The normal operating load is 68 to 75 imperial ton and the vehicle is used to carry hot steel slag and furnace waste from the steel manufacturing plant to the dump pile or waste tip.
Test Methodology
The overall objective was to demonstrate fuel economy improvements using low viscosity lubricants in an off-highway vehicle. To do this we needed to: • calculate brake specific fuel consumption (BSFC) during routine duty
• repeat the actual vehicle route multiple times per shift which we would need in order to statistically validate the data • repeat baseline testing between every candidate test
Using this methodology it would be possible to conduct sensitivities analysis to identify key external influences.
Figure 1
Figure 1 shows the fuel economy improvement for a single oil blended at different HTHS viscosity and also formulation modifications to the oil at equal HTHS. The results are taken from a heavy duty diesel engine dynamometer test using the worldwide harmonised transient cycle (WHTC).
Clearly the changes in the formulation are having effects outside of those that would be expected from HTHS alone, and the understanding of these differences is key to being able to balance a formulation in order to maximise fuel economy without compromising durability.
Data Precision and vehicles operating in the real world Due to differing daily duty cycles, engine to engine variability, and of course environmental factors, it is well known that fuel economy data precision is very hard to measure in real world applications. In a small bench test results can be very precise but as one moves from bench testing into engine testing, chassis dynamometer testing then track testing and finally into real world applications, that data precision is completely lost.
There are several on-road studies using passenger cars and heavy duty diesel vehicles, but what would this look like off-highway? At the chosen test site a variety of heavy machinery is owned and maintained. The company in question is Stein Incorporated, which operates a steel mill in the Cleveland area of Ohio, USA. Their equipment includes cranes, loaders, excavators, carriers, and several Euclid D35 trucks like the one involved in this trial – see Figure 2.
One of the key points was the requirement for repeat runs to enable a statistical sound judgement of any fuel economy improvement to be made. With just a few data points there could well be overlap of results particularly when we are looking for relatively small fuel economy gains. Good test repeatability together with a high number of test runs offers the best test differentiation.
The Test Route Figure 3 shows a satellite view of the test site. Superimposed is actual vehicle speed data taken throughout a typical day shift operation, which corresponds to about 8 to 10 full loads per day. Low speeds, 0 to 10 km/h are indicated in dark to light blue, medium speeds in the 10 to 20 km/h region by dark green to light green and higher speeds up to 36 km/h in yellow through to red.
Figure 3
The terrain is mostly level with the vehicle operating on dirt roads, although there are some paved sections. The weather during the trial was typical North Eastern USA climate (Ohio), having cold winters and hot summers.
Figure 2
Euclid is an alternative name to that given by General Motors as it is usually called the ‘Terex’. It is quite an old vehicle that is re-engined at fairly regular intervals. It is currently powered by a Detroit Diesel 60, 6 cylinder, 12.7 litre engine.
Instrumentation To enable brake specific fuel consumption to be calculated, accurate measurements of engine torque and fuel used are required. Strain gauges were fitted to the engine flywheel and also to the drive shaft. More gauges were fitted to the vehicle hydraulic pump for future analysis of hydraulic fluids. In the future it is also planned to test with lower HTHS oils.
A coriolis mass flow meter was fitted to measure actual engine fuel flow and turbine flow meters were fitted into the hydraulic
LUBE MAGAZINE NO.128 AUGUST 2015
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