Abstract: A connected impeller and shaft is provided. The shaft has a first part which provides a threaded portion carrying a thread which screws onto a corresponding threaded portion of the impeller. The shaft also has a second part which provides an abutment surface for engaging a corresponding abutment surface of the impeller when the threaded portions are screwed together, thereby tightening the threads to provide a rotationally fixed connection between the impeller and the shaft. The first part is rotationally fixed relative to the second part at a joint. The threaded portion of the shaft is axially spaced a first distance from the abutment surface of the shaft. The threaded portion of the shaft is axially spaced from the joint by a second distance which is greater than the first distance. The threaded portion of the shaft and the joint are on the same side of the impeller.

Abstract: A turbocharger has a casing system which houses a centrifugal impeller connected to a turbine by a shaft. The casing system includes an insert casing which forms a duct for feeding air to and through the impeller, and a volute casing which forms a volute for receiving compressed air from the impeller, the insert casing inserting into the volute casing. The casing system further includes a main casing which forms a housing for the shaft and for the shaft-side end of the impeller. The impeller includes a hub which has a radially outer annular rim, and has front and rear faces which converge towards the rim from respectively the inlet side and the shaft side of the hub. The impeller further includes a plurality of circumferentially arranged vanes on the front face of the hub. The impeller further includes a seal formation formed on the rear face at the rim.

Abstract: A connected impeller and shaft is provided. The shaft has a first part which provides a threaded portion carrying a thread which screws onto a corresponding threaded portion of the impeller. The shaft also has a second part which provides an abutment surface for engaging a corresponding abutment surface of the impeller when the threaded portions are screwed together, thereby tightening the threads to provide a rotationally fixed connection between the impeller and the shaft. The first part is rotationally fixed relative to the second part at a joint. The threaded portion of the shaft is axially spaced a first distance from the abutment surface of the shaft. The threaded portion of the shaft is axially spaced from the joint by a second distance which is greater than the first distance. The threaded portion of the shaft and the joint are on the same side of the impeller.

Abstract: A connector for connecting an impeller to a shaft is provided. The connector is formed as a unitary body. The connector has a sleeve portion which is frictionally connected on a radially outer surface of a shaft-side hub extension of the impeller. The connector further has a threaded portion carrying a thread which screws onto a corresponding threaded portion of the shaft, such that the connector provides a rotationally fixed connection between the impeller and the shaft. The hub extension has a central recess, and a part of the connector is inserted into the recess. The frictional connection between the sleeve portion and the radially outer surface of the hub extension transmits, in use, substantially all of the torque between the shaft and the impeller.

Abstract: A turbocharger has a casing system which houses a centrifugal impeller connected to a turbine by a shaft. The casing system includes an insert casing which forms a duct for feeding air to and through the impeller, and a volute casing which forms a volute for receiving compressed air from the impeller, the insert casing inserting into the volute casing. The casing system further includes a main casing which forms a housing for the shaft and for the shaft-side end of the impeller. The impeller includes a hub which has a radially outer annular rim, and has front and rear faces which converge towards the rim from respectively the inlet side and the shaft side of the hub. The impeller further includes a plurality of circumferentially arranged vanes on the front face of the hub. The impeller further includes a seal formation formed on the rear face at the rim.

Abstract: A connector for connecting an impeller to a shaft is provided. The impeller has a shaft-side hub extension with a central recess. The impeller is formed of a material having a greater coefficient of thermal expansion than the material of the shaft. The connector is inserted into the recess to frictionally connect an outwardly facing surface of the connector with a radially inner surface of the hub extension. The connector has a threaded portion carrying a thread which screws onto a corresponding threaded portion of the shaft, such that the connector provides a rotationally fixed connection between the impeller and the shaft. The connector is formed of a material having a coefficient of thermal expansion which is greater than the coefficient of thermal expansion of the material of the shaft.

Abstract: A connector for connecting an impeller to a shaft is provided. The connector is formed as a unitary body. The connector has a sleeve portion which is frictionally connected on a radially outer surface of a shaft-side hub extension of the impeller. The connector further has a threaded portion carrying a thread which screws onto a corresponding threaded portion of the shaft, such that the connector provides a rotationally fixed connection between the impeller and the shaft. The hub extension has a central recess, and a part of the connector is inserted into the recess. The frictional connection between the sleeve portion and the radially outer surface of the hub extension transmits, in use, substantially all of the torque between the shaft and the impeller.

Abstract: A two-stage turbocharger assembly for an internal combustion engine is provided. The assembly has a single low pressure turbocharger, and more than two high pressure turbochargers arranged in parallel with each other. The compressor outlet of the single low pressure turbocharger is operatively connected to the compressor inlets of the high pressure turbochargers. The turbine outlets of the high pressure turbochargers are operatively connected to the turbine inlet of the single low pressure turbocharger.

Abstract: A two-stage turbocharger assembly for an internal combustion engine is provided. The assembly has a low pressure turbocharger, and more than two high pressure turbochargers arranged in parallel with each other. The compressor outlet of the low pressure turbocharger is operatively connected to the compressor inlets of the high pressure turbochargers. The turbine outlets of the high pressure turbochargers are operatively connected to the turbine inlet of the low pressure turbocharger.

Abstract: A turbocharger has a shaft formed of a strong material such as steel and an impeller formed of a relatively weaker material such as aluminum alloy. The impeller is mounted on the shaft by means of an internally-threaded insert, for example also of steel, interference fitted into the impeller hub. To prevent loss of the interference fit between the insert and impeller during thermal and speed excursions of the impeller during operation of the turbocharger, a constraining ring is fitted to the hub of the impeller. The ring is of a material having a lower coefficient of thermal expansion than the material of the impeller and surrounds at least a part of that axial length of the impeller which overlies the insert.

Abstract: A turbocharged internal combustion engine is provided with a diverter valve arranged to divert part of the exhaust gas flow along a conduit for introduction into a turbine region. Exhaust gases flow from the conduit, through appropriate galleries in the turbocharger casing, into internal passages formed in at least some of the stator blades. From the internal passages, the exhaust gas passes through holes positioned near the downstream ends of the convex surfaces of the stator blades. In this manner, the diverted gas is introduced into the comparatively lower pressure of the turbine region thereby enabling the diverted exhaust gas to rejoin the mainstream exhaust gas and to do useful work in driving the rotor blades while, at the same time, avoiding choking the stator blades.

Abstract: A turbocharger for an internal combustion engine is of the type having an impeller mounted on a shaft carried by a bearing supplied with lubricating oil, the shaft being located in a bore and having an oil and air seal between the bearing and the impeller hub. The seal is a floating ring seal mounted in the bore and extending radially into a circumferential recess in the impeller hub. In use, the ring seal experiences a pressure differential across it which urges it to slide axially along the bore so that it forms a sealing interface with a side face of the recess. The shaft rotates relative to the ring seal, which is therefore subject to wear against the side face of the recess. Hence, a shoulder is provided in the bore to limit excessive axial sliding of the ring seal due to wearing away of the ring seal against the side face of the recess.

Abstract: A turbocharged internal combustion engine is provided with a diverter valve arranged to divert part of the exhaust gas flow along a conduit for introduction into a turbine region. Exhaust gases flow from the conduit, through appropriate galleries in the turbocharger casing, into internal passages formed in at least some of the stator blades. From the internal passages, the exhaust gas passes through holes positioned near the downstream ends of the convex surfaces of the stator blades. In this manner, the diverted gas is introduced into the comparatively lower pressure of the turbine region thereby enabling the diverted exhaust gas to rejoin the mainstream exhaust gas and to do useful work in driving the rotor blades while, at the same time, avoiding choking the stator blades.

Abstract: A turbocharger for an internal combustion engine is of the type having an impeller mounted on a shaft carried by a bearing supplied with lubricating oil, the shaft being located in a bore and having an oil and air seal between the bearing and the impeller hub. The seal is a floating ring seal mounted in the bore and extending radially into a circumferential recess in the impeller hub. In use, the ring seal experiences a pressure differential across it which urges it to slide axially along the bore so that it forms a sealing interface with a side face of the recess. The shaft rotates relative to the ring seal, which is therefore subject to wear against the side face of the recess. Hence, a shoulder is provided in the bore to limit excessive axial sliding of the ring seal due to wearing away of the ring seal against the side face of the recess.