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Chunxi L.,North China Electrical Power University | Ling W.S.,North China Electrical Power University | Yakui J.,Hebei Electric Power Research Institute
Energy Conversion and Management | Year: 2011

The influence of enlarged impeller in unchanged volute on G4-73 type centrifugal fan performance is investigated in this paper. Comparisons are conducted between the fan with original impeller and two larger impellers with the increments in impeller outlet diameter of 5% and 10% respectively in the numerical and experimental investigations. The internal characteristics are obtained by the numerical simulation, which indicate there is more volute loss in the fan with larger impeller. Experiment results show that the flow rate, total pressure rise, shaft power and sound pressure level have increased, while the efficiency have decreased when the fan operates with larger impeller. Variation equations on the performance of the operation points for the fan with enlarged impellers are suggested. Comparisons between experiment results and the trimming laws show that the trimming laws for usual situation can predict the performance of the enlarged fan impeller with less error for higher flow rate, although the situation of application is not in agreement. The noise frequency analysis shows that higher noise level with the larger impeller fan is caused by the reduced impeller-volute gap. © 2011 Elsevier Ltd. All rights reserved.

Zhao Z.-B.,North China Electrical Power University | Suo Z.-G.,Hebei Electric Power Research Institute
Gaodianya Jishu/High Voltage Engineering | Year: 2011

In accordance with the arbitrarily disposed grounding electrodes, taking the effect of grounding grid into account, we put forward a new method to inverse the parameters of horizontally stratified soil model on the basis of the Green function of horizontal multiple-layer soil and the calculation model of grounding grid with unequal spacing. The proposed method can be used in later expansion of station to select measurement electrode and the minimum distance of grounding grid in soil parameter measurement. In the validation of the method, the effectiveness of the equal-spacing four-electrode method, straight four-electrode method, and arbitrary four-electrode method is evaluated. By taking a simple grounding grid as example, the inversed soil model and grounding resistivity are compared for the cases with and without consideration of grounding grid. The effective range of the grounding grid is defined. It is required that, on the premise of measurement standard, the space between the connection line of measurement electrodes and the grounding gird edge is not less than 0.618 times that of the diagonal the grounding gird.

Ma L.,Ordnance Engineering College | Kang J.,Ordnance Engineering College | Meng Y.,Hebei Electric Power Research Institute | Lv L.,62191 Troops of PLA
Yi Qi Yi Biao Xue Bao/Chinese Journal of Scientific Instrument | Year: 2013

Aiming at the problem that at early stage of bearing fault, the feature components of the original vibration data are easy to be submerged in noise signal and can not be detected in time. According to the de-noising principle of Morlet wavelet transform, a method is presented, which determines the optimal scale parameter based on scale related power distribution, so that the signal is filtered under this scale and the impact feature components are extracted. The main filtering procedures include: the minimum Shannon entropy is used to optimize the Morlet wave shape factor, the best match between mother wavelet and signal fault feature is realized; the scale-power spectrum is plotted with the wavelet transform coefficients of the best Morlet continuous wavelet under different transform scales; and according to the accumulative characteristic of the fault feature power in specific scale range, the scale parameter with best filtering effect is selected from the extreme points in the scale power spectrum. The actual processing result for bearing full lifetime vibration datasets shows that the proposed method can extract the weak feature components and detect the existence of related outer-race fault in advance compared with root-mean-square trend. So this method can be regarded as an effective approach for diagnosing bearing incipient fault.

Li Z.,Hebei Electric Power Research Institute
Power and Energy - Proceedings of the International Conference on Power and Energy, CPE 2014 | Year: 2015

An optimization was performed for a sintering waste heat power unit with all data obtained in the site and under the unit normal operating conditions. The physical and mathematical model for the process of cooling and generation is established, which makes the net power generation as an objective function of the cooling machine imported ventilation, the thickness of sinter and the main steam pressure. Optimizing for single parameter, we found that each parameter had an optimal value for the system. In order to further optimize the system’s operating parameters, genetic algorithm was used to make the combinatorial optimization of the three parameters. Optimization results show that power generation capacity per ton is increased by 13.10%, and net power generation is increased by 16.17%. The optimization is instructive to the operation of sintering waste heat power unit. © 2015 Taylor and Francis Group.

Li Z.,Hebei Electric Power Research Institute
Power and Energy - Proceedings of the International Conference on Power and Energy, CPE 2014 | Year: 2015

In gas cooler, a key component of transcritical heat pump system, CO2 is always in supercritical status. A well design gas cooler should get the full informations of supercritcal CO2 in-tube cooling heat transfer characteristic. An EES program is developed to calculate the supercritical CO2 cooling heat transfer performances based on 4 selected correlation equations. According to the results and the thermopgysical parameters of supercritical CO2, such as specific heat, density, thermal conductivity and dynamic viscosity, two region, the starting area of supercritical region and the main supercritical region, is suggested for supercritical CO2 cooling heat transfer by temperature at 80°C. In the staring area, the variations of heat transfer and other parameters are intensive, while in the main supercritical region, the variations are clined to be stable. © 2015 Taylor and Francis Group.

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