A gas turbine again on the road
Some unusual proposals for an innovative
road tractor or cargo
It is known that, soon after the 2° Great War, many big road vehicles constructors begun to test gas turbine, as possible substitute of the more heavy and cumbersome reciprocating (diesel) engine.
The tests went on for almost one half of century but, inspite of this perseverance, our power plant, so successful in aeronautical applications, proved to be very disappointing on the road, staying unsolved many troubles :
- low thermal efficiency --> high fuel consumption;
- lack of motor retarding --> weak exhaust brake;
- low elasticity --> turbo lag;
- remarkable encumbrance of the exhaust system;
- pollution, because of the huge bulk of smoke to deal.
We can assume that many of these drawbacks may be charged, in more or less ratio, with a peculiarity of our engine : starving of air.
In fact a lot of air is requested to dilute the combustion gas to avoid an overheating of blades : all this means an overlabour of the compressor which needs a power no less than double the net work.
Moreover the need of a heat exchanger, necessary to recover the heat latent into exhaust gas, limits the possibility to increase the feeding air pressure which, to improve thermal efficiency, would be as important as it is supercharging for diesel engines.
To solve all these problems are here proposed some expedients, the first of them aims at sparing comburent air, saving up diluting flow : this target will be reached by means of two solutions, working in compound.
1st : a massive recourse to E.G.R. (Exhaust Gas Recirc.) system, with an effective precleaning and cooling plant, giving us, at the same time, a sound lowering of combustion gas temperature (and therefore NOX emissions).
2nd : the fell down of combustion gas heat will go on by means of a crossing through a heat exchanger, placed no more downstream the turbines, but before them; the warmth in excess is took away by the air coming from the compression / aftercooling set and is sent directly to the combustion chamber with full thermal recovery.
To get the wanted results our device must have a rather low thermal efficiency (no more than 40%), so having quite restricted dimensions and good streamlined behaviour, to not obstruct the flow of hot fluid. Because of the hight temperature of the comburent air and the absence of dilution, it has devised a redesign of the combustion liner, as further detailed.
This file collects some other suggestions, aiming at several targets, all conceived to renew the heavy commercial vehicle : lighter kerbweight, better grip and roadholding power, bifuel supplying, and moreover many other improvements, as illustrated in the following document.
All this will be detailed into the next chapters, structured according these items :
Engine …………………………………………………………………………………….……….….Page 6
Driveline ………………………………………………………………………………………………Page 24
Chassis : frame + suspensions + steering system ………………………….…Page 29
Cab.………………………………………………………………………………………………….....Page 36
Sketches ……………………………………………………………………………………………..Page 39
Contacts ………………………………………………………………………………………………Page 41
For a complete documentation download :
