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Technical Paper

Numerical study on the design of a passive prechamber on a heavy-duty hydrogen combustion engine

2024-04-09
2024-01-2112
Lean-burning hydrogen internal combustion engines are potentially a good option for future transportation solutions since they do not emit carbon-dioxide and unburned hydro-carbons, and the emissions of nitric-oxides can be kept low. However, under lean-burn conditions the combustion duration increases and the combustion stability decreases, leading to a reduced thermal efficiency. Turbulent jet ignition (TJI) can be used to extend the lean-burn limit, while decreasing the combustion duration and improving combustion stability. The objective of this paper is to investigate the feasibility of a passive prechamber TJI system on a heavy-duty hydrogen engine under lean-burn conditions using CFD modelling. The studied concept is mono-fuel, port-fuel injected, and spark ignited in the prechamber. The overall design of the prechamber is discussed and the effect of certain design parameters have on the engine performance are studied.
Technical Paper

The New Toyota 2.4L L4 Turbo Engine with 8AT and 1-Motor Hybrid Electric Powertrains for Midsize Pick-up Trucks

2024-04-09
2024-01-2089
It is more and more challenging for internal combustion engines in pick-up trucks which have heavy weight and high drag, to fulfill both strict fuel economy and emission regulations toward the target of “Carbon Neutrality”, while exceeding customer expectations. To overcome these difficult tasks, Toyota has developed the new 2.4L L4 turbocharged gasoline engine which for the first time complies with severe emission regulations such as Tier3 Bin30/LEVIII SULEV30 for body-on-frame midsize pick-up trucks. At the same time, both thermal-efficiency and maximum torque are improved by adopting high-speed combustion to the turbocharged engine based on the TNGA (Toyota New Global Architecture) platform, spray guide combustion by center direct injection in combustion chamber, quick light-off close-coupled three-way catalyst and a quick response turbocharger.
Technical Paper

Combustion Chamber Development for Flat Firedeck Heavy-Duty Natural Gas Engines

2024-04-09
2024-01-2115
The widely accepted best practice for spark-ignition combustion is the four-valve pent-roof chamber using a central sparkplug and incorporating tumble flow during the intake event. The bulk tumble flow readily breaks up during the compression stroke to fine-scale turbulent kinetic energy desired for rapid, robust combustion. The natural gas engines used in medium- and heavy-truck applications would benefit from a similar, high-tumble pent-roof combustion chamber. However, these engines are invariably derived from their higher-volume diesel counterparts, and the production volumes are insufficient to justify the amount of modification required to incorporate a pent-roof system. The objective of this multi-dimensional computational study was to develop a combustion chamber addressing the objectives of a pent-roof chamber while maintaining the flat firedeck and vertical valve orientation of the diesel engine.
Technical Paper

Downsizing a Heavy-Duty Natural Gas Engine by Scaling the Air Handling System and Leveraging Phenomenological Combustion Model

2024-04-09
2024-01-2114
A potential route to reduce CO2 emissions from heavy-duty trucks is to combine low-carbon fuels and vehicle electrification/hybridization. Hybridization offers the potential to downsize the engine. Although engine downsizing in the light-duty sector can offer significant fuel economy savings mainly due to increased part-load efficiency, its benefits and downsides in heavy-duty engines are less clear. As there has been limited published research in this area to date, there is a lack of a standardized engine downsizing procedure. This paper aims to use an experimentally validated one-dimensional phenomenological combustion model in a commercial engine simulation software GT-Power alongside turbocharger scaling methods to develop downsized engines from a baseline 6-cylinder (2.2 L/cyl, 26 kW/L) pilot-ignition, direct-injection natural gas engine.
Technical Paper

High-Efficiency Methanol Engine Development for Heavy Commercial Vehicles

2024-01-18
2024-01-5005
Under China’s “3060” target of carbon peak and carbon neutrality, heavy commercial vehicles are a key breakthrough point to promote the automobile industry to achieve carbon peaking and carbon neutrality goals. Green methanol, as a clean alternative fuel, are an effective technical route for heavy commercial vehicles to achieve energy conservation and emission reduction. Based on a 13L methanol engine, this study fully considers the methanol combustion characteristics, the ω shape combustion system of the base engine is redesigned as a pent-roof combustion chamber. The intake port is changed from a swirl port to a high-tumble port, and the piston crown is also adjusted adaptively. At the same time, the cam profile, cooling water jacket, intake and exhaust system are redesigned, and the turbocharger is re-matched according to the physical properties of methanol. CAE tools and means are used to optimize and determine the design proposal.
Technical Paper

Optimizing Closed Loop Air Mass Control in Naturally Aspirated Engines: A Differential Pressure Sensor Approach to Meet BS6 Emission Norms

2024-01-16
2024-26-0147
In order to meet future emission targets and to achieve better fuel efficiency, closed loop air mass control strategies have become essential across all vehicle segments. Closed loop airmass control mandates measuring fresh air mass entering the engine combustion chamber. However, in Naturally Aspirated (NA) engines, while measuring airmass using conventional air mass sensors (AMS), heavy pulsations in the Air-intake results in errors which would impact closed loop airmass control and lead to inconsistencies in emissions. To address this issue, we studied different approaches using AMS with Resonator, differential pressure sensor across the intake air filter and Lambda based airmass control. Based on this empirical study we found that modelling air mass with differential pressure sensor (Delta-P) using Bernoulli’s principle (Flow rate ∝ √Differential pressure) results in higher accuracies compared to conventional methods.
Technical Paper

Development of the Electrically Controlled Off-Road Small Diesel Engine below 19kW

2023-10-24
2023-01-1844
In these days, not only low exhaust emission but also carbon dioxide reduction is required to achieve carbon neutrality toward resolution of climate change. Though examination of electrification and decarbonized fuel is progressing, industrial machines have issues for high load factor and infrastructure development. Therefore, trends of off-road powertrain are expected to be diversified depending on usage environment or applications. As a result, in terms of diesel engines below 19 kW, it should be the best way for satisfying the social needs to develop new diesel engines which have high environmental performance by optimizing engine combustion. In the case of diesel engines below 19 kW, it is difficult for the engines to adopt the direct injection (DI) combustion system and the common rail system (CRS). The fuel spray of these small displacement engines by DI or CRS easily attaches the wall surface of combustion chamber due to the small bores and causes increasing fuel consumption.
Technical Paper

A Study on Developing MPI Hydrogen ICE over 2MPa BMEP for Medium Duty Vehicles

2023-09-29
2023-32-0037
Hydrogen ICE can achieve carbon neutrality and is adaptable to medium and heavy-duty vehicles, for which electricity is not always a viable option. It can also be developed using high-quality conventional diesel/gasoline engine technology. Furthermore, it allows for the conversion of existing engines to hydrogen ICE, making it highly marketable. The reliability and durability of MPI hydrogen ICE is better than that of DI, and MPI has an advantage over DI in terms of cruising range because the low-pressure injection of hydrogen reduces the remaining hydrogen in the tank. Improving MPI output is, however, an important subject, and achieving this requires suppressing abnormal combustion such as pre-ignition. In this study, an inline four-cylinder 5L turbo-charged diesel engine was converted to a hydrogen engine. Hydrogen injectors were installed in the intake ports and spark plugs were installed instead of diesel fuel injectors.
Technical Paper

A Dual-Fuel Model of Flame Initiation and Propagation for Modelling Heavy-Duty Engines with the G-Equation

2023-09-29
2023-32-0009
We propose a novel dual-fuel combustion model for simulating heavy-duty engines with the G-Equation. Dual-Fuel combustion strategies in such engines features direct injection of a high-reactivity fuel into a lean, premixed chamber which has a high resistance to autoignition. Distinct combustion modes are present: the DI fuel auto-ignites following chemical ignition delay after spray vaporization and mixing; a reactive front is formed on its surroundings; it develops into a well-structured turbulent flame, which propagates within the premixed charge. Either direct chemistry or the flame-propagation approach (G- Equation), taken alone, do not produce accurate results. The proposed Dual-Fuel model decides what regions of the combustion chamber should be simulated with either approach, according to the local flame state; and acts as a “kernel” model for the G- Equation model. Direct chemistry is run in the regions where a premixed front is not present.
Technical Paper

Effect of Wet Liner Vibration on Ring-liner Interaction in Heavy-duty Engines

2023-09-29
2023-32-0140
Lubricating oil consumption (LOC) is a direct source of hydrocarbon and particulate emissions from internal combustion engines. LOC also inhibits the lifetime of exhaust aftertreatment system components, preventing their ability to effectively filter out other harmful emissions. Due to its influence on piston ring- bore conformability, bore distortion is arguably the most critical parameter for engine designers to consider in prevention of LOC. Bore distortion also has a significant influence on the contact forces between the piston ring and cylinder wall, which determine the wear rate of the ring and cylinder wall and can cause durability issues. Two drivers of bore distortion: thermal expansion and head bolt stresses, are routinely considered in conformability and contact analyses. Separately, bore distortion/vibration due to piston impact and combustion/cylinder pressures has been previously analyzed in wet liner engines for coolant cavitation and noise considerations.
Technical Paper

Air Path Design, Technical Definition and Pre-Calibration of an Ultra-Lean Hydrogen Engine Based on OD/1D Simulation

2023-08-28
2023-24-0004
Transport sector decarbonization is a key requirement to achieve Green House Gases emissions reduction. Future regulations and the large deployment of Low Emission Zones (LEZ) will lead to deep changes in this sector. The green hydrogen appears as a promising fuel, containing no carbon. H2 Internal combustion engine (H2 ICE) offers the opportunities of quick refueling, known reliability, relative low total cost of ownership. It is based on mature manufacturing processes and tools. Hence this solution can be commercialized in a near future, offering a short term pathway to decarbonization and a H2 market growth accelerator. However, hydrogen combustion in air generates NOx emissions, which should be reduced close to zero to fulfill future requirements. The HyMot project gathers seven public and industrial partners to develop an H2 engine for Light Commercial Vehicle (LCV) application offering the same performances as the replaced Diesel Engine.
Technical Paper

Optical Diagnostic Study on Improving Performance and Emission in Heavy-Duty Diesel Engines Using a Wave-Shaped Piston Bowl Geometry and Post Injection Strategies

2023-08-28
2023-24-0048
This study explores the potential benefits of combining a wave-shaped piston geometry with post injection strategy in diesel engines. The wave piston design features evenly spaced protrusions around the piston bowl, which improve fuel-air mixing and combustion efficiency. The 'waves' direct the flames towards the bowl center, recirculating them and utilizing the momentum in the flame jets for more complete combustion. Post injection strategy, which involves a short injection after the main injection, is commonly used to reduce emissions and improve fuel efficiency. By combining post injections with the wave piston design, additional fuel injection can increase the momentum utilized by the flame jets, potentially further improving combustion efficiency. To understand the effects and potential of the wave piston design with post injection strategy, a single-cylinder heavy-duty compression-ignition optical engine with a quartz piston is used.
Technical Paper

Research on Design Development and Modification of a Steel Piston in a Heavy-Duty Diesel Engine

2023-04-24
2023-01-5023
The thermal and mechanical loads of the engine rise dramatically with the increase in engine power density, which places higher demands on the design of the piston. In this paper, the design development of a steel piston for a marine diesel engine belonging to 190 series heavy-duty diesel engines was studied. The design methods including material selection and structural design were used to finished the preliminary design. In the meanwhile, the design philosophies of the aluminum alloy piston and composite piston for the 190 series diesel engines were used for reference in the design process. The designed steel piston was tested in the engine durability bench test and simulated for reliability. The results showed that the failure of the steel piston occurred at the same position in both the test and the simulation. The cause of cracking in the steel piston was analyzed, and the insufficient strength of the local structure led to high-cycle fatigue failure.
Technical Paper

Experimental Investigations of Methane-Hydrogen Blended Combustion in a Heavy-Duty Optical Diesel Engine Converted to Spark Ignition Operation

2023-04-11
2023-01-0289
The global need for de-carbonization and stringent emission regulations are pushing the current engine research toward alternative fuels. Previous studies have shown that the uHC, CO, and CO2 emissions are greatly reduced and brake thermal efficiency increases with an increase in hydrogen concentration in methane-hydrogen blends for the richer mixture compositions. However, the combustion suffers from high NOx emissions. While these trends are well established, there is limited information on a detailed optical study on the effect of air-excess ratio for different methane-hydrogen mixtures. In the present study, experimental investigations of different methane-hydrogen blends between 0 and 100% hydrogen concentration by volume for the air-excess ratio of 1, 1.4, 1.8, and 2.2 were conducted in a heavy-duty optical diesel engine converted to spark-ignition operation. The engine was equipped with a flat-shaped optical piston to allow bottom-view imaging of the combustion chamber.
Technical Paper

An Optical Study of the Effects of Diesel-like Fuels with Different Densities on a Heavy-duty CI Engine with a Wave-shaped Piston Bowl Geometry

2023-04-11
2023-01-0261
The novel wave-shaped bowl piston geometry design with protrusions has been proved in previous studies to enhance late-cycle mixing and therefore significantly reduce soot emissions and increase engine thermodynamic efficiency. The wave-shaped piston is characterized by the introduction of evenly spaced protrusions around the inner wall of the bowl, with a matching number with the number of injection holes, i.e., flames. The interactions between adjacent flames strongly affect the in-cylinder flow and the wave shape is designed to guide the near-wall flow. The flow re-circulation produces a radial mixing zone (RMZ) that extends towards the center of the piston bowl, where unused air is available for oxidation promotion. The waves enhance the flow re-circulation and thus increase the mixing intensity of the RMZ.
Technical Paper

Optical Investigation of Mixture Formation in a Hydrogen-Fueled Heavy-Duty Engine with Direct-Injection

2023-04-11
2023-01-0240
Mixture formation in a hydrogen-fueled heavy-duty engine with direct injection and a nearly-quiescent top-hat combustion chamber was investigated using laser-induced fluorescence imaging, with 1,4-difluorobenzene serving as a fluorescent tracer seeded into hydrogen. The engine was motored at 1200 rpm, 1.0 bar intake pressure, and 335 K intake temperature. An outward opening medium-pressure hollow-cone injector was operated at two different injection pressures and five different injection timings from early injection during the intake stroke to late injection towards the end of compression stroke. Fuel fumigation upstream of the intake provided a well-mixed reference case for image calibration. This paper presents the evolution of in-cylinder equivalence ratio distribution evaluated during the injection event itself for the cylinder-axis plane and during the compression stroke at different positions of the light sheet within the swirl plane.
Technical Paper

Load variation using Ducted Fuel Injection - DFI, with different compression ratio in IC engine

2023-02-10
2022-36-0089
Compression ignition engines are widely used in the cargo and passenger transport sectors, this is due to their high energy efficiency and can operate with renewable fuels. The search for increased efficiency in internal combustion engines and reduced emissions are increasingly stringent, so to meet regulatory emission standards, new technologies are being studied and developed to reduce emissions generated by engines, in the case of diesel engines compression ignition, studies of techniques to reduce NOx and soot have been carried out. One of the techniques studied is the application of the DFI - Ducted Fuel Injection concept, which makes the fuel spray pass through a small cylindrical duct installed upstream of the injection orifice of the injector nozzle, thus improving the air/fuel, making it more homogeneous and allowing a more complete combustion. This work addresses a study of this application of DFI with different compression ratios.
Journal Article

Development of an Optical Investigation Method for Diesel and Oxymethylene Ether Spray in a Large-Bore Dual-Fuel Engine Using a Fisheye Optical System

2022-12-07
Abstract Optical combustion phenomena investigation is a common tool for passenger car and automotive engines. Large-bore engines for stationary and mobile applications, on the other hand, have a lower optical examination density. This is mainly due to the technically more complex design of the optical accesses that have to provide a larger field of view and withstand high mechanical and thermal loads. Nevertheless, an optical investigation of in-cylinder phenomena in large-bore engines is essential to optimize efficient and environmentally friendly combustion processes using new sustainable e-fuels. To realize a simple optical access with maximum observability of the combustion chamber, a fisheye optic for the direct integration into internal combustion engines was developed and used for in-cylinder Mie-scattering investigations of diesel and Oxymethylene Ether (OME3-5) pilot fuel spray of natural gas dual-fuel combustion processes in a MAN 35/44DF single-cylinder research engine.
Journal Article

Numerical Simulation of a Prechamber-Ignited Lean-Burn Gas Engine by Means of Predictive Combustion Models

2022-12-05
Abstract In the recent period, lean-burn gas operation has been gaining large attention both in the marine sector and for power generation since it allows to achieve very low Nitrogen Oxides (NOx) emissions and to reduce carbon footprint compared to conventional diesel engines. However, to ensure a stable and efficient combustion process, innovative ignition systems able to deliver high energy content have to be considered. The employment of an active Pre-Combustion Chamber (PCC) ignition system is nowadays considered one of the most effective solutions for large-bore gas engines. In active PCC engines, the lean gas mixture in the Main Chamber (MC) is ignited by hot jets flowing from the PCC, resulting from a near-stoichiometric gas spark-assisted combustion in the PCC.
Technical Paper

Research on the Condensation Effect on Combustion Stability in LP EGR System Engine

2022-09-13
2022-01-1154
In response to the national policy of energy conservation and emission reduction, more technologies that can improve the thermal efficiency of engines are gradually applied. Among them, EGR technology has high cost -performance in energy conservation,emission reduction and improving the thermal efficiency of engines. EGR technology redirects a portion of exhaust gas into the engine intake, mixes it with fresh air, and then re-burns it in the engine combustion chamber. Because of the mixture of high temperature exhaust gas and fresh air, if the temperature of the mixture is lower than the dew point temperature of condensate water, condensate water will be precipitated. Excessive condensate water will make the engine combustion worse, and even cause engine misfire. Based on a 1.5L low pressure EGR system engine, this paper studies the factors affecting the condensate generation and combustion stability.
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