[pschlik]

Traindude, on 26 January 2021 - 07:37 PM, said:

Sorry to bump this thread again, but I have another idea that may be worth implementing--variable main reservoir charging rates for diesels. On many diesels the air compressor was driven by the diesel engine, and consequently the rate at which the compressor pumps varies with prime mover speed. So if we add parameters ORTSMainResChargingRateAtIdle and ORTSMainResChargingRateAtMaxRPM, then we could potentially model this.

Yep! I would love to set this up as it feels pretty wrong completing an MR charging cycle in two seconds with the locomotive idle. However, rather than adding parameters for just idle and max rpm, I suggest implementing an (optional) CompressorSpeedTab inside the ORTSDieselEngines block or an ORTSCompressorSpeedCurves block, with the ability to enter a whole table of charging rates and RPMs, rather than just idle and max RPM. This would give extra flexibility and allow for more realistic modeling of cases where the compressor speed isn't strictly proportional to the engine speed, like GE locomotives, where compressor speed is minimized in idle, but maximized in notch 1. Simply having options for minimum and maximum RPM would be utterly incapable of replicating the GE configuration.




And as a side note, it would be nice if there was an option to set compressor speed as a volume rate, rather than a pressure rate. Real compressors are most often rated in the cubic feet of air they can displace per minute, but in Open Rails, this must be converted into psi per second or some equivalent. I would like to be able to just give the sim a number in ft^3/min and have it figure out what that should be in psi/s given the current locomotive's main reservoir volume...would save some effort doing those calculations myself.

[Weter]

Yes, but I thought, the IsAirCompressorElectricOrMechanical() parameter just points sim to that (electric=constant speed/mechanical=followed by diesel rpm)
But that param seen marked as not functioning somewhere short back...

It's very interesting, that GE has such kind of variator at compressor transmission-never heared that before. Thanks, psclik.

Our compressor's performance described at m^³/min, (6-7 usually) so I vote for "Yes" too.

Darwin, thanks for support.
Maybe, you are right and testing version inherits EP functions at distorted(unworking) conditions now...
But question about parameters needed is still open.

-Which equipment at WAG section and system type? Is distributor needed?
-Can be combination of Air SinglePipe and EP specified.
-What controller type at ENG section? And system type?
Remember, that 395 valves has both EPT and pure-auto(pneumatic) full service notches.

As soon as we have correct overcharge position now, I can rename "release" notch to "поездное" (running?) in translation.

[darwins]

Sorry, I did not fully understand the question.

For EP you should have distributor and auxiliary reservoir.

For Air Single Pipe you must have auxiliary reservoir - plus either distributor or graduated release triple valve or triple valve.

You can mix them in the same train.

EP will assume a twin pipe air brake system - OR does not yet have a model of the Russian single pipe EP system - possibly Cesar might have a suggestion for how to model that.

The 395 valve should work - the EP section should now be EP only without pneumatic.

The other sections should work for both.

[pschlik]

Weter, on 27 January 2021 - 08:27 AM, said:

It's very interesting, that GE has such kind of variator at compressor transmission-never heared that before. Thanks, psclik.

It is quite unique, I'll give GE that. The compressor is electrical, but as it is powered by an engine-driven alternator, the speed of the compressor still syncs up to the engine speed when activated. But that obviously has all the disadvantages of a shaft-driven compressor, so the engineers designing the things got clever and decided to wire the compressor so that it could run twice as fast as the engine when needed. As the engine speed is increased, the compressor returns to running in sync with the engine, allowing the compressor to always run at its most effective speed.

Of course, that behavior is pretty complicated, but a table of charging rate vs engine RPM is good enough to represent this behavior, as the compressor is still fundamentally connected to the engine, just in an atypical way.


And on a side note, EMD locomotives never bothered to go for an electric compressor. Their solution to make the compressor run faster when needed is to just automatically increase the RPM of the engine. A bit wasteful if you ask me! Of course, I don't expect this behavior to be modeled unless we can make custom engine control scripts. For now, putting the reverser in neutral and increasing the throttle manually is another way to achieve the same effect.

[cesarbl]

The changes in EP braking are available in testing versions.

Re the compressor charging rate, AirCompressorPowerRating expects a volume unit IIRC.

I have the intention of adding some parameters for main reservoirs, when I find time to do it.

[Weter]

Quote

putting the reverser in neutral and increasing the throttle manually is another way to achieve the same effect

So they do in shunters, having fourth notch of reverse handle, as mainline loco's main controller's handle is locked when reverse one is at neutral position.
That is used, as well for pumping-up long consists quicker during shunting ops.
In other cases, compressors linked with diesel by simple mechanical transmission and rotating continuously(so pneumo-system engaging their valves, when it's needed to pump MRs, and disengaging, when max working pressure reached) or rotating by electric motor, powered by auxiliary generator, in case of AC traction current system is present. Then it turned on/off by pneumo-electric sensor of MR pressure. Governor increasing diesel' rpm if power to compressor's motor supplied in insufficient quantity (at diesel's idle, for example)

Quote

I have the intention of adding some parameters for main reservoirs, when I find time to do it.

That's good news.

[Traindude]

Not sure whether this issue should be added to the steam discussion or the brake discussion, but I'd like to have the ability to specify the compressor steam usage, especially if the loco has multiple compressors in parallel. Using one steam usage rate for all compressors isn't realistic, and changing the compressor power rating doesn't make a difference.

[darwins]

Quote

Not sure whether this issue should be added to the steam discussion or the brake discussion, but I'd like to have the ability to specify the compressor steam usage, especially if the loco has multiple compressors in parallel. Using one steam usage rate for all compressors isn't realistic, and changing the compressor power rating doesn't make a difference.

Good point. Vacuum brakes allows ejector steam usage to be set, but then ejectors use a lot more steam than compressors anyway. Do you have any data for steam usage by different sizes of compressor?

[Traindude]

darwins, on 30 January 2021 - 12:04 AM, said:

Good point. Vacuum brakes allows ejector steam usage to be set, but then ejectors use a lot more steam than compressors anyway. Do you have any data for steam usage by different sizes of compressor?

Here's one table (the first one), look at the column steam consumption per 100 cubic feet of free air. There may be additional information for single-stage compressors in there as well.

[steamer_ctn]

Traindude, on 30 January 2021 - 12:16 PM, said:

Here's one table (the first one), look at the column steam consumption per 100 cubic feet of free air. There may be additional information for single-stage compressors in there as well.

So how can this value be converted to a per second or per hour figure? The cu ft of air used will vary with the number of cars attached to the train (ie extra air pipe, reservoirs, etc). Hence the steam consumption will vary as the amount of air required varies (train length, etc). So how could this be accurately be modeled?

Currently OR uses the cyl dia, cyl stroke, and number of strokes to calculate a fixed steam consumption. To model cross-compound compressors would be more challenging.


Given the fact that the compressor doesn't run very much, and based upon the timing tests, it doesn't appear to be a heavy steam user. So having the ability to set different steam consumption may not be a huge advantage.