Yanmar 3TNV82A Service Manual

Also see for 3TNV82A: Operation manual Service manual Service manual Troubleshooting manual

Contents

Yanmar 3TNV82A Service Manual Manual pdf 295 page image

TURBOCHARGERTNV DI Service Manual 10-11Turbocharger Component FunctionsTheory of OperationNormally aspirated engines produce horsepowerthat is limited by the atmospheric pressure of theinduction air. The turbocharger is an exhaust gaspressure driven device that adds to theatmospheric pressure, resulting in a boost inpressure at the combustion chambers. Thissubstantially increases the amount of fuel that canbe injected into the combustion chambers, whilemaintaining the proper fuel-to-air ratio. A slightparasitic loss is imposed on the engine because ofadded back pressure in the exhaust system. Thatloss is offset by horsepower gains. The net result issubstantially increased overall horsepower overnormally aspirated engines.The turbocharger consists of two maincomponents:• Turbine• CompressorTurbineThe turbine is driven by exhaust gas pressure fromthe engine and is coupled to a shaft on thecompressor side of the turbocharger.Exhaust gas velocity is accelerated at the nozzleportion in the turbine housing where thecross-sectional area is reduced. As exhaust passesover the turbine impeller at high linear velocity, theturbine shaft is rotated at proportionally high rpm.CompressorThe compressor is driven by a shaft on the turbineside of the turbocharger and increases theinduction air pressure at the intake manifold.The compressor impeller draws induction air intothe turbocharger, compresses it and directs it intothe engine at high pressure.A seal ring and heat insulating plate thermallyisolate heat energy, at the turbine side, from thebearings and the induction air, at the compressorside.BearingsThrust BearingA thrust force is continuously imposed on theturbine shaft during engine operation. A thrustbearing prevents the shaft from moving laterallyunder this thrust force.Radial BearingA floating radial bearing moves with the turbineshaft as oil films form on the inside and outsidebearing surfaces. The bearing slipping speed isslower than the turbine shaft speed, resulting inhigher dynamic stability and reduced mechanicalnoise.LubricationThe oil pump delivers oil from the engine to theturbocharger for cooling and lubrication of thebearings. As oil leaves the turbocharger, it isreturned to the engine.Compressor Side Sealing MechanismA seal ring and a seal plate form a double wallstructure at the rear of the compressor impeller.The seal ring and seal plate prevent Intake air andoil leakage.Waste Gate ModulationExcessive boost pressure that cannot beaccommodated by the engine can damage theturbocharger. The waste gate is a component thatmonitors intake boost pressure on the compressorside and diverts exhaust gases around theturbocharger turbine. The amount of exhaust gasdiverted is varied to limit turbine rpm and maintainthe intake pressure equal to, or less than thespecified maximum level. This improves theresponse to load variation in the low to medium rpmrange and minimizes black smoke.Waste Gate ControlA mechanical pressure sensor in the outlet of thecompressor side of the turbocharger opens andcloses the waste gate to maintain the specifiedintake pressure at the intake manifold.