High Pump Research Articles

An Impeller Optimization Method for the High Specific Speed Mixed-Flow Reactor Coolant Pump Applied to Marine Nuclear Power

The reactor coolant pump (RCP) is the only rotating equipment in the primary circuit system of a nuclear power plant and the “heart” of the nuclear reactor. The L formula is defined, and the L/himp is introduced to study the influence of impeller blade type on the performance of the RCP. Twenty groups of models are designed, the concept of arc height ratio is proposed from the perspective of himp and L, and the distribution of internal entropy production within the impeller of the RCP under different Ls and himps of the impeller blade type is analyzed. The results show that when himp remains un-changed and L increases, the low-pressure area at the inlet of the impeller expands while the high-pressure area at the outlet decreases under the design flow or large flow conditions. The smoother blade profile reduces the occurrence of secondary flow phenomena and makes the RCP pressure distribution more uniform. Under design flow and large flow conditions, smaller L/himp and higher himp lead to higher efficiency and head performance. However, higher efficiency and lower head performance can be achieved under small flow conditions with larger L/himp and lower himp.

Reducing industrial hydrogen demand through preheating with very high temperature heat pumps

Decarbonising industry while maintaining economic competitiveness and improving living standards is one of the main challenges of reaching net zero targets, and low-carbon process heating will play a key role in this. In this work we investigate the potential to reduce the energy demands of hydrogen-based industrial heating systems using very high temperature reverse Joule-Brayton cycle heat pumps as preheaters, considering their economics and technical challenges. A thermodynamic process model is used to assess performance at temperatures of 300–500 °C, and cost optimisation is used to conduct cost-benefit analysis of preheating green hydrogen using heat pumps. It is found that over this temperature range, heat pump coefficient of performance lies in the range 1.4–1.7, with the turbine meeting 30–40% of the compressor load. At the electricity prices currently paid by heavy industry in Western Europe, levelised cost of heat from these heat pumps would be less than 4.5p/kWh. Using 500 °C heat pumps as preheaters in hydrogen heating systems could reduce hydrogen demands by over 20% and provide savings on the cost of green hydrogen of at least 8% out to 2050. With process heat accounting for three-quarters of industrial energy use and half of this being at temperatures above 400 °C, these savings are significant and suggest that very high temperature heat pumps could make an important contribution to industrial decarbonisation.

Large regenerative parametric amplification on chip at ultra-low pump powers

Chip-based optical amplifiers can significantly expand the functionalities of photonic devices. In particular, optical-parametric amplifiers (OPAs), with engineerable gain spectra, are well suited for nonlinear-photonic applications. Chip-based OPAs typically require long waveguides that occupy a large footprint, and high pump powers that cannot be easily produced with chip-scale lasers. We theoretically and experimentally demonstrate a microresonator-assisted regenerative OPA that benefits from the large nonlinearity enhancement of microresonators and yields a high gain in a small footprint. We achieve 30-dB parametric gain with only 9 mW of cw pump power and show that the gain spectrum can be engineered to cover telecom channels inaccessible with Er-based amplifiers. We further demonstrate the amplification of Kerr-soliton comb lines and the preservation of their phase properties. Additionally, we demonstrate amplification by injection locking of optical parametric oscillators (OPOs), which corresponds to a regenerative amplifier pumped above the oscillation threshold. Dispersion engineering techniques such as coupled cavities and higher-order-dispersion phase matching can further extend the tunability and spectral coverage of our amplification schemes. The combination of high gain, small footprint, low pump power, and flexible gain-spectrum engineering of our regenerative OPA is ideal for amplifying signals from the nanowatt to microwatt regimes for portable or space-based devices where ultralow electrical power levels are required and can lead to important applications in on-chip optical-, and microwave-frequency synthesis and precise timekeeping.

Fiber-optic frequency comb generation using low-seed power FWM and Brillouin-assisted power equalization.

In this paper, we experimentally demonstrate an all-fiber broadband tunable optical frequency comb (OFC) operating in the C-band. The OFC is generated by broadening a power-equalized stimulated Brillouin scattering (SBS)-based seed comb (SBS-OFC) using four-wave mixing (FWM) in a highly nonlinear fiber (HNLF). The seed SBS-OFC is obtained from a pump and Stokes power recycling cavity, which yields ≈15 comb lines with 10.8GHz line spacing having 16dBm average power. The seed SBS-OFC is further power-equalized by a Brillouin-assisted power equalization (BAPE) technique to minimize the high pump contribution at the recycling cavity output. The power-equalized seed SBS-OFC, which has low-power of -4.5d B m at the BAPE cavity output, is propagated down a dual-pass 200m dispersion flattened HNLF. At the HNLF output, we obtain ≈140 comb lines within a 12nm bandwidth having 10.8GHz line spacing. We demonstrate wavelength tunability over a span of 35nm by using a tunable laser source as the Brillouin pump. We also observe and measure a secondary OFC generated during the power-equalization process by placing a 10% coupler inside the BAPE cavity. Our experimental results closely match the trends obtained in the simulation.

Research on the Thermal Effect of Micro-Channel Cooled Thin-Slab Tm:YAP Lasers

Using the finite element method and the heat conduction equation, the temperature, stress, and end-face deformation in Tm:YAP crystal under high pump power were analyzed. Combined with gradient doping technology, an effective way to improve the internal heat distribution of the crystal was studied. The results showed that when the total pump power was 200 W, under the same cooling conditions, the maximum temperature difference inside Tm:YAP decreased from 58 K to 25 K after gradient doping. The thermal stress and end-face thermal deformation were also significantly improved. In addition, a reasonable micro-channel structure also effectively removed the heat generated inside the crystal.

Universality class of the mode-locked glassy random laser

By means of enhanced Monte Carlo numerical simulations parallelized on GPUs we study the critical properties of the spin-glass-like model for the mode-locked glassy random laser, a 44-spin model with complex spins with a global spherical constraint and quenched random interactions. Implementing two different boundary conditions for the mode frequencies we identify the critical points and the critical indices of the random lasing phase transition with finite size scaling techniques. The outcome of the scaling analysis is that the mode-locked random laser universality class is compatible with a mean-field one, though different from the mean-field class of the Random Energy Model and of the glassy random laser in the narrow band approximation, that is, the fully connected version of the present model. The low temperature (high pumping) phase is finally characterized by means of the overlap distribution and evidence for the onset of replica symmetry breaking in the lasing regime is provided.

Enhanced Exhaust after-Treatment Warmup in a Heavy-Duty Diesel Engine System via Miller Cycle and Delayed Exhaust Valve Opening

The exhaust after-treatment (EAT) threshold temperature is a significant concern for highway vehicles to meet the strict emission norms. Particularly at cold engine start and low loads, EAT needs to be improved above 250 °C to reduce the tailpipe emission rates. Conventional strategies such as electrical heating, exhaust throttling, or late fuel injection mostly need a high fuel penalty for fast EAT warmup. The objective of this work is to demonstrate using a numerical model that a combination of the Miller cycle and delayed exhaust valve opening (DEVO) can improve the tradeoff between EAT warmup and fuel consumption penalty. A relatively low-load working condition (1200 RPM speed and 2.5 bar BMEP) is maintained in the diesel engine model. The Miller cycle via retarded intake valve closure (RIVC) is noticeably effective in increasing exhaust temperature (as high as 55 °C). However, it also dramatically reduces the exhaust flow rate (over 30%) and, thus, is ineffective for rapid EAT warmup. DEVO has the potential to enhance EAT warmup via increased exhaust temperature and increased exhaust flow rate. However, it considerably decreases the brake thermal efficiency (BTE)—by up to 5%—due to high pumping loss in the system. The RIVC + DEVO combined technique can elevate the exhaust temperature above 250 °C with improved fuel consumption—up to 10%—compared to DEVO alone as it requires a relatively lower rise in pumping loss. The combined method is also superior to RIVC alone. Unlike RIVC alone, the RIVC + DEVO combined mode does not need the extreme use of RIVC to increase engine-out temperature above 250 °C and, thus, provides relatively higher heat transfer rates (up to 103%) to the EAT system through a higher exhaust flow rate. The RIVC + DEVO combined method can be technically more difficult to implement compared to other methods. However, it has the potential to maintain accelerated EAT warmup with improved BTE and, thus, can keep emission rates at low levels during cold start and low loads.

A High Peak-efficiency Cross-coupled Charge Pump with Low Input Voltage for Energy Harvesting System

A high-efficient, low-voltage cross-coupled charge pump is presented in this paper. To decrease the conduction loss, a cross-coupled charge pump is proposed based on two auxiliary dynamic inverters to increase the clock swing. Meanwhile, a clocking scheme is designed to eliminate the reversion power losses. Based on proposed scheme, a higher output voltage is achieved by a three-stage topology by cascading the single stage. The proposed architectures of both single and three-stage charge pump are implemented under a standard 180nm CMOS technology. The post-layout simulation exhibits a peak power efficiency of 86.89% and 78.6%, respectively. And Monte Carlo (MC) simulation results indicate the proposed scheme features strong robustness to process variation.

Experimental study on hydraulic fracture propagation behavior of horizontal well on multilayered rock

A series of true axial hydraulic fracturing experiments were conducted to understand the complex hydraulic fracture initiation and propagation behavior of multilayered rocks. Moreover, a new and convenient grid measurement method was presented to describe hydraulic fracturing effectiveness. The experimental results revealed that transverse vertical and non-planar axial fractures could be created in the hydraulic fracturing of multilayered rocks. Moreover, the fracture area scanning results by the grid measurement method match the results indicated by the traditional Geomagic method. The fracture behavior close to the layer contact determines how complex the produced fishbone structure fracture system is. Near the hole zones, secondary axial and deviated transverse fractures were found due to multiple layers. The fracture system can be managed by modifying the fracturing treatment parameters. Low-principle horizontal stress contrast and low-viscosity fracturing fluid can produce complicated fractures, and an increase in perforation numbers can make the fracture more complex and produce abnormally high breakdown pressure. Larger fracture areas benefit from high perforation rates and pump rates, but larger fracture areas may not always benefit from a decreased fracturing fluid viscosity. The breakdown pressure was the highest for the samples with two sets of oriented perforations, and the stress shadowing effect should be considered in the multiple fracture treatment. The increase in the pump rate generates a more complex fracture path in the horizontal well despite the fracturing fluid types but also yields a high breakdown pressure. The increased fracturing fluid viscosity can constrain the random fracture extension, which is beneficial for decreasing the near-wellbore tortuosity. The occurrence of shear fracture along the interface in a multilayered formation could be a risk for proppant injection and placement.

ID: 212146 High Dose Intrathecal Pump Weaning and Surgical Explantation Strategy Following Delayed Intramedullary Catheter Recognition

A potential risk of intrathecal drug delivery (ITDD) is intramedullary catheter placement. This is generally recognized early, but we present a rare case of an intramedullary catheter in a patient with left lower extremity (LLE) chronic regional pain syndrome II (CRPS II) found 3 years after implantation.1,2

Longitudinal wall motion during peristalsis and its effect on reflux

In this study, for the first time, we consider longitudinal motion of the walls during peristalsis in a distensible tube and how this affects backward (or retrograde) flow, i.e. peristaltic reflux. Building on the analytical model developed by Shapiro et al. (J. Fluid Mech., vol. 37, no. 4, 1969, pp. 799–825) based on lubrication theory, we model peristalsis as a two-dimensional infinite sinusoidal wavetrain. We develop an objective function with high mechanical pumping efficiency and low reflux to find optimal peristalsis conditions. We show that optimal wall longitudinal motion contributes substantially to limiting reflux during peristalsis. The results suggest that the optimal form of wall longitudinal velocity is a linear function of the wall transverse coordinate, moving forward with the wave when the tube is distended and retracting when contracted. Our results are in general agreement with clinical observations of ureteral peristalsis.

Generation of vortex N 2 <i/> + lasing

Harnessing structured light is fascinating for its multidisciplinary applications, e.g., in remote driving microrobots, sensing, communications, and ultrahigh resolution imaging. Here, we experimentally demonstrated the generation of a vortex N2+ lasing pumped by a wavefront structured near-IR femtosecond pulse with orbital angular momentum. The topological charge of the N2+ lasing was measured to be twofold that of the pump beam. Compared to the case with a pump beam of a plane wavefront, the N2+ lasing generation efficiency is much higher for the vortex pump beam at high pumping energy, which has a higher clamping intensity by reducing the on-axis plasma density. Our results herald a march toward remote structured N2+ lasing.

Multipole polarization assisted optical bistability in a semiconductor quantum dot/metal nanoparticle hybrid molecule

We theoretically study the optical bistability assisted by multipole polarizations in a semiconductor quantum dot (SQD)/metal nanoparticle (MNP) hybrid molecule. We map out bistability phase diagrams within the parameter subspace spanned by (the pumping intensity Ipu, interparticle distance, d) under dipole and multipole approximations. It is shown that the Ipu-correlated bistable region will be broadened greatly in the strong exciton–plasmon coupling regime, and the corresponding lower (upper) bistable threshold is enlarged significantly due to multipole polarization (N = 10) in comparison to that in the dipole approximation (N = 1). However, under the same conditions, the d-correlated bistable region is shrunk at high pump intensities. Our contribution not only offers a better understanding of exciton–plasmon coupling systems but also expands the application of SQD/MNP hybrid molecules in the field of optical bistable nanodevices.

Improving clinical outcomes of Barrett’s esophagus with high dose proton pump inhibitors and cryoablation

Introduction Esophageal adenocarcinoma incidence has increased significantly despite surveillance endoscopy for Barrett’s esophagus (BE) and gastric acid supression medications. This prospective, cohort study’s aims were to determine the long-term efficacy of proton-pump inhibitors twice daily (PPI-BID) with cryotherapy (CRYO) for complete ablation of BE. Materials and Methods Consecutive BE patients were managed with a PPI-BID, CRYO ablation, follow-up protocol. Primary outcomes were to determine complete ablation rate of intestinal metaplasia (IM) or dysplasia/carcinoma, and factors affecting recurrence. Results Sixty-two patients were enrolled: advanced disease (11%), low-grade or indefinite dysplasia (26%), non-dysplastic BE (63%). In 58 completing CRYO, eradication was confirmed in 100% on surveillance endoscopy. Adverse events (5%) were minor (mild pain 4%). IM recurred in 9% after a mean of 52 months, all successfully re-ablated. No second recurrence occurred. The primary predictor of recurrence was noncompliance with PPI-BID. BE or cardia IM recurred in 35% of those taking proton pump inhibitors once daily or less compared with 0% in those on PPI-BID or dexlansoprazole daily (p<.001). Conclusions Minimizing acid reflux with at least PPI-BID combined with CRYO ablation appears to be the optimal cost-effective and safe BE treatment for any stage to minimize progression to adenocarcinoma by addressing both the stimulus that causes BE and the presence of goblet cells.

Laparoscopic Nissen Fundoplication

After medical management with high dose proton pump inhibitors proves to be refractory, a 63-year-old man with gastroesophageal reflux disease (GERD) prese

Multimode Graded Index Fiber with Random Array of Bragg Gratings and Its Raman Lasing Properties

Light propagation in multimode fibers is known to experience various nonlinear effects, which are being actively studied. One of the interesting effects is the brightness enhancement at the Raman conversion of the multimode beam in graded index (GRIN) fiber due to beam cleanup at Raman amplification and mode selective feedback in the Raman laser cavity based on fiber Bragg gratings (FBGs) with special transverse structure. It is also possible to explore random distributed feedback based on Rayleigh backscattering on natural refractive index fluctuations in GRIN fibers, but it is rather weak, requiring very high power multimode pumping for random lasing. Here, we report on the first realization of femtosecond pulse-inscribed arrays of weak randomly spaced FBGs in GRIN fibers and study Raman lasing at its direct pumping by highly multimode (M2~34) 940-nm laser diodes. The fabricated 1D–3D FBG arrays are used as a complex output mirror, together with the highly reflective input FBG in 1-km fiber. Above threshold pump power (~100 W), random lasing of the Stokes beam at 976 nm is obtained with output power exceeding 28 W at 174 W pumping. The beam quality parameter varies for different arrays, reaching M2~2 at the linewidth narrowing to 0.1–0.2 nm due to the interference effects, with the best characteristics for the 2D array.

Ultrafast dynamics of optically excited charge carriers in the room-temperature antiferromagnetic semiconductor α−MnTe

We report on time-resolved optical and terahertz ultrafast spectroscopy of charge-carrier dynamics in the room-temperature antiferromagnetic semiconductor $\ensuremath{\alpha}$-MnTe. By optically pumping the system with 1.55 eV photons at room temperature, we excite charge carriers in the conduction band through the indirect band gap and investigate the dynamical response of the nonequilibrium states using optical as well as terahertz transmission probes. Three relaxation processes are revealed by their characteristic relaxation times of the order of 1, 10, and 100 ps, whose exact values are a function of the pump fluence. For high pump fluences a nonlinear dependence on the pump fluence is observed both in the optical and terahertz probes.

Nonlinear operational optimization of an industrial power-to-heat system with a high temperature heat pump, a thermal energy storage and wind energy

The heat demand for industrial processes is often provided in the form of steam generated by various fossil fueled equipment. In order to reduce CO2 emissions, the heat demand has to be covered by renewable energy sources. Electrified steam generation relies on complex energy systems, that can be operated according to energy availability and cost developments. However, such a multi component industrial energy system poses a challenge in modeling and determining the cost- or emission-optimal operation of the system. This study develops a methodology to model a multi component industrial energy system on the basis of a case study. By optimal system operation, either costs or emissions are minimized in response to fluctuating renewable wind energy and electricity prices.A high temperature heat pump (HTHP), a sensible thermal energy storage (TES) and a wind turbine are combined to create an electrified energy system to supply super-heated steam. During periods of low wind speed, additional grid electricity is purchased to ensure a steady heat supply. The HTHP offers a high operational flexibility and thus, enables the charging and discharging of the TES. A model of the closed reverse Brayton cycle HTHP, which is able to simulate part load behavior, is created in a process simulation software and consolidated in nonlinear surrogate models. The component behavior of a TES is represented by a combination of equations based on heat exchanger relations. Finally, the resulting algebraic nonconvex, nonlinear optimization problem based on the proposed system is solved using the local interior point optimizer (IPOPT) solver equipped with a multi-start approach to determine an optimal operation over a reference week with respect to the current wind power generation, grid emissions and electricity prices.The results of the optimization show, that optimal operating strategies enable a high potential to decarbonize future industries at minimum operational costs or emissions.

Zeotropic mixtures R1234ze(Z)/acetone and R1234ze(Z)/isohexane as refrigerants in high temperature heat pumps: Influence of the accuracy in thermodynamic properties evaluations

High temperature heat pumps (HTHPs) represent an interesting option to upgrade waste heat up to 200 °C for industrial application. In order to achieve such high temperatures, suitable refrigerants are needed. In this paper, two zeotropic mixtures composed of a hydrofluoro-olefin (HFO) and a hydrocarbon, namely R1234ze(Z)/acetone and R1234ze(Z)/isohexane, were examined as the refrigerant for HTHP applications. The main objective of the present study is to determine the binary interaction parameters (BIPs) of the two zeotropic mixtures from experimentally-determined thermodynamic properties and analyze how HTHP performance assessment would change after tuning the BIPs. For R1234ze(Z)/acetone, after tuning the BIPs, the phase change temperature glide did not change that much. However, the composition corresponding to the highest temperature glide changed significantly. On the other hand, for R1234ze(Z)/isohexane, the phase change temperature glide changed significantly with tuned BIPs, while the composition for the maximum temperature glide was quite similar in the two cases. A thermodynamic optimization framework was used for simulation of the HTHP cycle. Simulation results using estimated BIPs showed that for R1234ze(Z)/acetone the optimum coefficient of performance (COP) was 3.95, while it slightly changed to 3.94 (around 0.25% change) after tuning the BIPs. However, the optimum composition of the mixture was quite different for the estimated and fitted BIPs. For R1234ze(Z)/isohexane the COP was 3.90 using estimated BIPs, while it changed to 3.83 (around 1.7% change) once the fitted BIPs were used. These results indicate the importance of tuning the BIPs for zeotropic mixtures and different impacts depending on the performance parameters analysed.

Thermodynamic performance of heat pump with R1234ze(E)/R1336mzz(E) binary refrigerant

In order to solve the temperature mismatch issue of cold and hot fluids in evaporation and condensation processes for heat pump system, binary refrigerant R1234ze(E)/R1336mzz is recommended in the present research due to its large temperature glide. Through theoretical analysis, multiple configurations under conditions of three different temperature heat sources (70/50 °C, 60/40 °C and 50/30 °C) and two different heat targets (steam above 100 °C and hot water with 70 °C) are constructed adopted Ebsilon code. The optimum mass proportion is obtained as 0.3/0.7 for R1234ze(E)/R1336mzz(E), because of its maximum temperature glide (can reach 21.52 °C) and excellent thermal performance (large COP, ECOP and exergy efficiency). COP of steam high temperature heat pump with R1234ze(E)(0.3)/R1336mzz(E)(0.7) binary refrigerant and the ratio of transferred heat of 110 °C condenser to all output heat (containing 110 °C and 100 °C steam intercooler and condensers) respectively increase up to 67.25% and 335.16% under some certain conditions, compared with that with pure R1336mzz(E). COP of hot water heat pump with R1234ze(E)(0.3)/R1336mzz(E)(0.7) binary refrigerant are respectively 10.31 and 6.89 under 60/40 °C and 50/30 °C heat source conditions, which greatly increases compared with that of heat pump with pure R1234ze(E) (6.67 and 5.03) and R1336mzz(E) (6.74 and 4.54). The present research may lay a foundation for binary refrigerant adoption to replace the scheme of multi-stage evaporator or multi-stage condenser, which could reduce the irreversible loss of phase change equipment and improve thermodynamic performance of heat pumps.