Conversion and operation of a Massey Ferguson 1100 farm tractor
a) General description of the converted tractor
The experiences from the conversion of this tractor have been reported (in Swedish) by Axelsson (1).
Table 3.12 gives the main data for the converted tractor. The gasifier system is shown in Fig. 3.8, and a picture of the converted tractor in Fig. 3.9.
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Figure 3.8 Schematic of the gasifier system used for a Massey Ferguson farm tractor
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Table 3.12 Specification of Massey Ferguson tractor converted to producer gas
V Originally 2.5 mz. This required cleaning every 20 hours which was not considered acceptable. |
The gasifier and the gas filter are mounted on consoles bolted to the body on the left side of the tractor. The free height of the gasifier above ground is 500 mm. The gas cooler is mounted on consoles in front of the engine cooler.
Only minor changes to the original tractor were necessary. The headlights were moved to the top of the roof, since the left light would otherwise have been obstructed by the gasifier. The air filter has been turned so that the insert can be removed from the right hand side of the tractor since the gas filter box on the left side of the tractor would prevent servicing of the air filter in its original position. A new opening has been made in the engine hood for the air inlet pipe to the air filter. The loose weights and their brackets on the front of the tractor have been removed, to make space for the gas cooler. The engine has been fitted with an extra speed governor, acting on the gas throttle in the gas/air mixer. The governor is driven by a V — belt from an extra pulley mounted on the fan shaft. The diesel injection system required the most substantial changes. The injection pump was of the distributor type with a centrifugal regulator. The original injection system gave injection at reduced engine speeds exceeding the amounts which are required for dual fuelling. The result of this is that the injection will be unnecessarily large at low speeds.
A constant injection amount was obtained by mounting an adjustment device for the fuel pressure normally used on pumps with an hydraulic speed governor. Fig. 3.10 shows the injection characteristics of the original and modified systems.
Overheating of the pump was avoided by leading the excess flow to the fuel tank as described in section 3.1.4. A radiation shield was also mounted to protect the pump and the fuel filter from being heated by the hot gasifier which is mounted on the same side as the pump. V The injection pump was fitted with an adjustable stop for the engine stop-lever, close to the zero injection position. With the lever at this stop the injection flow is less than required for idling, which means that the engine can be stopped just by closing the gas throttle even though the diesel flow cannot be shut off completely. The stop lever can also be adjusted by the driver to a full diesel position, enabling starting and driving on diesel oil, if required.
V These changes were not done originally. After 25 hours of operation the pump seized, and this was attributed to insufficient cooling and lubrication. After the changes described here, the pump operated satisfactorily
Pressure rise of the fuel pump MPa
The mounting of the injectors was also modified, since it turned out after a few hours of operation with the original design that the injectors were running hot and suffering from coke deposits in the nozzle holes. This was caused by a combination of the low injection flow in dual fuel mode, and the way the injectors were mounted in the cylinder head. The engine is equipped with a cylinder head covering all six cylinders. The holes for the injectors are made in the cast material. This leads to poor cooling of the injectors, partly because of the low thermal conductivity of the cast iron, partly because the wall thickness is large.
To improve the cooling of the injector a copper sleeve was mounted on the injector and by opening a connection between the space where the injectors are placed and the cooling water channels in the cylinder head. This change was fairly simple to make. After this
modification, it was necessary to drain the cooling water from the engine before removal of the injectors.
The total height of the gasifier above ground is 222 cm. The eye level of the driver is 225 — 240 cm, depending on how the seat is adjusted. The field of vision in the forward left direction is partly obstructed by the gasifier and the filter box. To the right and backwards, the field of vision is not affected.
b) Laboratory performance tests
Laboratory tests were carried out to establish the performance of the gasifier system and the converted engine.
A summary of the test results is given in Table 3.13 and Fig. 3.11. The maximum power in dual fuel mode was found to be 51 kW at about 2170 rpm (injection timing 30° before TDC). This is 79% of the maximum power for straight diesel operation at recommended injection timing (22° before TDC) and 76% of the diesel power at the same injection timing as for dual fuelling. As can be seen in Table 3.13, the diesel oil substitution was found to be 80-85% and the efficiency of the gasifier system about 70%. Solid residue in the ash pit was found to be up to 3.5% of the fuel consumption. This would account for a loss of about 5% at full power.
Tests were also made with injectors other than the original four hole type. Pintle type injectors in the original cylinder head showed no tendency for coking — the injectors are self cleaning — but the maximum power in dual fuel operation was 19 percent lower than for the four hole type. Straight diesel operation with this injector was not considered possible, since very smoky exhaust gases were already obtained at low powers. Two-hole injectors gave the same power output in dual fuel mode as the four-hole injectors for engine speeds up to 1900 rpm and slightly less above. For straight diesel operation, the power output was generally lower than for four-hold injectors over the whole speed range.
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Table 3.13 Results of laboratory tests with F-5/80-150 gasifier system mounted on a Massev — Ferquson 110 tractor.
c) Experiences from practical operation |
The tractor was used in practical operation for more than 2500 hours during a six year period at two large farms in southern Sweden. The tractor was mainly operated by agricultural students, since the regular tractor drivers were not interested in using it. The main reason given for this is that the daily service is time consuming, dirty and heavy. Preparation for operation requires 30 — 45 minutes. Large amounts of wood chips must be loaded on the roof for the operation during a full work shift.
Education of a new driver has required one to two weeks. Each student has been responsible for the tractor during one six month period.
The tractor has been used for the following types of work:
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Transport of beets, grain and fertilizers.
The gasifier system has worked satisfactorily. Average times between cleanings of different parts of the system and other service measures as well as failures are discussed in section 3.2.4. The injectors, which were believed to be critical for reliability, have not caused any trouble. One serious engine failure was experienced. This was probably caused by water sucked by the gas from an overfull condensate vessel in the gas cooler.