HMU terms
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HMU terms
Hi guys,
I'm a newbie is this field. I loosely understand that Hydromechanical unit (HMU) is a unit in the engine that takes gas control law from the Engine Control Unit (ECU) to control the Fuel Metering Valve (FMV) inside the HMU. I need to know some terms that are used within the HMU and FMV itself.
So my questions are:
1. Is there a difference between Main Metering Valve (MMV) and Fuel Metering Valve (FMV)? Or it's just 2 different terms for the same thing?
2. What is meant by Supply Pressure (psi) and Return Pressure (psi)?
3. What is meant by Fuel Flow Demand (pph)? From what I understand, this is a constant value, fed into the ECU acting as a reference point so that the control law can be determined. Can anyone verify this? If this is incorrect, kindly elaborate.
4. What is meant by MMV Feedback (inches), MMV Demand (inches), MMV Position (inches), Actual Fuel Flow (pph) and MMV Current (mA)? In order for a control law to be determined, which of these terms play a role?
5. What is meant by FMVTMC (mA)?
6. In what way does a Servo Pressure Compensation play a role in determining the control law for a MMV?
Note that I'm assuming FMV and MMV meant the same thing. Correct me if I'm wrong.
Thanks to everyone to took the time to read this and answer them. Really appreciate it
I'm a newbie is this field. I loosely understand that Hydromechanical unit (HMU) is a unit in the engine that takes gas control law from the Engine Control Unit (ECU) to control the Fuel Metering Valve (FMV) inside the HMU. I need to know some terms that are used within the HMU and FMV itself.
So my questions are:
1. Is there a difference between Main Metering Valve (MMV) and Fuel Metering Valve (FMV)? Or it's just 2 different terms for the same thing?
2. What is meant by Supply Pressure (psi) and Return Pressure (psi)?
3. What is meant by Fuel Flow Demand (pph)? From what I understand, this is a constant value, fed into the ECU acting as a reference point so that the control law can be determined. Can anyone verify this? If this is incorrect, kindly elaborate.
4. What is meant by MMV Feedback (inches), MMV Demand (inches), MMV Position (inches), Actual Fuel Flow (pph) and MMV Current (mA)? In order for a control law to be determined, which of these terms play a role?
5. What is meant by FMVTMC (mA)?
6. In what way does a Servo Pressure Compensation play a role in determining the control law for a MMV?
Note that I'm assuming FMV and MMV meant the same thing. Correct me if I'm wrong.
Thanks to everyone to took the time to read this and answer them. Really appreciate it
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Fuel Controls
Gday Newbie
I will take a stab at a few !
1- FMV and MMV same thing.
2- the fuel pump always supplies more fuel than required, the supply pressure could be anything up to 1000psi, fuel in excess of requirements is returned to the low pressure side of the pump, return pressure is much less than supply.
3 - pass
4- pass
5- Fuel metering valve torque motor current in mA.
6-pass
I am sure sonebody more knowledgeable than me will assist you.
I will take a stab at a few !
1- FMV and MMV same thing.
2- the fuel pump always supplies more fuel than required, the supply pressure could be anything up to 1000psi, fuel in excess of requirements is returned to the low pressure side of the pump, return pressure is much less than supply.
3 - pass
4- pass
5- Fuel metering valve torque motor current in mA.
6-pass
I am sure sonebody more knowledgeable than me will assist you.
Last edited by QF22; 20th May 2014 at 11:45. Reason: Spelling
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Q3&4
Looks to me as though you're reading American notes!
PPH I think is pounds per hour (most other people used kilos per hour).
Fuel flow demand is the amount of fuel flow computed/required to achieve the desired thrust/torque.
MMV Demand (called for valve position, computed by the ECU, to give required thrust), MMV Position (actual valve position). MMV Feedback (difference between called for and actual valve position, once this feedback signal returns to zero then the engine will be in a steady state).
Can I ask what you are aiming to achieve? I can't help thinking you're digging too deep if you are studying for a B1. On the other hand if you intend designing HMUs then you're on the wrong website!
PPH I think is pounds per hour (most other people used kilos per hour).
Fuel flow demand is the amount of fuel flow computed/required to achieve the desired thrust/torque.
MMV Demand (called for valve position, computed by the ECU, to give required thrust), MMV Position (actual valve position). MMV Feedback (difference between called for and actual valve position, once this feedback signal returns to zero then the engine will be in a steady state).
Can I ask what you are aiming to achieve? I can't help thinking you're digging too deep if you are studying for a B1. On the other hand if you intend designing HMUs then you're on the wrong website!
