What is Piston: Definition and 393 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.

View More On Wikipedia.org
Recent contents Top users
  1. G

    Volume ratio in an adiabatic gas expansion

    Homework Statement Consider a perfect monoatomic gas at pressure $p_i$ 1.2 atm and temperature $T_i$ 300K, that is in equilibrium inside a cylinder having a volume $V_i=1L$ and which piston has a mass of 1kg and is at an height of 50 cm. Admit that a mass M=3.13kg is over the piston. When that...
  2. L

    B Why Does a New Syringe Have an Open Piston?

    Why the piston in a new syringe is not completely closed,,? Is it just because of to differentiate from New one or it just have a scientific reason
  3. L

    How to calculate the pressure on a piston in a damper system?

    Hello all, I'm trying to calculate the pressures exerted back on a piston by a working hydraulic fluid in a damper system. I've attached a drawing of the system and the equations I'm using. Essentially the piston motion is restricted by flow through an orifice. I have data for the flow rates...
  4. R

    Resisting the force of a flow through a restricted area in a piston

    So I'm working on a method to allow control of a drop at different speeds. An idea my team had was to sit our test object on top of a piston, and drop the object by allowing the piston/plunger to drain out of a port at the bottom. We can't seem to wrap our heads around how the size of the...
  5. deckart

    Calculating Radial Piston Input Torque: An Interactive Spreadsheet Tool

    My math ability is very limited. How would I determine the input torque required to rotate this radial cylinder arrangement? I started an editable Google Sheet here: https://docs.google.com/spreadsheets/d/1w9VebhPT0S78buN_33hN0ekUggX26lyB4BVugedR1zM/edit?usp=sharing I'm hoping to have a calc...
  6. Aleoa

    I Perfect gas in a box with a piston

    We have a perfect gas in a closed box. On the top of the box there is a piston. We know that the molecules of the gas exert a pressure on the piston. Now let us put twice as many molecules in this tank, so as to double the density, and let them have the same speed, i.e., the same temperature. At...
  7. B

    Stationary vertical cylinder with heavy piston

    Hi, I'm just starting to learn thermodynamics and I'm completely stuck with a problem: 1. Homework Statement A stationary vertical cylinder, closed at the top, contains a gas whose volume may be changed with the aid of a heavy, frictionless piston of weight w. a) How much work is done by...
  8. B

    I Hydrogen plasma compression with liquid Mercury piston

    I'm working on a thought experiment. I want to know how much of the kinetic energy from a liquid mercury piston will be converted into work done on the hydrogen plasma in the form of compression, and how much work will be done on the piston in the form of compression. Note: assume piston walls...
  9. A

    Piston with crankshaft: what is the temperature of gas entering the cylinder?

    Homework Statement Homework EquationsThe Attempt at a Solution e) I know the temperature is lower in the transparent container but how do you represent this
  10. A

    Thermodynamics- Piston problem, pressure, internal energy

    Homework Statement Homework Equations F= ma P= F/A The Attempt at a Solution a). Assuming the piston is in equilibrium, I'm applying Newton's second law F=ma=0 Equals zero because it is not moving Note: P=F/A which I rearrange to solve for the force for F= PA. This represents the...
  11. EastWindBreaks

    Pressure of a piston cylinder device after heated

    Homework Statement I am confused on when will pressure of two states be the same for a piston cylinder device. Below are two problems where one's final pressure equals the initial pressure and one is not. Homework EquationsThe Attempt at a Solution Initially, I thought a piston-cylinder...
  12. EastWindBreaks

    Heated piston & cylinder device with saturated water and vapor states

    [Mentor note: Thread title changed to describe actual problem being presented] 1. Homework Statement Homework Equations The Attempt at a Solution I understand you have to interpolate temperature and pressure of the saturated vapor from the table, since there is no matched final specific...
  13. Jamie_Pi

    Calculate Final volume and temperature of piston

    Homework Statement One cylinder in the diesel engine of a truck has an initial volume of 640 cm3. Air is admitted to the cylinder at 30°C and a pressure of 1.0 atm. The piston rod then does 500 J of work to rapidly compress the air. What are its final temperature and volume? Homework Equations...
  14. S

    Seal friction needed for pneumatic/hydraulic piston

    Hello, I have a project that requires me to calculate break force friction of a piston seal on the cylinder wall. I have a double acting cylinder at very low pressure, 3.5" diameter bore, one side of the piston is air, the other side is water. What seal type, seal compression, lubrication and...
  15. F

    Insulated cylinder and compressing piston....

    Homework Statement Given a thermally insulated right circular cylinder. A piston is on top with weight Wp. Sand is placed on top of the piston with weight Ws. The pressure is only dependent on the weight of the piston and sand. The molar heat capacities are constant. a) Find the final...
  16. A

    Velocity of a piston in a piston-shaft mechanism

    Homework Statement In the figure, a piston P is connected to a cylinder. The piston is connected to a rotating wheel with two shafts AB and BC. The shaft AB is connected on the periphery of the wheel. The wheel is rotating with angular speed ω= 100 rad s-1. At the moment A,C and the center of...
  17. G

    Two gases separated by a piston

    Homework Statement [/B] Two ideal gases are contained adiabatically and separated by an insulating, fixed piston that blocks the molecules of gas 2 but allows the molecules of gas 1 through(in both directions). The initial pressures, volumes, temperatures and number of molecules on each side is...
  18. K

    Hydraulic piston force as a function of angle for a launcher

    Hello, A friend of mine challenged me with a question related to erection of missile launcher. For some reason and after too long struggling with it i gave up and trying now to figure out what is the point that I'm missing. The task is to fine the force that the piston is "feeling" as function...
  19. Mike Dacre

    Speed and pressure relative to a piston (fluids)

    I am studying for the MCAT and I got an interesting question from a Kaplan book: 15. A water tower operator is interested in increasing the pressure of a column of water that is applied to a piston. She hopes that increasing the pressure will increase the force being applied to the piston. The...
  20. E

    Ideal gas in a cylinder with a piston

    Homework Statement A vertical cylinder of radius r contains an ideal gas and is fitted with a piston of mass m that is free to move. The piston and the walls of the cylinder are frictionless, and the entire cylinder is placed in a constant-temperature bath. The outside air pressure is p0. In...
  21. C

    Gas work -- Heating the gas in a cylinder with a weighted piston on top

    Homework Statement In the open cylindrical chamber is the piston of the total mass m. The initial air pressure inside the container is pa, the initial temperature T0. The initial height of the piston above the bottom h0. Now we start the gas supply heat to the moment when the piston reaches the...
  22. Adrian379

    Thermodynamics problem: Piston in cylinder

    Homework Statement [/B] A horizontal cylinder with length L=1m and section S=2*10^(-3) is divided in two parts by a piston. In theese compartments is air at pressure p0=10^5N/m^2 and same temperature. The piston move with h=0,4m from initial position. Which is force to hold piston in this...
  23. Bonapartist

    Thermal energy problem: Gas expansion in cylinder

    Homework Statement A vertical heat-insulated cylinder is divided into two parts by a movable piston of mass m. Initially, the piston is held at rest. The top part is evacuated and the bottom part is filled with 1 mol of monatomic gas at temperature 300 K. After the piston is released and the...
  24. G

    In 3rd step of Carnot cycle, work done on the piston is pdV?

    Hello. First, look at the figure describing Carnot's cycle. In 1st step (A → B) and 2nd step (B → C), I fully understand that the work done on the pistol (surrounding) by the gas (system) is dW = pdV where dV = Adl since F = pA is the only force on the pistol from the gas (I assumed there...
  25. D

    Kinetic Theory - Mass on a piston

    Homework Statement A cylinder containing an ideal gas is in vertical position and has a piston of mass ##M## that is able to move up or down without friction (Fig. 13.2). If the temperature is increases, ...Fig (13.2) (a) both ##p## and ##V## of the gas will change. (b) only ##p## will...
  26. physea

    Piston Force Graphs: Manipulating Parameters in Combustion Pistons

    Hello guys! Can I view graphs of Piston Force versus Piston Displacement or time, in a combustion piston? I would be interested to see how the graph varies by manipulating parameters such as fuel amount, air amount, piston geometry, rpm, etc Thanks!
  27. R

    Programatically measure air pressure within a piston

    I am a software engineer. I am working on an experimental project to attempt to measure in real time the variation in air pressure (relative to the ambient pressure of the room) in a piston style apparatus. In this model, I am expectant that there will be a measureable change in the internal...
  28. P

    Angular Frequency of a Piston with Ideal Gas

    Homework Statement A frictionless piston of mass m is a precise fit in the vertical cylindrical neck of a large container of volume V. The container is filled with an ideal gas and there is a vacuum above the piston. The cross-sectional area of the neck is A. Assuming that the pressure and...
  29. J

    Isobaric vs. isothermal expansion

    We have a piston with ideal gas in it and a weight. The weight is placed on the piston. The gas is heated externally and the gas expands. Will the expansion be isobaric or isothermal? One argument would be: the expansion will be isobaric because the weight is providing constant pressure. The...
  30. S

    Determine the diameter of a piston

    Homework Statement Determine the diameter of a piston if the working stroke of a piston is ##h## and if a working cylinder ##(720^\circ )## describes the following ##p(V)## diagram, where on the ##x## axis is a ratio between the current volume of a piston and the total volume (swept + clearance...
  31. sliperyfrog

    How far does the piston move after energy is added?

    Homework Statement There are two rectangular canisters, both have a .25m cross sectional area that house 4 g of helium at 300 kelvin. The pistons are initially placed so that the enclosed volume is in a cube. The first canister's piston is locked in place, while the second canister is allowed...
  32. arpon

    B Adiabatic but permeable piston

    How can a permeable piston be adiabatic? If substances can go in and out of the cylinder and the substances have heat energy, heat can be exchanged through a permeable piston. I came across this term in the book, but cannot understand.
  33. grassstrip1

    Temperature Limits in Heat Conducting Piston Problem with Friction

    Homework Statement Air in an insulated cylinder is separated by a piston into two equal valves. When the pin is removed, the system comes to a new equilibrium position. There is friction between the piston and the cylinder walls but friction does not influence the mechanical equilibrium...
  34. D

    Atmospheric Pressure on Shaft of piston cylinder assembly

    Homework Statement In a vertical piston cylinder assembly, a vertical shaft whose cross sectional area is 0.8 cm^2 is attached to the top of the piston. Determine the magnitude F, of the force acting on the shaft, in N, required if the gas pressure inside the cylinder is 3 bar. The masses of...
  35. R

    Pressure on an open piston (derivation)

    Homework Statement http://imgur.com/a/QY1Fs Homework Equations F=dp/dt P=F/A The Attempt at a Solution I do not have the answer to this problem. Its not for homework so i won't be getting it either. I don't think my solution is correct though Let us consider a particle with speed V(x)...
  36. N

    Piston Pressure and Unit Conversion

    Problem: CO2 is contained in a vertical cylinder at a pressure of 30 atm by a piston with a mass of 57 lbm. If g is 32.4 ft/sec2 and the barometric pressure is 29.7 in. Hg what is the area of the piston? Relevant equations F = Ma/gc W = Mg/gc P= F/A gc = 32.174 lbm ft / (lbf sec2) 1 atm = 29.9...
  37. jsg94

    Piston force required (Disk brake system)

    Hello everyone, I'm currently working on a project where we need to change the little manual wheel (shown by red arrow) and replace it by a cylinder (either pneumatic or hydraulic). Right now, when the manual wheel is adjusted by rotating it to the right, the contracting rim will come closer...
  38. S

    Problem with boiling water and raising piston

    Homework Statement Consider a cylindrical tank closed by a movable piston with mass ##m=3 kg##. The radius of the cyclinder is ##r=7.5 cm##. In the tank there is a mass ##m'=2 kg## o water at temperature just below ##100°C##. At the base of the cyclindrical tank there is an electrical heater...
  39. KitsonSteam22

    How do you calculate the average force on a piston?

    1. How do you calculate the average force on a piston in one stroke from TDC to BDC given the following Kg forces and their distances in mm from TDC? 1 mm 2 mm 3 mm 4 mm 5 mm 6 mm 7 mm 8 mm 9 mm 10 mm 12 mm 13 mm 9.9 Kg 7.8 Kg 6.3 Kg 5.3 Kg 4.4 Kg 3.8 Kg 3.2...
  40. trigger701

    What moves the piston in a Carnot heat engine?

    Hi everyone, I have been looking at Carnot heat engines in a bid to better understand entropy, and I can't figure out how it actually does work. Why does the piston move? In some diagrams I have seen weights being removed from the piston, reducing the pressure at constant temperature and...
  41. Monsterboy

    Work done by compressed air on the piston

    Homework Statement A closed cylinder of 0.25 m diameter is fitted with a light friction-less piston.The piston is retained in position by a catch in the cylinder wall and the volume on one side of the piston contains air at a pressure of 750 kN/m2. The volume on the other side of the piston is...
  42. Nemo's

    Calculate Pressure in piston cylinder after heating

    Homework Statement Water is contained in a cylinder fitted with a frictionless piston (figure shows that atmospheric pressure acts on piston from above). The mass of the water is 0.45 kg, and the piston area is 0.186 m2. Initially, the water conditions are 110oC and 90% dryness fraction, and...
  43. M

    Thermodynamics, use of Cv and Cp

    I am studying for a thermo exam, and one of the problems I am doing deals with adiabatic expansion of a piston in a cylinder. When solving for work, the solution guide uses m*Cv*(T2-T1). I don't understand why they know how to use Cv instead of Cp. The pressure changes, so obviously you wouldn't...
  44. D

    Thermodynamics study questions

    THIS WAS MOVED FROM ANOTHER FORUM, SO THERE IS NO TEMPLATE. HOWEVER, THE OP DID SHOW SOME EFFORT Hello, I have been having troubles beginning these two problems given for exam prep. Was wondering if anyone could give guidance on where to begin. Problem 1: A cylinder with adiabatically...
  45. V

    Thermodynamics problem: Gas-filled cylinder & piston SHM oscillator

    Homework Statement An ideal gas enclosed in a vertical cylindrical container supports a freely moving piston of mass M. The piston and cylinder have equal cross sectional area A. When the piston is in equilibrium, the volume of the gas is V0 and its pressure is P0. The piston is slightly...
  46. H

    Thermodynamics piston stetch question

    Homework Statement Homework Equations specific volume = volume / mass dryness fraction = mass of vapor / total mass pressure The Attempt at a Solution part(a) is totally not relevant to part(b) and I finished part (b)i dryness fraction = 0.5244 specific volume = 0.0502 m^3/kg specific...
  47. N

    Calculating electrical generation from tidal piston

    I have been kicking around an idea for a while about generating electricity from ocean tides. The traditional approach is to use the flow of water through a channel to turn a turbine, which essentially blocks the channel for sea life and water craft. It seems more practical to use the rise and...
  48. G

    Work done by a gas in a piston

    Let's assume that weights are placed on a massless piston and below the piston is a gas. If we remove all the weights at once, the work done by the gas should be the difference between the forces exerted by the gas and the atmosphere multiplied by the change in volume. However, we know that the...
  49. R

    Applying first law of thermo to a closed spring piston

    Homework Statement A cylinder having a piston restrained by a linear spring (of spring constant 15 kN/m) contains 0.5 kg of saturated vapor water at 120ºC. Heat is transferred to the water causing piston to rise. If the piston’s cross sectional area is 0.05 m2 and the pressure varies linearly...
  50. dmetrd

    Confused about why atmospheric pressure won't move piston

    I'm feeling pretty silly not being able to understand this. Let's say that you have a piston (red) sitting inside of a housing (black) like this Let's say that something like this was lying on its side on a flat table. By my understanding, if the contact between the piston and the housing...
Back
Top