scholarly journals Jet ignition prediction in a zero-dimensional pre-chamber engine model

2021 ◽  
pp. 146808742110150
Author(s):  
Quentin Malé ◽  
Olivier Vermorel ◽  
Frédéric Ravet ◽  
Thierry Poinsot
Keyword(s):  
Present Model ◽  
Turbulent Jets ◽  
Specific Model ◽  
Optimum Size ◽  
Main Chamber ◽  
Balance Equations ◽  
Mixing Processes ◽  
Engine Model ◽  
Cylindrical Holes ◽  
Separate Balance

This paper presents a multi-chamber, multi-zone engine model to predict the ignition of a lean main chamber by a pre-chamber. The two chambers are connected by small cylindrical holes: the flame is ignited in the pre-chamber, hot gases propagate through the holes and ignite the main chamber through Turbulent Jet Ignition (TJI). The model original features are: (i) separate balance equations for the pre- and main chambers, (ii) a specific model for temperature and composition evolution in the holes and (iii) a DNS-based model to predict the ignition of the main chamber fresh gases by the burnt gases turbulent jets exiting the holes. Chemical reactions during TJI are the result of two competing mixing processes: (1) the hot jet gases mix with the fresh main chamber to produce heated zones and (2) at the same time, these hot gases cool down. (1) increases combustion and leads to ignition while (2) decreases it and can prevent ignition. The overall outcome (ignition or failure) is too complex to be modelled simply and the present model relies on recent DNSs of TJI which provided a method to predict the occurrence of ignition. Incorporating this DNS information into the engine model allows to predicts whether ignition will occur or not, an information which is not accessible otherwise using simple models. The resulting approach is tested on multiple cases to predict ignition limits for very lean cases, effects of H2 injection into the pre-chamber and optimum size for the holes connecting the two chambers as a function of equivalence ratio.

Turbofan Engine Health Assessment From Flight Data

2014 ◽  
Author(s):  
N. Aretakis ◽  
I. Roumeliotis ◽  
A. Alexiou ◽  
C. Romesis ◽  
K. Mathioudakis
Keyword(s):  
Probabilistic Neural Network ◽  
Health Assessment ◽  
Sole Source ◽  
Specific Model ◽  
Diagnostic Information ◽  
Diagnostic Methods ◽  
Diagnostic Process ◽  
Tracking Method ◽  
Engine Model ◽  
Automated Method

The paper presents the use of different approaches to engine health assessment using on-wing data obtained over a year from an engine of a commercial short-range aircraft. The on-wing measurements are analyzed with three different approaches, two of which employ two models of different quality. Initially, the measurements are used as the sole source of information and are post-processed utilizing a simple “model” (a table of corrected parameter values at different engine power levels) to obtain diagnostic information. Next, suitable engine models are built utilizing a semi-automated method which allows for quick and efficient creation of engine models adapted to specific data. Two engine models are created, one based on publicly available data and one adapted to engine specific on-wing “healthy” data. These models of different detail are used in a specific diagnostic process employing model-based diagnostic methods, namely the Probabilistic Neural Network (PNN) method and the Deterioration Tracking method. The results demonstrate the level of diagnostic information that can be obtained for this set of data from each approach (raw data, generic engine model or adapted to measurements engine model). A sub-system fault is correctly identified utilizing the diagnostic process combined with the engine specific model while the Deterioration Tracking method provides additional information about engine deterioration.

Combustion modelling of turbulent jet ignition in a divided combustion chamber

2021 ◽  
pp. 146808742110371
Author(s):  
Mattia Olcuire ◽  
Clara Iacovano ◽  
Alessandro d’Adamo ◽  
Sebastiano Breda ◽  
Tommaso Lucchini ◽  
...  
Keyword(s):  
Volume Ratio ◽  
Turbulent Jets ◽  
Combustion Regime ◽  
Nozzle Diameter ◽  
Turbulent Jet ◽  
Main Chamber ◽  
Lean Burn ◽  
Jet Flame ◽  
Chamber Volume ◽  
Combustion Modelling

Turbulent jet ignition is seen as one of the most promising strategies to achieve stable lean-burn operation in modern spark-ignition engines thanks to its ability to promote rapid combustion. A nearly stoichiometric mixture is ignited in a small-volume pre-chamber, following which multiple hot turbulent jets are discharged in the main chamber to initiate combustion. In the present work, a detailed computational investigation on the turbulent combustion regime of premixed rich propane/air mixture in a quiescent divided chamber vessel is carried out, to study the characteristics of the jet flame without the uncertainties in mixing and turbulent conditions typical of real-engine operations. In particular, the paper investigates the dependency of flame propagation on nozzle diameter (4, 6, 8, 12 and 14 mm) and pre-chamber/main-chamber volume ratio (10% and 20%); CFD results are compared to the experimental outcomes. Results show that the combustion regime in the quiescent pre-chamber follows a well-stirred reaction mode, rendering the limitation in using conventional flamelet combustion models. Furthermore, due to the very high turbulence levels generated by the outflowing reacting jets, also the main chamber combustion develops in a well-stirred reactor type, confirming the need for a kinetics-based approach to combustion modelling. However, the picture is complicated by thickened flamelet conditions possibly being verified for some geometrical variations (nozzle diameter and pre-chamber volume). The results show a general good alignment with the experimental data in terms of both jet phasing and combustion duration, offering a renewed guideline for combustion simulations under quiescent and low Damköhler number conditions.

Numerical Investigation of Pre-Chamber Jet Combustion in a Light-Duty Gasoline Engine

2020 ◽  
Author(s):  
Anqi Zhang ◽  
Xin Yu ◽  
Nayan Engineer ◽  
Yu Zhang ◽  
Yuanjiang Pei
Keyword(s):  
Gasoline Engine ◽  
Fuel Injection ◽  
Three Dimensional ◽  
Load Condition ◽  
Turbulent Jets ◽  
Main Chamber ◽  
Combustion Modeling ◽  
Complex Processes ◽  
History Of ◽  
Ignition And Combustion

Abstract Open-cycle engine simulations of a passive pre-chamber operating inside a direct-injected gasoline engine are performed and analyzed in this study. A comprehensive three-dimensional computational fluid dynamics (CFD) model has been formulated with state-of-the-art physical sub-models to account for the complex processes of engine gas exchange, fuel injection and mixing, ignition, and combustion. Numerical results are validated against experimental measurements under low load condition with high internal EGR. Realistic modeling considerations are discussed to ensure proper fidelity. In particular, the mixture conditions and flow motions could present very different features between the pre- and main chamber, which requires comprehensive simulation of the full engine cycle and imposes challenges for combustion modeling. Practically validated chemical kinetics models are essential for proper prediction of cylinder pressure history of pre-chamber jet combustion systems. Detailed analysis is then carried out to highlight key processes associated with pre-chamber operation, including residual scavenging, fuel/air mixture formation, flow pattern and turbulence development within the pre-chamber, and the ignition of main chamber mixture by issued turbulent jets. Numerical evaluation of pre-chamber design variants has been attempted, and less commonly investigated geometry parameters such as swirl nozzles and nozzle umbrella angle are found impactful for pre-chamber ignition performances.

scholarly journals Estimates of Power Consumed by Mixing in the Ocean Interior

2006 ◽  
Vol 19 (19) ◽  
pp. 4877-4890 ◽  
Author(s):  
Louis St. Laurent ◽  
Harper Simmons
Keyword(s):  
Thermohaline Circulation ◽  
Specific Model ◽  
Meridional Overturning Circulation ◽  
Basic Knowledge ◽  
Careful Examination ◽  
Mixing Efficiency ◽  
Mixing Processes ◽  
Power Estimate ◽  
Global Circulation ◽  
Bottom Waters

Abstract Much attention has focused on the power required for driving mixing processes in the ocean interior, the thermohaline circulation, and the related meridional overturning circulation (MOC). Recent estimates range from roughly 0.5 to 2 TW (1 TW = 1 × 1012 W), based on differing arguments for the closure of the MOC mass budget. While these values are both O(1) TW, the thermodynamic implications of the estimates are significantly different. In addition, these numbers represent an integral constraint on the global circulation, and the apparent discrepancy merits careful examination. Through basic thermodynamic considerations on water mass mixing, a mechanical power consumption of 3 ± 1 TW is found to be consistent with a basic knowledge of the distribution and magnitude of oceanic turbulence diffusivities. This estimate is somewhat independent of any specific model for mass closure of the MOC. In addition, this estimate is based on a thermocline diffusivity of only 0.1 cm2 s−1, with enhanced diffusivities acting only in the deep and bottom waters. Adding enhanced diffusivities in the upper ocean, or lowering the mixing efficiency below 20%, will increase the power estimate. Moreover, 3 TW is a reasonable estimate for the power availability to processes acting beneath the oceanic mixed layer.

Turbofan Engine Health Assessment From Flight Data

2014 ◽  
Vol 137 (4) ◽  
Author(s):  
N. Aretakis ◽  
I. Roumeliotis ◽  
A. Alexiou ◽  
C. Romesis ◽  
K. Mathioudakis
Keyword(s):  
Probabilistic Neural Network ◽  
Health Assessment ◽  
Sole Source ◽  
Specific Model ◽  
Diagnostic Information ◽  
Diagnostic Methods ◽  
Diagnostic Process ◽  
Tracking Method ◽  
Engine Model ◽  
Automated Method

The paper presents the use of different approaches to engine health assessment using on-wing data obtained over a year from an engine of a commercial short-range aircraft. The on-wing measurements are analyzed with three different approaches, two of which employ two models of different quality. Initially, the measurements are used as the sole source of information and are postprocessed utilizing a simple “model” (a table of corrected parameter values at different engine power levels) to obtain diagnostic information. Next, suitable engine models are built utilizing a semi-automated method which allows for quick and efficient creation of engine models adapted to specific data. Two engine models are created, one based on publicly available data and one adapted to engine specific on-wing “healthy” data. These models of different details are used in a specific diagnostic process employing model-based diagnostic methods, namely the probabilistic neural network (PNN) method and the deterioration tracking method. The results demonstrate the level of diagnostic information that can be obtained for this set of data from each approach (raw data, generic engine model or adapted to measurements engine model). A subsystem fault is correctly identified utilizing the diagnostic process combined with the engine specific model while the deterioration tracking method provides additional information about engine deterioration.

scholarly journals MATHEMATICAL MODELLING OF WAVE-INDUCED NEARSHORE CIRCULATIONS

1986 ◽  
Vol 1 (20) ◽  
pp. 122 ◽  
Author(s):  
Donghoon Yoo ◽  
Brian A. O'Connor
Keyword(s):  
Experimental Data ◽  
Present Model ◽  
Wave Climate ◽  
Mixing Processes ◽  
Diffraction Wave ◽  
Waves And Currents ◽  
Current Interaction ◽  
Induced Currents ◽  
Set Up ◽  
Wave Induced

The paper presents a mathematical model for describing wave climate and wave-induced nearshore circulations. The model accounts for current-depth refraction, diffraction, wave-induced currents, set-up and set-down, mixing processes and bottom friction effects on both waves and currents. The present model was tested against published experimental data on wave conditions within a model harbour and shown to give very good results for both wave and current fields. The importance of including processes such as advection, flooding and current-interaction in coastal models was demonstrated by comparing the numerical results without each process to the results from the complete scheme.

scholarly journals Reduction of soot carbon in the exhaust gases of a tractor gas-diesel engine

2021 ◽  
Vol 2094 (5) ◽  
pp. 052068
Author(s):  
A P Akimov ◽  
P L Lekomtsev ◽  
V A Likhanov ◽  
O P Lopatin ◽  
A O Vasiliev
Keyword(s):  
Natural Gas ◽  
Gas Phase ◽  
Turbulent Jets ◽  
Mixing Process ◽  
Mixing Processes ◽  
Carbon Particles ◽  
Air Jets ◽  
A Value ◽  
Soot Carbon ◽  
Gas Flame

Abstract The rate of oxidation of carbon (including its dispersed forms) has a value much higher than the rate of gasification. Therefore, in the initial part of the flame, when oxygen is still contained in the gas phase, the oxidation of soot will be the process on which the change in the size and concentration of dispersed carbon particles mainly depends. The intensity of oxidation and gasification of dispersed carbon in the flame largely depends on the development of the mixing process, determined by the aerodynamics of the fuel and air jets. The paper presents an analysis of the influence of mixing processes on the oxidation and gasification of dispersed carbon in a natural gas flame in the study of homogeneous flames and mixing of turbulent jets. The results of industrial studies of the mixing of fuel and air in a diffusion torch are taken into account. The results allow us to evaluate the influence of various aerodynamic factors on the processes occurring in the glowing flame of natural gas in the combustion chamber of gas diesel.

Model-Assisted Analysis of Simultaneous Paraffin and Asphaltene Deposition in Laboratory Core Tests

2005 ◽  
Vol 127 (4) ◽  
pp. 318-322 ◽  
Author(s):  
Shaojun Wang ◽  
Faruk Civan
Keyword(s):  
Experimental Data ◽  
Present Model ◽  
Momentum Balance ◽  
Balance Equations ◽  
Porosity And Permeability ◽  
Energy And Momentum ◽  
Assisted Analysis ◽  
Oil Gas ◽  
Deposition Models

A model for analysis and interpretation of the simultaneous deposition of paraffin and asphaltene in laboratory core tests is presented. This model incorporates the mass balance equations for the oil, gas, paraffin, and asphaltene pseudocomponents; the paraffin and asphaltene solubility and deposition models; the energy and momentum balance equations; and the porosity and permeability reduction models. This model is numerically solved and validated with two sets of laboratory experimental data. It is demonstrated that the present model satisfactorily represents the simultaneous deposition of paraffin and asphaltene and the resultant damage caused on the porosity and permeability of porous media. The model is used for determination of the various process parameters with the help of the experimental data obtained by laboratory core tests.

Effects of Ambipolar Diffusion on Prominence Thread Models

1994 ◽  
Vol 144 ◽  
pp. 315-321 ◽  
Author(s):  
M. G. Rovira ◽  
J. M. Fontenla ◽  
J.-C. Vial ◽  
P. Gouttebroze
Keyword(s):  
Energy Balance ◽  
Transition Region ◽  
Ambipolar Diffusion ◽  
Line Profiles ◽  
Balance Equations ◽  
Model Calculations ◽  
Partial Frequency ◽  
Frequency Redistribution ◽  
Partial Frequency Redistribution ◽  
Theoretical Structure

AbstractWe have improved previous model calculations of the prominence-corona transition region including the effect of the ambipolar diffusion in the statistical equilibrium and energy balance equations. We show its influence on the different parameters that characterize the resulting prominence theoretical structure. We take into account the effect of the partial frequency redistribution (PRD) in the line profiles and total intensities calculations.

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