High Pump Research Articles

Energy, exergy, energy-saving, economic and environmental analysis of a micro-gas turbine-PV/T combined cooling, heating and power (CCHP) system under different operation strategies: Transient simulation

A micro-gas turbine (MGT) combined cooling, heating and power system coupled with low concentrating photovoltaic/thermal-heat hump (LCPV/T-HP) and absorption chiller is proposed in this study. LCPV/T is used as the heat source of HP to realize mutual promotion. The performance of CCHP system under different operation strategies is dynamically simulated and analyzed by TRNSYS software from energy, exergy, energy-saving, economy and environment. The results demonstrate that both high temperature water source heat pump (HWHP) and low temperature water source heat pump (LWHP) achieved better COP in following electric load (FEL) mode. The average COP of HWHP and LWHP are 22.69% and 4.75% higher than the rated COP, respectively. Annual total cost per unit building area (ATCUBA) and carbon dioxide emissions per unit building area (CDEUBA) are also more advantageous in FEL mode, while primary energy consumption per unit building area (PECUBA), ATCUBA and CDEUBA seems less preferable in following thermal load (FTL) mode. The exergy efficiency and energy efficiency of the system in FEL mode are 19.96% and 41.90% in summer, and 25.13% and 59.36% in winter. Additionally, the equipment with higher exergy loss is mainly LCPV/T, gas-fired boiler, absorption refrigeration unit, MGT and hot water generator under the three operation strategies.

Energy absorbed from double quantum dot-metal nanoparticle hybrid system

This work proposes the double quantum dot (DQD)-metal nanoparticle (MNP) hybrid system for a high energy absorption rate. The structure is modeled using density matrix equations that consider the interaction between excitons and surface plasmons. The wetting layer (WL)-DQD transitions are considered, and the orthogonalized plane wave (OPW) between these transitions is considered. The DQD energy states and momentum calculations with OPW are the figure of merit recognizing this DQD-MNP work. The results show that at the high pump and probe application, the total absorption rate ({Q}_{tot}) of the DQD-MNP hybrid system is increased by reducing the distance between DQD-MNP. The high {Q}_{tot} obtained may relate to two reasons: first, the WL washes out modes other than the condensated main mode. Second, the high flexibility of manipulating DQD states compared to QD states results in more optical properties for DQD. The {Q}_{DQD} is increased at a small MNP radius on the contrary to the {Q}_{MNP} which is increased at a wider MNP radius. Under high tunneling, a broader blue shift in the {Q}_{tot} due to the destructive interference between fields is seen and the synchronization between {Q}_{MNP} and {Q}_{DQD} is destroyed. {Q}_{tot} for the DQD-MNP is increased by six orders while {Q}_{DQD} is by eight orders compared to the single QD-MNP hybrid system. The high absorption rate of the DQD-MNP hybrid system comes from the transition possibilities and flexibility of choosing the transitions in the DQD system, which strengthens the transitions and increases the linear and nonlinear optical properties. This will make the DQD-MNP hybrid systems preferable to QD-MNP systems.

Optimal Schedule the Operation Policy of a Pumped Energy Storage Plant Case Study Zimapán, México

Pumped-storage hydroelectric plants are an alternative to adapting the energy generation regimen to that of the demand, especially considering that the generation of intermittent clean energy provided by solar and wind power will cause greater differences between these two regimes. In this research, an optimal operation policy is determined through a simulation tool that allows the annual benefits under the energy arbitration service (purchase–sale) to be estimated, considering the variations of the energy price in Mexico. A case study is proposed in the Zimapán hydroelectric facility, where reservoir operation at the hourly level is simulated with records for a period of 3 years, considering historical values. The results establish that this type of pumped storage power plant obtains greater benefits by generating electrical energy during 8 h of high demand and pumping for more than 11 continuous hours in times of low demand. With this configuration, the PHES consumes 82.33 GWh/year more energy than it produces, and the energy generated is 210.83 GWh/year; however, when considering the energy arbitration service, a net income of more than USD 3.25 million per year is identified, which represents a 123.52% increase for the annual energy purchase.

Revealing the Evolution from Q-Switching to Mode-Locking in an Erbium-Doped Fiber Laser Using Tungsten Trioxide Saturable Absorber

Passively Q-switching and mode-locking technologies can generate short pulses with durations that differ by several orders of magnitude widely used in different applications. Recently, Q-switching and mode-locking realized in an identical laser cavity with saturable absorbers was reported. The analysis of pulse conversion is helpful for us to further understand the pulse dynamics of a laser. In this paper, the pulse evolution from Q-switching, Q-switched mode-locking to mode-locking, is demonstrated by using a tungsten trioxide saturable absorber in a ring-cavity erbium-doped fiber laser. Firstly, self-started Q-switching at 1563 nm is observed, the repetition rate continuously increases, and the duration decreases when the pump power increased. Then, with an adjusting intra-cavity state of polarization under a high pump power level, stable Q-switched mode-locking pulses evolved from Q-switching, are observed. The amplitude of the emerged pulse sequence with a period of 36.8 ns, determined by cavity length, is modulated by the Q-switched envelope with the period of 10.3 μs. By optimizing the intracavity polarization carefully, stable continuous wave mode-locking operation is achieved eventually. To the best of our knowledge, this is the first experimental demonstration of Q-switching and mode-locking, respectively, in an identical transition-metal-oxides-based pulsed fiber laser without modification of cavity structure.

A Multi‐Criteria Study of Optimal Working Fluids for High Temperature Heat Pumps

AbstractA bi‐objective optimization with respect to coefficient of performance (COP) and volumetric heating capacity (VHC) is performed for a high temperature heat pump. For fixed temperature levels of the heat source and sink, the values for temperature in the evaporator and condenser as well as the degree of vapor super‐heating and condensate sub‐cooling are optimized. Constraints are placed on the minimal pressure in the evaporator, the maximal pressure in the condenser and the compressor discharge temperature. Results are presented for a one‐stage and a two‐stage heat pump cycle. Cyclobutane and several butene isomers are identified as working fluids with a good compromise between COP and VHC from a CoMT‐CAMD approach based on PC‐SAFT and a realistic model for the ideal gas heat capacity.

Microsphere assisted pumping of the microchip laser for good output characteristics

The microsphere is directly coupled with a microchip laser for efficient pumping of the laser crystal without using bulky coupling optics. It produces high optical density pumping along the laser crystal resulting in laser emission with a reduced full width half maximum at low threshold pump power. Microsphere-assisted pumping of the continuous wave laser output provides higher optical efficiency of 57% with a pump power of 110 mW than the plain laser crystal, which is only about 10%. It can miniaturize existing microchip laser systems to produce low-cost portable handheld devices.

Butane-based heat pump for advanced GTCC applications: static and dynamic model validation

The Thermochemical Power Group (TPG) of the University of Genoa is investigating innovative solutions to increase the flexibility of gas turbine combined cycles (GTCC) and extend their operative range by integrating large size high performance heat pumps. Achieving this goal would make GTCCs more competitive in the future energy market, which will be characterized by a heavy presence of non-dispatchable renewable energy sources.Within this framework, the authors designed and built a new experimental facility to emulate advanced GTCCs at laboratory scale, integrating a 100 kWel micro gas turbine (MGT), a 10 kWel heat pump (HP) and a 180 kWh cold thermal energy storage (TES), with scale-up equations and dynamic models, capable of hardware-in-the-loop tests.The focus of this article is on the HP, which uses n-butane (R600) as working fluid and can be used both to heat and cool down the MGT compressor intake. The HP features one superheater and a 6-cylinder reciprocating compressor, which rotational speed can be continuously varied from 900rpm to 1800rpm.A dynamic model of the HP was developed in TRANSEO, with dedicated Matlab-Simulink® models. This model includes all the components of the HP closed loop, making it possible to simulate its performance and monitor all the main process parameters, such as compressor operation and condensing pressure. This model can be used to simulate the HP in various conditions, including part-load and transient operations, and to aid the design of the advanced GTCC control system. The evaporator and condenser models solve a system of non-linear equations to compute pressure, temperature, and distribution of the different phases of the working fluid along the heat exchangers. Such phase distribution is computed following a moving boundary approach.An experimental campaign was carried out to collect data regarding the stationary performance of the HP. Values of COP and thermal power were analysed as a function of compressor speed and pressure at the condenser, keeping the conditions at the evaporator constant. Then, its transient behaviour was characterized, observing its response to step changes of both evaporator and condenser thermal loads. The model was then successfully calibrated and validated on both stationary and transient data, showing good accuracy.Based on these results, it will be possible to integrate the HP model within larger system simulation tools. Having an accurate digital twin of the whole GTCC integrating HPs and TES will make possible to develop and verify complex control logics on many different scenarios, relying on a safe model-in-the-loop setup, before actual implementation in the field.

Efficient chip-based optical parametric oscillators from 590 nm to 1150 nm.

Optical parametric oscillators are widely used to generate coherent light at frequencies not accessible by conventional laser gain. However, chip-based parametric oscillators operating in the visible spectrum have suffered from pump-to-signal conversion efficiencies typically less than 0.1 %. Here, we demonstrate efficient optical parametric oscillators based on silicon nitride photonics that address frequencies between 260 THz (1150 nm) and 510 THz (590 nm). Pumping silicon nitride microrings near 385 THz (780 nm) yields monochromatic signal and idler waves with unprecedented output powers in this wavelength range. We estimate on-chip output powers (separately for the signal and idler) between 1 mW and 5 mW and conversion efficiencies reaching ≈15 %. Underlying this improved performance is our development of pulley waveguides for broadband near-critical coupling, which exploits a fundamental connection between the waveguide-resonator coupling rate and conversion efficiency. Finally, we find that mode competition reduces conversion efficiency at high pump powers, thereby constraining the maximum realizable output power. Our work proves that optical parametric oscillators built with integrated photonics can produce useful amounts of visible laser light with high efficiency.

Model-based optimization of Sliding Rotary Vane Pump for internal combustion engine cooling of heavy-duty vehicles

The reduction of CO2 and pollutant emissions of internal combustion engines (ICEs) keeping their performance close to the expectations is the main driver of the research in the transportation sector. To counteract the global warming issues international governments set strict emission limitations foreseeing severe penalties for exceeding them. The vehicle electrification surely helps to match these stringent requirements, but a net CO2 reduction can be achieved only if the electricity from the grid has low carbon content. This is not the case of most part of the Countries where the fossil fuels are still the main sources of electric energy production. Thus, considering also the still higher cost of the electric vehicles, the technological improvement of ICEs assumes a strategic importance in this transition period. Among the possible interventions ensuring to achieve this aim, the efficiency enhancement of ICE cooling pump is one of the most effective. As matter of fact, it is proven that the replacement of conventional centrifugal pump with Sliding Rotary Vane Pumps (SVRPs) lead to an interesting decrease of fuel consumption and CO2 emissions. Nevertheless, the design of this machines is not straightforward due to the complex thermo-fluid-dynamic phenomena taking place inside their chambers. This aspect is even more critical for wide operating range as in the case of heavy-duty vehicles. Here, high pump revolution speeds could be provided to satisfy the flow rate requirements thus involving efficiency deterioration due to friction losses enhancement. Therefore, to reduce the revolution speed needed by the pump to elaborate the required flow rate, a novel design strategy based on the enhancement of volumetric capability is presented. The pump resulting by this design approach was called Low Speed LS pump which was prototyped and experimentally characterized over a wide set of operating conditions. The indicated cycle was also measured to better assess the fluid-dynamic behaviour of the machine. The experimental results show a maximum efficiency close to 60% in accordance with the best literature results.

Colloidal Quantum Dot Infrared Lasers Featuring Sub-Single-Exciton Threshold and Very High Gain.

The use of colloidal quantum dots (CQDs) as a gain medium in infrared laser devices has been underpinned by the need for high pumping intensities, very short gain lifetimes, and low gain coefficients. Here, PbS/PbSSe core/alloyed-shell CQDs are employed as an infrared gain medium that results in highly suppressed Auger recombination with a lifetime of 485ps, lowering the amplified spontaneous emission (ASE) threshold down to 300µJcm-2 , and showing a record high net modal gain coefficient of 2180cm-1 . By doping these engineered core/shell CQDs up to nearly filling the first excited state, a significant reduction of optical gain threshold is demonstrated, measured by transient absorption, to an average-exciton population-per-dot 〈Nth 〉g of 0.45due to bleaching of the ground state absorption. This in turn have led to a fivefold reduction in ASE threshold at 〈Nth 〉ASE =0.70excitons-per-dot, associated with a gain lifetime of 280ps. Finally, these heterostructured QDs are used to achieve near-infrared lasing at 1670nm at a pump fluences corresponding to sub-single-exciton-per-dot threshold (〈Nth 〉Las =0.87). This work brings infrared CQD lasing thresholds on par to their visible counterparts, and paves the way toward solution-processed infrared laser diodes.

Optimization of collector area and storage volume in domestic solar water heating systems with on–off control—A thermal energy analysis based on a pre-specified system performance

Numerical simulations of solar water heating systems using on–off control were performed for four locations in the Portuguese territory, two collector types, and a wide range of parameters. Two main design parameters were considered: the collector area and the storage volume. An innovative technique was used to investigate the relationship between system performance and system parameters: a pre-specified annual solar fraction is selected and the optimal parameters needed to achieve this solar fraction are then computed. The optimum collector area is almost always higher for a double-glazed than for a single-glazed collector, suggesting that in Portugal, the single-glazed type is more effective for most solar water heating applications. This fact is more significant for lower solar fractions and warmer climates. A small increase in the optimum collector area leads to a very strong decrease in the optimum storage volume (an area increase of 1% leads to a volume decrease of 27%). Collector flow rate and storage volume increments result in lower collector areas. However, high flow rates lead to high pumping losses and lower collector efficiencies, and when the storage tank losses are significant, higher tank sizes may lead to higher collector areas. The solar fraction has a very strong impact on the collector area and storage volume (when the solar fraction increases from 0.5 to 0.99, the optimum collector area and storage volume increase about 17 and 56 times, respectively).

Comparison study of conventional and advanced exergy analysis on cascade high temperature heat pump system based on experiment

Cascade high temperature heat pump (CHTHP) has shown remarkable application potential for industrial waste heat recovery owing to its superiority of large temperature lift. Great efforts have been made to optimize the performance of CHTHP by means of conventional exergy analysis (CEA), which was not qualified to uncover the thermodynamic interactions among components. Thus, advanced exergy analysis (AEA) has been adopted to comparatively evaluate the relationships of reversibility among the CHTHP components. Herein, both CEA and AEA were based on the experiment results from a prototype which could realize maximum temperature lift of 100 °C.The CEA results show that total exergy efficiency is 43.23%, while AEA results indicate that endogenous part accounts for 98.27% of the total exergy destruction and 67.69% of it is avoidable. The AEA reveals that the highest improvement priority belongs to low temperature compressor (LTCOM), followed by cascade heat exchanger (CHE) and high temperature compressor (HTCOM) and that low temperature expansion valve (LTEV) and high temperature expansion valve (HTEV) has no improvement potential which is different from the results of CEA theory. Conclusively, AEA can give more detailed guidance about the potential for improvement.

The Combined Effects of the Membrane and Flow Channel Development on the Performance and Energy Footprint of Oil/Water Emulsion Filtration.

Membrane filtration is a promising technology for oil/water emulsion filtration due to its excellent removal efficiency of microdroplets of oil in water. However, its performance is highly limited due to the fouling-prone nature of oil droplets on hydrophobic membranes. Membrane filtration typically suffers from a low flux and high pumping energy. This study reports a combined approach to tackling the membrane fouling challenge in oil/water emulsion filtration via a membrane and a flow channel development. Two polysulfone (PSF)-based lab-made membranes, namely PSF- PSF-Nonsolvent induced phase separation (NIPS) and PSF-Vapor-induced phase separation (VIPS), were selected, and the flow channel was modified into a wavy path. They were assessed for the filtration of a synthetic oil/water emulsion. The results showed that the combined membrane and flow channel developments enhanced the clean water permeability with a combined increment of 105%, of which 34% was attributed to the increased effective filtration area due to the wavy flow channel. When evaluated for the filtration of an oil/water emulsion, a 355% permeability increment was achieved from 43 for the PSF-NIPS in the straight flow channel to 198 L m-2 h-1 bar-1 for the PSF-VIPS in the wavy flow channel. This remarkable performance increment was achieved thanks to the antifouling attribute of the developed membrane and enhanced local mixing by the wavy flow channel to limit the membrane fouling. The increase in the filtration performance was translated into up to 78.4% (0.00133 vs. 0.00615 kWh m-3) lower in pumping energy. The overall findings demonstrate a significant improvement by adopting multi-pronged approaches in tackling the challenge of membrane fouling for oil/water emulsion filtration, suggesting the potential of this approach to be applied for other feeds.

Gigahertz bursts with tunable pulse interval and pulse number based on sinusoidal saturable absorption

Optical pulse bursts are multiple pulses that arise from the balance between attractive and repulsive effects and are used for pulsed laser deposition, flow measurement, various micromachining, spectroscopic, and biomedicine. Different application fields have special requirements for the pulse burst, such as burst width, frequency, number of pulses per burst, and the pulse interval etc. Here, we propose and demonstrate the generation of GHz pulse bursts with both tunable pulse number and pulse interval in a nonlinear polarization rotation (NPR) mode-locked fiber laser for the first time. Taking advantage of the sinusoidal saturated absorption of the NPR, with the increase of pump power, only the number of pulses per burst increases one by one in a relatively low pump power range, while only the pulse interval increases gradually in a high pump power range. In addition, one pulse burst with a 22.8-GHz repetition rate is achieved, which is the highest intra-burst repetition rate directly obtained in all-fiber lasers to the best of our knowledge. The numerical results agree qualitatively well with the experiments. Our work gives an insight into the formation of pulse bursts in mode-locked fiber lasers.

Groundwater Level Forecasting in the Jakarta Groundwater Basin

Groundwater is an important source of fresh water worldwide. Jakarta, the capital city of the Republic of Indonesia, is a large city with a population of more than 10 million and the center of the country’s economy and urban development. However, Jakarta has many challenges related to groundwater management. Changes in well GWL serve as a direct indicator of the effects of groundwater evolution, and GWL time series usually contain important information about aquifer dynamics. Therefore, water managers and engineers must model and predict GWL, identify and measure groundwater resources, and maintain a balance between supply and demand. Measuring and analyzing the groundwater table (GWL) of an aquifer are an important and valuable activity in the management of groundwater resources, and information on GWL variability can be used to determine groundwater availability. Accurate and reliable groundwater level estimation is very important because it provides important information about the quantitative groundwater status of an aquifer. The main advantage of AI models is their ability to reproduce nonlinear and complex processes without a full understanding of the underlying physics. As a result, the use of AI techniques in GWL modeling continues to grow, attracting the attention of scientists around the world. Using a nonlinear autoregressive network with extrinsic input (NARX) with a timestep of 14 days, this study is aimed at predicting the volatility of Jakarta’s GWL. Based on the research results, both JKT-01 and JKT-03 show a linear downward trend. On the other hand, JKT-02 and JKT-04 show a stable linear trend. GWL increases the linear trend of JKT-05. Variable results are generated by model performance. Model performance ( R ) varied between 0.2 and 0.9 during the training phase and between 0.2 and 0.9 during the validation phase. The overall performance of the model varies from 0.3 to 0.9. The diverse lithology and high pumping capacity in Jakarta are the reasons for the different modeling results. Forecasts for 14 days (14 timesteps) show that GWL remains constant at certain well locations, while GWL decreases at other locations. This is a consideration that stakeholders can consider to reduce the small effect of the daily GWL pattern as a result of NARX modeling.

Design and simulation of widely tunable picosecond synchronously pumped terahertz parametric oscillator based on silicon waveguide platform

AbstractA picosecond synchronously pumped terahertz optical parametric oscillator based on silicon membrane waveguide (Si‐based WTPO) is proposed and numerically simulated. Through designing the structure parameters of the silicon membrane waveguide, a broadband terahertz frequency range is obtained by satisfying the phase matching condition. The parametric oscillation process and output characteristics of Si‐based WTPO are numerically analyzed by solving the four‐wave mixing coupled‐wave equations, and the result has indicated that the parametric oscillation within the resonant cavity can apparently enhance the output terahertz wave power. Meanwhile, high bandwidth and efficiency output terahertz wave can be obtained, and too high pump power will lead to a reaction of reverse conversion. Finally, the threshold pump power is calculated. The Si‐based WTPO system we proposed is expected to make some contributions to the study of compact and efficient terahertz wave sources.

PMON40 A Rare Etiology of Chronic Diarrhea: Zollinger-Ellison Syndrome

Abstract Introduction Zollinger-Ellison Syndrome (ZES) is a rare etiology of chronic diarrhea caused by a gastrin-secreting neuroendocrine tumor. Early suspicion can prevent multiple readmissions for recurrent diarrhea thus improving clinical outcomes through prompt diagnosis and treatment, as the following case highlights. Case presentation A 74-year-old African-American female with hypertension and chronic atrial fibrillation presented to the ED complaining of watery, non-bloody diarrhea for the past 3 weeks. She reports her symptoms worsened after completing a course of amoxicillin for pharyngitis one week prior. On further questioning, she reported intermittent diarrhea for over 20 years lasting approximately two days per episode. She denied recent travel, sick contacts, pet reptiles, and recent ingestion of undercooked meat. On arrival, she was afebrile and hemodynamically stable. She was admitted for an acute kidney injury with an elevated creatinine of 3.23 mg/dL (N: 0.6-1.1 mg/dL) due to dehydration. Her renal function improved with fluids, but she developed bloody diarrhea for which gastroenterology was consulted. Stool studies were negative for Shiga-toxin, C. difficile, lactoferrin, and parasites. Computed Tomography of the abdomen showed enteritis with fluid noted throughout the colon consistent with colitis. Unprepped colonoscopy revealed blood throughout the length of the colon, suggestive of an upper gastrointestinal bleed. Esophagogastroduodenoscopy (EGD) revealed multiple bleeding duodenal ulcers controlled with hemostasis. Her symptoms improved and she was discharged home on oral pantoprazole, and told to follow up outpatient. Two weeks later, she denied any new episodes of diarrhea, and a random serum gastrin level was elevated at 413 pg/mL (N: <180 pg/mL). Repeat gastrin level off pantoprazole for 7 days was also elevated at 678 pg/mL, and a serum Chromogranin A level was elevated at 629 pg/mL (N: <390 pg/mL). Repeat EGD found her Gastric pH to be 1 with multiple non-bleeding duodenal ulcers. Somatostatin receptor scintigraphy revealed a high intensity signal consistent with a duodenal gastrinoma causing ZES. She elected for surgical resection, and was discharged home on high dose pantoprazole. Three months later, she stated that her diarrhea had completely resolved. Conclusion This case confirms ZES as a rare cause of chronic diarrhea in the setting of multiple duodenal ulcers refractory to proton pump inhibitors. Diagnosis can be made with a fasting serum gastrin level >1000 pg/mL or >400 pg/mL with a gastric pH <1. A Secretin Stimulation Testing can also be used. Treatment starts with high dose proton pump inhibitors, octreotide for hormonal regulation, and surgical resection if necessary. Presentation: Monday, June 13, 2022 12:30 p.m. - 2:30 p.m.

Anomalous Dynamics of Defect-Assisted Phonon Recycling in Few-Layer Mo0.5W0.5S2.

Alloying has emerged as a new strategy to tune the function of 2D transition metal dichalcogenides (TMDCs). However, the lack of research on the electrical and structural properties of these alloys limits their practical applications. Here, femtosecond transient absorption spectroscopy with pump pulse tunability is performed to elucidate the ultrafast carrier dynamics in the few-layer Mo0.5W0.5S2 prepared by the liquid phase exfoliation method. An anomalous rebleaching of the ground state is observed at high pump fluence by 3.1 eV excitation. We ascribe this rebleaching of the ground state to the mechanism that the carriers trapped in the defect are thermally excited back to the untrapped exciton state due to the phonon recycling, which hinders the dissipation of nonradiative energy, through comparative experiments and global analysis. Our findings demonstrate a novel energy transfer channel assisted by defect in few-layer TMDCs which is critical for their advanced applications.

962 nm LD end-pumped Er:YSGG cascade pulsed lasers at room temperature

We demonstrate a pulsed cascade laser on LD end-pumped Er:YSGG crystal near 1.6 and 2.8 μm at room temperature for the first time. The slope efficiency of mid-infrared laser with the assistance of cascade process is significantly improved. Under the working frequency of 100 Hz and pump pulse width of 6 ms, a maximum power of 243 mW centered at 2.79 μm is achieved with increasing slope efficiency of 4.2 %, while the slope efficiency of non-cascade is only 1.9 %. Under high pump power, four laser wavelengths of 2.793, 2.821, ∼2.860, and 2.918 μm are discovered and the phenomenon is explained according to the Boltzmann factors. This work would be conducive to the exploration of pulsed cascade laser based on the Er:YSGG crystal.

Numerical study on static performance of hydrodynamic bearing in high-speed liquid hydrogen centrifugal pump

High speed liquid hydrogen centrifugal pump is regarded as one of the most potential transmitting equipment in hydrogen distribution. Due to the cryogenic physical properties of liquid hydrogen, lubrication in the high-speed pump remains a challenge for its further application. In this paper, a novel grooved bearing using liquid hydrogen as lubricant has been proposed for long term reliable operation. Static performances of the bearing, including pressure distribution, vapor volume fraction and load capacity, have been evaluated numerically focusing on the cavitation effect. Considering the coupled effects in the bearing, orthogonal design method is used to optimize the structural parameters. With the optimal parameters, the load capacities of both journal and thrust bearing can be improved by 30% and 50%, respectively. In addition, the optimized coupled bearing can suppress the cavitation effectively, which is expected to be used in high-speed centrifugal pump with long-term and stable operation.