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15 pages, 18156 KiB

Open AccessArticle

Experimental and Numerical Study of the Flammability Limits in a CH₄/O₂ Torch Ignition System

by Olexiy Shynkarenko, Domenico Simone, Jungpyo Lee and Artur E. M. Bertoldi

Energies 2022, 15(11), 3857; https://doi.org/10.3390/en15113857 - 24 May 2022

Viewed by 2163

Abstract

The current work is devoted to studying combustion initiation inside the methane-oxygen torch igniter for a hybrid rocket motor. The ignition system can generate a wide range of power and oxidizer-to-fuel ratios. It has a self-cooled vortex combustion chamber with one fuel jet [...] Read more.

The current work is devoted to studying combustion initiation inside the methane-oxygen torch igniter for a hybrid rocket motor. The ignition system can generate a wide range of power and oxidizer-to-fuel ratios. It has a self-cooled vortex combustion chamber with one fuel jet injector and one circumferential vortex oxidizer injector. The system adjusts the mass flow rates of the propellants through the control valves and organizes cooling of the wall and flame stabilization. Experimental analysis of the ignition limits was investigated on the laboratory test bench. The propellants’ pressure and mass-flow rates, combustion temperature, ignition delay, and spark frequency were controlled during the tests. The authors executed a series of tests with different propellants’ mass flow rates. As a result, the region of stable ignition was found as well as the regions of ignition failure or unreliable ignition. A previously validated numerical model was used to analyze the flow in the reliable ignition region and the ignition failures region. Several numerical simulations of the transient three-dimensional chemically reacting flow were implemented. Consequently, the ignition delay and the thermal impact on the combustion chamber wall were determined numerically. Results of the simulations were compared with theoretical and experimental data showing good correspondence. Full article

(This article belongs to the Special Issue Combustion and Propulsion Systems)

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14 pages, 3236 KiB

Open AccessArticle

Experimental Investigation of Multiple Fry Waste Soya Bean Oil in an Agricultural CI Engine

by Adhirath Mandal, HaengMuk Cho and Bhupendra Singh Chauhan

Energies 2022, 15(9), 3209; https://doi.org/10.3390/en15093209 - 27 Apr 2022

Cited by 11 | Viewed by 1816

Abstract

Meeting the growing energy demand for sustainability and environmental friendly fuels is a continuous process. Several oxygenated fuels were tried and tested according to the availability depending upon the geographical locations to find a solution against rapidly depleting fossil fuels (gasoline and diesel). [...] Read more.

Meeting the growing energy demand for sustainability and environmental friendly fuels is a continuous process. Several oxygenated fuels were tried and tested according to the availability depending upon the geographical locations to find a solution against rapidly depleting fossil fuels (gasoline and diesel). In the present investigation, the viability of waste fry cooking oil converted into biodiesel fuel and its various physiocochemical properties was evaluated. In this regard, the performance and emission of a CI engine was compared using biodiesel fuel and mineral diesel fuel. Experimental research was performed on a single-cylinder agricultural CI engine with indirect injection, and biodiesel fuel was used with three different types of fry oils. The fry oil was classified as one-time fry, two-time fry, and three-time fry. Engine efficiency and tail pipe emission attributes were evaluated for the three different fuels. The different fuel blends used for the experiment were B60 and B80 and were tested at full load, at different engine speed (rpm). It was found that brake specific fuel consumption (BSFC) increased with increasing speed, whereas brake thermal efficiency reduced with increasing engine speed. Brake thermal efficiency (BTE) reduces with increase in the engine speed because of a poor air–fuel ratio at high speed. CO₂ emission is higher because of the higher density and heating value of the biodiesel fuel, which depends on the blending ratio and the frying time of the fuel. It was also encountered that NO_x emission was higher for maximum test fuels except one-time fry waste cooking oil biodiesel at 60% blend, which showed lower NO_x than diesel fuel. Smoke opacity in both the blends have a decreasing trend with increasing speed and are lower than pure diesel. The 1FWCOB (fry waste cooking oil biodiesel), 2FWCOB, and 3FWCOB fuel exhaust gas temperature (EGT) is reduced because of higher cetane number and lower heating value. Based on the result obtained, it was concluded that by increasing the frying time of the soya bean waste cooking biodiesel, the emission characteristics and engine performance were affected. The need for sustainable fuel is important, thus the use of waste fry cooking oil is a potential replacement for diesel. Full article

(This article belongs to the Special Issue Combustion and Propulsion Systems)

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35 pages, 8722 KiB

Open AccessFeature PaperArticle

Sensitivity Analysis of a Two-Phase CFD Simulation of a 1 kN Paraffin-Fueled Hybrid Rocket Motor

by Benoit Dequick, Michel Lefebvre and Patrick Hendrick

Energies 2021, 14(20), 6794; https://doi.org/10.3390/en14206794 - 18 Oct 2021

Cited by 3 | Viewed by 4217

Abstract

At Université Libre de Bruxelles (ULB), research was performed on a 1 kN lab-scale Hybrid Rocket Motor (the ULB-HRM). It has a single-port solid paraffin fuel grain and uses liquid

N_{2} O

as an oxidizer. The first Computational Fluid Dynamics (CFD) model [...] Read more.

At Université Libre de Bruxelles (ULB), research was performed on a 1 kN lab-scale Hybrid Rocket Motor (the ULB-HRM). It has a single-port solid paraffin fuel grain and uses liquid

N_{2} O

as an oxidizer. The first Computational Fluid Dynamics (CFD) model of the motor was developed in 2020 and improved in 2021, using ANSYS Fluent software. It is a 2D axisymmetric, two-phase steady-state Reynolds-Averaged Navier–Stokes (RANS) model, which uses the average fuel and oxidizer mass flow rates as inputs. It includes oxidizer spray droplets and entrained fuel droplets, therefore adding many additional parameters compared to a single-phase model. It must be investigated how they affect the predicted operating conditions. In this article, a sensitivity analysis is performed to determine the model’s robustness. It is demonstrated that the CFD model performs well within the boundaries of its purpose, with average deviations between predicted and experimental values of about

1 %

for the chamber pressure and

5 %

for the thrust. From the sensitivity analysis, multiple observations and conclusions are made. An important observation is that oxidizer related parameters have the highest potential impact, introducing deviations of the predicted operating chamber pressure of up to 18%, while this is only about

6 %

for fuel-related parameters. In general, the baseline CFD model of the ULB-HRM seems quite insensitive and it does not suffer from an excessive or abnormal sensitivity to any of the major parameters. Furthermore, the predicted operating conditions seem to respond in a logical and coherent way to changing input parameters. The model therefore seems sufficiently reliable to be used for future qualitative and quantitative predictions of the performance of the ULB-HRM. Full article

(This article belongs to the Special Issue Combustion and Propulsion Systems)

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23 pages, 4062 KiB

Open AccessArticle

A Combustion Regime-Based Model for Large Eddy Simulation

by Eugenio Giacomazzi and Donato Cecere

Energies 2021, 14(16), 4934; https://doi.org/10.3390/en14164934 - 12 Aug 2021

Cited by 7 | Viewed by 2173

Abstract

The aim of this work is to propose a unified (generalized) closure of the chemical source term in the context of Large Eddy Simulation able to cover all the regimes of turbulent premixed combustion. Turbulence/combustion scale interaction is firstly analyzed: a new perspective [...] Read more.

The aim of this work is to propose a unified (generalized) closure of the chemical source term in the context of Large Eddy Simulation able to cover all the regimes of turbulent premixed combustion. Turbulence/combustion scale interaction is firstly analyzed: a new perspective to look at commonly accepted combustion diagrams is provided based on the evidence that actual turbulent flames can experience locally several combustion regimes although global non-dimensional numbers would locate such flames in a single specific operating point of the standard combustion diagram. The deliverable is a LES subgrid scale model for turbulent premixed flames named Localized Turbulent Scales Model (LTSM). This is founded on the estimation of the local reacting volume fraction of a computational cell that is related to the local turbulent and laminar flame speeds and to the local flame thickness. Full article

(This article belongs to the Special Issue Combustion and Propulsion Systems)

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13 pages, 5455 KiB

Open AccessArticle

The Implication of Injection Locations in an Axisymmetric Cavity-Based Scramjet Combustor

by Naresh Relangi, Antonella Ingenito and Suppandipillai Jeyakumar

Energies 2021, 14(9), 2626; https://doi.org/10.3390/en14092626 - 4 May 2021

Cited by 17 | Viewed by 3110

Abstract

This paper presents the effect of cavity-based injection in an axisymmetric supersonic combustor using numerical investigation. An axisymmetric cavity-based angled and transverse injections in a circular scramjet combustor are studied. A three-dimensional Reynolds-averaged Navier–Stokes (RANS) equation along with the k-ω shear-stress transport (SST) [...] Read more.

This paper presents the effect of cavity-based injection in an axisymmetric supersonic combustor using numerical investigation. An axisymmetric cavity-based angled and transverse injections in a circular scramjet combustor are studied. A three-dimensional Reynolds-averaged Navier–Stokes (RANS) equation along with the k-ω shear-stress transport (SST) turbulence model and species transport equations are considered for the reacting flow studies. The numerical results of the non-reacting flow studies are validated with the available experimental data and are in good agreement with it. The performance of the injection system is analyzed based on the parameters like wall pressures, combustion efficiency, and total pressure loss of the scramjet combustor. The transverse injection upstream of the cavity and at the bottom wall of the cavity in a supersonic flow field creates a strong shock train in the cavity region that enhances complete combustion of hydrogen-air in the cavity region compared to the cavity fore wall injection schemes. Eventually, the shock train in the flow field enhances the total pressure loss across the combustor. However, a marginal variation in the total pressure loss is observed between the injection schemes. Full article

(This article belongs to the Special Issue Combustion and Propulsion Systems)

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20 pages, 6681 KiB

Open AccessArticle

The Combustion Characteristics of Double Ramps in a Strut-Based Scramjet Combustor

by A. Antony Athithan, S. Jeyakumar, Norbert Sczygiol, Mariusz Urbanski and A. Hariharasudan

Energies 2021, 14(4), 831; https://doi.org/10.3390/en14040831 - 5 Feb 2021

Cited by 20 | Viewed by 3323

Abstract

This paper focuses on the influence of ramp locations upstream of a strut-based scramjet combustor under reacting flow conditions that are numerically investigated. In contrast, a computational study is adopted using Reynolds Averaged Navier Stokes (RANS) equations with the Shear Stress Transport (SST) [...] Read more.

This paper focuses on the influence of ramp locations upstream of a strut-based scramjet combustor under reacting flow conditions that are numerically investigated. In contrast, a computational study is adopted using Reynolds Averaged Navier Stokes (RANS) equations with the Shear Stress Transport (SST) k-ω turbulence model. The numerical results of the Deutsches Zentrum für Luft- und Raumfahrt or German Aerospace Centre (DLR) scramjet model are validated with the reported experimental values that show compliance within the range, indicating that the adopted simulation method can be extended for other investigations as well. The performance of the ramps in the strut-based scramjet combustor is analyzed based on parameters such as wall pressures, combustion efficiency and total pressure loss at various axial locations of the combustor. From the numerical shadowgraph, more shock interactions are observed upstream of the strut injection region for the ramp cases, which decelerates the flow downstream, and additional shock reflections with less intensity are also noticed when compared with the DLR scramjet model. The shock reflection due to the ramps enhances the hydrogen distribution in the spatial direction. The ignition delay is noticed for ramp combustors due to the deceleration of flow compared to the baseline strut only scramjet combustor. However, a higher flame temperature is observed with the ramp combustor. Because more shock interactions arise from the ramps, a marginal increase in the total pressure loss is observed for ramp combustors when compared to the baseline model. Full article

(This article belongs to the Special Issue Combustion and Propulsion Systems)

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Review

Jump to: Research

35 pages, 1652 KiB

Open AccessReview

Review on the Effect of the Phenomenon of Cavitation in Combustion Efficiency and the Role of Biofuels as a Solution against Cavitation

by Ludovic Lamoot, Brady Manescau, Khaled Chetehouna and Nicolas Gascoin

Energies 2021, 14(21), 7265; https://doi.org/10.3390/en14217265 - 3 Nov 2021

Cited by 3 | Viewed by 2444

Abstract

Concerning the problem of wanting the performance of heat engines used in the automotive, aeronautics, and aerospace industries, researchers and engineers are working on various possibilities for improving combustion efficiency, including the reduction of gases such as CO, NOx, and SOx. Such improvements [...] Read more.

Concerning the problem of wanting the performance of heat engines used in the automotive, aeronautics, and aerospace industries, researchers and engineers are working on various possibilities for improving combustion efficiency, including the reduction of gases such as CO, NOx, and SOx. Such improvements would also help reduce greenhouse gases. For this, research and development has focused on one factor that has a significant impact on the performance of these engines: the phenomenon of cavitation. In fact, most high-performance heat engines are fitted with a high-speed fuel supply system. These high speeds lead to the formation of the phenomenon of cavitation generating instabilities in the flow and subsequently causing disturbances in the combustion process and in the efficiency of the engine. In this review article, it is a question of making a state-of-the-art review on the various studies which have dealt with the characterization of the phenomenon of cavitation and addressing the possible means that can be put in place to reduce its effects. The bibliographic study was carried out based on five editors who are very involved in this theme. From the census carried out, it has been shown that there are many works which deal with the means of optimization that must be implemented in order to fight against the phenomenon of cavitation. Among these solutions, there is the optimization of the geometry of the injector in which the fuel flows and there is the type of fuel used. Indeed, it is shown that the use of a biofuel, which, by its higher viscosity, decreases the effects of cavitation. Most of these jobs are performed under cold fluidic conditions; however, there is little or no work that directly addresses the effect of cavitation on the combustion process. Consequently, this review article highlights the importance of carrying out research work, with the objective of characterizing the effect of cavitation on the combustion process and the need to use a biofuel as an inhibitor solution on the cavitation phenomenon and as a means of energy transition. Full article

(This article belongs to the Special Issue Combustion and Propulsion Systems)

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9 pages, 1482 KiB

Open AccessReview

Some Key Issues in Hypersonic Propulsion

by Claudio Bruno and Antonella Ingenito

Energies 2021, 14(12), 3690; https://doi.org/10.3390/en14123690 - 21 Jun 2021

Cited by 6 | Viewed by 2376

Abstract

This paper summarizes and discusses some critical aspects of flying hypersonically. The first is the L/D (lift over drag) ratio determining thrust and that in turn depends on the slenderness Küchemann’s τ parameter. This second parameter is found to depend on the relative [...] Read more.

This paper summarizes and discusses some critical aspects of flying hypersonically. The first is the L/D (lift over drag) ratio determining thrust and that in turn depends on the slenderness Küchemann’s τ parameter. This second parameter is found to depend on the relative importance of wave versus friction drag. Ultimately, all engineering drag is argued to depend on vorticity formed at the expense of the vehicle kinetic energy, thus requiring work by thrust. Different mixing strategies are discussed and shown to depend also on mechanisms forming vorticity when the regime is compressible. Supersonic combustion is briefly analyzed and found, at sufficiently high combustor Mach, to take place locally at constant volume, unlike conventional Brayton cycles. Full article

(This article belongs to the Special Issue Combustion and Propulsion Systems)

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