Specific air consumption equation?

In summary, the specific air consumption equation for a diesel engine is the weight of air required to combust one pound of fuel, which is typically around 14.5 pounds of air per pound of fuel. This is a pure ratio, and is unrelated to atmospheric pressure or fuel consumption in pounds per horsepower hour. The more common units now are kg / kW.hr. A diesel engine typically takes in more air than is needed for combustion, with the excess being used for compression ignition and complete fuel combustion.
  • #1
Webbd050
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what is the specific air consumption equation for a diesel engine?
 
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  • #2
I believe it used to be specified as the weight of air required to combust one pound of fuel. The figure will depend on the fuel grade, if I remember correctly it is usually about 14.5 pounds of air per pound of fuel.

The value of 14.5 is actually a pure ratio, but the “pound” is often still referenced.
This is quite unrelated to the atmospheric pressure at sea level measured in psi.

Fuel consumption was often specified in pounds per horsepower hour. Now the more common units are kg / kW.hr

A diesel engine usually takes in more air than is needed to burn the injected fuel. Only the air needed for stoichiometric combustion is counted for the specific air consumption, the excess is used to achieve the required compression ignition temperature when idling, and to guarantee complete fuel combustion.
 

FAQ: Specific air consumption equation?

What is the specific air consumption equation?

The specific air consumption equation is a mathematical formula used to calculate the amount of air consumed by an engine or machinery per unit of power output. It is typically expressed as a ratio of air consumption (in pounds or kilograms per hour) to shaft horsepower.

Why is the specific air consumption equation important?

The specific air consumption equation is important because it helps engineers and scientists understand the efficiency of an engine or machinery. It can also be used to compare the performance of different engines or to identify potential improvements in efficiency.

How is the specific air consumption equation calculated?

The specific air consumption equation is calculated by dividing the mass flow rate of air (in pounds or kilograms per hour) by the power output of the engine or machinery (in horsepower). The resulting value is then converted to a standard unit of measurement, such as pounds per horsepower-hour or kilograms per kilowatt-hour.

What factors affect the specific air consumption equation?

The specific air consumption equation is affected by several factors, including the type of engine or machinery, the air intake system, the fuel type and quality, and the operating conditions (such as altitude and ambient temperature). These factors can impact the amount of air required for combustion and the resulting power output.

How can the specific air consumption equation be used in practical applications?

The specific air consumption equation can be used in various practical applications, such as designing and optimizing engines, determining fuel efficiency, and identifying potential issues or improvements in machinery performance. It can also be used in industries such as aviation, where fuel consumption is a significant factor in aircraft design and operation.

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