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In this paper, a new physics-based model for the prediction of NOx emissions produced by diesel engines is presented. The aim of this work is to provide a reference model for the validation of control strategies and NOx estimators. The model describes the NOx production in the burned gas zone where the burned gas temperature sub-model is adapted to be generic and tunable. The model consists of three main sub-models for the estimation of the burned gas temperature, the concentration of the species in the burned gases and the NOx formation, respectively. A new model for estimating the burned gas temperature, known to have a strong impact on thermal NOx formation rate, is proposed. The model depends on the intake burned gas ratio and the combustion phasing computed from the cylinder pressure. This model has a limited number of calibration parameters identified so that NOx model output matches with experimental data measured in a four-cylinder, four-stroke, direct-injection diesel engine.

The hydrogen internal combustion engine is a promising alternative to fossil fuel-based engines, which, in a short time, can reduce the carbon footprint of the ground transport sector. However, the high heat release rates associated with hydrogen combustion results in higher NOx emissions. The NOx production can be mitigated by diluting the in-cylinder mixture with air, Exhaust Gas Recirculation (EGR) or water injected in the intake manifold. This study aims at assessing these dilution options on the emissions, efficiency, combustion performance and boosting effort. These dilution modes are, at first, compared on a single cylinder engine (SCE) with direct injection of hydrogen in steady state conditions. Air and EGR dilutions are then evaluated on a corresponding 4-cylinder engine by 0D simulation on a complete map under NOx emission constraint.

Recent work has demonstrated the potential of gasoline-like fuels to reduce NOx and particulate emissions when used in compression ignition engines. In this context, low research octane number (RON) gasoline, a refinery stream derived from the atmospheric crude oil distillation process, has been identified as a highly valuable fuel. In addition, thanks to its higher H/C ratio and energy content compared to diesel, CO2 benefits are also expected when used in such engines. In previous studies, different cetane number (CN) fuels have been evaluated and a CN 35 fuel has been selected. The assessment and the choice of the required engine hardware adapted to this fuel, such as the compression ratio, bowl pattern and nozzle design have been performed on a single cylinder compression-ignition engine.

The design and the supervision of hybrid electric vehicles (HEV) are strongly coupled. The mutual influence between the optimal components sizing and the optimal operating points choice makes the problem complex. This was previously exposed in literature for spark ignition (SI) HEV. In this paper, we address the same issue for diesel HEV. In this case, the energy management strategy must take nitrogen oxides (NOx) emissions into account in addition to fuel consumption. This paper presents an optimal supervision strategy and its impact on the electric components sizing. The energy management strategy is based on the equivalent consumption minimization strategy (ECMS) using Pontryagin's minimum principle. It allows an adjustable trade-off between NOx and fuel consumption to be minimized. It was validated experimentally with a hardware-in-the-loop test bed.

The selective catalytic reduction (SCR) based on urea water solution (UWS) is an effective way to reduce nitrogen oxides (NOx) emitted by engines. The high potential offered by this solution makes it a promising way to meet the future stringent exhaust gas standards (Euro6 and Tier2 Bin5). UWS is injected into the exhaust upstream of an SCR catalyst. The catalyst works efficiently and durably if the spray is completely vaporized and thoroughly mixed with the exhaust gases before entering. Ensuring complete vaporization and optimum mixture distribution in the exhaust line is challenging, especially for compact exhaust lines. Numerous parameters affect the degree of mixing: urea injection pressure and spray angle, internal flow field (fluid dynamics), injector location …. In order to quantify the mixture quality (vaporization, homogeneity) upstream of the SCR catalyst, it is proposed to employ non intrusive optical diagnostics techniques such as laser induced fluorescence (LIF).

Meeting Euro 6d NOx emission regulations lower than 80 mg/km for light duty diesel (60 mg/km gasoline) vehicles remains a challenge, especially during cold-start tests at which the selective catalyst reduction (SCR) system does not work because of low exhaust gas temperatures (light-off temperature around 200 °C). While several exhaust aftertreatment system (EATS) designs are suggested in literature, solutions with gaseous ammonia injections seem to be an efficient and cost-effective way to enhance the NOx abatement at low temperature. Compared to standard SCR systems using urea water solution (UWS) injection, gaseous NH3 systems allow an earlier injection, prevent deposit formation and increase the NH3 content density. However non-uniform ammonia mixture distribution upstream of the SCR catalyst remains an issue. These exhaust gas/ NH3 inhomogeneities lead to a non-optimal NOx reduction performance, resulting in higher than expected NOx emissions and/or ammonia slip.

Hydrogen may be used to feed a fuel cell or directly an internal combustion engine as an alternative to current fossil fuels. The latter option offers the advantages of already existing hydrocarbon fuel engines - autonomy, pre-existing and proven technology, lifetime, controlled cost, existing industrial tools and short time to market - with a very low carbon footprint and high tolerance to low purity hydrogen. Hydrogen is expected to be relevant for light and heavy duty applications as well as for off road applications, but currently most of research focus on small engine and especially spark ignition engine which is easily adaptable. This guided us to select modern high-efficient gasoline-based engines to start the investigation of hydrogen internal combustion engine development. This study aims to access the properties and limitations of hydrogen combustion on a high-efficiency spark ignited single cylinder engine with the support of the 3D-CFD computation.

The challenge for decreasing the emissions of compression ignition engines now remains mainly on NOx control. If the Lean NOx Trap (LNT) and Selective Catalytic Reduction by Urea (Urea-SCR) are very efficient, their extra-cost and management are a major issue for the OEMs. In that context, the selective catalytic reduction by hydrocarbons (HC-SCR) appears to be an interesting alternative solution, with a more limited NOx conversion efficiency but an easier packaging (diesel fuel as a reductant) and a limited price (reasonable coating cost / no PGM). In the framework of the RedNOx project, a prototype catalyst made of 2% silver on Alumina coated on cordierite was manufactured and tested on a synthetic gas bench. In parallel, an exhaust implementation study has been led to ensure the most suited conditions for injection. Thanks to SGB and simulation results, adapted engine tests have been designed and performed.

The Diesel engine has now become a vital component of the transport sector, in view of its performance in terms of efficiency and therefore CO2 emissions some 25 % less than a traditional gasoline engine, its main competitor. However, the introduction of more and more stringent regulations on engine emissions (NOx, PM) requires complex after-treatment systems and combustion strategies to decrease pollutant emissions (regeneration strategies, injection strategies, …) with some penalty in fuel consumption. It becomes necessary to find new ways to improve the Diesel efficiency in order to maintain its inherent advantage. In the present work, we are looking for strategies and technologies to reduce Diesel engine fuel consumption. Based on the observation that large Diesel engines have a better efficiency than the smaller ones, a detailed thermodynamic combustion analysis of one Heavy Duty (HD) engine and two Passenger car (PC) engines is performed to understand these differences.

Diesel spray mixture formation is investigated at target conditions using multiple diagnostics and laboratories. High-speed Particle Image Velocimetry (PIV) is used to measure the velocity field inside and outside the jet simultaneously with a new frame straddling synchronization scheme. The PIV measurements are carried out in the Engine Combustion Network Spray A target conditions, enabling direct comparisons with mixture fraction measurements previously performed in the same conditions, and forming a unique database at diesel conditions. A 1D spray model, based upon mass and momentum exchange between axial control volumes and near-Gaussian velocity and mixture fraction profiles is evaluated against the data.

This paper proposes a method to detect an intake manifold leakage for a Diesel engine with a dual loop EGR system. The intake manifold leak has a strong impact on the engine performances by changing the intake manifold burned gas ratio. This fault is analyzed according to the control structure used and also according to the EGR operating mode. The paper proposes a diagnosis algorithm to detect the intake manifold leak in sequential or simultaneous use of the two EGR paths. The sensors considered are the mass air flow meter, the intake manifold pressure sensor, the exhaust equivalence ratio sensor and the differential pressure sensor (across the HP EGR valve). The diagnosis is based on a criteria that uses the redundancy between these sensors and air system models or estimators. The diagnosis threshold depends on the engine operating conditions as well as the sensor or model dispersions.

The proposed Euro 7 regulation aims to substantially reduce the NOx emissions to 0.03 g/km, a trend also seen in upcoming China 6b and US EPA regulations. Meeting these stringent requirements necessitates advancements in Urea/Selective Catalytic Reduction (SCR) aftertreatment systems, with the urea deposit formation being a key challenge to its design. It’s proven that Computational Fluid Dynamics (CFD) can be an effective tool to predict Urea deposits. Transient wall temperature prediction is crucial in Urea deposit modeling. Additionally, fully understanding the kinetics of urea decomposition and by-products solidification are also critical in predicting the deposit amount and its location. In this study, we introduce (i) a novel film boiling model (IFPEN-BRT model) and (ii) a new urea by-product solidification model in the CONVERGE CFD commercial solver, and validate the results against the recent experiments.

According to thermodynamic analysis of ideal engine cycles, Otto cycle thermal efficiency exceeds that of the Diesel and Sabathe (or Dual) cycles. However, zero-dimensional calculations indicated that the brake thermal efficiency (BTE) of an actual Otto or Diesel engine could be higher with a Sabathe (or Seilliger) type cycle, within a limited peak firing pressure (PFP). To confirm these results with an actual engine, a three-injector combustion system (center and two sides) was utilized to allow more flexibility in the heat release rate (HRR) profile than the conventional single injector system in the previous study. The experimental result was qualitatively consistent with the calculated results even though its HRR had less peak and longer duration than ideal. In this study, a new thermodynamic cycle with higher HRR in the expansion stroke than the ideal Sabathe cycle, was thus developed. The proposed (higher) HRR was achieved by overlapped fuel injection with the three injectors.

This paper addresses the robustness of an optimal online energy management for diesel hybrid electric vehicle (HEV). Optimal strategy is based on the Equivalent Consumption Minimization Strategy (ECMS). Optimal torque split between engine and electric motor is found by minimizing fuel consumption and Nitrogen Oxides (NOx) emissions. Online adaptation is made in order to ensure battery charge sustainability and good driveability when driving conditions are unknown. The strategy is tested in simulation over one hundred driving cycles representative of real-world conditions. Results obtained with the online strategy are compared with those of an offline optimal strategy (knowing the driving cycle a priori). Even if a slight degradation is noticed in comparison to optimal case, fuel economy and NOx reduction - provided by hybridization - are conserved with the online strategy.

Current and future engine technologies and fuels are mutually dependent. The increased use of alternative fuels has been linked to deterioration in performance of injectors, fuel filters and engines as a result of insoluble deposit formation. The present work aimed to study the impact of Diesel/biodiesel blends formulation (biodiesel feedstock and content) and temperature on the oxidation stability based on total acid number (TAN). The biofuels used in the fuel matrix were: rapeseed, soy and palm methyl esters (RME, SME and PME respectively). The Diesel/biodiesel blends were made with 0%v/v, 5%v/v, 10% v/v and 20%v/v of biodiesel blended with additive-free new Diesel. The oxidation stability of Diesel/biodiesel blends was to evaluate during 6 months fuels storage, under 20°C and 40°C, and fuels severe oxidation into a reactor vessel to better understand the parameters leading to fuel oxidation on-board.

Recent work has demonstrated the potential of gasoline-like fuels to reduce NOx and particulate emissions when used in Diesel engines. In this context, straight-run naphtha, a refinery stream directly derived from the atmospheric crude oil distillation process, has been identified as a highly valuable fuel. The current study is one step further toward naphtha-based fuel to power compression ignition engines. The potential of a cetane number 25 fuel (CN25), resulting from a blend of hydro-treated straight-run naphtha CN35 with unleaded non-oxygenated gasoline RON91 was assessed. For this purpose, investigations were conducted on multiple fronts, including experimental activities on an injection test bed, in an optically accessible vessel and in a single cylinder engine. CFD simulations were also developed to provide relevant explanations.

This paper presents the evaluation of the impact of Diesel Exhaust Fluid (DEF) quality on the behavior of a controlled SCR system. Proper control of the Selective Catalytic Reduction system is crucial to fulfill NOx emissions standards of modern Diesel engines. Today, the urea concentration of DEF is not considered as a control system input. Moreover, Urea Quality Sensors (UQS) are now available to provide real time information of Diesel Exhaust Fluid quality. The impact of percent urea from 20 to 36% on the NOx emissions of a passenger car 2.2L Diesel engine is calculated using a reference SCR model and a reference SCR control tool in multiple NEDC transient conditions. Several control tunings are tested with different levels of feedback. Ammonia slip levels are also calculated.

Reduction of CO2 emissions is becoming one of the great challenges for future gasoline engines. Downsizing is one of the most promising strategies to achieve this reduction, though it facilitates occurrence of knocking. Therefore, downsizing has to be associated with knock limiting technologies. The aim of the current research program is to adapt the fuel Research-Octane-Number (RON) injected in the combustion chamber to prevent knock occurrence and keep combustion phasing at optimum. This is achieved by a dual fuel injection strategy, involving a low-RON naphtha-based fuel (Naphtha, RON 71) and a high-RON octane booster (Ethanol, RON107). The ratio of fuel quantity on each injector is adapted to fit the RON requirement as a function of engine operating conditions. Hence, it becomes crucial to understand and predict the mixture preparation, to quantify its spatial and cycle-to-cycle variations and to apprehend the consequences on combustion behavior - knock especially.

Future pollutant emissions legislations are expected to be increasingly stringent. To reduce Nitrogen Oxides (NOx) emissions produced by Diesel engines, advanced combustion technologies - like Low Temperature Combustion (LTC) -, vehicle hybridization and NOx after-treatment systems - such as Selective Catalytic Reduction (SCR) systems - can be considered, leading to a growing demand for NOx models. In this paper, we present a state-of-art of the different existing NOx models, from the black-boxes to the three-dimensional Computational Fluid Dynamics (CFD) codes. A way to classify these models is proposed. The paper also introduces the current applications for each subgroup of models. Then, a black-box and two grey-box NOx models are studied regarding their accuracy and their sensitivity to model inputs. These models are validated for two Diesel engines on steady-state operating points as well as on transient operations. The semi-physical models accurately predict NOx emissions.

In this study, the impact of the intake valve timing on knock propensity is investigated on a dual-fuel engine which leverages a low octane fuel and a high octane fuel to adjust the fuel mixture’s research octane rating (RON) based on operating point. Variations in the intake valve timing have a direct impact on residual gas concentrations due to valve overlap, and also affect the compression pressure and temperature by altering the effective compression ratio (eCR). In this study, it is shown that the fuel RON requirement for a non-knocking condition at a fixed operating point can vary significantly solely due to variations of the intake valve timing. At 2000 rpm and 6 bar IMEP, the fuel RON requirement ranges from 80 to 90 as a function of the intake valve timing, and the valve timing can change the RON requirement from 98 to 104 at 2000 rpm and 14 bar IMEP.