throttle losses?

Hello all:

I've been thinking about the throttle. It seems to lower the pressure by allowing a small amount of steam to expand to a lower pressure. But doesn't that mean you've wasted energy? The steam expanded without doing work, right? Wouldn't it be better to run the engine at minimum cutoff at full boiler pressure?

Dan

dullfig Wrote:
-------------------------------------------------------
> I've been thinking about the throttle. It seems to
> lower the pressure by allowing a small amount of
> steam to expand to a lower pressure. But doesn't
> that mean you've wasted energy? The steam expanded
> without doing work, right? Wouldn't it be better
> to run the engine at minimum cutoff at full boiler
> pressure?

My answer is, Hell YES!! This is a well-known issue but due to the requirements for massive changes in power outputs in road-going vehicles has largely been disregarded.

My recent rants related to the British loco 71000 "Duke of Gloucester" and the Dan Gelbart demo engine are directly related to this issue and show how cutoff "IF" conveniently available and flexible can be an effective and more efficient substitute for throttling.


Bill



Edited 1 time(s). Last edit at 01/19/2015 10:35AM by Bill Hinote.

So that is the problem I see with bash valve engines: with a fixed cutoff, the only way to vary power output is to vary input pressure, which means your efficiency suffers. A 5% cutoff means nothing if at cruse speed you have the steam throttled way back. On the other hand, if you are at full boiler pressure and 5% cutoff gives you cruise power, you have no power left for acceleration since your cutoff is fixed. Or am I missing something?

The Carters and others worked with variable pressure boilers. They used the throttle for startup and fine control. I think it makes more sense to hold a fairly high temperature and vary the pressure by changing the water flow in a fixed cut off engine. That system was used as the only speed control in a model boat. It's a lot easier to do with modern controllers than with mechanical ones.

Lohring Miller

corliss valve setup was good for full control of cutoff wasn't it? exhaust on a seperate valve with fixed timing. But I think they had the problem of wearing sideways on the seal after long run time. They had a cam opener and a latch kickoff for closure if I remember right, with latch position controlled by governor.

The main part I lack in my long delayed project is the throttle valve. Don't know where to buy one. And if it were avalible it might cost more than I want to pay. Balanced valve so it would move easy. I'm thinking corliss type valves in the heads might serve the purpose with full range for the intake from 0 to maybe 60%. And I have an old 2" thick slab of cast iron I could make heads out of. Might try it. I had cast and machened aluminum heads for it thinking of making a manifold with slide valve, but studying the slide valve diagrams in detail I don't like the lack of independant control between intake and exhaust or the extra space of passage valve to head which is that much wasted steam.

Is there such a thing as an electric solinoid steam valve? If so the cutoff could be controlled electrically. As long as the valve could handle long term rapid repetitive action.

Went searching. ASCO has some, 500,000 cycle life at 125 psi. less than 100 hours at 100 rpm. Much too short lived. it's a push-pull valve, rotery may be better.



Edited 1 time(s). Last edit at 01/31/2015 10:19PM by ReubenT.

May I suggest you take a serious look at the throttle in a White steam car.
After using them all, this one is by far the best one.
Jim

Jim Crank Wrote:
-------------------------------------------------------
> [attachment 2926 whitethrottle1.jpg]
>
> May I suggest you take a serious look at the
> throttle in a White steam car.
> After using them all, this one is by far the best
> one.
> Jim


Well thought out.

Looks like basically a needle valve with very course threads so it takes small amount of twist to open. That would work fine and last a long time. although don't think my current machening equipment could make one. My planned steam vehicle is to be a multipurpose heavy duty machine. Geared for road as well as offroad. governor controlled so it can be connected to any of several machines.

Jim:

It's looking to me more and more to me (aside from the fact that everything was mechanical and not automated), the White was a more advanced car than the Doble. Your thoughts?

Dan

I think there is more to it than that, Reuben.

Steam and for that matter water valves are famous for cutting their seats if the valve is just cracked open and there is a lot of pressure drop.

The White throttle is really two valves in series. The shut off valve has a conical needle working against a knife edge seat. It opens very quickly and is out of the way.

Once the valve is open, flow control is accomplished by varying the length of the restriction between the cylinderical portions of #180 and #184. The cylindrical portions of #180 and #184 are less likely to cut as the pressure drop is distributed over some area. It is not the end of the world if these cylindrical features do cut as the shut off is still between the conical needle and seat.

This is a clever design that has been recycled in industrial control valves during the following decades where cutting, cavitation and noise control are important.

I agree that the White throttle would be difficult to reproduce and no doubt, the working components were case hardened.

Dan, I too am greatly impressed with the engineering that went into the White cars. I disagree with the notion that the Whites were not "automated." Some sophisticated mechanical control systems were built before electrical/electronic systems became practical. Back in the White's days an engineer had to understand first principles and design his system accordingly.

Kerry

There have been several threads on throttles. My favorite thoughts are in this thread starting here. It describes a much easier to produce version of the White throttle.

Lohring Miller

Dan,
Where on earth did the idea get started that the White was not automated???
The White had a fully proportioning water and fuel system with two full time overrides, pressure and temperature. If you watch the pyrometer and vaporizer pressure as you drive, you see them constantly modulating the fuel flow to maintain the correct superheat. In fact, the White flowmotor system actually has two modes of operation, below and above 18 mph in high gear on a level road.
In point of fact the flowmotor White was so good that it has no valves to twiddle except for the main fuel shutoff, it takes care of itself perfectly IF you restored it strictly to factory specs and not one "improvement."
What doesn't get mentioned, is that each valve including the throttle had a precise screwed in and hardened seat, wire drawing doesn't happen. At least my 1910 never had a sign of it after all those years of use and that includes just creeping along in many parades in low gear.

After owning both, I'll take a late White any day over the Doble. I now bitterly regret ever letting it go after 14 years of trouble free driving. On nice weekendsI I used it just like a regular car and never once had trouble, can't say that about that damned Doble.
Yes, several people have made new throttles. Paper attached on the system.
Jim

Jim:

Boy did I step in it! I suppose I was talking automation as in "single button start" automation. You know, like get in the car, press one button, and wait for everything to be ready.

I agree with you, the White had many well thought out mechanical automation features that worked well. And I wouldn't mind owning a White myself

Dan

Why won't a ball valve work as long as its put before the super heater? I have been using Stanley style throttles and have trouble pulling them of the seat at high pressure. Thanks Bill Barnes

Bill
I used a full port 1000 PSI ball valve for the throttle on my big boat running 275 PSI steam pressure
One inch pipe size. Never had a problem in the 12 years I ran her.
Rolly

I use ball valves for the throttle on my Tug which is non superheated and operates at less than 100 psi, and on the Locomobile at 250 psi before the superheater. Make sure they are steam rated (300+ WSP). The one on the Tug has been running three seasons, no issues. Almost every valve on the tug and there are very many due to the redundancy is feedwater systems, isolation etc., are all steam rated ballvalves.

The only ballvalves I've ever heard of failing in steam service were not steam rated. Home Depot type.

-Ron

Dan,
Actually you were very close.
Once you got the pilot going and warmed up the main burner, this is 1910 remember no electric control system, you were almost right. Climb up and just open the main burner valve, crack the throttle, work out any water ( this you do with any steam car) then shift into high and away you go.

Bill,
Also had problems with both the Stanley and Doble throttles forcing the poppets off the seats, exact same design. Then consider the serious turbulent flow losses and extra force magnifying mechanism you needed to have, levers with Stanley and double cams with the Doble foot throttle. White had it right the first time.
Ball valves work just fine with low pressure and modest superheat, also used them. 1200 psi and 800° F may be another story, even with carbon seats..
Jim

Some years back I designed a balanced poppet throttle....then I saw a drawing of a Dutcher Industries throttle that was basically identical.

All files from this thread

File Name	File Size		Posted by	Date
whitethrottle1.jpg	187.5 KB	open | download	Jim Crank	02/01/2015	Read message
THE WHITE FLOWMOTOR CONTROL SYS-16-1	65.5 KB	open | download	Jim Crank	02/03/2015	Read message
The White Owners Fourteen Commandments-2.doc	25.5 KB	open | download	Jim Crank	02/03/2015	Read message
IMG_3023.JPG	587 KB	open | download	IronChief	02/03/2015	Read message
IMG_3879.JPG	535.1 KB	open | download	IronChief	02/03/2015	Read message
IMG_3883.JPG	415.8 KB	open | download	IronChief	02/03/2015	Read message
Throttle Valve1.png	31.7 KB	open | download	frustrated	02/03/2015	Read message