Trajectory-based combustion control for renewable fuels in free piston engines
Trajectory-based combustion control for renewable fuels in free piston engines
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DOI：
10.1016/j.apenergy.2016.11.045
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发表时间：
2017-02
期刊：
影响因子：
11.2
通讯作者：
Chen Zhang;Zongxuan Sun
中科院分区：
文献类型：
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作者：
Chen Zhang;Zongxuan Sun
为了进一步发挥自由活塞发动机（FPE）的灵活性，作者开发了一种先进的燃烧控制方法，即基于熵的燃烧控制。在这种控制方法的帮助下，FPE能够通过实现最佳活塞轨迹来优化发动机效率和排放。已经进行了大量的模拟，以证明这种燃烧控制对化石燃料的有效性。在本文中，调查扩展到可再生燃料。本文考虑七种可再生燃料，包括氢气、生物气、合成气、乙醇、二甲醚（DME）、生物柴油和费托燃料。研究中考虑了压缩比和活塞在两止点之间的运动规律对燃烧过程的影响，充分体现了FPE对燃料的适应性和对燃料杂质的容忍度。此外，模拟结果表明，在一个固定的CR，FPE的热效率仍然可以提高（5%的DME的情况下），通过改变活塞运动模式单独。此外，特定的非对称活塞轨迹被合成，以进一步提高发动机的热效率（氢的情况下为8%），同时减少NOx排放（氢的情况下减少约70%）。换句话说，由于其最终的燃料灵活性，燃料杂质的大容忍度和可控的活塞轨迹，FPE与基于熵的燃烧控制，使得可再生燃料和发动机操作的共同优化成为可能。
Previously, the authors have developed an advanced combustion control, namely the trajectory-based combustion control, to further leverage the flexibility of free piston engine (FPE). With the assistance of this control method, the FPE enables optimization of both engine efficiency and emissions by implementing optimal piston trajectories. Extensive simulations have been conducted to prove the effectiveness of this combustion control on fossil fuels. In this paper, the investigation is extended to renewable fuels. Seven renewable fuels are considered herein including hydrogen, biogas, syngas, ethanol, dimethyl ether (DME), biodiesel, and Fischer-Tropsch fuel. The influences of both compression ratio (CR) and piston motion pattern between the two dead centers on the combustion process are considered in the study, which demonstrates the ultimate fuel flexibility and large tolerance of fuel impurity possessed by the FPE. In addition, the simulation results show that at a fixed CR, the thermal efficiency of the FPE can still be enhanced (5% in DME case) by varying the piston motion patterns alone. Furthermore, specific asymmetric piston trajectories are synthesized to further improve the engine thermal efficiency (8% in hydrogen case) and reduce the NOx emission simultaneously (around 70% reduction in hydrogen case). In other words, due to its ultimate fuel flexibility, large tolerance of fuel impurity, and controllable piston trajectory, the FPE, with the trajectory-based combustion control, enables a co-optimization of renewable fuels and engine operation.