Capturing Cyclic Variability in Exhaust Gas Recirculation Dilute Spark-Ignition Combustion Using Multicycle RANS

2016 ◽  
Vol 138 (11) ◽  
Author(s):  
Riccardo Scarcelli ◽  
James Sevik ◽  
Thomas Wallner ◽  
Keith Richards ◽  
Eric Pomraning ◽  
...  
Keyword(s):  
Internal Combustion Engines ◽  
Initial Conditions ◽  
Exhaust Gas Recirculation ◽  
Spark Ignition ◽  
Operating Conditions ◽  
Combustion Stability ◽  
Exhaust Gas ◽  
Cyclic Variability ◽  
Ignition Characteristics ◽  
Gas Recirculation

Dilute combustion is an effective approach to increase the thermal efficiency of spark-ignition (SI) internal combustion engines (ICEs). However, high dilution levels typically result in large cycle-to-cycle variations (CCV) and poor combustion stability, therefore limiting the efficiency improvement. In order to extend the dilution tolerance of SI engines, advanced ignition systems are the subject of extensive research. When simulating the effect of the ignition characteristics on CCV, providing a numerical result matching the measured average in-cylinder pressure trace does not deliver useful information regarding combustion stability. Typically large eddy simulations (LES) are performed to simulate cyclic engine variations, since Reynolds-averaged Navier–Stokes (RANS) modeling is expected to deliver an ensemble-averaged result. In this paper, it is shown that, when using RANS, the cyclic perturbations coming from different initial conditions at each cycle are not damped out even after many simulated cycles. As a result, multicycle RANS results feature cyclic variability. This allows evaluating the effect of advanced ignition sources on combustion stability but requires validation against the entire cycle-resolved experimental dataset. A single-cylinder gasoline direct injection (GDI) research engine is simulated using RANS and the numerical results for 20 consecutive engine cycles are evaluated for several operating conditions, including stoichiometric as well as exhaust gas recirculation (EGR) dilute operation. The effect of the ignition characteristics on CCV is also evaluated. Results show not only that multicycle RANS simulations can capture cyclic variability and deliver similar trends as the experimental data but more importantly that RANS might be an effective, lower-cost alternative to LES for the evaluation of ignition strategies for combustion systems that operate close to the stability limit.

scholarly journals Capturing Cyclic Variability in EGR Dilute SI Combustion Using Multi-Cycle RANS

2015 ◽  
Author(s):  
Riccardo Scarcelli ◽  
James Sevik ◽  
Thomas Wallner ◽  
Keith Richards ◽  
Eric Pomraning ◽  
...  
Keyword(s):  
Internal Combustion Engines ◽  
Initial Conditions ◽  
Stability Limit ◽  
Operating Conditions ◽  
Combustion Stability ◽  
Navier Stokes ◽  
Cyclic Variability ◽  
Numerical Result ◽  
Ignition Characteristics ◽  
The Stability

Dilute combustion is an effective approach to increase the thermal efficiency of spark-ignition (SI) internal combustion engines (ICEs). However, high dilution levels typically result in large cycle-to-cycle variations (CCV) and poor combustion stability, therefore limiting the efficiency improvement. In order to extend the dilution tolerance of SI engines, advanced ignition systems are the subject of extensive research. When simulating the effect of the ignition characteristics on CCV, providing a numerical result matching the measured average in-cylinder pressure trace does not deliver useful information regarding combustion stability. Typically Large Eddy Simulations (LES) are performed to simulate cyclic engine variations, since Reynold-Averaged Navier-Stokes (RANS) modeling is expected to deliver an ensemble-averaged result. In this paper it is shown that, when using RANS, the cyclic perturbations coming from different initial conditions at each cycle are not damped out even after many simulated cycles. As a result, multi-cycle RANS results feature cyclic variability. This allows evaluating the effect of advanced ignition sources on combustion stability but requires validation against the entire cycle-resolved experimental dataset. A single-cylinder GDI research engine is simulated using RANS and the numerical results for 20 consecutive engine cycles are evaluated for several operating conditions, including stoichiometric as well as EGR dilute operation. The effect of the ignition characteristics on CCV is also evaluated. Results show not only that multi-cycle RANS simulations can capture cyclic variability and deliver similar trends as the experimental data, but more importantly that RANS might be an effective, lower-cost alternative to LES for the evaluation of ignition strategies for combustion systems that operate close to the stability limit.

A Converted Two-Stroke Cycle Engine for Compression Ignition Combustion

2014 ◽  
Vol 663 ◽  
pp. 331-335 ◽  
Author(s):  
Amin Mahmoudzadeh Andwari ◽  
Azhar Abdul Aziz ◽  
Mohd Farid Muhamad Said ◽  
Zulkarnain Abdul Latiff
Keyword(s):  
Internal Combustion Engines ◽  
Exhaust Gas Recirculation ◽  
Exhaust Emissions ◽  
Exhaust Gas ◽  
Cyclic Variation ◽  
Cyclic Variability ◽  
Auto Ignition ◽  
Compression Ignition Combustion ◽  
Gas Recirculation ◽  
Stroke Cycle

A new kind of alternative combustion concept that has attracted attention intensively in recent years is called controlled auto-ignition (CAI) combustion. CAI combustion has been proposed and partially implemented with the aim of both improving the thermal efficiency of internal combustion engines, achieving cleaner exhaust emissions and lower cyclic variation. An experimental study is conducted through a CAI two-stroke cycle engine in order to investigate the influence of internal exhaust gas recirculation (In-EGR) and external exhaust gas recirculation (Ex-EGR) variation in relation to combustion cyclic variability and exhaust emissions characteristics. Results implied that cyclic variation of both combustion-related and pressure-related parameter is substantially improved. Furthermore remarkable decreased exhaust emissions, unburned hydrocarbon (uHC), carbon monoxide (CO) and nitric dioxide (NOX), was observed.

Numerical Modelling of Internal Combustion Engines Fuelled by Hydrogen-Natural Gas Blends

2008 ◽  
Author(s):  
Antonio Mariani ◽  
Biagio Morrone ◽  
Andrea Unich
Keyword(s):  
Natural Gas ◽  
Internal Combustion Engines ◽  
Exhaust Gas Recirculation ◽  
Internal Combustion ◽  
Flame Speed ◽  
Operating Conditions ◽  
Nox Emissions ◽  
Exhaust Gas ◽  
Combustion Engines ◽  
Gas Recirculation

The strict rules that European Community has given for reducing vehicle emissions require new views on the choice of combustion engines and fuels. In fact, the rules will probably introduce in the near future limitations on carbon dioxide (CO2) emissions. Internal combustion engines are responsible for emission of unburned hydrocarbons (HC), nitrogen oxides (NOx) and particulate matter (PM). The aim of the present paper is the study of the effects of hydrogen-natural gas blends (HCNG) on the performance, efficiency and NOx emissions of internal combustion engines (ICE). A numerical engine model has been developed to display how the presence of hydrogen in such mixtures impacts on flame speed and burn rates. The model allows the comparison of different fuels, in terms of engine brake efficiency and pollutant emissions. An important variable for the combustion process is the ignition timing which is set employing Maximum Brake Torque (MBT) spark advance. Engine operating conditions considered in the numerical analysis have been obtained by imposing engine speed and load. Brake power, efficiency and NOx emissions are calculated for the most frequent operating conditions met by automotive engines, i.e. part load and low speed. The effect of natural gas (NG) enrichment by hydrogen on flame speed has been considered. Thus, faster combustion and the reduction of energy content in the air-fuel mixtures due to the lower density of hydrogen are taken into account. Hydrogen enrichment of natural gas improves combustion stability in critical conditions, allowing the use of extremely lean mixtures or high Exhaust Gas Recirculation rates. The results show that by employing an MBT spark advance, the HCNG blends furnish improvements of engine brake efficiency compared with compressed natural gas (CNG), which are more relevant at part loads and for the higher hydrogen content. Anyway, higher NOx emissions are observed due to the increased temperatures into the cylinders. Thus, the analysis also takes into account the Exhaust Gas Recirculation (EGR) dilution technique to reduce the NOx emissions. A large reduction of such pollutant, which has been estimated greater than 50%, can be achieved by using a 10% EGR. Furthermore higher engine efficiency is obtained using EGR due to reduced pumping work, reduced heat loss to the walls because of lower gas temperature and a reduction in the degree of dissociation in the high temperature burned gases.

MODELING NANOSECOND-PULSED SPARK DISCHARGE AND FLAME KERNEL EVOLUTION

2021 ◽  
pp. 1-22
Author(s):  
Joohan Kim ◽  
Vyaas Gururajan ◽  
Riccardo Scarcelli ◽  
Sayan Biswas ◽  
Isaac Ekoto
Keyword(s):  
Electrical Discharge ◽  
Internal Combustion Engines ◽  
Initial Conditions ◽  
Fuel Mixture ◽  
Spark Ignition ◽  
Combustion Stability ◽  
Flame Kernel ◽  
Wide Range ◽  
Challenging Environment ◽  
Kernel Growth

Abstract Dilute combustion, either using exhaust gas recirculation or with excess-air, is considered a promising strategy to improve the thermal efficiency of internal combustion engines. However, the dilute air-fuel mixture, especially under intensified turbulence and high-pressure conditions, poses significant challenges for ignitability and combustion stability, which may limit the attainable efficiency benefits. In-depth knowledge of the flame kernel evolution to stabilize ignition and combustion in a challenging environment is crucial for effective engine development and optimization. To date, comprehensive understanding of ignition processes that result in the development of fully predictive ignition models usable by the automotive industry does not yet exist. Spark-ignition consists of a wide range of physics that includes electrical discharge, plasma evolution, joule-heating of gas, and flame kernel initiation and growth into a self-sustainable flame. In this study, an advanced approach is proposed to model spark-ignition energy deposition and flame kernel growth. To decouple the flame kernel growth from the electrical discharge, a nanosecond pulsed high-voltage discharge is used to trigger spark-ignition in an optically accessible small ignition test vessel with a quiescent mixture of air and methane. Initial conditions for the flame kernel, including its thermodynamic state and species composition, are derived from a plasma-chemical equilibrium calculation. The geometric shape and dimension of the kernel are characterized using a multi-dimensional thermal plasma solver. The proposed modeling approach is evaluated using a high-fidelity computational fluid dynamics procedure to compare the simulated flame kernel evolution against flame boundaries from companion schlieren images.

scholarly journals Experimental study on knock sources in spark ignition engine with exhaust gas recirculation

2018 ◽  
Vol 165 ◽  
pp. 35-44 ◽  
Author(s):  
Mladen Božić ◽  
Ante Vučetić ◽  
Momir Sjerić ◽  
Darko Kozarac ◽  
Zoran Lulić
Keyword(s):  
Experimental Study ◽  
Exhaust Gas Recirculation ◽  
Spark Ignition ◽  
Spark Ignition Engine ◽  
Exhaust Gas ◽  
Gas Recirculation

scholarly journals Learning reference governor for cycle-to-cycle combustion control with misfire avoidance in spark-ignition engines at high exhaust gas recirculation–diluted conditions

2020 ◽  
Vol 21 (10) ◽  
pp. 1819-1834
Author(s):  
Bryan P Maldonado ◽  
Nan Li ◽  
Ilya Kolmanovsky ◽  
Anna G Stefanopoulou
Keyword(s):  
Combustion Process ◽  
Exhaust Gas Recirculation ◽  
Operating Conditions ◽  
Intake Manifold ◽  
Exhaust Gas ◽  
Model Free ◽  
Recirculation Rate ◽  
Valve Position ◽  
Gas Recirculation ◽  
Reference Governor

Cycle-to-cycle feedback control is employed to achieve optimal combustion phasing while maintaining high levels of exhaust gas recirculation by adjusting the spark advance and the exhaust gas recirculation valve position. The control development is based on a control-oriented model that captures the effects of throttle position, exhaust gas recirculation valve position, and spark timing on the combustion phasing. Under the assumption that in-cylinder pressure information is available, an adaptive extended Kalman filter approach is used to estimate the exhaust gas recirculation rate into the intake manifold based on combustion phasing measurements. The estimation algorithm is adaptive since the cycle-to-cycle combustion variability (output covariance) is not known a priori and changes with operating conditions. A linear quadratic regulator controller is designed to maintain optimal combustion phasing while maximizing exhaust gas recirculation levels during load transients coming from throttle tip-in and tip-out commands from the driver. During throttle tip-outs, however, a combination of a high exhaust gas recirculation rate and an overly advanced spark, product of the dynamic response of the system, generates a sequence of misfire events. In this work, an explicit reference governor is used as an add-on scheme to the closed-loop system in order to avoid the violation of the misfire limit. The reference governor is enhanced with model-free learning which enables it to avoid misfires after a learning phase. Experimental results are reported which illustrate the potential of the proposed control strategy for achieving an optimal combustion process during highly diluted conditions for improving fuel efficiency.

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