Dual-fuel genset is generation equipment that can either use a mixture of diesel fuel and natural gas as fuel or just use diesel fuel in the absence of natural gas. Fuel gas and diesel fuel are the two main fuels. Mixed fuel (15% -25% diesel, 85% – 75% natural gas or biogas) is used for generation under normal operating conditions. In the absence of fuel gas, diesel fuel may be used alone. The difference from full natural gas fueled genset is that, no spark plug is required for ignition during combustion. It makes use of the pressure explosion principle of diesel to ignite the fuel gas. Therefore, it not only has the excellent reliability of diesel genset, but also features the economic and environmental characteristics of natural gas and biogas gensets. The main characteristics of dual-fuel gensets are:
- Fully electronic control
- Output power not reduced
- Same load response capacity
- Optimized ratio of gas and diesel in any case
- Low emissions
- May well operate with diesel fuel alone
Aosif’s dual-fuel system has added a gas mixer both air filters of the engine. The gas mixer is mainly used for mixing air and fuel gas, after which the gas mixture is turbocharged and intercooled before transferred to the diesel engine. The design requires little alteration to the diesel engine body structure to complete the transformation into a dual-fuel system. System diagram is as follows.
When dual-fuel genset is started, the gas valve must be closed. Start the genset by the diesel engine starting method. Carry load after starting, turn the engine throttle to the right position (usually at the position slightly below the middle), and then slowly open the gas valve to supply gas after the genset is operating normally. After gas supply is connected, the fuel supply will be reduced automatically under the action of governor until genset has reached a steady speed. If too much gas is supplied, supply interruption will occur instantaneously, making an intermittent working sound. In such cases, supply from the gas valve should be reduced until normal operation is resumed. The speed adjustment method is same with that before modification, i.e., by changing the position of speed governing lever. To stop the machine, first close the gas valve and then close the throttle.