上游充通大学 SHANGHAI JIAO TONG UNIVERSITY Engineering Thermodynamics I Lecture 43 Chapter 10 Vapor and Combined Power Systems Spring,2017 强 Prof.,Dr.Yonghua HUANG AMLMAM http://cc.sjtu.edu.cn/G2S/site/thermo.html 1日G
Engineering Thermodynamics I Lecture 43 Spring, 2017 Prof., Dr. Yonghua HUANG Chapter 10 Vapor and Combined Power Systems http://cc.sjtu.edu.cn/G2S/site/thermo.html
Rankine Cycle Improvements Basic Rankine Cycle: IDEAL CYCLE Turbine Irreversibility WWWM 3 in the pump Pressure drop in the boiler 3 Boiler 2 out Irreversibility Cooling water in the turbine Pump Condenser ACTUAL CYCLE 2 >4 Pressure drop/ in the condenser 上游充通大 Wednesday,May 03,2017 2 SHANGHAI JIAO TONG UNIVERSITY
Wednesday, May 03, 2017 2 Rankine Cycle Improvements Basic Rankine Cycle: 1 2 3 4
Rankine Cycle Performance Trends Effect of superheat on performance: Purpose: Increase average temperature for heat addition at a given boiler pressure T increase in performance Increase in Wnet superheat T3 is limited by TH and materials TB Question: Why not increase Te instead? Answer: Need high steam quality at turbine outlet to avoid corrosion (want x4 0.9,better 0.95) -Would require higher boiler pressure materials,safety 上降文通大学 Wednesday,May 03,2017 3 SHANGHAI JIAO TONG UNIVERSITY
Wednesday, May 03, 2017 3 Rankine Cycle Performance Trends Effect of superheat on performance: • Purpose: Increase average temperature for heat addition at a given boiler pressure increase in performance T3 is limited by TH and materials Question: Why not increase TB instead? Answer: - Need high steam quality at turbine outlet to avoid corrosion (want x4 > 0.9, better > 0.95) - Would require higher boiler pressure materials, safety TB superheat
Continue Rankine Cycle Performance Trends Continue effect of superheat on performance: Consequence of superheating: △Tsup〔C) 7 X4 0 0.186 0.858 54 0.190 0.913 278 0.217 -(superheated) Note: Increasing ATsup does not have big effect on thermal efficiency,but is needed to increase x4 toa“practical"value！ 上游充通大学 Wednesday,May 03,2017 4 SHANGHAI JLAO TONG UNIVERSITY
Wednesday, May 03, 2017 4 Continue Rankine Cycle Performance Trends Continue effect of superheat on performance: • Consequence of superheating: DTsup ( oC) h x4 0 0.186 0.858 54 0.190 0.913 278 0.217 - (superheated) Note: • Increasing DTsup does not have big effect on thermal efficiency, but is needed to increase x4 to a “practical” value!
Continue Rankine Cycle Performance Trends Effect of boiler pressure on performance: T Increasing boiler pressure Increase 3 3 decreases heat input at in Wnet max relatively constant work output Decrease >Increase in efficiency in Wnet Upper limit depends on heat supply temperature and materials \Possible? Also decreases quality S 上游充通大 Wednesday,May 03,2017 5 SHANGHAI JIAO TONG UNIVERSITY
Wednesday, May 03, 2017 5 Continue Rankine Cycle Performance Trends Effect of boiler pressure on performance: - Increasing boiler pressure decreases heat input at relatively constant work output Increase in efficiency -Upper limit depends on heat supply temperature and materials - Also decreases quality TB Possible?