2 stroke thread (with occasional F1 relevance!)

[Tommy Cookers]

the crosshead diesel is an accident of history
steam recips (designed of course by shipbuilders) had double acting cylinders and so were crosshead designs
these people then went diesel double acting and so crosshead
then single acting but kept the crosshead

the huge cylinder size gives relatively less surface area and so less heat loss to coolant - so raises efficiency
all been said before of course

[PlatinumZealot]

A cross-head design means blow by . . .

You mean "reduced blow by"?

Yes!.. reduced.. typing from my phone

[PlatinumZealot]

A cross-head design means blow by . . .

You mean "reduced blow by"?

Yes!.. reduced.next to none. typing from my phone

[PlatinumZealot]

A cross-head design means blow by . . .

You mean "reduced blow by"?

Blow-by designed in, may be what he means. The piston doesn't need rings nor touch the cylinder wall. The volume beneath the cylinder can be used as a pump as a sort of forced induction. Blow-by would manifest as a sort of EGR, while being oil-free. The piston rod is what gets sealed from the crankcase, and also acts as the piston guide.

The pistons have monster sized rings! The rings look about 15mm thick. You still need rings to seal like a normal engine. There is a second type of oil called cylinder oil that is injected onto the rings to keep friction low and help the seal. The cylinder oil is burned off continuously and is extremely expensive. The mass flow rate is low so that helps keeps costs down.

The scavenge space is just like a plenum. The turbos blow into their from the air coolers and from there into the cylinders through the ports. There is no EGR. As the piston comes down to the port the boost pressure blows out the exhaust. It's important to keep the liners cool but not too cold... like 135 degrees celcius.

[Pinger]

There is a second type of oil called cylinder oil that is injected onto the rings to keep friction low and help the seal. The cylinder oil is burned off continuously and is extremely expensive. The mass flow rate is low so that helps keeps costs down.

Any more info on the oil? Manufacturer and exact name, viscosity grade, etc?

[gruntguru]

. . There is a second type of oil called cylinder oil that is injected onto the rings to keep friction low and help the seal. The cylinder oil is burned off continuously and is extremely expensive. The mass flow rate is low so that helps keeps costs down.

I hadn't heard of that oil being expensive. There are two main advantages to this system:
1. The rings are continuously supplied with new oil, without degraded detergency or solvency. This avoids buildup of carbon and varnish on the rings and bores. The consumption rate of this oil is no greater than if the cylinders were sharing the same oil as the crankcase.
2. The crankshaft assembly is lubricated by a separate system. The oil in this system is not being degraded continuously by exposure to high temperature and combustion gases, so it lasts much longer and can be designed for this more specialised task.

[gruntguru]

There is a second type of oil called cylinder oil that is injected onto the rings to keep friction low and help the seal. The cylinder oil is burned off continuously and is extremely expensive. The mass flow rate is low so that helps keeps costs down.

Any more info on the oil? Manufacturer and exact name, viscosity grade, etc?

You can Google "Marine Diesel Cylinder Oil".
Nothing fancy. This product from Castrol is SAE 50 with a high "Base Number" (TBN 70) to neutralise the acids formed by high sulphur fuels. https://msdspds.castrol.com/bpglis/Fusi ... ASW6UD.pdf

[PlatinumZealot]

. . There is a second type of oil called cylinder oil that is injected onto the rings to keep friction low and help the seal. The cylinder oil is burned off continuously and is extremely expensive. The mass flow rate is low so that helps keeps costs down.

I hadn't heard of that oil being expensive. There are two main advantages to this system:
1. The rings are continuously supplied with new oil, without degraded detergency or solvency. This avoids buildup of carbon and varnish on the rings and bores. The consumption rate of this oil is no greater than if the cylinders were sharing the same oil as the crankcase.
2. The crankshaft assembly is lubricated by a separate system. The oil in this system is not being degraded continuously by exposure to high temperature and combustion gases, so it lasts much longer and can be designed for this more specialised task.

The cylinder oil is very expensive in relative terms compared to the fuel oil and crank case (lube) oil.
Its formulation is of course very special to protect the liners and rings since in two stroke engines there is no "rest period" unlike four stroke engines as you know. Not to mention the engine runs on very agressive and "dirty" fuel like heavy fuel oil.

There is also a special timing mechanism to inject the cylinder oil. And the injection rate is adjusted based on conditions as well.

Very interesting engines - Slow speed diesel engines.. Really changed my view on two strokes. The form factor is very tall too so that might be a drawback on centre of gravity.. But then again the single exhaust valve is hydaulic.. So some weight savings up top. Lol.

[Tommy Cookers]

of course
this was the only type of CI engine that could correctly be called a diesel or Diesel
ie the heat is added at notionally constant pressure

does this still apply ie with this type of engine as currently or recently produced ?
the crosshead engine over a century having been both increased in displacement and confined to speeds below 100 rpm
(one can now run for at 10% power at 7 rpm - and with direct drive of the ship's propeller of course)
or confined in displacement and increased in rpm to the low hundreds

[PlatinumZealot]

There is a second type of oil called cylinder oil that is injected onto the rings to keep friction low and help the seal. The cylinder oil is burned off continuously and is extremely expensive. The mass flow rate is low so that helps keeps costs down.

Any more info on the oil? Manufacturer and exact name, viscosity grade, etc?

Chevron. Taro Special HT. Different grades available.

[PlatinumZealot]

of course
this was the only type of CI engine that could correctly be called a diesel or Diesel
ie the heat is added at notionally constant pressure

does this still apply ie with this type of engine as currently or recently produced ?
the crosshead engine over a century having been both increased in displacement and confined to speeds below 100 rpm
(one can now run for at 10% power at 7 rpm - and with direct drive of the ship's propeller of course)
or confined in displacement and increased in rpm to the low hundreds

The speed is just above 103 rpm to 125 rpm at full load for the slow speed engines ( power generation - I am not familiar with their use on ships, but ships require variable operating loads and speeds). You can hear each explosion when you stand beside the cylinders.

[gruntguru]

The cylinder oil is very expensive in relative terms compared to the fuel oil and crank case (lube) oil.

In other words cheap as manure compared to oil you put in your car.

[PlatinumZealot]

You typically burn 1kg per Megawatt hour of the cylinder oil.

So in F1 terms, over the race you would burn about a kilogram of this oil over two hours if the engine design requires a second oil only for clylinder lubrication.

[manolis]

BOEING / Gofly contest: Oh, BOEING


Hello all.

On Ausust 1, 2018 GoFly / Herox / BOEING (the big sponsor) deleted the Forum wherein the contestants of the GoFly / BOEING contest presented their opinions and their complaints.

GoFly’s / BOEING’s best response to contestants’ questions, was to shut down the annoying forum . . .

Each one of the contestants has paid 250 or 500 USD to GoFly / BOEING.
In return, all they took from GoFly / BOEING is the list with the ten winners.
No scoring, neither ranking, neither justification from the "97 judges"; just the ten winners alphabetically.


Take a look at http://www.pattakon.com/GoFly/index.html wherein some of the Open Forum Discussions have been “partially” saved and presented:

IS BOEING TRAPPED? : http://www.pattakon.com/GoFly/IS_BOEING_TRAPPED.html

20 minutes OR 20 miles? - Page 1 : http://www.pattakon.com/GoFly/20_minute ... miles.html

20 minutes OR 20 miles? - Page 2 : http://www.pattakon.com/GoFly/20_minute ... age_2.html

20 minutes OR 20 miles? - Page 3 : http://www.pattakon.com/GoFly/20_minute ... age_3.html

Note: the “20 minutes OR 20 miles” thread had in total 11 pages.

Design Discussion - Page 3 : http://www.pattakon.com/GoFly/Design_di ... 3Page.html

Design Discussion - Page 4 : http://www.pattakon.com/GoFly/Design_di ... Page4.html

Design Discussion - Page 5 : http://www.pattakon.com/GoFly/Design_di ... age_5.html

Debating Results of Phase I : http://www.pattakon.com/GoFly/Debating_ ... ase_I.html


The above discussions are indicative and show the appreciation, the trust and the confidence of the contestants for the GoFly / Herox / BOEING contest.


When you have time to spend, read the http://www.pattakon.com/GoFly/Posts_to_GoFly_Forum.htm and give your comments / questions.






Thanks
Manolis Pattakos

[PlatinumZealot]

The portable flyer looks like the best design. It doesnt look as far developed as the other designs though. Its only in 3D model stage it seems.