Development of a Post-Processing Methodology for Studying Thermal Stratification in an HCCI Engine

2012 ◽  
Author(s):  
Benjamin Lawler ◽  
Mark Hoffman ◽  
Zoran Filipi ◽  
Orgun Güralp ◽  
Paul Najt
Keyword(s):  
Mass Fraction ◽  
Thermal Stratification ◽  
Reaction Rates ◽  
Temperature Fields ◽  
Coolant Temperature ◽  
Analysis Tool ◽  
Gas Temperature ◽  
Post Processing ◽  
Hcci Engine ◽  
Mass Distributions

Naturally occurring thermal stratification significantly impacts the characteristics of HCCI combustion. The in-cylinder gas temperature distributions prior to combustion dictate the ignition phasing, burn rates, combustion efficiency, and unburned hydrocarbon and CO emissions associated with HCCI operation. Characterizing the gas temperature fields in an HCCI engine and correlating them to HCCI burn rates is a prerequisite for developing strategies to expand the HCCI operating range. To study the development of thermal stratification in more detail, a new analysis methodology for post-processing experimental HCCI engine data is proposed. This analysis tool uses the autoignition integral in the context of the mass fraction burned curve to infer information about the distribution of temperature that exists in the cylinder prior to combustion. An assumption is made about the shape of the charge temperature profiles of the unburned gas during compression and after combustion starts elsewhere in the cylinder. Secondly, it is assumed that chemical reaction rates proceed very rapidly in comparison to the staggering of ignition phasing from thermal stratification. The autoignition integral is then coupled to the mass fraction burned curve to produce temperature-mass distributions that are representative of a particular combustion event. Due to the computational efficiency associated with this zero-dimensional calculation, a large number of zones can be simulated at very little computational expense. The temperature-mass distributions are then studied over a coolant temperature sweep. The results show that very small changes to compression heat transfer can shift the distribution of mass and temperature in the cylinder enough to significantly affect HCCI burn rates and emissions.

Development of a Postprocessing Methodology for Studying Thermal Stratification in an HCCI Engine

2012 ◽  
Vol 134 (10) ◽  
Author(s):  
Benjamin Lawler ◽  
Mark Hoffman ◽  
Zoran Filipi ◽  
Orgun Güralp ◽  
Paul Najt
Keyword(s):  
Mass Fraction ◽  
Thermal Stratification ◽  
Reaction Rates ◽  
Combustion Efficiency ◽  
Temperature Fields ◽  
Coolant Temperature ◽  
Analysis Tool ◽  
Gas Temperature ◽  
Hcci Engine ◽  
Mass Distributions

Naturally occurring thermal stratification significantly impacts the characteristics of homogeneous charge compression ignition (HCCI) combustion. The in-cylinder gas temperature distributions prior to combustion dictate the ignition phasing, burn rates, combustion efficiency, and unburned hydrocarbon and CO emissions associated with HCCI operation. Characterizing the gas temperature fields in an HCCI engine and correlating them to HCCI burn rates is a prerequisite for developing strategies to expand the HCCI operating range. To study the development of thermal stratification in more detail, a new analysis methodology for postprocessing experimental HCCI engine data is proposed. This analysis tool uses the autoignition integral in the context of the mass fraction burned curve to infer information about the distribution of temperature that exists in the cylinder prior to combustion. An assumption is made about the shape of the charge temperature profiles of the unburned gas during compression and after combustion starts elsewhere in the cylinder. Second, it is assumed that chemical reaction rates proceed very rapidly in comparison to the staggering of ignition phasing from thermal stratification. The autoignition integral is then coupled to the mass fraction burned curve to produce temperature-mass distributions that are representative of a particular combustion event. Due to the computational efficiency associated with this zero-dimensional calculation, a large number of zones can be simulated at very little computational expense. The temperature-mass distributions are then studied over a coolant temperature sweep. The results show that very small changes to compression heat transfer can shift the distribution of mass and temperature in the cylinder enough to significantly affect HCCI burn rates and emissions.

Investigation of Filtered Rayleigh Scattering Techniques for Rig Testing Diagnostics

2014 ◽  
Author(s):  
Jordi Estevadeordal ◽  
Dmitry Opaits ◽  
Chiranjeev Kalra
Keyword(s):  
Rayleigh Scattering ◽  
High Pressures ◽  
Imaging Techniques ◽  
Mixing Layer ◽  
Temperature Measurements ◽  
Temperature Fields ◽  
Gas Temperature ◽  
Iccd Camera ◽  
Gas Molecules ◽  
Combustion Tests

A laboratory investigation of Filtered Rayleigh Scattering (FRS) techniques for high-resolution and high-accuracy temperature measurements in rig tests with high pressures and temperatures and combustion is presented. Imaging techniques based on filtered Rayleigh scattering have the potential for two-dimensional (2D) and near wall measurement of gas velocity and temperature fields among other properties. For gas temperature measurements, laser Rayleigh scattering from gas molecules are typically captured with an ICCD camera and temperature can be inferred from the number density measured from the image intensities. The accuracy challenges associated with property spatial variations, gas composition, and pressure and temperature conditions are investigated for the rig test environments. Representative examples including mixing layer, jet and vortex flows and flame and combustion tests are presented.

scholarly journals Numerical Modeling of Biomass and Solid Waste-Based Syngas Fuels Combustion

2015 ◽  
Vol 11 (2) ◽  
Keyword(s):  
Solid Waste ◽  
Mass Fraction ◽  
Mixture Fraction ◽  
Combustion Process ◽  
Plastic Waste ◽  
The Other ◽  
Gas Temperature ◽  
Saw Dust ◽  
Gas Fuel ◽  
Lower Heating

The combustion of syngas fuels in gas turbine combustor is presented in this paper. The principal objective is to test the performance of the combustion process using non-conventional fuels produced from the gasification of biomass and solid waste. Three dimensional syngas combustion simulations were performed in this study. The mixture fraction/pdf and the P1 radiation models were used to model the non-premixed turbulent combustion. The syngas fuels are derived from the gasification of wood saw dust, wooden pellet and nonrecycled solid waste plastics. The effect of syngas fuel compositions and lower heating values on the combustion process was investigated. The power from the combustor was kept constant at 60 kW for all the syngas fuels tested in this study. The results show a decrease of the peak gas temperature inside the combustor for the syngas fuels compared to conventional fossil gas fuel. The peak gas temperature inside the combustor decreases by 16.1%, 19.8%, and 17.2% respectively for the syngas 1 (derived from plastic waste), syngas 2 (derived from wood saw dust) and syngas 3 (derived from wooden pellets) compared to natural gas fuel. The highest average NO mass fraction at the combustor exit was obtained with syngas 1 (plastic waste) compared to the other syngas fuels due to the high lower heating value. The highest average CO2 mass fraction at the exit of the combustor was obtained with syngas 2 (wood saw dust) compared to the other syngas due to the high amount of CO2 in the syngas fuel (15%).

Effect of Size and Slip Coefficient of a Porous Manifold on Thermal Stratification in Storage Tanks

2009 ◽  
Author(s):  
N. M. Brown ◽  
F. C. Lai
Keyword(s):  
Experimental Data ◽  
Reynolds Number ◽  
Numerical Simulations ◽  
Storage Tank ◽  
Richardson Number ◽  
Thermal Stratification ◽  
Temperature Fields ◽  
Storage Tanks ◽  
Slip Coefficient ◽  
Wide Range

Numerical simulations have been performed to study the effects of size and slip coefficient of a porous manifold on the thermal stratification in a storage tank. The model is used to predict the development of flow and temperature fields during a charging process. Computations have covered a wide range of the Grashof number (1.8 × 105 < Gr < 1.8 × 108) and Reynolds number (10 ≤ Re ≤ 104), or in terms of the Richardson number, 10−2 < Ri < 105. The results obtained compare favorably well with the experimental data. In addition, the present results have confirmed the effectiveness of porous manifold in the promotion of thermal stratification and provide useful information for the design of such system.

Combustion Characteristics of Single Cylinder Diesel Engine Fueled with Blends of Thumba Biodiesel as an Alternative Fuel

2019 ◽  
Vol 969 ◽  
pp. 451-460
Author(s):  
Manpreet Singh ◽  
Mohd Yunus Sheikh ◽  
Dharmendra Singh ◽  
P. Nageswara Rao
Keyword(s):  
Diesel Engine ◽  
Heat Release ◽  
Heat Release Rate ◽  
Diesel Fuel ◽  
Release Rate ◽  
Mass Fraction ◽  
Pressure Rise ◽  
Cylinder Pressure ◽  
Gas Temperature ◽  
Edible Vegetable Oil

The rapid rise in energy requirement and problem regarding atmosphere pollutions, renewable biofuels are the better alternative choice for the internal combustion engine to partially or totally replace the pollutant petroleum fuel. In the present work, thumba (Citrullus colocynthis) non-edible vegetable oil is used for the production of biodiesel and examine its possibility as diesel engine fuel. Transesterification process is used to produce biodiesel from thumba non-edible vegetable oil. Thumba biodiesel (TBD) is used to prepare five different volume concentration (blends) with neat diesel (D100), such as TBD5, TBD15, TBD25, TBD35 and TBD45 to run a single cylinder diesel engine. The diesel engine's combustion parameter such as in-cylinder pressure, rate of pressure rise, net heat release rate, cumulative heat release, mean gas temperature, and mass fraction burnt analyzed through graphs and compared all thumba biodiesel blends result with neat diesel fuel. The mass fraction burnt start earlier for thumba biodiesel blends compared to diesel fuel because of less ignition delay while peak in-cylinder pressure, maximum rate of pressure rise, maximum net heat release rate, maximum cumulative heat release, and maximum mean gas temperature has found decreased results up to 1.93%, 5.53%, 4.11%, 4.65%, and 1.73% respectively for thumba biodiesel.

Numerical and Experimental Study of the Evaporation and Solid Layer Formation of a Bi-Component Droplet Under Various Drying Conditions

2014 ◽  
Author(s):  
Holger Grosshans ◽  
Matthias Griesing ◽  
Srikanth R. Gopireddy ◽  
Werner Pauer ◽  
Hans-Ulrich Moritz ◽  
...  
Keyword(s):  
Droplet Size ◽  
Mass Fraction ◽  
Numerical Study ◽  
Droplet Evaporation ◽  
Droplet Surface ◽  
Parameter Study ◽  
Layer Formation ◽  
Gas Temperature ◽  
Solid Layer ◽  
Initial Droplet

This paper presents a combined experimental and numerical study of the evaporation and solid layer formation of a single bi-component mannitol-water droplet in air. For spherically symmetric droplets, the problem is described mathematically by the unsteady, one-dimensional conservation equations of mass and energy. The effect of the formation of a solid layer at the droplet surface on the droplet evaporation and thermal diffusion rate is included in the present approach. The simulations are validated by comparison with experiments using acoustically levitated droplets. The study includes initial droplet diameters varying from 350 to 450 μm, gas temperatures ranging from 80 to 120 °C, and the initial mannitol mass fraction inside the droplet varies from 0.05 to 0.15. The numerical results are analyzed to identify the occurrence of solid layer formation, and the temporal evolutions of both the droplet size and mass are presented. A parameter study of the initial gas temperature, the initial droplet size, and the initial mannitol mass fraction inside the droplet on droplet evaporation and solid layer formation is presented. The present model accurately captures the initial stages of droplet drying under all conditions investigated.

Calculation of migration rates of vacancies and divacancies in α-Iron using transition path sampling biased with a Lyapunov indicator

2012 ◽  
Vol 1383 ◽  
Author(s):  
Massimiliano Picciani ◽  
Manuel Athènes ◽  
Mihai-Cosmin Marinica
Keyword(s):  
Time Scales ◽  
Reaction Rates ◽  
Model Potential ◽  
Analysis Tool ◽  
Path Sampling ◽  
Transition Path ◽  
Stable States ◽  
Transition Path Sampling ◽  
Reaction Rate Constants ◽  
Reactive Trajectories

ABSTRACTPredicting the microstructural evolution of radiation damage in materials requires handling the physics of infrequent-events, in which several time scales are involved. The reactions rates characterizing these events are the main ingredient for simulating the kinetics of materials under irradiation over large time scales and high irradiation doses. We propose here an efficient, finite temperature method to compute reaction rate constants of thermally activated processes. The method consists of two steps. Firstly, rare reactive trajectories in phase-space are sampled using a transition path sampling (TPS) algorithm supplemented with a local Lyapunov bias favoring diverging trajectories. This enables the system to visit transition regions separating stable configurations more often, and thus enhances the probability of observing transitions between stable states during relatively short simulations. Secondly, reaction constants are estimated from the unbiased fraction of reactive trajectories, yielded by an appropriate statistical data analysis tool, the multistate Bennett acceptance ratio (MBAR) package. We apply our method to the calculation of reaction rates for vacancy and di-vacancy migration in α-Iron crystal, using an Embedded Atom Model potential, for temperatures ranging from 300 K to 800 K.

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