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DUAL FUEL ENGINE

PRE-MIXED LOW-PRESSURE GAS INJECTION:

Advantages:

1. Low-pressure gas supply means low investment costs and low power consumption
2. Pilot fuel quantity below 1% of total heat release
3. DF engine can be operated on gas from idle
4. Low NOX emissions, Tier III compliant in ECAs without after treatment
5. Particulate matter emissions reduced to almost zero.
6. The amount of pilot fuel required for low pressure engines is much lower compared to high pressure engines which need more pilot fuel, especially in part load.
7. Due to a universal low pressure (< 10bar) gas supply system from the bunker to the injectors, the risk mitigation and safety requirements are achieved with less complex equipment, less capital expenditure and results in the lowest operational expenditure
8. the fuel gas handling and safety system need to be designed either for a low pressure (<10 bar) or a high pressure (up to 300 bar) system which leads to significant differences in space and safety requirements. Higher CAPEX and OPEX for the high-pressure system are to be expected.
9. Gas operation from idle to 100&load has no limitation.

Disadvantages:

1. The low pressure DF engine in back-up mode is less efficient than the high pressure DF engine. Because the engine is designed to be a gas engine and is optimised in the Otto cycle
2. low pressure DF engines have lower maximum output compared to that of high pressure DF engines of same size
3. KNOCKING
4. Methane slip which is more dangerous than co2.
5. Methane number is specific for the fuel.

H.P GAS INJECTION DUAL FUEL ENGINE:

Advantages:

1. IN PART LOAD H.P IS BETTER EFFICIENCY.
2. LESS METHANE SLIP.
3. Higher efficiency than l.p
4. Knocking is not there.

Disadvantages:

1. NO SIGNIFICANT NOX REDUCTION.
2. REQUIRE SCR OR ECR IN ORDER TO MEET IMO TIER 3 LEVEL.
3. The “high pressure DF engine” is a Diesel cycle engine and the amount of pilot fuel required is substantially higher. Under manoeuvring and idling speeds (15%-20% and below) the amount of pilot fuel may need to provide 100% of the energy required and consequently delivers the same emission as any other diesel engine.
4. USE COMPRESSOR OR CRYOGENIC PUMP.
5. High cost of installation and maintenance.