Simplified variable geometry turbocharger with increased flow range

Abstract

A variable geometry turbocharger is simplified yet able to maintain pulse energy. In a first embodiment, a turbine housing is provided with a pivoting flow control valve which pivots about a point near the entry to the turbine housing. By moving the valve about the pivot point, the effective volume of the turbine housing volute is varied, thus effectively reducing the volume of exhaust gas in the volute, allowing control of exhaust gas flowing to the turbine wheel. In the second embodiment of the invention, a rotating wedge segment within the volute is rotated from a first position to a second position, changing the effective volume of the volute and allowing control of exhaust gas flowing to the turbine wheel.

Description

FIELD OF THE INVENTION[0001]This invention addresses the need for a reduced cost, increased range, turbine flow control device, and accomplishes this by designing a simplified variable geometry turbocharger housing with controlled assymetric flow to the turbine wheel.BACKGROUND OF THE INVENTION[0002]Turbochargers are a type of forced induction system. They deliver air, at greater density than would be possible in the normally aspirated configuration, to the engine intake, allowing more fuel to be combusted, thus boosting the engine's horsepower without significantly increasing engine weight. A smaller turbocharged engine can replace a normally aspirated engine of a larger physical size, thus reducing the mass and aerodynamic frontal area of the vehicle.[0003]Turbochargers (FIG. 1) use the exhaust flow (100) from the engine exhaust manifold, which enters the turbine housing at the turbine inlet (51) of a turbine housing (2), to drive a turbine wheel (70), which is located in the turb...

AI Technical Summary

Benefits of technology

The present invention provides a simplified, low cost, variable geometry turbocharger with a divided turbine housing and flow controlling device that can change the effective exhaust mass flow to the turbine wheel, broadening the flow range and controlling it in a way that exceeds the range available with a symmetrically configured volute cross sectional areas without the flow controlling device. The turbucharger also includes a pivoting flow control valve or a rotating butterfly-configured flow control valve which can act as a smaller A / R turbine housing, and which can vary the flow from the large volute to the small volute and on to the turbine wheel, thus increasing the turbine stage flow range. These features make the variable geometry turbocharger more efficient, effective, and cost-friendly.

Problems solved by technology

These requirements are often compromised due to other demands such as architectural requirements (space availability) outside the turbine housing, method of location and mounting of the turbine housing to the bearing housing, and the transition from slice “A” to the turbine foot (51), which combine to force turbine housing volutes to be of rectangular or triangular section, as well as in circular, or combinations of all shapes.

The reasons for this cracking are many but predominant are the dross which is pushed through the pattern at the casting process which means that the integrity of the material near the tip of the divider wall is less than optimal, and the second is the fact that the temperature distribution around the volutes causes the casting to want to “unwind”.

The thermal forces generating the “unwinding” of the turbine housing are resisted by the vertical divider wall, the resultant being cracking in the wall.

While a crack does little physical damage, the next step in cracking is for pieces of cast iron divider wall to separate from the casting and be ingested by the turbocharger or engine which can cause terminal damage.

The function of the wastegate valve, in this manner, is to cut the top off the full load boost curve, thus limiting the boost level to the engine.

This, in effect reduces the effective flow to the turbine, when desired (e.g. to prevent overdriving of the turbine), while allowing the full range of the turbine housing flow to the turbine wheel when full flow is desired.

While a wastegate can be used to limit boost levels, its turbine power control characteristics are rudimentary and coarse.

However, if the wastegated turbocharger has a “dumb” actuator, which operates on a pressure or vacuum signal only and is operated at altitude, then the critical pressure ratio at which the valve opens is detrimentally affected.

Since the diaphragm in the actuator senses boost pressure on one side and barometric pressure on the other, the tendency is for the actuator to open later (since the barometric pressure at altitude is lower than that at sea level) resulting in over-boost of the engine.

The problem is that most wastegates are somewhat binary in their operation, which does not fit well with the linear relationship between engine output and engine speed.

VTG turbochargers have a large number of very expensive alloy components, which must be assembled and positioned in the turbine housing so that the guide vanes remain properly positioned with respect to the exhaust supply flow channel and the turbine wheel over the range of thermal operating conditions to which they are exposed.

These materials are very expensive to procure, machine, and weld (where required).

This translates to expensive actuators.

While VTGs of various types and configurations have been adopted widely to control both turbocharger boost levels and turbine backpressure levels, the costs of the hardware and implementation are high.

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