Small Set Of Generators Research Articles

Selecting Measurement Locations for Inverse Pellicular Modes Analysis

Inverse pellicular mode analysis is an approach to reconstruct an acoustic source from measurements in the sound field. After a source is reconstructed, the simulation can be used to predict the sound pressure level at some distance from the source. The method is especially useful for considering acoustic treatments such as partial enclosures and barriers. Pellicular modes are generated by assuming a thin acoustic layer around the source boundary and determining the acoustic modes. These acoustic modes are then used as structural modes and serve as basis functions for the inverse calculation. However, the quality of the reconstruction depends greatly on the selection of measurement locations. In this research, inverse pellicular mode analysis is used to reconstruct the normal boundary velocity on a small generator set. Different measurement set locations are considered and sound pressure levels in the field are calculated and compared to direct measurement to assess the quality of the reconstructed source. The reconstructed source is then utilized to predict the insertion loss of a partial enclosure.

Pollutant emissions, performance and combustion behaviour assessment of an Si gas engine fuelled with Lcv gas containing carbon monoxide and hydrogen diluted by nitrogen

This paper includes the experimental test data of an SI engine fuelled with simulated LCV gas (Low Calorific Value), which resembles synthesis gas in composition. The LCV gas was simulated by a mixture of carbon monoxide, hydrogen and nitrogen. During the experiment, the lower heating value of the LCV gas was altered by dilution with nitrogen. A single-cylinder Honda GX270 engine was adopted in the experiment to assess the impact of LCV gas on the system performance. This engine is typically used to power various machines and for electrical energy production in small generator sets. A modified engine was connected to an electric generator, which was loaded with an electric resistor. Engine operation was controlled using a microprocessor controller. All tests were performed at constant engine speed (3000 rpm). The engine was working at wide-open throttle for all mixtures. All mixtures were burned at stoichiometric conditions and with fixed value of ignition timing (30 deg bTDC). The indicated performance of the SI engine was evaluated based on the in-cylinder pressure measurements. No significant impact on the main internal parameters of the tested SI engine fuelled with simulated LCV gas diluted by nitrogen was observed. The experimental tests showed that the combustion duration increased for the mixtures with higher content of inert gas. Increase in the LHV raised the specific emissions of NOx and decreased specific emissions of CO and HC.

Improving the Properties of Pure Vegetable Oils to Use Directly in Diesel Engines

Some typical types of biofuels widely known today include: bioethanol (bioetanol), biodiesel (biodiesel), green diesel (diesel), biological kerosene (biokerosen-or reactive fuel). biological forces), other biological alcohols (methanol, butanol), bio ether, biogas, synthetic gas, solid biomass fuel. In fact, the two most important biofuels are bioetanol and biodiesel, because of the many properties they have: use for the two most common types of vehicles (gasoline and motor vehicles). diesel engine); has many properties similar to fossil fuels, but cleaner and cleaner; produced from abundant and renewable materials such as sugar, starch and animal and vegetable fats and oils. The paper presents results obtained from a method applied for improving the properties of pure bio-oil aiming a direct use as a fuel in conventional diesel engines. Some typical properties such as high viscosity, high surface tension, high density and high cloud point are considered to be improved within this study. Characteristics of the viscosity, density and the surface tension versus fuel temperature are established. Findings of this study provide a basis for calculation and design a heating system of bio-oil fuel and for improving some typical properties of this fuel in order to use directly in diesel engines of small generator sets or diesel engines used in agriculture, forestry fields or in small boats.

Improving the Properties of Pure Vegetable Oils to Use Directly in Diesel Engines

Some typical types of biofuels widely known today include: bioethanol (bioetanol), biodiesel (biodiesel), green diesel (diesel), biological kerosene (biokerosen-or reactive fuel). biological forces), other biological alcohols (methanol, butanol), bio ether, biogas, synthetic gas, solid biomass fuel. In fact, the two most important biofuels are bioetanol and biodiesel, because of the many properties they have: use for the two most common types of vehicles (gasoline and motor vehicles). diesel engine); has many properties similar to fossil fuels, but cleaner and cleaner; produced from abundant and renewable materials such as sugar, starch and animal and vegetable fats and oils. The paper presents results obtained from a method applied for improving the properties of pure bio-oil aiming a direct use as a fuel in conventional diesel engines. Some typical properties such as high viscosity, high surface tension, high density and high cloud point are considered to be improved within this study. Characteristics of the viscosity, density and the surface tension versus fuel temperature are established. Findings of this study provide a basis for calculation and design a heating system of bio-oil fuel and for improving some typical properties of this fuel in order to use directly in diesel engines of small generator sets or diesel engines used in agriculture, forestry fields or in small boats.

An algebra associated with a subspace lattice over a finite field and its relation to the quantum affine algebra [formula omitted

It is known that the incidence algebra of a subspace lattice over a finite field with q elements is a homomorphic image of the quantum algebra Uq1/2(sl2). In this paper, we extend this situation. For a fixed proper subspace (which is an object of the subspace lattice), we define naturally a new algebra H which contains the incidence algebra as a proper subalgebra, and show how it is related to the quantum affine algebra Uq1/2(slˆ2). We show that there is an algebra homomorphism from Uq1/2(slˆ2) to H, and that H is generated by its image together with the center. Moreover, we show that any irreducible H-module is also irreducible as a Uq1/2(slˆ2)-module and is isomorphic to the tensor product of two evaluation modules. We also obtain a small set of generators of the center of H.

The effect of using passive hybrid muffler on a small generator set noise fuelled by natural gas

A detailed experimental study has been conducted to evaluate the effect of a hybrid muffler (HM) installation on sound emission of a small generator set fuelled by natural gas, which was covered by an acoustic enclosure. Specifications of a reactive muffler were calculated according to recommendation of ASHRAE 2.6 technical committee and based on an appropriate muffler was selected. The selected muffler was added to the muffler installed by manufacturer on generator (GM) and formed hybrid muffler (HM). The sound of generator set was measured for GM and HM setups on four sides of the generator at five different loading conditions (0, 25, 50, 75 and 100% load) using a sound level meter. The results showed that application of HM could reduce the sound of generator at firing frequency (31.5 Hz) and frequencies greater than 1000 Hz, with the maximum values of 11.7 and 26 dB, respectively. The overall A-weighted generator sound was in the range of 73.2–85.8 dB (A) at all the loading conditions and sides by using HM. The acoustical performance of HM on the side with the maximum generator sound (side 1) increased from 5.1 dB (A) at no load to 10.61 dB (A) at full load conditions. Therefore, the HM usage could be recommended as a useful approach to attenuate the generator sound.

Experimental analysis of assessing of the tripping effectiveness of miniature circuit breakers in an electrical installation fed from a synchronous generator set

Due to the supply reliability concerns or to supply remote loads in some distribution networks, the synchronous generators are used as auxiliary power sources. In Poland the generators are usually connected to the network of TN (earthed neutral point) structures. Both TN-C and TN-S or their mixed arrangements TN-C-S are used. Overcurrent protection in these circuits, according to Polish and international standards and the recommendation of SEP (Association of Polish Electrical Engineers), should also act as anti-shock protection. The protection is considered to be effective (for 400V electrical installations) if the overcurrent protection trip takes less than 0.4s (maximum allowable time of touching voltage occurrence). The investigation performed by authors, showed that the producers of the generators usually use B or C characteristic circuit breakers and for large generator sets (greater than 100kVA) they recommend load split to the value of one fifth of the generator maximum power. Additionally, the most frequently excitation forcing equipment is mounted to keep short circuit current three times greater than nominal current of the generator. To assess the effectiveness of the anti-shock protection measures in circuits fed from auxiliary generator and for current lower than 32A, the set up including a self-exiting 5.5kVA and 400V generator, overcurrent protection and load was built in laboratory. The set up uses miniature circuit breakers and enables short circuits in different instants, compared to the initial phase angle of the generator voltage. Resultsof the performed short circuits showed, that for the self-excited generators (majority of small generator sets with stator current lower than 32A) the overcurrent protection cannot act as anti-shock protection, when breakers allowing full utilisation of the generator power. The alternative is to limit generator load or to introduce excitation forcing increasing device price. The proposed solution for these generators given by authors is to modify anti-shock protection system in such way, that the tripping occurs always in the time below 0.4s. Modifications include not only introduction of the measurements of currents, but also the measurements of the generator voltage. The short circuit is indicated not only by current increase, but also by voltage drop during short circuit. Experimentaldevice utilizing both measurements was build and tested for different initial short-circuit instants, with respect to the synchronous generator phase voltages. In every case, the switch-off time of the short circuit was not longer than 0.4s, what means that the protection against the risk of electric shock was effective. The settings of the device are fully adjustable, what means that levels of the measured quantities indicating trip as well as the reaction time are adjustable.

Small generators of cocompact arithmetic Fuchsian groups

In the study of Fuchsian groups, it is a nontrivial problem to determine a set of generators. Using a dynamical approach we construct for any cocompact arithmetic Fuchsian group a fundamental region in $\mathbf{SL}_2(\mathbb{R})$ from which we determine a set of small generators.

Modelling of the Operation of a Small Generator Set Powered by Scrubbed Biogas from Cow Dung

Modelling of the Operation of a Small Generator Set Powered by Scrubbed Biogas from Cow Dung

Coxeter–Chein Loops

In 1974, Orin Chein discovered a new family of Moufang loops which are now called Chein loops. Such a loop can be created from any group W together with ℤ2 by a variation on a semidirect product. We first settle an open problem, originally proposed by Petr Vojtěchovský in 2003, by finding a minimal presentation for the Chein loop with respect to a presentation for W. We then study these loops in the case where W is a Coxeter group and show that it has what we call a Chein-Coxeter system, a small set of generators of order 2, together with a set of relations closely related to the Coxeter relations and Chein relations. In particular, even if the Moufang loop is infinite, it is finitely presented. Viewing these presentations as amalgams of loops, we then apply methods due to Blok and Hoffman to describe a family of twisted Coxeter–Chein loops.

Discrete Moving Frames and Discrete Integrable Systems

Group-based moving frames have a wide range of applications, from the classical equivalence problems in differential geometry to more modern applications such as computer vision. Here we describe what we call a discrete group-based moving frame, which is essentially a sequence of moving frames with overlapping domains. We demonstrate a small set of generators of the algebra of invariants, which we call the discrete Maurer–Cartan invariants, for which there are recursion formulas. We show that this offers significant computational advantages over a single moving frame for our study of discrete integrable systems. We demonstrate that the discrete analogues of some curvature flows lead naturally to Hamiltonian pairs, which generate integrable differential-difference systems. In particular, we show that in the centro-affine plane and the projective space, the Hamiltonian pairs obtained can be transformed into the known Hamiltonian pairs for the Toda and modified Volterra lattices, respectively, under Miura transformations. We also show that a specified invariant map of polygons in the centro-affine plane can be transformed to the integrable discretization of the Toda Lattice. Moreover, we describe in detail the case of discrete flows in the homogeneous 2-sphere and we obtain realizations of equations of Volterra type as evolutions of polygons on the sphere.

Totally distributive toposes

A locally small category E is totally distributive (as defined by Rosebrugh and Wood) if there exists a string of adjoint functors t⊣c⊣y, where y:E→Ê is the Yoneda embedding. Saying that E is lex totally distributive if, moreover, the left adjoint t preserves finite limits, we show that the lex totally distributive categories with a small set of generators are exactly the injective Grothendieck toposes, studied by Johnstone and Joyal. We characterize the totally distributive categories with a small set of generators as exactly the essential subtoposes of presheaf toposes, studied by Kelly and Lawvere and by Kennett, Riehl, Roy, and Zaks.

Message passing for optimization and control of a power grid: Model of a distribution system with redundancy

We use a power grid model with M generators and N consumption units to optimize the grid and its control. Each consumer demand is drawn from a predefined finite-size-support distribution, thus simulating the instantaneous load fluctuations. Each generator has a maximum power capability. A generator is not overloaded if the sum of the loads of consumers connected to a generator does not exceed its maximum production. In the standard grid each consumer is connected only to its designated generator, while we consider a more general organization of the grid allowing each consumer to select one generator depending on the load from a predefined consumer dependent and sufficiently small set of generators which can all serve the load. The model grid is interconnected in a graph with loops, drawn from an ensemble of random bipartite graphs, while each allowed configuration of loaded links represent a set of graph covering trees. Losses, the reactive character of the grid and the transmission-level connections between generators (and many other details relevant to realistic power grid) are ignored in this proof-of-principles study. We focus on the asymptotic limit, N-->infinity and N/M-->D=O(1)>1 , and we show that the interconnects allow significant expansion of the parameter domains for which the probability of a generator overload is asymptotically zero. Our construction explores the formal relation between the problem of grid optimization and the modern theory of sparse graphical models. We also design heuristic algorithms that achieve the asymptotically optimal selection of loaded links. We conclude discussing the ability of this approach to include other effects such as a more realistic modeling of the power grid and related optimization and control algorithms.

A Note on Milnor–Witt K-Theory and a Theorem of Suslin

We give a simple presentation of the additive Milnor–Witt K-theory groups of the field F, for n ≥ 2, in terms of the natural small set of generators. When n = 2, this specializes to a theorem of Suslin which essentially says that .

A Construction of High Rate Quasi-Cyclic Regular LDPC Codes from Cyclic Difference Families with Girth 8

In this paper we propose a method of constructing quasi-cyclic regular LDPC codes from a cyclic difference family, which is a kind of combinatorial design. The resulting codes have no 4-cycle, i.e. cycles of length four and are defined by a small set of generators of codes with high rate and large code length. In particular, for LDPC codes with column weight three, we clarify the conditions on which they have no 6-cycle and their minimum distances are improved. Finally, we show the performance of the proposed codes with high rates and moderate lengths.

Groups with a small set of generators

<p>Following [22] we study the class S of all groups that admit a small set of generators. Here we adopt also another notion of smallness (P-small) introduced by Prodanov in the case of abelian groups. We push further some results obtained in [22] (by adding some new members of S) and partially resolve an open question posed in [22]. We show that in most cases the groups in S admit a P-small set of generators.</p>

The utilization of recuperated and regenerated engine cycles for high-efficiency gas turbines in the 21st century

Abstract In the gas-turbine field ‘simple-cycle’ engines (compressor + burner + expander) have been dominant across almost the full spectrum of power-generation and mechanical-drive applications. Paced by aerodynamic and materials-technology advancements, efficiency values have progressed significantly over the last five decades. However, to reduce specific fuel consumption further (by say a step change of 30–40%) and to reduce emissions significantly, more-complex thermodynamic cycles that include the use of exhaust-heat-recovery exchangers are necessary. Clearly, there are discrete applications where the use of recuperators or regenerators will find acceptance on a large scale, an example being for gas turbines rated at less than about 100 kW for hybrid automobiles and small generator sets. The role that recuperators and regenerators can play in future gas turbines is put into perspective in this paper. Innovative engineering concepts will be required to meet the demanding high-temperature operating environment and low-cost requirements, and these will essentially necessitate the utilization of ceramic-composite heat-exchanger configurations that are amenable to large-volume manufacturing methods.

5472341 Burner having low pollutant emissions

In the gas-turbine field ‘simple-cycle’ engines (compressor + burner + expander) have been dominant across almost the full spectrum of power-generation and mechanical-drive applications. Paced by aerodynamic and materials-technology advancements, efficiency values have progressed significantly over the last five decades. However, to reduce specific fuel consumption further (by say a step change of 30–40%) and to reduce emissions significantly, more-complex thermodynamic cycles that include the use of exhaust-heat-recovery exchangers are necessary. Clearly, there are discrete applications where the use of recuperators or regenerators will find acceptance on a large scale, an example being for gas turbines rated at less than about 100 kW for hybrid automobiles and small generator sets. The role that recuperators and regenerators can play in future gas turbines is put into perspective in this paper. Innovative engineering concepts will be required to meet the demanding high-temperature operating environment and low-cost requirements, and these will essentially necessitate the utilization of ceramic-composite heat-exchanger configurations that are amenable to large-volume manufacturing methods.

Using Noise Data From Underwater Gas Vents To Estimate the Noise Level of Subsea Blowouts

An acoustic subsea blowout-preventer control system must distinguish between transmitted signals and ambient noise. Noise levels taken near an underwater gas vent are presented. These data are extrapolated to determine a limit for designing an acoustic control system. Scaling criteria and hydrophone placement are discussed, and an acoustic control system designed to operate under severe blowout conditions is described. Introduction In floating drilling operations, it is necessary to be able to close the blowout preventers (BOP's) on wells that are being drilled if the redundant primary control systems fail. In shallow water this is usually done with the aid of divers. Where diving is more difficult, as in deeper water or where severe environmental conditions are anticipated, it has been common to use a drop in hydraulic pressure to automatically close the annular preventer. It is better, however, to selectively close preventer. It is better, however, to selectively close the major functions on the BOP stack or to release the riser remotely; this can be done with an acoustic backup system. To design an acoustic system, the maximum background noises at the time the system is to be used should be estimated. A blowout at a gas flow rate of about 100 MMscf/D probably will generate the maximum noise level anticipated at the BOP. Available noise data dealing with gas turbulence in air and cavitation noise are not directly applicable for estimating the noise of gas being released underwater. To our knowledge, no noise data regarding gas vented subsea have been published. Consequently, representative data were taken using an inactive dry gas vent. However, venting gas at the rate of 100 MMscf/D through existing underwater gas vents is impractical, so lower rates had to be used in actual field measurements. This paper presents noise levels taken near an underwater gas vent flowing at controlled rates up to 11.4 MMscf/D. These data are extrapolated to 100 MMscf/D to determine a limit for designing an acoustic control system. Scaling criteria and hydrophone placement are discussed, and an acoustic control system designed to operate under severe blowout conditions is described. Subsea Noise Tests Test Situation The data were taken from a vent in 84 ft of water. Gas was vented vertically through a 5.5-in.-ID pipe with no restrictions at the outlet (see Fig. 1). A calibrated hydrophone with a preamplifier was suspended 6 ft from the flare opening, at about 120 degrees from the vertical center line of the gas vent. The remaining sound measuring equipment was located on a vessel moored near the vent. Hard copies of each spectral analysis were obtained on site and the sound data were recorded on magnetic tape for further evaluation. All ship's power was shut down while taking data, and instrument power was furnished by a small generator set on styrofoam pads for sound insulation. The data were taken during pads for sound insulation. The data were taken during short sessions over 3 days, and ambient noise conditions were measured during each session. The data were corrected for hydrophone sensitivity, band-pass, and spreading loss. Data taken on the first 2 days were converted to reflect the ambient noise on the third day when the highest ambient noise was read (see Appendix A.) Test Results Noise spectra in the 1- to 50-kHz range from the subsea vent at rates varying from 0 (background) to 11.4 MMscf/D are presented in Fig. 2. JPT P. 259

Combating camelthorn in California

In the gas-turbine field ‘simple-cycle’ engines (compressor + burner + expander) have been dominant across almost the full spectrum of power-generation and mechanical-drive applications. Paced by aerodynamic and materials-technology advancements, efficiency values have progressed significantly over the last five decades. However, to reduce specific fuel consumption further (by say a step change of 30–40%) and to reduce emissions significantly, more-complex thermodynamic cycles that include the use of exhaust-heat-recovery exchangers are necessary. Clearly, there are discrete applications where the use of recuperators or regenerators will find acceptance on a large scale, an example being for gas turbines rated at less than about 100 kW for hybrid automobiles and small generator sets. The role that recuperators and regenerators can play in future gas turbines is put into perspective in this paper. Innovative engineering concepts will be required to meet the demanding high-temperature operating environment and low-cost requirements, and these will essentially necessitate the utilization of ceramic-composite heat-exchanger configurations that are amenable to large-volume manufacturing methods.