单缸摩托车发动机中低速性能优化

目的 解决某单缸摩托车发动机台架测试时中低速扭矩线性度差的问题.方法 基于CFD数值分析方法,运用热力学仿真分析软件GT-Power对发动机进行建模和标定,然后对原方案发动机进行摸底分析,最后通过优化配气机构和进排气系统来实现改善中低速性能的目标.结果 优化后的发动机台架测试结果中,发动机中低速扭矩线性度改善,动力性和经济性及排放都达到项目预期目标,峰值功率达到16 kW(9500 r/min),峰值扭矩达到18.6 N·m(7000 r/min),最低比油耗为183 g/(kW·h),CO、THC、NOx排放量分别为840、83、54 mg/km.配气机构运动学动力学性能与可靠性提升,进排气凸轮丰满系数分别达到5.14、5.15.结论 原方案中低速扭矩线性度差的原因为此转速段充气效率较低.优化凸轮型线、空滤器、消声器、排气管道参数能更好地利用进排气管道谐振效应来提升发动机中低速动力性能.

Performance Optimization of Single-cylinder Motorcycle Engine in Low and Medium Speed

This article aims at the problem of poor linearity of torque at low and medium speeds during bench testing of a single-cylinder motorcycle engine. With the CFD method, the thermodynamic simulation analysis software GT-power was used to build and calibrate the engine model, and then the original engine was conducted a thorough analysis. Finally, the goal of performance optimization at low and medium speeds was achieved by optimizing the valve train and intake and exhaust systems of the original plan. It was resulted that the linearity of torque was improved in low and medium speeds and the power performance, fuel economy and emission had reached the project''s expected goals in the optimized engine bench test results. The peak power reached 16 kW (9500 r/min), peak torque reached 18.6 N.m(7000 r/min), the minimum specific fuel consumption was 183 g/(kW.h), and the emissions of CO, THC, NOx were 840,83,54 mg/km respectively. The dynamic performance and reliability of the valve train were improved, the fullness coefficient of intake and exhaust cams reached 5.14 and 5.15 respectively. The reason for the poor linearity of the low-speed torque in the original scheme engine was the low volumetric efficiency in this speed range. Optimizing the parameters of cam profile, air filter, muffler and exhaust pipe could make better use of the resonance effect of intake and exhaust pipes to improve the low and medium speed dynamic performance of engine.