A great part of the projects in the engine design field are today facing new challenges in the basic engine design and calibration area. Most of the efforts have been driven by new emissions level regulations, which have become more and more demanding. Although the use of Exhaust Gas Recirculation (EGR) is nowadays often used for automotive Diesel engines to achieve NOx levels complying stringent legislations requirements, such as MAR-I, electronically controlled external EGR systems still presents an expensive technology, often unsuitable for small Diesel engines for off-road applications. An interesting and cost effective solution towards meeting those new emission requirements for smaller Diesel engines is the so-called internal EGR, which is obtained by modifying the valve train system. Among some few possibilities found in the market, one can add an extra intake valve lift event during the exhaust stroke in order to increase the level of exhaust residuals in the cylinder. That increased amount of gases with reduced concentration of O2 and increased concentration of CO2 contributes mainly to reduce the in-cylinder average temperature, which then reduces the NOx formation rates. That allows advancing of the start of combustion in order to reach very competitive fuel consumption. It has been researched and applied the internal EGR technology, so that a sufficient amount of exhaust gases is able to flow back to intake manifold, and finally fill the cylinder together with upcoming cooled air charge of the subsequent stroke. This technology is also known as AVL TINER® system, which stands for Technology for In-cylinder Nitrogen oxides Emission Reduction. This paper describes the extensive use of numerical simulation to successfully apply this technology and also investigate possible drawbacks and propose system pre-designs predicting their performance in advance prior to prototyping phase. Each of the sub-systems, which require modifications, demands specific types of numerical approach. The inlet valve changes have been studied via 1D engine flow simulation with GT-POWER with respect to the resultant level of extra residual gas fraction in different engine operating points. Then, the target valve lift is studied via cam lobe modifications and valve lift dynamics using a multibody numerical simulation approach via AVL EXCITE code. The mechanical fuel injection system is characterized via hydraulics simulation using AVL HYDSIM code, allowing the definition of the layout for a new fuel injection system hardware. The injection system has been tested on a system rig to validate the simulations prior to the engine tests. Individual Page 2 of 17 parts prototyping phase and their individual performance of the new components has been validated on the light of the specs provided by the simulations.The final engine dyno results proved the technical solution and showed reduction of 3% in BSFC and 2.9% in terms of fuel rate complying with MAR-I NOx emission levels.
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