A novel powder metallurgy （P/M） material with high wear resistance is developed in order to decrease the wear and lubricant-leakage of a diesel engine valve guide. The friction and wear tests of this material are co...A novel powder metallurgy （P/M） material with high wear resistance is developed in order to decrease the wear and lubricant-leakage of a diesel engine valve guide. The friction and wear tests of this material are conducted. It indicates that the wear resistance of the newly developed P/M material has been improved and much better than that of the formerly used alloy steel. Moreover, three different sealing structures are designed and theoretically analyzed with respect to the characteristic of hydrodynamic sealing. Through comparative experiments of component leakage and engine run-in for different valve guide structures, it proves that the structure with a machined sealing groove but not installed with a seal-ring cannot only reduce the specific lubricant consumption （SLC） of cylinder head, but also decrease the wear of valve stern and valve guide.展开更多
Multibarrier systems are commonly proposed for effective isolation of highly radioactive waste (HLW). Presently considered concepts take the host rock as a barrier claiming it to retard migration of possibly released ...Multibarrier systems are commonly proposed for effective isolation of highly radioactive waste (HLW). Presently considered concepts take the host rock as a barrier claiming it to retard migration of possibly released radionuclides from HLW containers to the biosphere. This capacity is small unless water-bearing fracture zones intersecting the blasted waste-containing tunnels and excavation-disturbance zones around them can be sealed by grouting and construction of bulkheads, but this is effective only for a very limited period of time as explained in the paper. The disturbed zones thence make the entire repository serve as a continuous hydraulic conductor causing quick transport of released radionuclides up to the biosphere. The dilemma can be solved by accepting the shortcircuiting function of the disturbed zones along the tunnels on the condition that totally tight waste containers be used. Deep holes bored in the site selection phase through the forthcoming repository can be effective pathways for radionuclides unless they are properly sealed. They are small-scale equivalents of tunnels but do not have any excavation damage and can be effectively sealed by using clay and concrete of new types. Applying this principle to very deep boreholes with a diameter of a few decimeters would make it possible to safely store slim, tight HLW canisters for any period of time.展开更多
基金This project is supported by National Natural Science Foundation ofChina(No.50135020), Key Science and Technology Research Project ofMinistry of Education, China (No.0203) and Provincial Science and Tech-nology Plan of Guangdong, China (No.2004B10301018).
文摘A novel powder metallurgy （P/M） material with high wear resistance is developed in order to decrease the wear and lubricant-leakage of a diesel engine valve guide. The friction and wear tests of this material are conducted. It indicates that the wear resistance of the newly developed P/M material has been improved and much better than that of the formerly used alloy steel. Moreover, three different sealing structures are designed and theoretically analyzed with respect to the characteristic of hydrodynamic sealing. Through comparative experiments of component leakage and engine run-in for different valve guide structures, it proves that the structure with a machined sealing groove but not installed with a seal-ring cannot only reduce the specific lubricant consumption （SLC） of cylinder head, but also decrease the wear of valve stern and valve guide.
文摘Multibarrier systems are commonly proposed for effective isolation of highly radioactive waste (HLW). Presently considered concepts take the host rock as a barrier claiming it to retard migration of possibly released radionuclides from HLW containers to the biosphere. This capacity is small unless water-bearing fracture zones intersecting the blasted waste-containing tunnels and excavation-disturbance zones around them can be sealed by grouting and construction of bulkheads, but this is effective only for a very limited period of time as explained in the paper. The disturbed zones thence make the entire repository serve as a continuous hydraulic conductor causing quick transport of released radionuclides up to the biosphere. The dilemma can be solved by accepting the shortcircuiting function of the disturbed zones along the tunnels on the condition that totally tight waste containers be used. Deep holes bored in the site selection phase through the forthcoming repository can be effective pathways for radionuclides unless they are properly sealed. They are small-scale equivalents of tunnels but do not have any excavation damage and can be effectively sealed by using clay and concrete of new types. Applying this principle to very deep boreholes with a diameter of a few decimeters would make it possible to safely store slim, tight HLW canisters for any period of time.
