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In the last couple of decades, countries have enacted new laws concerning environmental pollution caused by heavy-duty commercial and passenger vehicles. This is done mainly in an effort to reduce smog and health impacts caused by the different pollutions. One of the legislated pollutions, among a wide range of regulated pollutions, is nitrogen oxides (commonly abbreviated as NOx). The SCR (Selective Catalytic Reduction) was introduced in the automotive industry to reduce NOx emissions leaving the vehicle. The basic idea is to inject a urea solution (AdBlue™) in the exhaust gas before the gas enters the catalyst. The optimal working temperature for the catalyst is somewhere in the range of 300 to 400 °C. For the reactions to occur without a catalyst, the gas temperature has to be at least 800 °C. These temperatures only occur in the engine cylinder itself, during and after the combustion.

An afterburner-assisted turbocharged single-cylinder 425 cc two-stroke SI-engine is described in this simulation study. This engine is intended as a Backup Range Extender (REX) application for heavy-duty battery electric vehicles (BEV) when external electric charging is unavailable. The 425 cc engine is an upscaled version of a 125 cc port-injected engine [26] which demonstrated that the selected technology could provide a specific power level of 400 kW/L and the desired 150 kW in a heavy duty BEV application. The 425 cc single cylinder two-stroke engine is an existing engine as one half of a 850 cc snowmobile engine. This simulation study includes upscaling of the swept volume, impact on engine speed and gas exchange properties. In the same way as for the 125cc engine [26], the exhaust gases reaches the turbine through a tuned exhaust pipe and an afterburner or oxidation catalyst.

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.

Diesel engine manufacturers strive towards further efficiency improvements. Thus, reducing in-cylinder heat losses is becoming increasingly important. Understanding how location, thermal insulation, and engine operating conditions affect the heat transfer to the combustion chamber walls is fundamental for the future reduction of in-cylinder heat losses. This study investigates the effect of a 1mm-thick plasma-sprayed yttria-stabilized zirconia (YSZ) coating on a piston. Such a coated piston and a similar steel piston are compared to each other based on experimental data for the heat release, the heat transfer rate to the oil in the piston cooling gallery, the local instantaneous surface temperature, and the local instantaneous surface heat flux. The surface temperature was measured for different crank angle positions using phosphor thermometry.

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.

Biofuel can enable a sustainable transport solution and lower greenhouse gas emissions compared to standard fuels. This study focuses on biodiesel, implemented in the easiest way as drop in fuel. When mixing biodiesel into diesel one can run into problems with solubility causing contaminants precipitating out as insolubilities. These insolubilities, also called soft particles, can cause problems such as internal injector deposits and nozzle fouling. One way to overcome the problem of soft particles is by filtration. It is thus of great interest to be able to quantify fuel filters’ ability to intercept soft particles. The aim of this study is to test different fuel filters for heavy-duty engines and their ability to filter out synthetic soft particles. A custom-built fuel filter rig is presented, together with some of its general design requirements. For evaluation of the efficiency of the filters, fuel samples were taken before and after the filters.

Biodiesel is chemically unstable and sensitive to oxidation. Aging of biodiesel results in the formation of degradation products, such as short chain fatty acids (SCFA) and water. These products may cause corrosion of metals in fuel systems. When performing corrosion tests, biodiesel continuously degrades during the test, resulting in an uncontrolled test system. In order to obtain a stable corrosion testing system, a test fuel was developed using a saturated FAME (methyl myristate), which was doped with RME degradation products at levels typically seen in field tests. The test fuel was compared to RME with regards to structure, SCFA and water content before and after aging tests. In addition, an accelerated corrosion study of copper was performed in both the test fuel and in RME. The copper specimens were analyzed before and after test using light optical microscope and weight measurements. The Cu content in the test fuel and RME was also analyzed.

The use of Selective Catalytic Reduction (SCR) is becoming increasingly more popular as a way of reducing NOx emissions from heavy duty vehicles while maintaining competitive operating costs. In order to make efficient use of these systems, it's important to have a complete system approach when it comes to calibration of the engine and aftertreatment system. This paper presents a simplified model of a heavy duty SCR catalyst, primarily intended for use in combination with an engine-out emissions model to perform model based offline optimization of the complete system. The traditional way of modelling catalysts using a dense discretization of the catalyst channels and non-linear differential equation solvers to solve the heat and mass balance equations, requires too much computational power in this application. The presented model is also useful in other applications such as model based control.

In order to make efficient use of a Diesel engine equipped with an SCR system, it's important to have a complete system approach when it comes to calibration of the engine and the aftertreatment system. This paper presents a complete model of a heavy duty diesel engine equipped with a vanadia based SCR system. The diesel engine uses common rail fuel injection, a variable geometry turbocharger (VGT) and cooled EGR. The engine model consists of a quasi steady gas exchange model combined with a two-zone zero dimensional combustion model. The combustion model is a predictive heat release model. Using the calculated zone temperatures, the corresponding NOx concentration is given by the original Zeldovich mechanism. The SCR catalyst model is of the state space type. The basic model structure is a series of continuously stirred tank reactors and the catalyst walls are discretized to describe mass transport inside the porous structure.

Achieving upcoming HD emissions legislation, Euro VI/EPA 10, is a challenge for all engine manufacturers. A likely solution to meet the NOx limit is to use a combination of EGR and SCR. Combining these two technologies poses new challenges and possibilities when it comes to optimization and calibration. Using a complete system approach, i.e., considering the engine and the aftertreatment system as a single unit, is important in order to achieve good performance. Optimizing the complete system is a tedious task; first there are a large number of variables which affect both emissions and fuel consumption (injection timing, EGR rate, urea dosing, injection pressure, pilot/post injections, for example). Secondly, the chemical reactions in the SCR catalyst are substantially slower than the dynamics of the diesel engine and the rest of the system, making the optimization problem time dependent.

Increasingly stringent emission legislation as well as increased demand on fuel efficiency calls for further research and development in the diesel engine field. Spray formation, evaporation and ignition delay are important factors that influence the combustion and emission formation processes in a diesel engine. Increased understanding of the mixture formation process is valuable in the development of low emission, high efficiency diesel engines. In this paper spray formation and ignition under real engine conditions have been studied in an optical engine capable of running close to full load for a real HD diesel engine. Powerful external lights were used to provide the required light intensity for high speed camera images in the combustion chamber prior to ignition. A specially developed software was used for spray edge detection and tracking. The software provides crank angle resolved spray penetration data.

The tightening legislation in the on-road heavy-duty diesel area means that pollution control systems will soon be widely introduced on such engines. A number of different aftertreatment systems are currently being considered to meet the incoming legislation, including Diesel Particulate Filters (DPF), Diesel Oxidation Catalysts (DOC) and Selective Catalytic Reduction (SCR) systems. Relatively little is known about the interactions between lubricant-derived species and such aftertreatment systems. This paper describes the results of an experimental program carried out to investigate these interactions within DPF, DOC and SCR systems on a state-of-the-art 9 litre engine. The influence of lubricant composition and lube oil ash level was investigated on the different catalyst systems. In order to reduce costs and to speed up testing, test oil was dosed into the fuel. Tests without dosing lubricant into the fuel were also run.

In one dimensional engine simulation software, flow losses over complex geometries such as valves and ports are described using flow coefficients. It is generally assumed that the pressure ratio over the valve has a negligible influence on the flow coefficient. However during the exhaust valve opening the pressure difference between cylinder and port is large which questions the accuracy of this assumption. In this work the influence of pressure ratio on the exhaust valve flow coefficient has been investigated experimentally in a steady-flow test bench. Two cylinder heads, designated A and B, from a Heavy-Duty engine with different valve shapes and valve seat angles have been investigated. The tests were performed with both exhaust valves open and with only one of the two exhaust valves open. The pressure ratio over the exhaust port was varied from 1.1:1 to 5:1. For case A1 with a single exhaust valve open, the flow coefficient decreased significantly with pressure ratio.

Flow reversal chambers are common design elements in mufflers. Here an idealized flow reversal chamber with large cross-section but small depth has been studied. The inlet and outlet ducts as well as the cross-sectional area are fixed while the depth of the chamber can be varied. The resulting systems are then characterized experimentally using the two-microphone wave decomposition method and compared with results from both finite element modeling and various approaches using two-port elements. The finite element modeling results are in excellent agreement with the measurements over the whole frequency range studied, while two-port modeling can be used with engineering precision in the low frequency range. The influence of mean flow was studied experimentally and was shown to have relatively small influence, mainly adding some additional losses at low frequencies.

Spray and mixture formation in a compression ignition engine is of paramount importance for diesel combustion. In engine transient operation, when the load increases rapidly, the combustion system needs to handle low lambda (λ) operation while avoiding high particle emissions. Single-cylinder tests were performed to evaluate the effect of differences in cylinder flow on combustion and emissions at typical low λ transient operation. The tests were performed on a heavy-duty single-cylinder test engine with Lotus Active Valve Train (AVT) controlling the inlet airflow. The required swirl number (SN) and tumble were controlled by applying different inlet valve profiles and opening either both inlet valves or only one or the other. The operating point of interest was extracted from engine transient conditions before the boost pressure was increased and investigated further at steady state conditions.

A problem for the diesel engine that remains since its invention is injection nozzle hole fouling. More advanced injection systems and more complex fuels, now also including bio-components, have made the problem more intricate. Zinc and biodiesel have often been accused of being a big part of the problem, but is this really the case? In this study, nozzle fouling experiments were performed on a single cylinder engine. The experiments were divided in three parts, the first part studied the influence of zinc neodecanoate concentration on nozzle hole fouling, the second part studied the effect of neodecanoates of zinc, sodium, calcium, copper, and iron on fuel flow loss and in the last part it was examined how RME concentration in zinc neodecanoate contaminated petroleum diesel affected nozzle hole fouling propensity. After completed experiments, the nozzles were cut open and the deposits were analyzed in SEM and with EDX.

A turbocharged Diesel engine for heavy-duty on-road vehicle applications employs a compact exhaust manifold to satisfy transient torque and packaging requirements. The small exhaust manifold volume increases the unsteadiness of the flow to the turbine. The turbine therefore operates over a wider flow range, which is not optimal as radial turbines have narrow peak efficiency zone. This lower efficiency is compensated to some extent by the higher energy content of the unsteady exhaust flow compared to steady flow conditions. This paper experimentally investigates the relationship between exhaust energy utilization and available energy at the turbine inlet at different degrees of unsteady flow. A special exhaust manifold has been constructed which enables the internal volume of the manifold to be increased. The larger volume reduces the exhaust pulse amplitude and brings the operating condition for the turbine closer to steady-flow.

With stricter emission legislations and demands on low fuel consumption, new engine technologies are continuously investigated. At the same time the accuracy in the over all engine control and diagnosis and hence also the required estimation accuracy is tightened. Central for the internal combustion control is the trapped cylinder charge and composition Traditionally cylinder charge is estimated using mean intake manifold pressure and engine speed in a two dimensional lookup table. With the introduction of variable valve timing, two additional degrees of freedom are introduced that makes this approach very time consuming and therefore expensive. Especially if the cam phasers are given large enough authority to offer powerful thermal management possibilities. The paper presents a physical model for estimating in-cylinder trapped mass and residual gas fraction utilizing cylinder pressure measurements, and intake and exhaust valve lift profiles.

The emission control in heavy-duty vehicles today is based on predefined injection strategies and after-treatment systems such as SCR (selective catalytic reduction) and DPF (diesel particulate filter). State-of-the-art engine control is presently based on cycle-to-cycle resolution. The introduction of the crank angle resolved pressure measurement, from a piezo-based pressure sensor, enables the possibility to control the fuel injection based on combustion feedback while the combustion is occurring. In this paper a study is presented on the possibility to control NOx (nitrogen oxides) formation with a crank angle resolved NOx estimator as feedback. The estimator and the injection control are implemented on an FPGA (Field-Programmable Gate Array) to manage the inherent time constraints. The FPGA is integrated with the rest of the engine control system for injection control and measurement.