JET ENGINE FUEL SYSTEM

Summary

This video delves into the critical role of fuel systems in aircraft engines, focusing on the CFM 56-7 engine. It outlines the five key functions of aircraft fuel systems: increasing fuel pressure, heating, adjusting, filtering, and delivery to nozzles. The script explains the intricate process from fuel intake at the engine fuel pump to combustion in the chamber, including the crucial steps of oil-fuel heat exchange and filtration. It also touches on the HMU's role in fuel regulation and the importance of precise fuel planning for engine efficiency and safety.

Takeaways

• 🚀 The fuel systems in aircraft engines are crucial for ensuring safe and efficient operation, especially with fossil fuels which are easily ignited.
• 💧 Aircraft fuel systems serve five main purposes: increasing fuel pressure, heating, adjusting, filtering, and delivering fuel to the nozzles.
• 🛠️ The engine fuel pump is the first component in the CFM 56 engine's fuel system, responsible for pressurizing fuel and supplying it to the HMU and fuel nozzles.
• 🔥 The HMU (Hydromechanical Unit) adjusts fuel to the combustion chamber and servo fuel system based on inputs from the EEC and throttle.
• ♻️ Oil fuel coolers in the system facilitate heat exchange between oil and fuel, ensuring ideal combustion temperatures and preventing ice formation in fuel.
• 🚫 The high-pressure shut off valve in the HMU stops fuel flow to the combustion chamber when the throttle lever is turned off or in emergency situations.
• 📏 The fuel flow transmitter measures the amount of fuel passing through it, providing data for engine management and informing pilots about fuel usage.
• 🔍 The fuel nozzle filter cleans the fuel by filtering out organic and metal particles, ensuring a cleaner supply to the mechanical systems.
• 🔄 The fuel system includes a bypass mechanism that allows fuel to bypass filters if they become clogged, preventing system malfunctions.
• ✈️ Understanding the complex fuel systems in aircraft engines is vital for pilots and technicians to operate, maintain, and troubleshoot engines effectively.

Q & A

What is the primary function of aircraft fuel systems?

The primary function of aircraft fuel systems is to ensure that the appropriate amount of fuel is delivered to the combustion chamber in a safe and efficient manner.

Why is fuel considered more dangerous than other fluids in engines?

Fuel is considered more dangerous due to its easily ignitable nature, which poses a higher risk compared to other fluids used in engines.

What are the five general purposes of engine fuel systems in aircraft?

The five general purposes are increasing the pressure of the fuel, heating, adjusting, filtering, and sending it to the fuel nozzles.

How does adjusting fuel in aircrafts relate to pressing the accelerator pedal in cars?

Adjusting fuel in aircrafts works similarly to pressing the accelerator pedal in cars, as it controls the amount of fuel sent to the engine to manage acceleration.

What is the role of the engine fuel pump in the CFM 56-7 engine fuel system?

The engine fuel pump in the CFM 56-7 engine fuel system is responsible for supplying pressurized fuel to the HMU and the fuel nozzles, and its filters clean the fuel going to the HMU.

What is the purpose of oil fuel coolers in the fuel system?

Oil fuel coolers serve to heat the fuel to reach the ideal combustion temperature and to melt any frozen water particles in the fuel, ensuring efficient combustion and preventing system malfunctions.

What does the HMU (Hydromechanical Unit) do in the fuel system?

The HMU sends fuel adjusted to the combustion chamber and servo fuel system according to reference information from the EEC and throttle, and it also stops fuel flow to the combustion chamber when the fire extinguisher handle is activated.

What is the function of the fuel flow transmitter in the fuel system?

The fuel flow transmitter measures the amount of fuel passing through it and sends this information to the EEC, which helps in fuel planning and informs the pilot about fuel usage.

How do fuel nozzles contribute to efficient combustion?

Fuel nozzles ensure proper and efficient combustion by atomizing the adjusted fuel coming through the manifolds into the combustion chamber.

What happens to the fuel that the HMU does not use?

The fuel that the HMU does not use returns to the IDG oil cooler outlet, then through the oil/fuel heat exchanger back to the fuel pump.

How does the hydromechanical unit manage fuel for the engine servo system?

The hydromechanical unit provides fuel flow control to various units such as the fuel metering valve, transient bleed valve, and active clearance control valves for both high and low-pressure turbines, as well as variable bleed valves and variable stator vanes.

Outlines

00:00

🚀 Overview of Aircraft Fuel Systems

This paragraph introduces the critical role of fuel systems in the operation of various engines, particularly those using fossil fuels. It emphasizes the inherent danger of fuel due to its flammability and the systems' primary task of delivering the correct amount of fuel to the combustion chamber safely. The paragraph outlines the five main purposes of aircraft fuel systems: increasing fuel pressure, heating, adjusting, filtering, and delivering fuel to the nozzles. It also touches on the similarities between aircraft fuel systems and car accelerators, highlighting the complexity and precision required for aircraft systems due to atmospheric conditions. The CFM 56-7 engine fuel system is introduced as a case study for further exploration.

05:02

🔧 Detailed Operation of CFM 56 Engine Fuel System

This paragraph delves into the intricacies of the CFM 56 engine fuel system, starting with the engine fuel pump that receives fuel from the aircraft's main and wing tanks. It describes the pump's function to pressurize fuel and its components, including low and high-pressure elements and filters. The paragraph explains the role of oil fuel coolers in heat exchange between oil and fuel to achieve optimal combustion temperatures and to prevent ice formation in fuel. It also discusses the function of filters to remove impurities and the operation of the hydromechanical unit (HMU) in adjusting fuel flow based on signals from the engine electronic control (EEC) and throttle. The paragraph further explains the process of fuel passing through the system, including its heating, filtering, and eventual delivery to the combustion chamber via fuel nozzles, which atomize the fuel for efficient combustion.

10:04

📢 Conclusion and Call to Action

The final paragraph serves as a conclusion, summarizing the discussion on the CFM 56 engine fuel system and its components. It acknowledges the complexity of various fuel systems in aviation and the importance of understanding them for pilots and technicians. The paragraph concludes with a call to action, encouraging viewers to subscribe to the channel and like the video for more informative content. It also expresses hope that the information provided has been helpful in understanding the subject matter.

Keywords

💡Internal Combustion Engines

Internal combustion engines are a type of engine where the combustion of fuel occurs within the engine's cylinders, converting fuel into mechanical energy. This is a fundamental concept in the video as it sets the stage for discussing various engine types and their fuel systems. The script mentions that these engines, along with gas turbine and rocket engines, require complex fuel systems for safe and efficient operation.

💡Fuel Systems

Fuel systems are integral to the operation of engines, especially in aircraft. They are designed to deliver the right amount of fuel to the combustion chamber safely and efficiently. In the context of the video, the fuel system is crucial for the performance and safety of the aircraft, with the script detailing how it ensures the appropriate amount of fuel is delivered under various atmospheric conditions.

💡Combustion Chamber

The combustion chamber is where the fuel is ignited and burned to produce energy in an engine. The video emphasizes the importance of the fuel system in delivering fuel to the combustion chamber, highlighting the precision required for efficient and safe engine operation. The script describes how the fuel system must adjust to ensure proper fuel delivery to the combustion chamber.

💡Hydromechanical Unit (HMU)

The Hydromechanical Unit (HMU) is a critical component in the fuel system of aircraft engines, responsible for controlling fuel flow and pressure. The script explains that the HMU receives reference information from the Engine Electronic Control (EEC) and throttle to adjust the fuel sent to the combustion chamber and servo fuel system, illustrating its role in the complex operation of aircraft engines.

💡Fuel Nozzles

Fuel nozzles are the final component in the fuel system that sprays atomized fuel into the combustion chamber for efficient burning. The video script describes how fuel nozzles ensure proper and efficient combustion by atomizing the fuel, which is essential for the engine's performance and economy.

💡Fuel Pump

The fuel pump is the first unit in the engine's fuel system that receives fuel from the aircraft's fuel tanks. It pressurizes the fuel and sends it to various components, including the HMU and fuel nozzles. The script mentions that the fuel pump is attached to the rear of the Gear Box and works with mechanical power, highlighting its importance in the initial stage of the fuel delivery process.

💡Oil Fuel Coolers

Oil fuel coolers are units where heat exchange occurs between the oil and fuel systems without direct contact. The video script explains that these coolers are used to heat the fuel to the ideal combustion temperature and to melt any ice particles in the fuel, ensuring efficient combustion and preventing system malfunctions. They also cool the oil, preserving its properties and reducing consumption.

💡Throttle Lever

The throttle lever is the control used by pilots to manage the engine's fuel system. While the script mentions that the pilot controls the engine fuel system through the throttle lever, it also emphasizes that behind this simple control is a complex system of mechanisms and components that work together to regulate fuel flow.

💡Fuel Flow Transmitter

The fuel flow transmitter is a device that measures the amount of fuel passing through it. As described in the script, it sends electrical signals to the Engine Electronic Control (EEC) about the fuel consumption, which is vital for monitoring and managing the engine's performance.

💡Servo Systems

Servo systems in aircraft engines are mechanisms that use fuel pressure to operate various engine components. The script explains that the HMU provides fuel flow control to the servo system, which is separate from the engine's combustion systems. These systems are crucial for the precise operation of engine components such as valves.

💡EEC (Engine Electronic Control)

The Engine Electronic Control (EEC) is a system that controls various aspects of the engine's operation, including the fuel system. The video script mentions that the HMU receives signals from the EEC to adjust the fuel flow, indicating the EEC's role in the automated and precise control of the engine's performance.

Highlights

Fuel systems are crucial for the operation of engines, especially internal combustion, gas turbine, and rocket engines.

Fuel systems ensure the appropriate amount of fuel is delivered to the combustion chamber safely.

Aircraft engine fuel systems have five purposes: increasing pressure, heating, adjusting, filtering, and sending fuel to nozzles.

Adjusting fuel in aircrafts is analogous to pressing the accelerator pedal in cars.

Aircraft fuel systems require precise and controlled operation due to extraordinary atmospheric conditions.

The CFM 56-7 engine fuel system is widely used in the world of aircraft engine fuel systems.

The engine fuel pump is the first unit where fuel from the aircraft fuel system enters the engine.

The fuel pump supplies pressurized fuel to the HMU and fuel nozzles.

Oil fuel coolers are common units of the oil and fuel systems, facilitating heat exchange between oil and fuel.

The HMU sends fuel adjusted to the combustion chamber and servo fuel system based on reference information from the EEC and throttle.

The fuel flow transmitter measures the amount of fuel passing through it.

Fuel nozzles atomize the adjusted fuel for proper and efficient combustion.

The fuel system takes fuel from the aircraft fuel system and pressurizes it through the low-pressure pump element.

Oil fuel coolers melt frozen water particles in cold fuel coming from aircraft fuel tanks at high altitudes.

The fuel filter purifies the fuel from organic and metal particles before it reaches the mechanical systems.

The HMU provides fuel flow control to various engine components, including the fuel metering valve and active clearance control valves.

The fuel flow transmitter sends electrical signals to the EEC for correct fuel planning and informs the pilot about fuel usage.

Understanding complex aircraft engine fuel systems is beneficial for pilots and technicians in engine operation and troubleshooting.

Transcripts

Today, many systems are used for the operation of  engines, especially internal combustion engines,  

gas turbine engines and rocket engines. In fact,  these systems come together to help engines run  

safely and efficiently. The system we will examine  in this video is the fuel systems required for  

the operation of all engines using fossil fuels.  The fact that the fuel is easily ignited by its  

nature makes it much more dangerous than other  fluids used in the engine. For this reason, the  

most important and basic task of the fuel systems  used in aircraft is to ensure that the appropriate  

amount of fuel is delivered to the combustion  chamber in a safe and appropriate amount. 

Engine fuel systems in all aircraft generally have  five purposes. These are increasing the pressure  

of the fuel taken from the aircraft fuel system,  heating, adjusting, filtering and sending it to  

the fuel nozzles. Adjusting the fuel in aircrafts  actually works in a similar way to pressing the  

accelerator pedal in our cars. As it is known, to  the extent that we press the gas pedal in our car,  

fuel is sent to the engine combustion system  and our car accelerates. In aircrafts,  

although the pilot manages the engine fuel system  by controlling a throttle lever, much more complex  

and complicated systems are used to fulfill this  task. The extraordinary atmospheric conditions  

that aircraft encounter in the air require  much more precise and controlled operation of  

aircraft fuel systems compared to automobiles.  It even necessitates the production of fluids  

such as oil and fuel used in engines under special  conditions. Today, I will try to explain the CFM  

56-7 engine fuel system, which is widely used  in the world of aircraft engine fuel systems. 

In the fuel system of a typical CFM 56 engine,  the first unit in which the fuel from the  

aircraft fuel system enters the engine is the  engine fuel pump. The fuel pump is attached  

to the rear of the Gear Box and works with  the mechanical power it receives from it.  

There are two pressure elements and two filters  in the fuel pump as low and high pressure.  

The main task of the fuel pump is to supply  pressurized fuel to the HMU, that is, to the servo  

and measurement sections of the Hydromechanical  unit, as well as to the fuel nozzles. At the  

same time, the fuel filters on the pump undertake  the task of cleaning the fuel going to the HMU.  

The oil fuel coolers in the fuel system are  the common units of the oil and fuel systems.  

As a mechanical unit, the HMU send fuel adjusted  to the combustion chamber and servo fuel system  

according to the reference information  it receives from the EEC and throttle.  

In addition, when the throttle lever is turned off  and the fire extinguisher handle is activated, the  

fuel going to the combustion chamber is stopped  by the High pressure shut off valve in the HMU.  

Fuel flow transmitter, on the other hand, is a  unit that measures the amount of fuel passing  

through it. The task of the fuel nozzle filter,  which is another unit of the system, is to clean  

the fuel by filtering it, as in other filters. The  last part of our fuel system is the fuel nozzles.  

Fuel nozzles are responsible for ensuring  proper and efficient combustion by atomizing  

the adjusted fuel coming through the  manifolds into the combustion chamber.

After briefly recognizing the parts of the  fuel system, let's take a closer look at the  

operation of the system from the table. The  fuel coming from the aircraft fuel system,  

that is, the main and wing tanks, is taken to  the engine fuel system by the engine fuel pump.  

The fuel taken into the pump is first pressurized  by the centrifugal flow low pressure pump element.  

The pressurized fuel then goes to the IDG  integrated drive generator oil cooler, then  

to the main oil fuel heat exchanger unit. The oil  and fuel circulating in these two units exchange  

heat without physical contact with each other.  According to the laws of thermodynamics, hot oil  

transfers its heat to the fuel, that is, it cools.  What is systematically desired here is to reach  

the ideal combustion temperature of the fuel,  which is quite cold, that is, to ensure easy and  

efficient combustion. Another task of the oil fuel  cooler is to melt the frozen water particles in  

the cold fuel coming from the aircraft fuel tanks  at high altitudes. In fact, the fuel contains  

an acceptable amount of water and this situation  does not have a negative effect on combustion, but  

since the ice particles are solid, they can clog  the filters and cause malfunctions in the system.  

For these reasons, it is necessary to melt the  possible ice particles in the fuel by heating it.  

The purpose of cooling the oil is to preserve  the amount and properties of the oil.  

The oil circulating in the engine oil system  and aircraft generator gets extremely hot due  

to reasons such as circulating in areas close to  the hot areas of the engine and being used to cool  

the bearing parts that rub against each other.  If the heated oil is not cooled, it evaporates  

and is thrown into the atmosphere from the oil  tanks, and therefore oil consumption increases.  

In addition, the oil begins to lose its effective  lubricating properties due to overheating.  

In order to prevent these negative  situations, aeronautical engineers have  

succeeded in eliminating these problems with  the heat transfer between these two fluids.  

The fuel, which continues on its way in the system  passing through the oil fuel coolers, comes to the  

filters in order to be purified from the foreign  substances in it. Filters filter the organic and  

metal particles that come with the fuel, allowing  a cleaner fuel to go to the mechanical systems.  

If, for any reason, the fuel filter starts to  get dirty, a warning light may come on in the  

cockpit on some aircraft models. When the filter  is completely dirty, a bypass valve in the fuel  

filter body opens and sends the fuel to the high  pressure pump element without being filtered.  

The fuel pressure, which is further increased  in the gear type high pressure pump, is sent to  

the hydromechanical unit. The Servo washer filter  inside the fuel pump cleans the fuel going to the  

HMU servo section. In case the filter is clogged,  a by-pass valve at the filter outlet opens,  

allowing the fuel to go to the servo system  without being filtered. The servo fuel heater  

heats the fuel going to the servo system from  than hydromechanical unit (HMU). Servo fuel  

heater provides the cooling of the oil returning  to the tank by finishing the drain oil, that is,  

the lubrication task throughout the engine. The  other part of the fuel coming out of the high  

pressure pump is firstly sent to the fuel metering  valve by the Hydromechanical unit and then to the  

fuel flow transmitter after being adjusted at  the required rate. Then, the fuel is filtered  

again in the fuel nozzle filter and sent into the  combustion chamber, that is, to the fuel nozzles.  

The hydromechanical unit also provides fuel  for the operation of the engine servo system.  

Servo systems have no direct relationship  with the combustion systems of the engine.  

When it comes to the servo units of the engine,  the valves that open and close with the fuel  

pressure in various parts of the engine should  come to mind. The hydromechanical unit performs  

many tasks by receiving fuel measurement signals  from EEC and aircraft with throttle movements.  

The fuel pump always supplies the  HMU with more fuel than it can use.  

The fuel that the HMU does not use (bypass  fuel) returns to the integrated drive generator  

(IDG) oil cooler outlet and then through the  oil/fuel heat exchanger back to the fuel pump.  

The fuel flow transmitter provides the  correct fuel planning by sending the  

amount of fuel consumed in the system  to the EEC with electrical signals.  

In addition, this information informs the pilot  about the use of engine fuel in the cockpit.  

Then the fuel goes through the fuel nozzle filter  to the fuel nozzles. Fuel is transported to the  

fuel nozzles by steel fuel manifolds.  Fuel nozzles, on the other hand, provide  

efficient continuation of combustion by providing  atomized fuel to the engine combustion chamber. 

Also hydromechanical unit provides fuel flow  control to units such as Fuel metering valve,  

Transient bleed valve, High pressure turbine  active clearance control valve, Low pressure  

turbine active clearance control valve,  Variable bleed valves, Variable stator vanes.

Yes, guys, I just tried to explain the  operation of the fuel systems of the CFM  

56 engine by simplifying it. Many different types  of fuel systems and systems containing different  

parts are used in the field of aviation. It  is clear that understanding these complex  

systems will provide great convenience to  both pilots and technicians in terms of  

understanding how the engine works, as well  as finding and fixing possible malfunctions.  

Aircraft engine fuel system parts are  generally similar and perform the same tasks.  

I hope you can understand the subject in the  light of the information I have given. If you  

like my video, don't forget to subscribe to my  channel and click like. See you in new videos.