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The purpose of this study is to investigate the combustion of the n-Heptane droplets in the supersonic combustor with a cavity-based fuel injection configuration. The focus is on the impacts of the droplet size on combustion efficiency.

The finite volume solver is developed to simulate the two-phase reacting turbulent compressible flow using a single step reaction mechanism as finite rate chemistry. Three different fuel injection settings are studied for the considered physical geometry and flow conditions: the gas fuel injection, small droplet liquid fuel injection and big droplet fuel. The fuel is injected as a slot wall jet from the bottom of the cavity.

The results show that using the small droplet size, the complete fuel consumption and combustion efficiency can be achieved but using the big droplet sizes, most fuel exit the combustor in the liquid phase and gasified unburned fuel. It is also demonstrated that the cavity's temperature distribution of the liquid fuel case is different from the gas fuel, and two flame branches are observed there due to the droplet evaporation and combustion in the cavity.

To the best of the authors’ knowledge, this study is performed for the first time on the combustion of the n-Heptane fuel droplets in scramjet configuration, which is promising propulsion system for the future economic flights.

The reaction dynamics of combustible clouds at high temperatures and pressures are a common form of energy output in aerospace and explosion accidents. The cloud explosion process is often affected by the external initial conditions. This study aims to numerically study the effects of airflow velocity, initial temperature and fuel concentration on the explosion behavior of isopropyl nitrate/air mixture in a semiconstrained combustor.

The discrete-phase model was adopted to consider the interaction between the gas-phase and droplet particles. A wave model was applied to the droplet breakup. A finite rate/eddy dissipation model was used to simulate the explosion process of the fuel cloud.

The peak pressure and temperature growth rate both decrease with the increasing initial temperature (1,000–2,200 K) of the combustor at a lower airflow velocity. The peak pressure increases with the increase of airflow velocity (50–100 m/s), whereas the peak temperature is not sensitive to the initial high temperature. The peak pressure of the two-phase explosion decreases with concentration (200–1,500 g/m³), whereas the peak temperature first increases and then decreases as the concentration increases.

Chain explosion reactions often occur under high-temperature, high-pressure and turbulent conditions. This study aims to provide prevention and data support for a gas–liquid two-phase explosion.

Sustained turbulence is realized by continuously injecting air and liquid fuel into a semiconfined high-temperature and high-pressure combustor to obtain the reaction dynamic parameters of a two-phase explosion.

This study aims to deal with the large eddy simulation (LES) of an ignition sequence and the resulting steady combustion in a swirl-stabilized liquid-fueled combustor. Particular attention is paid to the ease of handling the numerical tool, the accuracy of the results and the reasonable computational cost involved. The primary aim of the study is to appraise the ability of the newly developed computational fluid dynamics (CFD) methodology to retrieve the spark-based flame kernel initiation, its propagation until the full ignition of the combustion chamber, the flame stabilization and the combustion processes governing the steady combustion regime.

The CFD model consists of an LES-based spray module coupled to a subgrid-scale ignition model to capture the flame kernel initiation and the early stage of the flame kernel growth, and a combustion model based on the mixture fraction-progress variable formulation in the line of the flamelet generated manifold (FGM) method to retrieve the subsequent flame propagation and combustion properties. The LES-spray module is based on an Eulerian-Lagrangian approach and includes a fully two-way coupling at each time step to account for the interactions between the liquid and the gaseous phases. The Wall-Adapting Local Eddy-viscosity (WALE) model is used for the flow field while the eddy diffusivity model is used for the scalar fluxes. The fuel is liquid kerosene, injected in the form of a polydisperse spray of droplets. The spray dynamics are tracked using the Lagrangian procedure, and the phase transition of droplets is calculated using a non-equilibrium evaporation model. The oxidation mechanism of the Jet A-1 surrogate is described through a reduced reaction mechanism derived from a detailed mechanism using a species sensitivity method.

By comparing the numerical results with a set of published data for a swirl-stabilized spray flame, the proposed CFD methodology is found capable of capturing the whole spark-based ignition sequence in a liquid-fueled combustion chamber and the main flame characteristics in the steady combustion regime with reasonable computing costs.

The proposed CFD methodology simulates the whole ignition sequence, namely, the flame kernel initiation, its propagation to fully ignite the combustion chamber, and the global flame stabilization. Due to the lack of experimental ignition data on this liquid-fueled configuration, the ability of the proposed CFD methodology to accurately predict ignition timing was not quantitatively assessed. It would, therefore, be interesting to apply this CFD methodology to other configurations that have experimental ignition data, to quantitatively assess its ability to predict the ignition timing and the flame characteristics during the ignition sequence. Such further investigations will not only provide further validation of the proposed methodology but also will potentially identify its shortfalls for better improvement.

This CFD methodology is developed by customizing a commercial CFD code widely used in the industry. It is, therefore, directly applicable to practical configurations, and provides not only a relatively straightforward approach to predict an ignition sequence in liquid-fueled combustion chambers but also a robust way to predict the flame characteristics in the steady combustion regime as significant improvements are noticed on the prediction of slow species.

The incorporation of the subgrid ignition model paired with a combustion model based on tabulated chemistry allows reducing computational costs involved in the simulation of the ignition phase. The incorporation of the FGM-based tabulated chemistry provides a drastic reduction of computing resources with reasonable accuracy. The CFD methodology is developed using the platform of a commercial CFD code widely used in the industry for relatively straightforward applicability.

THE rocket motor is a form of jet propulsion which is characterized by independence of the external atmosphere for combustion, relative independence of altitude and flight velocity upon thrust, small frontal area for high thrusts, simple construction and low weight, and high rate of fuel consumption. Its use was greatly developed during the war years and many applications are now familiar to all. Most of the work on rocket missiles, such as the anti‐aircraft barrages, fighter armament, etc., was performed with solid fuel rockets, but liquid fuels were developed by the Germans for the well‐known V.2, for the Me. 163 aircraft, the Henschel glide bomb and various other applications. They concentrated a great deal of effort on this work and considerable technical progress had been made with different systems. Three main systems emerged and these were distinguished by the oxygen bearing fluids they used. The fluids were:

The purpose of this paper is to numerically investigate the three-dimensional (3D) reacting turbulent two-phase flow field of a scaled swirl-stabilized gas turbine combustor using the commercial computational fluid dynamic (CFD) software ANSYS FLUENT. The first scope of the study aims to explicitly compare the predictive capabilities of two turbulence models namely Unsteady Reynolds Averaged Navier-Stokes and Scale Adaptive Simulation for a reasonable trade-off between accuracy of results and global computational cost when applied to simulate swirl-stabilized spray combustion. The second scope of the study is to couple chemical reactions to the turbulent flow using a realistic chemistry model and also to model the local chemical non-equilibrium(NEQ) effects caused by turbulent strain such as flame stretching.

Standard Eulerian and Lagrangian formulations are used to describe both gaseous and liquid phases, respectively. The computing method includes a two-way coupling in which phase properties and spray source terms are interchanging between the two phases within each coupling time step. The fuel used is liquid jet-A1 which is injected in the form of a polydisperse spray and the droplet evaporation rate is calculated using the infinite conductivity model. One-component (n-decane) and two-component fuels (n-decane+toluene) are used as jet-A1 surrogates. The combustion model is based on the mean mixture fraction and its variance, and a presumed-probability density function is used to model turbulent-chemistry interactions. The instantaneous thermochemical state necessary for the chemistry tabulation is determined by using initially the equilibrium (EQ) assumption and thereafter, detailed NEQ calculations through the steady flamelets concept. The combustion chemistry of these surrogates is represented through a reduced chemical kinetic mechanism (CKM) comprising 1,045 reactions among 139 species, derived from the detailed jet-A1 surrogate model, JetSurf 2.0 using a sensitivity based method, Alternate Species Elimination.

Numerical results of the gas velocity, the gas temperature and the species molar fractions are compared with their experimental counterparts obtained from a steady state flame available in the literature. It is observed that, SAS coupled to the tabulated flamelet-based chemistry, predicts reasonably the main flame trends, while URANS even provided with the same combustion model and computing resources, leads to a poor prediction of the global flame trends, emphasizing the asset of a proper resolution when simulating spray flames.

The steady flamelet model even coupled with a robust turbulence model does not reproduce accurately the trend of species with slow oxidation kinetics such as CO and H2, because of the restrictiveness of the solutions space of flamelet equations and the assumption of unity Lewis for all species.

This work is adding a contribution for spray flame modeling and can be seen as an extension to the significant efforts for the modeling of gaseous flames using robust turbulence models coupled with the tabulated flamelet-based chemistry approach to considerably reduce computing cost. The exclusive use of a commercial CFD code widely used in the industry allows a direct application of this simulation approach to industrial configurations while keeping computing cost reasonable.

This study is useful to engineers interested in designing combustors of gas turbines and others combustion systems fed with liquid fuels.

The future of the current family of wide‐bodied transports is examined in the environment of the changing world‐wide fuel supply situation. Synthetic hydrocarbon and cryogenic fuels are considered in the context of impact on airline fleets and their maintenance. The probability of the emergence of new technology aircraft, still utilising hydrocarbon fuel is considered in view of the possible shortening of their useful life by the introduction of cryogenic fuels. Possible effects on maintenance of the new technologies which would be included in such aircraft are discussed. Finally, the characteristics of the two most promising cryogenic fuels are compared and the effects of one of these fuels on fuel system design, maintenance, and service as well as facilities and equipment are reviewed.

This paper aims to present the production of waste plastic oil from landfill waste plastics, the performance and emissions of a compression ignition (CI) engine, using waste plastic oil, were tested and compared with using diesel oil. The physical characteristics, gross calorific value (MJ/kg), kinematic viscosity cst @40°C, specific gravity @15.6°C, cetane index, flash point and distillation temperature @90 per cent are determined. The experimental CI engine is a four-stroke, direct injection, single cylinder, 709 C.C. and has been tested with in-brake-specific fuel consumption (BSFC), brake conversion efficiency, brake-specific energy consumption and exhaust gas emissions.

The results show that the characteristics of liquid fuel from landfill plastics (LFLP3) are similar to diesel oil. The CI engine was able to run with LFLP3. The efficiency was slightly higher than that of diesel fuel, whereas the BSFC was lower. The exhaust-gas emission average for LFLP3 was reduced compared to diesel oil operation.

The efficiency of the CI engine using LFLP3 is slightly higher than diesel fuel at all load conditions. In this study, LFLP3 was a lower pollutant than diesel fuel. Environmental values and energy consumption are important when reviewing the ignition of any fuel in a combustion chamber.

The efficiency of the CI engine using LFLP3 is slightly higher than diesel fuel at all load conditions. In this study, LFLP3 was a lower pollutant than diesel fuel. Environmental values and energy consumption are important when reviewing the ignition of any fuel in a combustion chamber.

Utilizing renewable energy and developing new energy sources are practical responses to the shortage of fossil fuels and environmental regulations for carbon dioxide emissions. The purpose of this paper is to assess the practicability of using low heating value (LHV) fuel on an annular miniature gas turbine (MGT) via numerical simulations.

The MGT used in this study is MW‐44 Mark I, whose original fuel is liquid (Jet A1). Its fuel supply system is re‐designed to use biogas fuel with LHV. The simulations, aided by the commercial code CFD‐ACE+, were carried out to investigate the cooling effect in a perforated combustion chamber and combustion behavior in an annular MGT when using LHV gas. In this study, four parameters of rotational speeds are considered. At each specific speed, various mixture ratios of methane (CH₄) to carbon dioxide (CO₂) including 90, 80, 70, and 60 percent were taken into consideration as simulated LHV fuels.

The simulation results show the chamber design can create a proper recirculation zone to concentrate the flame at the center of the chamber, and prevent the flame from expanding to cause hot spot. Furthermore, the hot gas exhausted from combustor outlet is cooled down effectively by jet flow discharged from dilution holes, which prevent turbine blade from heat damage.

Simulation results demonstrate that CFD‐ACE+ can simulate flow field performance and combustion behavior in an annular MGT precisely. The results of these CFD analyses confirm that the methane fuel can be used in such small volume of MGT and still have high performance. With the aid of the constructed combustor model, the performance of a methane‐used MGT can be realized before the experiment procedure starts.

A recent two‐line news item in the International Herald Tribune highlighted an important aspect of Russia's interest in developing cryogenic‐fuelled aircraft. The item read simply “The airport in Vladivostok, in far eastern Russia, closed down on Tuesday because it had run out of fuel.” The air routes to Vladivostok from Moscow and other major Russian cities are extremely long and all kerosene loaded at Vladivostok has to be transported there for the purpose. Fuel supply routes extend over thousands of kilometres whether they involve the limited road and rail links in that part of the world or marine tankers using equally‐long and challenging sea routes.

Flight, even under the most routine conditions, sets high standards of quality for all materials employed. Specifications for aviation fuels have never been obtainable without careful compromise between conflicting requirements, and present developments towards flight at higher altitudes and higher speeds accentuate existing problems and reveal new ones. This article attempts to review the known major problems arising with aviation fuels under these conditions of severity, and to indicate a number of practicable solutions.