Performance Comparison of Advanced Transcritical Power Cycles with High-Temperature Working Fluids for the Engine Waste Heat Recovery
Сравнение характеристик усовершенствованных транс критических энергетических циклов с высокотемпературными рабочими телами для утилизации теплоты выхлопных газов двигателя
2021-09-17
SCID: 54.1/7yqyq9vn
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dual pressure cycleengine waste heat recoveryhigh-temperature working fluidssplit cycletranscritical power cycles
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Abstract (AI)
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.
Key Findings
1
After genetic-algorithm optimization, the split cycle with pentane achieved the highest work output of 49.96 kW and outperformed the dual-pressure cycle for all fluids except cyclopentane.
2
Among seven high-temperature working fluids at design conditions, the split cycle with butane achieved the highest work output of 48.71 kW.
3
For most working fluids, the split cycle produced more work than the dual-pressure cycle; its net work first increased and then decreased with turbine inlet pressure.
4
The split cycle has an optimal working-fluid split ratio, whereas dual-pressure-cycle net work increased with evaporation temperature.
5
The split cycle was recommended for engine waste-heat recovery because it generally delivered higher net work with fewer system components.
6
Two advanced transcritical cycles—a split cycle and a dual-pressure cycle—were thermodynamically modeled and compared for mobile-engine waste-heat recovery.
Research Object
Advanced transcritical power cycles (split and dual pressure) using high-temperature working fluids for mobile engine waste heat recovery
Research Subject
Comparative net-work performance, parameter effects, and optimization of split and dual pressure cycles with different high-temperature working fluids
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2021-09-17
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