Factors Influence CI Engine cycle

Following are the factors that influence compressed ignition (CI) engine cycle:

  1. Non-constant pressure combustion of the fuel
  2. Dissociation
  3. Blow-down losses
  4. Pumping losses

1. Non-constant pressure combustion of the fuel:

  • In the basic CI engine air cycle, it is assumed that the heat was added to the cycle at constant pressure.
  • In the case of high speed engines, it approaches a constant volume addition of heat process.
  • The low speed engines does it manage to approximate the constant pressure process.
  • The high speed engine diagram, on the other hand, tends toward the SI engine diagram with its much more pointed peak.

2. Dissociation:

Dissociation apparently exists in the CI engine combustion process, but does not show as pronounced an affect as it does in the Si engine. This is due to the heterogeneous mixture existing in the combustion chamber, as well as the excess air present. Both of these factors, apparently, tend to reduce dissociation by lowering the overall temperature of the combustion gases.

3. Blow-down process:

The four-stroke cycle CI engine has blow-down losses which are similar to those of the SI engine. The two stroke cycle engine, however, exhibits an appreciably greater loss than the comparable four-stroke cycle engine.

4. Pumping loss:

  • The pumping loss in a four-stroke cycle CI engine doesn’t exist, but it is rather small, because the air flow is not throttled for part.
  • Load operation.
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