Gas turbine performance metric: The work ratio is defined as the ratio of net work output from the plant to the turbine work.

Introduction / Context:
In gas turbines, a significant fraction of the turbine work is used to drive the compressor. The work ratio indicates how much of the turbine work is available as net useful output, and is a key cycle quality indicator.

Given Data / Assumptions:

• Turbine work W_t, compressor work W_c, net work W_net = W_t - W_c.
• Steady state Brayton cycle operation.
• Neglect auxiliary loads for clarity.

Concept / Approach:
Work ratio = W_net / W_t. A higher work ratio means less of the turbine work is internally consumed by the compressor, typically associated with lower pressure ratios, effective intercooling, or better component efficiencies. However, there is a tradeoff with thermal efficiency and specific work.

Step-by-Step Solution:

Verification / Alternative check:
Cycle calculations show that as pressure ratio increases, W_t rises but W_c rises too. The ratio provides a normalized measure to compare cycles and is independent of absolute scale.

Why Other Options Are Wrong:

• Compression ratio and pressure ratio are separate geometric or thermodynamic ratios, not the requested definition.
• None of these is incorrect because work ratio is the accepted term.

Common Pitfalls:
Confusing work ratio with back work ratio (W_c / W_t). Both are useful but represent different perspectives.

Final Answer:
work ratio