Mechanical Engineering - Steam Boilers and Engines - Discussion

The correct answer is: 180° to each other.

In a Tandem type compound engine, the high-pressure (HP) and low-pressure (LP) cylinders are arranged in tandem, meaning they are connected in series and share a common piston rod. The cranks for the HP and LP cylinders are typically arranged 180° out of phase with each other, which means:

- When the HP piston is at Top Dead Center (TDC), the LP piston is at the Bottom Dead Center (BDC).
- When the HP piston is at BDC, the LP piston is at TDC.

This 180° phase difference ensures:

- Balanced forces and moments.
- Reduced vibration.
- Efficient power transfer between cylinders.

The other options are incorrect:

- 90° to each other: This would result in uneven firing and vibration issues.
- 0° to each other: This would mean the cranks are in phase, leading to excessive vibration and imbalance.
- None of these: Incorrect, as 180° is the correct phase difference for tandem compound engines.