What is Engine: Definition and 999 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. UMath1

    Heat Engine Efficiency and Entropy

    In deriving the Carnot Efficiency, the assumption is made that theoretically most efficient engine will generate no net entropy, meaning that the entropy that enters the system during heat absorption must equal the entropy that leaves the engine during heat rejection. Why is the case? Why would...
  2. B

    How to Find the Number of Liters of Gas Used in a Gasoline Engine

    Homework Statement The problem is "A multicylinder gasoline engine in an airplane, operating at 2.40 10^3 rev/min, takes in energy 7.98 10^3 J and exhausts 4.50 10^3 J for each revolution of the crankshaft." and it wants me to find the liters of fuel consumed in 1 hr of operation if the heat...
  3. J

    Airplane question -- How to compensate for losing engine power on one wing....

    If the right wing right engine suddenly fails.which of the two rudders and how must be moved so that airplane maintains its attitude and flies straight (assuming the plane is on air not landing)
  4. marosa4

    How does momentum affect the motion of objects in a friction-less environment?

    What would the theoretical maximum possible speed be for a platform on a horizontal air-bearing (friction-less), if the only propulsion was a spring powered machine gun with unlimited steel balls? The balls go one way, the platform moves proportionally in the opposite direction. Ignore inertia...
  5. R

    Is a diamagnetic levitation engine possible?

    I recently saw the video of the frog being levitated with a big magnet. Would it be possible to flip the magnet over and use it to levitate a vehicle? How much energy would it take to levitate, say, a 1000kg vehicle above a dry lakebed?
  6. cosmik debris

    Automotive How is variable engine braking implemented in a vehicle ECU?

    Hi All, The ECU on my motor bike allows you to select different amounts of engine braking in it's various riding modes. I imagine that the ECU just opens up the throttle bodies a little so that at closed throttle the engine still delivers a bit of torque. Doing this will increase the idle speed...
  7. P

    How Efficient Can a Radiative Heat Engine Be for a Moon Base?

    Homework Statement The emission of radiation from the Sun’s disc is observed to peak at 0.5 μm wave- length and that from the Moon’s disc at 10.0μm. A heat engine to power a Moon base is to be constructed using radiation collected from the Sun. What is the maximum theoretical efficiency of such...
  8. G

    Real-time engine simulation - oil temperature

    Hi folks! A while ago, we discussed a real-time simulation of an oil cycle within a combustion engine. Back then I was focusing on volume flow and pressure and you were incredibly helpful in coming up with the required formulas, so thank you again for your help! I'm now moving to the next...
  9. F

    Understanding the Power of an Engine

    Hello, In mechanics, power is defined as the rate at which energy is either produced or consumer: ##\frac {E}{t}##. A different but equivalent definition is ##P= F v##. In the rotational world, we talk about rotational power and the expression becomes $$P= \tau {\omega}$$ where ##\tau## is...
  10. Kelly Andrew

    Why would a petrol engine stall at an altitude?

    The engine was used to propel a small home made air craft. It worked very well while it taxied away and went airborne, then at a certain altitude it stopped abruptly then came crashing down. Why? And what simple engine design can sustain the air craft?
  11. J

    Automotive 400 HP gasoline pickup engine vs 400 HP semi engine

    If you took a 400 horsepower gasoline pickup engine and a 400 horse power semi engine and hook them up to a transmission so that they had the same output rpm while each engine is at their peak horsepower rpm would they be able to pull the same load fairly similar?
  12. E

    Automotive Engine explodes during dyno test

    A high-performance diesel engine explodes into pieces while being run on a dyno test.
  13. M

    Calculating work done by a Carnot engine

    "A Carnot engine operates using a heat source at 500 °C, and a heat sink at room temperature (20 °C). Suppose that as a heat source, you use the combustion of 100 cubic feet of natural gas at room temperature and pressure (e.g. in a fuel cell of some kind). Under ideal conditions, what is the...
  14. O

    What is the Best 2D Physics Engine for a Real-Time Simulation Program?

    Hello! I'm trying to write a 2D program that uses simple physics. I was wondering what would be the best 2D physics engine to use in my case, and if it even matter what engine I choose. I also want my simulation to run in real time, so at least 30 fps on a decent home computer. I prefer a fast...
  15. W

    Can't find my Localhost Database Engine for SQL Server

    Hi All, I had to reinstall my SQL Server and I a having trouble finding the database engine which is the local host. Please see screenshots. Any ideas? Thanks.
  16. Omkar Bhalerao

    Engine & Dynamometer Coupling

    Can I use a Clutch Plate assembly along with drive shaft to connect Engine & dynamometer? I am facing an issue where in CRDi engine, at a position of accelerator pedal RPM is increasing from 1300 to 2000 without any change in accelerator pedal position. And a lot of vibrations takes place at...
  17. Jason Louison

    Automotive Computer Simulation of Engine Performance

    Hello Physics Forums! After almost a year of haggling and research, I think I have successfully made a engine simulation spreadsheet! :oldbiggrin: I have simulated the Nissan KA24DE Engine with two different cam profiles: As far as I'm concerned, there is still a lot of work to be done...
  18. Jason Louison

    Engine Finite Heat Release Model (With Heat Transfer) Help

    Hello Physics Forum Users! I have an annoying situation with the Finite Heat Release Equation used to simulate combustion and expansion processes in an internal combustion engine. The equation is as follows: Nomenclature: P = Cylinder Pressure (kPa) θ = Crank Angle (Deg) k = Specific Heat...
  19. D

    IC Engine Connecting Rod Mass Moment of Inertia Measurements

    Does anyone know of a source, on the Internet preferably, for component inertial data for a real IC engine? In particular, what I'd like to obtain (for some real engine, any engine) are these items: 1. Piston weight (including wrist pin) 2. Cylinder bore dimension 3. Connecting rod length...
  20. FreeBob

    Calculating equivalent horsepower for a jet engine

    Trying to remember some basics. I know the thrust of a jet engine. I'm thinking about equivalent HP. I can establish HP at a given speed, but what about while accelerating? I will display my ignorance here :( Power for static, non accelerating flight: Power = [Thrust x Airspeed] Thrust...
  21. X

    Thermal efficiency of a Diesel engine

    Hi, i’m learning about the thermal efficiency of a diesel cycle at university and I'm trying to understand the equation. The first law of thermodynamics states Wnet + Qnet = 0, but one of the attachments below says Qnet - Wnet = 0 and I don't understand how this is the case. Also, for process...
  22. jonnybmac

    What is the relationship between engine power, force, and speed?

    Homework Statement I am having difficulty understanding the conversion between power and rotation at the engine and at the wheel. Can you please state which parts are right and wrong, and why please as I think I've spent that long on researching I've confused myself with too much information...
  23. Pushoam

    Maximum work done by a Carnot engine

    Homework Statement Homework EquationsThe Attempt at a SolutionTaking the engine to be a Carnot engine, ## \eta = \frac { T_h – T_c } {T_h} = \frac { W} {Q_h} ## ...(1) ## Q_h = C(T_h – T_f) ...(2) \\ Q_c = C(T_f – T_c) ...(3) \\ W = Q_h – Q_c = C(T_h + T_c – 2 T_f) ## ...(4)Solving...
  24. yangshi

    What Are the Advantages of a Rotating Detonation Engine for Naval Ships?

    Just trying to understand how efficient RDE's are thermodynamically based on a 2016 paper from Bulat and Volkov titled "Detonation Jet Engine. Part 1 – Thermodynamic Cycle" and a 2013 paper by Nordeen et. al. titled "Thermodynamic Model of a Rotating Detonation Engine": Based on these papers...
  25. Pushoam

    Calculating Power Output of a p-V Engine

    Homework Statement Homework EquationsThe Attempt at a Solution P = 1500 * [area occupied by the cycle = ## 4 p_0 V_0 ## ] /60 = 15 kW Is this correct?
  26. S

    Engine flow rate with varying power settings

    Most engine specifications I have found only provide the engine mass flow rate for take-off setting. For example, the V2500 has a mass flow rate of 354.25 kg/s. How does the flow rate vary through different power settings? For example, if the engine is on idle, will the mass flow rate be 0...
  27. Franz Rojas Ayala

    Heat energy input from a hot source in a heat engine

    Greetings! I did the famous "Mass Lifter Heat Engine" experiment in which a mass is put at the top of a piston enclosed within a cylinder. The cylinder is connected to an aluminium canister of air and the air inside this canister expands and contracts the piston with thermal contact. We had 2...
  28. M

    I on my rocket engine thrust equation

    I have been working on a rocket engine and I have cad models and everything and I am getting ready to build it. Then, I was running over the numbers one more time and I realized that the thrust I was getting was completely different from what I should have been getting. The big problem is the...
  29. S

    Calculating suction area around the intake of a jet engine

    I am looking to calculate the area around the engine where, if an object enters this area, it would be "ingested" by the engine (subsonic flight). In other words, I am looking to draw the shape around the engine, where the air within that shape is disturbed air (being ingested by the engine)...
  30. A

    Turbo-Jet Engine for Medium RC Aircraft

    Hello , I am thinking to work on a RC aircraft ( Airplane ) that can load a small supply of Medical Firstaid in small range. So I need to make it fast and stable. So I'm thinking to use a small Turbo-jet engine in it which will be home-made. Please suggest me -- (1) Is that makes any sense ...
  31. tworitdash

    Solving Misfire in CNG Engine: Q&A

    I have some questions regarding my observations of a misfiring bi-fuel vehicle (CNG and Gasoline). 1. For same misfire rates, in Gasoline mode, the exhaust catalyst temperature is higher than the in CNG mode. 2. For lower misfire rates, in CNG, the temperature is higher than with higher...
  32. Abdul Waheed

    Selection of a suitable engine for developing a hover bike.

    I am trying to figure out the power required to lift a hover bike that would have four propellers and would weigh around 400-500 kg. how can i select an engine and find the required shaft power, rpm, engine cc and thrust required.
  33. W

    Why most engine wear occurs during cold start up?

    What is phyisical reason for 75%-90% wear engine occurs on cold start up? I can't find exact reason.. Is that beacuse ? 1) rich fuel mixture on choke, splash oil film from cylinder wall? 2)corrosive wear on cylinder and piston rings? 3)cold oil don't lubricated well?? (but oil when is cold...
  34. I

    How to calculate the efficiency of a fuel engine

    Homework Statement [/B] Im trying to find the efficiency of a gasoline engine regarded as a control volume. Am I right to use the HV as total energy input into the system? Assuming the enthalpy of formation of the fuel can't be found. I am really wondering if enthalpy of formation equals the...
  35. yrjosmiel

    Maximum delta-v of a rocket engine

    So I was browsing wikipedia when I encountered: What does this exactly mean? How does one calculate for this? << Adding link to the table >> https://en.wikipedia.org/wiki/Spacecraft_propulsion#Table_of_methods
  36. P

    (Just Released) New internal combustion engine technology

    please share with others
  37. T

    One Stroke Engine: The Efficiency and Elimination of 2 and 4 Stroke Designs

    Why can't u make two way port opens when it sucks in air and fuel but closes when combustion happens eliminating 2 stroke and even 4 stroke design
  38. orb_yt

    How are/were computers used in jet engine design?

    Hello all, I have been tasked with writing a very short article regarding the use of computers and software in early jet engine design up to modern times. I've been having a relatively hard time finding reading material through Google. I understand that modern jet engine designers use CAD...
  39. Y

    Reversibility of Two Stroke Engines: Exploring the Impact of Crosshead Bearings

    Are large two stroke engines with cross-head bearings reversible?
  40. L

    Please check my math about this engine efficiency calculation

    Hello. I wanted to see how much more efficient a car would be if hydrogen and oxygen (created through electrolysis of water) were injected into the engine alongside gasoline. I got lost when I found out that I would need 241.8 kJ/mol of water to electrolyze it...
  41. Domenico94

    Electric cars -- Does periodic coasting help efficiency?

    Hi. I'm a student of electrical engineering, and I've always been interested in the idea of electrical cars, so I came up with a question: let's suppose we want to have a normal trip with car, and then we're not interested in going so fast with it. When we are driving in this condition, it isn't...
  42. Toby_phys

    Efficiency of a Simple 3-Stage Ideal Gas Cycle: Analyzing Thermal Efficiency η

    A possible ideal-gas cycle operates as follows: 1. From an initial state (##p_1##, ##V_1##) the gas is cooled at constant pressure to (##p_1##, ##V_2##); Let's call the start and end temperature ##T_1## and ##T_2## 2.The gas is heated at constant volume to (##p_2##, ##V_2##);Lets call the...
  43. M

    2 body engine, final equilibrium temperate and work produced

    Homework Statement 2 bodies with contant heat capacity C and 2C, are initially at temp T and 2T. if a heat engine executing a reversible carnot cycle operates between the two bodies until their temperatures are equal, what is the final temp of the bodies and how much work is preformed by the...
  44. T

    Thermodynamics: The Jet Engine

    Good evening everyone,I had several questions regarding basic thermodynamics. After going to Paris Airshow (Le Bourget), lot's of questions came to my mind after looking at those beautiful Jet engines...I have always had a very basic understanding on these engines: a fan, a compressor (High and...
  45. T

    Automotive Engine Torque Control: A Guide to Automatics & DCTs

    Hi guys, I have a question about engine torque control in automatic transmissions and dual clutch transmissions. I've seen cases where the engine torque is decreased on an up-shift and increased during a downshift. Why is this done?
  46. J

    Replacing a diesel engine with an electric motor

    Hi all, I have a little project on my hands and I will go into a little detail to help everyone better understand. I built a mobile boutique out of a shuttle bus for my fiancé to run her business out of. There is a large rooftop air conditioner on top of the roof for cooling and the...
  47. P

    Engine Efficiency: Find ΔW & ΔQh

    Homework Statement An ideal gas with Cv = 5 2R, and γ = 1.4 starts at a volume of 1.5m3 , a pressure of 2.0×105Pa ,and a temperature of 300K. It undergoes an isobaric expansion until the volume is V , then undergoes an adiabatic expansion until the volume is 6.0m3 , and finally undergoes an...
  48. G

    What is the power of a car engine?

    Homework Statement The volume displacement in a car engine is 2000 cm3. During the power stroke, the mean pressure inside the cylinder is 15 bar. Compute the work performed by the engine in one revolution. Compute the engine's power assuming it runs at 3000 rpm. Homework Equations...
  49. Waggles

    Renewable Energy Concept - Stirling Engine Composting

    So I've got this crazy idea. To put it simply, to use the heat from anaerobic composting to power hot-air engine, specifically a Stirling Engine. Based solely on my own reading, the center of a closed composting heap can reach anywhere from 120-160 degrees without killing the microorganisms...
  50. L

    Force produced by flow in aircraft engine

    Homework Statement Consider an aircraft turbine as in the figure below. In the reference frame of the turbine, air of density ##\rho_0## comes into the turbine with speed ##U_0## through the entrance with cross sectional area ##S_0##. In the combustion zone, air is mixed with the fuel and...
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