Do we know if any teams use the turbine as an engine brake during deceleration? (i.e. MGU-H to ES)
Opposite essentially of the vaccuum that would get pulled in a typical otto cycle engine when you take your foot off the gas and the throttle plate closes, bringing the vehicle into noticeable deceleration.
I understand they can use the MGU-K to decelerate at a rate of 120 kW. But has anyone taken into account also using the MGU-H to capture this energy through compressing combustion chamber products on the exhaust stroke of the engine (compressing it against the turbine)?
Looking at some rough numbers for it, it looks like it's possible.
https://www.grc.nasa.gov/WWW/K-12/airpl ... trbth.html
https://www.mercedes-amg-hpp.com/formul ... ne-facts/#
Using this formula for Turbine Work / mass:
W/m = Cp*(Tin - Tout)
Power = (mass flow rate)*(W/m) = (mass flow rate)*Cp*(Tin - Tout)
Cp = 1.150 [kJ/(kg*K)] approximate value for dry air at around 500 C, roughly equal to Cp of combustion products
Tin = 1000 C = approx 1270 K
Tout = 500 C = approx 770 K
mass flow = 100 [kg/h] * 17 (Lean Air/Fuel Ratio + 1) * 1/3600 [h/s] = 0.472 [kg/s]
Power = 0.472 [kg/s] * 1.150 [kJ/(kg*K)] * (1270 [K] - 770 [K])
Power = 271.5 [kW]
Now, a couple things:
Obviously all of this power can't be devoted to the MGU-H, they likely won't run full fuel rate on deceleration, and there will be a stall limit to the turbine (variable geometry guide vanes would help but I'm not sure if it's legal).
But there looks to be some potential there, but it seems too easy for the rest of the teams to miss something like this.