Updated: 21 May 2003 |
Left: The French Velox boiler locomotive.
This was a 1937 reconstruction of an existing 4-6-0 locomotive by the Paris, Lyons & Mediterranean Railway. It was taken over by the French national Railways, and before the Second World War it was working express passenger trains up to 580 tons on the Paris-Dijon route.
Four-cylinder compound; boiler pressure 290 lb/sqin at 715 degF. |
A Velox boiler burns fuel oil or pulverised coal under pressure in a water-tube boiler. The pressure in the combustion chamber is about 35 lb/sqin, increasing the air density, and so making more oxygen available and allowing a higher firing rate. It contains only a small mass of water, so the boiler can raise steam from cold in 15 to 20 minutes. After stopping firing for an hour, apparently only 6 minutes were require to regain steam pressure.
Thinking about all that compressed air, you can probably see the way that this is going already. The Velox boiler requires an awful lot of ancillary equipment, all of which has to be carried around on the locomotive. The air compressor will use up a lot of power- which has to be available before you raise steam.
The Velox locomotive therefore carried the following around with it:
Corridors within the streamlined casing allowed inspection of the machinery en route.
The fuel, water and the auxiliary diesel-electric generator were carried in a 6-wheel tender.
Key to photograph above:
Key to diagram above:
Starting procedure:
Bibliography; Bell, 1946. Stoffels
Above: Side view of the French Velox locomotive, with its tender.
Above: The internals of the French Velox locomotive. Note the actual boiler (D) is completely buried by its ancillary equipment.
The high-pressure cylinders appear to be on the outside. The connecting-rod has been removed in this photograph.
A Auxiliary steam condenser
G Blower
M Steam admission pipes
B Feedwater treatment
H Air ducts from blower to combustion chamber
N Chimney
C Feedwater purifier
I Sand boxes
O Throttle valve
D Steam generator
J Economiser (feed heater)
P Reversing gear
E Gas turbine
K Blower starting motor
F Air entry to blower
L Braking air pump
Above: The steam circuit of the Velox locomotive.
1 Combustion chamber
9 Air compressor
17 Lube oil pump
25 Controller
2 Evaporator
10 Electric motor
18 Electric motor
26 Oil separator
3 Water separator
11 Steam turbine for pumps
19 Fuel oil prefilter
27 Superheated steam to HP cylinders
4 Superheater
12 Gearing
20 Fuel oil filter & heater
28 LP exhaust
5 Superheated steam reservoir
13 Feed pump 1
21 Air/oil metering unit
29 Chimney
6 Oil burner
14 Feed pump 2
22 Lube oil cooler
30 Fuel oil from tender
7 Steam turbine
15 Circulating pump
23 Aux steam condenser
8 Gas turbine
16 Fuel oil pump
24 Feed water heater
Above: The internals of the Velox loco from the other side.
Start diesel generating set.
Use electricity from this to start the two auxiliary turbine groups
Use electricity to preheat fuel and start combustion.
Change over to regular fuel oil supply. (???)
Steam turbines take over from electric starting motors.