Diploma thesis on power consumption at the blower

In the 1991 season, a thesis on the power consumption of the blower in the SF 6 was prepared. The aim of this work was to determine exactly which drive power is required under which conditions to drive the fan and which factors have an influence on this power consumption. In addition to a series machine, these measurements were also carried out on a test chopper that was equipped with the fan configuration of the later "Mammut". The differences in performance between these two configurations also had to be worked out.

Many thanks to Diplomengineer Johann Huber, who made this thesis available and agreed to its publication!

In the following, some measurement tables and the most important findings from them are briefly summarized (some images can be enlarged by clicking on them).

 

 

 

 

 

 

 

 

The crop flow in the SF 6...

 

 

 

 

 

 

 

...and the associated Powertrain

In order to measure all forces precisely, the two choppers were equipped with several sensors, including a torque measuring hub on the blower shaft.

Below are some measurement records that were recorded in practical field tests, the machine was equipped with a 231kW Volvo engine, a four-row maize header and a standard blower from the current series. The theoretical nominal speed of this fan was 1,277 min-1.

This measurement graph shows the power consumption at a cutting length of 8mm using the maximum engine power. The fluctuations in output were due to differences in the maize population and also due to a somewhat uneven intake-supply. The power consumption was between 43.9kW and 46.6kW, the maximum value was 61.3kW.

Next, it was investigated whether the distance between the fan blades and the blower base has an influence on the power consumption, see sketch.

As a result, the power consumption with a correctly adjusted fan was 39.5kW, with a badly adjusted fan it was 43.6kW.

In practice, there are also striking differences in throwing performance.

 

 

 

Now for the power consumption with different cutting lengths, whereby the fan was set correctly again and the forward speed of the machine was constant at 5.2 km / h. Result: The cutting length by itself has no effect on the fan. In practice, however, the greater the cutting length, the greater the mass throughput of the entire machine, which in turn naturally increases the power consumption of the blower accordingly.

The same or similar measurements were also carried out on a test chopper whose blower diameter was reduced from 730 mm to 560 mm, but the nominal speed was increased to approx. 1,600 rpm. In purely mathematical terms, this reduced the circumferential speed from 48.7 m/s to 46.9 m/s. Result with regard to the power consumption: No significant difference can be determined!

 

 

 

The results of the last table show the respective power consumption with an increase in the forward speed in 1 km/h steps from 2.0 km/h up to 9.0 km/h.

Finally, a drawing that shows the differences between the series machine and the test chopper. Due to the blower configuration, along with the shape of the ejection chute, the arrangement of the fuel tank and the extended wheelbase, this must be viewed as a prototype for the SF 7-series,  known under the sales name "Mammut".