Efficiency Improvements with Low Heat Rejection Concepts Applied to Low Temperature Combustion
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With increasingly stringent governmental regulations on engine emissions such as oxides of nitrogen (NO_(X)) and particulate matter (PM), there is a strong motivation to decrease the production and release of these harmful substances from internal combustion engines. Simultaneously, there are on-going efforts to increase fuel efficiency to curb usage of natural resources and emission of carbon. In general, improvements in one of these areas comes at the cost of the other; however, the results of a previous computational study have indicated that emissions can be decreased while simultaneously increasing efficiency through the application of low heat rejection (LHR) techniques to low temperature combustion (LTC). The goal of this study is to experimentally confirm these findings using a light duty, multi-cylinder diesel engine. LTC is realized through high levels of exhaust gas recirculation (EGR) and retarded injection timings while different degrees of LHR are achieved by means of higher coolant temperatures which should serve to decrease the temperature gradients across the cylinder walls. An energy balance is conducted on the engine to ensure the validity of the efficiency findings. By applying LHR techniques to LTC operation, the undesirable side effects of LTC were found to be mitigated. Specifically, the emissions of carbon monoxide (CO) and unburned hydrocarbons (HC) were reduced and the loss in engine efficiency was also diminished. NO_(X) and PM emissions did increase but they remained at acceptably low levels. In addition, the results of the energy balance substantiated these trends by properly accounting for the bulk of the input energy. While the full potential of improvements in LTC were not explored due to current engine limitations, these results point to the viability of further research into LHR-LTC concepts.
Low Temperature Combustion
Low heat rejection
Penny, Michael (2014). Efficiency Improvements with Low Heat Rejection Concepts Applied to Low Temperature Combustion. Master's thesis, Texas A & M University. Available electronically from