ringo wrote:You guys are looking at this from a motor with a load that is steady and induced by the motor itself. Such as drilling through a material or pumping water. Where that load does what the motor insists and the load has no other connection to anything else.
What you are not looking at is that the MGU motor/generator is the load on the turbine. even with a closed loop control system it will always be a load. No matter the complexity, the only way it will control the turbos speed is by braking the turbo.
Correct, the MGUH is a load on the turbine the same way as the compressor is a load on the turbine.
Also correct that the way the MGUH controls the turbo is by controllingits speed - ie braking the turbo.
ringo wrote:Now where i see a problem, is that 90% of the time you will be using MGUH as a brake. It's not many instances where a turbo is too slow. So you will be increasing back pressure and thus increase pumping losses on the pistons whenever the MGUH is behaving in this constantly corrective way, trying to control a turbo (which i don't see the point of constant control). Anyhow, i don't even think it has the physical capability to do this anyway. That thing will be heat soaked in no time, duty cycle will be a big factor. (Notice the rules permit a clutched MGUh, they know the thing can't constantly be engaged)
The turbine and MGUH will, of course, be sized to match the requirements of the engine. If there is too much back pressure during operation then they have screwed up the sizing of the turbine.
It seems self evident that at 10,500rpm, the point where maximum fuel flow kicks in, the turbine will be producing its maximum power. The compressor will be demanding its maximum amount of power at that point too (max boost).
The mass flow of the engine is far in excess of that required to simply drive the compressor. Thus the turbine is sized to take advantage of this, and the MGUH "brakes" the turbine to maintain speed control.
I would imagine at this point the back pressure is no more than for a conventional turbo.
As the engine speed increases the fuel flow remains the same and the engine air mass flow rate remains constant or nearly so. But there is less boost on the intake side, so there is less energy for the turbine. If the turbine were to maintain the same speed the back pressure would be reduced.
It is my opinion that the power generated by the turbine will fall off less than the demand for the compressor. Thus, as revs increase the MGUH will be able to make more power. I would think that backpressure would be maintained, rather than increased, as the ICE rpm rises.
As to the use of the clutch. This is not because the MGUH can't handle the duty cycle. It is because at certain load conditions the turbine power will match the compressor demand. If the MGUH remained connected always it would be a drag on the system, and would prevent the turbo from accelerating or, perhaps, would even slow it down, which would be undesirable.
The MGUH will be liquid cooled, and that will be a very important system.
ringo wrote:Real turbine control, comes from mass flow control. this has no adverse effects on temperatures or back pressure, which is healthy for overall power output and also component life. I am of the belief the wastegate will still be present because of the reduced cost in r&d and also the reliability, simplicity, reduced cooling demand, and also no negative impact on ICE efficiency.
You could argue that control of the compressor provides mass flow control. Remember that the engine will give nearly constant air mass flow from 10,500rpm to 15,000rpm, and this is controlled by the boost/air mass flow from the compressor, which is controlled by the MGUH.
A wastegate may be included as insurance against MGUH failure. But I don't believe it will be used for primary control.
Using a wastegate maybe simpler, easier and (as of now) more reliable, but it is also a waste of energy.
You could, conceivably, use a wastegate in conjunction with the MGUH, but I'm not sure why you would. To get any benefit from the MGUH the bypass from the wastegate would need to be small. Almost pointless, in fact.
ringo wrote:before i forget as well, if your mguh has a low power rating, it will not be able to do complete boost control. You will still need a waste gate. The only way you wont need a waste gate is if at the peak power at 10,500rpm the MGUH capacity plus the compressor's power is such that the turbine will be at a reasonably steady state and wont over speed with those two loads applied. Now we all know this will only work at one engine speed range.
What happens at other speed ranges? You may find that you have too big or too small a turbine, and your dependency on MGUH motoring will be too high (this remember is draining energy from your ES to drive the turbine and compressor, it's not free energy) or you will have a very inflexible turbine selection, that was simply sized around a generator load and wasn't sized for the engine itself.
Why would you design this system and then stick on an MGUH with insufficient generating capacity?
Why would you size the turbine incorrectly? Why would you do R&D for 3 years only to completely mess up the fundamental turbine/compressor/MGUH sizing?
ringo wrote:A motor cannot manipulate a turbines mass flow or inlet pressure. It can only motor it or load it. This doesn't change it's mass flow. It's only after it slows the turbine, backing up the flow, raising the temperatures, fatiguing the blades, then reducing the boost, which goes to the engine then a lower powered pulse comes out the valves do you get any semblance of mass flow reduction. It's quite clunky if you ask me, and a bit of hammer and tongs. It's not as delicate and finely controlled if you ask me.
As clunky as dumping excess energy out the exhaust?
