Defining the Boundary Conditions of the CFR Engine under MON Conditions, and Evaluating Chemical Kinetic Predictions at RON and MON for PRFs

Light-end fuels have recently garnered interest as potential fuel for advanced compression ignition (CI) engines. This next generation of engines, which aim to combine the high efficiency of diesel engines with the relative simplicity of gasoline engines, may allow engine manufacturers to continue improving efficiency and reducing emissions without a large increase in engine and aftertreatment system complexity. In this work, a 1D heavy-duty engine model was validated with measured data and then used to generate boundary conditions for the detailed chemical kinetic simulation corresponding to various combustion modes and operating points. Using these boundary conditions, homogeneous simulations were conducted for 242 fuels with research octane number (RON) from 40 to 100 and sensitivity (S) from 0 to 12. Combustion phasing (CA50) was most dependent on RON and less dependent on S under all conditions. Both RON and S had a greater effect on combustion phasing under partially premixed compression ignition (PPCI) conditions (19.3 deg) than under mixing-controlled combustion (MCC) conditions (5.8 deg). The effect of RON and S were also greatest for the lowest reactivity (RON > 90) fuels and under low-load conditions. The results for CA50 reflect the relative ignition delay for the various fuels at the start-of-injection (SOI) temperature. At higher SOI temperatures (>950K), CA50 was found to be less dependent on fuel sensitivity due to the convergence of ignition delay behavior of different fuels in the high-temperature region. Combustion of light-end fuels in CI engines can be an important opportunity for regulators, consumers, and engine-makers alike. However, selection of the right fuel specifications will be critical in development of the combustion strategy. This work, therefore, provides a first look at quantifying the effect of light-end fuel chemistry on advanced CI engine combustion across the entire light-end fuel reactivity space and provides a comparison of the trends for different combustion modes.

Download Full-text

Modelling of Self-Ignition in Spark-Ignition Engine Using Reduced Chemical Kinetics for Gasoline Surrogates

Fluids ◽

10.3390/fluids4030157 ◽

2019 ◽

Vol 4 (3) ◽

pp. 157 ◽

Cited By ~ 1

Author(s):

Ahmed Faraz Khan ◽

Philip John Roberts ◽

Alexey A. Burluka

Keyword(s):

Chemical Kinetics ◽

Octane Number ◽

Kinetic Mechanism ◽

Spark Ignition ◽

Chemical Kinetic ◽

Spark Ignition Engine ◽

Detailed Chemical Kinetics ◽

Kinetic Predictions ◽

Kinetic Mechanisms

A numerical and experimental investigation in to the role of gasoline surrogates and their reduced chemical kinetic mechanisms in spark ignition (SI) engine knocking has been carried out. In order to predict autoignition of gasoline in a spark ignition engine three reduced chemical kinetic mechanisms have been coupled with quasi-dimensional thermodynamic modelling approach. The modelling was supported by measurements of the knocking tendencies of three fuels of very different compositions yet an equivalent Research Octane Number (RON) of 90 (ULG90, PRF90 and 71.5% by volume toluene blended with n-heptane) as well as iso-octane. The experimental knock onsets provided a benchmark for the chemical kinetic predictions of autoignition and also highlighted the limitations of characterisation of the knock resistance of a gasoline in terms of the Research and Motoring octane numbers and the role of these parameters in surrogate formulation. Two approaches used to optimise the surrogate composition have been discussed and possible surrogates for ULG90 have been formulated and numerically studied. A discussion has also been made on the various surrogates from the literature which have been tested in shock tube and rapid compression machines for their autoignition times and are a source of chemical kinetic mechanism validation. The differences in the knock onsets of the tested fuels have been explained by modelling their reactivity using semi-detailed chemical kinetics. Through this work, the weaknesses and challenges of autoignition modelling in SI engines through gasoline surrogate chemical kinetics have been highlighted. Adequacy of a surrogate in simulating the autoignition behaviour of gasoline has also been investigated as it is more important for the surrogate to have the same reactivity as the gasoline at all engine relevant p − T conditions than having the same RON and Motored Octane Number (MON).

Download Full-text

The Calculation of Thermodynamic Non Equilibrium Combustion Product Compositions

Volume 2: Coal, Biomass and Alternative Fuels; Combustion and Fuels; Oil and Gas Applications; Cycle Innovations ◽

10.1115/99-gt-275 ◽

1999 ◽

Author(s):

C. D. Hurley ◽

M. Whiteman ◽

C. W. Wilson

Keyword(s):

Free Energy ◽

Constant Pressure ◽

Chemical Kinetic ◽

Equilibrium Conditions ◽

Combustion Chemistry ◽

Individual Product ◽

Kinetic Predictions ◽

The Individual ◽

The Relationship ◽

Non Equilibrium

A method is presented by which the product composition and temperature of constant pressure combustion reactions can be calculated for non equilibrium conditions, by constraining the products free energy and entropy. The calculations for a hydrogen/ oxygen system are compared with chemical kinetic predictions. From the calculated compositions the relationship between free energy and extent of reaction are derived and thence how the individual product mole fractions vary with extent of reaction. The application of these techniques to modelling combustion chemistry is discussed.

Download Full-text

Defining the Boundary Conditions of the CFR Engine Under RON Conditions for Knock Prediction and Robust Chemical Mechanism Validation

Volume 1: Large Bore Engines; Fuels; Advanced Combustion ◽

10.1115/icef2018-9640 ◽

2018 ◽

Cited By ~ 1

Author(s):

Saif Salih ◽

Daniel DelVescovo ◽

Christopher P. Kolodziej ◽

Toby Rockstroh ◽

Alexander Hoth

Keyword(s):

Boundary Conditions ◽

Turbulent Flame ◽

Kinetic Mechanism ◽

Reaction Rates ◽

Chemical Kinetic ◽

Chemical Mechanism ◽

Residual Fraction ◽

Engine Model ◽

Kinetic Mechanisms ◽

Burn Rate

In order to establish a pathway to evaluate chemical kinetic mechanisms (detailed or reduced) in a real engine environment, a GT Power model of the well-studied Cooperative Fuels Research (CFR) engine was developed and validated against experimental data for primary reference fuel blends between 60 and 100 under RON conditions. The CFR engine model utilizes a predictive turbulent flame propagation sub-model, and implements a chemical kinetic solver to solve the end-gas chemistry. The validation processes were performed simultaneously for thermodynamic and chemical kinetic parameters to match IVC conditions, burn rate, and knock prediction. A recently published kinetic mechanism was implemented in GT-Power, and was found to over-predict the low temperature heat release for iso-octane and PRF blends, leading to advanced knock onset phasing compared to experiments. Three reaction rates in the iso-octane and n-heptane pathways were tuned in the kinetic mechanism in order to match experimental knock-point values, yielding excellent agreement in terms of the knock onset phasing, burn rate, and the thermodynamic conditions compared to experiments. This developed model provides the initial/boundary conditions of the CFR engine under RON conditions, including IVC temperature and pressure, MFB profile, residual fraction and composition. The conditions were then correlated as a function of CFR engine compression ratio, and implemented in a 0-D SI engine model in Chemkin Pro in order to demonstrate an application of the current work. The Chemkin Pro and GT-Power simulations provided nearly identical results despite significant differences in heat transfer models and chemical kinetic solvers. This work provides the necessary framework by which robust chemical kinetic mechanisms can be developed, evaluated, and tuned, based on the knocking tendencies in a real engine environment for PRF blends.

Download Full-text

Effect of Fuel Reactivity on Ignitability and Combustion Phasing in a Heavy-Duty Engine Simulation for Mixing-Controlled and Partially-Premixed Combustion

ASME 2016 Internal Combustion Engine Fall Technical Conference ◽

10.1115/icef2016-9347 ◽

2016 ◽

Cited By ~ 3

Author(s):

Alexander K. Voice ◽

Praveen Kumar ◽

Yu Zhang

Keyword(s):

Boundary Conditions ◽

Ignition Delay ◽

High Efficiency ◽

Chemical Kinetic ◽

Compression Ignition ◽

Heavy Duty ◽

Engine Model ◽

Combustion Modes ◽

Partially Premixed ◽

Ci Engines

Light-end fuels have recently garnered interest as potential fuel for advanced compression ignition engines. This next generation of engines, which aim to combine the high efficiency of diesel engines with the relative simplicity of gasoline engines, may allow engine manufacturers to continue improving efficiency and reducing emissions without a large increase in engine and aftertreatment system complexity. In this work, a 1-D heavy-duty engine model was validated with measured data and then used to generate boundary conditions for the detailed chemical kinetic simulation corresponding to various combustion modes and operating points. Using these boundary conditions, homogeneous simulations were conducted for 242 fuels with research octane number (RON) from 40 to 100 and sensitivity (S) from 0 to 12. Combustion phasing (CA50) was most dependent on RON and less dependent on S under all conditions. Both RON and S had a greater effect on combustion phasing under partially-premixed compression ignition (PPCI) conditions (19.3°) than under mixing-controlled combustion (MCC) conditions (5.8°). The effect of RON and S were also greatest for the lowest reactivity (RON>90) fuels and under low-load conditions. The results for CA50 reflect the relative ignition delay for the various fuels at the start-of-injection (SOI) temperature. At higher SOI temperatures (>950K), CA50 was found to be less dependent on fuel sensitivity due to the convergence of ignition delay behavior of different fuels in the high-temperature region. Combustion of light-end fuels in CI engines can be an important opportunity for regulators, consumers and engine-makers alike. However, selection of the right fuel specifications will be critical in development of the combustion strategy. This work therefore provides a first look at quantifying the effect of light-end fuel chemistry on advanced CI engine combustion across the entire light-end fuel reactivity space, and provides a comparison of the trends for different combustion modes.

Download Full-text

Use of the Magnetostatic Analogue In Electromagnetic Lens Engineering

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100068795 ◽

1970 ◽

Vol 28 ◽

pp. 360-361

Author(s):

John W. Coleman

Keyword(s):

Boundary Conditions ◽

High Performance ◽

Force Fields ◽

Optical Design ◽

Direct Conversion ◽

Design Engineering ◽

Design Data ◽

Scalar Potentials ◽

Geometric Elements ◽

At Will

In the design engineering of high performance electromagnetic lenses, the direct conversion of electron optical design data into drawings for reliable hardware is oftentimes difficult, especially in terms of how to mount parts to each other, how to tolerance dimensions, and how to specify finishes. An answer to this is in the use of magnetostatic analytics, corresponding to boundary conditions for the optical design. With such models, the magnetostatic force on a test pole along the axis may be examined, and in this way one may obtain priority listings for holding dimensions, relieving stresses, etc..The development of magnetostatic models most easily proceeds from the derivation of scalar potentials of separate geometric elements. These potentials can then be conbined at will because of the superposition characteristic of conservative force fields.

Download Full-text