The Effects of Groundwater Depth on the Soil Evaporation in Horqin Sandy Land, China

The interactions between groundwater depth and soil hydrological processes, play an important role in both arid and semi-arid ecosystems. The effect of groundwater depth on soil water variations were neglected or not explicitly treated. In this paper, we combine a simulation experiment and a water flow module of HYDRUS-1D model to study the variation in soil evaporation under different groundwater depth conditions and the relationship between groundwater depth and evaporation efficiency in Horqin Sandy Land, China.The results showed that with an increase in groundwater depth, the evaporation of soil and the recharge of groundwater decrease. In this study, the groundwater recharge did not account for more than 21% of the soil evaporation for the depths of groundwater examined. The soil water content at 60 cm was less affected by the evaporation efficiency when the mean groundwater depth was 61 cm during the experimental period. In addition, the evaporation efficiency(the ratio of actual evaporation to potential evaporation) decreases with the increase in groundwater depth during the experiment. Furthermore, the soil evaporation was not affected by groundwater when the groundwater depth was deeper than 239 cm.

An FV-EE model to predict lean blowout limits for gas turbine combustors with different structures and sprays

The occurrence of Lean Blowout(LBO)is a disadvantage that endangers a stable operation of gas turbines.A determination of LBO limits is essential in the design of gas turbine combustors.A semiempirical model is one of the most widely used methods to predict LBO limits.Among the existing semiempirical models for predicting LBO limits,Lefebvre’s LBO model and the Flame Volume(FV)model are particularly suitable for gas turbine combustors.On the basis of Lefebvre’s and FV models,the concept of effective evaporation efficiency is introduced in this paper,and a Flame Volume-Evaporation Efficiency(FV-EE)model is derived and validated.LBO experiments are carried out in a model combustor with 23 different structures and 10 different sprays.The prediction uncertainty of the FV-EE model is less than±13%for all of these 33 structures and sprays,compared with±50%for the FV model and±60%for Lefebvre’s model.Furthermore,the prediction uncertainty of the FV-EE model is also less than±13%for other combustors from available literature.