Chamber Configuration Research Articles

ANALISIS KEKUATAN STRUKTUR SQUARE CHAMBER INJECTION MULTICASTING PYROGENIC IGNITER MENGGUNAKAN FINITE ELEMENT ANALYSIS (FEA)

It is necessary to analyze the structural strength of the square chamber component in the design of injection multicasting pyrogenic igniter to ensure that the structural components of the chamber are able to withstand loads from hydraulic piston pressure. Four square chamber configurations were analyzed using the Autodesk Inventor software FEA method. Load simulations are given at 10,000 N, 50,000 N, and 100,000 N. Von Mises stress, safety factor, and displacement are obtained for each design configuration. Where it is known that the structural design of the square chamber design configurations 1, 2, and 3 has optimal reliability at a load capacity of up to ± 10,000 N. As for the structural design of the square chamber design configuration 4, it is known to have optimal reliability at a load capacity of 50,000 N. However it is possible that it is reliable enough to withstand load capacities up to ± 100,000 N.

Experimental and numerical investigations on NH3/H2 fueled combustion in the combustor with block for improved micro power generation

To advance the application of zero-carbon fuels in micro combustion, enhance energy conversion, and reduce NOx emissions in NH3/H2-fueled micro power generators, a micro-combustor with an inserted block is proposed and tested under various chamber configurations and operational conditions. Experimental and numerical tests are conducted in micro-combustors with varied block settings, burner dimensions, NH3 blended ratios (mN), and fuel flow rates (Vf). The results indicate that mN significantly impacts the generation and consumption of H, O, and OH radicals, as well as NO, affecting flame regime and heat transfer. Specifically, adding 5∼15 % NH3 improves the operating performance of the burner, with the highest mean temperature achieved in combustor #24C3-0.4 at mN = 15 %. Block insertion alters flame characteristics and enhances gas-wall heat transfer, and the combustor with thinner blocks at higher mN and thicker blocks at lower mN contributes to better thermal performance. Furthermore, combustors with thinner blocks exhibit lower NO emissions. The working performance of the micro-thermophotovoltaic system can be enhanced by selecting the appropriate burner length with block thickness W = 0.4 mm and position Lb = 7 mm based on Vf. The maximum electrical power of 3.7 W is achieved with a burner length of 28 mm for the system using InGaAsSb cells at Vf = 1200 mL/min.

Numerical study on hydrogen mixing for different scramjet Engine combustion chamber configurations

Numerical study on hydrogen mixing for different scramjet Engine combustion chamber configurations

Improvement in uniformity of co‐linear pulsed electric field treatment chamber by sub‐electrodes and its optimization

AbstractThe uniformity of performance parameters such as electric field and temperature for a co‐linear pulsed electric field (PEF) processing system is one of main factors affecting the processing effect and quality of liquid food. We have proposed a co‐linear PEF treatment chamber configuration with sub‐electrodes to improve the uniformity and processing efficiency. We have first examined how the position of the sub‐electrodes alone affects the uniformity of the performance parameters. Then, we have investigated the variation of the uniformity while changing simultaneously the electrode radius, inter‐electrode gap, and position of sub‐electrodes. As a result, we have found that the most uniform field could be obtained when the electrode radius is 5.5 mm, the inter‐electrode gap is 15 mm, and the sub‐electrodes situate at the middle of the chamber. In this chamber, the region between 95% and 105% of the average electric field covers 83%, which shows much improvement compared to the formers' results, 69.5% and 76%, respectively. Also, the optimal treatment chamber provides greater average electric field under the same voltages as the voltages reported by the formers.Practical applicationsA novel treatment chamber with sub‐electrodes is proposed for pulsed electric fields food processing. The improved treatment design was obtained by changing position of sub‐electrodes, inner radius of electrodes and distance between electrodes. The more uniform electric field was obtained in treatment region. The temperature distribution was more uniformed by increasing flow rates and uniformed electric field strength. The treatment throughput was increased by sub‐electrodes.

Understanding the role of flux chamber configuration in the measurement of VOC emissions from porous media

The accurate quantification of volatile organic compound (VOC) emission rates from porous media to the air is a challenging problem, as measurements are affected by the chemical and physical characteristics of the porous media, and the operating parameters of the sampling device itself. The main objective of this study is to investigate how flux chamber (the most commonly used sampling device) configurations influence emission rate measurement from three selected porous media. Various parameters were studied, including sweep air flow rate, presence of a mixing fan, headspace volume and thickness of media. Controlled experiments focused on the behaviour of two VOCs commonly found in area sources: acetic acid and 1-butanol. Sweep gas flow rate emerged as the most influential factor, inducing turbulence and dilution over porous media surfaces and impacting emission rate measurements more significantly than headspace volume and fan installation. Variations in porous media properties also affected mass transfer, with emissions from coco coir showing higher mass transfer as its porosity and particle size facilitated gas transportation. While behaviour of acetic acid emission through the media supported the diffusion theory, emission of 1-butanol was affected by a combination of factors, highlighting the role of both diffusive and advective transport mechanisms. Understanding how flux chamber setups and porous media properties influence emission rates is crucial for accurately interpreting data. This knowledge also guides the design of studies, especially when investigating complex sources like biosolids and organic-amended soil.

Analysis of anterior segment in primary angle closure suspect with deep learning models

ObjectiveTo analyze primary angle closure suspect (PACS) patients’ anatomical characteristics of anterior chamber configuration, and to establish artificial intelligence (AI)-aided diagnostic system for PACS screening.MethodsA total of 1668 scans of 839 patients were included in this cross-sectional study. The subjects were divided into two groups: PACS group and normal group. With anterior segment optical coherence tomography scans, the anatomical diversity between two groups was compared, and anterior segment structure features of PACS were extracted. Then, AI-aided diagnostic system was constructed, which based different algorithms such as classification and regression tree (CART), random forest (RF), logistic regression (LR), VGG-16 and Alexnet. Then the diagnostic efficiencies of different algorithms were evaluated, and compared with junior physicians and experienced ophthalmologists.ResultsRF [sensitivity (Se) = 0.84; specificity (Sp) = 0.92; positive predict value (PPV) = 0.82; negative predict value (NPV) = 0.95; area under the curve (AUC) = 0.90] and CART (Se = 0.76, Sp = 0.93, PPV = 0.85, NPV = 0.92, AUC = 0.90) showed better performance than LR (Se = 0.68, Sp = 0.91, PPV = 0.79, NPV = 0.90, AUC = 0.86). In convolutional neural networks (CNN), Alexnet (Se = 0.83, Sp = 0.95, PPV = 0.92, NPV = 0.87, AUC = 0.85) was better than VGG-16 (Se = 0.84, Sp = 0.90, PPV = 0.85, NPV = 0.90, AUC = 0.79). The performance of 2 CNN algorithms was better than 5 junior physicians, and the mean value of diagnostic indicators of 2 CNN algorithm was similar to experienced ophthalmologists.ConclusionPACS patients have distinct anatomical characteristics compared with health controls. AI models for PACS screening are reliable and powerful, equivalent to experienced ophthalmologists.

Detection of hydrogen gas leak using distributed temperature sensor in green hydrogen system

This study addresses the challenges of hydrogen gas detection in pipelines, focusing on the highly flammable nature and low ignition energy of hydrogen. It highlights the limitations of traditional point-based detection methods and emphasizes the need for advanced safety technologies. An integrated approach combining onsite monitoring with Internet of Things (IoT) technology is proposed to enhance systematic safety management and quick leak detection in hydrogen infrastructures. The study reviews various hydrogen detection methods, emphasizing distributed temperature sensing (DTS) techniques to identify leaks through temperature variations. Over nine months of monitoring, the results indicate that DTS temperature variations are more influenced by sensor location than chamber configuration, suggesting that external DTS chamber installation is more effective for leak detection. Additionally, the study integrates Gaussian Process Regression with Machine Learning to predict temperature distribution in pipelines, providing valuable insights for future hydrogen leak detection research.

Malignant glaucoma: disease course and treatment

Diagnosis of malignant glaucoma presents a challenge due to subtle symptoms in early stages of the disease, making increased intraocular pressure a pivotal indicator, often accompanied by inflammation and corneal edema. Diagnostic modalities, including ultrasound biomicroscopy and anterior segment optical coherence tomography, play crucial roles in visualizing anatomical changes in the ciliary body and anterior chamber. The classic slit lamp examination, complemented by tonometry, remains a fundamental diagnostic tool. A stepwise therapeutic approach is essential, beginning with pharmacological interventions aimed at intraocular pressure reduction and subsequent restoration of the anterior chamber configuration. The first stage of treatment is pharmacotherapy. Laser therapies, such as iridotomy and Nd:YAG laser treatment, address angle closure. In resistant cases, a surgical approach, such as irydo-zonulo-hialoidotomy may be considered.

Design and application of bidirectional soft actuator with multiangle chambers

PurposeThis study aims to introduce a novel bidirectional soft actuator as an enhancement to conventional pneumatic network actuators. This improvement involves integrating air chambers positioned at specific angles to improve stability, adaptability and grasping efficiency in various environments.Design/methodology/approachThe design approach incorporates air chambers positioned at a 45° angle relative to the horizontal direction at the actuator's terminus, along with additional chambers at a 90° angle. Mathematical models are developed for longitudinal and transverse bending, as well as for obliquely connected cavities, based on the assumption of piecewise constant curvature. Analyses are conducted on output forces, bending characteristics and end contact areas for both transverse and longitudinal ends.FindingsThe proposed soft actuator surpasses traditional pneumatic network actuators in gripping area due to the inclusion of a diagonal air cavity and a transverse pneumatic network structure at the terminus. As a result, it provides torsion and gripping force in both directions. Testing on a dedicated platform with two variants of grippers demonstrates superior gripping force capability and performance in complex environments.Practical implicationsThrough the design of multiangle chambers, the soft actuator exhibits diverse driving angles and morphological variations, offering innovative design perspectives for industrial grasping.Social implicationsThe design of multiangle chambers facilitates personalized configurations of soft actuators by researchers, enabling tailored angles for specific interaction environments to achieve desired functionalities. This approach offers novel insights into soft actuator design, addressing more prevalent industrial grasping challenges.Originality/valueThis study introduces a novel soft actuator design that significantly enhances gripping capabilities in comparison to conventional pneumatic network actuators. The incorporation of specific air chamber configurations and mathematical modeling provides valuable insights for the development of adaptable and efficient robotic grippers for industrial and household applications.

Combustion behavior of NMP-001, a nitromethane-based green rocket propellant

Hydrazine’s carcinogenic and toxic nature makes its use in space propulsion expensive and necessitates careful launch campaign planning, which may cause delays. One already established alternative is to use energetic salt-based ionic solution propellants. However, the costs remain high because these salts are costly and highly regulated energetic materials. Additionally, propellants based on these energetic salts produce much higher temperatures during decomposition and combustion, as is the case for hydrazine. Consequently, expensive refractory metal-based alloys and high-temperature oxidation-resistant catalytic reactors must be used, which further drives up the costs. Alternatively, hydrogen peroxide may be used, though only in applications with a low specific impulse requirement. This study explores an alternative approach: using nitromethane, a commonly available laboratory solvent. NMP-001 is a nitromethane-based monopropellant that contains additives that allow for low-pressure combustion and reduce sensitivity to mechanical stimuli. Multiple combustion chamber configurations with varying characteristic lengths were tested in rocket combustion experiments. With the 11.5 m L∗-configuration, a 15.1 bar low-pressure limit could be determined. The 7.3 and 5.0 m L∗-configurations yielded a 16.2 and 28.3 bar low-pressure combustion limits, respectively. These outcomes are significantly below the 30 bar limit reported in the literature. Despite using only a simple heat-sink combustion chamber with a non-sophisticated injector element and a non-optimized propellant formulation, combustion was 83 to 95 % efficient with a C* ranged between 1133 to 1302 m/s. These figures are higher than for hydrogen peroxide and are comparable to the theoretical performance of state-of-the-art green liquid monopropellants.

Heat recovery of multistage circulated permeate gap membrane distillation for energy-efficient water production

Addressing the challenges of energy efficiency in the desalination industry, this study proposed an energy-efficient water desalination system, focusing on the novel innovative approach of gap water circulation in permeate gap membrane distillation (PGMD) systems. A counterflow multistage is considered and analyzed using combined heat-mass transfer modeling. In comparison to conventional PGMD configurations, the introduction of gap water circulation has visibly emerged to increase water productivity while decreasing energy consumption. This research systematically explored the impact of this innovation, employing a comprehensive methodology that includes modifying flow chamber configurations and analyzing operational parameters. The study was performed at different seawater intake flow rates, intake temperature, feed injection temperature, and different number of stages. It was found that increasing the number of stages in the counterflow configuration presented better energy efficiency and higher feed recovery ratios at different conditions. A remarkable reduction in Specific Thermal Energy Consumption (STEC) to 92 kWh/m3, coupled with a notable increase in flux values reaching 28 kg/m2.hr for the alternative modules due to the intensified turbulence and mixing. The study demonstrated the potential of gap water circulation in significantly enhancing the energy efficiency and productivity of MD systems compared to conventional PGMD systems.

The diffraction and re-initiation characteristics of gaseous detonations with an irregular cellular structure

Two-dimensional numerical simulations were performed in this study to look at the diffraction and subsequent evolution of an irregular structure detonation in a stoichiometric hydrogen-air mixture, propagating from a small-width pre-detonator (width d) into a larger-width testing channel (width D). By varying the ratio D/d from 1.1 to 5.5, three kinds of propagation modes and the corresponding dynamics of the irregular structure detonation waves are elucidated. The numerical results show that, for an irregular structure detonation wave, the D/d range from 1.0 to 1.1 corresponds to the supercritical mode, the critical mode for D/d ranging from 1.2 to 5.0, and a D/d larger than 5.0 results in the subcritical mode. Compared to the equivalent numerical study for regular structure detonations, the critical width ratios for the supercritical mode and the critical mode are found different for irregular structure detonation. Detonation waves with an irregular structure are more likely to change from the supercritical mode to the critical mode. In the critical mode, the re-initiation process of an irregular structure detonation could originate in two ways, i.e., the Mach reflection of the diffracting lead shock LS to form the main triple point TP1 or self-sustained triple points (the TP2∼TP4) from the diffracting cellular detonation front. On the other hand, the re-initiation process of a regular structure detonation could result solely from the Mach reflection of the LS to form the TP1. By defining the distance between the backward-facing step and the explosion bubble HS formed by the collision of the new triple points as the characteristic distance L (mm), it is shown that the irregular structure detonation requires a longer characteristic distance L than the regular structure detonation to generate the HS at the centerline. The findings of this study offer potential avenues for optimizing pre-detonator and combustion chamber configurations in detonation engines.

Maximizing power generation in single-chamber microbial fuel cells: the role of LiTa0.5Nb0.5O3/g-C3N4 photocatalyst

Microbial fuel cells (MFCs) have attracted a great deal of attention as a promising technology for recovering electricity from organic substances by harnessing the metabolic activities of microorganisms. The objective of this study is to assess the efficacy of a LiTa0.5Nb0.5O3/g-C3N4 (LTN/g-C3N4) heterojunction as a photocathode catalyst within a single-chamber microbial fuel cell operating under both light irradiation and dark conditions. X-Ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and Energy dispersive X-Ray spectroscopy (EDS) were used to conduct a comprehensive analysis of the composite catalyst, revealing its exceptional purity and unique properties. After 120 h of exposure to visible light, the maximal power density of the MFC containing LTN/g-C3N4-modified carbon cloth was determined to be 667.7 mW/m3. The power density achieved with the presence of light was approximately three times greater than the power density obtained without light in the MFC (235.64 mW/m3). In addition, the study determined that the removal efficiencies of chemical oxygen demand (COD) were 88.4% and 66.5% when exposed to light and in the absence of light, respectively. These findings highlight the potential of the non-precious LTN/g-C3N4 photocatalyst as a viable alternative for effective wastewater treatment and power generation in microbial fuel cells with a single chamber configuration.

Enhancing wave energy harvesting: Performance analysis of a dual chamber oscillating water column

This study investigates the hydrodynamic characteristics of a dual chamber oscillating water column (OWC) setup through a series of experiments, aiming to assess its potential for harvesting wave energy. The investigation involves varying frontwall drafts, power take-off (PTO) dampings, and incident wave conditions, while quantitatively evaluating the OWC system's performance using the capture width ratio (CWR) as the key metric. The findings indicate that the dual chamber configuration consistently exhibits enhanced performance for all combinations of orifice ratios, opening heights, and incident wave frequencies studied. As expected, increasing the opening height of the second chamber leads to improved performance of the OWC. Interestingly, the effect of varying applied PTO damping on improvement of CWR values is found to be relatively insensitive. The most significant improvements in CWR are observed for larger incident wave frequency values. For instance, for dimensionless wave frequency (Kh) values of 1.43 and 1.68, the CWR increases from 0.47 and 0.26 to 0.72 and 0.52, respectively, with the orifice ratio combination of τ1, 0.015, and τ2, 0.018. It is worth noting that the single chamber OWC operates most efficiently within the resonant frequency range of 0.94–1.23, while the dual chamber design extends this frequency range, enabling efficient wave energy capture over a wider spectrum of wave conditions. The dual chamber configuration offers considerable advantages for wave energy conversion applications by increasing the effective frequency bandwidth for optimal energy capture. The research findings suggest that this innovative design has the potential to significantly enhance the efficiency and adaptability of wave energy converters, contributing to the advancement of sustainable and renewable energy technologies.

Determination of Tissue Phantom Ratios of High Energy Photon Beams Using Monte Carlo Code

Monte Carlo codes are veritable tools in radiotherapy to understand the transport mechanism, dose distributions, and energy depositions of ionizing radiations traversing in different media. In some beam calibration protocols, a tissue-phantom-ratio at depths 20 cm and 10 cm (TPR20,10) in a phantom is used to determine the beam-quality conversion factor for different ion chambers. Thus, this study aims to evaluate the efficiency of Monte Carlo code in the determination of beam quality of high radiation energy beams similar to what is expected in clinical settings. Electron Gamma Shower National Research Council in Canada (EGSnrc) Monte Carlo Code was used to design complex ion chamber geometries according to the manufacturer’s specifications. Phase space files were used as x-ray beam radiation sources. Two set-ups (SAD and SSD) methods were used for the determination of TPR20,10 to conform to the accepted clinical procedures. Beam collimation was 10 cm by 10 cm field size with an ionization chamber placed at 20 cm and 10 cm in the water phantom to obtain doses at two points respectively. The TPR20,10 of each energy was obtained using the appropriate equations. The obtained results showed no significant difference between the measured and available TPR 20,10 data (p = 0.995). Ion chamber configurations and specifications were also found not to have a significant effect (p = 0.33) on the TPR 20,10 obtained values. The results obtained in this study are in agreement with the recommended standard values. The findings of this study show that the Monte Carlo codes can be used as a tool in determining x-ray beam quality indices of designed clinical linear accelerator (Linac) machines.

Research on the Performance of Biodiesel using Diesel Engines with Different Combustion Chamber Shapes

The performance dynamics of diesel engines powered by biodiesel are examined in this study, with a focus on the impact of various combustion chamber configurations. Understanding how diverse combustion chamber designs impact engine performance, emissions profiles, and combustion efficiency under varied operating situations is the main goal. The study used a 25% blend of Corn Oil Methyl Ester (COME25) biodiesel to test two types of engines: a Toroidal Cavity Piston (TCP) engine and a regular Hemispherical Cavity Piston (HCP) engine. When compared to the COME25 HCP engine, the TCP engine exhibits a notable 2.14% gain in Brake Thermal Efficiency (BTE) at maximum power. This improvement is attributable to the TCP engine's capacity to produce more cylinder swirl and turbulence, which leads to more effective combustion. This efficiency improvement comes with trade-offs, too, since full-power operation results in a simultaneous 28% reduction in Carbon Monoxide (CO) and a 25% reduction in Hydrocarbon (HC) emissions, but a 14% rise in nitrous oxide (NOx) emissions. These results demonstrate the intricate relationship between emissions control and combustion chamber shape. Along with the TCP engine and COME25 blend, the study also examines changes in Compression Ratio (CR). It finds that optimising both CR and combustion chamber geometry can result in a 9.6% decrease in Brake-Specific Fuel Consumption (BSFC) and a 2.31% rise in BTE. This illustrates the possible advantages of optimising engine settings to increase performance. The study offers insightful information for optimising diesel engines using biodiesel mixes, presenting a viable path for raising combustion efficiency and lowering emissions.

Development of a heat-penetration criterion to characterize steam chamber growth and propagation dynamics during a steam-assisted gravity drainage (SAGD) process

Steam chamber growth and propagation dynamics dictates the success of a steam-assisted gravity drainage (SAGD) process, which is an enhanced oil recovery (EOR) method for effectively and efficiently exploiting the enormous heavy oil and bitumen reserves. To set the baseline, this work is focused on the SAGD process with pure steam. After numerous trials and errors, a heat-penetration criterion has been developed and integrated into a reservoir simulator for the first time to characterize steam chamber growth and propagation dynamics conditioned to the production profiles during a steam-assisted gravity drainage process. More specifically, based on the heat transfer principle, a pore-scale heat-penetration criterion has been developed with respect to both heat conduction and convection for calibrating the temperature distributions ahead of the steam chamber interface (SCI). Subsequently, such a heat-penetration criterion has been upscaled to a grid-scale for its integration with a commercial reservoir simulator (i.e., CMG STARS), allowing us to pragmatically and accurately quantify the dynamic temperature field during a steam-assisted gravity drainage process. Furthermore, three sets of multiphase relative permeabilities are employed to evaluate comprehensive impacts of the thermally sensitive co/counter-current flows. Finally, such a heat-penetration criterion has been verified by reproducing the experimentally measured steam chamber during a steam-assisted gravity drainage process from a large-scale 3D physical model. With such an integrated method, good agreements between the measured and simulated data including production profiles and temperature distributions have been found, whereas the dynamics of production profiles and corresponding steam chamber propagations cannot be well reproduced solely with a commercial reservoir simulator. Sensitivity analysis has been performed to examine the effects of thermal-sensitive properties, steam chamber configuration, boundary, multiphase flow behaviour (e.g., co-current and counter-current flow), and gridblock dimension. In practice, the newly developed heat-penetration criterion can be seamlessly integrated with a commercial reservoir simulator. Such an integrated method can significantly reduce the model complexities and uncertainties, providing a simple and convenient way to dynamically and accurately characterize the steam chamber growth and propagation dynamics within a unified, consistent, and efficient framework.

Characteristics of cellular structure of detonation waves propagating in annular channels

This study investigates the characteristics of stable and unstable cells and wavefronts of detonation waves propagating in annular channels with different inner radii and channel widths using two-dimensional Euler equations along with a two-step induction-exothermic reaction kinetics. The results reveal that the effect of annular channels on the detonation cell structure depends on both the inner radius and channel width. To quantify this effect, a parameter σ is introduced, representing the ratio of the inner and outer radii of the channel. We have discovered that for values of the parameter σ exceeding a critical value σs, the detonation wavefront demonstrates characteristics similar to those observed in a straight channel scenario. On the contrary, when σ is below σs, the wavefront becomes distorted, potentially leading to Mach reflection as σ decreases further to another critical value σm. Additionally, the interaction among expansion waves induced by the inner walls leads to an augmented induced length and the potential occurrence of localized decoupling of the detonation wave, particularly for unstable detonation waves. However, it is worth noting that the re-initiation of the detonation wave may be triggered by the formation of hotspots resulting from the interaction between transverse shock waves and the detonation wave. This study aims to characterize the propagation characteristics of detonation waves within annular channels, with the objective of providing valuable insights for the design and optimization of annular chamber configurations in systems involving detonation.

Design and combustion characteristics analysis of a static shaft turbofan engine

Abstract A design scheme of a static shaft turbofan engine is proposed to meet the requirements of light weight and large thrust weight ratio of small aeroengine. As the core component of stable combustion, the thermal protection problem of the mid-mounted combustion chamber is particularly prominent. This paper designs a mid-mounted combustion chamber configuration that combines gas film cooling and central combustion. The influence of structural parameters on combustion characteristics is explored by numerical simulation, and the theoretical design and numerical simulation is verified based on combustion test results. The results show that the flame shape of the mid-mounted combustion chamber conforms to the characteristics of central combustion. The combustion effect of the nozzle with spray angle of 45° and flow rate of 1.87 kg/h meets the requirements of secondary combustion of the static shaft turbofan engine, and the air inlet of the combustion liner effectively increases the thickness of the cooling gas film. The experimental results are in good agreement with the numerical simulation results, and the temperature of the combustion liner wall can be reduced effectively. The above research provides a theoretical basis for the combustion chamber design of small static shaft turbofan engines and a reference for the thermal protection methods of small aeroengine combustion chambers.

Self-excited wave stabilization in a linear detonation combustor

Detonative combustors, such as rotating detonation engines, have increasingly been viewed as next-generation propulsion and power generation systems because they offer higher theoretical thermal efficiencies than conventional constant-pressure combustors. In order for these systems to be realized in a practical context, the impacts of inflow and outlet conditions, reactant mixing, and interactions between counter-propagating waves must be better understood. To examine these phenomena in a simplified geometry, the present work considers a methane-oxygen reflective shuttling detonation combustor with an open-closed chamber configuration. High-fidelity simulations are conducted for two equivalence ratio conditions (lean and rich), and comparisons are made to complementary experiments. The results show that self-sustained steady-state wave behavior consists of minimally-reacting left-running waves and right-running detonation waves. The lean case is found to establish steady-state operation after a shorter time and exhibit detonation waves after a shorter distance from the closed end of the chamber. The simulations are able to predict the experimentally observed trends in the wave velocity in the direction of propagation. Wave-relative averaged flow fields show considerable reactant stratification and parasitic combustion ahead of the waves, likely contributing to their low speeds and pressures relative to ideal detonations. Conditional statistics ahead and behind the waves indicate that peaks in heat release occur at both lean and rich conditions near the open end of the chamber, and incomplete fuel oxidation in the primary detonation waves leads to delayed oxygen consumption and higher temperatures downstream.