Exam Question

### (a) Requirement for Pilot Injection in Dual-Fuel Engines
Pilot injection is fundamentally required in a dual-fuel engine operating on natural gas due to the significant difference in auto-ignition properties between natural gas and diesel oil. The necessity can be broken down into the following key points based on chemical and physical principles:
1. **High Auto-Ignition Temperature of Natural Gas**: Natural gas, which is predominantly methane (CH4), has a very high auto-ignition temperature, approximately 580°C. This is the temperature at which it will spontaneously ignite without an external ignition source.
2. **Low Auto-Ignition Temperature of Diesel Fuel**: In contrast, marine diesel oil has a much lower auto-ignition temperature, typically in the range of 200°C to 300°C.