Spark-ignition engine

Definition

A spark-ignition engine is a type of internal combustion engine that uses an electric spark to ignite a mixture of fuel and air for combustion. This engine operates on the principle of the Otto cycle, where the combustion process occurs at a relatively lower compression ratio compared to diesel engines. Spark-ignition engines are commonly found in gasoline-powered vehicles and are known for their efficiency and responsiveness, making them a popular choice in the automotive industry.

5 Must Know Facts For Your Next Test

1. Spark-ignition engines typically use gasoline as fuel, which has a higher volatility compared to diesel fuel.
2. These engines generally operate at lower compression ratios than diesel engines, usually ranging from 8:1 to 12:1.
3. Spark-ignition engines can be classified into various types such as port fuel injection, direct injection, and dual-fuel systems.
4. The ignition timing in spark-ignition engines is crucial for optimal performance and is often adjusted based on engine load and speed.
5. Emissions from spark-ignition engines can include hydrocarbons, carbon monoxide, and nitrogen oxides, which are regulated by environmental standards.

Review Questions

• How does the Otto cycle define the operation of a spark-ignition engine?
  • The Otto cycle is fundamental to the operation of a spark-ignition engine as it outlines the four-stroke process involved in converting fuel into mechanical energy. It includes intake, compression, power, and exhaust strokes, with the spark plug playing a key role by igniting the fuel-air mixture during the power stroke. This cycle allows for efficient energy conversion, which is essential for vehicle performance.
• What are the environmental impacts associated with spark-ignition engines, and how can they be mitigated?
  • Spark-ignition engines produce various emissions that can harm the environment, including hydrocarbons, carbon monoxide, and nitrogen oxides. To mitigate these impacts, technologies such as catalytic converters, improved fuel formulations, and advancements in engine design can be employed. Additionally, transitioning to alternative fuels or hybrid systems can significantly reduce harmful emissions while maintaining performance.
• Evaluate the advantages and disadvantages of spark-ignition engines compared to diesel engines in automotive applications.
  • Spark-ignition engines have several advantages over diesel engines, including lighter weight, quieter operation, and quicker throttle response. They are also typically less expensive to manufacture and maintain. However, they operate at lower thermal efficiency and have higher emissions of certain pollutants. Diesel engines offer better fuel economy and torque characteristics but come with higher initial costs and noise levels. Understanding these trade-offs helps manufacturers optimize vehicle performance for specific applications.

Related terms

Otto cycle: A thermodynamic cycle that describes the functioning of a spark-ignition engine, consisting of two adiabatic processes and two isochoric processes.

Fuel-air mixture: The combination of fuel and air that is mixed together and compressed before ignition in a spark-ignition engine.

Compression ratio: The ratio of the maximum cylinder volume to the minimum cylinder volume, influencing the efficiency and power output of an internal combustion engine.