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Evaluation of Diesel Spray with Non-Circular Nozzle - Part I: Inert Spray

Southwest Research Institute-Khanh Cung, Ahmed Abdul Moiz, Bansal Shah, Vickey Kalaskar, Jason Miwa, Zainal Abidin
Published 2019-01-15 by SAE International in United States
Numerous studies have characterized the impact of high injection pressure and small nozzle holes on spray quality and the subsequent impact on combustion. Higher injection pressure or smaller nozzle diameter usually reduce soot emissions owing to better atomization quality and fuel-air mixing enhancement. The influence of nozzle geometry on spray and combustion of diesel continues to be a topic of great research interest. An alternate approach impacting spray quality is investigated in this paper, specifically the impact of non-circular nozzles. The concept was explored experimentally in an optically accessible constant-volume combustion chamber (CVCC). Non-reacting spray evaluations were conducted at various ambient densities (14.8, 22.8, 30 kg/m3) under inert gas of Nitrogen (N2) while injection pressure was kept at 100 MPa. Shadowgraph imaging was used to obtain macroscopic spray characteristics such as spray structure, spray penetration, and the spray cone angle. Analysis from image processing showed expected result of lower penetration rate and higher spray cone angle as ambient density increased. Two slot nozzles with different aspect ratios but similar flow area as compared with one…
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Investigation of an Advanced Combustion System for Stoichiometric Diesel to Reduce Soot Emissions

Southwest Research Institute-Avery Chase, Jason Miwa, Zainal Abidin, Khanh Cung
Published 2019-01-15 by SAE International in United States
Diesel engines are facing increased competition from gasoline engines in the light-duty and small non-road segments, primarily due to the high relative cost of emissions control systems for lean-burn diesel engines. Advancements in gasoline engine technology have decreased the operating cost advantage of diesels and the relatively high initial-cost disadvantage is now too large to sustain a strong business position. SwRI has focused several years of research efforts toward enabling diesel engine combustion systems to operate at stoichiometric conditions, which allows the application of a low-cost three-way catalyst emission control system which has been well developed for gasoline spark-ignited engines. One of the main barriers of this combustion concept is the result of high smoke emissions from poor fuel/air mixing. The current study focuses on improving the combustion system by investigating different fuel/air mixing strategies that enhance fuel spray - piston bowl interaction while simultaneously optimizing the fuel injection system. Computational Fluid Dynamics (CFD) simulations were carried out in conjunction with engine testing to evaluate different piston bowl designs as well as injector nozzle designs…
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Effect of Micro-Hole Nozzle on Diesel Spray and Combustion

Southwest Research Institute-Khanh Cung, Daniel Christopher Bitsis, Thomas Briggs, Vickey Kalaskar, Zainal Abidin, Bansal Shah, Jason Miwa
Published 2018-04-03 by SAE International in United States
The influence of nozzle geometry on spray and combustion of diesel continues to be a topic of great research interest. One area of promise, injector nozzles with micro-holes (i.e. down to 30 μm), still need further investigation. Reduction of nozzle orifice diameter and increased fuel injection pressure typically promotes air entrainment near-nozzle during start of injection. This leads to better premixing and consequently leaner combustion, hence lowering the formation of soot. Advances in numerical simulation have made it possible to study the effect of different nozzle diameters on the spray and combustion in great detail. In this study, a baseline model was developed for investigating the spray and combustion of diesel fuel at the Spray A condition (nozzle diameter of 90 μm) from the Engine Combustion Network (ECN) community. Upon validation of parameters such as spray penetration, lift-off length, and ignition delay the baseline simulation was extended to study different nozzle orifice diameters. All simulations were performed using a constant-volume combustion chamber (CVCC) geometry with similar ambient conditions of pressure (60 bar) and temperature (900 K). It was shown…
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HEUI Injector Modeling and ROI Experiments for High Injection Pressure of Diesel and Dimethyl Ether (DME)

Michigan Technological University-Xiucheng Zhu, Sanjeet Limbu, Khanh Cung, Seong-Young Lee
WM International Engineering-William De Ojeda
Published 2016-04-05 by SAE International in United States
Dimethyl Ether (DME) is considered a clean alternative fuel to diesel due to its soot-free combustion characteristics and its capability to be produced from renewable energy sources rather than fossil fuels such as coal or petroleum. To mitigate the effect of strong wave dynamics on fuel supply lines caused due to the high compressibility of DME and to overcome its low lubricity, a hydraulically actuated electronic unit injector (HEUI) with pressure intensification was used. The study focuses on high pressure operation, up to 2000 bar, significantly higher than pressure ranges reported previously with DME. A one-dimensional HEUI injector model is built in MATLAB/SIMULINK graphical software environment, to predict the rate of injection (ROI) profile critical to spray and combustion characterization. The outputs of model are compared with experimental ROI and injection duration data of both diesel and DME at injection pressures ranging from 750 to 2000 bar for single-hole and multi-hole nozzles. DME was found to have, with respect to diesel, longer injection delays leading to shorter injection durations for same injector command. The DME…
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Characteristics of Formaldehyde (CH2O) Formation in Dimethyl Ether (DME) Spray Combustion Using PLIF Imaging

SAE International Journal of Fuels and Lubricants

Michigan Technological Univ.-Khanh Cung, Xiucheng Zhu, Ahmed Abdul Moiz, Seong-Young Lee
WM International Engineering-William De Ojeda
  • Journal Article
  • 2016-01-0864
Published 2016-04-05 by SAE International in United States
Recognition of Dimethyl Ether (DME) as an alternative fuel has been growing recently due to its fast evaporation and ignition in application of compression-ignition engine. Most importantly, combustion of DME produces almost no particulate matter (PM). The current study provides a further understanding of the combustion process in DME reacting spray via experiment done in a constant volume combustion chamber. Formaldehyde (CH2O), an important intermediate species in hydrocarbon combustion, has received much attention in research due to its unique contribution in chemical pathway that leads to the combustion and emission of fuels. Studies in other literature considered CH2O as a marker for UHC species since it is formed prior to diffusion flame. In this study, the formation of CH2O was highlighted both temporally and spatially through planar laser induced fluorescence (PLIF) imaging at wavelength of 355-nm of an Nd:YAG laser at various time after start of injection (ASOI). The injection pressure was kept at 750 bar using a single-hole injector with diameter of 180 μm. The formation of CH2O is also correlated with time of…
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Development of Chemical Kinetic Mechanism for Dimethyl Ether (DME) with Comprehensive Polycyclic Aromatic Hydrocarbon (PAH) and NOx Chemistry

Michigan Technological Univ.-Khanh Cung, Jaclyn Johnson, Seong-Young Lee
Published 2015-04-14 by SAE International in United States
Dimethyl ether (DME) appears to be an attractive alternative to common fossil fuels in compression ignition engines due to its smokeless combustion and fast mixture formation. However, in order to fully understand the complex combustion process of DME, there is still a remaining need to develop a comprehensive chemical kinetic mechanism that includes both soot and NOx chemistry. In this study, a detailed DME mechanism with 305 species is developed from the basic DME mechanism of Curran et al. (2000) with addition of soot and NOx chemistry from Howard's mechanism et al. (1999), and GRI 3.0 mechanism, respectively. Soot chemistry in Howard mechanism consisting hydrogen abstraction acetylene addition (HACA) and growth of small polycyclic aromatic hydrocarbons (PAH), assesses over a wide range of temperature and is able to predict good to fair the formation of PAH up to coronene. The comparison of ignition delay of the developed DME mechanism with results from shock-tube experiment by Pfahl et al. (1999) shows good agreement over all temperature ranges. Soot and NO formation region from the developed mechanism…
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The Impact of Spark Discharge Pattern on Flame Initiation in a Turbulent Lean and Dilute Mixture in a Pressurized Combustion Vessel

SAE International Journal of Engines

Ford Motor Co-Garlan Huberts, Michael Czekala, Qiuping Qu
Michigan Technological Univ-Anqi Zhang, Khanh Cung, Seong-Young Lee, Jeffrey Naber
  • Journal Article
  • 2013-01-1627
Published 2013-04-08 by SAE International in United States
An operational scheme with fuel-lean and exhaust gas dilution in spark-ignited engines increases thermal efficiency and decreases NOx emission, while these operations inherently induce combustion instability and thus large cycle-to-cycle variation in engine. In order to stabilize combustion variations, the development of an advanced ignition system is becoming critical. To quantify the impact of spark-ignition discharge, ignitability tests were conducted in an optically accessible combustion vessel to characterize the flame kernel development of lean methane-air mixture with CO₂ simulating exhaust diluent. A shrouded fan was used to generate turbulence in the vicinity of J-gap spark plug and a Variable Output Ignition System (VOIS) capable of producing a varied set of spark discharge patterns was developed and used as an ignition source. The main feature of the VOIS is to vary the secondary current during glow discharge including naturally decaying and truncated with multiple strikes. These discharge patterns were studied to characterize the interaction of discharge phases and initial flame formation. High-speed Schlieren optical setup was employed for visualization with synchronous measurement of discharge waveforms. The…
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Numerical Study on Emission Characteristics of High-Pressure Dimethyl Ether (DME) under Different Engine Ambient Conditions

Khanh Cung, Meghraj Bhagat, Anqi Zhang
Michigan Technological Univ-Seong-Young Lee
Published 2013-04-08 by SAE International in United States
Particular matter (PM) has been greatly concerned over the recent decades due to the constantly increasing restriction on its effect on environmental aspect. Oxygenated fuel such as dimethyl ether (DME) has been known to have beneficial impact on diesel engine emissions in terms of zero soot formation. In current study, under several ambient conditions including surrounding gas temperature and oxygen percentages, soot and emission formation of DME spray is investigated to provide a comparison with other diesel surrogate (n-heptane) and JP-8 surrogate fuels. One important work is to develop a number of chemical kinetic mechanisms with soot chemistry including the growth of polycyclic aromatic hydrocarbon (PAH) and nitro oxides (NOx) formation. Using the developing detailed mechanisms, several numerical approaches were introduced to provide an integrated picture of emission formations. First, the Two-Stage Lagrangian (TSL) capable of implementing mixing effect of air/fuel mixture was used with analytical/experimental input of flame lift-off lengths. Secondly, the CFD simulation was performed to provide the information of the spray such as temperature, user-defined specie concentrations, and flame structure. From this…
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Experimental and Numerical Study of Water Spray Injection at Engine-Relevant Conditions

Sam Barros
Michigan Technological Univ-Meghraj Bhagat, Khanh Cung, Jaclyn Johnson, Seong-Young Lee, Jeffrey Naber
Published 2013-04-08 by SAE International in United States
Water spray characterization of a multi-hole injector under pressures and temperatures representative of engine-relevant conditions was investigated for naturally aspirated and boosted engine conditions. Experiments were conducted in an optically accessible pressure vessel using a high-speed Schlieren imaging to visualize the transient water spray. The experimental conditions included a range of injection pressures of 34, 68, and 102 bar and ambient temperatures of 30 - 200°C, which includes flash-boiling and non-flash-boiling conditions. Transient spray tip penetration and spray angle were characterized via image processing of raw Schlieren images using Matlab code. The CONVERGE CFD software was used to simulate the water spray obtained experimentally in the vessel. CFD parameters were tuned and validated against the experimental results of spray profile and spray tip penetration measured in the combustion vessel (CV). With the validated CFD model, water spray injection into an engine in-cylinder configuration was simulated. The CV experimental results showed that collapsing spray plumes were observed for higher temperature of the charge, showing reduced spray tip penetration. The engine CFD results showed that water injection…
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