The Best 21-22 tutorial on |diesel engine piston

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Diesel engine piston

The piston in an engine is like a busy worker. Its main job is to take the energy from burning fuel and use it to make the engine work.

First, the piston helps keep things in order inside the engine. It acts like a door that closes off the part of the engine where fuel is burning.

Next, the piston guides another part called the connecting rod. This rod, a big spinning part, links the piston and the engine’s crankshaft. The piston’s job is to help the connecting rod move up and down smoothly.

Now, let’s talk about how the piston turns burning fuel into power. When you burn fuel in an engine, it creates a lot of pressure. The piston uses this pressure to move. Imagine blowing up a balloon and then letting it go. The air rushes out, and the balloon moves. That’s a bit like what happens in an engine. When fuel burns, it pushes the piston down, and this motion turns the engine’s crankshaft, which powers the vehicle or machine.

Last but not least, the piston has another important job. It aids in removing heat produced by fuel combustion.
When you touch something hot, and it feels uncomfortable, the engine can get too hot if not managed properly.

So, in short, the piston is a multitasker in the engine world. It seals off the combustion chamber, guides the connecting rod, turns fuel pressure into movement, and keeps the engine from getting too hot.

The purpose of a Piston in the engine

The piston is the most important unit of any Engine.

  1. The Diesel Engine Piston transmits the force of expanding gas in the cylinder via a connecting rod to the crankshaft.
  2. Piston converts the energies from one form to another. ( Chemical energy to mechanical energy)
  3. The sealing effect between the piston and the cylinder liner is provided with the help of piston rings. The economy and efficiency of the engine are due to the contribution of the piston in an engine.
  4. The small end of the connecting rod is guided by the piston. Hence, the piston bears the side thrust.

Diesel engine piston for the marine engine

Diesel engine piston Parts identification

Top part of piston is known as piston crown. Piston crown comes in contact with the burning gasesand is heat-resisting steel.

Ring grooves on the circumference of the upper part of the piston crown accomodate the piston rings.

The part below the ring groove is the piston skirt. This part is of cast iron and the part between the ring grooves separation is the lands.

The piston pin is in the bosses of the reinforced parts.

Desired Qualities of Diesel Engine Piston

Designing the piston for an engine involves several important considerations:

Strength to Withstand Combustion Forces: The piston must be strong enough to handle the powerful forces generated during combustion. This durability prevents it from being harmed or deformed.
Reducing Weight: It’s crucial to minimize the weight of the piston. A lighter piston helps reduce the inertia caused by the engine’s moving parts. This makes the engine work better and use fuel more efficiently.

Heat Conductivity: The piston should be able to conduct heat effectively.
This helps spread out the heat created when the engine burns fuel, making it less likely for something harmful called “detonation” to happen and damage the engine.

Higher Compression Ratio: A well-designed piston allows for a higher compression ratio in the engine. This is essential for achieving better fuel efficiency and power output.

Low Thermal Expansion: The material used for the piston should have minimal thermal expansion. This means it shouldn’t change size significantly with temperature fluctuations. This quality ensures a proper fit with the cylinder block and other components, like aluminum pistons.

Uniform Bearing Effect: The design of the piston skirt should promote even contact and support under abnormal conditions. The piston’s uniform bearing effect keeps the engine stable and reliable

Design of diesel engine piston

 A piston is typically divided into two main parts: the crown and the piston skirts.
A unique material well known for its exceptional strength and resistance to corrosion is used to create the piston crown.

The piston’s crown is a critical component because it is constantly exposed to the extreme temperatures generated by the combustion process in the engine.
Engineers carefully consider how to make the piston work best and last long. They especially focus on choosing the right material for the piston’s top part, called the crown, because it has to endure tough conditions inside the engine.
The piston must effectively seal the combustion chamber to contain the high-pressure gases produced during combustion.

Additionally, the piston must efficiently transfer the force generated by the expanding gases to the engine’s crankshaft, converting it into mechanical work. A well-made piston helps diesel engines run smoothly, have a longer life, and work well.

Types of diesel engine piston fitting arrangements

Listed below are type of pistons.

  1. Crosshead Piston
  2. Trunk type piston

Crosshead Piston

Crosshead Type

In the crosshead type piston, the piston connects with the crankshaft. The piston connects to the crosshead bearing through the connecting rod. and to the crankshaft by piston rod and crosshead guide. This method arrangement reduces the side thrust on the piston.

Trunk Design Piston

Trunk Type piston
Image Credit:- MAN B&W

Trunk-design pistons are popularly used in four-stroke medium-speed engines. The skirt is long with trunk-type pistons. The piston connects to the connecting rod by a small end bearing. The piston pin is the axis of rotation for a small end-bearing


Difference in design of Crosshead type and trunk design piston

Trunk type Diesel engine piston

1. There is single connecting rod in trunk design piston.

2.   Trunk design piston engines have no diaphragm.

3.  In the trunk-type engine, the small end, connects with the piston through the gudgeon pin and small end bush assembly.

4. In the trunk-type engine, no separate lube oil is used for the cylinder liner.

5. The piston skirt takes the transverse thrust

6. Cross head assembly is not required to connect the connecting rod and piston.

7. High power is produced at medium and high speed.

8. Needs less space.

9. Reduced engine manufacturing cost

10. Engine height is less than the engine with the same speed and power.

11. Can use low-grade oil.

Crosshead Type Engine

1. Cross-head type engines use the connecting rod and piston rod

2. A diaphragm seprates Cylinder space and crankcase

3. In the crosshead type, the top part of the connecting rod connects to the crosshead, consisting of the block slipper. The lower part of the piston rod supports the assembly.

4. The lubrication system for the cylinder and crankcase is different.

6. Cross head assembly connects the connecting rod and piston rod

7. Crosshead type engine develops high torque at smallest speed.

8. Need of more Height and space for maintenance.

9. Manufacturing cost is high.

Advantages of Crosshead type Piston

1.   At lower rotational speed will develop high power

2.    Lube oil contamination by combustion products is less.

3.    The lubricating oil cost is low in cross head type.

Lubrication of Trunk type pistons

Supply of lubricating oil from the crankshaft cools the piston. The shaking effect of lubricating oil cools the crown and flows out through the centre of the joint screw. After cooling, the piston crown oil scatters on the cylinder wall. Lubricating oil flows down to the sump after cooling down the cylinder liner wall. 

Procedure for Inspection of Diesel engine piston

Overhauling Process of Piston

Pre-overhauling preparation

1. Close and lock the air starting system

2. Open the indicator cock

3. Cool down the engine.

4. Disconnect fuel and cooling water.

5. All the measuring and inspection tools should be ready with calibration, and working conditions 

6. Check the availability, workability, and validity of lifting and strops and shackles.

7. Personnel involved in the maintenance should have the adequate knowledge of working procedures.

8. Place the safety symbols as per the manufacturer’s recommendations near the maintenance area.

9. Confirm the availability of spares.

10. Check the workability of hydraulic tools.

11. Ensure the mobilization permission.

12. Undertake the risk assessment.

13. Carry out the ventilation of the crankcase with permission to undertake the job.

14. Rope off the working vicinity.

Overhaul Procedure of Diesel engine piston

Carry out the below procedure for the liners with flame mounting (design of piston)

1. Clean the cylinder liner top of the coking as the piston may stick in the deposits

  • Turn the piston to BDC
  • Remove the flame ring after Inserting and mounting the tool above the piston.
  •  Put an old discarded piston ring above the flame ring removal tool.
  • Install the liner holding tool on one of the cylinder head nut.
  • Turn the engine slowly to push out the flame ring.

Important procedures for Diesel engine piston

2. Dismount the crankcase cover for the cylinder section in question to dismount the platform to help access

3. Mount the supporting device on the crankcase cover frame.

4. Place the mandrel in the guide sleeve and push forward to rest the shoulder of mandrel in correct postion.

5. Turn the crankshaft till the center of the connecting rod screw is on a level to mandrel top

6. Bring the crank throw is in a position to loosen the both upper and lower connecting rod screw .

7. Install the piston lifting device after cleaning the threaded hole.

8. Mount the pipe for retaining of the cylinder liner

9. Grab the tackle in the lifting tool for the piston and tighten.

Before turning the crankshaft, loosen the rope.

Re-tighten the rope to suit the new position.

2nd Part of dismanteling procedures

10. Pull out the mandrel of the guide sleeve and dismount the supporting tool

11. Rotate the supporting tool to turn the position of torque exrension wrench.

12. Mount the supporting tool

13. Loosen and dismantle one of the upper connecting rod screws.

14. Fit the guiding pin in the threaded holeand tighten hard with tool

15. Mount the holding-up tool on the cover frame of the crank housing on the opposite side of the engine

16. Press the forked rod tool against the connecting rod and lock it in this position with the locking screw on the tool

17. Dismantle the remaining screws and the bearing cap.

Note:

Note: Guide pin is fitted to ensure the protection of any damage to the crank journal, joint faces and bearing surface.

18. Loosen the locking screw and release the forked rod tool, see fig. 8 for the connecting rod to swing free of the crank-pin for the proper dismanteling .

19Dismount the upper bearing shell with care.

20. Pull out the piston and the connecting rod throughout the cylinder liner and out of the engine.

21.Guide The connecting rod with care in order not to damage the cylinder liner skirt

Separation of Piston from connecting rod – Piston in Engine

1. Place the piston and connecting rod with care on wooden supports to avoid damage to the piston and rings

2. Mount the bearing cap with the screws forthe protection of threads in assembly.

3. Take out the shackle and piston lifting tool from the piston

4. Rest the connecting rod and piston in upright position with top face of the piston.

5 Arrest the connecting rod with wooden wedges for the swinging movement

7. Remove the securing ring, push out the piston gudgeon pin and lift away the con rod.

Removal of the Piston Ring ( Piston in Engine)

  1. Take out the piston rings with the help of piston ring expender tool

2.Clean and inspect the rings to ascertain for the acceptance of re-use.

3. Clean both sides of piston.

4. Carry out the inspection of piston ring grooves..

Important checks on Piston for Piston in Engine

2. Piston crown side wall and ring grooves for any wear marks

3. The top part of the piston for cracking caused due by the thermal ad mechanical stress

4. Entire piston for high-temperature corrosion. 5. for hot corrosion at the upper surface and acid (cold)corrosion at the lower part.

Piston Ring Grooves and Piston Rings ( Piston in Engine)

1. Make the piston rings free in the ring groove.

2. But clearance and radial clearance

3. Any wear, stepping, and scuffing at grooves.

Piston Skirt/ Sidewalls

Inspect the piston skirt for

1. Any rubbing marks

2. Wear of wear rings

Cooling Water section

1. Scaling by poor water quality

2. High-temperature congestion.

Condition for change of Piston for Marine Engines ( Piston in Engine

Abnormal conditions to change the piston.

  1. The wear limit on the testing mandrel has exceeded

2. Piston ring and piston groove clearance out of tolerance.

Conclusion on Piston in Engine

Hope the post ondes Piston in Engine have been useful to the engineers and engineering students.

Good Luck!!

Frequently Asked Questions

Chemical treatment is required, High thermal stress in piston and Piston of more complicated design

Deposit in cooling spaces, Impingement of fuel due to faulty injection, and insufficient piston cooling oil flow.

Not to be allowed to fall below manufacturer recommended value

Difficulty in formation of the oil wedge

Books on Marine Diesel Engines

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Handbook of Diesel Engines

Handbook of Diesel Engines

“This English translation … provides a good overview of the state of the art of modern diesel technology, manufacturing, and practice. … The 60 chapter contributors, almost all from German industries, provide good coverage of supercharging, fuel, injection systems, bearings, pistons, cooling, materials, lubrication, and emissions. … The handbook is a welcome addition to the existing resources on diesel engines and will be helpful to advanced students and practitioners in the field. Summing Up: Recommended. Mechanical engineering collections serving graduate students and above.” (A. M. Strauss, Choice, Vol. 48 (7), March, 2011)

Fundamentals of Medium/Heavy Duty Diesel Engines

Fundamentals of Medium Heavy Duty Diesel Engines

Based on the 2014 National Automotive Technicians Education Foundation (NATEF) Medium/Heavy Truck Tasks Lists and ASE Certification Test Series for truck and bus specialists, Fundamentals of Medium/Heavy Duty Diesel Engines is designed to address these and other international training standards. The text offers comprehensive coverage of every NATEF task with clarity and precision in a concise format that ensures student comprehension and encourages critical thinking. Fundamentals of Medium/Heavy Duty Diesel Engines describes safe and effective diagnostic, repair, and maintenance procedures for today’s medium and heavy vehicle diesel engines, including the most current, relevant, and practical coverage of: • HD-OBD emission diagnostics • Common rail injection systems

Pounder’s Marine Diesel Engines and Gas Turbines

Ponders 10

Pounder’s Marine Diesel Engines has served seagoing engineers, students of the Certificates of Competency examinations and the marine engineering industry throughout the world.

Now in its ninth edition, Pounder’s retains the directness of approach and attention to essential detail that characterized its predecessors. There are new chapters on monitoring control and HiMSEN engines as well as information on developments in electronic-controlled fuel injection. It is fully updated to cover new legislation including that on emissions and provides details on enhancing overall efficiency and cutting CO2 emissions.
After experience as a seagoing engineer with the British India Steam Navigation Company, Doug Woodyard held editorial positions with the Institution of Mechanical Engineers and the Institute of Marine Engineer

* Helps engineers to understand the latest changes to marine diesel engineers
* Careful organisation of the new edition enables readers to access the information they require
* Brand new chapters focus on monitoring control systems and HiMSEN engines.
* Over 270 high quality, clearly labelled illustrations and figures to aid understanding and help engineers quickly identify what they need to know.

Lamb’s Questions and Answers on the Marine Diesel Engine

Lambs Questions and Answers 7

The book is comprehensive and includes almost all topics needed to understand marine diesel engines. The book explains the role of heat in engineering science, the principles behind internal combustion engines, the role of fuels and lubricants, the cooling systems, the lubricating systems and the heat exchangers.

The book also explains the various parts of the marine engines and their functions. Air-storage tanks and air compressors are also dealt with in the book. Information on balancing and vibration, various instrumentation and control methods, along with the safety measures are covered in the book.

Lamb’s Questions and Answers on the Marine Diesel Engine was published by Butterworth-Heinemann in 1990. The eighth revised edition is available in hardcover.

A Pocket Book of Marine Engineering: Questions and Answers

A Pocket Book webp 7

A Pocket Book of Marine Engineering: Questions and Answers is a book that covers the topic of air filter for engine in great detail. This book is a great resource for anyone who wants to learn more about this topic. The author, John Myatt, is a world-renowned expert on marine engineering. In this book, he covers everything from the basics of how these engines work to more advanced topics like choosing the right air filter for your engine. If you’re looking for a comprehensive guide to air filter for engine, this is the book for you.

This handy pocket-sized guide is filled with hundreds of questions and answers on marine engineering, covering all the basics from engines and propulsion to steering and safety. It’s perfect for anyone who wants to learn more about this fascinating subject, whether they’re studying for a qualification or just interested in how boats work. With clear explanations and plenty of diagrams, this book is an essential reference for anyone with an interest in maritime engineering.

Blog Conclusion

We hope that you enjoyed our blog about Diesel engine pistons. A diesel engine piston is a vital component for the function of a diesel engine. The diesel piston is a rotating component connected to a crankshaft at the heart of the reciprocating motion. Our blog post is designed to help the readers understand the piston’s components and function. We would love to hear from you.

You may like to read our other related post: Cylinder Liners of Marine Diesel Engines | 22-23 The Best Tutorial

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