High Pressure Ratio Research Articles

The Potential of Dehydrated Geniotrigona thoracica Stingless Bee Honey against Metabolic Syndrome in Rats Induced by a High-Carbohydrate, High-Fat Diet

Background/Objectives: Metabolic syndrome (MS) is diagnosed when at least three out of five key risk factors are present: obesity, high blood pressure, insulin resistance, high triglycerides (TG) and low high-density lipoprotein (HDL). MS is often associated with chronic low-grade inflammation. Recent studies have shown that raw stingless bee honey (SBH) can alleviate MS risk factors. However, the high moisture content in raw SBH predisposes it to fermentation, which can degrade its quality. Therefore, dehydrating SBH is necessary to prevent the fermentation process. This study aimed to compare the effects of dehydrated (DeGT) and raw (RGT) SBH from Geniotrigona thoracica species on high-carbohydrate, high-fat diet (HCHF)-induced MS in rats. Methods: Twenty-four male Wistar rats were divided into four groups: control (C), HCHF-induced MS without treatment (MS), HCHF-induced MS treated with DeGT (MS+DeGT) and HCHF-induced MS treated with RGT (MS+RGT). Group C received standard rat chow, while the other groups were fed with HCHF diet for 16 weeks. In the final eight weeks, two HCHF-induced groups received their respective SBH treatments. Results: Both DeGT and RGT treatments reduced energy intake, fat mass, high blood pressure, inflammatory (tumour necrosis factor-alpha (TNF-α)) and obesity (the leptin/adiponectin (L/A) ratio, corticosterone, 11 beta-hydroxysteroid dehydrogenase type-1 (11βHSD1)) markers, as well as prevented histomorphometry changes (prevented adipocyte hypertrophy, increased the Bowman’s space area and glomerular atrophy). Additionally, DeGT increased serum HDL levels, while RGT reduced serum TG, leptin and other inflammatory markers (interleukin-6 (IL-6) and interleukin-1 beta (IL-1β)), as well as hepatosteatosis. Conclusions: While DeGT demonstrates potential as a preventive agent for MS, RGT exhibited more pronounced anti-MS effects in this study.

Design and performance evaluation of a reversible bladeless turbo machine

It is well known that bladeless or Tesla turbomachinery idea was proposed by Nikola Tesla over a century ago, and it has several distinct features, such as reversibility of operation, which includes expander and compressor operations obtained by reversing the rotational speed, provided that the statoric channels are purposely designed.The main objective of this paper is to design a reversible Tesla or bladeless machine with optimal design parameter choice that can operate both in compressor and expander modes. As a consequence of the high losses due to rotor and stator interactions, statorless (volute) configurations are investigated here, showing superior performance in both compressor and expander modes of operation. Numerical study has been conducted for both compressor and expander modes of this machine using air as working fluid. In compressor mode, numerical results have been validated with experimental data, while results for expander mode will be validated in the near future. The numerical results predict peak isentropic efficiencies of 57.5 % and 63.5 %, for the compressor and expander modes of operation excluding assembly losses, respectively, while rotor efficiency is quite high > 90 % at very low mass flow rates. Tests on Tesla machine prototype have shown an experimental isentropic efficiency of maximum 32.4 % when operating in compressor mode. The overall assembly efficiency is reduced, compared to numerical predictions, due to leakage and end wall losses. The CFD simulations could match the experimental results at high pressure ratio and low mass flow, with less than 2 % error on pressure ratio. Through the improvement of the sealing system and the reduction of losses (leakage and end wall friction), it is expected that overall prototype efficiency could improve by at least 10 percentage points.

Cooling System of A High-Pressure Centrifugal Compressor: Development and Impact on Wheel Temperatures (GT2024-121464)

Abstract High power density, low fuel consumption, and a compact design with competitive total costs of ownership are key requirements for internal combustion engines for conventional fuels and carbon-free or carbon-neutral future fuels. These requirements influence the development targets of charging systems and call for single-stage charging systems with increased charge air pressures. However, high compressor pressure ratios of the turbocharger lead to challenging material temperatures in aluminum alloy wheels. Consequently, creep becomes the fundamental lifetime-limiting damage mechanism for these wheels. In order to meet customer requirements regarding total costs of ownership, the lifetime is of major importance for the development of aluminum compressor wheels for turbochargers with pressure ratios beyond 6. This paper focuses on a high-pressure compressor design with a water-cooling system for a new turbocharger generation. The development of its components and their validation based on numerically predicted and measured wheel temperatures are discussed. After introducing the need for high-pressure ratios and the accompanying lifetime challenges, the paper presents the design strategy and methods of the development process. Finally, the paper summarizes the achievements obtained by this procedure. Detailed and rarely before documented temperature measurements from the rotating compressor wheel are published. As will be shown, the temperature measurements confirm the predictions from the pre-development phase. A comparison of the temperature measurements from the recently developed wheel with measurements carried out for a state-of-the-art wheel reveals the improvements achieved by this new generation of high-pressure compressors.

Research on Effect of Endwall Contouring of Vaned Diffuser on Stable Operating Range of Centrifugal Compressor

Abstract The study investigates the impact of diverse endwall contouring strategies on the operational stability of a high-pressure ratio centrifugal compressor stage. Employing numerical simulation techniques, this study examines the implications of contoured wall positions, specifically convex profiles at the pressure side and/or concave profiles at the suction side, as well as asymmetric endwall contouring, on both stage performance and internal flow field within the centrifugal compressor. And the stability enhancement mechanism of endwall contouring is clarified. The results demonstrate that employing full circular contoured vaned diffusers on the hub-side wall can achieve a maximum improvement in stall margin of 15.10%. Additionally, the diffuser featuring solely convex profiles at the pressure side on the hub-side wall exhibits an augmented stall margin by 8.39%, with a reduction in performance loss at low flow rate conditions. The asymmetric endwall contouring improves stall margin by 8.39%, and mitigates the performance loss across the entire operating range. At the near-stall point, the contoured endwalls redirect fluid towards the suction side, thereby mitigating the incidence at the vane leading edge and attenuating the interaction between the impeller trailing edge vortex and the diffuser leading edge vortex. Moreover, concave profiles serve to accelerate the fluid on the suction side along the flow direction, thereby suppressing the corner separation and weakening passage blockages. Simultaneously, the advantages of endwall contouring in vane diffusers extend to the improvement in the circumferential non-uniformity of flow fields and the enhancement in diffuser stability.

Numerical and experimental investigations of flow separation control through a linear compressor cascade

Modern large-scale gas turbines are equipped with high-pressure ratio compressors to increase engine work and its overall efficiency. Flow separation and energy losses are also two interrelated phenomenon associated with changes in compressor loading level and performance. This paper examines therefore the control of flow separation using a passive-control technique. An arced divergent-convergent slot grooved from the blade pressure side to its suction side was adopted to control flow separation, reducing the losses through a linear compressor cascade. The spanwise location of the slot was selected based on CFD simulations where the corner separation was predicted. The slot height in the spanwise direction was selected to be 8% of the blade height at the end-wall side. The present work was performed experimentally and numerically at an inlet Reynolds number,Rec=ρV∞C/μ=2.98×105\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${R}_{ec}=\\rho {V}_{\\infty }C/\\mu =2.98\ imes {10}^{5}$$\\end{document}, covering a wide range of incidence angles from +6∘to-6∘\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$+ 6^{ \\circ } {\ ext{ to}} - 6^{ \\circ }$$\\end{document}. The experimental work was carried out using a linear cascade test section consisting of six NACA 65-009 blade profiles integrated into a low-speed wind tunnel. A five-hole pressure probe system was used to obtain main flow parameters. Numerically, four turbulence models, including Spalart–Allmaras (S–A) model, Realizable (R k-ε) model, Shear-Stress Transport (SST k-ω) model, and Reynolds Stress model (RSM) were tested to predict the velocity and pressure fields. Good agreement between the experimental measurements and the numerical results, which were obtained using the RSM turbulence model in terms of velocity profiles and total pressure downstream of blades. It was observed also that the use of the arced-slotted blades for positive incident angles was more effective in reducing the separation than the negative and zero incident angles, approaching a maximum value of 33% for 6° with enhanced blade loading reaching 17.6%. It is to be concluded that, the use of arced slotted blade improves the compressor performance specially for positive incident angles.

Analysis of internal behavior of electrochemical hydrogen compressors at high pressures

We examined the internal behavior of an electrochemical hydrogen compressor under high-pressure conditions. In doing so, we focused on the changes in compressor efficiency and power consumption in response to intensified hydrogen back-diffusion under high pressures and various values of other parameters. First, as the operating temperature increased, the power consumed to achieve the same pressure ratio increased. This increased in power consumption was attributed to the fact that as the temperature increased, hydrogen back-diffusion intensified, which necessitated a net forward flux and induced flow losses. Second, as the relative humidity increased, power consumption decreased, and compressor efficiency increased. Although higher relative humidity intensifies back-diffusion, leading to flow losses, the accompanying significant decrease in ohmic losses increases compressor efficiency. By adjusting factors such as temperature and relative humidity, compressor efficiency can potentially be increased by up to 1.78 times. At high pressure ratios, hydrogen back-diffusion was inherently strong, and it became stronger at higher temperatures and relative humidities. Therefore, the compressor was more efficient when it was operated at lower temperatures and higher relative humidities. At the optimal operating temperature of 50 °C and 100 % relative humidity, the compressor efficiency peaked at 97.507 % when the pressure ratio was 100.

Enhancing thermodynamic performance with an advanced combined power and refrigeration cycle with dual LNG cold energy utilization

Utilizing waste heat to drive thermodynamic systems is imperative for improving energy efficiency, thereby improving sustainability. A combined cooling and power systems (CCP) utilizes heat from a temperature source to deliver both power and cooling. However, CCP systems utilizing LNG cold energy suffers from low second law efficiency due to significant temperature differences. To address this, an “Advanced Power and Cooling with LNG Utilization (ACPLU)” system is proposed, integrating a cascaded transcritical carbon dioxide (TCO2)-LNG cycle with an Organic Rankine cycle (ORC) for improved power generation and an absorption refrigeration system (ARS) for simultaneous cooling. This study evaluates the second law efficiency, net work output, and exergy destruction performance through a sensitivity analysis, optimizing variables such as heat source temperature, superheater temperature difference, ORC and CO2 turbine inlet and condenser pressures, evaporator temperature, and pinch point temperatures of heat exchangers and generator. Compared to previous studies on CCP systems, the ACPLU shows a superior performance, with a second law efficiency of 27.3 % and a net work output of 11.76 MW. Cyclopentane as an ORC working fluid resulted in the highest second law efficiency of 29.06 % and net work output of 12.27 MW. Parametric analysis suggested that heat source temperature significantly impacts net power output. The exergy analysis concluded that a high-pressure ratio and good thermal match between the heat exchangers enhance overall performance. Utilizing artificial neural network (ANN) to produce a multiple-input-multiple-output (MIMO) objective function and performing multi-objective optimization (MOO) using genetic algorithm (GA), an improved second law efficiency and net power output by 28.11 % and 14.16 MW respectively, with pentane as the working fluid, is demonstrated. An average cost rate of 9.121 $/GJ was observed through a thermo-economic analysis. The ACPLU system is promising for medium temperature waste heat recovery, such as, pharmaceutical manufacturing plants.

Flow Analysis of Centrifugal Compressor using ANSYS

Abstract: The aerodynamic and structural designs of the impeller are vital to the functioning of the entire compressor stage in centrifugal compressors. In contrast to previous years, there has been a greater demand for industrial centrifugal compressors to operate with greater efficiency and operational range. Although the efficiency of low-pressure-ratio centrifugal compressors has nearly achieved its maximum, intermediate and high-pressure ratio machines still lag behind the state-of-the-art in terms of efficiency. Maintaining maximum efficiency while extending the working range is a challenging task in centrifugal compressor design. Furthermore, a single design must be usable globally due to product globalisation, even in the face of technological disparities and variances in electricity frequency of up to 10 percent in some nations. Often operating at different rotational speeds, centrifugal compressors add another layer of complexity to the impeller structural design. A full-3D impeller design that is optimised for both structural integrity and aerodynamic performance is shown in this study .For air conditioning systems of the future, centrifugal compressor performance must be improved. This research focusses on systematic numerical simulation, a computationally efficient method of optimising centrifugal compressor performance. ANSYS simulations are used in conjunction with a thorough literature review on the aerodynamic behaviour of materials used in centrifugal compressors. For the purpose of performing flow simulations under subsonic circumstances with suitable boundary conditions and grid independence checks, geometric modelling was completed using CATIAV5R22 and imported into ANSYS. Tests were conducted using various aluminium materials and mass flow rates, and enhanced efficiency findings were confirmed by comparison with experimental data. Materials Processing and Characterisations is in charge of peer review.

Wear mechanisms and material deposition of high-performance polymer composites for hydrogen compression

The transistion to renewable energy production is a main component in achieving the climate targets defined in the 2015 Paris Agreement. Power-to-gas concepts, where electrical energy is stored as hydrogen gas, require the design and operation of state-of-the-art reciprocating compressor technology to realize high pressure ratios and high volumetric flow rates for gas supply demands. The main challenges in designing machines suited for these operating conditions are high thermo-mechanical stresses acting on the piston sealing rings. High shear loads and minimal ring gap sizes demand material pairings with excellent wear resistance and sliding properties. This work investigates the life cycle limiting wear mechanisms present in the piston compressor and develops advanced concepts for piston rings in cylinder tribo-contacts. PI and PPS polymers reinforced with carbon fiber were modified with dry lubricating PTFE to fulfil the requirements of this highly stressed tribo-system. Tribo-tests were performed against steel countersurfaces with a linear oscillating tribometer in pin-on-plate configuration. The failure mechanisms were analysed utilizing scanning electron microscopy on cross-sections cut into the depth of the countersurface material with focused ion beam milling. 2D scanning transmission electron microscopy mapping supported by energy dispersive X-ray spectroscopy were performed to analyze the depth profile of the deposited tribo-layer elements on the wear track.

Effects of real gas models on the wave dynamics and refrigeration of gas wave rotor

The gas wave rotor was usually designed and performed on the ideal gas model. However, the real gas effect could not be ignored anymore under high-pressure ratio conditions. In this study, for the first time, a two-dimensional computational model of a double-opening gas wave refrigerator (GWR) using a multi-parameter Benedict–Webb–Rubin equation of state is established and the influence of the real gas effect on gas wave dynamics and energy transfer processes in the GWR with discontinuous boundary conditions is thoroughly investigated. The numerical results show that the wave dynamics of the ideal gas and the real gas are similar under different operating conditions, but compression waves and expansion waves in real gas obviously lag behind the ideal gas. In addition, the low-temperature real gas is completely discharged earlier than the ideal gas and the difference between them gradually increases as the pressure ratio gets higher, which benefits the GWR compact structure design and cost reduction. At the same time, the temperature of the real gas being discharged is lower than that of the ideal gas. Therefore, the refrigeration efficiency of the isentropic expansion of the real gas will be improved compared with the operation in ideal gas. The research results on the real gas effect reveal the mechanism of wave dynamics and energy transfer, providing support for the optimization design of GWR.

Numerical investigation on the transverse jet into a supersonic crossflow with different pressure ratios

The jet can be applied to the yaw control of a projectile, however, the complex interaction of the jet with the supersonic mainstream makes the flow field complex and yaw force unpredictable. To reveal the evolution of flow structures under different pressure ratios (PRs), or momentum flux ratios, a transverse sonic jet injected into a supersonic laminar crossflow has been studied numerically. Large-eddy simulations are employed to simulate the flow fields and evolution tendency of flow structures under different PRs of 10, 50, 100, 300, and 500. Our results show clearly the shock and flow structures of the jet interaction with crossflow under different PRs. Moreover, we find that, with the increase of PR, a larger upstream recirculation zone (RZ) and jet shock core appear, which accelerates the transformation of the bow shock (BoS) and the instability of the jet shear layer due to its stronger interaction with the crossflow. In addition, a high PR also accelerates RZ instability and produces a strong compressing effect on the major counter-rotating vortex pair in the jet flow, which makes the streamwise vortex tube stronger in the wake. These findings provide important information for applications of jet control of projectiles.

Investigation of the Map Width Improvement in a Radially Reduced Diffuser Design Concept for a Centrifugal Compressor

Abstract Often, an improvement in performance at one operating point in a compressor/turbine operating map will lead to a reduction in performance at another area. For example, improving the efficiency of a compressor at design point (DP) may result in a reduction of efficiency at other operating points or it may result in a reduced stable operating range. In order to reduce the compressor cost and weight, a 15% radial reduction was applied to the diffuser passage length of a high pressure ratio centrifugal compressor. The diffuser endwall was diverged to achieve an appropriate area ratio from diffuser inlet to outlet. Two different vane shapes were considered with the radially reduced diffuser passage. The first diffuser vane was a scaled version of the baseline airfoil vane shape and this was used to develop an understanding of the impact of the passage length reduction and diverging endwall. The second vane geometry was parameterized using an unconventional method derived from published literature and optimized to improve performance at DP. Increased losses were generated through the diffuser passages of the radially reduced designs, but this was compensated for by lower losses through the volute due to more desirable flow at volute inlet. As a result, the radially reduced designs not only matched the performance of the baseline configuration, but also succeeded in achieving a marginal efficiency improvement. Furthermore, despite not being one of the goals of the optimization procedure, an extension of the stable operating range of 36% and 20% at the highest speed condition was achieved for the scaled and optimized designs, respectively. The current study focuses on understanding the physical reasons that generated this significant enhancement to the compressor operating range. In order to acquire the desired understanding, experimental data is presented to validate the Computational Fluid Dynamics (CFD) model and a detailed numerical investigation is presented to explain the changes in the flow field within the radially reduced designs. The study focuses on low flow rate operating points, necessitating the use of an Unsteady Reynolds Averaged Navier-Stokes (URANS) approach to analyse the flow. Detailed scrutiny of the flow field revealed a secondary flow feature in the diffuser passage which resulted in higher diffuser passage losses at DP but stabilised the flow as it developed for lower mass flow rate operating points.

Analysis and Optimization of the Performances of the Tandem Blade Radial Compressor Using the CFD

Centrifugal compressors are frequently used in both military and commercial areas because they can be easily manufactured and reach high-pressure compression ratios. The factor that limits the performance and operating range of compressors is flow instability. Many ideas have been put forward for performance improvement, but tandem blade radial compressors, which do not require an extra air system, have attracted the most interest. In this study, computational fluid dynamics (CFD) analyses were carried out on various parameters of the tandem blade (TB) radial compressor, and an optimization study was carried out to find the best design using a genetic algorithm on a whole operating curve. It was investigated how these parameters affected the efficiency and total pressure ratio between the determined lower and upper limits. The numerical analyses of the optimum design obtained as a result of the iterations were carried out. As a result of the iterations, three optimum designs were obtained and numerical analysis was carried out according to one of them, and then they were compared with the results in the literature. The general agreement of computational fluid dynamics and the literature data served as a validation for the computational approach. The error rates between the numerical analysis results and the experimental results in the literature were calculated for different flow rates and were found to be 1.98% as the highest and 0.35 as the lowest. The work carried out in this article will provide a valuable reference for future advanced tandem blade compressor designs.

The design and research of two-stage series-connected helium turbine expanders for hydrogen liquefaction system

The helium turbine expander, is a crucial part of hydrogen liquefaction systems, that determines the overall efficiency of the system. In this paper, a two-stage series-connected helium turbine expanders is designed to achieve a hydrogen liquefaction capacity of 1.7 tonnes per day (TPD). The proposed expander is based on the reverse Brayton cycle and realizes a high pressure ratio of 8.32 to meet the design objective. A dynamic design process in the expansion end is developed and numerically simulated based on the turbine expander design methodology. The off-rated condition performance of the turbine expander is predicted by adjusting the rotational speed and flow rate. The results show that the reasonable rotational speed range of the turbine expander is 46000–54000 RPM, and the reasonable flow coefficient range is 0.6–1.2, which can maintain a high level of efficiency. The internal flow characteristics of the turbine expander are analysed through numerical simulation. The results show that the outlet temperature is suitable for hydrogen liquefaction, and flow loss mainly occurs in the upper-middle part of the impeller and near the tip clearance, followed by the throat of the nozzle. In the prototype tests to verify the rationality of the design of the turbine expanders, the experimental results show that the two turbine expanders can achieve a temperature drop of 31 K, and isentropic efficiencies of 76.8 % and 80.5 %, respectively, which are higher than the design requirements of 75 %. The actual outlet temperature and isentropic efficiency are compared with the numerical simulation results. The errors are less than 4 % and 10 %, respectively, which means that the prototype manufacturing precision meets the system requirements perfectly. Thus, the design of the two-stage series-connected turbine expanders can satisfy the performance design requirements.

Experimental study of hydrogen jet dynamics: Investigating free momentum and impingement phenomena

There is a growing interest in the utilization of hydrogen (H2), as a zero-carbon fuel, in internal combustion engines (ICEs). Accordingly, the primary focus of this study is to investigate low-pressure H2 jet dynamics, which play a vital role in air-fuel mixing especially in direct injection (DI) engines. High-speed z-type schlieren imaging is employed in a constant volume chamber to study the effect of nozzle geometry (single-hole, double-hole, and multi-hole), pressure ratios (PR = injection pressure (Pi)/chamber pressure (Pch)), injection angle (10°, 15°, and 20°), and injection duration (ID) on the H2 jet characteristics. Image post-processing is executed in MATLAB and Python to extract the H2 jet characteristics, including penetration and cross-sectional area. The novelty stems from the comprehensive investigation of H2 jet dynamics and impingement phenomenon under various engine-like conditions. The results indicate that apart from the fact that higher pressure ratios (PRs) improve the air-fuel mixing, the single-hole nozzle induces the fastest H2 jet penetration and the smallest cross-sectional area. Conversely, the double-hole nozzle leads to the slowest penetration and the most expansive cross-sectional area. The performance of the multi-hole nozzle falls between that of the single-hole and double-hole nozzles. Additionally, changing the injection angle results in jet-piston impingement at the periphery, leading to higher H2 concentration in those areas. This negatively affects the formation of an optimal air-fuel mixture. It is also found that changing the injection duration (ID) has no noticeable impact on the H2 jet's behavior.

Numerical study on altitude-compensating mechanism of a permeable nozzle

A conceptual adaptive altitude compensation nozzle with a permeable wall (permeable nozzle for short) is proposed in the present study. The typical operating states of the nozzle are demonstrated using numerical methods and the underlying mechanism of its altitude compensation is interpreted. The numerical results show that, at low nozzle pressure ratios, the external atmosphere enters the nozzle through its permeable wall section, which inhibits the backflow at the nozzle wall, weakens the strength of the separated oblique shock, thus improves the low-altitude thrust performance of the nozzle. However, at high nozzle pressure ratios, the exhaust gas leaves the nozzle through its permeable wall, which weakens the expansion of the exhaust gas and reduces the thrust performance. The permeable nozzle is considered to possess altitude compensation ability when the enhancement in its low-altitude thrust performance surpasses the deterioration in high-altitude thrust performance. The thrust composition analysis of the permeable nozzle reveals that its altitude compensation ability derives from the internal pressure rise due to the atmospheric air penetration into the nozzle at low nozzle pressure ratios.

Research and Application of Diesel Engine Turbocharging Technology in Plateau Environment

This article summarizes the changes and correction methods of turbocharger compressor characteristics in plateau environments, providing a basis for the plateau matching of diesel engines and turbochargers. Analyze the current research status of plateau matching between fixed cross-section turbochargers, variable cross-section turbochargers, and two-stage turbocharging systems and diesel engines, and explore the potential of variable cross-section turbocharging (VGT), ordinary two-stage turbocharging (TST), and adjustable two-stage turbocharging (RTST) for diesel engine plateau power improvement. Through comparative analysis, the two-stage adjustable turbocharging system based on VGT combines the advantages of two-stage turbocharging and VGT technology, and has the characteristics of high pressure ratio and wide flow rate, which can significantly improve the comprehensive performance of diesel engines on high altitudes.

Refrigeration experiments of gas wave rotor based on calibration-free WMS-TDLAS method

The refrigeration efficiency is mainly dependent on the low temperature generated by gas wave dynamics in oscillation channel. In this paper, a temperature rapid monitoring method for short light path based on the calibration-free wavelength modulation spectroscopy-tunable diode laser absorption spectroscopy (WMS-TDLAS) method is proposed. The selection of absorption wavelength, measurement procedure and data processing are specifically introduced. The wave dynamics and medium temperature under different pressure ratios and rotary speeds are studied, and the energy transfer efficiency of the gas wave refrigerator is evaluated. As the pressure ratio increases, the temperature in the cold zone behind the expansion wave gradually decreases to 257.6 K and the relative humidity of the cold zone inside the channel increases, which is caused by local condensation. At the same time, the expansion refrigeration efficiency is increasing from 27.3 % to 64.9 %. The increasing rotary speed of rotor also benefit to refrigeration efficiency from 45.8 % to 75.6 % as low temperature decreases to 252.1 K, which illustrates that rotary speed has more improvement effect on refrigeration efficiency than just higher-pressure ratio.

Study on Seismic Mechanical Properties of Reinforced Concrete Energy Dissipation Wall and Seismic Response Analysis of Structure

Utilizing the nonlinear finite element analysis software, ABAQUS, an examination is undertaken to evaluate the ductility characteristics and seismic design methodologies pertinent to a representative reinforced concrete hollow high pier. The research encompasses several focal areas: elucidation of seismic design strategies related to ductility categories, exploration of plastic energy dissipation mechanisms, determination of ductility indices, and delineation of structural measures to enhance ductility. Employing the nonlinear FEA software, ABAQUS, it is recommended that the longitudinal reinforcement ratio for ductile piers fall within the range of 0.6% to 4%. Furthermore, for flexible bridge piers, the maximum spacing of confinement reinforcements should either exceed 100 mm, be sixfold the diameter of the longitudinal reinforcement, or equate to at least one-quarter of the pier column’s bending direction section width. Combined with the influence of high pier ductility seismic axial pressure ratio, reinforcement, concrete factors such as factor analysis results, put forward and checking a reinforced concrete hollow high pier ductility seismic optimization scheme, increase the strength of the plastic hinge area section, through the comparative analysis in different seismic strength of plastic hinge unit cloth, maximum ductility coefficient and pier top displacement to verify its influence on the ductile seismic.

Equivalent notional nozzle model for high nozzle pressure ratio leakage of petrochemical high-pressure facility

Little work has been performed in the petrochemical safety field involving supersonic flows during accidental leakage in petroleum processing. The key technical challenge is on the changing process of gas cloud expansion after the jet. To address this, an equivalent notional nozzle model was developed for high single phase NPR (NPR＞2) gas leakage scenarios in petrochemical high-pressure facilities. This model aimed to determine the essential physical parameters of the equivalent cloud formed after air is drawn in with high NPRs. By utilizing CO2 as the gas phase, the validity of the equivalent notional nozzle model was assessed based on three crucial shock structure properties and the axial and radial velocity fields, the chocked flow intensity was applied as an indicator for the consistent trend of the jet velocity and decompression process of the high NPR gas leakage. The research findings unequivocally demonstrate the efficacy of the equivalent notional nozzle model in facilitating rapid numerical calculations for assessing the impact of high-pressure jets in the petrochemical industry.