GATE ME 2020 Set 2 — Question 65
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Thermodynamics → IC Engines → Otto, Diesel & Dual Cycles
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Question
Keeping all other parameters identical, the Compression Ratio (CR) of an air standard diesel cycle is increased from 15 to 21. Take ratio of specific heats = 1.3 and cut-off ratio of the cycle .
The difference between the new and the old efficiency values, in percentage,
(\eta_{\text{new}}|_{CR=21}) - (\eta_{\text{old}}|_{CR=15}) = \text{_______} % (round off to one decimal place).
The difference between the new and the old efficiency values, in percentage,
(\eta_{\text{new}}|_{CR=21}) - (\eta_{\text{old}}|_{CR=15}) = \text{_______} % (round off to one decimal place).
Correct answer
4.6 to 4.9
Solution
The efficiency of an air-standard Diesel cycle is given by the formula:Where:
= Compression Ratio
= Ratio of specific heats
= Cut-off ratioGiven values:
First, calculate the common term in the bracket:
Case 1: Old efficiency ()
Case 2: New efficiency ()
Difference in efficiency values (in percentage):
Difference
Difference
Difference
Difference Rounding off to one decimal place, the difference is .Let's recheck calculations with higher precision for the given range.
Difference Rounding off to one decimal place, the difference is .The final answer is .
= Compression Ratio
= Ratio of specific heats
= Cut-off ratioGiven values:
First, calculate the common term in the bracket:
Case 1: Old efficiency ()
Case 2: New efficiency ()
Difference in efficiency values (in percentage):
Difference
Difference
Difference
Difference Rounding off to one decimal place, the difference is .Let's recheck calculations with higher precision for the given range.
Difference Rounding off to one decimal place, the difference is .The final answer is .
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