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Investigation and Optimization of Cam Actuation of an Over-Expanded Atkinson Cycle Spark-Ignited Engine

SAE International Journal of Advances and Current Practices in Mobility

Michigan Technological University-Zhuyong Yang, Niranjan Miganakallu Narasimhamurthy, Tyler Miller, Jeffrey Naber
  • Journal Article
  • 2019-01-0250
Published 2019-04-02 by SAE International in United States
An over-expanded spark ignited engine was investigated in this work via engine simulation with a design constrained, mechanically actuated Atkinson cycle mechanism. A conventional 4-stroke spark-ignited turbo-charged engine with a compression ratio of 9.2 and peak brake mean effective pressure of 22 bar was selected for the baseline engine. With geometry and design constraints including bore, stroke, compression ratio, clearance volume at top dead center (TDC) firing, and packaging, one over-expanded engine mechanism with over expansion ratio (OER) of 1.5 was designed. Starting with a validated 1D engine simulation model which included calibration of the in-cylinder heat transfer model and SI turbulent combustion model, investigations of the Atkinson engine including cam optimization was studied. The engine simulation study included the effects of offset of piston TDC locations as well as different durations of the 4-strokes due to the mechanism design. Incremental effects of adjusted combustion phasing, scaled valve durations, to a fully optimized cam duration and phasing are determined, and the impacts of each discussed. A constant speed load sweep was conducted to compare the…
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Influence of Elevated Injector Temperature on the Spray Characteristics of GDI Sprays

Michigan Technological University-Niranjan Miganakallu Narasimhamurthy, William Atkinson, Zhuyong Yang, Jeffrey Naber
Published 2019-04-02 by SAE International in United States
When fuel at elevated temperatures is injected into an ambient environment at a pressure lower than the saturation pressure of the fuel, the fuel vaporizes in the nozzle and/or immediately upon exiting the nozzle; that is, it undergoes flash boiling. It is characterized by a two-phase flow regime co-located with primary breakup, which significantly affects the spray characteristics. Under flash boiling conditions, the near nozzle spray angle increases, which can lead to shorter penetration because of increased entrainment. In a multi-hole injector this can cause other impacts downstream resulting from the increased plume to plume interactions.To study the effect of injector temperature and injection pressure with real fuels, an experimental investigation of the spray characteristics of a summer grade gasoline fuel with 10% ethanol (E10) was conducted in an optically accessible constant volume spray vessel. A gasoline direct-injection injector with six holes typical of a side-injection engine was studied. Optical diagnostics included high-speed photography with alternate frame imaging from Mie-Scattering and Shadowgraph techniques. Ambient conditions representing Early Injection (45°C, 1 bar) and Late Injection (180°C,…
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Investigation of Flow Conditions and Tumble near the Spark Plug in a DI Optical Engine at Ignition

Ford Motor Company-Michael Czekala, Qiuping Qu, Garlan Huberts
Michigan Technological University-Yanyu Wang, Jiongxun Zhang, Zhuyong Yang, Xin Wang, Paul Dice, Mahdi Shahbakhti, Jeffrey Naber
Published 2018-04-03 by SAE International in United States
Tumble motion plays a significant role in modern spark-ignition engines in that it promotes mixing of air/fuel for homogeneous combustion and increases the flame propagation speed for higher thermal efficiency and lower combustion variability. Cycle-by-cycle variations in the flow near the spark plug introduce variability to the initial flame kernel development, stretching, and convection, and this variability is carried over to the entire combustion process. The design of current direct-injection spark-ignition engines aims to have a tumble flow in the vicinity of the spark plug at the time of ignition. This work investigates how the flow condition changes in the vicinity of the spark plug throughout the late compression stroke via high-speed imaging of a long ignition discharge arc channel and its stretching, and via flow field measurement by particle imaging velocimetry. It is observed that the flow motion near the spark plug varies significantly cycle to cycle and can change direction from the bulk tumble flow near the time of ignition, especially when the ignition timing is late in the cycle at low tumble…
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Investigation of Combustion Knock Distribution in a Boosted Methane-Gasoline Blended Fueled SI Engine

Czestochowa University of Technology-Stanislaw Szwaja
Hitachi America Ltd-Yashodeep Lonari
Published 2018-04-03 by SAE International in United States
The characteristics of combustion knock metrics over a number of engine cycles can be an essential reference for knock detection and control in internal combustion engines. In a Spark-Ignition (SI) engine, the stochastic nature of combustion knock has been shown to follow a log-normal distribution. However, this has been derived from experiments done with gasoline only and applicability of log-normal distribution to dual-fuel combustion knock has not been explored. To evaluate the effectiveness and accuracy of log-normal distributed knock model for methane-gasoline blended fuel, a sweep of methane-gasoline blend ratio was conducted at two different engine speeds.Experimental investigation was conducted on a single cylinder prototype SI engine equipped with two fuel systems: a direct injection (DI) system for gasoline and a port fuel injection (PFI) system for methane. The experiments were conducted at 1500 rpm and 2000 rpm, 12.0 bar net indicated mean effective pressure wherein the engine was boosted using compressed air.E10 gasoline and methane were used in this study. The results from blending two fuels show that the log-normal distribution provides a good fit to the…
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