XXVII. USE OF BOTTLED PROPANE AND BUTANE FOR ROAD VEHICLES
According to Dr. Butefisch, it was aimed to turn 60-65% of all German cars and commercial vehicles to bottled gas fuel. Shortage of steel and labour interfered with this plan and priority had to be given to conversion of trucks and vans. Actually only about 35% conversion was achieved. The monthly consumption of liquid gas was 25-30,000 tons. This compared with total consumption of petrol and diesel oil apart from that used by the armed services of 50,000 tons a month.
Pure butane was never used in Germany as bottled gas for road vehicles. Pure propane was used for household heating and lighting and its was also considered desirable to use propane in the winter months for road vehicles. In summer a mixture containing up to 85% butane was considered satisfactory. In actual practice, a blend of butane and propane in the proportions which corresponded to availability was employed during the war.
Dr. Scholtz of Leuna was the inventor of much of the equipment used in connection with liquid gas vehicles. He supplied the following information on I.G. development of liquid gas vaporizers.
In the first gasifier to be produced in commercial quantity, liquid gas was vaporized by means of a hot water preheater and the resultant vapour let down in two stages, firstly to a pressure of 0.4 ats. and finally to -20 m.m. water pressure. The sub-atmospheric second-stage pressure ensured efficient closing of the second-stage let down valve when the engine was shut off, but it led to difficulty because of a variable air/fuel ratio at different throttle openings. Air leakages backwards into the second stage let down chamber were prevented by fitting a non-return valve (actually a gas mask valve was used) between this vessel and the jet chamber.
The second type of gasifier was similar to the first except that the second-stage let down pressure was atmosheric. In order to ensure that no leakage occurred when shutting off the engine, a stop valve was incorporated in the liquid feed line. This was connected so that as long as there was a positive engine oil pressure it remained open. This model was extremely satisfactory and Dr. Scholtz considered it to be the best gasifier which has been produced. It is, however, fairly expensive; a pre-war production cost of 200 marks was mentioned.
A cheaper type has been developed during the war costing only 25-30 marks to make. Some 100-150,000 of this type of gasifier have been manufactured by the German Solex Carburetter firm. The preliminary vaporization of the liquid gas is carried out in a coil heated by exhaust gases. The resulting vapour at a pressure of 1.2 ats. is let down first to 0.4 ats. and secondly to -5 m.m. water gauge This assures satisfactory closing of the second stage let down valve and eliminates the rather expensive oil operated stop valve. At the same time it is sufficiently near atmospheric to avoid wide fuel air ratio variations with speed.
A third type was being developed in which vaporization was brought about between the first and second let down stages.
Samples of these various types of gasifiers were procured at Leuna, together with detailed drawings. they were dispatched to London through the usual channels but so far they have not materialized.
Dr. Scholtz said that a liquid gas has been used for running-in all aero engines during the war. A report giving a detailed description of the set up employed is amongst the documents removed from Leuna.
Some experimental work had been carried out at Leuna with a car running on neat methanol and also on a mixture of methyl ether and methanol.