Perhaps this is relevant:
Post by Tom/CalClassic on Oct 23, 2010 at 9:30pm
Hi,
I knew I shouldn't put away my Convair manual...
The augmenter system of engine cooling was used on the CV-240 through CV-440 aircraft - they are the two large "exhaust pipes" that come out of the rear of the nacelle.
The description:
"Exhaust System:
The exhaust system of each engine includes an exhaust manifold assembly and two augmentor assemblies. Each manifold assembly consists of eight siamese stacks and two single stacks that collect the exhaust gases and direct them into the bell mouth of two heat-exchanger type augmentor ducts (a muff surrounding each augmentor catches engine-cooling air which is heated in the muff for use with the anti-icing and cabin heat system). Two augmentor ducts in each nacelle extend aft from the fire wall to the nacelle afterbody where the exhaust gases are ejected into the atmosphere. The cross-sectional area of each augmentor duct is considerably greater than the combined area of the siamese and single stacks which lead into it and, since the exhaust gases from the engine enter the augmentors at a speed of approximately 1475 knots, a low pressure condition is created, causing cooling air to be drawn across the engine. Thus jet exhaust thrust augmentation is utilized to effect low-drag cooling, as conventional cowl flaps are not required and the airplane is therefore, subject to less drag. It is estimated that use of the augmentor type exhaust system, in addition to its value as a heat exchanger, adds 7-11 knots to airspeed."
However, this also had a price. For one, it was quite noisy next to the augmentor tube exits. For another - also from the manual:
"The CB-16, generally a very reliable engine, is sometimes installed in an aircraft environment severe enough to make conservative operation mandatory to insure engine dependability. This is the case with the engine's installation in the Convair. One of the areas most likely to suffer is in high cylinder head temperatures, which, among other things cause cylinder head cracking. It behooves the pilot to operate his engines so as to keep CHT's as much within the limits as is possible, consistent with getting his flight flown. At times, a certain amount of compromise is necessary."
"...High surface winds should not be allowed to blow into the tail end of the augmentor tubes while on the ground"
"Under icing conditions, it is desirable to maintain CHT high enough to insure adequate carburetor air preheating. Over and above this is is necessary to compromise desired low CHT's to an extent that will provide adequate heat for wing and tail anti-icing. For maximum heat available during two-engine operation, the augmentor vanes should be placed in the maximum position from trail which will not induce after-burning, and the cowl doors should be regulated to maintain the CHT's at 204 to 232 deg. C (not operating past the MID position)."
Hope this helps,Tom Gibson
Calclassic Propliner Page
www.calclassic.com