Residual Energy Recovery Research Articles

Numerical investigation on energy change field in a centrifugal pump as turbine under different flow rates

The pump as turbine (PAT) is an economical and essential device that is widely used in micro hydropower and residual energy recovery. The energy change field, characterized by first and second energy change rate (LK1 and LK2), is investigated in main flow passage components of PAT under five flow rates ranging from 0.5QBEP to QBEP. The relationship between mean partial derivations of mechanical energy and flow rate is non-monotonic in the impeller, and it shows increasing and decreasing trends in the volute and draft tube, respectively. The large-LK2 regions exhibit positive correlation to complex internal flow structures. The mean LK1 (MLK1) in the impeller initially decreases and then increases slightly as flow rate increases, the opposite trends are observed in the volute and draft tube. There is a positive slope segment between the mean LK2 (MLK2) and flow rate in the impeller, which corresponds to the internal flow instability. The maximum values of MLK2 in the impeller and volute are 2.54 and 2.81, respectively, corresponding flow rates are 0.75QBEP and 0.875QBEP. As the flow rate increases, the standard deviations of MLK1 and MLK2 decreases significantly, and then reaches a steady value in impeller and volute region.

Optimization of geometric parameters of hydraulic turbine runner in turbine mode based on ISMA and BPNN

AbstractThe hydraulic turbine in turbine mode (TMHT) has significant advantages in residual energy recovery, but rapid optimization of its runner parameters has always been a challenge. To address this issue, the optimization algorithm ISMA‐BPNN is proposed based on the improved slime mold algorithm (ISMA) and back propagation neural network (BPNN). First, an efficiency characteristic neural network (ECNN) and a water head characteristic neural network (HCNN), which take the geometric parameters of the runner as input, and the efficiency and water head as outputs, respectively, are constructed by combining the orthogonal test‐based sample data, computational fluid dynamics (CFD), and BPNN. Then, the slime mold algorithm is improved and the optimal runner geometric parameters are obtained based on the ISMA, ECNN, and HCNN, to achieve rapid optimization of the TMHT runner. Finally, the CFD‐based numerical calculation accuracy is verified through real machine tests, and the feasibility of the ISMA‐BPNN‐based rapid optimization strategy for TMHT performance is further verified through CFD numerical simulation.

Parameter Optimization for Multistage Reluctance Coil Launcher With Residual Energy Recovery and Utilization Mode

Parameter Optimization for Multistage Reluctance Coil Launcher With Residual Energy Recovery and Utilization Mode

Multistage Reluctance Coil Launcher With Residual Energy Recovery and Utilization Mode

Launch efficiency has always been the focus of reluctance coil launchers research. In a traditional launch mode, the residual current in the drive coil creates a reverse force on the projectile. This is undesirable since the reverse force is in the opposite direction of movement, reducing the launch efficiency of the system. To address this problem, a multistage discharge circuit with the residual energy recovery and utilization mode is proposed in this article. As the projectile approaches the center of each stage of the drive coil, the current in the drive coil decays rapidly to zero by using the last stage capacitor to absorb the residual energy. The residual energy from the previous stages is eventually recovered by the last stage capacitor. This capacitor with residual energy is used to power the last stage drive coil of the reluctance coil launcher. This mode effectively suppresses the reverse force on the projectile and realizes the reuse of residual energy. Taking a four-stage reluctance coil launcher as an example, this article introduces the working principle of this mode in detail. The feasibility of the model is verified by finite-element simulation and experiments. Both simulation and experimental results show that this mode performs well in the recovery and reuse of residual energy and can effectively improve the launch efficiency of system.

Effect of temperature on the high-rate pulse charging of lithium-ion batteries

Based on the residual energy recovery in the electromagnetic emission scenario, the 30C pulse charging cycle experiments of LiFePO 4 batteries customized for electromagnetic emission at different charging temperatures were carried out to study the influence of charging temperature on battery aging. By adjusting the ambient temperature, heat dissipation conditions, and rest time, we studied the battery aging process at the average charging temperatures of 16 °C, 21 °C, 26 °C, 30 °C and 35 °C. Experimental results show that increasing charging temperature can significantly delay battery aging and prolong battery cycle life. In addition, when the average charging temperature is lower than 30 °C, the battery shows nonlinear aging; when the average charging temperature is higher than 30 °C, the battery shows linear aging in the early stage of cycling and nonlinear aging at the end of the cycle. The results of differential capacity analysis (DCA) show that the loss of lithium inventory is the primary aging mode of the battery and did not change with charging temperature. The aging mechanism of the battery under high-rate pulse charging was studied through multiscale post-test analysis. Analysis results showed that with the increase of charging temperature, the area of lithium-plating area decreases, and the thickness of SEI film increases. It can be inferred that when the average charging temperature is lower than 30 °C, lithium plating is the primary aging mechanism of the LiFePO 4 battery customized for electromagnetic emission. When the average charging temperature is higher than 30 °C, the growth of SEI film is the primary aging mechanism of the battery.

Gas extraction hood modeling in a steel converter for energy recovery using phase change materials

The steel industry is characterized by its energy-intensive processes. The steel forming process stands out, where the oxidation of carbon, when reacting, generates incomplete combustion gases at high temperature through the process basic oxygen injection in the furnace (BOF). A model of intermittent process and high temperature gas collection system is proposed and validated through experimental measurements. Through it, energy improvement opportunities are analyzed, highlighting energy recovery from high temperature flue gases by incorporating a phase change material (PCM) method for temporary energy storage. It was estimated that the fumes inside the hood could provide 77 GJ of available energy during the 15 min of oxygen injection (blowdown). With the use of a PCM device, between 13% and 32% residual energy recovery is obtained, equivalent to 10–25 GJ. In this way, a continuous heat flow could be generated during the whole process for steam generation through a cooling system in the gas collection system, with an electricity generation potential with a Rankine cycle of 14.5 MW.

Effect of blade width on ultra-low specific speed axial turbines

ABSTRACT Ultra-low specific speed axial turbines for cooling tower have some issues, such as low head, low efficiency, and turbulent internal flow. According to the orthogonal experiment and CFD analysis, it was found that the blade width was the main factor affecting the head, while the numbers of stay vanes and blades were the main factors affecting the efficiency. To further optimize the hydraulic performance of ultra-low specific speed axial turbines, six models of ultra-low specific speed axial turbines with different blade widths were designed. CFD numerical simulations showed that at different flow rates, with increasing blade width, the head gradually decreases and the efficiency shows a trend of first increasing and then decreasing. For the ultra-low specific speed axial turbine designed in this paper, when the blade width is 35 mm, the water head is 6.75 m, which meets the requirements of cooling tower turbines on head. At this blade width, the turbine achieves the highest efficiency of 81.15%, its flows are uniform, performance is stable. The internal flow field and pressure distribution of the runner are in better agreement with the design indexes of an ultra-low specific speed axial turbine. Thus, a high-efficiency ultra-low specific speed axial turbine suitable for cooling tower residual energy recovery is preferably selected.

A New Modular XRAM-Like Inductive High- Current Pulse Generator Circuit Topology

XRAM (MARX spelt back words) is currently a very important circuit for high current pulse generators. In our previous studies, an XRAM-like circuit was proposed based on multiple pulse transformer modules and a capacitor connected in parallel. Compared with the traditional XRAM circuit, the same number of inductive energy storage modules can be used to generate higher current pulses. This circuit is also capable to recover the residual energy and generate repetitive high-current pulses. However, this circuit topology requires more power electronic switches (three IGBT switches per pulse transformer module). In order to reduce the number of switches, by adding two IGBT switches in the capacitor module, a new modular XRAM-like circuit with reduced switches (one IGBT switch per pulse transformer module) is proposed in this paper. The change of the circuit topology makes the capacitor discharge the primary inductors of the pulse transformer in series during the residual energy recovery stage, instead of the parallel discharge in the previous circuit. This requires the closing time of the IGBT switch in each pulse transformer module ahead of the discharge start time of the capacitor. Working process of the proposed circuit was described in detail and simulations of a 12-module circuit were carried out to verify the circuit operation. Finally, the preliminary experimental results of a two-module laboratory prototype are presented. The results confirm the theoretical analysis and show the validity of the converter scheme.

Anaerobic digestion of wastewater generated from the hydrothermal liquefaction of Spirulina: Toxicity assessment and minimization

Previous studies demonstrate anaerobic digestion of hydrothermal liquefaction wastewater (HTL-WW) is significant to the sustainability of algal biofuel development for nutrient reuse and residual energy recovery. HTL-WW contains substantial amounts of residual energy but is toxic to anaerobes. With 6% HTL-WW converted from cyanobacteria (e.g. Spirulina), anaerobes were 50% inhibited. In this study, zeolite, granular activated carbon (GAC), and polyurethane matrices (PM) were used during a two-round anaerobic batch test with HTL-WW, and in the presence of each material, the total methane yields were 136mL/g COD, 169mL/g COD, and 168mL/g COD, respectively, being 11%, 37% and 36% higher than the control. GAC was considered promising due to its highest methane yield of 124mL/g COD at the second feeding, indicating a good recovery of adsorption capacity. The observed low methane production rates indicated the necessity for anaerobic process optimization. The physicochemical analysis of the digestates demonstrated that most of the compounds identified in the HTL-WW were degraded.

Controllable Pitch Propeller System Using the Shaft Line Energy

The newest technologies in the maritime field have gained a special dynamics over the last years. In particular it has been sought the improvement of the systems, procedures and rules related to environmental protection, but at the same time, lowering the fuel consumption has been targeted through various residual energy recovery methods, with an eye on lowering gas emissions in the atmosphere, in general, and CO2 in particular.This paper is aimed at just this target and it proposes a new controllable pitch propeller changing mechanism to be analysed, that would lead to lowering of energy consumption and by default to a reduction in the fuel consumption used by the diesel-generator.

Optimization of the Cavity Length of the Gyrotrons Operated at the Second Gyrofrequency Harmonic with One-stage Recovery of the Residual Energy of an Electron Beam

We find an optimal cavity length for gyrotrons operated at the second gyrofrequency harmonic with energy recovery for a 20% spread of transverse electron velocities, which is typical of such devices. It is shown that the efficiency-optimal length of the gyrotron cavity increases if the scheme of residual-energy recovery is used.

Role of recovery pass beam phase error in RF system design for same cell energy recovery FELs

Recovery of residual energy in the electron beam leaving the FEL interaction region allows considerable improvement in two problem areas of particular concern in high average power designs: (1) the RF power required to generate a given average optical output power is reduced, and (2) the power and energy of the beam which must be dumped are reduced, with concomitant reductions in the amount of heat which must be removed and in the radiation shielding requirements. Recirculation of the beam for a second pass through the linac allows the residual beam power to be recovered in the same RF structure used for acceleration, minimizing the investment in structure and yielding a compact layout. If the energy recovered from the beam is adjusted so that the part which interacted with the FEL optical fields is reduced to the same energy as the part of the beam which did not (“differential” energy recovery), then a relationship between the RF power required, the power delivered to the FEL optical mode, the beam current, and the linac structure's external coupling coefficient is established. For a 100 kW optical output example using eight TESLA-type super conducting cavities, a minimum of 250 kW of RF power is required if Q e is adjusted to 2×10 6. This would be less power than that required for beam loading in the injector linac.