There were numerous attempts at ‘steam generator’ arrangements for power, not all of which were strict monotubes (let alone tapered once-through with superheat, as with Doble). They can be nifty; you might get a kick out of the projected steam generator for the Cyclone ‘supercritical pressure engine’ which was, for a few shining minutes anyway, going to be the Lingenfelter Sledgehammer of steam LSR vehicles – but as a cheap method for onboard charging of a typical fireless locomotive they leave some things to be desired.
First, we might as well assume typical SG pressure range: no exotic German high pressures and distilled water; second, the only sensible regimen for much of the “SG’s” feedwater is to *recirculate the water mass in the ‘boiler’ (*at overcritical pressure and corresponding temperature) through what is essentially a steaming coil throttled on and off between appropriate limits – you could harden a Raspberry Pi with an SD card and do the necessary firing optimization, avoiding what is now near- rocket science tinkering with restoring weary and expensive Vapor-Clarkson pumps and blowers and spark and relays and stuff. The catch is that you need sufficient overpressure to sparge adequate steam mass flow through adequate volume to make up both the thermal and work ‘losses’ in the engine and ‘boiler’ even if well-insulated, so you need a somewhat hefty BFP equivalent, whereas the Lamont equivalent would do the makeup circulat