More than 140 MAN B&W gas engine orders have been confirmed since the first firm order was received in December 2012. Not only for natural gas (LNG), but also for methanol, ethanol, and liquid volatile organic compound (LVOC).
In combination with the general ongoing development of fuel equipment, this market situation has led to the introduction of a wide range of new fuel injection systems that did not exist before these gasified days. For example, our methane GI engine runs on 300 bar gas whereas the ethane version runs on 400 bar. Such a pressure increase means changes to the components.
However, the fuel injection equipment for heavy fuel has also seen new development, such as the top controlled exhaust valve (TCEV) and our fuel booster injection valve (FBIV). For the methanol version our FBIV has been further developed, as methanol operation requires cooling and sealing oil. The TCEV and FBIV combination means that the traditional hydraulic cylinder unit (HCU) can be omitted.
Besides the increasing focus on gas fuel engines, the focus on Tier III technologies has also increased. Exhaust gas recirculation (EGR) and selective catalytic reduction (SCR) optimised for low-sulphur fuel operation are now the standard and are based on continuous development and market feedback.
In combination with the general ongoing development of fuel equipment, the market situation has led to the introduction of a wide range of new fuel injection systems that did not exist before the introduction of gas. MAN Diesel & Turbo uses two different technologies for gas fuel injection. The distinction is made between liquefied gas and gaseous gas, concerning the form of the injected gas. We use the ME-GI technology for gaseous gas fuels and the ME-LGI technology for liquid gas fuels with a low flash point compared to diesel oil or heavy fuel oil.
FUEL BOOSTER INJECTION VALVE (FBIV):
To have a more flexible and fast responding fuel injection, the idea of having a fuel valve with direct control in terms of a control valve with on-board electronics and a feedback sensor has been investigated. This means that control takes place on the valve and does not need calculations by the engine computer system (design A). However, having each fuel valve equipped with an advanced closed-loop control valve with a feedback sensor is costly. Therefore, it has been decided to use a common control valve for the fuel valves, even though it is initiating a slower dynamic response compared to the directly mounted solution (design B); see Fig. 1.
Both solutions have been tested, and only a small difference is seen on the most dynamic demanding profile – double injection. However, the difference could not justify the cost premium of using a control valve on each fuel valve; see Fig. 2.
The ‘cycle-to-cycle’ variation has been measured during hundreds of revolutions at 25%, 50%, 75% and 100% load to test injection stability. Cylinder pressure variations increased with load, but never to more than the acceptable +/-5 bar on pmax. The variations in injection pressures and needle lift were very small; see Figs. 3 and 4.
The expected function of the chosen FBIV (design B) has been confirmed on several test engines. To confirm long-term reliability, an ongoing service test was initiated in February 2014. The FBIV is installed on one cylinder on an S50ME-B9.3 engine and has now reached 8,000 running hours without difficulties. An inspection of the components in the FBIV showed excellent condition.
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Source: Susanne Kindt, MAN Diesel & Turbo Ole Sørensen, MAN Diesel & Turbo
CIMAC Paper – 116.