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Impinged Diesel Spray Combustion Evaluation for Indirect Air-Fuel Mixing Processes and Its Comparison with Non-Vaporing Impinging Spray Under Diesel Engine Conditions

Michigan Technological University-Zhihao Zhao, Xiucheng Zhu, Jeffrey Naber, Seong-Young Lee
Published 2019-04-02 by SAE International in United States
Under low-temperature combustion for the high fuel efficiency and low emissions achievement, the fuel impingement often occurs in diesel engines with direct injection especially for a short distance between the injector and piston head/cylinder wall. Spray impingement plays an important role in the mixing-controlled combustion phase since it affects the air-fuel mixing rate through the disrupted event by the impingement. However, the degree of air entrainment into the spray is hard to be directly evaluated. Since the high spray expansion rate could allow more opportunity for fuel to mix with air, in this study, the expansion rate of impinged flame is quantified and compared with the spray expansion rate under non-vaporizing conditions. The experiments were conducted in a constant volume combustion chamber with an ambient density of 22.8 kg/m3 and the injection pressure of 150 MPa. The ambient temperature was set to 900 K and 1000 K to study the effect of ambient temperature on the air-fuel mixing process for combustion experiments. Under the non-reacting experiments, the chamber was filled with nitrogen at an ambient…
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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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