Difficulty: Easy
Correct Answer: forward curved
Explanation:
Introduction / Context:
Impeller blade exit geometry strongly affects compressor head, efficiency, and stability. Classifying blades as backward-, radial-, or forward-curved depends on the outlet angle relative to the tangent.
Given Data / Assumptions:
Concept / Approach:
Forward-curved blades turn the flow more in the direction of impeller rotation, increasing theoretical head but often at the cost of efficiency and surge margin compared to backward-curved designs used in modern compressors.
Step-by-Step Solution:
Verification / Alternative check:
Velocity triangles demonstrate that forward-curved blades yield larger whirl at exit, consistent with higher theoretical head.
Why Other Options Are Wrong:
They contradict the standard angle-based definitions.
Common Pitfalls:
Confusing blade metal angle definition with flow angles referenced to absolute vs. relative frames; here the conventional metal/relative angle convention is implied.
Final Answer:
forward curved
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