Pollution control strategies and techniques for combustion processes

Bakalářská práce se zabývá problematikou spalovacích procesů. V práci je uveden přehled a popis jednotlivých konstrukčních parametrů spalovacího zařízení a jejich vlivu na tvorbu emisí. Práce dále popisuje jednotlivé druhy emisí vznikajících při spalování, jejich vliv na životní prostředí a techniky používané pro jejich redukci. Práci uzavírá kapitola s přehledem emisních limitů v ČR.Bachelor’s thesis deals with the problems of combustion process. The work gives the overview and the description of individual design parameters of the combustion facility. The analysis of the influence of design parameters on emissions formation is followed by the description of individual kinds of emissions and their impact on the environment. Next the most used reduction techniques are described. The work is closed by the overview of the emission limits in the Czech Republic.

Application of recent methods for synthesis of heat exchanger network

Diplomová práce se zabývá problematikou syntézy sítě výměny tepla a srovnává současné metody, s důrazem na Pinch Design Method a deterministickou metodu. Pomocí softwaru Maple je vytvořen program pro návrh sítě výměny tepla deterministickou metodou. Tato metoda je aplikována na několika konkrétních příkladech.Master’s thesis deals with the problems of heat exchanger network synthesis and compare the present methods with emphasis on Pinch Design Method and deterministic method. Based on theoretical formulation of deterministic model the computer program for heat exchanger network synthesis was developed in the software Maple environment. Developed software implementation of deterministic method has been applied to several case studies.

Strategies for printing fibers and post-processing for ceramic matrix composites (CMCs)

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Extrusion deposition additive manufacturing utilizing high glass transition temperature latent cured epoxy systems

This paper investigates the formulation, chemo-rheological properties, and extrusion deposition additive manufacturing (AM) of high glass transition temperature (Tg) epoxies. Currently there are two methods of using thermoset materials in extrusion deposition AM. The first approach uses a reactive material that fully cross-links during the build process. The second approach, which is explored in this paper, uses a reactive material that requires a thermal curing cycle after deposition is completed. Yield stress fluids, needed for successful deposition, were produced by blending various ratios of rheology modifiers and other solids into latent curing epoxy systems. After analyzing the rheological properties of the various blends via shear, temperature, and cure rate, the preferred formulation was selected. Test specimens for flexural analysis and dynamic mechanical analysis were printed from down selected combinations. This work resulted in the identification of key parameters for printing latent cured epoxy systems were scaled for the first large scale 3D printed epoxy for composite tooling applications

Validation of New Process Models for Large Injection-Molded Long-Fiber Thermoplastic Composite Structures

This report describes the work conducted under the CRADA Nr. PNNL/304 between Battelle PNNL and Autodesk whose objective is to validate the new process models developed under the previous CRADA for large injection-molded LFT composite structures. To this end, the ARD-RSC and fiber length attrition models implemented in the 2013 research version of Moldflow was used to simulate the injection molding of 600-mm x 600-mm x 3-mm plaques from 40% glass/polypropylene (Dow Chemical DLGF9411.00) and 40% glass/polyamide 6,6 (DuPont Zytel 75LG40HSL BK031) materials. The injection molding was performed by Injection Technologies, Inc. at Windsor, Ontario (under a subcontract by Oak Ridge National Laboratory, ORNL) using the mold offered by the Automotive Composite Consortium (ACC). Two fill speeds under the same back pressure were used to produce plaques under slow-fill and fast-fill conditions. Also, two gating options were used to achieve the following desired flow patterns: flows in edge-gated plaques and in center-gated plaques. After molding, ORNL performed measurements of fiber orientation and length distributions for process model validations. The structure of this report is as follows. After the Introduction (Section 1), Section 2 provides a summary of the ARD-RSC and fiber length attrition models. A summary of model implementations in the latest research version of Moldflow is given in Section 3. Section 4 provides the key processing conditions and parameters for molding of the ACC plaques. The validations of the ARD-RSC and fiber length attrition models are presented and discussed in Section 5. The conclusions will be drawn in Section 6

Large scale reactive additive manufacturing and what to expect when scaling up

Additive manufacturing as a whole offers tremendous savings in time and cost for rapid prototyping and tooling. At present there is a significant number of thermoplastic printers available from small-scale filament-based extrusion to large scale pellet-based extrusion. Thermosets have seen less growth and have been primarily limited to small scale research setups. Recently, a large-scale thermoset printer, the Reactive Additive Manufacturing (RAM) printer was developed (cf. Figure 1). This printer consists of an overall build volume of 450 ft3 and a gantry speed up to 50 in/s. The RAM system is also equipped with a modular pumping station capable of pumping feedstock material at pressures of 3000 psi in 5 or 55 gallon reservoirs. This work intends to reveal the challenges of working with a large scale Direct Ink Writing (DIW) process and how to overcome them. Two material chemistries have been scaled up for this system and are presented herein: a peroxide cured vinyl ester and latent cured epoxy-anhydrides. Factors such as pumpability, printability, and performance vary significantly between these systems and are discussed using rheological characterization, modeling, printing setup and parameters, and part design. Figure Please click Additional Files below to see the full abstract

Increasing the Interlayer Bond of Fused Filament Fabrication Samples with Solid Cross-Sections using Z-Pinning

The mechanical properties of parts made by fused filament fabrication is highly anisotropic, with the strength across layers (z-axis) typically measuring ~50% lower than the strength along the direction of the extruded material (x-axis). A z-pinning method has been developed in which material is extruded in the z-direction to fill intentionally aligned voids in the x-y print pattern. In previous studies that involved a sparse rectilinear grid cross-section (35% infill), the z-pinning approach demonstrated more than a 3.5x increase in strength in the z-direction. The current study expanded these efforts to evaluate the use of z-pins in a printed sample with a solid cross-section. Although a solid cross-section is more common in structural components, it is much less forgiving of instabilities that may occur in the z-pinning approach (such as over-filling). Even though this study utilized a low pin volume (~43% fill factor), the pinning approach demonstrated a 40% increase in z-direction strength for solid samples that had similar printing times.Mechanical Engineerin

Printing criteria for material extrusion of high temperature thermoplastic composites

Over the last decade, the popularity of 3D printing has increased dramatically. Material extrusion (ME) is the most common type of 3D printing, which typically involves extruding a molten thermoplastic material through a small orifice in a specific pattern. Once considered only a technique for making non-functional prototypes, a wide range of ME systems are now using high performance materials for a variety of functional applications. However, the process science underlying the extrusion of these materials is not well understood. Therefore, the authors have developed a “printability” framework for evaluating extrusion-based printing criteria for a wide range of thermoplastic materials based on fundamental viscoelastic and thermo-mechanical properties. The framework establishes processing boundary conditions for the four basic modes of the ME process: pressuredriven extrusion, extruded geometry definition, geometry stability, and component integrity. The governing equations for each of these modes have been applied to a variety of high performance materials across a number of ME-based printing platforms, including the large-scale 3D printing of carbon fiber reinforced composites. Please click Additional Files below to see the full abstract

Additive Manufacturing of High Performance Semicrystalline Thermoplastics and Their Composites

This work investigates the use of two semi-crystalline high performance thermoplastics, polyphenylene sulfide (PPS) and poly (ether ketone ketone) (PEKK), as feedstock for fused filament fabrication process. Composites of PPS and PEKK are emerging as viable candidates for several components in aerospace and tooling industries and additive manufacturing of these materials can be extremely beneficial to lower manufacturing costs and lead times. However, these materials pose several challenges for extrusion and deposition due to some of their inherent properties as well as thermal and oxidative responses. To better understand the properties of such systems specific to 3D printing and determine the critical parameters that make them “printable”, various rheological and thermal properties have been studied for neat as well as short fiber reinforced PPS and PEKK systems. Attempts were also made to print these materials in a customized high temperature fused filament fabrication system.Mechanical Engineerin

Big Area Additive Manufacturing of High Performance Bonded NdFeB Magnets

Additive manufacturing allows for the production of complex parts with minimum material waste, offering an effective technique for fabricating permanent magnets which frequently involve critical rare earth elements. In this report, we demonstrate a novel method - Big Area Additive Manufacturing (BAAM) - to fabricate isotropic near-net-shape NdFeB bonded magnets with magnetic and mechanical properties comparable or better than those of traditional injection molded magnets. The starting polymer magnet composite pellets consist of 65 vol% isotropic NdFeB powder and 35 vol% polyamide (Nylon-12). The density of the final BAAM magnet product reached 4.8 g/cm3, and the room temperature magnetic properties are: intrinsic coercivity Hci = 688.4 kA/m, remanence Br = 0.51 T, and energy product (BH)max = 43.49 kJ/m3 (5.47 MGOe). In addition, tensile tests performed on four dogbone shaped specimens yielded an average ultimate tensile strength of 6.60 MPa and an average failure strain of 4.18%. Scanning electron microscopy images of the fracture surfaces indicate that the failure is primarily related to the debonding of the magnetic particles from the polymer binder. The present method significantly simplifies manufacturing of near-net-shape bonded magnets, enables efficient use of rare earth elements thus contributing towards enriching the supply of critical materials