NOx Emissions Of Diesel Engine Research Articles

Development of an EKF Observer for an automotive SCR system

Abstract In the recent years, engine developer attention is focused on the application of advanced control strategies for the SCR system, considered as the leading technology for the abatement of NOX emissions in Diesel engines. The most challenging task in SCR control is the optimization of the urea dosing strategy while reaching the balance between high NOX reduction efficiency and low NH3 slip in the tailpipe, especially during transients. In order to accomplish this task, an Extended Kalman Filter (EKF) estimator is developed, to be integrated in the closed loop control of SCR urea dosing. The EKF estimator is applied to a one-state model, in which the ammonia coverage ratio θ is the only dynamic process taken into account. To improve the model accuracy, an additional dynamics, related to total ammonia adsorption capacity Ω, is considered while conceiving the EKF. The recursive EKF algorithm allows achieving enhanced estimation accuracy with a slight increase of the computational burden that is still suitable with on-board application.

Emission and performance study emulsified orange peel oil biodiesel in an aspirated research engine

This study paves the way on reducing smoke emission and NOx emissions of research diesel engine by detailing the effect of water addition in biodiesel. Fuel samples were prepared with different concentrations of water in orange peel oil biodiesel (94% waste orange peel oil biodiesel + 4% water + 2% Span 80 (WOPOBDE1) and 90% waste orange peel oil biodiesel + 8% water + 2% Span 80 (WOPOBDE2). Span 80 was employed as a nonionic surfactant, which emulsifies water in biodiesel. Experimental results revealed that the nitrogen oxides and smoke emission of orange peel oil biodiesel emulsion were reduced by 11%–19% and 3%–21%, respectively, compared to that of neat orange peel oil biodiesel (WOPOBD). In addition, the introduction of orange peel oil–water emulsions in the diesel engine considerably reduced the emissions of unburned hydrocarbons and carbon monoxide. The overall hydrocarbon emission of WOPOBDE2 was 12.2% lower than that of WOPOBD and 16.3% lower than that of diesel. The overall CO emission of WOPOBDE2 was 17% lower than that of base fuel (WOPOBD) and 21.8% lower than that of diesel. Experimental results revealed that modified fuel had higher brake thermal efficiency and lower brake specific fuel consumption than that of base fuel at all engine brake power levels.

A Data-Driven Model Predictive Control Approach to Lean NOx Trap Regeneration

Lean NOx trap (LNT) is one of the most effective after-treatment technologies used to reduce NOx emissions of diesel engines. One relevant problem in this context is LNT regeneration timing control. This problem is indeed difficult due to the fact that LNTs are highly nonlinear systems, involving complex physical/chemical processes, that are hard to model. In this paper, a novel approach for regeneration timing of LNTs is proposed, allowing us to overcome these issues. This approach, named data-driven model predictive control (D2-MPC), does not require a physical model of the engine/trap system but is based on low-complexity polynomial prediction models, directly identified from data. The regeneration timing is computed through an optimization algorithm, which uses the identified models to predict the LNT behavior. Two D2-MPC strategies are proposed, and tested in a co-simulation study, where the plant is represented by a detailed LNT model, built using the well-known commercial tool AMEsim, and the controller is implemented in matlab/simulink.

Decentralized Feedback Control of Pumping Losses and NOx Emissions in Diesel Engines

A novel decentralized control architecture is developed based on a feedback from the pressure difference across the engine which is responsible for the pumping losses and the exhaust gas recirculation (EGR) flow in diesel engines. The controller is supplemented with another feedback loop based on NOx emissions measurement. Aiming for simple design and tuning, the two control loops are designed and discussed: one manipulates the variable geometry turbine (VGT) actuator and the other manipulates the EGR valve. An experimentally validated mean-value diesel engine model is used to analyze the best pairing of actuators and set points. Emphasis is given to the robustness of this pairing based on gain changes across the entire operating region, since swapping the pairing needs to be avoided. The VGT loop is designed to achieve fast cylinder air charge increase in response to a rapid pedal tip-in by a feedforward term based on the real-time derivative of the desired boost pressure. The EGR loop relies on a feedback measurement from a NOx sensor and a real-time estimation of cylinder oxygen ratio, χcyl. The engine model is used for evaluating the designed controllers over the federal test procedure (FTP) for heavy duty (HD) vehicles. Results indicate that the control system meets all targets, namely fast air charge and χcyl control during torque transients, robust NOx control during steady-state operation, and controlled pumping losses in all conditions.

Characterisation of the corrosion fatigue behaviour of brazed AISI 304L/BNi-2 joints in synthetic exhaust gas condensate

Exhaust gas recirculation (EGR) with brazed heat exchangers is commonly used for the reduction of NOx emissions of automotive diesel engines. Since the fatigue loading of brazed EGR coolers during the operation is superimposed by corrosive attack due to aggressive exhaust gases, the corrosion fatigue behaviour of brazed joints is relevant for the component design. In the present study, brazed AISI 304L/BNi-2 joints were cyclically tested in the synthetic exhaust gas condensate K2.2, using a corrosion cell, as well as in air after pre-corrosion acc. to VDA 230–214 with ageing durations of up to 6 weeks. A significant reduction of the fatigue strength at 2 × 106 cycles down to 43% was determined for superimposed and down to 22% for successive corrosion fatigue loading. A galvanostatic anodic polarisation of the specimens tested in situ was applied successfully for an efficient reproduction of the corrosion fatigue behaviour after the long-time and cost-intensive pre-corrosion. In this context, a novel test strategy with local strain measurements, using a newly developed extensometer, as well as electrical and electrochemical measurements was established for a precise corrosion fatigue assessment of the brazed joints. Microstructure-related corrosion fatigue damage mechanisms were evaluated using scanning electron microscopy.

Simultaneous Application of Exhaust Gas Recirculation and Non-Constant Injection Rates to Reduce NOx and Soot Emissions in Diesel Engines

A combination of EGR and variation of injection rate has been used to keep both NOx and soot emissions at an acceptable level. To do so, a two-dimensional multi-zone phenomenological diesel engine combustion model has been developed. The model consists of several sub-models for spray development, fuel atomization, evaporation, combustion, and emission formation. The fuel spray is divided into several small packets called zones, and consequently, the equations for conservation of mass and energy are solved for each individual zone at each time step, from which the cylinder temperature and pressure are calculated. Additionally, the formation of emissions is tracked as soon as the combustion starts. Moreover, parallel processing programming techniques have been utilized, which reduce the computational time of the model considerably, making it a fast and reliable tool for combustion simulation. Using the model, different rates of EGR are applied, which as expected shows a noticeable decrease in NOx emissions. Thanks to the modular design of the model, injection profile can be changed easily. Instead of using a constant rate injection, three different injection patterns are used. First, an upward step profile is used, in which fuel is initially injected with a lower and then with a higher rate. After that, a downward step profile was applied, which injects the fuel first with a lower and then a higher rate. Finally, a combination of the above profiles is used, i.e., the fuel is injected initially at a low rate, and then, the injection rate is increased, and finally decreased again. It is shown that use of EGR with a combined injection pattern at the same time can keep the NOx and soot emissions of the diesel engine at an acceptable level.

Research on Diesel Engine Energy Saving and Emission Reduction Based on Air System and NOx Virtual Sensor Model

As of the beginning of 2017, the number of motor vehicles in our country exceeded 300 million. Motor vehicle emissions are one of the most important sources of atmospheric haze. Therefore, vehicle emissions and energy consumption have always been important research directions for emission reduction and energy saving. In this paper, IOC (intake oxygen concentration) observer and feedforward controller of EGR and VGT are designed based on diesel engine air model. NOx virtual sensor model is designed to detect NOx emission as the feedback variable of IOC observer, and achieve the purpose of accurately measuring the amount of NOx, controlling the EGR valve and the VGT blade in real time, reducing the NOx emission of various diesel engines, improving the fuel economy of the engine and reducing the source of the haze, and there is an important reality in this research and the later promotion and social significance.

Diesel Engine NOx Emission Modeling Using a New Experiment Design and Reduced Set of Regressors

In this paper, NOx emissions from a diesel engine are modeled with nonlinear autoregressive with exogenous input (NARX) model. Airpath and fuelpath channels are excited by chirp signals where the frequency profile of each channel is generated by increasing the number of sweeps. Past values of the output are employed only in linear prediction with all input regressors, and the most significant input regressors are selected for the nonlinear prediction by orthogonal least square (OLS) algorithm and error reduction ratio. Experimental results show that NOx emissions can be modeled with high validation performance and models obtained using a reduced set of regressors perform better in terms of stability and robustness.

Reduction of the NOx emissions in vehicle diesel engine in order to fulfill future rules concerning emissions released into air

In the past period occurred information about a fact that in some of the motorcars was installed a software, which enabled to hide the over-limit values of the nitrogen oxides during the emission testing process. This affair is called “dieselgate”. It is a well-known fact that the actual emission limits are very hard and there is arising a serious problem for automobile factories to meet the demanding emission requirements. The emission standard Euro is an obligatory standard, which is valid within the European Union. On the present there is valid the newest standard Euro 6, which should help to eliminate most of the undesirable substances that are influencing quality of air. However, already in this year or during the next year 2018 there will be implemented a new, stricter emission standard Euro 7 in the EU. From this reason started to be used some of the alternative fuels in this branch. There was performed a study, which investigated emissions of the vehicle diesel engine during application of the experimental fuels. The experimental engine was equipped with the turbocharging and with the direct fuel injection. The different testing fuels were created using the ratios 0%, 50%, 80% and 100% between the biodiesel and the ULSDF (Ultra Low Sulphur Diesel Fuel), whereas the individually mixed fuels were marked B0:U100, B50:U50, B80:U20 and B100:U0. The first kind of the applied fuel is the pure ULSDF and the last fuel is the pure biodiesel. The experimental measurements were performed at the different engine loading levels and various engine speeds in order to investigate an influence of the mixed fuels on the engine operational characteristics.

A fuzzy logic urea dosage controller design for two-cell selective catalytic reduction systems

Diesel engines have dominated in the heavy-duty vehicular and marine power source. However, the induced air pollution is a big problem. As people's awareness of environmental protection increasing, the emission regulations of diesel-engine are becoming more stringent. In order to achieve the emission regulations, the after-treatment system is a necessary choice. Specifically, the selective catalytic reduction (SCR) system has been widely applied to reduce the NOX emissions of diesel engine. Different from single-cell SCR systems, the two-cell systems have various benefits from the modeling and control perspective. In this paper, the urea dosage controller design for two-cell SCR systems was investigated. Firstly, the two-cell SCR modeling was introduced. Based on the developed model, the design procedure for the fuzzy logic urea dosage controller was well addressed. Secondly, simulations and comparisons were employed via an experimental verification of the whole vehicle simulator. And the results showed that the designed controller simultaneously achieved high NOX reduction rate and low tail-pipe ammonia slip.

Combustion process and NOx emissions of a marine auxiliary diesel engine fuelled with waste cooking oil biodiesel blends

In order to reduce the harmful emissions from marine diesel engines, the use of alternative fuels is a promising option. In this study, the combustion process and NOx emissions and composition ratios of waste cooking oil biodiesel on a marine auxiliary diesel engine were investigated experimentally. Four different blended ratios of biodiesel and diesel were selected. The results showed that the peak of heat release rate (PHRR) decreased with the increasing biodiesel blended ratios at most of the operation conditions. The maximum reductions of PHRR were 11.04% and 19.86% at speeds of 1050 rpm and 1500 rpm. The brake specific fuel consumption (BSFC) increased but the brake thermal efficiency (BTE) changed little when the biodiesel blended ratio increased. The maximum increments of BSFC were reached at B50 and were 7.0%–8.3% and 5.1%–6.1% at 1050 rpm and 1500 rpm under different engine loads. With the increase of biodiesel blended ratios, NOx emissions decreased and NO2/NOx increased slowly due to the decline of in-cylinder temperature. While NO2/NOx decreased significantly with the increasing engine speed and load for the reduction of in-cylinder cooler regions. In general, the waste cooking oil biodiesel can be considered as an alternative fuel for marine auxiliary diesel engines.

Prediction of NOx emissions for high speed DI Diesel engines using a semi-empirical, two-zone model

In the present paper, the authors have applied a newly developed semi-empirical, zero-dimensional, two-zone model on two automotive DI Diesel engines: a heavy (truck) and a light-duty (passenger car) engine. The aim of the study is to examine model’s ability to predict NOx trends with the variation of engine load/speed, fuel injection timing, EGR rate, boost pressure and fuel injection pressure.The model makes use of cylinder geometrical data, basis engine operating data and the experimental combustion rate, as deduced from heat release analysis, to calculate engine tailpipe exhaust NO emissions and their formation history inside the combustion chamber. Apparently, combustion and hence NOx formation, occurs inside the burnt zone. The required air for the combustion is provided from the unburnt zone. The entrained air mass, at each time step, is calculated using a mean equivalence ratio value and the corresponding fuel mass burnt during the calculation time step (as defined by the experimental combustion rate). The mean equivalence ratio value, at each operating point, is obtained using a new correlation which makes use of parameters derived from the processing of the measured pressure trace, as well as typical engine operating parameters. NO (the predominant part of total NOx) is calculated using the extended Zeldovich mechanism at each time step (during combustion and expansion). Thus, the NO formation history inside the cylinder is provided, considering the two-zone approach. The specific concept of the two-zone approach combined with the utilization of engine’s measured parameters, the empirical correlation for the mean equivalent ratio and the simplicity of the model’s calculations, provide a robust and time efficient tool for NO prediction which can be applied on various engine configurations and operating conditions without extended calibration.The derived results reveal model’s ability to predict exhaust NO emissions and trends satisfactorily at a variety of engine settings. Considering its low computational cost, it can serve as a useful tool for emissions trade-off optimization studies, as well as for real-time model based NOx control applications.

NOx emission calculations for bulk carriers by using engine power probabilities as weighting factors

ABSTRACTAn important marine pollution issue identified by the International Maritime Organization (IMO) is NOx emissions; however, the stipulated method for determining the NOx certification value does not reflect the actual high emission factors of slow-speed two-stroke diesel engines over long-term slow steaming. In this study, an accurate method is presented for calculating the NOx emission factors and total amount of NOx emissions by using the actual power probabilities of the diesel engines in four types of bulk carriers. The proposed method is suitable for all types and purposes of diesel engines, is not restricted to any operating modes, and is highly accurate. Moreover, it is recommended that the IMO-stipulated certification value calculation method be modified accordingly to genuinely reduce the amount of NOx emissions. The successful achievement of this level of reduction will help improve the air quality, especially in coastal and port areas, and the health of local residents.Implications: As per the IMO, the NOx emission certification value of marine diesel engines having a rated power over 130 kW must be obtained using specified weighting factor (WF)-based calculation. However, this calculation fails to represent the current actual situation. Effective emission reductions of 6.91% (at sea) and 31.9% (in ports) were achieved using a mathematical model of power probability functions. Thus, we strongly recommend amending the certification value of NOx Technical Code 2008 (NTC 2008) by removing the WF constraints, such that the NOx emissions of diesel engines is lower than the Tier-limits at any load level to obtain genuine NOx emission reductions.

Method for reduction of the NOX emissions in marine auxiliary diesel engine using the fuel mixtures containing biodiesel using HCCI combustion

The marine auxiliary diesel engines installed in the large transoceanic ships are used in order to generate the electricity but at the same time these engines are able to produce a significant amount of the harmful exhaust gas emissions. Therefore the International Maritime Organisation (IMO) concluded an agreement, which has to control generating of gaseous emissions in maritime transport. From this reason started to be used some of the alternative fuels in this branch. There was performed a study, which investigated emissions of the auxiliary marine diesel engine during application of the experimental fuels. The different testing fuels were created using the ratios 0%, 50%, 80% and 100% between the biodiesel and the ULSDF (Ultra Low Sulphur Diesel Fuel). The experimental measurements were performed at the different engine loading levels and various engine speeds in order to investigate an influence of the mixed fuels on the engine operational characteristics.

Effect of Water Fuel Emulsion on Performance and NOx Emissions of Diesel Engine

NOx as one of the exhaust emissions is harmful to human health. Many methods can reduce NOx emissions, one of them is water in fuel emulsion. By using experiment, research has been conducted in surfactant selection. The results of experiment show 4 surfactant, which is best used to the diesel engine is tween 80 and span 80. This experiment needs some water contents variation emulsifier with 10%, 15%, and 20%. In this different variation of water is very influential on performance and NOx emissions. By using water fuel emulsion of 10% in SFOC has been increase 216,2 g/Kwh or 11.6% compared to Pertamina Dex of fuel. However, the water used in fuel emulsion of 15% and 20% in SFOC increased to compare 10% emulsion. The effect of water use in fuel emulsion has been reduce NOx emission. Water in fuel emulsion has been decrease 50.5%. Generally, the emission level of a diesel engine that using water in fuel emulsion has been improved until entering on Tier 3 specification of IMO rules

NOx emissions in direct injection diesel engines: Part 2: model performance for conventional, prolonged ignition delay, and premixed charge compression ignition operating conditions

Investigations from recent years have shown that at operating conditions characterized by long ignition delays and resulting large proportions of premixed combustion, the NOx emission trend does not correspond to the (usually) postulated correlation with an appropriately defined (adiabatic) burnt flame temperature. This correlation, however, is the cornerstone of most published NOx models for direct injection diesel engines. In this light, a new phenomenological NOx model has been developed in Brückner et al. (Part 1), which considers NOx formation from products of premixed and diffusion combustion and accounts for compression heating of post-flame gases, and describes NOx formation by thermal chemistry. In this study (Part 2), the model is applied to predict NOx emissions from two medium-speed direct injection diesel engines of different size and at various operating conditions. Single parameter variations comprising sweeps of injection pressure, start of injection, load, exhaust gas recirculation rate, number of injections, and end-of-compression temperature are studied on a single-cylinder engine. In addition, different engine configurations (valve timing, turbocharger setup) and injection parameters of a marine diesel engine are investigated. For both engines and all parameter variations, the model prediction shows good agreement. Most notably, the model captures the turning point of the NOx emission trend with increasing ignition delay (first decreasing, then increasing NOx) for both engines. The differentiation in the physical treatment of the products of premixed and diffusion with increasing ignition delay showed to be essential for the model to capture the trend-reversal. Specifically, the model predicted that peak NOx formation rates in diffusion zones decrease with increasing ignition delay, whereas for the same change in ignition delay, peak formation rates in premixed zones increase. This is caused by the high energy release in short time, causing a strong compression of existing premixed combustion product zones that mix at a slower rate and have less time to mix, significantly increasing their temperature. In contrast, the model under-predicts NOx emissions for very low oxygen concentrations, in particular below 15 vol.%, which is attributed to the simple thermal NOx kinetic mechanism used. It is concluded that the new model is able to predict NOx emissions for conventional diesel combustion and for long ignition delay operating conditions, where a substantial amount of heat is released in premixed mode.

Data-driven Model Predictive Control for Lean NOx Trap Regeneration

Lean NOx Trap (LNT) is one of the most effective after-treatment technologies used to reduce NOx emissions of diesel engines. One relevant problem in this context is LNT regeneration timing control. This problem is indeed difficult due to the fact that LNTs are highly nonlinear systems, involving complex physical/chemical processes that are hard to model. In this paper, a novel data-driven model predictive control (D2-MPC) approach for regeneration timing of LNTs is proposed, allowing us to overcome these issues. This approach does not require a physical model of the engine/trap system but is based on low-complexity polynomial prediction model, directly identified from data. The regeneration timing is computed through an optimization algorithm, which uses the identified model to predict the LNT behavior. The proposed D2-MPC approach is tested in a co-simulation study, where the plant is represented by a detailed LNT model, developed using the well-known commercial tool AMEsim, and the controller is implemented in Matlab/Simulink.

Least Square Adaptation of a Fast Diesel Engine NOx Emissions Model

The paper focuses on the development of an adaptive NOx emissions model, whose intended deployment is to provide accurate estimation, throughout engine lifetime, in correspondence of the engine exhaust port of a Diesel propulsion system. Particularly, black-box modelling approach is proposed, which specifically in this paper takes advantage of an intake manifold oxygen estimator previously developed. The resulting multi-linear regression model was preliminary validated in steady-state conditions. Upon successful verification of model accuracy, the above NOx predictor was integrated within a least-square adaptation algorithm, which relies on the experimental NOx measurement performed downstream the selective catalytic reduction catalyst. Therefore, it was possible to perform further validation analyses, both to assess prediction reliability in transient conditions, as well as to verify the adaptation capability of the proposed least-square-based algorithm.

Influence of hydrocarbon species on its adsorption on a VSCR catalyst under simulated diesel engine operating conditions

Vanadia-SCR (VSCR) is a proven technology for reducing diesel engine NOx emissions using urea hydrolysis derived NH3 as a reductant. It is also known that VSCR is active for hydrocarbon (HC) oxidation. However, HC species from diesel engine exhaust may be adsorbed onto VSCR at low exhaust temperatures such as under low engine load or idle conditions. The adsorbed HC may be gradually transformed into more stable coke during engine operation. The accumulated HC or coke on VSCR can result in decreased NOx conversion efficiency due to blockage of catalyst pores and active sites. In addition, rapid oxidation of accumulated HC or coke can lead to exotherms which can thermally damage the VSCR and may lead to vanadium and tungsten release. This work investigates the fundamental adsorption characteristics of HC species on a state-of-the-art VSCR catalyst in the low temperature region. Dodecane and toluene are used as model molecules for alkane and aromatic species from unburned diesel fuel, while squalane is used as a model molecule for unburned lube oil.

NOx emission on-line measurement for the diesel engine based on tunable diode laser absorption spectroscopy

An on-line measurement for the diesel engine NOx emission based on tunable diode laser absorption spectroscopy (TDLAS) technique is realized. Two absorption lines 1900.07059cm−1 and 1626.91952cm−1 are chosen for NO and NO2 measurement. Two ICL inter-band cascade (ICL) lasers are used to measure NO and NO2 separated. In this work, we use the TDLAS system to research the NOx emissions on a four-stroke four-cylinder diesel engine. Optical windows are installed on the exhaust pipe of the diesel engine symmetrical to realize the on-line measurement. The direct detection method is adopted in this work, which can avoid the effect from unknown concentration of particulate matter (PM) in the exhaust. The NOx emission characteristic under different load power and different rotating speed is researched. This work can support the research on the combustion process of diesel engines.