Lean Burn Spark Ignition Engine Research Articles

Influence of ethanol–gasoline–hydrogen and methanol–gasoline–hydrogen blends on the performance and hydrogen knock limit of a lean-burn spark ignition engine

This study investigates the effects of ethanol–gasoline and methanol–gasoline blends on the performance of a lean-burn spark ignition engine and the hydrogen knock limit of the engine with hydrogen-enriched fuel. The experimental setup includes liquid in-cylinder fuel injection and hydrogen port induction. Ethanol and methanol are blended with pure gasoline up to 50% by volume (20%, 35% and 50%) and all fuels are drip-fed with hydrogen until combustion knock is detected in step size of 2LPM. The hydrogen knock limit extension is achieved with ethanol–gasoline and methanol–gasoline blends and is further extended by spark-timing retardation. Retarded spark timing and ethanol–methanol blended fuels reduce the brake thermal efficiency, brake mean effective pressure, and peak in-cylinder pressure. The cyclic variation increases with ethanol and methanol addition and decreases with spark-timing retardation and hydrogen enrichment. Unlike hydrogen enrichment, ethanol and methanol addition reduce the CO2 and NOx emissions but increase the CO emission.

Fundamental study on lean operation limit of super lean-burn spark ignition engines: MIE transition and limit prediction

Fuel-lean combustion is challenging because of the difficulty in successful ignition-to-flame propagation transition in intense turbulence conditions. This study aims to elucidate the governing factor of fuel dependence on the lean limit through fundamental ignition experiments and numerical simulations. Previous scaling analysis has reported strong correlations between lean engine operation limit and Minimum Ignition Energy (MIE) transitions. Additionally, the temporal evolution of turbulent intensity in the engine cylinder plotted on Peters diagram suggested that the flame kernel growth occurs only in relatively weak turbulent intensity, u′, the condition under which u′ is lower than the MIE transition. To investigate the behavior of flame kernel growth in the vicinity of the MIE transition condition, we conducted ignition experiments under both laminar and turbulent conditions utilizing a constant volume chamber with counter-rotating fans. Flame initiation was achieved by spark discharge at various turbulent intensities. The results showed notable distinctions in flame kernel growth processes between below and above the MIE transition condition. For u′< MIE transition, flame kernel development is governed by molecular transports showing an apparent Lewis number effect, whereas for u′> MIE transition, the effect seems to disappear. Subsequently, experiments and numerical simulations on spherically propagating flames in quiescent mixtures with various blended fuels were conducted. The results indicated that fuels facilitating rapid flame kernel growth generally exhibited leaner engine operation limits, regardless of engine specifications. The present study successfully demonstrated that the fuels suitable for lean combustion could be predicted by investigation of spherically propagating flames in quiescent mixtures.

Influence of high compression ratio on the performance of ethanol-gasoline fuelled lean burn spark ignition engine at part throttle condition

As a viable solution to meet rising energy costs and reduce greenhouse gases, alcohol fuels are considered the most promising renewable fuel and ethanol is a potential fuel for spark ignition engines. In the present study, experiments were conducted on a spark ignition engine modified from a diesel engine that uses an ethanol-gasoline mixture as fuel under lean operating conditions. The engine was operated at 1500 rpm at a high compression ratio of 10.5:1. The different proportions of ethanol namely 5 %, 10 %, 20 %, and 30 % with gasoline, were studied and compared. The throttle was set to 25 % to operate the engine at various equivalence ratios to study the performance and emissions. Experimental outcomes reveal that 10 % ethanol with gasoline enhances the brake thermal efficiency and brake power by 7 % and 4.5 % respectively, due to an enhanced compression ratio. Further, the gasoline lean limit is also extended from 0.74 to 0.70 equivalence ratios. In addition, ethanol blending with gasoline enhances the combustion characteristics and heat release rates. The influence of ethanol greatly decreases cycle-by-cycle variations and hydrocarbon emissions. Adopting a high compression ratio and lean-burn operation can effectively improve performance and decrease emissions in an ethanol-gasoline-fuelled spark ignition engine.

Investigation of boost pressure and spark timing on combustion and NO emissions under lean mixture operation in hydrogen engines

Hydrogen may become a replacement for liquid fossil fuels, contributing to greenhouse gas emissions reductions by improving the thermal efficiency of boosted lean burn spark ignition engines. Single-zone engine combustion models are simple, but can yield useful results as a step in the design process for developing alternative fuel systems. The single-zone thermodynamic model is advanced by implementing a laminar flame speed sub-model to investigate combustion, an extended Zeldovich mechanism for nitric oxide emissions, and incorporating the Livengood-Wu integral model for knock characteristics. The results were validated using published experiments giving satisfactory predictions between simulation and experiment for spark timing variation, manifold air pressure, and equivalence ratios. A detailed analysis of boosted lean burn strategies showed that nitric oxide emissions increased with boosted pressure, hence emissions can be controlled through optimizing the excess air ratio and the start of combustion. Further techniques to achieve high thermal efficiency and to prevent knock for boosted lean burn hydrogen SI engine are discussed.

Analysis of combustion cyclic variation in a lean burn spark-ignited engine using large eddy simulation

The low-temperature combustion technique improves engine efficiency by reducing the thermal and exhaust losses. The representative method of low-temperature combustion technique is lean burn. However, lean burn has been limited because it increases the cycle-to-cycle variation (CCV) owing to poor initial ignition stability. To overcome the low initial ignition stability, increasing the spark energy intensity and strengthening the tumble motion have been proposed. Therefore, lean burn engines with ignition stability are being rapidly developed recently. In this study, the result of the LES simulation of a lean burn engine showed the importance of ignition delay increased more than that of a conventional gasoline engine. With the importance of ignition delay in lean burn condition, the sources of the ignition delay were analyzed. The primary ignition delay sources were the flow velocity near the spark plug and the subgrid-scale turbulent kinetic energy. Next, the parameters affecting the 5% mass fraction burned (MFB) duration were analyzed by comparing five characteristic cycles. Also, factors that decreased the correlation coefficient were analyzed by comparing with the outlying cycle. As a result of analyzing the cycle with a significant change in MFB 5 and MFB 50 ranking, the burn duration was found to be affected by curl TKE, SGS TKE, large-scale flow motion, and air–fuel ratio. Finally, methods to reduce CCV were proposed. The first method was to increase tumble X+ and tumble X- using pistons that enhance the wall flow. Consequently, the coefficient of variance (COV) during the ignition delay was reduced by 27%. The second method involved changing the injector target to enhance tumble Y. The enhanced tumble Y reduced the COV of burn duration by 11%.

Influence of high compression ratio and hydrogen addition on the performance and emissions of a lean burn spark ignition engine fueled by ethanol-gasoline

This paper investigates the effect of ethanol-gasoline-hydrogen in a lean-burn SI engine with different proportions such as E5, E10, E20, E30, and E40 at compression ratio 10.5:1. The results infer that the E10 blend is the optimized one. Further, E10 mixture investigates for 5% and 10% hydrogen addition on energy basis. Overall, this study establishes that the addition of ethanol enhances brake power by 9% and brake thermal efficiency by about 7%. Hydrogen enrichment to E10 mixture shows a significant enhancement in brake power and brake thermal efficiency at a lower equivalence ratio. Further, it observes that the lean limit had extended to a 0.47 equivalence ratio compared to a 0.5 equivalence ratio with the E10, and 0.54 with pure gasoline. The addition of hydrogen to E10, improves the combustion process and heat release rate while it reduces cycle-by-cycle variations and hydrocarbon emissions.

Single- and dual-channel nanosecond repetitively pulsed discharges at small and large spark gaps for turbulent premixed spherical flame initiation

This paper reports laminar/turbulent ignition probability (Pig,L/Pig,T) of single- and dual-channel nanosecond-discharge (SN and DN) at small and large inter-electrode gaps (dgap = 0.8 mm and 2.0 mm) using a lean n-butane/air mixture in a double-chamber fan-stirred explosion facility capable of generating near-isotropic turbulence over wide ranges of pulsed repetitive frequency (PRF = 1–100 kHz) and r.m.s. turbulence fluctuation velocity (urms = 0–4.9 m/s). The new DN configuration consists of two parallel anode electrodes with 2.6 mm apart and one central cathode electrode on the same vertical plane, which can generate two spatially separated and temporally synchronized discharges having an almost twice larger initial kernel size than the SN configuration. We apply the same total ignition energy Etot≈18 mJ via a train of 9 pulses/6 pulses for SN/DN experiments, each pulse having Eig≈2.2 mJ (SN) and/or 3.3 mJ (DN) except for the first pulse with the same 0.8 mJ regardless of PRF and dgap. Unlike the common notion that the larger ignition kernel leads to higher Pig,L, it is found that the DN configuration at small dgap = 0.8 mm is totally detrimental for spark ignition (SI) with Pig,L = 0% for all PRFs = 1–100 kHz, while the SN configuration at small dgap = 0.8 mm has its maximum Pig,L = 58% at PRF = 40 kHz showing the synergy effect. But the reverse is found at large dgap = 2.0 mm with Pig,L(DN) > Pig,L(SN). Moreover, when 1 m/s < urms < 4 m/s at PRF = 40 kHz and dgap = 2.0 mm, although both Pig,T(DN) and Pig,T(SN) decrease with increasing urms, Pig,T(DN) is noticeably higher than Pig,T(SN) showing ignition enhancement of dual-channel sparks at large dgap, Pig,T(DN) = Pig,T(SN) = 100% when urms < 1 m/s, and Pig,T(DN) = Pig,T(SN) = 0 % when urms ≥ 4.2 m/s. Finally, high-speed schlieren images of SN/DN kernel evolutions are used to comprehend these results that may be useful for the ignition strategy in lean-burn SI engines.

Lean Burn Flame Kernel Characterization for Different Spark Plug Designs and Orientations in an Optical GDI Engine

Lean burn spark ignition (SI) engines represent an effective solution for improving fuel economy and reducing exhaust emissions and can be implemented both in conventional and hybrid powertrains. On the other hand, lean operation increases cyclic variability with negative impact on power output, engine efficiency, roughness, and operating stability. Although this phenomenon has been widely investigated, the effects of flow field on the inception and development of flames in direct injection spark ignition (DISI) engines under lean burn conditions is not yet completely understood. In particular, the effect of spark plug geometry and electrode orientation with respect to tumble motion has been minimally investigated. For these reasons, two different spark-plug geometries (i.e., single- and double-ground electrode) and three different orientations (i.e., cross-, counter-, and uni-flow with respect to the direction of tumble motion) were investigated in an optically accessible DISI engine for understanding their influence on the initial phase of combustion. The relative air–fuel ratio (AFRrel) was changed from stoichiometric to lean burn (1.00 to 1.30) for different spark timings around the maximum brake torque setting at fixed engine speed (2000 rpm). An image processing procedure was developed for evaluating the morphological parameters of flame kernels and studying the effects of spark plug design on engine operating stability. With a focus on the correlation between the position where ignition occurs with the subsequent locations of the flame kernel during the first phases of the combustion process, the analysis allowed the gathering of a better understanding of the influence that the electrodes’ geometries and orientation can have on the first stages of combustion development.

Lean-burn air-fuel ratio control using genetic algorithm-based PI controller

Maximizing the fuel economy while lowering exhaust emissions highly depend on precise air-fuel ratio (AFR) control. The major challenge in the control of AFR is the time-varying delay, which is an inherent reason for performance degradation and instability. For analysis, the time delay is approximated by Padé approximation, leading to a non-minimum phase system that exhibits the difficulty of controlling due to its zeroes in the right half side of the s-plane. Moreover, dealing with uncertainties in fuel-path dynamics and minimizing the effect of external disturbances are key goals in the minimization of harmful emissions and maximization of fuel economy. This study puts forward an AFR control strategy in lean-burn spark-ignition (SI) engines by proposing a genetic algorithm (GA)-based proportional-integral (PI) control technique. The proposed PI controller aims at dealing with the aforementioned design challenges. The PI controller gains, namely, proportional (K_p), integral (K_i) gains are obtained with the proposed GA algorithm based on minimization of an objective function. The GA-based PI controller’s performance is analyzed with several methods in time-domain study. According to the obtained results, it has been revealed that the proposed GA-based PI controller improves the reference air-fuel ratio tracking performance in the existence of the time-varying delays in the closed-loop system, exhibiting good disturbance rejection properties, and is robust against system uncertainties. Thus, it can be effectively used for the accurate regulation of AFR under various operating conditions in SI engines.

An explicit robust stability condition for uncertain time-varying first-order plus dead-time systems

First-order plus dead-time (FOPDT) models are broadly used in process control to represent damped dynamic processes with time delays. An explicit condition for parameter- and delay-dependent robust stability of FOPDT systems with varying uncertain parameters and delay is derived in this paper. An internal model control (IMC) approach is proposed to parameterize stabilizing controllers that satisfy the output tracking objective in time-varying FOPDT systems represented by an uncertain first-order dynamic model with a time-varying delay in the control input. The small-gain theorem is used to derive an explicit necessary and sufficient parameter-dependent robust stability condition as a function of the nominal system gain, nominal varying delay, nominal time constant, and the bounds of the parameter uncertainties. An equivalent proportional-integral-derivative (PID) controller is then extracted to facilitate the implementation of the proposed IMC-based robust control. The application of the proposed explicit robust stability condition is studied in the context of air-fuel ratio (AFR) control in lean-burn spark ignition (SI) engines with a large time-varying transport delay in the control loop due to the placement of the universal exhaust gas oxygen (UEGO) sensor downstream the catalytic converter.

Lean combustion of stratified hydrogen in a constant volume chamber

To mitigate carbon emissions from the transportation sector, the application of hydrogen as a fuel for internal combustion engines was investigated. Owing to the merits of employing hydrogen in lean-burn spark-ignition engines, hydrogen stratified charge combustion (SCC) was tested in a constant-volume chamber. The mixture formation time (MFT) and ambient density were modulated to analyze their effects on the hydrogen SCC. Additionally, optical diagnostics were conducted to understand the behavior of the hydrogen flame. Short and long MFTs resulted in high and low burning velocities, respectively, based on the degree of fuel stratification. When the ambient density was high, nonlinear combustion characteristics were detected owing to the collapsed structure of the hydrogen jet. The measurement of a red-colored visible emission from the hydrogen SCC could be evidence of a hydrogen-rich combustion area. The local equivalence ratio and morphology of the hydrogen jet were the key parameters for the hydrogen SCC. By understanding the effects of MFT and ambient density on hydrogen SCC, high-efficient and clean transportation may be achievable with optimized injection and ignition timings.

Limitations of Natural Gas Lean Burn Spark Ignition Engines Derived From Compression Ignition Engines

Abstract Converting existing diesel engines to the spark ignition (SI) operation can increase the utilization of natural gas (NG) in heavy-duty applications, which can reduce oil imports in the US and curtail greenhouse-gas emissions. The NG operation at lean-burn conditions was evaluated inside a retrofitted heavy-duty direct-injection compression-ignition (CI) engine, where the diesel injector was replaced with a high-energy spark plug and NG was mixed with air in the intake manifold. Steady-state engine experiments that changed combustion phasing were performed at 13.3 compression ratio, lean equivalence ratio, medium load, and low-speed conditions, fueled with pure methane as NG surrogate. Results suggested that NG combustion inside such retrofitted engines is different from that in conventional SI engines due to the geometric characteristics of the diesel combustion chamber. In detail, the different conditions inside the bowl and the squish partitioned the combustion process into two distinct events in terms of timing and location. Moreover, the squish region helped stabilize the extreme lean operation by creating a highly turbulent flow into the bowl during the compression stroke. However, combustion efficiency and unburned hydrocarbon emissions were significantly affected by the fuel fraction that burned inside the squish region under less than optimal conditions during the expansion stroke. As a result, despite the combustion phasing being the primary control of engine’s indicated thermal efficiency, the combustion strategy for CI engines converted to NG SI should optimize the slower burning inside the squish region.

Hydrogen-natural gas combustion in a marine lean-burn SI engine: A comparitive analysis of Seiliger and double Wiebe function-based zero–dimensional modelling

With increasingly stringent emission regulations, marine natural gas engines need to improve their performance. Various proven advantages of hydrogen-natural gas (H-NG) blends make them a promising enhanced fuel solution. Although modelling of H-NG combustion has been investigated before, mostly using CFD models, the literature on the modelling capabilities of Seiliger-based and Wiebe-based zero-dimensional (0-D) models is limited for H-NG combustion. Especially for the application of marine lean-burn spark-ignited (SI) engines. Therefore, the aim of this paper is to compare the capabilities of Seiliger-based and double Wiebe function-based 0-D models to capture H-NG combustion in a marine SI engine for different H-NG fuel blends, engine leaning (lean-burn operation) and engine loads.In this work, measurements on a turbocharged, SI marine natural gas engine were used to develop a heat release rate model, which was subsequently used as a basis for the Seiliger and double Wiebe function-based H-NG combustion characterization models. Results from the two combustion modelling approaches were compared for different H-NG fuel blends, engine leaning (lean-burn operation) and engine loads. The modelling results were also compared against engine measurements for different experimental conditions.This paper shows that the Seiliger modelling approach can be used to define different physical phenomenon in H-NG combustion, while accurately capturing the effects of hydrogen addition and engine leaning on the H-NG combustion process at varying engine loads. This research also found that the variations in late burn phase present in lean-burn NG and H-NG combustion can be captured using the double-Wiebe modelling approach, however, clear trends of the Wiebe combustion parameters for varying fuel blends and engine loads could not be identified to accurately capture the H-NG combustion process. Furthermore, Wiebe-based modelling approach produced larger errors in the estimations of work output and combustion heat for all test conditions.

Experimental assessment of new insulation coatings for lean burn spark-ignited engines

Clean and highly efficient internal combustion engines will still be necessary in the future to meet the ambitious CO2 emissions reduction targets set for light-duty vehicles. The maximal efficiency of stoichiometric Spark-Ignited (SI) gasoline engines has been steadily increasing in recent years but remains limited by the important relative share of cooling losses. Low heat rejection engines using ceramic barrier coatings have been presented in the past but smart insulation coatings are gaining a renewed interest as a more promising way to further increase the engine maximal thermal efficiency. This article is highlighting some important effects of smart insulation coatings developed for lean-burn spark-ignited gasoline engines. Five different coatings with low heat conductivity and capacity are applied on aluminum engine parts with the atmospheric plasma spray technique and are tested with two different engines. The laser induced phosphorescence technique is firstly used in an optical single cylinder engine to quantify the thermal performance of these coatings in terms of temperature swing during combustion. A maximal increase in the piston surface temperature of around 100 °C is measured at low load, confirming thus the expected impact of the low heat conductivity and capacity, and suggesting thus a positive impact on fuel consumption. Thanks to the tests performed with a similar metal single cylinder engine, it is shown that the unburned hydrocarbon emissions can significantly increase by up to 25% if the open porosity on top of the coating is not properly sealed, while the surface roughness has no impact on these emissions. When applied on both the piston and the cylinder head, the optimized coating displays some distinct effects on the maximal heat release rate and NOx emissions, indicating that the thermal environment inside the combustion chamber is modified during combustion. Thanks to the temperature swing between cold and hot engine phases the volumetric efficiency can also be kept constant. However, no increase in efficiency can be measured with this optimized coating which suggests that the heat balance is not affected only by the reduction in the temperature differential between the walls and the gas.

Large-eddy simulation study of combustion cyclic variation in a lean-burn spark ignition engine

Multi-cycle large-eddy simulation (LES) was performed to investigate combustion cyclic variability (CCV) in a single cylinder spark ignition engine with a homogeneous lean (λ = 1.25) isooctane-air mixture. The aim was to obtain physical insights into the early stage of combustion and its influence on CCV. Propagation of the flame was modeled by a transport equation for the filtered flame surface density within the LES framework. The ignition process was represented by the imposed stretch spark ignition model (ISSIM-LES). Ten consecutive cold flow LES cycles followed by two initialization cycles (12 cycles in total) were used to perform the reactive simulations concurrently. The simulation results were compared with experimental data. Although the number of computed cycles was fairly low, the LES was able to reproduce the cyclic variability observed in experiments both quantitatively and qualitatively. Firstly, validation of the simulation was done by comparing measured pressure traces. Secondly, correlations between the timing of the 10% fuel burnt mass fraction with early flame kernel growth and initial-to-turbulent transition period (in which there was an asymmetric flame kernel that persisted through the early development periods) were determined. Thirdly, calculated results of the flame propagation were analyzed at two cross-sections (in swirl and tumble planes) of the combustion chamber, which highlighted differences in instantaneous flame structures and propagation characteristics between the fastest and slowest cycles. Good overall agreement was obtained between the measurements and simulation data. The results revealed that the instantaneous velocity and fluctuation of flows around the spark vicinity affect growth of the early flame kernel and cause combustion cyclic variability.

Observer-based internal model air–fuel ratio control of lean-burn SI engines

Precise control of air–fuel ratio (AFR) in lean-burn spark ignition (SI) engines can reduce carbon dioxide emissions and other harmful pollutants and improve fuel economy. However, the large time-varying delay caused by inherent engine cycle and gas transport is a major challenge in the AFR performance control. Furthermore, AFR measurement via a universal exhaust gas oxygen (UEGO) sensor often has a biased error and measurement noise that significantly affects states needed for the feedback control. Herein, an observer-based internal model controller (IMC) is proposed to accurately track the desired AFR values in the presence of system parameter uncertainty and large time-varying delay. This is accomplished by implementing a control law via approximating the system delay using Pade first-order technique, including a state observer plus an integrator for estimating the system state and even improving the steady-state error in state feedback. The stability of the overall closed-loop system is validated using robust Nyquist theorem. The results show that the proposed observer-based IMC design based on Pade first-order approximation has better performance than based on Pade second-order approximation and is easily implemented in real-time. Moreover, the control scheme can accurately control the AFR system under different operating conditions to demonstrate acceptable performance in terms of robustness and fast response. Besides, the comparisons to a PI combined with a Smith predictor is conducted to show its superiority.

Development and experimental validation of a field programmable gate array–based in-cycle direct water injection control strategy for homogeneous charge compression ignition combustion stability

Homogeneous charge compression ignition is a part-load combustion method, which can significantly reduce oxides of nitrogen (NO x) emissions compared to current lean-burn spark ignition engines. The challenge with homogeneous charge compression ignition combustion is the high cyclic variation due to the lack of direct ignition control. A fully variable electromagnetic valve train provides the internal exhaust gas recirculation through negative valve overlap which is required to obtain the necessary thermal energy to enable homogeneous charge compression ignition. This also increases the cyclic coupling as residual gas and unburnt fuel is transferred between cycles through exhaust gas recirculation. To improve combustion stability, an experimentally validated feed-forward water injection controller is presented. Utilizing the low latency and rapid calculation rate of a field programmable gate array, a real-time calculation of residual fuel mass is implemented on a prototyping engine controller. Using this field programmable gate array–based calculation, it is possible to calculate the amount of fuel and the required control interaction during an engine cycle. This controller prevents early rapid combustion following a late combustion cycle using direct water injection to cool the cylinder charge and counter the additional thermal energy from any residual fuel that is transferred between cycles. By cooling the trapped cylinder mass, the upcoming combustion phasing can be delayed to the desired setpoint. The controller was tested at several operating points and showed an improvement in the combustion stability as shown by a reduction in the standard deviation of combustion phasing and indicated mean effective pressure.

Feedforward Model Predictive Control of Fuel-Air Ratio for Lean-Burn Spark-Ignition Gasoline Engines of Passenger Cars

Precise fuel-air ratio (FAR) control on transient conditions is one of the key technologies for lean-burn spark-ignition (SI) engines. To improve fuel economy and reduce emissions, lean-burn engines must regulate their FAR immediately under different operating conditions. The precision of FAR control is limited by the large time-varying feedback delay which is caused by mixture combustion, exhaust gas transport, and lean $N{O_{x}}$ trap (LNT) module. Hence, a FAR predictive controller is proposed to track the desired FAR value precisely in the control framework of feedforward and feedback control. First of all, a feedforward predictive model for the FAR in the cylinder and a feedback predictive model for the FAR in the exhaust pipe with a time-delay characteristic are built respectively. Next, the FAR tracking requirement and the physical actuator constraints are transformed into the optimization objective function. Finally, a feedback/embedded feedforward predictive controller is designed, and the optimization problems are solved online to obtain the fuel injection quality. The simulation results based on GT-POWER illustrate that the proposed predictive control algorithm with feedforward predictive control can track the dynamic FAR precisely in a wide range. Meanwhile, the feedback controller decreases the effects of time delay and parameters uncertainty on the system dynamics.

Air–fuel ratio control of lean‐burn SI engines using the LPV‐based fuzzy technique

Control of air–fuel ratio (AFR) plays a key role in the minimisation of the carbon dioxide and harmful pollutant emissions and maximisation of fuel economy. An inherent time-varying delay existing in lean-burn spark ignition (SI) engines is a major challenge for the AFR control. Herein an unstable internal dynamics with a parameter dependent system caused by time delay is established to represent a dominating feature of AFR. The proposed control scheme, LPV-based fuzzy control technique, combines the features of LPV and fuzzy control to deal with the unstable internal dynamics of an AFR system with external disturbances and a high level of uncertainty in system parameters. Based on the desired error dynamics, an LPV dynamic error consisting of the unstable state and the AFR tracking error is determined. Subsequently, the proposed fuzzy control algorithm through a look-up table is used to stabilise the LPV dynamic error. Then, the tracking error moves along the desired error dynamics towards zero. The system stability is assured via Lyapunov stability criteria. Finally, the simulation results demonstrate the effectiveness and robustness of the proposed control scheme under different operating conditions. Also, compared with the baseline controller, i.e. proportional–integral controller with Smith predictor, demonstrates its superiority.

Model Prediction Control of Fuel-Air Ratio for Lean-Burn Spark Ignition Gasoline Engine

Higher fuel economy and lower exhaust emissions for lean-burn spark-ignition (SI) engines depend significantly on precise fuel-air ratio (FAR) control. In addition, in order to improve fuel economy and reduce emissions, it is crucial for lean-burn engine to change the FAR according to different operating conditions. However, the presence of large time-varying delay due to the engine combustion, exhaust emissions transmission and lean NOx trap (LNT) module in the engine is the primary limiting factor in the control of FAR. Hence, the FAR prediction control algorithm based on disturbance observer is proposed in this paper. First, a predictive model with time-delay characteristic is established. Second, state observer is designed to predict the future dynamic changes of the engine system, and disturbance observer is designed to estimate and predict disturbances. Finally, the physical constraints of the engine and the FAR control requirements are transformed into the optimization objective function, and the optimization problem is solved online to get the amount of fuel injection. The results of Matlab and GT-Power co-simulation show that FAR predictive control algorithm based on the disturbance observer not only can quickly track the desired FAR, but also can achieve a large range of precise control of FAR and reduce the delay and parameter uncertainty impact on system dynamics.