The design and analyses of a subsonic rocket was carried out with the utilization of CFD. The effects of several critical parameters on the rocket performance were investigated. An increment in Mach number at approximately 30% results in an increment of drag coefficient nearly 68%. Changing the turbulence intensity does not make any significant difference on drag coefficient. The drag coefficient obtained from k-ω is higher than that of obtained from k-ω SST.
Increasing air pollution has brought about the search for alternative fuels instead of conventional fuels. It is aimed to make existing internal combustion engines work with alternative fuels with the least structural changes. Natural gas (NG) is one of the most recent alternative fuel studies because it is both cheaper and more environmentally friendly. In this study, it was aimed to minimize the dependence on petroleum-based fuels by enabling an existing compression ignition (CI) engine to operate with spark ignition with NG. For this reason, in heavy-duty diesel engine; it was modeled as 0/1-dimensional with spark plug assembly instead of diesel injector and low-pressure NG fuel injector mounted on the intake manifold. Afterwards, the performance, combustion characteristics, and emission values of the engine, which were converted to NG, were compared with the experimentally validated diesel model. In addition to the comparisons made under similar conditions, the effects of start of combustion (SOC) time and Air/Fuel (A/F) ratio changes in NG use were performed parametrically. In the same conditions, it was observed that the power, fuel consumption, and efficiency of the engine increased in NG fuel use compared to diesel fuel use. However, with the parametric studies in NG use, an improvement of 84.5% was achieved in NOX emission without any performance loss compared to diesel use.
With developing in computer technology, 3D CFD IC engine simulations, which generally use reduced chemical kinetic mechanisms and simplified combustion models, can provide more accurate results along with less initial investment and calculation costs compared to experimental setup. In this study, a heavy-duty diesel engine effects on performance, combustion and emission characteristics by spraying natural gas from the intake port and transforming it into a spark-ignition engine were investigated through 3D ANSYS Forte CFD program. The spark time was accepted as 0.5 °CA bTDC, which was the start of injection time for the diesel injector. Analyzes were carried out at 2300 rpm, full load, 17.5: 1 of high compression ratio, constant air/fuel ratio. Six different global mesh sizes were used in the converted engine model. Performance, in-cylinder combustion, and emission values were examined for these six different global mesh sizes and the most suitable one was tried to be found. As a result of the global mesh size study, it was concluded that the most suitable size was 2.25 mm. In terms of performance, when the data obtained with usage of natural gas were compared to that of diesel fuel, the GIP, IMEP and ITE values were increased by 12.02%, 8.93%, and 8.7%, respectively, while the GISFC value was decreased by 9.78%. When the emission values were examined, it was seen that the engine met the Stage IIIB norms without usage of SCR, DPF and DOC under the conditions.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.