Modelling the exhaust gas recirculation mass flow rate in modern diesel engines

The intrinsic model accuracy limit of a commonly used Exhaust Gas Recirculation (EGR) mass flow rate model in diesel engine air path control is discussed in this paper. This EGR mass flow rate model is based on the flow of a compressible ideal gas with unchanged specific heat ratio through a restriction cross-area within a duct. A practical identification procedure of the model parameters is proposed based on the analysis of the engine data and model structure. This procedure has several advantages which include simplicity, low computation burden and low engine test cost. It is shown that model tuning requires only an EGR valve sweep test at a few engine steady state operating points. It is also shown that good model accuracy can be achieved when the control variables of other air path devices, e.g. The vane position of a Variable Geometry Turbocharger (VGT) and the torque demand of an Electric Turbo Assist (ETA), are kept constant during the EGR valve sweep test used to tune the model. Two different diesel engines are used in this work to demonstrate the model tuning procedure and the model validation results. Both engines are equipped with a high pressure external EGR system and a VGT. One of the engines has a relatively new air system device - an ETA. The model validation results of both engines show good model accuracy not only at steady state engine operating points but also during engine transients

Cylinder charge composition observation based on in-cylinder pressure measurement

[EN] Accurate cylinder charge and composition estimation is crucial for proper combustion control, however, current sensors and models show different issues for transient estimation. The work presented in this paper combines a novel technique for trapped mass estimation, which relies on the in-cylinder pressure resonance, with on-board engine sensors by taking into account the intake manifold dynamics with a closed-loop observer. The resonance method provides a measurement of trapped mass with one cycle resolution. This measurement feeds a Kalman filter to improve the transient and steady response of the intake charge and composition estimation. The observer was validated in a four stroke heavy-duty engine, showing fast transient capabilities and an adequate steady-state accuracy.This work was partially supported by Ministerio de Economia y Competitividad through Project TRA2016-78717-R. C. Guardiola research has been partially financed by the Fulbright Commission and the Spanish Ministerio de Educacion, Cultura y Deporte through grant PRX14/00274.Guardiola, C.; Pla Moreno, B.; Bares-Moreno, P.; Stefanopoulou, A. (2019). Cylinder charge composition observation based on in-cylinder pressure measurement. Measurement. 131:559-568. https://doi.org/10.1016/j.measurement.2018.08.024S55956813

Optimal air and fuel-path control of a diesel engine

The work reported in this thesis explores innovative control structures and controller design for a heavy duty Caterpillar C6.6 diesel engine. The aim of the work is not only to demonstrate the optimisation of engine performance in terms of fuel consumption, NOx and soot emissions, but also to explore ways to reduce lengthy calibration time and its associated high costs. The test engine is equipped with high pressure exhaust gas recirculation (EGR) and a variable geometry turbocharger (VGT). Consequently, there are two principal inputs in the air-path: EGR valve position and VGT vane position. The fuel injection system is common rail, with injectors electrically actuated and includes a multi-pulse injection mode. With two-pulse injection mode, there are as many as five control variables in the fuel-path needing to be adjusted for different engine operating conditions. [Continues.

Optimal Sensor Placement for High Pressure and Low Pressure EGR Estimation

[EN] 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. Experimental results from a 2.2 l. diesel engine are used to validate the presented techniques.Luján, JM.; Pla Moreno, B.; Bares-Moreno, P.; Aramburu-Orihuela, A. (2021). Optimal Sensor Placement for High Pressure and Low Pressure EGR Estimation. SAE International. 1-11. https://doi.org/10.4271/2021-01-042311

Automotive Powertrain Control — A Survey

This paper surveys recent and historical publications on automotive powertrain control. Control-oriented models of gasoline and diesel engines and their aftertreatment systems are reviewed, and challenging control problems for conventional engines, hybrid vehicles and fuel cell powertrains are discussed. Fundamentals are revisited and advancements are highlighted. A comprehensive list of references is provided.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/72023/1/j.1934-6093.2006.tb00275.x.pd

Effects of EGR transient operation on emissions and performance of automotive engines during RDE cycles

[ES] Hoy en día, las regulaciones sobre emisiones de los automóviles se están haciendo más estrictas. Además de los ciclos de homologación estándar, actualmente se están empezando a considerar nuevos métodos de homologación que tienen en cuenta las condiciones reales que se dan en la carretera. Los sistemas de Recirculación de Gases de Escape (EGR) son estrategias que han demostrado ser efectivas durante estacionarios y que también pueden ser usadas en ese tipo de ciclos dinámicos que corresponden a condiciones reales de conducción. Esta tesis se centra en la implementación de diferentes sistemas EGR para su uso en condiciones dinámicas en motores diésel turbosobrealimentados. En primer lugar, se lleva a cabo un análisis del ciclo de conducción para identificar las operaciones específicas de tipo transitorio más frecuentes en los ciclos dinámicos como WLTC y RDE. Los resultados muestran que la frecuencia en la que se producen fuertes transitorios en carga es mayor que en la que se producen transitorios de velocidad. Entre ellos, el número de operaciones de tipo Tip-out es superior a las de tipo Tip-Ins, especialmente en el rango de 1250-2000 rpm. Estos fuertes transitorios se repiten en el banco de ensayos de motor equipado con analizadores de gas de alta frecuencia, de forma que se registran la concentración instantánea de CO2 y NOx. También se ha realizado un estudio paramétrico de la actuación de la válvula de EGR durante la operación de varios transitorios fuertes, cuantificando el retraso en el transporte, la concentración de NOx y las partículas. El lazo de EGR de baja presión, LPEGR, ha resultado ser más efectivo cuando se operaba a plena carga, así como durante los transitorios, comparado con el lazo de EGR de alta presión, HPEGR. De esta forma, se propone la válvula de control más adecuada para LPEGR, lo que puede ser útil para la calibración de los transitorios de los motores diésel turbosobrealimentados. Además de ello, se señala el compromiso entre rendimiento y emisiones durante los transitorios de EGR. Al implementar la recirculación de los gases de escape a lo largo de todo el mapa del motor se minimiza la aparición de picos inesperados de emisión de NOx. Concretamente, las estrategias LPEGR consiguen reducir alrededor de un 20-60% los NOx emitidos durante los primeros pocos segundos con menos de un 5% de penalización en el rendimiento. Adicionalmente, en el documento también se presentan las simulaciones que se han realizado de los modelos unidimensionales de los transitorios. El control de la turbina de geometría variable juega un papel importante a la hora de calibrar el modelo para transitorios de EGR. Además de ello, se lleva a cabo una optimización de la separación de EGR para varios puntos estacionarios por medio de simulaciones que están basadas en el compromiso entre rendimiento y emisiones. Además, se propone un algoritmo para optimizar la separación de EGR, reduciendo en alrededor de un 80% el tiempo de cálculo de un DOE o un método de algoritmo genético. Finalmente, se crea un modelo simple de NOx 3D cuasi-estacionario para predecir las emisiones durante el transitorio en condiciones de conducción reales. La tasa de EGR, como tercera entrada del modelo, muestra una mejora significativa a la hora de predecir el transitorio de NOx con respecto al modelo 2D.[EN] The automotive emission regulations are getting more stringent these days. New methods of homologation are being considered other than standard cycles considering the real driving behavior on road. The EGR system is one of the proven and well tested strategies in steady state which can be used on those dynamic real driving conditions too. This dissertation focuses on implementation of different EGR systems during dynamic operations of turbocharged diesel engine. Firstly, a driving cycle analysis is carried out to identify the specific and frequent transient operations on dynamic cycles like WLTC and RDE. The results show that, the frequency of harsh load transients is higher than speed transients. Among them, the number of Tip-Out operations outnumber the Tip-Ins with higher density in 1250-2000 RPM range. Therefore, these harsh transients are repeated separately on the dynamic engine test bench equipped with high frequency gas analyzers to track the instantaneous CO2 and NOx concentration. A parametric study is carried out with EGR valve actuation during various severe load transients, quantifying the transportation delays, NOx concentration and particulate matter. The LPEGR is found to be more effective at the full load as well as during transient operations compared to HPEGR. The best suited LPEGR valve control is proposed, which can be helpful for transient calibration of a turbocharged diesel engine. Moreover, the trade-off between the performance and emission during EGR transients is also pointed out. The implementation of EGR all over the engine map minimizes the unexpected NOx peaks during transients. Specifically, LPEGR strategies manages to reduce around 20-60% of NOx in first few seconds with less than 5% of penalty in performance. Additionally, 1D model simulation results of load transient operations are presented in the document. The VGT control plays important role to calibrate the model for transient operations with EGR. Apart from this, the EGR split optimization on various steady points is carried out by simulations following the trade-off between performance and emissions. Furthermore, an algorithm to search the optimum split is proposed, reducing around 80% of the calculation time consumed by DOE or genetic algorithm method. Finally, a simple 3D quasi steady NOx model is created to predict the transient emissions in real driving conditions. EGR rate, as 3rd input in model shows significant improvement in prediction of transient NOx over the 2D model.[CA] En els darrers temps, les regulacions sobre emissions contaminants dels vehicles s'han fet més estrictes. A més dels cicles d'homologació estàndards, actualment s'estan començant a considerar nous mètodes d'homologació que tinguen en compte les condicions reals que es donen en la carretera. Els sistemes de Recirculació de Gasos d'Escapament (EGR) són estratègies que s'han demostrat com a efectives durant condicions estacionàries i que també poden ser emprades en aquest tipus de cicles dinàmics, que corresponen a condicions reals de conducció. Aquesta tesi està centrada en la implementació de diferents sistemes EGR per al seu ús en condicions dinàmiques en motors dièsel turbosobrealimentats. En primer lloc, es du a terme un anàlisi del cicle de conducció per a identificar les operacions específiques de tipus transitori més freqüents en els cicles dinàmics WLTC i RDE. Els resultats mostren que la freqüència a la que s'obtenen forts transitoris de càrrega és major que en aquella en la que es produeixen transitoris de velocitat. Entre aquestos, el nombre d'operacions de tipus Tip-out és superior a les del tipus Tip-ins, especialment en l'interval de 1250-2000 rpm. Aquestos forts transitoris es repeteixen en el banc d'assajos de motor equipat amb analitzadors de gasos d'alta freqüència, de manera que es registren les concentracions de CO2 i NOx. També s'ha realitzat un estudi paramètric de l'actuació de la vàlvula d'EGR durant l'operació de diversos transitoris forts, quantificant el retard en el transport, la concentració de NOx i les partícules. El llaç d'EGR de baixa pressió, LPEGR, ha resultat ser més efectiu quan s'operava a plena càrrega, així com durant els transitoris, comparat amb el llaç d'EGR d'alta pressió, HPEGR. D'aquesta forma, es proposa la vàlvula de control més adequada per a LPEGR, el que pot resultar útil per a la calibratge dels transitoris dels motors dièsel turbosobrealimentats. A banda d'això, s'ha assenyalat el compromís entre rendiment i emissions durant els transitoris d'EGR. Al implementar la recirculació dels gasos d'escapament a tot arreu del mapa del motor es minimitza l'aparició de pics inesperats d'emissió de NOx. Més concretament, les estratègies LPEGR aconsegueixen reduir al voltant d'un 20-60% els NOx emesos durant els primers pocs segons amb menys d'un 5% de penalització en el rendiment. Addicionalment, en el document també es presenten les simulacions que s'han realitzat dels models unidimensionals dels transitoris. El control de la turbina de geometria variable juga un paper important a l'hora de calibrar el model per a transitoris d'EGR. A més d'això, s'ha dut a terme una optimització de la separació d'EGR en diversos punts estacionaris per mitjà de simulacions que estan basades en el compromís entre rendiment i emissions. També es proposa un algoritme per a optimitzar la separació d'EGR, reduint al voltant d'un 80\% el temps de càlcul d'un DOE o un mètode d'algoritme genètic. Finalment, es crea un model simple de NOx 3D quasi-estacionari per a predir les emissions durant el transitori en condicions de conducció real. La taxa d'EGR, com a tercera entrada del model, mostra una millora significativa a l'hora de predir el transitori de NOx respecte al model 2D.Patil, CY. (2020). Effects of EGR transient operation on emissions and performance of automotive engines during RDE cycles [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/149498TESI

Development of a virtual methodology based on physical and data-driven models to optimize engine calibration

Virtual engine calibration exploiting fully-physical plant models is the most promising solution for the reduction of time and cost of the traditional calibration process based on experimental testing. However, accuracy issues on the estimation of pollutant emissions are still unresolved. In this context, the paper shows how a virtual test rig can be built by combining a fully-physical engine model, featuring predictive combustion and NOx sub-models, with data-driven soot and particle number models. To this aim, a dedicated experimental campaign was carried out on a 1.6 liter EU6 diesel engine. A limited subset of the measured data was used to calibrate the predictive combustion and NOx sub-models. The measured data were also used to develop data-driven models to estimate soot and particulate emissions in terms of Filter Smoke Number (FSN) and Particle Number (PN), respectively. Inputs from engine calibration parameters (e.g., fuel injection timing and pressure) and combustion-related quantities computed by the physical model (e.g., combustion duration), were then merged. In this way, thanks to the combination of the two different datasets, the accuracy of the abovementioned models was improved by 20% for the FSN and 25% for the PN. The coupled physical and data-driven model was then used to optimize the engine calibration (fuel injection, air management) exploiting the Non-dominated Sorting genetic algorithm. The calibration obtained with the virtual methodology was then adopted on the engine test bench. A BSFC improvement of 10 g/kWh and a combustion reduction of 3.0 dB in comparison with the starting calibration was achieved

Transient modelling of a diesel engine and air-path control

Due to the inherent nonlinearity of the diesel engine, real-time control of the variable geometry turbocharger (VGT) and exhaust gas recirculation (EGR) valve still remains a challenging task. A controller has to be capable of coping with the transient operating condition of the engine, the interactions between the VGT and EGR, and also the trade-off effect in this control problem. In this work, novel real-time fuzzy logic controllers (RFLC) were developed and tested. Firstly, the proposed controllers were calibrated and validated in a transient diesel engine model which was developed and validated against the Caterpillar 3126B engine test bed located at the University of Sussex. The controllers were then further tested on the engine test bed. Compared to conventional controllers, the proposed controllers can effectively reduce engine emissions as well as fuel consumption. Experimental results show that compared to the baseline engine running on the Nonroad Transient Cycle (NRTC), mean values of the exhaust gas opacity and the nitrogen oxides (NOx) emission production were reduced by 36.8% and 33%, respectively. Instant specific fuel consumption of the RFLC engine was also reduced by up to 50% compared to the baseline engine during the test. Moreover, the proposed fuzzy logic controllers can also reduce development time and cost by avoiding extensive engine mapping of inlet air pressure and flow. When on-line emission measurements were not available, on-board emission predictors were developed and tested to supply the proposed fuzzy logic controller with predictions of soot and NOx production. Alternatively, adaptive neuro fuzzy inference system (ANFIS) controllers, which can learn from fuzzy logic controllers, were developed and tested. In the end, the proposed fuzzy logic controllers were compared with PI controllers using the transient engine model

Switching strategy between HP (high pressure)- and LPEGR (low pressure exhaust gas recirculation) systems for reduced fuel consumption and emissions

EGR (Exhaust gas recirculation) plays a major role in current Diesel internal combustion engines as a cost-effective solution to reduce NO emissions. EGR systems will suffer a significant evolution with the introduction of NO after-treatment and the proliferation of more complex EGR architectures such as low pressure EGR or dual EGR. In this paper the combination of HPEGR (high pressure EGR) LPEGR (low pressure EGR) is presented as a method to minimise fuel consumption with reduced NOx emissions. Particularly, the paper proposes to switch between HPEGR and LPEGR architectures depending on the engine operating conditions in order to exploit the potential of both systems. In this sense, given a driving cycle, in the case at hand the NEDC, the proposed strategy seeks the EGR layout to use at each instant of the cycle to minimise the fuel consumption such that NO emissions are kept below a certain limit. The experimental results obtained show that combining both EGR systems sequentially along the NEDC allows to keep NO emission below a much lower limit with minimum fuel consumption.This work has been partially supported by Ministerio de Ciencia y Tecnologia through Project INNPACTO EGRCOEN.Lujan Martinez, JM.; Guardiola García, C.; Pla Moreno, B.; Reig, A. (2015). Switching strategy between HP (high pressure)- and LPEGR (low pressure exhaust gas recirculation) systems for reduced fuel consumption and emissions. Energy. 90:1790-1798. doi:10.1016/j.energy.2015.06.138S179017989

Investigation of Gasoline Partially Premixed Combustion with External Exhaust Gas Recirculation

The stringent emission regulations for Internal Combustion Engines (ICEs) spawned a great amount of research in the field of innovative combustion approaches characterized by high efficiency and low emissions. Previous research demonstrate that such promising techniques, named Low-Temperature Combustion (LTC), combine the benefits of Compression Ignition (CI) engines, such as high compression ratio and unthrottled lean mixture, with low engine-out emissions using a properly premixed air-fuel mixture. Due to longer ignition delay and high volatility compared to diesel, gasoline-like fuels show good potential for the generation of a highly premixed charge, which is needed to reach LTC characteristics. In this scenario, gasoline Partially Premixed Combustion (PPC), characterized by the high-pressure direct injection of gasoline, showed good potential for the simultaneous reduction of pollutants and emissions in CI engines. However, previous research on gasoline CI highlight that a key factor for the optimization of both efficiency and pollutants is the proper management of Exhaust Gas Recirculation (EGR). This work presents the experimental investigation performed running a light-duty CI engine, operated with gasoline PPC, and varying the mass of recirculated gases trapped in the combustion chamber. To guarantee the stability of gasoline autoignition in all the tested conditions, a specific experimental layout has been developed to accurately quantify the amount of trapped residual gases due to the internal and external EGR. The obtained results clearly highlight the impact of EGR on the combustion process and emissions, demonstrating that optimization of charge dilution with EGR is fundamental to guarantee the optimal compromise between efficiency and emissions over the whole operating range