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Viewing 1 to 30 of 242
2015-04-14
Technical Paper
2015-01-0801
Gregory K. Lilik, Charles J. Mueller, Cosmin E. Dumitrescu, Christopher R. Gehrke
Although the soot-formation process in diesel engines has been well characterized during the mixing-controlled burn, little is known about the distribution of soot throughout the combustion chamber after the end of appreciable heat release during the expansion and exhaust strokes. As such, a laser-induced incandescence (LII) technique was developed to visualize the distribution of soot within an optically accessible single-cylinder direct-injection diesel engine during this period. The developed LII diagnostic is semi-quantitative and features a vertically oriented and vertically propagating laser sheet that can be translated across the combustion chamber, with image acquisition occurring roughly perpendicular to the plane of the laser sheet.
2015-04-14
Technical Paper
2015-01-0797
Benjamin W Knox, Caroline L Genzale, Lyle M Pickett, Jose M Garcia-Oliver, Walter Vera-Tudela
This work contributes to the understanding of physical mechanisms that control flashback, or more appropriately ignition recession, in diesel-like sprays. Ignition recession is the process whereby a lifted flame retreats back towards the injector after end-of-injection under autoignition conditions. The motivation for this study is that failure of ignition recession can result in excessive lean-source unburned hydrocarbon emissions, especially for low-temperature combustion strategies. The Engine Combustion Network (ECN) Spray A dataset is used to link experimental test conditions to the existence of ignition recession. Then, a 1-D gas-jet model, capable of modeling non-reacting and reacting diesel spray conditions, is used to explain the experimental trends. Finally, the 1-D reacting gas-jet model is used to predict how a controlled ramp-down rate-of-injection can enhance the likelihood of ignition recession for conditions that would not normally exhibit ignition recession.
2015-04-14
Technical Paper
2015-01-0792
Guillaume LEQUIEN, Scott Skeen, Julien Manin, Lyle M Pickett, Oivind Andersson
The mechanisms driving the transition from ignition of the fuel-air mixture to the stabilization of the lift-off length of a diesel spray are not yet fully established. Previous experiments are supporting the idea of a lift-off length stabilization through auto-ignition processes occurring ahead of the high heat release reaction zone rather than flame propagation towards the upstream reactants [1,2]. Fuel properties such as the cetane number are directly affecting the ignition delay, and the ignition quality of the fuel is further affecting the lift-off length [1]. The present study aims to investigate the effect of low fuel cetane numbers on the ignition behaviour of diesel sprays and the transition to a stabilized lift-off position. Two different fuels issued from coal to liquid synthesis (Fischer-Tropsch type), having low cetane numbers, are tested.
2015-04-14
Technical Paper
2015-01-1696
Federico Perini, Kan Zha, Stephen Busch, Paul Miles, Rolf Reitz
In this work computational and experimental approaches are combined to characterize in-cylinder flow structures and local flow field properties during operation of the Sandia 1.9L light-duty optical diesel engine. A full computational model of the single-cylinder research engine was used that considers the complete intake and exhaust runners and plenums, as well as the adjustable throttling devices used in the experiments to obtain different intake swirl ratios. The in-cylinder flow predictions were validated against an extensive set of planar PIV measurements at different vertical locations in the combustion chamber for different swirl ratio configurations. Principal Component Analysis was used to characterize precession, tilting and eccentricity, and regional averages of the in-cylinder turbulence properties in the squish region and the piston bowl.
2015-04-14
Technical Paper
2015-01-0824
Jeremie Dernotte, John Dec, Chunsheng Ji
Future generations of internal combustion engines must provide high thermal efficiency across the operating range. Recently, low-temperature gasoline combustion (LTGC) engines (HCCI-like engines) have been demonstrated to provide high peak gross indicated thermal efficiency under a range of conditions. However, in order to develop strategies to further increase the indicated thermal efficiency, it is of interest to fully understand the causes of the combustion losses. In this context, the objective of this study is to develop a detailed understanding of the various factors affecting the trends in gross indicated thermal efficiency of a mid-size single cylinder LTGC engine by systematically investigating how the supplied fuel energy splits into the following four energy pathways: gross indicated thermal efficiency, combustion inefficiency, heat transfer and exhaust losses.
2015-04-14
Technical Paper
2015-01-0813
John E. Dec, Yi Yang, Chunsheng Ji, Jeremie Dernotte
Responding to the need to reduce petroleum consumption, gasoline in the U.S. now contains 10% ethanol (E10), and levels of 15% and 20% (E20) are being considered. Petroleum consumption can also be reduced by improving engine efficiency, and engines using low-temperature gasoline combustion (LTGC), which includes HCCI and partially stratified variants of HCCI, align with this goal. Adding ethanol changes the autoignition characteristics of gasoline, and it is important to understand how this affects the performance of premixed LTGC (i.e. HCCI) and the potential to use advanced techniques such as partial fuel stratification (PFS) that can improve the efficiency and load range of intake-boosted LTGC. Accordingly, a study was conducted comparing the performance of conventional petroleum-based gasoline (E0) with E10 and E20 for both premixed and PFS LTGC. The E10 and E20 were obtained by blending pure ethanol with the E0 (AKI=87) gasoline.
2015-04-14
Technical Paper
2015-01-1697
Daniel Freudenhammer, Brian Peterson, Carl-Philipp Ding, Benjamin Boehm, Sven Grundmann
Within automotive research and design, efforts are often focused on the engine geometry design for optimization of performance and efficiency. Within spark-ignition (SI) engines, the intake and cylinder geometry play an important role in defining the in-cylinder flow, which is regarded as a key parameter influencing charge-filling, mixture preparation, and combustion [1]. An efficient optimization of the intake- and in-cylinder geometry requires knowledge of the three-dimensional flow in the entire volumetric domain. Previous measurements however, have been limited to point-wise or planar velocimetry measurements. Magnetic resonance velocimetry (MRV) is an advanced diagnostic tool to investigate average 3D flow topology within the entire measurement domain in a fast and cost-efficient way. Since optical access is not needed for data acquisition, the use of MRV is convenient in highly complex geometries for which traditional velocimetry techniques are often limited.
2015-04-14
Technical Paper
2015-01-0796
Stephen Busch, Kan Zha, Paul C. Miles, Alok Warey, Francesco Pesce, Richard Peterson, Alberto Vassallo
Various pilot-main injection strategies are investigated for a part-load operating point in a single cylinder optical Diesel engine. With a pilot injection energizing signal that is advanced from the main injection by 300 µs or more, a 9 dB reduction in combustion noise is achieved. It is observed that as the energizing dwell between a single pilot and the main injection is decreased below 200 µs, combustion noise passes through a minimum and a further reduction of 3 dB is possible. This additional decrease in combustion noise is not associated with increases in smoke or NOx emissions. The injection schedules employed in the engine are analyzed with a hydraulic injection analyzer to provide rate shapes for each of the dwells tested. Two distinct injection events are observed even at the shortest dwell tested, and various rate shaping effects are observed with the main injection event as the dwell is adjusted.
2015-04-14
Technical Paper
2015-01-0946
Yongjin Jung, Julien Manin, Scott Skeen, Lyle M Pickett
A variation in spreading angle of diesel spray from a 3-hole nozzle injector was seen by a long distance microscopy in non-reacting and non-evaporating conditions. The variation from an axial single-hole injector with a nominally identical nozzle size does not occurred in non-reacting or reacting conditions. To investigate the effect of the variation in the spreading angle, liquid penetration length were measured by the Mie scattering in a horizontal configuration to avoid a temperature gradient within the combustion vessel. In addition, the diffused back illumination (DBI) was applied to the vertically injected configuration after matching an ignition delay in both configurations to be similar. Schlieren was employed to quantity the penetration and the spreading angle of vapor jet. The liquid penetration increased gradually after a rapid ramp-up region and starts a hump at around 600 us, which corresponds to the convergence of the spreading angle.
2015-04-14
Technical Paper
2015-01-1699
Kan Zha, Stephen Busch, Paul C. Miles, Sameera Wijeyakulasuriya, Saurav Mitra, P. K. Senecal
Asymmetrical in-cylinder flow structure has been reported in previous studies in a small-bore Diesel engine. It has been demonstrated that this flow field asymmetry leads to an asymmetrical mixture preparation process. To understand the evolution of this asymmetry, it is necessary to characterize the in-cylinder flow over the full compression stroke. Moreover, since bowl-in-piston cylinder geometries can substantially change the in-cylinder flow, characterization of these flows in light-duty engines requires the use of geometrically correct pistons. In this work, a realistic flow has been realized via a transparent piston top with the conventional re-entrant bowl geometry. However, optical distortion caused by the complex bowl geometry greatly complicates the analysis of images taken through the bottom of the piston; for example in the measurement of swirl-plane velocities using particle image velocimetry (PIV).
2015-04-14
Technical Paper
2015-01-0799
Scott Skeen, Julien Manin, Lyle M Pickett
Multiple injection strategies are commonly used in direct-injection compression-ignition engines to improve noise and emission characteristics. Early or “pilot” injections have been used in recent multiple injection strategies to distribute heat release more evenly thereby reducing engine noise. Late or “post” injections have shown promise for reducing engine out particulate matter (mainly soot). This work explores and compares the ignition and flame stabilization characteristics of high-pressure n-dodecane sprays under single (1.5 ms) and double (0.5/0.5 dwell/0.5 ms) injection timings at ambient temperatures of 800 K and 900 K, relevant for low temperature combustion (LTC) strategies. The fuel sprays are injected into an optically accessible, high-pressure combustion vessel that simulates the thermodynamic conditions of modern compression-ignition engines. High-speed schlieren imaging is used to provide a time-resolved measure of vapor penetration ignition.
2015-04-14
Technical Paper
2015-01-0818
Brian Peterson, Isaac Ekoto, William Northrop
Low-temperature gasoline combustion (LTGC) systems are recognized as a realizable strategy to improve fuel economy and engine-out emissions within gasoline engines. In particular, unthrottled operation and volumetric combustion promote higher engine efficiencies, while dilute mixtures and low-temperature combustion enable low nitric oxide emissions. The leading challenge within LTGC systems is the controlling of ignition timing for stable engine performance over a wide operating regime. Negative valve overlap (NVO) is a viable strategy that enables low-temperature gasoline combustion at low loads. In addition to capturing a large fraction of residuals, the strategy also enables partial fuel injection during the recompression period as a means of enhancing and controlling main combustion. Thermal effects of NVO fueling on main combustion are well understood, but chemical effects of the partial products of NVO reactions are uncertain.
2014-10-22
Article
Charged with overseeing the development and execution of the company’s technology strategy and plans, Dr. Ken Washington will pull from research and advanced engineering experience gained over the course of his 28-year career at Lockheed Martin and Sandia National Laboratories in the areas of nuclear engineering, information systems, super-computing, information privacy, and R&D space technologies.
2014-10-13
Journal Article
2014-01-2615
Magnus Sjöberg, Wei Zeng, Daniel Singleton, Jason M. Sanders, Martin A. Gundersen
Abstract Well-mixed lean SI engine operation can provide improvements of the fuel economy relative to that of traditional well-mixed stoichiometric SI operation. This work examines the use of two methods for improving the stability of lean operation, namely multi-pulse transient plasma ignition and intake air preheating. These two methods are compared to standard SI operation using a conventional high-energy inductive ignition system without intake air preheating. E85 is the fuel chosen for this study. The multi-pulse transient plasma ignition system utilizes custom electronics to generate 10 kHz bursts of 10 ultra-short (12ns), high-amplitude pulses (200 A). These pulses were applied to a custom spark plug with a semi-open ignition cavity. High-speed imaging reveals that ignition in this cavity generates a turbulent jet-like early flame spread that speeds up the transition from ignition to the main combustion event.
2014-10-13
Journal Article
2014-01-2657
Julien Manin, Scott Skeen, Lyle Pickett, Eric Kurtz, James E. Anderson
Abstract The Leaner Lifted-Flame Combustion (LLFC) strategy offers a possible alternative to low temperature combustion or other globally lean, premixed operation strategies to reduce soot directly in the flame, while maintaining mixing-controlled combustion. Adjustments to fuel properties, especially fuel oxygenation, have been reported to have potentially beneficial effects for LLFC applications. Six fuels were selected or blended based on cetane number, oxygen content, molecular structure, and the presence of an aromatic hydrocarbon. The experiments compared different fuel blends made of n-hexadecane, n-dodecane, methyl decanoate, tri-propylene glycol monomethyl ether (TPGME), as well as m-xylene. Several optical diagnostics have been used simultaneously to monitor the ignition, combustion and soot formation/oxidation processes from spray flames in a constant-volume combustion vessel.
2014-04-01
Journal Article
2014-01-1412
Lyle M. Pickett, Julien Manin, Alan Kastengren, Christopher Powell
A full understanding and characterization of the near-field of diesel sprays is daunting because the dense spray region inhibits most diagnostics. While x-ray diagnostics permit quantification of fuel mass along a line of sight, most laboratories necessarily use simple lighting to characterize the spray spreading angle, using it as an input for CFD modeling, for example. Questions arise as to what is meant by the “boundary” of the spray since liquid fuel concentration is not easily quantified in optical imaging. In this study we seek to establish a relationship between spray boundary obtained via optical diffused backlighting and the fuel concentration derived from tomographic reconstruction of x-ray radiography. Measurements are repeated in different facilities at the same specified operating conditions on the “Spray A” fuel injector of the Engine Combustion Network, which has a nozzle diameter of 90 μm.
2014-04-01
Journal Article
2014-01-1423
Shaoping Quan, Meizhong Dai, Eric Pomraning, P. K. Senecal, Keith Richards, Sibendu Som, Scott Skeen, Julien Manin, Lyle M. Pickett
Shock waves have been recently observed in high-pressure diesel sprays. In this paper, three-dimensional numerical simulations of supersonic diesel spray injection have been performed to investigate the underlying dynamics of the induced shock waves and their interactions with the spray. A Volume-of-Fluid based method in the CFD software (CONVERGE) is used to model this multiphase phenomena. An adaptive Mesh Refinement (AMR) scheme is employed to capture the front of the spray and the shock waves with high fidelity. Simulation results are compared to the available experimental observations to validate the numerical procedure. Parametric studies with different injection and ambient conditions are conducted to examine the effect of these factors on the generation of shock waves and their dynamics.
2014-04-01
Journal Article
2014-01-1429
Joseph Oefelein, Guilhem Lacaze, Rainer Dahms, Anthony Ruiz, Antony Misdariis
Abstract This paper first summarizes a new theoretical description that quantifies the effects of real-fluid thermodynamics on liquid fuel injection processes as a function of pressure at typical engine operating conditions. It then focuses on the implications this has on modeling such flows with emphasis on application of the Large Eddy Simulation (LES) technique. The theory explains and quantifies the major differences that occur in the jet dynamics compared to that described by classical spray theory in a manner consistent with experimental observations. In particular, the classical view of spray atomization as an appropriate model at some engine operating conditions is questionable. Instead, non-ideal real-fluid behavior must be taken into account using a multicomponent formulation that applies to hydrocarbon mixtures at high-pressure supercritical conditions.
2013-10-14
Journal Article
2013-01-2548
Julien Manin, Lyle M. Pickett, Scott A. Skeen
Despite ongoing research efforts directed at reducing engine-out emissions, diesel engines are known to be one of the largest sources of atmospheric particulate matter (i.e., soot). Quantitative measurements are of primary importance to address soot production during the combustion process in the cylinder of diesel engines. This study presents the capabilities of an extinction-based diagnostic developed to quantitatively measure the soot volume fraction in n-dodecane sprays injected in a high-pressure, high-temperature vessel. Coupled with high-speed imaging, the technique yields time-resolved measurements of the soot field by relying on a diffused back-illumination scheme to improve extinction quantification in the midst of intense beam steering. The experiments performed in this work used two wavelengths, which, when combined with the Rayleigh-Debye-Gans theory, provide information about the optical and physical properties of soot.
2013-10-14
Journal Article
2013-01-2627
Yi Yang, John E. Dec
This paper studies autoignition characteristics and HCCI engine combustion of ketone fuels, which are important constituents of recently discovered fungi-derived biofuels. Two ketone compounds, 2,4-dimethyl-3-pentanone (DMPN) and cyclopentanone (CPN), are systematically investigated in the Sandia HCCI engine, and the results are compared with conventional gasoline and neat ethanol. It is found that CPN has the lowest autoignition reactivity of all the biofuels and gasoline blends tested in this HCCI engine. The combustion timing of CPN is also the most sensitive to intake-temperature (Tin) variations, and it is almost insensitive to intake-pressure (Pin) variations. These characteristics and the overall HCCI performance of CPN are similar to those of ethanol. In contrast, DMPN shows multi-faceted autoignition characteristics. On the one hand, DMPN has strong temperature-sensitivity, even at boosted Pin, which is similar to the low-reactivity ethanol and CPN.
2013-10-14
Journal Article
2013-01-2531
Paul C. Miles, Dipankar Sahoo, Stephen Busch, Johannes Trost, Alfred Leipertz
Measurements of ignition behavior, homogeneous reactor simulations employing detailed kinetics, and quantitative in-cylinder imaging of fuel-air distributions are used to delineate the impact of temperature, dilution, pilot injection mass, and injection pressure on the pilot ignition process. For dilute, low-temperature conditions characterized by a lengthy ignition delay, pilot ignition is impeded by the formation of excessively lean mixture. Under these conditions, smaller pilot mass or higher injection pressures further lengthen the pilot ignition delay. Similarly, excessively rich mixtures formed under relatively short ignition delay conditions typical of conventional diesel combustion will also prolong the ignition delay. In this latter case, smaller pilot mass or higher injection pressures will shorten the ignition delay. The minimum charge temperature required to effect a robust pilot ignition event is strongly dependent on charge O2 concentration.
2013-09-08
Technical Paper
2013-24-0001
Lyle M. Pickett, Julien Manin, Raul Payri, Michele Bardi, Jaime Gimeno
Transients in the rate of injection (ROI) with respect to time are ever-present in direct-injection engines, even with common-rail fueling. The shape of the injection ramp-up and ramp-down affects spray penetration and mixing, particularly with multiple-injection schedules currently in practice. Ultimately, the accuracy of CFD model predictions used to optimize the combustion process depends upon the accuracy of the ROI utilized as fuel input boundary conditions. But experimental difficulties in the measurement of ROI, as well as real-world affects that change the ROI from the bench to the engine, add uncertainty that may be mistaken for weaknesses in spray modeling instead of errors in boundary conditions. In this work we use detailed, time-resolved measurements of penetration at the Spray A conditions of the Engine Combustion Network to rigorously guide the necessary ROI shape required to match penetration in jet models that allow variable rate of injection.
2013-09-08
Journal Article
2013-24-0061
Dipankar Sahoo, Paul C. Miles, Johannes Trost, Alfred Leipertz
Fuel tracer-based planar laser-induced fluorescence is used to investigate the vaporization and mixing behavior of pilot injections for variations in pilot mass of 1-4 mg, and for two injection pressures, two near-TDC ambient temperatures, and two swirl ratios. The fluorescent tracer employed, 1-methylnaphthalene, permits a mixture of the diesel primary reference fuels, n-hexadecane and heptamethylnonane, to be used as the base fuel. With a near-TDC injection timing of −15°CA, pilot injection fuel is found to penetrate to the bowl rim wall for even the smallest injection quantity, where it rapidly forms fuel-lean mixture. With increased pilot mass, there is greater penetration and fuel-rich mixtures persist well beyond the expected pilot ignition delay period. Significant jet-to-jet variations in fuel distribution due to differences in the individual jet trajectories (included angle) are also observed.
2013-04-08
Technical Paper
2013-01-1105
Federico Perini, Adam Dempsey, Rolf D. Reitz, Dipankar Sahoo, Benjamin Petersen, Paul C. Miles
In a recent study, quantitative measurements were presented of in-cylinder spatial distributions of mixture equivalence ratio in a single-cylinder light-duty optical diesel engine, operated with a non-reactive mixture at conditions similar to an early injection low-temperature combustion mode. In the experiments a planar laser-induced fluorescence (PLIF) methodology was used to obtain local mixture equivalence ratio values based on a diesel fuel surrogate (75% n-heptane, 25% iso-octane), with a small fraction of toluene as fluorescing tracer (0.5% by mass). Significant changes in the mixture's structure and composition at the walls were observed due to increased charge motion at high swirl and injection pressure levels. This suggested a non-negligible impact on wall heat transfer and, ultimately, on efficiency and engine-out emissions.
2013-04-08
Technical Paper
2013-01-0908
Katsufumi Kondo, Tetsuya Aizawa, Sanghoon Kook, Lyle Pickett
For better understanding of soot formation and oxidation processes applicable to diesel engines, the size, morphology, and nanostructure of soot particles directly sampled in a diesel spray flame generated in a constant-volume combustion chamber have been investigated using Transmission Electron Microscopy (TEM). For this soot diagnostics, the effects of the sampling processes, TEM observation methodology and image processing methods on the uncertainty in the results have not been extensively discussed, mainly due to the complexity of the analysis.
2013-04-08
Journal Article
2013-01-0946
Vicente Romero, Joshua Mullins, Laura Swiler, Angel Urbina
This paper discusses the treatment of uncertainties corresponding to relatively few samples of random-variable quantities. The importance of this topic extends beyond experimental data uncertainty to situations involving uncertainty in model calibration, validation, and prediction. With very sparse samples it is not practical to have a goal of accurately estimating the underlying variability distribution (probability density function, PDF). Rather, a pragmatic goal is that the uncertainty representation should be conservative so as to bound a desired percentage of the actual PDF, say 95% included probability, with reasonable reliability. A second, opposing objective is that the representation not be overly conservative; that it minimally over-estimate the random-variable range corresponding to the desired percentage of the actual PDF. The presence of the two opposing objectives makes the sparse-data uncertainty representation problem an interesting and difficult one.
2013-04-08
Journal Article
2013-01-0901
Emre Cenker, Gilles Bruneaux, Lyle Pickett, Christof Schulz
Within the Engine Combustion Network (ECN) spray combustion research frame, simultaneous line-of-sight laser extinction measurements and laser-induced incandescence (LII) imaging were performed to derive the soot volume fraction (fv). Experiments are conducted at engine-relevant high-temperature and high-pressure conditions in a constant-volume pre-combustion type vessel. The target condition, called "Spray A," uses well-defined ambient (900 K, 60 bar, 22.8 kg/m₃, 15% oxygen) and injector conditions (common rail, 1500 bar, KS1.5/86 nozzle, 0.090 mm orifice diameter, n-dodecane, 363 K). Extinction measurements are used to calibrate LII images for quantitative soot distribution measurements at cross sections intersecting the spray axis. LII images are taken after the start of injection where quasi-stationary combustion is already established.
2013-04-08
Journal Article
2013-01-0917
Jacqueline O'Connor, Mark Musculus
This work is a technical review of past research and a synthesis of current understanding of post injections for soot reduction in diesel engines. A post injection, which is a short injection after a longer main injection, is an in-cylinder tool to reduce engine-out soot to meet pollutant emissions standards while maintaining efficiency, and potentially to reduce or eliminate exhaust aftertreatment. A sprawling literature on post injections documents the effects of post injections on engine-out soot with variations in many engine operational parameters. Explanations of how post injections lead to engine-out soot reduction vary and are sometimes inconsistent or contradictory, in part because supporting fundamental experimental or modeling data are often not available. In this paper, we review the available data describing the efficacy of post-injections and highlight several candidate in-cylinder mechanisms that may control their efficacy.
2013-04-08
Journal Article
2013-01-0910
Jacqueline O'Connor, Mark Musculus
Partially premixed low-temperature combustion (LTC) using exhaust-gas recirculation (EGR) has the potential to reduce engine-out NOx and soot emissions, but increased unburned hydrocarbon (UHC) emissions need to be addressed. In this study, we investigate close-coupled post injections for reducing UHC emissions. By injecting small amounts of fuel soon after the end of the main injection, fuel-lean mixtures near the injector that suffer incomplete combustion can be enriched with post-injection fuel and burned to completion. The goal of this work is to understand the in-cylinder mechanisms affecting the post-injection efficacy and to quantify its sensitivity to operational parameters including post-injection duration, injection dwell, load, and ignition delay time of the post-injection mixture.
2013-04-08
Journal Article
2013-01-0912
Sanghoon Kook, Renlin Zhang, Kevin Szeto, Lyle M. Pickett, Tetsuya Aizawa
In-flame soot sampling based on the thermophoresis of particles and subsequent transmission electron microscope (TEM) imaging has been conducted in a diesel engine to study size, shape and structure of soot particles within the reacting diesel jet. A direct TEM sampling is pursued, as opposed to exhaust sampling, to gain fundamental insight about the structure of soot during key formation and oxidation stages. The size and shape of soot particles aggregate structure with stretched chains of spherical-like primary particles is currently an unknown for engine soot modelling approaches. However, the in-flame sampling of soot particles in the engine poses significant challenges in order to extract meaningful data. In this paper, the engine modification to address the challenges of high-pressure sealing and avoiding interference with moving valves and piston are discussed in detail.
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