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An Optical and Numerical Characterization of Directly Injected Compressed Natural Gas Jet Development at Engine-Relevant Conditions

Continental-Mike Hornby, Doug Cosby, Perry Czimmek
Ford Motor Co Ltd-Adam Smith
Published 2019-04-02 by SAE International in United States
Compressed natural gas (CNG) is an attractive, alternative fuel for spark-ignited (SI), internal combustion (IC) engines due to its high octane rating, and low energy-specific CO2 emissions compared with gasoline. Directly-injected (DI) CNG in SI engines has the potential to dramatically decrease vehicles’ carbon emissions; however, optimization of DI CNG fueling systems requires a thorough understanding of the behavior of CNG jets in an engine environment.This paper therefore presents an experimental and modeling study of DI gaseous jets, using methane as a surrogate for CNG. Experiments are conducted in a non-reacting, constant volume chamber (CVC) using prototype injector hardware at conditions relevant to modern DI engines. The schlieren imaging technique is employed to investigate how the extent of methane jets is impacted by changing thermodynamic conditions in the fuel rail and chamber.Post-processing of these optical results presents challenges because of the similarity between the density of methane and the background nitrogen. A methodology to interpret the jet extent in the high-speed movies is therefore proposed and used to quantify methane jet propagation and structure. The…
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Effects of Engine Speed on Spray Behaviors of the Engine Combustion Network “Spray G” Gasoline Injector

Robert Bosch LLC-Mohammad Fatouraie
University of Melbourne-Joshua Lacey, Michael Brear
Published 2018-04-03 by SAE International in United States
Non-reacting spray behaviors of the Engine Combustion Network “Spray G” gasoline fuel injector were investigated at flash and non-flash boiling conditions in an optically accessible single cylinder engine and a constant volume spray chamber. High-speed Mie-scattering imaging was used to determine transient liquid-phase spray penetration distances and observe general spray behaviors. The standardized “G2” and “G3” test conditions recommended by the Engine Combustion Network were matched in this work and the fuel was pure iso-octane. Results from the constant volume chamber represented the zero (stationary piston) engine speed condition and single cylinder engine speeds ranged from 300 to 2,000 RPM. As expected, the present results indicated the general spray behaviors differed significantly between the spray chamber and engine. The differences must be thoughtfully considered when applying spray chamber results to guide spray model development for engine applications. Overall, increases in engine speed correlated well with enhanced vaporization, loss of distinct plume structure, and enhanced spray collapse which led to reductions in wetted-footprint area. Furthermore, while loss of distinct plume structures appeared to be strongly dependent…
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The Direct Transition of Fuel Sprays to theDense-Fluid Mixing Regime in the Contextof Modern Compression Ignition Engines

Georgia Institute of Technology-Farzad Poursadegh
University of Melbourne-Joshua Lacey, Michael Brear, Robert Gordon
Published 2018-04-03 by SAE International in United States
Fuel supercriticality has recently received significant attention due to the elevated pressures and temperatures that directly-injected (DI) fuel sprays encounter in modern internal combustion (IC) engines. This paper presents a theoretical examination of conventional and alternative DI fuels at conditions relevant to the operation of compression ignition (CI) engines. The focus is to identify the conditions under which the injected liquid fuel can bypass the atomization process and directly transition to a diffusional mixing regime with the chamber gas. Evaluating the microscopic length-scales of the phase boundary associated with the injection of liquid nitrogen into its own vapor, it is found that the conventional threshold based on the interfacial Knudsen number (i.e. Kn = 0.1) does not adequately quantify the direct transition between sub- and supercriticality. Instead, a threshold that is an order of magnitude smaller is more appropriate for this purpose. Extending the analysis to a range of diesel fuel surrogates (e.g. n-heptane and n-dodecane), and alternative engine fuels that can be blended for use in CI engines (e.g. dimethyl ether and propane), it is then…
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A Comparison of Four Methods for Determining the Octane Index and K on a Modern Engine with Upstream, Port or Direct Injection

Ford Motor Company-Thomas G. Leone, James E. Anderson, Michael H. Shelby
University of Melbourne-Zhenbiao Zhou, Yi Yang, Michael Brear, Joshua Lacey
Published 2017-03-28 by SAE International in United States
Combustion in modern spark-ignition (SI) engines is increasingly knock-limited with the wide adoption of downsizing and turbocharging technologies. Fuel autoignition conditions are different in these engines compared to the standard Research Octane Number (RON) and Motor Octane Numbers (MON) tests. The Octane Index, OI = RON - K(RON-MON), has been proposed as a means to characterize the actual fuel anti-knock performance in modern engines. The K-factor, by definition equal to 0 and 1 for the RON and MON tests respectively, is intended to characterize the deviation of modern engine operation from these standard octane tests. Accurate knowledge of K is of central importance to the OI model; however, a single method for determining K has not been well accepted in the literature.This paper first examines four different methods for determining K, using literature results from a modern SI engine operating with direct injection (DI), port fuel injection (PFI) and homogeneous, upstream fuel injection (UFI). The test fuels were ethanol-gasoline blends spanning a wide range of RON and MON, together with isooctane as a reference. The…
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Optical Characterization of Propane at Representative Spark Ignition, Gasoline Direct Injection Conditions

Ford Motor Company of Australia-Charles Lakey, Steve Ryan, Brendan Butcher
RMIT University-Phred Petersen
Published 2016-04-05 by SAE International in United States
The focus of internal combustion (IC) engine research is the improvement of fuel economy and the reduction of the tailpipe emissions of CO2 and other regulated pollutants. Promising solutions to this challenge include the use of both direct-injection (DI) and alternative fuels such as liquefied petroleum gas (LPG).This study uses Mie-scattering and schlieren imaging to resolve the liquid and vapor phases of propane and iso-octane, which serve as surrogates for LPG and gasoline respectively. These fuels are imaged in a constant volume chamber at conditions that are relevant to both naturally aspirated and boosted, gasoline direct injection (GDI) engines. It is observed that propane and iso-octane have different spray behaviors across these conditions. Iso-octane is subject to conventional spray breakup and evaporation in nearly all cases, while propane is heavily flash-boiling throughout the GDI operating map. This severe flashing behavior has major implications for the design and calibration of LPG DI injection systems and engines.
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Refinement and Validation of the Thermal Stratification Analysis: A post-processing methodology for determining temperature distributions in an experimental HCCI engine

Clemson-ICAR-Zoran Filipi
General Motors Co.-Orgun Guralp, Paul Najt
Published 2014-04-01 by SAE International in United States
Refinements were made to a post-processing technique, termed the Thermal Stratification Analysis (TSA), that couples the mass fraction burned data to ignition timing predictions from the autoignition integral to calculate an apparent temperature distribution from an experimental HCCI data point. Specifically, the analysis is expanded to include all of the mass in the cylinder by fitting the unburned mass with an exponential function, characteristic of the wall-affected region.The analysis-derived temperature distributions are then validated in two ways. First, the output data from CFD simulations are processed with the Thermal Stratification Analysis and the calculated temperature distributions are compared to the known CFD distributions. The results show very good agreement between the calculated TSA and known CFD distributions, except at the leading (hottest) edge where the CFD distributions exhibit a discrete step change and the calculated TSA distributions show a smooth progression. Next, the analysis-derived temperature distributions are compared to optically measured distributions calculated from PLIF images. The calculated distributions agree very well with the optically measured distributions at TDC and around the phasing of the…
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