- Modern crosshead engine fitted with a centrally mounter exhaust valve utilize uniflow scavenging
- Because of this , 3 injectors are placed circumferentially around the cylinder head.
- The atmosing holes , which are of different design to those of centrally placed injectors are designed to inject the fuel into the air swirl without contacting the liner surface.
- A single injector could not be used because because it would result in poor air/fuel mixing with poor combustion and localized high temperature, although some ebgine utilizes 2 injectors per cylinder.
- Due to tangential design of the scavenge ports ,chatge air rotates around the cylinder acts in swirl action which promotes better mixing of fuel from 3 injectors and the air.
- This overall result in uniform temp distribution , more efficient combustion and lower exhaust temperature
1. High cost: Manganese bronze is a costly alloy, making it less economical for large propellers. 2. Low strength-to-weight ratio: Compared to other propeller materials like nickel-aluminum bronze or stainless steel, manganese bronze has a lower strength-to-weight ratio. 3. Susceptible to corrosion: Manganese bronze can corrode in seawater, especially when exposed to high velocities and turbulence. 4. Poor cavitation resistance: Manganese bronze is more prone to cavitation damage than other materials. 5. Difficult to cast and machine: Manganese bronze is challenging to cast and machine, making it less desirable for complex propeller geometries. 6. Limited weldability: Manganese bronze has poor weldability, making repairs and modifications difficult. Nickel-aluminum bronze or stainless steel are commonly used for propellers due to their: - High strength and durability - Excellent corrosion resistance - Good cavitation resistance - Ease of casting and machining - Weldability
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