Methanol Fueled Marine Diesel Engine

About Methanol Fueled Marine Diesel Engine :- :- 

Nowadays concerns about methanol have increased from the viewpoints of environmental protection and versatility of fuels at a global scale. Energetic research on methanol-fueled automobile engines has been forwarded from the viewpoints of low environmental pollution and the use of alternate fuel since the oil crisis, and they are now being tested on vehicles in various countries in the world. Desire for saving of maintenance cost and labour prevails as well as the environmental problems in the field of marine engines. From these motives scientists have carried out research and development of a methanol fueled marine diesel engine which is quite different from automobile engines in the size, main particulars, working condition and durability. Although scientists have made a great use of invaluable knowledge from automotive technology, some special studies were necessary due to these differences.  Ignition method is a typical one. Dual fuel injection system was tried for trouble-free ignition of methanol fuel.  This system is thought to be the most favourable ignition method for marine diesel engines which have to withstand quick load change and accept no misfiring. 

Influence Of Pilot Oil Injection Nozzle

The effect of the pilot oil injection nozzle has been confirmed by changing the number and diameter of nozzle holes and the direction of injection in the range. As a result, the one-hole nozzle is the best in terms of fuel consumption, the stability of cylinder pressure and the reduction in the quantity of pilot oil. 

However, the difference in performance among various types of nozzles is not remarkable. As mentioned later, when priority is given to the issues of startability, accelerating ability and sudden load change like the engagement of a clutch, or to the problem when the pilot oil injection nozzle holes have been closed, it can be said that the three-hole nozzle is the best and the largest possible nozzle hole diameter is desirable. Though the influence of the direction of the pilot oil injection nozzle in relation to the main fuel injection nozzle has also been confirmed, no improvement has been found. It is conjectured that the reasons for the above are that swirls in the combustion chamber of the experimental engine are not strong and the quantity of pilot oil is enough.

Influence of the Quantity of pilot Oil

It can be seen from this figure that the lowest points of specific fuel consumption differ with the specifications of pilot oil injection valves. That is, the percentage of pilot oil in total consumed fuel for the lowest point of specific fuel consumption is between 11 and 12% for the one-hole nozzle and that is near 15% for the three-hole nozzle. Thus, the lowest point shifts toward the larger percentage of pilot oil. Though the quantity of pilot oil can be decreased down to about 4% by making the pilot oil injection nozzle area smaller, proper quantity is considered to be 12-15% in practice, since the startability of an engine must be considered as mentioned later. Smoke density and NOx have also been measured during these tests. Though detailed results will be explained later, the results can be summarized as follows. Compared with a diesel engine being operated on gas oil, the smoke density is lower by one order by Bosch scale and NOx is about half under the same load condition. Thus, exhaust gas characteristics have been confirmed to be superior. 

Test Method

The stable combustion of dual fuel engines under normal operation can be ensured by pilot oil of several percent of total fuel which is injected under full load condition. However, a considerably large quantity of fuel is needed when starting engines, since accelerating torque is necessary in addition to normal running torque. For this reason, starting tests have been carried out under the following conditions. 

a) Constant quantity of methanol (full load) and varying quantity of pilot oil

b) Constant quantity of pilot oil and varying quantity of methanol

c) Operation on only pilot oil 

d) Starting on pilot oil and injection of methanol after that 

Conclusion

Tests have been carried out under static and dynamic conditions in order to grasp engine performance when methanol is applied to marine diesel engines. As a result, it has turned out that the performance of a methano1/oil burning engine can be improved near to the performance level of an oil burning engine by 

1. Optimizing the fuel injection system and the combustion chamber geometry

2. Adapting the fuel regulating system and the intake air system of the former.