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VMF513_Viper
12-25-2004, 03:29 AM
Many of us in the IL2 world know WEP or War Emergency Power is a direct result of the TuroboCharger and Supercharger. Turbochargers and Superchargers give the pilot a definate edge in speed and power to gain thr advantage over an enemy. In this Article I will explai nthe fundamentals of this basic little gadjet so that you may better understand how it works... Viper

Supercharging began during the 1920's as a way to break altitude records. Not being slow when it came to faster aircraft, the military quickly caught on. And right behind them were the engine manufacturers. Pratt & Whitney, Wright, and Allison all packed superchargers on their engines. Pilots and mechanics alike called them blowers.

Turbosupercharging (turbos for short) came along in the 1930's along with two-speed two-stage blowers. Using a variable speed supercharger and a governor to keep the speed set right, they allowed full sea-level power clear up to 30,000 feet or more. At such high altitudes engine power was usually half or a quarter of normal. With these new toys, aircraft got a whole lot faster! Blowing hot air A supercharger is a really simple mechanism. It consists of a wheel with many vanes radiating out from the center section. These vanes are straight-bladed to prevent them from cracking or breaking under high loads.

Mounted between the intake manifold and the carburetor, they supplied a pressurized mix of fuel and air to the engine. By using a pressurized fuel-air charge they delayed power loss brought on by climbing into thinner air. They were either run directly off the crankshaft (direct drive) or were geared off of it to increase blower speed. Blowers also came in five flavors. Some aircraft, like the early Wildcat, had a simple single-speed single-stage blower. It allowed full rated power up to around 12-15,000 feet, after which power fell off rather fast. A single-stage, two-speed model on the FM-2 or the P-40F allowed the pilot to "shift gears" on the blower by putting it in "high blower." Instead of spinning at five times crankshaft speed, it was now whirling at eight times crank speed. Which meant a setting of 2,500 RPM on the engine would have the blower running at 20,000 RPM.

It helped, but not nearly enough to hit the high altitudes required for long flights. After reaching 18,000 feet the engine would start to starve for air. Two-speed two-stage blowers had three different types. The Merlin engine had a two-speed two-stage blower with both blowers running on the same shaft. This had the effect of rapidly compressing the fuel-air charge, but couldn't be directly blown into the engine. At such high compression rates the fuel-air temperature was hideously high, and it needed to be cooled off.

So Rolls-Royce installed an "aftercooler" consisting of a radiator placed just in front of the intake manifold. Glycol was pumped from the aircraft radiator under the belly, up to the engine, where it hit a splitter. That splitter ran it down to the aftercooler's radiator, and then back up to the engine's hot coolant lines. From there the coolant ran back down to the radiator under the belly.

It worked; the fuel-air charge was cooled to the point it could be blown into the engine and not cause detonation. This allowed a maximum altitude of 30,000 feet to be reached with minimal power loss. To boot, it was entirely automatic in operation. Another type of two-speed two-stage model was the type the US used on the F6F, F4U, and F4F-4. It consisted of a single-speed single-stage blower running off the engine crank between the carburetor and the intake manifold.

Like the single-speed single-stage above, it constantly ran at a 5:1 ratio off the crankshaft. A second two-speed blower was piped directly into the carburetor, with an intercooler between the auxiliary blower and the carb. Takeoff was done using so-called "neutral blower" since the auxiliary blower was not running. When the pilot needed more power he shifted into "low" blower, which used a clutch to drive the auxiliary blower off the engine crank. Air went through the auxiliary blower, passed through an intercooler (air-to-air radiator), and then got dumped into the carb. The single-speed blower then compressed fuel with the pre-compressed air charge and sent it on to the engine.

If a pilot needed even more power, he hit "high" blower, which kicked the aux blower into high gear. Low blower was used between 5 and 18,000 feet, while high blower was used from 18,000 feet on up.


Only one aircraft used a variable-speed two-stage blower; the P-63 King Cobra. It had, like most other aircraft, a single-speed single-stage blower running off the crankshaft. But just in front of it was a variable-speed blower that had a real mess of gears to pick from. At 7,000 feet it cut in, and was entirely automatic in operation. As the air got thinner the blower would shift gears into a higher ratio, allowing smooth operation clear up to 25,000 feet. The P-63's airspeed vs. altitude curve resembles a backwards C because of this unit.

Infinite speed control Turbosuperchargers are a true marvel of operation. They take exhaust gas to crank a blower at infinitely variable speed, allowing full rated power beyond 35,000 feet. At such high altitudes an aircraft has a much higher ground speed, not to mention a longer range. Fighting at those altitudes requires a lot of horsepower to be generated, which the turbo does very well.

As an example, I'll use the greatest high-altitude fighter of the war: the P-47. It starts with air entering a duct under the engine that runs clear back to the tail. Air goes back to the turbo where it gets pressurized, just like in a blower, and passes through an intercooler. An intercooler is a two-chambered box where outside air and compressed air pass by each other, exchanging heat. This cools off the compressed air enough so it can be directly dumped into the engine and not cause problems. As this compressed air charge runs through the carb and towards the engine, it gets mixed with fuel. Then it's compressed again by a single-speed single-stage blower. The engine exhaust is routed past a waste-gate that controls exhaust back pressure to regulate the turbo speed. Too much pressure means the turbo is spinning too fast, and the waste-gate opens to dump more exhaust overboard.

If the turbo needs to spin faster, the waste-gate closes a bit to increase both exhaust pressure and turbo speed. As the exhaust hits the turbo it contacts a wheel with little "buckets" on it. That spins up both the exhaust wheel and the blower right above it. Both the blower and exhaust wheel sit on the same shaft, which is how a turbo regulates both manifold pressure and its own speed. When a pilot was running at cruise power and suddenly needed an extra kick, he could slam the throttle forward. This action closed the waste-gate, which in turn dramatically raised manifold pressure. As a result the pilot had a whole lot of power available at any altitude.

With such a variable speed, the turbo could give a little or a lot of additional air depending on the altitude. Controlling this beast were two things: the throttle, and the governor. The throttle opened or closed the waste-gate by a series of push-rods and a control unit. The governor worked with oil pressure; too much pressure meant the turbo was turning a tad too fast, so it would crack the waste-gate open. By lowering exhaust pressure the turbo slowed down, which reduced oil pressure. Not enough oil pressure meant the turbo had to really get moving, so the governor closed the waste-gate. That increased exhaust pressure and got the turbo spinning faster. In all it was an ingenious system of giving an engine maximum air charge to create maximum power at very high altitudes.

Viper

VMF513_Viper
12-25-2004, 03:29 AM
Many of us in the IL2 world know WEP or War Emergency Power is a direct result of the TuroboCharger and Supercharger. Turbochargers and Superchargers give the pilot a definate edge in speed and power to gain thr advantage over an enemy. In this Article I will explai nthe fundamentals of this basic little gadjet so that you may better understand how it works... Viper

Supercharging began during the 1920's as a way to break altitude records. Not being slow when it came to faster aircraft, the military quickly caught on. And right behind them were the engine manufacturers. Pratt & Whitney, Wright, and Allison all packed superchargers on their engines. Pilots and mechanics alike called them blowers.

Turbosupercharging (turbos for short) came along in the 1930's along with two-speed two-stage blowers. Using a variable speed supercharger and a governor to keep the speed set right, they allowed full sea-level power clear up to 30,000 feet or more. At such high altitudes engine power was usually half or a quarter of normal. With these new toys, aircraft got a whole lot faster! Blowing hot air A supercharger is a really simple mechanism. It consists of a wheel with many vanes radiating out from the center section. These vanes are straight-bladed to prevent them from cracking or breaking under high loads.

Mounted between the intake manifold and the carburetor, they supplied a pressurized mix of fuel and air to the engine. By using a pressurized fuel-air charge they delayed power loss brought on by climbing into thinner air. They were either run directly off the crankshaft (direct drive) or were geared off of it to increase blower speed. Blowers also came in five flavors. Some aircraft, like the early Wildcat, had a simple single-speed single-stage blower. It allowed full rated power up to around 12-15,000 feet, after which power fell off rather fast. A single-stage, two-speed model on the FM-2 or the P-40F allowed the pilot to "shift gears" on the blower by putting it in "high blower." Instead of spinning at five times crankshaft speed, it was now whirling at eight times crank speed. Which meant a setting of 2,500 RPM on the engine would have the blower running at 20,000 RPM.

It helped, but not nearly enough to hit the high altitudes required for long flights. After reaching 18,000 feet the engine would start to starve for air. Two-speed two-stage blowers had three different types. The Merlin engine had a two-speed two-stage blower with both blowers running on the same shaft. This had the effect of rapidly compressing the fuel-air charge, but couldn't be directly blown into the engine. At such high compression rates the fuel-air temperature was hideously high, and it needed to be cooled off.

So Rolls-Royce installed an "aftercooler" consisting of a radiator placed just in front of the intake manifold. Glycol was pumped from the aircraft radiator under the belly, up to the engine, where it hit a splitter. That splitter ran it down to the aftercooler's radiator, and then back up to the engine's hot coolant lines. From there the coolant ran back down to the radiator under the belly.

It worked; the fuel-air charge was cooled to the point it could be blown into the engine and not cause detonation. This allowed a maximum altitude of 30,000 feet to be reached with minimal power loss. To boot, it was entirely automatic in operation. Another type of two-speed two-stage model was the type the US used on the F6F, F4U, and F4F-4. It consisted of a single-speed single-stage blower running off the engine crank between the carburetor and the intake manifold.

Like the single-speed single-stage above, it constantly ran at a 5:1 ratio off the crankshaft. A second two-speed blower was piped directly into the carburetor, with an intercooler between the auxiliary blower and the carb. Takeoff was done using so-called "neutral blower" since the auxiliary blower was not running. When the pilot needed more power he shifted into "low" blower, which used a clutch to drive the auxiliary blower off the engine crank. Air went through the auxiliary blower, passed through an intercooler (air-to-air radiator), and then got dumped into the carb. The single-speed blower then compressed fuel with the pre-compressed air charge and sent it on to the engine.

If a pilot needed even more power, he hit "high" blower, which kicked the aux blower into high gear. Low blower was used between 5 and 18,000 feet, while high blower was used from 18,000 feet on up.


Only one aircraft used a variable-speed two-stage blower; the P-63 King Cobra. It had, like most other aircraft, a single-speed single-stage blower running off the crankshaft. But just in front of it was a variable-speed blower that had a real mess of gears to pick from. At 7,000 feet it cut in, and was entirely automatic in operation. As the air got thinner the blower would shift gears into a higher ratio, allowing smooth operation clear up to 25,000 feet. The P-63's airspeed vs. altitude curve resembles a backwards C because of this unit.

Infinite speed control Turbosuperchargers are a true marvel of operation. They take exhaust gas to crank a blower at infinitely variable speed, allowing full rated power beyond 35,000 feet. At such high altitudes an aircraft has a much higher ground speed, not to mention a longer range. Fighting at those altitudes requires a lot of horsepower to be generated, which the turbo does very well.

As an example, I'll use the greatest high-altitude fighter of the war: the P-47. It starts with air entering a duct under the engine that runs clear back to the tail. Air goes back to the turbo where it gets pressurized, just like in a blower, and passes through an intercooler. An intercooler is a two-chambered box where outside air and compressed air pass by each other, exchanging heat. This cools off the compressed air enough so it can be directly dumped into the engine and not cause problems. As this compressed air charge runs through the carb and towards the engine, it gets mixed with fuel. Then it's compressed again by a single-speed single-stage blower. The engine exhaust is routed past a waste-gate that controls exhaust back pressure to regulate the turbo speed. Too much pressure means the turbo is spinning too fast, and the waste-gate opens to dump more exhaust overboard.

If the turbo needs to spin faster, the waste-gate closes a bit to increase both exhaust pressure and turbo speed. As the exhaust hits the turbo it contacts a wheel with little "buckets" on it. That spins up both the exhaust wheel and the blower right above it. Both the blower and exhaust wheel sit on the same shaft, which is how a turbo regulates both manifold pressure and its own speed. When a pilot was running at cruise power and suddenly needed an extra kick, he could slam the throttle forward. This action closed the waste-gate, which in turn dramatically raised manifold pressure. As a result the pilot had a whole lot of power available at any altitude.

With such a variable speed, the turbo could give a little or a lot of additional air depending on the altitude. Controlling this beast were two things: the throttle, and the governor. The throttle opened or closed the waste-gate by a series of push-rods and a control unit. The governor worked with oil pressure; too much pressure meant the turbo was turning a tad too fast, so it would crack the waste-gate open. By lowering exhaust pressure the turbo slowed down, which reduced oil pressure. Not enough oil pressure meant the turbo had to really get moving, so the governor closed the waste-gate. That increased exhaust pressure and got the turbo spinning faster. In all it was an ingenious system of giving an engine maximum air charge to create maximum power at very high altitudes.

Viper

Taylortony
12-25-2004, 06:48 AM
well written http://forums.ubi.com/groupee_common/emoticons/icon_smile.gif btw the seneca does not have a wastegate so you have to be careful not to overboost it

LStarosta
12-25-2004, 08:16 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Many of us in the IL2 world know WEP or War Emergency Power is a direct result of the TuroboCharger and Supercharger. <HR></BLOCKQUOTE>

LOL. I thought it had something to do with injecting water or water methanol or other such similar solutions into the cylinders?