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Numerical Evaluation of Gasoline Compression Ignition at Cold Conditions in a Heavy-Duty Diesel Engine

Aramco Research Center-Yuanjiang Pei, Yu Zhang, Praveen Kumar, Tom Tzanetakis, Michael Traver
Argonne National Laboratory-Le Zhao, Muhsin Ameen
  • Technical Paper
  • 2020-01-0778
To be published on 2020-04-14 by SAE International in United States
Achieving robust ignitability for compression ignition of diesel engines at cold conditions is traditionally challenging due to insufficient fuel vaporization, heavy wall impingement, and thick wall films. Gasoline compression ignition (GCI) has shown good potential to offer enhanced NOx-soot tradeoff with diesel-like fuel efficiency, but it is unknown how the volatility and reactivity of the fuel will affect ignition under very cold conditions. Therefore, it is important to investigate the impact of fuel physical and chemical properties on ignition under pressures and temperatures relevant to practical engine operating conditions during cold weather. In this paper, 0-D and 3-D computational fluid dynamics (CFD) simulations of GCI combustion at cold conditions were performed. First, 0-D simulations were performed to evaluate the ignitability of different gasoline-like fuels and the impact of initial pressure and temperature on the autoignition behavior over a range of equivalence ratios and anti-knock indices (AKI). Gasolines with research octane numbers (RON) varied from 60 to 92 were investigated. The simulation results were then used to generate thermodynamic maps for ignitability for the different gasolines.…
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An Analytical Energy-budget Model for Diesel Droplet Impingement on an Inclined Solid Wall

Argonne National Laboratory-Roberto Torelli
Michigan Technological University-Jiachen Zhai, Nitisha Ahuja, Le Zhao, Xiucheng Zhu, Jeffrey Naber, Seong-Young Lee
  • Technical Paper
  • 2020-01-1158
To be published on 2020-04-14 by SAE International in United States
The study of spray-wall interaction is of great importance to understand the dynamics that occur during fuel impingement onto the chamber wall or piston surfaces in internal combustion engines. It is found that the maximum spreading length of an impinged droplet can provide a quantitative estimation of heat transfer and energy transformation for spray-wall interaction. Furthermore, it influences the air-fuel mixing and hydrocarbon and particle emissions at combusting conditions. In this paper, an analytical model of a single diesel droplet impinging on the wall with different inclined angles (α) is developed in terms of βm (dimensionless maximum spreading length, the ratio of maximum spreading length to initial droplet diameter) to understand the detailed impinging dynamic process. This analytical model is built up based on the energy conservation that considers kinetic energy, gravitation energy, and surface energy before impingement, as well as viscous dissipation, gravitation energy, adhesion energy, and deformation energy after impingement. The experimental work of diesel droplet impinging on an inclined wall is performed at a certain range of the impact Weber number (We…
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Understanding Fuel Stratification Effects on Partially Premixed Compression Ignition (PPCI) Combustion and Emissions Behaviors

Aramco Research Center-Kukwon Cho, Yu Zhang, Yuanjiang Pei
Argonne National Laboratory-Le Zhao, Muhsin Ameen
Published 2019-04-02 by SAE International in United States
Fuel stratification effects on the combustion and emissions behaviors for partially premixed compression ignition (PPCI) combustion of a high reactivity gasoline (research octane number of 80) was investigated using the third generation Gasoline Direct-Injection Compression Ignition (Gen3 GDCI) multi-cylinder engine. The PPCI combustion mode was achieved through a double injection strategy. The extent of in-cylinder fuel stratification was tailored by varying the start of second fuel injection timing (SOIsecond) while the first fuel injection event was held constant and occurred during the intake stroke. Based on the experimental results, three combustion characteristic zones were identified in terms of the SOIsecond - CA50 (crank angle at 50% cumulative heat release) relationship: (I) no response zone (HCCI-like combustion); (II) negative CA50 slope zone: (early PPCI mode); and (III) positive CA50 slope zone (late PPCI mode). Across the three zones, Zone II produced the best overall performance. In addition, a wider spray inclusion angle (130° vs. 100°) was found to allow for more retarded SOIsecond, thereby resulting in stronger fuel stratification and enhanced control authority over CA50. Finally,…
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Spray-Wall Dynamics of High-Pressure Impinging Combustion

Michigan Technological University-Zhihao Zhao, Xiucheng Zhu, Le Zhao, Jeffrey Naber, Seong-Young Lee
Published 2019-01-15 by SAE International in United States
The fuel spray impingement on the piston head and/or chamber often occurs in compact IC engines. The impingement plays one of the key roles in combustion because it affects the air-fuel mixing process. In this study, the impinged combustion has been experimentally investigated to understand the mechanism and dynamics of flame-wall interaction. The experiments were performed in a constant volume combustion chamber over a wide range of ambient conditions. The ambient temperature was varied from 800 K to 1000 K and ambient gas oxygen was varied from 15% to 21%. Diesel fuel was injected with an injection pressure of 150 MPa into ambient gas at a density of 22.8 kg/m3. The natural luminosity technique was applied in the experiments to explore the impinged combustion process. High-speed images were taken using a high-speed camera from two different views (bottom and side). An in-house Matlab program was used to post-process the images. The potential region of soot formation was found on the impinging plate based on the strength of local soot luminosity. The effect of air entrainment…
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Characterization of Impingement Dynamics of Single Droplet Impacting on a Flat Surface

Michigan Technological University-Le Zhao, Nitisha Ahuja, Xiucheng Zhu, Zhihao Zhao, Seong-Young Lee
Published 2019-01-15 by SAE International in United States
The liquid fuel spray impingement onto surfaces occurs in both spark ignited and compression ignited engines. It causes a fundamental issue affecting the preparation of air-fuel mixture prior to the combustion, further, affecting engine performance and emissions. To better understand the underlying mechanism of spray interaction with a solid surface, the physics of a single droplet impact on a heated surface was experimentally investigated. The experimental work was conducted at four surface temperatures where a single diesel droplet was injected from a precision syringe pump with a specific droplet diameter and impact velocity. A high-speed camera was used to visualize the droplet impingement process. Images from the selected test condition (We = 52 to 925, Re = 789 to 3330 based on initial droplet impingement parameters) were analyzed to qualify the impinging outcomes and quantify the post-impingement characteristics. In particular, splashing characteristics and the effect of the surface temperature on the temporal evolution of the droplet spreading factor, dynamic contact angle, contact line velocity, as well as heat flux were studied. The hydrodynamics of single…
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High Pressure Impinging Spray Film Formation Characteristics

Michigan Technological University-Le Zhao, Zhihao Zhao, Xiucheng Zhu, Nitisha Ahuja, Jeffrey Naber, Seong-Young Lee
Published 2018-04-03 by SAE International in United States
Fuel film formed in the spray-piston or cylinder wall impingement plays a critical role in engine performance and emissions. In this paper, the fuel film formation and the relevant film characteristics resulting from the liquid spray impinging on a flat plate were investigated in a constant volume combustion vessel by Refractive Index Matching (RIM) technique. The liquid film thickness was firstly calibrated with two different proportional mixtures (5% n-dodecane and 95% n-heptane; 10% n-dodecane and 90% n-heptane by volume) pumped out from a precise syringe to achieve an accurate calibration. After calibration, n-heptane fuel from a side-mounted single-hole diesel injector was then injected on a roughened glass with the same optical setup. The ambient temperature and the plate temperature are set to 423 K with the fuel temperature of 363 K. The effects of various ambient density (14.8, 22.8, and 30.0 kg/m3) and injector pressure (120 and 150 MPa) on the liquid film properties were studied. The analysis of film formation contain the spatial distribution and time-resolved evolution of fuel film thickness, the film wetted area, and the film…
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Splashing Criterion and Topological Features of a Single Droplet Impinging on the Flat Plate

Michigan Technological University-Le Zhao, Nitisha Ahuja, Xiucheng Zhu, Zhihao Zhao, Seong-Young Lee
Published 2018-04-03 by SAE International in United States
This paper aims to provide the experimental and numerical investigation of a single fuel droplet impingement on the different wall conditions to understand the detailed impinging dynamic process. The experimental work was carried out at the room temperature and pressure except for the variation of the impinged wall temperature. A high-speed camera was employed to capture the silhouette of the droplet impinging on wall process against a collimated light. Water, diesel, n-dodecane, and n-heptane were considered as four different droplets and injected from a precision syringe pump with the volume flow rate of 0.2 mL/min at various impact Weber numbers. The impingement outcomes after droplet impacting on the wall include stick, spread, rebound and splash, which depend on the controlling parameters of Weber number, Reynolds number, liquid and surface properties, etc. In this paper, the various splashing and non-splashing criteria were summarized based on the earlier research and applied to evaluate the current experimental data. It is found that the experimental results at various conditions overall show good agreement in predicting the splashing and non-splashing phenomena…
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Evaluation of Diesel Spray-Wall Interaction and Morphology around Impingement Location

Argonne National Laboratory-Roberto Torelli, Sibendu Som, Riccardo Scarcelli
Michigan Technological University-Le Zhao, Xiucheng Zhu, Jeffrey Naber, Seong-Young Lee
Published 2018-04-03 by SAE International in United States
The necessity to study spray-wall interaction in internal combustion engines is driven by the evidence that fuel sprays impinge on chamber and piston surfaces resulting in the formation of wall films. This, in turn, may influence the air-fuel mixing and increase the hydrocarbon and particulate matter emissions. This work reports an experimental and numerical study on spray-wall impingement and liquid film formation in a constant volume combustion vessel. Diesel and n-heptane were selected as test fuels and injected from a side-mounted single-hole diesel injector at injection pressures of 120, 150, and 180 MPa on a flat transparent window. Ambient and plate temperatures were set at 423 K, the fuel temperature at 363 K, and the ambient densities at 14.8, 22.8, and 30 kg/m3. Simultaneous Mie scattering and schlieren imaging were carried out in the experiment to perform a visual tracking of the spray-wall interaction process from different perspectives. The experiments provided the spatial distribution and time-resolved evolution of the spray impingement on the wall, as well as the post-impingement global spray characteristics under various operating conditions. A previously validated…
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Numerical Study on Evaporation of Spherical Droplets Impinging on the Wall Using Volume of Fluid (VOF) Model

Michigan Technological University-Sathya Prasad Potham, Le Zhao, Seong-Young Lee
Published 2017-03-28 by SAE International in United States
This paper aims to extend the existing Volume of Fluid (VOF) model by implementing an evaporation sub-model in an open source Computational Fluid Dynamics (CFD) software, OpenFOAM. The paper applies the new model to numerically study the evaporation of spherical n-heptane droplets impinging on a hot wall at atmospheric pressure and a temperature above the Leidenfrost temperature. Volume of Fluid (VOF) method is chosen to track the liquid gas interface and the capability of VOF method implemented in interDyMFoam solver of OpenFOAM to simulate hydrodynamics during droplet-droplet interaction and droplet-film interaction is explored. Firstly, the in-built solver is used to simulate problems in isothermal conditions and the simulation results are compared qualitatively with the published results to validate the solver. A numerical method for modeling heat and mass transfer during evaporation is implemented in conjunction with the VOF. An additional vapor phase is introduced apart from the liquid and gas phases to understand the mixing and diffusion of vapor and gas phases. The evaporation model is validated quantitatively and qualitatively with fundamental problems having analytical…
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An Experimental and Numerical Study of Diesel Spray Impingement on a Flat Plate

SAE International Journal of Fuels and Lubricants

Argonne National Laboratory-Roberto Torelli, Riccardo Scarcelli, Sibendu Som
Michigan Technological University-Le Zhao, Xiucheng Zhu, Henry Schmidt, Jeffrey Naber, Seong-Young Lee
  • Journal Article
  • 2017-01-0854
Published 2017-03-28 by SAE International in United States
Combustion systems with advanced injection strategies have been extensively studied, but there still exists a significant fundamental knowledge gap on fuel spray interactions with the piston surface and chamber walls. This paper is meant to provide detailed data on spray-wall impingement physics and support the spray-wall model development. The experimental work of spray-wall impingement with non-vaporizing spray characterization, was carried out in a high pressure-temperature constant-volume combustion vessel. The simultaneous Mie scattering of liquid spray and schlieren of liquid and vapor spray were carried out. Diesel fuel was injected at a pressure of 1500 bar into ambient gas at a density of 22.8 kg/m3 with isothermal conditions (fuel, ambient, and plate temperatures of 423 K). A Lagrangian-Eulerian modeling approach was employed to characterize the spray-gas and spray-wall interactions in the CONVERGETM framework by means of a Reynolds-Averaged Navier-Stokes (RANS) formulation. A set of turbulence and spray break-up model constants was identified to properly match the aforementioned measurements of liquid penetration within their experimental confidence intervals. An accuracy study on varying the minimum mesh size was…
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