Exhaust Gas Recirculation Flow Rate Research Articles

The combined effect of split fueling strategy and EGR on the combustion, performance, and emission characteristics of a CRDI biofuel engine

AbstractThe current research investigates the impact of a split fueling strategy combined with several flow rates of exhaust gas recirculation (EGR) on the combustion and emission characteristics of a diesel engine running on B20 waste cooking oil (WCO) biodiesel. A four‐stroke single‐cylinder common rail direct injection engine was employed for experiments. It operates with a B20 blend of WCO biodiesel at 600 bar pressure for varying pilot fueling conditions of 10%, 20%, and 30%. The B20 blend with 30% pilot fuel injection (B20P30) showed excellent performance and emission characteristics compared with B20 blend with 10% pilot fuel injection (B20P10) and B20 with 20% pilot fuel injection (B20P20). However, B20P30 had greater levels of nitrogen oxide (NOx) emissions than those by diesel. EGR discharge levels in 5% increments, ranging from 0% to 15% were introduced to address this issue. The experimental findings revealed that both cylinder peak pressure and heat release rate showed a reduction when the EGR flow rate was enhanced. The recirculation of exhaust gas into the combustion chamber led to a slight increase in the emission levels of hydrocarbon (HC), carbon monoxide (CO), and smoke, as well as a decrease in carbon dioxide (CO2). Nevertheless, the introduction of EGR significantly decreased NOx emissions by 22.94%, 35.05%, and 47.96% for EGR flow rates of 5%, 10%, and 15%, respectively, when compared with the engine operating without EGR. Overall, the two‐stage fueling strategy, B20P30 blended with 10% EGR corroborated to be beneficial in reducing NOx emissions with minimal performance penalties. Although there was a slight uptick in certain emissions, the overall trade‐off between emission reduction and performance was favorable. The culmination of this study is targeting the objectives of sustainable development goal 7 (clean energy) and goal 13 (climate action) to be achieved by 2030.

Thermal and chemical exhaust gas recirculation potential of punnai oil biodiesel-fuelled diesel engine for environmental sustainability.

Major energy production all over the world depends on fossil fuels. Recent research on alternative energy sources has raised major concerns about environmental impacts, future availability, and cost. Pollution from diesel engines also affects the environment negatively. As a result, there is a worldwide concern about reducing the pollutants emitted by diesel engines. In comparison to diesel fuel, biodiesel combustion produces reduced carbon monoxide (CO2) and unburned hydrocarbon (UHC) emissions but higher nitrogen oxide (NOx) emissions. The current study aims to investigate the thermal and chemical effects of exhaust gas recirculation (EGR) on the features of a diesel engine for environmental sustainability. The punnai oil was produced from kernels of punnai seeds and transesterified in two phases using alcohol with the existence of a catalyst. The higher viscosity of punnai oil biodiesel is diluted by mixing it with diesel fuel. Our previous investigation indicated that neat punnai oil biodiesel is a potential fuel; however, the findings showed that the addition of diesel is necessary to obtain acceptable engine performance. In this study, punnai oil biodiesel was mixed at a rate of 20% with diesel (B20) and run in a diesel engine with varied EGR rates under five different engine loads. This combined impact enhanced the maximum heat release rate (HRR) and maximum combustion pressure, according to the findings. The premixed burning fractions were commonly higher at all engine loads, whereas the diffusion combustion fractions were lower. When the centre of the HRR changed toward the top dead centre (TDC), combustion durations remained rather constant. The experimental results revealed the B20 blend at a 10% EGR flow rate produced 6.57% lower BTE, 37.04% higher BSEC, 2.47% higher EGT, 5.13% lower CO, 31.11% higher CO2, 3.13% higher UHC, 8.36% lower NOx, and 4% higher smoke opacity when compared with diesel in a standard diesel engine.

Characteristics of Integrated Air Control and Low-Pressure Exhaust Gas Recirculation Valve for Diesel Engines

The purpose of this study is to investigate the characteristics of a newly introduced integrated exhaust gas recirculation (EGR) valve. Traditionally, a exhaust-pressure regulating valve is installed to increase the EGR flow rate; the method used in this study induces an increase of the EGR flow by restricting fresh intake. Unlike the two-motor two-drive system of the low-pressure (LP)-EGR system, the air control valve (ACV) and EGR valve are constructed in a linked structure. The two valves can be controlled simultaneously by a single driver, which permits reductions in volume and weight. In order to compare the existing LP-EGR system with the integrated LP-EGR system, the characteristics of the system were analyzed by a rig test and an actual engine test. It was determined that as the EGR valve opened, the EGR rate was increased and the torque was decreased under the same load condition because of the pumping resistance caused by the ACV closing.

Experimental assessment of ozone production by multichannel plasma discharges for automotive applications

Ozone addition has come under study as a means of controlling ignition timing in low temperature combustion using highly dilute homogeneous mixture. In this context, this work aims to improve ozone production from air and simulated exhaust gas recirculation (EGR) in a homogeneous charge compression ignition engine using a cold plasma reactor based on multichannel dielectric barrier discharges. Ozone concentration was investigated as a function of energy deposition, gas characteristics, and distance from the source to measurement points. At a given specific input energy, experimental outcomes indicate a relatively high influence of the feeding EGR composition (O2–N2–CO2–CH4–H2O) and flow rate on the ozone production. However, no changes within experimental accuracy in ozone concentration were seen when changing the distance plasma-measurement points, allowing us to find the optimum position of the plasma reactor with respect to the engine inlet. In air, ozone concentration increased from 120 ppm to 1600 ppm, as the flow rate decreased from 200 to 2 slm. At a given voltage set point, the increase in gas pressure causes the decrease in energy deposition and thus the ozone concentration. In EGR mixtures, the lowest ozone concentration tends to stabilize around 50 ppm, which is acceptable for LTC applications.

Combustion analysis of modified light duty diesel engine under high pressure split injections with cooled EGR

The aim of the present research work is to study the combustion phenomenon in modified light duty diesel engine to run on Common rail direct injection (CRDI) system under cooled exhaust gas recirculation (EGR). The test engine is single cylinder 3.7 kW@1500 rpm direct injection diesel engine capable of injecting high pressure fuel for both retarded and split injections. The engine is fitted with separate electronic variable timing fuel injection kit instead of conventional fuel supply system. Retarded injection consists of single injection at 11° before top dead centre (BTDC) and split injection consists of both pilot injection at 54°BTDC of 10% mass share and main injection at 11°BTDC of 90% mass share. Diesel is injected directly in to the engine cylinder for both retarded and split injections at pressures of 200,230,250,300 and 350 bar respectively. Cooled EGR is circulated along with intake air for flow rates of 5% and 10% (wt/wt) basis. The experimental set up is capable of delivering precise control of fuel and EGR flow rates at all operating conditions. Test results show that there is trade-off exists between retarded and split injections at 350 bar injection pressure at full load conditions. Retarded injection has 34% brake thermal efficiency while split injection exhibits only 32.1% for 5% EGR flow rates. But higher EGR flow rates of 10% both retarded and split injection has nearly same brake thermal efficiency of 30.1%. Split injection reduced the combustion duration, ignition delay and exhaust gas temperatures for higher EGR flow rates compared to single retarded injection.

Effect of cooled EGR on modified light duty diesel engine for combustion, performance and emissions under high pressure split injection strategies

Environmental concerns demands light duty Engines to satisfy the stringent Euro VI emission norms. The aim of this study is to present the effect of cooled exhaust gas recirculation (EGR) on emission reduction. Tests are conducted on a modified single cylinder light duty diesel engine to run on high pressure common rail direct fuel injection. Diesel is injected directly in to the engine cylinder for both retarded and split injections at pressures of 200, 230, 250, 300 and 350 bar respectively. Cooled EGR is circulated along with intake air in to the inlet manifold of the engine for flow rates of 5% and 10%( wt/wt) of injected air respectively for both retarded and split injections. Single injection is retarded at − 11° ATDC and split injection consists of pilot injection at − 54°ATDC of 10% mass share and main injection at − 11°ATDC of 90% mass share. The result shows split injection (MPFI) decreases the ignition delay, In-cylinder combustion temperature and peak pressure for higher EGR flow rates compared to retarded single injection (SI) for all Injection pressure. Split injection reduced NOx from 1400 ppm to 200 ppm for 10% EGR flow rate at 350 bar injection pressure at full load operating conditions. Split injection at high Injection pressure decreases smoke by 10% as compared to retarded single injection. Test results show that there is trade-off exists between retarded and split injections at 350 bar injection pressure at full load conditions. Retarded injection has 33.61% brake thermal efficiency while split injection exhibits only 29.06% for 5% EGR flow rates. But higher EGR flow rates of 10% both retarded and split injection has nearly same brake thermal efficiency of 30.11%. Split injection reduced the combustion duration, ignition delay and exhaust gas temperatures for higher EGR flow rates compared to single retarded injection. The present research reveals that there exists an injection pressure map between the design operating pressure and maximum injection pressure. MPFI system under CRDI mode is very effective in reducing the NOx emissions with 10% EGR flow rates for maximum Injection pressure. While retarded SI injection is effective for moderate Injection pressure with the same EGR flow rates.

Experimental investigation of the effect of simultaneous nitrogen, hydrogen and EGR addition in a biodiesel operated CI engine

ABSTRACTInternal combustion engines continue to dominate in many fields like transportation, agriculture and power generation. Among the various alternative fuels, hydrogen is a long term renewable and less polluting fuel. Overcoming diesel engine emissions, especially NOx, requires investigation of new systems which can potentially steer the automobile industry towards further emissions reduction. Addition of hydrogen (H2) and nitrogen (N2) with exhaust gas recirculation (EGR) can lead to a new generation of low polluting compression ignition (CI) engines. In this experiment the H2, N2 and exhaust gas were inducted into the inlet manifold with inlet air. The experiments were conducted on a four-stroke, single-cylinder, water-cooled, direct injection (DI) diesel engine at a speed of 1500 rpm. The H2 and N2 were stored in a high pressure cylinder and supplied to the inlet manifold through water and air based flame arrestor at 2 bar pressure. The EGR valve is used to control the EGR to the inlet of the engine. Initially the engine was run for different H2 flow rate and optimized for maximum BTE. Then this (maximum BTE) flow rate of H2 was taken to optimize the EGR rate for 5%, 10% and 20%. The engine was run by different flow rates of N2 namely 2%, 3% and 4% with optimized EGR and H2 flow rate. The engine performance, emission and combustion parameters were analyzed at this condition which gives low NOx emission. The fuel used was a blend of 20% biodiesel and 80% diesel called B20. The experimental results show that the brake thermal efficiency (BTE) increased due hydrogen addition but the addition of EGR and N2 decreased the BTE. NOx emission decreased due to addition of EGR and N2. While the induction of H2 tended to decrease the emission of HC and CO, the addition of N2 and EGR with H2 tended to increase the above emissions. The heat release rate and cylinder pressure slightly decreased due to addition of N2 with H2 and EGR.

Analysis and prediction of transient opacity spikes using dimensional modeling

Dimensional modeling, GT-Power in particular, has been used for two related purposes—to quantify and understand the inaccuracies of transient engine flow estimates that cause transient smoke spikes and to improve empirical models of opacity or particulate matter used for engine calibration. It has been proposed by dimensional modeling that exhaust gas recirculation flow rate was significantly underestimated and volumetric efficiency was overestimated by the electronic control module during the turbocharger lag period of an electronically controlled heavy duty diesel engine. Factoring in cylinder-to-cylinder variation, it has been shown that the electronic control module estimated fuel–Oxygen ratio was lower than actual by up to 35% during the turbocharger lag period but within 2% of actual elsewhere, thus hindering fuel–Oxygen ratio limit–based smoke control. The dimensional modeling of transient flow was enabled with a new method of simulating transient data in which the manifold pressures and exhaust gas recirculation system flow resistance, characterized as a function of exhaust gas recirculation valve position at each measured transient data point, were replicated by quasi-static or transient simulation to predict engine flows. Dimensional modeling was also used to transform the engine operating parameter model input space to a more fundamental lower dimensional space so that a nearest neighbor approach could be used to predict smoke emissions. This new approach, intended for engine calibration and control modeling, was termed the “nonparametric reduced dimensionality” approach. It was used to predict federal test procedure cumulative particulate matter within 7% of measured value, based solely on steady-state training data. Very little correlation between the model inputs in the transformed space was observed as compared to the engine operating parameter space. This more uniform, smaller, shrunken model input space might explain how the nonparametric reduced dimensionality approach model could successfully predict federal test procedure emissions when roughly 40% of all transient points were classified as outliers as per the steady-state training data.

Analysis of different exhaust gas recirculation architectures for passenger car Diesel engines

Different Exhaust Gas Recirculation (EGR) system architectures have been evaluated by means of both experimental tests and numerical simulation; in addition to the experimental tests, a one-dimensional fluid-dynamic engine model has been built in order to assess the potential of a Dual Loop (DL) EGR system – a combination of Short Route (SR) and Long Route (LR) EGR systems. Substantial reductions of the NOx emissions have been achieved using the LR EGR layout both under steady state and transient operating conditions: a reduction of up to 15% over the first 60s of the Extra Urban Driving Cycle (EUDC) was obtained with the LR layout. An optimal combination of LR and SR has led to a further reduction of 5% of the nitrogen oxide emissions, due to a faster response of the EGR system during transients. Finally some fundamental knowledge that can be used to control the EGR flow rate more accurately has been gathered, by means of the numerical simulation, especially for the Dual Loop EGR system layout.

Quantitative feedback design of air and boost pressure control system for turbocharged diesel engines

For modern diesel engines, variable geometry turbocharger (VGT) is used to boost engine power output. In addition, exhaust gas recirculation (EGR) is utilized to reduce engine out NO x emission. To realize these functions, a multivariable control system needs to control both VGT and EGR valve to deliver desired intake manifold (or boost) pressure, and desired EGR flow rate. This two-input and two-output system is nonlinear with cross-couplings between the boost and EGR responses to the input actuators, the system parameters are varying with different engine operating conditions. This paper proposes a closed loop design of a multivariable VGT/EGR control system for a turbocharged diesel engine. The control system is synthesized based on quantitative feedback theory to maintain robust stability and performance via sequential MIMO loop shaping in the frequency domain. Experiment results are included from a turbocharged diesel engine to show the effectiveness of the proposed control design.

Computationally Efficient Whole-Engine Model of a Cummins 2007 Turbocharged Diesel Engine

This paper describes an accurate, flexible, and computationally efficient whole engine model incorporating a multizone, quasidimension combustion submodel for a 6.7-l six-cylinder turbocharged diesel engine with cooled exhaust gas recirculation (EGR), cooled air, and multiple fuel injections. The engine performance and NOx emissions predicative capability of the model is demonstrated at 22 engine operating conditions. The only model inputs are physical engine control module “control actions,” including injection rates, injection timings, EGR valve position, and variable geometry turbocharger rack position. The model is run using both “open” and “closed” loop control strategies for air/EGR path control, in both cases achieving very good correlation with experimental data. Model outputs include in-cylinder pressure and heat release, torque, combustion timing, brake specific fuel consumption, EGR flow rate, air flow rate, exhaust and intake pressure, and NOx emissions. The model predicts engine performance and emissions with average absolute errors within 5% and 18%, respectively, of true values with “open-loop” air/EGR control, and within 5% and 11% with “closed-loop” air/EGR control. In addition, accurate prediction of the coupling of the in-cylinder combustion and emission-production processes with the boosted, cooled air/EGR gas dynamics is a key characteristic of the model.

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.

Effect of exhaust gas recirculation (EGR) temperature for various EGR rates on heavy duty DI diesel engine performance and emissions

DI diesel engines are well established today as the main powertrain solution for trucks and other relevant heavy duty vehicles. At the same time emission legislation (mainly for NOx and particulate matter) becomes stricter, reducing their limit to extremely low values. One efficient method to control NOx in order to achieve future emissions limits is the use of rather high exhaust gas recirculation (EGR) rates accompanied by increased boost pressure to avoid the negative impact on soot emissions. The method is based on the reduction of gas temperature level and O2 availability inside the combustion chamber, but unfortunately it has usually an adverse effect on soot emissions and brake specific fuel consumption (bsfc). The use of high EGR rates creates the need for EGR gas cooling in order to minimize its negative impact on soot emissions especially at high engine load were the EGR flow rate and exhaust temperature are high. For this reason in the present paper it is examined, using a multi-zone combustion model, the effect of cooled EGR gas temperature level for various EGR percentages on performance and emissions of a turbocharged DI heavy duty diesel engine operating at full load. Results reveal that the decrease of EGR gas temperature has a positive effect on bsfc, soot (lower values) while it has only a small positive effect on NO. As revealed, the effect of low EGR temperature is stronger at high EGR rates.