does injection continue after the spark ?
is there one injection episode or multiple episodes (per cycle) ?
(starting injection 90 - 180 deg before the spark seems so old-fashioned and exposes the fuel to heat for a critically longer period ??)
Isn't fuel heating necessary? Regardless I believe there are multiple injections per cycle. As far as the timing is concerned, I imagine that's one of the more closely guarded secrets.
There is fuel heating prior to injection, and then there is the chance of pre-ignition due to early injection because it's exposed to the hot chamber longer. Maybe the fuel type is fine in the condition?
The process is probably simpler than we're thinking, just hard to get to work in a controllable fashion.
Gasoline is quite difficult to ignite as a liquid, in fact it's only combustible in vapor form. The fuel injectors spray fuel as small droplets which have smaller surface area than a homogeneous squirt of liquid fuel, this aids vaporization, and by consequence combustion. Heating fuel aids this vaporization, the problem with heating fuel excessively in the rail is that you can get vapor lock, then you get nothing. That's why using residual EGR to heat the fuel as it's injected is a viable strategy.
Here's some dork showing how fuel doesn't really burn in liquid states. Gasoline is at 9 min mark.
On the other hand, the Ilmor-badged chevy engined cars didn't have 8 failures in the month of May so while they are perhaps slower, they at least run reliably.
Didn't Andretti say Honda asked him if they wanted more reliability or more speed, and he said speed always.
Isn't fuel heating necessary? Regardless I believe there are multiple injections per cycle. As far as the timing is concerned, I imagine that's one of the more closely guarded secrets.
There is fuel heating prior to injection, and then there is the chance of pre-ignition due to early injection because it's exposed to the hot chamber longer. Maybe the fuel type is fine in the condition?
The process is probably simpler than we're thinking, just hard to get to work in a controllable fashion.
Gasoline is quite difficult to ignite as a liquid, in fact it's only combustible in vapor form. The fuel injectors spray fuel as small droplets which have smaller surface area than a homogeneous squirt of liquid fuel, this aids vaporization, and by consequence combustion. Heating fuel aids this vaporization, the problem with heating fuel excessively in the rail is that you can get vapor lock, then you get nothing. That's why using residual EGR to heat the fuel as it's injected is a viable strategy.
It´s diesel what barely ignites in liquid form. My father always use a mix gasoline-diesel (around 20-80%) when he need to burn some prunning or some procesionary moth nests (if that´s the name in english). 100% gasoline is dangerous and does not last enough to ignite anything, and 100% diesel would be almost imposible to ignite, so that mix gets the best of both
Isn't fuel heating necessary? Regardless I believe there are multiple injections per cycle. As far as the timing is concerned, I imagine that's one of the more closely guarded secrets.
There is fuel heating prior to injection, and then there is the chance of pre-ignition due to early injection because it's exposed to the hot chamber longer. Maybe the fuel type is fine in the condition?
The process is probably simpler than we're thinking, just hard to get to work in a controllable fashion.
Gasoline is quite difficult to ignite as a liquid, in fact it's only combustible in vapor form. The fuel injectors spray fuel as small droplets which have smaller surface area than a homogeneous squirt of liquid fuel, this aids vaporization, and by consequence combustion. Heating fuel aids this vaporization, the problem with heating fuel excessively in the rail is that you can get vapor lock, then you get nothing. That's why using residual EGR to heat the fuel as it's injected is a viable strategy.
Wouldn't fuel flash to vapor when injected after being heated and compressed at such high pressures?
Re: Honda Power Unit
Posted: 31 May 2017, 18:53
by godlameroso
That would be ideal actually. Vapor mixes with air much better than liquid, and you avoid wall wetting.
gruntguru wrote:
A quick calculation indicates a flow rate of 2.2 kg/minute (~3 L/min) for each injector if injection duration is less than 90 crankshaft degrees. This is a very-high-flow injector.
(starting injection 90 - 180 deg before the spark seems so old-fashioned and exposes the fuel to heat for a critically longer period ??)
I only chose those durations (90* and 180*) to illustrate how large the injector needs to be to squeeze the fuel delivery into such a short duration. Another poster has already claimed that 1.3 ms is not long enough to achieve proper mixing. Obviously a compromise is required.
A key benefit of DI is in-cylinder evaporation of the fuel - this needs time as well.
does injection continue after the spark ?
is there one injection episode or multiple episodes (per cycle) ?
(starting injection 90 - 180 deg before the spark seems so old-fashioned and exposes the fuel to heat for a critically longer period ??)
Isn't fuel heating necessary? Regardless I believe there are multiple injections per cycle. As far as the timing is concerned, I imagine that's one of the more closely guarded secrets.
There is fuel heating prior to injection, and then there is the chance of pre-ignition due to early injection because it's exposed to the hot chamber longer. Maybe the fuel type is fine in the condition?
The process is probably simpler than we're thinking, just hard to get to work in a controllable fashion.
They could carry the conduit from the reservoir to the injector through hot places of the PU so that it reaches the injector at the desired temperature ..... by trial error find the path for the conduit that maintains a stable temperature in any condition.
gruntguru wrote:
A quick calculation indicates a flow rate of 2.2 kg/minute (~3 L/min) for each injector if injection duration is less than 90 crankshaft degrees. This is a very-high-flow injector.
(starting injection 90 - 180 deg before the spark seems so old-fashioned and exposes the fuel to heat for a critically longer period ??)
I only chose those durations (90* and 180*) to illustrate how large the injector needs to be to squeeze the fuel delivery into such a short duration. Another poster has already claimed that 1.3 ms is not long enough to achieve proper mixing. Obviously a compromise is required.
A key benefit of DI is in-cylinder evaporation of the fuel - this needs time as well.
Isn't cylinder mixing aided by piston speed and corresponding turbulence?
Re: Honda Power Unit
Posted: 02 Jun 2017, 01:55
by gruntguru
Yep. Also by dispersion of droplets due to spray pattern and velocity (fuel pressure).
Isn't fuel heating necessary? Regardless I believe there are multiple injections per cycle. As far as the timing is concerned, I imagine that's one of the more closely guarded secrets.
There is fuel heating prior to injection, and then there is the chance of pre-ignition due to early injection because it's exposed to the hot chamber longer. Maybe the fuel type is fine in the condition?
The process is probably simpler than we're thinking, just hard to get to work in a controllable fashion.
They could carry the conduit from the reservoir to the injector through hot places of the PU so that it reaches the injector at the desired temperature ..... by trial error find the path for the conduit that maintains a stable temperature in any condition.
Fuel temperature would be precisely controllable. Either use a heat exchanger with variable coolant flow or by mixing hot and cold paths of fuel (or coolant) with a variable blending valve. Probably the latter for better response.
Re: Honda Power Unit
Posted: 02 Jun 2017, 09:38
by Big Mangalhit
I remember a while ago there was some leak of the Ferrari (HAAS?) engine telemetry screens. In those prints there was a value for FuelTempR and FuelTempL so I think yes they are highly regulated.
Clarification by Hasegawa about the "MGU-H only lasts for two races" statement. He said "that's the trend but their testing shows it capable of far longer". Mentions it's just a modification required and they have another revised version in testing now but they don't want to change it Canada unless a problem occurs.
He also mentions they have other upgrades they are meant to bring to Canada. Positive signs?
