity, nano-particle species diffusivity) and micro-organisms (species diffusivity) are considered. Buongiorno’s two-component nanoscale model is deployed and spherical nanoparticles in a dilute nanofluid considered. Using a similarity transformation, the nonlinear systems of partial differential equations is converted into nonlinear ordinary differential equations. These resulting equations are solved numerically using a central space finite difference method in the CodeBlocks Fortran platform. Graphical plots for the distribution of reduced skin friction coefficient, reduced Nusselt number, reduced Sherwood number and the reduced local density of the motile microorganisms as well as the velocity, temperature, nanoparticle volume fraction and the density of motile microorganisms are presented for the influence of wall velocity power-law index (m), viscosity parameter (c2), thermal conductivity parameter (c4), nano-particle mass diffusivity (c6), micro-organism species diffusivity (c8), thermophoresis parameter (Nt), Brownian motion parameter (Nb), Lewis number (Le), bioconvection Schmidt number (Sc), bioconvection constant (σ) and bioconvection Péclet number (Pe). Validation of the solutions via comparison related to previous simpler models is included. Further verification of the general model is conducted with the Adomian decomposition method (ADM). Extensive interpretation of the physics is included. Skin friction is elevated with viscosity parameter (c2) whereas it is suppressed with greater Lewis number and thermophoresis parameter. Temperatures are elevated with increasing thermal conductivity parameter (c4) whereas Nusselt numbers are reduced. Nano-particle volume fraction (concentration) is enhanced with increasing nano-particle mass diffusivity parameter (c6) whereas it is markedly reduced with greater Lewis number (Le) and Brownian motion parameter (Nb). With increasing stretching/shrinking velocity power-law exponent (m), skin friction is decreased whereas Nusselt number and Sherwood number are both elevated. Motile microorganism density is boosted strongly with increasing micro-organism diffusivity parameter (c8) and Brownian motion parameter (Nb) but reduced considerably with greater bioconvection Schmidt number (Sc) and bioconvection Péclet number (Pe). The simulations find applications in deposition processes in nano-bio-coating manufacturing processes

Emergence and spread of two SARS-CoV-2 variants of interest in Nigeria.

Identifying the dissemination patterns and impacts of a virus of economic or health importance during a pandemic is crucial, as it informs the public on policies for containment in order to reduce the spread of the virus. In this study, we integrated genomic and travel data to investigate the emergence and spread of the SARS-CoV-2 B.1.1.318 and B.1.525 (Eta) variants of interest in Nigeria and the wider Africa region. By integrating travel data and phylogeographic reconstructions, we find that these two variants that arose during the second wave in Nigeria emerged from within Africa, with the B.1.525 from Nigeria, and then spread to other parts of the world. Data from this study show how regional connectivity of Nigeria drove the spread of these variants of interest to surrounding countries and those connected by air-traffic. Our findings demonstrate the power of genomic analysis when combined with mobility and epidemiological data to identify the drivers of transmission, as bidirectional transmission within and between African nations are grossly underestimated as seen in our import risk index estimates

Integrating the HFACS Framework and Fuzzy Cognitive Mapping for In-Flight Startle Causality Analysis

This paper discusses the challenge of modeling in-flight startle causality as a precursor to enabling the development of suitable mitigating flight training paradigms. The article presents an overview of aviation human factors and their depiction in fuzzy cognitive maps (FCMs), based on the Human Factors Analysis and Classification System (HFACS) framework. The approach exemplifies system modeling with agents (causal factors), which showcase the problem space&rsquo;s characteristics as fuzzy cognitive map elements (concepts). The FCM prototype enables four essential functions: explanatory, predictive, reflective, and strategic. This utility of fuzzy cognitive maps is due to their flexibility, objective representation, and effectiveness at capturing a broad understanding of a highly dynamic construct. Such dynamism is true of in-flight startle causality. On the other hand, FCMs can help to highlight potential distortions and limitations of use case representation to enhance future flight training paradigms

Pseudoaneurysm as a complication of ankle arthroscopy

We present a case of a pseudoaneurysm of the anterior tibial artery following ankle arthroscopy with synovectomy, an extremely rare complication when standard anteromedial and anterolateral portals are used. The patient was diagnosed and treated with appropriate interventions which led to an uneventful recovery. Nevertheless, the potential sequelae of delayed diagnosis or misdiagnosis of the complication are dangerous; therefore, a high index of suspicion for a pseudoaneurysm must be maintained in the postoperative period

Integrating the HFACS Framework and Fuzzy Cognitive Mapping for In-Flight Startle Causality Analysis

This paper discusses the challenge of modeling in-flight startle causality as a precursor to enabling the development of suitable mitigating flight training paradigms. The article presents an overview of aviation human factors and their depiction in fuzzy cognitive maps (FCMs), based on the Human Factors Analysis and Classification System (HFACS) framework. The approach exemplifies system modeling with agents (causal factors), which showcase the problem space’s characteristics as fuzzy cognitive map elements (concepts). The FCM prototype enables four essential functions: explanatory, predictive, reflective, and strategic. This utility of fuzzy cognitive maps is due to their flexibility, objective representation, and effectiveness at capturing a broad understanding of a highly dynamic construct. Such dynamism is true of in-flight startle causality. On the other hand, FCMs can help to highlight potential distortions and limitations of use case representation to enhance future flight training paradigms

Sustainable energy development in Nigeria: wind, hydropower, geothermal and nuclear (Vol. 1)

In Nigeria, lack of adequate power supply has been recurrently cited as a hindrance to economic growth. This article provides an in-depth review on the wind, hydropower, geothermal and nuclear energy options in Nigeria, for a sustainable development of its power sector. The potential, current developmental stages, and prospects of each of the aforementioned energy conversion techniques, in the Nigerian context, are presented. The study reveals that although available data for each considered renewable energy option suggest renewable energy holds some potential, these data are not sufficient to make definitive global assessments of the country's prospects in this sector. Ground measured wind data are sparse and not consistent with satellite data. Hydropower resource databases have not been updated in a very long time. Geothermal records are only available for locations where oil explorations were previously performed. While these data might be useful for some local assessments, using them for global quantitative estimations would be misleading. A countrywide resource mapping across all technologies is required for a reliable outlook of sustainable energy development in Nigeria