Discusses the relationship between pumping speed and inlet pressure of an oil-sealed mechanical pump and the reason why its pumping efficiency drops down.

Connected with an extensive analysis,it can be concluded that when the regression line gets across the origin,the rate estimator of two sampling methods is equal to the sampling efficiency of regression estimator,when,the sampling efficiency ofis more efficient than the equiprobability sampling,and when and meanwhile,the rate estimator of equiprobability sampling is m.

l{ate I ranstormation Coefficient Method and Steam Extraction Coefficient as its theoretical principle to build up a evaluation system and mathematical model for analyzing operation thermal economy and system economy, and provide a powerful tool for power plant economic operation and scientific management.