燃料提纯对提升天然气发动机性能影响的研究

发布时间：2018-08-28 19:36

【摘要】：内燃机的缸内热-功转换效率在一定范围内随压缩比的增加而增加,例如压缩比在11:1左右,每提高一个单位,热效率可提高2至3个百分点。对于采用火花点火、预混燃烧方式的发动机,例如汽油机与绝大部分气体机,低速、大负荷条件下由于受爆震限制,其设计的压缩比通常都较低,如果燃料的辛烷值能得以提高,就可相应地提升发动机的压缩比从而改善其燃油经济性。本文利用发动机性能试验台架以及燃烧分析仪等相关试验设备,对一台增压中冷、火花塞点火、进气总管单点喷射、预混燃烧的天然气发动机进行性能优化研究。本研究首先对天然气进行提纯,使燃料的辛烷值比市场上的液化天然气有很大提高。进而提高天然气发动机的压缩比,提高发动机的热效率,达到改善动力性、提高经济性的目的。台架试验得出压缩比的最佳结果后,对发动机进行整车实际工况的验证试验。在一台搭载相同发动机的整车上,改装最佳压缩比CR13.6(Compression Ratio)活塞,使用液态甲烷作为燃料,对发动机在台架稳态试验的结果进行验证。此次研究将发动机的压缩比从原机的11.6逐步提高至12.6、13.6、14.6、15.6,然后分别测试发动机的各项性能,包括发动机整个工作循环的缸内燃烧过程、各项状态参数(如进排气压力等)和性能参数(功率、转矩、比气耗等)。分析压缩比、点火提前角、过量空气系数等对发动机的动力性、经济性、排放性能的影响。通过分析台架以及整车试验研究结果可知,在不改变其他机械结构及相关控制参数的前提下,提高压缩比对发动机的动力性几乎没有影响。提高压缩比后,发动机的NOx排放有所恶化。发动机经济性随着压缩比的提高有较大的优化,压在缩比13.6时达到最佳效果。同压缩比为11.6相比,比气耗在不同转速工况下,有4%~6%的下降。当压缩比进一步提高时,由于缸内燃烧情况恶化,特别是使用非液态甲烷时,爆震趋势愈发明显,导致经济性下降。
[Abstract]:The in-cylinder heat to power conversion efficiency of the internal combustion engine increases with the increase of compression ratio in a certain range. For example, the compression ratio is about 11:1, for each unit of increase, the thermal efficiency can be increased by 2 to 3 percentage points. For engines with spark ignition and premixed combustion, such as gasoline engines and most gas engines, the compression ratio is usually lower at low speed and under high load due to detonation restrictions. If the octane number of the fuel can be increased, the compression ratio of the engine can be raised accordingly and the fuel economy can be improved. In this paper, the performance optimization of a turbocharged intercooled, spark plug ignition, inlet manifold single point injection, premixed combustion natural gas engine is studied by using engine performance test bench and combustion analyzer. In this study, the octane number of the fuel is greatly improved than that of the liquefied natural gas in the market. Furthermore, the compression ratio of natural gas engine is improved, the thermal efficiency of engine is improved, the power performance is improved and the economy is improved. After the best result of compression ratio is obtained by bench test, the actual working condition of the engine is verified. In a whole vehicle with the same engine, the optimum compression ratio CR13.6 (Compression Ratio) piston is modified, and liquid methane is used as fuel to verify the results of engine steady state test. In this study, the compression ratio of the engine was gradually increased from 11.6 in the original engine to 12.6C13. 6 / 14.6 / 15.6. then the performance of the engine was tested separately, including the combustion process in the cylinder of the whole working cycle of the engine. State parameters (such as inlet and exhaust pressure) and performance parameters (power, torque, specific gas consumption, etc.). The effects of compression ratio, ignition advance angle and excess air coefficient on engine power, economy and emission performance are analyzed. Through the analysis of the test results of the bench and the whole vehicle, it can be seen that without changing other mechanical structures and related control parameters, the increase of compression ratio has little effect on the engine's dynamic performance. When the compression ratio is increased, the NOx emission of the engine becomes worse. The engine economy is optimized with the increase of compression ratio, and the best effect is achieved when the compression ratio is 13.6. Compared with the compression ratio of 11.6, the specific gas consumption decreased by 4% or 6% under different rotational speed conditions. When the compression ratio is further increased, the combustion situation in the cylinder deteriorates, especially when the non-liquid methane is used, the knock trend becomes more obvious, which leads to the decrease of the economy.
【学位授予单位】：湖南大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TK431

【相似文献】