Influence Of Exhaust Gas Recirculation Research Articles

Effect of exhaust gas recirculation on performance and emission characteristics of a diesel engine fuelled with tamarind biodiesel

ABSTRACTThe present research work focuses on the influence of exhaust gas recirculation (EGR) on the characteristics of the diesel engine operated with 20% tamarind seed methyl ester (TSME 20) as the renewable fuel. The use of TSME 20 as biodiesel results in closer performance characteristics with diesel fuel. However, TSME 20 biodiesel blend generated higher oxides of nitrogen (NOX) emissions at all operating conditions. Firstly, tests are performed using diesel and TSME 20 biodiesel blend at constant speed under different loads. Thereafter, experiments are conducted on TSME 20 with EGR rates at different concentrations. The test results revealed that with TSME 20 with 20% EGR rate, NOX emissions are reduced by 45.67% and 52.69% when compared to diesel and TSME 20. However, there is a slight reduction in brake thermal efficiency. Hence, the use of 20% EGR rate to TSME 20 is an optimum approach for better control of NOX emissions.Abbreviations BDC: bottom dead centre; BMEP: brake mean effective pressure; BSFC: brake-specific fuel consumption; BTE: brake thermal efficiency; CO: carbon monoxide; CO2: carbon dioxide; EGR: exhaust gas recirculation; FSN: filter smoke number; HC: hydrocarbon; kWh: kilo Watt hour; NOX: oxides of nitrogen; ppm: parts per million; SO: smoke opacity; TDC: top dead centre; TSME: tamarind seed methyl ester; TSME 20: 20% tamarind seed methyl ester; TSME 20–20%: tamarind seed methyl ester with 80% diesel; TSME 10% EGR: TSME 20 with 10% exhaust gas recirculation; TSME 20% EGR: TSME 20 with 20% exhaust gas recirculation; TSME 30% EGR: TSME 20 with 30% exhaust gas recirculation

Influence of Exhaust Gas Recirculation on Combustion and Emission Characteristics of Diesel Engine Fuelled with 100% Waste Cooking Oil Methyl Ester

The present research work deals with the application of 30% exhaust gas recirculation (EGR) in a direct injection compression ignition engine fuelled with 100% waste cooking oil methyl ester and conventional diesel. In the first phase of this research work, the performance, emission and combustion characteristics of diesel engine are investigated with the supply of fresh air–fuel mixture for conventional diesel and waste cooking oil methyl ester as fuels and in the second phase the fresh air–fuel mixture is blended with 30% exhaust gas. The study reveals that the 30% EGR addition decreased the brake thermal efficiency by 8 and 18% for conventional diesel and 100% waste cooking oil methyl ester as fuels. Nitrogen oxides emission is reduced to a great extent by 47.5% for diesel fuel and 58.9% for biodiesel fuel at full load condition. Further, the 30% EGR has substantially increased the carbon monoxide and unburnt hydrocarbon emissions for both the fuels at maximum brake mean effective pressure. In addition similar pattern of in-cylinder gas pressure, heat release rate, cumulative heat rate have been observed for fresh air fuel mixture and 30% EGR under various loading conditions.

Experimental study of the influence of exhaust gas recirculation on heat transfer in the firedeck of a direct injection diesel engine

Emissions control is a key topic for internal combustion engine development. One of the most widespread technologies to reduce the formation of nitrogen oxides is the recirculation of exhaust gas to the engine intake. Besides, carbon dioxide emissions from internal combustion engines can be reduced by increasing engine efficiency. A relevant factor for engine efficiency is heat rejection. The interaction between heat transfer and exhaust gas recirculation is not fully understood. In this paper, an experimental study is presented which aims to shed light on the influence of high pressure exhaust gas recirculation on heat transfer. Three operating points were analyzed. Heat flux was calculated at several locations of the firedeck from temperature measurements. The results showed that the influence of exhaust gas recirculation on heat transfer was significant. Reductions of heat flux up to 18% were observed. The largest reduction was found in the area near the center of the firedeck. To contextualize the findings in the framework of emissions reduction, the trade-off between nitrogen oxides and carbon dioxide was assessed for all test points.

Ignition delays in diesel combustion and intake gas conditions

Ignition delays in diesel combustion under several intake gas conditions, including different oxygen concentrations changed with exhaust gas recirculation quantities and different intake gas temperatures, were measured for four cetane numbers and three compression ratios in a single-cylinder, naturally aspirated, direct injection diesel engine (bore: 110 mm, stroke: 106 mm, and stroke volume: 1007 cm3). The engine has a common rail fuel injection system which can be set to optional injection timings and has an injector with a needle lift sensor to accurately estimate the injection timing. The intake oxygen concentrations were set by the quantity of exhaust gas recirculation gas, and the intake gas temperatures were changed with a water-cooled exhaust gas recirculation cooler and an electric heater in the intake pipe. Three compression ratios, 16.7, 18.0, and 21.3, were established with three pistons of different cavity volumes. Four fuels with different cetane numbers, 32 (CN32), 45 (CN45), 57 (CN57), and 78 (CN78), consisting of normal and isoparaffins, were examined for the three compression ratios, and the influence of exhaust gas recirculation and intake gas temperature is discussed for 12 combinations of compression ratios and cetane numbers. The results showed that the ignition delay increases linearly with the 1.67 power of the decrease in the intake oxygen concentration changed with cooled exhaust gas recirculation at the same cetane number and the same compression ratio. The ignition delay increases linearly with lowering intake gas temperatures, and the degree of increase in the ignition delay is more significant with lower cetane number fuels and lower compression ratios. Under practical conditions with the intake oxygen concentration between 21% and 11% and the intake gas temperature between 40°C and 100°C, the changes in ignition delays with the intake oxygen concentration are more significant than the changes with intake gas temperature. The ignition delay increases linearly with lowering compression ratios, and the degree of increase in the ignition delay with reductions in the compression ratio is larger in the cases with lower intake oxygen concentrations and lower cetane number fuels. The ignition delays at the higher compression ratios are significantly shorter than with the lower compression ratios in the case of the same in-cylinder gas temperature at top dead center due to higher in-cylinder gas pressures. The degree of increase in the ignition delay with lower cetane numbers is more significant at lower intake oxygen concentrations and lower compression ratios, and the ignition delay decreases linearly with the 0.25 power of the increase in cetane numbers.

Influence of exhaust gas recirculation on low-load diesel engine performance

In the condition of constant speed and light load, an experimental study of a turbocharged and intercooled diesel engine with exhaust gas recirculation (EGR) system focuses on the influence of different EGR rates on combustion process, dynamic performance, economic performance and emission performance of a diesel engine. With the increase of EGR rate, the oxygen concentration of the intake-side decreases, the fuel air equivalence ratio increases, and the maximum explosion pressure in the cylinder decreases. Meanwhile, the average temperature in the cylinder drops, the ignition delay is prolonged, the ignition timing delays, and the maximum heat release rate decreases. The increase of EGR rate makes NOx emissions decrease obviously and continue to decline. When EGR is low, the smoke rate enlarges slowly with the increase of EGR rate, and enlarges greatly at the rate higher than 43% and reaches the maximum at the rate of 57%. When EGR rate is higher than 61%, the smoke rate drops rapidly, and the content of CO and hydrocarbon (HC) increases rapidly with high EGR rate.

Experimental investigation of the combustion characteristics and the emission characteristics of biogas–diesel dual fuel in a common-rail diesel engine

An experimental study on biogas–diesel dual-fuel compression ignition was conducted in which biogas and diesel are used as the port-injected fuel and the directly injected fuel respectively. The effects of the total lower heating values QLHVs per cycle and the premixed ratio on the combustion characteristics and the emission characteristics are discussed in detail. The results show that, for constant QLHVs, the peak values of the heat release rate curves first decrease and then increase with increasing premixed ratio. Furthermore, the combustion phase is delayed. For a constant premixed ratio, with increasing QLHVs, the heat release rate curves change from a unimodal distribution to a bimodal distribution, and the ignition delay decreases constantly. With higher QLHVs, the nitrogen oxide emissions and the smoke emissions are relatively higher. In addition, the impacts of biogases with different components on the combustion and emissions were also researched. With increasing hydrogen, the combustion becomes increasingly concentrated, which leads to higher nitrogen oxide emissions. The proportion of carbon monoxide in the biogas has a great effect on the carbon monoxide emissions. Also, the influence of exhaust gas recirculation was also studied. With 60% exhaust gas recirculation, the nitrogen oxide emissions can be inhibited effectively.

Experimental and numerical study on NOx formation in CH4–air mixtures diluted with exhaust gas components

This study provides fundamental experimental evidence for the influence of exhaust gas recirculation (EGR) on the formation of NOx and reactivity of premixed flames at atmospheric pressure. The experiments are conducted in a twin counterflow apparatus using methane–air premixed flame compositions with and without EGR dilution. The nitric oxide concentration, temperature and flame burning velocity are measured with non-intrusive, laser diagnostic methods. The combined effects of N2, CO2, and H2O dilution are assessed at flame temperatures of 1850 K and 2000 K. These flames are also directly modeled using the experimental boundary conditions and the GRI-Mech 3.0, San Diego 2005, and Combustion Science and Engineering thermochemical mechanisms to assess the model performance in successfully capturing the EGR conditions.These experimental data confirm the view that EGR does reduce NO formation compared to cases without EGR; however, these reductions are realized only for sufficiently long post-flame residence times. This is due to differing NO formation rates, that are fast for the diluted case, but are slow for the undiluted flame compositions. The prediction of these residence times are obscured by high variability (factor of ≈ 4) and uncertainty (up to ≈ 99%) in the present thermochemical mechanisms. A reduced set of reactions which can assist in the optimization of these models is also presented.

Influence of exhaust gas recirculation on technical, economic, and environmental performance of high-uprated diesel aircraft engine

This paper considers the problem of reducing the nitrogen oxide emissions in exhaust gases (EG) of the diesel aircraft engine by exhaust gas recirculation (EGR). The main directions in improving a working process of diesel engines with EGR system were formulated.

Efficiency improvement of a spark-ignition engine at full load conditions using exhaust gas recirculation and variable geometry turbocharger – Numerical study

The numerical analysis of performance of a four cylinder highly boosted spark-ignition engine at full load is described in this paper, with the research focused on introducing high pressure exhaust gas recirculation for control of engine limiting factors such as knock, turbine inlet temperature and cyclic variability. For this analysis the cycle-simulation model which includes modeling of the entire engine flow path, early flame kernel growth, mixture stratification, turbulent combustion, in-cylinder turbulence, knock and cyclic variability was applied. The cylinder sub-models such as ignition, turbulence and combustion were validated by using the experimental results of a naturally aspirated multi cylinder spark-ignition engine. The high load operation, which served as a benchmark value, was obtained by a standard procedure used in calibration of engines, i.e. operation with fuel enrichment and without exhaust gas recirculation. By introducing exhaust gas recirculation and by optimizing other engine operating parameters, the influence of exhaust gas recirculation on engine performance is obtained. The optimum operating parameters, such as spark advance, intake pressure, air to fuel ratio, were found to meet the imposed requirements in terms of fuel consumption, knock occurrence, exhaust gas temperature and variation of indicated mean effective pressure. By comparing the results of the base point with the results that used exhaust gas recirculation the improvement in fuel consumption of 8.7%, 11.2% and 1.5% at engine speeds of 2000rpm, 3500rpm and 5000rpm is obtained. Additionally, by using the presented numerical methodology the influence of the specific operating parameter on the overall behavior of the complex charging system was shown.

Influence of exhaust gas recirculation on performance and emissions of diesel engine Vikyno RV125-2

This paper presents a research on the influence of exhaust gas recirculation (EGR) on performance and emissions of direct injection diesel engine VIKYNO RV125-2 using three-dimensional CFD code KIVA-3V. In this study, the engine runs at 2400 rpm, 80% nominal load, and EGR concentration is changed from 0% to 40%. Research results indicate that with 20% EGR, the engine power is reduced 3,16%, while the concentrations of both NOx and soot are reduced 12,11% and 67,1%, respectively.

Influence of Exhaust Gas Recirculation, and Injection Timing on the Combustion, Performance and Emission Characteristics of a Cylinder Head Porous Medium Engine

Homogeneous combustion has the potential of achieving both near-zero emissions and low specific fuel consumption. However, the accomplishment of homogeneous combustion depends on the air flow structure inside the combustion chamber, fuel injection conditions, and turbulence as well as ignition conditions. Various methods and procedures are being adopted to establish the homogeneous combustion inside the engine cylinder. In this research work, a highly porous ceramic structure was introduced into the combustion chamber (underside of the cylinder head). The influence of operating parameters such as exhaust gas recirculation (EGR) and injection timing on the combustion, performance, and emission characteristics of such developed engine was investigated in this research work.

Effects of exhaust gas recirculation in diesel engines featuring late PCCI type combustion strategies

The influence of exhaust gas recirculation (EGR) has been analyzed considering experimental results obtained from a Euro 5 diesel engine calibrated with an optimized pilot-main double injection strategy. The engine features a late premixed charge compression ignition (PCCI) type combustion mode. Different steady-state key-points that are representative of the engine application in a passenger car over the New European Driving Cycle (NEDC) have been studied. The engine was fully instrumented to obtain a complete overview of the most important variables. The pressure time history in the combustion chamber has been measured to perform calculations with single and three-zone combustion diagnostic models. These models allow the in-cylinder emissions and the temperature of the burned and unburned zones to be evaluated as functions of the crankshaft angle.The EGR mass fraction was experimentally varied within the 0–50% range. The results of the investigation have shown the influence that high EGR rates can have on intake and exhaust temperatures, in-cylinder pressure and heat release rate time histories, engine-out emissions (CO, HC, NOx, soot), brake specific fuel consumption and combustion noise for a PCCI type combustion strategy. The outputs of the diagnostic models have been used to conduct a detailed analysis of the cause-and-effect relationships between the EGR rate variations and the engine performance. Finally, the effect of the EGR on the cycle-to-cycle variability of the engine torque has been experimentally investigated.

A numerical investigation on the influence of EGR in a supercharged SI engine fueled with gasoline and alternative fuels

Alternative fuels are mostly extracted from renewable resources, and their emission levels can be lower than those of traditional fossil-based fuels. A computational fluid dynamics (CFD) method is utilized to investigate the effects of exhaust gas recirculation (EGR) and initial charge pressure on the emissions and performance of a SI engine. The engine is fueled separately by gasoline and some of potential alternative fuels including hydrogen, propane, methane, ethanol and methanol. The results of simulation are compared to the experimental data. In all validation cases, experimental and numerical results were observed to have good agreement with each other. The calculations are carried out for EGR ratios between 0% and 20% and four cases of initial pressure have been mentioned: Pin=1, 1.2, 1.4, 1.6bar. The effect of EGR on NOx emission of methane is more than other fuels and its effect on IMEP of hydrogen is less than other fuels. From the viewpoints of emission and power, 10% of EGR seems to be the most desirable amount. The most noticeable effect of supercharging is on gasoline unlike hydrogen, which seems to be affected the least. The comparison of results shows that hydrogen due to its high heating value and burning without producing any carbon-based compounds such as HC, CO and CO2 is an ideal alternative fuel compared to the other fuels.

609 HCCI 燃焼の筒内時系列分光計測による燃焼解析(OS8-2 内燃機関の燃焼改善II,OS8 内燃機関の燃焼改善)

Homogeneous Charge Compression Ignition (HCCI) combustion has attracted considerable interest as a new combustion concept for internal combustion engines because of their potential for high efficiency and can reduce nitrogen oxides (NOx) and particulate matter (PM) emissions simultaneously to provide low levels of exhaust pollutants. The HCCI combustion process has two issues to be resolved : ignition timing control, slower combustion. Authors focused combustion attention on exhaust gas recirculation (EGR) to resolve these issues. In this study, the influence of EGR when compression ratio changed in an HCCI engine was investigated by using an actual engine. Light absorption spectroscopic technique was used as the method for analyzing combustion characteristics.

The influence of Exhaust Gas Recirculation (EGR) on combustion and emissions of n-heptane/natural gas fueled Homogeneous Charge Compression Ignition (HCCI) engines

In Homogeneous Charge Compression Ignition (HCCI) combustion, a lean premixed charge combusts simultaneously in multiple sites. Utilizing highly diluted mixtures, and lack of any significant flame propagation, in-cylinder NO x formation is reduced. Making HCCI engine a feasible alternative to conventional engines requires several challenges to be resolved. Combustion timing control is one of the most important of these items. It should be done in order that heat is released at the most optimum phasing for efficiency and emissions. In this study, a Waukesha Cooperative Fuel Research (CFR) single cylinder research engine was used to be operated in HCCI combustion mode fueled by natural gas and n-heptane. The main goal of the experiments was to investigate the possibility of controlling combustion phasing and combustion duration using various Exhaust Gas Recirculation (EGR) fractions. For the analysis of the results, a modified apparent heat release model was developed. The influence of EGR on emissions was discussed. Results indicate that applying EGR reduces mean charge temperature and has profound effect on combustion phasing, leading to a retarded Start of Combustion (SOC) and prolonged burn duration. Heat transfer rate decreases with EGR addition. Under examined condition EGR addition improved fuel economy, reduced NO x emissions and increased HC and CO emissions.

Utilizing Water Emulsification to Reduce NOx and Particulate Emissions Associated with Biodiesel

A key barrier limiting extended utilization of biodiesel is higher NOx emissions compared to petrodiesel fuels. The reason for this effect is unclear, but various researchers have attributed this phenomena to the higher liquid bulk modulus associated with biodiesel and the additional heat released during the breaking of C-C double bonds in the methyl ester groups. In this study, water was incorporated into neat biodiesel (B100) as an emulsion in an attempt to lower NOx and particulate matter (PM) emissions. A biodiesel emulsion containing 10wt% water was formulated and evaluated against an ultra-low-sulfur petroleum diesel (ULSD) and neat biodiesel (B100) in a light-duty diesel engine operated at 1500 rpm and at loads of 68 and 102 Nm (50 and 75 ft-lbs). The influence of exhaust gas recirculation (EGR) was also examined. The incorporation of water was found to significantly lower the NOx emissions of B100 while maintaining fuel efficiency when operating at 0% and 27% EGR; however, NOx emissions were observed to increase slightly for the emulsified fuel when the engine load was raised to 102 Nm (75 ft-lbs). The soot fraction of the particulates (as determined using an opacity meter) was much lower for the B100 and B100-water emulsion compared to the ULSD. In contrast, total PM mass (for the three fuel types) was unchanged for the 0% EGR condition but was significantly lower for the B100 and B100-emulsion during the 27% EGR condition compared to the ULSD. Analysis of the emissions and heat release data indicate that water enhances air-fuel premixing to maintain fuel economy and lower soot formation. The exhaust chemistry of the biodiesel base fuels (B100 and water-emulsified B100) was found to be unique in that they contained measurable levels of methyl alkenoates, which were not found for the ULSD. These compounds were formed by the partial cracking of the methyl ester groups during combustion.

Experimental study of various effects of exhaust gas recirculation (EGR) on combustion and emissions of an automotive direct injection diesel engine

Abstract Cooled exhaust gas recirculation (EGR) is a common way to control in-cylinder NOx production and is used on most modern high-speed direct injection (HSDI) diesel engines. However EGR has different effects on combustion and emissions production that are difficult to distinguish (increase of intake temperature, delay of rate of heat release (ROHR), decrease of peak heat release, decrease in O2 concentration (and thus of global air/fuel ratio (AFR)) and flame temperature, increase of lift-off length, etc.), and thus the influence of EGR on NOx and particulate matter (PM) emissions is not perfectly understood, especially under high EGR rates. An experimental study has been conducted on a 2.0 l HSDI automotive diesel engine under low-load and part load conditions in order to distinguish and quantify some effects of EGR on combustion and NOx/PM emissions. The increase of inlet temperature with EGR has contrary effects on combustion and emissions, thus sometimes giving opposite tendencies as traditionally observed, as, for example, the reduction of NOx emissions with increased inlet temperature. For a purely diffusion combustion the ROHR is unchanged when the AFR is maintained when changing in-cylinder ambient gas properties (temperature or EGR rate). At low-load conditions, use of high EGR rates at constant boost pressure is a way to drastically reduce NOx and PM emissions but with an increase of brake-specific fuel consumption (BSFC) and other emissions (CO and hydrocarbon), whereas EGR at constant AFR may drastically reduce NOx emissions without important penalty on BSFC and soot emissions but is limited by the turbocharging system.

Biodiesel engine performance and emissions in low temperature combustion

Engine performance and emission comparisons were made between the use of soy, Canola and yellow grease derived B100 biodiesel fuels and an ultra-low sulphur diesel fuel in the high load engine operating conditions. Compared to the diesel fuel engine-out emissions of nitrogen oxides (NO x ), a high-cetane number (CN) biodiesel fuel produced comparable NO x while the biodiesel with a CN similar to the diesel fuel produced relatively higher NO x at a fixed start of injection. The soot, carbon monoxide and un-burnt hydrocarbon emissions were generally lower for the biodiesel-fuelled engine. Exhaust gas recirculation (EGR) was then extensively applied to initiate low temperature combustion (LTC) mode at medium and low load conditions. An intake throttling valve was implemented to increase the differential pressure between the intake and exhaust in order to increase and enhance the EGR. Simultaneous reduction of NO x and soot was achieved when the ignition delay was prolonged by more than 50% from the case with 0% EGR at low load conditions. Furthermore, a preliminary ignition delay correlation under the influence of EGR at steady-state conditions was developed. The correlation considered the fuel CN and oxygen concentrations in the intake air and fuel. The research intends to achieve simultaneous reductions of NO x and soot emissions in modern production diesel engines when biodiesel is applied.

A fundamental study on the control of the HCCI combustion and emissions by fuel design concept combined with controllable EGR. Part 2. Effect of operating conditions and EGR on HCCI combustion

In Part 1, the effects of octane number of primary reference fuels and equivalence ration on combustion characteristics of a single-cylinder HCCI engine were studied. In this part, the influence of exhaust gas recirculation (EGR) rate, intake charge temperature, coolant temperature, and engine speed on the HCCI combustion characteristics and its emissions were evaluated. The experimental results indicate that the ignition timing of the first-stage combustion and second-stage combustion retard, and the combustion duration prolongs with the introduction of cooled EGR. At the same time, the HCCI combustion using high cetane number fuels can tolerate with a higher EGR rate, but only 45% EGR rate for RON75 at 1800 rpm. Furthermore, there is a moderate effect of EGR rate on CO and UHC emissions for HCCI combustion engines fueled with n-heptane and RON25, but a distinct effect on emissions for higher octane number fuels. Moreover, the combustion phase advances, and the combustion duration shorten with the increase of intake charge temperature and the coolant out temperature, and the decrease of the engine speed. At last, it can be found that the intake charge temperature gives the most sensitive influence on the HCCI combustion characteristics.

A study of the influence of exhaust gas recirculation and stoichiometry on the heat release in the end-gas prior to knock using rotational coherent anti-Stokes-Raman spectroscopy thermometry

Heat release in the end-gas prior to autoignition was investigated using different experimental methods including transducers for heat flux and pressure as well as rotational coherent anti-Stokes-Raman spectroscopy, which is a laser-based method for non-intrusive instantaneous thermometry of the gas. The time history was examined in the cases of mixtures of various stoichio-metries, where some were diluted with exhaust gas recir-culation (EGR). The measured temperature history was compared with the isentropic temperature calculated from the cylinder pressure trace. This comparison revealed a difference in heat release from low-temperature reactions in the end-gas for the various mixtures tested at a constant indicated mean effective pressure and a fixed position of 50 per cent burnt charge. It is shown that lean mixtures tend to exhibit the highest knock intensity, mainly due to a decrease in specific heat, as compared to the richer mixtures, which result in an earlier knock onset and as a consequence higher knock intensity. Furthermore, the comparison of temperatures indicates that the rich mixtures have a high heat release from low-temperature chemistry, which to some extent negates the higher specific heat of the charge. As a consequence, a slight enrichment of the charge can lead to higher knock intensity in comparison with a stoichiometric mixture. In spite of the lower specific heat of the charge when a stoichiometric charge was diluted with cooled EGR, these mixtures showed a very low tendency to knock.