Modeling and Validation of a Split Cycle Clean Combustion Diesel Engine Concept

This paper is a part of the research happening at the University of Illinois at Chicago together with Caterpillar Inc. for the development and validation of a split cycle clean combustion engine (SCCCE) operating on diesel fuel. A two-cylinder variant of the SCCCE is modeled using Caterpillar's one-dimensional modeling software Dynasty, following the geometric and boundary specifications given by the University of Pisa in their paper by Musu et al. (2010, “Clean Diesel Combustion by Means of the HCPC Concept,” SAE Paper No. 2010-01-1256). The results are compared to validate our modeling methodology. The split cycle clean combustion (SCCC) concept may significantly reduce gaseous and particulate emissions while maintaining high engine efficiency compared to the current state of the art diesel engine. Some manufacturers have been prototyping gasoline engines based on the SCCC concept, but there are no diesel fuel powered SCCC engine prototypes existing in the market. This study will be a significant contribution in the performance evaluation of SCCC diesel engines at high load and part load conditions. A one-dimensional modeling technique was chosen for this study due to the need of a fast running model that could be improved using design of experiments (DOE) analysis. Computational fluid dynamics (CFD) modeling produces more accurate results but limits one's ability to model a large number of configurations due to its large computational overhead that slows down the overall simulation process, thus making CFD models not feasible for this DOE. In order to accurately model an SCCC engine, we first validated our modeling methodology by reproducing results of the CFD based model presented by University of Pisa in Musu et al. (2010, “Clean Diesel Combustion by Means of the HCPC Concept,” SAE Paper No. 2010-01-1256). A satisfactory comparison of results confirmed our modeling approach and enabled us to integrate more complex models that will be discussed in future publications.

Regulated emissions and speciated hydrocarbons from smokeless low-temperature combustion diesel engines with ultra-high exhaust gas recirculation and exhaust oxidation catalyst

With ultra-high exhaust gas recirculation (EGR) suppressing the in-cylinder soot and nitrogen oxides (NO x) formation as well as with the exhaust oxidation catalyst removing the engine-out total unburned hydrocarbon (THC) and carbon monoxide (CO) emissions, clean diesel combustion in terms of low regulated emissions (NO x, particulate matter, THC, and CO) can be established in an operating range up to 50 per cent load. However, unregulated emissions such as aldehydes, aromatics, and 1,3-butadiene, which are seen as a severe threat to human health, are concerned when operating the engine with ultra-high EGR. In this study, the THC emissions from a diesel engine operated with ultra-high EGR low-temperature combustion were speciated using Fourier transform infrared spectroscopy. Some unregulated toxic emissions including aldehydes, aromatics, 1,3-butadiene, and some low molecular hydrocarbons dramatically increase in the ultra-high EGR low-temperature combustion regime. The exhaust oxidation catalyst is effective to remove aldehydes and some unsaturated hydrocarbons, but aromatics and methane generated from the ultra-high EGR operation are hardly reduced, particularly at higher loads.