Difficulty: Easy
Correct Answer: polytropically
Explanation:
Introduction / Context:
Thermodynamic textbooks idealize compression as isentropic for efficiency calculations. Real compressors, however, exhibit losses and follow a polytropic path, which more accurately captures the small-step efficiency across many blade rows.
Given Data / Assumptions:
Concept / Approach:
Polytropic compression assumes p * v^n = constant with an exponent n between 1 (isothermal) and gamma (isentropic for ideal gas). This provides an incremental efficiency representation and aligns with measured compressor maps.
Step-by-Step Solution:
Ideal (reference) path: isentropic.Real path: polytropic with n slightly greater than isothermal and less than isentropic exponent-related equivalent.Therefore, “polytropic” best describes the practical compression process.
Verification / Alternative check:
Manufacturers quote polytropic efficiency to characterise multi-row compression more robustly than a single isentropic efficiency figure.
Why Other Options Are Wrong:
Common Pitfalls:
Confusing “closed cycle” with “isothermal”; the cycle closure does not imply isothermal compression.
Final Answer:
polytropically
Discussion & Comments