Assessment of Noise Signature for a Cavitating Centrifugal Pump

In recent days, sophisticated instruments have emerged to obtain an online measurement of performance parameters from centrifugal pump of different kinds and the signals can be directed to the hands of pump user through mobile application. With this in mind, a centrifugal pump of low specific speed was chosen for cavitation studies from 80% to 120% of nominal flow rate and for three different speeds. An assessment was carried out for cavitation noise signature from those operating condition of that pump. The result of cavitation noise based on peak magnitude as well as average revealed a nature in relation to cavitation coefficient and it greatly depends on the flow rate with respect to nominal flow rate. The noise envelope for the flow rate at best efficiency and above was having similar trend whereas at flows less than the nominal, it was totally different. So the criteria for finding the deviation in noise cannot be uniform for all flow rates. In this paper, the method adapted was to impose a trend line to the measured cavitation noise information and to find out the deviation with respect to normal operating condition. It was concluded that detection of abnormality in pumps due to cavitation effects requires the current operating condition to be diagnosed first and then proper criteria for deviation in noise has to be imposed.

A Robust Impedance Controller for Improved Safety in Human-Robot Interaction

This paper presents a novel impedance controller modified with a switching strategy for the purpose of improving safety in human-robot interactions. Under normal operating condition, an impedance controller is enabled when adequate tracking performance is maintained in the presence of bounded disturbances. However, if disturbances are greater than anticipated such that tracking performance is degraded, the proposed controller temporarily switches modes to a control strategy better apt to limit control inputs. With disturbances returning to the prescribed bounds, tracking performance will restored and the impedance controller will resume for nominal operation. The control parameters are constrained by a few conditions necessary for smooth operation. First, a pair of equality constraints is required for the control signal to be continuous when switching control modes. Second, a Lyapunov analysis is performed to formulate an equality constraint on the control parameters to ensure only a single switch occurs when changing control modes to avert control chatter. Third, a matrix inequality constraint is necessary to ensure a robust positive invariant set is formed for when impedance control is active. Numerical simulations are provided to illustrate the controller and conditions. The simulation results successfully validate the presented theory, demonstrating how the constraints yield a continuous control signal, eliminate switching chatter, and permit robustness to disturbances.

Solar photovoltaic module performance characterisation using single diode modeling

Single or double diode electrical modeling of SPV module gives valuable results which will help to identify the exact behavior of SPV module under the normal operating condition. Accurate modelling of SPV module will also help to calculate internal resistances (Rs, Rsh) and parasitic of the SPV module. The main contribution of this work is the stepwise simplification of the current equation of single and double diode electrical model of SPV module. Then the single diode model of SPV module having 36 SPV cells in series is simulated in LTspice simulator. Simulated results are compared with labelled electrical parameters which shows close proximity to the labelled parameter at particular values of series and shunt resistance. This paper also presents the effect of variation in series resistance (Rs) and shunt resistance (Rsh) on the performance of the SPV module under normal operating condition. The dependency of SPV electrical parameters (Imax, Vmax, Pmax, FF, η) with the variation of series resistance (Rs) and shunt resistance (Rsh) is simulated, and the effects are discussed in details.

Assessment of Noise Signature for a Cavitating Centrifugal Pump

In recent days, sophisticated instruments have emerged to obtain an online measurement of performance parameters from centrifugal pump of different kinds and the signals can be directed to the hands of pump user through mobile application. With this in mind, a centrifugal pump of low specific speed was chosen for cavitation studies from 80% to 120% of flow rate and for three different speeds. An assessment was carried out for cavitation noise signature from those operating condition of pumps. The result of cavitation noise based on peak magnitude as well as average of noise revealed a nature and it depends on the flow rate with respect to nominal flow rate. The noise envelope for the flow rate at best efficiency and above was having similar trend whereas at flows less than duty point it was totally different. So the criteria for finding the deviation in noise cannot be uniform for all flow rates. In this paper, the method adapted was to impose a trend line to the measured cavitation noise information to find out the deviation with respect to normal operating condition. It was concluded that detection of abnormality in pumps due to cavitation effects requires the operating condition to be diagnosed first and the proper criteria for deviation in noise has to be imposed.

The Influence of Pressure on the Discharge along Oil-Paper Interface under AC Stress

This study explores the influence of hydrostatic pressure on the discharge along the oil-paper interface under AC voltage, especially for the normal operating condition and breakdown. In this paper, an experimental platform was set up to record the partial discharge (PD) parameters of the test sample under different hydrostatic pressures, while the applied AC voltage was increased to final flashover voltage step by step. Experimental results showed that higher hydrostatic pressure had different effects on PD under different voltages. Higher pressure decreased the PD energy and increased the flashover voltage. Furthermore, under higher hydrostatic pressure, discharge traces (white mark) were found on the surface of the samples after intense discharging on the oil-paper interfaces, indicating that the hydrostatic pressure can affect the gas generation and dissipation process underneath the surface of the pressboards. Finally, the mechanism of how hydrostatic pressure influences the PD, flashover voltage, and white mark was interpreted based on the bubble theory. The results derived in this paper can be helpful for an optimal design and reasonable operation of oil-paper insulation systems, especially for power transformers.

ANALYSIS OF RADIATION SAFETY IN THE NPP SITE IN NORMAL OPERATION CONDITION

ANALYSIS OF RADIATION SAFETY IN THE NPP SITE IN NORMAL OPERATION CONDITION. Construction of nuclear power plant (NPP) requires an evaluation of radiation safety which proves that operation of the NPP under normal operating condition and postulated abnormal conditions is safe. Analysis of radiation safety at the NPP site under normal operating condition is required to complete the documents of site analysis and safety analysis. This study is aimed to obtain radiation dose in the environment of the NPPs at Sebagin site in province of Bangka Belitung. The doses were calculated using PC-Cream code. It is assumed that there are three 1000-MWe PWR operating in Sebagin site. Input data required for PC-Cream simulation are routine sourceterm of three 1000MWe-PWRs, meteorological data, and agricultural and animal production, and population distribution. The meteorological data consist of stability frequency of weather for 16 sectors (wind direction) taken from local weather data for 1 year. The data of agricultural and livestock production and population distribution are also taken for 1 year for 16 sectors and 20 radial directions. The results show that the maximum dose from all types of radionuclides and all pathways accepted by adult public around Sebagin site is approximately 0.053 mSv/year to the north direction in the radius of 1 km. This dose is far below the dose limit value of 1 mSv/year or dose constraint of 0.3 mSv/year as public acceptance criteria (BAPETEN). It can be concluded that radiation doses are influenced by activity and type of nuclides sourceterm, reactor layout, meteorological condition, and environmental condition.

Analytical Comparision between Single and Modular Fuel Cell Stack: Uniform Modular Cell Approch

A single fuel cell (FC) produces a very small voltage of about 0.6 -0.8 V under normal operating condition, and hence several individual cells are connected in series as a stack to get higher voltages suitable for practical loads. The stacks are then connected in series to get required values of DC voltage. The FC performance varies with the operating parameters such as temperature, humidity, fuel flow rate, ageing and fuel non uniform concentration. The FC stack underperforms when there is presence of bad cell in it. The Presence bad cell in a stack limits the current handling capacity of other healthy cells when it’s connected as a conventional single stack. This can be overcome by connecting the fuel cells in uniform modular cell configuration. In this paper a Uniform Modular Cell Configuration (UMCC) is proposed to gain the maximum power from the stack and the conventional Single or Uni Stack Configuration (USC) is compared with the proposed structure. A detail mathematical analysis of comparing both methods is described. Further the superiority of the proposed method is proven by carrirying out the simulations under steady state operating condition of a FC stack feeding to a constant current load.