Adjustable Compressor Inlet Blades for Turbocharger Surge Delay
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Solution Overview
Problem
Turbochargers for internal combustion engines face compressor surge issues at high load or low engine speed, and high exhaust gas recirculation, limiting the surge-free operation range, especially at low flow rates.
Innovation Solution
A centrifugal compressor with an adjustable inlet mechanism that allows the blades to pivot radially, reducing the inlet diameter and shifting the surge line to lower flow rates by forming an orifice of reduced diameter, thereby stabilizing the flow and preventing compressor surge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the compressor inlet diameter is reduced to delay surge to lower flow rates, then the surge-free operation range is improved, but the high-flow performance deteriorates
Solution Approach 1:
The inlet-adjustment mechanism employs movable blades that can pivot between multiple positions (open, closed, and intermediate) to dynamically adjust the effective inlet diameter. This dynamic adjustment allows the compressor to optimize its surge-free operation range at low flow rates while maintaining high-flow performance at higher flow rates, resolving the contradiction between reliability and productivity across different operating conditions
Solution Approach 2:
The mechanism changes the physical parameter of inlet diameter by pivoting blades to different angular positions. By adjusting this geometric parameter, the compressor can shift its surge line to accommodate varying flow rates, thereby improving surge-free operation at low flow while preserving high-flow capability when the blades are in the open position
2Reliability
If the inlet diameter is reduced to prevent flow instability and reduce blade incidence angles, then compressor surge is prevented, but the mass flow rate capability is reduced
Solution Approach 1:
The adjustable inlet mechanism provides dynamic control over the inlet diameter, allowing the system to adapt to different operating conditions. At low flow rates, the blades pivot to reduce the inlet diameter, stabilizing flow and preventing surge. At high flow rates, the blades return to the open position, restoring full mass flow rate capability and eliminating the trade-off between flow stability and quantity
3Reliability
If the blades are positioned to form a smaller orifice, then the surge line shifts to lower flow rates, but the compressor choking condition occurs at lower flow rates
Solution Approach 1:
The mechanism dynamically adjusts the blade position based on operating requirements. When surge prevention is needed, blades pivot to form a smaller orifice that shifts the surge line. When maximum flow capacity is needed, blades return to the open position, allowing the compressor to operate at higher flow rates before reaching choke conditions, thus resolving the contradiction between surge delay and flow rate capacity
Data Source
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AI summary
A centrifugal compressor for a turbocharger includes an inlet-adjustment mechanism in an air inlet for the compressor, operable to move between an open position and a closed position in the air inlet. The inlet-adjustment mechanism includes a plurality of blades disposed about the air inlet and each pivotable about one end of the blade, the blades extending through a slot in the air inlet wall when the blades are in the closed position so as to form an orifice of reduced diameter relative to a nominal diameter of the inlet. Movement of the inlet-adjustment mechanism from the open position to the closed position is effective to shift the compressor's surge line to lower flow rates.