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Siphon drainage using inclined borehole and 4 mm inner diameter pipes is an efficient and stable measure for long-term landslide drainage. In order to compare alternative drainage arrangements more efficiently, a numerical method is proposed for siphon drainage process simulation. The novelty of this method is to simulate the dynamic process of siphon drainage by a series of iterative seepage analyses. The whole drainage process is divided into many small time steps and each one corresponds to an independent seepage analysis. The iterative operation is fully automated by reading and rewriting the calculation document with Python code. The siphon flow rate in each analysis is determined by the total head at the siphon pipe inlet obtained from the previous analysis result. An empirical formula based on experimental data is used for flow rate calculation. SEEP3D is adopted to perform the three-dimensional seepage analysis. BUILD3D along with computer-aided design software is used to build the three-dimensional model with a realistic topographic surface. The proposed method is illustrated and validated with a case, the Shaqiucun landslide, China. A parameter study is carried out and the influence of parameter setting on the drainage effect is discussed.

Experimental investigation has been performed to study the leakage and wear characteristics of carbon seal working at high circumferential speed. To expand the scope of application, two newly designed carbon seals were compared: #1 Carbon Seal (CS1) with the inner diameter of 136 mm and including 4 segments, #2 Carbon Seal (CS2) with the inner diameter of 212 mm and including 6 segments. Air leakage tests were firstly conducted in the Medium-speed Seal Test Rig. The pressure ratio changed from 1.04 to 2.02 with the rotating speed varying from 0 to 18300 r/min. Of paramount concern was the durability test, including 300 h running time accumulated by three different working conditions, which was separately implemented on each carbon seal. The morphology variation of the friction surface, wear and leakage were recorded. Results indicated that the leakage monotonously increases with the pressure ratio and decreases with the rotating speed. Comparing with CS1, more typical features exist on the friction surface of CS2, which are generated by more severe wear. Continually, leakage characteristics deteriorate. Furthermore, fitted formula has been educed for the life prediction of carbon seal, which could provide some supports for aero-engine design.

Based on the theory of elastic fracture and using direct modeling method, a numerical model was developed for solving the composite stress intensity factor of semi-elliptical cracks on exchanger outer walls with inclined angles. The model exchanger had an outer diameter of φ50 mm, inner diameter of φ44 mm and length of 300 mm. The values of crack plane inclination β (0°, 10°, 20°, 30°, 40° and 45°), crack depth a (0.5 mm, 0.75 mm, 1 mm and 1.25 mm), and crack shape ratio a/b (0.4, 0.5, 0.55, 0.6, 0.7, 0.8, 0.9 and 1.0) were obtained and 3D surface crack model was established. The results were significance for the evaluation of the remaining life of exchanger components.

This study investigated changes in the retentive force of telescopic crowns fabricated by combining a zirconia primary crown and a fiber-reinforced composite (FRC) secondary crown.Primary zirconia crowns were produced with a nominal convergence angle of 0°. Forty-eight secondary crowns were milled from FRC and divided into three study groups (n=16/group) based on milling parameters and post-milling adjustment. The offset parameter used for the final milling step of the inner crown surface was adjusted for a tight initial fit in Group 1 (milling offset: +10 µm, i.e., 2 × 10 µm = 20 µm lower inner diameter compared with the CAD file of the crown) and for improved initial fit (milling offset: -10 µm, i.e., an enlargement of the inner crown diameter by 2 × 20 µm = 40 µm in relation to Group 1) in Groups 2 and 3. The inner surfaces of the secondary crowns were polished with diamond paste in Groups 1 and 2, and silicon points were used for Group 3. The retentive force was measured using a universal testing device. The secondary crown was placed on the primary crown, with the final fitting force set to a load of 100 N. This test was conducted before and after aging (10,000 insertion/removal cycles) under dry and wet conditions. A generalized linear model was used to estimate the differences in the retentive force to elucidate the effects of the milling parameters and polishing methods.We realized an initial retentive force of approximately 10 N. In Groups 2 and 3, the difference was statistically significant between the dry and wet conditions before aging (P0.05). There was no significant difference between the dry and wet conditions after aging in any of the groups (P0.05).An adequate initial retentive force can be achieved with telescopic crowns combining zirconia and FRC.

This paper presents a physical model for monolithic self-rolled-up microtube interdigital capacitors and elaborates their working mechanisms in comparison to on-chip planar interdigital capacitors. Besides the high-frequency phenomena such as the skin effect in thin, wide metal films, the model accounts for the complexities resulting from all possible 3D electrode configurations, such as the inner diameter dependent overlapping capacitances and edge capacitances between electrodes, as well as parasitic inductances within the rolled-up structure between the fingers, for integer and non-integer number of turns. The model is validated by the measured results of fabricated self-rolled-up membrane (S-RuM) interdigital capacitors over a wide range of layout and process parameters. This fully enables the structural design optimization for electrical performance of this 3D device architecture.

The trans-cell approach using a low-profile visualized intraluminal support (LVIS) device is sometimes used for aneurysm coil embolization. However, factors related to microcatheter passage remain uninvestigated. We aimed to examine in-vitro factors related to microcatheter passage using the trans-cell approach with an LVIS.Silicone vessel models (inner diameter, 4 mm) were created with different bend segments and a 4-mm hole assuming an aneurysm neck on the side of the greater curvature. The LVIS Blue (4.5 × 32 mm) was deployed at the bend segment, and passability on the trans-cell surface was evaluated by passing the microcatheter along the micro guidewire. A total of 800 passage experiments were performed using two types of microcatheter, ten types of silicone vessel, four cell widths, five cells with the same LVIS device, and two micro guidewire directions in the aneurysm.The Headway Duo microcatheter (35.5%, 142/400) tended to have better passability compared with the Headway 17 microcatheter (29.3%, 117/400) (p = 0.070). As the cell width and angle between the trans-cell surface and microcatheter direction increased, passability significantly increased (p = 0.027 and p 0.001, respectively). There was no significant difference in passability when the micro guidewire was directed to the proximal side versus the distal side (p = 0.45).A large cell width and an obtuse angle between the trans-cell surface and microcatheter direction facilitated good passability. Although statistically marginal, microcatheters with small ledges and small tips had relatively good passability.

Thermal stress failure is the bottleneck that is restricting the development of ultra-high temperature sensors, and reliable packaging is crucial in their development process. In this paper, a two-step packaging structure was proposed for the high temperature resistant failure packaging challenges of the ultra-high temperature Fabry–Perot optical fibre vibration sensor. First, a high temperature resistant AlN base was selected according to thermal simulation. A reliable bond between the AlN base and the 6H-SiC vibration-sensitive element was designed, which could effectively avoid the failure of thermomechanical stress adaptation during drastic temperature change. In addition, a high temperature resistant ZrO2 support tube with a length of 20 cm, an outer diameter of 16 mm, and an inner diameter of 12 mm was designed as the optical fibre lead-out support structure by using finite element simulation and optimisation. Moreover, the influence of fastening fixtures on the sensor mode was analysed. The simulated first-order resonance frequency of the sensor was 2644.9 Hz, while the actual measurement was 2620 Hz. The difference was only 0.9%. Finally, the validity of the design was verified by experiments, and the sensor achieved reliable operation at 1200 °C.

Sex-dependent radiation injury may be related to the differences in physiological characteristics between the sexes. This study aimed to better understand variations in airway dimensions among male and female Chinese non-smokers. This study included 970 adults and 45 children who underwent chest CT. All participants were non-smokers, without current or former chronic pulmonary disease, and all underwent CT examination. The CT images were quantitatively assessed, providing airway dimensions. The differences in inner diameter, wall thickness, wall area (WA), and WA% for each airway were compared between male and female patients. Sex is an important influencing factor in airway morphological parameters. These parameters are different between men and women: men have a larger airway diameter (P < 0.05) and smaller wall area (WA%, P < 0.05) compared with women. Younger women (

REBCO coil is a promising technology for superconducting magnetic energy storage system (SMES). Although degradation has been discovered in epoxy impregnated coil, it is essential to fill the coil with epoxy in such occasion. This paper describes preparation of large scale epoxy impregnated REBCO coil for SMES. The coil with inner diameter 320 mm and 268 turns was tested at 77 K both before and after epoxy impregnation. Consistency of Ic value and high n-value suggest that there was no degradation in the coil. Conduction cooled test was also carried out. Transport current was run up to 223 A at 50 K.

Purpose The use of self-tapping cortical screws is indicated in patients with metacarpal and phalangeal fractures requiring formal stabilization. The aim of this study was to systematically compare and evaluate the design parameters of 4 commercially available self-tapping screw systems. Methods We measured various design parameters of self-tapping cortical screws of different lengths from several manufactures using scanning electron microscopy. Screws were obtained in 8, 12, 16, and 20 mm lengths. The measured parameters included screw length, head height, pitch, outer diameter, inner diameter, terminal thread diameter, terminal thread-to-tip distance, thread-to-tip distance of 1 full revolution, and crest width. Data were assessed statistically using 1- and 2-way analysis of variance (ANOVA) tests, and the significance level was set at a P value Results There was variability in advertised screw lengths compared with measured screw lengths with 2 manufacturers. There was a statistically significant difference between the thread-to-tip distance and head height between screws while controlling for diameter. Conclusions Screw sizes and dimensions are critical in order to avoid complications such as prominent hardware and postoperative stiffness. Knowledge of the design parameters presented for each of the different manufacturers may prove useful to hand surgeons when selecting screws for fixation of metacarpal and phalangeal fractures. Clinical relevance Specific design characteristics of commonly used screws in hand surgery vary slightly by manufacturer and may have clinically relevant implications in fixation of metacarpal and phalangeal fractures.

Hollow-walled lattices are novel cellular materials with lower densities than conventional dense-walled lattices. However, their manufacturability by laser powder bed fusion (LPBF) is not yet established. This study investigates the LPBF manufacturability of Ti-6Al-4V hollow-walled struts with respect to strut outer diameter, wall thickness (controlled by laser scan path), and inclination angle, while the strut length is purposely limited to 10–15 mm, typical of lattice unit dimensions. The manufacturability was reliable for outer diameters exceeding 0.5 mm and wall thicknesses exceeding 0.24 mm over the inclines of 22.5°–90°. To ensure a manufacturable hollow cylindrical channel by LPBF, we recommend a minimum inner diameter of 4Dv(90) according to the feedstock powder size distribution. The average inconsistency of 5.13% between the designed and manufactured outer diameters was substantially lower than that achievable by conventional manufacturing. The findings of this study provide necessary guidance for the future manufacture of hollow-walled lattices by LPBF.

Magnetic resonance navigation (MRN) uses MRI gradients to steer magnetic drug-eluting beads (MDEBs) across vascular bifurcations. We aim to experimentally verify our theoretical forces balance model (gravitational, thrust, friction, buoyant and gradient steering forces) to improve the MRN targeted success rate. A single-bifurcation phantom (3 mm inner diameter) made of poly-vinyl alcohol was connected to a cardiac pump at 0.8 mL/s, 60 beats/minutes with a glycerol solution to reproduce the viscosity of blood. MDEB aggregates (25 ± 6 particles, 200 $$\mu {\text{m}}$$ ) were released into the main branch through a 5F catheter. The phantom was tilted horizontally from − 10° to +25° to evaluate the MRN performance. The gravitational force was equivalent to 71.85 mT/m in a 3T MRI. The gradient duration and amplitude had a power relationship (amplitude=78.717 $${(duration)}^{-0.525}$$ ). It was possible, in 15° elevated vascular branches, to steer 87% of injected aggregates if two MRI gradients are simultaneously activated ( $${G}_{x}$$ = +26.5 mT/m, $${G}_{y}$$ = +18 mT/m for 57% duty cycle), the flow velocity was minimized to 8 cm/s and a residual pulsatile flow to minimize the force of friction. Our experimental model can determine the maximum elevation angle MRN can perform in a single-bifurcation phantom simulating in vivo conditions.

The effect of distributor geometry on bubble characteristics in an air–kerosene system of a pressurized bubble column was evaluated. The experiment was carried out using a cylindrical stainless column with an inner diameter of 0.097 m and a height of 1.8 m under a system pressure up to 3.5 MPa. The gas holdup was calculated under pressure taps from 0.05 m to 0.85 m above the distributor along axial direction of the column. Bubble size was measured with an optical probe installed 0.5 m above the distributor. Perforated plates with four different hole sizes including 0.8 mm (20 each), 1 mm (12 each), 2 mm (3 each), and 3.46 mm (1 each) fixed with the same opening fraction (ϕo = 0.128%) were evaluated. Different opening fractions at 0.223% (21 holes), 0.128% (12 holes), 0.074% (7 holes), and 0.032% (3 holes) were also tested with a constant hole size (1 mm). The effect of the distributor geometry on bubble characteristics was determined with seven different types of perforated plates. The number of microbubbles was increased with decreasing opening fraction of the distributor. Based on dynamic gas disengagement (DGD) analysis, microbubbles were rarely generated in all distributors under conditions of Psys = 0.1 MPa at Ug = 12.3 mm/s. However, a significant number of microbubbles were generated at ϕo = 0.032% despite a low flow rate at Psys = 3.5 MPa. Microbubble ratio varied from 36% to 40% at ϕo = 0.128 %, while this ratio varied from 38% to 73% at ϕo = 0.032%.

It is difficult to perform intestinal anastomosis in low-birth-weight infants because the intestinal diameter is small and the discrepancy in diameter of the proximal and distal intestines is often large, but there has been no optimal-sized training model. Therefore, we developed a new intestinal anastomosis training model that imitated the size of the intestine in low-birth-weight infants, and evaluated its face and construct validity. Two intestinal models were developed with crossMedical, Inc. using a hydrophilic acrylic material (wet model) or a polyurethane soft resin (dry model). The inner diameter of the simulated intestinal tract was 15 mm on the oral end and 6 mm on the anal end. Thirteen pediatric surgeons performed anastomosis and responded to the questionnaire. In the questionnaire, the wet model had significantly higher scores than the dry model in “appearance”, “softness” and “usefulness for training”. In the anastomotic results of the wet model, the anastomosis leak pressure was significantly correlated with the number of intestinal anastomotic experiences in low-birth-weight infants (correlation coefficient = 0.64, P = 0.035). The wet-type intestinal anastomosis model showed good face validity. Its leak pressure had a significant correlation with clinical experience; thus, construct validity was demonstrated.

Microtubules (MTs) are hollow cytoskeletons with typically 15 nm inner diameter, which are crucial for various cellular activities including structural support, transport, and cell division. Becaus...

Introduction: The circle of Willis (CoW), which is located at the base of the brain is the most important anastomosis between the internal carotid and vertebral system. It is the main distributor of blood to the brain. Methods: CT head and CT angiography were performed using standard scan parameters. Only the tests with normal radiological reports and appropriate technical standards were included in the study. Component of circle of Willis: Anterior cerebral artery (ACA), Middle cerebral artery (MCA), Anterior communicating artery (Acom), Posterior Communicating artery (PCom), Basilar artery (BA) and Posterior cerebral artery (PCA) were identified and their internal diameter were measured. Results: Basilar artery was the artery with largest internal diameter with mean diameter of 2.5 ±0.52 mm. Men had significantly larger arterial sizes than women in all of the intracranial arteries examined except right PCom, Left PCom and right MCA. Right ACA had significantly larger internal diameter in

Hybrid rockets present a compromise between solid and liquid rockets. It has a simpler design than liquid rockets and higher performance than solid rockets. It is constructed from an oxidizer tank followed by a solid fuel grain. Therefore, the combustion is controlled. This paper presents an algorithm to construct the design space of the hybrid rocket motor for a single cylindrical port. A simple regression rate formula is used to treat the combustion. The inner diameter of the grain, outer diameter of the grain, and length of the grain are used as parameters to construct the design space and a single design point is chosen. The performance of this design point is presented with the combustion time.

We present pressure drop and HETP data for Sulzer MellapakPlus™ 452.Y packing measured using the C6/C7 system under total reflux at three pressures: 33 kPa, atmospheric pressure and 180 kPa. The data were obtained in a column with an inner diameter of 0.3 m with the bed consisting of 12 elements of packing (total height 2.52 m). The pressure drop data under the loading point were in good agreement with the data predicted by Sulcol software (v3.4.4, vendor provided); in the loading region, the Sulcol data were on the safe side. The maximum stable FG factor for the three pressures were 2.79, 2.41 and 2.17 Pa0.5, respectively. The HETP values for the expected industrial operating load range were almost constant, with mean values of 0.29, 0.28, 0.27 m obtained, respectively. Because the measurements were performed with different compositions of the C6/C7 mixture, recalculation utilizing known HETP dependence on the slope of the equilibrium curve was used to suppress the dependence of the separation efficiency on the composition.

The flow and heat transfer characteristics of gas-liquid Taylor flows in a horizontal tube with 3.12 mm inner diameter were studied numerically with the volume of fluid method. The bubbles are patc...

In this experimental study, permanent magnets with three different sizes (M-1: 32 mm inner diameter, 70 mm outer diameter and 15 mm thick, M-2: 25 mm inner diameter, 60 mm outer diameter and 10 mm thick, M-3: 22 mm inner diameter, 45 mm outer diameter and 9 mm thick) are fully submerged in the single-slope glass solar still. The performance of magnetic solar stills (MSS) with three different sizes at 2 cm depth water to ensure that magnets are fully submerged is compared with conventional solar still (CSS) at the location 17.3850°N, 78.4867°E. Tiwari model is adapted to calculate the heat transfer coefficients (HTC), internal and exergy efficiencies. MSS with M-1, M-2 and M-3 significantly enhanced the convective, radiative, and evaporative heat transfer rate for the 2 cm depth of water. This is due to the desired magnetic treatment of water, which reduces the surface tension and increases the hydrogen bonds. The MSS's total internal HTC, instantaneous efficiencies led CSS by 25.52%, 28.8%, respectively, with M-1. Having various magnetic fields due to different magnets sizes increases MSS's exergetic efficiency by 33.61% with M-1, 33.76% with M-2, and 42.25% with M-3. Cumulative yield output for MSS with M-1, M-2, and M-3 is 21.66%, 17.64%, 15.78% higher than CSS. The use of permanent magnets of different sizes in the MSS is a viable, economical and straight forward technique to enhance productivity.

MicroRNAs are a class of important biomarkers, and the simultaneous detection of multiple miRNAs can provide valuable information about many diseases and biological processes. Amplification-free determination has been developed for the analysis of multiple miRNAs because of its characteristic low cost and high fidelity. Herein, a method for the amplification-free analysis and simultaneous detection of multiple miRNAs based on a so-called pico-HPLC-LIF system is described. In this process, a bare open capillary with an inner diameter of 680 nm is used as a separation column for a sample volume of several hundreds of femtoliters (300 fL), followed by separation and detection. The technique has a zeptomolar limit of detection. The method was applied to detect cellular miRNA from adenocarcinomic human alveolar basal epithelial (A549) cell extracts, and the simultaneous detection of the mir-182, miR-155, and let-7a was achieved. The results showed that the expression of mir-182 and miR-155 was up-regulated and that of let-7a was down-regulated in A549 cells. This method for multiple miRNAs detection is expected to have broad applications in miRNA-based disease diagnosis, prognosis, treatment, and monitoring.

Gravity-driven infiltration into the shallow subsurface via small-diameter wells (SDWs), i.e., wells with an inner diameter smaller than 7.5 cm (3 inches) and no gravel pack) has proven to be a cost-efficient and flexible tool for managed aquifer recharge (MAR), as it provides relatively high recharge rates with minimal construction effort. SDWs have a significantly smaller open filter area than larger diameter wells with gravel pack, making the infiltration of low-quality waters through these wells more at risk clogging. To investigate their susceptibility for biological and physical clogging, 24 physical models with different well setups were evaluated by infiltrating either nutrient-poor but turbid water or nutrient-rich but clear water. The experiments showed that smaller diameters and the lack of a gravel pack increase the well's susceptibility to both kinds of clogging. However, this effect was observed to be much more pronounced for physical than for biological clogging. Our conclusion is that SDWs show severe disadvantages with respect to the infiltration of highly turbid waters in comparison to large diameter wells with a gravel pack. Nevertheless, this disadvantage is much less severe when it comes to the infiltration of clear but nutrient-rich waters (e.g., treated wastewater). Depending on the economic and geological circumstances of a MAR-project, this disadvantage could be outweighed by the significantly lower construction costs of SDWs.

Protein is the most important characteristic component of honey. The types and content of proteins in different kinds of honey are imparity, but those in the same kind of honey are very similar. Capillary zone electrophoresis (CZE) method, used to detect proteins, was developed for authenticating of four mono-floral honeys (n = 45), including medlar honey, chaste honey, jujube honey and locust honey. Electrophoresis conditions including capillary inner diameter (50–70 μm), pH (2.5–9), the concentration of anionic surfactant (0.3–0.5 mmol L−1), injection time (3–7 s) and separation voltage (3–7 KV) were optimized. The results showed that the honey sample was highly stable and the detection limit was 10%, the relative standard deviation of retention time and peak area were lower than 1.40% and 1.76%, respectively. The CZE fingerprints were established on the basis of different protein characteristics in different mono-floral honeys combined with chemometric analysis. All 45 honeys could be correctly identified according to their floral origins. This method does not need to confirm the type of protein, and has the advantages of simple and fast verification of the authenticity of honey.

Three novel glycolipids were synthesized by amide bond formation among a d-gluconolactone, 12-aminododecanoic acids, and a glycine. Self-assembly of the glycolipids in water produced nanotubes, in ...

PURPOSE To compare the retinal vessel diameters of healthy eyes and active central serous chorioretinopathy (CSC) eyes, and to evaluate possible effect of retinal vessel diameter alterations on the pathogenesis of CSC. METHODS This retrospective study included 39 patients with CSC and 34 healthy individuals. Spectralis optical coherence tomography + HRA with an infrared reflectance image were used to evaluate structure of retinal vessels in the circular region around the optic disc. For each eye, vertical inner and outer diameters of the four major arteries and veins were measured using infrared reflectance images, and vessel wall thicknesses were also calculated based on inner and outer diameters. RESULTS The 304 vessels of the 39 active CSC eyes and 266 vessels of the 34 healthy eyes were used in the analyses. The mean venous wall thickness in active CSC eyes was significantly thicker than that in healthy eyes (40.0 ± 4.9 vs. 33.5 ± 4.1 μm, P = 0.001), whereas the mean venous inner diameter in active CSC eyes was significantly narrower (52.5 ± 9.7 vs. 61.3 ± 8.1 μm, P = 0.001). Also, the mean venous outer diameter was wider in CSC eyes, albeit not significantly (131.1 ± 7.0 vs. 128.5 ± 8.4 μm, P = 0.074). CONCLUSION Our results suggest that the alterations of retinal venous diameters may play a potential role in the pathogenesis of CSC in addition to alterations in choroidal thickness.

In this work, we report a novel, mini microplasma-assisted gas-phase synthesis reactor which enables the localized deposition of high quality carbon nanotubes (CNTs). Analogous to conventional gas-phase growth, which utilizes the furnace heating to induce dissociation of the reactant species, formation of the catalyst nanoparticles, and nucleation of the CNTs, our process replaces the furnace with the microplasma as the sole reaction source. In doing so, this reactor takes full advantage of the merits of the microplasma apparatus, specifically atmospheric pressure operation, efficient dissociation of molecular species, and small size to synthesize highly crystalline small diameter single and double-walled CNTs at an estimated growth rate of 1000–6400 μm/s. In addition, being in gas phase and channeled through a 0.8 mm inner diameter ceramic reactor, the grown CNTs could be localized onto a substrate located downstream in the reactor.

Apoferritin (APO) with a diameter of ~12 nm is a naturally occurring protein assembly in living organisms. APO is made of 24 protein subunits that form a nanocage with an inner diameter of ~8 nm. Thus far, the loading of only a few nanoparticles inside the nanocage of APO has been reported. In this study, the mass loading of D-glucuronic acid (GA)-coated ultrasmall gadolinium oxide (Gd2O3) nanoparticles (UGNPs) (GA-UGNPs) (davg = 1.9 nm) inside and outside the nanocage of APO was investigated. The in vitro cytotoxicity and relaxometric properties were investigated. This study indicates that APO is an extremely useful bio-material, which can be used for mass loading of various nanoparticles for biomedical applications.

For present work, the distortions in the liner due to mechanical torque application are considered and an empirical correlation between its inner diameter and outer diameter had been determined. This empirical correlation can be utilized eventually to estimate the mechanical bore distortion after actually running of engine. For estimation of total distortion i.e; mechanical as well as thermal distortion is required. As it is not possible to measure mechanical distortion of an engine after running, there as to be provision of estimation of same.As after assembly,it can not be measured experimentally,a suitable empirical correlation between inner diameter and outer diameter of liner under mechanically distorted condition, mechanical distortion, is developed and mechanical distortion is found out. After running the engine actually, and by measuring total distortion after disassemblying the liner ,the thermal distortion can be found subtracting mechanical distortion .

Self-excited combustion instabilities in a mesoscale multinozzle array, also referred to as a micromixer-type injector, have been experimentally investigated in a lean-premixed tunable combustor operating with preheated methane and air. The injector assembly consists of sixty identical swirl injectors of 6.5 mm inner diameter, which are evenly distributed across the combustor dump plane. Their flow paths are divided into two groups – inner and outer stages – to form radially stratified reactant stoichiometry for the control of self-excited instabilities. OH PLIF measurements of stable flames reveal that the presence of radial staging has a remarkable influence on stabilization mechanisms, reactant jet penetration/merging, and interactions between adjacent flame fronts. In an inner enrichment case, two outer (leaner) streams merge into a single jet structure, whereas the inner (richer) reactant jets penetrate far downstream without noticeable interactions between neighboring flames. The constructed stability map in the 〈ϕi, ϕo〉 domain indicates that strong self-excited instabilities occur under even split and outer enrichment conditions at relatively high global equivalence ratios. This is attributed to large-scale flame surface deformation in the streamwise direction, as manifested by vigorous detachment/attachment movements. The use of the inner fuel staging method was found, however, to limit the growth of large-amplitude heat release rate fluctuations, because the center flames are securely anchored during the whole period of oscillation, giving rise to a moderate lateral motion. We demonstrate that the collective motion of sixty flames – rather than the individual local flame dynamics – play a central role in the development of limit cycle oscillations. This suggests that the distribution pattern of the injector array, in combination with the radial fuel staging scheme, is the key to the control of the instabilities.