Elliptical Pump Research Articles

Optimization Determination Method for the Explicit Equation of Scraper Motion Quantity in an Elliptical Rotor Scraper Pump

Addressing the inherent drawbacks of conventional positive displacement pumps, such as complex structure, poor sealing, low volumetric efficiency, and high noise, an innovative design of an elliptical rotor scraper pump (ERSP) was proposed. By segregating the pump chamber into high-pressure and low-pressure cavities, the scraper minimizes operational noise and significantly improves volumetric efficiency. To analyze the motion state of the ERSP, a mathematical model was established, determining the coordinated movement between the scraper and rotor using different optimization methods. The equations of coordinated action were derived and validated with relevant software through constraints applied to three algorithms and polynomial fitting. The flow field model of the ERSP was defined based on the established coordinated movement equation, and computational fluid dynamics (CFD) simulations were conducted to analyze pressure and velocity fields within the pump. A prototype of the ERSP was fabricated and tested, confirming its feasibility and advantages in enhancing fluid pressure and flow speed. This study provides valuable insights into the dynamic characteristics and structural optimization of fluid rotor pumps, contributing to anticipating and resolving potential faults and promoting the development of fluid power machinery.

High-efficiency broad-linewidth widely-tunable mid-infrared OPO based on fan-out PPLT

We reported a high-efficiency, broad-linewidth, wide-tuning-range singly-resonated optical parametric oscillator (OPO) based on a fan-out PPLT crystal. When the PPLT crystal was operated at 120 °C and pumped by Q-switched 1064 nm laser at 14.17 W with a circular pump profile, the overall output power of OPO was 7.22 W (η = 50.4%) for both the signal and idler waves. The central wavelength and linewidth of the mid-infrared (MIR) laser were 3770 nm and ∼40 nm. A wavelength tuning range of 3538–3941 nm was accomplished by adjusting the crystal period through simple mechanical movement. Due to the larger coverage of gratings with an elliptical pump profile, the output linewidth of the MIR laser was further broadened to ∼100 nm, which is ten times more than other non-fan-out PPLT OPOs. Both pumping methods with different profiles were operated at 30 kHz, 49.2 ns for the 1064 nm laser, the power fluctuation of the obtained MIR laser was within 3.5%.

Study of the Self-Locking Characteristics of the Swing Scraper of an Elliptical Rotor Scraper Pump

This paper proposes an Elliptical Rotor Scraper Pump (ERSP) to address traditional displacement pump defects, such as complex structures, poor self-sealing, low volume utilization, and considerable noise, etc. The ERSP utilizes a swing scraper instead of one rotor in a conventional multirotor pump or reciprocating moving vanes in a traditional vane pump and can achieve high-pressure output through pressure self-sealing. The swing scraper can divide the working chamber into high- and low-pressure rooms. Due to the small swing amplitude of the scraper, the ERSP has low operating noise. The ERSP rotor with an elliptical shape can significantly improve pump volume utilization, thus, forming a kind of fluid pump without a distribution valve, high pressure, and compact structure, and can work efficiently at high speed. This paper establishes a three-dimensional model and mathematical model for the ERSP, then develops the mathematical relationship between the scraper rotation angle and rotor rotation angle and carries out the simulation analysis based on MSC ADAMS. Then, the self-locking characteristics of the ERSP are studied through a force analysis of the swing scraper. Finally, our research group designs and produces a prototype based on existing research and verifies the superiority of the ERSP and the correctness of the non-self-locking condition through experiments. The results in this paper provide a reference for research on the self-locking characteristics of fluid rotor pumps and engineering optimization, which has great significance to the development of fluid power machinery.

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.

Enhancing SPDC brightness using elliptical pump shapes.

We report on the use of elliptical pump spatial modes to increase the observed brightness of spontaneous parametric downconversion in critically phase-matched crystals. Simulations qualitatively predict this improvement, which depends on the eccentricity and orientation of the pump ellipse. We experimentally confirm a factor of two improvement in brightness when compared to the traditional circular-symmetric pump spatial modes. These results support previous theoretical work that proposes the use of elliptical pump modes to enhance the performance of parametric processes in anisotropic materials.

Erratum: “Three-dimensional anisotropic thermal conductivity tensor of single crystalline β-Ga2O3” [Appl. Phys. Lett. 113, 232105 (2018)

\b{eta}-Ga2O3 has attracted considerable interest in recent years for high power electronics, where thermal properties of \b{eta}-Ga2O3 play a critical role. The thermal conductivity of \b{eta}-Ga2O3 is expected to be three-dimensionally (3D) anisotropic due to the monoclinic lattice structure. In this work, the 3D anisotropic thermal conductivity tensor of a (010)-oriented \b{eta}-Ga2O3 single crystal was measured by using a novel time-domain thermoreflectance (TDTR) method with a highly elliptical pump beam. Our measured results suggest that at room temperature, the highest in-plane thermal conductivity is along a direction between [001] and [102], with a value of 13.3+/-1.8 W/mK, and the lowest in-plane thermal conductivity is close to the [100] direction, with a value of 9.5+/-1.8 W/mK. The through-plane thermal conductivity, which is along the [010] direction, has the highest value of 22+/-2.5 W/mK among all the directions. Temperature-dependent thermal conductivity of \b{eta}-Ga2O3 was also measured and compared with a modified Callaway model calculation to understand the temperature dependence and the role of impurity scattering.

Flow fluctuation abatement of high-order elliptical gear pump by external noncircular gear drive

Large flow ripples restrict the development and application of high-order elliptical gear pumps badly. A new approach is proposed to reduce the flow fluctuations effectively by using a varying angular speed drive. Firstly the instantaneous flow rate model of the elliptical gear pump is established to analyze the effect of the eccentric ratio, number of order and module of the rotors on the flow rate. Then on the basis of the flow characteristics of the pump, an external noncircular gear drive is presented to cancel the low-frequency and large-amplitude flow ripples given by noncircular rotors completely, whose pitch curves are identified to be closed by the residue theorem. Finally, a pump prototype is made to prove that the flow pulsation of the elliptical gear pump can be reduced effectively by the external noncircular gear drive, which provides a favorable support for the design of high-performance pump with lager displacement and uniform flow.

Civil Engineering Tool Kit for Making Perfect Ellipses of Desired Dimensions on Very Large Surfaces

If an ellipse is to be drawn of given dimensions there is no formula, method or set of calculations and procedure available with the help of which we can draw ellipse of given length and width on large ground. Whenever a field engineer is to start the work of an ellipse-shaped structure like elliptical conference hall, screening chamber and pump chamber in disposal work etc. he finds difficulty to give demarcation of the structure on the big surface of the ground. No procedure is available, even in Google. A set of formulas with calculations has been made with the help of which one can draw an true and perfect ellipse of given length and width on the large ground very easily so as to start the construction work of elliptical structure. Based on these formulas a civil Engineering tool kit has been made with the help of which we can make perfect ellipse of desired dimensions on very large surface. The Patent of the tool kit has been filed in Intellectual Property India with Patent Filing Number: 201611026153 and Patent Application Filing Date: 30.07.2016. An App named ‘KC’s Mesh Formula’ has also been made to ease the calculation work. This can be downloaded from Play Store. After adopting these formulas and tool kit, a field engineer will not face difficulty in drawing ellipse on the ground to start the work.

A new elliptical-beam method based on time-domain thermoreflectance (TDTR) to measure the in-plane anisotropic thermal conductivity and its comparison with the beam-offset method.

Materials lacking in-plane symmetry are ubiquitous in a wide range of applications such as electronics, thermoelectrics, and high-temperature superconductors, in all of which the thermal properties of the materials play a critical part. However, very few experimental techniques can be used to measure in-plane anisotropic thermal conductivity. A beam-offset method based on time-domain thermoreflectance (TDTR) was previously proposed to measure in-plane anisotropic thermal conductivity. However, a detailed analysis of the beam-offset method is still lacking. Our analysis shows that uncertainties can be large if the laser spot size or the modulation frequency is not properly chosen. Here we propose an alternative approach based on TDTR to measure in-plane anisotropic thermal conductivity using a highly elliptical pump (heating) beam. The highly elliptical pump beam induces a quasi-one-dimensional temperature profile on the sample surface that has a fast decay along the short axis of the pump beam. The detected TDTR signal is exclusively sensitive to the in-plane thermal conductivity along the short axis of the elliptical beam. By conducting TDTR measurements as a function of delay time with the rotation of the elliptical pump beam to different orientations, the in-plane thermal conductivity tensor of the sample can be determined. In this work, we first conduct detailed signal sensitivity analyses for both techniques and provide guidelines in determining the optimal experimental conditions. We then compare the two techniques under their optimal experimental conditions by measuring the in-plane thermal conductivity tensor of a ZnO [11-20] sample. The accuracy and limitations of both methods are discussed.

Tunable Valley Polarization and Valley Orbital Magnetic Moment Hall Effect in Honeycomb Systems with Broken Inversion Symmetry.

In this Letter, a tunable valley polarization is investigated for honeycomb systems with broken inversion symmetry such as transition-metal dichalcogenide MX2 (M = Mo, W; X = S, Se) monolayers through elliptical pumping. Compared to circular pumping, elliptical pumping is a more universal and effective method to create coherent valley polarization. When two valleys of MX2 monolayers are doped or polarized, a novel anomalous Hall effect (called valley orbital magnetic moment Hall effect) is predicted. Valley orbital magnetic moment Hall effect can generate an orbital magnetic moment current without the accompaniment of a charge current, which opens a new avenue for exploration of valleytronics and orbitronics. Valley orbital magnetic moment Hall effect is expected to overshadow spin Hall effect and is tunable under elliptical pumping.

Scaling of energy characteristics of polycrystalline laser at room temperature

The lasing characteristics of lasers based on diffusion-doped polycrystalline samples excited at room temperature by an electric-discharge HF laser are studied. A sample doped from two sides (working surfaces) emitted laser radiation with the energy with the slope efficiency and the efficiency with respect to the absorbed energy in the case of an elliptical pump spot of size . It is found that the possibility of increasing the lasing energy of the samples of these types by increasing the pump spot area (at a constant pump energy density) is limited by the appearance of parasitic generation typical for disk lasers. The first results are reported on the laser based on a polycrystalline sample made by a technology that allows one to form a zero dopant concentration on the surface and a maximum concentration inside the sample (i.e., to create a sample with internal doping). The possibilities of increasing the laser energy at room temperature by using multilayer samples fabricated by this doping method are discussed.

Compact representation of the spatial modes of a phase-sensitive image amplifier

We compute the eigenmodes of a spatially-broadband optical parametric amplifier with elliptical Gaussian pump and show that the well-amplified eigenmodes can be compactly represented by a low-dimensional subspace of the first few Laguerre- or Hermite-Gaussian (LG or HG, respectively) modes of an appropriate waist size. We also show that the first few eigenmodes are well matched to single LG or HG modes. For sufficiently large pump waists, the optimum waist size of the compact basis is in the vicinity of the geometric average of the pump waist size and the inverse spatial bandwidth of the nonlinear crystal in the parametric amplifier. The use of such compact representation can greatly simplify numerical computation of the spatial eigenmodes of the amplifier and thus lead to improving the experiments on traveling-wave image amplification and spatially-broadband vacuum squeezing.

ASE and parasitic lasing in thin disk laser with anti-ASE cap

The amplified spontaneous emission (ASE) and parasitic lasing (PL) effects in thin disk laser with an anti-ASE cap have been investigated in detail by measuring both time-resolved radiated intensity at longer axis of elliptical pump profile (dominant ASE direction) and small signal gain (SSG) in laser amplifier. A cryogenically-cooled total-reflection active-mirror laser consisting of 9.8 at.% doped, 0.6-mm thick Yb:YAG and un-doped YAG trapezoidal ceramics cap was used as a sample. The phased transitions from spontaneous emission (SE) to ASE and from ASE to PL have been unambiguously observed. For several pump beam diameters, the ASE gain parameter g(0)l(ASE) at ASE threshold was about 3, and the SSG coefficient was down to about 65% until PL started. To the best of our knowledge, this is the first quantitative characterization of the ASE/PL effects in the thin disk laser with an anti-ASE cap.

Spatial modes of phase-sensitive parametric image amplifiers with circular and elliptical Gaussian pumps

We develop a method for finding the number and shapes of the independently squeezed or amplified modes of a spatially-broadband, travelling-wave, frequency- and polarization-degenerate optical parametric amplifier in the general case of an elliptical Gaussian pump. The obtained results show that for tightly focused pump only one mode is squeezed, and this mode has a Gaussian TEM(00) shape. For larger pump spot sizes that support multiple modes, the shapes of the most-amplified modes are close to Hermite- or Laguerre-Gaussian profiles. These results can be used to generate matched local oscillators for detecting high amounts of squeezing and to design parametric image amplifiers that introduce minimal distortion.

Polarization phenomena in resonantly pumped disordered semiconductor microcavities

We analyze the spatial distribution of the intensity of photoluminescence and its polarization in resonantly pumped semiconductor microcavities. The strong spin anisotropy of polariton-polariton interactions leads to the spontaneous formation of domains with strong circular polarization in real space under a uniformly polarized elliptical pump. These domains can serve as an experimental map of the disorder profile present in the system.

Phase-sensitive image amplification with elliptical Gaussian pump

We numerically analyze phase-sensitive parametric amplification and de-amplification of a multimode field representing a multi-pixel text image. We optimize pumping configuration and demonstrate that approximately 10-dB gain is achievable with relatively moderate approximately 10- kW total pump peak power available from compact pump sources.

Maximizing TEM 00 solar laser power by a light guide assembly-elliptical cavity

For maximizing TEM 00 solar laser power, a modified light guide assembly-elliptical cavity pumping approach is proposed. By observing refractive and total internal reflection principles, highly concentrated solar radiations from a primary parabolic mirror are firstly collected by a near-hexagonal input face and then transmitted, at low propagation angles, to a near-rectangular output end of the modified assembly. A sharp elliptical pump cavity with an intervening optics is utilized to further couple and concentrate the radiations from the assembly to a thin Nd:YAG rod. Optimum pumping parameters are found through ZEMAX™ non-sequential ray-tracing and LASCAD™ laser cavity analysis. Compared with the output performances of the parallel-packed light guide assembly-elliptical-cylindrical cavity, 45% increase in TEM 00, 10% in multimode solar laser powers are attained by the proposed approach. Experimental results on both the enhanced transmission efficiency of the assembly and the improved focusing capacity of the elliptical cavity with are finally provided.

Efficient Nd:YAG pumped mid-IR laser based on cascaded KTP and ZGP optical parametric oscillators and a ZGP parametric amplifier

Efficient conversion into the mid-IR of a low pulse-energy (2.5 mJ) Nd:YAG laser is achieved by cascaded KTiOPO 4 (KTP) and ZnGeP 2 (ZGP) optical parametric oscillators followed by a ZGP optical parametric amplifier. The first stage 2.13 μm degenerate KTP OPO uses four KTP crystals in a walk-off compensated geometry and an elliptical pump beam focal geometry to produce up to 2.2 W from 6.3 W incident. The 2.13 μm e-ray pumps a Type-I ZGP OPO, which produces 0.5 W of light in the 3.8–4.8 μm spectral region that in turn is amplified by a 2.13 μm o-ray pumped optical parametric amplifier generating 0.84 W with an M 2 of <2.

Nonlinear effects in spin relaxation of cavity polaritons

We present the general kinetic formalism for the description of spin and energy relaxation of the cavity polaritons in the framework of the Born-Markov approximation. All essential mechanisms of polaritons redistribution in reciprocal space together with final state bosonic stimulation are taken into account, from our point of view. The developed theory is applied to describe our experimental results on the polarization dynamics obtained in the polariton parametric amplifier geometry (pumping at so-called magic angle). We have experimentally confirmed that the anisotropy of the polariton-polariton interaction is responsible for the build up of the cross-linear polarisation of the signal. The long-living linear polarization is observed at zero detuning. Under elliptical pumping, we have directly measured in the time domain and modelled the effect of self-induced Larmor precession.

Method for generating solitons sustained by competing nonlinearities by use of optical rectification

We put forward a method for generating engineerable competing quadratic and cubic nonlinearities in suitable settings in which frequency generation is accompanied by optical rectification. The novel scheme is based on the full exploitation of the geometrical conditions that determine the magnitude of the rectified fields and translates the different orientations of an elliptical pump beam into tunable nonlinearities, which can be used to act on the spectral composition and overall features of optical solitons.