Honda Power Unit Hardware & Software

[etusch]

merso uses higher working temperetue this year. With my level of knowledge I can say that they are doing it for getting faster combustion by keeping h efficiency alive.

No, they are doing it to reduce radiator area.
If they wanted to increase combustion temperature for whatever reason all they had to do was decrease charge cooling.

exhaust and mgu-h ? is it still enough?

[godlameroso]

If your fluids are running at 105c, that may be fine for the engine but the MGU-K may be required to have fluids at 70c, so even though the MGU-K cooling requirement is smaller than the engine, it may require more robust cooling to achieve the desired temperatures. Whereas Mercedes can combine MGU-H and turbine cooling on one circuit and reduce packaging, perhaps Williams cannot due to budget.

The cooling package is still part of the chassis/aero. If they can't get it right because of budget limitations no engine will change that.

To say that Williams are slowest because of very special Merc ERS cooling requirements is plain speculation and clutching at straws.

I'm saying it's one of the factors that may affect them, there are a lot of things not up to par on that Williams car, and it is simply undeveloped. The engine was a big factor in it's improvement over 2019, and seeing as most teams will at worst break even with the aero changes the 2021 engine improvement will be magnified.

[godlameroso]

merso uses higher working temperetue this year. With my level of knowledge I can say that they are doing it for getting faster combustion by keeping h efficiency alive.

No, they are doing it to reduce radiator area.
If they wanted to increase combustion temperature for whatever reason all they had to do was decrease charge cooling.

Increase combustion speed by using higher working temperature. The combustion process has an endothermic component, in other words it takes energy to break the carbon bonds in gasoline, lowering chamber temperature. When there's more energy available in the environment, those bonds will break more readily, because there's less impact from the effect of fuel vaporization quenching the A/F mix.

Lubricants that don't vaporize and maintain viscosity at higher temperatures is a must.

[gruntguru]

merso uses higher working temperetue this year. With my level of knowledge I can say that they are doing it for getting faster combustion by keeping h efficiency alive.

No, they are doing it to reduce radiator area.
If they wanted to increase combustion temperature for whatever reason all they had to do was decrease charge cooling.

Increase combustion speed by using higher working temperature. The combustion process has an endothermic component, in other words it takes energy to break the carbon bonds in gasoline, lowering chamber temperature. When there's more energy available in the environment, those bonds will break more readily, because there's less impact from the effect of fuel vaporization quenching the A/F mix.

Equally important is heat transfer. Hotter chamber walls (and cooler combustion) = less heat loss from the combustion gas = higher TE = higher power.

[63l8qrrfy6]

From a strictly thermodynamic perspective it makes sense to increase the heat input by completely removing intercooling but in practice highly boosted engines are knock limited hence development goes into actually reducing the gas temperatures by charge cooling, miller cycle, extreme valve overlap and even intake de-tuning.

Reducing heat rejection to increase TE can be done by reducing the dT across the cylinder wall (as GG says, decrease gas temp, increase water temp or both) or by increasing the cylinder wall thermal resistance.
Most "adiabatic engine" research has focused on the latter and has been largely unsuccessful.

The idea of increasing the coolant water temperature to reduce radiator drag was first successfully used by the British during WW2. The downsides are an increase in coolant pressure required to avoid boiling which leads to higher pump drive power requirements and heavier coolant system plumbing.

The Honda paper has a very good graph showing the lap time gain as the coolant temperature is increased. I don't have a copy handy atm so can't point at the exact page but can't be hard to find.

Edit:

On page 52 of the Honda F1 technical review it shows that increasing the water temperature from 100 to 120C leads to an engine power loss of 2kW however the aero benefit is such that the lap time is actually reduced.

Of course these turbo engines where TE dictates the output will respond differently but it goes to show that the aerodynamic effects dominate.

[godlameroso]

From a strictly thermodynamic perspective it makes sense to increase the heat input by completely removing intercooling but in practice highly boosted engines are knock limited hence development goes into actually reducing the gas temperatures by charge cooling, miller cycle, extreme valve overlap and even intake de-tuning.

Reducing heat rejection to increase TE can be done by reducing the dT across the cylinder wall (as GG says, decrease gas temp, increase water temp or both) or by increasing the cylinder wall thermal resistance.
Most "adiabatic engine" research has focused on the latter and has been largely unsuccessful.

The idea of increasing the coolant water temperature to reduce radiator drag was first successfully used by the British during WW2. The downsides are an increase in coolant pressure required to avoid boiling which leads to higher pump drive power requirements and heavier coolant system plumbing.

The Honda paper has a very good graph showing the lap time gain as the coolant temperature is increased. I don't have a copy handy atm so can't point at the exact page but can't be hard to find.

Edit:

On page 52 of the Honda F1 technical review it shows that increasing the water temperature from 100 to 120C leads to an engine power loss of 2kW however the aero benefit is such that the lap time is actually reduced.

Of course these turbo engines where TE dictates the output will respond differently but it goes to show that the aerodynamic effects dominate.

Why do turbine engines never have to worry about detonation as long as there's no problem with the injectors? Why do ICE engines have to worry about detonation?

Answer: In a turbine engine, the fuel is sprayed directly into the combustor, the fuel doesn't have to mix with air then travel into the combustion chamber. Those PFI engines create a mixture outside the CC and the fuel vaporizes on the way to the CC. The fuel has cooled the intake ports and intake valves as it vaporizes and by the time it's in the CC, it's already pretty close to fuel vapor making it more volatile and ready to ignite.

These engines are DI so more heat in the chamber is more better-er because it helps the fuel vaporize quicker. The fuel gets shot right into the CC, so it doesn't have time to vaporize in the plenum(which is near head coolant temp-ish) or as it passes the intake valves. The faster the fuel vaporizes the less cylinder bore oil washing you have, a particular issue since the injectors are side mounted.

I absolutely do agree that this is an aero dominated formula, however if the power unit wasn't important the OEMs wouldn't be spending the kind of cash that can buy fully furnished private islands every year, for 30 or 40hp gains.

[63l8qrrfy6]

Why do turbine engines never have to worry about detonation as long as there's no problem with the injectors? Why do ICE engines have to worry about detonation?

Answer: In a turbine engine, the fuel is sprayed directly into the combustor, the fuel doesn't have to mix with air then travel into the combustion chamber. Those PFI engines create a mixture outside the CC and the fuel vaporizes on the way to the CC. The fuel has cooled the intake ports and intake valves as it vaporizes and by the time it's in the CC, it's already pretty close to fuel vapor making it more volatile and ready to ignite.

Wrong! The reason gas turbines don't knock is because combustion pressures are very small, about one order of magnitude lower compared to a boosted piston engine. They operate according to the Brayton cycle where combustion occurs at constant pressure. On top of this they use dillution air for film cooling combustion surfaces making the effective lambda huge compared to a conventional reciprocating engine.

[gruntguru]

Detonation occurs in SI piston (and Wankel etc) engines because the charge is pre-mixed prior to the initiation of combustion. Being pre-mixed, there is a quantity of charge in a combustible state and propagation of combustion through the charge at the speed of sound or thereabouts will create the shock wave we hear as detonation.

Diesel engines also have very high cylinder pressures but do not detonate because the charge is not pre-mixed and combustion can only proceed at the rate at which fuel is injected (diffusion combustion). Diesels do exhibit a type of detonation (Diesel knock) due to "ignition delay" - ignition does not start until a small amount of fuel has been injected. When ignition occurs there is a small quantity of pre-mixed charge and this will often detonate since Diesel fuel is low octane and cylinder temperature is well above the autoignition temperature of the mix. Diesel knock is most prevalent during warmup because ignition delay is longer due to the cooler charge air.

Turbine engines obviously are another engine that use diffusion combustion rather than pre-mixed combustion and detonation is therefore impossible.

[63l8qrrfy6]

Turbine engines obviously are another engine that use diffusion combustion rather than pre-mixed combustion and detonation is therefore impossible.

There are stationary gas turbines which operate with lean pre-mixed combustion and switch to diffusion during start up and shut down. They would knock if the pressure could be increased significantly but in practice the peak pressure is given by the overall compressor PR which is small compared to the peak combustion pressures in the SI engine.

Edit:
It would seem that pre-mixed combustion aero gas turbines are also ready to enter production. If the predicted reduction in emissions is observed in practice it should not be long (in aviation terms) before this would become the most common type of aero engine.

[godlameroso]

Why do turbine engines never have to worry about detonation as long as there's no problem with the injectors? Why do ICE engines have to worry about detonation?

Answer: In a turbine engine, the fuel is sprayed directly into the combustor, the fuel doesn't have to mix with air then travel into the combustion chamber. Those PFI engines create a mixture outside the CC and the fuel vaporizes on the way to the CC. The fuel has cooled the intake ports and intake valves as it vaporizes and by the time it's in the CC, it's already pretty close to fuel vapor making it more volatile and ready to ignite.

Wrong! The reason gas turbines don't knock is because combustion pressures are very small, about one order of magnitude lower compared to a boosted piston engine. They operate according to the Brayton cycle where combustion occurs at constant pressure. On top of this they use dillution air for film cooling combustion surfaces making the effective lambda huge compared to a conventional reciprocating engine.

Well turbine power output is determined by the compressor's..compression ratio, combustion pressure is the result of expanded air. The point of all this is to say that because fuel in a turbine engine burns pretty much instantaneously, there's little to no chance of it burning spontaneously despite astronomical compression ratios.

In these engines, timing is still an issue, which is why so much work goes into increasing the burn rate of fuel. The faster the fuel burns the lower the chance of detonation.

There are stationary gas turbines which operate with lean pre-mixed combustion and switch to diffusion during start up and shut down.

Pre-mixed combustion in this instance means a type of EGR, rerouting or staging air or fuel to maintain a lean condition to limit production of NOx. It's not pre-mixed in the same sense that the a/f ratio is pre-mixed in a piston engine.

Speaking of mixing, I wonder how Honda does it, Ferrari is claiming to be using a "swirl" chamber instead of tumble for 2021, which could mean a lot of things. Maybe swirl prevents charge reversion, an issue if the mach number is somewhere over .5

[63l8qrrfy6]

Well turbine power output is determined by the compressor's..compression ratio, combustion pressure is the result of expanded air. The point of all this is to say that because fuel in a turbine engine burns pretty much instantaneously, there's little to no chance of it burning spontaneously despite astronomical compression ratios.

There are stationary gas turbines which operate with lean pre-mixed combustion and switch to diffusion during start up and shut down.

Pre-mixed combustion in this instance means a type of EGR, rerouting or staging air or fuel to maintain a lean condition to limit production of NOx. It's not pre-mixed in the same sense that the a/f ratio is pre-mixed in a piston engine.

No it's not EGR, it's normal, lean air fuel mixture.

According to google the highest pressure ratio aero engine is the GE genx family with a PR of 58 and a combustor inlet temperature of 600C.
So for an inlet condition of 1 bar the fuel will be injected in air at 600C and 58 bar. As per the ideal Brayton cycle this pressure remains constant during heat addition.

Compare this to a current F1 engine which can be assumed to run at 4 bar PR and say a CR of 14 with 100C air temperature after charge cooling. Assuming adiabatic compression with air as an ideal gas the conditions at the end of the compression stroke are about 160 bar and close to 800C. That is before heat even being released from fuel at more or less constant volume (not constant pressure as in a gas turbine). You can go on and calculate what the conditions are after say 50% of the heat has been released but I am hoping that the point I am making is quite obvious by now.

[Rodak]

The idea of increasing the coolant water temperature to reduce radiator drag was first successfully used by the British during WW2. The downsides are an increase in coolant pressure required to avoid boiling which leads to higher pump drive power requirements and heavier coolant system plumbing.

Why would running at a higher coolant temperature increase pump power requirements? The coolant liquid isn't made denser and it's a closed system. Heavier plumbing I can see as the radiator and tubing would have to be a bit stronger, but not very much stronger for a 20°C temperature increase.

[63l8qrrfy6]

The idea of increasing the coolant water temperature to reduce radiator drag was first successfully used by the British during WW2. The downsides are an increase in coolant pressure required to avoid boiling which leads to higher pump drive power requirements and heavier coolant system plumbing.

Why would running at a higher coolant temperature increase pump power requirements? The coolant liquid isn't made denser and it's a closed system. Heavier plumbing I can see as the radiator and tubing would have to be a bit stronger, but not very much stronger for a 20°C temperature increase.

Pressure must be increased to avoid boiling.
For a mean coolant temperature of 130C the coolant can easily exceed 150C locally in the cylinder head water jacket.

Attempting to increase local flow velocities also result in an higher pressure drop and hence higher pump outlet pressure.

For reference Spitfires equipped with Merlin 61s could run the coolant system at 140C intermittently at a pressure of around 6 bar. This is still extraordinary by today's standards.

[godlameroso]

Well turbine power output is determined by the compressor's..compression ratio, combustion pressure is the result of expanded air. The point of all this is to say that because fuel in a turbine engine burns pretty much instantaneously, there's little to no chance of it burning spontaneously despite astronomical compression ratios.

There are stationary gas turbines which operate with lean pre-mixed combustion and switch to diffusion during start up and shut down.

Pre-mixed combustion in this instance means a type of EGR, rerouting or staging air or fuel to maintain a lean condition to limit production of NOx. It's not pre-mixed in the same sense that the a/f ratio is pre-mixed in a piston engine.

No it's not EGR, it's normal, lean air fuel mixture.

According to google the highest pressure ratio aero engine is the GE genx family with a PR of 58 and a combustor inlet temperature of 600C.
So for an inlet condition of 1 bar the fuel will be injected in air at 600C and 58 bar. As per the ideal Brayton cycle this pressure remains constant during heat addition.

Compare this to a current F1 engine which can be assumed to run at 4 bar PR and say a CR of 14 with 100C air temperature after charge cooling. Assuming adiabatic compression with air as an ideal gas the conditions at the end of the compression stroke are about 160 bar and close to 800C. That is before heat even being released from fuel at more or less constant volume (not constant pressure as in a gas turbine). You can go on and calculate what the conditions are after say 50% of the heat has been released but I am hoping that the point I am making is quite obvious by now.

Turbine pressure ratios are not measured the same way as in what you're describing in an ICE compadré.

Pressure ratio is air coming in and thrust coming out, it is not the same as the compression ratio, which is much higher than 68:1.
If we measure like for like then you'd have to measure intake pressure vs exhaust pressure of the ICE.

[63l8qrrfy6]

Turbine pressure ratios are not measured the same way as in what you're describing in an ICE compadré.

Pressure ratio is air coming in and thrust coming out, it is not the same as the compression ratio, which is much higher than 68:1.
If we measure like for like then you'd have to measure intake pressure vs exhaust pressure of the ICE.

Wrong again.
First of all I did not make a single reference to turbine pressure ratios. I have strictly talked about compressor pressure ratio which is the ratio of outlet pressure to inlet pressure.

I never said that pressure ratio is the same as the compression ratio either. For the ICE calculations I showed I only use the pressure ratio to estimate the initial conditions at the beginning of the compression stroke. I then use the compression ratio to calculate the gas conditions at the end of the compression stroke assuming adiabatic compression. It is all very basic thermodynamics.

As for aero engine compressor overall pressure ratios you don't have to take my word for it, just google it.

Edit:
Do you normally use the rate button when you run out of science?