Here’s the skinny: I’ve got an Otto cycle engine with a variable compression rat
ID: 1718853 • Letter: H
Question
Here’s the skinny: I’ve got an Otto cycle engine with a variable compression ratio, to which I am going to add a regenerator so that some of the heat that would normally be lost in the exhaust can be recovered and delivered to the air in the cylinder, right between the end of compression and the beginning of combustion. But I need to know what compression ratio will give me the highest thermal efficiency. Here’s where you come in, with your awesome calculating skills. Some data you may want to use: specific heat cv= 0.72 kJ/kgK, k=1.4, intake pressure 1 bar, intake temperature 300 K, temperature at the end of combustion 1500 K.
Explanation / Answer
effiency of regenerative cycle is = 0.8
heat rejected = mcv(T4-T1) = 864 KJ
it means input work for regenrative cycle = 864 KJ
output energy recycled for otto cycle = 0.8 * 864 = 691.2 KJ
Here we dont have any parameters for engine values.
if we have heat input or Temp T2 at end of compression then we can find the max compression ratio other wise efficiency is proportional to (compression ratio)0.4 .
note : time doesnt permit to calculate compression ratio