mx757 4 #26 November 22, 2004 your right.. they redirect flow, compress air.. redirect it more... Quote Share this post Link to post Share on other sites
gerrcoin 0 #27 November 22, 2004 QuoteThey both perform all four strokes; intake, compression, power, and exhaust. You need to change the word "strokes" above with "stages of internal combustion". The strokes in 4-stroke is refering to the movement of the piston within the cylinder, ie down on induction stroke, back up for compression, back down during ignition stroke and back up for exhaust. Turbine engines are a continuous ignition system, ie. a constant stream of fuel is injected into burner cans and the 'flame' is maintained while the engine is running. Reciprocating engines have an ignition stage, where the all the fuel in the cylinder is burned during the ignition stroke and burning stops before the next cycle, in this case every 4th stroke per cylinder. Reciprocating engines require external cooling, usually via a water jacket system or exposure to a moving airflow. Turbine engines use a proportion of the induction airflow, of the order of 3/4, to cool the exhausted gasses from the burner cans to the point where they no will longer melt the titanium alloy tubine blades. Another way of looking at this is that the turbine engine ingests more air than is required for cumbustion and only mixes about 1/4 of this with fuel for buring. The burnt mixture then heats the remaining gasses and accelerates them through the turbine section. The turbine extracts what energy it requires to turn the compressor section, via a central shaft, and what remains is thrust. [Edit]That last is for turbojets. Turboprop and turbofan engines extract much of the energy of the exhaust and transmit it via the compressor shaft, or a seperate concentric shaft, to drive the prop or fan. A proportion of the exhaust still produces direct thrust, but less than for the pure turbojet configuration.[/edit] Other differences are that turbine engines, particularly the turbine blades, are quite difficult to manufacture and only a few countries in the world are capable of making reliable engines. While turbine engines are expensive to make and run, they are less maintanence intensive, due to fewer moving parts, and provide a much better power to weight ratio. Gas turbine engines are more reliable when run constantly or for long periods, ie they are not as tolerant of the stop-start lifestyle of reciprocating engines. They can also use heavier and less refined fuels such as kerosene which is much cheaper to produce than gasoline. Quote Share this post Link to post Share on other sites
diverdriver 7 #28 November 22, 2004 Quoteor anyone else who knows!!! i have to write a short paper on the similarities and differences between the 4 stroke reciprocating engine and the gas turbine. sorry ive resorted to a useless thread but im stuck in a rut on this damn paper any help would be appreciated!!!!!! ive got some info... but not much/enough edit: i sure did spell half this post wrong, huh Similarities: they both have the 4 stages of producing power. Intake, compression, compustion, exhaust. Turbines do all four stages simultaneously. Pistons do it in stages. edit: then I read the rest of the post and see you already finished your paper. Oh well. Had to throw my bit in.Chris Schindler www.diverdriver.com ATP/D-19012 FB #4125 Quote Share this post Link to post Share on other sites
pilotdave 0 #29 November 22, 2004 Well when you look at the overall engines, not just one piston, they aren't so different in that respect. Here's a thermo difference... They do both compress, ignite, expand, and exhaust (the 4 stages as far as thermo is concerned), but they don't do it the same way. The piston engine combusts the fuel/air mixture at a constant VOLUME (the piston is approximately at top dead center at the point when the gases combust...barely changing in volume during the process). A gas turbine combusts the mixture at constant PRESSURE... the volume is allowed to change, but the combustion itself does not increase the pressure inside the engine. But what's similar is that the (positive) work is done during the expansion stage. Dave Quote Share this post Link to post Share on other sites
mx757 4 #30 November 22, 2004 for you lady pilots.. Solo The Earth rolls beneath my wings, My mind dwells on other things. For as my nose points to the sky, I can’t believe I’m going to fly. The months of waiting over now, My instructor says that I know how. And as the spinning wheels break free, I wish that he were here with me. Higher, higher the tip is lifting, Racing thoughts, my mind is shifting, What’s that he say’s on the rate of climb? I wish we’d had done this one more time. Five hundred feet, its now time to turn, There’s still so much I have to learn. Ease the stick and then the rudder, The trick is not to make her shudder, One thousand feet, stay in the turn, This times there’s not as much concern. Throttle back and trim her out. Seems there’s less to care about. Close down wind check now just in case, Runway on the left someplace? Handle Down, powers set. Oh, God, I haven’t spoken yet. Close down wind I call out with my name, Why no answer? Is this a game? Radio’s set I know its right. Settle down, no time for fright “Gear Down” I say without a doubt. Final turn I can’t break out. Power back she starts to sink, Easy does it, time to think. Two third’s ground, one third’s sky. Jeez, I think I’m a little high. Turning final all most over. Aim at black top not at clover. Hold her level till the last. My! The runways moving fast. Hold the nose up, Gee I’m clever Seems like she wants to fly forever. Thump! I’m down – It feels so good. Nothing to it, I knew I could. Take heart my friend and have a try. For now I know that I can fly Quote Share this post Link to post Share on other sites
CieloDiosa 0 #31 November 22, 2004 man i love flying ~boogie ho!! pull before impact! L.A.S.T#14, PMS #309, Ci EL O DI O SA Quote Share this post Link to post Share on other sites
airtwardo 7 #32 November 22, 2004 Quote Similarities: they both have the 4 stages of producing power. Intake, compression, compustion, exhaust. Quote In red neck venaculuar~Suck~Squish~Bang~Blow... ~ If you choke a Smurf, what color does it turn? ~ Quote Share this post Link to post Share on other sites
Tink1717 2 #33 November 22, 2004 Basically you can describe the difference as: 4 stroke= suck, squeeze, bang, blow. Turbine= sucksqueezebangblow.Skydivers don't knock on Death's door. They ring the bell and runaway... It really pisses him off. -The World Famous Tink. (I never heard of you either!!) AA #2069 ASA#33 POPS#8808 Swooo 1717 Quote Share this post Link to post Share on other sites
wingnut 0 #34 November 23, 2004 don't forget that with a turbne, depending on the type you can add an afterurner (augmentor).... nothing coole than an engine that a flame shoots 20 feet outthe backof on purpose...... like nos for a rosipricating engine but way cooler!!!..lol....... just pulled one of these out f an aircraft saturday at work......http://www.geae.com/engines/military/f110/f110-100-400.html nothing like throwingit into full agument (on a maintenance run) and watching the pounds per hour of fuel comsumption max out aroun 54,000 pounds per hour ______________________________________ "i have no reader's digest version" Quote Share this post Link to post Share on other sites
