Twin Engine Research Articles

An Optimal Speed Control Method of Multiple Turboshaft Engines Based on Sequence Shifting Control Algorithm

Abstract In order to overcome the problem of significant drop in operational efficiency remarkably while power turbine speed varies among a large range, an optimal speed control method of multiple turboshaft engines based on sequential shifting control (SSC) algorithm is proposed. Firstly, combined with multispeed gearboxes, a sequential shifting control algorithm of multiple turboshaft engines is proposed and designed to accomplish continuously variable speed control. Then, selecting the minimum engine fuel flow as the optimization objective, an integrated optimization method of optimal speed based on multiple engines and multispeed gearboxes is proposed to promote the operational economy. Finally, the simulation tests of the optimal speed control method of twin and triple turboshaft engines are conducted separately. The results demonstrate that the optimal speed control method of multiple turboshaft engines based on SSC algorithm can change the power turbine speeds by no more than 7% and the main rotor speed by over 8% simultaneously. In addition, compared with the fixed-ratio transmission (FRT), engine fuel flows decrease by more than 2% under different cruise states. It proves that the optimal speed control method is beneficial to obtain more superior overall performances of the integrated helicopter/multi-engine system without considerable loss of compressor surge margin.

Realizing Enhanced Thermoelectric Performance and Hardness in Icosahedral Cu5 FeS4-x Sex with High-Density Twin Boundaries.

Bornite (Cu5 FeS4 ) is an Earth-abundant, nontoxic thermoelectric material. Herein, twin engineering and Se alloying are combined in order to further improve its thermoelectric performance. Cu5 FeS4-x Sex (0 ≤ x≤ 0.4) icosahedral nanoparticles, containing high-density twin boundaries, have been synthesized by a colloidal method. Spark plasma sintering retains twin boundaries in the pellets sintered from Cu5 FeS4-x Sex colloidal powders. Thermoelectric property measurement demonstrates that alloying Se increases the carrier concentration, leading to much-improved power factor in Se-substituted Cu5 FeS4 , for example, 0.84 mW m-1 K-2 at 726 K for Cu5 FeS3.6 Se0.4 ; low lattice thermal conductivity is also achieved, due to intrinsic structural complexity, distorted crystal structure, and existing twin boundaries and point defects. As a result, a maximum zT of 0.75 is attained for Cu5 FeS3.6 Se0.4 at 726 K, which is about 23% higher than that of Cu5 FeS4 and compares favorably to that of reported Cu5 FeS4 -based materials. In addition, the Cu5 FeS4-x Sex samples containing twin boundaries also obtain improved hardness compared to the ones fabricated by melting-annealing or ball milling. This work demonstrates an effective twin engineering-composition tuning strategy toward enhanced thermoelectric and mechanical properties of Cu5 FeS4 -based materials.

Enhanced Catalytic Mechanism of Twin-Structured BiVO4.

Twin engineering is an efficient strategy to improve the photocatalytic activity of semiconductors (e.g., BiVO4). A systematic study that combines theory and experiments is conducted to reveal the underlying enhanced catalytic mechanism of twin-structured BiVO4. The key characteristic of twinned structures is the partial strain introduced by twin boundaries. Lattice distortion introduced by the twin boundaries leads to charge redistribution and built-in electronic fields between the twin boundaries and the bulk. The generated homojunctions possess a staggered band alignment structure, and their band offsets are increased by the Fermi-level pinning effect. The series of homojunctions in twinned structures is beneficial for facilitating charge separation. Additionally, lattice distortion around twin boundaries leads to the broken geometric symmetry of metal-oxygen polyhedrons in twinned crystals. The adsorption energies of adsorbates decrease significantly, resulting in reduction of the overpotential. The reduced overpotential favors acceleration of the oxygen evolution reaction on twinned structures.

Narrative as cultural representation

Abstract This paper addresses issues related to narrative, cognition, and culture within the framework of foreign- or second-language (L2) narrative discourse, using a methodology of connecting the story- and language-related qualities of narrative discourse. The term “coherence” refers to whether or not a text makes sense at a global level, whereas “cohesion” describes the linguistic relationships among clauses in a narrative, such as how its surface linguistic elements are linked together at a local level. The paper (1) examines oral narratives, (2) reveals how both coherence and cohesion serve as the twin engines of narrative, and (3) emphasizes the significance of noting not only the narrative content/structure but also the appropriate use of linguistic devices, to identify language-specific ways of expressing affective elements in narrative. That is, the paper suggests the importance of developing conceptual understanding of L2 forms (e.g., grammatical variables) and their stylistic significance.

H-infinity approach to design optimal output control for the aggregated interpolation model of helicopter motion

This paper presents the problem of designing a feedback control of the aggregated model describing helicopter flight dynamics under the influence of exogenous factors based on the H-infinity approach. The original nonlinear equations of dynamics are assumed to be linearized regarding to several flight modes that characterize with a set of precisely specified flight conditions such as an attitude of an aircraft, its forward speed and turn rate. Matrices of the linearized systems are dependent on the speed of the aircraft. Due to that the aggregated model comprises eight submodels corresponding to flight modes when the speed varies from hover to 140 kts in a certain regular interval. The proposed principle of designing includes two stages: on the first stage the feedback control input is selected for each submodel separately so that the H-infinity norm of the value functional with respect to the H-infinity norm of disturbances is minimum; on the second one the interpolation technique lying in the expansion of matrices in the basis of finite functions is applied. The solution method is experienced on three helicopter models: ZD559-Lynx, the twin engine, utility helicopter in the 4.5 -ton category; S123-Bo105, the twin engine helicopter in the 2.5 ton class; SA330-Puma, the twin engine, medium-support helicopter in the 6-ton category.

Technology and skill: Twin engines of growth

A model is developed in which two complementary forms of investment contribute to growth—technology and skill acquisition, and growth takes two forms—TFP and variety growth. The rate of TFP growth depends more heavily on the parameters governing skill accumulation, while variety growth depends, roughly, on the difference between the parameters governing technology and skill accumulation. Conditions for the existence of a BGP are established, and the effects of various parameters are characterized. In an example, subsidies to skill acquisition (technology acquisition) are powerful tools for stimulating TFP growth (variety growth). Investment incentives off the BGP are also explored.

A Differential Electric Drive for Electric Vehicles with an Independent Power Supply

In this paper, we consider the effectiveness of using a twin-engine electric drive from the point of view of acceleration dynamics and energy efficiency. To take into account the acceleration time of the electric vehicle and the energy consumed during the transition process, evaluation criterion G was introduced. By a “twin-engine system” is meant a system of electric drive of a wheel pair through two independent mechanical channels: the first is a “high-torque” channel implemented through the use of a gearbox with a high gear ratio, and the second is a “high-speed” channel implemented through the use of a gearbox with a low gear ratio or without a gearbox at all. The summation of power is carried out by means of a differential gear. We performed mathematical modeling of the operation of such a system. Asynchronous electric drives with vector control, which operate in the torque source mode, are used as electromechanical converters. An algorithm and a system for distributing torque between two channels are developed. The gear ratio of the “high-torque” channel gearbox was optimized by the criterion of G minimum. A quantitative comparison and analysis of transient acceleration processes in single- and twin-engine systems were performed based on the example of a 30-kW electric race car. It is concluded that it is effective to use a twin engine system for specific types of electric vehicles.

Biomimicry In Creative Contemporary Art Making Process

This research was conducted in order to distinguish the different between artist and designer in using biomimicry in creating and constructing their design and artwork. Biomimicry is a method of solving complex problems by looking into Mother Nature. We as human sometimes have our own limits in dealing with things that need to be solved. Nature had provided us with a vast range of knowledge. We just need to look in the right place. By using nature as our mentor, we get to experience the powerful healing effects it has by connecting to the natural world while also finding empowering relief to solve these challenges together. Science and art, the twin engine of creativity in any dynamic culture, are commonly thought of as being as different as day and night. In creating art, artist also shares the same opinion in seeking back inspiration by observing nature.Keywords: Biomimicry, sculpture, nature, dynamic culture.

Application case of digital twin technology in electric power system

The electric power system is an important part of the national economy. Substation, as a core element of the electric power system, has problems such as difficulties to supervise. This paper proposes the use of digital twin technology to solve the problem of regulatory difficulties. Firstly, the mathematical model of substation digital twin is established. Then the digital twin engine is designed based on the model, which realizes real-time orientation of the personnel through UWB location technology, realizes real-time monitoring of personnel, work, equipment operation, and work area through job management, realizes real-time monitoring of production data through equipment data mapping, realizes early warning and rapid emergency response through operation rules. At last, the prototype system is developed to verify the function. The experimental results show that the system can effectively improve the supervision capability of the substation. This solution can provide a useful reference for systems with similar needs.

Endogenous growth, human capital and the dynamic costs of recessions

PurposeThe purpose of the paper is twofold: to construct and analyze a novel endogenous growth model, in which unbounded growth is possible without the need to assume increasing returns to scale, and to use the model to estimate the long-run (or dynamic) costs of recessions.Design/methodology/approachIn the proposed model, endogenous technology and human capital accumulation serve as the “twin engines of growth.” Simulations are used to derive growth rates consistent with long-term experience of developed countries, to understand better the differences between balanced growth and unbounded growth and to provide an estimate of the dynamic costs of capacity utilization shocks that produce business cycle-like behavior.FindingsConservative calculations show that the costs of the capacity shocks can be large – about 1.5 percent of the present value of output over a 100-period horizon. The theoretical model also suggests that differences in the technology production and human capital accumulation functions, possibly due to differing institutions, may help explain diverse growth experiences.Originality/valueThe paper, for first time, combines two strands of the economic growth theory – endogenous technology and endogenous human capital production – into a single model. It uses the implications of the model to argue, through simulations, that the benefits of counter-cyclical policies are potentially large in the long run.

Assessment of Thermo-Electric Power Plants for Rotorcraft Application

Abstract This paper assesses a parallel electric hybrid propulsion system utilizing simple and recuperated cycle gas turbine configurations. An adapted engine model capable to reproduce a turboshaft engine steady state and transient operation is built in Simcenter Amesim and used as a baseline for a recuperated engine. The transient operation of the recuperated engine is assessed for different values of heat exchanger effectiveness, quantifying the engine lag and the surge margin reduction which are results of the heat exchanger addition. An oil and gas (OAG) mission of a twin engine medium helicopter has been used for assessing the parallel hybrid configuration. The thermoelectric system brings a certain level of flexibility allowing for better engine utilization, thus first a hybrid configuration based on simple cycle gas turbine scaled down from the baseline engine is assessed in terms of performance and weight. Following the recuperated engine, thermoelectric power plant is assessed and the performance enhancement is compared against the simple cycle conventional and hybrid configurations. The results indicate that a recuperated gas turbine based thermo-electric power plant may provide significant fuel economy despite the increased weight. At the same time, the electric power train can be used to compensate for the reduced specific power and potentially for the throttle response change due to the heat exchanger addition.

Twin engineering of photocatalysts: a minireview

Recent advances in twin engineering of photocatalysts have been highlighted in this mini-review, which is beneficial for the rational design and construction of novel highly-active photocatalysts.

Novel Shocks: Urban Renewal and the Origins of Neoliberalism. Myka Tucker-Abramson. New York: Fordham University Press, 2019. Pp. v+197.

Novel Shocks asks how novels of the 1950s and 1960s responded to New York City’s central role in urban renewal projects that paved the way for the “creative destruction” (2) associated with neoliberalism and US empire. New York City was at the center of so-called “urban decline” (1) ideology seeking to explain the inward “great migration of blacks, Latinos, and Puerto Ricans” and outward migration of “industry, commerce, and the white tax base” (1) to the emerging suburbs. While the Federal Housing Act of 1949 and Federal Highway Act of 1956 had national scope, New York reaped the lion’s share of material and ideological changes. NYC was the central testing ground of new urban/suburban relations “designed by planners, politicians, and downtown business interests” (1). The twin engines of suburbanization and urban renewal “helped the United States restabilize global capitalism after World War II by absorbing the surpluses of capital and labor whose stagnation manifested itself in the global Great Depression of the 1930s” (7). Tucker-Abramson focuses throughout on the violence wrought by international capitalism and its imminent resistance by insurgent communes, arguing that “urban renewal, in other words, formed the basis for the long and soon to be global struggle over the displacement and dispossession of urban populations that has been a defining feature of neoliberalism” (8).

Connecting L1 and L2 acquisition: From the perspective of macro and micro narrative structure

AbstractThe studies presented in this paper connect the story-related quality and the language-related quality of narrative discourse. The term “coherence” refers to whether or not a text makes sense at a global level, whereas “cohesion” describes the linguistic relationships among clauses in a narrative, such as how the surface linguistic elements of a text are linked to one another at a local level. Using a content-based narrative analysis, a trilogy – a set of three independent but interrelated studies – introduced in this paper quantitatively analyze oral personal narratives through three lenses. As examples of devices for cohesion, the paper qualitatively examines the use of two linguistic devices, tense (past and non-past) and voice (active and passive), and tries to show how narrators deploy organizational strategies in the use of these linguistic forms. The paper (1) examines varied topics in different narrative contexts (genre, topic, oral or written), (2) reveals how both coherence and cohesion serve as the twin engines of narrative, and (3) emphasizes the significance of paying attention not only to the narrative content/structure but also to the appropriate use of linguistic devices so that we can fully grasp language-specific ways of expressing affective elements in narrative.

Evaluation of Low-Cost Solutions to Support Flight Operations Quality Assurance

During the period 2003–2011, worldwide accident rates for business/corporate aviation were nearly four times that for commercial aviation. Flight Operations Quality Assurance (FOQA) or Flight Data Monitoring—the collection of real-time flight data for continuous safety improvement—has been routinely used by commercial aviation for over 50 years. Regulatory authorities only require airplanes over 27 tonnes maximum takeoff weight to operate an FOQA Program. Corporate/business aviation operators generally operate airplanes less than 20 tonnes using a diverse range of airplanes, which may include a single engine, twin engine, turbo-prop, and/or very light jets. This study investigates the use of low-cost, independent commercial off-the-shelf technologies using a combination of Global Positioning Systems and Attitude Heading & Referencing Systems to sense and record key flight data parameters in support of an FOQA program for corporate operators with diverse, lower-weight-category and legacy airplanes. The preliminary results suggest that such systems and Electronic Flight Information Systems (where installed) can usefully support an FOQA for lower-weight-category and legacy airplanes.

중형급 알루미늄 고속 Rigid Inflatable Boat 선형개발과 저항성능에 관한 연구

In this study, a high speed Rigid Inflatable Boat(RIB) with about 10 meters length is developed. Design speed of the boat is 30 knots (15.43 m/s) using 250 hp twin engines and main material is aluminum. Resistance performance related to the free running attitude as trim and sinkage are discussed and wave patterns are observed to make clear the relationship between the performance and wave characteristics using model test and CFD analysis. The results show that not only wave patterns but also free running attitude of the boat have a strong influence on resistance performance. CFD results including free surface give good relative tendency for effective power and the attitude comparing model test results. CFD analysis used in this study can be used at initial ship design stage of high speed boat.

The drivetrain and the steering mechanism for the twin engines tracked vehicle

The kinematic plan of the double flow transmission and the steering mechanism for the twin engines tracked vehicle is proposed. It could be used for the compact remotely operated vehicle or autonomous tracked chassis with twin electric engines. However, the plan is applied for skid steering wheeled vehicles or heavy transport vehicles. This plan makes it possible to use the parallel/series type hybrid propulsion system. In this case the powertrain is divided into two separate flows: heat engine with a gearbox and the reversible traction electric engine. The principle could be adapted for designing ships with diesel-electric hybrid propulsion system (it is possible to use internal combustion engine instead of electric engine), for the reduction unit modernization in the motor boat, and for special purpose ships design. Simplicity, portability, engine duplication, potential for energy recuperation during breaking/turning and providing turning around the center of gravity are the main advantages of this plan. The last two points are true for skid steering wheeled vehicles. The operating modes, the main kinematic and power aspects are provided. The required power of the electric engine traction in the hybrid transport tracked vehicle (weighing 45-50 tons) is estimated. The production of the hybrid propulsion system with proposed transmission based on Russian components is considered.

On the assessment of subjective response to tonal content of contemporary aircraft noise

The Effective Perceived Noise Level (EPNL) is the primary metric used for assessing subjective response to aircraft noise. The EPNL comprises calculation of the Perceived Noise Level (in PNdB), and takes into account flyover duration and the presence of pure tones to arrive at an adjusted EPNL value. With the presence of a single significant tone, EPNL has been found to be reasonably effective for the assessment of aircraft noise annoyance. Several authors have, however, suggested that EPNL is not capable of quantifying the subjective response to aircraft noise that contains multiple complex tones. The noise source referred to as “Buzz-saw” noise is a typical example of complex tonal content in aircraft noise with an important effect on both cabin and community noise impact. This paper presents the results of a series of listening tests where a number of participants were exposed to samples of aircraft noise with six variants of aircraft engines, assumed representative of the contemporary twin engine aircraft fleet. On the basis of the findings of these listening tests, the Aures tonality method significantly outperforms the EPNL tone correction method when assessing the subjective response to aircraft noise during take-off with the presence of multiple complex tones. The participants reported ‘high pitch’ as one of the least preferable aircraft noise characteristics, and consequently, the psychoacoustics metric Sharpness was found to be another important contributor to subjective response to the noise of two specific aircraft engine groups (out of the six considered). The limitations of Aures tonality are discussed, in particular for aircraft noise with both a series of complex tones spaced evenly across the frequency spectrum with relatively even sound levels and less subjectively dominant single frequency tones (compared to broadband noise). In line with these limitations, further work is proposed for more effective assessment of subjective response to aircraft noise containing significant tonal content in the form of numerous closely spaced or other complex tones.

Design and Application of a Multidisciplinary Predesign Process for Novel Engine Concepts

The purpose of this paper is to present a multidisciplinary predesign process and its application to three aero-engine models. First, a twin spool mixed flow turbofan engine model is created for validation purposes. The second and third engine models investigated comprise future engine concepts: a counter rotating open rotor (CROR) and an ultrahigh bypass turbofan. The turbofan used for validation is based on publicly available reference data from manufacturing and emission certification. At first, the identified interfaces and constraints of the entire predesign process are presented. An important factor of complexity in this highly iterative procedure is the intricate data flow, as well as the extensive amount of data transferred between all involved disciplines and among different fidelity levels applied within the design phases. To cope with the inherent complexity, data modeling techniques have been applied to explicitly determine required data structures of those complex systems. The resulting data model characterizing the components of a gas turbine and their relationships in the design process is presented in detail. Based on the data model, the entire engine predesign process is presented. Starting with the definition of a flight mission scenario and resulting top level engine requirements, thermodynamic engine performance models are developed. By means of these thermodynamic models, a detailed engine component predesign is conducted. The aerodynamic and structural design of the engine components are executed using a stepwise increase in level of detail and are continuously evaluated in context of the overall engine system.

Analysis and Development of Restrictor for Parallel Twin Engine in FSAE Cars

This research aims to the development of intake restrictor of a formula SAE car engine which is of 300cc parallel twin cylinder engine. In this paper we have considered different venturi designs which have different convergence and divergence angles. The main aim is to optimize the pressure and velocity of air which tends to offer better combustion reflects in performance. The parameters which are to be considered for design as well as analysis are mach number, intake velocity, mass flow rate, etc.., To perform this research we have chosen the Ansys fluent software tool and the analytical calculations were made for standard design. It is observed that the continuous variations in converging and diverging angles offers better results in both pressure and velocity characteristics of air entering for combustion.