小型农用柴油机高原增压匹配与适应性研究

中国高原地区运行的农业机械数量众多,为保证在这些地区使用的农业机械具有良好的高原适应性,以一款小型农用柴油机为研究对象,在海拔2000m的地区,根据设计开发目标,通过理论计算选取了合适的压气机和涡轮,并进行了配机试验。基于试验数据,采用GT-Power软件建立了该小型农用增压柴油机的仿真模型,模拟研究了该柴油机关键性能参数随海拔(0、2 000、4 000 m)变化的规律。研究结果表明:选配的涡轮增压器使得该小型农用柴油机达到了高原地区2000m的性能开发目标;在3个海拔下,柴油机与压气机的联合运行线均运行在效率相对较高的区域,并且低速时具有较大的喘振裕度,在高速时离阻塞线也有一定的距离;与平原地区相比,在海拔2 000和4 000 m时,小型农用柴油机的最大转矩分别降低了2.59%和7.19%,与已有的文献结论相比,最大转矩的降幅减小;在高原地区有针对性地进行增压匹配,能够保证柴油机良好的高原运行性能,并有利于提高柴油机的高原适应性。

Turbocharger matching in plateau area and adaptability of small agricultural diesel engine

The environment pressure and air density experience sharp declines at high altitude, which cause a large drop in the intake air mass flow rate of diesel engines. As a result, many aspects of engine performance are deteriorated, such as power, fuel consumption and emissions. Turbocharging matching provides a good technical solution for recovery diesel engine performance at high altitude. There is a large number of agricultural machinery operating in plateau area of China. In order to ensure that the agricultural machinery used in these areas had a good plateau adaptability, taking a small agricultural diesel engine as the research object, an appropriate compressor and turbine were selected respectively through theoretical calculation according to the design and development goals at altitude of 2 000 m. After that, the matching test of the small agricultural diesel engine and selected turbocharger was conducted at this altitude. Finally, the simulation model of the small agricultural turbocharged diesel engine was built by using GT-Power code based on test data. The change rule of diesel engine key performance parameters were simulated and investigated at altitudes of 0, 2 000 and 4 000 m. The results showed that the selected turbocharger made the small agricultural diesel engine achieve the development requirements at the altitude of 2 000 m. Low-end torque reached 120.1 N·m at 1 000 r/min, the peak torque was 180.2 N·m at 1 600 r/min, the rated power was 37.4 kW at 2 600 r/min, and the torque backup coefficient was 131% at this altitude. At 3 altitudes of 0, 2 000 and 4 000 m, the joint operation lines of the small agricultural diesel engine and the selected compressor were all operating in the relatively high efficiency area, and there were a large surge margin at low engine speeds, and also a certain distance from the choke line at high engine speeds. As the altitude went up, the engine torque and boost pressure decreased, while brake specific fuel consumption and turbine inlet gas temperature increased. What''s more, with respect to high engine speed, the change of altitude had a greater impact on engine power and economy performance at low engine speed. With the increase of altitude, decreasing amplitude of torque and percentage gain of fuel consumption was both rose at low engine speed, and these tendency were decline gradually with the increase of engine speed. In addition, the engine speed corresponding to the peak torque showed a tendency of gradually moving towards higher engine speed at high altitude. Compared with plain area, the maximum engine torque decreased by 2.59% and 7.19% respectively when it ran at altitudes of 2 000 and 4 000 m. Meanwhile, compared with the previous literatures conclusion, the decreasing amplitude of peak engine torque was smaller when the small agricultural diesel engine operating at altitudes of 2 000 and 4 000 m, respectively. It can ensure the good operation performance of diesel engine in plateau area, and also is beneficial to improve the plateau adaptability when diesel engine and turbocharger are matched at high altitude.