Cold Exhaust Gas Recirculation Research Articles

Comprehensive Analysis of Compression Ratio, Exhaust Gas Recirculation, and Pilot Fuel Injection in a Diesel Engine Fuelled with Tamarind Biodiesel

The global automotive industry is facing significant challenges, including dwindling fossil fuel reserves, rising crude oil prices, and increasingly strict emission regulations. To address these concerns, this study investigates the impact of the compression ratio (CR) and exhaust gas recirculation (EGR) on the performance and emissions of a common rail direct injection (CRDI) diesel engine fuelled with a 20% blend of tamarind seed methyl ester (TSME 20) biodiesel. The study employed an open-type electronic control unit to implement pilot fuel injection at a rate of 30%, 23° before the top dead centre (TDC), and at a higher pressure of 600 bar. Three CRs (16:1, 18:1, 20:1) and two types of EGR (hot and cold EGR at 10%) were evaluated. Diesel fuel at CR 18 was used as a baseline for comparison. The experimental procedure involved conducting tests with TSME 20 at CR 16, 18, and 20. Subsequently, TSME 20 at CR 20 + Hot EGR 10% and TSME 20 at CR 20 + Cold EGR 10% were examined. The results showed that TSME 20 operated at a higher CR (CR 20) exhibited improved diesel engine performance and significant reductions in harmful exhaust emissions. Additionally, cold EGR at 10% was more effective in reducing CO, CO2, and NOx emissions from TSME 20 than hot EGR. The findings of this study provide valuable insights into optimizing diesel engine operation to achieve a balance between performance enhancement and emission reduction through tamarind seed biodiesel blends and different EGR techniques. The implementation of these strategies holds considerable potential in addressing the automotive industry’s challenges, including ecological considerations and fuel price fluctuations.

Review on performance and emission of spark ignition engine using exhaust gas recirculation

ABSTRACT Modernizing electronic control and developing new exhaust gas recirculation (EGR) valves have made it possible to improve EGR accuracy and shorten transient response times. With this paper, we have outlined the findings of research on the effects of various EGR ratios on engine emissions, knock suppression, and charge combustion. Results from experiments conducted by many researchers are summed up as 15% − 18% EGR is found to successfully reduce NOx emissions without impacting engine performance. Because exhaust fumes dilute the fuel/air mixture, this can lead to inefficient combustion, which can lower brake thermal efficiency. According to the findings, selecting the right EGR ratio and spark timing is essential for maximizing engine performance. examined how cold EGR affected knock intensity. It was found that the maximum compression temperature decreased in range of 30–40 kelvin and the cylinder pressure decreased up to 0.4 bar as the EGR increased from 7 to 13%. This demonstrated that the knock was effectively repressed. Because of a buildup of carbon deposits, the EGR valve frequently sticks. In addition to higher fuel consumption or poorer performance, clogged EGRs frequently result in black smoke coming from the exhaust.

Numerical and Experimental Study on the Impact of Mild Cold Exhaust Gas Recirculation on Exhaust Emissions in a Biodiesel-Fueled Diesel Engine

Abstract This work evaluated the effect of cooled exhaust gas recirculation (EGR) on fuel consumption and pollutant emissions from a diesel engine fueled with B8 (a blend of biodiesel and no. diesel 8:92% by volume), experimentally and numerically. Experiments were carried out on a diesel power generator with varying loads from 5 kW to 35 kW and 10% of cold EGR ratio. Exhaust emissions (e.g., total hydrocarbons (THCs), nitrogen oxides (NOx), carbon monoxide (CO), etc.) were measured and evaluated. The results showed mild EGR and low biodiesel content have minor impact of engine-specific fuel consumption, fuel conversion efficiency, and in-cylinder pressure. Meanwhile, the combination of EGR and biodiesel reduced THC and NOx up to 52% and 59%, which shows promising effect on overcoming the particulate matter–NOx tradeoff from diesel engine. A three-dimensional computational fluid dynamics engine model incorporated with detailed biodiesel combustion kinetics and NOx formation kinetics was validated against measured in-cylinder pressure, temperature, and engine-out nitric oxide emission from diesel engine. This valid model was then employed to investigate the in-cylinder temperature and equivalence ratio distribution that predominate NOx formation. The critical results showed that the reduction of NOx emission by EGR and biodiesel is obtained by a little reduction of the local in-cylinder temperature and, mainly, by creating comparatively rich combusting mixture, which makes the combustion path pass through lower NOx zone in the ϕ–T diagram.

Experimental investigation of compressed natural gas using in an indirect injection diesel engine at different conditions

Because of deficiency of fossil fuels and stringent emission legislations of environmental pollutants, many researches have been done on the sustainable fuel resources. Natural gas ranks as one of the most popular alternative fuels for public transportation due to its lower impact on human health and air quality, low cost, and appropriate availability. The novelty of this experimental work is replacing different mass fractions of diesel fuel with natural gas in an indirect injection diesel engine and evaluating its effect on the emissions of soot and nitrogen oxides, and brake specific fuel consumption in the presence of cold exhaust gas recirculation. The test bed is provided in the internal combustion engine laboratory of the Ferdowsi University of Mashhad by modifications on a naturally aspirated indirect injection diesel engine. Experiments were done at different equivalence ratios with 1200, 2000, and 3000 rpm and at 25, 50, and 75% of the full load in each speed. Replacing 40% mass fraction of input diesel fuel by adding natural gas resulted in a maximum 74% reduction of soot; the reason is a decrease in carbon to hydrogen ratio in the mixture. Also adding 40% natural gas made a maximum 54% reduction in nitrogen oxides mainly because of more homogeneity in the fuel mixture which reduces hot spots in the combustion chamber, and lower nitrogen content in the fuel. Moreover, maximum decrease in brake specific fuel consumption was 15%, due to increase in power output meanwhile lubricated engine friction remains unchanged in each speed. These research engine improvements in average are 62% for NOx and 35% for soot emission indicating acceptable decrease in exhaust emissions in comparison with allowable decrease in Euro emission standards.

Experimental and numerical analyses of cold EGR effect on combustion, performance and emissions of natural gas lean-burn engine with pre-chamber combustion system

The pre-chamber combustion system is an attractive strategy to enable the operation of spark-ignition engines in lean conditions and to maintain a suitable combustion process. Also, cold exhaust gas recirculation (EGR) system can be used during air dilution operation to overcome issues of emissions. In this research, an experimental and numerical investigation has been carried out to evaluate the potential of pre-chamber combustion system combining with EGR system. The results show that the use of pre-chamber combustion and cold EGR at the same time in a lean-burn engine considerably reduced mass release of NOx from 8.83 g/kWh to 4.40 g/kWh (50% reduction) and slightly increased CO emission, while it had no significant effect on CO2 emission. The engine output power and IMEP decreased by 3–4% per 5% of cold EGR and the efficiency slightly decreased (lower than 1%). A gradual increase in cold EGR volume from 0% to 20% reduced the indicated work availability and heat loss availability by approximately 1.4%; however, on the contrary, the exhaust gas availability and the combustion irreversibility declined by 1.1% and 1.4%, respectively. Moreover, exergy efficiency decreased from 41.9% to 40.6%, with a slight reduction in entropy generation. The results indicated that an ideal range could be defined for cold EGR in an engine equipped with the pre-chamber combustion system in which pollutant emission is at the lowest level, and the engine output power is maintained to a great extent. The ideal range for the engine used in this study was EGR = 10%.

Thermodynamic evaluation of an ammonia-fueled combined-cycle gas turbine process operated under fuel-rich conditions

Ammonia is a promising energy carrier and carbon-free fuel for power generation using combined-cycle gas turbines. However, its use results in the generation of relatively large amounts of NOx in the combustor. To address this issue, we propose a combined-cycle configuration including exhaust gas recirculation (EGR), in which the gas turbine is operated under fuel-rich conditions and the uncombusted hydrogen is burned in the heat-recovery steam generator (HRSG). Thus, hydrogen in the flue gas of the gas turbine increases the output power and improves the thermal efficiency of the system. Furthermore, in the combined system with EGR, the exhaust gas does not contain O2 and the combustion temperature can be reduced without altering the equivalence ratio. The proposed system is evaluated by thermodynamic modeling, and we find that low NOx emissions can be achieved while maintaining high thermal efficiency. Cold EGR is likely to be required to maintain the turbine inlet temperature below a technically feasible level, and a tradeoff between thermal efficiency and the NOx concentration at the combustor outlet is observed. The ideal operating conditions for this process thus depend on the technically feasible turbine inlet temperature, EGR ratio, and the permissible NOx concentration in the exhaust gas.

The effects of compression ratio and EGR on the performance and emission characteristics of diesel-biogas dual fuel engine

In this study, an experimental investigation on diesel-biogas dual fuel (DF) engine is presented based on energy and exergy analyses. The effects of change in compression ratio (CR), exhaust gas recirculation (EGR) and EGR temperature on the performance and emission characteristics of DF engine have been studied. In the first stage, engine was studied with increasing CRs of 16.5, 17.5, 18.5 and 19.5 in stepwise manner. It was found that the higher CRs were not only advantageous to the engine performance from first and second-law point of view but also to the exhaust emissions. In the second stage, DF engine was studied at the highest CR (19.5) and the effects of EGR were analysed. The engine was studied with EGR percentages of 5%, 10% and 15%, which caused slight improvements in engine efficiency at low load and simultaneous decrease in oxides of nitrogen (NOx) emissions. However, high EGR percentages at high loads showed slight decrease in engine efficiency. In the third stage, hot EGR was employed and the results obtained were compared with the cold EGR case. The results showed that the highest efficiencies both at low and high loads were obtained with hot EGR cases and at the same time exhaust emissions could also be kept in check.

The use of CO2 as an additive for ignition delay and pollutant control in CH4/air autoignition

The effect of CO2 dilution on the adiabatic and isochoric autoignition of CH4/air mixtures is analyzed with Computational Singular Perturbation (CSP) algorithmic tools, with a particular emphasis on the determination of the features of the chemical dynamics that control ignition delay and emission formation. Increasing CO2 dilution causes longer ignition delays, lower final temperatures and decreased formation of NO and CO. These effects of CO2 dilution are shown to be entirely thermal, contrary to what happens with dilution with H2O, which also has chemical activity and can reduce ignition delay. For the same initial mole fraction of the diluent, the decrease in final temperature and in NO concentration is larger in the CO2 case whereas the decrease in CO is larger in the H2O case. The thermal effect of CO2 is entirely analogous with those of dilution with the chemically inert Ar, only stronger for the same percentage of initial dilution, because of the larger specific heat of CO2. The reactions that have the largest contribution to the characteristic explosive time scale of the system during ignition delay (H2O2(+M)→OH+OH(+M), CH3O2+CH2O→CH3O2H+HCO, CH4+CH3O2→CH3+CH3O2H, H+O2→O+OH, etc.) are not substantially affected by CO2 dilution, neither are the species that are pointed by CSP (CH3O2, H2O2, CH2O, etc.) as having the largest impact on the this timescale. The same holds for the modes that control CO and NO formation. The results point to the possibility of cold exhaust gas recirculation being used in order to produce mixtures with longer ignition delays and therefore substantial resistance to uncontrolled ignition.

Experimental investigation to study the effects of using hot and partially cold EGR in direct injection diesel engine

Major exhaust emissions from diesel engines are CO, CO2, PM, UHC and NOx, of which NOx is one of the most harmful. A number of techniques have been utilized to control NOx emissions and exhaust gas recirculation (EGR) is one of the widely used techniques that show outstanding results in NOx reduction in both light and heavy duty diesel engines. In the present study, the experiment has been conducted on a four-stroke, single-cylinder water cooled diesel engine. Here, a long-route EGR system was used in both hot (insulated) and partially cooled (without insulation) conditions. EGR rate was varied from 0 to 24% in steps of 6% and the engine ran at various load conditions. The research objective was to investigate the effects of varying EGR ratios and temperatures on engine performance parameters and determine the effective EGR rate where the engine gives high performance, low fuel consumption and produces low emissions.

An experimental investigation of performance and emission characteristics of diesel engine with blends of cottonseed oil methyl ester with cold and hot EGR

An experimental investigation of diesel engine using cottonseed oil biodiesel and its blends with exhaust gas recirculation (EGR) techniques has been carried out. An optimum nozzle opening pressure of 250 bar and lower static injection timing of 20° before top dead centre (bTDC) are considered because it has been observed that these conditions only give minimum emissions. From the test results, it could be noted that there is an increasing trend of emission characteristics of HC, smoke density and NOx for both cold and hot EGR for all blends of fuel with respect to brake power. As compared with cold EGR, the hot EGR gives lower emissions at all loads. In hot EGR, among the blends, at no-load and full-load conditions, the B100 gives the highest reduction in NOx of 14.23% and 7.91%, respectively. However, the use of EGR leads to a rise in soot emission because of soot–NOx trade-off for both the cases.

EXPERIMENTAL STUDY OF THE EFFECTS OF AIR-INJECTION, INJECTION TIMING AND COOLED EGR ON THE COMBUSTION, EMISSIONS AND PERFORMANCE OF A NATURE ASPIRATED DIRECT INJECTION DIESEL ENGINE

In this literature, a combined method has been employed to simultaneously reducesmoke (Soot) and oxide of nitrogen (Nox) and maintain the performance parameters of dieselengine. This includes creating an air jet by designing an air-cell inside the piston body, advancedinjection timing and using cold exhaust gas recirculation. The tested engine was an MT4.244engine that worked as natural aspiration. The air-cell causes reduction in both Soot and NOxemissions. Furthermore, applying cold EGR had a noticeable effect on NOx emission reduction.Advancing injection timing, the performance parameters of the engine could be improved. Thetests were done in 25%, 50%, 75% and 100% load conditions, for the engine speed of 2000 rpm.The results showed that by simultaneous reduction of Soot and NOx emissions, performanceparameters can be kept in a suitable range. The greatest reductions in NOx and Soot emissionshave been observed in 100% load. There have been no considerable changes in BSFC (BrakeSpecific Fuel Consumption and power) while injection timing advances have been applied for5° CA and 5% EGR.

Effect of EGR on Combustion and Emissions Characteristics of a CI Engine Fuelled with Waste Chicken Fat Biodiesel

Ever increasing demand and consequent rise in prices of petroleum products, stringent emission standards, the exponential depletion rate of fossil fuel reserves and escalation in the number of vehicles on the road have forced us to look for alternatives to meet the present and future demands of the energy requirements. Biodiesel production from waste oils and fats are cost effective methods which prevent the environmental pollution by proper disposal techniques. In this study, biodiesel was prepared from the waste effect chicken fat using the two stage esterification process. The present investigation deals with the cold exhaust gas recirculation (EGR) with the flow rates of 10, 20, 30% on a four stroke, single cylinder, direct injection (DI) diesel engine fueled with waste chicken fat biodiesel blends to reduce the NOx emissions of the engine. Experimental results showed higher oxides of nitrogen emissions when fueled with waste chicken fat biodiesel without EGR and found reduced NOx emissions about 25% when operating with B20 fuel blend with 30% EGR. The EGR level was optimized as 20% based on the significant reduction in NOx emissions, minimum possible smoke, CO, HC emissions and comparable brake thermal efficiency.

English

The main aim of this project is to investigate the effects of hot and cold Exhaust gas recirculation (EGR) methods on emissions and efficiency of the single cylinder, 4-stroke, direct injection diesel engine. For getting different EGR methods heat exchanger is provided. With and without Exhaust gas recirculation the performance characteristics like efficiencies, emissions were studied. In this project the different amounts of EGR like 10%, 15% and 20% of EGR is used to study the effects on the performance characteristics The recirculation of exhaust gas reduces the oxygen quantity in the combustion chamber and increases the temperature of intake charge which reduces the flame temperature and makes to lower NOx formation. By increasing the cooled EGR rates reduces the emissions more effectively. Experimental results shows that the cold EGR is much effective than the hot and intermediate EGR for the reduction of NOx emission. The increase in temperature of EGR gases causes to increase the combustion temperature which leads to increase in formation of NOx.

An experimental investigation on performance and emissions study with port injection using diesel as an ignition source for different EGR flow rates

Exhaust gas recirculation, EGR, is one of the most effective means of reducing NO x emissions from IC engines and is widely used in order to meet the emission standards. In the present work, experimental investigation has been carried out to study the NO x reduction characteristics by exhaust gas recirculation in a dual fueled engine using hydrogen and diesel. A single cylinder diesel engine was converted to operate on hydrogen-diesel dual fuel mode. Hydrogen was injected in intake port and diesel was injected directly inside the cylinder. The injection timing and injection duration of hydrogen were optimized initially based on the performance and emissions. It was observed that start of injection at 5° before gas exchange top dead center (BGTDC) and injection duration of 30° crank angle gives the best results. The flow rate of hydrogen was optimized as 7.5 lpm for the best start of injection and injection duration of hydrogen. Cold exhaust gas recirculation technique was adopted for the optimized injection parameter of hydrogen and flow rate. Maximum quantity of exhaust gases recycled during the test was 25% beyond this the combustion was not stable resulting in increase in smoke.

Combustion Control by EGR Management and Cyclic Dispersion Analysis of a HCCI Engine

Homogeneous Charge Compression Ignition (HCCI) engines could offer low NOx, PM emissions and high efficiency. However the operation region is limited because of knocking and misfire. Moreover the HCCI principal lacks direct combustion control and needs a system to control the combustion phasing with high accuracy. Cyclic dispersion is also a big problem in HCCI combustion. Today there exists various ways to control the HCCI combustion but these systems are heavy and complex. In this study, in order to develop a small and light HCCI engine, a simple HCCI combustion control system is proposed. DME (Di-methyl Ether) is used as a fuel to keep the structure small and light. This system uses throttles to change the mixing ratio of stoichiometric pre-mixture. hot EGR (Exhaust Gas Recirculation) gas and cold EGR gas. With this system, combustion control concept is evaluated and characteristics of cyclic dispersion are analyzed experimentally. Moreover, based on these results, reduction of cyclic dispersion is attempted by combustion control.

Characteristics of low temperature and low oxygen diesel combustion with ultra-high exhaust gas recirculation

Ultra-low NOx and smokeless operation at higher loads up to half of the rated torque is attempted with large rates of cold exhaust gas recirculation (EGR). NOx decreases below 6 ppm (0.05 g/kW h) and soot significantly increases when first decreasing the oxygen concentration to 16 per cent with cold EGR. However, after peaking at 12–14 per cent oxygen, soot then decreases sharply to essentially zero at 9–10 per cent oxygen while maintaining ultra-low NOx, regardless of fuel injection quantity and injection pressure. However, at higher loads, with the oxygen concentration below 9–10 per cent, the air-fuel ratio has to be over-rich to exceed half of the rated torque, and thermal efficiency, CO, and THC deteriorate significantly. As the EGR rate increases, exhaust gas emissions and thermal efficiency vary with the intake oxygen content rather than with the excess air ratio. Longer ignition delays due to either advancing or retarding the injection timing reduced the smoke emissions, but advancing the injection timing has the advantages of maintaining the thermal efficiency and preventing misfiring. A reduction in the compression ratio is effective to reduce the in-cylinder temperature and increase the ignition delay as well as to expand the smokeless combustion range in terms of EGR and i.m.e.p. (indicated mean effective pressure).

THE EFFECTS OF EXTERNAL EXHAUST GAS RECIRCULATION AND CETANE NUMBER IMPROVER ON THE GASOLINE HOMOGENOUS CHARGE COMPRESSION IGNITION ENGINES

The influences of cold exhaust gas recirculation (EGR) and cetane number (CN) improver-di-tertiary butyl peroxide (DTBP) on the combustion characteristics and emissions of the Homogenous Charge Compression Ignition (HCCI) combustion engines fueled with PRF90 fuels (a mixture of 90% iso-octane and 10% n-heptane by volume) were studied in this paper. The experiments were performed using 0%, 1%, 2%, 3%, and 4% (by volume) DTBP-PRF90 blends. The experimental results show that the operating range was remarkably extended to lower temperature and lower engine load with the DTBP addition in PRFRON90 fuel. With the improvement of HCCI combustion at the lower temperature and light load by CN improver, the combustion phase of higher temperature and large load can be retarded to the top dead center (TDC) by appropriated EGR rate. As a result, the indicated thermal efficiency and indicated specific fuel consumption (ISFC) were improved.

Heat Release Analysis on Combustion and Parametric Study on Emissions of HCCI Engines Fueled with 2-Propanol/n-Heptane Blend Fuels

This article investigates the inhibition effects of a 2-propanol additive on n-heptane homogeneous charge compression ignition (HCCI) combustion, analyzes the relationship between the emissions with the combustion parameters and fuel component, and evaluates the influence of cold exhaust gas recirculation (EGR) on HCCI combustion and emissions. The experiments were conducted on a single-cylinder HCCI engine using neat n-heptane and 10∼60% (by volume) 2-propanol/n-heptane blend fuels at 1800 rpm. The experimental results reveal that the ignition timing of the low-temperature reaction (LTR) is retarded, and the peak values of heat release during the LTR are decreased with an increase of 2-propanol in blend fuels. As a result, the ignition timing of the high-temperature reaction is delayed, both the maximum and lowest indicated mean efficient pressures (IMEP) are increased, and the combustion efficiency is also decreased. Parametric studies on CO and HC emissions show that the fuel volume with a high cetane ...