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A steam engine fundamentally operates by converting thermal energy into mechanical work, employing water vapor as the working fluid.
Answer: True
As defined, a steam engine functions as a heat engine, converting thermal energy into mechanical work. The process utilizes steam, typically water vapor, as the working fluid to exert pressure and drive mechanical components.
In a steam engine, mechanical work is exclusively generated by steam pressure acting upon turbine blades.
Answer: False
While steam pressure does act upon turbine blades in steam turbines, this statement is false as it excludes reciprocating steam engines, where steam pressure moves a piston. Mechanical work generation is not limited solely to turbine blades.
Steam engines are classified as internal combustion engines, with the justification that fuel is burned outside the working cylinder.
Answer: False
Steam engines are classified as external combustion engines because their fuel combustion occurs outside the working cylinder, distinguishing them from internal combustion engines where combustion happens within the cylinder.
The Rankine cycle represents the idealized thermodynamic cycle employed for the theoretical analysis of steam engine performance.
Answer: True
The Rankine cycle is indeed the standard theoretical model used to analyze the thermodynamic processes and efficiency of steam engines, encompassing the phase changes of water.
The Rankine cycle assumes heat transfer occurs at constant temperature, unlike the Carnot cycle.
Answer: False
In the Rankine cycle, heat addition (in the boiler) and heat rejection (in the condenser) occur at constant pressure (isobaric), whereas the Carnot cycle assumes heat transfer takes place isothermally (at constant temperature).
Pumping water as a liquid in the Rankine cycle requires more energy than compressing steam in the Carnot cycle.
Answer: False
The pumping of water in its liquid state requires substantially less energy compared to the compression of steam (a gas). This disparity in energy demand for the pump is a key factor contributing to the higher practical efficiency observed in the Rankine cycle relative to the theoretical Carnot cycle.
The theoretical efficiency limit for a steam engine is determined by the Carnot cycle's temperature difference.
Answer: True
The theoretical maximum efficiency for any heat engine, including a steam engine, is dictated by the Carnot cycle, which is contingent upon the temperature differential between the heat source and the cold sink.
Reciprocating steam engines exhausting to the atmosphere typically achieved efficiencies above 20%.
Answer: False
Reciprocating steam engines that exhausted steam directly to the atmosphere generally operated within a thermal efficiency range of 1% to 10%. Subsequent enhancements, including the incorporation of condensers, multiple expansion stages, and the utilization of higher pressures and temperatures, allowed efficiencies to increase, potentially reaching 10% to 20% or marginally higher.
Superheating increases steam engine efficiency by reducing condensation within the cylinders.
Answer: True
Superheating entails heating steam subsequent to its departure from the boiler, elevating its temperature beyond the saturated vapor point. This process transforms 'wet steam' into 'superheated steam,' thereby diminishing condensation within the engine cylinders and substantially enhancing overall engine efficiency.
A 'cold sink' is where waste heat is generated in a steam engine.
Answer: False
A cold sink is an indispensable component for all heat engines, including steam engines, serving as the repository for rejected waste heat at a lower temperature. Waste heat is generated throughout the engine's thermodynamic cycle, not solely at the cold sink.
Superheating increases steam engine efficiency by reducing condensation within the cylinders.
Answer: True
Superheating entails heating steam subsequent to its departure from the boiler, elevating its temperature beyond the saturated vapor point. This process transforms 'wet steam' into 'superheated steam,' thereby diminishing condensation within the engine cylinders and substantially enhancing overall engine efficiency.
A 'cold sink' is where waste heat is generated in a steam engine.
Answer: False
A cold sink is an indispensable component for all heat engines, including steam engines, serving as the repository for rejected waste heat at a lower temperature. Waste heat is generated throughout the engine's thermodynamic cycle, not solely at the cold sink.
The Rankine cycle assumes heat transfer occurs at constant temperature, unlike the Carnot cycle.
Answer: False
In the Rankine cycle, heat addition (in the boiler) and heat rejection (in the condenser) occur at constant pressure (isobaric), whereas the Carnot cycle assumes heat transfer takes place isothermally (at constant temperature).
Pumping water as a liquid in the Rankine cycle requires more energy than compressing steam in the Carnot cycle.
Answer: False
The pumping of water in its liquid state requires substantially less energy compared to the compression of steam (a gas). This disparity in energy demand for the pump is a key factor contributing to the higher practical efficiency observed in the Rankine cycle relative to the theoretical Carnot cycle.
The 'duty' of a steam engine historically measured its fuel consumption per hour.
Answer: False
Historically, a steam engine's energy efficiency was quantified by its 'duty.' This metric was defined as the amount of work, measured in foot-pounds, accomplished per bushel (approximately 94 lbs) of coal consumed. It was not a measure of fuel consumption per hour.
The theoretical efficiency limit for a steam engine is determined by the Carnot cycle's temperature difference.
Answer: True
The theoretical maximum efficiency for any heat engine, including a steam engine, is dictated by the Carnot cycle, which is contingent upon the temperature differential between the heat source and the cold sink.
Reciprocating steam engines exhausting to the atmosphere typically achieved efficiencies above 20%.
Answer: False
Reciprocating steam engines that exhausted steam directly to the atmosphere generally operated within a thermal efficiency range of 1% to 10%. Subsequent enhancements, including the incorporation of condensers, multiple expansion stages, and the utilization of higher pressures and temperatures, allowed efficiencies to increase, potentially reaching 10% to 20% or marginally higher.
Cylinder condensation and re-evaporation are minor efficiency losses in reciprocating steam engines.
Answer: False
The dominant efficiency loss in reciprocating steam engines is cylinder condensation and re-evaporation. This occurs when high-temperature steam condenses on cooler cylinder surfaces during admission and then re-evaporates during exhaust, wasting energy.
'Lead' in valve timing refers to closing the steam admission valve after the piston completes its stroke.
Answer: False
In steam engine valve timing, 'lead' refers to advancing the steam admission slightly before the piston reaches the end of its exhaust stroke. This ensures the clearance volume is filled with steam before the main power stroke begins, improving efficiency.
What is the fundamental function of a steam engine?
Answer: To convert thermal energy into mechanical work using steam.
The primary function of a steam engine is to serve as a heat engine, converting thermal energy, derived from fuel combustion or other heat sources, into useful mechanical work. This conversion process is facilitated by the expansion of steam.
Why are steam engines classified as external combustion engines?
Answer: Because the combustion process takes place outside the engine's working cylinder.
Steam engines are categorized as external combustion engines due to the location of the fuel combustion process. The heat generation occurs externally to the engine's working cylinder, ensuring that the combustion products remain separate from the steam directly responsible for driving the mechanical components.
What is the purpose of superheating steam in a steam engine?
Answer: To convert 'wet steam' into 'superheated steam', reducing condensation and increasing efficiency.
Superheating entails heating steam subsequent to its departure from the boiler, elevating its temperature beyond the saturated vapor point. This process transforms 'wet steam' into 'superheated steam,' thereby diminishing condensation within the engine cylinders and substantially enhancing overall engine efficiency.
What is the function of a 'cold sink' in the context of a steam engine?
Answer: A necessary part for rejecting waste heat at a lower temperature.
A cold sink is an indispensable component for all heat engines, including steam engines, serving as the repository for rejected waste heat at a lower temperature. In steam engines, this function is typically fulfilled by condensing the exhaust steam, frequently utilizing ambient resources such as water or air.
How does the Rankine cycle differ from the Carnot cycle regarding heat transfer?
Answer: Rankine cycle heat transfer is isobaric; Carnot cycle heat transfer is isothermal.
The Rankine cycle differentiates itself from the Carnot cycle in its heat transfer processes: heat addition (in the boiler) and heat rejection (in the condenser) occur at constant pressure (isobaric), whereas the Carnot cycle assumes heat transfer takes place isothermally (at constant temperature).
Why is pumping liquid water more efficient in the Rankine cycle compared to compressing gaseous steam in the Carnot cycle?
Answer: Pumping liquid water requires significantly less energy than compressing steam.
The pumping of water in its liquid state requires substantially less energy compared to the compression of steam (a gas). This disparity in energy demand for the pump is a key factor contributing to the higher practical efficiency observed in the Rankine cycle relative to the theoretical Carnot cycle.
What historical measure quantified a steam engine's energy efficiency based on coal consumption?
Answer: Duty
Historically, a steam engine's energy efficiency was quantified by its 'duty.' This metric was defined as the amount of work, measured in foot-pounds, accomplished per bushel (approximately 94 lbs) of coal consumed. James Watt's engines demonstrated a marked improvement in duty compared to their predecessors, such as the Newcomen engines.
Cylinder condensation and re-evaporation represent the primary source of what in reciprocating steam engines?
Answer: Efficiency loss
The dominant efficiency loss in reciprocating steam engines is cylinder condensation and re-evaporation. This occurs when high-temperature steam condenses on cooler cylinder surfaces during admission and then re-evaporates during exhaust, wasting energy.
What is 'lead' in the context of steam engine valve timing?
Answer: Advancing steam admission slightly before the piston reaches the end of its exhaust stroke.
In steam engine valve timing, 'lead' refers to advancing the steam admission slightly before the piston reaches the end of its exhaust stroke. This ensures the clearance volume is filled with steam before the main power stroke begins, improving efficiency.
The aeolipile, as described by Hero of Alexandria, constituted a complex steam engine utilized for industrial applications during the first century AD.
Answer: False
While Hero of Alexandria described the aeolipile in the first century AD, it was a rudimentary device demonstrating steam's reactive force, not a complex engine used for industrial purposes.
Jerónimo de Ayanz y Beaumont is credited with patenting the first steam-powered water pump specifically designed for mine drainage in the year 1606.
Answer: True
Jerónimo de Ayanz y Beaumont's 1606 patent for a steam-powered water pump marked a significant early development in applying steam power to industrial challenges like mine dewatering.
James Watt's principal innovation was focused on augmenting the operational speed of Thomas Newcomen's atmospheric engine.
Answer: False
While Watt's improvements significantly enhanced efficiency and power output, his primary contribution was not merely increasing speed but rather the development of the separate condenser, which drastically reduced fuel consumption.
Thomas Newcomen's atmospheric engine primarily utilized atmospheric pressure as its driving force, acting upon the piston subsequent to the condensation of steam within the cylinder creating a vacuum.
Answer: True
Newcomen's engine operated by condensing steam to create a vacuum, allowing the greater atmospheric pressure outside the cylinder to push the piston down, thus generating power.
Giovanni Branca detailed a rudimentary steam turbine concept in the year 1551.
Answer: False
While Giovanni Branca did describe a steam turbine concept, his work was published in 1629, not 1551.
The principal application for Thomas Newcomen's atmospheric engine was the operation of textile machinery.
Answer: False
Newcomen's engine, developed around 1712, was primarily designed and utilized for pumping water out of mines, a critical need for the burgeoning mining industry.
Jacob Leupold's design, published in 1720, incorporated a two-cylinder configuration for a high-pressure steam engine.
Answer: True
Jacob Leupold's 1720 publication described a two-cylinder high-pressure steam engine design, which was a notable advancement for its time.
Early steam-powered road vehicles encountered substantial commercial viability challenges, significantly exacerbated by legislative restrictions.
Answer: True
The development of early steam-powered road vehicles, commencing in the late 18th century, was impeded by numerous challenges. Foremost among these were legislative restrictions that curtailed or outright prohibited their operation on public roads, thereby significantly dampening their commercial viability despite technological advancements.
Richard Trevithick's 1804 locomotive is recognized as the world's first full-scale operational railway steam locomotive.
Answer: True
Richard Trevithick's 1804 locomotive holds the distinction of being the world's first full-scale, operational railway steam locomotive. Its successful demonstration, hauling a load along a Welsh tramway, proved the feasibility of steam power for rail transportation.
Richard Trevithick's 1804 locomotive was engineered to operate using low-pressure steam, aiming for enhanced efficiency.
Answer: False
Trevithick's locomotive was a pioneering example of a high-pressure steam engine, a design choice that allowed for a more compact and powerful engine compared to the low-pressure atmospheric engines prevalent at the time.
George Stephenson constructed the 'Rocket' locomotive specifically for service on the Stockton and Darlington Railway, commencing operations in 1825.
Answer: False
George Stephenson constructed the 'Locomotion No. 1' in 1825 for the Stockton and Darlington Railway, recognized as the world's inaugural public steam railway. Subsequently, he designed 'The Rocket' in 1829, which achieved victory in the Rainhill Trials.
James Watt is credited with the introduction of centrifugal governors as a mechanism for regulating steam engine speed.
Answer: True
James Watt incorporated the centrifugal governor into his improved steam engine designs to automatically control the engine's speed by adjusting the steam supply.
Richard Trevithick's 1804 locomotive is recognized as the world's first full-scale operational railway steam locomotive.
Answer: True
Richard Trevithick's 1804 locomotive holds the distinction of being the world's first full-scale, operational railway steam locomotive. Its successful demonstration, hauling a load along a Welsh tramway, proved the feasibility of steam power for rail transportation.
Trevithick's 1804 locomotive was engineered to operate using low-pressure steam, aiming for enhanced efficiency.
Answer: False
Trevithick's locomotive was a pioneering example of a high-pressure steam engine, a design choice that allowed for a more compact and powerful engine compared to the low-pressure atmospheric engines prevalent at the time.
George Stephenson constructed the 'Rocket' locomotive specifically for service on the Stockton and Darlington Railway, commencing operations in 1825.
Answer: False
George Stephenson constructed the 'Locomotion No. 1' in 1825 for the Stockton and Darlington Railway, recognized as the world's inaugural public steam railway. Subsequently, he designed 'The Rocket' in 1829, which achieved victory in the Rainhill Trials.
James Watt is credited with the introduction of centrifugal governors as a mechanism for regulating steam engine speed.
Answer: True
James Watt incorporated the centrifugal governor into his improved steam engine designs to automatically control the engine's speed by adjusting the steam supply.
Which device, described by Hero of Alexandria, demonstrated the principle of steam power in the first century AD?
Answer: The Aeolipile
The aeolipile, documented by Hero of Alexandria during the first century AD, was an early, rudimentary device that showcased the principle of steam power. It operated on jet propulsion, utilizing the reactive force of escaping steam to induce rotation in a sphere.
Who is recognized for developing the first commercially successful steam-powered device, a steam pump used in 1698?
Answer: Thomas Savery
Thomas Savery developed the first commercially successful steam-powered device, a steam pump employed in 1698 that operated by directly applying steam pressure to water. Jerónimo de Ayanz y Beaumont is also credited with an earlier patent for a steam pump in 1606.
What was the primary application of Thomas Newcomen's atmospheric engine, invented around 1712?
Answer: Pumping water out of mines
Thomas Newcomen's atmospheric engine, developed circa 1712, was predominantly employed for the critical task of pumping water from mines. Its efficacy was instrumental in facilitating deeper mining operations previously hindered by inundation.
What significant innovation did James Watt introduce between 1763 and 1775 that greatly improved engine efficiency?
Answer: The addition of a separate condenser
James Watt's pivotal innovation, developed between 1763 and 1775, was the incorporation of a separate condenser. By directing spent steam to an auxiliary vessel for condensation, his engine design achieved a dramatic increase in efficiency, enabling greater work output per unit of fuel consumed.
How did Watt's improved steam engines differ fundamentally from Newcomen's?
Answer: Watt introduced the separate condenser, improving efficiency, whereas Newcomen's relied on atmospheric pressure driving the piston after condensation.
Newcomen's engine functioned by condensing steam within the cylinder to create a vacuum, allowing ambient atmospheric pressure to drive the piston. Watt's subsequent improvements, while initially retaining atmospheric principles, achieved superior efficiency primarily through the introduction of a separate condenser. Later iterations of Watt's designs further enhanced performance by more effectively utilizing the pressure of expanding steam.
Which of the following was NOT mentioned as an early experimental steam-powered device?
Answer: Newcomen's atmospheric engine
The text mentions Hero's aeolipile, Branca's steam turbine concept, and Trevithick's locomotive as early experimental or developmental devices. Newcomen's atmospheric engine, while early, is generally considered a commercially successful application rather than purely experimental in the same vein.
What innovation did Jacob Leupold describe in 1720 that was significant for steam engine design?
Answer: A two-cylinder high-pressure steam engine design.
In his 1720 publication, 'Theatri Machinarum Hydraulicarum,' Jacob Leupold detailed a design for a two-cylinder high-pressure steam engine. This configuration employed pistons driven upwards by steam pressure, with gravity assisting their return, and utilized a common rotary valve for steam control.
Which of the following was a key innovation in Richard Trevithick's 1804 locomotive?
Answer: The use of high-pressure steam.
Trevithick's locomotive integrated several significant innovations, most notably its utilization of high-pressure steam. This design decision contributed to a reduction in the engine's overall weight and an increase in its efficiency relative to the lower-pressure atmospheric engines prevalent at the time.
George Stephenson built the 'Locomotion' for which historic railway in 1825?
Answer: The Stockton and Darlington Railway
George Stephenson constructed the 'Locomotion No. 1' in 1825 for the Stockton and Darlington Railway, recognized as the world's inaugural public steam railway. Subsequently, he designed 'The Rocket' in 1829, which achieved victory in the Rainhill Trials.
During the Industrial Revolution, the advent of stationary steam engines allowed factories to be strategically located near rivers, leveraging water power.
Answer: False
Stationary steam engines liberated factories from the necessity of being located near water sources like rivers, as they provided an independent and mobile power supply. This enabled factories to be situated in more advantageous locations, contributing to industrial expansion.
Steam engines exerted a minimal influence on the transformative changes observed in 19th-century transportation systems.
Answer: False
Steam engines played a pivotal and revolutionary role in 19th-century transportation, powering locomotives on railways and steamships, fundamentally altering travel and commerce.
What was a major consequence of stationary steam engines during the Industrial Revolution?
Answer: Factories could be located away from water sources, accelerating industrialization.
During the Industrial Revolution, stationary steam engines emerged as the predominant power source for factories. Their capacity to deliver consistent and substantial mechanical energy liberated manufacturing from dependence on water sources, thereby facilitating industrial expansion and urbanization.
Which mode of transport was significantly transformed by the steam engine in the 19th century?
Answer: Railways and steamships
Steam engines revolutionized transportation by supplanting sails on maritime vessels, leading to the advent of paddle steamers and subsequently screw-propelled steamships. Concurrently, they powered locomotives, which enabled the establishment of extensive railway networks, profoundly transforming both land travel and the logistics of freight transport.
A steam engine indicator is an instrument designed to trace a diagram representing fuel flow patterns throughout the engine's operational cycle.
Answer: False
A steam engine indicator does not trace fuel flow; rather, it records the pressure within the cylinder throughout the piston's stroke, generating a pressure-volume diagram used to analyze engine performance and horsepower.
The primary function of valve gear in a steam engine is to generate steam pressure within the boiler.
Answer: False
Valve gear is responsible for controlling the admission and exhaust of steam to and from the engine cylinder. Steam pressure is generated within the boiler through the heating of water.
Patented in 1849, the Corliss steam engine was characterized by its notable inefficiency and imprecise speed regulation.
Answer: False
The Corliss steam engine, patented in 1849, was renowned for its significant improvements in efficiency and its precise speed regulation, largely due to its innovative four-valve system with automatic variable steam cutoff.
Compound steam engines enhance operational efficiency by facilitating the expansion of steam within a single, large-diameter cylinder.
Answer: False
Compound steam engines improve efficiency by expanding steam sequentially through multiple cylinders of progressively increasing size, rather than in a single large cylinder. This staged expansion minimizes thermal losses.
Triple-expansion steam engines are designed to operate through four distinct stages of steam expansion.
Answer: False
Triple-expansion engines, by definition, utilize three stages of steam expansion, employing progressively larger cylinders. Quadruple-expansion engines utilize four stages.
Oscillating cylinder steam engines necessitate intricate valve gear mechanisms for the precise control of steam flow.
Answer: False
A key characteristic of oscillating cylinder steam engines is their simplified design, which often eliminates the need for complex external valve gear. The cylinder itself oscillates, aligning ports to control steam admission and exhaust.
The attainment of a reliable steam-tight seal for rotors presented a significant engineering challenge for numerous rotary steam engine configurations.
Answer: True
Many early rotary steam engine designs struggled with leakage past the rotor due to difficulties in maintaining a precise and steam-tight seal, which critically impacted their efficiency and practicality.
Within a steam plant, the two fundamental operational components are identified as the steam engine itself and the condenser.
Answer: False
The two fundamental components of a steam plant are the boiler (or steam generator) and the prime mover (typically a steam engine or turbine) that converts steam energy into mechanical work. While the condenser is crucial for efficiency, the boiler is the primary steam producer.
The primary function of the boiler within a steam system is to condense exhaust steam.
Answer: False
The boiler's function is to heat water and generate high-pressure steam. Condensation of exhaust steam occurs in the condenser, a separate component.
In fire-tube boilers, water circulates through tubes that are enveloped by hot combustion gases.
Answer: False
This describes a water-tube boiler. In a fire-tube boiler, hot combustion gases pass through tubes that are immersed in water.
Condensers in stationary steam engines, particularly those in power plants, frequently utilize cooling towers or ambient water sources such as rivers.
Answer: True
Condensers require a cold sink to reject waste heat, and power plants commonly employ cooling towers or direct water intake from rivers, lakes, or oceans for this purpose.
A steam injector operates by utilizing a jet of water to propel steam into the boiler.
Answer: False
An injector uses a jet of steam to force water into the boiler, overcoming boiler pressure. It is a method for boiler feedwater supply.
Safety valves constitute the sole mechanism employed to mitigate over-pressurization within steam boilers.
Answer: False
While safety valves are critical, steam boilers typically incorporate multiple safety mechanisms, including pressure gauges and often fusible plugs, to prevent dangerous over-pressurization.
A fusible plug is designed to melt and release steam if the boiler water level rises excessively high.
Answer: False
A fusible plug is a safety device that melts when the water level drops too low, exposing the plug to high temperatures. This melting releases steam, serving as a warning and potentially helping to extinguish the fire.
Stationary steam engines in power plants often use cooling towers or river water for their condensers.
Answer: True
Condensers require a cold sink to reject waste heat, and power plants commonly employ cooling towers or direct water intake from rivers, lakes, or oceans for this purpose.
An injector uses a jet of steam to force water into a boiler.
Answer: True
An injector utilizes a jet of steam to propel water into a boiler, thereby overcoming boiler pressure. It is a device for boiler feedwater supply.
Safety valves constitute the sole mechanism employed to mitigate over-pressurization within steam boilers.
Answer: False
While safety valves are critical, steam boilers typically incorporate multiple safety mechanisms, including pressure gauges and often fusible plugs, to prevent dangerous over-pressurization.
A fusible plug is designed to melt and release steam if the boiler water level rises excessively high.
Answer: False
A fusible plug is a safety device that melts when the water level drops too low, exposing the plug to high temperatures. This melting releases steam, serving as a warning and potentially helping to extinguish the fire.
Oscillating cylinder steam engines require complex valve gear to control steam flow.
Answer: False
A key characteristic of oscillating cylinder steam engines is their simplified design, which often eliminates the need for complex external valve gear. The cylinder itself oscillates, aligning ports to control steam admission and exhaust.
Achieving a steam-tight seal for rotors was a major problem for many rotary steam engine designs.
Answer: True
The principal impediment to the success of many rotary steam engine designs was the challenge of achieving and maintaining a steam-tight seal for the rotors. Leakage, exacerbated by wear and thermal expansion, critically diminished efficiency, and many designs also lacked effective mechanisms for controlling steam cutoff.
The two fundamental components of a steam plant are the engine and the condenser.
Answer: False
The two fundamental components of a steam plant are the boiler (or steam generator) and the prime mover (typically a steam engine or turbine) that converts steam energy into mechanical work. While the condenser is crucial for efficiency, the boiler is the primary steam producer.
The boiler's function is to condense exhaust steam.
Answer: False
The boiler's function is to heat water and generate high-pressure steam. Condensation of exhaust steam occurs in the condenser, a separate component.
Fire-tube boilers involve water flowing through tubes surrounded by hot gas.
Answer: False
This describes a water-tube boiler. In a fire-tube boiler, hot combustion gases pass through tubes that are immersed in water.
Stationary steam engines in power plants often use cooling towers or river water for their condensers.
Answer: True
Condensers require a cold sink to reject waste heat, and power plants commonly employ cooling towers or direct water intake from rivers, lakes, or oceans for this purpose.
An injector uses a jet of steam to force water into a boiler.
Answer: True
An injector utilizes a jet of steam to propel water into a boiler, thereby overcoming boiler pressure. It is a device for boiler feedwater supply.
Safety valves constitute the sole mechanism employed to mitigate over-pressurization within steam boilers.
Answer: False
While safety valves are critical, steam boilers typically incorporate multiple safety mechanisms, including pressure gauges and often fusible plugs, to prevent dangerous over-pressurization.
A fusible plug is designed to melt and release steam if the boiler water level rises excessively high.
Answer: False
A fusible plug is a safety device that melts when the water level drops too low, exposing the plug to high temperatures. This melting releases steam, serving as a warning and potentially helping to extinguish the fire.
Steam turbines necessitate the use of complex mechanisms, such as connecting rods, to generate rotary power.
Answer: False
A primary advantage of steam turbines is that they directly produce rotary motion without requiring connecting rods or other mechanisms to convert linear piston motion into rotation, unlike reciprocating engines.
A steam engine indicator traces a diagram of fuel flow throughout the engine cycle.
Answer: False
A steam engine indicator traces a diagram of cylinder pressure versus piston position (or volume), not fuel flow. This diagram is crucial for analyzing engine performance and calculating indicated horsepower.
The uniflow engine design improves efficiency by ensuring steam flows in only one direction through the cylinder.
Answer: True
The uniflow engine design seeks to enhance efficiency by ensuring unidirectional steam flow within the cylinder. This is accomplished by the piston itself regulating the exhaust port, which is exposed only at the terminal phase of the stroke. This design minimizes the thermal cycling of the cylinder walls that occurs in counterflow engines.
Valve gear is primarily responsible for generating steam pressure within the boiler.
Answer: False
Valve gear constitutes the mechanism responsible for regulating the steam valves, ensuring the precise timing of steam admission into and exhaust from the cylinder relative to the piston's stroke. Steam pressure is generated within the boiler.
Steam turbines offer smoother rotational output compared to reciprocating engines.
Answer: True
Steam turbines provide direct rotary power output, eliminating the need for conversion mechanisms like connecting rods and cranks. This results in smoother operation and often greater efficiency for large power outputs compared to reciprocating engines.
Fusible plugs are designed to release excess steam when the boiler water level is too high.
Answer: False
A fusible plug is a safety device that melts when the water level drops too low, exposing the plug to high temperatures. This melting releases steam, serving as a warning and potentially helping to extinguish the fire.
How does a steam engine convert linear piston motion into rotational motion?
Answer: Via a connecting rod and crank mechanism.
Mechanical work is generated when steam, produced by heating water, is introduced into a cylinder. The pressure of this steam drives a piston, producing linear motion. This linear motion is subsequently converted into rotational motion through a connecting rod and crank assembly, analogous to the mechanism in a bicycle.
The Corliss steam engine, patented in 1849, was particularly noted for which feature?
Answer: Its automatic variable steam cutoff and separate valves for admission/exhaust.
The Corliss steam engine, patented in 1849, was renowned for its significant improvements in efficiency and its precise speed regulation, largely due to its innovative four-valve system with automatic variable steam cutoff.
How did compound steam engines enhance efficiency compared to simple engines?
Answer: By expanding steam sequentially in cylinders of increasing size.
Compound steam engines enhanced efficiency through a process of staged steam expansion across successive cylinders of progressively larger diameters. This method reduced the temperature differential within each cylinder, thereby mitigating heat losses associated with condensation and re-evaporation, which are primary sources of inefficiency in simpler engine designs.
What problem did many rotary steam engine designs struggle to overcome?
Answer: Achieving and maintaining a steam-tight seal for the rotors.
The principal impediment to the success of many rotary steam engine designs was the challenge of achieving and maintaining a steam-tight seal for the rotors. Leakage, exacerbated by wear and thermal expansion, critically diminished efficiency, and many designs also lacked effective mechanisms for controlling steam cutoff.
In a steam plant, what is the role of the boiler?
Answer: To heat water and produce high-pressure steam.
The boiler functions as a pressure vessel wherein water is heated to generate steam. Its design incorporates features optimized for efficient heat transfer to the water, thereby producing the high-pressure steam essential for powering the engine.
Which safety device melts if the boiler water level drops too low?
Answer: Fusible plug
A fusible plug is a critical safety device, typically situated in the crown of a boiler's firebox. Should the water level recede to expose the plug to excessive temperatures, the low-melting-point material (often lead) within it melts, triggering the release of steam to alert the operator to a potentially hazardous low-water condition.
What advantage did steam turbines possess over reciprocating piston engines regarding mechanical output?
Answer: They provided direct rotary power without conversion mechanisms.
Steam turbines provided several distinct advantages over reciprocating piston engines, including enhanced efficiency, particularly at higher power outputs, a simpler mechanical design with fewer moving parts, and the direct generation of rotary power without the necessity of conversion mechanisms such as connecting rods. These attributes contributed to smoother operation and reduced maintenance requirements.
What is the purpose of a governor, like the centrifugal governor used by Watt?
Answer: To automatically regulate the engine's speed by adjusting steam supply.
A governor, exemplified by the centrifugal governor employed by James Watt, serves to automatically regulate the engine's speed. It achieves this by modulating the steam supply in response to load variations, thereby maintaining a relatively constant operational velocity.
How does the 'uniflow' engine design aim to reduce efficiency losses?
Answer: By ensuring steam flows in only one direction through the cylinder.
The uniflow engine design seeks to enhance efficiency by ensuring unidirectional steam flow within the cylinder. This is accomplished by the piston itself regulating the exhaust port, which is exposed only at the terminal phase of the stroke. This design minimizes the thermal cycling of the cylinder walls that occurs in counterflow engines.
Which of the following is a fundamental component of a steam plant?
Answer: Boiler
The boiler is a fundamental component of a steam plant, responsible for generating the high-pressure steam required to drive the engine or turbine.
What is the primary challenge associated with many rotary steam engine designs mentioned in the text?
Answer: Maintaining a steam-tight seal for the rotors.
The principal challenge faced by many rotary steam engine designs was achieving and maintaining a steam-tight seal for the rotors. Leakage, exacerbated by wear and thermal expansion, critically diminished efficiency, and many designs also lacked effective mechanisms for controlling steam cutoff.
How do multiple-expansion engines like triple-expansion engines improve efficiency?
Answer: By expanding steam in three or more stages using progressively larger cylinders.
Multiple-expansion engines improve efficiency by expanding steam sequentially through a series of cylinders of progressively increasing diameter. This staged expansion allows for more complete utilization of the steam's energy and reduces thermal losses compared to single-cylinder engines.
The widespread adoption of electric motors and internal combustion engines ultimately precipitated the decline in the commercial utilization of reciprocating piston steam engines.
Answer: True
Advances in alternative power sources, such as electric motors and internal combustion engines, along with the development of more efficient steam turbines, led to the gradual obsolescence of traditional reciprocating steam engines in many commercial applications.
Electricity generation became a primary application for steam turbines in the late 19th century.
Answer: True
From the late 19th century, the predominant application for steam turbines became electricity generation. Their inherent efficiency, capacity for high operating speeds, and smooth rotational output rendered them superior to reciprocating engines for driving electrical generators.
Modern large electrical power stations with steam cycles can achieve thermal efficiencies approaching 50%.
Answer: True
Modern large-scale electrical power stations that employ sophisticated steam cycles, incorporating features such as steam reheat and economizers, can achieve thermal efficiencies in the mid-40% range. The most advanced facilities approach or slightly exceed 50% thermal efficiency.
What factors contributed to the decline of reciprocating piston steam engines in commercial applications?
Answer: Advances in electric motors, internal combustion engines, and steam turbines.
The gradual replacement of reciprocating piston steam engines in commercial use was driven by advancements in alternative technologies. The increasing efficiency and practicality of electric motors and internal combustion engines, coupled with the superior efficiency and higher operating speeds of steam turbines, particularly in power generation, led to this transition.
What was the primary application for steam turbines starting in the late 19th century?
Answer: Electricity generation
From the late 19th century, the predominant application for steam turbines became electricity generation. They constitute the principal technology responsible for producing the majority of the world's electrical power, utilizing diverse heat sources to produce the requisite steam.
What is the main sector where steam turbines are predominantly used today?
Answer: Electricity generation
In contemporary applications, steam turbines are predominantly employed in the sector of electricity generation. They constitute the principal technology responsible for producing the majority of the world's electrical power, utilizing diverse heat sources to produce the requisite steam.