Limiting Factors
10-23-05, 11:14 AM
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Limiting Factors
Hello,
I have tried to search the answer for my question but did not found anything.
What ist actualy the limiting factor in turbocharging an rotary engine? The effects of to much boost in an piston engine are clear to me but what about the rotary?
I suppose one of the weak links are the apex seals right?
I have tried to search the answer for my question but did not found anything.
What ist actualy the limiting factor in turbocharging an rotary engine? The effects of to much boost in an piston engine are clear to me but what about the rotary?
I suppose one of the weak links are the apex seals right?
10-25-05, 09:58 PM
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Don't get mad if I overstate what, to you, is already obvious.
An "intercooler," classically, is a charge-air cooling device that is mounted between two separate stages of charge air compression. In a twin-sequential turbo setup, if you compress the charge air with one turbo, then cool it (intercooler) then compress it again with another turbo, then cool it, the last cooler before it hits the motor is called an aftercooler. Which is some Caterpillar diesels are labelled A.T.A.A.A.Cs: Air To Air After Cooled. So, if you ever run into the term "aftercooler" know that, really, that is what we call an "intercooler."
For most 4-stroke spark-ignited engines, it is a similar set of problems:
Detonation
Heat management
Internal component stress
For 4-stroke diesels, detonation isn't a problem, it's how they ignite and burn their fuel, so the problems are
Heat management
Internal component stress
Diesels use aftercoolers (now called intercoolers by most) to be able to cram more air into the cylinders more easily, for more power without overheating the pistons.
Spark-ignited engines use an intercooler to more easily cram more air into an engine, for more power without overheating the pistons, (or rotors) AND to avoid the fuel detonating like a diesel, which causes FAR higher pressure spiking than spark-ignited engines are designed to tolerate.
To limit temperature spikes in the motor itself and the air inside the motor, you intercool the incoming air itself. You also provide additional cooling to the combustion surfaces, such as rotors, pistons, cylinder heads, and rotor chambers to prevent softening, and to prevent hotspots that can ignite the fuel/air mixture in more places than just the spark plug.
Of course, there are also limits to how much extra stress the bearings and other parts can take just due to the extra power produced. But, detonation is usually the number one enemy. In piston engines, oil jets are used to spray up under the bottom of the piston domes (sometimes by drilling a couple holes in the base of the connecting rod, and allowing rod bearing oil to shoot up the cylinder.) Rotaries already cool the rotors with the oil in the eccentric shaft/rotor internal area.
Producing more power from the same sized engine will cause any flaws, imbalances, poor designs, inadequate or poorly routed coolant flow, inadequate strength of the actual engine and components, etc. to surface mighty fast.
For a rotary, ideally, you would be able to cool the rotor faces as well as the surfaces of the cases, and the incoming air. Bigger radiator, nice, big, efficient intercooler, and, a nice, big oil cooler. And lower compression than you would use in a non-boosted engine.
And, yes, the apex seals are vulnerable to cracking during detonation.
An "intercooler," classically, is a charge-air cooling device that is mounted between two separate stages of charge air compression. In a twin-sequential turbo setup, if you compress the charge air with one turbo, then cool it (intercooler) then compress it again with another turbo, then cool it, the last cooler before it hits the motor is called an aftercooler. Which is some Caterpillar diesels are labelled A.T.A.A.A.Cs: Air To Air After Cooled. So, if you ever run into the term "aftercooler" know that, really, that is what we call an "intercooler."
For most 4-stroke spark-ignited engines, it is a similar set of problems:
Detonation
Heat management
Internal component stress
For 4-stroke diesels, detonation isn't a problem, it's how they ignite and burn their fuel, so the problems are
Heat management
Internal component stress
Diesels use aftercoolers (now called intercoolers by most) to be able to cram more air into the cylinders more easily, for more power without overheating the pistons.
Spark-ignited engines use an intercooler to more easily cram more air into an engine, for more power without overheating the pistons, (or rotors) AND to avoid the fuel detonating like a diesel, which causes FAR higher pressure spiking than spark-ignited engines are designed to tolerate.
To limit temperature spikes in the motor itself and the air inside the motor, you intercool the incoming air itself. You also provide additional cooling to the combustion surfaces, such as rotors, pistons, cylinder heads, and rotor chambers to prevent softening, and to prevent hotspots that can ignite the fuel/air mixture in more places than just the spark plug.
Of course, there are also limits to how much extra stress the bearings and other parts can take just due to the extra power produced. But, detonation is usually the number one enemy. In piston engines, oil jets are used to spray up under the bottom of the piston domes (sometimes by drilling a couple holes in the base of the connecting rod, and allowing rod bearing oil to shoot up the cylinder.) Rotaries already cool the rotors with the oil in the eccentric shaft/rotor internal area.
Producing more power from the same sized engine will cause any flaws, imbalances, poor designs, inadequate or poorly routed coolant flow, inadequate strength of the actual engine and components, etc. to surface mighty fast.
For a rotary, ideally, you would be able to cool the rotor faces as well as the surfaces of the cases, and the incoming air. Bigger radiator, nice, big, efficient intercooler, and, a nice, big oil cooler. And lower compression than you would use in a non-boosted engine.
And, yes, the apex seals are vulnerable to cracking during detonation.
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