过热蒸汽比焓和密度的双线性拟合

针对过热蒸汽,将复杂二元函数拟合为双线性结构,利用二次优化原理推算其系统矩阵;改变两个变量的最高阶次可以调整该函数的拟合精度.该算法可看成最小二乘法的一种扩展.在一定范围内,过热蒸汽的比焓和密度被拟合成压力和温度的双线性函数.计算表明:在温度为673.15~833.15 K,压力为10~19.5 MPa时,采用3阶拟合函数,比焓和密度拟合的相对误差分别小于0.11%和0.54%.

Bilinear fit for the enthalpy and density of superheated steam

To the superheated steam,two-variable function was fitted into the bilinear form,and the coefficient matrix of the bilinear function was deduced from the quadratic optimization principle.Through changing the orders of the bilinear function,the fitting accuracy of the function could be adjusted.The method could be regard as an expansion of the Least Square Method.Within a certain range,the enthalpy and density of superheated steam could be fitted into bilinear functions with pressure and temperature as variables.The results of calculation showed that the relative errors of the fitted enthalpy and density were less than 0.11% and 0.54% respectively,when both the orders of the two variables were 3.