Power Loss Coefficient Research Articles

Investigation on the Influence of Gas Pressure on CO2 Arc Characteristics in High-Voltage Gas Circuit Breakers

CO<sub>2</sub> is identified as a promising alternative gas of SF<sub>6</sub>. The magnetohydrodynamics (MHD) arc model is established for a CO<sub>2</sub> circuit breaker. The influence of gas pressure is studied. The simulations are carried out for 0.5 MPa, 0.7 MPa and 0.9 MPa absolute filling pressure, allowing predictions of pressure and temperature distributions. The arc time constant θ and the power loss coefficient <em>Q</em> is extracted. The thermal interruption capability is estimated to grow with increasing filling pressure.

Calculation of Arc Power Losses in the Simplified Model of Intensively Blasted Electric Arc

In previous versions of the simplified model of intensively blasted electric arc burning in argon in the arc heater's anode channel, the authors used the constant total power loss coefficient for estimation of arc power losses in all anode channel individual parts. Using this approach, the model with relatively low computational complexity has led to very good agreement between the total computed and experimentally obtained values, but when the computed and measured power losses of individual anode channel segments have been compared, considerable differences have been revealed. In the modified model, theoretically computed net emission coefficient of argon is used in the energy equation to express the arc power losses. This way, satisfactory accordance is achieved between not only the total, but also partial measured and computed values. Exemplary results are given in figures and tables and discussed.

Arcing Time of a DC Circuit Breaker Based on a Superconducting Current-Limiting Technology

A dc circuit breaker (DCCB) based on a superconducting current-limiting technology was proposed for the interruption of short-circuit fault currents in high-voltage dc (HVDC) systems. The proposed DCCB includes a superconducting current-limiting module (SCLM), which is used to limit fault currents, and an interrupter module (IM), which uses a self-excited oscillation method to interrupt the limited current. The objective of this paper is to determine methods that reduce the arcing time of the proposed self-excited oscillation-type DCCB. The self-excited oscillation-type circuit breaker alone is generally unable to interrupt the fault current when it exceeds 8 kA. However, the proposed DCCB can interrupt a fault current of 30 kA when using the SCLM, which can limit a 30-kA fault current to approximately 3.5 kA within 2.5 ms. The arcing time of the IM was also significantly reduced as a result of the greatly reduced interrupting current. The effects of the IM parameters, including the commutation capacitance C 2 , the commutation inductance L 2 , the arc power loss coefficient N, and the arc time constant θ on the arcing time were analyzed. The arcing time can be reduced by increasing C 2 and N and reducing L 2 and θ.

Experimental investigations on flow characteristics of two parallel channels in a forced circulation loop with supercritical water

The instability of supercritical water flow inside two parallel channels is investigated experimentally in this paper. Two types of instabilities with various oscillation periods occur at different power region during the heating process, indicating the existence of two types of dynamic instabilities. The type I instability occurs when the outlet temperature of the test section surpasses the pseudo-critical temperature. Sudden increase of the pressure drop cause a big disturbance to the system which results in a periodic feedback between the pressure drop and the mass flow rate. Large oscillations were found in the entire system at low heating power during which the two parallel channels oscillates in phase with the whole system with a long oscillation period (20–300s). The type II instability occurs only in the heated section at high powers at which the two parallel channels oscillate 180° out of phase while the rest of the system is stable. The period of type II instability is relatively small, i.e. 2–5s. With Ambrosini’s non-dimensional parameters, a stability map was generated using the obtained instability data. Analysis of the instability map showed the expected result that no instability occurs when the exit fluid temperature is below the pseudo-critical temperature regardless of the system pressure, inlet temperature, heating power, and local loss coefficient. The influences of inlet mass flow rate, inlet fluid temperature and system pressure on instabilities were also studied.

Optical properties of aluminum nitride single crystals in the THz region

We report on measurements of the refractive indices and the absorption in bulk single crystals of aluminum nitride, in the region from 1 to 8 THz. The birefringence is approximately 0.2 and is larger than in the optical frequency range. Both indices exhibit normal dispersion with no pronounced absorption resonances. Optical power loss coefficients are approximately 2 cm−1 and 4 cm−1 and the estimated static dielectric constants are 7.84 and 9.22, for the ordinary and extraordinary polarization, respectively.

Performance Analysis of Double Nozzle Flapper Servo Valve Based on Liquid-Solid Couple Effect and Moving Grid Approach

When designing the servo valve with different structure parameters, the influence of the interaction between the liquid and the solid on the performance of servo valve can only be obtain by the method of experiment, and then it can increase the time and cost of designing the servo valve. The liquid-solid couple method can obtain the influence of structure parameters on the performance of servo valve under the circumstance of reducing the experimental cost and time. The paper chooses the servo valve of A and B as models for study, The text adopts FSI method to analyze the flow field of double nozzle baffle electro-hydraulic servo valve prestage through the software of ANSYS, research the change of the prestage flow field by deflection of loaded armature baffle components, contrast and analyze the change of velocity, pressure, power loss and flow coefficient of fixed choke, nozzle, return port, and the displacement of the valve core of slide valve, stress of armature baffle components, pressure at both ends of spool. Summarize the advantages and disadvantages of A and B servo valve, and find different parameters of servo valve have different performance, it is difficult to find a common structure and size. It can help us to select the requirement structure by using fluid-structure interaction, reduce experiments and save cost.

Total Cross Flow (TCF) Hydrostatic Journal Bearing: A Review

Hydrostatic bearings are used extensively in machine tool application due to their high load carrying capacity, no stick-slip, very low friction at low or zero speed, high stiffness and damping characteristics. If the features of circumferential grooved land and external return flow system incorporate in the conventional Hydrostatic bearing design , it turns to a new bearing design that is Total Cross Flow (TCF design = Conventional design + Circumferential grooved land + External return flow system) hydrostatic bearing. This new externally pressurized bearing overcomes most of the side effect of conventional journal Bearing (CJB) like undesirable hydrodynamic effect associated with the oil turbulence and critical rise in temperature. TCF bearing are also consider suitable for high speed application along with good damping and stiffness characteristic with low temperature rise. Reduce drag power loss, fast temperature stabilization, and stability at high rotational speed are the other meritorious properties of TCF bearing. A detailed summery of literature review on TCF bearing covering different performance characteristics like total power loss, recesses pressure, squeeze load, temperature distribution, fluid flow, damping and stiffness coefficients are discussed and tabulated. It is observed through literature review that most of the studies on TCF journal bearing are experimental except analytical study made by Kumar et al. [7] and it is emphasized to carry out analytical and modeling work to validate or to analyze different features and aspects related to bearing configuration, lubricant properties, and type of restrictors etc.

Performance analysis of a fully textured hybrid circular thrust pad bearing system operating with non-Newtonian lubricant

The present paper deals with the theoretical investigation of the influence of dimple geometry on fully textured hybrid thrust pad bearing and operating with non-Newtonian lubricant. The modified Reynolds equation which governs the flow of non-Newtonian lubricant in the clearance space has been solved using Finite Element Method. The simulated results indicate that the values of load carrying capacity, frictional power loss, maximum pressure and fluid film stiffness coefficient are significantly affected by the behavior of lubricant. The results presented in the study are expected to aid in determining the optimum value of dimple diameter and depth for the optimum bearing performance.

Analysis of energy indices of a power plant adapted for the production of heat integrated with the amine Carbon dioxide processing unit

Abstract The adaptation of a power plant for heat production is an effective way of realizing high-efficiency cogeneration, and although the consumption of chemical energy of fuel decreases in comparison with the separate production of electricity and heat leading to a certain reduction of CO 2 emission, the installation of CO 2 capture ought to be applied. The paper concerns an amine installation of CO 2 processing unit. The application such an installation (capture and compression of CO 2 ) requires the supplementing of the calculation algorithms of energy indices of an integrated power plant adapted for the production of heat. The paper presents characteristic indices of a power plant adapted for heat production, viz. power loss coefficient (PLC) and overall energy efficiency as well as coefficient of heat cogeneration (COHC). The internal electro-mechanical power and heat consumption have been analyzed concerning various values of the unit consumption of heat for the purpose of regenerating the sorbent. Formulae expressing the overall net energy efficiency of an adapted power plant concerning the analyzed variants of integrated power plants have been derived. The influence of the unit consumption of heat for the regeneration of the sorbent on overall net energy efficiency of the adapted power plant and the coefficient of heat cogeneration have been analyzed.

Calculation of the power loss coefficient of steam turbine as a part of the cogeneration plant

A cogeneration plant operates under very variable conditions within a reporting period (usually one year) and this frustrates the achievement of the high standards stipulated by the EU Directive from 2004. Taking into consideration these difficulties, one needs to start with the decomposition of the cogeneration plant in order to determine a virtual part of the plant that can meet the requirements of the Directive on the basis of conducted measurements and calculations. In this way, the plant can be partially qualified as eligible for economic and financial benefits.The focus of this paper is an analysis of the power loss coefficient of steam turbines for the generation of useful heat energy and electricity simultaneously. This applies to all cogeneration plants comprising extraction-condensing steam turbines and combined cycles (gas turbine and steam turbine) when heat is extracted prior to the bottoming cycle. The proposed procedure for calculation of power loss coefficient is easily applicable in industrial practice. The viability of the proposed method is demonstrated in the case of calculations for a 10 MWe (combined cycle gas turbine) plant.

Power Loss Analysis Based on Leakage Currentin PN Junctions

This paper is proposed to analyze the power loss from leakage current in p-n junctions in case of non-uniform defects. The different geometry p-n junctions have been fabricated by a standard 0.8 micron CMOS technology. The diode fabricated by the ion implantation process with two different condition. The reverse current and voltage (I-V)characteristics at varied temperature of p-n junctions have been measured. The power loss coefficient can be extracted from the leakage current versus temperature. Form the derivative of leakage current with temperature, the power loss with prediction trend curve can be obtained.

A unified view of energetic efficiency in active drag reduction, thrust generation and self-propulsion through a loss coefficient with some applications

An analysis of the energy budget for the general case of a body translating in a stationary fluid under the action of an external force is used to define a power loss coefficient. This universal definition of power loss coefficient gives a measure of the energy lost in the wake of the translating body and, in general, is applicable to a variety of flow configurations including active drag reduction, self-propulsion and thrust generation. The utility of the power loss coefficient is demonstrated on a model bluff body flow problem concerning a two-dimensional elliptical cylinder in a uniform cross-flow. The upper and lower boundaries of the elliptic cylinder undergo continuous motion due to a prescribed reflectionally symmetric constant tangential surface velocity. It is shown that a decrease in drag resulting from an increase in the strength of tangential surface velocity leads to an initial reduction and eventual rise in the power loss coefficient. A maximum in energetic efficiency is attained for a drag reducing tangential surface velocity which minimizes the power loss coefficient. The effect of the tangential surface velocity on drag reduction and self-propulsion of both bluff and streamlined bodies is explored through a variation in the thickness ratio (ratio of the minor and major axes) of the elliptical cylinders.

Minimum power consumption for drag reduction on a circular cylinder by tangential surface motion

AbstractWe investigate the effect of a prescribed tangential velocity on the drag force on a circular cylinder in a spanwise uniform cross flow. Using a combination of theoretical and numerical techniques we make an attempt at determining the optimal tangential velocity profiles which will reduce the drag force acting on the cylindrical body while minimizing the net power consumption characterized through a non-dimensional power loss coefficient (${C}_{\mathit{PL}} $). A striking conclusion of our analysis is that the tangential velocity associated with the potential flow, which completely suppresses the drag force, is not optimal for both small and large, but finite Reynolds number. When inertial effects are negligible ($\mathit{Re}\ll 1$), theoretical analysis based on two-dimensional Oseen equations gives us the optimal tangential velocity profile which leads to energetically efficient drag reduction. Furthermore, in the limit of zero Reynolds number ($\mathit{Re}\ensuremath{\rightarrow} 0$), minimum power loss is achieved for a tangential velocity profile corresponding to a shear-free perfect slip boundary. At finite $\mathit{Re}$, results from numerical simulations indicate that perfect slip is not optimum and a further reduction in drag can be achieved for reduced power consumption. A gradual increase in the strength of a tangential velocity which involves only the first reflectionally symmetric mode leads to a monotonic reduction in drag and eventual thrust production. Simulations reveal the existence of an optimal strength for which the power consumption attains a minima. At a Reynolds number of 100, minimum value of the power loss coefficient (${C}_{\mathit{PL}} = 0. 37$) is obtained when the maximum in tangential surface velocity is about one and a half times the free stream uniform velocity corresponding to a percentage drag reduction of approximately 77 %; ${C}_{\mathit{PL}} = 0. 42$ and $0. 50$ for perfect slip and potential flow cases, respectively. Our results suggest that potential flow tangential velocity enables energetically efficient propulsion at all Reynolds numbers but optimal drag reduction only for $\mathit{Re}\ensuremath{\rightarrow} \infty $. The two-dimensional strategy of reducing drag while minimizing net power consumption is shown to be effective in three dimensions via numerical simulation of flow past an infinite circular cylinder at a Reynolds number of 300. Finally a strategy of reducing drag, suitable for practical implementation and amenable to experimental testing, through piecewise constant tangential velocities distributed along the cylinder periphery is proposed and analysed.

Method for determining the power loss in the contact system

The authors offer conferencing method for determining the power loss coefficient for the contact network. Authors have received expressions for the equivalent value of loss coefficient for the existing power schemes contact network.

Rotordynamic Force Coefficients of Bubbly Mixture Annular Pressure Seals

As oil fields deplete, in particular in deep sea reservoirs, pump and compression systems work under more strenuous conditions with gas in liquid and liquid in gas mixtures, mostly inhomogeneous. Off-design operation affects system overall efficiency and reliability, including penalties in leakage and rotordynamic performance of secondary flow components, namely seals. The paper details a bulk-flow model for annular damper seals operating with gas in liquid mixtures. The analysis encompasses all-liquid and all-gas seals, as well as seals lubricated with homogenous (bubbly) mixtures, and predicts the static and dynamic force response of mixture lubricated seals; namely: leakage, power loss, reaction forces, and rotordynamic force coefficients, etc., as a function of the mixture volume fraction (βS), supply and discharge pressures, rotor speed, whirl frequency, etc. A seal example with a nitrogen gas mixed with light oil is analyzed. The large pressure drop (70 bar) causes a large expansion of the gas within the seal even for (very) small gas volume fractions (βS). Predictions show leakage and power loss decrease as β→1; albeit at low βS (< 0.3) (re)laminarization of the flow and an apparent increase in mixture viscosity, produce a hump in power loss. Cross-coupled stiffnesses and direct damping coefficients decrease steadily with increases in the gas volume fraction; however, some anomalies are apparent when the flow turns laminar. Mixture lubricated seals show frequency-dependent force coefficients. The equivalent damping decreases above and below βS ∼ 0.10. The direct stiffness coefficients show atypical behavior: a low βS = 0.1 produces stiffness hardening as the excitation frequency increases. Recall that an all liquid seal has a dynamic stiffness softening as frequency increases due to the apparent fluid mass. The predictions call for an experimental program to quantify the static and dynamic forced performance of annular seals operating with (bubbly) mixtures and to validate the current predictive model results.

A comparison of modeling methods for ring resonator circuits

We have previously introduced a "compound ring resonator circuit," in which several ring resonator (RR) cavities are coupled in a loop, and analyzed the resulting configuration with the coupling of modes in space (CMS) technique. In this work we compare the accuracy, simplicity and calculation time of three standard procedures, namely the FDTD, and the methods of coupling of modes in time (CMT) and CMS in the context of a two-dimensional (2D) complex ring resonator circuit. This provides a far more effective benchmark of the relative advantages of the methods than the analysis of far simpler structures performed by other authors. As part of these calculations, we further discuss the relationship between the power loss coefficients in the CMS and the CMT models. We verify that the CMT yields accurate and rapid results for small coupling coefficients and losses even for large waveguide circuits containing multiple rings.

Instrumentation error analysis of a paraboloid concentrator type solar cooker

An effective quality control is essential for a large-scale dissemination of solar thermal technologies on the products being offered by the industry to the end users. For this, there is a need to establish test procedures and methodologies for producing performance characteristic parameters, which could provide an equitable basis for comparison of performances of these products. At present, paraboloid concentrator type solar cooker technology is moving towards the phase of commercialization in India. For the thermal performance evaluation of paraboloid concentrator type solar cooker, Mullick et al. (1991) developed a test procedure that essentially recommends determination of optical efficiency factor ( F′η o) and heat loss factor ( F′U L) based on heating and cooling tests. Further a test method has been proposed by Funk (2000) for testing of all kind of solar cookers that characterizes the performance of solar cooker by two parameters, namely, adjusted cooking power ( P a) and overall heat loss coefficient ( U L) as obtained from heating test. These are the only test methods available for testing of paraboloid concentrator type solar cooker. The present communication analyzes the effect of instrumentation, on the values of F′η o, F′U L, P a and U L, which is supported by a large number of outdoor tests conducted on a paraboloid concentrator type solar cooker under heating and cooling test conditions. The role of individual associated parameters on F′η o, F′U L, P a and U L has been analyzed along with the estimation of overall error in these values due to the error in the determination of associated parameters. Though the maximum attainable accuracy in determining F′U L varies from 1.15% to 0.65% (for loads of 1.0 to 8.0 kg), the associated error in the determination of F′η o is quite high viz. 5.13% to 5.04% for the same load conditions. Similarly, the maximum attainable accuracy in the determination of standardized cooking power has been observed from 4.98% to 5.02% under the load conditions from 1.0 to 8.0 kg.

Reliable Multi-hop Routing with Cooperative Transmissions in Energy-Constrained Networks

We present a novel approach in characterizing the optimal reliable multi-hop virtual multiple-input single-output (vMISO) routing in ad hoc networks. Under a high node density regime, we determine the optimal cardinality of the cooperation sets at each hop on a path minimizing the total energy cost per transmitted bit. Optimal cooperating set cardinality curves are derived, and they can be used to determine the optimal routing strategy based on the required reliability, transmission power, and path loss coefficient. We design a new greedy geographical routing algorithm suitable for vMISO transmissions, and demonstrate the applicability of our results for more general networks.

Generalized collisional radiative model for light elements. Part B: Data for the Be isonuclear sequence

A first-stage collision database is assembled which contains electron-impact excitation, ionization, and recombination rate coefficients for Be, Be +, Be 2+, and Be 3+. The first-stage database is constructed using the R-matrix with pseudo-states, time-dependent close-coupling, and perturbative, distorted-wave methods. A second-stage collision database is then assembled which contains generalized collisional-radiative and radiated power loss coefficients. The second-stage database is constructed by solution of collisional-radiative equations in the quasi-static equilibrium approximation using the first-stage database. Both collision database stages reside in electronic form at the ORNL Controlled Fusion Atomic Data Center and in the ADAS database, and are easily accessed over the worldwide internet.

Interruption capability of CF/sub 3/I Gas as a substitution candidate for SF/sub 6/ gas

We studied the interruption performance of CF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> I gas because its environmental effect is smaller than that of SF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sub> gas with a model arc-extinguishing chamber. First, we measured the arc time constant and arc power loss coefficient using Mayr's equation. Comparing CF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> I with other gases, the arc time constants are SF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sub> <CF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> I<CO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> < H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> <Air<N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> . The arc power loss coefficient is H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> >SF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sub> >CO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> >Air>N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2 </sub> >CF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> I. Next, we evaluated the short line fault (SLF) interruption capability by measuring the di/dt-dv/dt characteristic. Consequently, the SLF interruption performance of pure CF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> I was about 0.9 times that of SF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sub> . However, CF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> I application to gas insulated switchgear (GIS) and gas circuit breakers (GCB) is difficult because the liquefying temperature of the gas is high. Therefore, we adopted a countermeasure to obtain a lower liquefying temperature mixing CF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> I with CO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> . The result showed that the SLF interruption performance of the mixture approximated that of pure CF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> I when the ratio of CF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3 </sub> I exceeds 20%