Engines Definition and 301 Threads

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. Hercuflea

    Where can I find resources for building stirling engines?

    Anyone have any good resources/how-tos on building miniature (or not so mini) stirling engines? They seem pretty simple to make, and the coke can ones are pretty cool.
  2. C

    Why are some car engines so loud?

    Why are the engines of sports cars so loud? I thought a good engine should be very quiet because all the work done must go to moving the car forward. If they produce so many noises, isn't that just wasting fuel/power? Is the production of big sounds a must for the working of the engines, or...
  3. E

    Cheap and low power diesel engines

    what is the cheapest and low power diesel engine available at present? i am seeking 3 KW engine with of minimum weight available for my college project.
  4. F

    Why dont jet engines work without a spiner in the center of the blades

    Just trying to complete my physics coursework on bloodhound ssc. Could anyone help to answer the question: why don't jet engines work in supersonic air without a spinner in the centre of the blades ? Thanks.
  5. I

    Calculating Exhaust Flow for Diesel Engines

    Is there a way you can calculate exhaust flow using intake flow and exhaust temp? Maybe I would need fuel quantity as well. I just need a rough idea.. It's for on a diesel.
  6. J

    Do all reversible engines become heat pumps?

    I have a cycle (and the gas is ideal) that starts at Pressure=4Po Volume=Vo and and Temperature=Th. First step it's cooled at constant volume to Tc and Po; Second step, it is reheated at constant pressure to Th and 4Vo, and lastly it is compressed at constant temperature to Vo and 4Po. For those...
  7. J

    Understanding Condensation & Vacuum in Steam Engines

    Hello everyone, Could someone help me with the following question: I'm trying to find out the equations that govern this process; why if you condense steam in a cylinder is a partial vacuum created (such as in early steam engines)? The pressure difference then causes the atmosphere to push...
  8. P

    Why do different car engines need different engine oils? I assume viscosity

    Does a stronger engine need a higher viscosity fluid? What's the reasoning behind this?
  9. E

    Automotive Why Diesel Engines Produce Less CO2: A Thermodynamic Approach

    As the title says, why diesel engines produce less CO2 than gasoline engines and how is this related to the more torque and less power in diesel engines? PLEASE only a fluid dynamics or thermodynamics approach. Spent hours on searching to find why petrol engines produce more CO2 emissions...
  10. M

    How do rocket engines account for backflow?

    When combustion occurs in a rocket engine, most of the high speed fluid passes out the back as exhaust. But surely some of it flows back through the fuel and oxidizer injector tubes? Wouldn't this decrease efficiency (and potentially even lead to safety risks)?
  11. A

    Comparison of two engines of the same displacement

    Hi all, I have this question, and hope you could help me to solve. There are two engines with the same displacement (say 250cc). One with smaller piston and the other bigger. Of course the first one will move longer. If everything else is the same or similar, generally, which engine is...
  12. H

    Thermodynamics/stirling engines

    Homework Statement Helium Gas (Cv=12.5) has initial temperature T1, pressure P1, and volume V1. It follows a stirling engine cycle, namely it is 1)heated at constant volume to a temperature T2 then is 2)expanded isothermally to volume V2. 3) It is then returned to a temperature T1 by an...
  13. K

    Automotive High compression turbocharged engines.

    I have seen some builds of naturally aspirated engines, originally using around 10:1 CR, being built up to 13:1+ CR and then having 15psi of boost thrown at them from an aftermarket turbo kit. I can't comprehend how this is possible without the engine melting, what do you need to do to make a...
  14. R

    Engineering Antimatter Engines and Electrical Engineering?

    Are there opportunities for EEs to be involved in research on antimatter engines? Considering antimatter engines are heavily based on magnetic principles, is it feasible to assume that antimatter engine design will be a subfield of EE? The gap between EE and theoretical physics is getting smaller.
  15. I

    Could google scholar replace other search engines?

    We have many engines to search the literature, such as sciencedirect and so on. And we also have google scholar to search the whole literature. Is it a good idea to use only google scholar since it looks complete enough? What's your opinion?
  16. smokingwheels

    Is reducing an engines fuel consumption by 85% impossible?

    I expect to be shot down in flames but I don't mine one bit. I have just done a bit of a drive in my 28 year old Nissan Bluebird Wagon about 10% city 90% HWY...NO Fancy EFI systems or direct injection here just a plain old carburetor running slightly rich at idle. I just did a rough...
  17. H

    Heat Engines and Work: Combining Two Engines

    Homework Statement There is a heat engine with Th on top at 100 J pointing down, Tc on bottom pointing down with 50 J and the work output is 50 J pointing right out of the engine. (ENGINE 1) a) Draw the diagram for a carnot refrigerator which draws 100 J of heat from the hot reservoir (Th...
  18. C

    Is this the reason diesel engines are less powerfull?

    Im studdying PV diagrams for dieslel and petrol engines, and I've noticed that for Diesel the fuel is combusted at constant pressure as opposed to petrol (gasoline) which is at constant volume. I know that the area inbetween the lines is the net work done by the engine. So if you look at the...
  19. S

    What Is the Purpose of a Water Cooling System Vent on a Boat?

    Hi, Can somone explain to me what this contraption is(Upon querying the boat-man,he replied it had something to do with water cooling the engines). (//postimage.org/image/4g03vm1bn/),but this "thing" was at the boat aft.Is this some kind of a siphon exit? Isn't the water input supposed...
  20. X

    What are the problems with Steam Engines?

    For some reason, steam power fascinates me very much. I had a couple questions about steam power and I figured this place was the best place to ask! Would it be naive of me to believe that any engine engineered correctly can be useful? What are the advantages and disadvantages of a steam...
  21. I

    Heat engines: how can we yield work?

    So, I'm studying for the MCAT. There..I've said it. :) But, it's not a homework question: I just don't understand the concept. My study book's thermodynamics section includes a very rough sketch of a heat engine to describe the 2nd Law of Thermodynamics. A side note in the text says that if...
  22. P

    ATH 101: Efficiency of Isobaric Expansion for Monatomic and Diatomic Gases

    In a heat engine we ultimately care about the efficiency of the entire cycle. That is, what percentage of the heat which flows into your system is converted to work. However, you could certainly ask that same question for an individual step in a cycle. Specifically, determine the efficiency of an...
  23. Astronuc

    Is Google Too Powerful in the Search Engine Market?

    It appears that the US government has determined that Google is perhaps too successful, or that in being successful in it's market has abused it's power/influence. U.S. Escalates Google Case by Hiring Noted Outside Lawyer...
  24. J

    Learning about engines on a budget

    I want to learn about engines. Besides reading up on different kinds, what's a good way to get my hands on small gasoline engines, and what kind of things should I do to get some hands on learning? thanks!
  25. M

    Noise in Engines: Investigating Chain & Sprocket Design

    hi.. can someone help me out with noise in engines.. i am specifically interested in noise due to running of chain on sprockets.. it is a sort of whistling noise... which are those parameters in design of sprocket and chain which contribute in noise.. we can also talk in terms of different...
  26. C

    Automotive Suralmo-Hyperbar engines for use in tanks

    Hello all, I am currently doing some for-fun reading on tank engines, and I've been told that a hyperbar engine would be an excellent choice for a tank engine. My question then is would a hyperbar engine provide a good power to weight ratio for a tank requiring a 1300kW engine? How would...
  27. Saladsamurai

    C/C++ C++ Text Geared Toward Physics Engines?

    Does anyone know of any good texts that are geared towards creating Physics Engines using c++? Or at the least, a text on creating physics engines in general? Any personal recommendations would be great.
  28. F

    Power of an Ideal Refrigerator - Carnot Engines

    Power of an Ideal Refrigerator -- Carnot Engines Homework Statement The inside of an ideal refrigerator is at a temperature T_c, while the heating coils on the back of the refrigerator are at a temperature T_h. Owing to a malfunctioning switch, the light bulb within the refrigerator remains...
  29. C

    Calculating Gasoline Needed for 50.0hp Heat Engine Output

    Homework Statement When gasoline(density=.7297 g/cm^3) is burned, it gives off 5.00 times 10^4 J/g(its heat of combustion). If a car's engine is 25% efficient, how much gasoline per hour must it burn in order to develop an output of 50.0hp. 1hp=746 W Homework Equations P=W/t e=W/Qh...
  30. C

    Rotary Vane Engines: Advantages & Disadvantages

    are the 'vanes' of a rotary vane engine a major disadvantage? granted that the vanes would be under considerable stress, but is it so much larger than the stress on connecting rod in reciprocating engines? and is sliding friction on sides very high compared to pistons? also, is sealing a major...
  31. A

    Automotive What are the key differences between Mopar and Ford V-8 engines?

    being a Mopar person and enjoying the simplicity of their engine lineup many times I've listened to a Ford person and walked away shaking my head. Mopar small blocks: 318 and 340. 273 was early and went bye-bye. 360 was smog 340. Mopar big blocks: 383 and 440. Hemi was heads stuck on 440. there...
  32. L

    Can gasoline engines run on diesel fuel and vice versa?

    what will happen if we put petrol in a diesel engine and diesel in a petrol engine? i think it will not work but why will it not work
  33. W

    Calculate Heat Flows in Engines Propelling a Car

    Homework Statement A certain engine can propel a 1600 kg car from rest to a speed of 22 m/s in 9.7 s with an efficiency of 23%. what is the rate of heat flow into the engine at the high temperature? what is the rate of heat flow out of the engine at the low temperature? Homework...
  34. B

    Calculate Magnitude of Work from 0.22 Lawnmower Engine in 1 Second

    A lawnmower engine with an efficiency of 0.22 rejects 9900 J of heat every second. What is the magnitude of the work that the engine does in one second? e = 0.22 Qc = 9900 J/s e = W/Qh Qh = Qc + W e = W / Qc + W 0.22 = W / 9900 + W 0.22(9900 + W) = W 2178 + 0.22W = W W = 2792.31...
  35. M

    PV diagrams for heat engines are legitimate ?

    PV diagrams for heat engines are "legitimate"? Hello forum Since my student days i was wondering about how is it possible to represent the cycle of the gas in a heat engine (e.g. otto cycle) in a PV or whatever diagram when it is obvious that the gas is not in equilibrium during the process...
  36. Y

    Motor bike engines acting as a gyroscope keeping the bike upright

    Dear All This is a rather strange question for you one that i can find no conclusive argument to. when riding a large motorbike i am informed that the engine must be reved at low speeds in order to keep the engine spinning at a sufficient speed to enable it to generate a strong enough...
  37. V

    Plastic combustion engines and why aren't they used

    The link is to an article that describes the history of plastic combustion engines! The reason they are not in your automobile is that those who are experts don't like the idea. There are incentives in the U.S. to make cars more fuel efficient by some 5 years from now but the plastic combustal...
  38. C

    What research has been done on optimizing combustion in automobile engines?

    I want to find papers of studies done on combustion in automobile engines. I know there was a lot of work doine on this, unfortunatelly I cannot find ANYTHING. If I type "combustion in engines" in the search field of any journal/search engine, I get completely unrelated junk. I'm looking for...
  39. C

    A different approach towards Thrust Engines

    Is there any Advanced concepts , theories out there; Instead of the combustion. We're not limited ; direct conversion of electricity to thrust is here, so if you have any ideas leave it here, *Electricity-conversion- microwave- to thrust (radiation pressure difference) *Electricity-conversion-...
  40. K

    Causes of inefficiency in engines

    What causes inefficiency in diesel or Otto engine? the publications do not explain and University professors could not explain realistically, so engines are as inefficient as were in XIX century, because nobody knows how to remove the inefficiency causes. I expect the those hide in poor design...
  41. I

    Newtons third law regarding spacecraft engines

    Hello PF members, I was wondering whether Newtons third law was exclusive to spacecraft thrust; space being empty and without enough particles for a force to push against. That in order to produce thrust in space, you would need to carry the fuel that you plan to eject with you...
  42. C

    Exhaust air flow parameters for car engines (otto & diesel cycles)?

    Does anyone know any sources (i.e. car manufacturers) that provide the exhaust air flow parameters for the some specific car engines? I need stats on various otto & diesel cycle engines (small compact car engines, large semi truck engines, etc.). When I say exhaust air flow parameters, I need to...
  43. A

    Spinning magnetic field through a coil-can this propel engines?

    Spinning magnetic field through a coil-can this propel engines?? Magnetic field through a coil produces torque in the coil. Suppose we have a coil.The set up is such that the magnetic field passes through the coil.Now,if we spin the magnetic field along with the coil,the coil will keep...
  44. I

    Can a Sterling Engine Generate Electricity in the Extreme Temperatures of Space?

    The temp. difference in sunlight and shade in space is quite large and so my thoughts are can one run a sterling engine in space to produce electricity.. ? .. Any thoughts?. http://en.wikipedia.org/wiki/Stirling_engine some videos of it on youtube as well... cheers
  45. A

    Thoughts on Stirling engines as source of electrical power in space

    Curious your thoughts about the use of a Stirling engine to power a space station, auxiliary power for space ships inside the inner solar system, and power for space colonies in the inner solar system. I think a Stirling engine would be great to generate an electrical field, and thus provide...
  46. G

    Why is cooling the gas necessary for efficient heat engines?

    By heating a gas inside a cylinder, you allow it to expand against a piston while maintaining a constant temperature. The energy that you add as heat goes into the PV work of the gas against the piston. To start again, you have to push the piston back to the start point, compress the gas...
  47. S

    How Much Does a Turbofan Engine Cost?

    What is the price of cheapest turbofan engine.Does soemone know the price of Pratt and Whitney PW600?
  48. A

    Heat Engines, Entropy and Counter-Intuitiveness

    I am not a physicist and have no mathematical understanding, but I am very interested in the fact that heat engines need a cold sink, simply by virtue of the Second Law of Thermodynamics. As I understand it, as the temperature of the cold sink rises, its entropy increases at a faster rate than...
  49. J

    Using two 18V engines instead of one 36V engine?

    Ok, so I am working on a project for the summer that involves building a robot-like RC car/atv (for off-road). I want to figure out the cheapest way to get an engine that will output 1hp (which I am pretty sure is pretty close to 36 VDC, correct me if I am wrong though). Is there a way to...
  50. M

    Maximizing Efficiency in Tandem Carnot Engines

    Please help with the following: Prove that the efficiency of two carnot engines operating in tandem, one going from a cold reservoir of temperature Tc to a hot reservoir of Ti, then the second going from a cold reservoir of temperature Ti, to a hot reservoir of temperature Th must be less than...
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