Improvement of bottoming cycle efficiency and heat rejection for HD truck applications by utilization of EGR and CAC heat
Improvement of bottoming cycle efficiency and heat rejection for HD truck applications by utilization of EGR and CAC heat
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DOI：
10.1016/j.enconman.2011.08.002
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发表时间：
2012
影响因子：
10.4
通讯作者：
D. Hountalas;Georgios C. Mavropoulos;C. Katsanos;W. Knecht
中科院分区：
文献类型：
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作者：
D. Hountalas;Georgios C. Mavropoulos;C. Katsanos;W. Knecht
考虑到持续上涨的燃料价格和全球变暖问题，降低用于各种应用的发动机的燃料消耗是非常重要的。特别重要的是在大型运输卡车中使用的HD柴油发动机，因为这些车辆具有广泛的操作时间表，它们的发动机具有在200- 400 kW范围内的高功率输出，并且它们的数量非常多。从目前的研究成果来看，除非采用新的思路或技术，否则HDDI柴油机的燃油消耗率在未来很难得到大幅度的降低。在此框架下，废热的利用变得不可避免，因为大约30-40%的燃料能量被排放到环境中。从废气中回收能量的一种有前途的技术是使用朗肯底循环。这种技术解决方案在过去已经过审查，具有非常积极的迹象和重大改进的巨大潜力。然而，必须解决各种技术挑战，其中最重要的是封装和从发动机冷却系统排出多余的热量。出于这个原因，在本工作中的仿真模型，它已经被开发来描述的朗肯底循环的操作被用来估计潜在的效率增益从其应用于重型卡车由柴油发动机提供动力。使用模拟特别注意EGR冷却器和CA冷却器（增压空气）热量的利用，以增加朗肯膨胀机的功率输出，从而提高bsfc降低潜力。此外，EGR和CAC热量的利用用于最小化朗肯循环对发动机冷却系统的负面影响，发动机冷却系统的能力在高负载下被超过。最后导致安装困难（较大的发动机散热器等）并且在某些情况下，消耗大量的产生的功率来驱动冷却风扇，这显然对BSFC降低潜力具有强烈的负面影响。出于这个原因，几种方案提出并在本工作中进行检查，以避免或尽量减少这个问题。结果产生的有机和蒸汽工作介质，揭示了一个很好的潜力，应用朗肯底循环在HD发动机的应用。此外，它揭示了EGR冷却器和CA冷却器的热量的利用超出其对bsfc减少潜力的积极影响，也有利于整个系统的封装，允许主热交换器尺寸的严重减少。
Considering continuously rising fuel prices and the global warming problem it is significantly important to reduce fuel consumption of engines used in various applications. Of specific importance is the HD diesel engine used in large haul trucks because these vehicles have an extensive operating schedule, their engines have a high power output in the range of 200–400kW and their number is significantly high. Considering current achievements, it appears that HDDI diesel engine bsfc cannot be significantly reduced in the future unless new ideas or techniques are employed. Under this framework the utilization of exhaust heat becomes inevitable because approximately 30–40% of fuel energy is rejected to the environment. A promising technique for the recovery of energy from the exhaust gas is the use of a Rankine bottoming cycle. This technical solution has been examined in the past with very positive indications and a strong potential for significant improvement. However various technical challenges have to be solved among which most important are packaging and rejection of excess heat from the engine cooling system. For this reason in the present work a simulation model which has been developed to describe the operation of a Rankine bottoming cycle is utilized to estimate the potential efficiency gain from its application on a heavy duty truck powered by a diesel engine. Using the simulation special attention is given to the utilization of EGR cooler and CA cooler (Charge Air) heat to increase the Rankine expander power output and thus improve bsfc reduction potential. Furthermore the utilization of both EGR and CAC heat amounts is used to minimize the negative impact of the Rankine cycle on the engine cooling system, the capacity of which is exceeded at high load. The last results to installation difficulties (larger engine radiator, etc.) and in some cases a significant amount of generated power is consumed to drive the cooling fan which obviously has a strong negative impact on the bsfc reduction potential. For this reason several scenarios are proposed and examined in the present work to avoid or minimize this problem. Results are produced for both organic and steam working media that reveal a very good potential for the application of Rankine bottoming cycles in HD engine applications. Furthermore it is revealed that the utilization of both EGR cooler and CA cooler heat beyond its positive effect on bsfc reduction potential is also beneficial for overall system packaging allowing the serious reduction of primary heat exchanger dimensions.