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.

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  1. Titan97

    Thermodynamics problem involving piston and spring

    Homework Statement [/B] Homework Equations $$W=P\Delta V$$ $$\Delta U=nC_v\Delta T$$ The Attempt at a Solution . [/B] The gas is slowly heated. The temperature increases and the pressure increases as well. But since volume increases, the increases in pressure is nullified. The process is...
  2. R

    Displacement of a spring within a piston

    Homework Statement The force generated by a spring is given by F=kx where k is the spring constant and x is the displacement of the spring. The spring in the below figure has a constant of 8 kN/cm. The pressures are P1=5000 kPa, P2=10,000 kPa, and P3=1000 kPa. The piston diameters are D1=8cm...
  3. C

    Pressure on Piston due to Compressible flow

    is it correct modeling mathematical model for Compressed air engine, As here air Flowing through Pipe in Kg/s and its not a continuous flow and flow through vent into the cylinder and pushes Piston and and Piston moves down. As I created model like this (P1*V1)^Y = (P2*V2)^Y So, P2 =...
  4. S

    How to Calculate change in volume produced by a piston?

    Homework Statement Hello all! I need a little bit of help with my physics homework! It asks me to calculate the change in volume produced by the piston, and it gives me the equation: ∆V= Ax∆dHomework EquationsThe Attempt at a Solution Now I know that A= 1x 10-^16m^2 And ∆d=1700nm My only...
  5. Mingsliced

    Offset Piston - Calculating Max. Angular Velocity

    Homework Statement After happily working my way through the earlier parts of this question, I'm pretty much at the end of my tether with the last two parts. Please find the diagram attached: A) Determine the value of the angle θ (measured from vertical) when the angular velocity of link AB a...
  6. ajayguhan

    Piston effort=load due to gas alone?

    In my book it is mentioned that piston effort along the line of stroke=(Force due to gas pressure)+(Inertia force) why we have to consider inertia force when it is a imaginary force which is considered only during non inertial frame? why we don't equate piston effort with gas force simple...
  7. R

    Piston and Cylinder: Force, Area, Distance

    i got a small doubt.. can any1 please xplain me. if we apply a certain force"F" on cylinder of area of cross section A=pi*d^2/4(thatis,the diameter of cyllinder is d),then how much distance will the piston head move ??:bow:
  8. rpthomps

    First Law of Thermodynamics - Piston

    A cylinder of cross-sectional Area A is closed by a massless piston. The cylinder contains n mol of ideal gas with specific heat ratio and is initially in equilibrium with the surrounding air at temperature T and pressure P. The piston is initially at height h1 above the bottom of the cylinder...
  9. R

    Net force acting on a piston shaft of an actuator

    Homework Statement A cylindrical piston shaft weighs 250 g and is held vertically inside an actuator (We can assume actuator is a box with hollow cylindrical space to fit the piston shaft). Compressed air at 100 psi is supplied at the bottom of the actuator and is acting on the piston upwards...
  10. D

    Determinig the position of the piston at state 2

    Homework Statement A piston-cylinder device attached below is shown in Figure 6.A-31where Patm = 100 kPa Tamb = 150°C piston Ac = 0.01m2 mp = 100 kg water T1 = 350°C P1 = 400 kPa z1 = 0.5m Figure 6.A-31: Piston-cylinder device. The initial position of the piston is z1 = 0.5 m and the piston...
  11. O

    Using a hot gas to drive a piston: entropy reduction?

    Suppose we have an insulated cylindrical container with a piston inserted from one end. Suppose the volume confined by the piston is full of a hot gas. Now let the gas drive the piston so that the volume is increased. Did the entropy of the system decrease because some of the energy of the...
  12. A

    Make a Toy Piston: Find Solution to Inner Can Size Issue

    I would like to make a simple piston from cans. Two cans. The problem is the inner can has to be thousands of an inch smaller (diameter) from the exterior for better sliding. Solution? Add a ring would not help much unless both are within a fraction of an inch.
  13. 1729

    Determining the mass of a free to move piston

    Homework Statement A vertical cylinder contains 50.0 mg of hydrogen gas. A free to move piston with area 27.0 cm2 is pressing down on the gas. The gas's temperature is equal to 25.0 degrees Celsius. A 30 degrees Celsius increase in temperature occurs and the piston is elevated by 2.00 cm. The...
  14. jdawg

    Finding work for a gas in a piston cylinder

    Homework Statement A gas in a piston-cylinder assembly undergoes a process for which the relationship between pressure and volume is pV2=Constant. The initial pressure is 1 bar, the initial volume is 0.1 m3, and the final pressure is 9 bar. Determine the final volume and the work for the...
  15. S

    Where/how to make a plastic piston valve

    I have a project for school and need to make a hand water pump. The thing is, it needs to be a "mini" pump. I will be using 2 mini 1 way check valves and a t fitting, but the problem is i cannot find a way to make the actual piston pump. I also need a spring to draw the piston back up so i can...
  16. Sirsh

    Thermodynamics - Mass on Vertical Piston

    I keep getting this question wrong, and I am struggling to understand why this is. Homework Statement Homework Equations F = p*A Ap = π*r2 The Attempt at a Solution Denoting patm as atmospheric force, and p0 as pressure inside the cylinder. Firstly, a force balance on the system. Force UP =...
  17. Rectifier

    Nitrogen in a cylinder - temperature, work and volume

    This problem was translated from Swedish, sorry for any grammatical errors. The problem A cylinder with nitrogen gas inside is closed by a tight piston (that can slide without friction against the walls of the cylinder). The piston weighs ##s=12.5 kg## and holds the ##m=28## grams of nitrogen...
  18. D

    Silly Question on Binding for Piston

    Hi, Another fellow engineer told me that for a dual connected piston guided inside a tube (as shown in the diagram below), the distance D1 has to be chosen correctly in order to avoid binding (I'm guessing from friction only) since there may be a side force present. This is ignoring gravity...
  19. M

    Does Conrod Length Affect Torque in Engines?

    Hi, Sorry if this is in the wrong thread I'm new to the forums. I was recently talking my mate about how engines produce power and torque and how there's so many factors in it. I mentioned the length of conrod would be a factor but my mate disagreed that it has no effect on torque. To my...
  20. terryds

    Piston Thermodynamics: Understanding Pressure and Temperature Changes

    By the formula PV/T = PV/T, If there is a piston, and it compresses, so the volume gets smaller, the temperature will go down too.. But, I think if the volume gets smaller, the space is smaller, so the gas particle will collide more frequently, which makes the temperature goes up. And, my logic...
  21. I

    Brake fluid volume calculation

    Hello. I am in the process of calculating the brake fluid volume in the reservoir. I have a front disc and rear drum brake system. While the piston travel is clear for the disc brake, my question is related to the drum brake wheel cylinder piston travel. Assuming that the liner wear is 8 mm...
  22. Absentee

    Heat of friction in cylinder-piston

    I believe I'm missing something, probably a very stupid question incoming: I am considering process with ideal gas expanding without piston-friction in constant temperature environment. Amount of heat taken from the reservoir is of the same amount as the work done by the expansion of the gas...
  23. Silverlight

    How to Find Force on Rubber Tube from Piston System?

    Hello, first of all, this isn't a homework/school related question. Long story short, my father works for a chemical plant and a few of their valve/piston/transfer system things have been breaking, which he assumes is because of too much force. With everyone in a dispute and doing their own...
  24. T

    Hydraulic Variable displacement piston Pump selection

    Hello everyone, I am designing one hydraulic system. In that system their is total 8 no of component function. When all the component work that time its take 150 Bar pressure and 140 lpm flow. but this all are all time not working together. they are hardly 4 to 5 time working together in day...
  25. R

    Pressure and force in a cylinder

    A cylinder containing oxygen gas O2 has a piston that can move unfazed by friction. The piston has a diameter of d = 16cm. The oxygen gas has a temp of 40,0 degrees Celsius and a pressure of 145kPa. The pressure outside the cylinder is 101kPa. The piston is held in a stationary position s =...
  26. R

    Contact pressure of piston rod onto a surface?

    I have two images below. This is a single piston with pressure inside, the variables are as listed. P_in = 2700 Pa. P_out = 0 Pa. R1 = Radius 1 = 10 cm. R2 = Radius 2 = 5 mm. P_contact = ? My solution to P_contact is as follows. Area A1 of piston at R1 = .0314m^2 and area A2 at R2 =...
  27. AdityaDev

    How Does Acceleration Affect Spring Stretch in an Adiabatic Piston System?

    Homework Statement An adiabatic piston of mass m equally divides an insulated container of volume V0 and length l filled with Helium.The initial pressures on both sides of the piston is P0 and the piston is connected to a spring of constant k. The container starts moving with acceleration a...
  28. P

    Calculating total bulk modulus of cylinder, piston and oil

    Hello, I have been thinking about following problem: I have some kind of piston and cylinder with oil. I know the pressure in oil. Let's say it is 500bar. I would want to know how much is displacement of piston. Let's say bulk modulus of oil is 3Gpa. Let's also say that bulk modulus of...
  29. C

    Calculate force to lift piston from a given closing pressure

    I am trying to calculate the force required to close the valve on an annular bop. A rubber ring (called a packing unit) closes around the pipe when a force is applied from underneath, as shown here. The actual valve has the hydraulic fluid coming into a chamber that goes the around the outside...
  30. Q

    Fluid problem -- Piston moving in an oil-filled cylinder

    Homework Statement A piston 10 is coaxially in diameter moves within a cylinder whose inner diameter is 10.006 in; The annular space between piston and cylinder is filled with oil having a kinematic viscosity is 0.004 feet ^ 2 / s and specific gravity of 0.85 If the piston makes its way with a...
  31. Rugile

    Moving cylinder with gas and piston

    Homework Statement A thin-walled cylinder of mass m is filled with monatomic ideal gas and is lying on a horizontal frictionless surface. The initial internal energy of gas is U = cT. There is a thin insulating piston in the middle of the cylinder of mass M. The piston and the cylinder are...
  32. B

    What is the kinetic energy of a block as water pours out of a container?

    Homework Statement A block of mass m is connected to a massless rod and plunger of area A1 on a cylindric container of water. At the bottom of the container there is a pipe that leads to an opening of area A2 where the water pours out at a velocity v. The block starts at rest with the...
  33. AdityaDev

    How does heating a gas in a vessel with a piston affect the pressure inside?

    If I fill a cylindrical vessel with a gas and put a piston of some mass on top of it and slowly heat the vessel, the piston will move up. But does the pressure inside the vessel change? ( vessel is insulated).if pressure doesn't change, how does the piston move up? Pressure on piston : ##P -...
  34. A

    Thermodynamics friction less piston problem

    Homework Statement Consider an ideal friction-less cylinder-piston arrangement, in which the piston is free to move between two sets of stops. When the piston rests on the lower stops, the volume available for the contained fluid is 0.5 m3; when the piston reaches the upper stops, the volume is...
  35. F

    Weakest Point of Cylinder in Pressure Piston Homework

    Homework Statement In a cylinder & piston system, where is the weakest point on the cylinder (the point that will break under increasing pressure)? You may assume the joint between edges are as strong as the material. This is homework for A-level students. Homework Equations P = F/A Surface...
  36. snowwhite

    Work problem -- Steam piston volume and work length

    Homework Statement Steam is raised as saturated steam at 6 bar (g) and supplied to the first ( high pressure ) piston. The steam then exhausts from piston 1 at 3 bar (g). The steam is thought to expand adiabatically in accordance with PV^( 135 .1)= Constant Given the initial volume is...
  37. S

    Why is the motion of a piston considered to be simple harmonic motion?

    I know this is simple, but I don't fully understand why the motion of a piston is considered to be simple harmonic? Wouldn't the piston and connecting rod have mass?
  38. R

    How Is Gauge Pressure Calculated in a Piston-Cylinder System?

    Homework Statement Find the gauge pressure of a piston-cylinder system, assuming that the piston perfectly covers the cylinder. The piston's radius is 5 cm, its mass is 3kg, and the force being applied to it is 75N in the same direction as gravity. Looks like this picture...
  39. H

    Piston Question: Have solution, don't understand rationale

    Homework Statement The drawing below shows a hydraulic chamber in which a spring (spring constant = 1580 N/m) is attached to the input piston (A1 = 15.3 cm2), and a rock of mass 41.9 kg rests on the output plunger (A2 = 66.6 cm2). The piston and plunger are nearly at the same height, and each...
  40. G

    Designing a Car Engine Piston: Thermodynamics Question

    Recently I have been studying thermodynamics and I wanted to analyze a fictitious car piston of my own design. Indeed I have quite some questions, but the most important is this one, and maybe someone could give me an opinion on my progress. I started off by selecting the fuel, which according...
  41. I

    Experiment on piston cylinder, issues with Ideal gas law

    Hello everyone, I have an rather large piston-cylinder containing gas that is compressed when the piston extends. Using three sensors I am measuring the pressure, temperature and volume of the gas while I force the piston out using a winch. The system is closed and no gas is released or added...
  42. Y

    Thermodynamics of heating water in a cylinder with piston

    Homework Statement Consider water contained in a cylinder at 25C with a frictionless piston with some weights on it. Initially the pressure inside the piston is 100kPa and then the water is heated such that the water does 290kJ/kg of work on the piston. Find the final temperature of the...
  43. P

    Gas Expansion in insulated cylinder (piston & Diaphragm)

    I attached an image of two expansion cases I am analyzing. Both cases involve an insulated cylinder that is divided by a separating element (diaphragm for case A and piston for B). The portion on the right is evacuated. The left contains a calorically perfect gas with an initial pressure and...
  44. A

    Effects of inertia forces and friction forces on a piston in engine

    Hello, I am curious regarding the forces other than the pressure created by combustion process in IC engine.Whether inertia and friction affect worth considering or not, I want to know magnitude and nature of these forces and their effects On efficiency and performance.Thank you...
  45. S

    Cylinder with piston separating two sections containing two gases.

    Homework Statement A closed, insulated cylinder is divided into two equal parts by a piston. One compartment contains Nitrogen at T=300K, P1=5bar, the other Carbon Dioxide at T=300K, P2=20bar. The cylinder contents then reach mechanical and thermal equilibrium. 1. Assuming that the gases...
  46. C

    Gas or liquid which can push piston

    Greetings .! This is regarding a lab experiment .I need to find out if we can boil or heat a liquid ,which is connected by with a manometer and a piston .We need to push the piston and also see the reading in the manometer. Which is the ideal liquid or gas , which will not eak or hold on to...
  47. Dishsoap

    External pressure on a piston with/without friction

    Homework Statement "A gas is enclosed in a cylinder with a piston of area A. The relation between the pressure and volume of the gas at a constant temperature T is shown in Figure B. On a similar figure, sketch graphs of the ratio of the external force F to the area A, F/A, as a function of...
  48. D

    Cylinder with piston, stationary state

    Homework Statement We have a horizontal cylinder with an ideal piston, both are made from a heat nonconductive material. There is 10 liters of steam at 3 bars and 200 degrees Celsius in the cylinder. The cylinder is surrounded with atmosfere with pressure of 1 bar and temperature at 20 degrees...
  49. U

    How much an unsealed piston will compress air

    I am having trouble wrapping my head around the idea of a piston/cylinder type arrangement where the piston has a small area around the outer circumference that would allow air to travel between the front and back of the piston. To clarify, imagine a completely sealed adiabatic cylindrical box...
  50. K

    Resultant force on the piston at the end of stroke

    Homework Statement my question is on part a , the ans is 4260N . but my answer is double of the ans given. why I'm wrong? the working is shown in the photo. Homework Equations The Attempt at a Solution
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