Stoichiometric air-fuel ratio of an SI engine is 14.7:1. If equivalence ratio (λ) is 0.92, the actual air-fuel ratio maintained during the engine operation is ______. [round off to 2 decimal places]
Official Answer Key:
13.47 to 13.57
Step-by-Step Solution & Explanation
The symbol λ used here denotes the relative (normalized) air-fuel ratio, λ = AFR_actual/AFR_stoichiometric (note: this is the reciprocal of the fuel-based equivalence ratio φ). Actual AFR = λ × AFR_stoich = 0.92 × 14.7 = 13.52, within the first accepted range (13.47–13.57). [The key also credits 14.7/0.92 = 15.98, the answer obtained if λ is instead interpreted as φ (fuel-rich definition); the paper's answer key accepted both interpretations due to this common ambiguity in nomenclature.]
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