Diesel particulate matter （DPM） is considered to be carcinogenic after prolonged exposure. With more diesel- powered equipment used in underground mines, miners＇ exposure to DPM has become an increasing concern. Th...Diesel particulate matter （DPM） is considered to be carcinogenic after prolonged exposure. With more diesel- powered equipment used in underground mines, miners＇ exposure to DPM has become an increasing concern. This paper used computational fluid dynamics method to study the DPM dispersion in a dead-end entry with loading operation. The effects of different push-pull ventilation systems on DPM distribution were evaluated to improve the working conditions for underground miners. The four push-pull systems considered include： long push and short pull tubing; short push and long pull tubing, long push and curved pull tubing, and short push and curved pull tubing. A species transport model with buoyancy effect was used to examine the DPM dispersion pattern with unsteady state analysis. During the 200 s of loading operation, high DPM levels were identified in the face and dead-end entry regions. This study can be used for mining engineer as guidance to design and setup local ventilation, select DPM control strategies and for DPM annual training for underground miners.展开更多
The Rankine cycle system for waste heat recovery of heavy-duty vehicle diesel engines has been regarded as a promising tech- nique to reduce fuel consumption. Its heat dissipation in the condensation process, however,...The Rankine cycle system for waste heat recovery of heavy-duty vehicle diesel engines has been regarded as a promising tech- nique to reduce fuel consumption. Its heat dissipation in the condensation process, however, should be take：l away in time, which is an energy-consuming process. A fan-assisted auxiliary water-cooling system is employed in this paper. Results at 1300 r/min and 50% load indicate that the cooling pump and cooling fan together consume 7.66% of the recovered power. What＇s worse for the heavy load, cooling accessories may deplete of all the recovered power of the Rankine cycle system. Af- terwards, effects of the condensing pressure and water feeding temperature are investigated, based on which a cooling power consumption model is established. Finally, an overall efficiency optimization is conducted to balance the electric power gener- ation and cooling power consumption, taking condensing pressure, pressure ratio and exhaust bypass valve as major variables. The research suggests that the priority is to increase condensing pressure and open exhaust bypass valve appropriately at high speed and heavy load to reduce the cooling power consumption, while at low speed and light load, a lower condensing pressure is favored and the exhaust bypass valve should be closed making the waste heat recovered as much as possible. Within the sub-critical region, a larger pressure ratio yields higher overall efficiency improvement at medium-low speed and load. But the effects taper off at high speed and heavy load. For a given vehicular heavy-duty diesel engine, the overall e：＇ficiency can be improved by 3.37% at 1300 r/min and 25% load using a Rankine cycle system to recover exhaust energy. The improvement becomes smaller as engine speed and load become higher.展开更多
文摘Diesel particulate matter （DPM） is considered to be carcinogenic after prolonged exposure. With more diesel- powered equipment used in underground mines, miners＇ exposure to DPM has become an increasing concern. This paper used computational fluid dynamics method to study the DPM dispersion in a dead-end entry with loading operation. The effects of different push-pull ventilation systems on DPM distribution were evaluated to improve the working conditions for underground miners. The four push-pull systems considered include： long push and short pull tubing; short push and long pull tubing, long push and curved pull tubing, and short push and curved pull tubing. A species transport model with buoyancy effect was used to examine the DPM dispersion pattern with unsteady state analysis. During the 200 s of loading operation, high DPM levels were identified in the face and dead-end entry regions. This study can be used for mining engineer as guidance to design and setup local ventilation, select DPM control strategies and for DPM annual training for underground miners.
基金supported by the National Basic Research Program of China("973"Project)(Grant No.2011CB707206)
文摘The Rankine cycle system for waste heat recovery of heavy-duty vehicle diesel engines has been regarded as a promising tech- nique to reduce fuel consumption. Its heat dissipation in the condensation process, however, should be take：l away in time, which is an energy-consuming process. A fan-assisted auxiliary water-cooling system is employed in this paper. Results at 1300 r/min and 50% load indicate that the cooling pump and cooling fan together consume 7.66% of the recovered power. What＇s worse for the heavy load, cooling accessories may deplete of all the recovered power of the Rankine cycle system. Af- terwards, effects of the condensing pressure and water feeding temperature are investigated, based on which a cooling power consumption model is established. Finally, an overall efficiency optimization is conducted to balance the electric power gener- ation and cooling power consumption, taking condensing pressure, pressure ratio and exhaust bypass valve as major variables. The research suggests that the priority is to increase condensing pressure and open exhaust bypass valve appropriately at high speed and heavy load to reduce the cooling power consumption, while at low speed and light load, a lower condensing pressure is favored and the exhaust bypass valve should be closed making the waste heat recovered as much as possible. Within the sub-critical region, a larger pressure ratio yields higher overall efficiency improvement at medium-low speed and load. But the effects taper off at high speed and heavy load. For a given vehicular heavy-duty diesel engine, the overall e：＇ficiency can be improved by 3.37% at 1300 r/min and 25% load using a Rankine cycle system to recover exhaust energy. The improvement becomes smaller as engine speed and load become higher.
