Computational modelling of thermal spraying processes

The main aim of this project is to model the effects of varied injection parameters on the gas dynamics and droplet dynamics of the HVSFS and SP- HVOFS processes for improving the droplet breakup and evaporation to enhance the nanoparticles heating and deposition efficiency. Thermal spraying processes are widely used to generate thermal-, corrosion-, and wear-resistant layers over the machine parts, to increase the durability of the equipment under severe environmental conditions. The liquid feedstock is used to achieve nanostructured coatings. It is used either in the form of a suspension or a solution precursor. The suspension is a mixture of solid nanoparticles suspended in a liquid medium consisting, for instance, of water, ethanol, or isopropanol. This dispersion mechanism in a liquid carrier provides adequate flowability to the nanoparticles, which cannot be handled by conventional gas- based feeding systems, whereas the solution precursor is mixed at the molecular level; hence, more uniform phase composition and properties are expected in the sprayed coatings as compared to the suspension and conventional powder spraying. Firstly, experiments are conducted to analyse the effects of different precursor concentrations, solvent types and injection nozzles on the size and morphology of synthesized nanoparticles. The results indicate that the particle size increased with increasing precursor concentration due to the variations in the physical properties of the mixture solution. The higher precursor concentrations had an adverse effect on the droplet atomization and evaporation process that led to bigger size particle formation. The use of aqueous solvent has some limits and with higher precursor concentration the surface tension increases that resulted in the reduction of droplets’ disintegration, and thus bigger size precursor droplets generate larger nanoparticles. A mixture of aqueous-organic solvents and pure organic precursors are preferred to improve the process efficiency of the nanoparticles size and morphology. Furthermore, the nanoparticles size can be controlled by using liquid feedstock atomization before injecting into the HVOF torch. A new effervescent injection nozzle is designed and compared to different types of existing injection nozzles, to see the variations in the droplet disintegration, and its effects on the performance of the HVOF torch processes. It is detected that the atomization would result in smaller size particles with homogeneous morphology. In a numerical study, different droplet injection types are analysed to see their effects on the gas and droplet dynamics inside the HVOF torch. The group-type injection (GTI) and effervescent-type atomization (ETI) are used effectively to overcome the heat losses and delays in the droplet evaporation. These approaches reduce the thermal and kinetic energy losses in the suspension-fed-HVOF torch, thereby improving the coating formation. The effects of using multicomponent water-ethanol mixture injection in the HVOF torch are also modelled, and its impact on the droplet breakup and evaporation are studied. The organic solvents have a low heat of vaporization and surface tension, and can effectively be used in the HVOF spraying process over the water-based solvents. Furthermore, nanoparticles are suspended in the liquid feedstock and injected into the HVOF torch. The effect of increasing nanoparticles’ concentration in the feedstock and its consequence on the gas dynamics, droplet breakup and evaporation are analysed. The augmentation in the nanoparticles loading in the suspension droplets can decrease the droplet breakup and evaporation rate because the required heat of vaporization increases significantly. Moreover, the size of injection droplet affects the droplet fragmentation process; bigger sized droplets observed a delay in their evaporation that resulted in coating porosity. The results suggest that smaller droplet sizes are preferred in coating applications involving a higher concentration of nanoparticles with high melting point. Further, the gas flow rates (GFRs) are regulated to control the droplet dispersion, atomization and evaporation inside the solution precursor fed-HVOF torch. The size of the droplet diameter is decreased by an increment in the GFR, as higher combustion rates increase the combustion flame enthalpy and kinetic energy. Moreover, the increase in the oxygen/fuel flow rates dilutes the injected precursor. It reduces ZrO2 concentration in the process and decreases the rate of particle collision; as a result, non-agglomerated nanoparticles can be obtained

Effects of angular injection, and effervescent atomization on high-velocity suspension flame spray process

This work presents the nanostructured coating formation using suspension thermal spraying through the HVOF torch. The nanostructured coating formation requires nanosize powder particles to be injected inside a thermal spray torch using liquid feedstock. The liquid feedstock needs to be atomized when injected into the high-velocity oxygen fuel (HVOF) torch. This paper presents the effects of angular injection and effervescent atomization of the liquid feedstock on gas and droplet dynamics, vaporization rate, and secondary breakup in the high-velocity suspension flame spray (HVSFS) process. Different angular injections are tested to obtain the optimum value of the angle of injection. Moreover, effervescent atomization technique based on twin-fluid injection has been studied to increase the efficiency of the HVSFS process. Different solid nanoparticle concentrations in suspension droplets are considered. In angular injection the droplets are injected into the core of the combustion zone; this immediately evaporates the droplets, and evaporation is completed within the torch. The value of 10°–15° is selected as the optimal angle of injection to improve the gas and droplet dynamics inside the torch, and to avoid the collision with the torch's wall. The efficiency of the effervescent atomization can be enhanced by using high gas-to-liquid mass flow rate ratio, to increase the spray cone angle for injecting the suspension liquid directly into the combustion flame. It is also found that the increment in the nanoparticle concentration has no considerable effects on the droplet disintegration process. However, the location of evaporation is significantly different for homogeneous and non-homogeneous droplets

Brazil's rise and the role of big business

The heart of Brazil’s recent rise in international relations lies in its growing influence in the global economic arena. This article evaluates one aspect of economic activity – the emergence of Brazilian transnational corporations. The article argues that an important legacy of decades of state intervention in the market fostered the successful internationalisation of big business in Brazil, impacting on Brazil’s international profile. However, this legacy also hampered its systemic competitiveness as evidenced by various international competitiveness rankings. The article concludes with some remarks on the long-run sustainability of Brazil’s current economic performance

Laughter

Set in Boise, “Laughter,” is centered on a gullible anti-heroine and an aspiring writer, who is infatuated with a poet. The novel is about relationships with parents, friends, strangers, complete strangers. An inquiry into what it means to live an authentic life; and what to make of “other” people in fiction: people in books, films, songs. It’s about blurriness: funniness and sadness; creepiness and devotedness; fiction and reality

Brazil's role in institutions of global economic governance : the WTO and G20

The article evaluates the extent to which Brazil's foreign policy actions, negotiating positions and diplomatic strategies in global governance institutions contribute to supporting its national interest and foreign policy aims. It compares Brazil's preferences and behaviour in the World Trade Organization (WTO) and Group of 20 (G20). For decades, Brazil's primary national interest has been national economic development. The article argues that Brazil is moving from a material interests based definition of its prime national interest to a more complex one that includes both material and prestige/status based aspects. Research demonstrates that Brazil has become increasingly focused on gaining recognition as a leader of developing countries, sometimes even at the cost of realising its full material interests. It considers the value of constructivist international relations theory to understanding Brazilian foreign policy

Measuring Factors Regarding Branded Lawn: Gauging the effect of Branding on Purchase Decision

Lawn was never such a popular formal wear fabric as it has become now. Using sophisticated technology, textile mills in cooperation with the local designers are producing the finest quality of lawn. The purpose of this research is to find out the effect of brands on the purchase of lawn and to understand the female buyer behavior for branded lawn. 150 females of posh areas of Karachi were chosen as the sample size for this research. Linear Regression technique was used to test the hypothesis. Keywords: Retail, Fundamentals, Brand Value

Zero Sympathy: Unaccompanied Minors\u27 Rights in the US Immigration System

This note analyzes the US Government\u27s approach to unaccompanied minors and the webs they must navigate when they are apprehended by the US immigration system. More importantly, this note calls for reformative approaches to children\u27s rights through acknowledging the differences between adults and children while simultaneously taking their vulnerability and autonomy into account. After explaining the migrant crisis along with its implications and examining the underlying reasons fostering this movement, this note discusses the legal options available for unaccompanied minors. It draws on the shortcomings of the immigration system as the system labels unaccompanied minors as dependent children, but also treats them as adults. Further, this note establishes and calls attention to the long-term impact of this system on detained children. The note concludes by examining international law more specifically, the Canadian approach outlining how the US system can adopt certain policies to better its treatment of unaccompanied minors and refrain from further human rights violations

POLITICAL DYNAMICS OF FUNDAMENTALISM: A CASE STUDY OF INDIA AND THE US

The inculcation of religion in politics traditionally creates a dogmatic society. The religious divides have become evident due to the influence of religious convictions on politics. Fascism and Communism were the essential products of such political practices where religious motivation was exploited to attain power. In the past few years, the re-emergence of such conduct has taken place in the largest democratic secular nations of India and the US. Therefore, a deeper understanding of the link between modern religious fundamentalism and political dynamics is essential to determine the motivation behind such political practices. The findings based on the discourse analysis suggest that violent religious interpretations have close ties to the political dynamics of these nations, consequently, promoting hate towards minorities and other religious factions. The Hindutva Ideology in India and White Supremacist or Alt-Right movement in the US are a direct consequence of the union of extreme religious believesand politics.   Bibliography Entry Mustansar, Mahrukh. 2020. "Political Dynamics of Fundamentalism: A Case Study of India and the US." Margalla Papers 24 (1): 54-66