The EGR (exhaust gas recirculation) technique can greatly reduce the NOx emission of diesel engines, especially when an EGR cooler is employed. Numerical simulations are applied to study the flow field and temperature...The EGR (exhaust gas recirculation) technique can greatly reduce the NOx emission of diesel engines, especially when an EGR cooler is employed. Numerical simulations are applied to study the flow field and temperature distributions inside the EGR cooler. Three different models of EGR cooler are investigated, among which model A is a traditional one, and models B and C are improved by adding a helical baffle in the cooling area. In models B and C the entry directions of cooling water are different, which mostly influences the flow resistance. The results show that the improved structures not only lengthen the flow path of the cooling water, but also enhance the heat exchange rate between the cool and hot media. In conclusion we suggest that the improved structures are more powerful than the traditional one.展开更多
For the improvement of reheat steam quality and performance of double reheat coal-fired utility boiler under wide load operation, a variety of temperature regulation ways were utilized to adjust the energy distributio...For the improvement of reheat steam quality and performance of double reheat coal-fired utility boiler under wide load operation, a variety of temperature regulation ways were utilized to adjust the energy distribution between different heating surfaces. In this paper, thermodynamic calculation based on the fundamental heat transfer theory was conducted for the analysis of temperature regulation strategy effects to steam temperature. In consideration of the specific overlapping heating surface arrangement, the compartment model was adopted to solve this problem. Response surface methodology(RSM) was used to analysis the effect of each temperature regulating variables on the steam temperature and boiler efficiency;then the polynomial model was fitted to predict the primary and secondary steam temperature simultaneously. Results showed that the flue gas recirculation rate has a relatively significant influence on the steam temperature, the maximum temperature deviation between fitting value and calculation value is 3.85℃ in 75% THA;the quadratic model can well predict the steam temperature under different operation conditions in wide load change. The variation of flue gas baffle has a significant influence on the boiler efficiency, compared to the flue gas recirculation and angle of burner oscillation. The influence of various factors on the reheat steam temperature is flue gas baffle > flue gas recirculation > angle of burner oscillation.展开更多
文摘The EGR (exhaust gas recirculation) technique can greatly reduce the NOx emission of diesel engines, especially when an EGR cooler is employed. Numerical simulations are applied to study the flow field and temperature distributions inside the EGR cooler. Three different models of EGR cooler are investigated, among which model A is a traditional one, and models B and C are improved by adding a helical baffle in the cooling area. In models B and C the entry directions of cooling water are different, which mostly influences the flow resistance. The results show that the improved structures not only lengthen the flow path of the cooling water, but also enhance the heat exchange rate between the cool and hot media. In conclusion we suggest that the improved structures are more powerful than the traditional one.
基金Financial support for this work by the National Key Research and Development Program of China(Grant No.2017YFB0602102)。
文摘For the improvement of reheat steam quality and performance of double reheat coal-fired utility boiler under wide load operation, a variety of temperature regulation ways were utilized to adjust the energy distribution between different heating surfaces. In this paper, thermodynamic calculation based on the fundamental heat transfer theory was conducted for the analysis of temperature regulation strategy effects to steam temperature. In consideration of the specific overlapping heating surface arrangement, the compartment model was adopted to solve this problem. Response surface methodology(RSM) was used to analysis the effect of each temperature regulating variables on the steam temperature and boiler efficiency;then the polynomial model was fitted to predict the primary and secondary steam temperature simultaneously. Results showed that the flue gas recirculation rate has a relatively significant influence on the steam temperature, the maximum temperature deviation between fitting value and calculation value is 3.85℃ in 75% THA;the quadratic model can well predict the steam temperature under different operation conditions in wide load change. The variation of flue gas baffle has a significant influence on the boiler efficiency, compared to the flue gas recirculation and angle of burner oscillation. The influence of various factors on the reheat steam temperature is flue gas baffle > flue gas recirculation > angle of burner oscillation.
