A series compensation enabled ZVS range enhancement of a dual active bridge converter for wide range load conditions

2014 ◽  
Author(s):  
Awneesh Tripathi ◽  
Krishna Mainali ◽  
Subhashish Bhattacharya
Keyword(s):  
Series Compensation ◽  
Dual Active Bridge ◽  
Wide Range ◽  
Load Conditions

A Study of Cavitation Flow in a Centrifugal Pump at Part Load Conditions Based on Numerical Analysis

2012 ◽  
Author(s):  
Jianping Yuan ◽  
Yanxia Fu ◽  
Shouqi Yuan
Keyword(s):  
Centrifugal Pump ◽  
Flow Rate ◽  
Suction Side ◽  
Cavitation Number ◽  
Flow Coefficient ◽  
Inlet Pipe ◽  
Part Load ◽  
Cavitation Inception ◽  
Wide Range ◽  
Load Conditions

In order to predict cavitation performance of the centrifugal pump, including cavitating structures and vapour volume at the blade suction side, as well as its relationship with the backflow in the impeller eye, a 3D numerical simulation of detailed steady and unsteady cavitating flow was applied to reproduce its inner flow fields at part load conditions (0.5Qd and 0.4Qd). The comparisons of cavitation characteristics of the current centrifugal pump at an on-design point (1.0Qd) and a high flow rate (1.2Qd) were achieved as well. In addition, Frequency analysis of pressure fluctuations at the blade passages and the inlet pipe were also obtained during cavitation for a flow coefficient of 50%. The results further show that successive blade cavitation patterns and the creeping cavitation number dropping appear for a wide range of flow rates when the inlet total pressure decreases from cavitation inception to the breakdown of the centrifugal pump, as is quite different from that when cavitation occurs at 1.0Qd or 1.2Qd. Unbalanced attached cavities on the blade suction side were also observed at 0.5Qd. Meanwhile, the unsteady behaviour of cavities attached to the blade suction side and cavitation number dropping depend on the flow rate and cavitation number. Another significant characteristic of the phenomenon is that all the domain frequencies in blade passages and inlet pipe at part load conditions are 0.048Hz∼48.285Hz, which is typically lower than the shaft rotational frequency of the model centrifugal pump.

Advanced Catalytic Pilot for Low NOx Industrial Gas Turbines

2002 ◽  
Author(s):  
Hasan Karim ◽  
Kent Lyle ◽  
Shahrokh Etemad ◽  
Lance Smith ◽  
William Pfefferle ◽  
...  
Keyword(s):  
High Pressure ◽  
Surface Temperature ◽  
Gas Turbines ◽  
Lean Burn ◽  
Pressure Testing ◽  
Wide Range ◽  
Industrial Gas Turbines ◽  
Design And Testing ◽  
Pilot Burner ◽  
Load Conditions

This paper describes the design and testing of a catalytically-stabilized pilot burner for current and advanced Dry Low NOx (DLN) gas turbine combustors. In this paper, application of the catalytic pilot technology to industrial engines is described using Solar Turbines’ Taurus 70 engine. The objective of the work described is to develop the catalytic pilot technology and document the emission benefits of catalytic pilot technology when compared to higher, NOx producing pilots. The catalytic pilot was designed to replace the existing pilot in the existing DLN injector without major modification to the injector. During high pressure testing, the catalytic pilot showed no incidence of flashback or autoignition while operating over wide range of combustion temperatures. The catalytic reactor lit off at a temperature of approximately 598K (325°C/617°F) and operated at simulated 100% and 50% load conditions without a preburner. At high pressure, the maximum catalyst surface temperature was similar to that observed during atmospheric pressure testing and considerably lower than the surface temperature expected in lean-burn catalytic devices. In single injector rig testing, the integrated assembly of the catalytic pilot and Taurus 70 injector demonstrated NOx and CO emission less than 5 ppm @ 15% O2 for 100% and 50% load conditions along with low acoustics. The results demonstrate that a catalytic pilot burner replacing a diffusion flame or partially-premixed pilot in an otherwise DLN combustor can enable operation at conditions with substantially reduced NOx emissions.

scholarly journals Optimized Hip-Knee-Ankle Exoskeleton Assistance Reduces the Metabolic Cost of Walking With Worn Loads

2021 ◽  
Author(s):  
Gwendolyn M Bryan ◽  
Patrick Franks ◽  
Seungmoon Song ◽  
Ricardo Reyes ◽  
Meghan O’Donovan ◽  
...  
Keyword(s):  
Body Weight ◽  
Muscle Activity ◽  
Metabolic Cost ◽  
Load Carriage ◽  
Heavy Load ◽  
Human In The Loop ◽  
Light Load ◽  
Wide Range ◽  
Ankle Exoskeleton ◽  
Load Conditions

Abstract BackgroundLoad carriage is a typical activity in a wide range of professions, but prolonged load carriage is associated with increased fatigue and overuse injuries. Exoskeletons could improve the quality of life of these professionals by reducing metabolic cost to combat fatigue and reducing muscle activity to prevent injuries. Current exoskeletons have reduced the metabolic cost of loaded walking by up to 23% when assisting one or two joints. Greater metabolic reductions may be possible with optimized assistance of the entire leg. MethodsWe used human-in the-loop optimization to optimize hip-knee-ankle exoskeleton assistance with no additional load, a light load (15% of body weight), and a heavy load (30% of body weight) for three participants. All loads were applied through a weight vest with an attached waist belt. We measured metabolic cost, exoskeleton assistance, kinematics, and muscle activity. We performed one-tailed paired t-tests to determine significant reductions for metabolic cost and muscle activity, and we performed an analysis of variance (ANOVA) to determine significant changes across load conditions for metabolic cost and applied power. ResultsExoskeleton assistance reduced the metabolic cost of walking relative to walking in the device without assistance for all tested conditions. Exoskeleton assistance reduced the metabolic cost of walking by 47% with no load (p = 0.02), 35% with the light load (p = 0.03), and 43% with the heavy load (p = 0.02). The smaller metabolic reduction with the light load may be due to insufficient participant training or lack of optimizer convergence. The total applied positive power was similar for all tested conditions, and the positive knee power decreased slightly as load increased. Optimized torque timing parameters were consistent across participants and load conditions while optimized magnitude parameters varied. ConclusionsWhole-leg exoskeleton assistance can reduce the metabolic cost of walking while carrying a range of loads. The consistent optimized timing parameters suggest that metabolic cost reductions are sensitive to torque timing. The variable torque magnitude parameters could imply that torque magnitude should be customized to the individual, or that there is a range of useful torque magnitudes. Future work should test whether applying the load to the exoskeleton rather than the person's torso results in larger benefits.

Advanced Catalytic Pilot for Low NOx Industrial Gas Turbines

2003 ◽  
Vol 125 (4) ◽  
pp. 879-884 ◽  
Author(s):  
H. Karim ◽  
K. Lyle ◽  
S. Etemad ◽  
L. L. Smith ◽  
W. C. Pfefferle ◽  
...  
Keyword(s):  
High Pressure ◽  
Surface Temperature ◽  
Gas Turbines ◽  
Lean Burn ◽  
Pressure Testing ◽  
Wide Range ◽  
Industrial Gas Turbines ◽  
Design And Testing ◽  
Pilot Burner ◽  
Load Conditions

This paper describes the design and testing of a catalytically stabilized pilot burner for current and advanced Dry Low NOx (DLN) gas turbine combustors. In this paper, application of the catalytic pilot technology to industrial engines is described using Solar Turbines’ Taurus 70 engine. The objective of the work described is to develop the catalytic pilot technology and document the emission benefits of catalytic pilot technology when compared to higher, NOx producing pilots. The catalytic pilot was designed to replace the existing pilot in the existing DLN injector without major modification to the injector. During high-pressure testing, the catalytic pilot showed no incidence of flashback or autoignition while operating over wide range of combustion temperatures. The catalytic reactor lit off at a temperature of approximately 598 K (325°C/617°F) and operated at simulated 100% and 50% load conditions without a preburner. At high pressure, the maximum catalyst surface temperature was similar to that observed during atmospheric pressure testing and considerably lower than the surface temperature expected in lean-burn catalytic devices. In single-injector rig testing, the integrated assembly of the catalytic pilot and Taurus 70 injector demonstrated NOx and CO emission less than 5 ppm @ 15% O2 for 100% and 50% load conditions along with low acoustics. The results demonstrate that a catalytic pilot burner replacing a diffusion flame or partially premixed pilot in an otherwise DLN combustor can enable operation at conditions with substantially reduced NOx emissions.

scholarly journals Current optimal control method for three-phase dual active bridge converter in light load conditions

2021 ◽  
Vol 300 ◽  
pp. 01009
Author(s):  
Xiaobin Mu ◽  
Xiang Wang ◽  
Fengjiao Dai
Keyword(s):  
Control Method ◽  
Storage System ◽  
Time Domain Analysis ◽  
Energy Storage System ◽  
Current Control ◽  
Dual Active Bridge ◽  
Light Load ◽  
Three Phase ◽  
Low Efficiency ◽  
Load Conditions

Three-phase dual active bridge converter has many performance advantages, and is widely used in electric vehicle charging, battery energy storage system, power electronic transformer, and other energy conversion occasions. However, in the traditional control method, it has the problem of low efficiency under light load conditions. In this paper, firstly, the power and current expressions of the converter under light load conditions are solved by time-domain analysis, and an optimal current control method under light load conditions is proposed. This control method can simultaneously realize the minimum inductance current stress and RMS. Finally, the effectiveness of this method is verified by experiments.

scholarly journals Adaptive Power Line Harmonic Detection for Active Filter Applications

2021 ◽  
Author(s):  
Weidong Liu
Keyword(s):  
Computer Simulation ◽  
Detection Method ◽  
Power Line ◽  
Active Filters ◽  
Adaptive Detection ◽  
Harmonic Detection ◽  
Complex Design ◽  
Wide Range ◽  
Adaptive Power ◽  
Load Conditions

The objective of this thesis research is to develop an efficient method for accurate detections of power line harmonic distortions for the control of active filters. The research has achieved its objective with four significant results. First, an adaptive power line harmonic detection method is developed, which is based on the findings of extensive research in the areas of inside and outside of power electronics controls. Second, a simple and practical formulation of the adaptive harmonic detection method is developed, which is simplified significantly from the original complex design formulations for noise cancellations. Third, vigorous verifications of effectiveness of the adaptive detection method using computer simulations are carried out, which cover the steady state operations, the dynamic operations, normal power line conditions, non-ideal supply and load conditions, etc. Fourth, experimental verifications of the accuracy of the adaptive detection method are conducted, which cover typical distorted power line conditions for normal and unbalanced operations. For illustration, this thesis presents carefully designed computer simulation and experimental case studies that cover a wide range of power line conditions.

scholarly journals Operation of Current-fed Dual Active Bridge DC-DC Converters for Microgrid

2019 ◽  
Vol 8 (2) ◽  
pp. 3167-3175
Keyword(s):  
High Frequency ◽  
Soft Switching ◽  
Switching Loss ◽  
Zero Voltage Switching ◽  
Dual Active Bridge ◽  
Light Load ◽  
Zero Current Switching ◽  
Zero Current ◽  
Cell Energy ◽  
Load Conditions

Dual Active Bridge (DAB) is an isolated bidirectional DC-DC converter, which comprises two full bridge converterslinked through a high frequency transformer. It haslow stresses and permits high frequency performance because of the soft-switching. All the switches in the converter achieves the turn ON & OFF during Zero Voltage Switching (ZVS) and Zero Current Switching (ZCS) to minimize switching loss. Generally, DAB is classified as two types, namely, voltage-fed and current-fed variants. At light load conditions, soft-switching is not realized in case of voltage-fed DAB topologies. The application of current-fed DAB converters is to reduce the losses at the time of switching under light load conditions and improves the efficiency. This paper describes the various topologies of voltage-fed and current-fed DAB used for different applications in microgrid and fuel cell energy generation system by using the simulation. The performance of voltage-fed and current-fed DAB with snubber-less converters are also demonstrated and their effectiveness are validated

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