System Startup Research Articles

Startup analyses of a megawatt heat pipe cooled reactor

Heat pipe cooled reactors experience temperature rises of up to 800 K during startup. The in-core heat pipes and the energy conversion system are initially frozen, which leads to a highly coupled heat transfer system that has significant safety challenges. This work modeled the system startup using a two-dimensional heat pipe model and an open-air Brayton cycle model coupled to the Heat Pipe Reactor TRANsient analysis code, HPRTRAN. The heat pipe model was validated with startup experiments showing that the predicted heat pipe wall temperature was within 30 K of the measured temperatures. The Brayton cycle model was validated against experimental data in the literature. The analysis code was then used to analyze a megawatt heat pipe reactor connected to an open-air Brayton cycle, which was used to study the influence of the external reactivity and the inherent feedback on the startup process. The simulations show that the reactor startup process is sensitive to the heat pipe operating state. The startup process can be divided into the subcritical stage, heat pipe startup stage, and increasing power stage. The power peak amplitudes are significantly reduced by slowing the angular speed of the control drum. Reducing the control drum angular speed from 0.1°/min to 0.05°/min reduced the first power peak from 2000 kW to 1000 kW. A modified reactor startup control strategy was then developed that ensures the core safety with the reactivity introduced in steps. Smaller reactivity insertions reduce the power peaks during the initial startup but lead to much longer startup times. A reasonable balance was obtained by repeated insertions of either 30 pcm or 60 pcm for safe startups of the heat pipe cooled reactor.

Dynamic modeling and numerical investigation of novel pumped thermal electricity storage system during startup process

As a novel energy storage technology suitable for large-scale application, pumped thermal electricity storage (PTES) technology has a high energy storage density and is not limited by specific geographical conditions. However, most of the current research on PTES is carried out around rated working conditions, and lack of research on dynamic characteristics, which makes it difficult to predict, regulate and optimize the performance of the system in the actual operation process. According to the system structure and the operating principle of each component, the dynamic simulation model of the PTES system based on closed Brayton cycle was established, the control strategy and dynamic performance of the system during the startup process were studied, and the influence of key parameters on the system startup performance was analyzed in this study. The simulation results show that for the charge process, the higher rotational speed increase rate, the faster rotational speed rises in the initial stage, but the system startup time is the same. For the discharge process, the rotational speed increase rate not only affects the system startup time but also cause great fluctuation and overshoot in the rotational speed when the rotational speed increase rate is unreasonable. For the system in this study, it is more reasonable to select 100 rpm/s for the rotational speed increase rate, considering safety and rapidity. The initial pressure of the system does not affect the steady-state pressure ratio but does affect the stable-state pressure. In order to make the system's pressure finally reach the rated value, the initial pressure of charging should be set to 4.45 MPa, and that of discharge should be set to 5 MPa. The dynamic simulation model and the results of dynamic characteristics analysis in this study can provide a reference for the design optimization and the formulation of actual operation control strategies of the PTES system.

The emergency start-up system for the internal combustion engine of vehicles operated, including in the Far North

The analysis of organizations operating in extreme natural and climatic conditions of the Far North will help to determine the areas of activity relevant for the application of an innovative system for emergency start of internal combustion engines. Prospects for development in the military industry. The parameters that determine the performance of the hydraulic starter are considered. Keywords: hydraulic starter, hydraulics, pneumohydroaccumulator, hydraulic accumulator, extreme natural and climatic conditions, specialized equipment, emergency start system

Optimization of Microalgae–Bacteria Consortium in the Treatment of Paper Pulp Wastewater

The microalgae–bacteria consortium is a promising and sustainable alternative for industrial wastewater treatment, since it may allow good removal of organic matter and nutrients, as well as the possibility of producing products with added value from the algae biomass. This research investigated the best bacterial and microalgae inoculation ratio for system start-up and evaluation of removing organic matter (as chemical oxygen demand (COD)), ammoniacal nitrogen (NH4+–N), nitrite nitrogen (NO2−–N), nitrate nitrogen (NO3−–N), phosphate phosphorus (PO43−–P) and biomass formation parameters in six photobioreactors with a total volume of 1000 mL. Reactors were operated for 14 days with the following ratios of pulp mill biomass aerobic (BA) and Scenedesmus sp. microalgae (MA): 0:1 (PBR1), 1:0 (PBR2), 1:1 (PBR3), 3:1 (PBR4), 5:1 (PBR5), and 1:3 (PBR6). Results show that COD removal was observed in just two days of operation in PBR4, PBR5, and PBR6, whereas for the other reactors (with a lower rate of initial inoculation) it took five days. The PBR5 and PBR6 performed better in terms of NH4+–N removal, with 86.81% and 77.11%, respectively, which can be attributed to assimilation by microalgae and nitrification by bacteria. PBR6, with the highest concentration of microalgae, had the higher PO43−–P removal (86%), showing the advantage of algae in consortium with bacteria for phosphorus uptake. PBR4 and PBR5, with the highest BA, led to a better biomass production and sedimentability on the second day of operation, with flocculation efficiencies values over 90%. Regarding the formation of extracellular polymeric substances (EPS), protein production was substantially higher in PBR4 and PBR5, with more BA, with average concentrations of 49.90 mg/L and 49.05 mg/L, respectively. The presence of cyanobacteria and Chlorophyceae was identified in all reactors except PBR1 (only MA), which may indicate a good formation and structuring of the microalgae–bacteria consortium. Scanning electron microscopy (SEM) analysis revealed that filamentous microalgae were employed as a foundation for the fixation of bacteria and other algae colonies.

Effect of initial bacterial diversity on anaerobic degradation of long-chain fatty acids

The effect of inocula from eight different digesters on the anaerobic degradation of palmitic acid (PA), stearic acid (SA), and oleic acid (OA) were evaluated in terms of degradation rate k, biodiversity, and key bacterial communities. The highest k were 0.213∙d−1, 0.110∙d−1, and 0.202∙d−1 for degradation of PA, SA, and OA, respectively. There was no significant correlation between the magnitude of k with bacterial diversity of the initial inoculum. 16S rRNA gene sequencing results at the end of each degradation process revealed that Syntrophomonas palmitatica, Smithella propionica, and Lentimicrobiaceae were the key bacteria in the methanogenic degradation of PA, Syntrophomonas sapovorans, S. propionica, and Lentimicrobiaceae were the key bacteria in the methanogenic degradation of SA, and Syntrophomonas zehnderi, Syntrophus aciditrophicus, and S. palmitatica were the key bacteria in the methanogenic degradation of OA. The information obtained from this study could be useful to guide selection of microbial sources for the start-up of continuous AD systems to treat wastes and wastewater that contain LCFAs.

Study on Thermal Shock Failure Characteristics of RPV During IVR System Start-Up for Typical Advanced PWR

When the large pressurized water reactor in-vessel retention (IVR) system is put into operation, the outer wall of the reactor pressure vessel (RPV) will experience severe temperature fluctuations and be subjected to high internal pressure loads at the same time. In order to ensure the structural integrity of the RPV under such conditions, first, through the severe accident system program, the case that has the greatest impact on the pressure-bearing thermal shock of the outer wall of the reactor pressure vessel was selected under the station blackout (SBO) accident. Then, based on this case, the fracture mechanics finite element method was used to calculate and evaluate the pressure thermal shock (PTS) of the RPV, and the final crack size at the end of the life of the core barrel and the lower head was obtained by fatigue crack expansion calculation. The maximum ratio of the stress intensity factor correction value and corresponding limit value under the PTS transient load is about 0.874, which meets the requirements of RCC-M specification. The results of the study indicate that the RPV will not experience fracture failure when the IVR system is put into service during the station blackout accident for the HPR1000 nuclear power plant.

Implementation of Scientific and Technical Approach to the Automotive Diesel Starting System Creation

Problem. This article indicates a way to solve the problem of complicated cold start and high smoky operation in preparation for accepting the load of a domestic diesel engine 4DTNA1 with direct fuel injection by optimizing the parameters of the components of the start-up system and automating the start-up and idling processes according to rational control algorithms. According to the necessity solving this problem, requirements have been formulated for organizing and conducting a multifactorial experimental study of the starting qualities of an automobile diesel engine. Goal. The main goal of the work is to form a scientific and technical approach to creating a system for starting a vehicle diesel engine, which will optimize its component’s properties and develop control algorithms. To achieve this goal it is necessary to create a plan of multifactorial research, develop and build a physical model for experimental research, perform research and evaluate the results. Methodology. The main provisions on the organization of a multifactorial experimental study of the starting qualities of an automobile diesel engine are highlighted. Design of experiments method used when creating a plan for experimental research. Results. The features and advantages of the created physical model in relation to traditional solutions for studying the starting qualities of automobile engines, including the control of an external load to reproduce the impact on engine oil of low temperature in conditions of difficult access to climatic chambers, are presented. The choice of a vortex-dimensional sample of a physical model for conducting start-up studies through a promising, reduced by 1-1.5 units, compression ratio and the possibility of a qualitative study of the effect of pre-start heating of the volume of the combustion chamber with a glow plug on starting parameters. Originality. The actual values of the selected 6 most influential linearly independent factors on the start-up process during the experimental study according to the accepted plan of 77 test cold starts are indicated. It is noted that the actual result of establishing certain controllable factors is random with a certain error in the vicinity of the exact value in accordance with the orthogonal plan of the experiment. Such a variation of real values requires the use of a special mathematical apparatus, implemented by the authors in the Approximation_LSM software product, when analyzing the results of a 6factor experimental study. Practical value. A rational mathematical plan of a six-factor experiment has been prepared as a clear example of recording the measured and calculated parameters of the next optimization.

Parameter identification of small distributed hydro generators during excitation system start‐up

Concerning the penetration of renewable energy resources into the power grid, investigation of the power system dynamics to meet the power demand and maintain stability has gathered momentum recently. On the other hand, evaluating the generator parameters in the distributed generation (DG) units as a subsystem of a large-scale power grid is crucial for control and stability analysis purposes. To this aim, a simple and efficacious algorithm to identify the operational parameters of synchronous generators (SGs) in small hydro DGs is proposed here. The required data for the SG identification using the recommended approach is gathered during excitation system start-up while the DG is disconnected from the grid. Using the proposed test procedure, the adverse impact of magnetic saturation on estimation results can be avoided. Furthermore, a straightforward parameter estimation (PE) procedure is established here to obtain the intended parameters from the recorded data. Finally, the proposed method was applied to a 10 MW hydro DG, and the results are discussed.

Indian Startup Ecosystem – Challenges and Opportunities

India is a growing market for entrepreneurs and businesses. The startup ecosystem in India has become a global topic of discussion. The business world has seen an explosion of ground-breaking startups giving solutions to genuine problems at a mass level in recent years, thanks to hundreds of bright young people deciding to pursue startups instead of joining multinational businesses and government enterprises. Young entrepreneurs starting tiny enterprises would undoubtedly help the Indian economy in the near future. Indigenous companies will not only make people's lives easier through their economical and convenient services, but they will also work as a vital booster for the Indian economy's development and prosperity. If you're just starting out in business, be prepared for both problems and possibilities that will arise. Entrepreneurs and startups cannot create a large business without overcoming these hurdles. This paper discusses the challenges and opportunities of startup system in India.

Numerical Study on Liquid-Return Characteristics in the Accumulator of the R290 Rotary Compressor

Liquid often exists in the accumulator of the rotary compressor during the process of startup or defrost of air-conditioning systems. Too much liquid entering the compressor cylinder would result in excessive pressure caused by the liquid compression, which is a great threat to the compressor. The liquid return through the liquid-return hole is the key to ensure the stable operation of the compressor. In this paper, the liquid-return characteristics in the liquid-return holes of the accumulator, including the mass-flow rate, liquid velocity and pressure difference between the liquid-return holes, during the startup process of the R290 rotary compressor are numerically investigated. The numerical simulation using the fluent volume of fluid (VOF) method was experimentally validated with the error of 1.55%. The comparison of liquid-return characteristics using different refrigerants is conducted. Effects of refrigerant solubility in the oil, refrigerant/oil-mixture type, liquid-return-hole diameter and compressor frequency on the liquid-return characteristics and liquid shape trough the liquid-return hole are discussed. The results show that the surface tension and viscosity of the liquid are the main factors affecting the liquid-return speed. The liquid-return rate of the refrigerant R290 is slower than that of other refrigerants R22 and R410A. The liquid-return rate increases with the increase in the compressor frequency. We conclude that for air-conditioning systems using R290 as refrigerant, increasing the number of return holes or the hole diameter is necessary to improve the liquid-return characteristics of the compressor. This research will provide theoretical guidance for the optimization of liquid return of rotary compressors using new refrigerants.

Biochar assisted cellulose anaerobic digestion under the inhibition of dodecyl dimethyl benzyl ammonium chloride: Dose-response kinetic assays, performance variation, potential promotion mechanisms

This study evaluated the inhibitory effect and mitigation strategy of dodecyl dimethyl benzyl ammonium chloride (DDBAC) suppression on anaerobic digestion. With the 12 h-suppression, only 16.64% of anaerobes were alive, and acetotrophic methanogens were significantly inhibited. As for batch test, DDBAC suppression significantly prolonged the start-up of systems and decreased the biogas production. In cellulose semi-continuous digestion process, the DDBAC suppression induced volatile fatty acids accumulation and pH decrease. However, the biochar amended reactor effectively mitigated the DDBAC suppression and achieved 370.5 mL/d·g-chemical-oxygen-demand biogas production. Moreover, 17.8% more protein in extracellular polymeric substances was secreted as the bio-barrier to defense the DDBAC suppression. Furthermore, microbial analysis showed that biochar addition selectively enriched directed interspecies electron transfer (DIET) participant bacteria (Anaerolineaceae and Syntrophomonas) and methanogens (Methanosaeta and Methanobacterium). Meanwhile, the potential metabolic pathway analysis showed that the abundance of amino acids and energy metabolism were increased 28% and 8%, respectively. The abundance of encoding enzyme related to hydrogenotrophic and acetotrophic methanogenesis enriched 1.88 times and 1.48 times, respectively. These results showed the performance and mechanisms involved in DIET establishment with ethanol stimulation biochar addition.

Responses of mesophilic anaerobic sludge microbiota to thermophilic conditions: Implications for start-up and operation of thermophilic THP-AD systems

Anaerobic digestion (AD) has been widely employed for wastewater and organic waste treatment, in which methanogenesis is highly driven by close microbial interactions among intricate microbial communities. However, the ecological processes underpinning the community assembly that support methanogenesis in such engineered ecosystems remain largely unknown, especially when exposed to challenging circumstances (e.g., high temperature, ammonium content). Here, eight AD bioreactors were seeded with four different inocula (two from full-scale mesophilic AD systems and the other two from lab-scale mesophilic AD systems), and were operated under thermophilic conditions (55 °C) for treating thermal hydrolysis process (THP) pre-treated waste activated sludge to investigate how mesophilic community responds to thermophilic conditions during the long-term cultivation. Results showed that the inocula collected from the full-scale systems were more resilient than that from the lab-scale systems, which may be primarily attributed to indigenous robust methanogens. As a result, the former efficiently generated methane which was predominantly contributed by Methanothermobacter and Methanosarcina (healthy AD ecosystem), while methanogenic activity was remarkably prohibited in the latter (dysfunctional AD ecosystem). Thermophilic environment was a strong selection force, resulting in the convergence of microbial communities in both the healthy and dysfunctional AD ecosystems. Deterministic processes predominated the community assembly regardless of AD ecosystem function, but stronger influences of stochastic processes were observed in dysfunctional AD ecosystems, which was likely attributable from the stronger effect of immigrants from the feedstock. As indicated by molecular ecological network analysis, the microbial network structures in the healthy AD ecosystems were more stable than those in the dysfunctional AD ecosystems. Although keystone taxa were different among the bioreactors, most of which played vital roles in organic hydrolysis/fermentation. To sum up, this study greatly improved our understanding of the relationships between microbiological traits and AD ecosystem function under thermophilic conditions, which could provide useful information to guide thermophilic AD (e.g., THP-AD) start-up and health diagnosis during operation.

Economic Framework of Smart and Integrated Urban Water Systems

Smart and integrated urban water systems have important roles in advancing smart cities, but their contributions go much further by supplying needed public services and connecting other sectors to meet sustainability goals. Achieving integration and gaining access to financing are obstacles to implementing smart water systems and both are implicit in the economic framework of smart cities. Problems in financing the start-up of smart water systems are reported often. The local and diverse nature of water systems is another barrier because an approach that works in one place may not work in another with different conditions. The paper identifies the challenges posed by the economic framework and provides examples from four cities with diverse characteristics. It outlines pathways to advance implementation of smart water systems by improving control strategies, advancing instrumentation and control technologies, and most of all, to help transform cities by raising customer awareness and trust through reliable and useful water information.

Optimal Dietary Crude Protein in Commercial Feeds for Shrimp and Halophytes in Marine Aquaponic Biofloc Systems

Formulated diets for animals is the primary source of nutrients in aquaponic systems that need to maintain beneficial bacteria as well as for plants. Dietary protein is one of the expensive macronutrients in fish diets, especially when fishmeal is used, and it is the source of nitrogen (N) for other biotic components. Biofloc has the potential to serve as the supplement diet for shrimp and reduce the need of expensive protein. However, it is not clear if low dietary protein will be adequate to support the three organisms (animals, plants, and bacteria) in an aquaponic system operated with biofloc technology. The aim of the present study was to investigate the effect of shrimp feed with different protein concentrations (30, 35, or 40%) on water quality and the growth performance of Pacific whiteleg shrimp (Litopenaeus vannamei) and three edible halophytic plants (Atriplex hortensis, Salsola komarovii, and Plantago coronopus) in biofloc-based marine aquaponics. The experiment was conducted for 12 weeks, the plants were harvested and seedlings transplanted every 4 weeks. Dietary protein content did not influence shrimp growth in the current study, indicating that feeds with lower protein concentrations can be used in biofloc-based marine aquaponic systems. During the early and mid-stages of cultivation, plants grew better when supplied diets with higher protein concentration, whereas no differences were observed for later harvests. Hence, for maximum production with mature systems or in the scenario of high concentration of nitrate, providing a higher protein concentration feed in the early stages of system start-up, and switching to a lower protein concentration feed in later stages of cultivation was recommended.

The problem of block synthesis of missile preparation and start-up control system for missile complexes

According to the analysis of trends in the use and development of missile weapons, it is shown that in the coming decades such weapons (missile, anti-aircraft missile, anti-ship systems) will remain one of the main units of the armed forces of the advanced countries. At the same time, in the conditions of independent Ukraine there is a need to create its own production of appropriate samples in a “closed cycle”. The synthesis of such weapons includes conducting comprehensive research on the principles of construction and operation of their basic elements, namely: substantiation of algorithms for launch equipment, control systems and navigation of missiles. The article deals with an example of a general solution to the problem.

Evolution of Electric Traction Vehicle Design Based on the Example of Škoda Locomotives

The article describes the evolution of Škoda electric locomotives, starting with vehicles supplied with 3 kV DC and 25 kV 50 Hz, initially featuring a resistor start-up (for DC supply), optionally high-voltage voltage regulation (for AC supply), and later with a pulse (thyristor) start-up. The railway network in Czechoslovakia was initially electrified with direct volt-age (including the Prague junction); however, learning the advantages of the 25 kV 50 Hz voltage developed in Germany led to some new sections of the ČSD network being electrified with alternating current. At the same time, Czechoslova-kia’s national manufacturer Škoda developed vehicles (locomotives, EMUs) suitable for DC and AC operation. Initially, these were single-system vehicles, as the development of multi-system ones was technically complicated at the time (only short-series production was practiced). The advent of pulse-starting traction motors not only provided more economical and simpler traction motor control but also simplified the construction of multi-system vehicles. The article discusses the specifics of both engine start-up systems and the evolution of DC and AC vehicle design and operation.

Ignition of a Cold Pulverized Coal Fuel by Means of an Electric Ignition System

Coal-fired generation has long been, and still is, one of the leaders in global electricity generation. The high share of coal-fired generation in the global energy mix is achieved due to the known advantages of this fuel, including high availability of reserves, relative ease of extraction, and the ability to organise reserves at plants to organise reliable equipment operation even in the event of fuel supply interruptions.  Coal combustion in modern industry requires the development of modern start-up systems for coal-fired boiler units without the use of fuel oil. Fuel oil is used for starting up boilers and maintaining the flame during transient operation or at low boiler loads. At the same time the use of fuel oil has a number of disadvantages, both technical and environmental. The greatest challenge in developing high-frequency ignition systems is to understand the chemical kinetics processes for the plasma chemical reaction of fuel mixture ignition. This paper presents experimental and industrial studies of the application of an electric ignition system for coal fuel based on a high-frequency power source. Experimental studies were carried out on a laboratory bench with a thermal capacity of 5 MW. Industrial tests were carried out at the operating enterprises of the power sector of the Russian Federation. Samples of fuel were lignite and hard coal of different thermal-technical composition. The principle of impact of this system on fuel ignition has been proposed.

Integrated self-forming dynamic membrane (SFDM) and membrane-aerated biofilm reactor (MABR) system enhanced single-stage autotrophic nitrogen removal

The membrane aerated biofilm reactor (MABR) is a novel bioreactor technology, facilitating single-stage autotrophic nitrogen removal. Two laboratory-scale MABRs equipped with non-woven fabrics were operated simultaneously without and with a self-forming dynamic membrane (SFDM) filtration module. After 87 days of operation (system start-up), the reactor incorporated with SFDM filtration showed better performance in terms of total nitrogen removal (>80%) and effluent suspended solid (less than1 mg/L) than the MABR in the up flow anaerobic sludge blanket (UASB) configuration (i.e., without SFDM). The incorporation of SFDM has the ability to retain more slow growing biomass (anammox) inside the reactor. Microbial characterization by 16S rRNA-based amplicon sequencing shows that the abundance and composition of microbial communities in two MABR systems were different, i.e., the genusRhodanobacterwas abundant in UASB-MABR, while Calorithrixwas dominant in SFDM-MABR. PCA-based statistical analysis demonstrated a positive association between reactor performance, membrane characteristics and microbial communities.

Dynamic interaction between clustered liquid propellant rocket engines under their asynchronous start-ups

A nonlinear mathematical model of the low-frequency dynamics of the clustered multi-engine rocket propulsion system has been developed and the computations of the engine transient processes during the start-ups of the four-engine propulsion system with a shared feed system have been made applied. Based on propulsion system start-up modeling the influence of the connectivity of engines in a cluster on the starting characteristics of individual engines is shown. In particular, an advanced nonlinear mathematical model of the pump cavitation phenomena is a distinctive feature of the mathematical model. The computation results showed that the asynchronous engines start-ups during rocket lift-off lead to severely nonlinear engine transients and clustered engine thrust misbalance. The influence of the rocket engines asynchronous start-ups on the clustered feed system transients depends on many factors, mainly on from the clustered feed system low-frequency dynamics, the magnitude of the disturbance and the phase difference between disturbances acting on different branches of the feed system. The deep lingering dips in the flow rate and pressure transients are possible due to the nonlinear dynamic interaction of the engines. In case of great pressure dips at the pump inlet (up to the pressure of saturated vapors during significant periods of start-up time) the cavitation breakdowns of the pumps of one or more engines from the cluster are possible. This can disrupt the operation of the entire propulsion system and leads to the failure of the launch vehicle mission.

Study on Time Factors in the Smoke Control Process of Highway Tunnel Fires

Fire is the most deadly risk during tunnel operation. Early rapid response and a reasonable smoke control plan are very important to evaluate tunnel fire performance. In order to study the relevant time factors for smoke management in a highway tunnel, firstly, the logical sequence and time of the fire alarm system (FAS) startup are investigated and analyzed. Then, according to the one-dimensional fluid mechanics model, the time rule of adjusting the airflow field in the tunnel from the normal operation stage to the emergency ventilation state is analyzed theoretically. Finally, the abovementioned theoretical formulas are verified through the employment of model experiments. The analysis shows that the time that passes from the start of the fire to when the exhaust fan is activated is close to 3 minutes. The time required to form a stable critical wind speed, however, is close to 7 minutes, which is longer than the 5 minutes it takes for the fire to reach its maximum temperature. Due to inertia, it takes about 0.5 to 2 minutes for the air velocity in tunnels of different lengths to drop from the traffic piston wind speed to the critical wind speed. If reverse smoke extraction is required, however, the duration is between 3 and 8 minutes. The conclusion is of guiding significance for the preparation of the emergency linkage control scheme for tunnels, as well as for the setting of initial boundary conditions for CFD fire simulations.