EFI on a 50cc engine
11-15-2008, 03:00 PM
#1
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EFI on a 50cc engine
It turns out my latest contract is helping design a new type of engine. It's neither gasoline nor a diesel cycle engine, but it will run on both.
http://liquidpiston.com/
We're building a prototype to prove that the cycle works.
Anyone here ever put EFI on a 50cc engine?
http://liquidpiston.com/
We're building a prototype to prove that the cycle works.
Anyone here ever put EFI on a 50cc engine?
11-15-2008, 03:30 PM
#2
Melting Slicks
I'm familiar with the company, one of my associates pointed it out to me earlier this year...
They took down the animation, but as I recall it was basically a "double rotary" kind of thing that had a rotating combustion chamber between the compression and expansion rotors some which way...
Lots of "design challenges" in that thing. The temperature of the combustion chamber and the heat rejected to the "block" was one, as well as leakage from the combustion area. Valves to constrain the pressure in the "chamber" looked like an issue too, since they would never see "cool" air and the combustion temperature with a 18+ pressure ratio was going to be over 3,000 F....
The combustion chamber has to be pretty tiny too, in order to get the high CR...
Also if there was an easy way to recover the water from a water injected (quasi-Rankine) combustion system there would be a lot of engines out there doing it right now.... The problem is that you have to condense the water (as well as the combustion byproducts that are in it) filter or clean it and then re-use it. Most water injection systems are open loop (as used on large power generation gas turbines), because of that difficulty. The problem is that open loop in a car means carrying (and pre-distilling) a lot of water and that isn't a practical solution...
They got an SBIR Phase I, did they ever get a Phase II?
Good luck, there are a lot of challenges to overcome to get that to work...
They took down the animation, but as I recall it was basically a "double rotary" kind of thing that had a rotating combustion chamber between the compression and expansion rotors some which way...
Lots of "design challenges" in that thing. The temperature of the combustion chamber and the heat rejected to the "block" was one, as well as leakage from the combustion area. Valves to constrain the pressure in the "chamber" looked like an issue too, since they would never see "cool" air and the combustion temperature with a 18+ pressure ratio was going to be over 3,000 F....
The combustion chamber has to be pretty tiny too, in order to get the high CR...
Also if there was an easy way to recover the water from a water injected (quasi-Rankine) combustion system there would be a lot of engines out there doing it right now.... The problem is that you have to condense the water (as well as the combustion byproducts that are in it) filter or clean it and then re-use it. Most water injection systems are open loop (as used on large power generation gas turbines), because of that difficulty. The problem is that open loop in a car means carrying (and pre-distilling) a lot of water and that isn't a practical solution...
They got an SBIR Phase I, did they ever get a Phase II?
Good luck, there are a lot of challenges to overcome to get that to work...
Last edited by Solofast; 11-15-2008 at 03:41 PM.
11-15-2008, 05:03 PM
#3
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His current engine looks nothing like the old one.
It's an interesting setup, though I cannot share right now what it looks like.
It's an interesting setup, though I cannot share right now what it looks like.
11-16-2008, 12:59 AM
#4
Melting Slicks
That's probably a good thing... Frankly I didn't think the old setup had much of a chance of working at all.
If you think about it, one of the toughest aspects of the Brayton cycle is the fact that the hot parts are exposed only to high temperature gases. That is, the maximum cycle temperature is limited because the parts that see very high temperature are exposed to in continuously. In a intermittent combustion engine you get to wash the parts with cool air for 25% of the time and that brings down the metal temperature by a significant amount. The previous setup had the worst of both worlds, so it was going to be difficult to make work...
If you think about it, one of the toughest aspects of the Brayton cycle is the fact that the hot parts are exposed only to high temperature gases. That is, the maximum cycle temperature is limited because the parts that see very high temperature are exposed to in continuously. In a intermittent combustion engine you get to wash the parts with cool air for 25% of the time and that brings down the metal temperature by a significant amount. The previous setup had the worst of both worlds, so it was going to be difficult to make work...
11-16-2008, 01:35 PM
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But turbine engines do that all the time.
The compressor is separate from the turbine which has a separate source for cooling.
The compressor is separate from the turbine which has a separate source for cooling.
11-16-2008, 05:43 PM
#6
Melting Slicks
Yes, turbines do it all the time, but not without an efficiency penalty. If you look at uncooled turbines you will see temperatures are limited to less than 2,000 F, which limits the efficiency and specific power (that is power made per unit of inlet air flow). If you cool the parts you can run hotter, but the cost of cooling is pretty nasty, in terms of lost performance (cooling air extracts a performance penalty) and cost (cooled parts are more expensive). With conventional intermittent combustion engines you can burn a stoichiometric air fuel ratio and, because it is intermittent and cooling air washes the surfaces on intake and compression, the average metal temperatures are sufficiently low that you can make parts live without much cooling.
Remember that if you are looking at an 18 to one compression ratio, the air at the outlet of the compressor is approximately 800 degrees F before the combustion process. After a constant volume combustion process (like these guys want to do) it will over 3600 degrees F and pressures are probably going to be on the order of 40 atmospheres or higher (over 500 psi). You will need to expect to do some serious cooling and it won't be easy to valve and control gas at that temperature and pressure. In an auto engine the exhaust valve only sees exhaust gas after the expansion process, where it is a lot cooler than that. Think exhaust temps for a diesel of around 1,000 F, and for a gasoline engine at 1300 or so (more for a turbo engine because you have a lower expansion ratio process in the combustion chamber, but you get the idea).
Not saying it can't be done, but it sealing such an engine and making it work day in and day out won't be an easy task.
Hey, if it were easy somebody else woulda done it...
Remember that if you are looking at an 18 to one compression ratio, the air at the outlet of the compressor is approximately 800 degrees F before the combustion process. After a constant volume combustion process (like these guys want to do) it will over 3600 degrees F and pressures are probably going to be on the order of 40 atmospheres or higher (over 500 psi). You will need to expect to do some serious cooling and it won't be easy to valve and control gas at that temperature and pressure. In an auto engine the exhaust valve only sees exhaust gas after the expansion process, where it is a lot cooler than that. Think exhaust temps for a diesel of around 1,000 F, and for a gasoline engine at 1300 or so (more for a turbo engine because you have a lower expansion ratio process in the combustion chamber, but you get the idea).
Not saying it can't be done, but it sealing such an engine and making it work day in and day out won't be an easy task.
Hey, if it were easy somebody else woulda done it...
Last edited by Solofast; 11-16-2008 at 05:46 PM.
11-17-2008, 11:26 AM
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I also asked over in CFOT.
It turns out there's a new scooter on the market with a 49cc EFI engine.
Direct injection to boot!
http://www.orbitalcorp.com.au/orbita...dioverview.htm
It turns out there's a new scooter on the market with a 49cc EFI engine.
Direct injection to boot!
http://www.orbitalcorp.com.au/orbita...dioverview.htm
11-18-2008, 06:58 PM
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Well, I had an interesting day today.
I got into work, after some doorslambing azzhat decided to wake the entire hotel up @ 3am.
My boss wants to talk to me about the meeting we had yesterday.
They need an engine management system that can run a 50cc engine on gas, carb, fuel injection, direct injection and diesel. As well as take data sample in the 100k hz range for monitoring combustion.
I laid out several ideas for them, lot of work over the weekend.
So today their telling me they want to wait on the system till they prove the current design will turn over, not to meantion run, which is understandable.
The bad part is do to the cost of the system they can't afford they can't afford to keep me on till the engine is running, and they asked if I could come back in three weeks!
(WHAT???!!!)
I told them they could try, but I couldn't guarantee anything.
Did I meantion I cancelled both a dentist appointment and another job interview to start there last week?
I got into work, after some doorslambing azzhat decided to wake the entire hotel up @ 3am.
My boss wants to talk to me about the meeting we had yesterday.
They need an engine management system that can run a 50cc engine on gas, carb, fuel injection, direct injection and diesel. As well as take data sample in the 100k hz range for monitoring combustion.
I laid out several ideas for them, lot of work over the weekend.
So today their telling me they want to wait on the system till they prove the current design will turn over, not to meantion run, which is understandable.
The bad part is do to the cost of the system they can't afford they can't afford to keep me on till the engine is running, and they asked if I could come back in three weeks!
(WHAT???!!!)
I told them they could try, but I couldn't guarantee anything.
Did I meantion I cancelled both a dentist appointment and another job interview to start there last week?
11-18-2008, 07:40 PM
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At least the phone rang three times that day with recruiters wanting me for more contracts. Kinda put the wind out of his sails. Got to love timing! 
11-18-2008, 08:19 PM
#12
Melting Slicks
I got a call yesterday from a job shop looking for somebody who had gas turbine accessories experience, he said he had a lot of open req's for shoppers, so it isn't like engineering work has stopped. Might be a problem if the big three let go of a lot of engineers (which I expect will happen with reduced development), but for right now there does seem to be engineering work out there....
11-18-2008, 09:08 PM
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I used to design ECMs for one of the big three. There's several ECMs that could probably do the job (hardware-wise), but the (expensive) snag would probably be the cost of custom software, depending on what the input signals are and what sort of control algorithms are needed for the engine.
