Variable Nozzle Turbocharger Thermal Deformation Control
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Solution Overview
Problem
Variable geometry turbochargers face challenges in maintaining reliability and turbine efficiency due to thermal deformation caused by temperature differences between the first nozzle ring and the support ring, leading to reduced parallelism and increased leakage flow.
Innovation Solution
Incorporating an absorbing unit, such as elongated pin holes or slits, in the support ring to absorb radial thermal expansion differences between the first nozzle ring and the support ring, minimizing thermal deformation and maintaining parallelism between the nozzle rings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the nozzle side clearance is set larger to maintain reliability, then the reliability is improved, but the turbine efficiency decreases due to increased leakage flow
Solution Approach 1:
The pin hole shape is changed from a standard circular hole to an elongated hole extending in the radial direction. This parameter change in the connecting structure allows the first nozzle ring to expand radially independently, maintaining parallelism and minimizing clearance to reduce leakage flow while ensuring reliability
Solution Approach 2:
The invention explicitly addresses thermal expansion by providing the first nozzle ring with radial expansion capability through the elongated pin holes. This allows the nozzle ring to expand in the radial direction in response to temperature changes without causing inclination or increasing clearance, thereby minimizing leakage flow while maintaining operational reliability
2Stability of the object's composition
If the first nozzle ring is rigidly connected to the support ring, then the structural stability is improved, but the thermal deformation causes inclination and reduces parallelism
Solution Approach 1:
The connection between the first nozzle ring and support ring is segmented through the use of discrete pin holes rather than a continuous rigid connection. The elongated pin holes allow independent radial movement while maintaining circumferential positioning, enabling the nozzle ring to accommodate thermal expansion without losing structural stability or parallelism
Solution Approach 2:
The connection structure is made dynamic by allowing radial movement through the elongated pin holes. This dynamic capability enables the first nozzle ring to adjust its radial position in response to thermal expansion while maintaining structural stability and parallelism, preventing inclination that would occur with a rigid fixed connection
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution effectively suppresses thermal deformation, minimizes nozzle side clearance, ensures operational stability, and enhances turbine efficiency by reducing leakage flow and maintaining reliable operation of the variable geometry turbocharger.
Implementation Method 1
a difference in ambient temperature (a difference in ambient gas temperature) between the first nozzle ring and the support ring may occur when the variable geometry turbocharger is in operation. In this case, the first nozzle ring is thermally deformed such that the opposed surface of the first nozzle ring is inclined with respect to a direction perpendicular to the axial direction due to a difference in thermal expansion (a difference in thermal deformation) in a radial direction between the first nozzle ring and the support ring
Data Source
AI summary
In a variable nozzle unit, at a position located away from and opposed to a first nozzle ring in a right-left direction, a second nozzle ring is provided integrally with the first nozzle ring through multiple connecting pins arranged in a circumferential direction. An inner edge portion of a support ring is connected to the first nozzle ring by riveting of one end portions of the multiple connecting pins. Each pin hole in the support ring is formed into such a shape extending in a radial direction of the support ring. A washer is provided between a rim of each pin hole in the support ring and a rivet head brought about by joining of the end portion of the corresponding connecting pin.