The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Hongzhang Chen - One of the best experts on this subject based on the ideXlab platform.
-
variable Pressure Pulsation frequency optimization in gas double dynamic solid state fermentation gdssf based on heat balance model
Process Biochemistry, 2015Co-Authors: Zhimin Zhao, Lan Wang, Hongzhang ChenAbstract:Heat accumulation is considered as the main limitation of microbial growth in solid-state fermentation (SSF). Gas double-dynamic solid-state fermentation (GDSSF) has been devised based on our years of research to strengthen heat transfer by periodic air Pressure Pulsation and cycle flow. The Pressure Pulsation frequency is a key parameter which determines heat removal efficiency. In this work, heat balance model integrating Pressure Pulsation frequency, microbial metabolism, evaporative cooling and heat exchange with air was established. Pressure Pulsation frequency was then optimized based on the heat balance model. Results indicated that the optimal Pressure Pulsation frequency was variable at different fermentation stages, under which the medium temperature increase extent reduced from 4.2 degrees C to 2.5 degrees C while the fermentation production (cellulase activity) increased by 9.23% than that under the conventional constant frequency. Therefore, the variable frequency was the preferred operation mode than the conventional constant one in GDSSF. The optimization method established in the present study has been proved effective and practical. (C) 2014 Elsevier Ltd. All rights reserved.
-
variable Pressure Pulsation frequency optimization in gas double dynamic solid state fermentation gdssf based on heat balance model
Process Biochemistry, 2015Co-Authors: Zhimin Zhao, Lan Wang, Hongzhang ChenAbstract:Heat accumulation is considered as the main limitation of microbial growth in solid-state fermentation (SSF). Gas double-dynamic solid-state fermentation (GDSSF) has been devised based on our years of research to strengthen heat transfer by periodic air Pressure Pulsation and cycle flow. The Pressure Pulsation frequency is a key parameter which determines heat removal efficiency. In this work, heat balance model integrating Pressure Pulsation frequency, microbial metabolism, evaporative cooling and heat exchange with air was established. Pressure Pulsation frequency was then optimized based on the heat balance model. Results indicated that the optimal Pressure Pulsation frequency was variable at different fermentation stages, under which the medium temperature increase extent reduced from 4.2 degrees C to 2.5 degrees C while the fermentation production (cellulase activity) increased by 9.23% than that under the conventional constant frequency. Therefore, the variable frequency was the preferred operation mode than the conventional constant one in GDSSF. The optimization method established in the present study has been proved effective and practical. (C) 2014 Elsevier Ltd. All rights reserved.
-
xanthan production on polyurethane foam and its enhancement by air Pressure Pulsation
Applied Biochemistry and Biotechnology, 2010Co-Authors: Zhiguo Zhang, Hongzhang ChenAbstract:In this study, we evaluated the feasibility of solid-state fermentation (SSF) on polyurethane foam (PUF) for xanthan production. The effects of air Pressure Pulsation (APP) on biomass accumulation and final xanthan concentration were also studied. Under suitable conditions (15% inoculum, 0.5-cm (side length) PUF cubes, 15 mL medium per gram cubes and 4.5 cm bed depth), the broth was dispersed on the PUF as a film. When the initial glucose concentration in the media was low (20 and 40 g L−1), there was no significant difference between the final xanthan concentration in static SSF and submerged fermentation (SMF). When high initial glucose concentrations (60 and 80 g L−1) were used, the final gum concentrations in SSF were much higher than those in SMF. When the APP technique was applied in xanthan production with a medium containing a high glucose concentration (80 g L−1), the oxygen consumption rate of Xanthomonas campestris was significantly enhanced at the later stages of fermentation, and both the biomass and xanthan concentration were improved. The results indicated that SSF on PUF is suitable for xanthan preparation, especially when the initial glucose concentration ranged from 60 to 80 g L−1. Those results also demonstrated that APP technology can be used to enhance xanthan yields.
-
temperature control at different bed depths in a novel solid state fermentation system with two dynamic changes of air
Biochemical Engineering Journal, 2005Co-Authors: Hongzhang ChenAbstract:A novel and effective bioreactor with two dynamic changes of air (including air Pressure Pulsation and internal air circulation) was developed and tested. It could enhance the heat transfer and effectively control the temperature variation in the process of solid-state fermentation (SSF) for cellulase production through changing the Pressure range of air Pulsation, air Pulsation period and rate of internal air circulation and so on. After the optimization of the operating conditions, the maximum temperature gradient in the dynamic system with a bed height of 9.0 cm was 0.12degreesC cm(-1). (C) 2004 Elsevier B.V. All rights reserved.
Ning Zhang - One of the best experts on this subject based on the ideXlab platform.
-
coherence analysis to detect unsteady rotating stall phenomenon based on Pressure Pulsation signals of a centrifugal pump
Mechanical Systems and Signal Processing, 2021Co-Authors: Ning Zhang, Bo Gao, Xiaokai LiuAbstract:Abstract Rotating stall, one of the intense unsteady flow phenomena, is detrimental to the stable operation of the pump. To investigate rotating stall characteristics in a centrifugal pump, Pressure signals are conducted based on the coherence analysis, meanwhile the unsteady evolution process of the stall structure is also depicted in detail. Results show that unsteady Pressure signals are significantly affected by rotating stall characterized by the increased Pulsation amplitude and low frequency components generated in the Pressure spectrum. The point at θ = 18° shows strong coherence characteristics with the other points. According to the coherence results, it is found that at the stall conditions 0.09ФN and 0.06ФN, the same stall frequency at 0.25fn could be captured. However the typical frequency at the stall condition 0.2ФN could not be identified. By using the numerical simulation method, the alternative blocked and unblocked processes caused by the stall cell in the impeller are obtained, and the same stall frequency at 0.25fn is observed for the pump working at 0.2ФN. So, it is concluded that for the stall frequency of the current model pump, they keep unchanged at different stall conditions. Finally, we believe that the current method could capture the rotating stall characteristics, which could be extended to the other fluid machineries.
-
ddes analysis of unsteady flow evolution and Pressure Pulsation at off design condition of a centrifugal pump
Renewable Energy, 2020Co-Authors: Ning Zhang, Bo Gao, Junxian Jiang, Xiaokai LiuAbstract:Abstract In the present paper, to investigate unsteady flow structures and Pressure Pulsations at off-design conditions, a low specific speed centrifugal pump is investigated by the DDES (Delayed Detached Eddy Simulation) method. Emphasis is laid on the unsteady evolution of flow structure and Pressure Pulsation at the stalled condition. Results show that the jet-wake flow pattern could be captured by the current numerical simulation method, and it shows a high calculation precision for the jet flow. Relative velocity decreases rapidly in the wake region towards the blade suction side. Significant inflection point exists between the jet and wake flow regions, and it almost keeps unchanged at the identical impeller-volute position under various flow rates. At the stalled status, the inflection point moves towards the blade Pressure side with the blade passing the volute tongue, and evident non-uniform flow distributions are formed in the blade channels characterized by the multiple vortices. The blade channel is gradually blocked by the corresponding stall cell when the blade approaches the volute tongue, and it indicates that the volute tongue has a significant effect on the evolution process of the stall structure. By combination analysis of the unsteady evolution of the stall structure and Pressure spectrum, the stall frequency at 0.25fn (being fn the impeller rotating frequency) is captured for the current model pump.
-
experimental and numerical investigation on the Pressure Pulsation and instantaneous flow structure in a nuclear reactor coolant pump
Nuclear Engineering and Design, 2018Co-Authors: Dan Ni, Ning Zhang, Minguan Yang, Zhong LiAbstract:Abstract The instantaneous vortical flow structure is one of the typical flow structures inside the nuclear reactor coolant pump (RCP), which would cause the unsteady Pressure Pulsations, vibrations of the unit and fatigue of components. Due to high safety requirement of the RCP during the actual operation of the nuclear power plants (NPPs), revealing instantaneous nature of vortical flow structure and its Pressure Pulsation becomes a crucial issue for studying the internal flow mechanism of the RCP. The purpose of this study is to shed comprehensive light on the Pressure Pulsation and instantaneous vortical flow structure in the RCP by using the experimental method and the numerical simulation method. Based on the result of comparison with the experiment and numerical simulation, it can be considered that the LES method can better identify instantaneous nature of vortical flow structures in the low frequency band. The instantaneous vortical flow structure is attached to the impeller RBPS (rotor blade Pressure surface) and transient jet wake vortex flow structures between the impeller and diffuser under the rotor-stator interaction effect are fairly obvious by Q-criterion. On the other hand, in the axial-vorticity component distribution, the rotor-stator interaction effect between the impeller and diffuser cannot be clearly revealed. From the three-dimensional structures, the main vortex structures are in the front and back cavity of the right-hand side near the discharge nozzle and the right-hand side below the discharge nozzle in the spherical casing. Meanwhile, combined with Pressure spectrum, it is convinced that their unsteady characteristic is the main reason that causes complex excitation frequencies in the low frequency band of the right-hand side near the discharge nozzle.
-
experimental and numerical analysis of unsteady Pressure Pulsation in a centrifugal pump with slope volute
Journal of Mechanical Science and Technology, 2015Co-Authors: Ning Zhang, Minguan Yang, Bo GaoAbstract:This study experimentally and numerically investigates the unsteady flow in a centrifugal pump with special slope volute under various conditions to illustrate the detailed flow structures and Pressure Pulsation within the model pump. Whole flow passage is considered during the numerical simulation; Pressure Pulsation signals are extracted using nine fast-response Pressure transducers. The Root mean square (RMS) method is introduced to deal with the discrete components at fBPF of the different monitoring points along the volute casing, which is an effective attempt to evaluate the overall pulsating level of the model pump. Results show that numerical method can predict the components at fBPF effectively; however, it has limited ability in capturing noise frequencies motivated by unsteady separate flow and non-linear interaction effect. Around the nominal flow rate, the predicted amplitudes at fBPF agree well with the experimental results, showing larger difference at the off-design conditions. To predict the pulsating level of the components at fBPF, two fitted equations of the RMS values versus the flow rate and specific speed are carried out, which would be very helpful in evaluating the Pressure Pulsation level in the centrifugal pump.
-
unsteady Pressure Pulsation and rotating stall characteristics in a centrifugal pump with slope volute
Advances in Mechanical Engineering, 2014Co-Authors: Ning Zhang, Minguan Yang, Bo GaoAbstract:Unsteady flow structures can lead to severe vibration in centrifugal pump if the eigenfrequency of the rotor is equal to excitation frequency. In order to reduce rotor-stator interaction in centrif...
Zhimin Zhao - One of the best experts on this subject based on the ideXlab platform.
-
variable Pressure Pulsation frequency optimization in gas double dynamic solid state fermentation gdssf based on heat balance model
Process Biochemistry, 2015Co-Authors: Zhimin Zhao, Lan Wang, Hongzhang ChenAbstract:Heat accumulation is considered as the main limitation of microbial growth in solid-state fermentation (SSF). Gas double-dynamic solid-state fermentation (GDSSF) has been devised based on our years of research to strengthen heat transfer by periodic air Pressure Pulsation and cycle flow. The Pressure Pulsation frequency is a key parameter which determines heat removal efficiency. In this work, heat balance model integrating Pressure Pulsation frequency, microbial metabolism, evaporative cooling and heat exchange with air was established. Pressure Pulsation frequency was then optimized based on the heat balance model. Results indicated that the optimal Pressure Pulsation frequency was variable at different fermentation stages, under which the medium temperature increase extent reduced from 4.2 degrees C to 2.5 degrees C while the fermentation production (cellulase activity) increased by 9.23% than that under the conventional constant frequency. Therefore, the variable frequency was the preferred operation mode than the conventional constant one in GDSSF. The optimization method established in the present study has been proved effective and practical. (C) 2014 Elsevier Ltd. All rights reserved.
-
variable Pressure Pulsation frequency optimization in gas double dynamic solid state fermentation gdssf based on heat balance model
Process Biochemistry, 2015Co-Authors: Zhimin Zhao, Lan Wang, Hongzhang ChenAbstract:Heat accumulation is considered as the main limitation of microbial growth in solid-state fermentation (SSF). Gas double-dynamic solid-state fermentation (GDSSF) has been devised based on our years of research to strengthen heat transfer by periodic air Pressure Pulsation and cycle flow. The Pressure Pulsation frequency is a key parameter which determines heat removal efficiency. In this work, heat balance model integrating Pressure Pulsation frequency, microbial metabolism, evaporative cooling and heat exchange with air was established. Pressure Pulsation frequency was then optimized based on the heat balance model. Results indicated that the optimal Pressure Pulsation frequency was variable at different fermentation stages, under which the medium temperature increase extent reduced from 4.2 degrees C to 2.5 degrees C while the fermentation production (cellulase activity) increased by 9.23% than that under the conventional constant frequency. Therefore, the variable frequency was the preferred operation mode than the conventional constant one in GDSSF. The optimization method established in the present study has been proved effective and practical. (C) 2014 Elsevier Ltd. All rights reserved.
Shengmei Yang - One of the best experts on this subject based on the ideXlab platform.
-
experimental study of lubricating oil impact on Pressure Pulsation for twin screw refrigeration compressor
International Journal of Refrigeration-revue Internationale Du Froid, 2020Co-Authors: Shengmei Yang, Hua Ouyang, Lee WangAbstract:Abstract An experimental investigation on Pressure Pulsations of twin-screw refrigeration compressor was conducted. The Pressure Pulsation energy at different radial locations on the screw housing, inside the discharge chamber, and the energy transmitting to downstream components during the working process were all tested. Various oil parameters have been investigated to disclose its influence on the Pressure Pulsation energy of twin-screw refrigeration compressors. With the total oil flow rate increasing, Pressure Pulsation was found attenuating above the 1st order of pumping frequency, while the amplitude reduction was found depended on the oil injection locations and oil distributions obviously. The final compression Pressure inside the screw lobe cavity before the internal discharge port opening was found to be much lower than the expected value based on the built-in radial Vi, and the Pressure continued increasing until the axial port opening around 5.45°. Several suggestions about design for lower Pressure Pulsations were recommended based on test findings.
Bo Gao - One of the best experts on this subject based on the ideXlab platform.
-
coherence analysis to detect unsteady rotating stall phenomenon based on Pressure Pulsation signals of a centrifugal pump
Mechanical Systems and Signal Processing, 2021Co-Authors: Ning Zhang, Bo Gao, Xiaokai LiuAbstract:Abstract Rotating stall, one of the intense unsteady flow phenomena, is detrimental to the stable operation of the pump. To investigate rotating stall characteristics in a centrifugal pump, Pressure signals are conducted based on the coherence analysis, meanwhile the unsteady evolution process of the stall structure is also depicted in detail. Results show that unsteady Pressure signals are significantly affected by rotating stall characterized by the increased Pulsation amplitude and low frequency components generated in the Pressure spectrum. The point at θ = 18° shows strong coherence characteristics with the other points. According to the coherence results, it is found that at the stall conditions 0.09ФN and 0.06ФN, the same stall frequency at 0.25fn could be captured. However the typical frequency at the stall condition 0.2ФN could not be identified. By using the numerical simulation method, the alternative blocked and unblocked processes caused by the stall cell in the impeller are obtained, and the same stall frequency at 0.25fn is observed for the pump working at 0.2ФN. So, it is concluded that for the stall frequency of the current model pump, they keep unchanged at different stall conditions. Finally, we believe that the current method could capture the rotating stall characteristics, which could be extended to the other fluid machineries.
-
ddes analysis of unsteady flow evolution and Pressure Pulsation at off design condition of a centrifugal pump
Renewable Energy, 2020Co-Authors: Ning Zhang, Bo Gao, Junxian Jiang, Xiaokai LiuAbstract:Abstract In the present paper, to investigate unsteady flow structures and Pressure Pulsations at off-design conditions, a low specific speed centrifugal pump is investigated by the DDES (Delayed Detached Eddy Simulation) method. Emphasis is laid on the unsteady evolution of flow structure and Pressure Pulsation at the stalled condition. Results show that the jet-wake flow pattern could be captured by the current numerical simulation method, and it shows a high calculation precision for the jet flow. Relative velocity decreases rapidly in the wake region towards the blade suction side. Significant inflection point exists between the jet and wake flow regions, and it almost keeps unchanged at the identical impeller-volute position under various flow rates. At the stalled status, the inflection point moves towards the blade Pressure side with the blade passing the volute tongue, and evident non-uniform flow distributions are formed in the blade channels characterized by the multiple vortices. The blade channel is gradually blocked by the corresponding stall cell when the blade approaches the volute tongue, and it indicates that the volute tongue has a significant effect on the evolution process of the stall structure. By combination analysis of the unsteady evolution of the stall structure and Pressure spectrum, the stall frequency at 0.25fn (being fn the impeller rotating frequency) is captured for the current model pump.
-
experimental and numerical analysis of unsteady Pressure Pulsation in a centrifugal pump with slope volute
Journal of Mechanical Science and Technology, 2015Co-Authors: Ning Zhang, Minguan Yang, Bo GaoAbstract:This study experimentally and numerically investigates the unsteady flow in a centrifugal pump with special slope volute under various conditions to illustrate the detailed flow structures and Pressure Pulsation within the model pump. Whole flow passage is considered during the numerical simulation; Pressure Pulsation signals are extracted using nine fast-response Pressure transducers. The Root mean square (RMS) method is introduced to deal with the discrete components at fBPF of the different monitoring points along the volute casing, which is an effective attempt to evaluate the overall pulsating level of the model pump. Results show that numerical method can predict the components at fBPF effectively; however, it has limited ability in capturing noise frequencies motivated by unsteady separate flow and non-linear interaction effect. Around the nominal flow rate, the predicted amplitudes at fBPF agree well with the experimental results, showing larger difference at the off-design conditions. To predict the pulsating level of the components at fBPF, two fitted equations of the RMS values versus the flow rate and specific speed are carried out, which would be very helpful in evaluating the Pressure Pulsation level in the centrifugal pump.
-
unsteady Pressure Pulsation and rotating stall characteristics in a centrifugal pump with slope volute
Advances in Mechanical Engineering, 2014Co-Authors: Ning Zhang, Minguan Yang, Bo GaoAbstract:Unsteady flow structures can lead to severe vibration in centrifugal pump if the eigenfrequency of the rotor is equal to excitation frequency. In order to reduce rotor-stator interaction in centrif...
