Current Issue : April - June Volume : 2015 Issue Number : 2 Articles : 5 Articles
Accurate tests and performance analysis of engines are required to minimize measurement errors and so the use of the advanced\ntest equipment is imperative. In other words, the reliable test results depend on themeasurement ofmany parameters and recording\nthe experimental data accurately which is depended on engine test unit. This study aims to design the control system of an internal\ncombustion engine test unit. In the study, the performance parameters of an available internal combustion engine have been\ntransferred to computer in real time.Adata acquisition (DAQ) card has been used to transfer the experimental data to the computer.\nAlso, a user interface has been developed for performing the necessary procedures by using LabVIEW. The dynamometer load, the\nfuel consumption, and the desired speed can easily be adjusted precisely by usingDAQcard and the user interface during the engine\ntest. Load, fuel consumption, and temperature values (the engine inlet-outlet, exhaust inlet-outlet, oil, and environment) can be\nseen on the interface and also these values can be recorded to the computer. It is expected that developed system will contribute\nboth to the education of students and to the researchers� studies and so it will eliminate a major lack....
An advanced and intensive computational solution development is integrated with an asymptotic technique, to examine the impact\nof the combustion surface morphology on the generated rotational flow field in a solid rocket chamber with wide ranges of forcing\nfrequencies. The simulated rectangular chamber is closed at one end and is open at the aft end. The upper and lower walls are\npermeable to allow steady and unsteady injected air to generate internal flow mimicking the flow field of the combustion gases\nin real rocket chamber. The frequencies of the unsteady injected flow are chosen to be very close or away from the resonance\nfrequencies of the adapted chamber. The current study accounts for a wide range of wave numbers that reflect the complexity of\nreal burning processes. Detailed derivation for Navier-Stokes equations at the four boundaries of the chamber is introduced in the\ncurrent study. Qualitative comparison is performed with recent experimental work carried out on a two-inch hybrid rocket motor\nusing a mixture of polyethylene and aluminum powder.The higher the percentage of aluminum powder in the mixture, the more\nthe corrugations of the combustion surface. This trend is almost similar to the computational and analytical results of a simulated\nsolid rocket chamber....
Micro-nanocrystalline microstructures which are characterized by TiB2 platelets of the average thickness close to or smaller than\n1 ????m can be achieved in nearly full-density solidified TiC-TiB2 ceramic composites with Cr-based alloy phases by combustion\nsynthesis in ultra-high gravity field of 2500 g. The filler phases in ceramic composites are actually Cr-based alloy with a little\nsolidified solution of Ni atoms and Al atoms. The hardness, flexural strength, and fracture toughness of the materials are 18.5 �±\n1.5 GPa, 650 �± 35MPa, and 16.5 �± 1.5MPa?m0.5, respectively. The improved fracture toughness of TiC-TiB2 ceramic composites\nresults from crack deflection, crack bridging, and pull-out by a large number of fine TiB2 platelets and plastic deformation with\nsome Cr-based alloy phases....
In the recent decades changes in fire regimes led to higher vulnerability of fire prone ecosystems, with vegetation being the\nonly component influencing fire regime which can be managed in order to reduce probability of extreme fire events. For these\nmanagement practices to be effective reliable information on the vegetation flammability is being crucial. Epiradiator based testing\nmethods are one of the methods commonly used to investigate vegetation flammability and decrease in ignition frequency is always\ninterpreted as a decrease in flammability. Furthermore, gathered information is often combined into a single flammability score.\nHere we present results of leaf litter testing which, together with previously conducted research on similar materials, show that\nmaterial with very low ignition frequency under certain testing conditions can be extremely flammable if testing conditions are\nslightly changed. Additionally, our results indicate that combining measured information into one single flammability score, even\nthough sometimes useful, is not always meaningful and should be performed with caution....
Syngas from biomass and solid waste is a carbon-neutral fuel believed to be a promising fuel for future engines. It was widely\nused for spark-ignition engines in the WWII era before being replaced with gasoline. In this paper, the technological development,\nsuccess, and challenges for application of syngas in power generating plants, the trends of engine technologies, and the potential\nof this fuel in the current engine technology are highlighted. Products of gasification vary with the variation of input parameters.\nTherefore, three different syngases selected from the two major gasification product categories are used as case studies. Their fuel\nproperties are compared to those of CNG and hydrogen and the effects on the performance and emissions are studied. Syngases\nhave very low stoichiometric air-fuel ratio; as a result they are not suitable for stoichiometric application. Besides, syngases have\nhigher laminar flame speed as compared to CNG. Therefore, stratification under lean operation should be used in order to keep\ntheir performance and emissions of NOx comparable to CNG counterpart. However, late injection stratification leads to injection\nduration limitation leading to restriction of output power and torque. Therefore, proper optimization of major engine variables\nshould be done in the current engine technology....
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