The Process of Combustion in Engines

P M V SubbaraoProfessor

Mechanical Engineering Department

Creation of Right Environment for Digestion of

Diet …...

Events in Combustion Processes

• Pre-processing of fuel an air.

• The initiation & stabilization of reaction.

• Execution and completion of the reactions.

• Post reaction events.

Pre-processing of fuel & Air

Pre mixing of fuel and air No Pre mixing of fuel and air

Partial Pre mixing of fuel and air

Status of Fuel & Air Before Onset of Combustion

Care for Occurrence of Combustion

• Occurrence of combustion in SI Engine : A Child Care Event.

• Occurrence of combustion in CI Engine: A Teen Care Event.

CI Engine SI Engine

Type of Fuel Vs Combustion Strategy

• Highly volatile with High self Ignition Temperature: Spark Ignition. Ignition after thorough mixing of air and fuel.

• Less Volatile with low self Ignition Temperature: Compression Ignition , Almost simultaneous mixing & Ignition.

Types of Digestion of Diet

• Artificial Perturbation of fuel-air Mixture.

– All pre-process should be completed before perturbation.

– Digestion succeeds all the preprocess.

– Pre-mixed digestion/combustion.

• Natural Perturbation of fuel-air Mixture.

– A degree of pre-processing initiates the perturbation.

– However, pre-processes are accelerated during perturbation.

– Pre-process continue till the end of digestion.

– Simultaneous/Diffusive digestion/combustion.

What is the impact of combustion strategy on cycle area?

What needs to be studied to judge the suitability of a given strategy???

Gross Thermal Energy release in an Engine

• m number of reactants convert into n number of products, in order to release the required heat in an engine cycle.

• True available air will influence the number and quantity of products.

• The fraction of fuel chemical energy available to the cycle from actual combustion is quantified using combustion efficiency.

• The Gross chemical energy release due to actual combustion with in the engine is:

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