MAN Diesel & Turbo show new 4T50ME-GI LPG dual fuel research engine.

By Keith Henderson at May 11, 2011 23:09
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Earlier this year, MAN Diesel & Turbo announced its plans for a program of ME-GI testing during 2011 at the company’s Diesel Research Centre in Copenhagen Denmark.

To enable the full-scale demonstration and performance verification tests of the GI principle for all kinds of marine applications, the 4T50ME-X R&D research engine has been rebuilt as a 4T50ME-GI specification engine. After this rebuild it will be able to carry out ME-GI dual fuel testing on LPG (Liquid Petroleum Gas) and HDO.fuels. The newly rebuilt 4T50ME-GI engine was revealed this week to an invited group of guests from the shipping and propulsion business sector.

Market research indicates that, in future, gas applications may be installed not only on LNG carriers, but also on LPG, RoRo, and container vessels, i.e. in principle all types of vessels.

The special parts to operate on LPG are: a ventilation system for venting the space between the inner and outer pipes of the double-wall piping. A sealing oil system, delivering sealing oil to the gas valves separating control oil and gas and an inert gas system to enable purging of the LPG system on the engine with inert gas.

Operation on dual fuel requires the injection of both pilot fuel and gas fuel into the combustion chamber. The pilot oil valve is a standard ME fuel oil valve without any changes, except for the nozzle. A common rail (constant pressure) gas supply system is fitted for high pressure gas distribution to each valve

Since the density of LPG fuel is higher than the density of Natural Gas, the GI/LPG components can be designed much smaller, although LPG needs to be pressurized to the higher pressure of 8,000 psi (550 bar) instead of 3,600-4,300 psi (250-300 bar) for Natural Gas. This pressure is  necessary to achieve a full atomisation of the liquid in the injector nozzles. In comparison, HFO, which  has a slightly higher density, requires an injection pressure of 8,700-11,600 psi (600-800 bar). The temperature of the engine has to be controlled at the required temperature of approx 95 degF (35 degC).

According to MAN Diesel & Turbo estimates, the additional cost of including a gas supply system and the additional GI components on the  engine, would increase the engine price by around 20 to 30 per cent. Against this increased capital cost is the through life saving on fuel costs depending on the propane/butane prices which can fluctuate greatly depending on economic, political and climatic factors.

Comparison of emission levels shows that there are benefits in the full range when using LPG as fuel: a 17 per cent reduction in CO2, 12 per cent reduction in NOx,, a 92 per cent reduction in SOx and a 37 per cent reduction in particulates.

Caption: Emission comparison between HFO burning K50MC-C and LPG burning S50ME-GI.
Source: MAN Diesel & Turbo SE.


Caption: Graphical rendering of a MAN B&W 6S70ME-GI engine with gas components shown in blue.
Image credit: MAN Diesel & Turbo SE.

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