Search Results

In pursuing sustainable automotive technologies, exploring alternative fuels for hybrid vehicles is crucial in reducing environmental impact and aligning with global carbon emission reduction goals. This work compares methanol and naphtha as potential suitable alternative fuels for running in a battery-driven light-duty hybrid vehicle by comparing their performance with the diesel baseline engine. This work employs a 0-D vehicle simulation model within the GT-Power suite to replicate vehicle dynamics under the Worldwide Harmonized Light Vehicles Test Cycle (WLTC). The vehicle choice enables the assessment of a delivery application scenario using distinct payload capacities: 0%, 25%, 50%, and 100%. The model is fed with engine maps derived from previous experimental work conducted in the same engine, in which a full calibration was obtained that ensures the engine's operability in a wide region of rotational speed and loads.

Ammonia has emerged as a promising carbon-free alternative fuel for internal combustion engines (ICE), particularly in large-bore engine applications. However, integrating ammonia into conventional engines presents challenges, prompting the exploration of innovative combustion strategies like dual-fuel combustion. Nitrous oxide (N2O) emissions have emerged as a significant obstacle to the widespread adoption of ammonia in ICE. Various studies suggest that combining exhaust gas recirculation (EGR) with adjustments in inlet temperature and diesel injection timing can effectively mitigate nitrogen oxides (NOx) emissions across diverse operating conditions in dual-fuel diesel engines.

Methanol is currently being evaluated as a promising alternative fuel for internal combustion engines, due to being attainable by carbon neutral or negative pathways (renewable energy and carbon capture technology). The low ignitability of methanol has made it attractive mostly as a fuel for spark ignition engines, however the low sooting properties of the fuel could potentially reduce the NOx-soot tradeoff present in compression ignition engines. In this work, using a 4-cylinder engine with compression ratio modified from 16:1 to 19:1, methanol combustion is evaluated under five operating conditions in terms of fuel consumption, criteria pollutants, CO2 emissions and engine efficiency in addition to the qualitative assessment of the combustion stability. It was found that combustion is stable at medium to high loads, with medium load NOx emissions levels at least 30% lower than the original diesel engine and comparable emissions at maximum load conditions.

The transportation industry has been scrutinized for its contribution towards the global greenhouse gas emissions over the years. While the automotive sector has been regulated by strict emission legislation globally, the emissions from marine transportation have been largely neglected. However, during the past decade, the international maritime organization focused on ways to lower the emission intensity of the marine sector by introducing several legislations. This sets limits on the emissions of different oxides of carbon, nitrogen and sulphur, which are emitted in large amounts from heavy fuel oil (HFO) combustion (the primary fuel for the marine sector). A 40% and 70% reduction per transport work compared to the levels of 2008 is set as target for CO2 emission for 2030 and 2050, respectively. To meet these targets, commonly, methanol, as a low-carbon fuel, and ammonia, as a zero-carbon fuel, are considered.

In several regions, such as Europe, California, among others, the switch to Electric Vehicles (EVs) has been heavily pushed by policymakers for their high powertrain efficiency and zero tailpipe emissions compared to conventional Internal Combustion Engine Vehicles (ICEVs). Consequently, only zero tailpipe emission vehicles will be sold in Europe from 2035 for the passenger cars and vans segment. But an EV does emit CO2 emissions across its life cycle, mainly during production, and the Well-to-Tank (WTT) phase, i.e., from the electricity generation used to charge the batteries. Nonetheless, due to the high efficiency of the electric powertrain, the energy consumption is significantly less, making the cost of operation significantly low for EVs. Thus, clean electricity grid and cheap energy costs can make EVs one of the best options for decarbonizing transportation systems.

A commercially available fuel, E85, a blend of ~85% ethanol and ~15% gasoline, can be a viable substitute for fossil fuels in internal combustion engines in order to achieve a reduction of the greenhouse gas (GHG) emissions. Ethanol is traditionally made of biomass, which makes it a part of the food-feed-fuel competition. New processes that reuse waste products from other industries have recently been developed, making ethanol a renewable and sustainable second-generation fuel. So far, work on E85 has focused on spark ignition (SI) concepts due to high octane rating of this fuel. There is very little research on its application in CI engines. Alcohols are known for low soot particle emissions, which gives them an advantage in the NOx-soot trade-off of the compression ignition (CI) concept.

De-fossilization is an increasingly important trend in the energy sector. In the transport sector the de-fossilization efforts have been centered in promoting the electrification of vehicles, nonetheless other pathways, like the use of carbon neutral or carbon-offsetting fuels under current vehicle fleets, are also worth considering. Low-carbon fuels (LCF) can be synthetized from sources that can take advantage of the carbon already present in the atmosphere (either by technologies like direct carbon capture or biological processes like photosynthesis in biofuels) and use energy from renewable sources for the necessary industrial processes. Although, LCFs can be compared to fossil fuels as energy sources for internal combustion engines, their composition is not the same and their properties can modify the engine combustion and emissions.

In the recent years, the interest in heavy-duty engines fueled with Compressed Natural Gas (CNG) is increasing due to the necessity to comply with the stringent CO2 limitation imposed by national and international regulations. Indeed, the reduced number of carbon atoms of the NG molecule allows to reduce the CO2 emissions compared to a conventional fuel. The possibility to produce synthetic methane from renewable energy sources, or bio-methane from agricultural biomass and/or animal waste, contributes to support the switch from conventional liquid fuels to CNG. To drive the engine development and reduce the time-to-market, the employment of numerical analysis is mandatory. This requires a continuous improvement of the simulation models toward real predictive analyses able to reduce the experimental R&D efforts. In this framework, 1D numerical codes are fundamental tools for system design, energy management optimization, and so on.

In the challenge to reduce CO2, NOx and PM emissions, the application of natural gas or biogas in engines is a viable approach. In heavy duty and marine, either a conventional dual fuel (CDF), or a reactivity-controlled compression ignition (RCCI) approach is feasible on existing diesel engines. In both technologies a pilot diesel injection is used to ignite the premixed natural gas. However, the influence of injection-timing and -pressure on the start of combustion timing (SOC) is opposite between both modes. For a single operating point these relations can be explained by a detailed CFD simulation, but an intuitive overall explanation is lacking. This makes it difficult to incorporate both modes into one engine application, using a single controller. In an experimental campaign by the authors, on a medium speed engine, the lowest emissions were found to be very close to the SOC corresponding to the transition from RCCI to CDF.

The need to control global warming by regulating automotive emission levels has led to a lot of changes in the policies of different countries globally, specifically the United States (US) and the European Union (EU). More recently, the governments have been strongly pushing the integration of Electric Vehicles (EVs) in the market to replace the conventional Internal Combustion Engine (ICE) vehicles for CO₂ emissions reduction, with the enforcement of 50% EV sales by 2030 in the US and complete 100% by 2035 in the EU for passenger cars. However, these policies are misleading by considering EVs as zero emission vehicles, as there is no such technology yet available that has zero emissions during its lifecycle. During the manufacturing phase, any vehicle produced gives out emissions, with EVs emitting even higher than the conventional ICE vehicles with their battery manufacturing.

A wider use of biofuels in internal combustion engines could reduce the emissions of pollutants and greenhouse gases from the transport sector. In particular, due to stringent emission regulatory programs, compression ignition engine requires interventions aimed at reducing their polluting emissions. Ethanol, a low carbon fuel generally produced from biomass, is a promising alternative fuel applicable in compression ignition engines to reduce CO2 and soot emissions. In this paper, the application of a dual fuel diesel-ethanol configuration in a light-duty compression ignition engine has been numerically investigated. Ethanol is injected into the intake port, while diesel fuel is directly injected into the combustion chamber of the analyzed engine. CFD simulations have been carried out by means of the AVL Fire 3-D code. The operation at given engine load and speed has been simulated considering different diesel injection timings.

CO2 is a greenhouse gas that is believed to be one of the main contributors to global warming. Recent studies show that a combination of methanol as a renewable fuel and advanced combustion concepts could be a promising future solution to alleviate this problem. However, high unburned hydrocarbon (UHC) and carbon monoxide (CO) emissions can be stated as the main drawback in low load operations when using methanol under advanced combustion concepts. This issue can be mitigated by modifying the stratification of the local equivalence ratio to achieve a favorable level. The stratifications evolved, and the regimes that can simultaneously produce low emissions, and high combustion efficiency can be identified by sweeping the injection timing from homogeneous charge compression ignition (HCCI) to partially premixed combustion (PPC). Understanding how the stratification of the local equivalence ratio for methanol evolves during the sweep is essential to gain these benefits.

In recent years the research on Diesel engines has been increasingly shifting from performance and refinement to ultra-low emissions and efficiency. In fact, the last two attributes are key for the powertrain competitiveness in the propulsion electrified future, especially in the European market where 95gCO2/km fleet average and Euro6D RDE Step2 are phasing in at the same time. The present paper describes some of the most innovative research that GM and Istituto Motori Napoli are performing in the field, exploring how the steel-based additive manufacturing can be used to create innovative combustion bowl features that optimize the combustion process to a level that was not compatible with standard manufacturing technologies.

Plug-in Hybrid Electric Vehicles (PHEVs) can be considered as the most promising technology to achieve the European CO2 targets together with a moderate infrastructure modification. However, the real benefits, in terms of CO2 emissions, depend on a great extent on the energy source (fuel and electricity mix), user responsibility, and vehicle design. Moreover, the electrification of the powertrain does not reduce other emissions as NOx and particulate matter (mainly soot). In the last years, low temperature combustion (LTC) modes as the reactivity controlled compression ignition (RCCI) have shown to achieve ultra-low NOx and soot emissions simultaneously due to the use of two fuels with different reactivity together with high exhaust gas recirculation (EGR) rates. Therefore, the aim of this work is to assess, through numerical simulations fed with experimental results, the effects of different energy sources on the performance and emissions of a series RCCI PHEV.

Gas engines (fuelled with CNG, LNG or Biogas) for generation of power and heat are, to this date, taking up larger shares of the market with respect to diesel engines. In order to meet the limit imposed by the TA-Luft regulations on stationary engines, lean combustion represents a viable solution for achieving lower emissions as well as efficiency levels comparable with diesel engines. Leaner mixtures however affect the combustion stability as the flame propagation velocity and consequently heat release rate are slowed down. As a strategy to deliver higher ignition energy, an active pre-chamber may be used. This work focuses on assessing the performance of a pre-chamber combustion configuration in a stationary heavy-duty engine for power generation, operating at different loads, air-to-fuel ratios and spark timings.

Compression ignition engines are widely used for transport and energy generation due to their high efficiency and low fuel consumption. To minimize the environmental impact of this technology, the pollutant emissions levels at the exhaust are strictly regulated. To reduce the after-treatment needs, alternative strategies as the low temperature combustion (LTC) concepts are being investigated recently. The reactivity controlled compression ignition (RCCI) uses two fuels (direct- and port- injected) with different reactivity to control the in-cylinder mixture reactivity by adjusting the proportion of both fuels. In spite of the proportion of the port-injected fuel is typically higher than the direct-injected one, the characteristics of the latter play a main role on the combustion process. Use of gasoline for direct injection is attractive to retard the start of combustion and to improve the air-fuel mixing process.

The increasingly stringent emissions regulations together with the demand of highly efficient vehicles from the customers, lead to rapid developments of distinct powertrain solutions, especially when the electrification is present in a certain degree. The combination of electric machines with conventional powertrains diversifies the powertrain architectures and brings the opportunity to save energy in greater extents. On the other hand, alternative combustion modes as reactivity controlled compression ignition (RCCI) have shown to provide simultaneous ultra-low NOx and soot emissions with similar or better thermal efficiency than conventional diesel combustion (CDC). In addition, it is necessary to introduce more renewable fuels as ethanol to reduce the total CO2 emitted to the atmosphere, also called well-to-wheel (WTW) emission, in the transport sector.

With demanding emissions legislations and the need for higher efficiency, new technologies for compression ignition engines are in development. One of them relies on reducing the heat losses of the engine during the combustion process as well as to devise injection strategies that reduce soot formation. Therefore, it is necessary a better comprehension about the turbulent kinetic energy (TKE) distribution inside the cylinder and how it is affected by the interaction between air flow motion and fuel spray. Furthermore, new diesel engines are characterized by massive decrease of NOx emissions. Therefore, considering the well-known NOx-soot trade-off, it is necessary a better comprehension and overall quantification of soot formation and how the different injection strategies can impact it.

The introduction of new light-duty vehicle emission limits to comply under real driving conditions (RDE) is pushing the diesel engine manufacturers to identify and improve the technologies and strategies for further emission reduction. The latest technology advancements on the after-treatment systems have permitted to achieve very low emission conformity factors over the RDE, and therefore, the biggest challenge of the diesel engine development is maintaining its competitiveness in the trade-off “CO2-system cost” in comparison to other propulsion systems. In this regard, diesel engines can continue to play an important role, in the short-medium term, to enable cost-effective compliance of CO2-fleet emission targets, either in conventional or hybrid propulsion systems configuration. This is especially true for large-size cars, SUVs and light commercial vehicles.

Reactivity controlled compression ignition (RCCI) combustion has demonstrated to be able to avoid the NOx-soot trade-off appearing during conventional diesel combustion (CDC), with similar or better thermal efficiency than CDC under a wide variety of engine platforms. However, a major challenge of this concept comes from the high hydrocarbon (HC) and carbon monoxide (CO) emission levels, which are orders of magnitude higher than CDC and similar to those of port fuel injected (PFI) gasoline engines. The higher HC and CO emissions combined with the lower exhaust temperatures during RCCI operation present a challenge for current exhaust aftertreatment technologies. RCCI has been successfully implemented on different compression ignition engine platforms with only minor modifications on the combustion system to include a PFI for feeding the engine with the low reactivity fuel.