Otto Cycle Design

Design Constraints:

Based on the ideal Otto cycle, a single cylinder, spark ignition, four stroke engine is to be designed. The engine should run at 3600 rpm and produce 18 horsepower. The intake air conditions are as follows: The temperature of the air is a 77°F, the pressure is 1 atmosphere, and the relative humidity is 71%. The heat loss to the surroundings from combustion is assumed to be 22% of the total potential energy released. The bore and the stroke is assumed to be the same size. Also, a compression ratio of at least 8.5:1 is required. The engine is to run on natural gas.

The composition of the natural gas analyzed is:

Natural Gas Composition |

Component: | Percent by Volume: |

CH4 | 81.0 |

C2H6 | 5.4 |

C3H8 | 4.8 |

C4H10 | 3.4 |

N2 | 5.4 |

Natural Gas as a Fuel:

Natural gas has many uses, one of them being engine fuel. Natural gas is one of the only alternative fuels to oil that can be used to power large transportation vehicles.

Benefits:

There are some benefits to using natural gas as an engine fuel. Natural gas burns approximately 65 percent cleaner than coal and 25 percent cleaner than oil per kilowatt hour. Comparing natural gas to diesel fuel: Natural gas emits 99% less sulfur dioxide, 80% less carbon monoxide, and 25% less carbon dioxide. Another benefit to using natural gas as a fuel is cost. On an energy-equivalent basis, abundant supplies of natural gas are available at less than half the price of a barrel of oil and when used for transportation purposes, natural gas is approximately 20 to 30 percent more affordable than gasoline and diesel. There is also enough domestic natural gas to last 100 years.

Drawbacks:

Natural gas is colorless, odorless, tasteless, and extremely flammable. Detecting a leak of natural gas can be extremely difficult making natural gas dangerous. Natural gas contains carbon monoxide which is deadly if inhaled; it is amongst the top of the list for carbon monoxide related deaths....