Analysis of Turbo Combustor

P M V Subbarao

Professor

Mechanical Engineering Department

A Device to Anchor the Flame….The Cause of Major component of Running Cost…..

Reciprocating Engine Vs Jet Engine

Fire is An Accident…

How to make it More reliable Resource….

Laws of Combustion

• A Special Device is required to hold the flame, called Burner.

• The maximum quantity of fuel that can be handled by a single burner is limited.

• The maximum allowable air to establish efficient combustion of a given amount of fuel is limited.

• The maximum temperature due to efficient combustion is always higher than the maximum safe temperature: limited by turbine blades.

• Infra structure should be provided to facilitate these conditions.

Requirements of A Reliable Combustion

MATt Theory

• Mixing: Fuel preparation systems.

• Air: Draught systems.

• T : Preheating of fuel.

• t : Dimensions of combustion chamber. : Turbulence generation systems.

Combustion Section• The combustion section contains the combustion

chambers, igniter plugs, and fuel nozzle or fuel injectors.

• Designed to burn a fuel-air mixture and to deliver combusted gases to the turbine at a temperature not exceeding the allowable limit at the turbine inlet.

• Theoretically, the compressor delivers 100 percent of its air by volume to the combustion chamber.

• The fuel-air mixture suitable for efficient combustion has a ratio of l5 parts air to 1 part fuel by weight.

Combustion Section Contd…….

• Approximately 25 – 30 percent of total compressor air is used to attain the desired fuel-air ratio.

• The remaining 70 -- 75 percent is used to form an air blanket around the burning gases and to dilute the temperature.

• The diluted temperature may reach as high as 1500º C, by approximately one-half of the flame temperature.

• This ensures that the turbine section will not be destroyed by excessive heat.

Air Distribution in A Combustor

Compressor end Turbine end

Functions• The air used for burning is known as primary air; • Remaining for cording is secondary air. • Secondary air is controlled and directed by holes and

louvers in the combustion chamber liner. • Igniter plugs function during starting only; they are shut

off manually or automatically. • Combustion is continuous and self-supporting. • After engine shutdown or failure to start, a pressure -

actuated valve automatically drains any remaining unburned fuel from the combustion chamber.

• The primary function of the combustion section is, of course, to bum the fuel-air mixture, thereby adding heat energy to the air.

• To do this efficiently, the combustion chamber must

• Provide the means for mixing the fuel and air to ensure good combustion.

• Bum this mixture efficiently.

• Cool the hot combustion products to a temperature which the turbine blades can withstand under operating conditions.

• Deliver the hot gases to the turbine section.

• The location of the combustion section is directly between the compressor and turbine sections.

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• The combustion chambers are always arranged coaxially with the compressor and turbine, regardless of type, since the chambers must be in a through-flow position to function efficiently.

• All combustion chambers contain the same basic elements:

• A casing • A perforated inner liner. • A fuel injection system. • Some means for initial ignition. • A fuel drainage system to drain off unburned fuel

after engine shutdown.

Basic Anatomy of A Combustor

Casing

LinerSwirler

Liner holes

Classification of Combustors

• Basis for this classification:• A burner handles finite amount of fuel.• Arrangement of multiple burners.• There are currently three basic types of Burner

Arrangements• The multiple-chamber or can type. • The annular or basket type. • The can-annular type.