Gas Recirculation System Research Articles

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.

Passive Containment Cooling System (PCCS) response with Drywell Gas Recirculation System (DGRS) activated during a severe accident scenario with release of non-condensable gas

Abstract The paper presents the experimental results of an integral containment test named T2.1 performed in the PANDA facility. Test T2.1 investigated the effect of a Drywell Gas Recirculation System (DGRS) activation on a Passive Containment Cooling System (PCCS), during a postulated severe accident with release of hydrogen later during the transient (in PANDA facility Helium is used to simulate hydrogen). The containment initial thermal-hydraulic conditions (e.g. temperature, pressure, gas composition, decay heat, etc.) in test T2.1 represent the situation predicted at 1 h after a Loss of Coolant Accident (LOCA) for a specific ESBWR design. Test T2.1 simulated the decay heat which would be released during a transient of about 12.5 h, including structural heat release in the early phase. Test T2.1 includes four main phases. The first phase, lasting for about 10,000 s simulated a LOCA 1 h after SCRAM. The second phase, helium was injected for about 7200 s and the DGRS was activated. The third phase was carried on from 17,200 s to about 43,200 s by keeping the DGRS in operation. In the fourth phase the DGRS was switched off and was observed the PCCS response.

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.

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.

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.

Foam Heat Exchangers: A Technology Assessment

Open-cell porous metal foams have received attention for use in compact heat exchangers due to their increasing availability and improved thermal performance. In recent years, considerable research has been conducted on use of metallic and nonmetallic foams to further improve performance of state-of-the-art heat exchangers. In this paper, we report preliminary results from fabrication, development and experimental investigation of thermal-hydraulic performance of high-temperature metal foam heat exchangers for automotive exhaust gas recirculation (EGR) system. A brief review of nickel–chromium and stainless-steel foam heat exchanger technology and of recent efforts on their manufacturing techniques for a liquid-to-air heat exchange application is presented. Measured heat transfer and pressure drop data for foam heat exchangers and their comparison with performance of a conventional wavy plate-fin heat exchanger are discussed. Technical challenges and risks associated with foam heat exchangers are discussed, along with recommendations for future development.

B-splines for Diesel Engine Emission Modeling

The equivalence between linear interpolation and B-spline functions of degree 1 is described. The equivalence is used to express interpolation based diesel engine NOX and soot emission models as B-spline functions, and to apply data fitting methods for B-spline functions to perform calibration of the models. This strategy leads to that the model calibration can be calculated directly by means of analytically solving a minimization problem. The B-spline representation also makes it possible to control the smoothness and extrapolation behavior of the interpolation maps in the models in a controlled manner. The models have been calibrated using measured steady-state data from a 5-cylinder Volvo passenger car diesel engine with a displacement volume of 2.4 liters, equipped with a turbocharger, an exhaust gas recirculation system, and a common rail injection system. The calibrated model for NOX emissions predicts the NOX mass flow with a root mean square error of 1.6 mg/s, and the calibrated model for soot emissions predicts the soot mass flow with a root mean square error of 0.65 mg/s. The described equivalence between linear interpolation and B-spline functions of degree 1 could also be used for calibration of other models of similar structure.

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.

Condensation Analysis of Exhaust Gas Recirculation System for Heavy-Duty Trucks

The exhaust gas recirculation (EGR) system has been widely used in the automotive and heavy-duty trucks to reduce NOx, SOx, and other controlled emissions. A liquid-cooled or air-cooled heat exchanger is the main constituent of the EGR system. The heat exchanger decreases the temperature of the exhaust gases mixture that flows through the EGR channels and the lower temperatures reduce the content of the controlled gas emissions. Condensation of water vapor is an undesirable by-product of the EGR systems because, in combination with the emission gases, it forms the corrosive sulfuric and nitric acids. The U.S. EPA has suggested that engine makers should turn off their EGR systems periodically to avoid the formation of the corrosive sulfuric and nitric acids. In order to accurately predict the corrosion process, a condensation model has been developed to investigate the rates of formation and diffusion of nitric acid and sulfuric acid to the cold tube surface. A three-dimensional computational fluid dynamics (CFD) simulation has been conducted for a typical EGR cooler during normal operating conditions of Tier 4 heavy-duty trucks. A lumped, 1D heat and mass transfer model has also been developed to study the most important physical aspects of the condensation process. The CFD and the analytical results of the rate of condensation and local fluid properties are an important and inexpensive complement to more expensive experimental measurements and testing. Such models may be used to improve the design and to optimize the operating conditions of the EGR systems and may become valuable tools in the design and manufacturing of the next generation of EGR systems for diesel engines. The model developed is general and the techniques and numerical results of this study may be extended to engine reliability, corrosion reduction, and damage prevention of other industrial engines.

A Research of Corrosion for Generated Condensate at Intercooler in Emission Recirculation Engine System

Because of environmental pollution caused by automobile exhaust gas regulations have been strengthened. Engine development has already progressed a lot. Thus, in recently, exhaust gas recirculation system is being developed in industry. Exhaust gas recirculation can be satisfied the emission regulations. However, engine related parts are changed environment. When the exhaust gas recirculation, corrosive elements are recycled into the gas phase. Depending on the temperature of the gas condensate composition and concentration is changing. Containing NO3- condensate can cause corrosion for metal parts. In this study, the exhaust gas emissions to satisfy the circular engine intercooler parts of the system in the circulation of the condensate corrosion due to gas condensate were investigated.

Experimental study on performance and emissions of a high speed diesel engine fuelled with n-butanol diesel blends under premixed low temperature combustion

In the present paper, results of an experimental investigation carried out in a modern diesel engine running at different operative conditions and fuelled with blends of diesel and n-butanol, are reported. The exploration strategy was focused on the management of the timing and injection pressure to achieve a condition in which the whole amount of fuel was delivered before ignition. The aim of the paper was to evaluate the potential to employ fuel blends having low cetane number and high resistance to auto-ignition to reduce engine out emissions of NOx and smoke without significant penalty on engine performance. Fuel blends were mixed by the baseline diesel (BU00) with 20% and 40% of n-butanol by volume. The n-butanol was taken by commercial production that is largely produced through petrochemical pathways although the molecule is substantially unchanged for butanol produced through biological mechanisms.The experimental activity was performed on a turbocharged, water cooled, DI diesel engine, equipped with a common rail injection system. The engine equipment includes 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 2500rpm and 0.8MPa of BMEP exploring the effect of start of injection, O2 concentration at intake and injection pressure on combustion behavior and engine out emissions. The in-cylinder pressure and rate of heat release were investigated for the neat diesel and the two blends to evaluate engine performance and exhaust emissions both for the conventional diesel and the advanced premixed combustion processes.The management of injection pressure, O2 concentration at intake and injection timing allowed to realize a partial premixed combustion by extending the ignition delay, particularly for blends. The main results of the investigation made reach smoke and NOx emissions due to the longer ignition delay and a better mixing control before combustion. The joint effect of higher resistance to auto ignition and higher volatility of n-butanol blends improved emissions compared to the neat diesel fuel with a low penalty on fuel consumption.

Passive containment cooling system (PCCS) response with Drywell Gas Recirculation System (DGRS) activated during a postulated Loss of Coolant Accident (LOCA)

Passive Containment Cooling Systems (PCCS) are characterizing the design of several advanced LWR such as SBWR, ESBWR, ABWR-II, etc. These systems should ensure the mitigation of postulated accidents both under Design Basic Accident (DBA) and Beyond DBA (BDBA) conditions. Some ALWR designs integrated in the PCCS a system called Drywell Gas Recirculation System (DGRS). The DGRS works like a fan, with inlet flow lines connected to the Passive Cooling condenser (PCC) vent lines and the outflow line connected to the Drywell (DW). The present paper presents the experimental results of an integral containment test performed in the PANDA facility. The initial conditions (temperature, pressure, gas composition, decay heat, etc.) for the test represent the containment situation 1 h after a Loss of Coolant Accident (LOCA). The test consists of two phases (6 h each) for a total duration of about 12 h. In the first phase has been simulated the response of the PCCS to a LOCA, in the second phase the DGRS has been activated and has been investigated the effect of such activation on the overall PCCS response. The test shows that the activation of the DGRS has an effect on the overall PCCS characteristics, i.e. composition of gas mixture in the PCC tubes, stratification in the Wetwell (WW), DW–WW pressure differences, timing for the opening of the Vacuum Breakers (VB) and overall containment pressure.

Coke-free dry reforming of model diesel fuel by a pulsed spark plasma at low temperatures using an exhaust gas recirculation (EGR) system

Dry reforming of diesel fuel, an endothermic reaction, is an attractive process for on-board hydrogen/syngas production to increase energy efficiency. For operating this dry reforming process in a vehicle, we can use the exhaust gas from an exhaust gas recirculation (EGR) system as a source of carbon dioxide. Catalytic dry reforming of heavy hydrocarbon is a very difficult reaction due to the high accumulation of carbon on the catalyst. Therefore, we attempted to use a non-equilibrium pulsed plasma for the dry reforming of model diesel fuel without a catalyst. We investigated dry reforming of model diesel fuel (n-dodecane) with a low-energy pulsed spark plasma, which is a kind of non-equilibrium plasma at a low temperature of 523 K. Through the reaction, we were able to obtain syngas (hydrogen and carbon monoxide) and a small amount of C2 hydrocarbon without coke formation at a ratio of CO2/Cfuel = 1.5 or higher. The reaction can be conducted at very low temperatures such as 523 K. Therefore, it is anticipated as a novel and effective process for on-board syngas production from diesel fuel using an EGR system.

Study of Hg and SO 3 behavior in flue gas of oxy-fuel combustion system

Oxy-fuel combustion systems have been under development to reduce CO 2 emissions from coal-fired power plants. In oxy-fuel combustion system, Hg in the flue gas causes corrosion in CO 2 purification and compression units. Also, SO 3 in the flue gas corrodes the equipment and ducts of oxy-fuel combustion system. Therefore, Hg and SO 3 need to be removed. Babcock-Hitachi conducted tests using a 1.5 MWth Combustion & Air Quality Control System (AQCS) test facility which consists of oxygen supply unit, furnace, Selective Catalytic Reduction (SCR) catalyst, Clean Energy Recuperator (CER), Dry Electrostatic Precipitator (DESP), flue gas recirculation system, Wet Flue Gas Desulfurization (WFGD), and CO 2 Compression and Purification Unit (CPU). In both cases of air and oxy-fuel combustion, the Hg removal across the DESP could be improved, and SO 3 concentration at the DESP outlet could be reduced to less than 1 ppm by installing a CER upstream of the DESP and reducing the gas temperature at the DESP inlet. Hg was not dissolved in the drain recovered from CO 2 compressor, and may be adsorbed at an inner part of CO 2 compressor. This indicated that Hg needs to be removed at a location upstream of the CO 2 compressor to prevent corrosion of the compressor.

In-Cylinder Equivalence Ratio Measurements in an EGR Equipped Engine

A single-cylinder natural gas fueled engine equipped with an exhaust gas recirculation (EGR) system was ignited using a laser. The broadband emission from the spark kernel was spectrally resolved, and the peaks corresponding to Hα, N, and O atoms were measured for a range of conditions with global equivalence ratios ranging between 0.6 and 1.0 and for exhaust gas recirculation fractions up to 29%. The (Hα/O) and (Hα/N) peak intensity ratios from the spectral scans correlated extremely well (R2>0.97) with local oxygen based equivalence ratios. Appropriate relations were developed to relate such values to global equivalence ratios and the EGR rate. For a homogeneous intake charge, the present laser induced breakdown spectroscopy diagnostic enables an estimation of one of the two values, global equivalence ratio or EGR rate, with the knowledge of the other.

High-Temperature Galling Characteristics of TI-6AL-4V with and without Surface Treatments

Galling is a severe form of surface damage in metals and alloys that typically arises under relatively high normal force and low sliding speed and in the absence of effective lubrication. It can lead to macroscopic surface roughening and seizure. The occurrence of galling can be especially problematic in high-temperature applications like diesel engine exhaust gas recirculation system components and adjustable turbocharger vanes, because suitable lubricants may not be available, moisture desorption promotes increased adhesion, and the yield strength of metals decreases with temperature. Oxidation can counteract these effects to some extent by forming lubricative oxide films. Two methods to improve the galling resistance of titanium alloy Ti-6Al-4V were investigated: (a) applying an oxygen diffusion treatment and (b) creating a metal–matrix composite with TiB2 using a high-intensity infrared heating source. A new oscillating three-pin-on-flat, high-temperature test method was developed and used to characterize galling behavior relative to a cobalt-based alloy (Stellite 6B, HP Alloys, Windfall, IN). The magnitude of the oscillating torque, the surface roughness, and observations of surface damage were used as measures of galling resistance. Due to the formation of lubricative oxide films, the galling resistance of the Ti alloy at 485°C, even nontreated, was considerably better than it was at room temperature. The infrared (IR)-formed composite displayed reduced surface damage and lower torque than the substrate titanium alloy.