Variations of compression ratios

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SUMMARY

The discussion focuses on the variations of compression ratios in diesel and Otto cycles used in automobile engines. It establishes that petrol engines require a compression ratio below 10:1 for high-octane fuel and 8:1 for unleaded petrol (ULP) to prevent premature ignition. In contrast, diesel engines necessitate a higher compression ratio of approximately 20:1 for fuel ignition upon injection, although this can be reduced to about 16:1 with the use of a charger to boost air pressure. The conversation also raises the question of alternative engine cycles beyond Otto, diesel, and Seillinger.

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  • Understanding of Otto cycle principles
  • Knowledge of diesel engine operation
  • Familiarity with compression ratios in internal combustion engines
  • Basic concepts of forced induction systems
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  • Research alternative engine cycles beyond Otto and diesel, such as the Atkinson cycle
  • Explore the impact of compression ratios on engine efficiency and performance
  • Learn about the role of turbochargers and superchargers in modifying compression ratios
  • Investigate the thermodynamic principles governing combustion in different engine types
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Hi,all. What changes the variations of compression rations in diesel and otto cycles which are
always used in the engines. Are there any cycles used in automobile engines other than otto, diesel or seillinger?
 
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In a petrol engine, the fuel must not ignite under compression until the spark occurs.
So compression ratio must be below about 10:1 for high octane and 8:1 for ULP.

Diesel fuel must ignite as it is injected so it needs about 20:1 compression to get high temperature.
If a charger is used to boost input air pressure then only about 16:1 will be needed to get same pressure.
 
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