Current Issue : January - March Volume : 2017 Issue Number : 1 Articles : 5 Articles
Turbulent reacting flows in a generic swirl gas turbine combustor are investigated numerically. Turbulence is modelled by a URANS\nformulation in combination with the SST turbulence model, as the basic modelling approach. For comparison, URANS is applied\nalso in combination with the RSM turbulence model to one of the investigated cases. For this case, LES is also used for turbulence\nmodelling. For modelling turbulence-chemistry interaction, a laminar flamelet model is used, which is based on the mixture\nfraction and the reaction progress variable. This model is implemented in the open source CFD code OpenFOAM, which has\nbeen used as the basis for the present investigation. For validation purposes, predictions are compared with the measurements for\na natural gas flame with external flue gas recirculation. A good agreement with the experimental data is observed. Subsequently,\nthe numerical study is extended to syngas, for comparing its combustion behavior with that of natural gas. Here, the analysis is\ncarried out for cases without external flue gas recirculation. The computational model is observed to provide a fair prediction of\nthe experimental data and predict the increased flashback propensity of syngas....
This study presents a numerical analysis of the melting process of phase change materials (PCMs) within a latent heat thermal\nenergy storage (LHTES) system employing zigzag plate. The numerical model used NaCl-MgCl2 mixture as PCMs and hot air as\nheat transfer fluid (HTF). An experimental system was built to validate the model, and the experimental data agrees reasonably\nwell with the simulation results. The simulation results revealed the effects of the Reynolds and Stefan numbers and the surface\ntopography of the zigzag plate on the charging process. Besides, the effect of the relationship between Reynolds and Stefan numbers\non the charging process under a new boundary condition employing a fixed input power was studied. It is found that by modifying\nthe shape of the zigzag plate surface it is feasible to enhance the heat transfer of the LHTES unit remarkably. The melting rate of\nPCMs increases with the value of Ste or Re numbers with only one of them changing; however, the melting rate of PCMs decreases\nwith the increasing Ste (or decreasing Re) in a fixed input power condition....
The free-piston gasoline engine linear generator (FPGLG) is a new kind of power plant\nconsisting of free-piston gasoline engines and a linear generator. Due to the elimination of the\ncrankshaft mechanism, the piston motion process and the combustion heat release process affect each\nother significantly. In this paper, the combustion characteristics during the stable generating process\nof a FPGLG were presented using a numerical iteration method, which coupled a zero-dimensional\npiston dynamic model and a three-dimensional scavenging model with the combustion process\nsimulation. The results indicated that, compared to the conventional engine (CE), the heat release\nprocess of the FPGLG lasted longer with a lower peak heat release rate. The indicated thermal\nefficiency of the engine was lower because less heat was released around the piston top dead centre\n(TDC). Very minimal difference was observed on the ignition delay duration between the FPGLG\nand the CE, while the post-combustion period of the FPGLG was significantly longer than that of the\nCE. Meanwhile, the FPGLG was found to operate more moderately due to lower peak in-cylinder\ngas pressure and a lower pressure rising rate. The potential advantage of the FPGLG in lower NOx\nemission was also proven with the simulation results presented in this paper....
A detailed single zone, zero dimensional model of diesel multiple-injection system\nwas developed from first principle, for compression, combustion and expansion\nprocesses for direct injection diesel engine. Equilibrium equation of Extended Zeldolvich\nMechanism (EZM) for NOx formation was incorporated to predict NOx\nemission. A different approach was assumed for the equilibrium temperature. An\napproach of using the average cycle temperature within NOx formation region was\nused in the EZM equilibrium equation. The model codes were implemented in\nMATLAB. This model is developed to investigate the effects of both single and multiple-\npulse fuel injection strategies on engine performance and NOx emissions. The\nresults obtained from the model were validated with experimental data available in\nthe literature. Results obtained showed that the use of average cycle temperature\nwithin the NOx formation temperature region could be useful in predicting NOx\nformation with reasonable degree of accuracy. Injection timing, mass ratio of injected\nfuel, and dwell between pulses have significant effects on the NOx emission\nand engine performance. The results also show that as the number of pulses increases,\nNOx emission and engine performance decrease. For optimal balance between\nNOx and engine performance, mass of the pilot injection should be between 10 and\n25% of the total mass of fuel used per cycle....
This experiment aims to summarize the properties of glazed tiles that heated by the low-carbon\ncatalytic combustion furnace of natural gas. The tiles heated by the catalytic combustion furnace\nare more fine and glossy than the conventional ones. This conclusion provides a new way to glazed\ntile heating industry. Only with a better understanding of catalytic combustion, can the application\nbenefit our environment and industry....
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