Mechanical Power Production Research Articles

Comparative study of energy performance and water savings between hygroscopic and rankine cycle in a nuclear power plant. Case study of the HTR-10 reactor

The use of nuclear energy can contribute to achieving positive socio-economic and environmental benefits, but nuclear power plants are one of the most water-intensive industries in the world. The use of Small Modular Reactor (SMR) technologies is increasing due to their interesting advantages such as reduction of construction costs and use in remote areas, which favors distributed generation. Hygroscopic Cycle Technology (HCT) can be of great interest for power generation in nuclear power plants, due to the potential improvement in terms of energy efficiency and water savings. This study presents the benefits of implementing HCT in an existing SMR, the HTR-10, based on the classical Regenerative Rankine Cycle (RRC). The HTR-10 is used to produce electricity and thermal energy for District Heating (DH). Analytical models of both cycles have been developed to compare them in terms of energy production and water consumption. Sensitivity analyses of the influence of the main variables have been performed. The results show that by varying the condensing pressures, the thermal power for DH and the net mechanical power production of the HCT increase up to 2.5 % and 1 %, respectively, with respect to the RRC. The maximum tolerable ambient temperature for the plant with the HCT is 43.12 °C, increasing the availability of the plant and avoiding water consumption between 70000 and 88000 m3/year, depending on the operating conditions. Extrapolation of the results suggests that HCT can improve the energy production of nuclear power plants in a more sustainable way, contributing significantly to the energy transition.

Speed-specific optimal contractile conditions of the human soleus muscle from slow to maximum running speed.

The soleus is the main muscle for propulsion during human running but its operating behavior across the spectrum of physiological running speeds is currently unknown. This study experimentally investigated the soleus muscle activation patterns and contractile conditions for force generation, power production and efficient work production (i.e. force-length potential, force-velocity potential, power-velocity potential and enthalpy efficiency) at seven running speeds (3.0 m s-1 to individual maximum). During submaximal running (3.0-6.0 m s-1), the soleus fascicles shortened close to optimal length and at a velocity close to the efficiency maximum, two contractile conditions for economical work production. At higher running speeds (7.0 m s-1 to maximum), the soleus muscle fascicles still operated near optimum length, yet the fascicle shortening velocity increased and shifted towards the optimum for mechanical power production with a simultaneous increase in muscle activation, providing evidence for three cumulative mechanisms to enhance mechanical power production. Using the experimentally determined force-length-velocity potentials and muscle activation as inputs in a Hill-type muscle model, a reduction in maximum soleus muscle force at speeds ≥7.0 m s-1 and a continuous increase in maximum mechanical power with speed were predicted. The reduction in soleus maximum force was associated with a reduced force-velocity potential. The increase in maximum power was explained by an enhancement of muscle activation and contractile conditions until 7.0 m s-1, but mainly by increased muscle activation at high to maximal running speed.

ENERGY CONSUMPTION ANALYSIS FOR AN EV POWERTRAIN USING THREE BLDC IDENTICAL MOTORS

Using more than one motor in an EV (Electric Vehicle) powertrain enhances the vehicle’s torque, acceleration, and speed capabilities. A more tractive force produced by the electric powertrain requires more electric current from the battery. In modern EVs, mechanical power production can be approached to the wheels reducing the mechanical losses in the transmissions. It is the case with multiple-motor powertrains. Several advantages regarding vehicle control, physical performance, and energy efficiency improvement are obtained. In the current study, a BLDC (brushless dc) motor is investigated from the efficiency point of view to build a multiple-motor powertrain. A new methodology uses analytic calculations, simulations, and physical measurements. A powertrain with three identical motors results in a new vehicle configuration. Each motor's energy consumption improvements are analyzed following a normalized testing procedure. The results are compared with those of a single-motor powertrain.

Energy and Exergy-Based Screening of Various Refrigerants, Hydrocarbons and Siloxanes for the Optimization of Biomass Boiler–Organic Rankine Cycle (BB–ORC) Heat and Power Cogeneration Plants

The cogeneration of power and heat was investigated for Biomass Boiler–Organic Rankine Cycle (BB–ORC) plants with the characteristics of typical units, such as the 1 MWel Turboden ORC 10 CHP. The thermodynamic analysis of the ORC unit was undertaken considering forty-two (42) dry and isentropic candidate pure working fluids. Only subcritical Rankine cycles were considered, and the pinch point temperature differences for the evaporation and condensation heat exchangers were kept constant at 10 °C in all cases. The study provides an original and unique screening of almost all pure working fluids that are considered appropriate in the literature under the same operation and optimization conditions and compiles them into a single reference. In its conclusions, the study provides useful fluid selection and design guidelines, which may be easily followed depending on the optimization objective of the ORC designer or operator. In general, hydrocarbons are found to lie in the optimum middle range of the fluid spectrum, between the siloxanes that maximize the production of mechanical power and the refrigerants that maximize the production of heat. Specific hydrocarbon fluids, such as cyclopentane, heptane, hexane, benzene, and toluene, are found as rational options for maximum mechanical efficiency when operating with practically feasible condensation pressures between 10 and 200 kPa. At condensation pressures below 10 kPa, ethylbenzene, o-xylene, m-xylene, p-xylene, and nonane are also found to be feasible options. Finally, cyclopentane, hexane, and MM (hexamethyldisiloxane) are selected as the most appropriate options for cogeneration plants aiming simultaneously at high mechanical power and maximum temperature water production.

Synergistic integration of molten hydroxide direct carbon fuel cell and Stirling heat engine for efficient and clean coal use

To reuse the exhaust heat produced by molten hydroxide direct carbon fuel cells (MHDCFCs), a new combined system mainly composed of an MHDCFC, a regenerator, and a Stirling heat engine (SHE) is theoretically integrated for fuel-to-power efficiency enhancement. Mathematical formulas of the performance indicators for the combined system are derived based on the first and second laws of thermodynamics, from which the feasibility and effectiveness of the combined system are evaluated from both energetic and exergetic viewpoints. Moreover, the optimum working regions of the combined system are further specified by using a multi-objective function paying equal attention to both efficiency and power output. Results show that SHEs can be effectively acted as bottoming cycles for MHDCFC for additional mechanical power production. Numerical calculations indicate that the maximum power density and its corresponding energy efficiency and exergy efficiency of the proposed system are, respectively, about 97.6%, 97.1% and 99.2% greater than that of the single MHDCFC. Furthermore, extensive parametric studies show that increasing working temperature, volume ratio, hot-side working substance temperature or mean pressure is beneficial for the overall system performance, while increasing reactor compartment width may degrade the overall system performance.

The Use of Organic Rankine Cycles for Recovering the Heat Lost in the Compression Area of a Cryogenic Air Separation Unit.

The use of organic Rankine cycles (ORCs) is a viable solution for the recovery of waste heat. For an air separation unit (ASU) with a production of operating in Romania, the value of utilization of the heat transferred to the cooling system of the compression area represents 21% of the global system electrical energy input. To recover this thermal energy and transform it into mechanical energy, an ORC system was proposed. To maximize the production of mechanical power, an exergy analysis was performed. Exergy analysis was used to choose the most suitable organic fluid and find the optimum constructive structure of the Rankine cycle. The calculation of the exergy destruction in the key apparatuses of the system allowed investigation into the optimization search procedure. The large exergy destruction in the liquid preheater suggested the decrease in the temperature difference in this part of the evaporator by increasing the inlet temperature of the liquid; and an internal recuperative heat exchanger was used for this purpose. When permitted, the overheating of the vapors also reduced the temperature difference between the heat source and the organic fluid during the heat transfer process. The analysis was comparatively performed for several organic fluids such as R-245fa, R123, n-pentane and R717. The use of ammonia, that offered the possibility of superheating the vapors at the turbine inlet, brought a gain of mechanical power corresponding to 6% economy in the electrical energy input of the global plant.

Only the Good Die Old? Ontogenetic Determinants of Locomotor Performance in Eastern Cottontail Rabbits (Sylvilagus floridanus).

SynopsisFor many animals, the juvenile stage of life can be particularly perilous. Once independent, immature animals must often complete the same basic survival functions as adults despite smaller body size and other growth-related limits on performance. Because, by definition, juveniles have yet to reproduce, we should expect strong selection for mechanisms to offset these ontogenetic limitations, allowing individuals to reach reproductive adulthood and maintain Darwinian fitness. We use an integrated ontogenetic dataset on morphology, locomotor performance, and longevity in wild cottontail rabbits (Sylvilagus floridanus, Allen 1848) to test the hypothesis that prey animals are under selective pressure to maximize juvenile performance. We predicted that (1) juveniles would accelerate more quickly than adults, allowing them to reach adult-like escape speeds, and (2) juveniles with greater levels of performance should survive for longer durations in the wild, thus increasing their reproductive potential. Using high-speed video and force platform measurements, we quantified burst acceleration, escape speed, and mechanical power production in 38 wild-caught S. floridanus (26 juveniles, 12 adults; all rabbits >1 kg in body mass were designated to be adults, based on published growth curves and evidence of epiphyseal fusion). A subsample of 22 rabbits (15 juveniles, 7 adults) was fitted with radio-telemetry collars for documenting survivorship in the wild. We found that acceleration and escape speed peaked in the late juvenile period in S. floridanus, at an age range that coincides with a period of pronounced demographic attrition in wild populations. Differences in mass-specific mechanical power production explained ∼75% of the variation in acceleration across the dataset, indicating that juvenile rabbits outpace adults by producing more power per unit body mass. We found a positive, though non-significant, association between peak escape speed and survivorship duration in the wild, suggesting a complex relationship between locomotor performance and fitness in growing S. floridanus.

Proposal and 3E (energy, exergy, and exergoeconomic) assessment of a cogeneration system using an organic Rankine cycle and an Absorption Refrigeration System in the Northeast Brazil: Thermodynamic investigation of a facility case study

This paper proposes a cogeneration system to achieve the partial electric and thermal demands of a building in the public University. This proposed system comprises an Internal Combustion Engine (ICE), an organic Rankine cycle (ORC), and equipment that will operate as a sink. For the latter, two types of equipment were selected: a cooling tower and an Absorption Refrigeration System (ARS). The building selected to propose the cogeneration system is the Institute of Sustainable Energies (IES), located at the Federal University of Paraíba (UFPB), in the Northeast of Brazil. The performance of the system based on energetic and exergetic points of view operating under two distinct modes; ORC Simple (ORC-S) and ORC Combined (ORC-C), was compared. Both modes are based on the energy availability of the ICE exhaust gases. The thermodynamic models for both modes were developed based on the first and second laws of thermodynamic considering input parameters, such as inlet temperature, pressure ratio, and outlet temperature of the expander and the cold-water storage tank. For the exergoeconomic technique, the SPECO Method (Specific Exergy Costing) was used and implemented along with the Thermodynamic model. The ORC system studied uses a scroll expander and operates with R-134a as the working fluid and water/ammonia pair for the single-effect ARS. The results showed that the ORC-C mode can meet from 18.9% to 37.5% of the IES electricity demand, while the ORC-S mode can meet from 12.4% to 24.5%. The thermodynamic analysis reported that the ORC-C allowed a 33.6% increase in mechanical power production, an increase from approximately 4.5% to 34.5% in energy efficiency as well as exergy efficiencies around 40% and reduction of the total destroyed exergy. From the exergoeconomic point of view, the specific cost of the chilled water has a slight influence on the total cost of the products, while the specific cost of hot water has a strong influence on the total cost of the products (a variation of approximately 46% for a distinct heat source).

Differential activation of lumbar and sacral motor pools during walking at different speeds and slopes.

Organization of spinal motor output has become of interest for investigating differential activation of lumbar and sacral motor pools during locomotor tasks. Motor pools are associated with functional grouping of motoneurons of the lower limb muscles. Here we examined how the spatiotemporal organization of lumbar and sacral motor pool activity during walking is orchestrated with slope of terrain and speed of progression. Ten subjects walked on an instrumented treadmill at different slopes and imposed speeds. Kinetics, kinematics, and electromyography of 16 lower limb muscles were recorded. The spinal locomotor output was assessed by decomposing the coordinated muscle activation profiles into a small set of common factors and by mapping them onto the rostrocaudal location of the motoneuron pools. Our results show that lumbar and sacral motor pool activity depend on slope and speed. Compared with level walking, sacral motor pools decrease their activity at negative slopes and increase at positive slopes, whereas lumbar motor pools increase their engagement when both positive and negative slope increase. These findings are consistent with a differential involvement of the lumbar and the sacral motor pools in relation to changes in positive and negative center of body mass mechanical power production due to slope and speed.NEW & NOTEWORTHY In this study, the spatiotemporal maps of motoneuron activity in the spinal cord were assessed during walking at different slopes and speeds. We found differential involvement of lumbar and sacral motor pools in relation to changes in positive and negative center of body mass power production due to slope and speed. The results are consistent with recent findings about the specialization of neuronal networks located at different segments of the spinal cord for performing specific locomotor tasks.

A semi-analytic method to optimize tidal farm layouts – Application to the Alderney Race (Raz Blanchard), France

The purpose of this paper is to present a semi-analytic model designed to optimize tidal farm layouts by maximizing the mechanical power production. A meta-heuristics method is used to find the turbine placement which minimizes the flow interaction between the turbines. The velocities in the wakes of turbines are simulated with an analytic model. The methodology is first applied to idealized cases: constant current magnitude and direction, and flow aligned with the turbines. Those preliminary tests permit to test the consistency of the results. In particular, they show that the optimal density of the devices grows with increasing turbulent intensities or increasing upstream velocity magnitude. The methodology is then applied to a site located in the Alderney Race (Raz Blanchard in French), situated between the Alderney Island and La Hague Cape (France). The results show that the optimal placement is influenced by the asymmetry of the tidal current and that the best layout is strongly dependent on the directional spreading of the current with respect to the predominant direction.

ENGLISH

3 ABSTRACT: In modern wind turbines, the energy conversion process uses the basic aerodynamic force of lift to produce a net positive torque on a rotating shaft, resulting first in the production of mechanical power and then its conversion to electricity in a generator. Wind turbines, unlike most other turbines, can produce power only in response to the wind that is available at the time. The output of a wind turbine is thus inherently fluctuating with the wind and can't be directly dispatched for a purpose. Apart from this, the output depends on individual components like rotor dimension, transmission shaft, gear box and alternator. Since the wind turbine is relatively large, expensive, and Wind Energy Conversion System (WECS) is complex, it is not convenient to do research on actual wind farm. Therefore, WECS model development for steady and dynamic state analysis and design has been research issue in recent years. This paper presents a new block-based approach for WECS dynamic modeling. The blocks (modules) developed by Aalborg University - Denmark, RISO national laboratory based on Kaimal Spectra have been customized, updated and integrated into MATLAB/SIMULINK platform and then utilized to simulate performance of 5kW WECS. In addition to the developed block sets, in this paper, a proportional-integral controller is designed to control the turbine pitch and integrated with the simulation models. The simulation result demonstrates that the model output is in agreement with what is expected. The system has advantages like: research cost reduction, ease in application and control, flexibility and completeness for analysis in MATLAB/SIMULINK environment. The system can be used for assessment of power quality and design of wind turbine system for grid connection.

The Relative Effect of an Aquatic Environment on Jumping Kinetics between Older and Younger Adults

In comparison with the land environment, our previous work suggests that jumping movements performed in the aquatic environment elicit greater propulsive mechanical power production. While this knowledge is insightful, our previous work involved healthy, young participants. It is important to expand this research to populations that may benefit from a powerful, low-impact method of functional movement training. PURPOSE: The purpose of this study was to evaluate the relative effect of the aquatic environment on jumping kinetics between older and younger adults. METHODS: Twelve college-aged males (YA; 23.8 ± 2.5 years) and twelve recreationally active older adults (OA; 57.3 ± 4.4 years) performed 3 countermovement jumps (CMJ) on land and immersed in water at the level of the xiphoid process. Force platform data was processed for the following variables: Peak propulsive power, take-off velocity, and peak take-off force. A 2 (environment) by 2 (age) repeated measures ANOVA was used to identify main effects and interactions. RESULTS: Peak propulsive power, take-off velocity, and peak take-off force were lower (p < 0.001) for older adults in both environments (OA: 5.7 kW, 2.8 m/s, 1584 N; YA: 8.9 kW, 4.0 m/s, 2109 N). Regardless of age, peak propulsive power (kW) and take-off velocity (m/s) were greater (p < 0.001) for jumps performed in the water (9.8 kW vs. 4.8 kW; 5.1 m/s vs. 2.3 m/s), while peak take-off force (N) was greater (p = 0.004) for jumps performed on land (1990 N vs. 1703 N). CONCLUSION: The absence of age and environment interactions on peak propulsive power and peak take-off force suggest that older and younger adults exhibit similar kinetic responses to jumping movements performed in the aquatic environment. Results of the present study suggest that the aquatic environment may be preferential for older adults performing explosive movements. Specifically, the aquatic environment may enhance training, with a focus on augmenting mechanical power production and take-off velocity. Further research may identify additional justification for prescribing jumping movements in the aquatic environment.

Wake Effect and Power Production of Wind Turbine Arrays

This study experimentally investigated the influence of wake effect and production of mechanical power in wind tunnel of wind turbine arrays. Wind turbine arrays consist of 2 rows with 3 columns for spacing wind turbines in rows apart in the windward direction 1.77 rotor diameters and apart in the crosswind direction 8.85 rotor diameters. The wake characteristics such as profiles of time averaged velocity, turbulence intensity, centerline velocity deficit and wake radius for far wake regions in position 1, 2, and 3 were measured and analysed. The vertical and lateral profiles of velocity and turbulence intensity were studied. Concerning the results from measured data, empirical relations for the centerline velocity deficit, turbulence intensity and wake radius were proposed. Based on the experimental results, the power loss is due to the wake flow of upwind turbine approximately 20% when the downwind distance 8.85 rotor diameters. This is different with numerical result study that 11% at downwind distance is 8.85 rotor diameters. This difference results from the influence of ambient turbulence on the production of mechanical power of the wind turbine.

A computational assessment of the aerodynamic performance of a tilted Darrieus wind turbine

The aerodynamic performance of a Darrieus wind turbine operating with the rotation axis tilted with respect to the free-stream wind speed is investigated in this paper. An Unsteady Reynolds Averaged Navier Stokes (URANS) Computational Fluid Dynamics (CFD) model is proposed in order to provide wind turbine manufacturers with a reliable simulation tool to forecast the power conversion characteristics of vertical axis wind turbine prototypes that operate in tilted conditions. The outputs of the model are compared against experimental performance of a non-tilted rotor corrected to the standard sea level conditions. Two different tilted configurations are studied (i.e., a tilt angle of 10° and 20°) and the aerodynamic performance is presented in terms of the mechanical power production and the power coefficient. A sensible decrease in the power production is observed for increasing tilt angles. Comprehensive physical interpretations of the results are provided, considering also the predictions of a methodology based on semi-empirical methods.

Diversity powers performance at Catalyst Energy

Purpose – This paper aims to observe how the Catalyst Energy college of engineering for women has played a significant role in helping to train women in fields such as mechanical engineering, electrical engineering and power production and so overcome a shortage of qualified women in these fields. Design/methodology/approach – The paper examines what gave rise to the diversity initiative at Catalyst Energy’s Ahmedabad plant, India, and the success that it has achieved. Findings – This paper reveals that, of the first batch of 30 students, in 1995, eight made it to Catalyst Energy. The number has grown every year since then. Practical implications – It explains that Catalyst is working towards having women make up half its workforce, as it moves away from being dominated by Gujarati males. Social implications – It touches on some of the reasons that women are under-represented in Indian companies. Originality/value – It reveals that globalization is a key pressure in encouraging Catalyst to make its workforce more diverse.

A Study of Vector-Valued Binary Scaling Functions and Parseval Frames with Integer Dilation Constant

Mechanical engineering is a discipline of engineering that applies the principles of physics and materials science for analysis, design, manufacturing, and maintenance of mechanical systems. It is the branch of engineering that involves the production and usage of heat and mechanical power for the design, production, and operation of machines and tools. It is one of the oldest and broadest engineering disciplines. The notion of orthogonal vector-valued binary wavelet packs is introduced. Their traits is investigated by virtue of time-frequency analysis method and finite group theory. Orthogonality formulas are established. Orthonormal wavelet pack bases are obtained. A novel method for constructing a kind of orthogonal shortly supported vector-valued wavelets is presented.

Calcium signalling indicates bilateral power balancing in theDrosophilaflight muscle during manoeuvring flight

Manoeuvring flight in animals requires precise adjustments of mechanical power output produced by the flight musculature. In many insects such as fruit flies, power generation is most likely varied by altering stretch-activated tension, that is set by sarcoplasmic calcium levels. The muscles reside in a thoracic shell that simultaneously drives both wings during wing flapping. Using a genetically expressed muscle calcium indicator, we here demonstrate in vivo the ability of this animal to bilaterally adjust its calcium activation to the mechanical power output required to sustain aerodynamic costs during flight. Motoneuron-specific comparisons of calcium activation during lift modulation and yaw turning behaviour suggest slightly higher calcium activation for dorso-longitudinal than for dorsoventral muscle fibres, which corroborates the elevated need for muscle mechanical power during the wings' downstroke. During turning flight, calcium activation explains only up to 54 per cent of the required changes in mechanical power, suggesting substantial power transmission between both sides of the thoracic shell. The bilateral control of muscle calcium runs counter to the hypothesis that the thorax of flies acts as a single, equally proportional source for mechanical power production for both flapping wings. Collectively, power balancing highlights the precision with which insects adjust their flight motor to changing energetic requirements during aerial steering. This potentially enhances flight efficiency and is thus of interest for the development of technical vehicles that employ bioinspired strategies of power delivery to flapping wings.

The metabolic and mechanical costs of step time asymmetry in walking

Animals use both pendular and elastic mechanisms to minimize energy expenditure during terrestrial locomotion. Elastic gaits can be either bilaterally symmetric (e.g. run and trot) or asymmetric (e.g. skip, canter and gallop), yet only symmetric pendular gaits (e.g. walk) are observed in nature. Does minimizing metabolic and mechanical power constrain pendular gaits to temporal symmetry? We measured rates of metabolic energy expenditure and calculated mechanical power production while healthy humans walked symmetrically and asymmetrically at a range of step and stride times. We found that walking with a 42 per cent step time asymmetry required 80 per cent (2.5 W kg(-1)) more metabolic power than preferred symmetric gait. Positive mechanical power production increased by 64 per cent (approx. 0.24 W kg(-1)), paralleling the increases we observed in metabolic power. We found that when walking asymmetrically, subjects absorbed more power during double support than during symmetric walking and compensated by increasing power production during single support. Overall, we identify inherent metabolic and mechanical costs to gait asymmetry and find that symmetry is optimal in healthy human walking.

The measurement of maximal (anaerobic) power output on a cycle ergometer: a critical review.

The interests and limits of the different methods and protocols of maximal (anaerobic) power (P max) assessment are reviewed: single all-out tests versus force-velocity tests, isokinetic ergometers versus friction-loaded ergometers, measure of P max during the acceleration phase or at peak velocity. The effects of training, athletic practice, diet and pharmacological substances upon the production of maximal mechanical power are not discussed in this review mainly focused on the technical (ergometer, crank length, toe clips), methodological (protocols) and biological factors (muscle volume, muscle fiber type, age, gender, growth, temperature, chronobiology and fatigue) limiting P max in cycling. Although the validity of the Wingate test is questionable, a large part of the review is dedicated to this test which is currently the all-out cycling test the most often used. The biomechanical characteristics specific of maximal and high speed cycling, the bioenergetics of the all-out cycling exercises and the influence of biochemical factors (acidosis and alkalosis, phosphate ions…) are recalled at the beginning of the paper. The basic knowledge concerning the consequences of the force-velocity relationship upon power output, the biomechanics of sub-maximal cycling exercises and the study on the force-velocity relationship in cycling by Dickinson in 1928 are presented in Appendices.

On the mechanical efficiency of dielectric barrier discharge plasma actuators

The mechanical power production and electrical power consumption of the dielectric barrier discharge plasma actuator is investigated for different operating conditions. The ratio of these two values delivers the mechanical efficiency of the actuator as a flow acceleration device. The general trend is that higher carrier frequencies and voltages lead to higher values of the efficiency. The values that were found for the mechanical efficiency are very small, the highest recorded value is only 0.18%.