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. M

    A Work done during adiabatic expansion on piston

    Does the work "extracted" from a gas (with the same initial properties) against a piston while expanding change based on the mass of the piston? For example, I have a specific volume of compressed air inside a cylinder with a piston positioned horizontally with stops. The air temperature is...
  2. T

    How to mechanically produce modified SINE wave motion

    Piston displacement as a function of time produces a sine wave. I need to modify the motion so the the time the piston spends at both the bottom of the stroke and the top of the stroke are extended. The motion curve would approximate a clipped audio wave. The attached image shows three motions...
  3. litmusgod

    A Adiabatic compression of piston and finding the velocity ratio of gas

    But when I solved, Air-Air is coming with highest velocity ratio than the others, which cannot be possible as helium - air and helium- helium is supposed to be faster. I will attach the picture of the formula i used . It's work equation . So basically during equilibrium state the pressure acting...
  4. N

    I 3D Printed Piston | Lower mass = Power

    This is a piston I had DMLS printed from AlSi10mg - the geometry is derived from generative design using some basic inputs and a starting shape. It's really just an experiment whether a consumer grade design and print can be bolted in and work for a time. After machining, it is predicted to...
  5. T

    Total force from air spring model (double acting piston)

    Hi everyone, I'm an electrical engineer working on making a linear model for a power take-off system. I've gotten inertial, friction, and hydraulic/electric components done, but what is really confusing me is the gas system; I haven't taken ANY thermodynamics. To simplify it, it is modeled as a...
  6. G

    Compressor driven by an electromagnet

    Figures: Attempt at a Solution: $$L=0,015\, \textrm{m}\qquad R_2=0,01\, \textrm{m}$$ $$R_1-R_2=R_D=0,0075\, \textrm{m}$$ $$L=0,04$$ $$\rho_1=\dfrac{p_1}{R^2T_1}=\dfrac{p_1\bar{M}}{RT_1}=1,164\, \textrm{kg}/\textrm{m}^3$$ Calculate total volume ##V_A+V_B##: $$V_B=\pi \cdot R_2^2\cdot...
  7. J3J33J333

    Why don't cars use something like a rail gun instead of combustion?

    Why don't cars use something like a rail gun instead of combustion to drive pistons?
  8. I

    I Resulting force on a chamfered pneumatic piston

    I was reading up on forces on hydraulic/pneumatic cylinders, and I've been thinking of this for a while: So for a pneumatic cylinder, the force on the piston is simply: P = F/a F = P x a where a = area of the piston that the air pressure is acting on. So what would happen if the piston is...
  9. The Bill

    Thermal insulating materials suitable for making piston and cylinder?

    What materials would be suitable for a cylinder and piston that is thermally insulating, reasonably durable for low speeds and very slow cycle rates, and not be a carbon or silicon based polymer? I've been looking at manual lever operated espresso machines lately. Particularly ones that are...
  10. S

    I Water Tank Overflow Air Piston concept/question

    I am trying to determine the minimum piston weight/force that would be required to push the air from the air tank into the top of the supply tank, filling up the supply tank and purging the discarded water thru the outlet supply pipe. We can assume no friction loss and sufficient air in the air...
  11. N

    Engineering Help with triple piston circuit

    HI! everyone :) in today's electronics class the teacher asked us to make a simultaneous circuit of 3 pistons, with ladder language. What am I supposed to do: Upon energizing the circuit, they should expand one piston after the other; from A to C. When piston C expands, it should return to...
  12. questionmonkey123

    Constant pressure process (piston) on gas violates Newtons 2nd law?

    I often see this set up in thermodynamic problems and need clarification on how Newton's Laws are involved for the piston: Gas inside a piston cylinder (1) is heated expanding the gas and raising the piston (initially at rest) to a height (2) in a constant pressure quasi-equilibrium process...
  13. ikihi

    I Compressing gas with piston: reasons for temperature increase?

    So when volume decreases, pressure increases according to Boyle's Gas Law and the ideal Gas Law. In other words, compressing gas into a smaller volume increases the vapor pressure. And also, According to Gay-Lussac's Law and ideal Gas Law, when pressure increases on a gas, temperature also...
  14. L

    Number of moles necessary to get piston back to initial position

    a) ##T_A=\frac{p_AV_A}{nR}=300.7K, P_A V_A=kL^2=nRT_A##, ##P_B S=k\frac{L}{2}\Rightarrow P_B V_B=k(\frac{L}{2})^2 \Rightarrow P_B=\frac{kL^2}{2V_A}=\frac{P_AV_A}{2V_A}=\frac{P_A}{2}##, ##W_{spring\to gas}=\int_{L}^{L/2}kxdx=-\frac{3}{8}kL^2=-\frac{3}{8}nRT_A####\Rightarrow Q=L+\Delta...
  15. Istiak

    Calculate the volume change with gas temperature for this piston in a cylinder

    Solution attempt : Option : I am sure that my work is wrong. But, I must add solution attempt in PF that's why I just added that. How can I solve the problem?
  16. SchroedingersLion

    A Solve Asymmetric Piston Problem: A Guide for SL

    Greetings! Can you help me understand what this text book problem asks of me? The situation was considered in the text: In equilibrium, the forces on both sides of the piston are equal: ##A_1P_1 = A_2P_2##. This is the first equation. It should also answer part 3 of the question. The piston...
  17. brotherbobby

    Brake mechanism in a car and pressurised oil

    (I must confess I couldn't get far, owing mostly to the term "an average distance (of 12 cm) from the axis". Axis of the (peached coloured) wheel at the center with the arrow pointing down? Is the arrow the location of the "axis" of the wheel? Let me see.) Objective : To find the oil pressure...
  18. S

    Position of piston related to ideal gas

    a. The piston will be at rest when all its kinetic energy converted into work to push the gas, so: $$\frac{1}{2}m_0 c^2=P_0. \Delta V$$ $$\frac{1}{2}m_0 \frac{29}{4} \frac{P_0.V_0}{m_0}=P_0.\Delta V$$ $$\frac{29}{8} V_0=\Delta V$$ $$\frac{29}{8} L_0 = L_0 - L$$ $$L=-\frac{21}{8} L_0$$ My...
  19. mavidias

    Cylindrical container with a piston

    Please help by answering ALL parts
  20. J

    Ideal gas law problem -- Pneumatic piston movement with air temperature changes

    I have come up with the change in height as 170 cm. My professor does not want to solve for the problem for a reason I do not understand. 170 cm is not part of the answer key. The answer according to the answer key is 65 cm. My attempt is: Initial temperature: p=F/A; (50 *9.8) / (pi * 0.05^2)...
  21. Andrea Vironda

    Sensor for detecting piston axial position

    Hi, I have a steel piston running below a 3-4 mm thick steel wall. I'd need to know the piston position below the wall without drilling the wall. I'm thinking to an inductive sensor but I think it will not work because it will detect all the time something in front of him (the fixed wall)...
  22. S

    Piston Engine versus Jet Engine Power

    Hello All The power output of piston engines fitted to aircraft were (and still are?) specified in terms of their HP rating, whereas jet engines are typically rated in terms of their trust. For example, a Mosquito two engined fighter/bomber was equipped with two Merlins, each producing...
  23. Hiero

    Adiabatic expansion of a piston in a cylinder filled with ideal gas

    I was puzzling over how to solve this and finally peeked at the solution. They used the relevant equation above. I disagree with this though. The problem specifically says “the piston is allowed to slide freely!” This means that we don’t let it happen slowly. So then we are not in...
  24. Polar24

    Can this version of pneumatic piston sustain a certain load on its own?

    Hey guys I am a freshman design student and I have been doing a project in which I am using a pneumatic piston that I designed, I don't have depth knowledge about pneumatics but I tried something. I am using simple concept for this if the cylinder is already pressurized and I am able to join...
  25. A

    Gas - cylinder - piston problem

    Summary:: Seeking explanation to classical gas - cylinder - piston problem, not the solution. Problem 1.15 from 7th edition of Introduction to Chemical Engineering Thermodynamics by Smith, Van nes and Abbot) Classical problem, given: - gas in a confined cylinder - piston with weight is placed...
  26. cwill53

    Mean Force in a Piston Rod

    I found the correct solution using the equation that relates force and pressure, but I don't REALLY understand what the question is asking and what is actually going on in the machine. I want a better understanding of everything that's going on, not just an answer. Below is a clear diagram and a...
  27. P

    Piston Between Two Ideal Gases

    Attempted Solution: Gas Entropy This system is isothermal: the energy of each gas remains constant. $$dU = 0$$ By the combined statement of the first and second laws, $$dU = TdS - PdV$$ Therefore, $$0 = TdS - PdV$$ $$dS = \frac {PdV}{T}$$ Therefore, $$dS_1 = \frac {P_1 dV_1}{T} = \frac {P_1...
  28. M

    Velocity / Acceleration Diagrams of a Mechanism - Piston and a rotating rod

    Summary:: This is a question about finding the acceleration of a point in a mechanism Hi, I have a question about the mechanism shown in the attached picture: Question: We are told that \omega = 6 rad/s and the first part is asking me to find the acceleration of point P on the piston when...
  29. vxiaoyu18

    Asking for help with a physical problem that uses a piston to push water

    Consult a physical problem that USES piston to absorb water: Pistons with surface areas S1, S2 and S are placed horizontally at the same height (H). S1 = S2 S=S1+S2 When F starts moving to the left, how do you calculate its force? Is F=ρgHS? (*The friction force doesn't have to be calculated.)
  30. E

    Ignoring the acceleration of a piston in thermodynamics

    I was just reading a set of thermodynamics lecture notes and came across the following In most thermodynamics problems I have done, it is indeed assumed that the piston does not accelerate so we can simply equate forces on the piston. However, I don't fully understand the line of reasoning...
  31. kraub

    What is the required piston force for a crane boom with specific dimensions?

    Hello, I have 2 pics about my case, I has designed crane boom and the problem has occurred when i came this point. As you see the pics, i want to find piston force. Could you help me about this ? (Dimensions=mm )
  32. PainterGuy

    Pressure felt by a piston, Mach number of speaker making the sound

    Hi, Once someone wrote the following to me in response to my query. My query was somewhat unrelated to it and I don't even have the copy of query anymore. The pressure felt by the piston at any time is the average component of momentum of a gas molecule that is normal to the piston times the...
  33. N

    Finding stress and elongation in piston

    I am really just totally stuck. I think you need to find force being applied onto the rod but I cannot figure that out
  34. Harveylanc

    Reciprocating Piston Pump Air/N2 SCFM Flow

    Hello Everyone. I am new to the forums so I hope I am posting this in the best section. I am looking to buy a gas booster that is electrically powered. The factory cannot give me any sort of flow chart so that I can determine how long it would take to boost air or nitrogen from a lower pressure...
  35. Ben Harris

    I Piston in a tube connected to a vessel filled with air

    Hi there, i have been working with a problem the past few days and have a hard time with some of the assumptions being made. The problem involves a piston in a tube which is connected to a vessel filled with air. The air behaves as an ideal gas to which the product PV^ζ is a constant. The...
  36. Chestermiller

    Thermodynamics: Gas Expansion with Piston Friction

    A friend of mine and I have been discussing how to apply the first law of thermodynamics to analyze the quasi static expansion of an ideal gas in a cylinder featuring a piston having both mass and friction (with the cylinder). We have identified two different systems that can be used in the...
  37. B

    Work done on the system through a piston?

    I am stuck on like the first page of thermal physics. It seems like the signs of the work done on the system are opposite when the volume is expanded and compressed. But when I imagine myself pushing or pulling the piston, I get confused from W = \textbf{F}\cdot \textbf{d} This work will be...
  38. G

    Zero Friction Piston Ring question

    I learned this in college too. I once know the name of these zero friction piston rings but I have forgot. If I knew the name I could do Google search and learn more about them. College professor said, grooves are .020" wide and .020" deep. Pressure drop across the grooves make them act like...
  39. J

    Angular Velocity Problem — a Piston and a Crank

    Homework Statement I have been set this question and I am struggling with parts b and c. I think I am nearly there but can't quite get over the line. Please could someone give me a nudge in the right direction. [/B] 1. (a) For the mechanism shown in FIGURE 1 determine for the angle θ = 45°: (i)...
  40. Gregs6799

    Mass of air in the piston

    Homework Statement Homework Equations pV = (m/Mr)RT (this is the formula given but I got the wrong answer using it) The Attempt at a Solution Mass = PV / RT R = 8.314 P1 x V2 / R x T1 M = 220 x 0.1 / 8.314 x 298 = 788.549kg Mass = 788.549kg P = 440000 V = 0.1 R = 8.314 T = 298...
  41. I

    I What is the Mass of a Piston?

    I am trying to teach myself Physics, so I can use it in engineering for my own devices. The project I am working on right now is a very simple spring based launcher. This is frustrating me to no end. Here is my objective. I want to lunch a golf ball about 10 or so feet. I know that I need to...
  42. E

    How to calculate the required length of an axial pump piston

    Based on other parameters how do you calculate the required length of a piston inside the cylinder block of an axial piston pump? What are the relevant equations? I've found many for the required diameter but not the length.
  43. E

    Selecting an Axial Piston Pump for a 1000m Manned Submersible Application

    So I posted yesterday about appropriate pumps for pumping water out of a ballast tank in a manned submersibles at a depth of 1000m. I decided to switch to an axial piston pump. I got that the require pump head is approx. 410 m and the required power input provided by the pump is approx. 18 000W...
  44. CLARA

    A vertical cylinder fitted with a heavy leak-proof piston wi

    Homework Statement HERE IS THE QUESTION A vertical cylinder fitted with a heavy leak-proof piston with diameter 84.0 mm contains air (under the piston) of density 1.59 kg/m3 in thermodynamic equilibrium with the surrounding atmosphere, which is at 100 kPa and 39 oC. Determine the mass of the...
  45. T

    Nitrogen pneumatic gas ram -- force to compress the piston in a cylinder

    Hi, Can some one point me to where I can workout the amount of force required to compress a niitrogen filled ram. Ram has an 80 mm bore and 172 mm stroke. We have filled it with nitrogen to both 1 and 1.5 bar. thanks Brett
  46. C

    Pressure on Piston: Conservation of Energy Explained

    Homework Statement Suppose there is a tank filled with water and a piston of area S exerts a force F on the water. Suppose I divide the water boundary touching the piston to - N small equal " square " molecules. Then , the force on the upper face of each molecule is F/N . Also, the area of...
  47. 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...