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With the rising interest in hydrogen fuel cell vehicles (FCV) to reduce the global warming impact of the automotive sector, the industry and car manufacturers are shifting towards producing H2-based or electricity-based vehicles. Plug-in passenger FCVs with a range-extender architecture (FCREx), could be a more versatile with a lower total cost of ownership (TCO) alternative to other FCV configurations, given the current H2 cost. In this investigation, a validated fuel cell (FC) stack model was integrated into a complete FCREx model to study the potential of this architecture in terms of H2 consumption and cradle-to-grave GHG and NOX emissions. First, the FC stack model was calibrated using experimental data. Then, a FC system model including the balance of plant (BoP) was developed and adjusted to the stack specifications. The BoP air management strategy was optimized to ensure maximum performance in steady conditions.

Low pressure exhaust gases recirculation (LP-EGR) is becoming a state-of-the-art technique for Nitrogen oxides (NOx) reduction in compression ignited (CI) engines. However, despite the pollutant reduction benefits, LP-EGR suffers from strong non-linearities and delays which are difficult to handle, resulting in reduced engine performance under certain conditions. Measurement and observation of oxygen concentration at the intake have been a research topic over the past few years, and it may be critical for transition phases (from low pressure to high pressure EGR). Here, an adequate selection of models and sensors is essential to obtain a precise and fast measurement for control purposes. The present paper analyses different sensor configurations, with oxygen concentration measurements at the intake and exhaust manifold and combines observation techniques with sensor models to determine the potential of each configuration.

Dual-fuel combustion engines have shown the potential to extend the operating range of Homogeneous Charge Compression Ignition (HCCI) by using several combustion modes, e.g. Reactivity Controlled Compression Ignition (RCCI) at low/medium load, and Partially Premixed Compression (PPC) at high load. In order to optimize the combustion mode operation, the respective sensitivity to the control inputs must be addressed. To this end, in this work the extremum seeking algorithm has been investigated. By definition, this technique allows to detect the control input authority over the system by perturbing its value by a known periodic signal. By analyzing the system response and calculating its gradient, the control input can be adjusted to reach optimal operation. This method has been applied to a dual-fuel engine under fully, highly and partially premixed conditions where the feedback information was provided by in-cylinder pressure and NOx sensors.

The passive pre-chamber ignition concept has shown the potential of increasing the combustion efficiency at high load by allowing more advanced combustion phasing due to its rapid combustion. The optimization of the spark advance and the dilution rate is currently a challenging task that would allow these types of engines to maintain spark ignited (SI) engines pollutants with even higher combustion efficiencies than diesel engines. This paper is focused on the automatic calibration of a SI engine, when using the passive-chamber ignition concept. The sensitivity of the combustion efficiency to spark advance and dilution rate has been studied and an extremum seeking approach has been designed to optimize the control inputs by rejecting disturbances and maintaining certain limitations of cycle-to-cycle variability and misfires.

Knock is an abnormal phenomenon with in-cylinder pressure oscillations, which must be avoided to protect the engine from damage and to avoid excessive noise. Conventional control algorithms delay the combustion with the spark to avoid high knocking rates but reduce the thermal efficiency and restricts the performance of a spark ignition engine. The detection and characterization of low-knocking cycles might be used for improving knock control algorithms, however, it is a challenging task, as normal combustion also excite the different resonance modes and might be confused with knock. Most of the methods found in literature for knock detection use 0-Dimensional indicators, regardless of the angular evolution of the pressure oscillations. In this paper, the in-cylinder pressure oscillations evolution during the piston stroke is analyzed by using various time-frequency transformations.

In a context of increasing emission regulations, turbocharged gasoline engines are increasingly present in the automotive industry. In particular, the twin-entry and double-entry radial inflow turbines are widespread used technologies to avoid interferences between exhaust process of consecutive firing order cylinders. In this study, a passenger car twin-entry type turbine has been tested under highly pulsating flow conditions by means of a specifically built gas stand, trying to perform pulses with similar features as the ones that can be found in a real reciprocating engine. For this purpose, the turbine has been instrumented with multiple pressure, temperature and mass flow sensors, using a uniquely designed rotating valve for generating the pulses. The test bench setup is flexible enough to perform pulses in both inlet branches separately as well as to use hot or ambient conditions with minimal changes in the installation.

Fuel-to-air ratio stimulation, also called λ cycling or λ modulation, is a natural consequence of controlling fuel-to-air ratio in closed-loop with a switch-type λ-sensor. Nowadays, wideband λ-sensors are broadly extended and fuel-to-air ratio stimulation is an additional option that can or not be implemented in the control strategies to improve TWC conversion efficiency through the increase of the catalyst activity. The present work focus on the suitability of applying fuel-to-air ratio stimulation in a turbocharged GDI engine equipped with a close-coupled TWC. In particular, the influence of the main parameters such as stimulation amplitude and frequency on tailpipe emissions at steady-state conditions is assessed. The potential of λ cycling in order to reduce pollutant emissions in the face of fuel-to-air ratio disturbances has also been evaluated. Results show how a proper λ modulation decreases NOx emissions at lean conditions.

Direct injection compression ignited (CI) engines are today's most efficient engine technology, granting efficiencies exceeding 40% for their optimal operation point. In addition, a strong technological development has allowed the CI engine to overcome its traditional weak points: both its pollutant emissions and the gap in specific power regarding its competitor, i.e. the spark ignited (SI) engine, have been noticeably reduced. Particularly, the increase in specific power has led to the downsizing as an effective method to improve vehicle efficiency. Despite the reduction in total displacement, the cylinder displacement of current CI engines is still around 0.5 liters. For some applications (urban light duty vehicles, Range Extenders…) it may be interesting to reduce the engine displacement to address power targets around 20kW with high efficiencies.

The development of one cycle resolution control strategies and the research at HCCI engines demands an accurate estimation of the trapped mass. In contrast to current methods for determining the mass flow, which are only able to determine averaged values of the flow entering the cylinders, the present paper proposes a methodology based on the in-cylinder pressure resonance. The determination of such frequency allows inferring the cylinder mass with one cycle resolution. In addition, the method permits determining error metrics based on the mass conservation principle. Validation results for a reactivity controlled compression ignition (RCCI) engine equipped with electrohydraulic variable valve timing (VVT) are presented to illustrate the performance of the method.

This paper shows the potential of a multicalibration approach for reducing fuel consumption while keeping pollutant immissions. The paper demonstrates that the current engine control approach with a single fixed calibration involves important fuel penalties in areas with low vehicle densities where local pollution is not an issue, while the NOx emissions in urban areas are usually too high to fulfill air quality standards. The proposed strategy is based on using information about the vehicle location and the NOx concentrations in the ambient to choose a suitable calibration amongst a set of possibilities. To assess the potential of such a strategy experimental tests have been done with a state-of-art turbocharged Diesel engine. First, a design of experiments is used to obtain three different calibrations.

In order to further reduce NOx emissions in increasing HP EGR cooler performance, several OEMs have decided to use a secondary cooling loop dedicated to bring cold water (around 35°C) to the HP EGR heat exchanger. Nevertheless, strongly cooled EGR gases can condensate in the cooler-producing acidic liquids which can corrode some parts in the loop. It is therefore necessary to define EGR components compatible with such kind of environment and constraints. Testing was performed on a 2.0-liter EU4 diesel engine, using a large panel of current fuels including neat biodiesels from soybean, rapeseed or palm, as well as low and high sulfur petroleum-based diesels. In order to cover all existing cycle conditions, the HP EGR is cooled from 20°C to 90°C independently from the engine coolant circuit.

Despite the development in NOx aftertreatment for Diesel engines, EGR is a cost-effective solution to fulfill current and future emission regulations. There is a wide bibliography discussing the global effects of EGR on combustion and emissions. However, little has been published concerning the effects of the unsuitable EGR and air distribution among cylinders. Since current HSDI engines operate with EGR rates as high as 50% the effect of the unequal EGR distribution becomes important. In addition, cylinder-to-cylinder charge dispersion becomes a critical aspect on the control of low temperature combustion systems. In concordance with the aspects outlined before, the aim of this paper is to study the effects of the EGR cylinder to cylinder distribution on the engine performance and emissions. To cope with this objective, experiments have been conducted in a HSDI engine with two different EGR systems.

Characterization of radial turbine performance is usually represented by turbine characteristics maps. These maps illustrate the relationship between the most representative variables which describe the system behavior. Many times, due to design constrains available in these test beds, it is not possible to get measurements of the different variables at different turbine rotational speeds over a wide range of expansion ratios. Sometimes this represents a problem when an appropriate engine simulation must be carried out due to the lack of reliable information to run the simulation in operation points where there are no available turbine data. Although an extrapolation could be done using mathematical methods, there are no physics behind which assures an acceptable confidence in the new generated information. The present paper develops a physics based method for the extrapolation of the radial turbine maps to zones where there is no experimental information.

Testing was performed on a 2.0 liter diesel engine with high pressure (HP) and low pressure (LP) EGR, using standard European low sulfur diesel as well as fatty acid methyl ester (FAME) biodiesel fuels produced from soy, rapeseed and palm feedstock, both neat and blended with 50% standard diesel. In the HP EGR configuration, fuel injection, air flow and EGR rate were adapted to achieve the same engine load and NOx emissions for all fuels at the selected test points. Higher brake specific fuel consumption and lower smoke emissions were observed for the biodiesels compared to the standard diesel. In the LP EGR configuration, large reductions in NOx and smoke were observed for all fuels compared to HP EGR. In addition, water condensed in the charge air cooler at coolant temperatures below 30°C. This condensate was collected and analyzed, finding similar volumes and acidity for condensates from all the diesel and biodiesel fuels.