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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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DOE OSTI2016

Feedforward Control of Fuel Distribution on Advanced Dual-Fuel Engines with Varying Intake Valve Closing Timings

This study examines the dynamics and control of an engine operated with late intake valve closure (LIVC) timings in a dual-fuel combustion mode. The engine features a fuel delivery system in which diesel is direct-injected and natural gas is port-injected. Despite the benefits of LIVC and dual-fuel strategy, combining these two techniques resulted in efficiency losses due to the variability of the combustion process across cylinders. The difference in power production across cylinders ranges from 9% at an IVC of 570°ATDC* to 38% at an IVC of 620 °ATDC and indicates an increasingly uneven fuel distribution as the intake valve remains open longer in the compression stroke. This paper describes an approach for controlling the amount of fuel injected into each cylinders’ port of an inline six- cylinder heavy-duty dual-fuel engine to minimize the variations in fuel distribution across cylinder. Since measuring the actual fuel reaching each cylinder is not a practical option on stock engines, this study aimed to produce a feedforward control technique. Using a model developed on an engine simulation software, the optimal fuel injection amounts at each cylinder port across 125 operating conditions (consisting of sweeps of five engine speeds, five engine loads, and five IVC timings) were determined by using PI controllers that adjust the amount of fuel injected at each port based on the amount of fuel reaching the cylinders. The results from the PI controller were expressed as a function of the operating condition (engine speed, engine load, and IVC timing); and consequently, could be reproduced without relying on a measurement of the amount of fuel reaching each cylinder. The feedforward control strategy, unlike the PI controller, is easily implementable on a stock engine and significantly reduces the variations in fuel distribution across cylinders.

Kassa, Mateos↗

DOE OSTI2024

Next Gen High Efficiency Boosted Engine Development

This work represents an advanced engineering research project partially funded by the U.S. Department of Energy (DOE). Ford Motor Company, FEV North America, and Oak Ridge National Laboratory collaborated to develop a next generation boosted spark ignited engine concept. The project goals, specified by the DOE, were 23% improved fuel economy and 15% reduced weight relative to a 2015 or newer light-duty vehicle. The fuel economy goal was achieved by designing an engine incorporating high geometric compression ratio, high dilution tolerance, low pumping work, and low friction. The increased tendency for knock with high compression ratio was addressed using early intake valve closing (EIVC), cooled exhaust gas recirculation (EGR), an active pre-chamber ignition system, and careful management of the fresh charge temperature. Engine weight reduction measures were implemented throughout the engine system making use of composite materials, advanced manufacturing techniques, and architectural choices. This report outlines the analytical, design, fabrication, and test work conducted for the duration of the project. The combustion system stability, EGR tolerance, and knock resistance were validated on a single cylinder engine. An inline six-cylinder engine was then designed targeting application in the Ford F150. Multi-cylinder engines were produced and tested achieving the target vehicle fuel economy improvement of 23% assessed using measured engine fuel consumption combined with a vehicle drive cycle simulation. Actions were identified and designs were demonstrated to achieve the 15% weight reduction target. This project included items covering a range of technology readiness levels. Some of the technologies explored are production ready, while others were investigated to understand the limitations for what can be achieved in a stoichiometric, gasoline-fueled, spark-ignited internal combustion engine.

42 ENGINEERING↗

DOE OSTI2016

Modeling and control of fuel distribution in a dual-fuel internal combustion engine leveraging late intake valve closings

In internal combustion engines, cycle-to-cycle and cylinder-to-cylinder variations of the combustion process have been shown to negatively impact the fuel efficiency of the engine and lead to higher exhaust emissions. The combustion variations are generally tied to differences in the composition and condition of the trapped mass throughout each cycle and across individual cylinders. Thus, advanced engines featuring exhaust gas recirculation, flexible valve actuation systems, advanced fueling strategies, and turbocharging systems are prone to exhibit higher variations in the combustion process. In this study, the cylinder-to-cylinder variations of the combustion process in a dual-fuel internal combustion engine leveraging late intake valve closing are investigated and a model to predict and address one of the root causes for these variations across cylinders is developed. The study is conducted on an inline six-cylinder heavy-duty dual-fuel engine equipped with exhaust gas recirculation, a variable geometry turbocharger, and a fully flexible variable intake valve actuation system. The engine is operated with late intake valve closure timings in a dual-fuel combustion mode in which a high reactivity fuel is directly injected into the cylinders and a low reactivity fuel is port injected into the cylinders. The cylinder-to-cylinder variations observed in the study have been associated with the maldistribution of the port-injected fuel, which is exacerbated at late intake valve timings. The resulting difference in indicated mean effective pressure between the cylinders ranges from 9% at an intake valve closing of 570° after top dead center to 38% at an intake valve closing of 620° after top dead center and indicates an increasingly uneven fuel distribution. The study leverages both experimental and simulation studies to investigate the distribution of the port-injected fuel and its impact on cylinder-to-cylinder variation. The effects of intake valve closing as well as the impact of intake runner length on fuel distribution were quantitatively analyzed, and a model was developed that can be used to accurately predict the fuel distribution of the port-injected fuel at different operating conditions with an average estimation error of 1.5% in cylinder-specific fuel flow. A model-based control strategy is implemented to adjust the fueling at each port and shown to significantly reduce the cylinder-to-cylinder variations in fuel distribution.

Kassa, Mateos↗

DOE OSTI2019

Enterprise: a reduced-scale, flexible fuel, single-cylinder crosshead marine diesel research engine

A custom-built 1/10 scale, flexible-fuel, single-cylinder crosshead marine diesel research engine, dubbed the Enterprise, was designed and built as a platform for conducting marine lubricant research. The engine design was focused on maintaining lubricant boundary conditions similar those of full-scale engines. The Enterprise has a rated speed of 625 rpm to match the linear mean piston speed of full-scale marine engines with the reduced stroke and is capable of 18 bar brake mean effective pressure (BMEP). A high-swirl, uniflow-scavenged, two-stroke combustion system was designed to operate on either distillate diesel or heavy fuel oil (HFO). A hydraulic electronic unit injector (HEUI) fuel injection system with two injectors having customized three-hole nozzles provides fueling and is driven by the MAHLE Flexible ECU (MFE). Intake air boost is provided using a variable speed industrial air compressor along with closed-loop electronically controlled pressure regulation. Exhaust backpressure is also controlled electronically using an electro-pneumatic butterfly valve. A customized, miniaturized Hans Jensen Lubetronic cylinder lubrication system, which is capable of delivering 0.88 mg of cylinder oil per lubricator per injection to the ring pack at up to the maximum engine overspeed rating of 656 rpm, was commissioned for the Enterprise. Four independently temperature-controlled cooling zones are used to provide control of the liner temperature profile. The four coolant zones as well as the system oil and cylinder oil supplies are all controlled within 1°C for consistent thermal boundary conditions. The engine is instrumented with an in-cylinder pressure transducer as well as an inline torque transducer and numerous process temperature and pressure measurements to allow for detailed thermodynamic efficiency analysis, and experimental facilities allow for precise measurement of liner wear and characterization of deposits on the piston and rings. A radio telemetry system from IR Telemetrics is used to measure piston crown temperatures during engine operation. Engine design considerations and experimental facilities are described in detail, along with the results of a study investigating the impact of both system oil and cylinder oil viscosity on friction and efficiency. A test matrix was designed to compare base stock chemistries and viscosities for both system and cylinder oils. Experiments were completed using a fuel economy test protocol that was defined, consisting of repeating six speed/load operating conditions. An automated dynamometer control system was implemented to ensure repeatability of the test procedure. Preliminary testing indicated that the coolant, oil, and exhaust temperatures reach a steady state within 5 minutes of changing operating conditions. The system oil viscosity was found to have a significant impact on friction, with a reduction in viscosity from SAE 30 to SAE 20 resulting in over 6% reduction in friction mean effective pressure (FMEP) and over a 2% reduction in brake-specific fuel consumption (BSFC). Chemistry effects were also evident in the system and cylinder oils. Repeatability comparisons between the individual repetitions of each operating condition were used to ensure that results are statistically valid. For the initial cylinder oil viscosity experiments, observed changes were within the established/normal repeatability; ongoing experiments will determine whether improvements in boundary condition control will enable cylinder friction changes of this magnitude to be measured on this engine platform.

Kaul, Brian↗