Exhaust stack meaning11/25/2023 ![]() Which means the angle of divergence is for all practical purposes is 5 degrees according to turbine nozzle design. Given the velocity is determined predominantly by steam and the energy (ability to do work) is determined overwelmingly by the steam, we can consider the gas jet to be a steam jet. This information based on the results of the Illinois tests. In this case, the velocity of the steam is over 6 times faster than the combusion gases. This comes from the fact that energy in the steam is 18 times the energy in the air. The documents from Illinois support this and provide some other surprising points.įirst point, the amount of energy transferred to the combustion gases is so small that for all practical purposes, the average velocity through the stack is determined predominantly by the Steam. This assumption is consistent with pretty much everything on this thread and the documents presented. Nozzle size, stack size and nozzle placement must take into account this 5 degrees. This pretty much determines the front end design. Furthermore I deduced the steam jet expands at 5 degrees from the nozzle. I deduced that the Stack taper must be 5 degrees (taper ~ 11.4) based on my study of divergent nozzles in steam turbines. In order to get good n, then good detail engineering is required.Ĥ years ago I designed the Stack and front end for my 4-4-0. I could see that it would quickly be put into being a cut and paste exercise. My fingers were in the pie for the last revision for our certificate requirements, I'd have put more emphasis on drawing a heat ballance for the system but there is lots of disinterest in generating such work. The issue comes down to one of time and interests- I have little enough time and it would require some quite serious work to get it to be worth building.ĭetails matter- it's why at work I have to explain _why_ we have a deairator, and why it gains about 3-4% n on the cycle.lots of "engineers" (engineering techinicans with a marine certificate) don't understand where the heat goes away, and why.the interest isn't there. ![]() I've considered what would be required to make a SGS engine to compete in IMLEC and get efficency #'s that better Lionel's 2-8-2, which is really probably close to a proper FGS loco. I've been re-reading it to see what else I can pick up. I have a copy of "The Red Devil" sitting on my desk here at work, currently on page 99. I know that the #'s that Micheal Guy's calculator produced are not perfect, but they provided a strong basis for the size that dad is currently using. They are engineering guidance, and that's the best that they can be used for. The same thing with the 1/7th cylinder area for the blast nozzle. The "1:6 myth", is not correct- it falls within the ranges that JJG Koopmans thesis work out. Please note that what I am trying to communicate here is extremely condensed, the test reports on which Iīase my explanations are thousands of pages together. This also happens to be the consequence of the 1:3-1:6 rule, a longer chimney is however better, so it would be an improvement on the 1:6 rule.Īlso the orifice distance to throat/choke x/d should be around 6, based on Goss and BR tests, but also the consequence of 1:3. Why d/D reflects the steam to ejected mixture ratio can only be explained by the area size through which the mixture has to be drawn.Īs for the chimney length to its diameter ratio L/D, I have investigated the BR tests and it appears that the lower limit for proper functioning is 2, In a live steam model more air is normally drawn through the boiler so a ratio of 1:3.5 appears ok. The chimney entrance d/D reflects that of the steam to mixture to be ejected. Regarding your questions (which I did not see due to the page shift), the ratio of the orifice diameter to that of I would like to understand some clear guidelines coming from all of this. Robmort wrote:This was and still is a very interesting thread, but the arguments and conclusions are dispersed and the calculations in places are unfortunately obscure.
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