Exhaust Gas Recirculation Percentage Research Articles

Effects of Fuel Injection Parameters on the Morphological Characteristics of Soot Particulates and Exhaust Emissions from a Light-Duty Diesel Engine

The aim of this paper is to investigate the effects of injection parameters and the exhaust gas recirculation (EGR) rate on the morphological characteristics of soot particulates and exhaust emissions in a common-rail direct-injection (DI) diesel engine with a piston displacement of 1.58 L. To investigate the influences of injection parameters and the EGR rate on the particulate morphology and exhaust emission characteristics, several different injection parameters and two EGR rates were investigated. The particulate morphology (including primary particles), the size of the soot agglomerates, the number of agglomerates, and the fractal dimension were also investigated under various injection strategies, pilot injection quantities, and percentage of EGR. The dependence of air pollution components in engine emissions, such as soot, nitrogen oxide (NOx), carbon monoxide (CO), and hydrocarbon (HC), upon pilot injection parameters and percentage of EGR at constant operating conditions was measured. A thermopho...

Optimization of Injection System Parameters and EGR on Jatropha Biodiesel Engine using Taguchi Approach

The diesel engine injection system parameters apart from the operating parameters such as load and speed significantly affect its performance and exhaust emissions. The effect is even adverse sometimes when the engine is tried with some alternative fuels, such as Jatropha biodiesel due to its physico-chemical properties. For better performance and to meet out stringent emission norms, these parameters have to be optimized. An experimental investigation and analysis carried out to simultaneously optimize injection system parameters and exhaust gas recirculation (EGR) levels of small direct injection diesel engine for lower fuel consumption and higher thermal efficiency and peak cylinder pressure is presented in this paper. During the experiments, the different parameters such as fuel type, injection timing, injector opening pressure, nozzle configuration, nozzle tip protrusion, percentage of exhaust gas recirculation (EGR), load torque and speed were changed. Taguchi's signal-to-noise ratio approach was applied to obtain an optimal setting of these parameters. From the experimental results and further analysis it is concluded that under 95% confidence interval the injection timing 340°CA, injector opening pressure 250 bar, nozzle configuration 5x0.18, EGR 0%, load torque 15Nm, speed 1800rpm with Jatropha biodiesel, gave the maximum peak cylinder pressure, while the lowest BSFC with diesel fuel was obtained with nozzle configuration 4x0.18, load torque 15Nm and speed 1800rpm and the highest brake thermal efficiency with nozzle configuration 4x0.18, tip protrusion 2mm, load torque 15Nm and speed 1800rpm. However, the significant control parameters responsible for brake thermal efficiency with their percentage contribution were load torque (79.13%), speed (17.54%), nozzle configuration (1.33%) and tip protrusion (0.96%).

Performance studies of a low heat rejection engine operated on non-volatile vegetable oils with exhaust gas recirculation

During recent decades, considerable effort has been expended world-wide to reduce dependency on petroleum fuels for power generation and transportation through the search for suitable alternative fuels that are environmentally friendly. In this respect, vegetable oils are a promising alternative to diesel fuel. However, the high viscosity, poor volatility and cold flow characteristics of vegetable oils can cause some problems such as injector coking, severe engine deposits, filter gumming and piston ring sticking and thickening of lubrication from long-term use in diesel engines. These problems can be eliminated or minimised by transesterification of the vegetable oils to form monoesters. Although transesterification improves the fuel properties of vegetable oil, the viscosity and volatility of biodiesel are still worse than those of petroleum diesel fuel. The performance of a diesel engine with such biodiesel operation can be improved further with the concept of the low heat rejection (LHR) engine. In the LHR engine, combustion surfaces on the pistons, cylinder walls and valves can be coated with ceramic materials. The objective of this study was to apply the LHR engine concept for improving engine performance when either honge biodiesel, known as honge oil methyl ester (HOME), or neem biodiesel, known as neem oil methyl ester (NOME) oils was used as an alternative fuel. For this purpose, experiments were conducted on a single cylinder, four-stroke, direct injection, water-cooled compression ignition engine using diesel, HOME and NOME oils at different injection timings of 19, 23 and 27° before top dead centre (BTDC) with and without the induction of exhaust gas recirculation (EGR). The percentage of EGR was varied from 5 to 20% in steps of 5%. The results showed that specific fuel consumption and brake thermal efficiency were improved for both of the biodiesel fuels in the LHR engine. An EGR of 10% resulted in better performance with trade-off between oxides of nitrogen and hydrocarbons/carbon monoxide emissions and hence 10% EGR is taken as the best of the range from 5 to 20%. However, readings with other EGR ratios are not reported.

An experimental investigation on performance, emissions, and combustion in a manifold injection for different exhaust gas recirculation flowrates in hydrogen—diesel dual-fuel operations

Hydrogen is receiving considerable attention as an alternative fuel to replace the rapidly depleting petroleum-based fuels. Its clean burning characteristics help to meet the stringent emission norms. In this experimental investigation a single-cylinder diesel engine was converted to operate in hydrogen—diesel dual-fuel mode. Hydrogen was injected in the intake manifold and the diesel was injected directly inside the cylinder. The injection timing and the injection duration of hydrogen were optimized on the basis of performance and emissions. Best results were obtained with hydrogen injection at gas exchange top dead centre with an injection duration of 30° crank angle. The flowrate of hydrogen was optimized as 7.5l/min with optimized injection timing and duration. The optimized exhaust gas recirculation (EGR) flowrate was 20 per cent at 75 per cent load. The optimized timings were chosen on the basis of performance, emission, and combustion characteristics. The EGR technique was adopted in the hydrogen—diesel dual-fuel mode by varying the EGR flowrate from 0 per cent to 25 per cent in steps of 5 per cent. The maximum quantity of exhaust gases recycled during the test was 25 per cent (up to 75 per cent load); beyond that unstable combustion was observed with an increase in smoke. The brake thermal efficiency with 20 per cent EGR decreases by 9 per cent compared with diesel. The nitrogen oxide (NO x) emission in hydrogen manifold injection decreases by threefold with 20 per cent EGR operation at full load. The NO x emission tends to reduce drastically with increase in the EGR percentage at all load conditions owing to the increase in heat capacity of the exhaust gases. The smoke decreases by 80 per cent in the dual-fuel operation compared with diesel at 75 per cent load.

LPG fueled diesel engine using diethyl ether with exhaust gas recirculation

The present investigation was to study the effect of Exhaust Gas Recirculation (EGR) on homogeneous charge ignition engine. A stationary four stroke, single cylinder, direct injection (DI) diesel engine capable of developing 3.7 kW at 1500 rpm was modified to operate in HCCI mode. In the present work the diesel engine was operated on 100% Liquified Petroleum Gas (LPG). The LPG has a low cetane number ( < 3 ) , therefore Diethyl ether (DEE) was added to the LPG for ignition purpose. DEE is an excellent ignition enhancer (cetane number >125) and has a low auto ignition temperature (160 °C). Experimental results showed that by EGR technique, at part loads the brake thermal efficiency increases by about 2.5% and at full load, NO concentration could be considerably reduced to about 68% as compared to LPG operation without EGR. However, higher EGR percentage affects the combustion rate and significant reduction in peak pressure at maximum load.

Enhancement of the combustion process in dual-fuel engines at part loads using exhaust gas recirculation

Dual-fuel engines at part loads inevitably suffer from lower thermal efficiency and higher carbon monoxide and unburned fuel emission. The present work was carried out to investigate the combustion characteristics of a dual-fuel (diesel-gas) engine at part loads, using a single-zone combustion model with detailed chemical kinetics for combustion of natural gas fuel. The authors have developed software in which the pilot fuel is considered as a subsidiary zone and a heat source derived from two superimposedWiebe combustion functions to account for its contribution to ignition of the gaseous fuel and the rest of the total released energy. The chemical kinetics mechanism consists of 112 reactions with 34 species. This quasi-two-zone combustion model is able to establish the development of the combustion process with time and the associated important operating parameters, such as pressure, temperature, heat release rate (HRR), and species concentration. Therefore, this paper describes an attempt to investigate the combustion phenomenon at part loads and using hot exhaust gas recirculation (EGR) to improve the above-mentioned drawbacks and problems. By employing this technique, it is found that lower percentages of EGR and allowance for its thermal and radical effects have a positive influence on performance and emission parameters of dual-fuel engines at part loads. Predicted values show good agreement with corresponding experimental values under special engine operating conditions (quarter-load, 1400 r/min). Implications are discussed in detail.

The effect of fuel octane and dilutent on homogeneous charge compression ignition combustion

This paper presents some experimental operating and combustion properties of homogeneous charge compression ignition (HCCI) combustion. HCCI operating range, start of combustion, burn duration, indicated mean effective pressure, indicated specific emissions, and indicated specific fuel consumption are evaluated as charge dilution and octane number are varied. Primary reference fuels with octane numbers of 20, 40, and 60 are used in this study. The autoignition properties of the air-fuel mixture are varied by changing the fuel octane number, percentage of exhaust gas recirculation (EGR), and air-fuel ratio, while holding the intake temperature, engine speed, and compression ratio constant. Results show that both the start of combustion and the burn duration are sensitive to mixture dilution (excess air or EGR). The fuel octane number is not an effective method of controlling the start of combustion or the burn duration but can be used to increase the load range of the HCCI engine. Both the NO x emissions and the indicated specific fuel consumption increase as the octane number is increased due to lower dilution and higher peak temperatures. Correct amounts of dilution are critical in controlling HCCI combustion. Separating dilution into EGR and excess air, it is found that a given amount of EGR is more effective at controlling the start of combustion and the burn duration than the same amount of excess air.

Understanding of controlled autoignition combustion in a four-stroke gasoline engine

Controlled autoignition (CAI) combustion has recently emerged as a viable alternative combustion process to the conventional spark ignition or compression ignition process for internal combustion engines, owing to its potential for high efficiency and extremely low NOx and particulate emissions. Since CAI combustion is a process dominated by chemical kinetics of the fuel-air mixture, an engine simulation model with detailed chemical kinetics has been developed and applied to a four-stroke gasoline engine fuelled with isooctane. After calibration and validation, the engine simulation model was used to study the effects of the intake temperature, exhaust gas recirculation (EGR), the air-fuel ratio, the compression ratio and the engine speed on CAI combustion in a four-stroke gasoline engine. The characteristics of CAI combustion investigated include the autoignition timing, the partial burning and knocking combustion and NO emission. Results show that CAI combustion could be achieved within a limited speed and load range. The lower end of the CAI combustion range was affected by partial burning, and the higher end of its operation was limited by knocking combustion. Among the engine parameters investigated, the intake charge temperature and EGR had the greatest effect on the CAI combustion process. The effect of EGR was further analysed in terms of its thermal (increase in heat capacity), dilution, chemical and charge heating effects by means of a series of simulation studies. It was found that the charge heating effect caused advanced ignition timing, faster heat release rate and moderate reduction in the CAI combustion duration. The thermal effect (increased heat capacity) retarded ignition, extended combustion duration and slowed down heat release rate. The dilution effect also resulted in longer combustion duration and slower burning but it did not affect the ignition timing. The chemical effect was found to accelerate the combustion process when the percentage of EGR was large.

Studies of NOx, CO, soot formation and oxidation from a direct injection stratified-charge engine using the k-ɛ turbulence model

In this investigation, a model has been developed to predict the performance and emissions—NOx, CO and soot—in a direct injection stratified-charge engine with a Texaco controlled combustion system. This model uses the k-ε turbulence model to determine characteristic velocities for heat transfer calculations and has only an empirical constant, by comparison with the Woschni equation in which separate constants are used for each process in the four-stroke cycle to determine the velocity for use in the Reynolds number. The modified Keck and Blizard model is used for combustion calculation by considering the rapid compression effects on the turbulence intensity. An extended Zel'dovich mechanism has been used to predict NOx emissions. To predict CO emissions, the Zeleknik and McBride models have been used. The model of Hiroyasu and Kodota has been used to predict the mass of soot formed and oxidized. Comparison of the model predictions with available experimental data shows a good agreement. Moreover, the program has a high flexibility for parametric studies to calculate the effect of engine parameters such as fuel-air ratio, engine speed, injection timing period and percentage of exhaust gas recirculation on the performance and emissions characteristics of the engine.