What is Engines: Definition and 301 Discussions

An engine or motor is a machine designed to convert one form of energy into mechanical energy. Heat engines convert heat into work via various thermodynamic processes. The internal combustion engine is perhaps the most common example of a heat engine, in which heat from the combustion of a fuel causes rapid pressurisation of the gaseous combustion products in the combustion chamber, causing them to expand and drive a piston, which turns a crankshaft. Electric motors convert electrical energy into mechanical motion, pneumatic motors use compressed air, and clockwork motors in wind-up toys use elastic energy. In biological systems, molecular motors, like myosins in muscles, use chemical energy to create forces and ultimately motion.

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  1. berkeman

    Useful EE Links and Search Engines

    I came across another good search engine today looking for a datasheet, so I thought I'd try starting this thread for folks to post useful links. The links should be to technical content, and not to paid services. Good free datasheet search engine: http://www.datasheetpro.com/ Good way to...
  2. S

    Combustion Engines: Can Oxygen Be Used?

    Can pure oxygen be used in internal combusion gas or diesel engines? If no, what percentage could be used?
  3. S

    Thermal Radiation and Heat Engines

    Hey all, This is a simple question: Lets say we have a solid hot-body in outer-space that's emitting thermal radiation. Assuming that it doesn't sublimate, will it simply radiate black-body radiation until it reaches absolute zero? This doesn't sound right. Thanks
  4. N

    Comparing Motorcycle & Car Engines: Rpm vs. Torque

    Now, everyone knows that motorcycle engines work at much higher rpms than car engines. They also produce lesser torque than a car, because (and correct if I'm wrong) bikes don't have as much load on them as cars do. Can anybody tell me what goes in an engine that decides that when power is...
  5. M

    If my rocket has two rocket engines going off each at an impulse at 20.00 N/S .

    If my rocket has two rocket engines going off each at an impulse at 20.00 N/S... If my rocket has two rocket engines going off each at an impulse at 20.00 N/S, then would the total amount of impulse my rocket has be 40.00 N/S? Please answer seriosuly only this is extremely important and...
  6. wolram

    How are these crafts engines protected from ingress of debris?

    How are these crafts engines protected from ingress of debris?
  7. J

    Calculating Work and Efficiency of an Aircraft Engine | Heat Engines Homework

    Homework Statement An aircraft engine akes in 9000 Joules of heat and discards 6400 J each cycles a) What is the mechanical work output of the engine during one cycle? b) What is the thermal efficiency of the engine? Homework Equations e=W/Qh The Attempt at a Solution A) Qh =...
  8. I

    Stirling Engines: Solving the Equation Puzzle

    I have a pretty broad question. I, with several others, am working on some stirling engines for a science fair of sorts. I have done enough research to understand the concept of how they work. I also understand that there are several different types; single cylinder, double cylinder etc. What I...
  9. C

    Toroidal Engines: Challenges & Credibility

    what is it that stops various toroidal engines, like the rotoblock engine, trochilic engine, myt engine or the engine from being successfull? sealing/efficiency/lubrication problems? or they can't find a strong enough material to withstand the pressure? and is there any credibility to the claims...
  10. C

    Nick's Search for Streaming Time in Hobby Rocket Engines

    Hello, I am building a device that tests the maximum thrust of hobby rocket engines, and I need to know if there is any way to get "streaming time." Time that is recorded at certain intervals. Can someone give me a link? Thanks! ~Nick
  11. B

    Two Carnot Engines working in Series Problem

    I was wondering if anyone would be able to help with this question; Two carnot engines operate in series between a source 800K and a sink of 290K. The first engine rejects 400kJ to the second engine. If both engines have the same efficiency, calculate; (i) the temperature for the source of...
  12. Saladsamurai

    Why do Jet Engines Have a Compressor?

    So like it says. It may be a silly question, but I am doing some reading on jet engines (on Wiki) and I am having trouble finding an explanation as to why we want to increase the pressure of the air before it goes into combustion. Does this just another way of increasing the thrust? Thanks...
  13. hagopbul

    C/C++ Learn C/C++ to Add Effects to 3D Objects with Physics Engines

    i need to learn c/c++ to add effect on 3d objects and to use agia physix engine (like adding gravity , refraction,...etc) and i don't know where to start and what to read and what to learn there is so much books and so much programs and lectures (i don't mean the 101 books i mean after that)...
  14. E

    Carnot engines and refrigerators

    Homework Statement I am not necessarily having a problem with a particular homework problem. It is more of a conceptual issue. I have been reading about Carnot engines and refrigerators. In trying to understand the topic better, I did a little more digging and looked up how a refrigerator...
  15. J

    (Thermodynamics) Engines Working in Pairs; Calculating Carnot effiency

    Homework Statement At a steam power plant, steam engines work in pairs, the heat output of the first one being the approximate heat input of the second. The operating temperatures of the first are 720C and 428C, and of the second 417C and 260C. If the heat of combustion of coal is 2.8 *...
  16. C

    How does charge air cooling work in a charge air-cooled engine?

    could anyone tell me how the charge air is used to cool the engine in a charge air-cooled engine?(i mean apart from the charge coming in and cooling, is there a mechanism for cooling the charge before intake)
  17. S

    Chromium use in Gas Turbine Engines help

    Hi all, I'm hoping that someone may be able to help! I'm doing a project which has involved me looking at the use of superalloys in Gas Turbine engines (i.e. Rolls Royce, GE etc). As part of that I am looking in particular at the use of Chromium within these engines, does anybody have any...
  18. B

    Can Jet Engines Run Without Gasoline?

    I don't know a lot about jet engines and how they exactly work but is it possible to run a jet engine without gasoline? Are there any different fuels that can be used for the engine to give more propulsion or give it more time in the air?
  19. J

    Using Maxwell SV for Ion Engines

    I had a question about the Maxwell SV program and was hopping someone might be able to answer it for me. Using the Maxwell program I have made a whole bunch of different cases of magnet geometries for an 8cm Ion Engine and they all seem to be good. The only problem is that when I try save the...
  20. Holocene

    The physics behind air/fuel ratios in 4-stroke engines.

    Correct me if I'm wrong, but the hottest combustion temperatures will result when the air/fuel ratio is ideal, or stoichiometric, no? I ask, because there seems to be this mentality that a lean mixture will result in even hotter temperatures, and could cause engine damage. This has not...
  21. A

    How do aeroplane wings support the forces and engines?

    I was just wondering how these amazing engineering feats support the loads on their wings? Specifically the larger passenger aeroplanes.. such as the 737 and 747. The wings must undergo an extreme number of forces of great magnitude.. how do they not snap off? How the they support their own...
  22. Z

    Road to faster search engines?

    Might a road to significantly faster search engines (25% faster) be via use of a cache of say the 100,000 most frequent search words and phrases utilized, typical for over a year? Might one have perhaps a number of distributive caches for a multitude of different processors and associated memories?
  23. M

    Thermo reversible heat engines physics question

    I am having trouble with this question...It is from "applied thermodynamics for engineering technologists" by Eastop (Q5.2 if anyone has it)... The Question: Two reversible heat engines operate in series between a source at 527°C and a sink at 17°C. If the engines have equal efficiencies and...
  24. W

    How does entropy affect heat engines?

    I'm having trouble trying to get my head around the role entropy plays in a heat engine. When the energy from a hot reservoir enters the engine, it brings a certain amount of entropy with it. Then, the "waste heat" (which is energy) gets rid of the entropy. But, why does it take less energy to...
  25. P

    Thermodynamics (Carnot Engines)

    1. The amount of heat that an engine rejects to the cold reservoir is 3 times the amount of work that it does. What is the efficiency of the engine? e = W/ Qh = 1 - Qc/Qh For this problem, I said e= w/3w. Thus e would equal 1/3 = 0.333. This however is not correct. What did I do wrong...
  26. V

    Compression Ignition Engines: Converting kmol/kmol to kmol/kg Fuel

    Hey guys, Just trying to understand this piece of information I have been given. It is for a compression ignition engine. I can see where they get the 115.954 kmol/kmol fuel and 120.204 kmol/kmol fuel from but don't understand how to change the units 0.7027 kmol/kg fuel and 0.7285 kmol/kg...
  27. E

    Why the Carnot cycle is not used with real engines?

    I have a question on Why the Carnot cycle is not used with real engines? I need to refer to real cycles in my explanation.
  28. H

    Heat Engines and the Carnot Cycle

    [SOLVED] Heat Engines and the Carnot Cycle Homework Statement The operating temperatures for a Carnot engine are Tc and Th= Tc + 55K. The efficiency of the engine is 15%. How do i find Tc?
  29. Greg Bernhardt

    Can Alternative Technologies Overcome the Cost of Fuel in Vehicle Progression?

    What do people think of the developments and future of Waste Exhaust Heat Recovery? Thermoelectric Conversion of exhaust heat into electric power to drive auxiliaries. Thermodynamic Conversion of waste exhaust ( + radiator + Charge air cooler + EGR cooler) heat into additional...
  30. M

    Jet Engines: How Do They Move Forward?

    O.k i understand that a jet engine gains its thrust by pushing heated air out its nozzel, but i was wondering if that the reason it goes forward is because the speed of it being released out the rear nozzel is moving faster than the air can get pushed out of the way so the some of the force is...
  31. X

    Electric Car Internal Design & Engines

    Anyone with any idea about the basic internal design & engines in an electric car?
  32. wolram

    Two Engines, One Control System: Impossible or Inevitable?

    http://news.uk.msn.com/Article.aspx?cp-documentid=7279188 Surly both engines do not share a single control system.
  33. C

    Diesel Engines - Power question

    Homework Statement Please can someone help me with this... I have a question on a four stroke diesel engine. I have been given the stroke length of 500mm and the bore size of 300mm. The compression ratio as 18/1 and the speed of revolution of 600rpm. Also the ambient air conditions are...
  34. L

    What is the efficiency of the engines?

    Homework Statement A 3250 km aircraft takes 12.5 minutes to achieve its cruising altitude of 10 km and cruising speed of 850 km/h. If the plane's engines deliver, on the average, 1500 hp of power during this time, what is the efficiency of the engines? Homework Equations Efficiency =...
  35. D

    Small engines vs. big engines?

    If you were a car manufacturer, which of the following cars would you choose to manufacture, supposing you are only allowed to manufacture either kind: 1) a car with a small engine but with a turbocharger; or 2) a car with a big engine Assume that both cars have other variables constant...
  36. F

    Thermodynamics: entropy and engines

    Entropy and Engines Homework Statement A heat engine has the following diagram associated with it. There is a heat source which supplies 1000 J of heat energy during one cycle and remains at a constant temperature of 400 K. A heat sink exhausts 700 J of heat during a cycle at a constant...
  37. Astronuc

    Geared turbofans for large engines

    Source: CBS MarketWatch Interesting developments! Certainly - if this works - it will dramatically reduce fuel consumption. "1,500 fewer airfoils" seems awfully large. But then I haven't counted the blades in current turbine design. I curious as to what the typical blade number is per...
  38. A

    Discussing Advantages/Disadvantages of 2-Stroke Turbocharged CI Engines

    ok now my practicals are 15 days away and i n my friends constantly discuss about advantages and disadvantages of several combinations like 2-stroke SI engine with supercharging or 4stroke CI with CRDi etc etc. since people here are more experienced and have far more facilities than i do, i want...
  39. A

    How Much Work Can a Reversible Heat Engine Generate?

    [/B]Homework Statement What is the maximum amount of mechanical work that can be got by a reversible engine working from a finite heat source of thermal capacity, C=1000J/K, if it is initially at 373K and the engine discharges to a bath of virtually infinite heat capacity at 273K? [You may...
  40. P

    Finding the Point to Shut Off Engines for a Traveler in Space

    Homework Statement A traveler in space is moving left and right on y = x^2. He shuts off the engines and continues on the tangent line until he reaches point (4, 15). At what point on the curve should he shut off the engines to reach that point? The Attempt at a Solution Ok, the...
  41. E

    Valve Spring Dynamics on 4-Stroke Engines

    Hi guys, i am doing some calculations on the valve spring of a 4 stroke, 4 cylinder motor vehicle engine. To my understanding, valve bounce will occur once the valve spring is operated at a speed over their natural frequency (which i calculated to be 5500 rev/min). If i were to push the...
  42. E

    How to get the toppest place in search engines?

    i see that pf is the very first results while searching for a physics forum. why?? is it because it has more vistors than other sites? what's google ranking or other search engines base on?
  43. W

    Find When Engines Should Be Turned Off for Spaceship to Reach Space Station

    Homework Statement The position of a spaceship is: r(t)=(3+t)i +(2+ln(t))j+(7-\frac{4}{t^2+1})k and the coordinated of the space station are (6,4,9). The captian wants the spaceship to coast into the the space station. When should the engines be turned off? Homework Equations r(t)=(3+t)i...
  44. B

    Noisy Engines: Exploring the Causes

    hi to all, this is my first post here n quite a stupid one:shy::shy: last day i had a discussion with my friend over this.. what exactly is the reason behind that sound of the engine? i mean is it the sound of the explosion of the charge or is the sound of the expanding gases comin out to the...
  45. wolram

    Coupling Two Engines: Best Method & Firing Order?

    I have in mind to recreate a Brit v twin (in a fashion) using two single cylinder engines coupled together, as i see it i have three options for the linking method, chain, toothed belt, or gears, gears would be the most (ridged) coupling, the chain and belt would have some flex, the other...
  46. S

    Why do rocket engines work in the vacuum of space?

    I have a feeling someone is going to be like "Duhhh" on this one. But I got to thinking. I recall reading somewhere that the guy that came up with the rocket engine for use in space got an F on his paper because "I think" the professor said that there would be nothing to push back on the...
  47. P

    Solving Sound Intensity with 2 Shut-Off Engines

    Homework Statement A person is a certain distance away from a plane with three equally noisy engines at 120 dB. What is the sound intensity if two of the engines are shut off? Homework Equations B (in dB) = log I/Io The Attempt at a Solution using this equation: 120 dB = 10 log...
  48. A

    Making an Informed Decision on Physics Engines for Games

    Hi I was wondering which of the following titles I should buy with regards to building a fairly simple physics engine for a game idea I have. I don't want to rush in I want to spend my money wisely. The titles are (roughly) as follows: Real Time Collision Detection Game Physics Game Physics...
  49. A

    Efficiency of Two Carnot Engines in Series

    Homework Statement There are two Carnot engines in series, so that the heat exhaust from the first engine drives the second. Find the overall efficiency of the arrangement which contains only the efficiences of the individual engines. Homework Equations \epsilon = \frac{W}{Q_{input}}...
  50. ShawnD

    Why are big engines so horribly inefficient?

    If you look at any car that has 2 available engines, the big engine's gas mileage sucks compared to the small engine. Just as an example, a 2.4L honda accord uses 9.7L of fuel to go 100km while the 3.0L model needs 11.5L of fuel to go that same distance. Since EPA fuel estimates are done...
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