变海拔柴油机可变喷嘴增压系统控制策略研究

Control Strategy of Variable Nozzle Turbocharging System for Diesel Engine at Different Altitudes

根据柴油机的变海拔性能恢复目标,通过热力学分析,对某V型6缸柴油机增压系统运行参数进行估算,确定了可变喷嘴式的增压系统方案,并选择了合适的匹配点,完成了涡轮增压器的选配。基于原机结构参数,采用GT-Power软件建立了性能仿真模型并完成了校核,分别计算了匹配可变喷嘴增压系统的柴油机外特性和部分负荷的变海拔性能,最终确定了增压系统的全工况控制策略。研究结果表明:在外特性工况下,基于高海拔匹配的增压系统通过采用较小的喷嘴环开度可以满足增压系统的功耗需求,实现柴油机的变海拔功率恢复目标;随着海拔的降低,增压系统可以根据进气功耗的变化适当增大喷嘴环开度来实现增压系统变海拔控制目标,同时,保证柴油机的正常运行;在全工况范围内,随着海拔的上升,柴油机对应工况点的喷嘴环开度逐渐减小,在3 000 m以上海拔的高负荷工况采用最小喷嘴环开度。随着负荷的降低,最低燃油消耗运行点从低海拔低转速区偏移至高海拔低转速区。

Aiming to achieve the goal of performance recovery of diesel engine at high altitude,a V-type six-cylinder diesel engine was determined via the parameter estimation and thermodynamics analysis for turbocharging scheme.The original matching scheme was not suitable for altitude varying in large range operation condition.A variable nozzle turbocharging system was matched for diesel engine and it showed that no fallacies existed from the operation lines.A simulation model was established with GT-Power software and verified by test data.The simulation model was applied to performance prediction under different working conditions.Then the operating performance of engine at different altitudes was calculated,including the external characteristics and part load characteristics.The control strategy of variable nozzle turbocharging system for full operation conditions can be obtained in the end.It showed that the air demand of diesel engine can be satisfied with small opening of nozzle ring at high altitude and full load condition,and the goal of power restoring would be achieved.The charging system needed to increase the opening of nozzle ring to improve engine performance with the drop of altitude.The opening of nozzle ring should be deduced generally as the altitude increased in the whole operation area,moreover,it needed to adopt the minimum nozzle ring opening if the altitude was above 3 000 m except under some low load conditions.The operating point of the lowest fuel consumption would transfer from low-speed and low-altitude area into low-speed and high-altitude area with the fall of engine load.