|
Figure 1 Rolls Royce DART turboprop
|
Rolls Royce Dart is a pioneering turboprop originally
designed in 1945 that is still in service today. It is simple single shaft
turboprop with a 2 stage compressor with both the centrifugal stages being the
superchargers of Eagle and Griffon piston engine. A single 2 stage turbine
drives both the compressors and the propeller. The later variants have 3 stage
turbines. The production was continued till 1987. Dart 21(1910 SHP) has a mass
flow rate of 9.7 kg/s and the much later Dart 201 (2970 SHP) has a mass flow
rate of 12.25 kg/s.
The intake to the engine is a circular one with an
annular duct leading to the eye of the first stage centrifugal compressor. Oil
tank around the intake is cast integral with the casing of the compressor. A
secondary air intake supplies air to the oil cooler mounted on top of the
centrifugal compressor casing. The centrifugal compressor is in tandem
arrangement on the same shaft. Each impeller has 19 vanes and has guide vanes
made from steel. The combustion chamber is a straight flow combustion chamber.
The tubes are arranged diagonally to increase the burning length. The flame
tube has fuel atomizers at the front end of each tube for downstream injection.
The igniter plugs are placed in number 3 and number 7 chambers of the
combustor. The turbine is an axial flow type and has three stages. All
blades are of made from Nimonic alloy and are secured on the disk by FIR tree
roots. The jet pipe is coaxial with the engine main shaft, but the exhaust unit
has a slight inclination to suit the installation on the aircraft. Maximum
temperature in the jet pipe is of the order of 650 degree Celsius. The output
from the engine is through a double reduction gearbox with helical high speed
gear train and a final helical gear drive. The two gear trains are connected by
three lay shafts to distribute the torque from the driving gear to the driven
gear. All gears and propeller shaft are carried in roller or ball bearings.
Bevel gears from one of the lay shafts provide the necessary drive for the fuel
pump, oil pump and the propeller control unit.
|
Figure 2 Rolls Royce Tyne turboprop
|
Rolls Royce Tyne Is a twin spool turbo prop
that set new high standard for the pressure ratio and fuel economy when it was
designed in 1955. The engine is very successful and was in production for 30
years with the last engines delivered in 1990s. The Tyne -22 engines powered
the Transalls C-160 aircraft in Germany until 2019. Safran aircraft engines,
under contract with the French Government, is committed to provide Tyne 21 to
the French Navy up to 2035.
The
Rolls Royce Tyne has an annular intake that is similar to the AI20 series with
seven hollow supporting struts. This annular intake surrounds the reduction
gear box housing and is cast in magnesium alloy. This casing also forms part of
the oil tank which is also annular. Anti-icing is done by hot oil circulated
through the hollow struts and by hot air tapped from the high pressure
compressor .
The low
pressure compressor has six axial stages whose rotor discs are made of steel.
The first stage rotor disk is integral to the shaft. The other 5 stages are
splined to the shaft. The rotor blades are made of “216 light alloy” and are
fixed to the rotor disk with individual steel pins. The stator blades are made
of “431 aluminium alloy” and fixed using tongues in groves. The first stage
stator blades are hollow and use HP bleed air for anti icing. First stage also
has provisions for water injection to increase power in take off rating. Both
the front and rear bearings are roller bearing type. The entire low pressure
section casing is a single piece steel unit. Bleed valves are used in the top
casing to prevent surge whenever LP and HP spool speeds are unmatched.
The
high pressure compressor has 9 axial stages made of steel discs. The first 2
stages are attached to the shaft with steel bolts. The other 7 stages are fit
using splines on the shaft. The rotor blades of the first 7 stages are made of
Titanium and the last 2 stages are made of steel. The HP stator blades are made
of “734 steel” and the casing is also a centrifugally cast steel component. The
front bearing is a roller bearing while the rear bearing is a ball bearing. The
pressure ratio and mass flow are similar to AI20, being 13.97:1 and 21.1 kg
respectively.
The
combustion chamber is a 10 flame tube can-annular type. The tube are made of
Nimonic steel and the annular casing is made from sheet steel. The flame tubes
contain double twin-flow coaxial burners. The high energy igniters are in tubes
3 and 8.
The
high pressure turbine is made of single steel disk with Nimonic blades attached
to it using FIR tree roots. The steel disk is bolted to the shaft using 10
tapered bolts. The high pressure turbine shaft is splined on to the high
pressure compressor shaft. The rotor blades are tip shrouded. The stator vanes
and rotor blades are air cooled. The casing is centrifugally cast steel. The
gas temperature is of the order of 1000 degree Celsius.
The low
pressure turbine has 3 stages. The low pressure turbine shaft is splined on to
the low pressure compressor shaft. The last rotor of the stage 3 is integral to
the shaft. All the rotor blades are made of Nimonic alloy and are attached to
the disks using FIR tree roots. The first stage LP nozzle guide vanes have
thermocouples at their leading edges. The temperature at the exit of the LP
turbine is 453 degree Celsius. The read of the low pressure turbine shaft is
supported on roller bearings and the front of the shaft rides on the high
pressure turbine shaft on a plain bearings.
The
epicyclic gear train is driven from the front end of the low pressure
compressor shaft. The planet wheel carrier of the final drive is integral to
the propeller shaft. The gear ratio is 0.064:1. Various propellers ranging from
4.42m diameter to 5.49 m diameter are used with this engine. The gear box also
incorporates a torque meter. The entire engine weighs around 995 kg (Mk 515)
and produces 5730 equivalent HP (Mk 515).
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Figure 3 Allison /
Rolls Royce 501-D13 turboprop engine
|
The Allison 501 is the commercial derivative of the original
Allison T56 turbo prop engine. This engine is a single shaft constant speed
type and is the first turboprop to go into production in the US. This engine was designed for the Lockheed
Electra L-188 aircraft matched to a Hamilton Standard propeller. The Hamilton Standard propeller has wide
chord blades with root cuffs to improve the airflow into the engine, as can be
seen in the Figure 3.
The gear box was placed below the engine so that on the aircraft, inlet to the
engine is above the propeller and is safer from foreign object ingestion.
As mentioned above, the inlet to the engine is above the propeller
and the air passes through a S duct to enter the engine. The power section of
the engine is the same as that of the T56 engine and operates at 13,820 RPM.
The compressor casing is made in 4 quadrants, permanently bolted together.
The gearbox is an inverted T56 gearbox with a drive ratio of
13.54(Spur gear reduction ratio = 3.13, planetary gear reduction ratio = 4.33).
The engine weighs approximately 832 kg and generates 3.94 SHP (D13 variant). It
also generates 3.1 kN of jet reactive thrust.
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Figure 4 Allison /
Rolls Royce T56 turboprop engine
|
The Rolls Royce Allison T56 is a very successful large single
shaft turboprop that has the longest running continuous production of any
turboprop. It is derived from the Allison T38 turboprop in 1954 and is still
used on the Northrop Grumman E2D Hawkeye aircraft and C-130 aircrafts around
the world. Rolls Royce plans to support these engines up to 2040.
The intake to the engine has a curved duct that is below the spinner
in the C-120 aircraft. The intake is a one piece magnesium alloy casting with 8
radial struts. The casting supports the rear of the propeller shaft and the
front bearing of the engine.
The compressor is a 14 stage axial compressor with dove-tailed
rotor blades made of aluminium. The blades are coated with Titanium nitride for
erosion resistance. The entire rotor assembly is tie bolted and the shaft runs
on one ball bearing and one roller bearing. The mass flow rate is around 15.2
kg/s (A-427 variant) with a pressure ratio of 9.6.
The combustion chamber is can-annular type and has 6 stainless
steel tubes. There are 2 diametrically opposite igniters for primary ignition.
The turbine is a 4 stage axial flow turbine with disks made from
“TIMKEN 16-25-6”. The blades are attached to the disks with FIR tree roots.
Turbine entry temperature is 971 degree Celsius. T-56A variant has air cooled
blades with TIT = 1077 degree Celsius. Gas generator RMPM = 13,820 RPM. The jet
pipe is a simple straight flow of circular cross section, fixed area, made of
stainless steel.
The gear box weighs 204 kg and is made of magnesium alloy. It has
a primary spur gear reduction stage followed by planetary reduction stage
giving an overall reduction ratio of 13.54. The entire gear box is braced to
the engine with 2 pin jointed struts, as shown in Figure 4.
The startup torque is provided by Bendix-Utica air turbine starter mounted on
the propeller gear box. The ignition is provided by Bendix-Scintilla high
energy ignition.
The fuel control system is hydro-mechanical type with provisions
for automatic control of start, co-ordinated fuel flow, propeller pitch and
turbine gas temperature. The engine weighs around 746 kg and generates 3730
equivalent HP (A-7 variant)
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Figure 5 Rolls Royce AE2100 turboprop engine
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The Rolls Royce AE2100 is a free turbine turboprop designed to
replace the successful T56 in regional transport, high lift and maritime patrol
aircraft. It is derived from AE3007 turbo fan engine and uses the same 2 shaft
core. This engine has high thermodynamic power (of the order of 6000 HP) but it
is de-rated to produce around 4000 HP. This enables it to deliver the rated
power at hot and high altitude airfields. It is the first engine to employ
FADEC control of both the engine and the propeller.
The compressor has 14 stages with the first 5 stages employing
variable inlet guide vanes. The mass flow rate is 16.96 kg/sec with a pressure
ration of 16.6 (AE2100A variant). The combustion chamber is an annular
combustor with 16 air-blast fuel nozzles and 2 high energy igniters. The HP
turbine is a 2 stage axial design with air-cooled vanes. The first stage has
single crystal blades and the second stage has solid blades without cooling.
The power turbine has 2 un-cooled stages with the nozzle guide vanes of the
second stage using thermocouples in the leading edges similar to the Tyne RB109
engine. The gear box is rated for a life of 30,000 hours and has an alternator
on its rear face. The accessory gearbox is under the engine, driven from the
front of the compressor with a permanent magnet alternator providing power for
the FADEC. The FADEC controls both the propeller and the engine and provides
single lever control for the pilot. The AE 2100A engine is flat rated at 4152
SHP and uses a Dowty 381 6 bladed propeller at 1100 RPM.
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Figure 6 PW127 engine
(2132 SHP ) used on the ATR72 aircraft
|
Pratt & Whitney Canada had excess design capacity
in the 1970s after the completion of PT6 series engine and JT15D series
engines. The project on developing PW100 series engines was initiated to utilise
this spare design capacity to develop a replacement engine for the Rolls-Royce
Dart engine.
PW100 series engines are three shaft free turbine
turboprop engines. They are of higher power compared to the widely used PT6
series of engines. They are targeted at regional transport aircraft such as the
ATR72 series aircraft. The propeller reduction gearbox in this series is close
to the turbine end compared to the PT6 series engine in which the gearbox is on
the compressor side.
Intake to the engine is located below the propeller
axis. This intake leads to an S bend duct. There is also a secondary duct
that forms a bypass passage that prevents the foreign object getting ingested
into the engine. The PW 100 series engines have 2 centrifugal compressors
back to back. The LP compressor is powered by the LP turbine and the HP
compressor is powered by the HP turbine. The radial outlet of the LP
compressor is directed into the HP compressor through curved pipes. The
combustion chamber is an annular reverse flow type combustor with 14 air-blast
fuel nozzles around the periphery of the engine. Ignition is provided by two
spark igniters. Both HP turbine and LP turbine are single-stage turbines while
the power turbine is a two-stage turbine with shrouded tips. Two lay shafts are
used in the gearbox to transfer the power to the driven shaft from the driving
shaft. The output propeller shaft is offset above the gearbox. Maximum
propeller speed can be up to 1200 RPM. The PW100 series engines are
controlled by hydro-mechanical fuel control units while the PW150 engines have
a full authority digital engine control system. These engines typically weigh from
390 kg (PW118) to 690 kg (PW150A) and power levels range from 1500 SHP (PW118)
to 3047 SHP (PW150A). The major performance parameters of this series of
engines in listed in Table
1.
|
Figure 7 The AI20D
engine from Ivchecnko Progress, with power = 2725 SHP
|
The AI 20 series of engines were designed to by “Ivchenko
Progress” design bureau in Ukraine headed by Dr A G Ivchenko. This series of
engines are relatively of higher power in the range of 4000 equivalent HP at
sea level conditions. They have a typical service life of 20,000
hours. They are all single shaft turboprop engines.
The inlet to the engine is of a concentric entry type
where the inner and outer cones are connected by 6 hollow radial struts. There
are inlet guide vanes downstream of these radial struts leading to the
compressor. The outer casing carries the accessories and the mountings at the
front. The inner casing carries the reduction gearbox, just in front of the
compressor. The mass flow rate of these engines are in the order of 20.4 Kg per
second. The compressor is an axial flow compressor with four bypass valves
which are used to prevent surging during the starting and the transient phases
of the operation. There are 10 stages in the compressor with the pressure ratio
of around 7.6 at take off rating and 9.2 at Cruise rating. The combustion
chamber is an annular competition chamber with 10 burner cones and 2 pilot
burners with igniter plugs for ignition. The casing of the combustion chamber
is also a load carrying member in the engine. The turbine is an axial flow
turbine with three stages and the rotor blades are shrouded at both the inner
and outer ends. They are installed in pairs using pins during assembly. The
maximum entry temperature from the combustion chamber into the turbine is 900
degree Celsius at sea level condition. The rotor speed is of the order of 12,300
RPM. The jet pipe downstream of the turbine is a fixed area type with five
radial struts to support the central cone of the nozzle and rear bearing. The
nozzle area is 2250 sq mm. The output from the engine is through a planetary
gearbox with two stages. It also incorporates a 6 cylinder torque meter
used to measure the torque load on the engine from the propeller. The engine
has two starter/generators that can either be powered from a ground power unit
or an onboard auxiliary power unit. The weight of the engine is around 1080 kg
with the AI20D variant engine delivering 2725 equivalent HP and the AI20DK
variant delivering 5180 equivalent HP.
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Figure 8 The AI24
engine from Ivchenko Progress, with power = 2550SHP
|
The AI24 turboprop engine is a conservatively
designed shaft turboprop of 2550 SHP power (AI24T variant of the AI24 engine
delivers 2820 HP at a rotor speed of 15800 RPM.). It was first used in 1960 for
the AN24 aircraft, driving a 4 blade propeller. The gas turbine rotor speed is
of the order of 15,100 RPM (13,900 RPM at ground idle). These series engines
are generally flat rated to give their nominal output up to 3500 m. TBO is of
the order of 3000 hours in 1966 and was later improved to 4000 hours in 1968.
Service life is of the order of 22000 hours for the AI24 series-2 engine.
The
construction of the AI24 engine is similar to that of the AI20 engine. It is a
single shaft turboprop with a large magnesium alloy casting which consists of
an inner and outer Core that are joined by 4 radial struts. The reduction
gearbox is also of a two-stage planetary type incorporating an integral
hydraulic torque meter and negative thrust transmitter for propeller auto
feathering. The compressor is a 10 stage axial flow compressor consisting of a
stainless steel rotor comprising of rigidly connected disks carrying dovetailed
blades. The combustion chamber is an annular combustion chamber compressing of
left and right bolted halves of spot welded heat resistant steel containing 8
simplex burners inserted into swirl vane heads. The turbine is a three-stage
axial unit with solid blades in FIR tree roots. The jet pipe is fixed area type
as there is no afterburner. The inner and outer rings are connected by three
hollow struts carrying 12 thermocouples to monitor the turbine outlet
temperature. The outer flanges are connected to the turbine stage 3 nozzle
guide vanes. AI24 has a hydro-mechanical fuel control system and it also has
provisions for auto relief upon over torque load, auto shutdown and feathering.
The weight of the engine is around 600 kg.
Table 1 Major
specifications of relevant turboprop engines
Engine Model Number
|
Equivalent power 9kW)
|
Power (kW)
|
Propeller RPM
|
Aircraft
/ Year
|
SFC
(µg/J)
|
PW118
|
1411
|
1342
|
1300
|
EMB - 120
1986
|
84.2
|
PW118A
|
1411
|
1342
|
1300
|
EMB - 120 Brasilia
1987
|
85.2
|
PW119B
|
1702
|
1626
|
1300
|
Dornier 328
1993
|
82.8
|
PW120
|
1566
|
1491
|
1200
|
ATR 42
1983
|
82
|
PW120A
|
1566
|
1491
|
1200
|
Bombardier Q100
1984
|
82
|
PW121
|
1679
|
1603
|
1200
|
Bombardier Q100 and ATR 42
1987
|
80.6
|
PW121A
|
1718
|
1640
|
1200
|
ATR 42 - 400 and
ATR 42 MP Surveyour
1995
|
80.1
|
PW123
|
1866
|
1775
|
1200
|
Bombardier Q300
1987
|
79.4
|
PW123AF
|
1866
|
1775
|
1200
|
Bombardier CL-215T and CL415
1989
|
79.4
|
PW123B
|
1958
|
1864
|
1200
|
Bombardier Q300
1991
|
78.2
|
PW123C
|
1687
|
1603
|
1200
|
Bombardier Q300
1984
|
81.6
|
PW123D
|
1687
|
1603
|
1200
|
Bombardier Q200
1994
|
81.6
|
PW123E
|
1866
|
1775
|
1200
|
Bombardier Q300 and 15 Q300-50
1995
|
79.4
|
PW124B
|
|
1611
|
1200
|
ATR 72
1988
|
79.1
|
PW125B
|
1958
|
1864
|
1200
|
Fokker 50
1987
|
78.2
|
PW126
|
2078
|
1978
|
1200
|
Jetstream ATP
1987
|
78.1
|
PW126A
|
2084
|
1985
|
1200
|
Jetstream ATP
1989
|
77.9
|
PW127
|
2147.6
|
2051
|
1200
|
Bombardier Q300 and ATR 72
1987
|
77.6
|
PW127A
|
|
1864
|
|
Antonov AN - 140
|
|
PW127AF
|
|
1775
|
|
Bombardier 415 SuperScooper
|
|
PW127B
|
2147.6
|
2051
|
1200
|
Fokker 60
1992
|
77.6
|
PW127C
|
2147.6
|
2051
|
1200
|
XAC Y7 - 200A
|
77.6
|
PW127D
|
2147.6
|
2051
|
1200
|
Jetstream 61
1993
|
|
PW127E
|
1876
|
1790
|
1200
|
ATR 42 - 500 and
ATR 72 - 500
1994
|
80.1
|
PW127F
|
2147.6
|
2051
|
1200
|
ATR 42 - 500 and
ATR 72 - 500
|
77.6
|
PW127G
|
2646.5 (military)
2580 (civil)
|
2177
|
|
Airbus Military C295 and
XAC MA60 cargo
1997
|
76.6
|
PW127H
|
|
2051
|
|
Ilyushin II - 114 - 100
1999
|
77.6
|
PW127J
|
2147.6
|
2051
|
1200
|
XAC MA60
1999
|
77.6
|
PW150A
|
4095
|
3781
|
1020
|
B - 720
1996
Bombardier Q400
2000
Antonov AN-132
2015
|
73.2
|
PW150B
|
4095
|
3781
|
1020
|
SAC (Shaanxi) Y-8F-600
|
|
AI-20K
|
2983
|
|
1075
|
II-18V, II-18E, II-20, AN-10A,
AN-12
|
100.58
|
AI-20A
|
2983
|
|
|
AN-10 , II-18A, II-18B
1961
|
|
AI-20M
|
3169
|
|
|
AN-12BK ,
II - 18/20/22/38
|
89.08
|
AI-20DK
|
3863
|
|
|
AN-8, AN-12M
|
|
AI-20DM
|
3863
|
|
|
BE-12
|
84.51
|
AI-20D Series 5
|
3863
|
|
|
AN-32B, AN-32P, AN-32V
|
84.51
|
AI-24
|
1901+30kN static thrust
|
1901
|
1245
|
AN-24A,AN-24V
|
85.0
|
RR-DART Mk 201
|
|
2215
|
|
Avro/HS/BAe 748
|
93.96
|
RR Tyne Mk 21
|
4552
|
|
|
S.C.5 Belfast heavy lift aircraft
|
81.9
|
RR 501
|
2307 + 3 kN static thrust
|
2307
|
|
Lockheed L188 Electra
|
84.67
|
Allison T56
|
2783
|
|
|
C-130H
|
|
RR AE 2100A
|
|
3096
|
1100
|
Shinmaywa US-2, C-130J, Dirgantara, Saab 2000
|
69.31
|