FEV and LeiMot partners create lighter diesel engine with AM » 3dpbm
Reducing vehicle weight reduces CO2 emissions and remains a major concern for automakers. FEV and its partners in the LeiMot (Lightweight Engine) research project are using additive manufacturing to demonstrate further emission savings from combustion engines. FEV engineers were able to make engine functions, such as cooling or oil circulation, more efficient. Large assemblies of a benchmark passenger car diesel engine weigh approximately 21% less.
The German Federal Ministry for Economic Affairs and Energy funds the LeiMot research project. FEV leads the research consortium, consisting of a renowned automotive manufacturer, research institutes, technical schools, development service providers, OEMs and automotive suppliers. LeiMot empowers conventional production processes by exposing them to the growing benefits of additive manufacturing.
Modern all-aluminum combustion engines have already reached a very respectable weight, thus reducing emissions. Other innovations can only be achieved with AM. Hence FEV’s focus on the cylinder head and crankcase of a modern two-litre diesel engine. Both components were manufactured by laser powder bed fusion. Ralf Bey, LeiMot project leader, described the materials used: “AlSi10Mg aluminum alloy, but fiber reinforced plastics were also considered. The assemblies thus produced weigh approximately 21% less. At the same time, new engine components compatible with the installation (cylinder head and crankcase) increase the efficiency of the drive.
The cylinder head loses mass and retains its load capacity
The redesigned cylinder head alone saves 2.3 kilograms of weight, or 22 percent, compared to the original component. High-stress mechanical areas have been reinforced to accommodate bending loads due to combustion; the overall motor structure supports torsional loads.
“The exhaust duct could be 3D printed directly with thermal insulation through additive manufacturing,” Bey said. “It not only warms up the exhaust after-treatment systems faster. The inlet temperature of the turbine and therefore the efficiency of the turbocharger is also increased.
The redesigned crankcase further reduced the overall engine weight by 5.1 kilograms. The crankcase has been redesigned using the so-called short-skirted design with an aluminum substructure (seat plate). The base diesel engine’s reduced-friction main bearing diameters allowed engineers to replace the steel bearing caps with the bedplate.
The crankcase bulkheads have been designed to withstand horizontal load structures, which have been reinforced where appropriate with transverse rib composite. Additional reinforcement was provided by two lightened link tubes around the balance shafts. Based on topological analyses, low-load areas were optimized by lattice structures and cavities.
The side covers of the crankcase were, moreover, made of phenolic resin reinforced with fiberglass; they weighed about 15 percent less.
Less water brings more cooling
The new cross-flow cooling system has further reduced weight by lowering cylinder temperatures in a targeted manner and reducing the amount of water required. One of the main design differences was that the individual cooling lines in the cylinder head replaced the large volume water jacket. This reduced combustion chamber temperatures by up to 40%. Despite 40% less coolant, the wall temperatures were significantly lower than those of the reference engine: the warm-up phase after a cold start can be shortened and the drive power of the water pump can be reduced .
Advanced oil circuit reduces pressure loss
A developed oil circuit has created further advantages during cold starts and under normal operating conditions. Optimization measures include a new type of line routing that replaces sharp deviations with turns. The cutaway design changes also improved oil flow through the engine. These changes reduced the pressure loss in the cylinder head and the crankcase by 22%. An inverted siphon prevented oil from flowing out when the engine was stopped. As a result, proper oil pressure for the valve train was available sooner after engine start, and hollow bulkheads were used for oil return.