斯特林机加热管积碳对其换热与循环特性的影响

Effect of Heat Transfer and Cycle Characteristics on Carbon Deposition in Stirling Engine Heating Pipes

以柴油机尾气为碳源,考察发动机加热管内流体雷诺数、流体温度和积碳时间对积碳量的影响规律,分析积碳量对加热管换热特性以及对发动机运行性能的影响。研究表明:同一工况下,管内积碳量随积碳时间近似线性增加(180 h);积碳量受雷诺数和流体温度影响较大,雷诺数为10 434时,积碳量最大,管内流体温度为110℃时,积碳量为1.645 6 g,约为190℃时积碳量(0.165 1 g)的10倍;积碳量较少时,可以强化加热管的换热性能,但随着积碳量的增加,换热性能逐渐降低;利用SIMPLE模型考察了管内积碳对斯特林循环的影响,随着积碳量的增加,斯特林发动机的循环效率和循环功率都先增加后减少。结合效能分析,提出在循环功率降低到初始状态功率以下时,此时单位面积积碳量约为5.11~6.88 mg/cm^2,雷诺数在3 688~33 523范围内,建议对斯特林发动机进行积碳检测和清洗。

The diesel gas is as the carbon source,the effects of Reynolds number,temperature,time on carbon deposition,its effect on heat transfer characteristics of heating pipes and overall performance of the Stirling engine are thoroughly investigated. The result shows that the amount of carbon deposition increases linearly with time(180 h) under the same working conditions. The total amount of carbon deposition is affected by the Reynolds number and temperature significantly. The amount of carbon deposition is the largest when Reynolds number is 10 434 among all experiment cases. The amount of carbon deposition is 1. 645 6 g at 110 ℃,which is about 10 times higher than that of 0. 165 1 g at 190 ℃. A little carbon deposition can enhance heat transfer of the heating pipes. However,the heat transfer performance deteriorates gradually with increase of carbon deposition. At the end,the effects of carbon deposition on overall performance of Stirling engine are investigated with Improved SIMPLE Analytical model. The effects of carbon deposition on cycle output power and cycle efficiency of Stirling engine also shows similar variation trend as in experiments. The performance of Stirling engine improves with the increasing amount of carbon deposition within certain amount of carbon deposition,and then worsens with the increasing amount of carbon deposition.A suggestion can be proposed,that the carbon deposition in the Stirling engine should be cleaned when the cycle power is less than the initial state power( without carbon deposition),and the carbon deposition per unit area is about 5. 11 mg/cm^2~ 6. 88 mg/cm^2 with the Reynolds number 3 688 ~ 33 523.