Engine Exhaust Gas Recirculation Research Articles

Effects of Blended Diesel-Biodiesel Fuel on Emissions of a Common Rail Direct Injection Diesel Engine with Different Exhaust Gas Recirculation Rates.

The aim of the study was to investigate the exhaust gas emissions and fuel consumption of a common rail direct injection (CRDI) diesel engine using mixed diesel (B10) and biodiesel (B20-B100) fuels. The study's primary objective was to determine the effects of blended diesel-biodiesel fuel on CRDI emissions based on different exhaust gas recirculation (EGR) rates, including carbon monoxide (CO), carbon dioxide (CO2), oxygen (O2), nitrogen oxide (NOx), and hydrocarbon (HC) emissions, smoke opacity, exhaust gas temperature, and fuel consumption. The CRDI experiments involved adjusting the different engine speeds (1400-3000 rpm) and EGR rates (0 and 12.5%), which were analyzed to determine their impact on these parameters for both blended diesel and biodiesel fuels. The results showed that under the conditions of no EGR (0%), the CO and HC emissions and the smoke opacity were lower than those with a 12.5% EGR rate for all fuel types and all cases. With 12.5% EGR rate, the O2 emissions and the EGT of the CRDI diesel engine decreased, which resulted in significantly lower NOx emissions because of EGR into the combustion chamber. For the maximum engine speed of 3000 rpm and with no EGR, the CO and HC emissions and the smoke opacity were lower than those with a 12.5% EGR rate for all fuel types. With a 12.5% EGR rate at 3000 rpm, the O2 emissions and the exhaust gas temperature were reduced by 0.07% and 2.27%, respectively, and the NOx emissions were reduced by 2.54%. However, with EGR, the CO and HC emissions and the smoke opacity increased by 7.70%, 18.61%, and 0.4%, respectively. Furthermore, the fuel consumption of pure biodiesel (B100) at 3000 rpm with a 12.5% EGR rate was reduced by 2.81% compared to that with a 0% EGR rate. Because the temperature in the combustion chamber is high enough for the engine to run, the EGR reuses a portion of the exhaust gases and can help to minimize the quantity of fuel in the combustion chamber. As a suggestion based on these observations, biodiesel fuel should not exceed B80 because the viscosity and density of fuel that are too high may affect the fuel injection system, both the injectors, and the pressure pump, causing the injectors to be unable to work correctly. These findings can contribute to the development of strategies and technologies for reducing emissions and improving fuel efficiency in CRDI diesel engines.

Effect of Variable-Nozzle-Turbocharger-Coupled Exhaust Gas Recirculation on Natural Gas Engine Emissions and Collaborative Optimization

Equivalent combustion natural gas engines typically utilize exhaust gas recirculation (EGR) systems to tackle their high thermal burden and NOx emissions. Variable nozzle turbochargers (VNT) can increase the engine intake and EGR rate simultaneously, resulting in NOx reduction while ensuring robust power performance. Using a VNT along with engine bench testing, the impact of VNT- and EGR-coordinated control on the performance and emissions of equivalent combustion natural gas engines was investigated under different operating conditions. Subsequently, multi-objective optimization was performed using a support vector machine. The results demonstrated that the use of VNTs in equivalent combustion natural gas engines could bolster the capacity to introduce EGR under several operative conditions and extend the scope of EGR regulation, thereby decreasing the engine’s thermal burden, improving fuel efficiency, and curbing emissions. Owing to the implementation of a multi-objective optimization method based on a support vector regression model and NSGA-II genetic algorithm, VNT and EGR control parameters could be optimized to slightly improve the economy and significantly reduce NOx emissions while maintaining the original engine power performance. At 20 operating points optimized for validation, brake-specific fuel consumption (BSFC) and NOx decreased by 0.94% and 47.0%, respectively, and CH4 increased by 3.7%, on average.

Matching and optimization to minimize fuel consumption and NOx emission for a marine diesel engine with turbo-assisted exhaust gas recirculation

Exhaust gas recirculation (EGR) and two-stage turbocharging technology are widely used in marine diesel engines due to their advantages of reducing nitrogen oxides (NOx) emission and improving fuel economy respectively. The matching of EGR, two-stage turbocharging and diesel engine is significant to realize both advantages simultaneously. Turbo-assisted EGR (TA EGR) can achieve high EGR rate and lower fuel consumption due to a turbocharger driving EGR. In this study, a 1D model of the diesel engine with TA EGR coupling two-stage turbocharging system was established by GT-Power. A theoretical matching method was proposed based on the requirements of excess air coefficient and EGR rate. The matching laws of the coupling system were studied, and the preliminary matching results achieved good effects. A fully connected neural network was used as the optimization agent model of the 1D model, and the NSGA II algorithm was used to carry out the multi-parameter and multi-objective optimizing matching. Considering constrained and unconstrained conditions, independent optimizing matching was carried out under each single load, and the weighted brake specific fuel consumption (BSFC) and weighted NOx under all loads were taken as the target to carry out comprehensive optimizing matching. The results showed that the optimization performance is worse under constrained conditions, while TA EGR coupling adjustable two-stage turbocharging system can achieve comprehensive optimal BSFC and NOx, with weighted BSFC decreasing by 3.57% and weighted NOx decreasing by 75.28% compared with experimental results of the original engine.

Exhaust gas recirculation in a compression-ignition engine with nano coated Al2O3-TiO2 and ethanol fuel

Ethanol is a fuel that is sustainable, made from biomaterials, and oxygenated. It has the potential to lower the amount of particle emissions produced by diesel engines, as well as the amount of CO2 produced during its life cycle. Even though it was indicated by the exhaust gas recirculation (EGR) approach, the pistons, valves, and cylinder heads of the CI engine were coated in a ceramic compound composed of Al2O3 and TiO2. The exhaust gas recirculation (EGR) technology allows for the cooling and redirection of exhaust gas that has been removed from the cylinders of the exhaust system. Following the application of thermal coating to the piston, the performance of the engine's combustion system improved. The elimination of carbon monoxide, hydrocarbons, and smoke is a direct result of the addition of ethanol. According to the findings, there is a decrease in the amount of NOX emissions up to 11.72 g/kWh and 9.49 g/kWh produced by the cooled EGR engine.

Design of an Optimum Compact EGR Cooler in a Heavy-Duty Diesel Engine towards Meeting Euro 7 Emission Regulations

Exhaust gas recirculation (EGR) has been an efficient emission treatment strategy employed in internal combustion engines (ICEs) to cope with NOx emission limits since the introduction of Euro 4 regulations for heavy-duty commercial vehicles. A portion of the exhaust gas is fed back into the intake port, replacing O2 in the fresh air with inert CO2 from the exhaust gas, resulting in a reduction in the combustion temperature and, hence, a reduction in NOx emissions. Considering the high exhaust temperature, this process increases the charge mixture temperature and degrades the volumetric efficiency of the engine. EGR coolers have been introduced as vital parts of EGR exhaust treatment systems with the aim of reducing the intake port temperature to increase volumetric efficiency and further reduce combustion temperatures. EGR coolers are heat exchangers (HXs) that generally employ engine coolant to reduce the EGR temperature with effectiveness values around 0.7~0.85 and downgrade with engine usage owing to soot deposition. Increasing the effectiveness of the EGR cooler has a positive effect on engine volumetric efficiency and reduces NOx, particulate matter (PM), and fuel consumption. The current study involved the design of a microchannel HX for a 500 PS heavy-duty Euro 6 diesel engine EGR cooler. The mechanical and thermal-hydraulic design calculations of the proposed HX were performed using Mathematica software. The optimum HX dimensions for the required boundary conditions were determined, and the performance of the EGR cooler was analyzed for the current and proposed options. Furthermore, Diesel-RK software was used to model the engine performance with NOx, PM, CO2 emissions, and fuel consumption predictions. The results show that the newly proposed microchannel HX design improves NOx, PM, and specific fuel consumption by 6.75%, 11.30%, and 0.65%, respectively.

Exhaust Gas Recirculation on a Nano-Coated Combustion Chamber of a Diesel Engine Fueled with Waste Plastic Oil

Managing waste plastic is becoming a severe challenge. The industry and researchers have been looking at various opportunities in line with circular economy principles for effective plastic waste management. In that context, plastic waste valorization to oil as a substitute to fossil fuel has gained recent attention. In the literature, there exist few studies showing the use of oil derived from waste plastics in blends with other conventional fuels in compression ignition (CI) engines; however, studies on CI engines that use 100% waste-derived fuels are limited. Additionally, the exhaust gas recirculation (EGR) concepts and the use of nano-coated chambers (like pistons, valves and cylinders heads) have been gaining interest purely from the engine performance enhancement perspective in recent years. Therefore, this study investigates engine performance by combining exhaust gas from the EGR technique and waste plastic oil (WPO) as inputs, followed by thermal coatings in the CI engine chambers for performance enhancement. The experimental setup of the engine is developed, and the engine’s piston, valve and cylinder heads are coated with Al2O3-SiO4 material. The CI engine’s energy, emission, and combustion characteristics are tested, followed by a scenario analysis compared with diesel-only fuel. The tested scenarios include a WPO + Al2O3-SiO4, WPO + Al2O3-SiO4 + 10% EGR, and WPO + Al2O3-SiO4 + 20% EGR. The results show that the piston crown’s thermal coating increased the combustion performance. Significant impacts on the carbon monoxide, hydrocarbons, and smoke characteristics are observed for different %EGR rates. The results also showed that the cooled EGR engine has decreased nitric oxide emissions. Overall, the results show that WPO combined with exhaust gas could be a potential fuel for future CI engines.

Parametric investigation of a large marine two-stroke diesel engine equipped with exhaust gas recirculation and turbocharger cut out systems

Albeit the exhaust gas recirculation (EGR) is widely used to reduce the nitrogen oxides (NOx) emissions from large marine two-stroke engines, several challenges emerge for the engine–turbocharging system matching considering the contradictory requirements of the engine and its subsystems operation. Such challenges become more pronounced in complex engine configurations that include parallel turbochargers and the EGR system along with cut out and bypass branches. This study aims at parametrically investigating a large marine two-stroke engine equipped with an EGR system, two parallel turbochargers of different size, and cut out branches. The turbocharging system characteristics are selected targeting the minimisation of the engine specific fuel consumption whilst ensuring compliance with the respective NOx emissions limits and satisfying imposed constraints for the compressors operation. A detailed model of the zero/one dimensional type is developed in the GT-SUITE software and used to simulate the investigated engine along with its subsystems. Simulation runs are performed to investigate the engine with four different turbocharger configurations of varying capacity ratio and under various operating conditions in terms of the EGR rate and engine load. The simulation results are analysed to reveal the impact of the turbocharger selection of the engine performance and emissions parameters. Furthermore, modulation schemes with EGR blower speed control, exhaust gas bypass and cylinder bypass are investigated to overcome the mismatch on the engine components flow rates and avoid turbocharger operational issues. The derived results demonstrate that the lowest weighted BSFC is achieved for the case of 70:30 capacity ratio between the large and small turbochargers, whilst the engine operation with the EGR is associated with a 2.6% penalty in the weighted BSFC. The EGR blower speed control is found sufficient to avoid the compressor overspeed at high engine loads exhibiting the lower BSFC penalty, whereas the cylinder bypass control is appropriate for controlling the compressor speed at low engine loads. This study contributes on delineating the underlying parameters and interactions between the engine components for the investigated marine two-stroke engine and provides recommendations for the engine–turbocharging system matching procedure.

Expansion of the functional abilities of the internal combustion engine exhaust gas recirculation method as a means of reducing harmful emissions

Road transport, as is known, provides high mobility of the population and significant cargo turnover both on a regional and interstate scale. Unlike large stationary sources of pollution, road transport is a huge number of mobile units of equipment operating in various working conditions. Therefore, the report and control of harmful car emissions is difficult. Other consequences of rapid motorization of society are traffic congestion, increased delivery time for goods and passengers, noise and stress of road users, etc. Based on the analysis of the conditions and operating modes of a car in a dense traffic flow, typical for urbanized areas, the article shows the possibility of using the well-known method of exhaust gas recirculation for a new purpose. This is the forced idle mode of the engine, which occurs when the car is braked by the engine without shutting down the transmission, which is present in modern standards for limiting harmful emissions. It is shown that in the indicated mode, it is possible to carry out complete recirculation of gases in order to achieve short-term isolation of the engine from the atmosphere. At the same time, the usage of the gas recirculation method for the main purpose is not excluded – to reduce the emission of nitrogen oxide NO in the engine.

Control-Oriented Physics-Based NOX Emission Model for a Diesel Engine With Exhaust Gas Recirculation

Abstract Stringent NOX emission norm for heavy duty vehicles motivates the use of predictive models to reduce emissions of diesel engines by coordinating engine parameters and aftertreatment. In this paper, a physics-based control-oriented NOX model is presented to estimate the feedgas NOX for a diesel engine. This cycle-averaged NOX model is able to capture the impact of all major diesel engine control variables including the fuel injection timing, injection pressure, and injection rate, as well as the effect of cylinder charge dilution and intake pressure on the emissions. The impact of the cylinder charge dilution controlled by the engine exhaust gas recirculation (EGR) in the highly diluted diesel engine of this work is modeled using an adiabatic flame temperature predictor. The model structure is developed such that it can be embedded in an engine control unit without any need for an in-cylinder pressure sensor. In addition, details of this physics-based NOX model are presented along with a step-by-step model parameter identification procedure and experimental validation at both steady-state and transient conditions. Over a complete federal test procedure (FTP) cycle, on a cumulative basis the model prediction was more than 93% accurate.

Analysis of the influence of dienitro on co and nox emissions in diesel public transport buses with egr and scr systems

Transport of people and goods has always been associated with the generation of some pollution, whether atmospheric, sound or visual. Managing the urban environment presents a major challenge: preserving environmental resources and also ensuring decent living conditions for the current population and for future generations. In the era of motorized and carbonized transport, vehicles are the main source of emission of atmospheric pollutants, mainly in large urban centers and important precursors of ozone. An important advance in minimizing vehicle emissions was the introduction of cleaner and additive fuels into the Brazilian market. The aim of this study was to evaluate the influence of the use of 0.15% dienitro on S50 Diesel in engines with EGR (Exhaust Gas Recirculation) and S10 Diesel in engines with SCR (Selective Catalytic Reduction) and EGR system. The tests were performed with a gas analyzer directly on the exhaust of vehicles with engine speed of 1300 rpm. Results show CO emission reductions of 72.8, 37.9, 15.7% and NOx emission reductions of 48.0, 48.5 and 31.0%, respectively for the S50 EGR, S10 SCR and S10 EGR system. This additive has a slight increase of 1 or 1.5 points in cetane number, low vaporization enthalpy (energy to vaporize) and high combustion enthalpy, ie, Dienitro increased cetane number, faciliting the start of combustion and reducing CO. On the other hand, a fuel that releases less energy during combustion consequently produces lower temperatures within the combustion chamber, ie additives with lower combustion enthalpy have lower NOx emissions.

Experimental study on diesel engine exhaust gas recirculation performance and optimum exhaust gas recirculation rate determination method.

In order to study the exhaust gas recirculation (EGR) performance of marine diesel engines, a venturi high-pressure EGR device was established to overcome the exhaust gas reflow problem based on a certain type of turbocharged diesel engine. The EGR performance test is accomplished and an optimal EGR decision-making optimization method based on grey correlation coefficient modified is proposed. The results show that the venturi tube EGR can basically meet the injection requirements of high-pressure exhaust gas and achieve good results. Through the venturi tube EGR, the NOX emissions reduce significantly with the maximum drop of 30.6%. The explosive pressure in cylinder reduces with the EGR rate increases and the cylinder pressure curve shows a single peak at low-speed conditions and double peaks at high-speed condition. However, the fuel consumption rate, NOX and smoke have been negatively affected. Due to small samples, the traditional evaluation method is difficult to determine the optimal EGR rate reasonably, while the proposed method can effectively solve this problem. It can weaken the shortcomings of subjective judgement and greatly improve the rationality of decision-making results.

Potential for energy and emissions of asymmetric twin-scroll turbocharged diesel engines combining inverse Brayton cycle system

In this paper, a new combined cycle of asymmetric twin-scroll turbocharged diesel engine cycle and inverse Brayton cycle (IBC) for use is proposed. The use of a single asymmetric twin-scroll turbocharged diesel engine cycle is simple in structure and can improve the trade-off between low fuel consumption and nitrogen oxide emissions; however, both the engine exhaust gas recirculation (EGR) rate and the exhaust energy utilization should be further improved. A test bench experiment was performed to validate the numerical models of the single-cycle and combined-cycle approaches. Based on the models, the influence laws of the critical system parameters (turbine asymmetry and the IBC turbine throat area) on the engine performance characteristics were studied. The combined cycle was found to achieve improvements in both the engine EGR rate and the power. Given the same EGR rates at different engine speeds, the power improvement of the combined cycle was found to increase with increasing engine speed and decreasing turbine asymmetry, reaching a maximum of 5.00%. Moreover, further power improvements with an increasing IBC turbine throat area were observed, with the maximum power improvement of 5.78%. Compared with the power turbine, the combined cycle can utilize more waste heat at low and medium engine speeds; thus, the combined cycle is well-suited for use in heavy-duty diesel engines. The new combined cycle described in this report has great potential to provide substantial gains in both engine emissions and energy.

Influence of Exhaust Gas Recirculation on Dairy Scum Biodiesel Operated Diesel Engine Performance

Effort towards prospective utilization of dairy waste scum oil methyl ester (DSOME) is extremely pronounced as a promising sustainable unconventional fuel for diesel engine as they have intrinsic oxygen content emits less HC and CO emission and contradictorily increases the NOx. In this regard, the present study elucidates the influence of engine exhaust gas recirculation (EGR) on diesel engine performance, combustion and emission characteristics operated with DSOME-B20 (20% dairy scum biodiesel, by volume). The brake thermal efficiency (BTE) and brake specific fuel consumption (BSFC) are appreciably improved for 5% and 10% EGR in comparison with 15% EGR rate. Mainly, about 49-57% of NOx can be reduced with 5-15% EGR rate but increasing EGR rate more than 10% dilutes the fresh intake air hence reduces the NOx and increases the HC, CO emissions. Hence use of 5-10% EGR in diesel engine is advantageous to get considerably improved performance and reduced HC, CO and NOx emissions.

Solving the problem of air quality in Indian cities by retrofitting the EGR

This paper touches problem of transportation pollution focusing on NOx reducing in the India. There were India country chosen for study as the second populated country and most polluted cities in the world. As from statistics, it is known that more than 65% of Indian cars are old and they are the main reason of air pollution. Most of the old cars do not have any control measures for eliminating deadli-est gases. Dumping the old cars is not possible, as the poor owns most of the old cars. For eliminating the pollution from old cars, the possible remedy is to control the emission of pollutants. Comparing to all gases in exhaust, nitrogen oxides are the dangerous one. It can may cause up to death. The best method to control the NOx gas is EGR (Exhaust Gas Recirculation) valves. This research mainly focuses on the possible ways of installing EGR in old engines and fabricate an EGR in one of the Indian cars. Maruti Suzuki 800 is best of for fabricating EGR, as it is a base model and most sold Indian car. As the result, there tremendous decreasing in NOx emission also the emission CO2 was reduced. The investigation about fabricating EGR in old vehicle results a positive output after calculated the cost of the fabrication, time consumption, work challenges and other facts. As Indian government adopt this concept, they can reduce the pollu-tion from all types of vehicles to a great extend in few years of time with low investment.

A real-time capable mixing controlled combustion model for highly diluted conditions

A new real-time capable heat release rate model is presented that captures the high dilution effects of exhaust gas recirculation (EGR). The model is a Mixing Controlled Combustion type with enhancements to account for wall impingements, pilot injections, charge dilution caused by EGR at part load. The model was parameterised in two steps using a small set of measured data: the majority of model parameters were identified without EGR before identifying additional EGR related constants. The model performance was assessed based on key metrics: start of combustion; peak heat release and point of peak heat release and cylinder pressure. The model was evaluated over the full engine speed, load and EGR operating envelope and cylinder pressure metrics were predicted with R2 values above 0.94. With EGR, the model was able to predict qualitatively and quantitatively the performance whilst being parameterised by only by a small dataset. The model can be used to enable the engineering of robust new control algorithms and controller hardware for future engines using offline processes.

Effect of addition of hydrogen and exhaust gas recirculation on characteristics of hydrogen gasoline engine

The effects of exhaust gas recirculation (EGR) on combustion and emissions under different hydrogen ratios were studied based on an engine with a gasoline intake port injection and hydrogen direct injection. The peak cylinder pressure increases by 9.8% in the presence of a small amount of hydrogen. The heat release from combustion is more concentrated, and the engine torque can increase by 11% with a small amount of hydrogen addition. Nitrogen oxide (NOx) emissions can be reduced by EGR dilution. Hydrogen addition offsets the blocking effect of EGR on combustion partially, therefore, hydrogen addition permits a higher original engine EGR rate, and yields a larger throttle opening, which improves the mechanical efficiency and decreases NOx emissions by 54.8% compared with the original engine. The effects of EGR on carbon monoxide (CO) and hydrocarbon (HC) emissions are not obvious and CO and HC emissions can be reduced sharply with hydrogen addition. CO, HC, and NOx emissions can be controlled at a lower level, engine output torque can be increased, and fuel consumption can be reduced significantly with the co-control of hydrogen addition and EGR in a hydrogen gasoline engine.

Assessment for innovative combustion on HCCI engine by controlling EGR ratio and engine speed

HCCI (homogeneous charge compression ignition) combustion offers both high efficiency and very low NOx and particulate matter emissions. However, the operating range of HCCI engines is limited by an excessive PRR (pressure rise rate) in high load region, which is the main reason of engine knock. For this problem shown in HCCI combustion, ignition timing should be retarded after TDC (top dead center) by controlling gas temperature properly, and in addition, combustion duration also needs to be ensured adequately. EGR (exhaust gas recirculation) gas is known to have impacts on the history of gas temperature, and the objective of this study is to investigate the influence of EGR ratio on combustion characteristics. The computational modeling work is conducted by using a single-zone code with detailed chemical kinetics. Then, in order to investigate the influence of EGR ratio and the engine speed, contribution matrix has been used to extract important reaction paths from a reaction mechanism.

Investigation of butanol-fuelled HCCI combustion on a high efficiency diesel engine

Highly-diluted diesel homogeneous charge compression ignition (HCCI) combustion can achieve ultra-low NOx and soot emissions but its implementation is impeded by the lack of control on the ignition timing and excessively early combustion phasing (before TDC) that limit the achievable engine load and result in a reduced energy efficiency. The low volatility and high reactivity of common diesel fuels make it non-conducive for HCCI combustion; hence in this work, n-butanol that has a low reactivity and high volatility is studied for HCCI combustion on a single-cylinder high compression ratio (18.2:1) diesel engine without any modifications to the air-path system. The results indicate that n-butanol-fuelled HCCI combustion offers the benefit of ultra-low NOx and smoke emissions with minimal requirements for intake dilution through exhaust gas recirculation (EGR). The low reactivity helps in realizing an optimal combustion phasing, and thermal efficiency levels comparable to that of conventional diesel combustion are consistently achieved. At low-to-mid engine loads (4–7bar IMEP), the emissions are largely insensitive to the boost pressure, and the boost selection is primarily governed by the trade-off between the combustion instability and the thermal efficiency. At higher engine loads, both boost and EGR are required to limit the high pressure rise rates and to modulate the combustion phasing for high thermal efficiency. The load range is extended up to 10bar IMEP in n-butanol HCCI mode while maintaining ultra-low NOx and soot emissions with improved performance characteristics compared to diesel HCCI.

Control strategy of mode transition between low-temperature combustion and conventional combustion in a light-duty diesel engine

Combustion mode transition between low temperature combustion (LTC) and conventional combustion was carried out in a light duty diesel engine. The characteristics of combustion mode transition with various operating parameters including exhaust gas recirculation (EGR) rate changing, EGR path length, engine speed and EGR control system were investigated based on the in-cylinder pressure of each cycle. When the combustion mode transition from low-temperature combustion to conventional combustion occurred, indicated mean effective pressure and hydrocarbon emission were rapidly decreased because of non-optimized injection timing and EGR rate. On the other hand, indicated mean effective pressure and hydrocarbon emission were not changed significantly for the mode transition from conventional combustion to low-temperature combustion. Faster mode transition was obtained with shorter exhaust gas recirculation path. The noise level, as represented by the maximum pressure rise rate, and hydrocarbon emission were significantly influenced by residual gas, fuel injection pressure and engine speed. For the smooth mode transition, injection strategy was modulated by cycle-by-cycle. Injection timing and injection quantity were varied and pilot injection strategy was introduced to attenuate rapid changes of indicated mean effective pressure and maximum pressure rise rate.

Characterization of Soot Deposition and Particle Nucleation in Exhaust Gas Recirculation Coolers

Cooled exhaust gas recirculation (EGR) is used to control engine out NOx (oxides of nitrogen) emissions from modern diesel engines by re-circulating a portion of the exhaust gases into the intake manifold of an engine after cooling it through a heat exchanger commonly referred to as an EGR cooler. However, EGR cooler fouling due to presence of soot particles and hydrocarbons (HC) in engine exhaust leads to a decrease in cooler efficiency and increased pressure drop across the cooler. This can adversely affect the combustion process, engine durability, and emissions. In this study, a multicylinder diesel engine was used to produce a range of engine out HC and soot concentrations to investigate soot deposition and particle nucleation in an EGR cooler. A portion of the engine exhaust was passed through an EGR cooler, while particle size and HC concentration measurements were made at the cooler inlet and outlet. Tests were conducted over a range of EGR cooler coolant temperatures and engine out soot and HC concentrations to determine the impact on the nucleation and accumulation modes of the exhaust particle size distributions. A reduction in the accumulation mode particle concentration at the EGR cooler outlet was observed for high soot concentrations indicating soot deposition within the EGR cooler. As the EGR coolant temperature was reduced, the outlet accumulation mode particle concentration was reduced further, indicating increased soot deposition in the cooler due to increased thermophoresis. There were no signs of diffusiophoresis due to HC diffusion within the cooler over the range of conditions used in the study. A significant increase in outlet nucleation mode particle concentration was observed for the low soot concentrations. This mode increased with either increasing HC concentration or decreasing coolant temperature, indicating the saturation ratio (SR) dependence of the nucleation mode formation. However, as the soot concentration was increased, the nucleation mode disappeared because of HC adsorption onto the increased soot surface area. Copyright 2012 American Association for Aerosol Research