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Questions and Answers
What is the primary function of an accumulator in a fuel injection system?
What is the primary function of an accumulator in a fuel injection system?
- To act as a fuel metering device in all system types
- To generate high pressure fuel for injection
- To dampen pressure fluctuations within the system (correct)
- To regulate fuel flow to individual cylinders
In a pump-line-nozzle (PLN) system, how is the high pressure in the fuel achieved?
In a pump-line-nozzle (PLN) system, how is the high pressure in the fuel achieved?
- By an accumulator connected to a low pressure pump
- By a series of valves located at the cylinder head
- By a plunger/barrel system within the high pressure pump (correct)
- By a single nozzle that increases the fuel pressure
What is the distinguishing feature of a hole-type nozzle compared to a pintle nozzle?
What is the distinguishing feature of a hole-type nozzle compared to a pintle nozzle?
- It regulates the timing of fuel injection
- It uses a needle to control the fuel flow
- It has a variable injection orifice controlled by a pintle
- It uses multiple orifices at an angle to achieve fuel distribution (correct)
In common rail systems, what is the key metering component of the fuel injection system?
In common rail systems, what is the key metering component of the fuel injection system?
Why are fuel injection lines kept as short as possible in PLN systems?
Why are fuel injection lines kept as short as possible in PLN systems?
How does a PLN system with multiple pumps ensure equal fuel delivery to each cylinder?
How does a PLN system with multiple pumps ensure equal fuel delivery to each cylinder?
What is the primary function of the solenoid valve in a radial-piston distributor pump?
What is the primary function of the solenoid valve in a radial-piston distributor pump?
In a PLN system, how is the plunger's vertical motion achieved?
In a PLN system, how is the plunger's vertical motion achieved?
How does the timing device in a radial-piston distributor pump affect fuel injection?
How does the timing device in a radial-piston distributor pump affect fuel injection?
What component is responsible for the final control of the fuel entering the combustion chamber?
What component is responsible for the final control of the fuel entering the combustion chamber?
Which of the following best describes a key difference between radial-piston and axial-piston pumps?
Which of the following best describes a key difference between radial-piston and axial-piston pumps?
In a unit injector system, what is the relationship between the high-pressure pump and the nozzle?
In a unit injector system, what is the relationship between the high-pressure pump and the nozzle?
What is the primary advantage of a unit pump system over a unit injector system?
What is the primary advantage of a unit pump system over a unit injector system?
How are the control and regulation signals generated for radial piston distributor pumps?
How are the control and regulation signals generated for radial piston distributor pumps?
What does the term 'infinitely variable' refer to, in the context of fuel injection in the provided content?
What does the term 'infinitely variable' refer to, in the context of fuel injection in the provided content?
Which of the following is NOT a benefit of diesel engines equipped with unit injection systems?
Which of the following is NOT a benefit of diesel engines equipped with unit injection systems?
What component is responsible for transmitting force from the eccentric shaft to the delivery plunger in a high-pressure fuel pump?
What component is responsible for transmitting force from the eccentric shaft to the delivery plunger in a high-pressure fuel pump?
During which stroke of the pump plunger is fuel drawn into the element chamber?
During which stroke of the pump plunger is fuel drawn into the element chamber?
What action causes the outlet valve in a high-pressure pump to open?
What action causes the outlet valve in a high-pressure pump to open?
In first-generation high-pressure fuel systems, where is excess fuel returned when the engine is idling?
In first-generation high-pressure fuel systems, where is excess fuel returned when the engine is idling?
What is the primary effect of compressing and then expanding fuel in a high-pressure pump?
What is the primary effect of compressing and then expanding fuel in a high-pressure pump?
What mechanism is used in more efficient high-pressure pumps to control fuel delivery?
What mechanism is used in more efficient high-pressure pumps to control fuel delivery?
What is the function of the servo control mechanism in fuel injectors?
What is the function of the servo control mechanism in fuel injectors?
What prevents fuel from escaping the element chamber after the inlet stroke?
What prevents fuel from escaping the element chamber after the inlet stroke?
What type of actuator is primarily responsible for controlling the diesel injector?
What type of actuator is primarily responsible for controlling the diesel injector?
How are common-rail diesel injectors connected to the fuel rail?
How are common-rail diesel injectors connected to the fuel rail?
What is the primary function of the copper gasket, also known as a 'washer', in the diesel injector system?
What is the primary function of the copper gasket, also known as a 'washer', in the diesel injector system?
What determines the injection time in a common-rail diesel injection system?
What determines the injection time in a common-rail diesel injection system?
In the common rail injector, what causes the nozzle to transition from a closed to an open state?
In the common rail injector, what causes the nozzle to transition from a closed to an open state?
What is the initial state of the solenoid valve in the injector when it is not activated?
What is the initial state of the solenoid valve in the injector when it is not activated?
What is the purpose of the 'pickup current' sent to the solenoid valve?
What is the purpose of the 'pickup current' sent to the solenoid valve?
What primarily determines the rate of movement of the nozzle needle?
What primarily determines the rate of movement of the nozzle needle?
What is the primary function of the switching valve integrated within a fuel injector?
What is the primary function of the switching valve integrated within a fuel injector?
In a common-rail system, what determines the amount of fuel delivered at a constant pressure?
In a common-rail system, what determines the amount of fuel delivered at a constant pressure?
What is a significant advantage of separating pressure generation and fuel injection functions in modern systems?
What is a significant advantage of separating pressure generation and fuel injection functions in modern systems?
What is the purpose of the pressure-control valve in a first-generation common-rail system?
What is the purpose of the pressure-control valve in a first-generation common-rail system?
In second generation common rail systems, where is the fuel delivery controlled to maintain rail pressure?
In second generation common rail systems, where is the fuel delivery controlled to maintain rail pressure?
What is the function of the pressure-relief valve in the second-generation common-rail systems?
What is the function of the pressure-relief valve in the second-generation common-rail systems?
How does fuel-delivery control on the suction side of the pump affect the system?
How does fuel-delivery control on the suction side of the pump affect the system?
What is a benefit of multiple injection events in a common-rail system?
What is a benefit of multiple injection events in a common-rail system?
What is the primary factor that limits the air/fuel ratio at maximum engine power in a CI engine, as described in the text?
What is the primary factor that limits the air/fuel ratio at maximum engine power in a CI engine, as described in the text?
What happens to the internal thermodynamic efficiency when the air-fuel ratio, $\alpha$, is less than the stoichiometric air-fuel ratio, $\alpha_{st}$?
What happens to the internal thermodynamic efficiency when the air-fuel ratio, $\alpha$, is less than the stoichiometric air-fuel ratio, $\alpha_{st}$?
According to the information provided, how does the air-fuel cycle efficiency, $\eta_{a f}$, behave when the air-fuel ratio, $\alpha$ is below the stoichiometric air-fuel ratio, $\alpha_{st}$?
According to the information provided, how does the air-fuel cycle efficiency, $\eta_{a f}$, behave when the air-fuel ratio, $\alpha$ is below the stoichiometric air-fuel ratio, $\alpha_{st}$?
How does increasing the air-fuel ratio, $\alpha$, affect the fuel conversion efficiencies (both normal and indicated) according to the text?
How does increasing the air-fuel ratio, $\alpha$, affect the fuel conversion efficiencies (both normal and indicated) according to the text?
At what value of the air-fuel ratio, $\alpha$, does the indicated mean effective pressure (imep) reach its peak?
At what value of the air-fuel ratio, $\alpha$, does the indicated mean effective pressure (imep) reach its peak?
How does the air-fuel ratio range differ between SI and CI engines, based on their control characteristics, as mentioned in the text?
How does the air-fuel ratio range differ between SI and CI engines, based on their control characteristics, as mentioned in the text?
Why is the performance of piezoelectric injectors not considered superior enough to justify their cost compared to solenoid injectors, in general?
Why is the performance of piezoelectric injectors not considered superior enough to justify their cost compared to solenoid injectors, in general?
What primary engine condition is being considered in the analysis of efficiency distributions?
What primary engine condition is being considered in the analysis of efficiency distributions?
Flashcards
Accumulator
Accumulator
A component in fuel injection systems that absorbs pressure fluctuations, ensuring consistent fuel delivery.
Fuel injector
Fuel injector
The component in a fuel injection system that regulates the amount of fuel injected into the combustion chamber.
Fuel injection nozzle
Fuel injection nozzle
A device within the fuel injector that precisely controls the fuel flow into the combustion chamber.
Throttling pintle nozzle
Throttling pintle nozzle
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Hole-type nozzle
Hole-type nozzle
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Pump-line-nozzle (PLN) system
Pump-line-nozzle (PLN) system
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In-line PLN system
In-line PLN system
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Distributor PLN system
Distributor PLN system
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Unit Injector System
Unit Injector System
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Radial-Piston Pump
Radial-Piston Pump
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Cam Ring
Cam Ring
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Solenoid Valve
Solenoid Valve
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Unit Pump System
Unit Pump System
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High-Pressure Chamber
High-Pressure Chamber
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Unit Injection System
Unit Injection System
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Injection Pressure
Injection Pressure
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Inlet Stroke
Inlet Stroke
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Delivery Stroke
Delivery Stroke
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High-Pressure Pump Inlet Valve
High-Pressure Pump Inlet Valve
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High-Pressure Pump Outlet Valve
High-Pressure Pump Outlet Valve
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Metering Unit
Metering Unit
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Servo Control
Servo Control
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Fuel Return System
Fuel Return System
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Pressure Control Valve
Pressure Control Valve
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ECU's role in fuel injection
ECU's role in fuel injection
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Fuel quantity and injection time
Fuel quantity and injection time
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Common-rail system
Common-rail system
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Pressure control on high-pressure side
Pressure control on high-pressure side
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Pressure control on suction side
Pressure control on suction side
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Pressure relief valve function
Pressure relief valve function
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Suction side fuel-delivery control benefits
Suction side fuel-delivery control benefits
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Injector
Injector
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Common Rail
Common Rail
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Washer
Washer
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Injection Time
Injection Time
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Crankshaft Position Sensor
Crankshaft Position Sensor
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Pilot Injection
Pilot Injection
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Multiple Injection Events
Multiple Injection Events
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Internal Thermodynamic Efficiency (⌘✓i)
Internal Thermodynamic Efficiency (⌘✓i)
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Air-Fuel Cycle Efficiency (⌘a f)
Air-Fuel Cycle Efficiency (⌘a f)
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Fuel Conversion Efficiency
Fuel Conversion Efficiency
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Indicated Mean Effective Pressure (imep)
Indicated Mean Effective Pressure (imep)
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Brake Mean Effective Pressure (bmep)
Brake Mean Effective Pressure (bmep)
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Air-Fuel Ratio (↵)
Air-Fuel Ratio (↵)
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Stoichiometric Ratio (↵st)
Stoichiometric Ratio (↵st)
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Combustibility Field
Combustibility Field
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Study Notes
Fuel Injection Systems for CI Engines
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Fuel injection systems deliver fuel to cylinders at the correct time and meter the fuel based on the load.
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Proper atomization of the fuel is essential, achieved through high pressures (up to 3000 bar) and small injector holes.
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Fuel droplet size is inversely proportional to injection speed.
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Efficient mixing with air and maximizing air utilization for combustion are crucial.
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Fuel injection systems consist of a nozzle and injector.
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Pump-line-nozzle (PLN): oldest system, each cylinder has a pump feeding an injector; a single pump system is often preferred due to cost.
- The pump meters the fuel.
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Unit injector: a single unit containing both injector and pump; eliminates high-pressure lines, lowers potential for unwanted injections.
- The pump meters the fuel.
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High-pressure fuel systems have historically increased from around 10 bar to over 2000 bar.
Components in Fuel Injection Systems
- Low-pressure components deliver fuel from the tank to the high-pressure components. Fuel tanks hold fuel, below its flashpoint. Fuel supply pumps draw fuel from the tank and provide it to the high-pressure pump. Fuel coolers reduce the temperature of excess fuel to protect the tank. Filters prevent contaminants, while heaters prevent fuel freezing.
- High-pressure components generate and send fuel to the combustion chamber. A high-pressure pump powers this, with multiple types; often piston- or rotary-based, directly powered by the engine.
Pump-Line-Nozzle (PLN) Systems
- Oldest system; each cylinder has a pump connected to an injector.
- Single rotary pump (distributor) is another variant of the PLN system.
- Plunger/barrel system in each pump creates injection pressure and metering.
Nozzle and Injector
- Injectors are often nozzle holders (e.g., pump-line-nozzle systems).
- Unit injectors provide more injection functions.
- Nozzle types include throttling pintle and hole-type nozzles.
- Throttling pintle: needle opens/closes the injection orifice.
- Hole-type: multiple holes at specific angles to direct fuel. Includes a control (Servo) mechanism, allowing a complex injection procedure, which could include multiple and fast injections (e.g., pilot, main and end injections).
Distributor Pump Systems
- Feeds all cylinders' injectors in PLN system.
- Types: radial or axial.
- Axial (fig. 12.3): Rotating cam plate drives pistons to generate both rotation and lifting motions, to send fuel to numerous cylinders. Each stroke is determined by the drive shaft.
Unit Injector Systems
- Unit injectors combine injector and pump into a single unit.
- Unit pump systems are separate pump and injector components, connected by a high-pressure line.
Common Rail System
- Separates pressure generation (pump) from fuel injection components.
- Rail/accumulator acts as a pressure reserve.
- Pressure variable, adapting to load changes.
- Valuable for adjustable injection and start control.
Fuel Injection
- Injectors spray fuel directly into combustion chambers.
- ECU controls injector operation (opening/closing), defining the quantity of fuel based on pressure and opening/closing time(s).
Pressure Control
- High-pressure control is done in multiple ways.
- One method involves a pressure-control valve on the high-pressure side, allowing excess fuel to return.
- A second method controls fuel delivery on the suction side; a metering unit regulates the exact quantity of fuel for proper injection.
High-Pressure Pump
- Radial-piston pump are frequently implemented as the high-pressure pump in passenger-car systems.
- Drive shaft is coupled to engine via different mechanical links (gears, belts, chains).
- A centralized bearing houses the pump.
Injector
- Servo control system is used for injector control.
- Solenoid/piezoelectric actuators (depending on the system) control the injector's nozzle.
Multiple Injections
- Multiple injections (e.g., pilot, main, end injections) require specific timing to avoid blending of fuel injections.
Piezoelectric System
- Piezoelectric materials are used in place of solenoids to control injectors.
- Hydraulic coupler is often used for amplification.
CI Engine Performance
- CI engine efficiency depends on the air-fuel ratio.
- Excessive soot formation is an issue at higher fuel quantities.
- Brake mean effective pressure (bmep) is linked to maximum fuel conversion efficiency in CI engines.
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