Yuri Wright

Last Name

Wright

First Name

Yuri

ORCID

0000-0001-8552-5532

Organisational unit

01159 - Lehre Maschinenbau und Verfahrenstechnik

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Publications 1 - 10 of 29

CMC Model Applied to Marine Diesel Spray Combustion: Influence of Fuel Evaporation Terms
Srna, Aleš; Bolla, Michele; Boulouchos, Konstantinos; et al. (2014)
SAE Technical Papers
This study presents an application of the conditional moment closure (CMC) combustion model to marine diesel sprays. In particular, the influence of fuel evaporation terms has been investigated for the CMC modeling framework. This is motivated by the fact that substantial overlap between the dense fuel spray and flame area is encountered for sprays in typical large two-stroke marine diesel engines which employ fuel injectors with orifice diameters of the order of one millimeter. Simulation results are first validated by means of experimental data from the Wärtsilä optically accessible marine spray combustion chamber in terms of non-reactive macroscopic spray development. Subsequently, reactive calculations are carried out and validated in terms of ignition delay time, ignition location, flame lift-off length and temporal evolution of the flame region. Finally, the influence of droplet terms on spray combustion is analyzed in detail. The effect of evaporation into the mixture fraction variance transport equation was seen to play a prominent role concerning autoignition and flame stabilization: both ignition delay and flame lift-off length are considerably increased when evaporation effects are included. This was found to be attributed to the strong spatial overlap between evaporation and combustion - typical for marine sprays - leading to an increase in the local scalar dissipation rate in the evaporating region. Overall, inclusion of evaporation terms resulted in improved agreement with experimental data. These findings are contrary to previous investigations for typical automotive diesel sprays reporting only a minor influence of evaporation. Consequently, this study constitutes an extension of former analyses to large marine fuel injection configurations and emphasizes the importance of such effects for the simulation of marine diesel sprays.
Conditional Moment Closure Approaches for Simulating Soot and NOx in a Heavy-Duty Diesel Engine
Trivedi, Shrey; Gkantonas, Savvas; Wright, Yuri; et al. (2021)
SAE Technical Papers
A heavy-duty diesel engine (ETH-LAV single cylinder MTU396 heavy duty research engine) was simulated by RANS and advanced reacting flow models to gain insight into its soot and NOx emissions. Due to symmetry, a section of the engine containing a single injector-hole was simulated. Dodecane was used as a surrogate to emulate the evaporation properties of diesel and a 22-step reaction mechanism for n-heptane was used to describe combustion. The Conditional Moment Closure (CMC) method was used as the combustion model in two ways. In a more conventional modelling approach, CMC was fully interfaced with the CFD and a two-equation model was employed for determining soot while the extended Zeldovich mechanism was used for NOx. In a second approach called the Imperfectly Stirred Reactor (ISR) method, the CMC equation was integrated over space and the previous RANS-CMC solution was further analysed in a post-processing step with the focus on soot. Here, a complex sectional soot model called the Napoli sectional (NAPS) model was used to calculate soot particle size distributions (PSD). Three different cases with variations in the start of injection (SOI) were analysed. The calculated pressure trace showed very good agreement with the experiment for all conditions studied. The resulting soot mass fraction from the simulations was found to increase as the SOI was progressed closer to the top dead centre (TDC). The opposite behaviour was observed for NOx in that its mass fraction decreased with progressing SOI. These trends show good agreement with the results from experiments and are consistent with previous studies. Finally, the ISR results for soot were analysed for both two-equation and NAPS models. Soot mass fraction and PSDs were overestimated by the ISR model but the sooting trends for varying conditions were correctly captured.
Calibration of a model for selective catalytic reduction with ammonia, including NO oxidation, and simulation of NOx reduction over an Fe–zeolite catalyst under highly transient conditions
Sharifian, Leila; Wright, Yuri; Boulouchos, Konstantinos; et al. (2013)
International Journal of Engine Research
Systematic assessment of data-driven approaches for wall heat transfer modelling for LES in IC engines using DNS data
Impagnatiello, Matteo; Bolla, Michele; Keskinen, Karri; et al. (2022)
International Journal of Heat and Mass Transfer
Data-driven (DD) methods offer a promising pathway towards novel modelling solutions in fluid flow and heat transfer. In this study, we investigate the application of DD neural network (NN) methods on wall heat transfer modelling in the context of wall-modelled large-eddy simulation (WMLES) in engines, focusing on the systematic evaluation of criteria for the successful DD model generation. High-fidelity input data for model training and testing is generated by spatial filtering of DNS and wall-resolved LES fields in several engine and engine-like configurations. The NN-based models are constructed using different input data and wall-adjacent cell schemes, while cell size and network complexity are also varied. The evaluated NN-based models demonstrate improved performance with respect to classical wall functions, indicating promising potential for engineering applications. In particular, better modelling results were obtained with the inclusions of a wall-normal cell Reynolds number and of data from the second wall-normal cell. Such a two-cell input format appears to offer a good compromise between performance and complexity. Both the present NN models and literature reference approaches generally perform better in unburned regions than in burned ones. In near-wall regions with flame fronts, we present an analysis dividing samples into “unburned”, “burned”, and “flame boundary” zones exposing different characteristics and a varying degree of modelling difficulty.
Comparison and Sensitivity Analysis of Turbulent Flame Speed Closures in the RANS G-Equation Context for Two Distinct Engines
Koch, Jann; Xu, Guoqing; Wright, Yuri; et al. (2016)
SAE International Journal of Engines
Three-dimensional reactive computational fluid dynamics (CFD) plays a crucial role in IC engine development tasks complementing experimental efforts by providing improved understanding of the combustion process. A widely adopted combustion model in the engine community for (partially) premixed combustion is the G-Equation where the flame front is represented by an iso-level of an arbitrary scalar G. A convective-reactive equation for this iso-surface is solved, for which the turbulent flame speed ST must be provided. In this study, the commonly used and well-established Damköhler approach is compared to a novel correlation, derived from an algebraic closure for the scalar dissipation of reaction progress as proposed by Kolla et al. [1]. The predictions from the two correlations are probed towards their sensitivities by means of experimental data from two distinctly different engine configurations: 1) a lean burn spark ignition natural gas engine for power generation, derived from a flat head/bowl-in piston compression ignition engine with roughly two liters of displacement per cylinder, and, 2) a small bore 250 cc single cylinder port fuel injected gasoline engine with a typical four-valve pent roof arrangement. The sensitivity of the flame speed closures towards the in-cylinder turbulent flow field is investigated for a sweep in turning speed for both engines close to full load. The numerical predictions in terms of pressure trace as well as heat release rates for both engines are compared to experimental test bench data and the predictive capabilities of the proposed closures for the two considerably different engine scales are studied. Additionally, the impact of two different RANS turbulence models (k-ε RNG and standard k-ω) on the results is discussed. The combustion regime is further classified in the Borghi diagram throughout the combustion event, where the flame speed closures are further investigated with emphasis on the early and late combustion stages.
Modeling Split Injections of ECN “Spray A” Using a Conditional Moment Closure Combustion Model with RANS and LES
Blomberg, Christopher; Zeugin, Lucas; Pandurangi, Sushant; et al. (2016)
SAE International Journal of Engines
This study investigates n-dodecane split injections of “Spray A” from the Engine Combustion Network (ECN) using two different turbulence treatments (RANS and LES) in conjunction with a Conditional Moment Closure combustion model (CMC). The two modeling approaches are first assessed in terms of vapor spray penetration evolutions of non-reacting split injections showing a clearly superior performance of the LES compared to RANS: while the former successfully reproduces the experimental results for both first and second injection events, the slipstream effect in the wake of the first injection jet is not accurately captured by RANS leading to an over-predicted spray tip penetration of the second pulse. In a second step, two reactive operating conditions with the same ambient density were investigated, namely one at a diesel-like condition (900K, 60bar) and one at a lower temperature (750K, 50bar). For the diesel-like condition, both modeling approaches captured first injection ignition delay, overall soot mass and soot location well. Due to an under prediction of spray tip expansion during combustion in combination with the slight over-prediction of the vapor tip penetration, RANS-CMC’s reactive spray penetration length nonetheless agreed well with the experiment. However, RANS-CMC did not capture full combustion recession towards the injector location after the end of the first injection. LES-CMC showed accurate predictions of the second injection ignition delay and improvements with respect to combustion recession, and flame structure. For the low temperature condition, RANS-CMC accurately predicted ignition timing. Here LES-CMC slightly under-predicted ignition delay. Ignition location and flame structure are in reasonable agreement with the experiment for both numerical setups. In accordance to the experiment it was seen that for both RANS- and LES-CMC the first injection does not auto-ignite and the second injection was necessary to create the appropriate local conditions for ignition to occur. Furthermore, the simulations did not predict any soot at the lower temperature, in agreement with the experimental observations. The findings suggest that LES may be necessary in the case of split injections towards accurate two-phase flow field predictions and - even more so - to capture full combustion recession for diesel-like conditions. The proposed RANS- and LES-CMC models show considerable promise for the challenging dynamics of auto-igniting fuel sprays with multiple injections.
Flamelet Generated Manifolds Applied to Dual-Fuel Combustion of Lean Methane/Air Mixtures at Engine Relevant Conditions Ignited by n Dodecane Micro Pilot Sprays
Seddik, Omar; Pandurangi, Sushant; Bolla, Michele; et al. (2019)
SAE Technical Papers
Asynchronicity in opposed-piston RCMs: Does it matter?
Goldsborough, S. Scott; Cheng, Song; Kang, Dongil; et al. (2024)
Proceedings of the Combustion Institute
Rapid Compression Machines (RCMs) are widely utilized to study combustion phenomena at engine-relevant conditions, and significant efforts are typically made to create a quiescent environment, particularly for investigations of autoignition chemistry. Opposed-piston configurations can be advantageous due to shorter compression times and reduced surface area to volume ratios. Each side must be actuated simultaneously, but this can be challenging in practice. These devices, like most RCMs, utilize hydraulics for actuation, speed control and arrestation of the piston at the end of the stroke; there is no mechanical control or linkage of the two piston trajectories. To quantify the magnitudes and effects of piston asynchronous behavior, this work employs both detailed experimental measurements and, for the first time, high-fidelity, Direct Numerical Simulation (DNS). The boundary conditions are carefully considered applying insight from high-resolution linear variable differential transformer (LVDT) measurements of the piston trajectory and a zero-dimensional kinematics model of the piston-shaft assembly. Sufficient resolution in the piston crevice region is used. The complicated fluid dynamical behavior that can evolve during piston compression and the ensuing delay processes due to offset timings from toffset = 0–10 ms is elucidated. It is found that near toffset = 6 ms and beyond, the boundary layer on the face of the first-seating piston can be sufficiently perturbed, due initially to reemergence of gas from the crevice of the first-seating piston, so that the adiabatic core can become degraded at long ignition delay times. Substantial mixing of colder gas into the interior of the reaction chamber can alter the measurements, similar to effects previously observed for improper piston crevice configuration. Experimental techniques to mitigate asynchronous behavior are discussed and demonstrated.
Transient simulation of NOx reduction over a Fe-Zeolite catalyst in an NH3-SCR system and study of the performance under different operating conditions
Sharifian, Leila; Wright, Yuri; Boulouchos, Konstantinos; et al. (2012)
SAE International Journal of Fuels and Lubricants
Investigation of the Ignition Process of Pilot Injections Using CFD
Barro, Christophe; Seddik, Omar; Wright, Yuri; et al. (2019)
SAE Technical Papers

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