多元混合物相包线的Newton-Raphson算法

NEWTON-RAPHSON METHOD FOR CONSTRUCTING THE PHASE ENVELOPES OF MULTICOMPONENT MIXTURES

详细介绍了一种计算多元混合物相包线的Newton Raphson多变量迭代算法。以Newton Raphson方法为代表的多变量迭代算法 ,其关键在于选择迭代变量和计算初值。在每一计算点分析各变量变化的敏感性 ,选择出适当的指定变量和迭代变量 ,并利用已求点的性质 ,通过两点三次样条插值为新计算点提供初值。对 4种典型的油气藏混合流体的相包线进行了计算 ,结果表明 ,该算法对于不同组成特点的多组分流体混合物均可以稳定、快速地收敛。相包线上临界点、温度和压力极值点的计算结果与丹麦相态计算软件包的计算结果相符。

A Newton Raphson algorithm for constructing the phase envelopes of multicomponent mixtures is introduced. In this method a sensitivity analysis is used to select iteration variable and spline extrapolation for determination of the initial value.Calculation example proves that the algorithm is efficient and stable for multicomponent mixtures with different composition charactersitics. The critical points determined by spline interpolation during phase envelope construction are close to those calculated by rigorous critical criteria.