The structure of flat, counter-flow diffusion flames

It is shown that the establishment of a large flat diffusion flame in the counter-flow régime of opposed jets of two gaseous reactants could very considerably extend the range of applicability of flame-kinetics studies by structure analysis. Suitable flames are stabilized and their characteristics and behaviour described. The flow patterns, spectrum , refractive index fields, temperature distributions and gas composition at a few selected points are studied for ethylene flames by methods including the use of thermocouples, sodium line reversal, illuminated particle tracks, interferometry and gas chromatography. The aerodynamic and thermal structures are analyzed to yield the distribution of the rate of heat release per unit volume. The following are among the conclusions: two stagnation points and two planes which particles cannot cross occur when the centres of the reaction and aerodynamic systems are made to coincide—this can be prevented by displacing the plane of stoichiometry from that of aerodynamic symmetry; the radial component of flow velocity is proportional to radial distance in the central parts. Isotherms are parallel to each other and to the flame, away from the edges, but maximum temperatures occur at the periphery, at least for some flames. The heat release profile shows regions where small amounts of heat are absorbed; C 2 H 6 and H 2 appear on the oxidant side of the flame. The most significant observation is that the zone of heat release is about ten times wider than would be expected of the equivalent pre-mixed flame and this makes the method applicable to the study of faster flame reactions.

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Zero Dimensional Quasi-Predictive Thermodynamic Simulation for Establishing Initial Cylinder Conditions for CFD Simulation of Diesel Combustion

Volume 2: Emissions Control Systems; Instrumentation, Controls, and Hybrids; Numerical Simulation; Engine Design and Mechanical Development ◽

10.1115/icef2015-1166 ◽

2015 ◽

Author(s):

Ryan A. Bandura ◽

Timothy J. Jacobs

Keyword(s):

Experimental Data ◽

Heat Release ◽

Cfd Simulation ◽

Fuel Injection ◽

Initial Conditions ◽

Thermodynamic Simulation ◽

Operating Conditions ◽

Gas Composition ◽

Gas Temperature ◽

Rate Of Heat Release

Computational fluid dynamics (CFD) is now a ubiquitous computational tool for engine design and diagnosis. It is often necessary to provide well-known initial cycle conditions to commence the CFD computations. Such initial conditions can be provided by experimental data. To create an opportunity to computationally study engine conditions where experimental data are not available, a zero-dimensional quasi-predictive thermodynamic simulation is developed that uses well-established spray model to predict rate of heat release and calculated burned gas composition and temperature to predict nitric oxide (NO) concentration. This simulation could in turn be used in reverse to solve for initial cylinder conditions for a targeted NO concentration. This paper details the thermodynamic simulation for diesel engine operating conditions. The goal is to produce a code that is capable of predicting NO emissions as well as performance characteristics such as mean effective pressure (MEP) and brake specific fuel consumption (BSFC). The simulation uses general conservation of mass and energy approaches to model intake, compression, and exhaust. Rate of heat release prediction is based on an existing spray model to predict how fuel concentrations within the spray jet change with penetration. Rate of heat release provides predicted cylinder pressure, which is then validated against experimental pressure data under known operating conditions. An equilibrium mechanism is used to determine burned gas composition which, along with burned gas temperature, can be used for prediction of NO in the cylinder. NO is predicted using the extended Zeldovich mechanism. This mechanism is highly sensitive to temperature, and it is therefore important to accurately predict cylinder gas temperature to obtain correct NO values. Additionally, MEP and BSFC are determined. The simulation focuses on single fuel injection events, but insights are provided to expand the simulation to model multiple injection events.

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The Influence of Reduxco Catalyst in the Diesel Fuel on Energy Parameters, Exhaust Gas Composition and Rate of Heat Release of a Diesel Engine

10.4271/2020-01-2061 ◽

2020 ◽

Author(s):

Jerzy Cisek ◽

Szymon Lesniak ◽

Vitaliy Mokretskyy ◽

Włodzimierz Przybylski

Keyword(s):

Diesel Engine ◽

Heat Release ◽

Diesel Fuel ◽

Exhaust Gas ◽

Gas Composition ◽

Energy Parameters ◽

Rate Of Heat Release

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Numerical Analysis of Mild Combustion Regimes Under Air and Oxyfuel Conditions

Volume 1: Boilers and Heat Recovery Steam Generator; Combustion Turbines; Energy Water Sustainability; Fuels, Combustion and Material Handling; Heat Exchangers, Condensers, Cooling Systems, and Balance-of-Plant ◽

10.1115/power-icope2017-3015 ◽

2017 ◽

Author(s):

Wang Lin ◽

Liu Zhaohui ◽

Richard L. Axelbaum

Keyword(s):

Heat Release ◽

Reaction Rate ◽

Diffusion Flames ◽

Chemical Mechanism ◽

Reaction Pathways ◽

Combustion Condition ◽

Counter Flow ◽

Mild Combustion ◽

Order Of Magnitude ◽

Combustion Regimes

Reactive structures of hot diluted methane counter-flow diffusion flames have been characterized under air-fuel and oxy-fuel combustion condition, by using a standard OPPDIF code with a WSGGM model and a validated detail chemical mechanism. The result shows the gaseous radiation makes the peak temperature be lower and the distributions of temperature change greatly. Characteristic of vanishing of pyrolytic region and increasing of thickness of heat release zones are investigated in detail. The reason for these is the overlap of zones for the positive heat release and the negative heat release. Meanwhile, the combustion regions are established based on Xf –Tf –ΔT sketch map. The results show that MILD combustion is easier to be achieved under oxy-fuel conditions but it is also easier to blown off. Moreover, reaction pathways for feedback combustion and MILD combustion under both air- and oxy-fuel conditions are analyzed. The chemical reaction rate decreases one order of magnitude under MILD combustion. Also, the decreasing of the production of OH and H and the addition of CO2 makes the C1 branch the C2 branch changes greatly under both conditions for MILD combustion.

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Nitric oxide formation in strained laminar hydrogen-air counter flow diffusion flames

10.2514/6.1995-132 ◽

1995 ◽

Author(s):

J Zhao ◽

K Isaac

Keyword(s):

Nitric Oxide ◽

Diffusion Flames ◽

Oxide Formation ◽

Counter Flow ◽

Nitric Oxide Formation

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Pulsating diffusion flames fed with biomass particles in counter-flow arrangement: Zeldovich and Lewis numbers effects

Sustainable Energy Technologies and Assessments ◽

10.1016/j.seta.2021.101263 ◽

2021 ◽

Vol 46 ◽

pp. 101263

Author(s):

Shahin Akbari ◽

Moein Farmahini Farahani ◽

Sadegh Sadeghi ◽

Masoud Hajivand ◽

Fei Xu ◽

...

Keyword(s):

Diffusion Flames ◽

Counter Flow ◽

Biomass Particles

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An Improved Rate of Heat Release Model for Modern High-Speed Diesel Engines

Journal of Engineering for Gas Turbines and Power ◽

10.1115/1.4036101 ◽

2017 ◽

Vol 139 (9) ◽

Cited By ~ 3

Author(s):

Peter G. Dowell ◽

Sam Akehurst ◽

Richard D. Burke

Keyword(s):

Heat Release ◽

Diesel Engines ◽

Engine Speed ◽

Fuel Injection ◽

Maximum Pressure ◽

Injection Model ◽

Wall Impingement ◽

Small Set ◽

Rate Of Heat Release ◽

Engine System

To meet the increasingly stringent emissions standards, diesel engines need to include more active technologies with their associated control systems. Hardware-in-the-loop (HiL) approaches are becoming popular where the engine system is represented as a real-time capable model to allow development of the controller hardware and software without the need for the real engine system. This paper focusses on the engine model required in such approaches. A number of semi-physical, zero-dimensional combustion modeling techniques are enhanced and combined into a complete model, these include—ignition delay, premixed and diffusion combustion and wall impingement. In addition, a fuel injection model was used to provide fuel injection rate from solenoid energizing signals. The model was parameterized using a small set of experimental data from an engine dynamometer test facility and validated against a complete data set covering the full engine speed and torque range. The model was shown to characterize the rate of heat release (RoHR) well over the engine speed and load range. Critically, the wall impingement model improved R2 value for maximum RoHR from 0.89 to 0.96. This was reflected in the model's ability to match both pilot and main combustion phasing, and peak heat release rates derived from measured data. The model predicted indicated mean effective pressure and maximum pressure with R2 values of 0.99 across the engine map. The worst prediction was for the angle of maximum pressure which had an R2 of 0.74. The results demonstrate the predictive ability of the model, with only a small set of empirical data for training—this is a key advantage over conventional methods. The fuel injection model yielded good results for predicted injection quantity (R2 = 0.99) and enabled the use of the RoHR model without the need for measured rate of injection.

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