Circular Port Research Articles

Performance investigation and optimization analysis for vapor injection rotary compressor oriented to circular end-plate injection port without check valve

Vapor refrigerant injection technique can effectively improve the performance and heating capacity of the rotary compressor heat pump systems in cold regions. However, due to the arrangement of the check valve at the injection port of the rotary compressor, the compressor manufacturing process needs to be improved to a large extent, which prevents the application of the vapor refrigerant injection technique. The manufacturing process of the vapor injection rotary compressor using a circular end-plate injection port without check valve is very simple. In order to avoid the backflow in the injection process and affect the performance of the compressor, the general expressions of the envelopes and the effective injection areas of the injection ports are developed based on an analytical geometry method in this paper. Meanwhile, a numerical model for predicting the performance of the vapor injection compressors is proposed. The effects of different operating conditions, different end of injection rotation angles, and different injection port radii on the upper and lower limits of injection pressure, injection ratio, and the system performance were analyzed. According to the prediction results, the optimal design scheme of the injection compressor using a circular end-plate injection port without check valve is proposed. The results indicate that at low ambient temperatures, the optimal design of the injection port structure has increased the heating capacity 12.1–28.3% over the traditional compressor without injection, and COP also has been increased 1.6–3.6%.

Unsteady characteristic and flow mechanism of a scroll compressor with novel discharge port for electric vehicle air conditioning

• The transient characteristic and flow of the scroll compressor is studied using CFD. • Gas is under compressed in downside chamber and over compressed in upside chamber. • The pressure difference between the two chambers is caused by the discharge timing. • A novel discharge port is proposed to improve the compressor efficiency by 2.4%. • The largest pressure unbalance between the upside and downside chambers reduces 50%. Scroll compressor is a key component of the air conditioner/heat pump system in electric vehicle. This paper focuses on the impacts of discharge port design on the transient performance and flow mechanism of the scroll compressor. A three-dimensional unsteady computational fluid dynamic model is established and validated. The computational domain includes inlet duct, scroll working chamber, discharge port, check valve, plenum chamber and outlet duct. R134a is used as the working fluid. The impacts of the position of the conventional circular port on the transient characteristic and flow loss mechanism of the scroll compressor are studied. It is found that large pressure difference between the two central chambers is resulted from discharging time difference of the two chambers. It inevitably leads to under compression in downside chamber and over compression in the upside chamber at designed condition. The conventional circular discharge port cannot address this problem. Therefore, a novel discharge port with a tail is proposed to retard the discharge time of the downside chamber and advance that of the upside chamber. It is found that the isentropic efficiency of the scroll compressor is improved by 2.4%. The maximum pressure unbalance between the upside chamber and downside chamber is reduced by 50%.

Research and development of a permanent-magnet synchronous frequency-convertible centrifugal compressor

Permanent-magnetic Synchronous Frequency-convertible (PSF) compressor as a new technology has been widely used in heating, ventilation and air conditioning. In this paper, a PSF centrifugal compressor was designed and developed. Some key technologies such as large working range 3-Dimensional impeller, 360° circular refrigerant injection port, two-stage impeller directly driven by PSF motor and high-speed inverter were adopted to improve the compressor efficiency. The theoretical comparison of conventional frequency-convertible centrifugal compressor and PSF centrifugal compressor was conducted to show the performance improvement. Then, a comprehensive experimental investigation was carried out to evaluate operating characteristics of the developed compressor. Experimental results showed that the adiabatic efficiency of PSF compressor reached 75.9%~88.5%. The mechanical efficiency, motor efficiency and inverter efficiency of PSF compressor was also greatly improved. Rated COP of PSF centrifugal chiller reached 7.0, and IPLV reached 11.7. The PSF centrifugal chiller has excellent system performances under both rated and partial load conditions.

Experimental analysis of condensation heat transfer and frictional pressure drop in a horizontal circular mini channel

The present study aims to investigate the effect of working fluid, mass flux, vapour quality and saturation temperature on local condensation Heat Transfer Coefficient (HTC) and local Frictional Pressure Drop (FPD) in a horizontal circular mini-channel. The refrigerants HFO-1234yf and HFC-R134a have been used as a working fluids. The mass flux was varied from 200 to 800 kg/m2 s whereas two distinct saturation temperatures were used: 35 °C and 40 °C. The experimental analysis was carried out using horizontal circular single port mini-channel of hydraulic diameter 1 mm. During experiment, inlet condition of refrigerant was maintained to be saturated vapour. The results show that HTC and FPD increases with increase in vapour quality and mass flux whereas decreases with increase in saturation temperature. The experiment results of present study and previously published results are compared with various predictive models. Models which show minimum deviation from experimental results were used to develop new modified model to predict HTC with MARD of ± 15 % and FPD with MARD of ± 10 %.

Small-Scale Static Fire Tests of 3D Printing Hybrid Rocket Fuel Grains Produced from Different Materials

The last decade has seen an almost exponential increase in the number of rocket launches for sounding missions or for delivering payloads into low Earth orbits. The emergence of new technologies like rapid prototyping, including 3D printing, is changing the approach to rocket motor design. This project conducted a series of small-scale static fire tests of fused deposition manufacturing hybrid rocket motors that were designed to explore the performance of a variety of commonly available fused deposition manufacturing materials. These materials included acrylonitrile butadiene styrene, acrylonitrile styrene acrylate, polylactic acid (PLA), polypropylene, polyethylene terephthalate glycol, Nylon, and AL (PLA with aluminum particles). To test the performance of small-scale fuel grains, a modular apparatus with a range of sensors fitted to it was designed and manufactured. The small-scale testing performed static burns on two fuel grains of each material with initial dimensions of 100 mm long and 20 mm in diameter with a 6 mm straight circular combustion port. The focus of this study was mainly on the regression rates of each material of fuel grains. Acrylonitrile styrene acrylate and Nylon showed the highest regression rates, while the polyethylene terephthalate glycol regression rates were relatively poor. Also, the acrylonitrile butadiene styrene and acrylonitrile styrene acrylate demonstrating relatively high regression rates when compared to existing hybrid fuels like hydroxyl-terminated polybutadiene.

Compact Full Band OMT Based on Dual-Mode Double-Ridge Waveguide

A nonstandard dual mode, double-ridge waveguide is utilized to design a compact orthomode transducer (OMT). The OMT is terminated with a standard circular waveguide common port and two standard isolated rectangular waveguide ports. The proposed structure exploits a one-fold symmetry to eliminate the coupling to the in-band higher order odd modes within the common port. The proposed concept is utilized to design a full ${K}$ 1-band OMT that is essential for space and mobile applications. Furthermore, the performance of the proposed OMT design is verified through a back-to-back measurement showing an excellent agreement between the full-wave simulations and measurements. Nevertheless, the proposed design achieves a measured matching level of 19 dB for the two modes and isolation level between them beyond 30 dB over the entire band.

A mixed computational and experimental approach to improved biogas burner flame port design

Anaerobic digestion is a well-known and potentially beneficial process for rural communities in emerging markets, providing the opportunity to generate usable gaseous fuel from waste resources. With recent developments in low-cost digestion technology, communities across the world are gaining affordable access to the benefits of anaerobic digestion derived biogas. For example, biogas provides a more efficient and cleaner burning alternative to biomass (wood, charcoal, dung), effectively reducing harmful emissions and fuel consumption.This study sought to develop and test a design approach for optimizing flame port geometry for household biogas-fired burners. The approach consists of a multi-component simulation that incorporates three-dimensional CAD designs with simulated chemical kinetics and computational fluid dynamics. The simulated flame port designs included an array of circular and rectangular geometries using a widely available biogas burner. The three highest performing designs identified were manufactured and tested experimentally to validate model outputs and to compare against a baseline port geometry. In the experiment, each of the three designs suggested improved thermal efficiency relative to the baseline. A configuration of four millimeter circular ports resulted in a 7.17% improvement, raising an average thermal efficiency of 53.0% to 56.8%. The results indicated that hydraulic diameter, velocity and mixture density are relevant factors in port geometry design to improve the thermal efficiency of a biogas burner. Conversely, the emissions predictions made by the model were found to be unreliable and incongruent with laboratory experiments.

Experimental study on NOx emissions of pulverized bituminous coal combustion preheated by a circulating fluidized bed

This study investigated nitrogen oxide (NOx) emissions of pulverized coal combustion preheated by a circulating fluidized bed (CFB). During the test process, high-temperature fuel preheated in a CFB was burned in a down-fired combustor (DFC). The effect of air distribution on NOx emissions was studied in the DFC, including three types of secondary air nozzle structures, five secondary air ratios, and three tertiary air position arrangements. Under stable conditions, the conversion ratio of fuel-nitrogen to N2 in the CFB was 41.4%, which resulted in lower NOx emissions in the platform. In this study, secondary air could be injected into the combustor at the top (annular) or through the side wall (circular) of the DFC, both with high combustion efficiency. This means that the secondary air is completely separated from the burner, and burner structure is greatly simplified. NOx emissions from secondary air nozzle structures of center, annular, and circular ports were 565.66, 345.45, and 220.38 mg/Nm3 (@6% O2) respectively. NOx emissions initially decreased then increased with increases in secondary air ratio with the annular nozzle structure. NOx emissions could be further inhibited by rationally arranging tertiary air positions.

On the prediction of uniformity of air flow out from manifold distribution

AbstractComputational fluid dynamics (CFD) was used to simulate a closed‐end multiple outlet pipe to examine the effect of different exit port geometry and size of perforation on performance of manifold distribution. To obtain an optimum design, the amount of fluid discharging from any opening in a pipe is greatly concern in engineering applications because uniform flow distribution has significant influence on the performance of manifold distribution. In this investigation, the vertical manifold system was used to study the hydrodynamics of air flow and simulate with computational fluid dynamics (CFD). Firstly, three different exit port geometry (circular, rectangular and square) are chosen to investigate the effect of exit port on mass flow rate uniformity effusing from distribution manifold. The best performance, which most closely approximating uniform outflow was achieved by the rectangle exit ports. Secondly, three different perforation size (3, 4 and 5 mm) of circular exit port were selected to reach to the finding of uniformity. Results show the 5 mm diameter orifices exit port achieve the uniform outflow of all. The ratio of the total opening area for all cases to the cross‐sectional area of the cylindrical pipe is identical for these two cases. Thirdly, the effect of perforation diameter with variable pipe ratio for equal number of orifices was investigated. The analysis for investigating the changes in the discharge angle of the stream between the orifices of multi‐perforated pipes perform for all cases. Standard k–ϵ turbulence model was considered for the numerical simulation, the finding results of numerical simulation were evaluated by the laboratory experiments.

A compact five-port waveguide structure and its application as a three-way power divider.

A compact five-port waveguide structure consisting of three rectangular ports, one coaxial port, and one circular waveguide port is proposed. The three rectangular waveguides are uniformly distributed in space at angles of 120°, and the coaxial and circular waveguides are located at the top and bottom, respectively, of the rectangular waveguides. The ideal scattering matrix is derived from the symmetry properties of the structure. If the circular and coaxial ports are matched, then the entire five-port waveguide structure is automatically matched. Two connected inserted coaxial probes, a frustum, and a coaxial transition are used to match the five-port waveguide structure with a relatively wide bandwidth. The theoretical and experimental results are generally consistent with each other. With the circular port connected to the load, the five-port waveguide structure becomes a reciprocal TEM mode-to-three-way TE10 mode power divider. Measurements indicate that from 8 to 9.6 GHz, the return losses at the three rectangular ports and the coaxial port are greater than 20 dB and 17 dB, respectively. The isolation among the three rectangular ports is higher than 20 dB. The amplitude and phase imbalances in the division of power are less than 0.1 dB and 2°, respectively. The volume of the five-port waveguide structure is as small as 1.5 λ × 1.5λ × λ.

Duckbill elastomer check valve use effects on domestic wastewater discharging marine outfalls initial dilution performance improvement

Most of the domestic wastewater discharging marine outfall diffusers have simply opened circular ports on the diffuser pipe wall. In order to protect the diffuser from seawater intrusion and clogging by sediments during lower flow rate periods, “duckbill” check valve (DBV) can be mounted on circular ports. Because of the DBV use instead circular ports at the same conditions, jet velocity at port could be increased. It was reported in some of the studies that the initial dilution was also increased in changed diffusers with DBVs. In this study, the initial dilution estimations of multiport diffusers were compared before and after DBV mounted conditions of horizontally opened circular sharp edged ports on the thin pipe wall. For Q = 0.5 m3/s design flow rate, t = 30-year lifespan, H = 20–50 m port depths and, ρa = 1,015–1,035 kg/m3 receiving water densities, 12 different diffusers with d = 150 mm diameter sized circular ports were designed. With the same total head, all diffusers were converted to 150-mm DBV nozzles. All hydraulic parameters and initial dilutions of before and after DBV usage were recalculated from the literature data for line source in this study. Dilution comparisons for the end of the project were shown that all DBV used results were lower than circular port results as ΔS (%) from −0.19 to −19.18 ranges. Except for two of the lower density values at the shallowest port depths, ΔS (%) had similar results for project start year.

Modeling Flow Turbulence in a Continuous Casting Slab Mold Comparing the use of Two Bifurcated Nozzles with Square and Circular Ports

Flow patterns of liquid steel in a thick slab mold, fed by bifurcated nozzles, are modeled through water modeling using characterization techniques such as particle image velocimetry (PIV), ultrasound velocimetry probe (UPV), and mathematical simulations using the large eddy simulation (LES) model. Geometries of nozzle ports include circular and square shapes with similar cross-section area. Square ports deliver wandering jets that occupy about 66% of the port area, and are raveled during their pass through the mold impacting the narrow face. Circular ports deliver compact jets mainly through the lower edge occupying only about 45% of the port area. The analysis of the flow structures indicates that the circular ports form more turbulent jets than square ones for the same flow rate of liquid. Mathematical simulations, using the LES model, predict acceptably well measured velocity fields. Slag entrainment through mechanisms of shear-drag forces at the metal–slag interface is estimated through a critical capillary number which involves slag viscosity, interfacial tension, and fluid velocity. At deep nozzle immersions, this capillary model predicts more slag entrainment using the bifurcated nozzle with circular ports.

Efficient FEM-Based Modal Circuit Representation of Arbitrarily Shaped Plate Pairs

A novel finite element method-based technique for the calculation of all circuit parameters of an efficient broadband equivalent network representation of parallel-plane pairs with arbitrary geometry is presented. It is based on an eigenvalue analysis in combination with the solution of the quasi-static Poisson equation for the magnetic vector potential. Compared with a recently presented simple finite difference scheme, the suggested FEM approach considerably reduces the modeling and computational effort, enabling an adaptive meshing in the presence of small circular ports. The proposed approach is validated by a practical example, demonstrating the considerable computational savings and the versatility for practical applications.

Numerical study of air-core vortex dynamics during liquid draining from cylindrical tanks

An air core is often formed during liquid draining from cylindrical tanks. An understanding of the mechanism behind its formation and the parameters that accentuate its growth is central to the development of an air-core vortex suppression strategy. In the present study, liquid draining from a cylindrical tank is investigated with the aid of computational fluid dynamics tools. A qualitative and a quantitative comparison of the temporal variation of critical height against available experiments is reported. A systematic investigation has revealed that, drain port shape, size, pressurization, initial rotation, etc, play a vital role in the formation of an air core vortex and its growth. These variables were also observed to influence critical height and total drain time, both of which are of engineering interest. Towards the development of a gas-core suppression strategy, the circular drain port is modified to either a stepped or a bell mouth shape. Although the new drain port shapes have delayed the gas-core from entering the drain-port, they were found to be only marginally advantageous.

Design exploration of three-dimensional transverse jet in a supersonic crossflow based on data mining and multi-objective design optimization approaches

The information in the three-dimensional transverse injection flow field is very important for the design of a scramjet combustor, and it should be explored by using the data mining and multi-objective design optimization methods. In the current study, the three-dimensional Reynolds-averaged Navier–Stokes (RANS) equations coupled with the two equation SST k-ω turbulence model has been utilized to simulation the transverse injection flow field with a freestream Mach number 3.75, and the influence of the turbulence model on the flow field properties has been evaluated as well. At the same time, three grid scales have been employed to perform the grid independency analysis, and the predicted results have been compared with the available experimental data in the open literature in order to carry out the code validation process. Further, the effect of the injector geometric configuration on the mixing efficiency of the transverse injection flow field has been investigated, and four different configurations have been considered in the current study, namely the square port, the diamond port, the equilateral triangular port and the circular port. The obtained results show that the case with the square injection port can obtain the largest mixing efficiency, and it can offer the rapidest near-field mixing between the injectant and the air. At last, the transverse injection flow field with the square injection port has been optimized by the surrogate-based evolutionary algorithm, and the relationships between the design variables and the objective functions have been explored by the variance analysis method. It is shown that the jet-to-crossflow pressure ratio has a high remarkable impact on the total pressure recovery efficiency, as well as the number of the injection ports on the drag force performance. The drag force increases with the increase of the number of the injection ports due to the deeper penetration of the rear jets.

Efficient Broadband Circuit-Modeling Approach for Parallel-Plane Structures of Arbitrary Shape

A methodology for creating highly efficient and inherently stable equivalent-circuit models for arbitrarily shaped parallel-plane pairs is presented. Based on Green's function with accelerated convergence, a general impedance expression is derived for circular ports, comprising the static capacitance and inductances and a small number of resonant terms. It can be directly cast into an equivalent multiport circuit for arbitrary number of ports, enabling the application in a SPICE circuit-simulation environment for broadband system analysis with active, passive, and nonlinear components. The equivalent-circuit elements are determined by a simple finite-difference scheme in combination with an analytical port model, which allows us to perform the required modal and the quasi-static analysis with a uniform mesh. Validation by numerical full-wave field simulations demonstrates the versatility of the suggested approach and the high computational savings of several orders of magnitude in frequency and time domain.

A comparative study of the port geometrical effects on sharp corners’ jet triple flames

The performance of sharp corners’ jet triple flames was modulated by compromising the increase in both the number of sharp corners between 3 and 16 and the overall perimeter up to 218% with the reduction in vertex angle to 30°. While the turbulent kinetic energy peak value correlated with the vertex angle and its average value depended on the number of corners, the entrainment rate gain was pronounced in accordance with the perimeter. By having each port stabilizing the inner flame wing such that the sharp corners lay on the diffusion flame envelope at its base, the flow strain due to corners increased the triple flame stability limit to a maximum of 9.2m/s and minimized the NOx emissions to 14ppm. Upon incorporating the swirl impact, the highest firing rate was reached at a jet velocity of 26.3m/s at which excessive entrainment of reactants into corners provided a compact flame with a firing intensity of 50.3MJ/m3. While the flame length was related to the extent of jet deformation from the circular shape, a flame shortening by 67% was verified by an enhancement of 192% over the circular port entrainment rate. Improved combustion efficiencies with respective decrease in CO and HC emissions to 61ppm and 0.04% were reported by maximizing the effect of sharp edged appendices. The swirl introduced a favorable advection transport, whereby the turbulence peaks at corners merged to provide a relative increase of 11.8 times in the average turbulence energy. By effectively combining the active and passive control techniques via providing swirl and modulating the port geometry, the lean operation limit extended by 19% from that of the circular port whereby NOx emissions for triple flames case II had a minimum of 4ppm.

Design, fabrication, and performance testing of a vacuum chamber for pulse compressor of a 150 TW Ti:sapphire laser

A vacuum chamber, to house the optical pulse compressor of a 150 TW Ti:sapphire laser system, has been designed, fabricated, and tested. As the intensity of the laser pulse becomes very high after pulse compression, there is phase distortion of the laser beam in air. Hence, the beam (after pulse compression) has to be transported in vacuum to avoid this distortion, which affects the laser beam focusability. A breadboard with optical gratings and reflective optics for compression of the optical pulse has to be kept inside the chamber. The chamber is made of SS 316L material in cuboidal shape with inside dimensions 1370×1030×650 mm3, with rectangular and circular demountable ports for entry and exit of the laser beam, evacuation, system cables, and ports to access optics mounted inside the chamber. The front and back sides of the chamber are kept demountable in order to insert the breadboard with optical components mounted on it. Leak tightness of 9×10−9 mbar-lit/sec in all the joints and ultimate vacuum of 6.5×10−6 mbar was achieved in the chamber using a turbo molecular pumping system. The paper describe details of the design/ features of the chamber, important procedure involved in machining, fabrication, processing and final testing.

Circular Ports in Parallel-Plate Waveguide Analysis With Isotropic Excitations

Exact and consistent modeling of circularly shaped ports in the power/ground plane analysis under the assumption of isotropic excitations is addressed in this paper. Novel expressions are first derived for accurate calculation of the parallel-plate impedance of circular ports in the cavity resonator method. These ports are usually approximated as either rectangular or linear ones, leading to inaccurate results at high frequencies. The second part of this paper develops a novel semianalytical approach, derived from the contour integral equation, for modeling of circular ports assuming infinitely large reference planes. It will be shown that the radial waveguide method is a low frequency approximation of our approach and neglects the scattering among the open ports. The analytical solutions for infinite planes are then combined with the contour integral method to model finite-sized power planes. This improves the computational efficiency since a discretization of circular ports is avoided, especially for problems with a large number of circular ports.

Extension of the Contour Integral Method to Anisotropic Modes on Circular Ports

In the analysis of power/ground planes in multilayer substrates, circular ports are often used for modeling of via transitions. The electric and magnetic fields on excited ports are usually assumed to be isotropic. This assumption may not hold in certain scenarios such as vias in very close proximity, where anisotropic modes can be excited. This paper first extends voltage and current definitions of circular ports to account for the non-uniform field distribution along the port perimeter and the anisotropic propagating modes. The effect of these modes on the parallel-plate impedance can be captured in the contour integral method (CIM) by discretizing the port perimeter with line segments. However, the computation time grows rapidly as the number of modeled ports increases. Therefore, the CIM is extended here to incorporate analytical modal expressions to improve the computational efficiency based on the new port definition. The derivation starts with solutions under the assumption of infinite planes, and then is expanded to take finite plane boundaries into consideration. Application examples using the extended CIM will be demonstrated and validated against the conventional CIM with ports modeled numerically. The significance of anisotropic propagating modes for dense via arrays will also be discussed.