MARINESHELF publishes articles contributed by seafarers and other marine related sites solely for the benefit of seafarers .All copyright materials are owned by its respective authors or publishers.
In order to optimise the exhaust valve operation over the normal load
range, the closing point of the exhaust valve is changed over 70-85% x MCR.
During VEC operation the exhaust valve is closed EARLIER which means that
the compression stroke of the piston is increased. This will lead to higher
compression pressures and temperatures.
For instance if the normal closage of the exhaust valve is 130o
BTDC, and this gives a compression ratio of 10.6, then by closing the valve 10o
earlier, the compression ratio will increase to 11.2, and the compression
pressure will rise by 4 bar, for the same scavenge air/load setting.
The unit achieves this by leaking some of the oil contained in the high
pressure pipe when the valve is in the OPEN position. This will cause
the valve to slightly close, but will mean that the exhaust valve will be fully
closed EARLIER than normal. Hence the piston can start to pressurise the
cylinder contents earlier. The amount the valve closes is dependant on the
position of the VEC shaft and eccentric mounted on the side of the exhaust
valve actuator.
9 comments:
Nice to read your post about Variable Exhaust Valve Closing(VEC). I like all information you had posted because it is too informative and understood to all.
You have explained Variable Exhaust Valve Closing(VEC)in a very easy way, i think it won't be difficult to understand by anyone.
Too appreciative and informative post. I have gained too useful information through your post.
I have gained very good information with this piece of information.
Every-time when I read your post, I found that here you had shared too useful information that is so fabulous.
exhaust valves
It is very nice post having too interesting post.
This is too informative and wonderful post having great contents.
It is a very helpful information. Also can you please share with us the provision provided to leak off some oil pressure that is required for VEC. Is it the attained by altering the throttle valve setting which is provided to ensure a virtual tappet for hydraulic exhaust valves?
Is compression ratio can vary for particular engine????????
Post a Comment