空气循环制冷系统稳态性能的模拟及实验研究

发布时间：2018-05-04 07:50

  本文选题：空气制冷 + 透平膨胀机　； 参考：《天津商业大学》2014年硕士论文

【摘要】：空气循环制冷系统的制冷剂是空气，作为天然制冷剂，对环境无任何污染，是未来可选择的替代制冷剂；但空气循环制冷系统性能系数偏低，因此对于空气制冷系统而言，改善其制冷性能意义重大。更重要的是，由于空气中的水蒸气在涡轮中冷凝成水或结冰，这对系统的运行危害极大。不仅要提高空气制冷系统的效率，同时也要降低系统中空气含湿量，对这两方面进行研究具有重要的理论及实际意义。 为了有效降低涡轮进口压缩空气的含湿量，本文在原有空气循环制冷系统中增加了高效气水分离器，除去涡轮进口湿空气中携带的冷凝游离水，并对低温箱进行改进，以提高系统运行的性能。试验台改进后，在不同的工况条件下，对三种回热循环流程的空气制冷系统的性能进行数值模拟和实验研究，最后分析结果，得出如下结论： (1)模拟和实验结果表明，对系统的制冷效率而言，压气机进口压力的升高，增大了涡轮的膨胀比，降低了涡轮的出口温度，提高了系统COP和制冷量。模拟结果显示，在二级回热流程下，，当压气机进口压力由170kPa升高到200kPa时，系统COP升高了约33%。在相同条件下实验值的增幅稍小，约升高了30%。对系统的除水性能而言，模拟和实验结果表明，压气机进口压力的升高对涡轮进口空气的含湿量几乎没有影响，但涡轮中水蒸气的冷凝量随着压气机进口压力的升高显著增加，实验中无回热方案下增加最明显。 (2)模拟和实验结果表明，在系统中增设回热器及相应的水分离器，可显著提高系统制冷效率和除水性能。模拟结果表明，与无回热相比，二级回热系统中的涡轮进口含湿量最多可下降44%，而相同条件下实验值稍小，约为40%。同时，回热器的增加也提高了系统制冷量，改善了系统COP。实验结果表明，在压气机进口压力为200kPa时，二级回热系统的COP较无回热系统提高了约40%，相同条件下模拟结果COP的增幅约为48%。 (3)模拟和实验结果表明，系统COP和系统制冷量均随制冷温度的升高而增加。实验结果表明，对二级回热流程，当压气机进口压力为200KPa时，制冷温度从-20℃升高到-10℃时，系统的COP从0.23升高到0.38，升高了约65%，而相同条件下的仿真结果系统COP仅升高了36%。对于除水性能而言，模拟结果表明，涡轮进口空气含湿量和涡轮中水蒸气的冷凝量都随制冷温度的升高而增加。在压气机进口压力为200kPa时，当系统制冷温由-25℃升高到-5℃时，涡轮进口空气含湿量由0.927g/kg增至1.24g/kg，增加了约34%。 (4)实验结果表明，随压气机压比的升高，涡轮膨胀比不断增大且增大速率变快。涡轮的折合流量随涡轮膨胀比的增加而增大，且当涡轮膨胀比约为3时，折合流量达到最大值。
[Abstract]:The refrigerant of the air cycle refrigeration system is air. As a natural refrigerant, it is not polluting the environment and is the alternative refrigerant in the future. However, the performance coefficient of the air cycle refrigeration system is low, so for the air refrigeration system, It is of great significance to improve its refrigeration performance. More importantly, because the vapor in the air condenses into water or freezes in the turbine, it does great harm to the operation of the system. Not only to improve the efficiency of air refrigeration system, but also to reduce the moisture content of air in the system, it is of great theoretical and practical significance to study these two aspects. In order to effectively reduce the moisture content of the compressed air at the inlet of the turbine, an efficient air-water separator is added to the original air cycle refrigeration system to remove the condensed free water carried in the wet air at the inlet of the turbine, and the cryogenic box is improved. To improve the performance of the system. After the improvement of the test rig, the performance of the air refrigeration system of three regenerative cycle processes is simulated and experimentally studied under different operating conditions. Finally, the results are analyzed and the following conclusions are obtained: 1) the simulation and experimental results show that the increase of compressor inlet pressure increases the expansion ratio of the turbine, decreases the outlet temperature of the turbine, and increases the system COP and refrigerating capacity for the refrigeration efficiency of the system. The simulation results show that when the inlet pressure of the compressor increases from 170kPa to 200kPa, the COP of the system increases about 33% under the two-stage regenerative process. Under the same conditions, the experimental value increased slightly, about 30%. The simulation and experimental results show that the inlet pressure of the compressor has little effect on the moisture content of the inlet air, but the condensing capacity of the steam in the turbine increases significantly with the increase of the inlet pressure of the compressor. In the experiment, the increase is most obvious under the scheme of no regenerative heat. 2) the simulation and experimental results show that the cooling efficiency and water removal performance of the system can be significantly improved by adding a regenerator and a corresponding water separator in the system. The simulation results show that the inlet moisture content of the turbine in the secondary regenerative system can be decreased by up to 44 and the experimental value under the same conditions is slightly smaller than that of the non-regenerative system, which is about 40 parts. At the same time, the increase of regenerator also increases the cooling capacity of the system and improves the system COP. The experimental results show that when the inlet pressure of the compressor is 200kPa, the COP of the secondary regenerative system is about 40% higher than that of the non-regenerative system, and the increase of COP is about 48% under the same conditions. The simulation and experimental results show that both the system COP and the cooling capacity increase with the increase of the refrigeration temperature. The experimental results show that when the inlet pressure of the compressor is 200KPa, the COP of the system increases from 0.23 to 0.38 when the inlet pressure of the compressor is increased from -20 鈩

本文编号：1842198