How Has the Mark I Producer Been Improved
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Some Interesting Pointers on Methods by Which More Satisfactory Operation Could Be Achieved,
By John Stewart
AQUESTION which is of national importance: " Is the official gas scheme sound? " is raised. in. "The Commercial Motor " for May 22. Under that beading you review the position, and you rightly say in conclusion: " What the other manufacturers want, and what the operator must have, is the best that can be obtained."
In the same issue you illustrate a gas producer and to elicit information for the public you add the question: " Is This the Government Mark II Producer? " and say: " It functions on the down-draught principle."
What is the position? In the Mark I design the gas outlet was diametrically opposite the air-inlet tuyere, which had to project well into the body of fuel. Also the gas outlet was shielded by a perforated cover-plate forming a box, in an effort to prevent fine ash entering the gas cooling and cleaning system. The disposition of these parts, i.e., the air inlet and gas outlet, could only produce a partially blimp-shaped combustion zone and high' temperature of exit gases, because of the extreme brevity of fuel space between the two parts in the horizontal cross-wise direction. It was in reality an apprentice makeshift scheme wholly unworthy of the Fuel Research Department's prolonged effort and costly experiment at much public expense, against which the Duke of Montrose has been kicking in the House of Lords.
You have suggested that Mark II, as illustrated, may be the Government new and revised design about which Lord Leathers, Minister of War Transport, has spoken favourably and is backing for the first 10,000 passenger vehicles to be equipped with the "official" producer-gas outfits. [We have since ascertained that this is not the final design.—En.] In any Mark II, as a substituted improvement on Mark J, the alternatives presenting themselves to the designers as means for overcoming the defect above men
tioned were: (1) They could raise, or lower, substantially the position of the gas outlet and thus lengthen the course of the gas through the fuel; (2) Avoid, so far as possible, the tar trouble of an upward move, by deciding in favour of lowering the gas outlet. This having been done, you say it "functions on the downdraught principle."
I would point out that the disadvantage of that principle in• the past has always been inability to control and complete the combustion process so as to leave ash alone on the grate or bottom, of the producer. Obviously, if the cross-draught tuyere is as in Mark I the spherical combustion zone will also remain as in that design or exhibit a slight downward tendency. The fuel below that zone cannot, however, be consumedand must remain merely as a heated fuel bed supporting the ash or clinker at that part until it is removed at the end of the working day. Moreover the grate is such and so placed that it cannot but fail to deal with the ash formed in the greater part of the combustion zone and can be of little real service as an aid to efficiency of gasification. Ash formed beyond the vicinity of the grate will fall towards the gas-downtake side of the fuel bed and remain thete.
It will thus be seen that this Mark II is not entitled
to be classed as a down-draught gas producer. It remains, as in Mark I, a cross-draught, whereby combustion is effected and the products of combustion are merely carried in a downward direction to the exit pipe, which of itself does not warrant the down-draught title,
• I have the temerity to express the conviction that your suggestion anent this Mark II being the Government's approved design is not adequately sustained by even a cursory inspection of the aforementioned characteristics. One of course deplores such a finding, but these times are too serious and the motor vehicle too important in its war function to permit. of palaver.