PL EN Your account Create account

Registered articles list

Performance of a Small Indirect-Injection Diesel Engine with Intermetallic Thermal Barrier Coated Pistons

Amid the increasing regulations of emissions from internal combustion, a new coating technology is implemented to improve efficiency of a small indirect-injection diesel engine. During combustion in conventional engines approximately one third of fuel energy is lost due to the heat transfer, close to a half is converted to the useful work, and the remainder is rejected with the exhaust gases. The idea of designing a Low Heat Rejection (LHR) engine has been explored in literature to reduce the heat rejected to the cooling system while increasing the fuel energy converted into useable work. This improved thermal efficiency has also led to measured gains in fuel economy and emissions reduction. To achieve this semi-adiabatic environment, ceramic-based Thermal Barrier Coatings (TBCs) have been traditionally used to insulate combustion chambers due to the drastically reduced thermal conductivity when compared to engine block, head, and pistons metallic material. However, due to a mismatch of thermophysical properties between ceramics and the metals, these coatings are prone to failure far below the intended service life of the engine. A multilayer Intermetallic Thermal Barrier Coating has been developed at the University of Windsor using a Cold Spray method. The coating is composed of layers of SHS717 stainless steel (Fe, Cr, Mo, W, C, Mn, Si & B) and layers of aluminum acting as bond coats. This coating properties match the thermophysical properties of metallic engine components. The similarity between materials is expected to lead to improved durability of the new coating when compared to traditional ceramic TBCs. In this study, initial testing of the intermetallic TBC was conducted on the crown of aluminum pistons tested in a small indirect-injection diesel engine operating at full load and various engine RPMs. Indicated and brake performance metrics were analyzed to determine changes in engine performance characteristics when compared to baseline uncoated engine operation. An apparent heat release analysis was completed to determine the change of heat rejection of the engine operating with the TBCs, as well as an energy balance analysis to determine the improvements in the fuel energy conversion. The results from this analysis indicated that indeed the heat transfer losses were reduced with a concurrent modest gain in engine output.
Topic: Engine combustion
Author: Jeff Carlo Canape
Co-authors: Andrzej Sobiesiak