增压器原理简介上汽菲亚特红岩动力总成有限公司PPT课件

1、1it is not so simpleEnergy from exhaustPower to compressorMore air to enginemore fuelMore energy from exhaustMore power to compressormore fuel第1页/共10页2consequences An equilibrium is reached as the injected fuel quantity is controlled BUT At HIGH engine speed (more gas flow) the boost pressure can be

2、 higher than necessary (more air than the amount needed to burn all the fuel) Overstressing Increased fuel consumption At LOW engine speed (less gas flow) the boost pressure is low and as a consequence the fuel quantity (and the engine power / torque) needs limitation (or/and the smoke level increas

3、es) The build-up process is slow and it takes time for the engine to reach the required torque (“Turbo Lag”)第2页/共10页3Turbo LagTorque NmIncreasing engine speedSMOKE increase第3页/共10页4Turbo with Wastegate A by-pass on the exhaust, reducing gas flow through the turbocharger. When the valve is open at hi

4、gh engine speed, it will reduce boost pressure. This is an energly loss, but a SMALLER turbine can be used, with better low speed performances and better transient response Normally the valve is directly opened by an actuator controlled by boost pressure第4页/共10页5Turbo with WastegateTurbineCompressor

5、Exhaust gas INExhaust gas OUTAir OUTWastegate valve (flap)Wastegate valve actuator第5页/共10页6Variable geometry tubochargerFirst solution: moving vanes in the fixed part, changing the direction of gas flow on the turbine wheel and the section of passage for gasClosed position(low engine speed)Open posi

6、tion(high engine speed)Honeywell GarretBorg Warner - KKK第6页/共10页7Variable geometry tubochargerSecond solution: axial moving ring, changing the section of passage for gasClosed position(low engine speed)Open position(high engine speed)Cummins HolsetCURSOR engines第7页/共10页8VGT control The VGT is normal

7、ly actuated by a pneumatic cylinder (but solutions with electrical actuators are in development In all cases to exploit all VGT advantages an electronic control system is required (incorporated into the engine ECU) VGT actuator position is controlled using inputs from different sensors Boost pressur

8、e and temperature Ambient temperature and pressure Turbo speed (FPT patent) Exhaust backpressure The control system includes a pressure control valve and air compressed piping第8页/共10页9ResultsThe FIXED GEOMETRY turbo has low performances at low speedThe WASTEGATE turbo has better low speed performances (as the turbine is smaller)At high speed the WASTEGATE turbo boost pressure is limited by the bypass valveThe VGT has very good low speed performancesAt high speed the VGT has a con