We have finalized the fuel and cooling system layout which is pretty unique and pretty exciting. We really had to work at this to incorporate fuel as a coolant as Andy had envisioned. A comprimise was made to add a larger heat exchanger instead of only using the wings and tanks as heat exchangers, as there are times where the amount of fuel in the tanks just wouldn't provide enough heat dissapation needed.
So following our super scientific Power Point, the fuel will come from the selected wing tank through a filter in the wing root to the duplex fuel valve. Airflow Performance boost pumps plumbed in parrellel will push the fuel forward of the firewall into a 1.5-2 gallon non-vented header tank and pressurize the tank and lines to 51 psi. Located on the header tank will be a pressure sensor, coolant outlet and return fittings, and injector rail outlet fitting.
The pressurized tank will allow the entire fuel rail to be pressurized at the required 51 psi controlled by a pressure relief valve located after the rail. The relief port will return to the selected tank via the duplex fuel valve. The ECU will control the fuel boost pumps which will have internal overpressure protection as well. In the event of a pump failure, the ECU will automatically turn on the secondary pump and provide annunciation to the cockpit.
From the header tank will also be a coolant circuit. Airflow performance pumps will be variable speed and controlled by the ECU depending on engine temperature. The primary pump, plumbed in series with the secondary pump, will not have flow throug capability to assist in keeping the engine temperature optimum. The secondary pump will have flow through capability and will be activated by the ECU if the temperature rises beyond limits and/or the primary pump fails. After the engine cooling jacket, a thermostat will direct fuel either to return to the header tank or to a heat exchanger (radiator) to dissapate excess heat.
Once challenge that this solution takes care of is a requirement to heat the fuel prior to the injector rail to a minimum of 130 degrees F. This provides better combustion in the cylinders, keeping in mind that the Jet A combusts via spark, not compression. We did not want to have an inline, power zapping, electric heater for the fuel. While the engine will start and run fine on cold fuel, the optimum performance will be gained once the fuel is warm. Testing will determine if we will need to add an inline heater for cold weather ops prior to take off, but no heater will be needed in flight.
Our next area of focus is on the details of the electrical system/controls/ECU. We're planning a call with Andy early next week to get a production update and discuss the cockpit controls needed as well as ECU interface with avionics.
You say the primary coolant pump does not have flow-through capability - so if it fails how does the in-series secondary coolant pump continue to cool the engine?
PWM on brush type DC motors could be a bad idea. Others have noted a serious reduction in pump life and some pumps plain don't like it and don't respond well at low duty cycles. Better test that thoroughly on the bench before getting married to the idea in the airframe.
Complicated system, lots of places for something to go wrong.
If you want to warm the fuel, a simple tubing loop in the coolant would do the trick. You won't be able to sink much heat into the fuel for long at high power with a small header tank capacity.
Not to question the experts here, but one immediate concern would be a leak in the coolant system eliminating pressure for the injectors. A cracked block or cracked exchanger/radiator could effectively stop fuel flow to the engine by allowing the pressure to bleed off. Is there some type of check valve on the coolant inlet from the header tank? I suppose the leak would have to be more than a small crack with two pumps operating.
Also, Is there any concern that that radiator cannot give up enough heat in ground ops? What happens during the OSH departure parade, where you are idling for 30 minutes at a dead stop in 100* ambients? To make the worst case worse, assume you started the engine already heat soaked. Don't know the boiling point for jet A, but being a multi fuel engine, this seems to be an issue running on gas, even at 50 PSI. Maybe an electric fan?
You say the primary coolant pump does not have flow-through capability - so if it fails how does the in-series secondary coolant pump continue to cool the engine?
PWM on brush type DC motors could be a bad idea. Others have noted a serious reduction in pump life and some pumps plain don't like it and don't respond well at low duty cycles. Better test that thoroughly on the bench before getting married to the idea in the airframe.
Complicated system, lots of places for something to go wrong.
If you want to warm the fuel, a simple tubing loop in the coolant would do the trick. You won't be able to sink much heat into the fuel for long at high power with that small header tank capacity.
Ross, Don at Airflow said the PWM isn't a concern at all. I don't know all the technical details but he didn't anticipate any issues or longevity concerns with his pumps and variable speed.
We looked at a liquid to liquid heat exchanger for warming the fuel, but the most increase you can get is about 40F, not enough to get to the 130F. We're trying to avoid electric heaters since they pull so much power which could impact operations with a limited electrical system capability.
Ya'll are not crazy. It was originally marketed as the "Higgs Diesel".
https://www.facebook.com/AdvancedCo...-ace-379-engine-to-give-refe/601078573388897/
Ross, do you have any pics or designs for a HX? I'm only finding some diesel truck stuff at this point before trying to roll my own as a test.
Ross, do you have any pics or designs for a HX? I'm only finding some diesel truck stuff at this point before trying to roll my own as a test.
Then it becomes a question of how to decide where the fuel goes based on heat, wing first then up through the system then to HX first or to small HX then to wing, etc. What we are afraid of is getting to a low tank level and running out of options to get rid of the heat.
One point seemingly overlooked here (and it might be me) is the fact that aircraft using fuel for cooling "stuff" are dealing with thousands of gallons and rely on huge thermal mass. There is very little "cooling" due to the airflow over the wings. The concept was explored quite a bit with wartime development and found unworkable for engine cooling. Seems to me that pumping a high thermal load into a small and rapidly diminishing quantity of fuel is a thermal runaway event in the making.
You are quoting data and products that were originally used to write the original papers.
Two strokes have notoriously poor fuel consumption due to "short circuiting" The papers you have read were based on engines that were using a simple carburetor for fuel supply.
AH
Neither the Hooper or E-330 are diesels, they are heavy fuel capable, SI designs. I am confused...
The Hooper engine has dreadful BSFC- especially on Jet A.
I have emailed back and forth a number of times with Andrew over the past couple of years. I was also able to visit Andrew at Osh Kosh and I'm really looking forward to seeing him get into the production stage of his 4 cyl.
I sent him an email after the holidays but I have not had a reply as of yet. I'm guessing he is up to his eyeballs in all the tasks required to keep this project moving forward.
Does anyone have any updates on the current status on the testing / certification / availability of his 4 cyl engines.
I'm dying to get any info that anyone has.... Jeff
Andrew if you happen to read this I'm the guy in Minneapolis with the motorcycles
Tim just posted over on the RV-10 Facebook Group about the current status. https://www.facebook.com/groups/249625742733962/?ref=share
I Don't Facebook..............
I Don't Facebook..............
Me either... Can some provide a loose translation?