Unit 7

Question 1

What is the primary function of microturbines?

Answer 1

Generate electricity and heat on a small scale

Microturbines are low-power versions of traditional gas turbines, used in distributed generation systems.

Question 2

Microturbines can generate electricity from about ______ to ______.

Answer 2

20 kW to 1 MW

This range allows for various applications, from small facilities to larger complexes.

Question 3

What is the typical size of a 20 kW microturbine?

Answer 3

About the size of a small household refrigerator

This compact size allows for easy installation in limited spaces.

Question 4

What type of fuel is commonly used in microturbines?

Answer 4

Natural gas

Other fuels like propane and light oils can also be utilized, depending on environmental regulations.

Question 5

What are some undesirables associated with the high speeds of microturbines?(3)

Answer 5

• Noise
• Electrical frequencies in the 1000 to 3000 Hz range
• Lubrication concerns

These issues are addressed through soundproof enclosures and air bearings.

Question 6

How is the operation of a microturbine controlled?

Answer 6

Fully automatic with minimal input from the engineer/operator

Start-up, operation, and shutdown are managed by an internal computer system.

Question 7

What happens to the exhaust gas from a microturbine?

Answer 7

It enters a boiler to heat water or create steam

The cooled exhaust gas is then released into the atmosphere.

Question 8

What is the role of the alternator in a microturbine system?

Answer 8

Produces electricity and outputs it to a converter

The converter synchronizes voltage, phasing, and frequency to meet facility or grid demands.

Question 9

What is direct generation in the context of power distribution?

Answer 9

Power generation within traditional power distribution networks

It can also involve generation by the customer, reducing distribution networks and environmental impact.

Question 10

What is the significance of excess air in the combustion process of microturbines?

Answer 10

It allows for an extremely rapid combustion process

This contributes to the efficiency and effectiveness of energy generation.

Question 11

What type of bearing is used in a microturbine?

Answer 11

Foil bearings

Foil bearings are a type of air bearing that support the turbine shaft.

Question 12

How does the turbine shaft in a microturbine avoid contact with the foil bearings?

Answer 12

The working fluid (air) pushes the foil away from the shaft

This occurs as the shaft rotates to a certain speed.

Question 13

What is a key feature of foil bearings regarding pressurization?

Answer 13

Require no external pressurization system

This makes the hydrodynamic bearing self-starting.

Question 14

How many start/stop cycles can foil bearings endure due to their anti-wear coating?

Answer 14

Over 100,000 cycles

This durability is a significant advantage of foil bearings.

Question 15

What is the main advantage of foil bearings compared to traditional bearing designs?

Answer 15

Elimination of oil systems

Traditional bearings require oil systems for lubrication.

Question 16

What components of a microturbine require periodic attention?(2)

Answer 16

• Starting components
• Batteries

These components need regular maintenance to ensure proper operation.

Question 17

During routine operation, what temperatures should be checked in a microturbine?(2)

Answer 17

• Turbine temperature
• Compressor temperature

Monitoring these temperatures is crucial for operational efficiency.

Question 18

What are the big 4 of controls that are usually checked in any facility?

Answer 18

• Level
• Flow
• Pressure
• Temperature

These controls are essential for maintaining system performance.

Question 19

What is the purpose of internal combustion (IC) engine gen-sets?

Answer 19

To provide emergency or standby power during outages

Commonly used in large buildings and industrial plants to ensure uninterrupted electricity.

Question 20

What types of facilities typically require uninterrupted electricity?(4)

Answer 20

• Large buildings
• Industrial plants
• Hospitals
• Emergency lighting

These facilities need continuous power for industrial processes and safety.

Question 21

What are the startup and shutdown procedures for an internal combustion engine gen-set?

Answer 21

Perform routine inspection and maintenance, check oil, check cooling system, start engine

These procedures ensure the generator operates correctly during power failures.

Question 22

What does synchronization mean in the context of gen-sets?

Answer 22

Incoming standby electrical power must match the utility power

This includes matching voltage, phase sequence, phases, and frequencies.

Question 23

List the four conditions that must be the same during synchronization.

Answer 23

• Voltage
• Phase sequence
• Phases
• Frequencies

These conditions ensure compatibility between the gen-set and the facility’s electrical system.

Question 24

What type of engine is typically used in a standby generator?

Answer 24

Natural gas fired engine

This type of engine is common for providing power to critical systems during outages.

Question 25

What is the role of **auxiliary power** in hospitals?

Answer 25

To provide for all power requirements during outages ## Footnote Hospitals require reliable power for critical operations.

Question 26

Fill in the blank: The operator should perform routine inspection and maintenance on the equipment which may include checking the _______.

Answer 26

oil ## Footnote Regular maintenance is crucial for the reliable operation of the generator.

Question 27

What is the importance of **lubrication** in pre-start checks for gen-sets?

Answer 27

Critical for rotating equipment and reciprocating machines ## Footnote The type and level of lubrication are pertinent to each gen-set, and pressures and temperatures must remain within desired ranges during operation.

Question 28

What should be ensured regarding the **cooling system** during pre-start checks?

Answer 28

Valves and devices are set and functioning properly ## Footnote Temperatures are very important, and some systems may include a circulating pump with associated pressures.

Question 29

What does **exhaust temperature** indicate in diesel engines?

Answer 29

Load and combustion efficiency ## Footnote Knowing the normal range values is important if equipped with temperature sensing devices.

Question 30

What are the **different methods** used for starting gen-sets?(3)

Answer 30

* Electric Start * Compressed Air Starting Motor * Compressed Air to Cylinder Starting ## Footnote Each method has its own operational characteristics and requirements.

Question 31

In the **Electric Start** method, what component rotates the engine?

Answer 31

Starter motor via a ring gear on the flywheel ## Footnote Batteries supply the required voltage, usually 12, but 6 or 24 is not uncommon.

Question 32

What is the energy supply for the **Compressed Air Starting Motor**?

Answer 32

Compressed air ## Footnote The motor operates similarly to an air turbine, with supply pressure generally about 2000 kPa (290.1 psi).

Question 33

What is a critical aspect of **startup energy** checks for gen-sets?

Answer 33

Adequate supply of electrical DC or compressed air ## Footnote If DC batteries are used, fluid levels and voltages are crucial; for compressed air, cylinder pressure is critical.