Use of Vegetable Oil Lubricant in a Low Heat Rejection Engine to Reduce Particulate Emissions

Thermal barrier coated diesel engines, also known as low heat rejection (LHR) engines, have offered the promise of reducing heat rejection to the engine coolant and thereby increasing overall thermal efficiency. However, the larger market potential for thermal barrier coated engines may be in retrofitting in-service diesel engines to reduce particulate emissions. Prior work by the authors has demonstrated a significant decrease in particulate emissions from a thermal barrier coated, single-cylinder, indirect injection (IDI) diesel engine, primarily through reduction of the volatile (VOF) and soluble (SOF) fraction of the particulate. This prior work relied on conventional, commercially available, petroleum-based lubricants. The present study concerns the additional benefits for particulate reduction provided by vegetable oil lubricants. These lubricants are derived from renewable resource materials and can provide a reduction in lubricant generated particulate matter. The single-cylinder IDI engine was operated with and without thermal barrier coated components, and with petroleum-based lubricants and a vegetable oil lubricant for comparison purposes. Evaluation of the potential benefits of the vegetable oil lubricant are based on differences in total particulate emissions. In addition, four-ball wear test data on this vegetable oil formulation shows that similar or improved wear friction characteristics when compared with commercial petroleum and synthetic lubricants.