43 Questions
Describe the function of a main engine turbocharger.
To increase engine power output by compressing the air before it enters the engine cylinders, allowing more fuel to be burned and increasing efficiency.
What is meant by the term pulse system in large medium speed diesel engine turbochargers?
The term pulse system refers to a turbocharging system where exhaust gas flows in pulsating form into the turbine, with each gas pulse fed to a corresponding nozzle ring segment of the expansion turbine.
What advantage does the pulse system have over the constant pressure system in turbochargers?
The pulse system allows for efficient scavenging of the engine cylinders by overlapping the opening times of inlet and exhaust valves after the pulse decay, resulting in better performance compared to the constant pressure system.
What are the advantages of pressure charging by means of an exhaust gas turbocharger system?
Advantages include increased engine power output, reduced specific fuel consumption, lower initial engine cost, space savings, increased reliability, and reduced maintenance costs.
How does a turbocharger work in relation to the engine exhaust gases?
A turbocharger comprises a gas turbine driven by the engine exhaust gases mounted on the same spindle as a blower, with the power generated in the turbine equal to that required by the compressor.
Explain the effects of undercooling the charge air on the engine.
Undercooling the charge air can lead to reduced engine efficiency and power output, potentially causing incomplete combustion and increased emissions.
Explain why the charge air cooler has fins attached to its tubes.
Fins are attached to the tubes to increase the surface area for better heat transfer between the air and the cooling medium.
What is the purpose of zinc anodes in air coolers?
Zinc anodes are sacrificial elements that help prevent galvanic corrosion by corroding themselves instead of the main structure of the cooler.
What is the purpose of vent cocks in air coolers?
Vent cocks are used to release trapped air from the system, ensuring optimal heat transfer efficiency by eliminating air pockets.
What is the purpose of tube fins in air coolers?
Tube fins increase the surface area of the tubes, enhancing heat transfer efficiency by promoting better contact between the air and the tube surface.
How does fouling of air passages affect engine performance?
Fouling of air passages can restrict airflow, leading to reduced efficiency in the combustion process, lower power output, and potentially increased fuel consumption.
Explain the significance of the air seal in an intercooler construction.
The air seal, maintained by a fitted rubber joint ring, prevents leaks and ensures that the charged air flows through the designated passages for effective cooling.
What is the role of cast iron water boxes in an intercooler construction?
The cast iron water boxes are attached to the tube plates and facilitate the circulation of cooling water, allowing for efficient heat dissipation from the tubes.
What is the main reason for surging in a turbocharger?
A change in 'Mass Air Flow'.
Where does the surging vibration emanate from in a turbocharger?
The compressor end of the rotating element.
What happens if the pressure in the scavenge manifold is equal to or higher than the discharge pressure of the compressor?
Air will attempt to flow back through the rotating impeller.
What does the back flow of air in a turbocharger cause?
It throws the rotating element into a vibration, producing a barking noise.
What analogy is used to describe the situation when air flows back through the rotating impeller in a turbocharger?
Like a centrifugal pump attempting to pump against a closed valve.
Explain why surging in a turbocharger can produce various noises like coughing and barking.
Surging causes vibrations due to the back flow of air through the rotating impeller.
What is the impact of surging on the efficiency of a turbocharger?
Surging reduces the efficiency of the turbocharger.
How does surging in a turbocharger affect power output?
Surging can reduce the power output of the engine.
What happens if the Air Mass flow drops due to issues like dirty filters or blocked coolers?
The Pressure Ratio Increases
What will happen if the Air Mass Flow continues to drop beyond a certain point?
The Pressure Ratio will suddenly drop over the edge of the graph causing a sudden pressure drop, leading to Turbocharger Surge.
What will cause the Turbocharger to Surge?
Pressure in the scavenge space being higher than that being delivered by the blower.
What action will cause the Turbocharger to Surge?
Pressure Ratio suddenly dropping over the edge of the graph.
What is the significance of marking the spot for each speed in turbocharger operation?
To create an operating line across various speeds of the Turbocharger.
How is the Pressure Ratio affected when the Air Mass flow drops?
The Pressure Ratio Increases
What happens if the Air Mass flow continues to drop?
Pressure Ratio will suddenly drop over the edge of the graph, causing a sudden pressure drop.
What is the consequence of the Pressure Ratio suddenly dropping over the edge of the graph?
Turbocharger Surge
Explain the importance of keeping the turbocharger intake filter clean.
To prevent debris and contaminants from entering the turbocharger, which can cause damage and reduce efficiency.
Why is water-washing the turbine and compressor side of the turbocharger necessary?
To remove heavy fuel deposits that can accumulate and affect the turbocharger's performance.
What is the function of a main engine turbocharger?
To increase the air intake pressure into the engine, allowing for better combustion and increased power output.
Explain why a thrust bearing is needed in large medium speed diesel engine turbochargers.
A thrust bearing is needed to withstand the axial loads generated by the turbocharger rotor.
What are four possible causes of poor turbocharger performance?
Heavy fouling, worn bearings, air leaks, and excessive exhaust gas temperature.
What is meant by the term 'pulse system' in large medium speed diesel engine turbochargers?
The pulse system refers to a method of turbocharging where exhaust gas pulses are used to drive the turbine.
Explain the advantage the pulse system has over the constant pressure system.
The pulse system provides quicker response and better low-end torque compared to the constant pressure system.
Why is it important to assess cylinder and power distribution of individual units on a regular basis?
To ensure balanced power output and performance across all cylinders, preventing uneven stress and wear.
Describe how the turbocharger is lubricated.
The turbocharger is lubricated by engine oil, which is supplied through dedicated oil lines to reduce friction and heat.
Explain the potential causes of abnormal turbocharger vibration when operating at a steady speed.
Potential causes can include imbalance, misalignment, worn bearings, worn compressor or turbine wheels, or foreign object damage.
Describe how the causes of abnormal turbocharger vibration can be minimized.
Minimization can be achieved through regular maintenance, proper alignment, balancing, use of quality parts, and avoiding foreign object damage.
What is the impact of surging on the efficiency of a turbocharger?
Surging can reduce efficiency by causing fluctuations in airflow and pressure, leading to potential damage to the turbocharger components.
Explain the role of a thrust bearing in large medium speed diesel engine turbochargers.
The thrust bearing helps to counteract axial thrust forces generated by the turbocharger rotor, ensuring stable and reliable operation.
What analogy is commonly used to describe the situation when air flows back through the rotating impeller in a turbocharger?
The analogy of 'coughing and barking' is often used to describe the noise produced when air flows back through the turbocharger impeller.
Test your knowledge on the function of a main engine turbocharger. Learn about how a turbocharger operates and its importance in engine performance. Explore the advantages of pressure charging through this quiz.
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