Abstract: Liquefied Natural Gas (LNG) fleets are coasting with various condition and behavior. These variable leads to different type of LNG fleets build every year with unavoidable generated Boil-off Gas (BOG). Estimation of BOG generated inside LNG tank play significant role in determines the ship specification and management method of BOG including venting, propulsion or requalification. Hence, in the present study, the right choices of boundary condition and parameter have been implementing in order to have good estimation amount of BOG evaporates for specific LNG tank. Three dimensional model of cargo with capacity 160000 m3 LNG carrier are simulate using ANSYS Fluent with specific ambient air temperature of 5oC and ambient seawater temperature of 0oC have been chosen as a calculation case, gain the total heat transfer rate and Boil-off Rate (BOR). The result shows that the calculation model and simulation are feasible with typical LNG fleet specification and International Marine Organization (IMO) standard.
Abstract: Diesel engines generate undesirable exhaust emissions during combustion process and identified as major source pollution in the worldwide ecosystem. To reduce emissions, the improvements throughout the premixing of fuel and air have been considered especially at early stage of ignition process. Purpose of this study is to clarify the effects of swirl velocity on flow fuel-air premixing mechanism and burning process in diesel combustion that strongly affects the exhaust emissions. The effects of physical factors on mixture formation and combustion process to improve exhaust emissions are discussed in detail. This study investigated diesel combustion fundamentally using a rapid compression machine (RCM) together with the schlieren photography and direct photography methods. RCM was used to simulate actual phenomenon inside the combustion chamber with changing design parameter such as swirl velocity, injection strategies and variable nozzle concept. The detail behavior of mixture formation during ignition delay period was investigated using the schlieren photography system with a high speed digital video camera. This method can capture spray evaporation, spray interference and mixture formation clearly with real images. Ignition process and flame development were investigated by direct photography method using a light sensitive high-speed color digital video camera. Moreover, the mechanism and behavior of mixture formation were analyzed by newly developed image analysis technique. Under high swirl condition, the ignition delay is extended, the higher heat losses and unutilized high-density oxygen associated with slower initial heat recovery begins might be the explanation for the longer combustion duration, reductions of pick heat release and promote combustion and soot oxidation. The real images of mixture formation and flame development reveal that the spray tip penetration is bended by the high swirl motion, fuel is mainly distributed at the center of combustion chamber, resulting that flame is only formed at the center region of the combustion chamber. It is necessary for high swirl condition to improve fuel-air premixing.
Abstract: Flow rate measurements are among the most important operations in modern industries dealing with increasingly expensive fluids such as petroleum, natural gas and water. The accuracy of flow meters depends mainly on their position in a pipe network and their operating conditions. Pipe fittings such as valves and bends generate turbulence and swirl and distort the flow distribution in the pipe, leading to a substantial amount of measuring error. For accurate flow rate measurements, the standards ISO 5167 specify either a sufficient straight piping lengths or the inclusion of a flow conditioner between the flow distortion and the flow meter. Flow conditioners serve to reduce the developing length between pipe fittings and flow meters and to create fully developed flow condition within short distances. In the present study, numerical modeling of the flow development upstream and downstream of the orifice plate which used circle grid fractal flow conditioner has been made. Computational Flow Dynamics techniques have been used to predict the flow development downstream the flow conditioners.
Abstract: In the previous study, the relationship between leakage and the contact width size that prevent leakage for 25A size of new metal gasket has been examined. In this study, large size of new metal gasket which are 50A, 80A and 100 A sizes were evaluated by using same approach of leak measurement and the relationship between leakage and the contact width. A new approach of leak measurement was performed to clarify the relationship between the presence of leak produced by the water pressure test and the amount of helium leak rate using helium leak test. Moreover, comparing the evaluation results of the relationship between the clamping load and the contact width by using the finite element method (FEM) analysis with the experimental results of the clamping load and the leakage, the contact width which affects the occurrence of leakages on new metal gasket was clarified. The results obtained for these gaskets indicated that the contact width is similar.
Abstract: In this paper, plasma transfer arc welding using hard faced material Colmonoy which is deposited on a annular groove of a circular grid plate made up of SS 304 was studied. Hard face deposition made by Plasma Transferred Arc Welding (PTAW) on a annular groove of a grid plate at relatively high temperature, generates residual stresses due to differential shrinkage of the molten deposit, process-induced thermal gradients and difference in coefficients of thermal expansion between the colmonoy deposit and base material SS 304. However, the magnitude and distribution of the residual stresses vary depending on the heat input, deposition process, and the geometry of the component. Finite element analysis of residual stress is performed with commercial FEA package of ANSYS 12.0 which includes moving heat source, material deposit, temperature dependent material properties, metal plasticity and elasticity. Coupled thermo-mechanical analysis is done for welding simulation and the element birth and death technique is employed for simulation of filler metal deposition. Finally residual stress is evaluated so that annealing is performed accordingly to relieve residual stresses in order to carry out fracture analyses thereafter.
Abstract: LAT (Laser Assisted Turning) is an effective machining method for difficult to cut materials. Especially, because of the characteristics of a significant reduction in machining costs and flexibility in its machining, the applications of LAT have been largely extended to various machining fields. However, Studies on LAT are still staying at the beginning of research and represent a limitation in which a LAT process was applied to round members only. According to increases in customized production of special purpose parts, the researches on LAT for clover or polygon section members are necessary. In this paper, a LATM (laser assisted turn-mill) process was proposed to complement LAT.
Abstract: The article examines the influence of compressive forces on the deformation of the cylindrical roller. We considered the features of deformation of two cylindrical bodies with identical elastic properties and elastic plastic deformation of the deforming element of the solid parts. Duing the process we calculated deformation of the cylindrical deforming element which is located between the two contracting rigid planar faces of it with a light contact and general deformations. It is shown that the relative deformation of the reels when they are loading does not depend much on the diameter, but depends only on the loading force. It’s produced by computer simulation of compression of a cylindrical roller with two absolutely rigid plates using the software like Pro/E, Solidworks and ANSYS. We obtain the results of experimental investigations of the deformation roller during its compression of flat plates with a hardness of HRC = 65. It was revealed that the deformation roller obtained experimentally is almost identical with the calculated values. It is shown that deformation of the roller shall not exceed two percent of its diameter, and in the calculations determining the parameters of the contact zone can not take into account its deformation.
Abstract: The Polytetrafluoroethylene (PTFE or Teflon) based propellants may be used in Pulsed Plasma Thruster, laser ablation thruster and other advanced propulsion systems. Because of the complex behaviors and phenomena of PTFE in ablation process, the study on thrusters’ operation process becomes complicated. Thermal and mechanical events are investigated, including phase transition, thermo-chemical and optical property variations, and multi-pulses laser ablation of PTFE. Considering more details including internal absorption of radiation, reflectivity of material, surface emission, a one-dimensional ablation model is developed and implemented numerically using a non-uniform grid, and implicit finite-volume method to gain greater insight into the process of laser ablation. The model is validated against analytical solutions and is in accordance with previous experimental results. The parameters of optical transmittance, reflectance and absorption coefficients are measured in experiments and are used in the numerical simulation. The laser ablation characteristics of PTFE are investigated, including the effects of wavelength and multipulses. It’s indicated that the laser ablation processes are influenced intensively by changing the laser wavelength and the effects of multiple pulses are also significant. The above numerical simulation provides insight into physical mechanisms of laser ablation, and suggests potential ways of improving thruster’s efficiency
Abstract: This research presents results obtained from numerical analysis of a circular composite plate under impact of drop hammer and internal pressure load simultaneously. Influence of reinforced orientationangles of the multi-layer composite plate with fixed boundary conditions on displacements and axial stresses along the radius direction was studied. Employing ABAQUS software results for reinforcedorientation angles of [0/90/0]s, [0/45/60]s, [0/45/90]s, [0/30/60]s, [0/30/75]s, [0/15/30/60/75/90],[0/45/90/90/-45/0] are compared. Finding indicated that the reinforcedorientation angles have considerable effect on the axial stresses changing from compressive to tensile stresses. [0/45/90/90/-45/0]s showed the minimum displacements and axial stresses.
Abstract: The endwall and blade film cooling systems are the typical solution adopted within gas turbines to allow further increase of turbine inlet temperature, avoiding critical material thermal stresses. Due to complex secondary flow field in the blade passage, endwallis more difficult to cool than blade surfaces. In the matter of fact, in endwall film cooling studies, it is necessary to investigate the interaction between coolant air and the secondary flow. In present study, the flow field of high-pressure turbine cascade has been investigated by 5-holes pitot tube to reveal the secondary flows behavior under the influenced of purge flows while the heat transfer measurement was conducted bythermochromic liquid crystal (TLC). Experimental has significantly captured theaerodynamics effect of purge flowat blade downstream close to the endwall region. Furthermore, TLC measurement illustrated that the film cooling effectiveness and heat transfer coefficient contours were strongly influenced by the secondary flow on the endwall.