Engine Dissection Report - Spring 1999

 

The engine dissection report should be a professional document. You must use a word processor. Your report may contain graphs, tables, drawings, and equations which will clarify the text. Be sure to reference all ideas, equations, figures or quotes that you take from other sources. Note that this is a group assignment.

 

The general goal of this report is to convey to the reader (1) a general idea of how the engine operates, (2) a detailed account of your observations on the design features of a particular aspect of engine operation, and (3) the results of some engineering calculations that predict the performance of the engine.

 

1.0 Introduction

  • This section briefly lays out the exercise to be performed. After reading this section, the reader should know in broad terms what you did, and your goal in doing this. (For example, you tore apart and rebuilt a small engine to understand how the design details support the overall operation of the engine.)

    • 2.0 Procedure

  • This should be an overview of what you did, not a blow-by-blow description of each nut and bolt extracted. For example, this might describe the order of disassembly, the order of reassembly, and how you ran the engine. You should include anything noteworthy, such as points where the suggested procedure list was in error or inadequate, and details that were not in the list that you felt the reader should know about. In other words, you are writing a road map that somebody can follow to repeat what you did.

    • 3.0 Description of Specific Design Features

  • This section should describe how the details of the design provide support for the overall operation of the engine. Remember that everything you see in the engine was put there for a purpose! Use the notes you generated in your journal to describe the intent of the designer behind each of the features.

    • A. Air/Fuel Subsystem

  • How are the air and fuel mixed and moved into the combustion chamber at the right time? What becomes of the products?
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    B. Mechanical Drive Train

  • How does the burning air/fuel mixture cause a reasonably smooth motion of the output shaft that can be used for powering a lawn mower or snow blower?
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    C. Lubrication Subsystem

  • How are the parts that contact each other, and are in motion with respect to each other, kept from wearing away?
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    D. Cooling Subsystem

  • What keeps the engine from becoming so hot that it destroys itself?
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    E. Ignition Subsystem

  • How is the fuel/air mixture ignited, and how is this made to occur at exactly the right time?
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    F. Start/Stop

  • How do we get the engine running, and how do we stop it?

    • 4.0 Engine Performance Estimation

  • Using the procedure discussed in class and the measurements made on the engine, make a plot of distance from bottom dead center (x-axis) vs. force on the piston (y-axis) for the compression stroke. Assume the valves are both closed at bottom dead center and the initial pressure is atmospheric. Estimate the work required to do the compression. (Note that work equals force times distance, but since the force varies, you will need to break up calculation into small slices as described in class.)

    Use the temperature and pressure in the cylinder after the combustion has occurred (given in class) to estimate the work generated during the power stroke. Then use an engine speed of 2000 RPM to estimate the power output (in Horsepower) for your engine. Note that you get only one compression and power stroke pair for each two engine cycles. The other cycle involves moving the exhaust out of the cylinder and pulling the fresh fuel/air charge in.

    Finally, for this same condition, estimate the air flow required by the engine in cubic feet/minute.

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    5.0 Conclusion

  • Bring out the major points you feel are worth emphasis. Make any recommendations you feel are appropriate.
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    Appendix

  • Answers to all questions raised in the dissection instructions above. This portion of the report may be handwritten, and may include hand drawings where they are helpful.
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    Report Grading:

    1. Quality of written English - 10 points

    2. Introduction content - 5

    3. Procedure content - 10

    4. Description of specific design features - 30

    5. Engine performance calculation - description of procedure - 10

    6. Engine performance calculation - results - 10

    7. Conclusion content - 5

    8. Appropriate appendix content - 15

    9. General appearance of report - 5

    Total - 100