Difference between revisions of "Engineering Analysis -(Group 10)"

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Determine the thermal efficiency of the 4 stroke engine in design.
Determine the thermal efficiency of the 4 stroke engine in design.
*Volume in combustion chamber with piston at highest point
*Volume in combustion chamber with piston at lowest point
*Temperature inside combustion chamber

Revision as of 15:42, 16 November 2012

Gate 3 - Product Analysis (Group 10)

Engineering Analysis

The most important part of the snow blower would have to be the engine since this is what powers both the linear drive and auger drive. Therefore, it would be crucial to determine the thermal efficiency of the engine during the design/testing stages of the design process. By determining the maximum potential efficiency of the engine in design, designers are able to gauge whether the engine performance is acceptable and make adjustments accordingly. Below is an example of what how the engineering analysis applied to this task may look like.

Problem Statement

Determine the thermal efficiency of the 4 stroke engine in design.

Given diagram.png


  • Any energy lost to friction is negligible
  • Engine is based on Otto cycle (ideal case for 4 stroke engine)
  • Air acts as an ideal gas
  • Only fuel/air present in the fuel/air mixture used for combustion
  • No unintended heat transfer
  • Value of k is based on the temperature in the combustion chamber according to predetermined table values for k

Governing Equations



  • Given the values of the maximum and minimum volumes in the combustion chamber, plugging in those values into the compression ratio, r ,will provide the compression ratio for the engine.
  • Plugging in the values of r and k into the thermal efficiency equation for an Otto cycle will provide the ideal efficiency of this engine.

Solution Check

  • Check to see if units were carried throughout (maximum and minimum volumes were measured in same units).
  • Check to see if efficiency is reasonable (an abnormally high efficiency would be unreasonable for an engine such as this)


  • The efficiency calculated through this analysis would be an ideal efficiency. This means that basically what is being determined is the efficiency based solely on the compression ratio and temperature inside the combustion chamber.
  • In order to get a more accurate estimation of engine efficiency important factors that were left negligible such as unintended heat loss and energy lost due to friction would need to be accounted for.
  • In order for these values to be accounted for, a functioning model of the engine would need to be created and thus a more accurate efficiency can be determined.
  • This more accurate efficiency would help designers even further to determine what changes need to be made to improve efficiency of the engine.