An Investigation of Fundamental Combustion Properties of the Oxygenated Fuels DME and OME1

2020 ◽  
Author(s):  
John M. Ngugi ◽  
Sandra Richter ◽  
Marina Braun-Unkhoff ◽  
Clemens Naumann ◽  
Uwe Riedel
Keyword(s):  
Gas Turbines ◽  
Fossil Fuels ◽  
Laminar Flame ◽  
Chemical Kinetic ◽  
Transport Sector ◽  
Renewable Energy Resources ◽  
Fuel Blend ◽  
Design And Optimization ◽  
Elevated Pressures ◽  
Combustion Properties

Abstract Demands of energy will increase worldwide. The use of alternative and renewable energy resources is an attractive option to counteract climate change connected with the burning of fossil fuels. Moreover, improvements in fuel flexibility are a pre-requisite to meet the challenge of a sustainable production of energy in the near future. Within this context, oxygenated molecules, in particular ethers are of high interest because they can be produced renewably. In addition, ethers are promising considerably reduced emissions of particles and soot. In future, ethers might play a role as an alternative fuel (blend) for power generation in gas turbines and in the transport sector. Dimethylether (DME: CH3OCH3) and oxymethylenether (OMEn: CH3O(CH2O)nCH3) are regarded as some of the most promising alternatives to fossil fuels, in particular in compression ignition engines. In this work, we report on a combined experimental and modeling study: The oxidation of mixtures of dimethylether as well as of the simplest oxymethylenether (OME1) was investigated. The focus was put on two fundamental combustion properties: (i) ignition delay times measured in a shock tube device, at ambient and elevated pressures up to 16 bar, for stoichiometric mixtures, and (ii) laminar flame speed data, at ambient and elevated pressures up to 6 bar, determined for OME1. The experimental data base was used for the validation of several detailed chemical-kinetic reaction mechanisms taken from literature. Sensitivity analysis was performed for the two selected targets to allow a better insight into the oxidation network within the envisaged wide parameter range. The findings of the present work will contribute to a better understanding of the combustion of these specific ethers, and to the design and optimization of burners and engines as well.

Skeletal Kinetic Modeling for the Combustion of Endothermic Hydrocarbon Fuel in Hypersonic Vehicle

2021 ◽  
pp. 1-24
Author(s):  
Hui-Sheng Peng ◽  
Bei-Jing Zhong
Keyword(s):  
Surrogate Model ◽  
Laminar Flame ◽  
Combustion Process ◽  
Hydrocarbon Fuel ◽  
Kinetic Mechanism ◽  
Chemical Kinetic ◽  
Vital Role ◽  
Reacting Flow ◽  
Combustion Properties ◽  
Endothermic Hydrocarbon Fuel

Abstract Chemical kinetic mechanism plays a vital role in the deep learning of reacting flow in practical combustors, which can help obtain many details of the combustion process. In this paper, a surrogate model and a skeletal mechanism for an endothermic hydrocarbon fuel were developed for further investigations of the combustion performance in hypersonic vehicles: (1) The surrogate model consists of 81.3 mol% decalin and 18.7 mol% n-dodecane, which were determined by both the composition distributions and key properties of the target endothermic hydrocarbon fuel. (2) A skeletal kinetic mechanism only containing 56 species and 283 reactions was developed by the method of “core mechanism​ sub mechanism”. This mechanism can be conveniently applied to the simulation of practical combustors for its affordable scale. (3) Accuracies of the surrogate model and the mechanism were systematically validated by the various properties of the target fuel under pressures of 1-20atm, temperatures of 400-1250K, and equivalence ratios of 0.5-1.5. The overall errors for the ignition and combustion properties are no more than 0.4 and 0.1, respectively. (4) Laminar flame speeds of the target fuel and the surrogate model fuel were also measured for the validations. Results show that both the surrogate model and the mechanism can well predict the properties of the target fuel. The mechanism developed in this work is valuable to the further design and optimization of the propulsion systems.

Numerical Study on the Effect of Real Syngas Compositions on Ignition Delay Times and Laminar Flame Speeds at Gas Turbine Conditions

2013 ◽  
Author(s):  
Olivier Mathieu ◽  
Eric L. Petersen ◽  
Alexander Heufer ◽  
Nicola Donohoe ◽  
Wayne Metcalfe ◽  
...  
Keyword(s):  
Ignition Delay ◽  
Delay Time ◽  
Gas Turbines ◽  
Ignition Delay Time ◽  
Laminar Flame ◽  
Numerical Study ◽  
Fuel Mixture ◽  
Flame Speed ◽  
Operating Conditions ◽  
Combustion Properties

Depending on the feedstock and the production method, the composition of syngas can include (in addition to H2 and CO) small hydrocarbons, diluents (CO2, water, and N2), and impurities (H2S, NH3, NOx, etc.). Despite this fact, most of the studies on syngas combustion do not include hydrocarbons or impurities and in some cases not even diluents in the fuel mixture composition. Hence, studies with realistic syngas composition are necessary to help designing gas turbines. The aim of this work was to investigate numerically the effect of the variation in the syngas composition on some fundamental combustion properties of premixed systems such as laminar flame speed and ignition delay time at realistic engine operating conditions. Several pressures, temperatures, and equivalence ratios were investigated. To perform this parametric study, a state-of-the-art C0-C5 detailed kinetics mechanism was used. Results of this study showed that the addition of hydrocarbons generally reduces the reactivity of the mixture (longer ignition delay time, slower flame speed) due to chemical kinetic effects. The amplitude of this effect is however dependent on the nature and concentration of the hydrocarbon as well as the initial condition (pressure, temperature, and equivalence ratio).

Laminar Flame Speed Measurements and Modeling of Pure Alkanes and Alkane Blends at Elevated Pressures

2011 ◽  
Vol 133 (9) ◽  
Author(s):  
William Lowry ◽  
Jaap de Vries ◽  
Michael Krejci ◽  
Eric Petersen ◽  
Zeynep Serinyel ◽  
...  
Keyword(s):  
High Pressure ◽  
Natural Gas ◽  
Gas Turbines ◽  
Laminar Flame ◽  
Flame Speed ◽  
Published Data ◽  
Laminar Flame Speed ◽  
Binary Blends ◽  
Elevated Pressures ◽  
True Value

Alkanes such as methane, ethane, and propane make up a large portion of most natural gas fuels. Natural gas is the primary fuel used in industrial gas turbines for power generation. Because of this, a fundamental understanding of the physical characteristics such as the laminar flame speed is necessary. Most importantly, this information is needed at elevated pressures to have the most relevance to the gas turbine industry for engine design. This study includes experiments performed at elevated pressures, up to 10 atm initial pressure, and investigates the fuels in a pure form as well as in binary blends. Flame speed modeling was done using an improved version of the kinetics model that the authors have been developing over the past few years. Modeling was performed for a wide range of conditions, including elevated pressures. Experimental conditions include pure methane, pure ethane, 80/20 mixtures of methane/ethane, and 60/40 mixtures of methane/ethane at initial pressures of 1 atm, 5 atm, and 10 atm. Also included in this study are pure propane and 80/20 methane/propane mixtures at 1 atm and 5 atm. The laminar flame speed and Markstein length measurements were obtained from a high-pressure flame speed facility using a constant-volume vessel. The facility includes optical access, a high-speed camera, a schlieren optical setup, a mixing manifold, and an isolated control room. The experiments were performed at room temperature, and the resulting images were analyzed using linear regression. The experimental and modeling results are presented and compared with previously published data. The data herein agree well with the published data. In addition, a hybrid correlation was created to perform a rigorous uncertainty analysis. This correlation gives the total uncertainty of the experiment with respect to the true value rather than reporting the standard deviation of a repeated experiment. Included in the data set are high-pressure results at conditions where in many cases for the single-component fuels few data existed and for the binary blends no data existed prior to this study. Overall, the agreement between the model and data is excellent.

An Investigation of Combustion Properties of Butanol and its Potential for Power Generation

2017 ◽  
Author(s):  
Torsten Methling ◽  
Sandra Richter ◽  
Trupti Kathrotia ◽  
Marina Braun-Unkhoff ◽  
Clemens Naumann ◽  
...  
Keyword(s):  
Ignition Delay ◽  
Laminar Flame ◽  
Cone Angle ◽  
Transformation Method ◽  
Chemical Kinetic ◽  
Reaction Model ◽  
Ignition Delay Times ◽  
Combustion Properties ◽  
Delay Times ◽  
Reaction Models

Over the last years, global concerns about energy security and climate change have resulted in many efforts focusing on the potential utilization of non-petroleum-based, i.e. bio-derived, fuels. In this context, n-butanol has recently received high attention because it can be produced sustainably. A comprehensive knowledge about its combustion properties is inevitable to ensure an efficient and smart use of n-butanol if selected as a future energy carrier. In the present work, two major combustion characteristics, here laminar flame speeds applying the cone-angle method and ignition delay times applying the shock tube technique, have been studied, experimentally and by modeling exploiting detailed chemical kinetic reaction models, at ambient and elevated pressures. The in-house reaction model was constructed applying the RMG-method. A linear transformation method recently developed, linTM, was exploited to generate a reduced reaction model needed for an efficient, comprehensive parametric study of the combustion behavior of n-butanol/hydrocarbon mixtures. All experimental data were found to agree with the model predictions of the in-house reaction model, for all temperatures, pressures, and fuel-air ratios. On the other hand, calculations using reaction models from the open literature mostly overpredict the measured ignition delay times by about a factor of two. The results are compared to those of ethanol, with ignition delay times very similar and laminar flame speeds of n-butanol slightly lower, at atmospheric pressure.

A Detailed and Reduced Reaction Mechanism of Biomass-Based Syngas Fuels

2010 ◽  
Vol 132 (9) ◽  
Author(s):  
Marina Braun-Unkhoff ◽  
Nadezhda Slavinskaya ◽  
Manfred Aigner
Keyword(s):  
Reaction Mechanism ◽  
Laminar Flame ◽  
Chemical Kinetic ◽  
Laminar Flame Speed ◽  
Predictive Capability ◽  
Kinetic Reaction ◽  
Auto Ignition ◽  
Combustion Properties ◽  
Detailed Chemical ◽  
Good Agreement

In the present work, the elaboration of a reduced kinetic reaction mechanism is described, which predicts reliably fundamental characteristic combustion properties of two biogenic gas mixtures consisting mainly of hydrogen, methane, and carbon monoxide, with small amounts of higher hydrocarbons (ethane and propane) in different proportions. From the in-house detailed chemical kinetic reaction mechanism with about 55 species and 460 reactions, a reduced kinetic reaction mechanism was constructed consisting of 27 species and 130 reactions. Their predictive capability concerning laminar flame speed (measured at T0=323 K, 373 K, and 453 K, at p=1 bar, 3 bars, and 6 bars for equivalence ratios φ between 0.6 and 2.2) and auto ignition data (measured in a shock tube between 1035 K and 1365 K at pressures around 16 bars for φ=0.5 and 1.0) are discussed in detail. Good agreement was found between experimental and calculated values within the investigated parameter range.

An Investigation of Combustion Properties of a Gasoline Primary Reference Fuel Surrogate Blended With Butanol

2019 ◽  
Author(s):  
Sandra Richter ◽  
Marina Braun-Unkhoff ◽  
Jürgen Herzler ◽  
Torsten Methling ◽  
Clemens Naumann ◽  
...  
Keyword(s):  
Chemical Kinetic ◽  
Reaction Model ◽  
Attractive Alternative ◽  
Kinetic Reaction ◽  
Heat Engines ◽  
Elevated Pressures ◽  
Ignition Delay Times ◽  
Comprehensive Knowledge ◽  
Combustion Properties ◽  
Primary Reference

Abstract Currently, many research studies are exploring opportunities for the use of novel fuels and of their blends with conventional, i.e. petroleum-based fuels. To pave the way for their acceptance and implementation in the existing energy market, a comprehensive knowledge about their combustion properties is inevitable, among others. Within this context, alcohols, with butanol in particular, are considered as attractive candidates for the needed de-fossilization of the energy sector. In this work, we report on the oxidation of mixtures of n-heptane/i-octane (PRF90, primary reference fuel, a gasoline surrogate) and addition of n-butanol, 20% and 40%, respectively, in a combined experimental and modeling effort. The focus was set on two fundamental combustion properties: (i) Ignition delay times measured in a shock tube, at ambient and elevated pressures, for stoichiometric mixtures, and (ii) Laminar burning velocities, at ambient and elevated pressures. Moreover, two detailed chemical kinetic reaction mechanisms, with an in-house model among them, have been used for investigating and analyzing the combustion of these mixtures. In general, the experimental data agree well with the model predictions of the in-house reaction model, for the temperatures, pressures, and fuel-air ratios studied. Room for improvements is seen for PRF90. The results achieved were also compared to those of n-butanol reported recently; the findings demonstrated clearly the effect of the n-butanol sub model on binary fuel-air mixtures consisting of PRF and n-butanol. From the present work it can be concluded that the addition of n-butanol to gasoline appears to be an attractive alternative fuel for most types of heat engines.

HEEDS Optimized HyChem Mechanisms

2017 ◽  
Author(s):  
Graham Goldin ◽  
Zhuyin Ren ◽  
Yang Gao ◽  
Tianfeng Lu ◽  
Hai Wang ◽  
...  
Keyword(s):  
High Temperature ◽  
Ignition Delay ◽  
Laminar Flame ◽  
Chemical Kinetic ◽  
Flame Speed ◽  
Cfd Simulations ◽  
Transportation Fuels ◽  
Ignition Delay Times ◽  
Combustion Properties ◽  
Fuel Pyrolysis

Transportation fuels consist of a large number of hydrocarbon components and combust through an even larger number of intermediates. Detailed chemical kinetic models of these fuels typically consist of hundreds of species, and are computationally expensive to include directly in 3D CFD simulations. HyChem (Hybrid Chemistry) is a recently proposed modeling approach for high-temperature fuel oxidation based on the assumptions that fuel pyrolysis is fast compared to the subsequent oxidation of the small fragments, and that, although their proportions may differ, all fuels pyrolyse to similar sets of these fragment species. Fuel pyrolysis is hence modeled with a small set of lumped reactions, and oxidation is described by a compact C0-4 foundation chemistry core. The stoichiometric coefficients of the global pyrolysis reactions are determined to match experimental or detailed mechanism computational data, such as shock-tube pyrolysis products, ignition delays and laminar flame speeds. The model is then validated against key combustion properties, including ignition delays, laminar flame speeds and extinction strain rates. The resulting HyChem model is relatively small and computationally tractable for 3D CFD simulations in complex geometries. This paper applies the HEEDS optimization tool to find optimal pyrolysis reaction stoichiometric coefficients for high-temperature combustion of two fuels, namely Jet-A and n-heptane, using a 47 species mechanism. It was found that optimizing on experimental ignition delay and laminar flame speed targets yield better agreement for ignition delay times and flame speeds than optimizing on pyrolysis yield targets alone. For Jet-A, good agreement for ignition delays and flame speeds were obtained by using both ignition delay and flame speeds as targets. For n-heptane, a trade-off between ignition delay and flame speed was found, where increased target weights for ignition delay resulted in worse flame speed predictions, and visa-versa.

scholarly journals Biofuels Analysis Based on the THDI Indicator of Sustainability

2021 ◽  
Vol 9 ◽  
Author(s):  
Umberto Lucia ◽  
Giulia Grisolia
Keyword(s):  
Fossil Fuels ◽  
Road Transport ◽  
Energy Resources ◽  
Transport Sector ◽  
Renewable Energy Resources ◽  
The Road ◽  
Current Shift ◽  
Micro Organisms ◽  
New Jobs

Energy resources, and their management, represent an open ongoing problem of our present days. An increasing interest in the analysis of the limits of fossil fuels’ use, and their availability, is growing in order to find solutions to the undesired impact of some anthropic activities to the environment. So, nowadays, aThe current shift to renewable energy resources has become a fundamental requirement. In this context, biofuels from micro-organisms can represent a response to the requirement of reducing the environmental impact, but also to generatinge new jobs. In this paper, the analysis of the biofuels from micro-organisms is developed by introducing the Thermodynamic Human Development Index (THDI). In particular, we show how its performance can be improved by using the third-generation biofuels in the road transport sector, and how it increases by exploiting biofuels derived from mutualistic species of some micro-organisms. The result consists inis affected by the fundamental role of the mutualistic behaviour of these species in order to increase the overall sustainability.

scholarly journals On the Flame Shape in a Premixed Swirl Stabilised Burner and its Dependence on the Laminar Flame Speed

2021 ◽  
Author(s):  
Nikolaos Papafilippou ◽  
Muhammad Aqib Chishty ◽  
Richard Bart Gebart
Keyword(s):  
Flame Front ◽  
Gas Turbines ◽  
Fossil Fuels ◽  
Numerical Solutions ◽  
Laminar Flame ◽  
Methane Combustion ◽  
Axial Direction ◽  
Flame Speed ◽  
Laminar Flame Speed ◽  
Flame Shape

AbstractGas turbines for power generation are optimised to run with fossil fuels but as a response to tighter pollutant regulations and to enable the use of renewable fuels there is a great interest in improving fuel flexibility. One interesting renewable fuel is syngas from biomass gasification but its properties vary depending on the feedstock and gasification principle, and are significantly different from conventional fuels. This paper aims to give an overview of the differences in combustion behaviour by comparing numerical solutions with methane and several different synthesis gas compositions. The TECFLAM swirl burner geometry, which is designed to be representative of common gas turbine burners, was selected for comparison. The advantage with this geometry is that detailed experimental measurements with methane are publicly available. A two-stage approach was employed with development and validation of an advanced CFD model against experimental data for methane combustion followed by simulations with four syngas mixtures. The validated model was used to compare the flame shape and other characteristics of the flow between methane, 40% hydrogen enriched methane and four typical syngas compositions. It was found that the syngas cases experience lower swirl intensity due to high axial velocities that weakens the inner recirculation zone. Moreover, the higher laminar flame speed of the syngas cases has a strong effect on the flame front shape by bending it away from the axial direction, by making it shorter and by increasing the curvature of the flame front. A hypothesis that the flame shape and position is primarily governed by the laminar flame speed is supported by the almost identical flame shapes for bark powder syngas and 40% hydrogen enriched methane. These gas mixtures have almost identical laminar flame speeds for the relevant equivalence ratios but the heating value of the syngas is more than a factor of 3 smaller than that of the hydrogen enriched methane. The syngas compositions used are representative of practical gasification processes and biomass feedstocks. The demonstrated strong correlation between laminar flame speed and flame shape could be used as a rule of thumb to quickly judge whether the flame might come in contact with the structure or in other ways be detrimental to the function of the combustion system.

A Study On Fundamental Combustion Properties of Oxymethylene Ether-2

2021 ◽  
Author(s):  
John Mburu Ngugi ◽  
Sandra Richter ◽  
Marina Braun-Unkhoff ◽  
Clemens Naumann ◽  
Markus Köhler ◽  
...  
Keyword(s):  
Experimental Data ◽  
Ignition Delay ◽  
Laminar Flame ◽  
Cone Angle ◽  
Sensitivity Analyses ◽  
Chain Reactions ◽  
Design And Optimization ◽  
Ignition Delay Times ◽  
Combustion Properties ◽  
Delay Times

Abstract Oxymethylene ethers (OMEn, n=1-5) are a promising class of synthetic fuels that have the potential to be used as diesel additives or substitutes. A comprehensive understanding of their combustion properties is required for their safe and efficient utilization. In this study, a combined experimental and modeling work on oxidation of OME2 is reported: (i) Ignition delay time measurements of stoichiometric OME2 / synthetic air mixtures diluted 1:5 with nitrogen using the shock tube method at pressures of 1, 4, and 16 bar, and (ii) laminar flame speeds of OME2 / air mixtures using the cone angle method at pressures of 1, 3 and 6 bar. The experimental data obtained have been used for validation of three detailed reaction mechanisms of OME2. The results of ignition delay times showed that OME2 exhibits a two-stage ignition in the lower temperature region. The mechanism from Cai et al. (2020) best predicted the temperature and pressure dependence of ignition delay times. For laminar flame speeds, the experimental data were well matched by the mechanism from Ren et al. (2019) for all the conditions of pressures and equivalence ratios considered. From sensitivity analyses, it was observed that chain reactions involving small radicals, i.e., H, O, OH, HO2, and CH3 control the oxidation of OME2. The results obtained in this work will contribute to a better understanding of the combustion of oxymethylene ethers, and thus, to the design and optimization of burners and engines as well.

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