No description available.

No description available.

No description available.

No description available.

No description available.

Helical twin screw compressors are being increasingly used in the oil and gas process industry and for refrigeration and air conditioning duties. This machine is capable of high reliability. To achieve it both thermodynamic efficiency and rotor forces must be taken into consideration at the design stage. In this study, a computer program for analysing the forces in a twin screw compressor has been developed. It takes into account all significant factors and includes a rotor profile generation program and a geometrical characteristics calculation program. The programs developed have been integrated with an existing performance simulation program and used to investigate several design aspects of a refrigeration twin screw compressor and an unusual refrigeration system design. A comprehensive examination of lobe tip designs suggests that lobe tip design parameters must be optimised if minimum power consumption is to be achieved and the use of a sealing strip gives an advantage. A para meter study for optimum rotor geometrical parameter combinations has shown that the 4+5 and 5+6 combinations have in general high efficiencies, but less rigidity, while the 5+7 and 4+6 combinations give the opposite results. The highest wrap angle and length/diameter ratio do not always lead to the highest compressor performance. A comprehensive examination of the influence of the slide valve on compressor performance and bearing forces has been conducted. Procedures for determining the optimum slide stop and volume ratios are presented. The detrimental effect of the non-return valve in a refrigeration system driven by a twin screw compressor has been examined. A non-reversing clutch fitted to the prime mover is an alternative, but must be designed according to the shut down torque which is higher than the normal running torque. This is demonstrated. An analytical model for axial-torsional coupled vibration in an Oil-injected twin screw compressor has been created. A frequency analysis of all the excitations has been conducted by using an FFT technique. It is found that the fundamental harmonic dominates the gas torque, while the first two harmonics dominate the axial forces.

We use a sample of Milky Way (MW) analogues for which we have stellar and disc gas mass measurements, published measurements of halo gas masses of the MW and of similar galaxies, and the well-established value of the cosmological baryon fraction to place a lower bound on the mass of the Galaxy of 7.7 x 10(11) M-circle dot and estimate that the mass is likely to be >= 1.2 x 10(12) M-circle dot. Although most dynamical analyses yield measurements consistent with these results, several recent studies have advocated for a total mass well below 10(12) M-circle dot. We reject such low-mass estimates because they imply a Galactic baryon matter fraction significantly above the universal value. Convergence between dynamical mass estimates and those based on the baryonic mass is an important milestone in our understanding of galaxies.

Thermal barrier coatings (TBCs) are a simple and proven method to protect hot section components. Suspension Plasma Spray (SPS), an emerging process technology to generate TBCs, compared with traditional Atmospheric Plasma Spray APS, can deposit thinner coat-ings with finer microstructure. Operating parameters play an important role in developing certain properties of coating. In this thesis work, power level, gas flow rate, number of spray-ing strokes, spray gun's nozzle size i.e. internal diameter and suspension rate were controlled to produce coatings with different microstructures and porosity levels. According to the ex-perimental results, the power level of plasma gun play an essential role on coating micro-structure, for instance, the density of vertical cracks increased with growing the power level. The number of spraying strokes showed also an impact on coating porosity. However, due to different nozzle sizes i.e. diameter, the same coating property were controlled by different operating parameters. For coatings deposited by small and large nozzles, their coating thick-ness and roughness mainly relied on power level and gas flow rate. In contrary, it seems that the coating roughness was not influenced by the same parameters when it was deposited by medium nozzle. Also, gas flow rate do not have as big as influence on coating thickness

One of the tools that is used when developing an engine control system is the Mean Value Engine Model (MVEM). The thesis examines the possibility of using an MVEM that originally was designed to model a SAAB B235R engine to model the considerably different GM Ecotec LNF engine. Engine data was measured at Vehicular Systems laboratory and the measurements were then used to tune the parameters of the MVEM’s submodels. The majority of the components in the original MVEM could be tuned to a good or acceptable performance without any modifications. The submodels describing the port air mass flow, compressor air mass flow and turbine efficiency would all benefit from being modified or replaced, this was however only done for the turbine efficiency model, leaving the improvements of the remaining two submodels as future work.

The increased demand for liquefied natural gas (LNG) has led to the construction of several new LNG terminals in the United States (US) and around the world. To ensure the safety of the public, consequence modeling is used to estimate the exclusion distances. The purpose of having these exclusion distances is to protect the public from being reached by flammable vapors during a release. For LNG industry, the exclusion zones are determined by the half lower flammability limits (half LFL, 2.5% V/V). Since LNG vapors are heavier‐than‐air when released into atmosphere, it goes through stages, negative, neutral and positive buoyant effect. In this process, it may reach the half LFL. The primary objective of this dissertation is to advance the status of LNG vapor dispersion modeling, especially for complex scenarios (i.e. including obstacle effects). The most used software, box models, cannot assess these complex scenarios. Box models simulate the vapor in a free‐obstacle environment. Due to the advancement in computing, this conservative approach has become questionable. New codes as computational fluid dynamics (CFD) have been proven viable and more efficient than box models. The use of such advance tool in consequence modeling requires the refinement of some of the parameters. In these dissertation, these parameters were identified and refine through a series of field tests at the Brayton Firefighter Training Field (BFTF) as part of the Texas A&M University System (TAMUS). A total of five tests contributed to this dissertation, which three of them were designed and executed by the LNG team of the Mary Kay O'Connor Process Safety Center (MKOPSC) and the financial support from BP Global SPU Gas (BP). The data collected were used as calibration for a commercial CFD code called CFX from ANSYS. Once the CFD code was tuned, it was used in a sensitivity analysis to assess the effects of parameters in the LFL distance and the concentration levels. The dissertation discusses also the validity range for the key parameters.