Urban and extra-urban hybrid vehicles: a technological review

Pollution derived from transportation systems is a worldwide, timelier issue than ever. The abatement actions of harmful substances in the air are on the agenda and they are necessary today to safeguard our welfare and that of the planet. Environmental pollution in large cities is approximately 20% due to the transportation system. In addition, private traffic contributes greatly to city pollution. Further, “vehicle operating life” is most often exceeded and vehicle emissions do not comply with European antipollution standards. It becomes mandatory to find a solution that respects the environment and, realize an appropriate transportation service to the customers. New technologies related to hybrid –electric engines are making great strides in reducing emissions, and the funds allocated by public authorities should be addressed. In addition, the use (implementation) of new technologies is also convenient from an economic point of view. In fact, by implementing the use of hybrid vehicles, fuel consumption can be reduced. The different hybrid configurations presented refer to such a series architecture, developed by the researchers and Research and Development groups. Regarding energy flows, different strategy logic or vehicle management units have been illustrated. Various configurations and vehicles were studied by simulating different driving cycles, both European approval and homologation and customer ones (typically municipal and university). The simulations have provided guidance on the optimal proposed configuration and information on the component to be used

Marine dual fuel engines modelling and optimisation employing : a novel combustion characterisation method

Dual fuel (DF) engines have been an attractive alternative of traditional diesel engines for reducing both the environmental impact and operating cost. The major challenge of DF engine design is to deal with the performance-emissions trade-off via operating settings optimisation. Nevertheless, determining the optimal solution requires large amount of case studies, which could be both time-consuming and costly in cases where methods like engine test or Computational Fluid Dynamics (CFD) simulation are directly used to perform the optimisation. This study aims at developing a novel combustion characterisation method for marine DF engines based on the combined use of three-dimensional (3D) simulation and zero-dimensional/one-dimensional (0D/1D) simulation methods. The 3D model is developed with the CONVERGE software and validated by employing the measured pressure and emissions. Subsequently, the validated 3D model is used to perform a parametric study to explore the engine operating settings that allow simultaneous reduction of the brake specific fuel consumption (BSFC) and NOx emissions at three engine operation conditions (1457 r/min, 1629 r/min and 1800 r/min). Furthermore, the derived heat release rate (HRR) is employed to calibrate the 0D Wiebe combustion model by using Response Surface Methodology (RSM). A linear response model for the Wiebe combustion function parameters is proposed by considering each Wiebe parameter as a function of the pilot injection timing, equivalence ratio and natural gas mass. The 0D/1D model is established in the GT-ISE software and used to optimise the performance-emissions trade-off of the reference engine by employing the Nondominated Sorting Genetic Algorithm II (NSGA II). The obtained results provide a comprehensive insight on the impacts of the involved engine operating settings on in-cylinder combustion characteristics, engine performance and emissions of the investigated marine DF engine. By performing the settings optimisation at three engine operating points, settings that lead to reduced BSFC are identified, whilst the NOx emissions comply with the Tier III NOx emissions regulation. The proposed novel method is expected to support the combustion analysis and enhancement of marine DF engines during the design phase, whilst the derived optimal solution is expected to provide guidelines of DF engine management for reducing operating cost and environmental footprint.Dual fuel (DF) engines have been an attractive alternative of traditional diesel engines for reducing both the environmental impact and operating cost. The major challenge of DF engine design is to deal with the performance-emissions trade-off via operating settings optimisation. Nevertheless, determining the optimal solution requires large amount of case studies, which could be both time-consuming and costly in cases where methods like engine test or Computational Fluid Dynamics (CFD) simulation are directly used to perform the optimisation. This study aims at developing a novel combustion characterisation method for marine DF engines based on the combined use of three-dimensional (3D) simulation and zero-dimensional/one-dimensional (0D/1D) simulation methods. The 3D model is developed with the CONVERGE software and validated by employing the measured pressure and emissions. Subsequently, the validated 3D model is used to perform a parametric study to explore the engine operating settings that allow simultaneous reduction of the brake specific fuel consumption (BSFC) and NOx emissions at three engine operation conditions (1457 r/min, 1629 r/min and 1800 r/min). Furthermore, the derived heat release rate (HRR) is employed to calibrate the 0D Wiebe combustion model by using Response Surface Methodology (RSM). A linear response model for the Wiebe combustion function parameters is proposed by considering each Wiebe parameter as a function of the pilot injection timing, equivalence ratio and natural gas mass. The 0D/1D model is established in the GT-ISE software and used to optimise the performance-emissions trade-off of the reference engine by employing the Nondominated Sorting Genetic Algorithm II (NSGA II). The obtained results provide a comprehensive insight on the impacts of the involved engine operating settings on in-cylinder combustion characteristics, engine performance and emissions of the investigated marine DF engine. By performing the settings optimisation at three engine operating points, settings that lead to reduced BSFC are identified, whilst the NOx emissions comply with the Tier III NOx emissions regulation. The proposed novel method is expected to support the combustion analysis and enhancement of marine DF engines during the design phase, whilst the derived optimal solution is expected to provide guidelines of DF engine management for reducing operating cost and environmental footprint

Development of an Artificial Neural Network to Predict In-Use Engine Emissions

A method to predict in-use diesel engine emissions is developed based on engine dynamometer and in-use data acquired at the West Virginia University Center for Alternative Fuels, Engines, and Emissions. (WVU CAFEE). The model accounts for the effects of road grade on generated emissions; a need for this model is evident in literature. Current modeling methods do not account for the effects of road grade, and have been shown to under-predict NOx by as much as 57%. It is determined through present research and a review of relevant literature that an artificial neural network (ANN) was the most applicable modeling method.;A modular ANN was developed to predict the heavy duty diesel engine emissions. The two modules were trained independently, the first module was trained with data acquired through in-use testing, and the second module was trained with data acquired via engine dynamometer testing. The first module predicted the engine speed and torque associated with the inputs of road grade and vehicle speed, while the second ANN employed the first ANN\u27s outputs, and predicts the emitted quantities of NOx, CO2, HC, and CO. A series of training and verification runs are conducted in order to determine the optimum ANN characteristics. Once the ANN was finalized, it was trained with and employed to predict the emissions associated with a variety of routes.;When the ANN was trained with a combination of in-use and engine dynamometer data, the ANN is able to predict NOx emissions associated with that same route within 6% of the measured values. The average difference between the measured and predicted CO2 values for the same training and verification scenario mentioned above was less than 15%. It was also demonstrated that the ANN was able to predict emissions that are associated with routes that differ from those by which it is trained. When the ANN was trained with in-use data from a specific route, it was able to predict the NOx and CO2 emissions associated with a different route with percent differences from the measured values of 20% or less

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

Multi-objective and multi-model shape optimization of turbocharger turbines over real-world drive cycles for low carbon vehicles

Turbocharging is the established method for downsizing internal combustion (IC) engines to lower CO2 emissions and fuel consumption while meeting the desired performance. Turbochargers for automotive engines commonly utilize radial turbines for exhaust energy extraction. However, the design of a turbocharger turbine is subject to conflicting requirements. A crucial consideration when matching a turbocharger to an engine is the ability to meet the specified low-end torque target while minimizing the turbine inlet pressure (particularly at high engine speed) to reduce the engine pumping work. Conventionally, the matching procedure used in the industry relies on experimentally measured compressor and turbine performance maps to model turbocharger operation within engine cycle simulation software. In this way, the compressor and turbine configuration that best meets the specified customer requirements is down-selected. Thus, only existing turbine geometries can be evaluated during the conventional matching process. This makes it a passive process as the turbine aerodynamic performance and inertia cannot be modified during the matching evaluations. Ideally, what is needed is a framework that physically models both the turbine and engine with sufficient accuracy and allows turbine geometric changes to be accounted for. To this end, the objective of this work is to establish a novel and fast-running framework that allows turbine shape optimization based on engine-level objectives and constraints, and understand from a fluid dynamic perspective why a given turbine design is better for the engine. An in-house reduced-order model (meanline code) to estimate aerodynamic performance and a neural network-based inertia prediction tool for radial turbines are developed. These are integrated in a validated engine model to provide a framework for modelling the engine-turbine interaction using a numerically inexpensive technique. It allows the effect of turbine geometric changes on inertia and aerodynamic performance to be reflected in the exhaust boundary conditions and thereby in the overall performance of the engine. A genetic algorithm is employed within the framework, providing an opportunity for single-objective (for example, weighted cycle-average BSFC) or multi-objective (for example, weighted cycle-averaged BSFC and engine transient response) shape optimization of turbine meridional geometry. The framework has been applied to a Renault 1.2L turbocharged gasoline engine to minimize the fuel consumption and therefore CO2 emissions, while meeting a sensible transient response constraint. Turbine shape optimization was carried out over a cluster of weighted part-load operating points that represent the World harmonized Light vehicles Test Cycle (WLTC). The design candidates lying on the Pareto front present improvements of up to 0.4% in the weighted cycle-averaged fuel consumption, and up to 8% in transient response. Dynamic vehicle simulations over the WLTC are used to confirm the improvement observed in fuel consumption. Based on the meridional parameters obtained from the 1D optimization, 3D designs are created for both the turbine housing and the rotor. Finally, CFD evaluation and experimental testing are performed to verify the performance of optimized designs. 3D CFD predictions showed good agreement with experimental results, lying within the range of experimental uncertainty. The CFD analysis also showed a significant reduction in secondary flow features in the optimized design compared with the baseline turbine. While the developed framework can be used to improve existing turbine designs, it also facilitates the development and optimization of `tailor-made' turbines for new low carbon engine projects. Even though, for the particular case described, the optimization process indicates a moderate 0.2--0.4% reduction in the weighted cycle-averaged BSFC, this would translate to a reduction of at least 270,000 tonnes of CO2 considering the lifetime of all GDI engines manufactured each year in the EU. Thus, the developed turbine optimization framework has a massive potential, especially because it requires no new or additional technology.Open Acces

The architecture of pneumatic regenerative systems for the diesel engine

For vehicles whose duty cycle is dominated by start-stop operation, fuel consumption may be significantly improved by better management of the start-stop process. Pneumatic hybrid technology represents one technology pathway to realise this goal. Vehicle kinetic energy is converted to pneumatic energy by compressing air into air tank(s) during the braking. The recovered air is reused to supply an air starter, or supply energy to the air path in order to reduce turbo-lag. This research aims to explore the concept and control of a novel pneumatic hybrid powertrain for a city bus application to identify the potential for improvements in fuel economy and drivability. In order to support the investigation of energy management, system architecture and control methodologies, two kinds of simulation models are created. Backward-facing simulation models have been built using Simulink. Forward-facing models have been developed in the GT-POWER and Simulink co-simulation. After comparison, the fully controllable hybrid braking system is chosen to realize the regenerative braking function. A number of architectures for managing a rapid energy transfer into the powertrain to reduce turbo-lag have been investigated. A city bus energy control strategy has been proposed to realize the Stop-Start Function, Boost Function, and Regenerative Braking Function as well as the normal operations. An optimisation study is conducted to identify the relationships between operating parameters and respectively fuel consumption, performance and energy usage. In conclusion, pneumatic hybrid technology can improve the city bus fuel economy by at least 6% in a typical bus driving cycle, and reduce the engine brake torque response and vehicle acceleration. Based on the findings, it can be learned that the pneumatic hybrid technology offers a clear and low-cost alternative to the electric hybrid technology in improving fuel economy and vehicle drivability

Bandwidth Based Methodology for Designing a Hybrid Energy Storage System for a Series Hybrid Electric Vehicle with Limited All Electric Mode

The cost and fuel economy of hybrid electrical vehicles (HEVs) are significantly dependent on the power-train energy storage system (ESS). A series HEV with a minimal all-electric mode (AEM) permits minimizing the size and cost of the ESS. This manuscript, pursuing the minimal size tactic, introduces a bandwidth based methodology for designing an efficient ESS. First, for a mid-size reference vehicle, a parametric study is carried out over various minimal-size ESSs, both hybrid (HESS) and non-hybrid (ESS), for finding the highest fuel economy. The results show that a specific type of high power battery with 4.5 kWh capacity can be selected as the winning candidate to study for further minimization. In a second study, following the twin goals of maximizing Fuel Economy (FE) and improving consumer acceptance, a sports car class Series-HEV (SHEV) was considered as a potential application which requires even more ESS minimization. The challenge with this vehicle is to reduce the ESS size compared to 4.5 kWh, because the available space allocation is only one fourth of the allowed battery size in the mid-size study by volume. Therefore, an advanced bandwidth-based controller is developed that allows a hybridized Subaru BRZ model to be realized with a light ESS. The result allows a SHEV to be realized with 1.13 kWh ESS capacity. In a third study, the objective is to find optimum SHEV designs with minimal AEM assumption which cover the design space between the fuel economies in the mid-size car study and the sports car study. Maximizing FE while minimizing ESS cost is more aligned with customer acceptance in the current state of market. The techniques applied to manage the power flow between energy sources of the power-train significantly affect the results of this optimization. A Pareto Frontier, including ESS cost and FE, for a SHEV with limited AEM, is introduced using an advanced bandwidth-based control strategy teamed up with duty ratio control. This controller allows the series hybrid’s advantage of tightly managing engine efficiency to be extended to lighter ESS, as compared to the size of the ESS in available products in the market