Validation of engine combustion models against detailed in-cylinder optical diagnostics data for a heavy-duty compression-ignition engine

Abstract

Three different approaches for modelling in-cylinder compression-ignition engine processes for partially premixed combustion modes are compared with experimentally observed cylinder pressure and in-cylinder images of liquid-and vapour-fuel penetration, ignition, combustion, and soot formation in an optically accessible heavy-duty direct injection engine. A multi-dimensional computational fluid dynamics model for engine combustion, KIVA-3V, served as a common platform into which three different combustion submodels were integrated: (1) characteristic time combustion (KIVA-CTC); (2) representative interactive flamelet (KIVA-RIF); and (3) direct integration using detailed chemistry (KIVA-CHEMKIN). Three different engine operating strategies with significant premixing of fuel and air prior to ignition were investigated: low-temperature combustion achieved by charge dilution, with fuel injection either (1) early, or (2) late in the engine cycle, and (3) long ignition delay, hightemperature combustion (i.e. no charge dilution) with fuel injection near top dead centre of the piston stroke.Comparison of simulated cylinder pressure and heat-release rates with the experimental results shows that all the combustion submodels predict the cylinder pressures and heat-release rates reasonably well, but predictions of in-cylinder phenomena were significantly different among the submodels. The KIVA-CHEMKIN submodel predictions agree best with experimental observations of the location of ignition sites and the spatial distribution of soot and OH. The KIVA-RIF model, which uses global quantities to account for turbulence-chemistry interactions, under-predicts the flame lift-off, while ignition sites and species distributions are broader than observed experimentally. The KIVA-CTC submodel greatly over-predicts the spatial extent and total amount of in-cylinder soot.

Gradient effects on two-color soot optical pyrometry in a heavy-duty DI diesel engine

“…Furthermore, many soot models are phenomenologically based, so that the soot and soot luminosity predictions can be directly compared to the spatial and temporal evolution of in-cylinder soot observed in experiments. Indeed, in a previous study, the predictions of the same phenomenological soot model used in the current study agreed well with optical/imaging observations of the spatial and temporal development of in-cylinder soot [15]. Accordingly, with three-dimensionally resolved distributions of soot temperature and volume fraction, these models can predict the resulting soot radiative emission.…”

“…The fuel was a 2007 emissions-certification grade ultralow-sulfur number 2 diesel fuel that was typical of U.S. diesel fuel, having a cetane number of 46. Additional fuel specifications can be found in [15].…”

A review of the combustion and emissions properties of advanced transportation biofuels and their impact on existing and future engines

“…A cartoon of one possible diesel low-temperature combustion process is provided in Fig. 5 [123,229,353,354].…”

Evaluation of the necessity of exhaust gas recirculation employment for a methanol/diesel reactivity controlled compression ignition engine operated at medium loads

“…It was found that further refinement of the computational mesh would lead to the increase of computational time without significantly improving the accuracy of the prediction. The subgrid-scale turbulence-chemistry interaction is not taken into consideration for RCCI combustion due to its nearly complete premixed and/or partially premixed combustion as demonstrated by Singh et al [31]. In this study, the simulation started from IVC timing to EVO timing regardless of intake and exhaust processes.…”