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Viewing 151 to 180 of 112267
2018-04-03
Technical Paper
2018-01-0143
Ganeswar Sahu, K.S.Gopala Krishnan, Mandar Kulkarni, Vikram Chauhan
With increasing market competition in low cost and mid-range vehicles, it’s important to delight the customer with value for money in terms of better NVH and higher fuel efficiency. Exhaust system plays an important role in noise attenuation and has to be worked upon for the better NVH characteristics without affecting engine performance. This can be achieved using Absorptive/Hybrid mufflers. Glass-wool’s effectiveness is governed by its physical and mechanical properties; this paper focuses on the sensitivity analysis of above properties using CAE for improving the acoustic simulation and its correlation with Testing and subsequently establishing process for acoustical development of mufflers.The study of Porous material in an acoustic field is based on Biot theory.
2018-04-03
Technical Paper
2018-01-0189
Aimilios Sofianopoulos, Mozhgan Rahimi Boldaji, Benjamin Lawler, Sotirios Mamalis
Paper Title: “Analysis of Thermal Stratification Effects in HCCI engines using Large Eddy Simulations and Detailed Chemical Kinetics” The widespread practical application of Homogeneous Charge Compression Ignition (HCCI) has limited controllability and narrow load range due to high heat release rates. It has been shown that thermal stratification affects ignition and heat release in HCCI and therefore can dictate its upper load limit. Thus, fundamental understanding of thermal stratification in HCCI combustion is necessary, along with the development of appropriate models to simulate it. A 3-D Computational Fluid Dynamics (CFD) model of single cylinder from a 2.0L production engine (LNF type) was developed using CONVERGE CFD, in which large eddy simulations (LES) are combined with combustion modeling using detailed chemical kinetics. The modeling framework is validated against experimental data of HCCI combustion in the modeled engine using negative valve overlap.
2018-04-03
Technical Paper
2018-01-0190
Ahmed Abdul Moiz, Pinaki Pal, Daniel Probst, Yuanjiang Pei, Yu Zhang, Sibendu Som, Janardhan Kodavasal
A Machine Learning - Genetic Algorithm (MLGA) approach was developed to virtually discover optimum designs using training data generated from high-fidelity simulations. Machine learning (ML) presents a pathway to transform complex physical processes that occur in a combustion engine into compact informational processes. In the present work, a total of over 2000 sector-mesh computational fluid dynamics (CFD) simulations of a heavy-duty engine were performed. These were run concurrently on a supercomputer to reduce overall turnaround time. The engine being optimized was run on low-octane (RON70) gasoline fuel using a partially-premixed advanced combustion approach. A total of nine input parameters (or features) were varied, and the CFD simulation cases were generated by randomly sampling points from this nine-dimensional input space.
2018-04-03
Technical Paper
2018-01-0191
Mani Sarathy, Nour Atef, Adamu Alfazazi, Jihad Badra, Yu Zhang, Tom Tzanetakis, Yuanjiang Pei
Toluene primary reference fuel (TPRF) (mixture of toluene, iso-octane and heptane) is a suitable surrogate to represent a wide spectrum of real fuels with varying octane sensitivity. Investigating different surrogates in engine simulations is a prerequisite to identify the best matching mixture. However, running 3D engine simulations using detailed models is currently impossible and reduction of detailed models is essential. This work presents an AramcoMech reduced kinetic model developed at KAUST for simulating complex TPRF surrogate blends. A semi-decoupling approach was used together with species and reaction lumping to obtain a reduced kinetic model. The model was widely validated against experimental data including shock tube and rapid compression machine ignition delay times, premixed laminar flame speeds, and jet stirred reactor speciation measurements.
2018-04-03
Technical Paper
2018-01-0192
David L. Reuss, Ziyang zhong, Xiaofeng Yang, Tang-Wei Kuo, Volker Sick
A large eddy simulation computed 35 consecutive motored cycles for comparison with PIV velocity measurements in the TCC-III engine. As a most basic comparison, this study focuses on the intracycle evolution and cycle to cycle variability, CCV, of the volume average kinetic energy. One purpose is to assess efficacy of comparing the kinetic energy of the two-component two-dimensional velocity in the restricted regions of the PIV measurements, with the three-component three-dimensional data of the LES. A second is to examine how well this simulation captured the kinetic energy production and dissipation through the motored cycles. The volume-averaged kinetic energy from the three-dimensional three-component LES is sampled from the entire cylinder volume and in slabs. These slabs are volumes with areas and thickness equal to the PIV field-of-view and laser sheet thickness. The differences between samples using different slab thickness and cutting planes are assessed.
2018-04-03
Technical Paper
2018-01-0185
Varun Haresh Nichani, Roberto Jaime, Satbir Singh, Xiaofeng Yang, Volker Sick
Large-eddy simulations (LES) of a motoring single-cylinder engine with transparent combustion chamber (TCC-II) are carried out using a commercially available computer code, CONVERGE. Numerical predictions are compared with high-speed particle image velocimetry (PIV) measurements. Predictions of two spatial discretization schemes namely, numerically stabilized central difference scheme (CDS) and fully upwind scheme are compared. Four different sub-grid scale (SGS) models; a non-eddy viscosity dynamic structure turbulence (DST) model of Pomraning and Rutland [AIAA Journal, 40, 2002], one-equation eddy-viscosity (1-Eqn) model of Menon et al. [Computers and Fluids, 1995], a zero-equation eddy-viscosity model of Vreman [Physics of Fluids, 2004] and the zero-equation standard Smagorinsky model [Smagorinsky, 1963] are employed on two different grid configurations. Additionally, simulations are also performed by deactivating the LES SGS models.
2018-04-03
Technical Paper
2018-01-0188
Guangfei Zhu, Krishna Pattabiraman, Federico Perini, Christopher Rutland
A swept-volume method of calculating the volume swept by the flame during each time step is developed and used to improve the calculation of fuel reaction rates. The improved reaction rates have been applied to the ignition model and coupled with the level set G-equation combustion model. In the ignition model, a single initial kernel is formed after which the kernel is convected by the gas flow and its growth rate is determined by the flame speed and thermal expansion due to the energy transfer from the electrical circuit. The predicted ignition kernel size was compared with the available experimental data and good agreements were achieved. Once the ignition kernel reaches a size when the fully turbulent flame is developed, the G-equation model is switched on to track the mean turbulent flame front propagation.
2018-04-03
Technical Paper
2018-01-0181
Vignesh Pandian Muthuramalingam, Anders Karlsson
This work utilizes previously developed VSB2 (Volvo Stochastic Blob and Bubble) multicomponent fuel spray model to study significance of using non-ideal thermodynamics for droplet evaporation under direct injection engine like operating conditions. Non-ideal thermodynamics is used to account for vapor-liquid equilibrium arising from evaporation of multicomponent fuel droplets. In specific, the evaporation of ethanol/iso-octane blend is studied in this work. Two compositions of the blend are tested, E-10 and E-85 respectively (the number denotes percentage of ethanol in blend). The VSB2 spray model is implemented into OpenFoam CFD code which is used to study evaporation of the blend in constant volume combustion vessel. Liquid and vapor penetration lengths for the E-10 case are calculated and compared with the experiment. The simulation results show good agreement with the experiment. Simulation is performed with two methods- ideal and non-ideal thermodynamics respectively.
2018-04-03
Technical Paper
2018-01-0182
Chaolin Zhang, Bo Hu, Chenguang lai, Hailin Zhang, Ling Qin, Xiaoli Leng, Wenpeng Huang
One-dimensional(1D) simulation tools, the computing speed of which is relatively fast , usually solve simple complexity problems. The solving process of 1D tools is mostly based on one-dimensional dynamic equations and empirical laws and in some cases it cannot obtain a similar accuracy with the three-dimensional(3D) simulation tools, which is usually time-consuming. The 1D-3D co-simulation, which combines the advantages of the two simulation tools while minimizes the disadvantages, is a method that integrates and runs the two simulation tools concurrently. Specially, coupled simulations can offer detailed information where needed 3D domain while offer system level information in the rest of the whole system. The approach not only minimizes the computational cost, but avoids demand for imposing accurate boundary conditions to the 3D simulation.
2018-04-03
Technical Paper
2018-01-0183
Jinlong Liu, James Szybist, Cosmin Dumitrescu
Modern 3D CFD IC engine simulations are extremely complex for the regular user due to the use of complex phenomenological sub-models with solution-adaptive mesh refinement and coarsening, and improved chemistry solvers. This study used ANSYS® Forte, Version 17.2, an IC engine CFD software package, to investigate two tuning constants that influence flame propagation in 3D CFD SI engine simulations: the stretch factor coefficient, C_ms and the flame development coefficient, C_m2. After identifying several C_m2-C_ms pairs that matched experimental data at one operating conditions, simulation results showed that except for HC emissions, the engine models that used different C_m2-C_ms sets predicted similar combustion performance, when the spark timing, engine load, and engine speed were changed from the operating condition used to validate the CFD simulation.
2018-04-03
Technical Paper
2018-01-0179
mohammed jaasim Mubarak ali, Francisco Hernandez Perez, Aliou sow PhD, Hong Im
Super-knock that occurs in spark ignition (SI) engines is investigated using two-dimensional (2D) numerical simulations. The temperature, pressure, velocity, and mixture distributions are obtained and mapped from a top dead center slice of full cycle three-dimensional (3D) engine simulations. Ignition is triggered at one end of the cylinder and a hot spot of known temperature was used to initiate a pre-ignition front to study super-knock. The computational fluid dynamics code CONVERGE was used for the simulations. A minimum grid size of 25 μm was employed to capture the shock wave and detonation inside the domain. The Reynolds averaged Navier-Stokes (RANS) method was employed to represent the turbulent flow and gas phase combustion chemistry was represented using a reduced chemical kinetic mechanism for primary reference fuels. A multi-zone model, based on a well-stirred reactor assumption, was used to solve the reaction terms.
2018-04-03
Technical Paper
2018-01-0178
Mozhgan Rahimi Boldaji, Aimilios Sofianopoulos, Sotirios Mamalis, Benjamin Lawler
A CFD investigation has been conducted to study the efficiency and emissions characteristics of Thermally Stratified Compression Ignition (TSCI) combustion with direct water injection. The motivation for using this new low temperature combustion mode is its ability to control the heat release process by introducing a forced thermal stratification using direct injection of water. The added degree of control over the combustion process allows for a significantly broader operable load range compare to HCCI. The effect of injection parameters including the mass, pressure, start of injection (SOI) timing, and spray pattern have been shown previously to affect the heat release of TSCI and its induced thermal stratification. In the present work, the efficiency and emissions considerations were investigated in detail. The 3-D CFD model was implemented in CONCERGE CFD coupled with detailed chemical kinetics.
2018-04-03
Technical Paper
2018-01-0180
Sundararaj Senthilkumar, Ssheshan P, U Chandrasekhar PhD
Design of Gas turbine engines demands for better aerodynamic characteristics, which in turn helps in controlling emissions. The need of an innovative and high precision aerodynamic design changes require a large amount of testing with less product development duration. So the development of an integrated approach for predicting flow in a gas turbine combustor is of cardinal important in the field of gas turbine engines. In the present work, it is aimed at developing an integrated approach for combustor modeling involving rapid prototyping and water tunnel testing to assess the cold flow numerical simulations; the physical model will be subjected to cold flow visualization and parametric studies and CFD analysis to demonstrate its capability for undergoing rigorous cold flow testing. A straight through annular combustors with axial swirler is chosen for the present study because of it has low pressure drop, less weight and used widely in modern day aviation engines.
2018-04-03
Technical Paper
2018-01-0174
Marco Del Pecchia, Sebastiano Breda, Alessandro D'Adamo, Stefano Fontanesi, Adrian Irimescu, Simona Merola
The detailed study of part-load conditions is essential to characterize engine-out emissions in key operating conditions. The relevance of part-load operation is further emphasized by the recent regulation (e.g. WLTP standard). The combustion development at part-load operations depends on a complex interplay between moderate turbulence levels (low engine speed and tumble ratio), low in-cylinder pressure and temperature and stoichiometric-to-lean mixture quality (to maximize fuel efficiency at partial loads). From a modelling standpoint, the reduced turbulence intensity compared to full-load operations complicates the interaction between different sub-models (e.g. re-consideration of the flamelet hypothesis adopted by common combustion models). In this paper the authors focus on chemistry-based simulations for laminar flame speed of gasoline surrogates at conditions typical of part-load operations.
2018-04-03
Technical Paper
2018-01-0176
Jann Koch, Stefan Geringer, Daniele Farrace, Sushant Pandurangi, Michele Bolla, Yuri M. Wright, Konstantinos Boulouchos
Large Eddy Simulation (LES) of premixed turbulent combustion in a confined cylinder setup at engine relevant conditions has been carried out for three different initial turbulence intensities, mimicking different flame propagation regimes. Direct Numerical Simulation (DNS) of the setup under investigation provides the reference data to be compared against. The DNS fields have been filtered on the LES grid and are used as initial conditions for the LES at onset of combustion, guaranteeing a direct comparability of the single realizations between the modeled and reference data. Two different combustion models, the G-Equation and LES-CMC premixed are compared with respect to their predictive capabilities as well as their usability and computational cost. While the G-Equation is a widely adopted approach for industrial applications and usually relies on a tunable turbulent flame speed closure, the novel LES-CMC comes as a tuning parameter free model.
2018-04-03
Technical Paper
2018-01-0173
Vesselin Krassimirov Krastev, Luca Silvestri, Gino Bella
The interest in URANS/LES hybrids, for the simulation of turbulent flows in Internal Combustion Engines, is consistently growing. An increasing number of applications can be found in the specialized literature for the past few years, including both seamless and zonal hybrid formulations. Following this trend, we have already developed a DES-based zonal modeling technique, which was found to have adequate scale-resolving capabilities in several engine-like reference tests. In the present paper we further extend our study, by evaluating the effects of the underlying turbulence model and of the grid quality/morphology on the scale-resolved part of the flow. For that purpose, we consider DES formulations based on an enhanced version of the k-g URANS model and on the URANS form of the popular RNG k-e model. The simulated test cases include a static intake valve geometry and a reference reciprocating piston/cylinder assembly.
2018-04-03
Technical Paper
2018-01-0175
Douglas P. Breden, Anand Karpatne, Laxminarayan Raja
The maximum lifetime of a spark plug is limited by electrode erosion. Over the course of millions of repeated sparking events, the electrode material ablates and the electrode gap increases which degrades performance. Once a critical gap is reached, the spark plug is no longer operational and must be replaced. Due to the long relevant time scales over which erosion occurs, and the difficulty of analyzing the spark plug environment during operation, determining spark plug lifetime typically requires extensive field testing. The objective of this work is use a computational model that can accurately simulate the electrode erosion process and make predictions on the effective lifetime. The problem is challenging in that there are a vast range of time scales, all of which must be resolved to model the erosion. Time scales range from milliseconds needed to resolve arc physics up to days and weeks for time timescales of electrode deformation due to ablation.
2018-04-03
Technical Paper
2018-01-0169
Victor Tizon Otero, Stephen Samuel
The thermal management of a Formula 1 car is a challenging task as it involves multiple components, systems and multiple sources of thermal energy. The present work attempts to model a representative F1 car following 2018 F1 regulations directly linked to the cooling systems requirements and performance. The main purpose of this work is to simulate the steady and transient behavior of the cooling system when the vehicle is in a qualifying lap, and during the entire race, including the wait in the starting grid and the pit stops. This model includes the sub-models representing internal combustion engine, hybrid powertrain, vehicle, driver and an appropriate cooling system composed of radiators, pumps and expansion tanks. This work validates the cooling system of a representative 2018 F1 car for the Silverstone Circuit. This model is capable of simulating the overall thermal performance of the F1 car for sizing the cooling system for most of the F1 circuits.
2018-04-03
Technical Paper
2018-01-0170
Andreas Kaechele, Marco Chiodi, Michael Bargende
The simulation of transient engine behavior has gained importance mainly due to stringent emission limits, measured under real driving conditions, and the concurrently demanded vehicle performance. This is especially true for turbocharged engines, as combustion engine and turbocharger form a complex system in which the components influence each other causing for example the well-known turbo-lag. Because of this strong interaction, the components cannot be analyzed separately during a transient load case as they mutually determine their boundary conditions. Three dimensional simulations of full engines in stationary operating points have become practicable several years ago and will remain a valuable tool in virtual engine development; however the next logical step is to extend this approach into the transient domain.
2018-04-03
Technical Paper
2018-01-0172
Yu-Hung Chang, Angela Wu, David Reuss, Volker Sick
Turbulent flow within the cylinder of a reciprocating internal combustion (IC) engine plays a fundamental role that affects engine performance, exhaust emissions, and in particular, their cycle-to-cycle variation. In efforts to predictively simulate engine performance, large-eddy simulation (LES) continues to find increasing interest and with enhanced computational capabilities, LES begins to become a design tool. Validation of LES as well as further enhancements can be guided by experimental data, such as results from particle image velocimetry (PIV) measurements. In this context, this paper discusses the analysis of subgrid-scale (SGS) contributions to LES and assesses appropriate cut-off scales at which the SGS model can derive quantitative scaling information from resolved scale input. Residual stress is one of the most frequently unclosed parameters in SGS models.
2018-04-03
Technical Paper
2018-01-0171
Abhishek Y. Deshmukh, Tobias Falkenstein, Heinz Pitsch, Maziar Khosravi, David van Bebber, Michael Klaas, Wolfgang Schroeder
The obligation for the development of highly efficient and low-emission combustion engines has renewed the interest in Compressed Natural Gas (CNG) engines using a Direct Injection (DI) system. DI-CNG is a promising technology because it can take advantage of high compression ratio potentially surpassing the thermal efficiency of spark-ignition engines, as well as eliminating the problem of low volumetric efficiency in port-injected gas engines by removing throttle valves similarly to diesel engines. Additionally, in contrast to diesel fuel, CNG burns without soot emissions due to high hydrogen to carbon ratio. It is presently available at low cost from natural sources and may be available through renewable sources in future as world-wide researchers are trying to synthesize carbon-based fuels using electricity. However, DI-CNG engines have not been widely used so far despite of these advantages, partly due to design problems.
2018-04-03
Technical Paper
2018-01-0225
Bradley Denton, Daniel Christopher Bitsis, Jason Miwa
With increasing diesel engine emissions regulations and the desire to increase overall thermal efficiency of the engine, various combustion concepts have been explored. One of the potential pathways to higher efficiency is through reduction of in-cylinder heat transfer. In this paper, a concept aimed at decreasing in-cylinder heat transfer through increased piston temperature is explored. In order to increase piston temperature and ideally reduce in-cylinder heat transfer, a Zero-Oil-Cooling (ZOC) piston concept was explored. To study this concept, the test engine was modified to allow piston oil cooling to be deactivated so that its impact on parameters such as BTE, piston temperature, and emissions could be evaluated. The engine was equipped with in-cylinder pressure measurement for combustion analysis as well as a piston temperature telemetry system to evaluate piston crown temperature. This paper will discuss the process by which the engine was modified to achieve ZOC and tested.
2018-04-03
Technical Paper
2018-01-0204
Daniele Farrace, David Sakellarakis, Michele Bolla, Yuri M. Wright, Konstantinos Boulouchos
Formation of soot in an auto-igniting n-dodecane spray under diesel engine relevant conditions has been investigated numerically. The bulk of research thus far has addressed turbulence-chemistry interaction by coupling highly diffusive turbulence models with more sophisticated combustion models. Instead, this study employs the advanced sub-grid scale k-equation model in the framework of a Large Eddy Simulation (LES) together with the uninvolved Direct Integration approach. A reduced n-heptane chemical mechanism has been employed and artificially accelerated in order to predict the ignition for n-dodecane accurately. Soot processes have been modelled with an extended version of the semi-empirical, two-equation model of Leung, which considers C2H2 as the soot precursor and accounts for particle inception, surface growth by C2H2 addition, oxidation by O2, oxidation by OH and particle coagulation.
2018-04-03
Technical Paper
2018-01-0202
Devyani Patil, Yue Wang, Long Liang, Karthik Puduppakkam, Ahmed Hussein, Chitralkumar Naik, Ellen Meeks
Advanced research in Spark Ignition (SI) engine has been focused on dilute combustion concepts. For example, exhaust gas recirculation is used to lower both fuel consumption and pollutant emissions while maintaining or enhancing engine performance, durability and reliability. These advancements achieve higher engine efficiency but may deteriorate combustion stability. One symptom of instability is a large Cycle to Cycle Variations (CCV) in the in-cylinder flow and combustion metrics. Large-Eddy Simulation (LES) is a Computational Fluid Dynamics (CFD) method that may be used to quantify CCV through numerical prediction of the turbulent flow and combustion processes in the engine over many engine cycles. In this study, we focus on evaluating the capability of LES to predict the in-cylinder flows and gas exchange processes in a motored SI engine installed with a transparent combustion chamber (TCC), comparing with recently published data.
2018-04-03
Technical Paper
2018-01-0201
Yashas Karaya, Srinivasa Krishna Addepalli, J M Mallikarjuna
Gasoline direct injection (GDI) engines have gained popularity in the recent times because of lower fuel consumption and exhaust emissions. But in these engines, the mixture preparation plays an important role which affects combustion, performance and emission characteristics of the engine. The mixture preparation, in turn, depends mainly upon fuel injector location and orientation. Therefore, in this study, an attempt has been made to understand the effect of fuel injector location and nozzle-hole orientation on the mixture preparation, performance and emission characteristics of a GDI engine. The mixture stratification inside the combustion chamber is characterized by a parameter called “stratification index” which is based on average equivalence ratio at different zones in the combustion chamber. The analysis is carried out on a four-stroke wall-guided GDI engine by computational fluid dynamics (CFD) analysis using the CONVERGE software.
2018-04-03
Technical Paper
2018-01-0200
Corinna Netzer, Tim Franken, Lars Seidel, Harry Lehtiniemi, Fabian Mauss
Water injection is a promising technology to improve the fuel efficiency of turbo-charged gasoline engines. Additionally, this technology is believed to enable the efficient operation of the three-way-catalyst also at high load conditions. In this numerical analysis, we investigate the effect of water on the combustion chemistry and the thermodynamics using 3D CFD RANS. In the first step, the influence of different amounts of steam on ignition delay time, laminar flame speed and heat capacity is investigated. In the second step, the impact of water vaporization is analyzed for different injection strategies, such as port and direct injection. Therefore, the water mass flow and the injection pressure are varied. A steady-state, medium speed, high-load operating point is investigated with focus on the effect of water injection on fuel efficiency, knock tendency and exhaust temperature.
2018-04-03
Technical Paper
2018-01-0198
Riccardo Scarcelli, Anqi Zhang, Thomas Wallner, Douglas Breden, Anand Karpatne, Laxminarayan Raja, Isaac Ekoto, Benjamin Wolk
While the spark-ignition (SI) engine technology migrates towards challenging combustion regimes (dilute and boosted operation), advanced ignition technologies generating non-equilibrium types of plasma have continued to receive significant attention from the automotive industry as a potential replacement for conventional spark-plugs. However there are no models currently that can describe the non-thermal plasma ignition process in the computational fluid dynamics (CFD) codes that are widely used in the engine multi-dimensional modeling community. A key question for the engine modelers that are trying to describe the non-equilibrium ignition physics concerns the characteristics of the non-equilibrium plasma. A key challenge is represented by the plasma formation timescale (nanoseconds) that can hardly be resolved within a full engine cycle (milliseconds) simulation.
2018-04-03
Technical Paper
2018-01-0197
Raouf Mobasheri, Mahdi Seddiq
An advanced 3D-CFD computational study was done in order to study the simultaneous effects of diesel injection pressure and single injection timing on the amounts of pollutant emissions and engine performance in a heavy duty, single cylinder iso-butanol/Diesel reactivity controlled compression ignition (RCCI) engine. A reduced chemical n-heptane-n-butanol-PAH mechanism which consists of 76 species and 349 reactions was used to simulate the combustion process of the dual-fuel diesel engine. The baseline operation case was validated with Wang et al. research work and good agreements between in-cylinder mean pressure, the rate of heat release and amounts of pollutant emissions such as NOx, Particulate Matter (PM), unburnt hydrocarbons (UHC) and carbon monoxide (CO) was obtained. Twenty-one different strategies based on two variables (diesel direct injection timing and diesel injection pressure) have been investigated.
2018-04-03
Technical Paper
2018-01-0196
Noah Van Dam, Magnus Sjöberg, Sibendu Som
Large-eddy Simulations (LES) have been carried out to investigate spray variability and its effect on cycle-to-cycle flow variability in a direct-injection spark-ignition (DISI) engine under non-reacting conditions. Initial simulations were performed of an injector in a constant volume spray chamber. Detailed measurements of the spray including quantitative mixing data are used to validate a simulation spray set-up for the stepped-bore multi-hole gasoline direct injection (GDI) injector. A random seed perturbation methodology was used to generate shot-to-shot spray variability in the LES, and comparisons of both mean and standard deviations were made for quantities with sufficient experimental data. After validation, the same spray set-up was used to simulate the same injector in an optically accessible DISI engine.
2018-04-03
Technical Paper
2018-01-0195
Federico Perini, Kenji Hiraoka, Yuji Oda, Akihiro Yuuki, Christopher Rutland, Rolf Reitz
Modeling ignition kernel development in spark ignition engines is crucial to capturing the sources of cyclic variability, both with RANS and LES simulations. Appropriate kernel modeling must ensure that energy transfer from the electrodes to the gas phase has the correct timing, rate and locations, until the flame surface is large enough to be represented on the mesh by the G-Equation level-set method. However, in most kernel models, geometric details driving kernel growth are missing: either because it is described as Lagrangian particles, or because its development is simplified, i.e., down to multiple spherical flames. In this work, we focused on the geometry of kernel development, and developed a new, Triangulated Lagrangian Ignition Kernel model. One (or multiple, if it restrikes) spark channel is initialized as a one-dimensional Lagrangian particle thread.
Viewing 151 to 180 of 112267