Qian Li

Parallel pump systems are widely used in industries. However, pumps are often operating under off-design conditions due to many reasons, which reduces the efficiency and reliability of the pumps. This paper aims at reducing the power consumption of parallel pump systems and improving the reliability of pumps by improving the operation points of pumps. To achieve this goal, a combination of selecting the proper number of pumps to put into operation and their speed is needed. Also, a control valve is adopted to further improve the operation points. The optimization model is built for a parallel pump system. Particle swarm optimization algorithm is used to solve the problem. Experimental verification shows that the proposed method improves the reliability and can also reduce power consumption for some cases compared to conventional PID speed regulation method. But for cases with large flow, extra power might be needed because the control valve introduces extra flow resistance in order to improve the operation point. The proposed method can be easily extended to applications based on their requirements on reliability.

Dynamic modulus tests were conducted on three asphalt mixtures under different loading modes.The effects of loading mode,confining pressure and strain level on the master curve of dynamic modulus were studied.The functions of shift factor-confining pressure and dynamic modulus-confining pressure for asphalt mixtures were developed using Fillers-Moonan-Tschoegl model and improved Sigmoidal model,respectively.It is found that twice-fitting can eliminate the dependency of dynamic modulus extreme in the master curve on shift factor model.The uniaxial compressive,indirect tensile and four-point bending dynamic modulus values of asphalt mixtures are different at the same reduced frequency,especially at low temperatures or high loading frequencies.However,there are nice linear correlations between them.The confining pressure has significant effect on triaxial compressive dynamic modulus at high temperatures or low loading frequencies.The four-point bending dynamic modulus is sensitive to the change of strain level.