水利水电工程专业英语水电站与水轮机篇（参考）.docxVIP

水利水电工程专业英语——水电站与水轮机篇1. Energy and Power of Water Flow1. 水流的能量和功率As may be recalled from mechanics of fluids, the energy and power of a quantity of water in steady flow from A to B can be determined using Bernoulli’s theorem for specific energy. From the principle of conservation of energy it follows that the energy eA at A equals the energy eB at B plus the energy eAB released as the water flows from A to B. Assuming that the weight of the water is 1N, Bernoulli’s equation, which in effect expresses the law of conservation of energy, may then be written as （1）回顾流体力学，可以使用伯努利定理的比能来确定从A 到 B的一定量的稳定水流的能量和功率。根据能量守恒定律，A点的能量eA等于B点的能量eB加上水流从A到B的能量损失eAB。假设水体的质量是1N，那么实际上表述能量守恒的伯努利方程可以写作： （1）Where and are respectively the elevations above a datum plane O-O of the centers of gravity of the stream cross sections at A and B(m), and are respectively the pressures at the centers of gravity of the cross sections at A and B(Pa), is the water density (kgm-3), and are respectively the average velocities of water at A and B(ms-1), g is the free fall accelerations (ms-2), and and are numerical coefficients accounting for a non-uniform velocity distribution over the cross sections (they are always larger than unity and generally range between 1.03 and 1.1).其中和分别表示A和B处水流断面重心在基准面O-O以上的高程（m），和 分别是A和B处水流断面重心的压力（Pa），是水的密度（kgm-3）， 和 分别是A和B处水的平均速度（ms-1），g是自由落体加速度，且和是考虑断面非均匀分布速度的数字系数（它们通常比单位的大，且通常范围为1.03-1.1）。The first terms, z, on either side of Eq.(1), known as the elevation heads or potential heads, define the specific potential energy of water due to the elevation with respect to the selected datum. The second terms, , called the pressure heads, define the specific potential energy of water due to the respective pressure. The total specific potential energy may, therefore, be written as e=z+. It is the same for any point of a cross section, since an increase in z always produces a matching decrease in . Accordingly, the potential energy at a cross section may be evaluated in terms of t