Exhaust Gas Recirculation System Research Articles

EGRと水エマルジョン燃料の組み合わせによる NOx 低減技術

IMO NOx regulation Tier 3 will come into force in 2016 and require NOx emission below a cycle value of 3.4 g/kWh in Emission Control Areas for marine low speed two-stroke engines. To comply with this regulation, a combined EGR (exhaust gas recirculation) & WEF (water emulsified fuel) system has been developed with minimum penalty in fuel oil consumption. A full-scaled Kawasaki-MAN B&W 2S50ME-C was provided for the test together with two turbochargers, one with cut-off system and the other with VT (variable turbine nozzle area) mechanism. A wet scrubber was also incorporated in the system to remove SOx and PM in the re-circulating gas and thus to prevent corrosion and contamination in the scavenging air system during EGR operation. The water treatment system, one of the most important systems for EGR, was developed to effectively remove PM from the washing water out of the scrubber using a special compact settling tank, too. The paper reports promising outcome from the tests and effectiveness of the combined system developed.

Model-based Decoupling Control of VGT and EGR with Active Disturbance Rejection in Diesel Engines

Exhaust gas recirculation (EGR) system and variable geometry turbocharger (VGT) system are applied in diesel engine to reduce PM and NOX. Cooperative control of EGR and VGT has tremendous impact on the emission reduction. In order to gain more fine-grained control of intake mass flow rate and intake boost pressure, a new decoupling method based on active disturbance rejection control (ADRC) beyond the traditional feedback control is proposed in this paper. When EGR valve controls the intake mass flow rate, the fluctuation of air mass caused by VGT is regarded as disturbance, estimated and cancelled by ADRC, so does the boost pressure control. Meanwhile, a model based dynamic feed-forward controller is applied to further speed the system up. Simulation results show that the response speed and tracking accuracy of both boost pressure and intake mass flow rate are dramatically enhanced simultaneously in various transient conditions. Furthermore, the proposed method also has remarkable advantages over traditional solution in terms of disturbance rejection performance.

VGT and EGR Control of Common-Rail Diesel Engines Using an Artificial Neural Network

In diesel engines, variable geometry turbocharger (VGT) and exhaust gas recirculation (EGR) systems are used to increase engine specific power and reduce NOx emissions, respectively. Because the dynamics of both the VGT and EGR are highly nonlinear and coupled to each other, better performance may be attained by substituting nonlinear multiple input, multiple output (MIMO) controllers for the existing conventional lookup table-based linear controllers. This paper presents a coordinated VGT/EGR control system for common-rail direct injection diesel engines. The objective of the control system is to track target mass air flow and target intake manifold pressure by adjusting the EGR and VGT actuator positions. We designed a nonlinear MIMO control system using a neural control scheme that adopts an indirect adaptive control approach. The neural control system is comprised of a neural network identifier, which mimics the target air system, and a neural network controller, which calculates the actuator positions. The proposed control system has been validated with engine experiments under transient operating conditions. It was demonstrated from experimental results that the proposed control system shows improved target value tracking performance over conventional VGT/EGR control system.

Influence of high and low pressure EGR and VGT control on in-cylinder pressure diagrams and rate of heat release in an automotive turbocharged diesel engine

An experimental study was developed to compare high and low pressure exhaust gas recirculation systems (HP and LP EGR) fitted on an automotive turbocharged diesel engine, analysing the effects of their control on fuel consumption, pollutant emissions and combustion process. An extensive range of operating modes was considered at different engine part-load conditions, starting from the reference one without EGR, then considering the simple activation of the HP or LP EGR circuit, followed by the simultaneous application of high and low pressure recirculation and the addition of variable geometry turbine (VGT) control. The paper focused on different goals: firstly, to highlight the change of selected operating parameters (intake pressure and mass flow rate, EGR fraction) in the different configurations affecting the development of in-cylinder pressure curves, ignition delay and combustion process. Secondly, to analyse how rate of heat release is affected by the different EGR and VGT control strategies. Finally, to justify the observed trends of fuel consumption, NOx and soot emissions according to the pressure diagrams and heat release curves, as LP EGR and a different VGT position allowed reductions of 2.1, 50 and 22.8% of these parameters referring to the standard operating mode in the presented experimental point.

Mass air flow control of common-rail diesel engines using an artificial neural network

This paper presents a non-linear control system design for managing the mass flow rate in a common-rail direct-injection diesel engine. In diesel engines, exhaust gas recirculation systems are used to reduce the nitrogen oxide emissions. Since an exhaust gas recirculation system has highly non-linear characteristics and is coupled with a variable-geometry turbocharger, it requires a non-linear control system, which can substitute for an existing conventional lookup-table-based controller, in order to secure a control performance in the transient operating regime. In this project, the objective of the control system is to track the target mass air flow by adjusting the exhaust gas recirculation valve lift. In order to accomplish this objective, a non-linear control system is proposed that adopts a neural-network-based control scheme and an indirect adaptive control approach. The neural adaptive controller determines the position of the exhaust gas recirculation valve lift for tracking target values, based on measured values. An error back-propagation algorithm for online training of neural networks is employed. The proposed control system was validated with engine experiments under transient operating conditions. It was demonstrated from experimental results that the proposed control system shows an improved target-value-tracking performance, when compared with conventional mass air flow controllers.

Impact of Intake CO2 Addition and Exhaust Gas Recirculation on NOx Emissions and Soot Reactivity in a Common Rail Diesel Engine

The impact of intake CO2 addition and exhaust gas recirculation (EGR) on engine combustion characteristics, NOx emissions, and soot oxidative reactivity was studied in a common rail diesel engine equipped with a cooled EGR system. The engine test results and the heat release analysis show that the reduced flame temperature, induced by the reduction of the oxygen concentration (dilution effect) is the dominant mechanism via which CO2 and EGR lower NOx emissions in diesel engines. On the other hand, the collected soot from the engine tests was examined for its oxidative reactivity using a thermogravimetric analyzer (TGA). Results show that EGR has a significant effect on soot reactivity and results in higher initial active sites compared to the CO2 case. We conclude that the reduced flame temperature (thermal effect) which is a consequence of the dilution effect is responsible for the observed increase in soot reactivity. These results confirm observations from our past work on flame soot, which showed that the peak adiabatic flame temperature is the governing factor affecting soot reactivity. These findings imply that driving the combustion concepts toward low temperature is favorable to effectively control engine pollutants, including soot reactivity.

A Study on Reduction of Oxides of Nitrogen With Jatropha Oil Based Bio Diesel

The Continuous depleting oil resources and stringent emission norms leads to increase in interest in Biodiesel fuel. Biodiesel is a renewable fuel made from vegetable oil or animal fats. World’s maximum biodiesel is produced from edible oils, raising the concern for the global scarcity of edible oil supply. In order to defeat the situation, research has been conducted to produce biodiesel by using non-edible oils like Jatropha. Jatropha Biodiesel (JOME) is being accepted as promising renewable alternatives to diesel fuels. Jatropha Biodiesel have advantages over the conventional diesels, as they are known to produce reduced emissions like CO, HC and Smoke, but the NOx Emission is found to be increased. Use of the Cooled Exhaust Gas Recirculation (EGR) system is one of the most effective techniques currently available for reducing NOx. In the present study performance and emission parameters of a four stroke four cylinder diesel engine fuelled with neat Jatropha Biodiesel with cooled EGR is experimentally investigated. The study showed that the effect of increased NOx emission was found to be reduced with the EGR.

Strategies for emission control in diesel engine to meet Euro VI

Diesel engines are among the most effective engines in the world. Known as strong, economical and robust, they are also recognized for their traditional smoke and high level of nitrous oxides, NOx emissions. In the present study, a basic diesel engine that meets Euro III emissions standards with NOx concentration limited to 5.0g/kWh and the particulate matter limited to 0.100g/kWh was performed in order to evaluate its potential of attending Euro VI standards by developing Exhaust Gas Recirculation (EGR) technique. Euro VI will be used in the European community only in 2013 with NOx limited to 0.4g/kWh and particulate matter to 0.01g/kWh. The main idea is to achieve Euro VI emissions level, changing the EGR components and tuning the injection system. In order to reduce the investigation phase, statistics evaluation were used to define one specific speed and load that render the worst condition to create a high EGR volume at lower speed. The study was driven in two steps. Firstly, it was identified the components of EGR system which had more influence towards NOx reduction associated with fuel consumption and the particulate matter. Secondly, the components improved were implemented to analyze the engine potential. In total three different EGR configurations were performed and the best results obtained with the last version was NOx value equal 0.58g/kWh, what means 8.6 times less than the start values and MIRA, one indicative of particulate matter, which reached 0.1g/kWh, 62.96% smaller than 0.27g/kWh at the beginning. Also, the specific fuel consumption achieved of 208g/kWh was less than the value early defined as a goal which was of 210g/kWh. After these results were obtained in the worst operational condition, it was assumed that the engine had potential to reach Euro VI. Thus, it was submitted to one integral test, the same as the one done during the certification process. The final test showed satisfactory results which means that the strategies used in the present study can be applied to get some insight into engines nowadays and in the future.

Effects of gasoline–diesel and n-butanol–diesel blends on performance and emissions of an automotive direct-injection diesel engine

In the present paper, results of an experimental investigation carried out in a modern diesel engine running at different operating conditions and fuelled with blends of gasoline–diesel and n-butanol–diesel, are reported. The exploration strategy was focused on the management of injection pressure and timing to achieve a condition in which the whole amount of fuel was delivered before ignition. The aim of the paper is to evaluate the effects of fuel blends, which have low cetane number (CN) and are more resistant to auto-ignition than diesel fuel, on performance and engine-out emissions. Blends were mixed by the baseline diesel (D00) with 40% of commercial unleaded gasoline (G40) and 40% of n-butanol (B40). Fuel consumption and engine-out gaseous and smoke emissions from fuel blends were measured and compared to the neat diesel fuel. The investigation was performed on a turbocharged, water-cooled, direct-injection diesel engine, equipped with a common-rail injection system. The engine equipment included an exhaust gas recirculation system controlled by an external driver, a piezo-quartz pressure transducer to detect the in-cylinder pressure signal and a current probe to acquire the energizing current to the injectors. Engine tests were carried out at two engine operating conditions: 2000 r/min at 0.5 MPa and 2500 r/min at 0.8 MPa brake mean effective pressure, exploring the effect of start of injection, O2 concentration at intake and injection pressure on combustion behaviour and engine-out emissions. Taking advantages of the higher resistance of G40 and B40 to auto-ignition, it was possible to extend the range in which a partial premixed combustion was achieved. The management of injection pressure, O2 concentration at intake and injection timing allowed partial premixed combustion to be obtained by extending the ignition delay, both for diesel fuel and blends. The longer ignition delay and the better mixing before combustion made more advanced injection timings, which reduced smoke and nitrogen oxide emissions, possible. The joint effect of higher resistance to auto-ignition and higher volatility of n-butanol and gasoline improved the emissions of the blends compared to the neat diesel fuel, with a low penalty on fuel consumption.

Analysis of different exhaust gas recirculation architectures for passenger car Diesel engines

Different Exhaust Gas Recirculation (EGR) system architectures have been evaluated by means of both experimental tests and numerical simulation; in addition to the experimental tests, a one-dimensional fluid-dynamic engine model has been built in order to assess the potential of a Dual Loop (DL) EGR system – a combination of Short Route (SR) and Long Route (LR) EGR systems. Substantial reductions of the NOx emissions have been achieved using the LR EGR layout both under steady state and transient operating conditions: a reduction of up to 15% over the first 60s of the Extra Urban Driving Cycle (EUDC) was obtained with the LR layout. An optimal combination of LR and SR has led to a further reduction of 5% of the nitrogen oxide emissions, due to a faster response of the EGR system during transients. Finally some fundamental knowledge that can be used to control the EGR flow rate more accurately has been gathered, by means of the numerical simulation, especially for the Dual Loop EGR system layout.

Systems optimisation of an active thermal management system during engine warm-up

Active thermal management systems offer a potential for small improvements in fuel consumption that will contribute to upcoming legislation on carbon dioxide emissions. These systems offer new degrees of freedom for engine calibration; however, their full potential will only be exploited if a systems approach to their calibration is adopted, in conjunction with other engine controls. In this work, a design-of-experiments approach is extended to allow its application to transient drive cycles performed on a dynamic test stand. Experimental precision is of crucial importance in this technique since even small errors would obscure the effects of interest. The dynamic behaviour of the engine was represented mathematically in a manner that enabled conventional steady state modelling approaches to be employed in order to predict the thermal state of critical parts of the engine as a function of the actuator settings. A 17-point test matrix was undertaken, and subsequent modelling and optimisation procedures indicated potential 2–3% fuel consumption benefits under iso-nitrogen oxide conditions. Reductions in the thermal inertia appeared to be the most effective approach for reducing the engine warm-up time, which translated approximately to a 1.3% reduction in the fuel consumption per kilogram of coolant. A novel oil-cooled exhaust gas recirculation system showed the significant benefits of cooling the exhaust gases, thereby reducing the inlet gas temperature by 5 °C and subsequently the nitrogen oxide emissions by 6%, in addition to increasing the warm-up rate of the oil. This suggested that optimising the thermal management system for cooling the gases in the exhaust gas recirculation system can offer significant improvements. For the first time this paper presents a technique that allows simple predictive models of the thermal state of the engine to be integrated into the calibration process in order to deliver the optimum benefit. In particular, it is shown how the effect of the thermal management system on the nitrogen oxides can be traded off, by advancing the injection timing, to give significant improvements in the fuel consumption.

Precedent-Free Fault Isolation in a Diesel Engine Exhaust Gas Recirculation System

In this paper, a recently introduced model-based method for precedent-free fault detection and isolation (FDI) is modified to deal with multiple input, multiple output (MIMO) systems and is applied to an automotive engine with exhaust gas recirculation (EGR) system. Using normal behavior data generated by a high fidelity engine simulation, the growing structure multiple model system (GSMMS) approach is used to construct dynamic models of normal behavior for the EGR system and its constituent subsystems. Using the GSMMS models as a foundation, anomalous behavior is detected whenever statistically significant departures of the most recent modeling residuals away from the modeling residuals displayed during normal behavior are observed. By reconnecting the anomaly detectors (ADs) to the constituent subsystems, EGR valve, cooler, and valve controller faults are isolated without the need for prior training using data corresponding to particular faulty system behaviors.

Investigation on combustion characteristics and emissions of diesel/hydrogen mixtures by using energy-share method in a diesel engine

Abstract Considering hydrogen as a clean alternative fuel for engines, this paper is to develop a procedure to add hydrogen in an intake manifold and to design an exhaust gas recirculation ( EGR ) system for a direct injection diesel engine. The cylinder gas pressure, air mass flow, fuel mass flow, and emissions (such as CO, CO 2 , HC, NO X , and smoke) were measured under various engine loads and 0%–40% EGR ratios adjusting the hydrogen-energy-share ratio at 0%–20%, meaning that the energy of hydrogen replaced 0%–20% that of diesel fuel. The combustion characteristics such as cyclic variations, heat release rate, brake thermal efficiency, and specific fuel consumption ( SFC ) were determined. The results show that the variation coefficient values of indicated mean effective pressure ( IMEP ) are from 0.9% to 2.8%. The rate of decrease in the smoke emission is 37.6%, and that in the NO X emission is 59.5% for a 60% load, 40% EGR ratio, and 20% added hydrogen.

Experimental study on the effects of HP and LP EGR in an automotive turbocharged diesel engine

An experimental investigation was performed with a view to comparing high and low pressure exhaust gas recirculation systems (HP and LP EGR) fitted on an automotive turbocharged diesel engine, focusing on analysing their influence on fuel consumption, pollutant emissions and the combustion process. Following the development of a prototype cooled LP EGR circuit, the main engine and turbocharger parameters were measured in six part-load operating conditions related to the European driving cycles. Different operating modes were considered, from the simplest and most commonly investigated (without EGR, with HP or LP EGR) to more complex schemes, namely the simultaneous application of high and low pressure recirculation and the addition of variable nozzle turbine (VNT) control. The extensive experimental database made it possible to confirm literature concerning the comparison of recirculating systems and the potential of LP EGR on engine intake temperature and NOx reductions. New aspects were also analysed, such as the balance of the high and low pressure EGR rate in order to achieve maximum NOx reductions in simultaneous applications, the interactions between EGR circuit management and the application of VNT control in order to improve the trade-off between fuel consumption and NOx and soot emissions.

Tier 4 Interim 배기규제 만족을 위한 56kW급 오프로드 차량 EGR 적용에 관한 연구

비도로용 차량의 경우 대부분 디젤엔진을 사용하여 엔진의 특성상 PM과 NOx의 배출이 많은 단점이 있다. 승용 및 상용 디젤 차량의 경우 CRDI 및 후처리 장치를 적용하였고 후처리 장치로 DOC/DPF를 장착함으로써 PM은 약 90% 이상 저감 가능하다. 상반관계인 NOx는 EGR 사용을 통해 1차적으로 NOx 배출량을 감소시키고 LNT, Urea-SCR 등의 DeNOx 시스템으로 NOx의 배출량을 보다 현저히 저감시켜 배기규제를 만족시키고 있다. 본 연구에서는 tier 4 interim 배기규제를 만족하기 위해 56㎾급 오프로드 차량으로 연구를 진행하였다. NOx의 감소를 위해 WGT와 전자 제어방식의 HPL EGR 시스템을 적용하였고 CO와 THC, PM 배출가스를 줄이기 위해 DOC와 DPF를 사용하였다. EGR 시스템을 적용하기 위해 각 조건에 대한 기본 실험을 실시하여 EGR map을 작성하였다. 작성된 map을 NRTC 모드에서 시험하여 map의 적용성을 검증하고 tier 4 interim 배기규제 만족여부를 파악하였다.

Analysis of the Impact of the New Emissions Limits on the Temperatures of the Vehicle Floor

The Kyoto Protocol established the reduction of pollutant emissions limits for all sectors of industrial economy in 8%, compared to 1990´s levels, to be adopted in the period between 2008 and 2012. Individual countries defined a progressive scale for the emission reduction applied to automotive vehicles. These new emission limits are reached altering the calibration of the Electronic Central Unit (ECU), altering the volume and the composition of the catalytic converters and also adding new components to the engine, such as EGR (exhaust gas recirculation) system and phasing sensor. This work evaluates the impact of these modifications in the exhaust system temperatures and in the peripherical devices. In order to meet the requirements of the new emissions limits, the volume of the catalytic converter is higher, increasing the heat rejected. It provokes a temperature raise on the exhaust system and under the vehicle pavement, which impact the functionality of some components and also the passenger's thermal comfort. It is observed that the new emission standards in Brazil resulted in an increase of the vehicle temperatures, affecting the passengers’ thermal comfort, and eventually producing more emissions due to the use of an air conditioning system.

Soot particle size and pollutant emissions characterization from a LD diesel engine equipped with high pressure and low pressure EGR system and operated with conventional and PCCI combustion

The paper analyses the soot Particle Size Distribution Function (PSDF) measurements carried out at the exhaust of a modern automotive diesel engine equipped with a low-pressure Exhaust Gas Recirculation (EGR) system and operating with conventional and Premixed Charge Compression Ignition (PCCI). The results have indicated significant benefits in terms of exhaust raw particle number emission with the adoption of low-pressure EGR system and PCCI calibration and, thanks to the peculiarity of the operating mode of Low Pressure EGR (LPEGR) system, have highlighted the complex link between in-cylinder charge composition and the PSDF characteristics.

Implementation of an experimental pilot reproducing the fouling of the exhaust gas recirculation system in diesel engines

The European emission standards EURO 5 and EURO 6 define more stringent acceptable limits for exhaust emissions of new vehicles. The Exhaust Gas Recirculation (EGR) system is a partial but essential solution for lowering the emission of nitrogen oxides and soot particulates. Yet, due to a more intensive use than in the past, the fouling of the EGR system is increased. Ensuring the reliability of the EGR system becomes a main challenge. In partnership with PSA Peugeot Citroen, we designed an experimental setup that mimics an operating EGR system. Its distinctive features are (1) its ability to reproduce precisely the operating conditions and (2) its ability to measure the temperature field on the heat exchanger surface with an Infra Red camera for detecting in real time the evolution of the fooling deposit based on its thermal resistance. Numerical codes are used in conjunction with this experimental setup to determine the evolution of the fouling thickness from its thermal resistance.

Performance Analysis of a Dual Fuel Engine Using LPG and Diesel with EGR System

This work is aimed at investigating the performance and emission characteristics of a Dual fuel engine operated with Diesel as primary fuel and ignition source and LPG as secondary fuel with EGR (Exhaust Gas Recirculation) system. In dual fuel operation, much of the energy released comes from the combustion of the gaseous fuel, while only a small amount of diesel fuel provides ignition through timed cylinder injection. The effects of Diesel and LPG substitution ratios, engine speed, and load on the equivalent brake specific fuel consumption and gaseous emissions of hydrocarbons, carbon monoxide and nitrogen oxides are examined for LPG-diesel fuel operation and then compared with the original diesel operation. The concept recirculation of the exhaust gases (EGR), re-burning a part of the exhaust gases is being widely used in many practical situations. The results show that, over a wide range of operating conditions (engine speed, load), the dual fuel engine clearly shows the benefits of reduced NOX emissions. However, under low loads, the results indicate high CO and HC emissions and a higher BSFC when compared to those of the corresponding diesel engine. The LPG addition has been premixed with the engine intake air after the pilot injection of the Diesel in small percentages, in order to improve the engine combustion and to reduce pollutant emissions during the mixing-controlled combustion phase. Experiments show that, using the LPG as an additive fuel, while performing the Diesel fuel main injection keeps the unchanged engine efficiency with respect to the traditional Diesel fuel operation mode.

Computer Aided Engineering Applications in Exhaust Gas Recirculation System Development Process

In view of validity,systematicness and integrity issues of computer aided engineering(CAE) applications in the traditional development process of the diesel exhaust gas recirculation(EGR) system,in order to upgrade development capacity of engine manufactures,research has been done on the application of development process with CAE.Based on redefining the CAE elements of engine,taking "Engine-Subsystem-Component" as developing mode,EGR development process based on CAE technologies is established.The results indicate that the EGR system determined by simulation is feasible.NOx emission reduced by about 20% without obviously affecting the power and economy performance,meeting the development requirements.The development process based on CAE can improve development cycles,costs and quality,which realizes the systematicness,completeness and integrity,providing a new method for effective development of the EGR system.