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Technical Paper

Understanding Limits to the Mechanical Efficiency of Opposed Piston Engines

A study of the crank and gear-train dynamics of a two-stroke opposed piston diesel engine design uncovered a disconnect between the thermodynamic process and its conversion to mechanical work. The classic two-stroke opposed piston design phases the intake piston to lag the exhaust piston in order to achieve favorable gas exchange, overcoming the disadvantage of piston-controlled ports. One result of this is that significantly more of the engine torque is delivered by the leading crank than from the trailing one. This paper will examine why this torque difference occurs showing that it is not simply a proportioning of the available thermodynamic work but a result of a fundamental mechanical loss mechanism that limits the achievable brake efficiency of this engine architecture. This analysis will provide a basis for developing effective design solutions to overcome the mechanical loss by providing an understanding of this loss mechanism.
Journal Article

Optimization of an Advanced Combustion Strategy Towards 55% BTE for the Volvo SuperTruck Program

This paper describes a novel design and verification process for analytical methods used in the development of advanced combustion strategies in internal combustion engines (ICE). The objective was to improve brake thermal efficiency (BTE) as part of the US Department of Energy SuperTruck program. The tools and methods herein discussed consider spray formation and injection schedule along with piston bowl design to optimize combustion efficiency, air utilization, heat transfer, emission, and BTE. The methodology uses a suite of tools to optimize engine performance, including 1D engine simulation, high-fidelity CFD, and lab-scale fluid mechanic experiments. First, a wide range of engine operating conditions are analyzed using 1-D engine simulations in GT Power to thoroughly define a baseline for the chosen advanced engine concept; secondly, an optimization and down-select step is completed where further improvements in engine geometries and spray configurations are considered.
Technical Paper

Study of diesel Engine Performance Using High Sulfur Fuel

While most of the industrialized world's diesel fuel usage for on-highway applications is shifting toward ultra-low sulfur diesel (ULSD) (≤ 50 ppm) or “sulfur-free” (≤ 15 ppm) content fuel, some markets for high-sulfur diesel (HSD) fuel still persist. Among these are off-roadway engines, marine, military fuel use worldwide, and general diesel fuel use in the Middle East and in some developing markets. A stock-production medium-duty engine underwent a dynamometer durability test with high-sulfur (10,000 ppm) diesel to approximate the worst case for sulfur content among global road fuels, and medium-high sulfur diesel (3,000 ppm) for engine break-in. Testing was completed successfully; however performance degradation with these fuels was observed which might have practical significance in other diesel applications for these markets.