Diesel Engine System Research Articles

A Differential Flatness Theory Approach to Embedded Adaptive Control of Turbocharged Diesel Engines

The use of efficient embedded control systems in the transportation industry and particularly in turbocharged Diesel engines requires the programming of elaborated nonlinear control and filtering methods. To this end, in this paper nonlinear control for turbocharged Diesel engines is developed with the use of Differential flatness theory and adaptive fuzzy control. It is shown that the dynamic model of the turbocharged Diesel engine is differentially flat and admits dynamic feedback linearization. It is also shown that the dynamic model can be written in the linear Brunovsky canonical form for which a state feedback controller can be easily designed. To compensate for modeling errors and external disturbances an adaptive fuzzy control scheme is implemented making use of the transformed dynamical system of the diesel engine that is obtained through the application of differential flatness theory. The control algorithm aims at satisfying the $$H_\infty $$ tracking performance criterion, which means that the influence of the modeling errors and the external disturbances on the tracking error is attenuated to an arbitrary desirable level. After transforming the MIMO diesel engine system into the canonical form, the resulting control inputs are shown to contain nonlinear elements which depend on the system’s parameters. The nonlinear terms which appear in the control inputs are approximated with the use of neuro-fuzzy networks. Moreover, since only the system’s output is measurable the complete state vector has to be reconstructed with the use of a state observer. It is shown that a suitable learning law can be defined for the aforementioned neuro-fuzzy approximators so as to preserve the closed-loop system stability. With the use of Lyapunov stability analysis it is proven that the proposed observer-based adaptive fuzzy control scheme results in $$H_{\infty }$$ tracking performance.

Performance evaluation of a urea-selective catalytic reduction system in a marine diesel engine

A numerical simulation of the droplet distribution at the exhaust duct for a static mixer and injection location was performed for marine selective catalyst reduction. Through experiments with this auxiliary marine urea-selective catalyst reduction system, the ammonia slip, selective catalyst reduction system pressure drop, and NOx reduction rate in accordance with the space velocity (i.e. engine load) were investigated. Under incremental and random experimental conditions, the ammonia slip of this urea-selective catalyst reduction system is below 3 ppm, which satisfies International Maritime Organization Tier III regulations.

Application of an EGR system in a direct injection diesel engine to reduce NOx emissions

This work presents the application of an exhaust gas recirculation (EGR) system in a direct injection diesel engine operating with diesel oil containing 7% biodiesel (B7). EGR rates of up to 10% were applied with the primary aim to reduce oxides of nitrogen (NOx) emissions. The experiments were conducted in a 44 kW diesel power generator to evaluate engine performance and emissions for different load settings. The use of EGR caused a peak pressure reduction during the combustion process and a decrease in thermal efficiency, mainly at high engine loads. A reduction of NOx emissions of up to 26% was achieved, though penalizing carbon monoxide (CO) and total hydrocarbons (THC) emissions.

A New Approach for NOx Soft Sensors for the Aftertreatment of Diesel Engines

To maintain the NOX concentration at an appropriate level, traditionally an air-path control that regulates the intake and exhaust system of diesel engines aims to control the mass air flow and the manifold absolute pressure, which influence the production of NOX. To improve the control accuracy, a more recent approach takes the NOX concentration directly as a controlled output variable, but the sensors monitoring the NOX concentration are slow to respond. Consequently, a direct sensor is inappropriate as a feedback controller. Instead a mechanism called a soft sensor, which computes the NOX concentration from state quantities of diesel engines, is used. Because the prediction accuracy from the sensor model greatly affects the control performance, it is important to improve the model accuracy. However, deviations in the steady state indicate an insufficient model accuracy. This study proposes a method to construct an adaptive NOX soft sensor that corrects the parameters of the sensor model sequentially using the simultaneous perturbation stochastic approximation while comparing the values computed by the software to actual measurements as well as examines the effectiveness of the proposed method experimentally.

On Decoupling Control of the VGT-EGR System in Diesel Engines: A New Framework

In this brief, a novel decoupling solution is proposed for the variable-geometry turbine (VGT) and exhaust gas recirculation (EGR) system of diesel engines based on the principle of active disturbance rejection control. This complex, double-input, double-output, VGT-EGR system is treated as two ideal, decoupled integrators for the purpose of control design, while all other dynamics that deviate from the ideal model, including cross coupling and dynamic variations due to operating point changes, and all other uncertainties are treated as the total disturbance to be estimated and canceled. Since the estimation of the total disturbance is bandwidth limited in the VGT-EGR system, feedforward controllers, one static and one dynamic, are used to speed up the response. The proposed controller is simple to implement, easy to tune, and able to handle a wide range of uncertainties without retuning or gain-scheduling. Its effectiveness has been validated in simulation, experimental tests, as well as in mathematical analysis, proving the inverse relationship between the tracking error and the controller bandwidth.

Characterization of multi-hole nozzle sprays and internal flow for different nozzle hole lengths in direct-injection diesel engines

Multi-hole nozzles have a wide range of application in the fuel supply system of modern diesel engines, although single-hole nozzles dominate basic internal flow and spray research. The parameters of the nozzle geometry are crucial factors that can alter the internal flow dynamics of the nozzle and the consequent spray behaviours. The novelty of this study lies in implementing the application of practical prototype mini-sac multi-hole diesel nozzles to experimental and numerical studies. The internal flow and spray characteristics generated by practical multi-hole (10-hole) nozzles with different sac wall thicknesses (0.4 mm, 0.6 mm and 0.8 mm) were investigated in conjunction with a series of experimental and computational methods using a constant injection quantity (2 mm3/hole). Globally, the analysis mainly concentrated on different nozzle flow dynamics, different injection processes and different spray morphologies. Specifically, the high-speed video observation method was applied to visualize the injection processes and the spray evolution of different nozzles inside a high-pressure vessel. Furthermore, numerical simulations were conducted to reveal the three-dimensional nature of the internal flow inside different configurations; this was instructive in helping us to understand better the mechanism behind the spray behaviours. The results indicate that intense cavitating, turbulent and spiral rotating flow patterns occur inside practical multi-hole nozzles, and the consequent sprays emerging from the nozzles are perturbed, asymmetrical and unstable in both the near field and the far field. Moreover, a decrease in the nozzle hole length can increase the effects of cavitation, turbulence, the void fraction and the axial and radial injection velocity components on the nozzle hole exit; this is accompanied by an intriguing longer injection duration, wider near-field and far-field spray widths, a lower injection rate, and overlapping or even shorter spray propagation. However, these changes are not linear, and different parameters have different sensitivities to the variation in the nozzle hole length.

Optimizations of the waste heat recovery system for a large marine diesel engine based on transcritical Rankine cycle

The aim of this study is to investigate the economic performance of the waste heat recovery (WHR) system for a marine diesel engine. Four waste heat sources, which are exhaust gas, cylinder cooling water, scavenge air cooling water and lubricating oil of a marine diesel engine, are first applied to drive the transcritical Rankine cycle (TRC). R1234yf, R1234ze, R134a, R152a, R236fa and R290 are employed in the system as working fluids. The effects of expander inlet pressure and temperature on net power output, thermal efficiency, total cost, mass flow rate, and available efficiency of the WHR system are analyzed. The levelized energy cost is used to evaluate the economic optimizations and their corresponding optimal parameters in the WHR system. The results show that the optimal levelized energy cost of R236fa is the most excellent and is lower than that of R1234ze, R134a, R152a, R1234yf or R290 by 5.07%, 6.25%, 7.42%, 9.77% or 12.11%, respectively. The payback period, fuel oil saving, and CO2 emission reduction are applied to assess the suitability of these working fluids. Furthermore, the economic optimization correlations in terms of dimensionless optimal pressures and temperature difference ratios are proposed for the system design of the optimal operating conditions.

Adaptive Sliding-Mode Observer Design for a Selective Catalytic Reduction System of Ground-Vehicle Diesel Engines

In this work, we investigate the adaptive sliding-mode observer design problem for the selective catalytic reduction (SCR) system in diesel-engine aftertreatment systems. First, an uncertain three-state model is obtained. Two kinds of uncertainties are considered: uncertainties with slow variations and uncertainties with fast variations. For the uncertain model, an adaptive sliding-mode observer is proposed. Then, the observer gain tuning method is developed based on the stability analysis of the estimation error system. The proposed observer design method is applied to an SCR system of a medium-duty diesel engine. Experimental results and comparisons are provided to illustrate the advantages of the designed observer according to the proposed algorithm. Compared with the open-loop SCR model and the Luenburger-like observer, the proposed adaptive sliding-mode observer can achieve better performance.

Combustion and emission characteristics of a lateral swirl combustion system for DI diesel engines under low excess air ratio conditions

In order to improve the utilization of air in the cylinder, decrease the thermal load and improve the emission performance of diesel engines, a new lateral swirl combustion system (LSCS) has been proposed in this study. An experimental investigation of the LSCS at various excess air ratios was conducted using a 132mm single-cylinder direct injection (DI) engine. The experimental results indicate that, compared to a double swirl combustion system (DSCS), the LSCS achieves better fuel consumption and lower soot emissions. The fuel consumption was decreased by 4–5g/(kWh) at each excess air ratio, corresponding to a reduction of about 1.13–2.8%. The decreasing trend of soot formation was also clear, with a significant reduction in the range of 63.4–70.8%. The LSCS also showed excellent performance under an excess air ratio of 1.3–1.6. At an excess air ratio of 1.3, the brake-specific fuel consumption (BSFC) of the LSCS was 228g/(kWh), the soot emission level was 1.1 Filter Smoke Number (FSN) and the exhaust temperature was about 560°C. Related numerical research on the impact of in-cylinder fuel/air equivalence ratio, in-cylinder temperature and in-cylinder velocity of the DSCS and the LSCS was performed, and the results show that a large proportion of the fuel/air diffusion was at the bottom of the chamber in the LSCS (away from the cylinder head). The lower concentration of the fuel/air mixture near the cylinder head in the LSCS had a positive effect and reduced the thermal load so that less engine heat was taken away by the cooling water in the water jacket of the cylinder head. Due to the lower thermal load and higher efficiency, the exhaust temperature of the LSCS was higher than that of the DSCS. The higher exhaust temperature had a positive influence on soot oxidation, which caused the soot decrease in the LSCS. It is suggested that the LSCS, with its excellent fuel consumption and low soot emission, has better application prospects in diesel engines, than the DSCS under a low excess air ratio.

Analysis upon fuel injection quantity variation of common rail system for diesel engines

Fuel injection quantity variation of common rail system has effect on the stability and reliability of diesel engines. For purpose of investigating the influence rule and mechanism of fuel injection quantity variation caused by parameters, taking account of the influence of fuel physical properties on dynamic injection characteristics of the system, a bond graph model of common rail injector has been proposed based on bond graph methodology and the state equations of the system are obtained. Comparisons between calculated fuel injection quantities by the numerical model and experimental measurements at different rail pressures and injection pulse widths indicate that the developed model can reasonably predict the fuel injection quantity characteristic of the system. Fuel injection quantity variation characteristics caused by the parameters of common rail injector have been analyzed in entire operating conditions. The selected parameters are delivery chamber diameter, needle seat semi-angle, needle cone semi-angle, ball valve seat semi-angle, nozzle hole diameter, inlet orifice diameter and outlet orifice diameter. The variation rules of quantitative percentages are obtained by quantitative analysis upon fuel injection quantity variation influential factors. It is concluded that ball valve seat semi-angle, nozzle hole diameter, inlet orifice diameter and outlet orifice diameter have the most significant effect on fuel injection quantity variation, and the followed are delivery chamber diameter and needle seat semi-angle. In addition, needle cone semi-angle also results in the variation of fuel injection quantity, but the effect is insignificant.

Multi-sliding surface control for the speed regulation system of ship diesel engines

The steady and reliable operation of a ship’s diesel engine is important to the ship’s electrical power system and the engine’s performance, and stable control of rotational speed is crucial to a diesel engine’s emission, economy and power performance. A ship’s diesel engine is a nonlinear and time-varying system. A traditional proportional–integral–derivative (PID) controller cannot regulate the speed under different working conditions. In this paper, a nonlinear mathematical model for speed regulation of diesel engines is established according to experiments and a multi-sliding surface variable structure controller for speed regulation of diesel engine is established by sliding mode control. A bulk cargo ship 500-I was analysed as an example. The MATLAB/Simulink simulation took the navigation environment and the effect of the ship propeller on the diesel engine into consideration. A simulation model considering the whole ship–engine–propeller system is built and some conclusions can be drawn from the simulation. The multi-sliding surface control can restrain the overshoot and realize a quick track of the targeted value with high accuracy and strong robustness. In addition, the fuel consumption and CO2 emission of this sliding mode variable structure control is reduced by 4.6% compared with traditional PID control.

An integration of multi-criteria decision making techniques with a delay time model for determination of inspection intervals for marine machinery systems

For certain critical equipment items in marine machinery systems, the optimum maintenance strategy would be a scheduled on-condition operation. This involves inspection of the equipment items in order to monitor their performance degradation and, invariably, carry out repair or replacement tasks. The main challenge with this type of maintenance approach is the determination of the appropriate interval for performing the inspection task. This paper presents a methodology which integrates multi-criteria decision making (MCDM) tools with a delay time model for the determination of optimum inspection intervals for marine machinery systems. With this approach, multiple decision criteria are modelled with the delay time concept and aggregated with MCDM tools such that different criteria can be applied simultaneously in the ranking of different inspection interval alternatives. The applicability of the proposed methodology is demonstrated using the case study of a water cooling pump of the central cooling system of a marine diesel engine.

Effect of injector parameters on the injection quantity of common rail injection system for diesel engines

In this paper, the bond graph model of common rail injector was proposed in consideration of the effects of variable liquid capacitance and fuel physical property on the injection characteristics of the injector. State equations were derived based on the model, which were numerically solved by programming in Matlab. Comparisons between the simulation results and the experimental data show that the numerical model can effectively predict the injection quantity of the system. Effect of variation of delivery chamber diameter, needle seat semi-angle, needle cone semi-angle, ball valve seat semi-angle, nozzle hole diameter, inlet orifice diameter and outlet orifice diameter on fuel injection quantity had been analyzed. The influence rules of various parameters on the fuel injection quantity had been established. The experiments were conducted using face centered central composite design. A second order polynomial response surface model had been developed for predicting fuel injection quantity, as a function of the independent variables. Analysis of variation was used to determine the significance interactions which primarily affect the fuel injection quantity. It had been concluded that six interaction factors including delivery chamber diameter with nozzle hole diameter, needle seat semi-angle with needle cone semi-angle, needle seat semi-angle with nozzle hole diameter, needle cone semi-angle with nozzle hole diameter, nozzle hole diameter with inlet orifice diameter, and nozzle hole diameter with outlet orifice diameter have significant effect on the fuel injection quantity of the system.

Modeling of pressure line behavior of a common rail diesel engine due to injection and fuel variation

Common rail diesel engines with electronic fuel injection can accurately meter the fuel injection quantity with more accurate fuel injection control capability. In this work a common rail fuel injection system of a single cylinder diesel engine has been proposed and the important parameters like injection pressure, energizing time and high pressure pipes diameter and length are designed such that to be compatible with the engine basic design in case of pressure waves and injected mass variations. A one-dimensional approach has been used to model the injector using AMESim code in which Adiabatic models have been used to model injector system. Injected mass quantity has been calculated for different working point of fuel injection system that can be utilized as engine electronic control maps as inlet parameters. Results indicated that pressure fluctuation at the injector inlet is increased by decreasing pipe diameter while tube length has no significant effect on pressure waves. It is also shows that using biodiesel as fuel will lead to decrease in injection quantity but there is no significant impact on pressure fluctuations.

Improvement on the linear and nonlinear auto-regressive model for predicting the NOx emission of diesel engine

Given the increasingly stringent emission regulations, an accurate model of emission prediction is required for the aftertreatment systems of diesel engines. For example, the selective catalytic reduction system can realize higher accuracy emission control if the mass of nitrogen oxides (NOx) is known. Given its simplicity, convenience, and effectiveness, the method of data-driven modeling has been widely researched and considered a primary method to estimate the NOx mass before it reaches the aftertreatment device of a diesel engine. To fully use the known engine operating data and therefore improve the prediction accuracy, this study proposes and develops a general linear and nonlinear auto-regressive model with exogenous inputs (GNARX) for NOx prediction. A recursive least square algorithm with forgetting factor is given to estimate the model parameters, and a new simulated annealing based pruning algorithm is developed to identify the model structure. The proposed methods are first used to model the simulation and engineering data to validate their effectiveness and superiority in comparison to the conventional methods. Based on gray relational analysis, the main factors that influence NOx formation, such as the net engine torque, turbo speed, and accelerator pedal position, are then determined as the inputs for modeling the NOx emission of the diesel engine. The results show that the modeling and prediction accuracy of the GNARX model are higher than those of other models, which indicates that the GNARX model is feasible to predict NOx emission.

The general theory of the Quasi-reproducible experiments: How to describe the measured data of complex systems?

In this paper, we suggest a general theory that enables to describe experiments associated with reproducible or quasi-reproducible data reflecting the dynamical and self-similar properties of a wide class of complex systems. Under complex system we understand a system when the model based on microscopic principles and suppositions about the nature of the matter is absent. This microscopic model is usually determined as “the best fit" model. The behavior of the complex system relatively to a control variable (time, frequency, wavelength, etc.) can be described in terms of the so-called intermediate model (IM). One can prove that the fitting parameters of the IM are associated with the amplitude-frequency response of the segment of the Prony series. The segment of the Prony series including the set of the decomposition coefficients and the set of the exponential functions (with k=1,2,…,K) is limited by the final mode K. The exponential functions of this decomposition depend on time and are found by the original algorithm described in the paper. This approach serves as a logical continuation of the results obtained earlier in paper [Nigmatullin RR, W. Zhang and Striccoli D. General theory of experiment containing reproducible data: The reduction to an ideal experiment. Commun Nonlinear Sci Numer Simul, 27, (2015), pp 175–192] for reproducible experiments and includes the previous results as a partial case. In this paper, we consider a more complex case when the available data can create short samplings or exhibit some instability during the process of measurements. We give some justified evidences and conditions proving the validity of this theory for the description of a wide class of complex systems in terms of the reduced set of the fitting parameters belonging to the segment of the Prony series. The elimination of uncontrollable factors expressed in the form of the apparatus function is discussed.To illustrate how to apply the theory and take advantage of its benefits, we consider the experimental data associated with typical working conditions of the injection system in a common rail diesel engine. In particular, the flow rate of the injected fuel is considered at different reference rail pressures. The measured data are treated by the proposed algorithm to verify the adherence to the proposed general theory. The obtained results demonstrate the undoubted effectiveness of the proposed theory.

평균값 모델을 활용한 WGT 디젤엔진의 과급압력 및 EGR율 보정 방법 개발

Abstract : Globally, many researchers have been trying to improve the fuel economy of a vehicle for satisfying future CO 2 regulation and minimizing air pollution problem. For the same background, diesel engine and vehicle system optimization using simulation models have been key technologies for the improvement of vehicle system efficiency. Therefore, in this study, calibration method for the air breathing system of a WGT diesel engine using mean value model has been composed for efficient engine and vehicle optimization simulation researches. And virtual WGT performances have been calculated for a 2 cylinder downsized diesel engine system. From these researches, the calibration method for the boost pressure and EGR rate of a virtual diesel engine related with WGT performances could be composed and some of technical issue related with downsized diesel engine could be investigated. Key words :WGT(웨이스트게이트형 터보과급기), Diesel engine( 디젤엔진), Engine calibration( 엔진보정), Mean value model(평균값모델), EGR(배기가스재순환)

Characteristics of pressure wave in common rail fuel injection system of high-speed direct injection diesel engines

The latest generation of high-pressure common rail equipment now provides diesel engines possibility to apply as many as eight separate injection pulses within the engine cycle for reducing emissions and for smoothing combustion. With these complicated injection arrangements, optimizations of operating parameters for various driving conditions are considerably difficult, particularly when integrating fuel injection parameters with other operating parameters such as exhaust gas recirculation rate and boost pressure together for evaluating calibration results. Understanding the detailed effects of fuel injection parameters upon combustion characteristics and emission formation is therefore particularly critical. In this article, the results and discussion of experimental investigations on a high-speed direct injection light-duty diesel engine test bed are presented for evaluating and analyzing the effects of main adjustable parameters of the fuel injection system on all regulated emission gases and torque performance. Main injection timing, rail pressure, pilot amount, and particularly pilot timing have been examined. The results show that optimization of each of those adjustable parameters is beneficial for emission reduction and torque improvement under different operating conditions. By exploring the variation in the interval between the pilot injection and the main injection, it is found that the pressure wave in the common rail has a significant influence on the subsequent injection. This suggests that special attentions must be paid for adjusting pilot timing or any injection interval when multi-injection is used. With analyzing the fuel amount oscillation of the subsequent injections to pilot separation, it demonstrates that the frequency of regular oscillations of the actual fuel amount or the injection pulse width with the variation in pilot separation is always the same for a specified fuel injection system, regardless of engine speed, fuel amount, injection pulse, and injection pressure.

Coordinated Performance Optimization of a Variable Geometry Compressor With Model Predictive Control for a Turbocharged Diesel Engine

The concept of variable geometry compressor (VGC) has been recently proposed as a future improvement for automotive turbochargers to further increase the efficiency and boosting at low engine speed, and to provide a more direct control over the stability margin at medium–high engine load. This paper presents a control design for the air path system of an automotive diesel engine equipped with exhaust gas recirculation (EGR), variable geometry turbine (VGT), and VGC systems. Starting from a validated model, a study of the steady-state and dynamic responses is conducted to understand the influence of the VGC combined with VGT–EGR actuators on the performance of the system. Then, a feedback control strategy that coordinates the VGC actuator with the existing VGT–EGR controller based on model predictive control is proposed to optimize the compressor performance. The new methodology shows how the VGC can be used to increase the stability range of the compressor while providing the opportunity to improve its efficiency, by means of shifting the surge limit and reshaping the peak efficiency region of the machine. Simulation results on a vehicle acceleration profile with gear shift transients are provided to verify the effectiveness of the proposed methodology.

Reduction of pollutant emissions by developing a variable valve timing system in a direct injection diesel engine using computational fluid dynamics modeling

In this work, the fluid flow in a direct injection compression ignition engine and its effects on performance and pollutant emissions are studied by using computational fluid dynamics simulation through developing of variable valve timing system by combination of the optimum valve lifting and late inlet valve closing (LIVC) strategies. For this purpose, an improved version of ECFM‐3Z combustion model coupled with advanced models for NOx and soot formation was used to predict and simulate the combustion characteristics. First, the calculated in‐cylinder pressure, heat‐release rate, soot, and NOx were compared with experimental data and good agreement was obtained. To improve the performance and reduce the emission, various angles of LIVC and different types of valve lifting were compared with those of engine basic mode, and then optimum inlet valve closing (IVC) angle and optimum valve lift were determined. Results showed that in constant opening duration of the inlet valve, the volumetric efficiency increases by increasing the valve lift. In addition, the 25% increase of valve lift relative to basic mode along with optimized IVC angle of 70° crack angle after bottom dead center improves volumetric efficiency and brake power, and reduces considerably soot, NOx, and brake‐specific fuel consumption, while CO emission is increased slightly. © 2016 American Institute of Chemical Engineers Environ Prog, 35: 1430–1440, 2016