Aspects Of Combustion Research Articles

Science and technology of ammonia combustion

Abstract This paper focuses on the potential use of ammonia as a carbon-free fuel, and covers recent advances in the development of ammonia combustion technology and its underlying chemistry. Fulfilling the COP21 Paris Agreement requires the de-carbonization of energy generation, through utilization of carbon-neutral and overall carbon-free fuels produced from renewable sources. Hydrogen is one of such fuels, which is a potential energy carrier for reducing greenhouse-gas emissions. However, its shipment for long distances and storage for long times present challenges. Ammonia on the other hand, comprises 17.8% of hydrogen by mass and can be produced from renewable hydrogen and nitrogen separated from air. Furthermore, thermal properties of ammonia are similar to those of propane in terms of boiling temperature and condensation pressure, making it attractive as a hydrogen and energy carrier. Ammonia has been produced and utilized for the past 100 years as a fertilizer, chemical raw material, and refrigerant. Ammonia can be used as a fuel but there are several challenges in ammonia combustion, such as low flammability, high NOx emission, and low radiation intensity. Overcoming these challenges requires further research into ammonia flame dynamics and chemistry. This paper discusses recent successful applications of ammonia fuel, in gas turbines, co-fired with pulverize coal, and in industrial furnaces. These applications have been implemented under the Japanese ‘Cross-ministerial Strategic Innovation Promotion Program (SIP): Energy Carriers’. In addition, fundamental aspects of ammonia combustion are discussed including characteristics of laminar premixed flames, counterflow twin-flames, and turbulent premixed flames stabilized by a nozzle burner at high pressure. Furthermore, this paper discusses details of the chemistry of ammonia combustion related to NOx production, processes for reducing NOx, and validation of several ammonia oxidation kinetics models. Finally, LES results for a gas-turbine-like swirl-burner are presented, for the purpose of developing low-NOx single-fuelled ammonia gas turbine combustors.

Ignition study of Prunus Domestica oil as an alternate in unmodified diesel engine

ABSTRACT This work presents the feasibility of Prunus Domestica methyl ester (PDME) as an alternate fuel on diesel blended fuel to evaluate the engine characteristics. Six blends of neat baseline diesel, biodiesel (PDME), a blend of diesel -biodiesel (20%, 40%, 60%, 80% and 100%) and neat diesel are prepared which are tested on a diesel engine. The experimental results were revealed that the replacement of diesel by PDME has shown a slight reduction in brake thermal efficiency with a slight increase in brake specific fuel consumption. Further, the PDME addition to diesel reduced the unburned hydrocarbon, CO, and NOx. Critical analysis in combustion aspects is also carried out and it is witnessed with prolonged ignition delay during PDME addition with diesel.

Experimental study of methyl tert-butyl ether as an oxygenated additive in diesel and Calophyllum inophyllum methyl ester blended fuel in CI engine

This work presents the effect of the ternary oxygenated additive on diesel biodiesel blended fuel to evaluate the engine characteristics. The Calophyllum inophyllum trees being abundant in India can lessen the dependence on petroleum imports to a specific extent. Methyl tertiary butyl ether is used as an oxygenated additive for the ternary blends preparation as 5-20% by volume. Seven blends of neat baseline diesel, biodiesel (Calophyllum inophyllum Methyl Ester), a blend of diesel (50%)-biodiesel (50%), a blend of diesel (50%)-biodiesel-methyl tert-butyl ether (5, 10, 15, and 20%) are prepared which are tested on a single cylinder, constant speed diesel engine. The experimental results were revealed that the replacement of biodiesel by MTBE has shown a slight reduction in brake thermal efficiency with a slight increase in brake-specific fuel consumption. Further, the MTBE addition in ternary blends reduced the unburned hydrocarbon, CO, and NOx by 63.9, 6.4, and 3.37% respectively. In addition, the carbon dioxide emission is almost similar to diesel fuel at a higher addition of MTBE with diesel-biodiesel blend. In the combustion point of view, the addition of 5% MTBE resulted in 3.49 and 5.1% reduction of peak pressure and heat release rate are observed as compared to diesel fuel. Critical analysis in combustion aspects is also carried out and it is witnessed with prolonged ignition delay during MTBE addition with diesel-biodiesel blends.

Flexoelectricity and the Formation of Carbon Nanoparticles in Flames

The formation of carbon nanoparticles in flames involves a nucleation step that remains poorly understood. Experimentally, carbon nuclei formation is known to depend strongly on the electrical aspects of combustion, but modes of interaction between charged species in the flame and carbon precursors have yet to be found. We present evidence for flexoelectrically polarized aromatics contributing to carbon nanoparticulate nucleation. We imaged the nascent nanoparticles using high resolution transmission electron microscopy, which revealed that the majority of aromatics in the early carbon nanoparticles are fullerene-like and curved. The curvature induces a significant molecular flexoelectric dipole moment in the polyaromatic hydrocarbons. This electric polarization allows these molecules to strongly interact with chemi-ions produced during combustion, which we demonstrate using electronic structure calculations. The results indicate that the physical interaction between fullerene-like polar aromatics and chemi-ions is critically assisting the nucleation and opens a new route to reduce pollution and improve flame-produced nanomaterials.

Limitation of Atmospheric Composition by Combustion–Explosion in Exoplanetary Atmospheres

Abstract This work presents theoretical studies that combine aspects of combustion and explosion theory with exoplanetary atmospheric science. Super-Earths could possess a large amount of molecular hydrogen depending on disk, planetary, and stellar properties. Super-Earths orbiting pre-main-sequence M-dwarf stars have been suggested to possess large amounts of O2(g) produced abiotically via water photolysis followed by hydrogen escape. If these two constituents were present simultaneously, such large amounts of H2(g) and O2(g) can react via photochemistry to form up to ∼10 Earth oceans. In cases where photochemical removal is slow, hence O2(g) can indeed build up abiotically, the atmosphere could reach the combustion–explosion limit. Then, H2(g) and O2(g) react extremely quickly to release energy and form liquid water together with modest amounts of hydrogen peroxide. These processes set constraints for H2(g) and O2(g) atmospheric compositions in Super-Earth atmospheres. Our initial study of the gas-phase oxidation pathways for modest conditions (Earth’s insolation and ∼10th of a percent of H2(g)) suggests that H2(g) is oxidized by O2(g) into H2O(g) mostly via HOx and mixed HOx–NOx catalyzed cycles. Regarding other pairs of atmospheric species, we find that CO–O2 could attain explosive–combustive levels on mini gas planets for midrange C/O in the equilibrium chemistry regime (p > ∼1 bar). Regarding (CH4–O2), a small number of modeled rocky planets assuming Earth-like atmospheres orbiting cooler stars could have compositions at or near the explosive–combustive level although more work is required to investigate this issue.

Effect of DEE Oxygenate on Diesel in Algal Biodiesel-Diesel Blends on the Combustion Phenomenon of DI Compression Ignition Engines

Biodiesel derived from Stoechospermum marginatum is analysed in a CI engine to understand its feasibility to be used as fuel. In this study, Soxhlet extraction method was applied to extract the bio oil from the brown sea weed (S. Marginatum) with n-hexane as solvent. Considering the low FFA content through titration, base single stage transesterification process with methanol and NaOH at molar ratio of 8:1 is used and it yielded 84.5% of bio diesel. The test fuel is prepared with processed algae bio diesel and Di-Ethyl Ether in different blend ratios namely D80AB20, D70AB20DEE10 and D60AB20DEE20. The variation in combustion aspects are evaluated with constant concentration of algal bio diesel at 20% with variation in diesel and oxygenate concentrations. Consequential variation is observed in the combustion behaviour of CI engine on fuelling with test fuels. Comparable in-cylinder pressure is observed in bio-diesel blends and oxygenated blends. D70AB20DEEE10 exhibits superior heat release rate and pressure rise at all loads. The peak in-cylinder pressure and variation in ignition delay are also analysed in this study.

A numerical study of NOx and soot emissions in methane/n-heptane triple flames

Abstract There is significant interest worldwide in using cleaner/renewable fuels, such as syngas and biogas, in transportation and power generation systems. We report herein a computational study to investigate NOx and soot emissions in n-heptane/methane triple flames in an opposed-jet configuration. The objective is to evaluate various fuel injection scenarios in a dual-fuel engine using a simple configuration to emulate important aspects of diesel combustion. Simulations are performed by combining a detailed fuel and NOx chemistry model with a soot model. Three blending strategies are examined. For each strategy, NOx, PAH and soot emissions, and thermal efficiency are characterized by varying the energy content between the two fuels, while keeping the total energy input rate fixed. As methane in the blend is increased, the benzene emission index and soot emission decrease with all three strategies, but the reduction is more pronounced with strategies 2 and 3. In addition, it leads to higher efficiency with strategies 2 and 3, but lower efficiency with strategy 1. Thus strategy #1 yields higher NOx, PAH and soot emissions, and lower efficiency compared to other two strategies, and is not recommended.

Comparison of Near-Nozzle Spray Performance of Gas-to-Liquid and Jet A-1 Fuels Using Shadowgraph and Phase Doppler Anemometry

The gas-to-liquid (GTL) fuel, a liquid fuel synthesized from natural gas through Fischer–Tropsch process, exhibits better combustion and, in turn, lower emission characteristics than the conventional jet fuels. However, the GTL fuel has different fuel properties than those of regular jet fuels, which could potentially affect its atomization and combustion aspects. The objective of the present work is to investigate the near-nozzle atomization characteristics of GTL fuel and compare them with those of the conventional Jet A-1 fuel. The spray experiments are conducted at different nozzle operating conditions under standard ambient conditions. The near-nozzle macroscopic spray characteristics are determined from the shadowgraph images. Near the nozzle exit, a thorough statistical analysis shows that the liquid sheet dynamics of GTL fuel is different from that of Jet A-1 fuel. However, further downstream, the microscopic spray characteristics of GTL fuel are comparable to those of the Jet A-1 fuel.

Effect of CO2 dilution on propane–air isothermal catalytic combustion on platinum

The present work aims to investigate several kinetic aspects of catalytic combustion of the stoichiometric propane–air mixture on a platinum wire in the presence of progressive CO2 dilution, using a micro-calorimetric method. The method allowed the determination of the induction periods and of the reaction rates during transient and steady-state regimes at different initial pressures P 0 (10–101 kPa), wire temperatures T w (470–575 K) and gas-phase composition. The kinetic parameters were evaluated from regression analysis using empirical and mechanistic models. The dilution with CO2 of the stoichiometric propane–air mixture (4.02% propane) was 10, 20, 30, 40, 50%. For additions equal to or greater than 23%, the gaseous system is outside the flammability limits reported in the literature. The kinetic characteristics of the catalytic combustion remain similar for the whole range, even for 50% CO2 addition when the propane concentration in mixture diminishes to 2%, a concentration smaller than the lower explosion limit in air in normal conditions.

Investigations of microwave stimulation of a turbulent low-swirl flame

Irradiating a flame by microwave radiation is one of several plasma-assisted combustion (PAC) technologies that can be used to modify the combustion chemical kinetics in order to improve flame-stability and to delay lean blow-out. One practical implication is that engines may be able to operate with leaner fuel mixtures and have an improved fuel flexibility capability including biofuels. In addition, this technology may assist in reducing thermoacoustic instabilities that may severely damage the engine and increase emission production. To examine microwave-assisted combustion a combined experimental and computational study of microwave-assisted combustion is performed for a lean, turbulent, swirl-stabilized, stratified flame at atmospheric conditions. The objectives are to demonstrate that the technology increases both the laminar and turbulent flame speeds, and modifies the chemical kinetics, enhancing the flame-stability at lean mixtures. The study combines experimental investigations using hydroxyl (OH) and formaldehyde (CH2O) Planar Laser-Induced Fluorescence (PLIF) and numerical simulations using finite rate chemistry Large Eddy Simulations (LES). The reaction mechanism is based on a methane (CH4)–air skeletal mechanism expanded with sub-mechanisms for ozone, singlet oxygen, chemionization, electron impact dissociation, ionization and attachment. The experimental and computational results show similar trends, and are used to demonstrate and explain some significant aspects of microwave-enhanced combustion. Both simulation and experimental studies are performed close to lean blow off conditions. In the simulations, the flame is gradually subjected to increasing reduced electric field strengths, resulting in a wider flame that stabilizes nearer to the burner nozzle. Experiments are performed at two equivalence ratios, where the leaner case absorbs up to more than 5% of the total flame power. Data from experiments reveal trends similar to simulated results with increased microwave absorption.

An analysis of the structure of an n-dodecane spray flame using TPDF modelling

With a view to understanding ignition and combustion behaviours in diesel engines, this study investigates several aspects of ignition and combustion of an n-dodecane spray in a high pressure, high temperature chamber, known as Spray A, using data resulting from modelling using the transported probability density function (TPDF) method. The model has been validated comprehensively with good to excellent agreement in our previous work against all available experimental data including for mixture-fraction and velocity fields in non-reacting cases, and flame lift-off length and ignition delay in reacting cases. This good agreement encourages further investigation of the numerical model results to help understand the structure of this flame, which serves to complement the experimental information that is available, which is very limited due to the difficult experimental conditions in which this flame exists. For example, quantitative experimental measurements of local mixture-fraction, temperature, velocity gradients, etc. are not yet possible in reacting cases. Analysis of the model results shows that two-stage ignition is found to occur across the ambient temperature conditions considered: the first stage is rapidly initiated on the lean side where temperatures are high and sequentially moves to richer, cooler conditions. The first stage is extremely resilient to turbulence, occurring in a region of very low Damköhler number. The second stage of ignition occurs first in rich mixtures in a region behind the head of the fuel jet where mixture gradients are low, and appears to be influenced strongly by turbulence. Relative to a homogeneous reactor, it is delayed on the lean side but advanced on the rich side, suggesting entrainment and mixing from the early igniting lean regions into richer mixtures is an important moderator of the ignition process. The second-stage ignition front propagates at very high velocities initially, suggesting it is a sequential ignition moving according to gradients of ignition delay and/or residence time. The flame stabilises however on the lean side in a region of much lower velocity, where turbulent velocity fluctuations are sufficiently high such that turbulent transport influences the propagation. It stabilises in a region of low Damköhler number which implies that a competition of chemistry versus micro-mixing might also be involved in stabilisation. The stabilisation mechanism is investigated by an analysis of the transport budgets, showing the flame is stabilised by autoignition but moderated by turbulent diffusion. Further analysis of the flame index supports this stabilisation mechanism, and demonstrates the simultaneous existence of non-premixed and premixed combustion modes in the same flame. Analysis of the flow fields also reveals that local entrainment and dilatation are important flow features near the flame base.

Engine Performance and Emission having Jatropha Diesel Blend

The performance of a four stroke, single cylinder, direct injection CI engine is evaluated having fuel as neat jatropha-diesel blend in proportion 2:1 on a volume basis. The experimentations were conducted to test engine performance and emission characteristics at throttle settings of 25%, 50%, 75% and 100% and variable loads covering under load to overloading of engine operation. The effect of jatropha blend on engine brake power, brake thermal efficiency and specific fuel consumption were observed at different loads and throttle openings along with exhaust emissions and exhaust gas temperatures. Compared to jatropha blend diesel provides better performance for entire operating range (of loads and throttle openings) but effect of varying load /throttle settings on performance characteristics are of similar nature. The jatropha blend produces lower hydrocarbon and NO x emission, highlights the positive aspects of combustion and the allowance of higher effective compression ratio of the blend.

Direct combustion of recyclable metal fuels for zero-carbon heat and power

It is becoming widely recognized that our society must transition to low-carbon energy systems to combat global climate change, and renewable energy sources are needed to provide energy security in a world with limited fossil-fuel resources. While many clean power-generation solutions have been proposed and are being developed, our ability to transition to a low-carbon society is prevented by the present lack of clean and renewable energy carriers that can replace the crucial roles that fossil fuels play, due to their abundance, convenience and performance, in global energy trade and transportation. Any future low-carbon energy carriers that aim to displace or supplement fossil fuels must have high energy densities for convenient trade and storage, and should be consumable within efficient high-power-density engines for transportation, heavy machinery, and other off-grid energy applications.Hydrogen and batteries have been widely studied but they are not suitable for use as international energy-trading commodities and they cannot provide the energy density and safety demanded by society. Metal fuels, produced using low-carbon recycling systems powered by clean primary energy, such as solar and wind, promise energy densities that are competitive to fossil fuels with low, or even negative, net carbon dioxide emissions. To date, however, few practical high-power-density end-use devices for generating heat or power from metal fuels have been proposed.This paper proposes a novel concept for power generation in which metal fuels are burned with air in a combustor to provide clean, high-grade heat. The metal-fuel combustion heat can be used directly for industrial or residential heating and can also power external-combustion engines, operating on the Rankine or Stirling cycles, or thermo-electric generators over a wide range of power levels. A design concept is proposed for a metal-fuelled combustor that is based upon extensive experimental and theoretical studies of stabilized and propagating metal flames performed at McGill University. This paper also reviews the fundamental and applied aspects of metal-fuel combustion in order to provide the framework needed to assess any potential metal engine technologies. The energy and power densities of the proposed metal-fuelled zero-carbon heat engines are predicted to be close to current fossil-fuelled internal-combustion engines, making them an attractive technology for a future low-carbon society.

Specific Features of Solid Fuels Combustion in Oxygen Atmosphere with Recirculation of CO2

<p>Aspects of coal combustion have been experimentally studied under oxyfuel conditions, one of the promising technologies for carbon capture and storage (CCS). Here, the thermogravimetric analysis (TGA) method was chosen as an experimental technique. Coal pyrolysis tests performed under an O<sub>2</sub>/CO<sub>2</sub> atmosphere were compared with a conventional O<sub>2</sub>/N<sub>2</sub> environment in terms of reaction rate and total volatile yield. Combustion of the resulting chars in the corresponding atmospheres revealed somewhat different combustion rates with a less vigorous reaction in the O<sub>2</sub>/CO<sub>2</sub> medium. The two manipulated factors – namely, the inherently different char reactivities due to the different atmospheres they were obtained in and the different atmospheres of the actual combustion process – were distinguished by performing another series of tests with chars pyrolysed under identical conditions using a standard routine. These chars also showed a weaker reaction in O<sub>2</sub>/CO<sub>2</sub> atmosphere, which was attributed to the lower binary diffusion coefficient of the O<sub>2</sub>/CO<sub>2</sub> pair. The activity of the char – CO<sub>2 </sub>gasification reaction in an O<sub>2</sub>/CO<sub>2</sub> environment was also investigated and revealed some contribution of this reaction to the conversion process. This was particularly noticeable at temperatures above 750 °C and under an internal diffusional controlled regime (zone II), implying displacement of oxygen out of the char particle pore volume, which allowed free reaction of CO<sub>2</sub> on the developed pore surface. Non-isothermal kinetic analysis of the intrinsic kinetics of the oxidation reaction in O<sub>2</sub>/CO<sub>2</sub> revealed no particular difference compared to the O<sub>2</sub>/N<sub>2</sub> medium, at least when the char-CO<sub>2 </sub>reaction was inhibited. The obtained data were used to develop a coal combustion model under O<sub>2</sub>/CO<sub>2</sub> conditions, which was then incorporated as a combustion module into circulating fluidized bed (CFB) computation software.</p>

Experimental study of ignition timing and supercharging effects on a gasoline engine fueled with synthetic gases extracted from biogas

This paper presents the experimental results of two series of tests developed in a gasoline spark ignition engine fueled with synthetic gases obtained from catalytic decomposition of biogas. The first group of tests was carried out in order to analyze the effects of the ignition timing in the combustion of such gases. It was found that depending on the composition of the gaseous blends the optimum ignition timing is quite different. The selection of the right equivalence ratio and spark timing allowed the achievement of efficiencies above the gasoline. It was also detected that the variation in the ignition timing has an important effect on parameters of combustion like maximum pressures, mass fraction burned, heat release ratio and cyclic irregularity. Such effects were extended to some pollutants like HC and NOx, which are strongly influenced by the combustion temperatures. The second group of tests consisted in the increase of the intake pressure over the atmospheric through supercharging the intake air. The increase in the boost pressure involved an increment in the mass flow of air–fuel mixture aspired and consequently, the engine performance improved. This entailed that the torque and the efficiencies raised, reaching values higher than gasoline at atmospheric conditions. The increment in the energy released implied higher maximum pressures, but other aspects of combustion were not influenced by boost pressures. However, pollutant emissions presented some variations in these tests, caused mainly for the increase in the power generated and the changes in the flow of air–fuel mixture.

Performance of a Direct Injection Diesel Engine Using Jatropha Diesel Blends as Fuel

Jatropha bio diesel blended with mineral diesel in proportion 2:1 by volume is used to conduct performance test and emission characteristics of a single cylinder direct injection diesel engine. Jatropha-diesel blend is used to perform engine performance and emission tests at variable loads & throttle settings (25%, 50%, 75% and 100%). Observed data were utilized to obtain various performance parameters such as brake power, brake specific fuel consumption, brake thermal efficiency at various loads and throttle settings. Simultaneously observations were also made to obtain exhaust gas temperatures and exhaust emissions (CO, CO2, HC and NOx). In existing engine diesel provides higher and economic power generating capacity for entire operating ranges but effect of varying load /throttle on performance behavior were fantastically similar. Reduced HC and NOx emission with the blend also better, highlights some positive aspects of combustion and allowance for higher compression ratio with the blend.

Special Issue on Innovative Technologies on Combustion of Biofuels in Engines: Issues and Challenges

Special Issue on Innovative Technologies on Combustion of Biofuels in Engines: Issues and Challenges

Application of biomass fast pyrolysis part II: The effects that bio-pyrolysis oil has on the performance of diesel engines

This study used the fast pyrolysis method to produce bio-oil from coffee bean residue. The oil was mixed with diesel fuel through emulsification to produce emulsified fuel with varying proportions. A single-cylinder diesel engine connected to a 12-kW power generation system was used as the test system to examine the performance indices of a diesel engine under various loads and rotational speeds when using three fuel mixtures with varying proportions of bio-oil (i.e., CPO (coffee bean residue pyrolysis oil) 0 (100% diesel), CPO 5 (5 vol.% bio-oil/95 vol.% diesel), and CPO 10 (10 vol.% bio-oil/90 vol.% diesel)). According to the results, compared to CPO 0, the addition of CPO 5 and CPO 10 increased the fuel consumed for the same power output. Although CPO 5 and CPO 10 had lower heating values that reduced combustion efficiency, the water content and emulsification properties of these fuels enhanced certain aspects of combustion. Increasing the proportion of bio-oil effectively reduced NOx emissions, but in certain situations, denser smoke was produced. The smoke resulted from the added bio-oil, which reduced heating values and combustion efficiency. The emulsification properties of the oil contributed to microexplosion of oil droplets, which enhanced combustion characteristics.

EFFECT OF FUEL PROPERTIES ON SPRAY CHARACTERISTICS OF ALTERNATIVE JET FUELS USING GLOBAL SIZING VELOCIMETRY

Increasing oil prices and strict emission policies drive the need for cleaner, alternative energy sources. Gas-to-liquid (GTL) jet fuel, a synthetic jet fuel produced from natural gas using Fischer−Tropsch synthesis, has grabbed global attention due to its cleaner combustion aspects when compared to conventional jet fuels. Since the production methodology of GTL and conventional jet fuels are different, their chemical and physical properties are different from each other. Consequently, these differences can affect atomization, mixing, combustion, and pollutant formation in the combustion chamber. Atomization is the precursor to evaporation and mixing processes. Hence, it is important to study atomization in detail in order to gain a better understanding of the other processes that directly affect combustion and emission characteristics. In this work, the microscopic spray characteristics of two GTL fuels and conventional Jet A-1 fuel are investigated and compared with each other. The spray characteristics of these fuels are studied for three injection pressures at different spatial locations downstream of a pressure swirl nozzle exit using a planar-laser diagnostic technique known as global sizing velocimetry. The results demonstrate that the influence of change in the fuel physical properties is insignificant on the spray characteristics at high injection pressures. Furthermore, the spray characteristics of the GTL fuels are found to be similar to those of the conventional Jet A-1 fuel.

Recovery of Light Oil by Medium Temperature Oxidation

We study one aspect of combustion in porous media for the recovery of light oil. We assume that there is a temperature range above low temperature combustion where oxygen is added to the aliphatic oils to form oxygenated compounds and below the temperature where cracking and coke formation occurs. In the intermediate range oil is combusted to form small combustion products like water, CO $$_2$$ , or CO. We call this medium temperature oxidation (MTO). Our simplified model considers light oil recovery when it is displaced by air at medium pressures in linear geometry, for the case when water is absent. The resulting MTO combustion displaces all the oil. There are adjacent vaporization and combustion zones, traveling with the same speed. The MTO reaction is assumed to be slow, so that vaporization is much faster. The solution of the model equations leads to a thermal wave upstream, a MTO wave in the middle and a cold isothermal Buckley–Leverett gas displacement process downstream. One of the unexpected results is that vaporization occurs upstream of the combustion zone. In the initial period the recovery curve is typical of gas displacement, but after a critical amount of air has been injected the cumulative oil recovery increases linearly until all oil has been recovered. In our model, the oil recovery is independent of reaction rate parameters, but the recovery is much faster than for gas displacement. Finally, the recovery is slower for higher boiling point and higher oil viscosity, but faster at higher injection pressure. We give a simple engineering procedure to compute recovery curves for a variety of different conditions.