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.

Developing Tier 5 engine raw emissions model

Abstract. The renewal of emission legislation has posed even more challenges to engine manufacturers with the tightening of emission limits. To get below the limit values, the engine requires modern technology and a complex exhaust aftertreatment (EAT) system, which has increased the importance of information related to the engine’s raw emissions. Especially the soot emissions produced by the engine, because in order to achieve the best fuel efficiency and avoid faults, the regeneration of the particulate filter must be carried out in a timely manner. The most common method of measuring the amount of soot in commercial machines and particle filters is the pressure drop across the filter, the accuracy of which is insufficient under certain conditions. Various models to estimate the raw emissions produced by the engine have been developed for control purposes. The goal of this work was to develop a raw emission model for the engine of the future Tier 5 emission legislation for the control of the EAT system. AGCO has used a raw emission model before, but since the previous emission limits were achieved without an exhaust gas recirculation (EGR) system, the latest emission model did not include EGR. One of the challenges of the work, and one of the main purposes, was to find out how the EGR’s effect on emissions can be modelled. In addition, when developing the model, it had to be considered that it will be used to estimate raw emissions in real driving conditions, which is why its calculation must be fast and at the same time sufficiently accurate. The work has familiarized itself with the formation principles of different emissions in the combustion process and investigated the importance of the engine control parameters affecting them. At the time the work was performed, the mentioned Tier 5 engine was still in the development phase and therefore the model was created using the existing test data from older engine. The model was created with Simulink, which is a MATLAB graphical environment that can be used to model and simulate dynamic systems in various areas of technical computing. Simulations have been run with the created model at steady operating points, as well as with a test cycle (NRTC) designed for off-road vehicles. Based on the simulation results, the created model is a potential alternative to models based on more complex physical and chemical phenomena. However, the accuracy of the model can be improved, as it was created entirely using already existing measurement data, and the necessary tests for the final calibration of the model could not be performed. In case of NOx emissions, the accuracy of the model was good, as the correlation of the NOx emissions estimated in the NRTC simulation with the measured ones was 0.9513. In the case of soot emissions, there was much more room for improvement, as the correlation with the measured values was only 0.7702. The poor accuracy for soot emissions is due to the highly nonlinear behavior of soot in transient situations. The structure of the created model is very simple, and its calibration does not require an unreasonable amount of effort, which is why it is a potential alternative for evaluating raw engine emissions in real-time applications.Tier 5 moottorin raakapäästömallin suunnittelu. Tiivistelmä. Päästölainsäädännön uudistuminen on asettanut moottorivalmistajille entistä enemmän haasteita tiukentuvien päästörajojen myötä. Raja-arvojen alle pääsemiseen vaaditaan moottorilta modernia teknologiaa sekä monimutkaista pakokaasunpuhdistusjärjestelmää, mikä on lisännyt moottorin raakapäästöihin liittyvän informaation merkitystä. Etenkin moottorin tuottamien nokipäästöjen, sillä parhaan polttoainetehokkuuden saavuttamiseksi ja vikojen välttämiseksi partikkelisuodattimen regenerointi on suoritettava oikea-aikaisesti. Yleisin nokimäärän mittausmenetelmä kaupallisissa koneissa ja partikkelisuodattimissa on paine-ero suodattimen yli, minkä tarkkuus on tietyissä olosuhteissa riittämätön. Erilaisia malleja, joilla arvioidaan moottorin tuottamia raakapäästöjä, on kehitetty ohjaustarkoituksiin. Tämän työn tavoitteena oli kehittää raakapäästömalli tulevan Tier 5 päästölainsäädännön moottorille pakokaasunpuhdistusjärjestelmän ohjausta varten. AGCO:lla on ollut käytössä raakapäästömalli aiemminkin, mutta koska aiemmat päästörajat on saavutettu ilman pakokaasunkierrätysjärjestelmää (EGR), ei viimeisin päästömalli sisältänyt EGR:ää. Yksi työn haasteista, ja päätarkoituksista oli selvittää, kuinka EGR:n vaikutus päästöihin voidaan mallintaa. Lisäksi mallin kehittämisessä oli huomioitava, että sitä tullaan käyttämään raakapäästöjen arviointiin todellisissa ajo-olosuhteissa, minkä vuoksi sen laskennan täytyy olla nopeaa ja samanaikaisesti riittävän tarkkaa. Työssä on perehdytty eri päästöjen muodostumisperiaatteisiin moottorin paloprosessissa, sekä tutkittu niihin vaikuttavien moottorinohjausparametrien merkitystä. Työn suoritusaikaan mainittu Tier 5 moottori on yhä ollut kehitysvaiheessa, joten malli on luotu hyväksikäyttäen olemassa olevaa testausdataa vanhemmasta moottorista. Malli on luotu Simulinkillä, mikä on MATLABin graafinen ympäristö, jolla voidaan mallintaa ja simuloida dynaamisia järjestelmiä eri teknisen laskennan osa-alueilla. Luodulla mallilla on ajettu simulointeja tasaisissa toimintapisteissä, sekä off-road ajoneuvoille suunnitellulla testisyklillä (NRTC). Simulointituloksien perusteella, luotu malli on potentiaalinen vaihtoehto monimutkaisemmille fyysisiin ja kemiallisiin ilmiöihin perustuville malleille. Mallin tarkkuudessa on kuitenkin parannettavaa, sillä se luotiin kokonaan valmista mittausdataa käyttäen, eikä tarvittavia testejä mallin lopullista kalibrointia varten päästy suorittamaan. NOx päästöjen osalta mallin tarkkuus oli tyydyttävä, sillä NRTC:n simuloinnissa arvioitujen NOx päästöjen vastaavuussuhde mitattujen kanssa oli 0.9513. Nokipäästöjen kohdalla jäi huomattavasti enemmän parannettavaa, sillä korrelaatio mitattujen arvojen kanssa oli vain 0.7702. Heikko tarkkuus nokipäästöjen kohdalla johtuu noen voimakkaasti epälineaarisesta käyttäytymisestä transientti tilanteissa. Luodun mallin rakenne on hyvin yksinkertainen, sekä sen kalibrointi ei vaadi kohtuuttoman paljon vaivaa, minkä vuoksi se on potentiaaline vaihtoehto moottorin raakapäästöjen arviontiin reaaliaikaisissa sovelluksissa

Catalog of selected heavy duty transport energy management models

A catalog of energy management models for heavy duty transport systems powered by diesel engines is presented. The catalog results from a literature survey, supplemented by telephone interviews and mailed questionnaires to discover the major computer models currently used in the transportation industry in the following categories: heavy duty transport systems, which consist of highway (vehicle simulation), marine (ship simulation), rail (locomotive simulation), and pipeline (pumping station simulation); and heavy duty diesel engines, which involve models that match the intake/exhaust system to the engine, fuel efficiency, emissions, combustion chamber shape, fuel injection system, heat transfer, intake/exhaust system, operating performance, and waste heat utilization devices, i.e., turbocharger, bottoming cycle

Predicting NOx emissions in diesel engines via sigmoid NARX models using a new experiment design for combustion identification

Diesel engines are still widely used in heavy-duty engine industry because of their high energy conversion efficiency. In recent decades, governmental institutions limit the maximum acceptable hazardous emissions of diesel engines by stringent international regulations, which enforces engine manufacturers to find a solution for reducing the emissions while keeping the power requirements. A reliable model of the diesel engine combustion process can be quite useful to search for the best engine operating conditions. In this study, nonlinear modeling of a heavy-duty diesel engine NOx emission formation is presented. As a new experiment design, air-path and fuel-path input channels were excited by chirp signals where the frequency profile of each channel is different in terms of the number and the direction of the sweeps. This method is proposed as an alternative to the steady-state experiment design based modeling approach to substantially reduce testing time and improve modeling accuracy in transient operating conditions. Sigmoid based nonlinear autoregressive with exogenous input (NARX) model is employed to predict NOx emissions with given input set under both steady-state and transient cycles. Models for different values of parameters are generated to analyze the sensitivity to parameter changes and a parameter selection method using an easy-to-interpret map is proposed to find the best modeling parameters. Experimental results show that the steady-state and the transient validation accuracies for the majority of the obtained models are higher than 80% and 70%, respectively

analysis of the impact of diesel ethanol fuel blends on ci engine performance and emissions via multi zone combustion modelling

Abstract Nowadays the high competition reached in the automotive market forces original equipment manufacturers (OEMs) towards the implementation of more and more innovative solutions. Strict emission standards and fuel economy targets make the work hard to be accomplished. Therefore modern engines feature complex architecture and embed new devices for exhaust gas recirculation (LP-HP EGR), turbocharging (e.g. multi-stage compressors), gas after-treatment (e.g. DPF, SCR, LNT) and fuel injection. This results in increased costs for engine and components as well as great complexity for the overall powertrain management. An alternative solution to comply with emissions and CO 2 standards is to supply the engine with alternative fuel blends that allow reducing significantly engine pollutants thus lowering the complexity of the after-treatment path. The paper deals with the analysis of the impact of different fuel blends Diesel-Ethanol on the performance and NOx / Particulate emissions in a common-rail CI engine. The simulation analyses are performed by a multi-zone phenomenological model of fuel spray, combustion and emissions mechanisms, that takes into account the influence of the specific fuel blend on the fuel-air mixture formation and the in-cylinder gas mixture evolution. Model validation is carried out vs. experimental data collected on an automotive common-rail CI engine, fuelled by a E20 blend and operating at different working conditions. Afterwards simulations are performed by spanning the fuel blends and the combustion control parameters (i.e. injection pattern and EGR) with the aim of optimizing combustion tuning vs. fuel blend

Data driven nonlinear dynamic models for predicting heavy-duty diesel engine torque and combustion emissions

Diesel engines' reliable and durable structures, high torque generation capabilities at low speeds, and fuel consumption efficiencies make them irreplaceable for heavy-duty vehicles in the market. However, ine ciencies in the combustion process result in the release of emissions to the environment. In addition to the restrictive international regulations for emissions, the competitive demands for more powerful engines and increasing fuel prices obligate heavy-duty engine and vehicle manufacturers to seek for solutions to reduce the emissions while meeting the performance requirements. In line with these objectives, remarkable progress has been made in modern diesel engine systems such as air handling, fuel injection, combustion, and after-treatment. However, such systems utilize quite sophisticated equipment with a large number of calibratable parameters that increases the experimentation time and effort to find the optimal operating points. Therefore, a dynamic model-based transient calibration is required for an e cient combustion optimization which obeys the emission limits, and meets the desired power and efficiency requirements. This thesis is about developing optimizationoriented high delity nonlinear dynamic models for predicting heavy-duty diesel engine torque and combustion emissions. Contributions of the thesis are: (i) A new design of experiments is proposed where air-path and fuel-path input channels are excited by chirp signals with varying frequency pro les in terms of the number and directions of the sweeps. The proposed approach is a strong alternative to the steady-state experiment based approaches to reduce the testing time considerably and improve the modeling accuracy in both steady-state and transient conditions. (ii) A nonlinear nite impulse response (NFIR) model is developed to predict indicated torque by including the estimations of friction, pumping and inertia torques in addition to the torque measured from the engine dynamometer. (iii) Two different nonlinear autoregressive with exogenous input (NARX) models are proposed to predict NOx emissions. In the first structure, input regressor set for the nonlinear part of the model is reduced by an orthogonal least square (OLS) algorithm to increase the robustness and decrease the sensitivity to parameter changes, and linear output feedback is employed. In the second structure, only the previous output is used as the output regressor in the model due to the stability considerations. (iv) An analysis of model sensitivities to parameter changes is conducted and an easy-tointerpret map is introduced to select the best modeling parameters with limited testing time in powertrain development. (v) Soot (particulated matter) emission is predicted using LSTM type networks which provide more accurate and smoother predictions than NARX models. Experimental results obtained from the engine dynamometer tests show the e ectiveness of the proposed models in terms of prediction accuracies in both NEDC (New European Driving Cycle) and WHTC (World Harmonized Transient Cycle) cycle

Combustion of Gaseous Alternative Fuels in Compression Ignition Engines

The problem of alternative fuels for combustion engines has been growing in importance recently. This is connected not only with decreasing fossil fuel resources, but also with the growing concern for the natural environment and the fight against global warming. This paper discusses the possibility of utilizing alternative gaseous fuels in compression-ignition engines, using dual-fuel, gas-liquid operation strategy. Current state of the art of this technology had been introduced, along with its benefits and challenges to be countered. The discussion had been supported by authors own research experience on dual-fuel engines. The latest results of research on the impact of gas composition on combustion process in the Common Rail dual fuel engine had been presented, at the same illustrating the environmental benefits of using gaseous fuels. The Utilization of gaseous fuels with varying composition was illustrated systematically, starting with natural gas. The possibility of using fuels with lower content of methane (the so-called low-calorie gases) was shown by the impact of depleting natural gas with carbon dioxide. Industrial gases, such as syngas contain a large amount of hydrogen, carbon monoxide or higher hydrocarbons (ethane, propane). The possibility of fueling CI engines with these gasses was presented by the influence of enriching natural gas with mentioned components. The results cover engine dynamometer tests for different operating conditions with the analysis of the combustion process and detailed emission measurements discussion. The results of experimental studies were supplemented by simulation results, using mathematical models, developed by the authors for multi-fuel enginesr

Estimating soot emission in diesel engines using gated recurrent unit networks

In this paper, a new data-driven modeling of a diesel engine soot emission formation using gated recurrent unit (GRU) networks is proposed. Different from the traditional time series prediction methods such as nonlinear autoregressive with exogenous input (NARX) approach, GRU structure does not require the determination of the pure time delay between the inputs and the output, and the number of regressors does not have to be chosen beforehand. Gates in a GRU network enable to capture such dependencies on the past input values without any prior knowledge. As a design of experiment, 30 different points in engine speed - injected fuel quantity plane are determined and the rest of the input channels, i.e., rail pressure, main start of injection, equivalence ratio, and intake oxygen concentration are excited with chirp signals in the intended regions of operation. Experimental results show that the prediction performances of GRU based soot models are quite satisfactory with 77% training and 57% validation fit accuracies and normalized root mean square error (NRMSE) values are less than 0.038 and 0.069, respectively. GRU soot models surpass the traditional NARX based soot models in both steady-state and transient cycles

In-Cylinder Pressure-Based Control of Premixed Dual-Fuel Combustion

[ES] La actual crisis climática ha instado a la comunidad investigadora y a los fabricantes a brindar soluciones para hacer que el sector del transporte sea más sostenible. De entre las diversas tecnologías propuestas, la combustión a baja temperatura ha sido objeto de una extensa investigación. La combustión premezclada dual-fuel es uno de los conceptos que abordan el compromiso de NOx-hollín en motores de encendido por compresión manteniendo alta eficiencia térmica. Esta combustión hace uso de dos combustibles con diferentes reactividades para mejorar la controlabilidad de este modo de combustión en un amplio rango de funcionamiento. De manera similar a todos los modos de combustión premezclados, esta combustión es sensible a las condiciones de operación y suele estar sujeta a variabilidad cíclica con gradientes de presión significativos. En consecuencia, se requieren estrategias de control avanzadas para garantizar un funcionamiento seguro y preciso del motor. El control en bucle cerrado es una herramienta eficaz para abordar los desafíos que plantea la combustión premezclada dual-fuel. En este tipo de control, para mantener el funcionamiento deseado, las acciones de control se adaptan y corrigen a partir de una retroalimentación con las señales de salida del motor. Esta tesis presenta estrategias de control basadas en la medición de la señal de presión en el cilindro, aplicadas a motores de combustión premezclada dual-fuel. En ella se resuelven diversos aspectos del funcionamiento del motor mediante el diseño de controladores dedicados, haciéndose especial énfasis en analizar e implementar estas soluciones a los diferentes niveles de estratificación de mezcla considerados en estos motores (es decir, totalmente, altamente y parcialmente premezclada). Inicialmente, se diseñan estrategias de control basadas en el procesamiento de la señal de presión en el cilindro y se seleccionan acciones proporcionales-integrales para asegurar el rendimiento deseado del motor sin exceder las limitaciones mecánicas del motor. También se evalúa la técnica extremum seeking para realizar una supervisión de una combustión eficiente y la reducción de emisiones de NOx. Luego se analiza la resonancia de la presión en el cilindro y se implementa un controlador similar a aquel usado para el control de knock para garantizar el funcionamiento seguro del motor. Finalmente, se utilizan modelos matemáticos para diseñar un modelo orientado a control y un observador que tiene como objetivo combinar las señales medidas en el motor para mejorar las capacidades de predicción y diagnóstico en dicha configuración de motor. Los resultados de este trabajo destacan la importancia de considerar el control en bucle cerrado para abordar las limitaciones encontradas en los modos de combustión premezclada. En particular, el uso de la medición de presión en el cilindro muestra la relevancia y el potencial de esta señal para desarrollar estrategias de control complejas y precisas.[CA] L'actual crisi climàtica ha instat a la comunitat investigadora i als fabricants a brindar solucions per a fer que el sector del transport siga més sostenible. D'entre les diverses tecnologies proposades, la combustió a baixa temperatura ha sigut objecte d'una extensa investigació. La combustió premesclada dual-fuel és un dels conceptes que aborden el compromís de NOx-sutge en motors d'encesa per compressió mantenint alta eficiència tèrmica. Aquesta combustió fa ús de dos combustibles amb diferents reactivitats per a millorar la controlabilitat d'aquest tipus de combustió en un ampli rang de funcionament. De manera similar a tots els tipus de combustió premesclada, aquesta combustió és sensible a les condicions d'operació i sol estar subjecta a variabilitat cíclica amb gradients de pressió significatius. En conseqüència, es requereixen estratègies de control avançades per a garantir un funcionament segur i precís del motor. El control en bucle tancat és una eina eficaç per a abordar els desafiaments que planteja la combustió premesclada dual-fuel. En aquesta mena de control, per a mantindre el funcionament desitjat, les accions de control s'adapten i corregeixen a partir d'una retroalimentació amb els senyals d'eixida del motor. Aquesta tesi presenta estratègies de control basades en el mesurament del senyal de pressió en el cilindre, aplicades a motors de combustió premesclada dual-fuel. En ella es resolen diversos aspectes del funcionament del motor mitjançant el disseny de controladors dedicats, fent-se especial èmfasi a analitzar i implementar aquestes solucions als diferents nivells d'estratificació de mescla considerats en aquests motors (és a dir, totalment, altament i parcialment premesclada). Inicialment, es dissenyen estratègies de control basades en el processament del senyal de pressió en el cilindre i se seleccionen accions proporcionals-integrals per a assegurar el rendiment desitjat del motor sense excedir les limitacions mecàniques del motor. També s'avalua la tècnica extremum seeking per a realitzar una supervisió d'una combustió eficient i la reducció d'emissions de NOx. Després s'analitza la ressonància de la pressió en el cilindre i s'implementa un controlador similar a aquell usat per al control de knock per a garantir el funcionament segur del motor. Finalment, s'utilitzen models matemàtics per a dissenyar un model orientat a control i un observador que té com a objectiu combinar els senyals mesurats en el motor per a millorar les capacitats de predicció i diagnòstic en aquesta configuració de motor. Els resultats d'aquest treball destaquen la importància de considerar el control en bucle tancat per a abordar les limitacions trobades en la combustió premesclada. En particular, l'ús del mesurament de pressió en el cilindre mostra la rellevància i el potencial d'aquest senyal per a desenvolupar estratègies de control complexes i precises.[EN] The current climate crisis has urged the research community and manufacturers to provide solutions to make the transportation sector cleaner. Among the various technologies proposed, low temperature combustion has undergone extensive investigation. Premixed dual-fuel combustion is one of the concepts addressing the NOx-soot trade-off in compression ignited engines, while maintaining high thermal efficiency. This combustion makes use of two fuels with different reactivities in order to improve the controllability of this combustion mode over a wide range of operation. Similarly to all premixed combustion modes, this combustion is nevertheless sensitive to the operating conditions and traditionally exhibits cycle-to-cycle variability with significant pressure gradients. Consequently, advanced control strategies to ensure a safe and accurate operation of the engine are required. Feedback control is a powerful approach to address the challenges raised by the premixed dual-fuel combustion. By measuring the output signals from the engine, strategies can be developed to adapt and correct the control actions to maintain the desired operation. This thesis presents control strategies, based on the in-cylinder pressure signal measurement, applied to premixed dual-fuel combustion engines. Various objectives were addressed by designing dedicated controllers, where a special emphasis was made towards analyzing and implementing these solutions to the different levels of mixture stratification considered in these engines (i.e., fully, highly and partially premixed). At first, feedback control strategies based on the in-cylinder pressure signal processing were designed. Proportional-integral actions were selected to ensure the desired engine performance without exceeding the mechanical constraints of the engine. Extremum seeking was evaluated to track efficient combustion phasing and NOx emissions reduction. The in-cylinder pressure resonance was then analyzed and a knock-like controller was implemented to ensure safe operation of the engine. Finally, mathematical models were used to design a control-oriented model and a state observer that aimed to leverage the signals measured in the engine to improve the prediction and diagnostic capabilities in such engine configuration. The results from this work highlighted the importance of considering feedback control to address the limitations encountered in premixed combustion modes. Particularly, the use of the in-cylinder pressure measurement showed the relevance and potential of this signal to develop complex and accurate control strategies.This thesis was financially supported by the Programa Operativo del Fondo Social Europeo (FSE) de la Comunitat Valenciana 2014-2020 through grant ACIF/2018/141.Barbier, ARS. (2022). In-Cylinder Pressure-Based Control of Premixed Dual-Fuel Combustion [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/18327