Dual-stage Configuration Research Articles

Design and performance investigation of a triple blade dual stage Savonius-alike hydrokinetic turbine from low flow stream reserves

ABSTRACT A trending technology that is being employed to generate hydro energy from low-flow stream reserves is the Savonius-alike hydrokinetic turbine (SAHT). Clearance between the stages of a dual-stage two-bladed SAHT was found to improve its performance at low flow speeds; however, the impact of clearance on the triple-bladed configuration of SAHT was not studied earlier. In this paper, a triple blade dual stage configuration of SAHT is designed, and its performance is investigated in a water flume under various stage clearances (0,5,10,15 and 20 mm), low flow speeds (0.45,0.55 and 0.65 m/s) and different brake loads. Detailed turbine performance under different design and off-design conditions are investigated to obtain meaningful performance insights. The findings show that torque production by the turbine increases with the increase of brake load, with maximum hydrodynamic torque generated at the highest brake load. The highest coefficient of performance and torque of 0.071 and 0.261 are obtained at a stage clearance of 5 mm, tip speed ratio of 0.273, and free-stream flow speed of 0.55 m/s. The present SAHT under design condition has improved performance compared to a dual blade dual stage SAHT exhibiting a wider tip speed ratio range for its application in low flow stream reserves. Further, this turbine may also be recommended for torque generation to work as a motor in a flow speed condition less than 0.5 m/s. The novelty of this work is the application of an additional flow control measure in the form of flow-through clearance to negotiate vertical water thrust through the clearance and exert additional pressure on the advancing blades of the SAHT in the upper stage.

Performance analysis of dual-stage vertical axis hydrokinetic turbine (VAHT) with azimuth variation at open canal hydrokinetic power plant

For several decades, the use of hydropower generation using hydrokinetic turbines has grown rapidly, aiming to get energy alternatives and reduce the dependency on fossil energy. Despite it has low efficiency, the vertical axis hydrokinetic turbine (VAHT) has been used to utilize hydro energy and has a promising result. A previous study had stated that the utilization of cascaded blade enhances the performance of VAHT. However, this technology produces fluctuating torque and power during its rotation. Hence the dual-stage VAHT is proposed to overcome this issue to improve VAHT’s efficiency. This research analyzes the dual-stage VAHT’s performances by variating its inter-stage azimuth of 45°, 60°, 75°, and 90°. For each stage, there is six blades that attach at three arms. The computational fluid dynamics (CFD) simulation is employed as its capability to provide in-depth information regarding flow phenomenon, force, and torque. This simulation has proven that the dual-stage configuration has an impact on reducing torque fluctuation of VAHT and show that different of inter-stage azimuth angle brings to different torque fluctuation pattern. The average torque value produced by the new turbine with variations in shift between stages of 45°, 60°, 75° and 90° is 10,119.21 Nm, 10,656.13 Nm, 10,490.31 Nm, and 10,457.3 Nm, respectively.

A 23.3 dBm CMOS power amplifier with third-order gm cancellation linearization technique achieving OIP3 of 34 dBm

PurposeThe purpose of this paper is to implement a highly linear 180 nm complementary metal oxide semiconductor (CMOS) power amplifier (PA) to meet the stringent linearity requirement of an long term evolution (LTE) signal with minimum trade-off to power added efficiency (PAE).Design/methodology/approachThe CMOS PA is designed in a cascaded dual-stage configuration comprises a driver amplifier and a main PA. The gate voltage (VGS) of the driver amplifier is tuned to optimize its positive third-order transconductance (gm3) to be canceled with the main PA’s fixed negative gm3. The gm3 cancellation between these stages mitigates the third-order intermodulation product (IMD3) that contributes to enhanced linearity.FindingsFor driver’s VGS of 0.82 V with continuous wave signal, the proposed PA achieved a power gain of 14.5 dB with a peak PAE of 31.8% and a saturated output power of 23.3 dBm at 2.45 GHz. A maximum third-order output intercept point of 34 dBm is achieved at 20.2 dBm output power with a corresponding IMD3 of −33.4 dBc. When tested with a 20 MHz LTE signal, the PA delivers 19 dBm maximum linear output power for an adjacent channel leakage ratio specification of −30 dBc.Originality/valueIn this study, a novel cascaded gm3 cancellation technique has been implemented to achieve a maximum linear output power under modulated signals.

Enhanced triple-pass hybrid erbium doped fiber amplifier using distribution pumping scheme in a dual-stage configuration

An enhanced triple-pass hybrid optical fiber amplifier in a dual-stage configuration is presented by utilizing a combination of hafnium-bismuth erbium-doped fiber (HB-EDF) and bismuth erbium-doped fiber (Bi-EDF) as gain medium. The total Erbium-doped fiber length was only 199 cm, and both HB-EDF and Bi-EDF were forward pumped by 1480 nm with an optimum pump power of 170 mW and 110 mW, respectively to provide flat gain and wideband amplification. At high input power of -10 dBm, a flat gain of about 19 dB with gain fluctuation of less than 2 dB was observed over wideband ranging from 1555–1600 nm. On the other hand, the noise figure varied from 4.8–9.3 dB within the flat gain region. The triple-pass Erbium-doped fiber amplifier has been enhanced by utilizing distribution pumping scheme in the configuration. This improvised configuration minimised the cost of the amplifier yet having the comparable performance with the dual-pump configuration. A flat gain of 17.2 dB with the corresponding noise figure below 8 dB was obtained within 1555–1600 nm.

Linear and Nonlinear Noise Characterisation of Dual Stage Broadband Discrete Raman Amplifiers

We characterise the linear and nonlinear noise of dual stage broadband discrete Raman amplifiers (DRAs) based on conventional Raman gain fibres. Also, we propose an optimised dual stage DRA setup that lowers the impact of nonlinear noise (generated in the amplifier) on the performance of a transmission link (with 100-km amplifier spacing). We numerically analyse the design of a backward pumped cascaded dual stage 100-nm DRA with high gain (∼20 dB) and high saturated output power (>23 dBm). We show that the noise figure (NF) of the dual stage DRA is mainly dominated by the first stage irrespective of the type of gain fibre chosen in the second stage, and we also demonstrate that optimising the length and the type of Raman gain fibre can have significant impact on the size of inter/intrasignal nonlinearities generated. Here, we report a theoretical model to calculate the nonlinear noise power generated in transmission spans with dual stage DRAs considering piecewise signal power evolution through the Raman gain fibres. The predicted signal-to-noise ratio (SNR) performances are calculated from the combined contributions from NF and nonlinear product power obtained using the proposed analytical model for transmission systems deployed with 100-km transmission span compensated by different dual stage DRAs. Finally, an optimised IDF 6 km–SMF 10 km dual stage configuration has been identified using the theoretical model, which allows maximum SNR of 14.6 dB at 1000 km for 1 THz Nyquist wavelength division multiplexed signal and maximum transmission reach of 3400 km at optimum launch power assuming 8.5 dB HD-FEC limit of the Nyquist PM-QPSK signal.

Broadband Polarization Beam Splitter on a Silicon Nitride Platform for O-Band Operation

Wideband polarization beam splitters (PBS) are a key building block in polarization management circuits for wavelength division multiplexing applications. A broadband PBS on a 300-mm silicon nitride (SiN) photonic platform is reported based on phase-controlled directional coupler (DC). Unlike classical DC-based PBS made on silicon, the proposed configuration leverages the comparatively lower birefringence in SiN to yield wideband and efficient splitting. A semi-analytical approach, based on transfer matrix modeling and 3-D finite difference time domain, has been used to design and optimize the structure for O-band operation. The proposed PBS has been experimentally demonstrated showing insertion loss (IL) lower than 0.6 dB and extinction ratio (ER) as high as 10 dB over 95-nm bandwidth for both polarizations. Furthermore, this simplified architecture eases cascading, allowing the demonstration of IL below 1.1 dB and ER larger than 24 dB over 85-nm wavelength range in a dual-stage configuration.

A Comparative Study and Radial Performance Evaluation for Reflective EDFA Configurations with Optimized Intrinsic Parameter Sets

For the improvement of Gain and Reduction in Noise Figure, a range of Erbium Doped Fiber Amplifier (EDFA) based configurations from simple Single Pass (SP) EDFA to Quadruple Pass with Filter (QPF) EDFA have been investigated. Modified Giles model for rate and propagation equations has been proposed and subsequently used for Gain and Noise Figure evaluation for all configurations. The influence of EDFA based configurations on its internal design parameters is investigated to obtain an optimum design parameter set. Among the single stage EDFA configurations, Reflective Double pass with Filter (DPF) with a high optimum Numerical Aperture gives good radial performance with high signal overlap factor of 0.563 and Pump overlap factor of 0.834. For the dual stage configurations, second stage of Reflective QPF EDFA gives best signal overlap of 0.6727 and pump overlap of 0.8827, whereas it has the lowest pump threshold of 0.47 mW, hence highest pumping efficiency. At 1550 nm of input signal wavelength, maximum gain of 27.66 dB and low Noise figure of 5.4 dB was obtained in QPF EDFA at lowest pump power of 20 mW. Thus QPF EDFA is suitable choice for preamplifier applications at 1550 nm.

Autopsy study of irreversible foulants on polyvinylidene fluoride hollow-fiber membranes in an immersed microfiltration system operated for five years

Membrane autopsies were performed to understand causes of irreversible fouling on fouled membranes that were used for five years to treat surface water. The results of the autopsies of the membranes taken from the 1st and 2nd stages, i.e., a dual stage configuration to obtain 99% water recovery, showed that fouling layers occurred in both stages and severe fouling of the 2nd stage membrane was obvious. The severe flux decline in the 2nd stage illustrated the importance of the feed water quality. Compositional analyses by scanning electron microscopy with energy dispersive X-ray spectroscopy noted a great increase in the amount of Al on the 2nd stage membrane. Infrared spectra revealed that carboxylic acids, polysaccharide, and aromatic compounds originating from the feed water remained in the membrane. This study suggests that coagulation pretreatment should be implemented with great care because large amounts of Al remain on the membrane surface. In addition, cleaning should be performed in response to both organic and inorganic foulants. The fouling layer on the membrane captured the substantial amounts of inorganics such as Al in addition to organic foulants such as polysaccharide/protein-like compounds.

Evaluating the effects of CO2 capture benchmarks on efficiency and costs of membrane systems for post-combustion capture: A parametric simulation study

Membrane separation is considered to be the most promising alternative to chemical absorption for decarbonizing fossil fuel power generating systems. However, the implementation of a membrane system has several implications for the energy and economic performances of power plants. Indeed, membrane systems allow for the non-negligible reduction of power plant capacity, which can negatively affect its efficiency. This aspect, combined with the additional capital and operating expenses, is also responsible for an increase in the electricity generation costs.Currently, the majority of studies neglected to investigate the influence of CO2 separation targets on costs, thus limiting their investigation to the case of geological storage or enhanced oil recovery (EOR) that mean CO2 purity levels after compression higher than 95%. But for certain valorization aims, like CO2 hydrogenation or solar thermochemical conversion, lower CO2 quality standards may be sufficient; to the best of our knowledge there is currently no study allowing to know the cost of CO2 capture in this unusual framework.The aim of this paper was to analyze the effects of CO2 purity targets on the energy requirement for the separation and compression operations and costs of membrane systems, considering as a study case the recovery of CO2 from flue gases of a coal-fired power plant and using a Polyactive membrane. The CO2 separation process was first investigated by exploring several membrane system concepts. Then, by focusing on dual-stage configurations, the entire carbon capture and storage (CCS) chain was analyzed. From an energy view point, the study quantified the impact of CO2 capture retrofit intervention on the power plant’s net efficiency and the extent of CO2 emissions reduction. Besides, the economic analysis allowed for an evaluation of the specific cost of the CO2 capture and the mitigation cost with or without credits for EOR. Finally, an energy and economic comparison was made with the CO2 capture based on chemical scrubbing.With a CO2 separation cost of 20÷33 $/tonne, a single stage membrane system with feed compression and permeate vacuum pumping represents the most interesting option to be used in combination with CO2 recycling technologies requiring a medium-low CO2 purity level (70÷80%). Simulation results also revealed that dual stage membrane systems envisaged are economically competitive compared to amine absorption processes in the case of geological storage, involving a cost of CO2 capture of 36÷41 $/tonne.

Design and performance evaluation of narrowband rectangular optical filter based on stimulated Brillouin scattering in fiber

We propose a rectangular optical filter based on stimulated Brillouin scattering (SBS) in fiber with tunable bandwidth from 50 MHz to 4 GHz at 15-MHz tuning resolution. The steep-edged rectangular shape of the filter is precisely controlled utilizing digital feedback compensation of the multi-tone pump light. The passband ripple is $$\sim $$~1 dB by nonlinearity management of the pump light and using the fiber with a single Brillouin peak. The filter selectivity is improved to more than 40 dB by using pump-splitting dual-stage configuration. We analyze the noise performance of the proposed SBS filter and demonstrate a sub-band extraction of a multi-band orthogonal frequency division multiplexing (OFDM) signal. Furthermore, we validate the amplification performance with different gains for OFDM signal, which shows the potential capability of the filter in the fields of optical signal processing.

Brillouin Rectangular Optical Filter With Improved Selectivity and Noise Performance

We demonstrate a high selectivity rectangular optical filter based on stimulated Brillouin scattering (SBS) effect in fiber with bandwidth from 1 to 3 GHz. By using pump-splitting dual-stage configuration, the filter selectivity has been improved by more than 16 dB and exceeded 40 dB within 2-GHz bandwidth. The filter shape is well controlled by using precise digital feedback compensation and nonlinearity management. We also analyze the noise performance of both the single-stage and dual-stage filters by evaluating the signal-to-noise ratio of the amplified signal using coherent detection. The results show that the dual-stage approach performs better than the single-stage architecture in achieving higher selectivity and improving noise performance. The inherent tuning flexibility with improved performance makes the proposed SBS filter one of the best candidates for microwave photonic applications.

High Gain / Low NF EYDFA with Distributed Pumping

Optical amplifiers are an indispensable part of today’s network and face increasingly stringent demands on their performance in terms of peak gain, noise figure, cost, compactness, etc with growing transmission rates, increasing link lengths, wavelength division multiplexing and the continual improvisation of technology. Erbium-Ytterbium codoped fiber amplifier ( EYDFA ) an improvement of Erbium doped fiber amplifier (EDFA), helps overcome the limitation of increase in the concentration of excited erbium ions by countering the pairs quenching phenomenon. This paper investigates the role of optical pumping in dual stage single pass EYDFA and the strong dependence of gain on the pump power till a stage of saturation is reached is observed. Further, an amplifier with high gain of 40-46 dB at 1550nm with low noise figure is simulated for very short lengths of active fiber. General Terms Compact in-line amplifier, dual stage configuration, high gain, low noise figure, optical amplifier

Dielectric Elastomer Jet Valve for Magnetic Resonance Imaging-Compatible Robotics

This paper presents the design and experimental characterization of a binary jet valve, specifically developed to control an all-polymer needle manipulator during intramagnetic resonance imaging (MRI) prostate interventions (biopsies and brachytherapies). The key feature of the MRI-compatible valve is its compact dual-stage configuration. The first stage is composed of a low-friction jet nozzle, driven by a small rotary dielectric elastomer actuator (DEA). The second stage provides sufficient air flow and stability for the binary robotic application through an independent air supply, activated by a bistable spool. A hyperelastic stress-strain model is used to optimize the geometrical dimensions of the DEA jet assembly. Fully functional valve prototypes, made with 3M's VHB 4905 films, are monitored with a high-speed camera in order to quantify the system's shifting dynamics. The impact of nozzle clearance, dielectric elastomer film viscoelasticity, mechanical friction, and actuator torque generation on overall dynamic behavior of two different valve setups is discussed. Results show an overall shifting time of 200–300 ms when the friction of the nozzle and DEA actuation stretches are minimized. Low shifting time combined with compactness, simplicity, and low cost suggest that the low friction DEA-driven jet valves have great potential for switching a large number of pneumatic circuits in an MRI environment as well as in traditional pneumatic applications.

Regenerative SPM-Based Wavelength Conversion and Field Demonstration of 160-Gb/s All-Optical 3R Operation

In this paper, we describe a 160-Gb/s all-optical 3R regenerator consisting of a wavelength converter based on self-phase-modulation (SPM) and a non-linear optical loop mirror (NOLM). Particularly, we focus on the simple method to improve the performance of dual-stage wavelength conversion. The dual-stage configuration is useful to alleviate pulse-to-pulse interaction, which degrades both conversion bandwidth and regenerative effect. Total conversion performance, however, strongly depends on waveform distortion at the 1st-stage conversion. Against this, we found that when setting the wavelength shifts of the 1st -stage: ??1 and the 2nd-stage: ??2 to be ??1??2 0). The physical mechanism proving the benefit of the proposed conversion scheme is discussed through both numerical simulations and wavelength conversion experiments. The 3R performance assisted by the regenerative wavelength converter was evaluated by 160-Gb/s field transmission experiments which were conducted in the optical test-bed of Japan Gigabit Network II (JGN II). At a 3R-interval of 380 km, a Q-factor improvement of greater than 7 dB was achieved by applying the wavelength-converter assisted all-optical 3R regenerator.

Dual-stage superfluorescent fiber source with 1.16-W output power centered at <inline-formula><math altimg="none" display="inline" overflow="scroll"><mrow><mn>1561</mn><mspace width="0.3em" /><mi>nm</mi></mrow></math></inline-formula>

A 1.16-W superfluorescent fiber source (SFS) centered at 1561 nm with a 3-dB bandwidth of 8 nm has been achieved, under the pumping of a 3.56-W 976-nm laser diode array. The optical conversion efficiency reaches 32%. The source is constructed in a dual-stage configuration. The first stage is an ASE seed source with output power about 30 mW in the C band. The second stage is a backward-pumped high-power erbium-ytterbium-codoped double-clad fiber amplifier. An interesting phenomenon has been observed: low-power ASE seed source causes laser oscillation in the SFS, yet a relatively high-power ASE seed source prevents the SFS from lasing. The Rayleigh backscattering and the saturation effect of the amplifier are considered to explain the phenomenon.

Dual-stage Er/Yb doped fiber amplifier for gain and noise figure enhancements

Gain and noise figure enhancements in an Er/Yb doped fiber amplifier (EYDFA) are demonstrated using a dual-stage amplifier configuration. In comparison to a conventional single-stage amplifier, the gain in this amplifier is enhanced at all wavelengths between 1530 to 1560nm for the input signal powers of -40 and 0dBm. A maximum gain improvement of 7.3dB is obtained at a small signal (-40dBm) wavelength of 1534nm. The noise figure of the design is also enhanced at all wavelengths between 1530 to 1560nm with a maximum reduction of 3.0dB obtained at the small signal wavelength (-40dBm) of 1542nm. The total pump power used in this design is fixed at 140mW. This improvement of gain and noise characteristics is attributed to the efficient pump power distribution within the amplifier and also the addition of a midway optical isolator between the two amplifier stages. The isolator blocks the backward propagating ASE to increase the population inversion at the first stage and thus, enhances the amplifier gain and noise figure. These results show that the usage of a dual-stage configuration with a midway optical isolator is an invaluable consideration when constructing a practical EYDFA.

Fiber amplifiers for coherent space communication

We report on the application of double-clad doped fiber amplifiers for coherent space communication systems using a master oscillator power amplifier (MOPA) design at 1.06 /spl mu/m. The master oscillator is either a single-frequency Nd:YAG solid-state laser or a distributed-feedback fiber laser. The power amplifier is a diode-laser-pumped double-clad Nd doped fiber with polarization control, 20 dB gain, and about 1.3 W output power. A dual stage configuration using a solid-state Nd:YAG amplifier as second stage is presented as well, increasing the output power to 3.5 W with 28 dB gain. We also report on the possibility to integrate a single-frequency fiber laser, an all-fiber phase modulator, and a fiber amplifier to build an all-fiber phase-modulated MOPA. Up to 1 W continuous-wave output phase-modulated with a bandwidth of 196 MHz has been achieved.

Low noise, high efficiency L-band EDFA with 980nmpumping

Low noise figures of 3.3–3.9 dB have been acheived in flat gain L-band EDFAs over 30 nm with < 1 dB gain variation. A dual-stage configuration with optimised use of backward amplified spontaneous emission is employed for low noise and high efficiency operation with only 980 nm pumping.

Dual stage actuators for high density rotating memory devices

Maintaining the trend towards higher track densities and data rates in rotating memory devices require track following servo systems of increasing bandwidth for reliable storage and retrieval (R/W) of data. The bandwidth requirements are even more severe in the emerging portable computing applications. Increase in bandwidth under strict constraints on over-sampling is limited by the presence of mechanical resonance modes and other nonlinearities in the voice coil motor (VCM) actuators. One approach to overcoming the problem is by using a dual or a compound actuator. In such a mechanism, a VCM is used as a primary stage while the recording head is mounted on the secondary stage which in turn is mounted on the VCM. The secondary stage provides rapid small-motion and position correction to the recording head. Several dual-stage configurations have been proposed using electrostatic, piezoelectric and electromagnetic secondary actuators. The paper proposes a piezoelectric stack micro-actuator design for a disk drive. It preserves the present suspension and head assembly. A prototype of the actuator is designed, fabricated, and tested. The test results are presented. A dual actuator tracking servo system is proposed. The scheme is a promising alternative for providing high bandwidth actuation for future high performance drives.