Neural Network Controller Development and Implementation for Spark Ignition Engines with High EGR Levels

Past research has shown substantial reductions in the oxides of nitrogen (NOx) concentrations by using 10% -25% exhaust gas recirculation (EGR) in spark ignition (SI) engines (see Dudek and Sain, 1989). However, under high EGR levels, the engine exhibits strong cyclic dispersion in heat release which may lead to instability and unsatisfactory performance preventing commercial engines to operate with high EGR levels. A neural network (NN)-based output feedback controller is developed to reduce cyclic variation in the heat release under high levels of EGR even when the engine dynamics are unknown by using fuel as the control input. A separate control loop was designed for controlling EGR levels. The stability analysis of the closed-loop system is given and the boundedness of the control input is demonstrated by relaxing separation principle, persistency of excitation condition, certainty equivalence principle, and linear in the unknown parameter assumptions. Online training is used for the adaptive NN and no offline training phase is needed. This online learning feature and model-free approach is used to demonstrate the applicability of the controller on a different engine with minimal effort. Simulation results demonstrate that the cyclic dispersion is reduced significantly using the proposed controller when implemented on an engine model that has been validated experimentally. For a single cylinder research engine fitted with a modern four-valve head (Ricardo engine), experimental results at 15% EGR indicate that cyclic dispersion was reduced 33% by the controller, an improvement of fuel efficiency by 2%, and a 90% drop in NOx from stoichiometric operation without EGR was observed. Moreover, unburned hydrocarbons (uHC) drop by 6% due to NN control as compared to the uncontrolled scenario due to the drop in cyclic dispersion. Similar performance was observed with the controller on a different engine

Diesel engine performance comparisons of high temperature and low temperature combustion with conventional and biodiesel fuels

The main objective of the work underlying the dissertation was in-cylinder simultaneous reduction of nitrogen oxides (NOx) and particulate matter (PM) in diesel-/biodiesel-fuelled engines. Empirical investigations were performed for comparisons between (1) engine cycle performance of conventional diesel high and low temperature combustion processes (HTC and LTC), and (2) the use of neat commercial biodiesel and conventional diesel in the HTC and LTC modes. A four-cylinder common-rail direct-injection (DI) diesel engine and a single-cylinder DI engine with mechanical injection configuration were employed. The tests were conducted under independently controlled single- and multi-event injections, exhaust gas recirculation (EGR), boost and backpressure to achieve the LTC mode. Furthermore, engine cycle, chemical kinetics and multi-dimensional simulations were performed primarily as tools facilitating the explanation of empirical results. Deduced from extensive empirical analyses, the exhaust emissions and fuel efficiency of the diesel engines employed characterised strong resilience to biodiesel fuels when the engines were operated in conventional HTC cycles. The results offered a promising perspective of the neat biodiesel fuels. As the engine cycles approached the LTC, dissimilar engine performance between the use of conventional diesel and biodiesel fuels was observed. In the late single-shot strategy with heavy EGR rates (EGR-incurred LTC), which could be utilised to improve the fuel efficiency of diesel/biodiesel LTC cycles at low loads, the biodiesel was found to sustain a broader range of loads than the diesel fuel. This was mainly attributable to the biodiesel\u27s higher Cetane number (CN) and combustion-accessible fuel oxygen. At high load LTC, the diesel fuel early-multiple injections with EGR facilitated mixture homogeneity that is more difficult to generate with a single pulse injection. Conversely, the biodiesel early-injection strategy presented numerous challenges apropos of the homogeneous fuel/air mixture formation, especially at medium-to-high load conditions. This was attributed to the low volatility and high viscosity and CN of the investigated biodiesel fuel. The empirical analyses, especially involving the EGR-incurred LTC, presented a platform for model-based control with an improved ignition delay correlation. The new correlation, which considered the CN and oxygen concentrations in the fuel and intake air, captured the ignition delay trends with good agreement

Excess Air Ratio Management in a Diesel Engine with Exhaust Backpressure Compensation

The paper investigates the operation of a wideband universal exhaust gas oxygen (UEGO) sensor in a diesel engine under elevated exhaust backpressure. Although UEGO sensors provide the excess air ratio feedback signal primarily in spark ignition engines, they are also used in diesel engines to facilitate low-emission combustion. The excess air signal is used as an input for the fuel mass observer, as well as to run the engine in the low-emission regime and enable smokeless acceleration. To ensure a short response time and individual cylinder control, the UEGO sensor can be installed upstream of a turbocharger; however, this means that the exhaust gas pressure affects the measured oxygen concentration. Therefore, this study determines the sensor’s sensitivity to the exhaust pressure under typical conditions for lean burn low-emission diesel engines. Identification experiments are carried out on a supercharged single-cylinder diesel engine with an exhaust system mimicking the operation of the turbocharger. The apparent excess air measured with the UEGO sensor is compared to that obtained in a detailed exhaust gas analysis. The comparison of reference and apparent signals shows that the pressure compensation correlations used in gasoline engines do not provide the correct values for diesel engine conditions. Therefore, based on the data analysis, a new empirical formula is proposed, for which the suitability for lean burn diesel engines is verified.© 2020 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).fi=vertaisarvioitu|en=peerReviewed

Modeling, control, and implementation of enhanced premixed combustion in diesel engines

Three different combustion modes for simultaneous low-nitrogen oxides (NOx) and low-particulate-matter (PM) called enhanced-premixed combustion (EPC) are described in this thesis for diesel engines. a) Multi-pulse EPC: This combustion mode was implemented with multi-pulse fuel-injection events early during the compression stroke and a heavy use of EGR. This type of combustion was characterized by a short combustion duration which increased the rate-of-pressure rise and maximum pressures in comparison to the conventional diesel combustion mode. The combustion phasing for this mode was kinetics controlled and this combustion mode was largely applicable to mid-load engine operating conditions. b) EGR enabled EPC with single injection: This combustion mode was implemented with a single-injection close to top-dead center and a heavy use of EGR. The use of closed-loop control on combustion phasing via a cylinder pressure based control was found to be an important enabler for stabilizing this type of combustion. This combustion mode was applied mainly at low-load engine operating conditions. c) Combustion mode with a split heat-release characteristic: This combustion mode consisted of a part of the fuel delivery very early during the compression stroke and a part of the fuel delivery close to the top-dead-centre (TDC). The part of fuel injected close to TDC experienced conventional high-temperature combustion and oxidized the carbon-monoxide produced earlier in the cycle, thereby improving combustion efficiency. The split nature of the combustion limited the rate-of-pressure rise associated with the multi-pulse EPC combustion. The implementation of EPC were associated with fuel-efficiency penalty either due to off-phasing of combustion event, UHC and carbon-monoxide or oil-dilution. Specific strategies have been presented to overcome each of these limitations. A production version of 2.0 Liter, 4-cylinder FORD common-rail diesel engine was modified for the EPC experiments to run in a single-cylinder mode using a prototype intake and exhaust manifold and using independent fuel-injection strategies

A Challenging Future for the IC Engine: New Technologies and the Control Role

[FR] Un challenge pour le futur du moteur a` combustion interne : nouvelles technologies et ro¿le du contro¿le moteur ¿ Les nouvelles normes sur les e¿missions, en particulier le CO2, pourraient re¿duire l¿utilisation du moteur a` combustion interne pour les ve¿hicules. Cet article pre¿sente une revue de diffe¿rentes technologies en cours de de¿veloppement afin de respecter ces normes, depuis de nouveaux concepts de combustion jusqu¿a` des syste`mes avance¿s de suralimentation ou de post-traitement. La plupart de ces technologies demande un contro¿le pre¿cis des conditions de fonctionnement et impose souvent de fortes contraintes lors de l¿inte¿gration des syste`mes. Dans ce contexte et en profitant des dernie`res avance¿es dans les mode`les, les me¿thodes et les capteurs, le contro¿le moteur jouera un ro¿le clef dans la mise en œuvre et le de¿veloppement de la prochaine ge¿ne¿ration de moteurs. De l¿avis des auteurs, le moteur a` combustion interne restera la technologie dominante pour les ve¿hicules des prochaines de¿cennies.[EN] New regulations on pollutants and, specially, on CO2 emissions could restrict the use of the internal combustion engine in automotive applications. This paper presents a review of different technologies under development for meeting such regulations, ranging from new combustion concepts to advanced boosting methods and after-treatment systems. Many of them need an accurate control of the operating conditions and, in many cases, they impose demanding requirements at a system integration level. In this framework, engine control disciplines will be key for the implementation and development of the next generation engines, taking profit of recent advancements in models, methods and sensors. According to authors¿ opinion, the internal combustion engine will still be the dominant technology in automotive applications for the next decades.F. Payri; Luján, JM.; Guardiola, C.; Pla Moreno, B. (2015). A Challenging Future for the IC Engine: New Technologies and the Control Role. Oil & Gas Science and Technology ¿ Revue d¿IFP Energies nouvelles. 70(1):15-30. doi:10.2516/ogst/2014002S153070