CFD study of filtration process in moulded filters within a vacuum pump

Air/Oil filtration through filters is commonly utilised in the vacuum industry where oil lubricated pumps are used across a number of different applications such as food and packaging, industrial, pharmaceutical, R&D, forming and drying. The air/oil filters are crucial in the reduction of exhaust emissions, which, when suspended as fine particulate matter can cause great harm to the environment, climate, equipment life and public health. However, the behaviour of flow through the filters is not fully understood and much of the design and development work is based on historical know-how and experimental studies. Computational Fluid Dynamics (CFD) is a powerful tool to understand the flow characteristics and droplet trajectory through the filters which is challenging through experimental techniques. In this study, a CFD model is developed by using the commercial ANSYS FLUENT code. Oil droplets from the pump entering the filter are treated as a discrete phase. Euler-Lagrangian frame is used to characterise the multiphase flow, K-Ɛ as a turbulence model, Rosin-Rammler distribution of oil droplets, User Defined Functions (UDF) are written for droplet injection, distribution and deposition. Various methodologies and tests were developed to obtain the required data to feed into the model and validate the data predicted by the computational model. The obtained computational data agrees well with the experimental data

Polymetallic triplet emitters

This work is concerned with the synthesis and property investigation of a relatively new class of cyclometallated Ir(III) and Pt(II) complexes in which two metal centres are coordinated to a common heterocycle resulting in a rigid polymetallic assembly. Highly luminescent materials which can emit and absorb in a red region of the spectrum were targeted. There are three main parts of the thesis. The first part investigates how luminescent properties of the diplatinum systems are affected by the bridging ligand. A series of novel mono- and dinuclear Pt(II) complexes has been prepared and their luminescent and redox properties investigated. The main observation is that the introduction of the second metal centre leads to a substantial red-shift in absorption and emission. In the second part the role of changing the ligand substituents in a cyclometallated complex has been investigated to determine the extent to which luminescence is affected by the nature of the substituents. A series of mono- and dinuclear Pt(II) complexes have been prepared using substituted pyrazine bridging ligands. It was found that electron donating substituents such as –OMe in the benzene cyclometallating ring cause a red-shift, while electron withdrawing substituents such as –F cause a blue-shift in emission. The final part of the work describes the synthesis of cyclometallated homometallic bis Ir(III) complexes. A series of bis- Ir(III) complexes have been prepared using a terdentate cyclometallating N^C^N coordinating 1,3-di(2-pyridyl)benzene derivative as an auxiliary ligand. It was found that the nature of the bridging ligand determines the overall stability of the complex. Pyrimidine-linked systems were found to be the most stable, while pyrazine analogues readily photodecompose/isomerise. Pyridazine-linked systems lead to ionic complexes where one chloride ligand is shared by two Iridium metal centres

Highly Luminescent Dinuclear Platinum(II) Complexes Incorporating Bis-Cyclometallating Pyrazine-Based Ligands: A Versatile Approach to Efficient Red Phosphors

A series of luminescent dinuclear platinum­(II) complexes incorporating diphenylpyrazine-based bridging ligands (L^<i>n</i>H₂) has been prepared. Both 2,5-diphenylpyrazine (L²H₂) and 2,3-diphenylpyrazine (L³H₂) are able to undergo cyclometalation of the two phenyl rings, with each metal ion binding to the two nitrogen atoms of the central heterocycle, giving, after treatment with the anion of dipivaloyl methane (dpm), complexes of formula {Pt­(dpm)}₂L^<i>n</i>. These compounds are isomers of the analogous complex of 4,6-diphenylpyrimidine (L¹H₂). Related complexes of dibenzo­(f,h)­quinoxaline (L⁴H₂), 2,3-diphenyl-quinoxaline (L⁵H₂), and dibenzo­[3,2-a:2′,3′-c]­phenazine (L⁶H₂) have also been prepared, allowing the effects of strapping together the phenyl rings (L⁴H₂ and L⁶H₂) and/or extension of the conjugation from pyrazine to quinoxaline (L⁵H₂ and L⁶H₂) to be investigated. In all cases, the corresponding mononuclear complexes, Pt­(dpm)­L^<i>n</i>H, have been isolated too. All 12 complexes are phosphorescent in solution at ambient temperature. Emission spectra of the dinuclear complexes are consistently red shifted compared to their mononuclear analogues, as are the lowest energy absorption bands. Electrochemical data and TD-DFT calculations suggest that this effect arises primarily from stabilization of the LUMO. Introduction of the second metal ion also has the effect of substantially increasing the molar absorptivity and, in most cases, the radiative rate constants. Meanwhile, extension of conjugation in the heterocycle of L⁵H₂ and L⁶H₂ and planarization of the aromatic system favored by interannular bond formation in L⁴H₂ and L⁶H₂ leads to further red shifts of the absorption and emission spectra to wavelengths that are unusually long for cyclometalated platinum­(II) complexes. The results may offer a versatile design strategy for tuning and optimizing the optical properties of d-block metal complexes for contemporary applications

Highly Luminescent Dinuclear Platinum(II) Complexes Incorporating Bis-Cyclometallating Pyrazine-Based Ligands: A Versatile Approach to Efficient Red Phosphors

A series of luminescent dinuclear platinum(II) complexes incorporating diphenylpyrazine-based bridging ligands ((LH2)-H-n) has been prepared. Both 2,5-diphenylpyrazine ((LH2)-H-2) and 2,3-diphenylpyrazine ((LH2)-H-3) are able to undergo cyclometalation of the two phenyl rings, with each metal ion binding to the two nitrogen atoms of the central heterocycle, giving, after treatment with the anion of dipivaloyl methane (dpm), complexes of formula \{Pt(dpm)\}(2)L-n. These compounds are isomers of the analogous complex of 4,6-diphenylpyrimidine ((LH2)-H-1). Related complexes of dibenzo-(f,h)quinoxaline ((LH2)-H-4), 2,3-diphenyl-quinoxaline ((LH2)-H-5), and dibenzo{[}3,2-a:2',3'-c]phenazine ((LH2)-H-6) have also been prepared, allowing the effects of strapping together the phenyl rings ((LH2)-H-4 and (LH2)-H-6) and/or extension of the conjugation from pyrazine to quinoxaline ((LH2)-H-5 and (LH2)-H-6) to be investigated. In all cases, the corresponding mononuclear complexes, Pt(dpm)(LH)-H-n, have been isolated too. All 12 complexes are phosphorescent in solution at ambient temperature. Emission spectra of the dinuclear complexes are consistently red shifted compared to their mononuclear analogues, as are the lowest energy absorption bands. Electrochemical data and TD-DFT calculations suggest that this effect arises primarily from stabilization of the LUMO. Introduction of the second metal ion also has the effect of substantially increasing the molar absorptivity and, in most cases, the radiative rate constants. Meanwhile, extension of conjugation in the heterocycle of (LH2)-H-5 and (LH2)-H-6 and planarization of the aromatic system favored by interannular bond formation in (LH2)-H-4 and (LH2)-H-6 leads to further red shifts of the absorption and emission spectra to wavelengths that are unusually long for cyclometalated platinum(II) complexes. The results may offer a versatile design strategy for tuning and optimizing the optical properties of d-block metal complexes for contemporary applications