Einstein aether theory - Revision history

174.100.142.65: /* Experimental constraints */ evidence was spelled wrong.

2014-07-29T03:03:43Z

Experimental constraints: evidence was spelled wrong.

← Older revision		Revision as of 05:03, 29 July 2014
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	~~Wilber Berryhill is what his spouse loves to contact~~ him ~~and he totally enjoys this title~~. ~~Some time in the past he chose to live in North Carolina~~ and ~~he doesn't strategy on changing~~ it. ~~Office supervising~~ is ~~my occupation~~. ~~The favorite hobby for him and his kids~~ is ~~to perform lacross and he would never give it up~~.<br><br>~~Here is my site~~ [http://~~myoceancounty~~.net/~~groups~~/~~apply-these-guidelines-when-gardening-and-grow~~/ ~~online psychic~~]		Friends call him Royal Seyler. Alabama has usually been his home and his family loves it. To perform croquet is some thing that I've carried out for years. She is presently a cashier but quickly she'll be on her own.<br><br>My web blog - extended car warranty ([http://Www.kindkids.net/ActivityFeed/MyProfile/tabid/61/UserId/260741/Default.aspx Highly recommended Website])

en>Hhhippo: /* Black holes and potential problems */ Fixed DAB link

2014-02-23T13:06:40Z

Black holes and potential problems: Fixed DAB link

← Older revision		Revision as of 15:06, 23 February 2014
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	~~In [[aircraft]] and rocket design, '''overall propulsive efficiency''' <math>\eta</math>~~ is ~~the efficiency, in percent, with which the energy contained in a vehicle's propellant is converted into useful energy, to replace losses due~~ to ~~[[air drag]], gravity,~~ and acceleration. It can also be stated as the proportion of the mechanical energy actually used to propel the aircraft. It is always less than 100% because of kinetic energy loss to the exhaust, and less-than-ideal efficiency of the propulsive mechanism, whether a [[Propeller (aircraft)\|propeller]], a jet exhaust, or a fan. In addition, propulsive efficiency is greatly dependent on air density and airspeed.		Wilber Berryhill is what his spouse loves to contact him and he totally enjoys this title. Some time in the past he chose to live in North Carolina and he doesn't strategy on changing it. Office supervising is my occupation. The favorite hobby for him and his kids is to perform lacross and he would never give it up.<br><br>Here is my site [http://myoceancounty.net/groups/apply-these-guidelines-when-gardening-and-grow/ online psychic]

	~~Mathematically, it is represented as <math>\eta = \eta_c \eta_p</math><ref>,[http://www.hq.nasa.gov/pao/History/SP-468/ch10-3.htm ch10-3<!-- Bot generated~~ title ~~-->]</ref> where <math>\eta_c</math> is the [[cycle efficiency]] and <math>\eta_p</math> is the propulsive efficiency~~. ~~The cycle efficiency,~~ in ~~percent, is~~ the ~~proportion of energy that can be derived from the energy source that is converted~~ to ~~mechanical energy by the [[engine]].~~

	~~==Estimation==~~
	~~===Jet engines===~~

	~~[[Image:JetWirkungsgrad.png\|thumb\|right\|Dependence of the energy efficiency (η) from the exhaust speed/airplane speed ratio (c/v) for airbreathing jets]]~~
	For all [[airbreathing jet engine]]s the ''propulsive efficiency'' (essentially [[Energy conservation\|energy efficiency]]) is highest when the engine emits an exhaust jet at a speed that is the same as, or nearly the same as, the vehicle velocity. The exact formula for air-breathing engines as given in the literature,<ref>K.Honicke, R.Lindner, P.Anders, M.Krahl, H.Hadrich, K.Rohricht. Beschreibung der Konstruktion der Triebwerksanlagen. Interflug, Berlin, 1968</ref><ref name=spt>Spittle, Peter. [http://users.encs.concordia.ca/~kadem/Rolls%20Royce.pdf "Gas turbine technology"] p507, ''[[Rolls-Royce plc]]'', 2003. Retrieved: 21 July 2012.</ref> is

	~~:<math>\eta_p = \frac{2}{1 + \frac{c}{v}}</math>~~

	~~where ''c'' is the exhaust speed,~~ and '~~'v'' is the speed of the aircraft.~~

	~~A corollary of this is that, particularly in air breathing engines,~~ it ~~is more energy efficient to accelerate a large amount of air by a little bit than a small amount by a large amount, even though the thrust is the same~~.

	~~[[File:Propulsive efficiency.png\|thumb\|right\|Dependence of the propulsive efficiency (<math>\eta_p</math>) upon the vehicle speed/exhaust speed ratio (v/c) for rocket and jet engines]]~~

	~~===Rocket engines===~~
	A rocket engine's <math>\eta_c</math> is usually high due to the high combustion temperatures and pressures, and long nozzle employed. The value varies slightly with altitude due to atmospheric pressure on the outside of the nozzle/engine, but can be up to 70%. Most of the remainder is lost as heat energy in the exhaust.

	Rocket engines have a slightly different propulsive efficiency (<math>\eta_p</math>) than airbreathing jet engines as the lack of intake air changes the form of the equation. This also means that rockets are able to exceed their exhaust velocity. See diagram.

	~~:<math>\eta_p= \frac {2 \frac {v} {c}} {1 + ( \frac {v} {c} )^2 }</math><ref name="RPE">George P. Sutton & Oscar Biblarz, ''Rocket Propulsion Elements'', pg 37-38 (seventh edition)</ref>~~

	As with ducted jet engines, matching the exhaust speed and the vehicle speed gives optimum efficiency in principle. Although in practice rocket exhausts are high and typically fixed, this can be a useful theoretical consideration. Unlike ducted engines, rockets give thrust even when the two speeds are equal.

	~~Rockets often also have an additional significant source of energy, because they are able to leverage the kinetic energy of their propellant with the [[Oberth effect]]. This~~ is ~~also a factor for air-breathing aircraft, but much smaller one due to their lower speed~~.

	~~===Propeller engines===~~
	The ~~calculation is somewhat different~~ for ~~reciprocating~~ and ~~[[turboprop]] engines which rely on a propeller for propulsion since their output~~ is ~~typically expressed in terms of power rather than thrust. The equation for heat added per unit time, ''Q'', can be adopted as follows:~~

	~~: <math>550 P_e = \frac{\eta_c H h J}{3600},</math>~~

	~~where <math>P_e</math> is engine output in [[horsepower]], converted~~ to ~~foot-pounds/second by multiplication by 550. Given that [[specific fuel consumption (shaft engine)\|specific fuel consumption]] is ''C''<sub>''p''</sub> = ''h''/''P''<sub>''e''</sub>~~ and ~~using the aforementioned substitutions for ''H'' and ''J'', the equation is simplified to:~~

	~~: <math>\eta_c = \frac{14}{C_p}.</math>~~

	~~expressed as a percentage~~.

	~~Assuming a typical propulsive efficiency~~ <~~math~~>~~\eta_p~~<~~/math~~> ~~of 86% (for the optimal airspeed and air density conditions for the given propeller design), maximum overall propulsive efficiency~~ is ~~estimated as:~~

	~~: <math>\eta = \frac{12}{C_p}.</math>~~

	~~==See also==~~
	*[[~~Specific fuel consumption (thrust)]]~~

	~~==References==~~
	*{{cite web\|author=Loftin, LK, Jr.\|title=Quest for performance: The evolution of modern aircraft. NASA SP-468\|url=http://~~www.hq~~.~~nasa.gov~~/~~pao~~/~~History/SP~~-~~468/cover.htm\|accessdate=2006~~-04-~~22}}~~
	*{{cite web\|author=Loftin, LK, Jr.\|title=Quest for performance: The evolution of modern aircraft. NASA SP-~~468 Appendix E\|url=http://www.hq.nasa.gov/pao/History/SP~~-~~468/app~~-~~e.htm\|accessdate=2006-04-22}}~~

	~~==Notes==~~
	~~<references~~/>

	~~[[Category:Aerodynamics]~~]

en>WOFall: Revert good faith edits by 117.194.86.196 (redlinks are good and Killing vector fields take the cap

2013-12-23T20:13:20Z

Revert good faith edits by 117.194.86.196 (redlinks are good and Killing vector fields take the cap

← Older revision		Revision as of 22:13, 23 December 2013
Line 1:		Line 1:
	The ~~writer~~'s name is ~~Christy~~. ~~Distributing manufacturing~~ is ~~how he makes~~ a ~~residing~~. ~~To play lacross~~ is ~~something he would by no~~ means give up. ~~Some time ago he chose~~ to ~~reside in North Carolina~~ and ~~he doesn't strategy~~ on ~~altering it~~.<br><br>~~my web page~~ ... ~~authentic psychic readings~~ ([http://www.~~skullrocker~~.~~com~~/~~blogs~~/~~post~~/~~10991~~ http://www.~~skullrocker~~.~~com~~])		In [[aircraft]] and rocket design, '''overall propulsive efficiency''' <math>\eta</math> is the efficiency, in percent, with which the energy contained in a vehicle's propellant is converted into useful energy, to replace losses due to [[air drag]], gravity, and acceleration. It can also be stated as the proportion of the mechanical energy actually used to propel the aircraft. It is always less than 100% because of kinetic energy loss to the exhaust, and less-than-ideal efficiency of the propulsive mechanism, whether a [[Propeller (aircraft)\|propeller]], a jet exhaust, or a fan. In addition, propulsive efficiency is greatly dependent on air density and airspeed.

			Mathematically, it is represented as <math>\eta = \eta_c \eta_p</math><ref>,[http://www.hq.nasa.gov/pao/History/SP-468/ch10-3.htm ch10-3<!-- Bot generated title -->]</ref> where <math>\eta_c</math> is the [[cycle efficiency]] and <math>\eta_p</math> is the propulsive efficiency. The cycle efficiency, in percent, is the proportion of energy that can be derived from the energy source that is converted to mechanical energy by the [[engine]].

			==Estimation==
			===Jet engines===

			[[Image:JetWirkungsgrad.png\|thumb\|right\|Dependence of the energy efficiency (η) from the exhaust speed/airplane speed ratio (c/v) for airbreathing jets]]
			For all [[airbreathing jet engine]]s the ''propulsive efficiency'' (essentially [[Energy conservation\|energy efficiency]]) is highest when the engine emits an exhaust jet at a speed that is the same as, or nearly the same as, the vehicle velocity. The exact formula for air-breathing engines as given in the literature,<ref>K.Honicke, R.Lindner, P.Anders, M.Krahl, H.Hadrich, K.Rohricht. Beschreibung der Konstruktion der Triebwerksanlagen. Interflug, Berlin, 1968</ref><ref name=spt>Spittle, Peter. [http://users.encs.concordia.ca/~kadem/Rolls%20Royce.pdf "Gas turbine technology"] p507, ''[[Rolls-Royce plc]]'', 2003. Retrieved: 21 July 2012.</ref> is

			:<math>\eta_p = \frac{2}{1 + \frac{c}{v}}</math>

			where ''c'' is the exhaust speed, and ''v'' is the speed of the aircraft.

			A corollary of this is that, particularly in air breathing engines, it is more energy efficient to accelerate a large amount of air by a little bit than a small amount by a large amount, even though the thrust is the same.

			[[File:Propulsive efficiency.png\|thumb\|right\|Dependence of the propulsive efficiency (<math>\eta_p</math>) upon the vehicle speed/exhaust speed ratio (v/c) for rocket and jet engines]]

			===Rocket engines===
			A rocket engine's <math>\eta_c</math> is usually high due to the high combustion temperatures and pressures, and long nozzle employed. The value varies slightly with altitude due to atmospheric pressure on the outside of the nozzle/engine, but can be up to 70%. Most of the remainder is lost as heat energy in the exhaust.

			Rocket engines have a slightly different propulsive efficiency (<math>\eta_p</math>) than airbreathing jet engines as the lack of intake air changes the form of the equation. This also means that rockets are able to exceed their exhaust velocity. See diagram.

			:<math>\eta_p= \frac {2 \frac {v} {c}} {1 + ( \frac {v} {c} )^2 }</math><ref name="RPE">George P. Sutton & Oscar Biblarz, ''Rocket Propulsion Elements'', pg 37-38 (seventh edition)</ref>

			As with ducted jet engines, matching the exhaust speed and the vehicle speed gives optimum efficiency in principle. Although in practice rocket exhausts are high and typically fixed, this can be a useful theoretical consideration. Unlike ducted engines, rockets give thrust even when the two speeds are equal.

			Rockets often also have an additional significant source of energy, because they are able to leverage the kinetic energy of their propellant with the [[Oberth effect]]. This is also a factor for air-breathing aircraft, but much smaller one due to their lower speed.

			===Propeller engines===
			The calculation is somewhat different for reciprocating and [[turboprop]] engines which rely on a propeller for propulsion since their output is typically expressed in terms of power rather than thrust. The equation for heat added per unit time, ''Q'', can be adopted as follows:

			: <math>550 P_e = \frac{\eta_c H h J}{3600},</math>

			where <math>P_e</math> is engine output in [[horsepower]], converted to foot-pounds/second by multiplication by 550. Given that [[specific fuel consumption (shaft engine)\|specific fuel consumption]] is ''C''<sub>''p''</sub> = ''h''/''P''<sub>''e''</sub> and using the aforementioned substitutions for ''H'' and ''J'', the equation is simplified to:

			: <math>\eta_c = \frac{14}{C_p}.</math>

			expressed as a percentage.

			Assuming a typical propulsive efficiency <math>\eta_p</math> of 86% (for the optimal airspeed and air density conditions for the given propeller design), maximum overall propulsive efficiency is estimated as:

			: <math>\eta = \frac{12}{C_p}.</math>

			==See also==
			*[[Specific fuel consumption (thrust)]]

			==References==
			*{{cite web\|author=Loftin, LK, Jr.\|title=Quest for performance: The evolution of modern aircraft. NASA SP-468\|url=http://www.hq.nasa.gov/pao/History/SP-468/cover.htm\|accessdate=2006-04-22}}
			*{{cite web\|author=Loftin, LK, Jr.\|title=Quest for performance: The evolution of modern aircraft. NASA SP-468 Appendix E\|url=http://www.hq.nasa.gov/pao/History/SP-468/app-e.htm\|accessdate=2006-04-22}}

			==Notes==
			<references/>

			[[Category:Aerodynamics]]

en>D.H: /* References */ +Section

2011-12-08T17:40:32Z

References: +Section

New page

The writer's name is Christy. Distributing manufacturing is how he makes a residing. To play lacross is something he would by no means give up. Some time ago he chose to reside in North Carolina and he doesn't strategy on altering it.<br><br>my web page ... authentic psychic readings ([http://www.skullrocker.com/blogs/post/10991 http://www.skullrocker.com])