Cavity Pump Research Articles

A Novel Thermal Analysis Method Based on a Multi-Physics Two-Way Coupled Method and Its Application to Submersible Permanent Magnet Synchronous Motors

As a submersible permanent magnet synchronous motor (SPMSM) must function in downhole high temperature crude oil for long periods of time, the accurate prediction of its temperature rise is crucial to improve the stability of the motor. However, the analysis of its temperature field involves multiple physical fields, such as the electric field, the magnetic field, the fluid field and so on, and it is difficult to calculate accurately. Motor loss is usually loaded as a fixed value when calculating the temperature field, while in reality, the loss always changes with temperature. Therefore, the calculation of temperature is inaccurate using this one-way coupled method. In this paper, the relationship between loss and temperature is investigated and an electromagnetic-thermal fluid multi-physics two-way coupled analysis method suitable for SPMSM is proposed. The loss can be loaded as a variable by this new two-way coupled method, which significantly improves the temperature calculation accuracy. In order to prove the feasibility of the two-way coupled method, experiments based of a prototype of high torque and low speed SPMSM and cavity pump are conducted with the fiber Bragg grating (FBG) sensor measuring SPMSM temperature. Finally, the multi-physics two-way coupled method proposed in this paper is proven to be rational and feasible in the analysis of the SPMSM temperature rise.

Robust Pulse-Pumped Quadratic Soliton Assisted by Third-Order Nonlinearity

The generation of a quadratic soliton in a pulse-pumped microresonator has attracted significant interest in recent years. The strong second-order nonlinearity and high peak power of pumps offer a straightforward way to increase efficiency. In this case, the influence of the third-order nonlinearity effect becomes significant and cannot be ignored. In this paper, we study the quadratic soliton in a degenerate optical parametric oscillator driven synchronously by the pulse pump with third-order nonlinearity. Our simulations verify that the robustness of quadratic soliton generation is enhanced when the system experiences a perturbation from pump power, cavity detuning, and pump pulse width. These results represent a new way of manipulating frequency comb in resonant microphotonic structures.

Analysis of Thermal Effects in Kilowatt High Power Diamond Raman Lasers

Chemical vapor deposition (CVD) diamond crystal is considered as an ideal material platform for Raman lasers with both high power and good beam quality due to its excellent Raman and thermal characteristics. With the continuous development of CVD diamond crystal growth technology, diamond Raman lasers (DRLs) have shown significant advantages in achieving wavelength expansion with both high beam quality and high-power operation. However, with the output power of DRLs reaching the kilowatt level, the adverse effect of the thermal impact on the beam quality is progressively worsening. Aiming to enunciate the underlying restrictions of the thermal effects for high-power DRLs (e.g., recently reported 1.2 kW), we here establish a thermal-structural coupling model, based on which the influence of the pump power, cavity structure, and crystal size have been systematically studied. The results show that a symmetrical concentric cavity has less thermal impact on the device than an asymmetrical concentric cavity. Under the ideal heat dissipation condition, the highest temperature rise in the diamond crystal is 23.4 K for an output power of ~2.8 kW. The transient simulation further shows that the heating and cooling process of DRLs is almost unaffected by the pump power, and the times to reach a steady state are only 1.5 ms and 2.5 ms, respectively. In addition, it is also found that increasing the curvature radius of the cavity mirror, the length and width of the crystal, or decreasing the thickness of the crystal is beneficial to alleviating the thermal impact of the device. The findings of this work provide some helpful insights into the design of the cavity structure and heat dissipation system of DRLs, which might facilitate their future development towards a higher power.

Seven-Rod Pumping Concept for Highly Stable Solar Laser Emission

A seven-rod solar laser head was conceptualized and numerically studied to improve the tracking error compensation capacity and power stability in end-side-pumping schemes. It was composed of a first-stage heliostat–parabolic mirror system, a second-stage fused silica aspheric lens and a third-stage conical pumping cavity, within which seven Nd:YAG rods were mounted. Highly stable solar laser emission, with a power loss inferior to 5% for tracking errors up to ±0.4°, could potentially be enabled with seven 4 mm diameter, 13 mm length rods. The tracking error width at 10% laser power loss was about 1.0°, which is 1.65 times higher than the experimental record, attained by a dual-rod side-pumping prototype. Furthermore, a total multimode laser power of about 41.2 W could also be achieved, corresponding to 23.3 W/m2 collection and 2.5% solar-to-laser power conversion efficiencies, which are 1.65 and 1.36 times higher than those obtained with the dual-rod side-pumping prototype. They are also 1.27 and 1.12 times higher than the multirod experimental records in multimode regime for the same rod material.

Interaction between orthogonal components of single, dual and bound state vector solitons from a fiber laser

We report the interaction between orthogonal components of three types of vector solitons which are generated in a passively mode-locked fiber laser. By adjusting pump power and cavity birefringence, single, dual and bound state vector solitons can be selectively acquired, while all the types of vector solitons reveal energy exchange phenomenon on spectral sidebands. Moreover, the numerical simulation fully reproduces the experimental results, which confirms that the soliton separation is the key parameter that determines the formation of energy exchange sidebands. These results would provide inspirations for the evolution of interaction between solitons and greatly enhance the understanding of soliton dynamics.

Highly Efficient Four-Rod Pumping Approach for the Most Stable Solar Laser Emission.

We report a significant numerical improvement in multi-rod laser efficiency, with an enhanced solar tracking error compensation capacity for a heliostat-parabolic system. The solar laser head was composed of a fused silica conical lens and a single conical pump cavity ensuring multiple passes through four 4.55 mm diameter, 15 mm length Nd:YAG rods. 0.76° tracking error width at 10% laser power loss, and total multimode laser power variation of 0.05% at ±0.1° solar tracking error and 0.30% at ±0.2° solar tracking error were numerically calculated, being 1.27, 74.80 and 21.63 times, respectively, more than the experimental record in solar tracking error compensation capacity attained with a dual-rod side-pumping horizontal prototype pumped by the same heliostat-parabolic system. Additionally, the end-side-pumping configuration of the four-rod solar laser-enabled 43.7 W total multimode solar laser power, leading to 24.7 W/m2 collection efficiency and 2.6% solar-to-laser power conversion efficiency, being 1.75 and 1.44 times, respectively, more than that experimentally obtained from the dual-rod side-pumping prototype. The significant improvement in solar tracking error compensation capacity with a highly efficient end-side-pumping configuration is meaningful because it reduces the cost of high-precision trackers for solar laser applications.

Flow mechanism and axial force distribution characteristics of multistage pump cavity.

The gap leakage between the impeller ring leads to the change of the pump cavity flow characteristics, resulting in the uneven pressure distribution of shroud, which causes the axial force of the cavity to change. In this paper, the flow in the front and the rear cavity of the multistage centrifugal pump was taken as the research object. Through the numerical method, the radial flow velocity, the leakage flow size and its direction, the core zone rotation factor of the front and the rear cavity of the multistage pump impeller at all stages and the axial force of pump cavity were studied. The results show that the leakage in the front cavity of multistage pump impeller at all stages flows inward along radial direction (i.e. it flows from the inlet of pump cavity to the front ring clearance). The rotation factor in core zone is higher than 0.5, and with the increase of rotation factor, the axial force of the front pump cavity increased. The leakage in the rear pump cavity flows outward along radial direction (i.e. it flows from the rear ring to the inlet of pump cavity). The rotation factor in core zone is less than 0.5, and with the increase of rotation factor, the axial force decreased gradually. Besides, the radial velocity and rotation factor in the front and the rear multistage pump of impellers were obviously along the axial direction at three regions, the regions are pump case boundary layer, core zone and impeller boundary layer. The flow in the core zone is dominated by circumferential circular motion, and the radial velocity in the core zone is 0. It is shown that the direction of the leakage in the pump cavity and the rotation effect of the flow micelle in the mainstream core zone are the main factors affecting the axial force of the pump cavity, and the research results can provide theoretical guidance for the calculation and suppression of axial force of multistage pumps.

Most efficient simultaneous solar laser emissions from three Ce:Nd:YAG rods within a single pump cavity

We report here, to the best of our knowledge, the most efficient simultaneous emissions of three continuous-wave 1064 nm solar laser beams. A fused silica aspheric lens was used to couple the concentrated solar radiation from the focal zone of a 0.4 m 2 effective collection area primary parabolic mirror into three 2.5 mm diameter, 25 mm length 0.1 at.% Ce:1.1 at.% Nd:YAG laser rods within a single conical pump cavity. For 356 W incoming solar power, 16.5 W continuous-wave total multimode solar laser power was measured, corresponding to 4.64% solar-to-laser conversion efficiency, 41.25 W/m 2 collection efficiency, and 7.64% slope efficiency, which are 1.24, 1.27, and 1.11 times, respectively, higher than previous records by pumping a single 4.5 mm diameter, 35 mm length 0.1 at.%Cr:1.0 at.%Nd:YAG ceramic laser rod. The three-rod Ce:Nd:YAG solar laser also provided 2.13, 2.25 and 1.50 times enhancements in solar-to-laser conversion efficiency, collection efficiency, and slope efficiency, respectively, as compared to previous records by pumping three 3.0 mm diameter, 25 mm length 1.0 at.% Nd:YAG rods within the same single conical pump cavity. • Most efficient simultaneous emissions of three 1064 nm solar laser beams. • 4.64% solar power-to-laser power conversion efficiency attained. • 41.25 W/m 2 solar laser collection efficiency achieved. • 7.64% solar laser slope efficiency was calculated.

Side-pumped efficient Ce:Nd:YAG solar laser in a multi-pass scheme

We studied possible techniques for increasing the power-to-power conversion efficiency of the Ce:Nd:YAG solar laser using a simulation model developed with the Monte-Carlo photon tracing method framework. It is suggested that the multi-passage of photons through a medium can enhance the absorption probability. The effectiveness of the multi-pass scheme is experimentally investigated. The application of the multi-pass pumping scheme for Ce:Nd:YAG solar lasers is demonstrated. It is shown that the pumping efficiency in the Ce:Nd:YAG solar laser with the multi-pass pumping cavity is increased by 20%, paving the way for higher power-to-power conversion efficiency.

Numerical analysis on the performance and axial force characteristics of low specific speed and high head aviation fuel pump

The research on the axial force is an important issue for the fuel pump. For the aviation fuel pumps with low specific speed and high head, due to the larger projection area of its impeller cover, and the higher fluid pressure in the pump cavity are more likely to cause an excellent axial force. The performance and axial force characteristics of low specific speed and high head aviation fuel pump was numerically simulated and analyzed. The results of the study showed that the main parts of the fuel pump that generate axial force are the front cover, the rear cover, the impeller and the inducer. The axial force can be reduced by increasing the diameter of the rear cover labyrinth ring and adding the balancing holes. Thus, reducing the loss of the fuel pump and improving the hydraulic efficiency, and the problem of excessively high temperature of the fluid in the pump is solved. This study is helpful to improve the operation stability of fuel pump, and provide reference for subsequent research.

Efficient TEM00-mode solar laser using four Nd:YAG rods/four off-axis parabolic mirrors pumping approach

A four-rod/four-TEM00-mode beam off-axis parabolic mirror solar pumping concept is proposed. Four off-axis parabolic mirrors with 10 m2 total collection area were used as the primary solar concentrators to pump four 3.1-mm diameter, 84-mm length neodymium-doped yttrium aluminum garnet (Nd:YAG) rods within four 2V-shaped pump cavities through four secondary fused-silica aspheric concentrators and four rectangular fused-silica light guides, ensuring a good absorbed pump power distribution within each rod and avoiding the serious thermal lensing and thermal stress issues associated with classical single large rod solar lasers. The laser design parameters were optimized using ZEMAX© and LASer Cavity Analysis and Design (LASCAD©) analysis software to maximize the TEM00-mode laser power. 155.29-W TEM00-mode total laser power was numerically calculated, corresponding to 15.5 W / m2 solar laser collection efficiency and 1.72% solar-to-TEM00-mode laser conversion efficiency, respectively. This result represents an improvement of nearly 2 and 1.24 times, in solar laser collection efficiency and solar-to-TEM00-mode laser conversion efficiency, respectively, as compared with the previous experimental records of the TEM00-mode solar laser pumped through the parabolic mirror primary concentrator. It provides also a 1.14 and 1.19 times improvement, as compared to the previous numerical record of the TEM00-mode solar laser pumped by the Fresnel lens primary solar concentrator.

Mode-locking threshold decrease in a fiber laser by heterochromic optical pulse injection

A Yb-doped fiber laser mode locked by a nonlinear amplifying loop mirror (NALM) with a figure-9 configuration is experimentally realized. By coupling heterochromic 1580-nm optical pulses into the circular part of the Yb-doped laser oscillator, a new injection-induced Q-switched mode-locking (Q-ML) like transition state is found for the first time to the best of our knowledge. We have investigated the envelope interval and duration of this Q-switched envelope by changing the pump power, injection power, and cavity length detuning. Experimental results have shown the injected pulses serve as a complementary source for establishing mode-locking (ML). As a result, the self-starting ML threshold of the Yb-doped fiber laser is significantly reduced from 355 to 171 mW, which is only half that in the non-injection case. This optical pulse injection assisted ML process is observed with a real-time oscilloscope, revealing stable and consistent buildup dynamics. Our finding may provide a new approach for understanding the buildup dynamics and building mode-locked fiber lasers with low threshold and high consistency.

Ce:Nd:YAG Solar Laser with 4.5% Solar-to-Laser Conversion Efficiency

The efficiency potential of a small-size solar-pumped laser is studied here. The solar laser head was composed of a fused silica aspheric lens and a conical pump cavity, which coupled and redistributed the concentrated solar radiation from the focal zone of a parabolic mirror with an effective collection area of 0.293 m2 to end-side pump a Ce (0.1 at%):Nd (1.1 at%):YAG rod of 2.5 mm diameter and 25 mm length. Optimum solar laser design parameters were found through Zemax© non-sequential ray-tracing and LASCAD™ analysis. The utilization of the Ce:Nd:YAG medium with small diameter pumped by a small-scale solar concentrator was essential to significantly enhance the end-side pump solar laser efficiency and thermal performance. For 249 W incoming solar power at an irradiance of 850 W/m2, 11.2 W multimode solar laser power was measured, corresponding to the record solar-to-laser power conversion efficiency of 4.50%, being, to the best of our knowledge, 1.22 times higher than the previous record. Moreover, the highest solar laser collection efficiency of 38.22 W/m2 and slope efficiency of 6.8% were obtained, which are 1.18 and 1.02 times, respectively, higher than the previous records. The lowest threshold solar power of a Ce:Nd:YAG solar-pumped laser is also reported here.

Tracking error compensation capacity measurement of a dual-rod side-pumping solar laser

We present here the first experimental results of tracking error compensation capacity of a solar-pumped laser, with a largely enhanced tracking error tolerance achieved by pumping two laser rods simultaneously. A large aspherical fused silica lens, with an input face of 46 mm radius of curvature and 84 mm diameter, provided an efficient focusing of the concentrated solar radiation from the focal spot of the parabolic mirror onto the two laser rods, mounted within two semicylindrical pump cavities. A large improvement in tracking error compensation capacity was experimentally obtained, leading to an enhancement in tracking error width at 10% laser power loss (TEW10%) of 14.0 and 6.0 times in its vertical and horizontal setups, respectively, as compared to previous results by numerically simulated single-rod scheme. Regarding the numerical dual-rod scheme, an improvement of 3.5 and 1.5 times in the vertical and the horizontal setups, respectively, was also obtained by the present scheme. In comparison to the previous dual-rod scheme using a semicylindrical lens and a CPC pump cavity, the TEW10% was enhanced by 3.9 and 1.7 times, respectively, with the vertical and the horizontal setups.

40 W Continuous Wave Ce:Nd:YAG Solar Laser through a Fused Silica Light Guide

The solar laser power scaling potential of a side-pumped Ce:Nd:YAG solar laser through a rectangular fused silica light guide was investigated by using a 2 m diameter parabolic concentrator. The laser head was formed by the light guide and a V-shaped pump cavity to efficiently couple and redistribute the concentrated solar radiation from the parabolic mirror to a 4 mm diameter, 35 mm length Ce(0.1 at.%):Nd(1.1 at.%):YAG laser rod. The rectangular light guide ensured a homogeneous distribution of the solar radiation along the laser rod, allowing it to withstand highly concentrated solar energy. With the full collection area of the parabolic mirror, the maximum continuous wave (cw) solar laser power of 40 W was measured. This, to the best of our knowledge, corresponds to the highest cw laser power obtained from a Ce:Nd:YAG medium pumped by solar radiation, representing an enhancement of two times over that of the previous side-pumped Ce:Nd:YAG solar laser and 1.19 times over the highest Cr:Nd:YAG solar laser power with a rectangular light-guide. This research proved that, with an appropriate pumping configuration, the Ce:Nd:YAG medium is very promising for scaling solar laser output power to a higher level.

Research on the Modified Mathematical Prediction Model of Impeller Cover Side Cavity Liquid Pressure for Centrifugal Pumps

Accurate calculation of pressure distribution in the impeller cover side cavity is the key to predict the axial force of centrifugal pump. The existing calculation models almost does not involve the prediction of cavity pressure when the radial clearances of different sealing rings are matched with the diameter of different balance holes. On the basis of the original prediction model of pump cavity pressure, a mathematical model of pressure distribution of impeller cover side cavity with different radial clearance of sealing ring and the diameter of balance hole was established by introducing potential head correction coefficient and flow proportional coefficient. In order to improve the calculation accuracy of rotation coefficient for rear pump cavity, the balance aperture length ratio and the rotation undetermined coefficient were introduced in the calculation equation of original rotation coefficient. A test bed for pressure and leakage was designed and established, and the pressure of impeller cover side cavity and balance hole leakage was systematically tested when the radial clearance of sealing ring and the diameter of balance hole were different. Experimental results showed that the radial clearance of rear sealing ring and the diameter of balance hole had different effects on the radial pressure gradient of pump cavity. The diameter of balance hole had little effects on the pressure of the front pump cavity. When the clearance of the front and rear sealing rings were the same, the pressure of rear pump cavity was generally higher than that of the front pump cavity. For the equilibrium chamber liquid, increasing the diameter of balance hole could relieve the pressure, and increasing the radial clearance of sealing ring could increase the pressure. Combined with the test data, the potential head correction coefficient, the rotation undetermined coefficient and the flow proportional coefficient of different specific areas were calibrated, with a specific solution equation. In this study, the reliability of the proposed pressure mathematical model for impeller cover side cavity was verified by three cases. The results showed that the theoretical prediction value was more consistent with the actual measured value, proving that the proposed mathematical model had high accuracy and universality.

Research and Test on Mathematical Model of Pressure in Pump Cavity and Balance Cavity of Centrifugal Pump

The pressure distribution law and calculation of impeller side cavity is one of the important topics in the pump industry, but there is no more accurate calculation method at present. On this basis, a mathematical model of pump cavity pressure distribution and balance cavity pressure under design conditions was derived in this paper. By changing the radial clearance of front and back sealing rings and the diameter of the balance hole on the same impeller, the pressure distribution of front and rear cavities and the balance cavity pressure of the pump were systematically tested by a specially designed device. In the test, the curve of pressure loss coefficient and relative radius of pump cavity under different sealing ring radial clearance was obtained, which could solve the calculation problem of the pressure distribution of front and rear pump cavities. The test curve of the relationship between flow coefficient ratio and specific surface area essentially reflected the coupling regulation effect of balance holes and the rear sealing ring on the balance cavity pressure, which could not only solve the calculation problem of the balance cavity pressure, but also provide the theoretical basis for controlling the pressure and cover force of balance cavity and select different combinations of the radial clearance of the rear sealing ring and the diameter of balance holes. The results showed that the theoretical prediction value was more consistent with the actual measured value, which proved that the proposed mathematical model has high accuracy and universality. This study provides a new way to more accurately calculate the pump cavity pressure distribution and balance cavity pressure and laid a theoretical basis for the study of impeller cover force with significant academic and application value.

Highly Efficient Solar Laser Pumping Using a Solar Concentrator Combining a Fresnel Lens and Modified Parabolic Mirror

Solar-pumped lasers (SPLs) allow direct solar-to-laser power conversion, and hence, provide an opportunity to harness a renewable energy source. Herein, we report significant improvements in end-side-pumped solar laser collection efficiency and beam brightness using a novel 1.5-m-diameter compound solar concentrator combining a Fresnel lens and modified parabolic mirror. A key component of this scheme is the off-axis-focused parabolic mirror. An original dual-parabolic pump cavity is another feature. To determine the dependence of the SPL performance on the distance between the focus and central axis of the modified parabolic mirror, several systems with different distances were optimized using TracePro and ASLD software. It was numerically calculated that end-side pumping a 5-mm-diameter, 22-mm-long Nd:YAG crystal rod would generate 74.6 W of continuous-wave solar laser power at a collection efficiency of 42.2 W/m2, i.e., 1.1 times greater than the previous record value. Considering the laser beam quality, a brightness figure of 0.063 W was obtained, which is higher than that of other multimode SPL designs with end-side pumping. Thus, our SPL concentrator offers the possibility of achieving a beam quality as high as that obtainable via side pumping, alongside highly efficient energy conversion, which is characteristic to end-side pumping.

Modulation instability of Kerr optical frequency combs in dual-coupled optical cavities

Kerr optical frequency combs generated in a coherently driven Kerr nonlinear resonator have the potential for a wide range of applications. However, in a single cavity which is a widely adopted configuration for Kerr optical frequency-comb generation, modulation instability is suppressed in the normal dispersion regime, and the pump-to-comb conversion efficiency is extremely low for a single dissipative Kerr soliton (DKS) in the anomalous dispersion regime. Dual-coupled cavities have been proposed to generate Kerr optical frequency combs in the normal dispersion regime, and have the potential to remarkably increase conversion efficiency for Kerr optical frequency combs. Here, we investigate modulation instability and Kerr optical frequency-comb formation in dual-coupled cavities. Based on solutions of the continuous-wave steady state, we obtain a quadric algebraic equation describing the modulation instability gain, and we find that it is intensely influenced by the scaled free spectral range mismatch between the two cavities. Our numerical simulations demonstrate that platicons can be generated via a pump scanning scheme for the case that both the two cavities possess normal dispersion, and a single DKS can be generated in the cavity with anomalous dispersion while the dispersion of the other cavity is normal. The conversion efficiency of a single DKS is determined by the pump power and detunings as well as intrinsic quality factors of two cavities. Our analysis of modulation instability provides a powerful tool for Kerr optical frequency-comb generation via pump modulation and cavity detuning tuning scheme in dual-coupled cavities.

Modeling, Kinematic Characteristics Analysis and Experimental Testing of an Elliptical Rotor Scraper Pump

Against the backdrop of the rapid burgeoning of international energy engineering, the efficient utilization of energy is a paramount factor. The key idea in this paper is to propose an elliptical rotor scraper pump (ERSP) in order to address the imperfections and defects of traditional volume pumps, such as their labyrinthine design, low volume utilization efficiency and undesirable sealing performance. The ERSP can dramatically achieve the aims of ameliorating pump structure and improving energy efficiency. One of the Roots pump's rotors or the vane pump's shifting blade is replaced by a swing scraper in the ERSP. It is worth noting that a small swing range is a high-priority feature of the scraper; the scraper not only serves the purpose of dividing the pump cavity and self-sealing the unit but also reduces the noise level when working. A vital function of ERSP is the efficient conversion of mechanical energy into fluid pressure energy by changing the volume. Simultaneously, based on theoretical analysis, the mathematical model of the ERSP is established, and its kinematic characteristics are investigated, using ADAMS to verify the kinematic rationality of the ERSP. Ultimately, the research group manufactured a prototype of the pump, based on the previous simulation results and calculations, and experiments verified the feasibility of the pump. The design and research of the ERSP have essential reference significance for the development of fluid energy machinery technology.