Excitation Characteristics Research Articles

Study on the characteristics of axial fluid excitation on fuel rods with spacer grids

Grids, supporting fuel rods, consist of dimples and mixing vanes. These complex structures cause turbulent flow field with complex vortex. The vibration of fuel rod by the high-velocity coolant may lead to grid to rod fretting (GTRF). In order to obtain the behavior of the fretting wear, it is crucial to investigate the induction mechanism of fuel rod by the flow field evolvement. In this paper, the effects of two structures with different geometric were discussed by numerical simulation. The generation and evolution of the fluid forces are analyzed in detail. The results show that the fluid forces mainly originate from the pressure asymmetry. Moreover, the clamping structures play a dominant role in both excitation and fluctuation of the fluid forces. The study obtained the effect of intrinsic structure on fluid excitation, and it can provide a basis for the fluid excitation boundary of the fretting wear of fuel rods.

Mechanical Performance Analysis and Experimental Study of Four-Star-Type Crank-Linkage Mechanism

Mechanical performance analysis and experimental study of the mechanics of the four-star-type crank-linkage mechanism of the marine air compressor were carried out to improve the submerged floating performance and stealth performance of the underwater vehicle and to meet the demand of its large diving depth. Firstly, we analyzed the forces on the four-star-type crank-linkage mechanism, derived the inertia forces and moments of the crank-linkage mechanism, and proved the advantages of the four-star-type crank-linkage mechanism in balancing the second-order reciprocating inertia forces. The static strength of some parts was calibrated, and the modal analysis of the four-star-type crank-linkage mechanism was carried out. Second, a flexible crankshaft dynamics model was established to study the influence of kinematic pair parameters on the excitation characteristics of the main bearing. The mechanical performance analysis of the mechanics of the four-star-type crank-linkage with clearance was carried out. Finally, a test bench of four-star-type crank-linkage mechanism was designed and built independently to analyze the effects of clearance size and rotational speed on the acceleration of the motion and vibration acceleration of the slider. The results show that the first-order reciprocating inertia force and second-order reciprocating moment of inertia mainly exist in the four-star-type crank-linkage mechanism. The friction force of the revolving pair can suppress part of the resonance peak, but it will broaden the excitation band and excite high-frequency vibration. The larger the clearance of the four-star-type crank-linkage mechanism kinematic pair, the higher the crankshaft speed, the larger the acceleration amplitude, and the more concentrated the phase trajectory. The research results of this paper can guide the low-noise design of other types of air compressors, help to improve the overall level of marine air compressors, and show future directions for the vibration control of four-star-type air compressors.

Research on the mechanism and restraining measures of ferroresonance in distribution network based on ATP-EMTP

In order to monitor the three-phase voltage of the busbar to ground, the substation bus is usually connected to the electromagnetic voltage transformer by YN connection in the distribution network. Under certain conditions, the excitation characteristics are easy to saturate, and the inductance parameters match the system capacitance, excite ferromagnetic resonance, cause damage to fuses or voltage transformers, and seriously affect the safe and stable operation of the power system.By analyzing typical single-phase ground faults, this paper introduces the generation mechanism of ferromagnetic resonance and the main suppression measures at this stage. The electromagnetic transient analysis software ATP-EMTP is used to analyze the operation of a typical transformer, and the change of ferromagnetic resonance waveform after the neutral point of the voltage transformer is replaced by resonant eliminator and arc suppression coil grounding. The results show that when eliminating the single-phase ground fault, it is easy to cause the frequency division resonance of the system, and the use of these two measures can effectively suppress the ferromagnetic resonance of the system.

Study on Pressure Pulsation and Force Characteristics of Kaplan Turbine

With the continuous increase in the size and power generation of turbines, the operational characteristics of turbines under off-design conditions are gradually receiving attention. In this paper, the Reynolds time-averaged method (RANS) is applied to the unsteady calculation of three different flow rate of a large Kaplan turbine under three heads: high head, rated head and low head. The focus is on the internal flow pattern of the turbine and the hydraulic excitation characteristics under low flow conditions. The unsteady characteristics of pressure pulsation, axial force of runner, radial force of runner and hydraulic torques along blade shank (τb) for six blades are analyzed. The results show that the pressure pulsation in the vaneless space is larger under low flow conditions, and frequencies of 0.33–1 fn ( fn is the rotating frequency of the runner) can be observed at monitoring points at different heights in the vaneless space. The analysis of the flow field under low flow conditions reveals the presence of larger scale vortices in the vaneless space. The position and intensity of vortices fluctuate periodically and cause larger amplitude pressure fluctuations. The frequency of 0.33–1 fn can also be observed for axial force, radial force, and τb for six blades due to the influence of vortices in the vaneless space. The low-frequency pulsations of pressure, force and τb are much greater under the low head and high head condition than that under rated head condition. The amplitude of pulsation of various parameters is the smallest under the low flow and rated head compared to that under the low flow conditions of other heads. The flow passage under low head is more influenced by the flow rate. Low-frequency pulsations occur under both the low flow and medium flow conditions. The asymmetry of the flow in the vaneless space causes unbalanced force and hydraulic instability of the runner, which seriously threatens the safe and stable operation of the turbine.

Stability Analysis of Hydrodynamic Mechanical Seals in Multifrequency Excitation

The dynamic characteristics of the complex relationship among the sealing system, excitation, and response have a considerable impact on the operational reliability of hydrodynamic mechanical seals, which is a critical issue in the field of sealing theory and technology. Scholars at home and abroad have established dynamic models and calculated the displacement responses of dynamic and static rings in the time domain based on the force on these rings so that the response results can be used for system stability analysis. Neither are the excitation characteristics of cavitation load extracted, nor are the distance response and system leakage rate of the dynamic and static rings analyzed under coupled cavitation and random excitation. In this study, under different operating conditions of the hydrodynamic mechanical seal system, the liquid film evaporation load and seismic load are applied to study the frequency domain response of the distance between the dynamic and static rings and the system leakage rate. The following conclusions have been obtained: Assuming that the chamber pressure is 0.5 MPa and the spring specific pressure is 0.055 MPa, during stable operation, the distance between the moving and stationary rings at 1500 rpm~3000 rpm speeds is 1.12 μm~3.05 μm. For a specific spring pressure of 0.055 MPa, medium pressures of 0.2 MPa~1.0 MPa, and spindle speeds of 1500 rpm~3000 rpm, the excitation force is 30 N, and the frequency is 30 Hz, And the seismic load is assumed to be sinusoidal, the excitation force is 6 N, the fundamental frequency is 120 Hz, and the system leak rate is in 0.1 mL/min~1.3 mL/min. Under multi-frequency excitation coupling, the distance between the dynamic and static rings will decrease as the pressure of the medium in the sealing cavity increases, and this will increase with the increase in the rotating speed. The leakage rate of the system will increase with the increase in the rotating speed and the pressure of the medium, and the test value is largely consistent with the theoretical value.

Electronic Structure, Aromaticity and Optical Properties of Dehydro[10]annulene.

Dehydro[10]annulene had been prepared experimentally recently, which is considered to be a highly rigid structure with planar configuration. In this paper, the electronic structure and bonding character of dehydro[10]annulene had been studied by means of molecular orbital (MO), density of states (DOS), bond order (BO) and interaction region indicator (IRI) analyses. The delocalization characters of out-of-plane and in-plane π-electrons (πout - and πin -electrons) of the bond regions were studied by using localized orbital locator (LOL). The anisotropy of the induced current density (AICD), iso-chemical shielding surface (ICSS) and anisotropy of the gauge-including magnetically induced current (GIMIC) were used to investigate the molecular response to external magnetic field, including the induced ring current and the magnetic shielding characteristic. The results showed that the electron delocalization of dehydro[10]annulene is mainly contributed by πout system. The apparent clockwise current in the πout system proved that dehydro[10]annulene is πout aromatic. Finally, the photophysical properties and (hyper)polarizability of dehydro[10]annulene were studied by TD-DFT calculation. The results showed that dehydro[10]annulene has strong local excitation characters. Its (hyper)polarizability decreases with the increase of frequency and has the characteristics of nonlinear anisotropy.

Electronic Excitation Characteristics and Spectral Behavior of Phosphate Anions.

Absorption spectra are fundamental bases for the qualitative and quantitative analysis of the target chemical, and the development of an analytical model can be improved by studying its characteristics and rules. In the present study, the electronic excitation characteristics of phosphate anions (H2PO4-, HPO42-, and PO43-) were analyzed based on the charge-transfer spectrum. In addition, the absorption spectra of phosphate anions at the energy level of PBE0/6-311+G (d,p) were recorded based on the time-dependent density functional theory (TD-DFT) method. Different (HPO42-)n·(H2O)10-n molecular clusters were theoretically constructed, and the combined TD-DFT method and independent gradient model revealed that red shift of the maximum absorption wavelength (λmax) with the increase of phosphate anion concentration (0-10 mM) may be caused by the decrease of hydrogen bond interaction. In addition, the prominent dispersion in the short-wave region mainly resulted in the red shift of λmax with the increase in optical path length (1-100 mm). Moreover, with the increase in spectral bandwidth (0.4-3.0 nm), λmax slightly blue-shifted because of the increase in energy through the slit, and repeatability of the corresponding absorbance measurement at λmax gradually improved. As the spectral bandwidth increased, light monochromaticity became poor, resulting in the decrease of the linearly fitted correlation coefficient of the concentration-absorbance curve. Finally, the multivariate analysis of variance results showed that the optical path length was the most significant factor that influenced the absorption spectral characteristics of phosphate anions. This study provides a basis for the qualitative and quantitative analysis of phosphate anions by using absorption spectra and also renders a theoretical reference for absorption spectroscopy of other chemicals.

Nonlinear excitation and mesh characteristics model for spiral bevel gears

Accurate and rapid calculation of nonlinear excitation (NE) and loaded mesh characteristics (LMC) of gear pairs is a key to achieving rapid iterative optimization of gear system designs. Therefore, an analytical model (AM) was proposed for the accurate and numerically efficient calculation of NE and LMC for application to spiral bevel gears (SBG). First, a tooth contact analysis of an SBG was completed using Coons surface technology and mesh theory to determine the contact path and unloaded transmission error (UTE). Thus, an AM for the principal and relative normal curvatures of the SBG was derived using the Euler's formula. Based on the traditional calculation method for a Hertz contact ellipse, the relation between the relative curvatures was introduced to derive the formulas for the major and minor axes using the Muller's method, which could improve the programmability and avoid numerical instability of the program. Then, analytical models for the contact ellipse and pressure distribution on the contact tooth surfaces were derived using the Hertz model and geometric theory. Subsequently, based on a single tooth LMC, infinitesimal method, elasticity, and series stiffness model, a single mesh stiffness (SMS) model for SBGs was developed, which incorporates transverse tooth stiffness, transverse gear foundation stiffness, axial tooth stiffness, axial gear foundation stiffness, and Hertz nonlinear contact stiffness. Based on the SMS and UTE, compliance and load matrices were established, and the time-varying mesh stiffness, loaded transmission error, mesh force, and multi-tooth LMC models of the SBG were determined. Finally, the proposed method was validated against nonlinear FE simulations using examples. Compared to FE simulations, the proposed method requires significantly less computational effort and can be further extended to optimization or system analysis problems.

Studying excited-state-specific perturbation theory on the Thiel set.

We explore the performance of a recently introduced N5-scaling excited-state-specific second order perturbation theory (ESMP2) on the singlet excitations of the Thiel benchmarking set. We find that, without regularization, ESMP2 is quite sensitive to π system size, performing well in molecules with small π systems but poorly in those with larger π systems. With regularization, ESMP2 is far less sensitive to π system size and shows a higher overall accuracy on the Thiel set than CC2, equation of motion-coupled cluster with singles and doubles, CC3, and a wide variety of time-dependent density functional approaches. Unsurprisingly, even regularized ESMP2 is less accurate than multi-reference perturbation theory on this test set, which can, in part, be explained by the set's inclusion of some doubly excited states but none of the strong charge transfer states that often pose challenges for state-averaging. Beyond energetics, we find that the ESMP2 doubles normoffers a relatively low-cost way to test for doubly excited character without the need to define an active space.

A Feasible Strategy for a Highly Efficient Thermally Activated Delayed Fluorescence Emitter Over 900 nm Based on Phenalenone Derivatives.

Near-infrared (NIR) organic light-emitting diodes (OLEDs) suffer from the low external electroluminescence (EL) quantum efficiency (EQE), which is a critical obstacle for potential applications. Herein, 1-oxo-1-phenalene-2,3-dicarbonitrile (OPDC) is employed as an electron-withdrawing aromatic ring, and by incorporating with triphenylamine (TPA) and biphenylphenylamine (BBPA) donors, two novel NIR emitters with thermally activated delayed fluorescence (TADF) characteristics, namely OPDC-DTPA and OPDC-DBBPA, are first developed and compared in parallel. Intense NIR emission peaks at 962 and 1003 nm are observed in their pure films, respectively. Contributed by the local excited (LE) characteristics in the triplet (T1 ) state in synergy with the charge transfer (CT) characteristics for the singlet (S1 ) state to activate TADF emission, the solution processable doped NIR OLEDs based on OPDC-DTPA and OPDC-DBBPA yield EL peaks at 834 and 906 nm, accompanied with maximum EQEs of 0.457 and 0.103 %, respectively, representing the state-of-the-art EL performances in the TADF emitter-based NIR-OLEDs in the similar EL emission regions so far. This work manifests a simple and effective strategy for the development of NIR TADF emitters with long wavelength and efficiency synchronously.

Primary motor hand area corticospinal excitability indicates overall functional recovery after spinal cord injury.

After spinal cord injury (SCI), the excitability of the primary motor cortex (M1) lower extremity area decreases or disappears. A recent study reported that the M1 hand area of the SCI patient encodes the activity information of both the upper and lower extremities. However, the characteristics of the M1 hand area corticospinal excitability (CSE) changes after SCI and its correlation with extremities motor function are still unknown. A retrospective study was conducted on the data of 347 SCI patients and 80 healthy controls on motor evoked potentials (MEP, reflection of CSE), extremity motor function, and activities of daily living (ADL) ability. Correlation analysis and multiple linear regression analysis were conducted to analyze the relationship between the degree of MEP hemispheric conversion and extremity motor function/ADL ability. The CSE of the dominant hemisphere M1 hand area decreased in SCI patients. In 0-6 m, AIS A grade, or non-cervical injury SCI patients, the degree of M1 hand area MEP hemispheric conversion was positively correlated with total motor score, lower extremity motor score (LEMS), and ADL ability. Multiple linear regression analysis further confirmed the contribution of MEP hemispheric conversion degree in ADL changes as an independent factor. The closer the degree of M1 hand area MEP hemispheric conversion is to that of healthy controls, the better the extremity motor function/ADL ability patients achieve. Based on the law of this phenomenon, targeted intervention to regulate the excitability of bilateral M1 hand areas might be a novel strategy for SCI overall functional recovery.

Momentum dependence of the spectral weight in late transition metal phthalocyanine β-phases

The exciton dispersion in metal-free-phthalocyanine and cobalt-phthalocyanine as well as the momentum dependence of the spectral weight of the Q-band excitation in zinc-, copper-, nickel-, cobalt-, and metal-free-phthalocyanine β-phase thin films were evaluated using electron energy loss spectroscopy. We demonstrate that the lowest exciton in β-H2Pc and β-CoPc shows a negative dispersion which can be modeled taking into account charge transfer exciton coupling. The analysis of the momentum dependent spectral weight indicates substantial quadrupolar character of the Q-band excitations, which also points towards the admixture of charge transfer excitons.

Coupled Excitation Strategy for Crack Initiation at the Adhesive Interface of Large-Sized Ultra-Thin Chips

The initial excitation of interface crack of large-size ultra-thin chips is one of the most complicated technical challenges. To address this issue, the reversible fracture characteristics of a silicon-based chip (chip size: 1.025 mm × 0.4 mm × 0.15 mm) adhesive layer interface was examined by scanning electron microscope (SEM) tests, and the characteristics of a cohesive zone model (CZM) unit were obtained through peel testing. The fitting curve of the elastic bilinear model was in high agreement with the experimental data, with a correlation coefficient of 0.98. The maximum energy release rate required for stripping was GC = 10.3567 N/m. Subsequently, a cohesive mechanical model of large-size ultra-thin chip peeling was established, and the mechanical characteristics of crack initial excitation were analyzed. The findings revealed that the larger deflection peeling angle in the peeling process resulted in a smaller peeling force and energy release rate (ERR), which made the initial crack formation difficult. To mitigate this, a coupling control method of structure and force surface was proposed. In this method, through structural coupling, the change in chip deflection was greatly reduced through the surface coupling force, and the peeling angle was greatly improved. It changed the local stiffness of the laminated structure, made the action point of fracture force migrate from the center of the chip to near the edge of the chip, the peeling angle was increased, and the energy release rate was locally improved. Finally, combined with mechanical analysis and numerical simulation of the peeling process, the mechanical characteristics of peeling were analyzed in detail. The results indicated that during the initial crack germination process, the ERR of the peel interface is significantly increased, the maximum stress value borne by the chip is significantly reduced, and the peel safety and reliability are greatly improved.

Synaptic and circuit mechanisms prevent detrimentally precise correlation in the developing mammalian visual system.

The developing visual thalamus and cortex extract positional information encoded in the correlated activity of retinal ganglion cells by synaptic plasticity, allowing for the refinement of connectivity. Here, we use a biophysical model of the visual thalamus during the initial visual circuit refinement period to explore the role of synaptic and circuit properties in the regulation of such neural correlations. We find that the NMDA receptor dominance, combined with weak recurrent excitation and inhibition characteristic of this age, prevents the emergence of spike-correlations between thalamocortical neurons on the millisecond timescale. Such precise correlations, which would emerge due to the broad, unrefined connections from the retina to the thalamus, reduce the spatial information contained by thalamic spikes, and therefore we term them 'parasitic' correlations. Our results suggest that developing synapses and circuits evolved mechanisms to compensate for such detrimental parasitic correlations arising from the unrefined and immature circuit.

Mapping charge-transfer excitations in Bacteriochlorophyll dimers from first principles

Photoinduced charge-transfer excitations are key to understand the primary processes of natural photosynthesis and for designing photovoltaic and photocatalytic devices. In this paper, we use Bacteriochlorophyll dimers extracted from the light harvesting apparatus and reaction center of a photosynthetic purple bacterium as model systems to study such excitations using first-principles numerical simulation methods. We distinguish four different regimes of intermolecular coupling, ranging from very weakly coupled to strongly coupled, and identify the factors that determine the energy and character of charge-transfer excitations in each case. We also construct an artificial dimer to systematically study the effects of intermolecular distance and orientation on charge-transfer excitations, as well as the impact of molecular vibrations on these excitations. Our results provide design rules for tailoring charge-transfer excitations in Bacteriochloropylls and related photoactive molecules, and highlight the importance of including charge-transfer excitations in accurate models of the excited-state structure and dynamics of Bacteriochlorophyll aggregates.

Photoluminescence Spectral Patterns and Parameters of Milk While Souring

For the efficient production and processing of milk, it is important to control its quality indicators. Optical spectroscopy, in combination with statistical analysis methods, can be a useful method of evaluation due to its speed, non-invasiveness, and relative cheapness. This investigation is aimed at studying of the interrelations of the spectral patterns, the absorption parameters, and the photoluminescence values of cow’s milk during its souring. The spectral characteristics of excitation and photoluminescence were measured on a diffraction spectrofluorometer in the range of 200–500 nm. For establishing an effective control procedure during milk souring, the most informative method is found to be the use of the excitation wavelengths of 232 nm, 322 nm, 385 nm and 442 nm. These ranges correspond to the amino acids of milk proteins, the fatty acids of milk fat, and the aromatic fragments of vitamins. When using the photoluminescence flux ratios Φ232/Φ322 and Φ385/Φ442, linearly approximated dependences on acidity can be obtained with determination coefficients of 0.88–0.94. The proposed photoluminescent method can be used as a non-destructive and fast-acting tool for monitoring the properties of milk during fermentation, as well as for the subsequent creation of a portable and inexpensive sensor based on this method.

Sn2+/Mn2+ co-doped germanate glass with quasi-sunlight spectrum visible-emission and its high-quality w-LED application

Light sources with the spectrum distribution approaching the sunlight, even in the visible range, are preferred. Up to now, sunlight simulator is still a great challenge to the scientists. In this work, the Sn2+/Mn2+ doped germanate glasses with the emission near to the sunlight spectral distribution in the visible wavelength region were developed, and the corresponding applications in w-LEDs were demonstrated. The spectral properties including excitation and emission characteristics, concentration quenching, fluorescence dynamics for Sn2+ and Mn2+ single-doped germanate glasses were studied. It is found that both Sn2+ and Mn2+ single-doped glasses can be effectively excited by broadband ultraviolet and subsequently generate broadband visible emissions. However, the emission from each of single-doped glasses does not cover full visible wavelength range. Fortunately, it is found that the lack of the red spectral component in the broadband visible emission of Sn2+ single-doped glass can be compensated by the broadband red emission of Mn2+. On that base, the Sn2+/Mn2+ co-doped germanate glasses were fabricated and studied. Broadband emission covering full visible range, good luminescence thermal stability and excellent chromatic performance were realized in the co-doped glasses by optimizing concentration and engineering energy transfer. Finally, a prototype w-LED was assembled by the Sn2+/Mn2+ co-doped germanate glass and a 310 nm LED chip. The prototype w-LED reveals the sunlight-like visible spectrum, good color coordinates (0.380, 0.371), low correlated color temperature (CCT) of 3811 K and high color rendering index of 95.3, indicating that the Sn2+/Mn2+ co-doped germanate glasses are promising candidate to develop high performance w-LED.

Double Fano sensing mechanism of waveguide coupled surface plasma

Based on the optical properties of waveguide-coupled surface plasmon resonance, a sensor of surface plasmon coupled waveguide resonance with double discrete states generated by the upper and lower waveguide structures combined with prisms and Au films, respectively, is proposed. In this paper, the sensing structure is studied numerically and analytically, and the transmission characteristics of surface equipartition excitations are analyzed and elaborated in-depth in combination with the reflection angle spectrum, as well as the generation and evolution mechanism of dual Fano resonance at different incidence angles at fixed wavelengths. The structural model of Fano resonance sensing based on angle modulation is established, and the sensing characteristics are analyzed to produce electromagnetic field enhancement at low-angle Fano. The mathematical model between structural parameters and spectral performance is established using back propagation (BP) neural network, and the particle swarm optimization (PSO) algorithm is used to find the input structural parameters corresponding to the optimal performance, The results show that the quality factor of resonance (FOM) and sensitivity is significantly improved; When it is used in the field of biosensing, the response curves of Fano with different angles of high and low to concentration are quite different, thus realizing high precision detection of different concentrations of solutions and reflecting excellent sensing performance.

Vibration response mechanism of fixed-shaft gear train with cracks based on rigid-flexible coupling dynamics and signal convolution model

Affected by external flexible transfer path of fixed-shaft gear train, internal gear meshing vibration signals that representing the healthy state of gear will convolve with modal information of gearbox housing and become much more complicated. Moreover, gear crack fault features of fixed-shaft gear train are relatively weak and complex, which are difficult to diagnose. Therefore, to reveal the origination mechanism of crack fault, a rigid-flexible coupling dynamics model of fixed-shaft gear train with full consideration of flexible housing is firstly established, then a signal convolution model is proposed to solve housing vibration response signal by combining internal excitation and external transfer path. Thereinto, as internal influence factor, time-varying meshing stiffness that drives excitation forces is used to reflect excitation characteristics under normal and crack state; as external influence factor, flexible transfer path that includes modal characteristics of gearbox housing is calculated by finite-element-method. Through the established models, modulation sideband features of housing vibration response signals are selected as crack fault indicator. Corresponding vibration response mechanism is revealed clearly under normal and different crack degrees in simulations. Experimental results keep good consistency at crack fault features with simulation signals and verify the effectiveness of the proposed models.

High-sensitivity photonic crystal fiber methane sensor with a ring core based on surface plasmon resonance and orbital angular momentum theory

ObjectiveWith the advent of optical fiber sensing technology, photonic crystal fiber (PCF) sensors based on surface plasmon resonance (SPR) have become a research hotspot. Herein, a PCF-SPR methane sensor with a ring-core structure is designed based on the orbital angular momentum (OAM) theory. To our best knowledge, this type of sensor has not been reported yet. MethodsThrough the finite element method, the PCF structure is designed and the appropriate filling material is selected. ResultsThe sensor consists of a three-layer clad air hole and an extra-large central gas channel, forming a ring core for beam transmission. By adding high refractive index material Amethyst and methane sensitive material to the central gas channel, the mode field is improved and the methane concentration is detected efficiently. Numerical results show that the sensor can stably transmit OAM modes and excite SPR with the OAM2,1 mode, namely the HE3,1 eigenmode. With the help of methane sensitive film, changes in methane concentration can greatly affect the refractive index distribution in PCF and alter the excitation characteristics of SPR. In the methane concentration range of 0–3.5 %, the resonance wavelength shifts from 4.52 µm to 4.58 µm. The average wavelength sensitivity reaches 17.07 nm/%, and the corresponding detection limit is 117 ppm. The results reveal that the designed PCF-SPR methane concentration sensor has excellent performance, which can stably transmit OAM mode while achieving SPR effect. It has great innovation and commercial potential in the petroleum, biomedical, chemical, and other industry.