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Effects of Numerical Schemes on Large Eddy Simulation of Turbulent Planar Gas Jet and Diesel Spray

SAE International Journal of Fuels and Lubricants

Univ. of Wisconsin Madison-Chi-Wei Tsang, Christopher Rutland
  • Journal Article
  • 2016-01-0866
Published 2016-04-05 by SAE International in United States
Three time integration schemes and four finite volume interpolation schemes for the convection term in momentum equation were tested under turbulent planar gas jet and Sandia non-reacting vaporizing Spray-H cases. The three time integration schemes are the first-order Euler implicit scheme, the second-order backward scheme, and the second-order Crank-Nicolson scheme. The four spatial interpolation schemes are cubic central, linear central, upwind, and vanLeer schemes. Velocity magnitude contour, centerline and radial mean velocity and Reynolds stress profiles for the planar turbulent gas jet case, and fuel vapor contour and liquid and vapor penetrations for the Diesel spray case predicted by the different numerical schemes were compared. The sensitivity of the numerical schemes to mesh resolution was also investigated. The non-viscosity based dynamic structure subgrid model was used. The numerical tool used in this study was OpenFOAM. Results showed that the first-order Euler implicit schemes predict wider range of length scales as seen in velocity and fuel vapor contour plots, while the second-order time integration schemes predict more small scale structures. The non-monotonic central schemes show less…
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Comparison of Compression Ignition Engine Noise Metrics in Low-Temperature Combustion Regimes

SAE International Journal of Engines

Univ of Wisconsin Madison-Jaal Ghandhi
Univ. of Wisconsin Madison-Arsham J. Shahlari
  • Journal Article
  • 2013-01-1659
Published 2013-04-08 by SAE International in United States
Many combustion researchers use peak pressure rise rate or ringing intensity to indicate combustion noise in lieu of microphone data or using a combustion noise meter that simulates the attenuation characteristics of the engine structure. In this paper, peak pressure rise rate and ringing intensity are compared to combustion noise using a fully documented algorithm similar to the ones used by combustion noise meters. Data from multiple engines operating under several low-temperature combustion strategies were analyzed. The results suggest that neither peak pressure rise rate nor ringing intensity provides a direct correlation to engine noise over a wide range of operating conditions. Moreover, the estimation of both metrics is often accompanied by the filtering of the pressure data, which changes the absolute value of the results. Thus, all ringing intensity and peak pressure rise rate data should be provided with the filter characteristics to allow an independent assessment of the noise potential. The major difference between ringing intensity and peak pressure rise rate on the one hand and noise on the other appears to be…
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Experimental Investigation of Light-Medium Load Operating Sensitivity in a Gasoline Compression Ignition (GCI) Light-Duty Diesel Engine

Univ. of Wisconsin Madison-Paul Loeper, Youngchul Ra, Cory Adams, David E. Foster, Jaal Ghandhi, Michael Andrie, Roger Krieger
General Motors Company-Russ Durrett
Published 2013-04-08 by SAE International in United States
The light-medium load operating range (4-7 bar net IMEP) presents many challenges for advanced low temperature combustion strategies utilizing low cetane fuels (specifically, 87-octane gasoline) in light-duty, high-speed engines. The overly lean overall air-fuel ratio (Φ≺0.4) sometimes requires unrealistically high inlet temperatures and/or high inlet boost conditions to initiate autoignition at engine speeds in excess of 1500 RPM. The objective of this work is to identify and quantify the effects of variation in input parameters on overall engine operation. Input parameters including inlet temperature, inlet pressure, injection timing/duration, injection pressure, and engine speed were varied in a ~0.5L single-cylinder engine based on a production General Motors 1.9L 4-cylinder high-speed diesel engine.With constraints of combustion efficiency, noise level (pressure rise rate) and emissions, engine operation sensitivity due to changes in inlet temperature between 50-90C was first examined for fixed fueling rates. This experiment was then repeated at different inlet pressures and engine speeds. Finally, constant load experiments were performed in which perturbations in injection strategies (timing, duration, and pressure) were executed to assess overall system sensitivity.…
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An Optical Investigation of Fuel Composition Effects in a Reactivity Controlled HSDI Engine

SAE International Journal of Engines

Univ. of Wisconsin Madison-Matthew Blessinger, Joshua Stein, Jaal Ghandhi
  • Journal Article
  • 2012-01-0691
Published 2012-04-16 by SAE International in United States
Reactivity controlled compression ignition combustion was investigated for three fuel combinations: isooctane-diesel, PRF90-diesel, and E85-diesel. Experiments were conducted at 1200 rpm, 160 kPa absolute intake pressure, and fixed total fuel energy using ‘optimal’ operating condition for each fuel combination that were chosen based on combustion performance from SOI timing and premixed energy fraction sweeps. The heat release duration was found to scale with the difference in reactivity between the premixed and direction injected fuel; a small difference gives rise to short heat release duration, similar to that of HCCI combustion. Conversely, as the difference increases, the heat release period lengthens. The high-speed optical data confirmed that the combustion occurred in a staged manner from the high-reactivity zones, which were located at the periphery of the chamber, to low-reactivity zones in the field of view. Further, the range of ignition timing across the imaged area was found to scale with the difference in the two fuel's reactivity. In cases where there was a small difference in reactivity, the ignition took place in a relatively narrow window…
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Numerical Investigation of High Powered Diesel Mode Transition Using Large Eddy Simulations

Univ. of Wisconsin Madison-Siddhartha Banerjee, Christopher Rutland
Published 2012-04-16 by SAE International in United States
Numerical investigation is carried out to explore various strategies of combustion mode switching in a diesel engine operating at high power. Numerical results are compared with high power single cylinder (CAT 3401E) experiments for combustion phasing and emission characteristics. In this study CFD calculations are carried out using the KIVA CFD code with Large Eddy Simulation turbulence model and Direct Chemistry Solver sub-models. The advanced turbulence and combustion sub-models enabled more realistic visualization of the effects of single-cycle mode switching on in-cylinder flow structures, fuel-air mixing behavior and combustion phasing.Two circumstances of mode switch are presented in this study. Mode switches are performed from traditional High Temperature Combustion to early injection PCCI combustion and vice versa. In this investigation several aspects of combustion control are investigated. The effects of fast response controls such as fuel injection timing on in-cylinder combustion are studied. Slow response controls, such as EGR and intake boost are not realized in single cycle mode switching. The effects of such transients on CA501 and emission characteristics are presented.It is found that in-cylinder…
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On LES Grid Criteria for Spray Induced Turbulence

Univ. of Wisconsin Madison-Siddhartha Banerjee, Christopher Rutland
Published 2012-04-16 by SAE International in United States
Using non-viscosity dynamic structure Large Eddy Simulations (LES) turbulence model, spray=induced turbulence is investigated on a number of different Computational Fluid Dynamics (CFD) grids of varying mesh sizes (from 0.5 to 2 mm mesh). Turbulent flow is induced inside a quiescent chamber by liquid fuel spray and then left to decay after end of injection by virtue of its molecular viscosity and turbulent dissipation. Coherent structures (CS) of this turbulent flow are constructed and visualized using λ2 definition. Using CS, analysis is performed on the turbulent flow around the liquid spray jet. These CS from LES are then compared against the results from RANS calculations as well. The visualization of CS helps to explain the mechanism of fuel-air mixing obtained from LES results and its difference with RANS calculations. It is found that LES model from finer CFD mesh predicts fuel-air mixing by virtue of breaking down of large eddies to number of smaller eddies while RANS model predicts diffusion of fuel-rich pockets resulting in fuel-air mixing predictions.It is observed that with finer CFD grids,…
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Pulsed Regeneration for DPF Aftertreatment Devices

Univ. of Wisconsin Madison-Jian Gong, Christopher J. Rutland
Published 2011-09-11 by SAE International in United States
DPF regenerations involve a trade-off between fuel economy and DPF durability. High temperature regenerations of DPFs have fewer fuel penalties but simultaneously tend to give higher substrate temperatures, which can reduce thermal reliability. In order to weaken the trade-off, the integrated system-level model [1,2,3,4] is used to conduct optimization studies and explore novel regeneration strategies for DPF aftertreatment devices. The integrated model developed in the Engine Research Center (ERC) includes sub-models for engines, emissions, aftertreatment devices and controllers. Based on the engine and regeneration fuel economy, multiple and single cycle regeneration tests are performed and analyzed. The optimal soot loadings to initiate and terminate regenerations are discussed. A pulsed regeneration strategy, which is characterized by injecting multiple pulses of fuel (upstream of a DOC) during regenerations, is investigated. It is found that pulsed regeneration has the potential to reduce regeneration fuel penalties without generating significantly high wall temperatures that can reduce DPF durability.
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A Detailed Study of In-Cylinder Flow and Turbulence using PIV

SAE International Journal of Engines

Univ. of Wisconsin Madison-Douglas Heim, Jaal Ghandhi
  • Journal Article
  • 2011-01-1287
Published 2011-04-12 by SAE International in United States
In-cylinder velocity measurements were acquired in a two-valve, single-cylinder research engine to study the bulk fluid motion and small-scale turbulence. Different port geometries (two), different port orientations (two) and both shrouded and non-shrouded intake valves were tested to vary the intake-generated flow. Tests were performed at engine speeds of 300, 600, 900 and 1200 RPM with an atmospheric intake pressure. Prior to testing on the engine, the different head configurations were tested on a steady flow bench. Particle image velocimetry data were taken on a single plane, parallel to the piston surface, in the engine using both a low magnification to characterize the large-scale flow phenomena, and a high magnification to characterize the turbulence field. The low-magnification results showed that the swirl center location was relatively insensitive to engine speed, but did change position throughout the cycle. The solid-body rotation rate was found to be comparable to the steady-flow bench swirl ratio for swirl-dominated flows, and the decay in the rotation rate during the cycle was measured. The high magnification data (acquired at TDC) were…
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Coupling of Scaling Laws and Computational Optimization to Develop Guidelines for Diesel Engine Down-sizing

Univ. of Wisconsin Madison-Hai-Wen Ge, Chang-Wook Lee
Ford Forschungszentrum Aachen GmbH-Werner Willems
Published 2011-04-12 by SAE International in United States
The present work proposes a methodology for diesel engine development using scaling laws and computational optimization with multi-dimensional CFD tools. A previously optimized 450cc HSDI diesel engine was down-scaled to 400cc size using recently developed scaling laws. The scaling laws were validated by comparing the performance of these two engines, including pressure, HRR, peak and averaged temperature, and pollutant emissions. A novel optimization methodology, which is able to simultaneously optimize multiple operating conditions, was proposed. The method is based on multi-objective genetic algorithms, and was coupled with the KIVA3V Release 2 code to further optimize the down-scaled diesel engine. An adaptive multi-grid chemistry model was used in the KIVA3V code to reduce the computational cost of the optimization. The computations were conducted using high-throughput computing with the CONDOR system. An automated grid generator was used for efficient mesh generation with 12 variable piston bowl geometry parameters, including the bore size. Injection timing, spray angle, number of nozzle holes, and swirl ratio were also considered as design parameters. To fully utilize the benefits of the down-scaled…
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Numerical Study of Diesel Combustion Regimes

Univ. of Wisconsin Madison-Siddhartha Banerjee, Christopher Rutland
Published 2011-04-12 by SAE International in United States
Numerical investigation is carried out in order to explore diesel combustion using advanced turbulence and combustion models. Turbulence is modeled by one-equation non-viscosity dynamic structure Large Eddy Simulation (LES) model. Sub-grid fuel-air mixing is calculated using a dynamic scale similarity sub-grid scalar dissipation model to represent the local state of combustion. Fuel-air mixing time scale is used in order to determine the local in-homogeneity and rate of mixing of fuel and air.Diesel combustion is studied and compared with experimental results for high power diesel engine setup at different conditions representing both low temperature combustion and traditional high temperature combustion regimes. Further studies are carried out in diesel engine to investigate in-cylinder fuel air mixing and the onset of ignition. Engine experiments were conducted to investigate Low Temperature Combustion (LTC) and conventional diesel combustion modes by varying fuel injection event(s) and intake charge conditions such as Exhaust Gas Recirculation (EGR). Additionally a preliminary numerical investigation is carried out in order to study the effects of mixed mode combustion in a high powered diesel engine. A single…
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