，题目是《Technical Principles of Vehicle Engines Using Natural Gas》
Technical Principles of Vehicle Engines Using Natural Gas
Natural gas has been a popular choice for powering vehicles due to its environmental and cost benefits compared to traditional gasoline and diesel fuels. Natural gas is composed mainly of methane with some additional hydrocarbons, and when combusted creates fewer harmful emissions than other fossil fuels. Natural gas powered vehicles are often used for municipal and public transportation fleets, such as school buses, where the cost and emissions benefits can be most pronounced.
Natural gas vehicles use a type of internal combustion engine known as a spark-ignited (SI) engine. The SI engine is similar to the internal combustion engines found in other motor vehicles, but is specialized to efficiently combust natural gas fuel. In the SI engine, igniting a mixture of air and natural gas leads to a spark combustion, allowing for efficient combustion of the fuel and a larger power output from a smaller engine.
The proper functioning of an SI engine is dependent on a tight control of the engine’s operational parameters, such as the combustion timing and fuel injection, to ensure efficient combustion and performance. This is normally achieved through the application of an electronic management system that constantly adjusts these parameters to maintain the target engine performance.
The QC/T 691-2002 standard is the most commonly used standard for the evaluation and certification of vehicle engines using natural gas. The standard establishes the performance requirements for SI engines, as well as the methodologies for testing and certifying compliance. The requirements of the standard cover topics such as engine powers, torque, emissions, and efficiency, and include a variety of test procedures to ensure that engines with different designs and power ratings meet the required performance levels.
In order to obtain certification, SI engines must pass a variety of tests, including cold-start, idle-speed, EGR, MVRA and exhaust smoke tests. The certification process also requires engine components such as injectors, valves and pumps to be tested for quality and performance. By ensuring the compliance of all components, the QC/T 691-2002 standard provides assurance that vehicle engines using natural gas are safe and efficient.
It is important for vehicle owners and operators to understand the technical principles and performance requirements established in the QC/T 691-2002 standard to ensure that their vehicles are operating in accordance with the standard. A proper understanding of this performance standard is critical to ensuring that natural gas powered vehicles reach their full potential in terms of environmental and cost effectiveness.
By meeting the requirements established by the QC/T 691-2002 standard, vehicle owners and operators can ensure that their vehicles are operating safely, efficiently and optimally using natural gas fuel. Proper application and maintenance of these standards are essential for successful implementation of natural gas powered vehicles.
