mlm1234
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Why does 4 stroke have higher thermel efficency but 2 stoke has higher mechahanical output efficincy
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mnot
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(Original post by mlm1234)
Why does 4 stroke have higher thermel efficency but 2 stoke has higher mechahanical output efficincy
2 stroke has lower pumping losses per cycle.

4 stroke is easier to control fuel injection & timing including how & where the fuel & air are mixed as well as more complex operating methods. Their is a lot which goes into it but you get better flame propagation, better swirl, better combustion.
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mlm1234
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(Original post by mnot)
2 stroke has lower pumping losses per cycle.

4 stroke is easier to control fuel injection & timing including how & where the fuel & air are mixed as well as more complex operating methods. Their is a lot which goes into it but you get better flame propagation, better swirl, better combustion.

hi sorry to bother u
can i check this with you about otto diesel and carnot cycles
I just want to check my comments i made, if it makes sense before i submit

Summery statement ive made

Otto and Diesel both have practical and theory cycles whereas carnot has only theoretical cycle.
If heat engines where running the theory cycles of Otto and Diesel, there would higher effiency than their practical cycles.
Diesel Theory cycle has greater output and effiency than Otto cycle by looking at PV digrams.
the Carnot cycle would have the highest efficiency, it determines the maximum possible efficiency in heat engines.
Theory assumptions for carnot cycle. (do these assumptions apply to diesel and otto cycle aswell?)
There is zero wasted energy as it is because assumed there is no friction and output work is maximised.
There is a cold and heated reservoir, greater the difference in temperatures greater the efficiency. As thermal energy isn't lost, no energy is wasted so temperature difference doesn't decrease so efficiency remains high.
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mnot
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(Original post by mlm1234)
hi sorry to bother u
can i check this with you about otto diesel and carnot cycles
I just want to check my comments i made, if it makes sense before i submit

Summery statement ive made

Otto and Diesel both have practical and theory cycles whereas carnot has only theoretical cycle.
If heat engines where running the theory cycles of Otto and Diesel, there would higher effiency than their practical cycles.
Diesel Theory cycle has greater output and effiency than Otto cycle by looking at PV digrams.
the Carnot cycle would have the highest efficiency, it determines the maximum possible efficiency in heat engines.
Theory assumptions for carnot cycle. (do these assumptions apply to diesel and otto cycle aswell?)
There is zero wasted energy as it is because assumed there is no friction and output work is maximised.
There is a cold and heated reservoir, greater the difference in temperatures greater the efficiency. As thermal energy isn't lost, no energy is wasted so temperature difference doesn't decrease so efficiency remains high.
Im not really understanding what this chunk of text is tbh.

I have never overlaid an Otto & Carnot cycle im not really sure why you would, given Carnot is theoretical I think you could only fairly compare theoretical PV diagrams of each, and given the applied nature of Otto, miller, diesel etc. im not sure what benefit in comparing them is. Although nowadays modern 4-stokes use much more complex strategies to maximise thermal efficiency than just a blanket "Otto cycle" and also recover the thermal losses elsewhere in the supporting system other than just where combustion takes place.

Also if you've just put this on the internet their is now a chance this gets picked up by similarity checkers.
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mlm1234
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(Original post by mnot)
Im not really understanding what this chunk of text is tbh.

I have never overlaid an Otto & Carnot cycle im not really sure why you would, given Carnot is theoretical I think you could only fairly compare theoretical PV diagrams of each, and given the applied nature of Otto, miller, diesel etc. im not sure what benefit in comparing them is. Although nowadays modern 4-stokes use much more complex strategies to maximise thermal efficiency than just a blanket "Otto cycle" and also recover the thermal losses elsewhere in the supporting system other than just where combustion takes place.

Also if you've just put this on the internet their is now a chance this gets picked up by similarity checkers.
tutor said put general comment on diesel carnot and otto cycle. and that throw me so trying to write general comments on the theory of the 3 cycles.

do thoery cycles follow carnot assumptions?

There is zero wasted energy as it is because assumed there is no friction and output work is maximised.
There is a cold and heated reservoir, greater the difference in temperatures greater the efficiency. As thermal energy isn't lost, no energy is wasted so temperature difference doesn't decrease so efficiency remains high.
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