Optimism the Keynote of Producer-gas Conference
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Exchange of Views Among Prominent Personalities, Including Research Scientists, Manufacturers and Operators, Augurs Well for Furtherance of Solid-fuel Movement. Conflicting Opinions on Details, but Unanimity on General Practicability
EXCELLENT support was afforded the conference held last Thursday by the Producer Gas Association, those who took active part including representatives of the following bodies:—The Department of Scientific and Industrial Research; Dupuy Gas Producers, Ltd.; Eastern National Omnibus Co., Ltd.; Enness Gas Producers, Ltd.; Ford Motor Co., Ltd.; Fuel Research Station; Gas Light and Coke Co.; Sentinel Waggon Works (1936), Ltd.; Thomas Tilling, Ltd.; and Worldwin Products, Ltd.
Many practical suggestions were made for surmounting obstacles in. the way of producer-gas progress, and much new light was thrown upon the numerous problems associated with the movement.
One of these is the difficulty of accustoming drivers to the new technique and of gaining their interest and co-operation when they find themselves with a harder job than that of handling liquid-fuel vehicles. Mr. Eustace, secretary of the Association, described in some detail a well-thought-out scheme for training'men and voiced the opinion that driving any producer-gas vehicle should be a reserved occupation for men not less than twenty-five years of age. He thought a two-day course, including theory and practice, would suffice, and advocated granting a certificate and a National Service badge.
Practical Man's Valuable Views , An employee of the Gas Light and Coke Co., with six years' practical produccr-gas experience, gave valuable views. He thought the advice handed out by the average demonstrator on delivering a new plant was inadequate, and spoke of four days' training in actual service. He personally showed the new drivers coming under his jurisdiction all the " dodges." To get over the " harder-job " complex, he advocated encouragement by emphasizing that they were one ahead of the oil and petrol men.
Another speaker suggested that the need for paying higher wages tended to spoil the economic attractions of gas and, in a different connection, that transport and service engineers should take a more personal interest, drive more themselves and find out the faults first-hand with a view to remedying them—in short, get right down to the matter.
Mr. Fry, the chairman of the Association, commented that driving gas was ultimately only a matter of common sense once the man realized that he was making fuel as he used it and that it had to be made while going downhill.
Filtration was dealt with comprehensively by Mr. Cook, M.Sc. (Department of Scientific and Industrial Research), Fabric, in his experience, would be the best filtering medium (it was 95 per cent. efficient), but for the fact it failed with moist gas. This ruined its prospects. The alternatives, sisal and oiled coke, were efficient and moisture-proof. With these, extensive experiments had been made, by means of exhausters, engine-bench tests and road tests, different densities of packing, temperatures, and many kinds of sisal having been investigated.
Outlining typical filter characteristics, he explained how, during the first five or six hours, sisal extracted inefficiently, passing about 30 mg. per cubic m. Then the dust-concentration curve flattened out to, say, 20 mg. per cubic m., remaining fairly constant for 35-40 hours.
In tie latest type recently developed, known as the H filter, there were two compartments—a churn packed with sisal and a cylinder with a 10-in.-diameter pad. This was superior to anything else tried yet and gave cylinder-bore wear (using anthracite)
o greater than with petrol. The method of using it, roughly, was to clean the churn every five or six days, leaving the pad dirty, and to clean the pad during the time the sisal was
dirty. The indication that the pad required cleansing was pressure drop in the system.
Methodical Routine To a suggestion that this scheme was complicated, Mr. Cook said that, in fact, it was not so difficult. For example, one might do the pad on Monday and the churn on Saturday. Asked for a precise figure for cylinderbore wear, he gave 0.003 in. per 1,000 miles and, for the life of sisal, about three •months, after which the fibre began to break up.
In view of the fact that drivers had hitherto been mollycoddled, said Mr. Holder (Dupuy) and did not know how to judge when to clean filtering media, being unfamiliar with their appearance, filters should be of a type that was not subject to channelling, but became choked up; then they could go on without doing harm until excessive resistance compelled cleaning. That did happen with the two-stage filter, commented Mr. Cook.
The meeting pricked up its ears when Dr. Burns, of the Gas Light and Coke Co„ moved on to the platform to give a description of a new electrostatic filter, for which his company is responsible. It comprises a tube in the gas line, along the axis of which an electrode passes. This is connected with a source of h.t. current, supplied by a separate coil. Thence the gas travels to a low point of entry on a receptacle, packed, in respect of its upper part, with steel wool, which is earthed. This picks up the positively charged particles in the gas stream and subsequently deposits them, This speaker informed the company that it had now worked successfully for three months without being touched. The tube is 2 ft. by 4 ins., whilst the box measures, roughly, 2 ft, in each direction. With this filter in use cylinder-bore wear is 0.0014 in. per 1,000 miles.
A statement by Mr. Cook was to the effect that, although cylinder-bore wear with producer gas was freely thought to result from corrosion as well as abrasion, his tests pointed to its being due solely to abrasion. .This was queried by a member of the Thomas Tilling company, who said that ammonia, sulphur compounds, etc., present in producer gas, were bound to cause corrosion, He advocated the use of upper-cylinder lubricant. Petrol and oil, he said, to some extent, acted a3 such, but gas did nnt, because it was dry.
Filtering Medium Absorbs Acids In defence of his statement, Mr. Cook argued that sisal had a capacity for absorbing the acids referred to.. He had found that, with both cold and hot jacket conditions, wear was practically non-existent with proper sisal or fabric filtration.
Another speaker referred to engine seizures he had experienced with gas, which were cured by an oil drip feed to the upper parts of the cylinder.
A magnification of the filtration problem occurred, said Mr. Morison (Eastern National Omnibus Co., Ltd.) with the 7-8-litre engines commonly used on buses. The research engine was half that size. His experience with a fabric and coke filter was that channelling was pronounced and he caused a stir by saying that his figure for cylinder-bore wear had been as bad as 0.001 in. per' 150 miles. He then tried washing the gas with a water filter and got water in the engine, which led to the development of a water separator. This was satisfactory and, after two years of experiments, which represented 5,200 miles, his cylinder-bore wear was 0.001 in. per 3,737 miles.
Another argument for water filtration was that the characteristic remained a straight line indefinitely. Furthermore, sisal was imported and an object of the association was to use home products. Sisal was already difficult to get; the water filter was easy.
• Referring again to acid productS, Mr. Cook informed his audience that he had 'had'gas from a sisal filter analysed and -found only' traces of ammonia. The -sisal was definitely taking it out. He had tested _many water • washers and 'found them inferior in efficiency.
• A member of the company raised this rather interesting point. The small particles which the best filters failed to extraCt. appeared to have a hardness equal to that of talc, which was not an abrasive—indeed, almost a lubricant. Therefore, in his opinion, they were of little consequence. A sulphur content of 20 per cent, was not, in itself, deleterious. It would burn and oxides be exhausted, but after standing wear would occur. Some 40-50 per cent, of substances in gas made from Progasite were soluble in water; therefore, washing was desirable.
• Mr. Fitton, of the Fuel Research Station, then spoke on the matter of fuels and told of a vast number that the Station had tried out, which included both fuels it had prepared itself and proprietary fuels. Its recommendedfuel specification, which was the result of extensive research and extremely careful consideration, limited the tar content to 15 oz. per ton. Above this, the risk of valves sticking was prevalent. Ash content was limited to 4' per cent.; with more, clinker became a nuisance. The figures were not absolutely rigid. The more reactive fuels could stand a slightly higher percentage. It was important that ma.nufacturers of fuel, should stick to the specification.
Medium-temperature Carbonization The quantities of anthracite falling witliin the given limits were sufficient for only 10,000 vehicles, which was not enough, and the Station was looking for something else. A promising scheme was for ordinary gas works to modify the process commonly used, in the production of coke. That would solve the problem. Broadly speaking, the aim was carbonizing, at medium temperatures. The difficulty was to achieve a fuel of suitable reactivity with low tar content, and this was not easy.
Progress, however, had been encouraging; 10 _works were, to his knowledge, carbonizing on a large scale and making satisfactory fuels, but there was much more to be done yet. Evidence existed that it could be done. He suggested that it was a question of time. There was anthracite for the present need, and the future fuel problem was not serious.
He described in some detail the nature of the tests which the Fuel Station carried out, and from which fuels were classed under the following headings, all trials being made with the " emergency " producer:—(1) very good; (2) good commercial fuel; (3) fair, subject to limitations; (4) can be used, but not recommended.
It was possible, he said, to improve fuel by doping. The most promising method was to spray medium-temperature coke with sodium carbonate. The resultant substance was not ideal for the " emergency " plant, but in the Brush-Koela (specifically named), which possessed a number of refinements, it was satisfactory.
At this point Mr. Holder inquired whether the result of the improvements effected to cleaners would allow the tar-content limit to be raised. The 'answer was definitely km," because it was undesirable for tar to reach the filter.
The representative of p.s.v. operation on producer gas, being concerned with questions of range and producer capacity, asked a question about fuel density. He received the answer that some fuel companies were bricketing to increase density.
Axle and Compression Ratios
With regard to alterations to compression and axle ratios, Mr. Gardner told of a 3-tonner of well-known make which had been converted to gas with a compression ratio of 7 to 1. Mechanical breakages had resulted, so a new engine had been installed, and the axle ratio lowered with no compression alteration. The performance had then been just as good. From his remarks, it -Seemed that he advocated the lowering of the final-drive' ratio in preference to the raising of the compression ratio.
Sparking plugs he regarded as of great importance. Some which were wholly suitable for petrol did not fire gas at all. He made specific reference to a Champion plug expressly constructed for gas.
Hot-spot elimination was important. It was easy to make the niistake of running the gas line too near the exhaust pipe. He preferred the fitting of a " booster " carburetter to using the standard carburetter; it was the more economical practice.
• Inexplicable, but, nevertheless, fact, was the way cylinder wear occtirreit. the wear causing ovality was fore and aft, not port and starboard. Another puzzling phenomenon was that the white metal of main bearings got stained Wank.
Steam-engine Practice Against upper-cylinder lubrication was the argument that, when dry, cylinder walls were less adhesive. For this reason steam-engine makers used graphited rings.
Commenting on the foregoing compression-ratio views, Mr. Eustace related a case where 51 to 1 gave a crawl hill-climb in third, as opposed to a 15 m.p.h. ascent in the same gear with 8 to 1.
Agreeing about the bore ovality, a speaker told of the formation of a pit near the inlet valve. This appeared to be where a' jet of gas impinged and suggested corrosion. To 'measure cylinder wear, he found an ordinary internal micrometer of little use. He had made a special instrument with balls and wedges, which was more informative and practically eliminated the risk of error.
A difficulty arising in the case of big engines through compression raising was that starting was practically impossible, either by hand or with the starter. Lowering axle ratios meant loss of speed, which was no good for bus work.
Experiences with an Albion 6-7tonner were related by 'Dr. Eaton (Gas Light and Coke Co.). • For efficient cooling he had mounted the tubes on the top of the cab, whilst, to avoid stress, he had incorporated a loop in the gas line; both proved effective. The engine had done 22,000 miles prior to the conversion, for which it had been overhauled, had Centrard liners fitted, and had the compression ratio raised to 8 to 1, There had been no alteration to the final drive.
Since then it had covered 5,750 miles, engaged on coke delivery work, making many calls. Ample power was developed. On this service, with a maximum pay-load of 8 tons, 31 lb of Progasite were used per mile. This was a high figure. On long hauls it
would be lower. The driver, more, over, kept the engine running while loading. The vehicle had formerly averaged 5 m.p.g. on petrol, so 17.5 lb. of Progasite represented one gallon of petrol. In addition to the solid fuel, three gallons of petrol were used per week. The vehicle would cover 90 miles per charge; there had been no trouble from clinker.
For filtration, he used 78 lb. of oiled coke and sisal grass, the coke measuring 1-4 in and being treated with 3 pints of oil to 109 lb. Because, in his opinion, the filter was too small and the gas speed too high, in 5,650 miles cylinder wear had been 9.004 in. per 1,000 miles.
Producer Gas Has Come to Stay?
Mr. Morison (chief engineer, Eastern National Omnibus Co., Ltd.) made some interesting and optimistic remarks, He stressed the importance of maintaining good joints. Starts could be made with poking after two hours' standing at terminal points. An adequate cleaning staff was needed, because there were dirt and dust with producer gas, and cleanliness was more important in the case of passenger vehicles. Filling up the hopper was a messy job. His consumption was 2 lb. per mile, which represented a saving of 2d. per mile. Against this there were heavier maintenance and upkeep costs.
After the war, when revenues would be short, he anticipated that the economy of solid fuel would enable many operators to continue running profitable services. For the publicservice vehicle, he concluded, producer gas had come to stay.
The producer-gas movement should certainly benefit from this interchange of views, and the Association which sponsored this conference deserves eon.gratulation for its saccess. We hope it will be followed by others.