The idea is fairly simple -- replace the throttle valve of a spark ignited internal combustion engine with a mixing valve that merges fresh air and exhaust air.

The original "throttle closed" setting would correspond to the mixing valve feeding the engine a little bit of fresh air and a lot of recirculated air.

The original "full throttle" setting would correspond to the mixing valve feeding the engine all fresh air and no recirculated air.
-- goldbb, May 19 2010

Smokey's Adiabatic Engine http://www.rexresea...m/yunick/yunick.htm
Not completely related, but really interesting. [MisterQED, May 21 2010]

Hmm.....
-- RayfordSteele, May 20 2010


Interesting. Would probably be efficient at extracting any unburned hydrocarbons in the exhaust, but because of the heat would also cause unnecessary heating of intake air + potential pre-ignition. So neutral vote.
-- acurafan07, May 20 2010


// unnecessary heating of intake air //

That could be overcome by having a large finned cooling section on the exhaust, followed by an air-to-air intoercooler on the induction side. Neither would be very heavy, but they would be bulky and would vary in effectiveness depending on ambient temperature. Also, the finned cooler would collect a lot of condensate.
-- 8th of 7, May 20 2010


acurafan07, provided that the intake manifold has low enough thermal mass, heating the intake air isn't *necessarily* bad. It reduces the intake air's density, reducing the mass of air and fuel entering the engine, which reduces fuel consumption. In fact, as much of the control over the engine's power comes from the heat of the recirculated exhaust gas, as from it's lack of oxygen.

8/7, Condensate could potentially be a good thing. It could be used for water injection, to reduce knocking and NOx.
-- goldbb, May 20 2010


I thought of this years ago (oh god decades) around the time Smokey Yunick published his ultra high heat engine. I gave up on the idea as knocking and O2 monitoring would have been tough at the time. They still would be an issue now, but not an insurmountable one. You'd have to account for the O2 levels in the exhaust and have a fast reacting ignition timing system to keep from knocking with the wide range of temperatures but it's doable. (+) Also make sure you include a spark arrestor.
-- MisterQED, May 21 2010


A spark arrestor isn't strictly necessary. 8/7's suggestions for coolers would be one way to avoid backfiring; direct injection of fuel into the cylinder would be another.

Knocking too isn't necessarily an issue, if exhaust gas condensate could be separated and sprayed into the intake.
-- goldbb, May 23 2010


//A spark arrestor isn't strictly necessary. 8/7's suggestions for coolers would be one way to avoid backfiring; direct injection of fuel into the cylinder would be another.// I thought about that, but even a direct injection system wants you to wait for the spark for correct timing, a hot ember will still get you. Even if it didn't, any particulates would be bad.

//Knocking too isn't necessarily an issue, if exhaust gas condensate could be separated and sprayed into the intake.// Yes, water injection helps, but for best power timing is crucial. You always want to be on the verge of knocking even accounting for all the variables.
-- MisterQED, May 24 2010


How much exhaust gas can you mix with the fuel and air before either the fuel fails to ignite or the flame speed is so low as to be inpractical? I believe 15% is about the max. so this would give you a range from 100% to 85% throttle. Not useful.
-- Twizz, May 24 2010


//how much exhaust gas can you mix// you need enough Oxygen to burn the fuel...
-- FlyingToaster, May 24 2010


Besides needing at least some oxygen to burn the fuel, you also need the flame front, once initiated by the spark, to travel at a reasonable speed so that half of the combustion event will occur before top dead center, and half after top dead center.

Well, usually... I suppose that if one used Transonic corporation's fancy supercritical fluid fuel injectors, flame front speed will equal the diffusion speed of the fuel into the air, which will probably be fairly constant regardless of how much recirculated exhaust gas is in the air.
-- goldbb, May 25 2010



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