The future heavy duty powertrain market is expected to be more diverse, with a gradual shift towards cleaner and more sustainable alternative fuels. Among various options, the hydrogen Internal Combustion Engine (ICE) holds the promise of significantly reducing carbon emissions while leveraging existing ICE technology. However, it also faces substantial challenges related to engine performance, fuel storage and delivery, infrastructure development, economic feasibility, safety and market acceptance. This paper focuses on performance challenges of hydrogen engine, including knock and pre-ignition, as well as low thermal efficiencies, and introduces the Opposed-Piston Two-Stroke Hydrogen ICE (OP2S-H2ICE) as a potential solution. The study demonstrates that OP2S-H2ICE can operate using direct injection, compression-ignition (CI) combustion solely with hydrogen, under various low-load to partial load conditions. Specifically, as the load increases, the combustion transitions from partial-premixed controlled CI combustion towards mixing controlled CI combustion, resulting in thermal efficiency and power density comparable to those of diesel on the same OP engine platform. Compared with conventional four-stroke engine, the OP2S offers the flexible control of trapped temperature through scavenging by retaining more internal residual inside the cylinder. This feature enables the OP2S-H2ICE to overcome the high autoignition temperature, achieving CI combustion even at low load conditions. Initial tests demonstrated that ITE up to 47% can be achieved at these conditions with hydrogen CI combustion.

In the United States (US), the off-road sector (i.e., agriculture, construction, etc.) contributes to approximately 10% of the country’s transportation greenhouse gas (GHG) emissions, similar to the aviation sector. The off-road sector is extremely diverse; as the EPA MOVES model classifies it into 11 sub-sectors, which include 85 different types of equipment. These equipment types have horsepower ranging from 1 to greater than 3000 and have very different utilization, which makes decarbonization a complex endeavor. To address this, Argonne’s on-road vehicle fleet model, VISION, has been expanded to the off-road sector. The GHG emission factors for several energy carriers (biofuels, electricity, and hydrogen) have been incorporated from Argonne’s GREET model for a sector-wide well-to-wheel (WTW) GHG emissions analysis of the present and future fleet. Several technology adoption and energy decarbonization scenarios were modeled to better understand the appropriate actions required to drive towards net-zero emissions of the off-road sector. Results show that WTW decarbonization up to 67% can be achieved from 2023 to 2050 in a business-as-usual scenario. But with aggressive sales increases of electric and hydrogen powertrains, WTW decarbonization up to 77% can be achieved, which can further increase to 85% if electricity production is aggressively decarbonized by 2035.

The leaders of the Departments of Energy, Transportation, Housing and Urban Development, and the Environmental Protection Agency released the U.S. National Blueprint for Transportation Decarbonization, the landmark interagency framework of strategies and actions to remove all emissions from the transportation sector by 2050. As a result, the transportation industry is encouraged to reduce its carbon footprint by using low-carbon-intense fuel. The rail transportation sector has expressed interest in electrification as a solution for locomotive engines running on short line rails. However, the long-haul locomotive is still difficult to electrify and locomotive engines are expected to operate for a long lifetime. Because of these challenges, the rail industry must look for a short-term solution to reduce its carbon footprint. One promising solution is using net-zero and/or low-carbon fuels, such as biodiesel. Previous research on other internal combustion engines has shown that biodiesel has the potential to reduce emissions, especially particulate matter emissions. This paper investigates the combustion characteristics of plant-based biodiesel. The experiment was carried out on a 4-stroke single-cylinder locomotive engine under various speed load conditions. The combustion characteristics were investigated by using heat release rate analysis and exhaust emissions measurement. The higher cetane number of biodiesel fuel is effective in shortening the ignition delay. Moreover, using biodiesel significantly reduced soot emissions and decreased CO and CO2 emissions.

The multimode engine research focuses on the benefits of light-duty vehicle engines which can operate in multiple modes depending on the vehicles’ load. Low temperature combustion can improve efficiency and reduce emissions during low-load operation, while spark ignition performance is maintained in high-load operation. These advanced engines can be optimized to run on blends of biobased fuels. This analysis models scenarios for potential market adoption of co-optimized multimode vehicles fueled by three different bioblendstocks: Ethanol, Isopropanol, and Isobutanol. We combine vehicle sales modeling, systems dynamics modeling of the biorefining industry, and life cycle assessment to estimate environmental impacts across a wide parameter space for incremental vehicle cost and engine efficiency improvement. Analysis reveals that co-optimized multimode fuels and vehicles can reduce light-duty greenhouse gas (GHG) emissions by 5% in 2050, relative to a business-as-usual scenario. Results indicate that co-optimized multimode vehicles can be cost competitive with conventional gasoline and can be strategically leveraged in tandem with electrification. Co-optimized vehicles could play a role in the early years, while electric vehicles could become more competitive in the later years, highlighting their complementary roles for GHG reductions.

Pre-chamber spark-ignition (PCSI) is a leading advanced ignition concept for internal combustion engines with the potential to enable diesel-like efficiency in medium-duty/heavy-duty (MD/HD) natural gas (NG) engines. By leveraging distributed ignition sources from multiple turbulent jets, the PCSI technology can deliver extremely short combustion duration in ultra-lean mixtures and significantly improve the engine thermal efficiency. However, in the automotive industry there is a lack of adequate science base and predictive simulation tools required for commercial development of PCSI engines. In this study, Reynolds-Average Navier-Stokes simulations are carried out to describe the combustion process in lean-burn NG engines, focusing on the combustion modeling approach. Two combustion models, multi-zone well-stirred reactor (MZ-WSR) and G-equation, are used to simulate the combustion process in an MD NG engine equipped with a fueled-PCSI system for four operating conditions close to the lean operating limit. A skeletal chemical mechanism and a laminar flame speed tabulation are used to compute the combustion accurately. Simulation results are compared with experimental data regarding measured cylinder pressure, heat release rate, and combustion duration. By dividing the PCSI combustion process into four distinct phases, the difference between the two models' results for each phase is analyzed in detail. The MZ-WSR model overestimates the combustion duration for early flame kernel growth in the pre-chamber due to the lack of a specific formulation to take turbulence-chemistry interaction into account. Despite the prolonged combustion duration and low pressure built-up inside the pre-chamber, the model matches the combustion rate in the main-chamber. In contrast, the G-equation model delivers good agreements for the pre-chamber combustion and turbulent jet-driven combustion processes. However, the model starts to underestimate the combustion rate in the main-chamber, especially under ultra-lean mixture conditions. Finally, improvements are needed for both models to simulate the later combustion stage that occurred in the near-wall regions.

Lean burn natural gas engines offer low particulate emissions than diesel counterparts and provides higher efficiency when compared to stoichiometric operation. However, with the lean burn strategy, three-way catalysts (TWC) compatibility is lost due to the oxidized exhaust stream. In comparison, the exhaust gas recirculation (EGR) dilution strategy can maintain compatibility with emission after-treatment systems. The maximum tolerated EGR levels are limited by the combustion stability degradation resulting from unfavorable mixture gas composition. Pre chamber spark ignition (PCSI) systems, known to increase dilution tolerance in SI engines under lean conditions, was evaluated as a means to improve EGR dilution tolerance. Scavenging of residuals within the pre-chamber is typically a concern with these systems and as such studies on these systems working with various levels of EGR ratios are rare. In this work, an unscavenged (or unfueled, or passive) PCSI system installed in a medium-duty natural gas engine is modeled using CONVERGE CFD code. Simulation results are compared against the experimental data in terms of in-cylinder pressure and heat release rates from low to high (10% to 22%) EGR levels. The prediction capability of two combustion models, a multi-zone well-stirred reactor model and a flamelet-based combustion model, i.e. G-equation, are compared and evaluated under these conditions within the RANS framework. The G-equation model predictions agreed well with experiments up to 18.8% EGR dilution level. In comparison, the MZ-WSR model predicted slow prechamber combustion at all dilution levels which influenced the main chamber combustion phasing.

Lean combustion in an internal combustion engine is a promising strategy to increase thermal efficiency by leveraging a more favorable specific heat ratio of the fresh mixture and simultaneously suppressing the heat losses to the cylinder wall. However, unstable ignition events and slow flame propagation at fuel-lean condition lead to high cycle-to-cycle variability and hence limit the high-efficiency engine operating range. Pre-chamber ignition is considered an effective concept to extend the lean operating limit, by providing spatially distributed ignition with multiple turbulent flame-jets and enabling faster combustion rate compared to the conventional spark ignition approach. From a numerical modeling perspective, to date, still the science base and available simulation tools are inadequate for understanding and predicting the combustion processes in pre-chamber ignited engines. In this paper, conceptually different RANS combustion models widely adopted in the engine modeling community were used to simulate the ignition and combustion processes in a medium-duty natural gas engine with a pre-chamber spark-ignition system. A flamelet-based turbulent combustion model, i.e., G-equation, and a multi-zone well-stirred reactor model were employed for the multi-dimensional study. Simulation results were compared with experimental data in terms of in-cylinder pressure and heat release rate. Finally, the analysis of the performance of the two models is carried out to highlight the strengths and limitations of the two formulations respectively.

The application of the Livengood-Wu (LW) integral method as a tool to estimate knock onset in spark ignited (SI) engines and combustion phasing in advanced compression ignition (ACI) engines has been demonstrated through simulations several times. In this study, the effect of uncertainties associated with parameters required for the LW integral method, when used as a tool for model based control of ignition timing in an ACI engine, were experimentally studied using five full boiling range gasoline fuels. As a first step, the method was applied to experimental data from a rapid compression machine and it was found that the ability of the LW integral method to predict ignition timing was very sensitive to the performance of the chemical kinetic model of each fuel. The method was subsequently applied to experimental data from a single-cylinder gasoline engine with simple approximations for the LW integral input parameters, and it was found that the predicted time of ignition was significantly different from the actual start of combustion. Systematic evaluation of various parametric uncertainties conducted thereafter showed that the uncertainty in cylinder charge temperature has the greatest influence. Improved methods of estimating cylinder charge temperature are proposed to account for the previously determined corrections, to enable the use of the LW integral method for model based control of ignition timing.

Long-term petroleum prices and increasingly-stringent emissions regulations are driving manufacturers and users alike to consider alternatives to diesel-fueled engines. Mixing controlled combustion of alcohol fuels, such as ethanol, has been identified as a promising technology based the low propensity for particulate and NOx production, but the higher heats of vaporization and auto-ignition temperatures of these fuels make their direct use in diesel engine architectures a challenge. However, because alcohol fuels do not form appreciable levels of soot even in mixing-controlled (MCCI) mode, and because stoichiometric air/fuel ratios (AFR) can be used to simplify NOx aftertreatment, engine design optimization efforts can be targeted to maximize thermal efficiency. Therefore, to realize the potential of alcohol-fueled combustion, engineering insight is required to understand how design parameters, such as increased engine insulation, piston bowl geometry, or spray targeting, should be optimally utilized. In this work, a computational fluid dynamics (CFD) modeling framework is developed and validated in order to identify pathways to improve the performance of an ethanol-fueled engine operating in an MCCI mode at a stoichiometric AFR. To evaluate the use of TBCs as an engine insulation method, a simplified 1-D conjugate heat transfer (CHT) modeling framework is employed. The CFD model is first validated against baseline engine data over selected inlet air heating temperatures for two piston bowl-injector configurations that define the extrema of the design space. The addition of the 1-D CHT model only increases the computational expense by 15% relative to traditional approaches, yet offers more accurate heat transfer predictions over constant temperature boundary conditions. The model is then used to explore the efficacy of injector orientations and piston bowl geometries in improving the indicated thermal efficiency of alcohol fueled compression ignition engines. Using a design of experiments approach, several candidate designs were identified that improved fuel-air mixing, shortened the combustion duration, and increased thermal efficiency. The most promising design was then fabricated and tested in a Caterpillar 1Y3700 Single Cylinder Oil Test Engine (SCOTE). The engine testing confirmed the findings from the CFD simulations, and found that the co-optimized injector and piston bowl design yielded over 2-percentage point increase in thermal efficiency at the same equivalence ratio (0.96) and over 6-percentage point increase at the same engine load (10.1 bar indicated mean effective pressure), while satisfying design constraints for peak pressure and maximum pressure rise rate.

Heavy-duty vehicles require expensive aftertreatment systems for control of emissions such as particulate matter (PM) and nitrogen oxides (NOx) to comply with stringent emission standards. Reduced engine-out emissions could potentially alleviate the emission control burden, and thus bring about reductions in the cost associated with aftertreatment systems, which translates into savings in vehicle ownership. This study evaluates potential reductions in manufacturing and operating costs of redesigned emission aftertreatment systems of line-haul heavy-duty diesel vehicles (HDDVs) with reduced engine-out emissions brought about by co-optimized fuel and engine technologies. Three emissions reduction cases representing conservative, medium, and optimistic engine-out emission reduction benefits are analyzed, compared to a reference case: the total costs of aftertreatment systems (TCA) of the three cases are reduced to $11,400(1.63 ¢/km), $9,100 (1.30 ¢/km), and $8,800 (1.26 ¢/km), respectively, compared to $12,000 (1.71 ¢/km) for the reference case. The largest potential reductions result from reduced diesel exhaust fluid (DEF) usage due to lower NOx emissions. Downsizing aftertreatment devices is not likely, because the sizes of devices are dependent on not only engine-out emissions, but also other factors such as engine displacement. Sensitivity analysis indicates that the price and usage of DEF have the largest impacts on TCA reduction.

This report summarizes the off-road vehicles stakeholder workshop that was focused on research, technical challenges, and future direction related to off-road vehicles and held at Argonne National Laboratory in October 2018. The views expressed in this report are those of the workshop participants. Topics discussed and included in this report are engine efficiency and emissions; efficient fluid power; and system integration, control, and new technologies. The purposes of this workshop were to: 1) Discuss and exchange information on the current state of technology for off-road vehicles; 2) Work collectively to address the technical challenges; and 3) Help shape the future direction for off-road vehicles research and development (R&D). The report highlights some key points, takeaways, and technical challenges and ideas to inform DOE R&D programs for the off-road sector. The workshop objectives were to: • Identify the barriers to cost-effective, high-efficiency, off-road vehicles; • Identify pre-competitive research topics that could have the biggest impact in overcoming barriers; and • Identify metrics that should be applied to program progress and ambitious but realistic goals. Customer acceptance, reliability, and system durability are some of the market barriers to new technology that were discussed during the workshop. Participants agreed that a comprehensive strategy is required to explore ways to improve engine efficiency while lowering emissions (i.e., NOx, GHG, etc.) and at the same time, meet customer needs and expectations. A full system optimization was recommended for off-road vehicles. It was noted that off-road vehicles are very diverse with a wide range of engine size and vehicle applications. A need for R&D for transient operations and other operating conditions was identified, as off-road vehicles are currently optimized for steady state. Fuel type for these vehicles has an important role. Fuel cost and fuel delivery to the work-site are challenging for any new fuel. Increased vehicle electrification is one of the new technologies discussed during the workshop. Electric propulsion for off-road vehicles has limited applications in the near term, but hybridization seems more promising. Furthermore, electrification requires better batteries and, possibly, the use of higher-voltage systems. Developing more efficient component technologies, including pumps, motors, and valves, is important for more efficient fluid power systems. New work-circuit architectures that can decrease throttling losses and better integrate the work circuit and engine can offer significant efficiency gains. Autonomous vehicles for off-road sectors were also discussed. Autonomous vehicles for off-road space are very appealing for some markets due to shortage in skilled labor and its significant impact on productivity, vehicle weight, and therefore, energy use and emissions. Autonomous driving for mining and farming applications is more feasible because the routes are predefined, but for other applications, such as forestry and construction vehicles, autonomous driving would be very challenging.

This report examines the potential benefits, feasibility, and barriers to the use of biofuels in place of heavy fuel oil (HFO) and marine gas oil for marine vessels. More than 90% of world’s shipped goods travel by marine cargo vessels powered by internal combustion (diesel) engines using primarily low-cost residual HFO, which is high in sulfur content. Recognizing that marine shipping is the largest source of anthropogenic sulfur emissions and is a significant source of other pollutants including particulates, nitrogen oxides, and carbon dioxide (CO2), the International Maritime Organization enacted regulations to lower the fuel sulfur content from 3.5 wt.% to 0.5 wt.% in 2020. These regulations require ship operators either to use higher-cost, low-sulfur HFO or to seek other alternatives for reducing sulfur emissions (i.e., scrubbers, natural gas, distillates, and/or biofuels). The near-term options for shipowners to comply with regulations include fueling with low-sulfur HFO or distillate fuels or installing emissions control systems. However, few refineries are equipped to produce low-sulfur HFO. Likewise, the current production rates of distillates do not allow the necessary expansion required to fuel the world fleet of shipping vessels (which consume around 330 million metric tons). This quantity is more than twice that used in the United States for cars and trucks. The other near-term option is to install emission control systems, which also requires a significant investment. All of these options significantly increase operational costs. Because of such costs, biofuels have become an attractive alternative since they are inherently low in sulfur and potentially also offer greenhouse gas benefits. Based on this preliminary assessment, replacing HFO in large marine vessels with minimally processed, heavy biofuels appears to have potential as a path to reduced emissions of sulfur, CO2, and criteria emissions. Realizing this opportunity will require deeper knowledge of (1) the combustion characteristics of biofuels in marine applications, (2) their compatibility for blending with conventional marine fuels (including HFO), (3) needs and costs for scaling up production and use, and (4) a systems assessment of their life cycle environmental impacts and costs. It is recommended that a research program investigating each of these aspects be undertaken to better assess the efficacy of biofuels for marine use.

Biofuels produced from nonedible sources that are cultivated on marginal lands represent a viable source of renewable and carbon-neutral energy. In this context, biodiesel obtained from Jatropha and Karanja oil seeds have received significant interest, especially in South Asian subcontinent. Both of these fuels are produced from nonedible plant seeds with high oil content, which can be grown on marginal lands. In this research, we have investigated the performance and emission characteristics of Jatropha and Karanja methyl esters (biodiesel) and their blends with diesel. Another objective is to examine the effect of long-term storage on biodiesel's oxidative stability. The biodiesels were produced at Indian Institute of Technology Kanpur, (IIT Kanpur), India, and the engine experiments were performed in a single cylinder, four-stroke, compression ignition engine at Argonne National Laboratory (ANL), Chicago. An endoscope was used to visualize in-cylinder combustion events and examine the soot distribution. The effects of fuel and start of injection (SOI) on engine performance and emissions were investigated. Results indicated that ignition delay was shorter with biodiesel. Consequently, the cylinder pressure and premixed heat release were higher for diesel compared to biodiesel. Engine performance data for biodiesel (J100, K100) and biodiesel blends (J30, K30) showed an increase in brake thermal efficiency (BTE) (10.9%, 7.6% for biodiesel and blend, respectively), brake specific fuel consumption (BSFC) (13.1% and 5.6%), and nitrogen oxides (NOx) emission (9.8% and 12.9%), and a reduction in brake specific hydrocarbon emission (BSHC) (8.64% and 12.9%), and brake specific CO emission (BSCO) (15.56% and 4.0%). The soot analysis from optical images qualitatively showed that biodiesel and blends produced less soot compared to diesel. The temperature profiles obtained from optical imaging further supported higher NOx in biodiesels and their blends compared to diesel. Additionally, the data indicated that retarding the injection timing leads to higher BSFC, but lower flame temperatures and NOx levels along with higher soot formation for all test fuels. The physicochemical properties such as fatty acid profile, cetane number, and oxygen content in biodiesels support the observed combustion and emission characteristics of the fuels tested in this study. Finally, the effect of long-term storage is found to increase the glycerol content, acid value, and cetane number of the two biodiesels, indicating some oxidation of unsaturated fatty acids in the fuels.

Superior spray behavior of fuels in internal combustion engines lead to improved combustion and emission characteristics therefore it is necessary to investigate fuel spray behavior of new alternative fuels. This study discusses the evolution of the in-nozzle orifice parameters of a numerical simulation and the evolution of spray parameters of fuel spray in a constant-volume spray chamber during an experiment. This study compares mineral diesel, biodiesels (Karanja-and Jatropha-based), and their blends with mineral diesel. The results show that mineral diesel provides superior atomization and evaporation behavior compared to the biodiesel test fuels. Karanja biodiesel provides superior atomization and evaporation characteristics compared to Jatropha biodiesel. The qualitative comparison of simulation and experimental results in tandem shows that nozzle-hole design is a critical parameter for obtaining optimum spray behavior in the engine combustion chamber. (C) 2015 Elsevier Ltd. All rights reserved.