Wright R-3350
| Wright R-3350 Cyclone 18 | |
|---|---|
 R-3350 Cyclone 18 / Duplex Cyclone |
|
| Type: | Radial engine |
| Design country: | |
| Manufacturer: | |
| Production time: |
1941 to 1957 |
| Number of pieces: |
approx. 33,000 |
The Wright R-3350 Cyclone 18 or R-3350 Duplex Cyclone is an air-cooled aircraft engine from the American manufacturer Curtiss-Wright . The turbocharged double radial engine with 18 cylinders was developed from 1935 and manufactured until 1957.
With a displacement of 3350 cubic inches (approx. 54.9 liters; the value is also included in the type designation; the R means radial engine ), the engine has an output of between 1640 and 2800 kW (2230 or 3808 hp) depending on the version.
history
The decision to develop the engine was made in 1935 when the need for particularly powerful engines had become foreseeable. The first test model ran in May 1937, but it turned out to be very prone to failure. The work progressed relatively slowly. In 1940 the US Department of War issued a tender for a new long-range bomber. Three of the four submitted designs were equipped with the R-3350. Then the engine moved to the center of the test department. The engine's maiden flight took place in 1941 in the Douglas XB-19 .
For the large-scale production of the engines, Dodge , owned by Chrysler Motor Corporation since 1928 , built the Dodge Chicago Aircraft Engine Plant from 1942 , which began production in the spring of 1944. After the end of the war, the Tucker Corporation , among others, used the factory to produce the Tucker '48 .
The R-3350s were used in the Boeing B-29 from 1943 . However, the engine remained vulnerable at first and showed a tendency to overheat. Various efforts have been made to improve cooling at low airspeeds. When the B-29 became operational in 1944, however, the problems were not completely resolved. There were repeated engine failures and fires immediately after take-off.
Investigations showed that the air ratio of the individual cylinders was very different. Because the mixture was sometimes too lean, the internal cooling of individual cylinders was too low, which led to overheating. In particular, the lower cylinders of the rear star, which were farthest from the carburetor , tended to do this . Towards the end of 1944, Curtiss-Wright decided to replace the carburetor with direct injection .
When R-3350 production was discontinued in 1957, the production of piston engines at Curtiss-Wright also ended.
construction
The R-3350 is an air-cooled four-stroke - gasoline engine in double star arrangement with two times nine cylinders supercharged by a two-speed centrifugal compressor .
Turbo compound engine
From 1950, the R-3350 was expanded to include three exhaust gas turbines , which delivered their power to the engine shaft via fluid couplings and gear sets ( turbo-compound motor ), the additional type designation was TC . For engine charging, however, the same two-speed radial compressor, driven by the rear crankshaft stub, was retained in the TC engines of all series; So it is not a turbocharged engine in the usual sense, but a compressor engine with mechanical charging and exhaust gas turbines that generate additional shaft power.
The exhaust gas turbines are arranged radially behind the rear cylinder plane between the crankcase and the housing of the radial compressor, which increases the overall length of the engine by 11 inches (approx. 27.9 cm). Each turbine receives the exhaust gas from six cylinders. The turbines work on the principle of the impulse turbine , here only the kinetic energy of the exhaust gas flowing out of the cylinders is used and not the pressure gradient. This has the advantage that there is only very little additional back pressure in the exhaust system and that there is only little reaction to the gas exchange in the cylinders.
The turbine wheels have a diameter of 11.45 inches (approx. 29.1 cm) and consist of a steel hub with 54 blades made of Stellite-31 welded on . The turbine speed is 16,000 / min for cruising power and 19,000 / min for take-off power. A fan impeller on the turbine shaft blows cooling air through the impellers through holes in the blade roots. The gear ratio of the turbine rotors to the crankshaft is 6.52: 1. The fluid couplings supplied with pressurized oil from the engine lubrication have the task of dampening torsional vibrations, which are caused by the intermittent impact of the pulsating exhaust gas column of the individual cylinders, and keeping them away from the crankshaft; Furthermore, the clutches run empty after the engine has been switched off and thereby decouple the turbine rotors from the crankshaft during the subsequent starting process, so they do not have to be turned by the starter . The exhaust gas turbines deliver up to 370 kW (503 hp) of additional drive power to the crankshaft, but significantly increase the mechanical complexity and susceptibility of the engine.
The MTBO was 3500 hours at the beginning of the 1950s. The specific fuel consumption is around 243 g / kWh.
The turbo-compound engine, which is also used in the Lockheed Super Constellation and Douglas DC-7 , never proved to be particularly reliable and was always a reason for complaints and delays in civil aviation, which earned these machines the somewhat derisive nickname, they are the "best three-engine in the world" (alluding to the fact that one of the four engines often failed or had to be turned off during the flight and continued to fly with three engines).
use
Civil aircraft
- Lockheed Constellation
- Lockheed Super Constellation (Turbo Compound)
- Lockheed Starliner (Turbo Compound)
- Douglas DC-7 (Turbo Compound)
Military aircraft
- Boeing B-29 Superfortress
- Boeing C-97 Stratofreighter
- Canadair CL-28 Argus
- Consolidated B-32 Dominator
- Douglas A-1 Skyraider
- Douglas BTD Destroyer
- Fairchild AC-119 Shadow and Stinger
- Fairchild C-119F, -G Flying Boxcar
- Lockheed P2V / P-2 Neptune
- Martin P5M Marlin
- Martin JRM-1 and -3 Mars
Military prototypes
Tractor pulling
variants
- R-3350-13: 2232 hp / 1641 kW
- R-3350-23: 2230 HP / 1640 kW
- R-3350-24W: 2548 HP / 1900 kW
- R-3350-18DA: 3250 HP / 2389 kW
- R-3350-32W: 3808 HP / 2800 kW
- R-3350-53: 2738 hp / 2013 kW
- R-3350-85: 2548 hp / 1900 kW
- R-3350-89A: 3536 HP / 2600 kW
- R-3350-93W: 3536 HP / 2600 kW
Technical data R-3350-988TC18EA-2 (Lockheed L-1649 Starliner)
- Construction: air-cooled 18-cylinder double radial engine with three shaft power exhaust gas turbines (turbo-compound)
- Principle of operation: valve-controlled four-stroke - gasoline engine
- Charging: a single-stage two-speed - centrifugal compressor
- Fuel: AvGas 115/145
- Mixture formation : Bendix PR-58-S-2 direct fuel injection
- Injection pump: 2 × Bendix D9H3
- Ignition: Low-voltage double ignition , a Bendix-Scintilla DLN-9 magneto and two ignition distributors
- Ignition time : 25 ° before TDC (optional 30 °)
- Bore : 6 1 ⁄ 8 inches (155.6 mm)
- Stroke : 6 5 ⁄ 16 inches (160.3 mm)
- Compression : 6.7: 1
- Displacement: 54.87 liters
- Maximum take-off power: 2535 kW (3400 bhp) at 2900 rpm (2 bar boost pressure)
- Maximum continuous output: 2088 kW (2800 bhp) at 2600 rpm (1.7 bar boost pressure)
- Travel power: 1417 kW (1900 bhp) at 2400 rpm (1.37 bar boost pressure)
- Full pressure altitude : 6096 m
- Compressor ratio 1st gear: 6.46: 1
- Compressor ratio 2nd gear: 8.67: 1
- Propeller ratio: 0.355: 1
- Exhaust turbine ratio: 6.52: 1
- Length: 2274 mm
- Diameter: 1437 mm
- Dry matter: 1699 kg
- specific power: 46.20 kW / l
- Power-to-weight ratio : 0.67 kg / kW
- specific consumption: 231 g / kWh
- Quantity: 283 (June 1954 to November 1958)
See also
Individual evidence
- ^ Curtiss-Wright Co. (1956): Facts about the Wright Turbo-Compound (PDF, 3.0 MB, engl.)
- ↑ Photo gallery - Image 3 - Aviation legend. In: Spiegel Online photo gallery. October 19, 2010, accessed June 9, 2018 .
- ^ Wright Aircraft Engines Direct Injection Turbo Compound Models Operating Instructions Curtiss-Wright Corporation October 1957
- ↑ Carl Kuhn: Turbo compounds. (No longer available online.) Archived from the original on November 8, 2016 ; accessed on November 8, 2016 . Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.
- ↑ Reinhard Müller: Junkers aircraft engines . Aviatic Verlag, ISBN 3-925505-79-2 , p. 210 .
