One small change solves the two-stroke engine's biggest problems

Lineslinger

Lineslinger

VIP MEMBER
Joined
Feb 26, 2017
Messages
1,927
Country flag
Progressive technology is always interesting to me...this is an interesting mod to a 2 cycle.

One small change solves the two-stroke engine's biggest problems

The defining characteristic of a two-stroke engine is to fire (combust) every time the piston is at top dead center. This makes them highly power dense, but also notoriously makes two-stroke engines dirty, inefficient, and not prone to long lifespans.
newatlas.com
 
One small change indeed! Rotary exhaust valves are great projects for inexperienced graduates to embark on but the reasons you don’t see them in general use everywhere are - sealing, cooling, wear, lubrication, poor combustion chamber shape - to name five. There is also the heavy and expensive supercharger that is needed. Do not confuse them with sleeve valves which , after much development work, have been used successfully in some aircraft engines.
As always, prove me wrong.
 
The inlet rotary (disc) valves were used by several manufacturers and do work well but they are just an alternative way of controlling the fresh charge flow into the crankcase. This thread is about a design bypassing the crankcase.
 
hybridracer said:
The inlet rotary (disc) valves were used by several manufacturers and do work well but they are just an alternative way of controlling the fresh charge flow into the crankcase. This thread is about a design bypassing the crankcase.
Click to expand...
The Rotax RV340 twin in 1975 was a potent race engine for Ski-Doo, who then went on to use them 25 years.
 
hybridracer said:
The inlet rotary (disc) valves were used by several manufacturers and do work well but they are just an alternative way of controlling the fresh charge flow into the crankcase. This thread is about a design bypassing the crankcase.
Click to expand...
That's what I get for breezing thru posts to get "caught up" after being offline for a couple of days.
 
grandpaul said:
That's what I get for breezing thru posts to get "caught up" after being offline for a couple of days.
Click to expand...
Sorry, I had just had a team’s meeting with Network Rail, (they are responsible for our national railway infrastructure), about our Heritage railway and was a bit tired.
 
hybridracer said:
Sorry, I had just had a team’s meeting with Network Rail, (they are responsible for our national railway infrastructure), about our Heritage railway and was a bit tired.
Click to expand...
The bypassing of the crankcase in the intake circuit (that small 2 stroke engines rely upon) by using a blower (here a forced variable induction) is usual for diesel 2 strokes (search Detroit Diesel or EMD on W.W.W.). And these have their own drawbacks. Not sure about rotary valves in the exhaust would effectively, on the long run, work as intended. I'm thinking of suit/sludge buildup at or around the valves, the necessity to have two sets of rings on the piston (one to limit the intake charge to go into the crankcase and the other one to seal the combustion chamber when on compression. The addition of seals to the blower rotor (s) is another concern with oil and air charge leaking through them. And I could go on on this system. Would it still need oil for combustion is another thing. This Otto engine does not lubricate the top of the cylinders/top piston rings. So if using gasoline (not mixed with oil) it will seize. And then, I can't see how it would work with an EGR system as it would probably clog after some (short) time when using a mixed fuel (oil + gas) if so use. Just my 2 cents.
Frank
 


Write your reply...
Back
Top