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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.

A viable option to reduce global warming related to internal combustion engines is to use renewable fuels, for example methanol. However, the risk of knocking combustion limits the achievable efficiency of SI engines. Hence, most high load operation is run at sub-optimal conditions to suppress knock. Normally the fuel is a limiting factor, however when running on high octane fuels such as methanol, other factors also become important. For example, oil droplets entering the combustion chamber have the possibility to locally impact both temperature and chemical composition. This may create spots with reduced octane number, hence making the engine more prone to knock. Previous research has confirmed a connection between oil droplets in the combustion chamber and knock. Furthermore, previous research has confirmed a connection between oil droplets in the combustion chamber and exhaust particle emissions.

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.

Modern spark-ignited (SI) engines offer excellent emission reduction when operated with a stoichiometric mixture and a three-way catalytic converter. A challenge with stoichiometric compared to diluted operation is the knock propensity due to the high reactivity of the mixture. This limits the compression ratio, thus reducing engine efficiency and increasing exhaust temperature. The current work evaluated a model of conditions at inlet valve closing (IVC) and top dead center (TDC) for steady state operation. The IVC temperature model is achieved by a cycle-to-cycle resolved residual gas fraction estimator. Due to the potential charge cooling effect from methanol, a method was proposed to determine the fraction of fuel sourced from a wall film. Determining the level of charge cooling is important as it heavily impacts the IVC and TDC temperatures.

Stoichiometric operation of a Port Fueled Injection (PFI) Spark-Ignited (SI) engine with a three-way catalytic converter offers excellent CO2 reduction when run on renewable fuel. The main drawbacks with stoichiometric operation are the increased knock propensity, high exhaust temperature and reduced efficiency. Knock is typically mitigated with a reactive knock controller, with retarded ignition timing whenever knock is detected and the timing then slowly advanced until knock is detected again. This will cause some cycles to operate with non-ideal ignition timing. The current work evaluates the possibility to predict knock using the measured and modelled temperatures at Inlet Valve Closing (IVC) and Top Dead Center (TDC). Feedback effects are studied beyond steady state operation by using induced ignition timing disturbances.

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.

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.

This paper investigates the FPGA resources for the implementation of in-cycle closed-loop combustion control algorithms. Closed-loop combustion control obtains feedback from fast in-cylinder pressure measurements for accurate and reliable information about the combustion progress, synchronized with the flywheel encoder. In-cycle combustion control requires accurate and fast computations for their real-time execution. A compromise between accuracy and computation complexity must be selected for an effective combustion control. The requirements on the signal processing (evaluation rate and digital resolution) are investigated. A common practice for the combustion supervision is to monitor the heat release rate. For its calculation, different methods for the computation of the cylinder volume and heat capacity ratio are compared. Combustion feedback requires of virtual sensors for the misfire detection, burnt fuel mass and pressure prediction.

The constrained indicated efficiency optimization of the set-point reference for in-cycle closed-loop combustion regulators is investigated in this article. Closed-loop combustion control is able to reduce the stochastic cyclic variations of the combustion by the adjustment of multiple-injections, a pilot and main injection in this work. The set-point is determined by the demand on engine load, burned pilot mass reference and combustion timing. Two strategies were investigated, the regulation of the start of combustion (SOC) and the center of combustion (CA50). The novel approach taken in this investigation consists of including the effect of the controlled variables on the combustion dispersion, instead of using mean-value models, and solve the stochastic optimization problem. A stochastic heat release model is developed for simulation and calibrated with extensive data from a Scania D13 six-cylinder engine. A Monte Carlo approach is taken for the simulations.

Power dense internal combustion engines (ICEs) are interesting candidates for onboard charging devices in different electric powertrain applications where the weight, volume and price of the energy storage components are critical. Single-cylinder naturally aspirated two-stroke spark-ignited (SI) engines are very small and power dense compared to four-stroke SI engines and the installation volume from a single cylinder two-stroke engine can become very interesting in some concepts. During charged conditions, four-stroke engines become more powerful than naturally aspirated two-stroke engines. The performance level of a two-stroke SI engines with a charging system is less well understood since only a limited number of articles have so far been published. However, if charging can be successfully applied to a two-stroke engine, it can become very power dense.

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.

Pilot injections are normally used for the reduction of diesel engine emissions and combustion noise. Nonetheless, with a penalty on the indicated thermal efficiency. The cost is reduced by the minimization of the pilot mass, which on its counterpart increases the risk of pilot misfire. Pilot misfire can have a higher penalty on the indicated efficiency if it is not compensated adequately. This paper investigates how in-cycle closed-loop combustion control techniques can reduce the effects of pilot misfire events. By closed-loop combustion control, pilot misfire can be detected and counteracted in-cycle. Two injection strategies are investigated. The first is the control of the main injection, the second includes an additional second pilot injection. Based on the in-cycle misfire diagnose, two architectures are investigated. The first uses a cycle-to-cycle controller to set the main injection under each scenario.

In-cylinder heat losses in diesel engines reduce engine efficiency significantly and account for a considerable amount of injected fuel energy. A great part of the heat losses during diesel combustion presumably arises from the impingement of the flame. The present study compares the heat losses at the point where the flame impinges onto the piston bowl wall and the heat losses between two impingement points. Measurements were performed in a full metal heavy-duty diesel engine with a small optical access through a removed exhaust valve. The surface temperature at the impingement point of the combusting diesel spray and at a point in between two impingement points was determined using phosphor thermometry. The dynamic heat fluxes and the heat transfer coefficients which result from the surface temperature measurements are estimated. Simultaneous cylinder pressure measurements and high-speed videos are associated to individual surface temperature measurements.

The introduction of renewable alcohols as fuels for heavy-duty engines may play a relevant role for the reduction of the carbon footprint of the transport sector. The direct injection of ethanol as main fuel and diesel as pilot fuel in the engine combustion chamber through two separate injectors may allow good combustion controllability over the entire engine operating range by targeting diffusive combustion. Closed-cycle combustion simulations have been carried out using AVL FIRE coupled to AVL TABKIN for the implementation of the Flamelet Generated Manifold (FGM) chemistry reduction technique in order to investigate the influence of the injection system geometry and the injection strategy of pure ethanol and diesel fuel on ignition characteristics and combustion at different operating conditions.

For the reduction of emissions and combustion noise in an internal combustion diesel engine, multiple injections are normally used. A pilot injection reduces the ignition delay of the main injection and hence the combustion noise. However, normal variations of the operating conditions, component tolerances, and aging may result in the lack of combustion i.e. pilot misfire. The result is a lower indicated thermal efficiency, higher emissions, and louder combustion noise. Closed-loop combustion control techniques aim to monitor in real-time these variations and act accordingly to counteract their effect. To ensure the in-cycle controllability of the main injection, the misfire diagnosis must be performed before the start of the main injection. This paper focuses on the development and evaluation of in-cycle algorithms for the pilot misfire detection. Based on in-cylinder pressure measurements, different approaches to the design of the detectors are compared.

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.

The demand for high-efficiency engines has never been greater as energy consumption and emission reductions are key ingredients for continued competitiveness in today’s transportation industry. A main contributor to recent and future improvement of the internal combustion engine is the gas exchange process. By utilizing the exhaust energy in the turbine stage of an exhaust turbocharger, the pumping work can be improved resulting in significant gains of engine system efficiency. Two main aspects can be identified with regards to the turbine design that are crucial: The level of exhaust pulse separation and turbine efficiency at high pressure ratios. For a pulse-turbocharged engine both aspects need to be considered in order to gain full benefit of the exhaust energy utilization process. In this study, a novel axial turbine stage concept with divided inlets is presented.

In-cylinder heat losses in diesel engines decrease engine efficiency significantly and account for approximately 14-19% [1, 2, 3] of the injected fuel energy. A great part of the heat losses during diesel combustion presumably arises from the flame impingement onto the piston. Therefore, the present study investigates the heat losses during flame impingement onto the piston bowl wall experimentally. The measurements were performed on a full metal heavy-duty diesel engine with a small optical access through a removed exhaust valve. The surface temperature at the impingement point of the flame was determined by evaluating a phosphor’s temperature dependent emission decay. Simultaneous cylinder pressure measurements and high-speed videos are associated to the surface temperature measurements in each cycle. Thus, surface temperature readings could be linked to specific impingement and combustion events.

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.