Behotec JB220涡喷发动机评测
作者：COLIN STRAUS图片：COLIN STRAUS
原载《Radio Control Jet International》杂志2015年2-3月刊
The comprehensive JB220 package contains everything required with the exception of the ECU battery pack – note the separate turbine and ECU manuals
Turbine Package Contents:
Behotec JB220 Turbine
Fuel Pump
ProJet Hornet III ECU
(Electronic Control Unit)
GSU (Ground Support Unit)
I/O Board
Leads
Fuel Tubing
Electronic Fuel Valve
Electronic Kerostart Valve
Fuel Filter
Festo ‘Y’ Connector
Filter type Clunk
Instruction Manuals
Probably the most popular size of model turbines over the last 15 years has been those of around 112 mm in diameter, dating from the original KJ66 and early commercial auto-start turbines. The subject of this month’s turbine test, the Behotec JB220, was the first example of this size engine to breach the 200 Newton thrust level, quite amazing really as it was not that many years ago that 80 Newtons was the expected level for turbines of this size.
RCJI has long wanted to test the JB220, but with the demand being so high there was a long wait, pushing us down the list, however just after the JetPower 2014 show we received the email confirmation that the test engine had shipped. The carton arrived safely after its short trip from Germany, a substantial cardboard box with formed foam internal moulding holding all the components securely and with excellent protection from damage.
The compact turbine just oozes quality and solidity, but is no heavier than the competition
In the Box
The turbine package is quite comprehensive, and contains everything required to operate the engine apart from the ECU battery, so includes the turbine itself, fuel pump, ProJet ECU and matching GSU, I/O board, fuel and kerostart valves along with fuel tubing, leads, filter etc. Looking first at the turbine, this is a very nice piece of work, with the first impression being that the entire engine is of very sturdy and solid construction, ranging from the machined aluminium starter bullet through the particularly stiff main case, complete with machined retaining rings for the mounting clamps, and on to the long and very neatly produced tailcone.
The starter bullet, support struts and front cover are all anodised black whilst the main case is also anodised, but this time in an anthracite colour, with the tailcone section having a bright finish. The temperature sensor and kerostart plug are internally mounted resulting in a smooth and uncluttered outward appearance, whilst there are a total of four connections, these being for the fuel and kerostart lines, as well as the main power and data cables from the ECU.
The machining work in the engine is very nice, and the compressor and intake are particularly well manufactured, as can be seen in one of the photos. Although buried a long way forward of the rear of the tailpipe the turbine wheel also looks very neatly produced. Notably the manual specifies that the turbine should be serviced after 50 hours of use, which is double the more normal 25 hours suggested by certain other turbine manufacturers, thus enabling less downtime for a frequently flown model.
The ECU itself is the latest Hornet III from ProJet, and although not the smallest ECU around, certainly continues the rugged theme, as it is well protected within a neat, moulded casing, this having Behotec branding.
The fuel pump is quite conventional and utilises a brushed motor, but does incorporate a useful mounting flange, which will make installation very simple compared to the many fuel pumps which leave mounting to the user’s imagination.
Other items supplied are fairly standard, as might be expected, however unlike most turbines, two separate English language instruction manuals are supplied, one covering the engine and the second the ECU. No FOD guard is supplied; however one is available as an option from Behotec.
As mentioned no battery is included, the instructions recommend a 3S LiPo of at least 2500 mAh and this is what we used for the testing, it proved to provide plenty of power for multiple starts and did not require recharging during the testing process.
This nice close-up shot shows the quality of the machining of the compressor
With the long tailpipe it was a challenge to get this sharp photo of the turbine wheel
Not the smallest ECU on the market,but probably the most well protected within its tough, moulded case On Test
With the engine and ancillary parts having been inspected and photographed it did not take long to mount the turbine onto my test rig. Slightly unusually these days, the JB220 has not yet moved to install the fuel and kerostart valves under the front cover of the engine, these still having to be mounted by the owner externally, but even with this the entire fuel and electrical system was quickly completed and connected to the rig fuel tank and the receiver being used.
Programming the turbine to the radio system was quite straightforward following the detailed instructions in the ProJet manual, and it was equally simple to prime the fuel lines in preparation for the first start. Kerosene with 5% oil was used for all of the test running,however the manual states that diesel fuel can also be used, which could be useful in areas where kerosene/paraffin are not easily available.
The actual start was very straightforward, although it took somewhat longer than some other turbines, taking in total around 80 seconds from the commencement of the start to the point where control is passed from the ECU to the radio system.
It should be noted that part of the reason for the extended start time is that the version III of the Hornet ECU carries out a calibration exercise as part of every start sequence, this ensuring the best performance and throttle response whenever the turbine is run.
Starts with the engine still warm take almost exactly the same time as cold starts, so can be allowed for when awaiting a flying slot at busy events. I did note a small amount of flame from the tailcone during the first start, this also being present during further starts, although this should be eliminated with some small adjustments to the start parameters.
Once through the start process the engine was put through the regular test regime, with data being collected throughout the rpm range. No problems were found, with the engine running perfectly throughout, no vibration at all being detected below around half power, but a small rumbling being noticed at the high power settings, not so much a vibration but a product of the sheer volume of air being passed through the engine.
The rpm appeared to be very stable at all of the throttle settings selected as part of the testing process, and both acceleration and deceleration proved trouble free, with excellent times of almost exactly 4 seconds being noted for the engine to go from idle at 35,000 to the full power speed of 123,000, and to then drop back to idle.
Powerful…
The power figures did prove to be a surprise to me – I had heard good things about the JB220, but had anticipated a performance close to the stated 220 Newton figure, even this would have been the best performance of any engine in this category by some margin. In fact the results obtained were even more impressive, with a full power corrected thrust of no less than 230.6 Newtons, which equates to 23.5 kg or 51.8 lb.
This is an amazing power output for an engine of this size, particularly as it was done in such a fuss-free manner, and makes the JB220 the turbine with the best power to weight ratio of all those so far tested by RCJI,and not by any small amount, in fact the calculated figure of 4.23 is well above the closest competitor’s figure of 3.94.
Fuel consumption was also above the specified figure of 730 cc per minute, being measured at 805 cc per minute, but this is no surprise given that the power output is so far above that claimed.
The fuel pump is simple to mount with its neat front plate, pre-drilled for mounting screws
Mounted on the test rig, the JB220 greatly impressed the testing team! Conclusion
The Behotec JB220 is a very impressive turbine, being of superb quality and very solid, yet comparatively light construction. The performance is class leading, and running characteristics excellent, so this engine must be one of the prime contenders for anyone looking for a compact, reliable and exceptionally powerful turbine in this size class.
Contacts：
www.behotec.com
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