Browsing by Subject "combustion"

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Additive Manufacturing of Si-SiC Cermets for Combustion Device Applications
(University of Texas at Austin, 2021) Radyjowski, P.P.; Bourell, D.L.; Kovar, D.; Ellzey, J.L.
Traditional manufacturing methods for high-temperature devices are time intensive and limited to simple shapes. Additive manufacturing (AM) reduces lead times and opens the design space to more complex geometries. Indirect laser sintering of siliconized silicon carbide (Si-SiC) cermets was evaluated for creating devices compatible with combustion environments. Heat recirculating combustors especially benefit from geometric flexibility. Si-SiC process improvements are presented for the production of cermet combustors. The effect of flame on the material was studied by directly exposing samples to hot combustion products at 1000°C and 1260°C for 10 hours. Subsequently, three experimental Si-SiC combustors were manufactured and fired to evaluate the practical aspects of cermet applications. Each device was operated for 70 hours under excess-air methane flames with solid temperatures up to 1405°C. The surface oxidation and phase changes were assessed. Operating temperatures between 1200°C and 1350°C reduce damage to the material and give a promise of long-term, high-temperature operation.
Combustion Emissions Modeling and Testing of Conventional Diesel Fuel
(American Society of Mechanical Engineers, 2010-05) Liu, H-P.; Strank, S.M.; Werst, M.D.; Hebner, R.E.; Osara, J.
This paper presents emissions modeling and testing of a four-stroke single cylinder diesel engine using conventional No. 2 diesel fuel. A system level engine simulation tool developed by Gamma Technologies, GT-Power, has been used to perform engine combustion simulations. The simulation approach is a predictive combustion simulation, direct-injection jet modeling, which is primarily used to predict the burn rate and NOx emissions. Crank angle dependent fuel injector sac pressure profiles have been measured during combustion tests and used as fuel jet inputs in the combustion modeling to predict injected fuel mass and fuel jet velocity as a function of time. In each emissions test, an in-cylinder pressure profile was measured and used for combustion model calibration to assure a correct burn rate profile was predicted and the exhaust emissions prediction was based on a calibrated burn rate profile which closely resembled the one measured in the test. Engine emissions, which include NOx , HC, CO, and CO2 , measured at various engine speeds and loads were compared to those predicted by the combustion simulations. The maximum differences between simulation-predicted and test-measured emissions data are 30% for the NOx emissions and 68% for the CO2 emissions. However, the results for CO and HC emissions could differ by more than an order of magnitude under the conditions tested. The modeling and testing evaluation of conventional diesel was chosen to provide a comparative baseline analysis that can be extended for predicting combustion emissions of renewable feedstock fuels in development.
Combustion Emissions Modeling and Testing of Neat Biodiesel Fuels
(American Society of Mechanical Engineers, 2010-05) Liu, H-P.; Strank, S.M.; Werst, M.D.; Hebner, R.E.; Osara, J.
This paper presents emissions modeling and testing of a four-stroke single cylinder diesel engine using pure soybean, cottonseed, and algae biodiesel fuels. A system level engine simulation tool developed by Gamma Technologies, GT-Power, has been used to perform predictive engine combustion simulations using direct-injection jet modeling technique. Various physical and thermodynamic properties of the biodiesel fuels in both liquid and vapor states are required by the GT-Power combustion simulations. However, many of these fuel properties either do not exist or are not available in published literatures. The properties of the individual fatty esters, that comprise a biofuel, determine the overall fuel properties of the biofuel. In this study, fatty acid profiles of the soybean, cottonseed, and algae methylester biodiesel fuels have been identified and used for fuel property calculations. The predicted thermo-physical properties of biodiesels were then provided as fuel property inputs in the biodiesel combustion simulations. Using the calculated biodiesel fuel properties and an assumed fuel injector sac pressure profile, engine emissions of the conventional diesel and biodiesel fuels have been predicted from combustion simulations to investigate emission impacts of the biodiesel fuels. Soybean biodiesel engine emissions, which include NOx, HC, CO and CO2 , measured at various engine speeds and loads in actual combustion emissions tests performed in this study were also compared to those predicted by the combustion simulations.