What is Piston: Definition and 392 Discussions

A piston is a component of reciprocating engines, reciprocating pumps, gas compressors, hydraulic cylinders and pneumatic cylinders, among other similar mechanisms. It is the moving component that is contained by a cylinder and is made gas-tight by piston rings. In an engine, its purpose is to transfer force from expanding gas in the cylinder to the crankshaft via a piston rod and/or connecting rod. In a pump, the function is reversed and force is transferred from the crankshaft to the piston for the purpose of compressing or ejecting the fluid in the cylinder. In some engines, the piston also acts as a valve by covering and uncovering ports in the cylinder.

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  1. T

    Work & Final Temperature in Piston Cylinder (Check my work)

    If someone or a few people, just look this over and tell me if I'm right or if I did something wrong I'd be so grateful. I think it's all there but I'm not sure, there might be something off. Homework Statement Air (which behaves like an ideal gas) undergoes adiabatic expansion in piston...
  2. I

    Thermodynamics - Piston Cylinder

    A piston-cylinder device initially contains 1.4-kg saturated liquid water at 200 C. Now heat is transferred to the water until the volume quadruples and the cylinder contains saturated vapour only. Determine: (a) the volume of the tank, -> Use P1 = P2 to solve -> find Vg at 200oC (b) the...
  3. G

    Diameter of football player's Piston

    Homework Statement A 54.0kg cheerleader uses an oil-filled hydraulic lift to hold four 120kg football players at a height of 1.30m . If her piston is 19.0cm in diameter, what is the diameter of the football players' piston? Homework Equations I think the only equation needed is...
  4. N

    Calculating work done in a piston

    I come from a civil engineering background and I'm about to start a masters in nuclear energy. I have no experience in thermodynamics and I've been doing a bit of revision before the course commences to get me up to speed but I'm really stuck on the following problem although it should be pretty...
  5. B

    Gas expanding against a piston

    Homework Statement Consider a cylindrical piston in which an ideal gas is kept. The gas is currently at pressure P1, volume V1, and temperature T. The temperature T is assumed to be constant throughout the experiment. The piston is massless and frictionless. On the piston is a block of mass...
  6. B

    Conceptual question about gas expanding against piston

    I'm trying to consolidate my understanding of gas thermodynamics. If anywhere my reasoning is wrong, please correct me. Consider a cylindrical piston in which an ideal gas is sealed. The piston is well insulated, and it is assumed that all points in the gas are at temperature T and this...
  7. L

    Thermodynamics - Freely moving piston and rigid cylinder ideal gas problem

    I'm a third year chemical engineering major and this is my first real thermodynamics class, so I'm not entirely sure what I'm doing. Any help is greatly appreciated! Homework Statement A rigid horizontal cylinder contains a freely moving piston. Initially, it divides the cylinder into equal...
  8. T

    1st Law of Thermo, work in a piston.

    Homework Statement Air is expanded in a piston-cylinder arrangement at a constant P of 200kPa from a volume of 0.1 m3 to a volume of 0.3m3. Then the temperature is held constant during an expansion to a volume of 0.5m3. Predict the total work done in the air. Homework Equations W = ∫PdV...
  9. J

    A question about position of piston after achieving thermal equilibrium

    A vertical cylindrical container contains some helium gas that is in thermodynamic equilibrium with the surroundings. The gas is confined by a movable heavy piston. the piston is slowly elevated a distance H from its equilibrium position and then kept in the elevated position long enough for the...
  10. S

    Ideal Gas in Piston (Constant Pressure vs Rate of collision)

    A syringe contains ideal gas. The piston is frictionless and no gas escapes. Once heated slowly, the piston moves outwards. The piston stops moving when the temperature is steady. The pressure of the gas after the piston stops moving remains the same (no change in pressure). What can we say...
  11. A

    Calculating a force on a piston

    I have what I think for me is an interesting subject, which deserves some thought about how to correctly calculate the force acting on a Otto cycle piston, and whether that force is from compression pressure, or the force acting from the crank and conrod. You have an engine running and...
  12. C

    Calculating Torque of Spring Actioned Piston

    hi guys, this is my first post (and i am don't know much physics), i have a problem that I've ilustrated in a drawing that i attach to this post. Ok so it goes something like this ... if the spring is compressed manually , when i release it how do i calculate the torque of the wheel? this is...
  13. P

    Convert crank driven system to an air piston one

    Hi!, nice place you got yourselves here, so I'm a mechanical engineer working as a maintenance supervisor working for a dairy and food corporation specializing in UHT milk and milk derivatives (varietieshttps://www.physicsforums.com/Nexus/editor/menupop.png of yogurt, cheese, butter, ice cream...
  14. M

    Pressure in a piston cylinder assembly when both volume and temperature change

    I have a problem in relation to the pressure in a closed piston and cylinder assembly, I know the compression ratio and want to work out the pressure when the volume is at its lowest, boyles law only seems to works if the temperature remains constant but I know that as the piston moves and the...
  15. S

    Thermodynamics- piston cylinder- 2nd law of thermodyamics

    ( part a only I don't understand how you know from this question that it is a constant pressure process. I thought it is a polytropic process. So it will have a pVγ curve. I was drawing a pV curve. The answer is a straight line parallel to x- axis. My question: How do I know from...
  16. S

    Thermodynamics; Finding Work of a Piston cylinder Device

    Homework Statement An insulated piston-cylinder device contains 5 kg of water at 100oC with a quarter of the mass is vapor. The water is compressed reversibly to 900 kPa. Find the work done during this process. Let the ambient temperature to be 27oC. Homework Equations I can use the...
  17. K

    Gas Compression in piston and resulting oscillations

    Homework Statement A cylinder is filled with .1 moles of an ideal gas at STP, and a piston of mass 1.4Kg seals the gas in the cylinder with a frictionless seal, as shown in the figure below. The trapped column of gas has an initial height 2.4. The piston and cylinder are surrounded by air...
  18. M

    Automotive Exploring the Production Process of Piston Rings

    Can anyone help me to answer how the production process of a piston ring?
  19. B

    Velocity of piston help

    Homework Statement The instantaneous configuration of a slider crank mechanism has a crank GH 10cm long, the connecting rod HP is 50cm. The crank makes an angle of 60 degree with the inner dead centre position and is rotating at 110 rev/min. Determine the velocity of the piston P and the...
  20. G

    Electromagnetic Piston using a holding magnet and permanent magnets?

    Dear all - I am new here so please be gentle :smile: I have searched the site for a few days but alas still have a few questions on something i am hoping to make...so with your kind help - here we go! I am looking to make a type of electromagnetic piston, basically i want to have an...
  21. M

    What is the feasability of a Neutron Piston?

    Hello all, this is my first post so hopefully its not overly foolish. I propose a mechanical piston driven by a cylinder that is filled with Uranium Hexafluoride and an inert gas (Nitrogen?). As the piston descends, the the UF6 is compressed and the neutron flux spikes. The increased...
  22. B

    Velocity at Piston P and angular velocity of link HP help

    Homework Statement The instantaneous configuration of a slider crank mechanism has a crank GH 10cm long, the connecting rod HP is 50cm. The crank makes an angle of 60 degree with the inner dead centre position and is rotating at 110 rev/min. Determine the velocity of the piston P and the...
  23. D

    Flowrates in gravity system + piston pump

    Hi all I hope you can help me here. I am trying to model an elevated vat which is using gravity to supply water to a filler. The pipeline has filters and bends in it which lead to headlosses. The filler supplys a fixed volume of liquid to a bottle at set time intervals. The filler is...
  24. V

    Calculating the bounce of a rubber ball off of a domed piston

    Homework Statement I'm supposed to design an "invention" using gas laws, and I've chosen to use Boyle's. But it turns out that a whole bunch of other science is involved, and I just can't handle it all. At it's simplest, this is what the invention is: A giant rubber ball, with a person seated...
  25. B

    Calculating Piston Movement in a Container

    in a container there are some pistons of different areas. If we apply a force at one of the pistons and move it a distance. How can we determine the distance moved by the other pistons?
  26. C

    Help with material selection - Car Piston

    Hi guys, 1st year mech engineering student looking to get some input on a recent project for my Material Selection class I have to select an alternative material that could be used to make a car piston For simplicity I'll only be forcusing on the piston itself, not the con rods or anything...
  27. K

    F=ma applied to slider crank piston motion

    I'm struggling to apply F=ma to the motion of a slider crank, more specifically the piston. I want to find out how much force is nessesary to keep the piston in motion. Essentially, in the mechanism there is acceleration and deceleration, does that mean only at some points in the cycle there is...
  28. C

    A cylinde with a piston in contact with a heat reservoir at 353 k.

    A cylinde with a piston in contact with a heat reservoir at 353 k. While keeping this gas at constant temp and pressure of 1.01 x 10E5 n/m2 we permit he gas to expand by 1.5E-5 m3. How much heat does the gas absorb? Is it just p x v = w and w = q to get an answer of 1.15 j? Cause i feel like...
  29. N

    Thermal Expansion of Brass piston in Steel cylinder

    Homework Statement You have been assigned to design brass pistons to slide inside steel cylinders. The engines in which these pistons will be used will operate between 20.0 degrees Celsius and 150.0 degrees Celsius. Assume that the coefficients of expansion are constant over this temperature...
  30. H

    Gauss-accelerated piston to replace mainspring in airrifles

    I was wondering if I could match and exceed the 20-joule effect of a springpowered rifle by replacing the spring with a suitable length of iron behind the original piston, so the eddycurrents can do its thang. I was wondering how much energy that's needed for a...say...35 joule of power in...
  31. A

    Piston problem ( closed system )

    Homework Statement 1. A piston cylinder arrangement ( A = 0.25 m^2, P1= 200 KPa, V1= 0.05 m^3. is loaded with a linear spring. in the current configuration the spring exerts no force on the piston head. if the atmospheric pressure is 101 KPa, what is the mass of the piston head. Heat is now...
  32. A

    Automotive Does the Force Generated in a Piston Engine Vary During the Down Cycle?

    Assuming you have a uniform expansion of gasses upon their ignition from the top most piston position to the bottom, would the force generated on the crankshaft vary at different points in the down cycle? My logic tells me that when you are in the top most part of the cycle, you would have a...
  33. M

    Ideal Gas Law Gas in a Piston Problem

    Homework Statement A gas is in a piston which is at 25 degrees celsius with a volume 4.0L is held in a room at atmospheric pressure. If the temperature is increased to 193 degrees celsius, the piston expands to it's maximum volume. If the pressure in the room is then increased to 4.3 atm, what...
  34. S

    What are the drawbacks of free piston engines and how can they be improved?

    There are following problems associated with free piston engines (generators). Do you know if there exist some ways to overcome it? 1)Free piston engine burns oil.What could be done to reuse oil similar to four-stroke engine? 2)Free piston engine produces very short explosions which are...
  35. O

    What factors determine the maximum power of a 4-stroke engine per cylinder?

    Is there any equation for calculating the maximum power possible for a given 4 stroke engine? per cylinder. I guess it would involve: Octain rating of fuel used RPM CC some factor of bore X Stroke And an efficiency of 100%!
  36. L

    Pressure in Cylinder following Piston Engagement

    Homework Statement I have been passed the following problem in work - this is a real life question, and not a homework assignment. I'm hoping I have provided enough information for someone to help point me in the right direction - I'm really stuggling and would love any help you could offer...
  37. L

    Pressure in Cylinder following Piston engagement

    Homework Statement I have been passed the following problem in work - this is a real life question, and not a homework assignment. I'm hoping I have provided enough information for someone to help point me in the right direction - I'm really stuggling and would love any help you could offer...
  38. H

    Force of seat belt on person in when car collides into a piston

    A car moving at 20 m/s runs into a piston that compresses air in a cylinder and stops the car at 0.3m. The 70kg person stops in the same distance because of the seat belt. Determine the average force of the seat belt on person during the stop and what assumptions did you make? ~we just...
  39. djh101

    Velocity of a Piston Homework: Find Velocity at t=1/1200min

    Homework Statement In the engine, a 7-inch rod is fastened to a crank of radius 5 inches. The crankshaft rotates counterclockwise at a constant rate of 200rpm. Find the velocity of the piston at t=1/1200min. Homework Equations θ = 400πt \frac{dx}{dθ} = -5sinθ -...
  40. N

    Water Piston Engine: Learn What It Is & How It Works

    Water Piston Engine...! what do you know about water piston engine ! is there any online documents you provide me with , because I couldn't find anything online! I know it uses no cylinders and the thrust is generated by the water somehow! I wish I can find something to read about the...
  41. L

    Thermodynamics piston problem.

    Homework Statement An ideal gas at 300 K and 1.5x10^5 Pa is contained in a piston cylinder device. The piston is 0.1m above the base of the cylinder, has a diameter of 0.15 m and is allowed to move freely. Heat is transferred to the cylinder causing the piston to move a distance of 0.05 m. The...
  42. H

    Calculating Piston Ring Twist Analytically

    Hi, I have found many papers using analytical methods to calculate the static twist in piston rings. All the papers that i found have used the results of that analytical tool but no one explained how the tool works. Can anyone find a paper in which the analysis to calculate piston ring twist is...
  43. T

    Building a rotary piston engine

    This project is a basic 6 inch rotary piston engine. The rotary engine project is to build a external combustion chamber that will redirect the expanding heat into a rotor housing and turn a rotor with a single piston vane 340 degrees to the exhaust port. The basic piston,rod and crank...
  44. J

    Calculating Final Height with Piston Design

    Homework Statement As a mechanical design project, we have to design a device that will lift a 1kg weight off the ground as high as possible when the only source of energy provided is 1.35L of 80psi compressed air. (it has to stay there so a slingshot/cannon is out of the equation) We are...
  45. S

    Work in Adiabatic/ Isothermal and Piston

    Homework Statement Is work greater in adiabatic or isothermal process? A piston with oxygen has a final volume 1/4 the initial. The temperature is also 5 times greater. Determine pressure change, heat released or absorbed, and work done on or by gas. Homework Equations the work for adiabatic...
  46. E

    Piston Pressure: Forces, Physics & Thermodynamics

    http://imageshack.us/photo/my-images/40/fdsfsadf.png/ So here's an image of a piston. First of all, this is for a thermodynamics class. Is thermodynamics considered to be "physics?" Do physics majors take thermodynamics? So my question is: When writing the forces on the piston, it is obvious...
  47. T

    Pulling a Piston - Thermodynamics Question

    Hi, I'm studying thermodynamics and I got a question, it's not a homework or anything, it simply isn't covered in my book and it got me thinking I know that if I have cylinder filled with gas, with a piston on top and there are weights on it maintaining an equilibrium if I remove the weights...
  48. P

    What Causes Overheating in Jaguar XK8's Engine Cylinders?

    1A Jaguar XK8 convertible has an eight-cylinder engine. At the beginning of its compression stroke, one of the cylinders contains 498 cm^3 of air at atmospheric pressure (1.01 x 10 ^5 Pa) and a temperature of 27.0 C. At the end of the stroke, the air has been compressed to a volume of 46.3 cm^3...
  49. F

    Calculating Volume & Pressure of Big Air Piston

    Hi all I have a question which came up in one of our physics class and thought you can help out :) It is not homework! The objective is to calculate the volume and pressure of the air coming out of the following experiment: Imagine a huge piston and cylinder. The surface of the piston...
  50. N

    Piston question to find temperature and pressure

    Homework Statement Air is contained in a vertical cylinder fitted with a frictionless piston and a set of stops. The cross sectional area of the piston is 0.05m^2. The air, which is initially at 0.21 MPa and 430 C, is cooled as result of heat transfer to the surroundings. Assuming that during...
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