Transient Engine Operating Conditions Research Articles

Low Temperature Combustion Modeling and Predictive Control of Marine Engines

The increase of popularity of reactivity-controlled compression ignition (RCCI) is attributed to its capability of achieving ultra-low nitrogen oxides (NOx) and soot emissions with high brake thermal efficiency (BTE). The complex and nonlinear nature of the RCCI combustion makes it challenging for model-based control design. In this work, a model-based control system is developed to control the combustion phasing and the indicated mean effective pressure (IMEP) of RCCI combustion through the adjustments of total fuel energy and blend ratio (BR) in fuel injection. A physics-based nonlinear control-oriented model (COM) is developed to predict the main combustion performance indicators of an RCCI marine engine. The model is validated against a detailed thermo-kinetic multizone model. A novel linear parameter-varying (LPV) model coupled with a model predictive controller (MPC) is utilized to control the aforementioned parameters of the developed COM. The developed system is able to control combustion phasing and IMEP with a tracking error that is within a 5% error margin for nominal and transient engine operating conditions. The developed control system promotes the adoption of RCCI combustion in commercial marine engines.

Development of the predictive based control of an autonomous engine cooling system for variable engine operating conditions in SI engines: design, modeling and real-time application

This study includes the design of an autonomous cooling system and implementation of the system on gasoline-fueled internal combustion engine by using model predictive control (MPC) technique. The system designed with MPC provides superior performance in terms of engine thermal management compared to the conventional cooling system. This controller structure is selected because it can be easily adaptable to the multivariable control system and is relatively easy to adjust. In the first part of the study, a multi input multi output (MIMO) model for a gasoline engine cooling system is developed under different operating conditions by using system identification techniques. Then, the performance of the proposed predictive based engine cooling system is tested for both steady and transient engine operating conditions. The experimental results showed that the designed autonomous thermal management system outperforms compared to the conventional cooling system in terms of reducing fuel consumption, shortening of the engine warm-up time and improvement of the exhaust emission characteristics.

Normal-gamma distribution–based stochastic knock probability control scheme for spark-ignition engines

Spark timing, one of the essential parameters to control combustion in spark-ignition gasoline engines, is often advanced to optimize the power output and fuel economy. An overly advanced spark timing, or equivalently a large spark advance, however, can lead to severe knocking under heavy load engine operating conditions. In a trade-off between engine damage avoidance and power enhancement, the knock probability has to be regulated at a low percentage. Based on the observation that the logarithm of the knock intensity under steady operating conditions follows a normal distribution, in this research, a Bayesian knock probability estimation method is proposed using the normal-gamma distribution and the observed knock intensity. Based on the estimation, a spark advance control algorithm is also developed. The proposed knock probability control algorithm is validated on a full-scale test bench with a production spark-ignition engine. The results show that the proposed method is capable of regulating the knock probability to be close to the target percentage. With different parameter settings, the controller can further be configured to behave more aggressively or conservatively in knock probability estimation and regulation. In comparison with the conventional controller and the maximum likelihood–based controller, and in the tip-in/tip-out test, the proposed method also presents a quick response to transient engine operating conditions and a low spark advance dispersion after the spark advance converges close to the borderline.

A novel fuzzy logic variable geometry turbocharger and exhaust gas recirculation control scheme for optimizing the performance and emissions of a diesel engine

Variable geometry turbocharger and exhaust gas recirculation valves are widely installed on diesel engines to allow optimized control of intake air mass flow and exhaust gas recirculation ratio. The positions of variable geometry turbocharger vanes and exhaust gas recirculation valve are predominantly regulated by dual-loop proportional–integral–derivative controllers to achieve predefined set-points of intake air pressure and exhaust gas recirculation mass flow. The set-points are determined by extensive mapping of the intake air pressure and exhaust gas recirculation mass flow against various engine speeds and loads concerning engine performance and emissions. However, due to the inherent nonlinearities of diesel engines and the strong interferences between variable geometry turbocharger and exhaust gas recirculation, an extensive map of gains for the P, I, and D terms of the proportional–integral–derivative controllers is required to achieve desired control performance. The present simulation study proposes a novel fuzzy logic control scheme to determine appropriate positions of variable geometry turbocharger vanes and exhaust gas recirculation valve in real-time. Once determined, the actual positions of the vanes and valve are regulated by two local proportional–integral–derivative controllers. The fuzzy logic control rules are derived based on an understanding of the interactions among the variable geometry turbocharger, exhaust gas recirculation, and diesel engine. The results obtained from an experimentally validated one-dimensional transient diesel engine model showed that the proposed fuzzy logic control scheme is capable of efficiently optimizing variable geometry turbocharger and exhaust gas recirculation positions under transient engine operating conditions in real-time. Compared to the baseline proportional–integral–derivative controllers approach, both engine’s efficiency and total turbo efficiency have been improved by the proposed fuzzy logic control scheme while NOx and soot emissions have been significantly reduced by 34% and 82%, respectively.

Investigation on the Control Strategy for Marine Selective Catalytic Reduction System

Selective catalytic reduction (SCR) system has been proven to be an effective technology for the removal of NOx emitted from marine diesel engines. In order to comply with stringent International Maritime Organization (IMO) Tier III NOx emission regulations, a number of engine manufacturers have developed their own SCR systems. This paper focuses on modeling of an SCR reactor and developing model-based urea dosing control strategy. A mathematical model of SCR reactors has been established. Model-based control strategy relies on the three-state and one-state reactor models established to accomplish urea dosing algorithm and is promising in limiting excessive NH3 slip. The SCR reactor model is further used in a simulation for the purpose of developing model-based urea dosing control strategies. The simulation results show that the NO sliding mode control requires a massive prestudy of the NOx reduction capability of the catalyst in order to set an appropriate control objective for each operating condition. However, this calibration work can be omitted in the optimal control and NH3 sliding mode control, which mitigates the workload of the controller design. The optimal control strategy presents a satisfied control performance in limiting NH3 slip during transient state engine operating conditions.

Analysis of semi-physical neural network structure for model-based ignition timing control of multi-fuel SI engines

This research investigates the use of a semi-physical neural network for combustion phasing control of a multi-fuel spark ignition engine. The influence of model structure and training data set composition are each analysed for their influence on combustion phasing control accuracy under steady-state and transient engine operating conditions. The model structure developed for this research utilises both fuel sensitive and combustion related physical models as inputs, with an aim to minimise neural network size and increase its generalisation capability. Optimisation of the network structure is also studied to evaluate overall robustness and ensure control stability. Real-time engine test results show satisfactory combustion phasing control performance with multiple fuels for both steady state and transient conditions. Moreover, demonstration of the differences of controller performance brought by the steady state and transient training data samples will be also provided.

Air System Modeling of Light-duty Diesel Engines with Dual-loop EGR and VGT Systems

This paper investigates an air system model for a light duty diesel engine with a dual-loop exhaust gas recirculation (EGR) system and variable geometric turbocharger (VGT). The proposed model estimates unmeasurable engine states using only equipped sensors on mass product engines. The maximum error of thermodynamic states are only when the temperature, pressure and mass are less than 5% and the maximum error of the mass flow rate model is less than 0.003 kg/s. Temperature dynamics and transport delay are obtained to improve the estimation performance in transient engine operating conditions. The model is validated under engine experiments.

Exhaust Pressure Estimation Using a Diesel Particulate Filter Mass Flow Model in a Light-Duty Diesel Engine Operated With Dual-Loop Exhaust Gas Recirculation and Variable Geometry Turbocharger Systems

This paper presents a novel method to estimate an exhaust pressure at 357 different steady-state engine operating conditions using a diesel particulate filter (DPF) mass flow model to precisely control the air quantity for a light-duty diesel engine operated with dual-loop exhaust gas recirculation (EGR) and variable geometry turbocharger (VGT) systems. This model was implemented on a 32 bit real-time embedded system and evaluated through a processor-in-the-loop-simulation (PILS) at two transient engine operating conditions. And the proposed model was validated in a vehicle. By applying Darcy's law, the DPF mass flow model was developed and shows a root mean square error (RMSE) of 3.7 g/s in the wide range of the DPF mass flow and above 99% linear correlation with actual values. With such reasonable uncertainties of the DPF mass flow model, the exhaust pressure was estimated via the application of a nonlinear coordinate transformation to the VGT model. The DPF mass flow based exhaust pressure estimation exhibits below 6% error of the exhaust pressure under steady-state conditions. The method was also validated through the PILS and the vehicle test under transient conditions. The results show a reasonable accuracy within 10% error of the exhaust pressure.

A Feed-Forward Approach for the Real-Time Estimation and Control of MFB50 and SOI In Diesel Engines

Feed-forward low-throughput models have been developed to predict MFB50 and to control SOI in order to achieve a specific MFB50 target for diesel engines. The models have been assessed on a GMPT-E Euro 5 diesel engine, installed at the dynamic test bench at ICEAL-PT (Internal Combustion Engine Advanced Laboratory at the Politecnico di Torino) and applied to both steady state and transient engine operating conditions. MFB50 indicates the crank angle at which 50% of the fuel mass fraction has burned, and is currently used extensively in control algorithms to optimize combustion phasing in diesel engines in real-time. MFB50 is generally used in closed-loop combustion control applications, where it is calculated by the engine control unit, cycle-by-cycle and cylinder by-cylinder, on the basis of the measured in-cylinder pressure trace, and is adjusted in order to reduce the fuel consumption, combustion noise and engine-out emissions. A feed-forward approach has been developed in this paper. This approach is capable of predicting MFB50 on the basis of several parameters, such as, the in-chamber thermodynamic conditions, the injected fuel quantities and timings, the injection pressure, the oxygen concentration and the engine speed and load. The approach has also been inverted in order to predict the start of injection required to achieve a specific MFB50 target in real time. This method can be used in model-based real-time control algorithms to adjust the engine parameters in order to prevent the occurrence of nonoptimal combustion cycles.

Nonlinear sliding mode observer for exhaust manifold pressure estimation in a light-duty diesel engine

In this paper, a sliding mode observer is proposed to estimate exhaust pressure for a diesel engine equipped with variable geometry turbocharger (VGT) and exhaust gas recirculation (EGR) systems. Since the exhaust pressure directly affects generation of the VGT power and the EGR rate in the cylinder, the exhaust pressure information is important for precise control of the VGT and EGR systems. In order to estimate the exhaust pressure accurately, a dynamic model of intake and exhaust pressure was derived. Furthermore, the mass flow rate and temperature of the air system in the diesel engines were modeled by consideration of physical phenomena and the thermodynamic law. Based on the developed models, a nonlinear sliding mode observer was designed to estimate the exhaust pressure. Convergence of the proposed observer was verified by the Lyapunov stability criterion. The proposed observer was implemented on a real-time embedded system and validated with the engine experiments. The experimental results show that the observer estimates the exhaust pressure accurately in both steady and transient engine operating conditions. Moreover, as a case study, the estimation results of the proposed observer could be applied for detecting a fault of the EGR system. The fault of the EGR system was detected precisely using the estimation result and the limited sensor information in mass-produced engines.

SI and HCCI Combustion Mode Transition Control of an HCCI Capable SI Engine

The combustion mode transition between spark ignition (SI) and homogeneous charge compression ignition (HCCI) combustion of an internal combustion (IC) engine is challenging due to the distinct engine operating parameters over the two combustion modes and the cycle-to-cycle residue gas dynamics during the mode transition. The control problem becomes even more complicated for a multicylinder engine without camless variable valve actuators. This paper studies the combustion mode transition problem of a multicylinder IC engine equipped with dual-stage valve lift and electrical variable valve timing (VVT) systems. Hardware-in-the-loop (HIL) simulations were used as a tool to develop and validate the proposed control strategies. Based on the HIL simulation results, this paper shows that smooth combustion mode transition can be realized in a few engine cycles. During the mode transition, a model-based linear quadratic tracking strategy was used to track the desired engine manifold pressure through the engine throttle control to maintain the engine AFR in a desired range; the fuel quantity of individual cylinder was controlled via the iterative learning; and engine spark was maintained for the SI-HCCI (or spark assistant) hybrid combustions during the combustion mode transition. The HIL simulations demonstrated the effectiveness of the developed control strategies under both steady state and transient engine operating conditions. As a result, it is feasible to have a smooth combustion mode transition for an HCCI capable SI engine equipped with dual-stage valve lift and electrical VVT systems.

Development and experimental validation of a control-oriented Diesel engine model for fuel consumption and brake torque predictions

This article describes the development and experimental validation of a control-oriented, real-time capable, Diesel engine instantaneous fuel consumption and brake torque model under warmed-up conditions with only two inputs: torque request and the engine speed and no other measurements. Such a model, with the capability of reliably and computationally efficiently estimating the aforementioned variables at both steady-state and transient engine-operating conditions, can be utilized in the context of real-time control and optimization of hybrid power train systems. Although Diesel engine dynamics are highly non-linear and very complex, by considering the Diesel engine and its control system, that is, engine control unit together as an entity, it becomes possible to predict the engine instantaneous fuel consumption and torque based on only those two inputs. A synergy between different modelling methodologies including physically based grey-box and data-driven black-box approaches were integrated in the Diesel engine model. The fuelling and torque predictions have been validated by means of experimental data from a medium-duty Diesel engine at both steady-state and transient operations, including engine start-ups and shutdowns.

Simulating the Effects of Fuel Injection on Combustion

Historically, automotive design engineers have faced multiple challenges in analysing the interaction between injection and combustion. An Integrated Simulation approach can provide engine designers with a tool that allows the simultaneous analysis and design of the fuel injection and combustion processes, under steady-state and transient engine operating conditions.

Study on Direct Measurement of Diesel Exhaust Gas Flow Rate(Development of Vortex Exhaust Gas Flowmeter)

The partial flow dilution tunnel system is one of the most typical systems to measure the particulate matter emission from diesel engines. This system requires to lead the exhaust gas to the tunnel at a constant split ratio, and to confirm the uniformity of the split ratio during test. Due to lack of real time measurement procedure of exhaust gas flow in transient condition, partial flow dilution system is currently applied only to steady-state engine operating conditions. This paper describes a vortex exhaust gas flow meter with resonator developed to realize the direct flow rate measurement in transient engine operating conditions. Results of the several scheduled driving tests defined for emission test lead that the developed gas flow meter system has enough accuracy in measuring the exhaust gas flow rate in transient conditions.

Study on Direct Measurement of Diesel Exhaust Gas Flow Rate(Transient Characteristics of Ultrasonic Exhaust Gas Flowmeter)

The partial flow dilution system is one of the typical measurement systems for particulate matter emission from diesel engines. In this system, exhaust gas at a transient flow rate should be transferred to a dilution tunnel at a constant split ratio of exhaust gas. The current partial flow dilution system is used under steady-state engine operating conditions in lieu of direct flow rate measurement of exhaust gas. Therefore development of an exhaust gas flowmeter is indispensable in the partial flow dilution system for transient engine operating conditions. An ultrasonic exhaust gas flowmeter had been developed. As for the developed ultrasonic exhaust gas flowmeter, the transient characteristics measuring exactly and instantaneously temperature, pressure and velocity that are the components of the exhaust gas mass flow rate, has not been perfectly verified. We have inspected the transient characteristics of the developed ultrasonic exhaust gas flowmeter by using a laser Doppler velocimeter and numerical calculation. Consequently, an ultrasonic exhaust gas flowmeter has been confirmed to be capable of measuring the exhaust gas flow rate with sufficient transient characteristics.

In-cylinder fuel behaviour and exhaust emissions during the cold operation of a spark ignition engine

A model has been developed from experimental results to describe the passage and utilization of fuel after injection to its exhaust as fuel products or loss to the crankcase during warm-up after a cold start. Engine-out emissions of unburned hydrocarbons (HCs) and carbon monoxide can be predicted for both quasi-steady and transient engine operating conditions during warm-up. The model is phenomenological. Model coefficients, which are either constants or simple functions of engine coolant temperature, have been determined for best matching of predictions to experimental data covering a wide range of conditions. The model has been used to investigate the variation in in-cylinder fuel film mass, fuel lost to the crankcase, exhaust air—fuel ratio variations and engine-out emissions. The dependence of these on steady and transient engine operating conditions is described.

Temperature and exhaust gas conversion efficiency of catalytic converters for natural gas vehicles

Experiments were conducted to investigate the temperature profile and the emissions conversion efficiency of catalytic converters for natural gas vehicles. Two types of the catalyst structure and several transient engine operating conditions were used. The dual-bed catalyst effectively reduced the emissions in a transient period due to the low heat capacity of the front bed. The lanthanoid additives were effective in improving catalyst durability. When the natural gas fueled engine were operated outside of a very narrow window of excess air ratio (from 0.993 to 1.004), the HC and NOx conversion efficiency dropped off. The drop-off were especially fast on the lean side of the window.

Study of the steady and transient temperature field and heat flow in the combustion chamber components of a medium speed diesel engine using finite element analyses

The present work describes the development of a model for the calculation of the temperature field and heat flow in the combustion chamber components of internal combustion piston engines, which occur both under steady and transient engine operating conditions. Two and three-dimensional finite-element analyses were implemented for the representation of the complex geometry metal components (piston, liner and cylinder head). The model is applied for the piston and liner of a medium speed diesel engine, for which relevant experimental data exist in the literature. Special care is given for accurately specifying the thermal boundary conditions (temperatures and heat transfer coefficients). Gas side boundary conditions are calculated using a thermodynamic cycle simulation code, including spatial variation of the gas side heat transfer coefficient. Coolant sides (water on the external liner surface and oil on the piston undercrown surface) boundary conditions are calculated using correlations pertaining to real engine conditions. Also an effort is made to model the piston-ring belt-liner complex thermal paths using equivalent thermal circuits. A satisfactory degree of agreement is found between theoretical predictions and experimental measurements, revealing that the finite-element methods presented are successful in formulating this kind of problem, giving accurate results with reasonable computational cost. The utilization of the model reveals very clearly the essential role of engine operating transients (sudden changes in speed and/or load) in the generation of sharp temperature excursions in the metal components until a new steady state is reached. The phenomenon should be taken into account for correct engine design and safe operation (i.e. the avoidance of high local stresses).