The cation–anion substitution results in spectral tuning and thermal stability optimization in Sr2Si1−xAlxO4−2xNx:Eu phosphors.

To efficiently recover the waste heat of mobile engine, two advanced transcritical power cycles, namely split cycle and dual pressure cycle, are employed, based on the recuperative cycle. Performances of the two cycles are analyzed and compared through the development of thermodynamic models. Under given gas conditions, seven high-temperature working fluids, namely propane, butane, isobutane, pentane, isopentane, neopentane, and cyclopentane, are selected for the two cycles. At the design system parameters, the highest work 48.71 kW, is obtained by the split cycle with butane. For most of fluids, the split cycle has a higher work than the dual pressure cycle. Furthermore, with the increase of turbine inlet pressure, net work of the split cycle goes up firstly and then decreases, while the work of dual pressure cycle increases slowly. For the split cycle, there exists a split ratio to get the maximum network. However, for the dual pressure cycle, the larger the evaporation temperature, the higher the net work. On this basis, system parameters are optimized by genetic algorithm to maximize net work. The results indicate that the highest work 49.96 kW of split cycle is obtained by pentane. For the considered fluids, except cyclopentane, split cycle always has a higher work than dual pressure cycle. Due to the higher net work and fewer system components, split cycle is recommended for the engine waste heat recovery.

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As an efficient method for the waste heat recovery of gas turbine, supercritical carbon dioxide (S-CO 2 ) power cycle has gained much attention, due to the high efficiency and compact structure. Thus, in this work, a novel S-CO 2 power cycle is developed for the waste heat recovery via the modification of dual heated cascade cycle with an intercooler (intercooling cycle). Compared with the dual heated cascade cycle (original cycle) and the intercooling cycle, the novel cycle has independent pressures at different heaters and turbines. To analyze the system performance, thermodynamic models are established and a genetic algorithm (GA) is applied to optimize the decision variables with the maximization of net work. These variables include two turbine inlet temperatures, a middle pressure, a low pressure, and a split ratio. Thereafter, thermodynamic parameters of the considered three cycles are obtained under different waste gas temperatures. For the recovery of 600 C waste gas, the novel cycle has the highest net work 3957.87 kW, while the lowest net work 3735.32 kW is obtained by the original cycle. For the effects of decision variables, a higher high-temperature turbine inlet temperature means a lower net work, while the increase of low-temperature turbine inlet temperature results in small increases of cycle performances. On the other hand, under the constraints of the pinch point, with the increase of low and middle pressures, the net work of the novel cycle increases. A higher net work is usually obtained at a lower split ratio. Furthermore, at different waste gas inlet temperatures, the highest cycle efficiency is always derived by the proposed cycle. For the net work, the proposed cycle has the highest value in the temperature range 600 C-750 C.