Three-dimensional Multi-physics Modeling Methodology to Study Engine Cylinder-kit Assembly Tribology and Design Considerations

Download or read book Three-dimensional Multi-physics Modeling Methodology to Study Engine Cylinder-kit Assembly Tribology and Design Considerations written by Sadiyah Sabah Chowdhury and published by . This book was released on 2021 with total page 223 pages. Available in PDF, EPUB and Kindle. Book excerpt: Engine cylinder-kit tribology is pivotal to durability, emission management, friction, oil consumption, and efficiency of the internal combustion engine. The piston ring pack dynamics and the flow dynamics are critical to engine cylinder-kit tribology and design considerations. A three-dimensional (3D), multi-physics methodology is developed to investigate the liquid oil- combustion gas transport and oil evaporation mechanisms inside the whole domain of the cylinder kit assembly during the four-stroke cycle using multiple simulation tools and high-performance computing. First, a CASE (Cylinder-kit Analysis System for Engines) 1D model is developed to provide necessary boundary conditions for the subsequent steps of the chain of simulations. Next, the ring-bore and ring groove conformability along with the twist angle variation across the circumference are investigated by modeling a twisted ring via a 3D ring FEA contact model. The ring twist induces change in ring location which subsequently changes the cylinder kit geometry dynamically across the cycle. The dynamically varying geometries are generated using the LINCC (Linking CASE to CFD) program. Finally, a three-dimensional multiphase flow model is developed for the dynamic geometries across the cycle using CONVERGE. The methodology is first applied on a small-bore (50 mm) engine running at 2000 rpm. Next, a CASE 1-D model is developed and calibrated via HEEDS across a range of load-speed operating conditions of a Cummins 6-cylinder, 137.02 mm bore, Acadia engine. The 1800 RPM, full load condition with a positively twisted second ring is selected for the experimental validation of the 3-D methodology. A study of the second ring dynamics in the small-bore engine showed the effect of negative ring twist on the three-dimensional fluid flow physics. The oil (liquid oil and oil vapor) transport and combustion gas flow processes through the piston ring pack for the twisted and untwisted geometry configurations are compared. A comparison with the untwisted geometry for this cylinder-kit shows that the negatively twisted second ring resulted in a higher blowby but lower reverse blowby and oil consumption. The comparison of the model predicted oil consumption with existing literature shows that oil consumption is within the reasonable range for typical engines. The blowby, second land pressures and third land pressures comparison with the experimental results of Cummins Acadia engine showed considerable agreement. The reverse blowby and oil consumption along with the liquid oil and oil vapor mass fraction distribution pattern across the cycle are also analyzed.In the later section of this work surface texture characterization of a novel Abradable Powder Coating (APC) and stock piston skirt coatings of a Cummins 2.8 L Turbo engine is conducted. The surface texture and characteristic properties varying across the piston skirt are obtained and analyzed via a 3D optical profiler and OmniSurf3D software. The engine operating conditions are found through a combination of measurements, testing, and a calibrated GT-Power model. The variable surface properties along with other geometric, thermodynamic, material properties are utilized to build a model in CASE for both APC and stock coated pistons. The Surface texture analysis shows that the APC coating has a unique feature of mushroom cap-like surface and deeper valleys that could potentially be beneficial for lubrication and oil retention. Comparison of different performance parameters from CASE simulation results shows that APC has the potential to be a suitable candidate for piston skirt coating.