Building an SES Boiler

[Toymaker]

My goal is to build a clone, or close copy, of the SES boiler-burner assembly. I'll present all the data I have on this unit, starting with a few specs:

Steam output: 1000 F at 1000 psi.
Steam flow range: 27 to 550 kg/hr (60 to 1200 lbs/hr)
Fuel flow: 1.8 to 45 kg/hr (4-100 lb/hr)
Burner’s firing rate: 640 kW = 864 hp
Burner Efficiency: 77%

In the late 1960s to mid 1970s, Scientific Energy Systems, or SES, designed, built, and tested a low emissions Rankine cycle automotive steam engine, which of course included a rather compact, powerful monotube boiler-burner. Below is the best photo of the boiler I've been able to find:

In order to fully vaporize the fuel, a small amount of hot exhaust gases are vented into the fresh air intake, raising intake air temperature up to approx 300 F. Finely atomized fuel is sprayed into the hot intake air which is drawn into the blower fan which further mixes the fuel and air. By the time the fuel-air mix reaches the Meker style burner plate, all the fuel is in a gaseous state. Below is a cross-section view:

Below are the stainless steel boiler tubes.

I'm currently working towards making the blower impeller shown below. Both the base and cover shield will be fabricated using a metal spinning technique,...should be interesting as I've never done this before.
Inlet Diameter - 12.7 cm (5 In)
Discharge Diameter - 22.9 cm (9 In)
Discharge Blade Height - 2.3 cm (0.90 In)

 

[Toymaker]

A little more detail showing airflow entering the impellor, then exiting the impellor and flowing through a vaneless diffuser area before the airflow is redirected upwards through a set of guide-vanes (vanned diffuser) which act to straighten the swirling airflow. Finally the fuel-air mixture is directed through a honeycomb structure which further acts to straighten airflow.

After exiting the honeycomb structure, airflow is forced through a flame holder, consisting of a perforated piece of sheet metal, each hole being 0.84mm (0.033 in), which all together make up approximately 18% of the open area.

 

[jumps4]

Interesting project Toymaker
This should require a Water feed pump with pressure in excess of steam output pressure.
What is your idea for this pump and how will it be powered?
Steve

 

[Toymaker]

Interesting project Toymaker
This should require a Water feed pump with pressure in excess of steam output pressure.
What is your idea for this pump and how will it be powered?
Steve

If I cool the re-circulated feed water down to about 30 C I could use most any off-the-shelf pressure washer. All the commercial pressure washers I've looked at come with a warning to not use hot water. So, if I want to use a "hot well", holding water at 100 C, but not yet boiling, as the feed water, then I need a different pump.

Around August of last year I built my own feed pump for a different project needing only 3 LPM at about 600 psi,... a sort-of-summary post is here: Axial Swash Plate Feed Pump The pump is powered by a 1kW DC motor sold mostly for small electric scooters, and the motor is powered by a PWM motor controller board, which allows rpm control of the pump. Being able to adjust pump rpm, and therefore flow rate and pressure, by simply turning a volume control knob is a big advantage.

There are no plastic parts in my pump so I'm certain it will pump 100 C water. To increase the flow rate I will need to build a different pump that has larger diameter pistons.

 

[jumps4]

All the pumps that come to mind at these pressures are as you said pressure washer or hydraulic.
You could make a gear pump with stainless parts that uses a packing on both ends to hold water and keeps the bearings external away from hot water.
there may be a medical or food industry design.

Steve

 

[Toymaker]

All the pumps that come to mind at these pressures are as you said pressure washer or hydraulic.
You could make a gear pump with stainless parts that uses a packing on both ends to hold water and keeps the bearings external away from hot water.
there may be a medical or food industry design.

Steve

When I search the internet for high pressure water pumps, very few gear pumps are found, most pumps found are plunger type. A few gear pumps are sold for irrigation use, but their pressures are typically 100 psi or less. Nearly all the gear pumps I find are sold for pumping hydraulic oil, or fuels. Many gear pumps use PEEK gears and are limited to 70 C or less.

I haven't found a single pressure washer that uses a gear pump, they all use plunger pumps. Comparing the two designs, it seems the gear pump would be much easier and cheaper to manufacture compared to a plunger pump. So why not use a gear pump for pressure washers??....I can only guess at why.

Perhaps the reason is due to shaft seals. In a plunger pump, the drive shaft is isolated from the pressurized water, eliminating the need for extensive packing which creates extra drag on the shaft; a simple oil seal is all that is needed for the plunger pump design.

 

[Steamchick]

re:
"I can only guess at why."
Well my GUESS is leakage. A piston pump can have good sealing capable of the high pressure required at the output. And because of the incompressibility of liquids, the piston pump develops the pressure instantly, upon moving.
A gear pump seals well at the gear-to-gear interface, but leaks at the sides of meshed gears, so at high pressures, or on systems where internal back-leakage cannot be tolerated, gears cannot do an adequate job. Working clearance between an oil pump rotor and the housing should be about the same as the size of a molecule of the liquid. Water (H2O) is incredibly small, yet oils can be a few microns. The clearance is needed to prevent "back-flow" - so should be small, but need lubrication between the moving gear and static housing, so a "single molecule" size should be the target. Yet "rolling" a single molecule means a lot of resistance - fluid viscosity friction. So bigger clearances have to be used, which means higher loses through back-flow, and all losses are lost efficiency. And piston pumps are just more efficient that way. - But it is only my GUESS! - Any pump engineers out there to teach me the real answer?
K2

 

[Toymaker]

Seems likely I will need to make a slightly enlarged copy of my swash plate feed pump at some future date.

For now, I've been focusing on how to make the impeller. An old technique for shaping sheet metal into round shapes is "metal spinning". A wood form is mounted on the lathe and a flat aluminum disc is held tightly against the disk. As the disc spins the malleable aluminum is pushed over the form using various tools until the disc takes the shape of the form. Two forms will be needed for the impeller, one for the base and one for the cover or shield.

I've already made both forms while I wait for the 5052 aluminum plates to arrive from AliExpress.

The sheet metal disk is placed between the two pieces of wood and the lathe's tailstock is pushed against the smaller piece to hold the disc in place. I'm a little concerned my wood form may be too thin towards the outer circumference so I added several coats of polyurethane, allowing the urethane to soak into the wood giving it additional strength.
This will be my first attempt at metal spinning, so wish me luck

 

[Scott_M]

Hi Toymaker
Following along with great interest!
I have done some metal spinning and I agree that your form is pretty thin at the big end. Can you glue another block of wood to it to thicken it up?
I have done 2 different spinning jobs and made my forms out of aluminum. I was surprised how much force is needed to get the metal to move. I was spinning brass sheet. I fear that your form will fail with the force needed. I can see some cracks in the form, they will not like the amount of pressure you will need to put on them.
I may be wrong but you should at least try and back up your form with another block of wood.

Best of luck

Scott