Key factors considered when the power density of 2-stroke diesel engines is being increased:

The turbocharger must be matched to the engine so that it delivers the required charge air pressure and flow over the engine's operating range. The matching is done by:

1. Determining the engine's air demand: the required air mass flow and pressure ratio at each engine speed/load (from the engine's scavenging and combustion requirements).
2. Selecting a turbocharger whose compressor map (pressure ratio vs flow) and turbine map match the engine's requirements, so that the operating point lies within the compressor's efficient region and away from the surge and choke lines.
3. Matching the turbine to the exhaust energy available, so that the turbine drives the compressor to deliver the required boost.
4. Adjusting the turbocharger (e.g. the nozzle area, or using a variable geometry turbocharger) to match the engine over the whole load range, avoiding surge at low load and over-speed at high load.
5. Verifying the match by testing (the engine and turbocharger are tested together) and adjusting the turbocharger or the engine parameters.

The matching ensures the engine gets the correct air/fuel ratio and boost for efficient, clean combustion at all loads.

The engine performance is matched to the propulsion power by:

1. Determining the propeller demand: the power required by the propeller at each ship speed (the propeller curve, P = K x N^3).
2. Selecting the engine so that its power output at the rated speed matches the propeller demand at the design ship speed, with a suitable margin (e.g. 10-15% sea margin).
3. Matching the engine's torque and speed to the propeller (via the reduction gear or directly for a direct-drive engine).
4. Ensuring the engine can deliver the required power over the operating range (the engine's load curve matches the propeller curve).
5. Adjusting the engine (e.g. the fuel injection, the turbocharger) so that it operates efficiently at the design point and over the range.

The matching ensures the engine and propeller work together efficiently, giving the required ship speed with minimum fuel consumption.

The intermediate shafting system (the shaft between the engine and the propeller) must be designed to transmit the engine power to the propeller. The calculation is influenced by:

1. The engine power and speed: the torque transmitted (T = P/omega) determines the shaft diameter required to transmit the power without exceeding the allowable shear stress.
2. The propeller diameter and speed: the propeller determines the torque and the thrust; a larger propeller at lower speed gives a higher torque for the same power, requiring a larger shaft.
3. The shaft length and the number of bearings: the shaft must be supported by intermediate bearings, and the shaft diameter and the bearing spacing are calculated to prevent excessive deflection and whirling.
4. The torsional vibration: the shafting system must be checked for torsional vibration (the natural frequencies must not coincide with the engine's excitation frequencies), and a damper or a different shaft size may be needed.
5. The axial load (thrust) and the bending loads: the shaft must withstand the propeller thrust and the bending from the weight and the misalignment.
6. The material and the safety factor: the shaft is made of a suitable material with a safety factor to allow for fatigue and the service conditions.

The calculation ensures the shafting is strong enough to transmit the power reliably and safely.