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Heavy-duty transportation is one of the sectors that contributes to greenhouse gas emissions. One way to reduce CO2 emissions is to use drop-in fuels. However, when drop-in fuels are used, i.e., higher blends of alternative fuels are added to conventional fuels, solubility problems and precipitation in the fuel can occur. As a result, insolubles in the fuel can clog the fuel filters and interfere with the proper functioning of the injectors. This adversely affects engine performance and increases fuel consumption. These problems are expected to increase with the development of more advanced fuel systems to meet upcoming environmental regulations. This work investigates the composition of the deposits formed inside the injectors of the heavy-duty diesel engine and discusses their formation mechanism. Injectors with internal deposits were collected from field trucks throughout Europe. Similar content, location and structure were found for all the deposits in the studied injectors.

Increasing concern for air pollution together with the introduction of new types of fuels pose new challenges to the exhaust aftertreatment system for heavy-duty (HD) vehicles. For diesel-powered engines, emissions of particulate matter (PM) is one of the main drawbacks due to its effect on health. To mitigate the tailpipe emissions of PM, heavy-duty vehicles are since Euro V equipped with a diesel particulate filter (DPF). The accumulation of particles causes flow restriction resulting in fuel penalties and decreased vehicle performance. Understanding the properties of PM produced during engine operation is important for the development and optimized control of the DPF. This study has focused on assessing the reactivity of the PM by measuring the oxidation kinetics of the carbonaceous fraction. PM was sampled from two different heavy-duty engines during various test cycles.

The formation of deposits in the fuel systems of heavy-duty engines, using drop-in fuels, has been reported in recent years. Drop-in fuels are of interest because they allow higher levels of alternative fuels to be blended with conventional fuels that are compatible with today’s engines. The precipitation of insolubles in the drop-in fuel can lead to clogging of fuel filters and internal injector deposits, resulting in increased fuel consumption and engine drivability problems. The possible mechanisms for the formation of the deposits in the fuel system are not yet fully understood. Several explanations such as operating conditions, fuel quality and contamination have been reported. To investigate injector deposit formation, several screening laboratory test methods have been developed to avoid the use of more costly and complex engine testing.

One way to reduce carbon dioxide emissions from the current heavy-duty vehicles fleet is to replace fossil fuel with renewable fuel. This can be done by blending so-called drop-in fuels into the standard diesel fuel. However, problems such as insoluble impurities may arise when the fuels are mixed. These precipitates, known as soft particles, can cause deposits in the fuel system, e.g., injectors and fuel filters, reducing the engine´s performance. The most used drop-in fuel today is biodiesel which, is blended with different concentrations. To better understand how soft particles are formed in the vehicle´s fuel system, the degradation of biodiesel blends in the engine has been investigated. This study explores biodiesel blends´ degradation process by comparing the incoming fuel with the return fuel from a modern diesel engine to investigate how the fuel is affected by this process. The engine was run using different blends of biodiesel fuel.

Heavy-duty transportation accounts for significant part of the greenhouse gas emissions. Currently the most common powertrain for long-haul trucks is compression-ignited engines. In order to reduce the greenhouse gas emissions of these engines, renewable fuels, such as biodiesel can be used. Today biodiesel is used as a drop-in fuel, however when biodiesel is mixed with conventional diesel, soft particles may form. Soft particles have been identified as a mixture of insoluble impurities and degradation products in the fuel. These soft particles can lead to deposits in the injection and fuel filtration system, leading to reduced engine performance. In this paper, zinc-neodecanoate and soft particles from the degradation of biodiesel is studied. In both cases, the emphasis is on soap type contaminants. Zinc-neodecanoate has shown to lead to nozzle fouling, while soft particles from degradation of biodiesel have been found in diesel fuel filters.

The ignition dynamics of an ethanol-diesel direct injection compression ignition engine is investigated based on 3D RANS simulations. Experimental results of a previous test campaign on a single-cylinder research engine equipped with two direct injectors are used to validate the CFD model. Four reference engine conditions are considered, including split and overlapped injections of ethanol and diesel at low and high load. Combustion driven by the separate direct injection of pure ethanol and diesel as pilot fuel is simulated with AVL Fire and AVL Tabkin adopting the flamelet generated manifold combustion model. The in-cylinder pressure and apparent rate of heat release traces computed in the simulations are found to be consistent with the corresponding experimental results.

In heavy-duty engines, Euro VI legislation regulates the total particle number (PN) in the exhaust based on the particle measurement program (PMP) guidelines. By PMP directives, the exhaust sample is diluted and conditioned to contain non-volatile particles before measuring the PN. The fraction of non-volatile and volatile particles changes along the exhaust after-treatment system and could affect the total PN measured. Therefore, it is of interest to compare the performance of the dilution systems at different positions along the after-treatment system. For this purpose, a standard PMP compliant two-stage dilution system (DS1) with evaporation tube (ET) was compared with a close coupled two-stage ejector dilution system (DS2). In DS2, the non-volatile PN was measured with a dilution temperature of 350°C (same as the DS1 ET temperature) while the volatile PN was measured with a dilution temperature of 150°C.

Particles emitted from internal combustion engines have adverse health effects and the severity varies based on the particle size. A diesel particulate filter (DPF) in the after-treatment systems is employed to control the particle emissions from combustion engines. The design of a DPF depends on the nature of particle size distribution at the upstream and is important to evaluate. In heavy-duty diesel engines, the turbocharger turbine is an important component affecting the flow and particles. The turbine wheel and housing influence particle number and size. This could potentially be used to reduce particle number or change the distribution to become more favourable for filtration. This work evaluates the effect of a heavy-duty diesel engine’s turbine on particle number and size distribution.

Diffusive combustion of direct injected ethanol is investigated in a heavy-duty single cylinder engine for a broad range of operating conditions. Ethanol has a high potential as fossil fuel alternative, as it provides a better carbon footprint and has more sustainable production pathways. The introduction of ethanol as fuel for heavy-duty compression-ignition engines can contribute to decarbonize the transport sector within a short time frame. Given the resistance to autoignition of ethanol, the engine is equipped with two injectors mounted in the same combustion chamber, allowing the simultaneous and independent actuation of the main injection of pure ethanol and a pilot injection of diesel as an ignition source. The influence of the dual-fuel injection strategy on ethanol ignition, combustion characteristics, engine performance and NOx emissions is evaluated by varying the start of injection of both fuels and the ethanol-diesel ratio.

Renewable fuels from different feedstocks can enable sustainable transport solutions with significant reduction in greenhouse gas emissions compared to conventional petroleum-derived fuels. Nevertheless, the use of biofuels in diesel engines will still require similar exhaust gas cleaning systems as for conventional diesel. Hence, the use of diesel particulate filters (DPF) will persist as a much needed part of the vehicle’s aftertreatment system. Combustion of renewable fuels can potentially yield soot and ash with different properties as well as larger amounts of ash compared to conventional fossil fuels. The faster ash build-up and altered ash deposition pattern lead to an increase in pressure drop over the DPF, increase the fuel consumption and call for premature DPF maintenance or replacement. Prolonging the maintenance interval of the DPF for heavy-duty trucks, having a demand for high up-time, is highly desirable.

Particle emissions from heavy-duty engines are regulated both by mass and number by Euro VI regulation. Understanding the evolution of particle size and number from the exhaust valve to the tail pipe is of vital importance to expand the possibilities of particle reduction. In this study, experiments were carried out on a heavy-duty Euro VI engine after-treatment system consisting of diesel oxidation catalyst, diesel particulate filter and selective catalytic reduction (SCR) unit with AdBlue injection followed by ammonia slip catalyst. The present work focusses on the SCR unit with regard to total particle number with and without nucleation particles both. Experiments were conducted by varying the AdBlue injection quantity, SCR inlet temperature [to vary the reaction temperature], exhaust mass flow rate [to vary the residence time in SCR], and fuel injection pressures [to vary inlet particle number and inlet NOx].

Renewable fuels have an important role to create sustainable energy systems. In this paper the focus is on biodiesel, which is produced from vegetable oils or animal fats. Today biodiesel is mostly used as a drop-in fuel, mixed into conventional diesel fuels to reduce their environmental impact. Low quality drop-in fuel can lead to deposits throughout the fuel systems of heavy duty vehicles. In a previous study fuel filters from the field were collected and analyzed with the objective to determine the main components responsible for fuel filter plugging. The identified compounds were constituents of soft particles. In the current study, the focus was on metal carboxylates since these have been found to be one of the components of the soft particles and associated with other engine malfunctions as well. Hence the measurement of metal carboxylates in the fuel is important for future studies regarding the fuel’s effect on engines.

Knock in heavy duty (HD) spark ignition (SI) engines is exacerbated by a large bore diameter and a higher flame travel distance. An increase in turbulence close to TDC can improve combustion speed and reduce knock through low residence time for end gas auto-ignition. Since HD SI engines are usually derived from diesel engines, it is common to have a swirl motion that does not dissipate into turbulence. To increase flame speed and limit knock, squish can be used to produce turbulence close to TDC. In this study, two different piston bowl geometries are examined: the re-entrant and quartette. The influence of squish area on turbulence production by these piston geometries were investigated using motored simulations in AVL FIRE. The effect of increased turbulence on knock reduction was analyzed using a calibrated 1D GT-Power model of a HD SI engine and the performance improvement was estimated.

The global demand for decreased emission from engines and increased efficiency drives manufactures to develop more advanced fuel injection systems. Today's compression-ignited engines use common rail systems with high injection pressures and fuel injector nozzles with small orifice diameters. These systems are highly sensitive to small changes in orifice diameters since these could lead to deteriorations in spray characteristics, thus reducing engine performance and increasing emissions. Phenomena that could create problems include nozzle fouling caused by metal carboxylates or biofuels. The problems increase with extended use of biofuels. This paper reports on an experimental study of nozzle hole fouling performed on a single-cylinder engine. The aim was to identify if the solubility of the fuel has an effect on deposit build-up and, thus, the reduction in fuelling with associated torque loss, and if there is a probability of regenerating the contaminated injectors.

Fuel filters serve as a safety belt for modern compression ignition engines. To meet the requirements from environmental regulations these engines use the common rail injection system, which is highly susceptible to contamination from the fuel. Furthermore, the public awareness towards global warming is raising the need for renewable fuels such as biodiesel. An increased fuel variety brings a higher requirement for fuel filters as well. To better understand the process of filtration, awareness of the different possible contaminants from the field is needed. This study used several chemical characterization techniques to examine the deposits from plugged fuel filters collected from the field. The vehicle was run with a biodiesel blend available on the market.

Increasing demands for more efficient engines and stricter legislations on exhaust emissions require more accurate control of the engine operating parameters. Engine control is based on sensors monitoring the condition of the engine. Numerous sensors, in a complex control context, increase the complexity, the fragility and the cost of the system. An alternative to physical sensors are virtual sensors, observers used to monitor parameters of the engine thus reducing both the fragility and the production cost but with a slight increase of the complexity. In the current paper a virtual intake manifold cylinder port pressure sensor is presented. The virtual sensor is based on a compressible flow model and on the pressure signal of the intake manifold pressure sensor. It uses the linearized pressure coefficient approach to keep vital performance behaviors while still conserving calibration effort and embedded system memory.

Thermal Barrier Coatings (TBCs) may be used on the inner surfaces of exhaust manifolds in heavy-duty diesel engines to improve the fuel efficiency and prolong the life of the component. The coatings need to have a long thermal cyclic life and also be able to reduce the temperature in the substrate material. A lower temperature of the substrate material reduces the oxidation rate and has a positive influence on the thermo-mechanical fatigue life. A test rig for evaluating these properties for several different coatings simultaneously in the correct environment was developed and tested for two different TBCs and one oxidation-resistant coating. Exhausts were redirected from a diesel engine and led through a series of coated pipes. These pipes were thermally cycled by alternating the temperature of the exhausts. Initial damage in the form of cracks within the top coats of the TBCs was found after cycling 150 times between 50°C and 530°C.

Internal combustion engines for plug-in hybrid heavy duty trucks, especially long haul trucks, could play an important role in facilitating use of battery power. Power from a low carbon electricity source could thereby be employed without an unattractive vehicle cost increase or range limitation. The ideal engine should be powered by a widely available affordable liquid fuel, should minimize air pollutant emissions, and should provide lower greenhouse gas emissions. Diesel engines could fall short in meeting these objectives, especially because of high emissions. In this paper we analyze the potential for a flex fuel gasoline-alcohol engine approach for a series hybrid powertrain. In this approach the engine would provide comparable (or possibly greater) efficiency than a diesel engine while also providing 90 around lower NOx emissions than present cleanest diesel engine vehicles. Ethanol or methanol would be employed to increase knock resistance.

Renewable fuels are essential in the field of heavy duty transportation if we are to reach a fossil-free society in the foreseeable future. However renewable diesel fuels based on fatty acid methyl ester (FAME) might face problems with degradation and with cold flow properties. From the perspective of an engine, this may cause problems in the fuel injection system, such as fuel filter clogging and injector deposits. These phenomena, especially fuel filter clogging, can be connected to gel-like soft particles, which could originate from degradation products as well as from byproducts created during biodiesel refining. In this study, soft particles from the degradation of bio-based diesel fuel were examined. The tested fuels included hydrogenated vegetable oils (HVO), rapeseed methyl ester (RME) and 10% blend of rapeseed methyl ester with standard diesel (B10).

Gaseous methane fuel for internal combustion engines have proved to be a competitive source of propulsion energy for heavy duty truck engines. Using biogas can even reduce the carbon footprint of the truck to near-zero levels, creating fully environmentally friendly transport. Gas engines have already been on the market and proved to be a popular alternative for buses and waste transport. However, for long haulage these gas engines have not been on par with the equivalent diesel engines. To improve the power and efficiency of EURO VI gas engines running stoichiometrically, a direct way forward is adding more boost pressure and spark advance in combination with more EGR to mitigate knock. Using in-cylinder turbulence to achieve higher mixing rate, the fuel can still be combusted efficiently despite the increased fraction of inert gases.