Full Operating Conditions Research Articles

New radial turbine dynamic modelling in a low-temperature adiabatic compressed air energy storage system discharging process

It is challenging to gain insight of a Compressed Air Energy Storage (CAES) system dynamic behaviour under various operation conditions due to its complexity with mixed mechanical, thermal, chemical and electrical processes in one. Although a number of studies are reported on CAES steady state and dynamic modelling to reveal its characteristics, few studies have been reported in whole CAES system dynamic modelling involving a radial turbine. This paper explores a new method to analyse the transient performance of the radial turbine while it is integrated with whole low temperature Adiabatic-CAES system. The proposed modelling method approximates the average air flow within single stator/rotor stage. By applying the principle of energy and torque balance on the transmission shaft, the dynamic speed-torque characteristics of the turbine is obtained with a “quasi dynamic iterative searching” process. The model is then integrated to a simulation platform, which is created to synchronise the wide range of time scale dynamic responses including heat transfer, mechanical and electrical energy conversion processes. As every component of the low temperature adiabatic CAES system is built on its fundamental physical and engineering principles, the model is capable of revealing the system transient characteristics. Based on the model, various simulation studies are conducted and the results are compared with the operation data from the literature. It provides a valuable tool for preliminary design of a radial turbine to test its suitability in full and partial load operation conditions, and analyse its transient behaviours.

Energy Saving in Spirit Distillation

A simplified continuous wine spirit distillation plant was designed with the aim of saving energy, constructed and subsequently tested under full operational conditions. Duplication of the purification processes encountered in 6-column still operation was eliminated and the number of separate distillation columns reduced from six to four. The excellent separation of the alcohol from the impurities, achieved in a spacious purification column through adequate dilution of alcohol with water, is one of the outstanding characteristics of the adapted design. In addition, facilities for continuous caustic soda treatment of the impurities drastically reduced the percentage of feints. During distillation a continuous production of high quality spirit, with the still operating at 99% efficiency, was achieved. Distillation of inferior quality wine had no adverse effect on the quality of the distillate. Losses were minimal and steam consumption was reduced from 6,9 kg/L Absolute Alcohol, to 4,9 kg/LAA produced. The percentage feints requiring redistillation was reduced from ca. 20% to 1,0%.

Performance and Equivalent Loads of Wind Turbines in Large Wind Farms

Ten simulations of large wind farms have been performed using a fully coupled LES and aero-elastic framework to form a database of full turbine operational conditions in terms of both production and loads. The performance is examined in terms of averaged power production and thrust, as well as 10min equivalent flapwise bending, yaw, and tilt moment loads. Certain scenarios operating below rated wind speed shows unexpected peaks in the loads. The influence on the operating conditions are examined for various parameters and compared relative to an effective power production per area.

A novel cascade organic Rankine cycle (ORC) system for waste heat recovery of truck diesel engines

Waste heat recovery (WHR) of engines has attracted increasingly more concerns recently, as it can improve engine thermal efficiency and help truck manufacturers meet the restrictions of CO2 emission. The organic Rankine cycle (ORC) has been considered as the most potential technology of WHR. To take full advantage of waste heat energy, the waste heat in both exhaust gases and the coolant need to be recovered; however, conventional multi-source ORC systems are too complex for vehicle applications. This paper proposed a confluent cascade expansion ORC (CCE-ORC) system for engine waste heat recovery, which has simpler architecture, a smaller volume and higher efficiency compared with conventional dual-loop ORC systems. Cyclopentane is analyzed to be regarded as the most suitable working fluid for this novel system. A thermodynamic simulation method is established for this system, and off-design performance of main components and the working fluid side pressure drop in the condenser have been taken into consideration. System performance simulations under full engine operating conditions are conducted for the application of this system on a heavy-duty truck diesel engine. Results show that the engine peak thermal efficiency can be improved from 45.3% to 49.5% where the brake specific fuel consumption (BSFC) decreases from 185.6g/(kWh) to 169.9g/(kWh). The average BSFC in the frequently operating region can decrease by 9.2% from 187.9g/(kWh) to 172.2g/(kWh). Compared with the conventional dual-loop ORC system, the CCE-ORC system can generate 8% more net power, while the total volume of heat exchangers is 18% less.

Experimental study on the performance of a turbocompound diesel engine with variable geometry turbocharger

Turbocompounding is a key technology to satisfy the future requirements of diesel engine’s fuel economy and emission reduction. A turbocompound diesel engine was developed based on a conventional 11-Liter heavy-duty diesel engine. The turbocompound system includes a power turbine, which is installed downstream of a Variable Geometry Turbocharger (VGT) turbine. The impacts of the VGT rack position on the turbocompound engine performance were studied. An optimal VGT control strategy was determined. Experimental results show that the turbocompound engine using the optimal VGT control strategy achieves better performance than the original engine under all full load operation conditions. The averaged and maximum reductions of the brake specific fuel consumption (BSFC) are 3% and 8% respectively.

Results of Testing of the GTÉ-110 Gas-Turbine Low-Emission Combustor in Full Operating Conditions

The results of testing the GTE-110 gas-turbine low-emission combustor (LEC) at an operating pressure of 1500 kPa are presented. It is shown that the developed technical solution provides pulsation-free changeover to low-emission operation of the LEC. The measurements confirm low NOx emissions and high combustion efficiency in the 50 – 100% load range. The stages of LEC development, the justification of the technical solution, and the results of testing the pilot LEC at an inlet air pressure of 350 kPa were detailed earlier in [1]. Comparing and analyzing the results of tests at reduced and full air pressures reveal that the combustor wall temperatures, gas temperature profiles, and combustion efficiencies are identical. Moreover, the results confirm the adequate simulation of acoustic boundary conditions at test facilities providing reduced and full operating conditions.

A high spatio-temporal resolution optical pyrometer at the ORION laser facility.

A streaked pyrometer has been designed to measure the temperature of ≈100 μm diameter heated targets in the warm dense matter region. The diagnostic has picosecond time resolution. Spatial resolution is limited by the streak camera to 4 μm in one dimension; the imaging system has superior resolution of 1 μm. High light collection efficiency means that the diagnostic can transmit a measurable quantity of thermal emission at temperatures as low as 1 eV to the detector. This is achieved through the use of an f/1.4 objective, and a minimum number of reflecting and refracting surfaces to relay the image over 8 m with no vignetting over a 0.4 mm field of view with 12.5× magnification. All the system optics are highly corrected, to allow imaging with minimal aberrations over a broad spectral range. The detector is a highly sensitive Axis Photonique streak camera with a P820PSU streak tube. For the first time, two of these cameras have been absolutely calibrated at 1 ns and 2 ns sweep speeds under full operational conditions and over 8 spectral bands between 425 nm and 650 nm using a high-stability picosecond white light source. Over this range the cameras had a response which varied between 47 ± 8 and 14 ± 4 photons/count. The calibration of the optical imaging system makes absolute temperature measurements possible. Color temperature measurements are also possible due to the wide spectral range over which the system is calibrated; two different spectral bands can be imaged onto different parts of the photocathode of the same streak camera.

Study of production optimization and effect of hydroxyl gas on a CI engine performance and emission fueled with biodiesel blends

Depletion and environmental impacts of the fossil fuel are the major concerns to think about the alternative energy sources to reduce the load on petroleum fuel. Researchers worldwide are working years to improve the biodiesel fuel economy and emission characteristic. At the same time, they are working on fuel development so that can be used in the IC engine without significant modification in vehicle design. Among different alternative fuels biodiesel as well as hydroxyl gas (HHO, also known as Oxyhydrogen gas) are renewable, recyclable and non-polluting fuel. In this study, HHO gas has been introduced with ordinary diesel (OD) and 20% (v/v) palm biodiesel blended with OD (PB20) for evaluating the engine performance and emission characteristics. Optimum yield of HHO was found using single anode and two cathodes from a solution containing 1% KOH and 100 ml of water producing 2150 cc of HHO gas when electrolysis was carried out for 15 min. Using the HHO generator, about 2% more power and 5% less consumption was observed for biodiesel blended fuel in a single cylinder CI engine at full load variable speed operating conditions. Besides, on an average 20% and 10% reduction of CO and HC emission were observed respectively.

Rotary jet head - a device for accelerating the fermentation process in brewing

The world beer market is dominated by lagers, with production estimated at hundreds of millions of hectolitres per year. The vast majority of the beer is produced using CCT (cylindro-conical tank) technology. Fermentation and maturation are time-consuming processes and the bottlenecks of beer production. A rotary jet head (RJH) – a device originally used as a cleaning device – is proposed for use as a tool to provide homogeneity in the tank and to increase the activity of the yeast cells by keeping them in suspension during the fermentation process. The main objective of the study was to analyse the impact of mixing the content of the fermentation tank (by the means of an RJH) on the time of fermentation, maturation and cooling. The experiments were carried out under full industrial operational conditions. It was concluded that mechanical mixing, in a CCT of 3800 hL, shortened the time of lager beer production process by ca. 15%, the time of fermentation by ca. 24 h and the cooling time by ca. 35 h. Copyright © 2016 The Institute of Brewing & Distilling

Effect of kinetics on the thermal performance of a sorption heat storage reactor

To reach high solar fractions for solar thermal energy in the built environment, long-term heat storage is required to overcome the seasonal mismatch. A promising method for long term heat storage is to use thermochemical materials, TCMs. In this research, a lab-scale test thermochemical heat storage system is tested experimentally and modeled numerically. Water-zeolite 13X is used as the working pair in an open packed bed reactor. The purpose of this study is to understand the effects of the kinetic parameters for the adsorption of water vapor on zeolite 13X (2mm spherical beads), on the thermal performance of a sorption heat storage packed bed reactor. A mathematical model is developed incorporating the kinetics model and the isotherm curves and including the heat losses from the side wall of the reactor, and is validated by comparing the calculated temperature profiles with experimental ones from a lab-scale test setup. The numerical and experimental results are used to calculate the heat fluxes in the reactor and are compared to evaluate the thermal performance of the reactor. With the validated model, a parameter study is carried out into the effect of the reaction kinetics and the gas flow rate on thermal performance of a thermochemical heat storage reactor under full scale normal operating conditions. From this work, predictions of the thermal dynamics of an adsorption bed on reactor scale can be achieved, which can and will be used for further studies on the design and optimization of a thermochemical heat storage system.

Selection of important initiating events for Level 1 probabilistic safety assessment study at Puspati TRIGA Reactor

This paper attempts to present the results in identifying possible important initiating events (IEs) as comprehensive as possible to be applied in the development of Level-1 probabilistic safety assessment (PSA) study. This involves the approaches in listing and the methods in screening and grouping IEs, by focusing only on the internal IEs due to random failures of components and human errors with full power operational conditions and reactor core as the radioactivity source. Five approaches were applied in listing the IEs and each step of the methodology was described and commented. The criteria in screening and grouping the IEs were also presented. The results provided the information on how the Malaysian PSA team applied the approaches in selecting the most probable IEs as complete as possible in order to ensure the set of IEs was identified systematically and as representative as possible, hence providing confidence to the completeness of the PSA study. This study is perhaps one of the first to address classic comprehensive steps in identifying important IEs to be used in a Level-1 PSA study.

Thermal behavior analysis of PWR fuel during RIA at various fuel burnups using modified theatre code

The fuel irradiation and burnup causes geometrical and dimensional changes in the fuel rod which affects its thermal resistance and ultimately affects the fuel rod behavior during steady-state and transient conditions. The consistent analysis of fuel rod thermal performance is essential for precise evaluation of reactor safety in operational transients and accidents. In this work, analysis of PWR fuel rod thermal performance is carried out under steady-state and transient conditions at different fuel burnups. The analysis is performed by using thermal hydraulic code, THEATRe. The code is modified by adding burnup dependent fuel rod behavior models. The original code uses as-fabricated fuel rod dimensions during steady-state and transient conditions which can be modified to perform more consistent reactor safety analysis. AP1000 reactor is considered as a reference reactor for this analysis. The effect of burnup on steady-state fuel rod parameters has been investigated. For transient analysis, hypothetical reactivity initiated accident was simulated by considering a triangular power pulse of variable pulse height (relative to the full power reactor operating conditions) and pulse width at different fuel burnups which corresponds to fresh fuel, low and medium burnup fuels. The effect of power pulse height, pulse width and fuel burnup on fuel rod temperatures has been investigated. The results of reactivity initiated accident analysis show that the fuel failure mechanisms are different for fresh fuel and fuel at different burnup levels. The fuel failure in fresh fuel is expected due to fuel melting as fuel temperature increases with increase in pulse energy (pulse height). However, at relatively higher burnups, the fuel failure is expected due to cladding failure caused by strong pellet clad mechanical interaction, where, the contact pressure increases beyond the cladding yield strength.

Comparison Between Different Design Topologies for Multi-Megawatt Direct Drive Wind Generators Using Improved Second Generation High Temperature Superconductors

Various design topologies were investigated to study the weights and costs for a direct drive wind turbine generator using improved second generation (2G) YBCO high temperature superconductors (HTS). Five different design topologies using combinations of air core, iron core, salient and non-salient configurations for both stator and rotor were considered for a generator with the nominal rating of 10 MW, 8 RPM and 3300 V. The main objective of the investigation was to minimize the HTS quantities and the reduction of total cost to achieve the same rating performance. The electromagnetic design was performed using transient finite element modeling including the improved HTS conductor characteristic properties. The mechanical design includes the support structures for both full load operation and sudden three-phase terminal fault conditions which can cause severe stresses.

Two devices for mitigating odontocete bycatch and depredation at the hook in tropical pelagic longline fisheries

AbstractOdontocete bycatch on and depredation from tropical pelagic longlines is globally widespread, having negative impacts on the economic viability of affected fisheries and on the conservation of affected odontocete populations. Reports by fishers that depredating odontocetes avoid gear tangles has underpinned the development of simulated structures to physically deter depredating odontocetes. This study assessed the efficacy of two such devices developed to mitigate odontocete depredation and associated bycatch. Of particular interest was their impact on (i) soak depth and (ii) sink rate using truncated trials, before determining their impact under full operational conditions on rates of (iii) catch of the five most economically important fish, and (iv) odontocete depredation and bycatch, on changes in (v) fish survival and size, and (vi) setting and hauling speed. The results indicated that the inclusion of devices on longlines had negligible impact on soak depth, thus were unlikely to impact on the suite of fish specifically targeted and caught. The sink rate was slowed, perhaps by drag, trapped air, or propeller wash, although the addition of weight might remedy this if the devices were to be used in areas where seabird bycatch could occur. Most importantly, trials conducted in Australian and in Fijian waters indicated that pooled fish catch rates (i.e. albacore, yellowfin, bigeye, mahi mahi, and wahoo) increased in the presence of the devices, possibly because more fish were attracted by them or because more depredators were deterred. Catch rates on control gear next to gear with devices attached were higher than more distant control gear, suggesting the influences of the devices may have extended to adjacent branchlines. The size of caught fish was mostly unaffected, although the survival of yellowfin and bigeye increased significantly in the presence of the devices. Hauling was slowed by the use of the devices and the need for an extra crewmember during setting and hauling, which could be cost prohibitive in some fisheries, especially if economic benefits from their use are not obvious. Despite the small sample size, odontocete bycatch only occurred on unprotected fishing gear and all individuals were released alive, although their fate was uncertain; there was evidence of injuries sustained from the event. The outcomes are positive and should motivate stakeholders to view such devices as a potentially effective tool for mitigating odontocete bycatch and depredation in this and similar longline fisheries. Future efforts should focus on improving operational integration and reducing implementation costs to encourage voluntary uptake and thus avoid non-compliance and the need for costly monitoring. The use of this technology could bring about marked improvements to the conservation situation for affected odontocete populations and to the economic situation for affected longline fisheries.

Reactivity considerations for the on-line refuelling of a pebble bed modular reactor—Illustrating safety for the most reactive core fuel load

In the multi-pass fuel management scheme employed for the pebble bed modular reactor the fuel pebbles are re-circulated until they reach the target burn-up. The rate at which fresh fuel is loaded and burned fuel is discharged is a result of the core neutronics cycle analysis but in practice (on the plant) this has to be controlled and managed by the fuel handling and storage system and use of the burnup measurement system. The excess reactivity is the additional reactivity available in the core during operating conditions that is the result of loading a fuel mixture in the core that is more reactive (less burned) than what is required to keep the reactor critical at full power operational conditions. The excess reactivity is balanced by the insertion of the control rods to keep the reactor critical. The excess reactivity allows flexibility in operations, for example to overcome the xenon build up when power is decreased as part of load follow. In order to limit reactivity excursions and to ensure safe shutdown the excess reactivity and thus the insertion depth of the control rods at normal operating conditions has to be managed. One way to do this is by operational procedures. The reactivity effect of long-term operation with the control rods inserted deeper than the design point is investigated and a control rod insertion limit is proposed that will not limit normal operations. The effects of other phenomena that can increase the power defect, such as higher-than-expected fuel temperatures, are also introduced. All of these cases are then evaluated by ensuring cold shutdown is still achievable and where appropriate by reactivity insertion accident analysis. These aspects are investigated on the PBMR 400MW design.

Simulation and analysis of the central cavity receiver’s performance of solar thermal power tower plant

Solar central receiver, which plays a dominant role in the radiation–heat conversion, is one of the most important components in the solar tower plants. Its performance can directly affect the efficiency of the entire solar power generation system. In this study, an integrated receiver model for full range operation conditions was proposed in order to simulate and evaluate the dynamic characteristics of a solar cavity receiver. It mainly couples the radiation–heat conversion process, the determination of convective heat transfer coefficient, the temperature computation of receiver walls and the calculation and analysis of the thermal losses. Based on this model, the dynamic characteristics of the solar cavity receiver were tested by encountering a sudden solar radiation disturbance. In addition, the thermal loss was also calculated and analyzed with different wind conditions. The results indicated that the parameters of the receiver had a significant variation under the sharp disturbance of DNI if no control rules were imposed. The wind conditions can obviously affect the thermal losses and the value reaches its maximum when the wind blows from the side of the receiver (α = 90°). In order to verify the validity of this model, the simulation results were used to compare the design points under the same input conditions, and the results showed that simulation data had a good agreement with design data.

Electrolyzer switching strategy for hydrogen generation from variable speed wind generator

This paper presents a new switching strategy for electrolyzer used in hydrogen generation which is connected to the terminal of a wind farm. The output of wind generator, in general, fluctuates greatly due to the random wind speed variations, which has a serious influence on the power system operation. In this study, the wind farm is composed of variable speed wind turbines (VSWT) driving permanent magnet synchronous generators (PMSG). The hydrogen generator (HG) is composed of rectifier and 10 electrolyzer units where each unit is controlled by the chopper circuit. To smoothen the wind farm line power, at first, a reference for the line power is generated from the difference of exponential moving average of wind farm output and its standard deviation. Then the switching strategy is developed in such a way that the proposed cooperative system can smoothen the wind farm line power fluctuation as well as generating hydrogen gas absorbing the fluctuating portion of wind farm output that lies above the reference line power. This novel switching strategy helps each electrolyzer unit working in full load and shift operation conditions and hence increases its lifespan and efficiency. The performance of the proposed system is investigated by simulation analyses, in which simulations are performed by using PSCAD/EMTDC.

A New Generation of SiC Schottky Diodes with Improved Thermal Management and Reduced Capacitive Losses

With the help of an improved die attach the Rth,jc of SiC Schottky diodes can be reduced by 40-50% at a given chip size. This enables a significant higher power density for these SiC diode chips, resulting in a chip shrink of ~ 35% for a given nominal current. This has a significant impact not only on the cost position of the device but also on the switching performance of the diodes, as their capacitive charge directly scales with the chip area. Of course these advantages are accompanied by a small penalty in static losses as the Vf of the diodes at nominal current also slightly increases by the chip shrink. However, the reduction of switching losses dominates upon the marginally increased static losses besides full load operation conditions (which are pretty exceptional in today’s SiC Schottky diode applications) combined with frequencies below 130 kHz. This allows a better competitive positioning against fast Si-based diodes and improved system efficiency at the same time.

Thermal hydraulics in the hot pool of Fast Breeder Test Reactor

Sodium cooled Fast Breeder Test Reactor (FBTR) of 40 MWt/13 MWe capacity is in operation at Kalpakkam, near Chennai. Presently it is operating with a core of 10.5 MWt. Knowledge of temperatures and flow pattern in the hot pool of FBTR is essential to assess the thermal stresses in the hot pool. While theoretical analysis of the hot pool has been conducted by a three-dimensional code to access the temperature profile, it involves tuning due to complex geometry, thermal stresses and vibration. With this in view, an experimental model was fabricated in 1/4 scale using acrylic material and tests were conducted in water. Initially hydraulic studies were conducted with ambient water maintaining Froude number similarity. After that thermal studies were conducted using hot and cold water maintaining Richardson similitude. In both cases Euler similarity was also maintained. Studies were conducted simulating both low and full power operating conditions. This paper discusses the model simulation, similarity criteria, the various thermal hydraulic studies that were carried out, the results obtained and the comparison with the prototype measurements.

Functional simulator of 3-axis parallel kinematic milling machine

Parallel kinematic machines (PKM) are research-and-development topic in many laboratories although many of them, unfortunately, have no PKM at all. Therefore, the use of low cost but functional simulator of a 3-Axis parallel kinematic milling machine is suggested as a help to acquire the basic experiences in the PKM field. The idea is based on the possibility that the simulator could be driven and controlled by a conventional 3-Axis Computer Numerical Control machine tool (CNC). The paper describes the development procedure of a simulator including the selection of a corresponding parallel mechanism, kinematic modelling, and the programming algorithm. The functional simulator idea has been verified by successful making of some standardized test pieces of soft material, under full operational conditions.