Investigation of Advanced Fueling and High Efficiency Strategies in HSDI Diesel Engines
Motivation:
Cost-effective low-pressure fueling hardware, Understanding heat transfer losses which play an important role in improved efficiency, Understanding cycle- to-cycle combustion sensitivity and instability which limit market acceptance.
Objectives:
- Investigate the feasibility of a low-pressure direct-injection system (such as market-type multi-hole GDI hardware) for use with the LTC combustion strategies.
- Investigate and quantify the sources of cycle-to-cycle combustion sensitivity and instability to improve the engine industry’s ability to design and manufacture high efficiency engines.
- Use engine experiments with well-controlled boundary and initial conditions to assess the sources of instability related to stochastic variations in operating parameters (e.g., trapped charge temperature), fuel properties, and cyclic coupling.
- Couple the experimental effort with a computational effort to further isolate the parameters influencing cycle-to-cycle and cylinder-to-cylinder fluctuations.
- Identify operating strategies to maintain the benefits of advanced combustion (i.e., high thermal efficiency and low NOx and soot emissions) while minimizing cycle-to-cycle variability.
- Compare cyclic instability of conventional and advanced combustion modes over a range of conditions.
Figure 1. Change in operating conditions required to reproduce experimentally observed variation in IMEP (top), CA50 (middle), and peak pressure rise rate (bottom). The predictions were made by a response surface model trained using CFD modeling with small perturbations to the intake and fueling conditions. The inputs highlighted with the red box shows the dominant factors controlling variability of each predicted output (i.e., these parameters require the smallest change to reproduce the experimentally observed variations).
Simulation of Low-Carbon Powertrains
Motivation:
This is a new DERC project starting in January of 2023 with a focus on simulation of low carbon powertrains used in applications that are difficult to electrify. The project is based on the results of the 2021 survey regarding DERC member interest in low carbon fuels, where 88% of the votes are for fuels that have cetane numbers less than 20. From a combustion standpoint, many of these low carbon, low cetane fuels are well-suited for spark-ignited operation; accordingly, the largest challenges exist in utilization of these fuels in applications that require a diesel-like torque curve and transient response.
Objectives:
- Achieve a diesel-like (mixing controlled) combustion process using alternative fuels.
- Employ engineering-level CFD modeling to improve the understanding of combustion and emissions formation for compression ignition operation of low-carbon fuels.
- Provide insight into modeling challenges and approaches for design and analysis of engines operating on low-carbon fuels.
- Assessment of well-to-wheels CO2 and greenhouse gas emissions for low carbon fuels and competing technologies.
- Pre-competitive evaluation of technologies that have the potential to achieve ultra-low well-to-wheels CO2 emissions.
Pilot-Ignition of Natural Gas-Hydrogen Blends for High Efficiency and Low Emissions
Motivation:
Blending green hydrogen into natural gas pipelines is being widely considered as a transition to a low-carbon fuel solution. The impact of hydrogen blending on engine combustion for pilot ignition and reactivity controlled compression-ignition combustion, along with potential optimization to achieve improved thermal efficiency, reduced emissions, and better transient control is being explored in this project.
Objectives:
- Evaluate impacts of employing alternative and low-carbon fuels with modest (e.g., CH4) to large (e.g., H2) carbon displacement for use in advanced dual-fuel combustion strategies.
- Computationally evaluate pathways to achieve high-efficiency combustion while meeting emissions and pressures rise rate constraints.
- Compare the emissions and performance of DPI and RCCI operation using conventional and alternative fuels by applying fuel-specific kinetic submodels.
- Identify advantages, challenges, and opportunities that arise when blending hydrogen into natural gas for dual-fuel combustion strategies.
Figure 1. Decarbonized-Engine Research Consortium Lab Schematic.
Figure 2. Combustion performance of CH4/C2H6 (left), CH4/C3H8 (middle), and CH4/H2 (right) premixed mixtures under Diesel Pilot Ignition (DPI) mode.
Highly-Resolved Simulation of Fuel Injection
Motivation:
The underpinning motivation of the highly-resolved simulation of fuel injection project is to understand the jet breakup and the subsequent jet development. The results can lead to a control strategy for on-demand excitation or damping of the atomization process and to an improved model of jet spreading and mixing. Phase one of the work focused on the near-field jet breakup. Phase two targets the region beyond the near-field and aims to develop a two-phase self-similarity model of the flow. Phase three aims to investigate mixing and vaporization.
Objectives:
- Use linear and spatial interfacial instability analysis to understand the underpinnings of the fuel jet breakup process. Identify the most dominant factors influencing breakup behavior.
- Generalize interfacial instability by non-linearizing the governing equations and in particular to treatment of the interfacial constraints.
- Characterize the self-similarity development for sprays under various conditions.
- Employ the self-similarity treatment to develop new models for spray development.
Figure 1. Render of the liquid isosurface extracted from a VoF simulation at nominal ECN Spray A conditions. The internal flow within the Spray A nozzle geometry is also a part of the simulation.
