115-677: The Packard V-1650 Merlin is a version of the Rolls-Royce Merlin aircraft engine , produced under license in the United States by the Packard Motor Car Company . The engine was licensed to expand production of the Rolls-Royce Merlin for British use. The engine also filled a gap in the U.S. at a time when similarly powered American-made engines were not available. The first V-1650s, with
230-479: A "universal" propeller shaft, allowing either de Havilland or Rotol manufactured propellers to be used. The first major version to incorporate changes brought about through experience in operational service was the XX, which was designed to run on 100- octane fuel. This fuel allowed higher manifold pressures , which were achieved by increasing the boost from the centrifugal supercharger . The Merlin XX also utilised
345-552: A French Farman patent license. The Merlin 28 was used for the Avro Lancaster bomber. The USAAF V-1650-1 version of this engine was used in the Curtiss P-40Fs . The initial Packard modifications to this engine changed the main crankshaft bearings from a copper-lead alloy to a silver-lead combination and featured indium plating. This had been developed by General Motors' Pontiac Division to prevent corrosion, which
460-636: A Merlin 65 as the Mustang X in October 1942, the production V-1650-3 engined P-51B (Mustang III) entering service in 1943. The two-speed, two-stage supercharger section of the two-stage Merlins and V-1650-3 featured two separate impellers on the same shaft that were normally driven through a gear train at a ratio of 6.391:1. A hydraulic gear change arrangement of oil-operated clutches could be engaged by an electric solenoid to increase this ratio to 8.095:1 in high speed blower position. The high speed gear ratio of
575-940: A Merlin X with a two-speed supercharger in high gear generated 1,150 hp (860 kW) at 15,400 feet (4,700 m) and 1,160 hp (870 kW) at 16,730 feet (5,100 m). From late 1939, 100-octane fuel became available from the U.S., West Indies , Persia , and, in smaller quantities, domestically, consequently, "... in the first half of 1940 the RAF transferred all Hurricane and Spitfire squadrons to 100 octane fuel." Small modifications were made to Merlin II and III series engines, allowing an increased (emergency) boost pressure of +12 pounds per square inch (183 kPa; 1.85 atm). At this power setting these engines were able to produce 1,310 hp (980 kW) at 9,000 ft (2,700 m) while running at 3,000 revolutions per minute. Increased boost could be used indefinitely as there
690-621: A build-up of lead in the combustion chambers, causing excessive fouling of the spark plugs . Better results were achieved by adding 2.5% mono methyl aniline (M.M.A.) to 100-octane fuel. The new fuel allowed the five-minute boost rating of the Merlin 66 to be raised to +25 pounds per square inch (272 kPa; 2.7 atm). With this boost rating the Merlin 66 generated 2,000 hp (1,500 kW) at sea level and 1,860 hp (1,390 kW) at 10,500 ft (3,200 m). Starting in March 1944,
805-526: A car’s exhaust note, while a supercharged engine maintains the louder exhaust note of a normally aspirated car. Turbocharged engines are more prone to heat soak of the intake air (since turbocharging can place the hot exhaust components near the intake air system), although this can be overcome through the use of an intercooler . The majority of aircraft engines used during World War II used mechanically driven superchargers because they had some significant manufacturing advantages over turbochargers. However,
920-523: A dynamic compressor are: Common methods of driving a supercharger include: Fuels with a higher octane rating are better able to resist autoignition and detonation . As a result, the amount of boost supplied by the superchargers could be increased, resulting in an increase in engine output. The development of 100-octane aviation fuel, pioneered in the USA in the 1930s, enabled the use of higher boost pressures to be used on high-performance aviation engines and
1035-461: A higher altitude of over 19,000 ft (5,800 m); and also improved the design of both the impeller, and the diffuser which controlled the airflow to it. These modifications led to the development of the single-stage Merlin XX and 45 series. A significant advance in supercharger design was the incorporation in 1938 of a two-speed drive (designed by the French company Farman ) to the impeller of
1150-415: A limiting factor in engine performance. Extreme temperatures can cause pre-ignition or knocking , which reduces performance and can cause engine damage. The risk of pre-ignition/knocking increases with higher ambient air temperatures and higher boost levels. Turbocharged engines use energy from the exhaust gas that would normally be wasted, compared with a supercharger which mechanically draws power from
1265-573: A narrow range of load/speed/boost, for which the system must be specifically designed. Positive displacement pumps deliver a nearly fixed volume of air per revolution of the compressor (except for leakage, which typically has a reduced effect at higher engine speeds). The most common type of positive-displacement superchargers is the Roots-type supercharger . Other types include the rotary-screw , sliding vane and scroll-type superchargers. The rating system for positive-displacement superchargers
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#17327733027791380-520: A new 1,100 hp (820 kW)-class design known as the PV-12, with PV standing for Private Venture, 12-cylinder , as the company received no government funding for work on the project. The PV-12 was first run on 15 October 1933 and first flew in a Hawker Hart biplane ( serial number K3036 ) on 21 February 1935. The engine was originally designed to use the evaporative cooling system then in vogue. This proved unreliable and when ethylene glycol from
1495-476: A nominal 150-octane rating. Using such fuels, aero engines like the Rolls-Royce Merlin 66 and Daimler-Benz DB 605 DC produced power outputs of up to 2,000 hp (1,500 kW). One disadvantage of forced induction (i.e. supercharging or turbocharging) is that compressing the intake air increases its temperature. For an internal combustion engine, the temperature of the intake air becomes
1610-769: A one-stage supercharger , equivalent to the Merlin XX, were used in the P-40F Kittyhawk fighter and in Canadian-built Hawker Hurricanes . Later versions based on the Merlin 60 series included a more advanced two-stage supercharger for improved performance at high altitudes. It found its most notable application in the North American P-51 Mustang fighter, improving the aircraft's performance so it could escort Allied heavy bombers from Britain to Germany and back. At
1725-493: A problem after some months due to the physical and mental effects of wartime conditions such as the frequent occupation of air-raid shelters . It was agreed to cut the punishing working hours slightly to 82 hours a week, with one half-Sunday per month awarded as holiday. Record production is reported to have been 100 engines in one day. Immediately after the war the site repaired and overhauled Merlin and Griffon engines, and continued to manufacture spare parts. Finally, following
1840-505: A total displacement of 426 cu in (7.0 L)). However, because 6–71 is the engine's designation rather than that of the blower, the actual displacement of the blower is less; for example, a 6–71 blower pumps 339 cu in (5.6 L) per revolution. Other supercharger manufacturers have produced blowers rated up to 16–71. Dynamic compressors rely on accelerating the air to high speed and then exchanging that velocity for pressure by diffusing or slowing it down. Major types of
1955-476: A two-stage inter-cooled supercharger with a more compact layout. Nonetheless, turbochargers were useful in high-altitude bombers and some fighter aircraft due to the increased high altitude performance and range. Turbocharged piston engines are also subject to many of the same operating restrictions as those of gas turbine engines. Turbocharged engines also require frequent inspections of their turbochargers and exhaust systems to search for possible damage caused by
2070-495: Is not the case because the output of the engine depends solely on the mass of air it can be made to consume efficiently, and in this respect the supercharger plays the most important role ... the engine has to be capable of dealing with the greater mass flows with respect to cooling, freedom from detonation and capable of withstanding high gas and inertia loads ... During the course of research and development on superchargers it became apparent to us that any further increase in
2185-457: Is that a supercharger is a form of forced induction that is mechanically powered (usually by a belt from the engine's crankshaft ), as opposed to a turbocharger , which is powered by the kinetic energy of the exhaust gases. However, up until the mid-20th century, a turbocharger was called a "turbosupercharger" and was considered a type of supercharger. The first supercharged engine was built in 1878, with usage in aircraft engines beginning in
2300-430: Is that the intake air is warmer than at high altitude. Warmer air reduces the threshold at which engine knocking can occur, especially in supercharged or turbocharged engines. Methods to cool the intake air at ground level include intercoolers/aftercoolers , anti-detonant injection , two-speed superchargers and two-stage superchargers. In supercharged engines which use a carburetor , a partially-open throttle reduces
2415-417: Is too large for the engine displacement. For this reason, supercharged engines are common in applications where throttle response is a key concern, such as drag racing and tractor pulling competitions. A disadvantage of supercharging is that the engine must withstand the net power output of the engine plus the power to drive the supercharger. Additionally, turbochargers provide sound-dampening properties to
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#17327733027792530-557: Is usually based on their capacity per revolution . In the case of the Roots blower, the GMC rating pattern is typical. The GMC rating is based on how many two-stroke cylinders - and the size of those cylinders - that it is designed to scavenge , with GMC's model range including 2–71, 3–71, 4–71 and 6–71 blowers. The 6–71 blower, for example, is designed to scavenge six cylinders of 71 cu in (1.2 L) each, resulting in an engine with
2645-663: The 1925 Delage , and the 1926 Bugatti Type 35C . Amongst the most famous supercharged cars is the Bentley 4½ Litre ("Blower Bentley"), which was introduced in 1929. In 1935, the development of screw-type superchargers reached a milestone when Swedish engineer Alf Lysholm patented a design for a rotary-screw compressor with five female and four male rotors. In the 21st century, supercharged production car engines have become less common, as manufacturers have shifted to turbocharging to achieve higher fuel economy and power outputs. For example, Mercedes-Benz's Kompressor engines of
2760-677: The Air Ministry had provided a total of £1,927,000 by December 1939. Having a workforce that consisted mainly of design engineers and highly skilled men, the Derby factory carried out the majority of development work on the Merlin, with flight testing carried out at nearby RAF Hucknall . All the Merlin-engined aircraft taking part in the Battle of Britain had their engines assembled in the Derby factory. Total Merlin production at Derby
2875-457: The Air Ministry , the Ministry of Aircraft Production and local authority officials. Hives was an advocate of shadow factories , and, sensing the imminent outbreak of war, pressed ahead with plans to produce the Merlin in sufficient numbers for the rapidly expanding Royal Air Force. Despite the importance of uninterrupted production, several factories were affected by industrial action . By
2990-473: The Battle of Britain Memorial Flight , and power many restored aircraft in private ownership worldwide. In the early 1930s, Rolls-Royce started planning its future aero-engine development programme and realised there was a need for an engine larger than their 21-litre (1,296 cu in) Kestrel , which was being used with great success in a number of 1930s aircraft. Consequently, work was started on
3105-602: The Lockheed Constellation , and the C-124 Globemaster II . In the 1985 and 1986 World Rally Championships, Lancia ran the Delta S4 , which incorporated both a belt-driven supercharger and exhaust-driven turbocharger. The design used a complex series of bypass valves in the induction and exhaust systems as well as an electromagnetic clutch so that, at low engine speeds, a boost was derived from
3220-541: The Second Tactical Air Force (2TAF) also began using 100/150 grade fuel. This fuel was also offered to the USAAF where it was designated "PPF 44-1" and informally known as "Pep". Production of the Rolls-Royce Merlin was driven by the forethought and determination of Ernest Hives , who at times was enraged by the apparent complacency and lack of urgency encountered in his frequent correspondence with
3335-601: The Supermarine Spitfire and the Hawker Hurricane ; the latter designed in response to another specification, F36/34. Both were designed around the PV-12 instead of the Kestrel, and were the only contemporary British fighters to have been so developed. Production contracts for both aircraft were placed in 1936, and development of the PV-12 was given top priority as well as government funding. Following
3450-756: The Thompson Trophy . Many of these engines remain heavily used to this day in Drag Racing , Hydroplane racing , and Land Speed Racing at places like the Bonneville Salt Flats . The Mynarski Lancaster flown by the Canadian Warplane Heritage Museum in Hamilton, Ontario, Canada, one of only two Lancasters flying in the world, uses four Packard Merlin engines. Work continues on increasing the power output of
3565-528: The gas turbine and a pre-turbine section of the exhaust system. The size of the ducting alone was a serious design consideration. For example, both the F4U Corsair and the P-47 Thunderbolt used the same radial engine , but the large barrel-shaped fuselage of the turbocharged P-47 was needed because of the amount of ducting to and from the turbocharger in the rear of the aircraft. The F4U used
Packard V-1650 Merlin - Misplaced Pages Continue
3680-503: The time between overhauls (TBO) was typically 650–800 hours depending on use. By then single-stage engines had accumulated 2,615,000 engine hours in civil operation, and two-stage engines 1,169,000. In addition, an exhaust system to reduce noise levels to below those from ejector exhausts was devised for the North Star/Argonaut. This "cross-over" system took the exhaust flow from the inboard bank of cylinders up-and-over
3795-526: The 1,700 hp (1,300 kW) 42-litre (2,560 cu in) Rolls-Royce Vulture used four Kestrel-sized cylinder blocks fitted to a single crankcase and driving a common crankshaft, forming an X-24 layout. This was to be used in larger aircraft such as the Avro Manchester . Although the Peregrine appeared to be a satisfactory design, it was never allowed to mature since Rolls-Royce's priority
3910-398: The 1.6 litre Mercedes 6/25 hp and 2.6 litre Mercedes 10/40 hp , both of which began production in 1923. They were marketed as Kompressor models, a term which was used for various models until 2012. Supercharged racing cars from around this time included the 1923 Fiat 805-405 , the 1923 Miller 122 the 1924 Alfa Romeo P2 , the 1924 Grand Prix season car from Sunbeam,
4025-409: The 1910s and usage in car engines beginning in the 1920s. In piston engines used by aircraft, supercharging was often used to compensate for the lower air density at high altitudes. Supercharging is less commonly used in the 21st century, as manufacturers have shifted to turbochargers to reduce fuel consumption and increase power outputs. There are two main families of superchargers defined according to
4140-569: The Bentley marque and the factory. Today it is known as Bentley Crewe. Hives further recommended that a factory be built near Glasgow to take advantage of the abundant local work force and the supply of steel and forgings from Scottish manufacturers. In September 1939, the Air Ministry allocated £4,500,000 for a new Shadow factory. This government -funded and -operated factory was built at Hillington starting in June 1939 with workers moving into
4255-471: The German engines being significantly larger in displacement. Two-stage superchargers were also always two-speed. After the air was compressed in the low-pressure stage , the air flowed through a heat exchanger (" intercooler ") where it was cooled before being compressed again by the high-pressure stage and then possibly also aftercooled in another heat exchanger. While superchargers were highly used in
4370-421: The Merlin 130/131 versions specifically designed for the de Havilland Hornet . Ultimately, during tests conducted by Rolls-Royce at Derby , an RM.17.SM (the high altitude version of the Merlin 100-Series) achieved 2,640 hp (1,970 kW) at 36 lb boost (103"Hg) on 150-octane fuel with water injection. With the end of the war, work on improving Merlin power output was halted and the development effort
4485-462: The Merlin 60 series gained 300 hp (220 kW) at 30,000 ft (9,100 m) over the Merlin 45 series, at which altitude a Spitfire IX was nearly 70 mph (110 km/h) faster than a Spitfire V. The two-stage Merlin family was extended in 1943 with the Merlin 66, which had its supercharger geared for increased power ratings at low altitudes, and the Merlin 70 series that were designed to deliver increased power at high altitudes. While
4600-669: The Merlin 60-series. The first 60-series engine ran in March 1941, and was first flown in July the same year. When only 63 examples of the otherwise-cancelled Wellington VI were produced, these engines were instead introduced on the Spitfire IX as the Merlin 61. This model was later produced by Packard as the V-1650-3 and became known as the "high altitude" Merlin destined for the P-51, the first two-stage Merlin-Mustang conversion flying with
4715-476: The Merlin 66-powered Spitfire IXs of two Air Defence of Great Britain (ADGB) squadrons were cleared to use the new fuel for operational trials, and it was put to good use in the summer of 1944 when it enabled Spitfire L.F. Mk. IXs to intercept V-1 flying bombs coming in at low altitudes. 100/150 grade fuel was also used by Mosquito night fighters of the ADGB to intercept V-1s. In early February 1945, Spitfires of
Packard V-1650 Merlin - Misplaced Pages Continue
4830-408: The Merlin X. The later Merlin XX incorporated the two-speed drive as well as several improvements that enabled the production rate of Merlins to be increased. The low-ratio gear, which operated from takeoff to an altitude of 10,000 ft (3,000 m), drove the impeller at 21,597 rpm and developed 1,240 hp (920 kW) at that height; while the high gear's (25,148 rpm) power rating
4945-673: The Merlin for the Unlimited Class racers at the Reno Air Races . Innovations, such as the use of Allison V-1710 connecting rods and the replacement of the intercooler with ADI (Anti-Detonation Injection) (50% Distilled Water and 50% Methanol ), nearly identical in chemical composition to the Luftwaffe's wartime MW 50 system, and similar to the water injection system used on Pratt & Whitney engines during World War II, have allowed great increases in power output. Many of
5060-553: The Merlin ran only on 100-octane fuel, and the five-minute combat limitation was raised to +18 pounds per square inch (224 kPa; 2.3 atm). In late 1943 trials were run of a new "100/150" grade (150-octane) fuel, recognised by its bright-green colour and "awful smell". Initial tests were conducted using 6.5 cubic centimetres (0.23 imp fl oz ) of tetraethyllead (T.E.L.) for every one imperial gallon of 100-octane fuel (or 1.43 cc/L or 0.18 U.S. fl oz/U.S. gal), but this mixture resulted in
5175-742: The Merlin under license, with a $ 130,000,000 order being placed. The first Packard-built engine, designated V-1650-1 , ran in August 1941. The first American model was a version of the Mark XX, designated the V-1650-1 by the American military and the Packard Merlin 28 by the British. This engine used a single-stage, two-speed supercharger, the gear changing mechanism of which originally came from
5290-526: The Merlin were the Fairey Battle , Hawker Hurricane and Supermarine Spitfire . The Merlin remains most closely associated with the Spitfire and Hurricane, although the majority of the production run was for the four-engined Avro Lancaster heavy bomber. The Merlin continued to benefit from a series of rapidly-applied developments, derived from experiences in use since 1936. These markedly improved
5405-521: The Merlin's components itself. Hillingdon required "a great deal of attention from Hives" from when it was producing its first complete engine; it had the highest proportion of unskilled workers in any Rolls-Royce-managed factory”. Engines began to leave the production line in November 1940, and by June 1941 monthly output had reached 200, increasing to more than 400 per month by March 1942. In total 23,675 engines were produced. Worker absenteeism became
5520-425: The Merlin's technical improvements resulted from more efficient superchargers , designed by Stanley Hooker , and the introduction of aviation fuel with increased octane ratings . Numerous detail changes were made internally and externally to the engine to withstand increased power ratings and to incorporate advances in engineering practices. The Merlin consumed an enormous volume of air at full power (equivalent to
5635-402: The Peregrine and Vulture were both cancelled in 1943, and by mid-1943 the Merlin was supplemented in service by the larger Griffon . The Griffon incorporated several design improvements and ultimately superseded the Merlin. Initially the new engine was plagued with problems such as failure of the accessory gear trains and coolant jackets. Several different construction methods were tried before
5750-499: The Spitfire and Hurricane planes powered by the Rolls-Royce Merlin engine were equipped largely with single-stage and single-speed superchargers. In 1942, two-speed two-stage supercharging with aftercooling was applied to the Rolls Royce Merlin 61 aero engine. The improved performance allowed the aircraft they powered to maintain a crucial advantage over the German aircraft they opposed throughout World War II, despite
5865-520: The Spitfire used a variation of this exhaust system fitted with forward-facing intake ducts to distribute hot air out to the wing-mounted guns to prevent freezing and stoppages at high altitudes, replacing an earlier system that used heated air from the engine coolant radiator. The latter system had become ineffective due to improvements to the Merlin itself which allowed higher operating altitudes where air temperatures are lower . Ejector exhausts were also fitted to other Merlin-powered aircraft. Central to
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#17327733027795980-444: The U.S. became available, the engine was adapted to use a conventional liquid-cooling system. The Hart was subsequently delivered to Rolls-Royce where, as a Merlin testbed , it completed over 100 hours of flying with the Merlin C and E engines. In 1935, the Air Ministry issued a specification, F10/35 , for new fighter aircraft with a minimum airspeed of 310 mph (500 km/h ). Fortunately, two designs had been developed:
6095-436: The United States patented the design for an air mover for use in blast furnaces and other industrial applications. This air mover and Birmingham's ventilation compressor both used designs similar to that of the later Roots-type superchargers . In March of 1878, German engineer Heinrich Krigar obtained the first patent for a screw-type compressor. The design was a two-lobe rotor assembly with identically-shaped rotors, however
6210-403: The air density at 30,000 ft (9,100 m) is 1 ⁄ 3 of that at sea level, resulting in 1 ⁄ 3 as much fuel being able to be burnt in a naturally aspirated engine, therefore the power output would be greatly reduced. A supercharger/turbocharger can be thought of either as artificially increasing the density of the air by compressing it or as forcing more air than normal into
6325-430: The air/fuel mix is being compressed by a supercharger blower to 20.7 psi before entering the engine; +25 means that the air/fuel mix is now being compressed to 39.7 psi. The Americans measured their boost ratings using inches of mercury (inHg). One pound-force per square inch equals 2.036 inHg or 6.895 kPa, and a standard atmosphere is 101.325 kPa =29.92 inHg =14.70 lbf/in. In early Merlin engines
6440-477: The altitude performance of the Merlin engine necessitated the employment of a two-stage supercharger. As the Merlin evolved so too did the supercharger; the latter fitting into three broad categories: The Merlin supercharger was originally designed to allow the engine to generate maximum power at an altitude of about 16,000 ft (4,900 m). In 1938 Stanley Hooker, an Oxford graduate in applied mathematics, explained "... I soon became very familiar with
6555-478: The basic design of the Merlin was set. Early production Merlins were unreliable: common problems were cylinder head cracking, coolant leaks, and excessive wear to the camshafts and crankshaft main bearings . The prototype, developmental, and early production engine types were the: The Merlin II and III series were the first main production versions of the engine. The Merlin III was the first version to incorporate
6670-593: The benefit to the operational range was given a much higher priority to American aircraft because of a less predictable requirement on the operational range and having to travel far from their home bases. Consequently, turbochargers were mainly employed in American aircraft engines such as the Allison V-1710 and the Pratt & Whitney R-2800 , which were comparably heavier when turbocharged, and required additional ducting of expensive high-temperature metal alloys in
6785-470: The company convention of naming its piston aero engines after birds of prey, Rolls-Royce named the engine the Merlin after a small, Northern Hemisphere falcon ( Falco columbarius ). Two more Rolls-Royce engines developed just prior to the war were added to the company's range. The 885 hp (660 kW) Rolls-Royce Peregrine was an updated, supercharged development of their V-12 Kestrel design, while
6900-488: The construction of the Merlin supercharger and carburettor ... Since the supercharger was at the rear of the engine it had come in for pretty severe design treatment, and the air intake duct to the impeller looked very squashed ..." Tests conducted by Hooker showed the original intake design was inefficient, limiting the performance of the supercharger. Hooker subsequently designed a new air intake duct with improved flow characteristics, which increased maximum power at
7015-524: The coolant through an aircraft radiator system at a maximum rate of 36 U.S. gallons (136 litres, 30 Imperial gallons) per minute, depending on engine rpm. This combined system reduced the charge temperature to suitable levels. Throttle valves in the updraft carburettor throat were controlled by an automatic boost control through the throttle linkage to maintain the selected manifold pressure with changes in altitude. The valves were only partially open during ground and low-level operation to prevent overboosting of
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#17327733027797130-494: The critical take off stage of flight. The double staging of the compressed fuel/air mixture provided the boost pressure through a diffuser to the intake manifolds that increased the critical altitude of the power plant. The ability of the supercharger to maintain a sea level pressure in the induction system to the cylinders allowed the Packard Merlin to develop more than 1,270 horsepower (950 kW) above 30,000 feet (9,100 m). The two-stage impeller created extreme heating of
7245-410: The cylinder every time the piston moves down on the intake stroke. Since a supercharger is usually designed to produce a given amount of boost at high altitudes (where the air density is lower), the supercharger is often oversized for low altitude. To prevent excessive boost levels, it is important to monitor the intake manifold pressure at low altitude. As the aircraft climbs and the air density drops,
7360-503: The design did not reach production. Also in 1878, Scottish engineer Dugald Clerk designed the first supercharger which was used with an engine. This supercharger was used with a two-stroke gas engine. Gottlieb Daimler received a German patent for supercharging an internal combustion engine in 1885. Louis Renault patented a centrifugal supercharger in France in 1902. The world's first series-produced cars with superchargers were
7475-483: The design of the two-stage supercharger forged ahead, Rolls-Royce also continued to develop the single-stage supercharger, resulting in 1942 in the development of a smaller "cropped" impeller for the Merlin 45M and 55M; both of these engines developed greater power at low altitudes. In squadron service the LF.V variant of the Spitfire fitted with these engines became known as the "clipped, clapped, and cropped Spitty" to indicate
7590-780: The early 2000s (such as the C 230 Kompressor straight-four, C 32 AMG V6, and CL 55 AMG V8 engines) were replaced around 2010 by turbocharged engines in models such as the C 250 and CL 65 AMG models. However, there are exceptions, such as the Audi 3.0 TFSI supercharged V6 (introduced in 2009) and the Jaguar AJ-V8 supercharged V8 (upgraded to the Gen III version in 2009). In the 1930s, two-speed drives were developed for superchargers for aero engines providing more flexible aircraft operation. The arrangement also entailed more complexity of manufacturing and maintenance. The gears connected
7705-538: The end of its production run in 1950, 168,176 Merlin engines had been built; over 112,000 in Britain and more than 55,000 under licence in the U.S. The existing Rolls-Royce facilities at Osmaston, Derby were not suitable for mass engine production although the floor space had been increased by some 25% between 1935 and 1939; Hives planned to build the first two or three hundred engines there until engineering teething troubles had been resolved. To fund this expansion,
7820-510: The engine and first ran it in 1933 as a private venture. Initially known as the PV-12 , it was later called Merlin following the company convention of naming its four-stroke piston aero engines after birds of prey . The engine benefitted from the racing experiences of precursor engines in the 1930s. After several modifications, the first production variants of the PV-12 were completed in 1936. The first operational aircraft to enter service using
7935-472: The engine before discharging the exhaust stream on the outboard side of the UPP nacelle. As a result, sound levels were reduced by between 5 and 8 decibels . The modified exhaust also conferred an increase in horsepower over the unmodified system of 38 hp (28 kW), resulting in a 5 knot improvement in true air speed. Still-air range of the aircraft was also improved by around 4 per cent. The modified engine
8050-676: The engine's performance and durability. Starting at 1,000 horsepower (750 kW) for the first production models, most late war versions produced just under 1,800 horsepower (1,300 kW), and the very latest version as used in the de Havilland Hornet over 2,000 horsepower (1,500 kW). One of the most successful aircraft engines of the World War II era, some 50 versions of the Merlin were built by Rolls-Royce in Derby , Crewe and Glasgow , as well as by Ford of Britain at their Trafford Park factory , near Manchester . A de-rated version
8165-423: The engine. As air density decreases with increased altitude, the throttle valves were progressively opened in response to the reducing atmospheric pressure. This system provided full power within engine boost limitations up to the critical altitude of 26,000 feet (7,900 m). The British measured boost pressure as lbf/in (psi). The normal atmospheric pressure at sea level is 14.7 psi, so a reading of +6 means that
8280-412: The engine. Therefore turbocharged engines usually produce more power and better fuel economy than supercharged engines. However, turbochargers can suffer from turbo lag (especially at lower RPM), where the exhaust gas flow is initially insufficient to spin the turbocharger and achieve the desired boost level, thus leading to a delay in the throttle response . This is often a result of a turbo charge which
8395-768: The extreme heat and pressure of the turbochargers. Such damage was a prominent problem in the early models of the American Boeing B-29 Superfortress high-altitude bombers used in the Pacific Theater of Operations during 1944–45. Turbocharged piston engines continued to be used in a large number of postwar airplanes, such as the B-50 Superfortress , the KC-97 Stratofreighter , the Boeing 377 Stratocruiser ,
8510-523: The fastest Unlimited racers increase Merlin manifold pressures as high as 145 inHg (56.6 psi, 4.8 atm) to obtain up to 2,835 kW (3,800 horsepower), achieving Mustang speeds up to 490 mph. Related development Comparable engines Related lists Rolls-Royce Merlin The Rolls-Royce Merlin is a British liquid-cooled V-12 piston aero engine of 27-litre (1,650 cu in) capacity . Rolls-Royce designed
8625-428: The fuel supply line together with a diaphragm fitted in the float chamber, jocularly nicknamed " Miss Shilling's orifice ", after its inventor, went some way towards curing fuel starvation in a dive by containing fuel under negative G; however, at less than maximum power a fuel-rich mixture still resulted. Another improvement was made by moving the fuel outlet from the bottom of the S.U. carburettor to exactly halfway up
8740-401: The fuel/air mixture during the compression process, and, to prevent detonation of the compressed charge, it was necessary to cool the mixture prior to entry into the cylinders. The cooling was accomplished in an intercooler passage cast into the wheel case housing between the first and second-stage impellers and an additional cooling fin and tube core placed between the outlet of the blower and
8855-484: The great Ford factory at Manchester started production, Merlins came out like shelling peas ...". Some 17,316 people worked at the Trafford Park plant, including 7,260 women and two resident doctors and nurses. Merlin production started to run down in August 1945, and finally ceased on 23 March 1946. Total Merlin production at Trafford Park was 30,428. As the Merlin was considered to be so important to
8970-464: The impellers was not as high as the ratio used in the Allison , but impeller speed is not the only factor that determines engine performance, which is also a function of the size and pitch of the impeller blades. The gear-driven supercharger is a parasitic accessory; therefore, impeller gearing and blade profiles are carefully designed for maximum power at altitude without compromise of available power at
9085-421: The induction manifold to the cylinders. Ethylene glycol coolant was circulated by a pump through these to carry off the excess heat generated by the impellers. Without the intercooler the temperature increase in the charge could be as high as 205 °C (401 °F).. The glycol mixture used for cooling was independent of the main engine cooling system and used a centrifugal pump driven by the engine to circulate
9200-428: The level maximum speed of the Spitfire by 10 mph (16 km/h) to 360 mph (580 km/h). The first versions of the ejector exhausts featured round outlets, while subsequent versions of the system used "fishtail" style outlets, which marginally increased thrust and reduced exhaust glare for night flying. In September 1937 the Spitfire prototype, K5054 , was fitted with ejector type exhausts. Later marks of
9315-481: The maximum boost pressure at which the engine could be run using 87-octane fuel was +6 pounds per square inch (141 kPa; 1.44 atm ). However, as early as 1938, at the 16th Paris Air Show , Rolls-Royce displayed two versions of the Merlin rated to use 100-octane fuel. The Merlin R.M.2M was capable of 1,265 hp (943 kW) at 7,870 feet (2,400 m), 1,285 hp (958 kW) at 9,180 feet (2,800 m) and 1,320 hp (980 kW) on take-off; while
9430-552: The maximum manifold (boost) pressure was +12 on 100 octane fuel. This was increased in later models. In the United States many war surplus engines and airframes were sold relatively cheaply – two of the most popular items were North American P-51 Mustangs and Packard V-1650 Merlin engines, several of which were "souped up" and modified for air racing in the Bendix Trophy , the Cleveland Air Races , and
9545-666: The method of gas transfer: positive displacement and dynamic superchargers. Positive displacement superchargers deliver an almost constant level of boost pressure increase at all engine speeds, while dynamic superchargers cause the boost pressure to rise exponentially with engine speed (above a certain threshold). Another family of supercharger, albeit rarely used, is the pressure wave supercharger . Roots blowers (a positive displacement design) tend to be only 40–50% efficient at high boost levels, compared with 70-85% for dynamic superchargers. Lysholm-style blowers (a rotary-screw design) can be nearly as efficient as dynamic superchargers over
9660-444: The mid-1900s and during WWII , they have largely fallen out of use in modern piston-driven aircraft . This can largely be attributed to the higher temperature and lighter alloys that make turbochargers more efficient than superchargers, as well as the lower maintenance due to less moving parts. Due to the reduced air density at higher altitudes, supercharging and turbocharging have often been used in aircraft engines. For example,
9775-424: The number of required sub-contracted parts such as crankshafts, camshafts and cylinder liners eventually fell short and the factory was expanded to manufacture these parts "in house". Initially the local authority promised to build 1,000 new houses to accommodate the workforce by the end of 1938, but by February 1939 it had only awarded a contract for 100. Hives was incensed by this complacency and threatened to move
9890-476: The oil leaks that had been a problem with the early Merlin I, II and III series. The process of improvement continued, with later versions running on higher octane ratings, delivering more power. Fundamental design changes were also made to all key components, again increasing the engine's life and reliability. By the end of the war the "little" engine was delivering over 1,600 hp (1,200 kW) in common versions, and as much as 2,030 hp (1,510 kW) in
10005-562: The outbreak of World War Two, the British aviation industry expanded greatly. There was great need for the Rolls-Royce Merlin engine with shadow factories being established in Crewe, Manchester, and Glasgow. This was not enough to meet increasing demand with the British government looking to expand production using U.S. manufacturers. An agreement was reached between Rolls-Royce and the Packard Motor Car Company in September 1940 to manufacture
10120-598: The premises in October, one month after the outbreak of war. The factory was fully occupied by September 1940. A housing crisis also occurred at Glasgow, where Hives again asked the Air Ministry to step in. With 16,000 employees, the Glasgow factory was one of the largest industrial operations in Scotland. Unlike the Derby and Crewe plants, which relied significantly on external subcontractors , it produced almost all
10235-522: The production of the Rolls-Royce Avon turbojet and others, the factory was closed in 2005. The Ford Motor Company was asked to produce Merlins at Trafford Park , Stretford , near Manchester , and building work on a new factory was started in May 1940 on a 118-acre (48 ha) site. Built with two distinct sections to minimise potential bomb damage, it was completed in May 1941 and bombed in
10350-454: The prototype high-altitude Vickers Wellington V bomber, Rolls-Royce started experiments on the design of a two-stage supercharger and an engine fitted with this was bench-tested in April 1941, eventually becoming the Merlin 60. The basic design used a modified Vulture supercharger for the first stage while a Merlin 46 supercharger was used for the second. A liquid-cooled intercooler on top of
10465-473: The same month. At first, the factory had difficulty in attracting suitable labour, and large numbers of women, youths and untrained men had to be taken on. Despite this, the first Merlin engine came off the production line one month later and it was building the engine at a rate of 200 per week by 1943, at which point the joint factories were producing 18,000 Merlins per year. In his autobiography Not much of an Engineer , Sir Stanley Hooker states: "... once
10580-475: The shortened wingspan , the less-than-perfect condition of the used airframes , and the cropped supercharger impeller. The use of carburettors was calculated to give a higher specific power output, due to the lower temperature, hence greater density, of the fuel/air mixture compared to injected systems. Initially Merlins were fitted with float controlled carburettors. However, during the Battle of Britain it
10695-437: The side, which allowed the fuel to flow equally well under negative or positive g. Further improvements were introduced throughout the Merlin range: 1943 saw the introduction of a Bendix-Stromberg pressure carburettor that injected fuel at 5 pounds per square inch (34 kPa ; 0.34 bar ) through a nozzle directly into the supercharger, and was fitted to Merlin 66, 70, 76, 77 and 85 variants. The final development, which
10810-431: The success of the Merlin was the supercharger. A.C. Lovesey , an engineer who was a key figure in the design of the Merlin, delivered a lecture on the development of the Merlin in 1946; in this extract he explained the importance of the supercharger: The impression still prevails that the static capacity known as the swept volume is the basis of comparison of the possible power output for different types of engine, but this
10925-425: The supercharger casing was used to prevent the compressed air/fuel mixture from becoming too hot. Also considered was an exhaust-driven turbocharger , but although a lower fuel consumption was an advantage, the added weight and the need to add extra ducting for the exhaust flow and waste-gates meant that this option was rejected in favour of the two-stage supercharger. Fitted with the two-stage two-speed supercharger,
11040-400: The supercharger to the engine using a system of hydraulic clutches, which were initially manually engaged or disengaged by the pilot with a control in the cockpit. At low altitudes, the low-speed gear would be used, to prevent excessive boost levels. At higher altitudes, the supercharger could be switched to a higher gear to compensate for the reduced intake air density. In the Battle of Britain
11155-500: The supercharger. In the middle of the rev range, a boost was derived from both systems, while at the highest revs the system disconnected the drive from the supercharger and isolated the associated ducting. This was done in an attempt to exploit the advantages of each of the charging systems while removing the disadvantages. In turn, this approach brought greater complexity and affected the car's reliability in WRC events, as well as increasing
11270-457: The throttle can be progressively opened to obtain the maximum safe power level for a given altitude. The altitude at which the throttle reaches full open and the engine is still producing full rated power is known as the critical altitude . Above the critical altitude, engine power output will reduce as the supercharger can no longer fully compensate for the decreasing air density. Another issue encountered at low altitudes (such as at ground level)
11385-408: The two-speed superchargers designed by Rolls-Royce, resulting in increased power at higher altitudes than previous versions. Another improvement, introduced with the Merlin X, was the use of a 70%–30% water-glycol coolant mix rather than the 100% glycol of the earlier versions. This substantially improved engine life and reliability, removed the fire hazard of the flammable ethylene glycol , and reduced
11500-403: The volume of a single-decker bus per minute), and with the exhaust gases exiting at 1,300 mph (2,100 km/h) it was realised that useful thrust could be gained simply by angling the gases backwards instead of venting sideways. During tests, 70 pounds-force (310 N ; 32 kgf ) thrust at 300 mph (480 km/h), or roughly 70 hp (52 kW) was obtained, which increased
11615-514: The war effort, negotiations were started to establish an alternative production line outside the UK. Rolls-Royce staff visited North American automobile manufacturers to select one to build the Merlin in the U.S. or Canada. Henry Ford rescinded an initial offer to build the engine in the U.S. in July 1940, and the Packard Motor Car Company was selected to take on the $ 130,000,000 Merlin order (equivalent to $ 2.83 billion in 2023 dollars ). Agreement
11730-546: The weight of engine ancillaries in the finished design. Twincharged engines have occasionally been used in production cars, such as the 2005-2013 Volkswagen 1.4 litre and the 2017-present Volvo B4204T43/B4204T48 2.0 litre four-cylinder engines. In 1849, G. Jones of Birmingham, England began manufacturing a lobe pump compressor to provide ventilation for coal mines. In 1860, the Roots Blower Company (founded by brothers Philander and Francis Marion Roots) in
11845-488: The whole operation, but timely intervention by the Air Ministry improved the situation. In 1940 a strike took place when women replaced men on capstan lathes , the workers' union insisting this was a skilled labour job; however, the men returned to work after 10 days. Total Merlin production at Crewe was 26,065. The factory was used postwar for the production of Rolls-Royce and Bentley motor cars and military fighting vehicle power plants. In 1998 Volkswagen AG bought
11960-426: Was 1,175 hp (876 kW) at 18,000 ft (5,500 m). These figures were achieved at 2,850 rpm engine speed using +9 pounds per square inch (1.66 atm ) (48") boost. In 1940, after receiving a request in March of that year from the Ministry of Aircraft Production for a high-rated (40,000 ft (12,000 m)) Merlin for use as an alternative engine to the turbocharged Hercules VIII used in
12075-522: Was 32,377. The original factory closed in March 2008, but the company maintains a presence in Derby. To meet the increasing demand for Merlin engines, Rolls-Royce started building work on a new factory at Crewe in May 1938, with engines leaving the factory in 1939. The Crewe factory had convenient road and rail links to their existing facilities at Derby. Production at Crewe was originally planned to use unskilled labour and sub-contractors with which Hives felt there would be no particular difficulty, but
12190-695: Was also the basis of the Rolls-Royce/Rover Meteor tank engine. Post-war, the Merlin was largely superseded by the Rolls-Royce Griffon for military use, with most Merlin variants being designed and built for airliners and military transport aircraft . The Packard V-1650 was a version of the Merlin built in the United States. Production ceased in 1950 after a total of almost 150,000 engines had been delivered. Merlin engines remain in Royal Air Force service today with
12305-625: Was concentrated on civil derivatives of the Merlin. Development of what became the "Transport Merlin" (TML) commenced with the Merlin 102 (the first Merlin to complete the new civil type-test requirements) and was aimed at improving reliability and service overhaul periods for airline operators using airliner and transport aircraft such as the Avro Lancastrian , Avro York (Merlin 500-series), Avro Tudor II and IV (Merlin 621), Tudor IVB and V (Merlin 623), TCA Canadair North Star (Merlin 724) and BOAC Argonaut (Merlin 724-IC). By 1951
12420-988: Was designated the "TMO" and the modified exhaust system was supplied as kit that could be installed on existing engines either by the operator or by Rolls-Royce. Power ratings for the civil Merlin 600, 620, and 621-series was 1,160 hp (870 kW) continuous cruising at 23,500 feet (7,200 m), and 1,725 hp (1,286 kW) for take-off. Merlins 622–626 were rated at 1,420 hp (1,060 kW) continuous cruising at 18,700 feet (5,700 m), and 1,760 hp (1,310 kW) for take-off. Engines were available with single-stage, two-speed supercharging (500-series), two-stage, two-speed supercharging (600-series), and with full intercooling, or with half intercooling/charge heating, charge heating being employed for cold area use such as in Canada. Civil Merlin engines in airline service flew 7,818,000 air miles in 1946, 17,455,000 in 1947, and 24,850,000 miles in 1948. From Jane's : Most of
12535-409: Was fitted to the 100-series Merlins, was an S.U. injection carburettor that injected fuel into the supercharger using a fuel pump driven as a function of crankshaft speed and engine pressures. At the start of the war, the Merlin I, II and III ran on the then standard 87-octane aviation spirit and could generate just over 1,000 hp (750 kW) from its 27-litre (1,650-cu in) displacement:
12650-462: Was found that if Spitfires or Hurricanes were to pitch nose down into a steep dive, negative g -force ( g ) produced temporary fuel starvation causing the engine to cut-out momentarily. By comparison, the contemporary Bf 109E , which had direct fuel injection , could "bunt" straight into a high-power dive to escape attack. RAF fighter pilots soon learned to avoid this with a "half-roll" of their aircraft before diving in pursuit. A restrictor in
12765-430: Was no mechanical time limit mechanism, but pilots were advised not to use increased boost for more than a maximum of five minutes, and it was considered a "definite overload condition on the engine"; if the pilot resorted to emergency boost he had to report this on landing, when it was noted in the engine log book, while the engineering officer was required to examine the engine and reset the throttle gate. Later versions of
12880-502: Was possible with lubricating oils that were used at that time. The bearing coating also improved the break-in (running-in) and load-carrying abilities of the surface. In answer to a request from the British Air Ministry for a high-altitude Merlin for the pressurised Wellington VI high-altitude bomber, a Rolls-Royce team under the direction of Stanley Hooker developed a Merlin with two-stage supercharging, which became
12995-408: Was reached in September 1940, and the first Packard-built engine, a Merlin XX, designated the V-1650-1, ran in August 1941. Total Merlin production by Packard was 55,523. Critical altitude In an internal combustion engine , a supercharger compresses the intake gas, forcing more air into the engine in order to produce more power for a given displacement . The current categorization
13110-600: Was refining the Merlin. As a result, the Peregrine saw use in only two aircraft: the Westland Whirlwind fighter and one of the Gloster F.9/37 prototypes. The Vulture was fitted to the Avro Manchester bomber, but proved unreliable in service and the planned fighter using it – the Hawker Tornado – was cancelled as a result. With the Merlin itself soon pushing into the 1,500 hp (1,100 kW) range,
13225-506: Was used to vastly increase the power output for several speed record airplanes. Military use of high-octane fuels began in early 1940 when 100-octane fuel was delivered to the British Royal Air Force fighting in World War II. The German Luftwaffe also had supplies of a similar fuel. Increasing the octane rating became a major focus of aero engine development for the remainder of the war, with later fuels having up to
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