Packard V-1650
Encyclopedia
The Packard V-1650 was a liquid cooled 27 litre
(1649 in3) 60° V12
piston
aircraft engine
variant of the Rolls-Royce Merlin
produced under licence (in the United States) by the Packard Motor Car Company
. The engine was licensed in order to provide a 1500 hp-class design at a time when US engines of this rating were not considered ready for use even after years of development.
The first V-1650s with a simple one-stage supercharger
powered variants of the Curtiss P-40
(Kittyhawk) fighter. Later versions included a much more advanced two-stage supercharger that greatly improved performance at high altitudes. It found its most famous application in the North American P-51 Mustang fighter, where it vastly improved that aircraft's performance at altitude. This fitting transformed the Mustang into an outstanding fighter with the range and performance to escort heavy bombers over the continent. By 1944, P-51B, P-51C and P-51D "Merlin" Mustangs were able to escort Allied heavy bombers in daylight all the way to Berlin and there to defeat German fighters that rose to meet them. By late 1944, the Allies had won air supremacy over the whole of Germany, and Germany's defeat in World War II began to appear inevitable.
had offered to manufacture 1,000 aircraft a day if the Government would let him do it his way, and during a discussion with Secretary of the Treasury Henry Morgenthau Jr.
regarding what the Ford company might produce, Ford's son Edsel
tentatively agreed to make 6,000 Rolls-Royce liquid-cooled engines for Great Britain and 3,000 for the U.S. However, at the beginning of July, Henry Ford stated that he would manufacture only for defense, not for Britain, and the entire deal was declared off. Members of the Defense Advisory Commission subsequently began negotiations with other manufacturers in an effort to place the $130,000,000 Rolls-Royce order, and Packard Motor Car Company was eventually chosen because the engine's British parent company was impressed by its high-quality engineering. Agreement was reached in September 1940, and the first Packard-built engine, designated V-1650-1, ran in August 1941.
The first American version of the Merlin was the Packard Merlin 28 (Mark XX), designated the V-1650-1 by the American military. This engine used a single stage, two speed supercharger. As the Merlin 28, it was used for the Avro Lancaster
bomber. The USAAF V-1650-1 version of this engine was used in the P-40Fs. The initial Packard modifications were done on this engine by changing the main 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 was possible with lubricating oils that were used at that time. The bearing coating also improved break-in and load-carrying ability of the surface.
The real improvement Packard incorporated into the Merlin was adopting the Wright supercharger
drive quill. This modification was designated the V-1650-3 and became known as the "high altitude" Merlin destined for the P-51. The two speed, two stage supercharger section of the -3 featured two separate impellers on the same shaft which 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 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 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 which increased the critical altitude of the power plant.
The ability of the supercharger to maintain a sea level atmosphere in the induction system to the cylinders allowed the Packard Merlin to develop more than 1270 hp at altitudes beyond 30000 feet (9,144 m). The two stage impeller created extreme heating of 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.
Ethylene glycol coolant was circulated by a pump through this passage to carry off the excess heat generated by the impellers. Without the intercooler the temperature of the charge could be as high as 400 °F (204 °C). The intercooler in itself was not adequate to deal with the high temperature and an additional cooling fin and tube core was placed between the outlet of the blower and the induction manifold to the cylinders. This radiator was known as an aftercooler and served as a reservoir for the supercharger cooling system. 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 the coolant through an aircraft radiator system at a maximum rate of 30 Imperial gallons (136 litres, 36 US gallons) per minute, depending on engine rpm.
This combined system reduced the charge temperature to suitable levels. The throttle valves in the updraft carburettor throat were controlled by an automatic boost control through the pilot's linkage to maintain the selected manifold pressure during changes in altitude. The valves were only partially open during ground and low level operation to prevent overboosting of the engine. As air density decreases with an increase in altitude, the throttle valves were moved to an open position by boost pressure corresponding to aircraft altitude. This system provided full power within engine boost limitations up to the critical altitude of 26000 feet (7,924.8 m).
The Americans measured their boost ratings using inches of mercury (inHg). One pound-force per square inch equals 1 lbf/in2 or 1 lbf/in2, and a standard atmosphere is 101.325 kPa =29.92 inHg =14.70 lbf/in². In early Merlin engines the maximum manifold (boost) pressure was +18. This was increased in later models.
engines and airframes were sold relatively cheaply – two of the most popular items were P-51 Mustang
s 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 the Thompson Trophy
.
Work continues on increasing the power output of 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-Detonate Injection) (50% Distilled Water and 50%) Methanol, have allowed great increases in power output. Many of the fastest Unlimited racers are pushing their Merlins to manifold pressures as high as 145 inHg to obtain the 3,800 horsepower it takes to get a Mustang to go 490 mph.
Litre
pic|200px|right|thumb|One litre is equivalent to this cubeEach side is 10 cm1 litre water = 1 kilogram water The litre is a metric system unit of volume equal to 1 cubic decimetre , to 1,000 cubic centimetres , and to 1/1,000 cubic metre...
(1649 in3) 60° V12
V12 engine
A V12 engine is a V engine with 12 cylinders mounted on the crankcase in two banks of six cylinders, usually but not always at a 60° angle to each other, with all 12 pistons driving a common crankshaft....
piston
Internal combustion engine
The internal combustion engine is an engine in which the combustion of a fuel occurs with an oxidizer in a combustion chamber. In an internal combustion engine, the expansion of the high-temperature and high -pressure gases produced by combustion apply direct force to some component of the engine...
aircraft engine
Aircraft engine
An aircraft engine is the component of the propulsion system for an aircraft that generates mechanical power. Aircraft engines are almost always either lightweight piston engines or gas turbines...
variant of the Rolls-Royce Merlin
Rolls-Royce Merlin
The Rolls-Royce Merlin is a British liquid-cooled, V-12, piston aero engine, of 27-litre capacity. Rolls-Royce Limited designed and built the engine which was initially known as the PV-12: the PV-12 became known as the Merlin following the company convention of naming its piston aero engines after...
produced under licence (in the United States) by the Packard Motor Car Company
Packard
Packard was an American luxury-type automobile marque built by the Packard Motor Car Company of Detroit, Michigan, and later by the Studebaker-Packard Corporation of South Bend, Indiana...
. The engine was licensed in order to provide a 1500 hp-class design at a time when US engines of this rating were not considered ready for use even after years of development.
The first V-1650s with a simple one-stage supercharger
Supercharger
A supercharger is an air compressor used for forced induction of an internal combustion engine.The greater mass flow-rate provides more oxygen to support combustion than would be available in a naturally aspirated engine, which allows more fuel to be burned and more work to be done per cycle,...
powered variants of the Curtiss P-40
Curtiss P-40
The Curtiss P-40 Warhawk was an American single-engine, single-seat, all-metal fighter and ground attack aircraft that first flew in 1938. The P-40 design was a modification of the previous Curtiss P-36 Hawk which reduced development time and enabled a rapid entry into production and operational...
(Kittyhawk) fighter. Later versions included a much more advanced two-stage supercharger that greatly improved performance at high altitudes. It found its most famous application in the North American P-51 Mustang fighter, where it vastly improved that aircraft's performance at altitude. This fitting transformed the Mustang into an outstanding fighter with the range and performance to escort heavy bombers over the continent. By 1944, P-51B, P-51C and P-51D "Merlin" Mustangs were able to escort Allied heavy bombers in daylight all the way to Berlin and there to defeat German fighters that rose to meet them. By late 1944, the Allies had won air supremacy over the whole of Germany, and Germany's defeat in World War II began to appear inevitable.
Design and development
In June 1940, Henry FordHenry Ford
Henry Ford was an American industrialist, the founder of the Ford Motor Company, and sponsor of the development of the assembly line technique of mass production. His introduction of the Model T automobile revolutionized transportation and American industry...
had offered to manufacture 1,000 aircraft a day if the Government would let him do it his way, and during a discussion with Secretary of the Treasury Henry Morgenthau Jr.
Henry Morgenthau, Jr.
Henry Morgenthau, Jr. was the U.S. Secretary of the Treasury during the administration of Franklin D. Roosevelt. He played a major role in designing and financing the New Deal...
regarding what the Ford company might produce, Ford's son Edsel
Edsel Ford
Edsel Bryant Ford , son of Henry Ford, was born in Detroit, Michigan, USA. He was president of Ford Motor Company from 1919 until his death in 1943.-Life and career:...
tentatively agreed to make 6,000 Rolls-Royce liquid-cooled engines for Great Britain and 3,000 for the U.S. However, at the beginning of July, Henry Ford stated that he would manufacture only for defense, not for Britain, and the entire deal was declared off. Members of the Defense Advisory Commission subsequently began negotiations with other manufacturers in an effort to place the $130,000,000 Rolls-Royce order, and Packard Motor Car Company was eventually chosen because the engine's British parent company was impressed by its high-quality engineering. Agreement was reached in September 1940, and the first Packard-built engine, designated V-1650-1, ran in August 1941.
The first American version of the Merlin was the Packard Merlin 28 (Mark XX), designated the V-1650-1 by the American military. This engine used a single stage, two speed supercharger. As the Merlin 28, it was used for the Avro Lancaster
Avro Lancaster
The Avro Lancaster is a British four-engined Second World War heavy bomber made initially by Avro for the Royal Air Force . It first saw active service in 1942, and together with the Handley Page Halifax it was one of the main heavy bombers of the RAF, the RCAF, and squadrons from other...
bomber. The USAAF V-1650-1 version of this engine was used in the P-40Fs. The initial Packard modifications were done on this engine by changing the main bearings from a copper lead alloy to a silver lead combination and featured indium
Indium
Indium is a chemical element with the symbol In and atomic number 49. This rare, very soft, malleable and easily fusible post-transition metal is chemically similar to gallium and thallium, and shows the intermediate properties between these two...
plating. This had been developed by General Motors' Pontiac Division
Pontiac
Pontiac was an automobile brand that was established in 1926 as a companion make for General Motors' Oakland. Quickly overtaking its parent in popularity, it supplanted the Oakland brand entirely by 1933 and, for most of its life, became a companion make for Chevrolet. Pontiac was sold in the...
to prevent corrosion which was possible with lubricating oils that were used at that time. The bearing coating also improved break-in and load-carrying ability of the surface.
The real improvement Packard incorporated into the Merlin was adopting the Wright supercharger
Supercharger
A supercharger is an air compressor used for forced induction of an internal combustion engine.The greater mass flow-rate provides more oxygen to support combustion than would be available in a naturally aspirated engine, which allows more fuel to be burned and more work to be done per cycle,...
drive quill. This modification was designated the V-1650-3 and became known as the "high altitude" Merlin destined for the P-51. The two speed, two stage supercharger section of the -3 featured two separate impellers on the same shaft which 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 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 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 which increased the critical altitude of the power plant.
The ability of the supercharger to maintain a sea level atmosphere in the induction system to the cylinders allowed the Packard Merlin to develop more than 1270 hp at altitudes beyond 30000 feet (9,144 m). The two stage impeller created extreme heating of 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
Intercooler
An intercooler , or charge air cooler, is an air-to-air or air-to-liquid heat exchange device used on turbocharged and supercharged internal combustion engines to improve their volumetric efficiency by increasing intake air charge density through nearly isobaric cooling, which removes...
passage cast into the wheel case housing between the first and second stage impellers.
Ethylene glycol coolant was circulated by a pump through this passage to carry off the excess heat generated by the impellers. Without the intercooler the temperature of the charge could be as high as 400 °F (204 °C). The intercooler in itself was not adequate to deal with the high temperature and an additional cooling fin and tube core was placed between the outlet of the blower and the induction manifold to the cylinders. This radiator was known as an aftercooler and served as a reservoir for the supercharger cooling system. 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 the coolant through an aircraft radiator system at a maximum rate of 30 Imperial gallons (136 litres, 36 US gallons) per minute, depending on engine rpm.
This combined system reduced the charge temperature to suitable levels. The throttle valves in the updraft carburettor throat were controlled by an automatic boost control through the pilot's linkage to maintain the selected manifold pressure during changes in altitude. The valves were only partially open during ground and low level operation to prevent overboosting of the engine. As air density decreases with an increase in altitude, the throttle valves were moved to an open position by boost pressure corresponding to aircraft altitude. This system provided full power within engine boost limitations up to the critical altitude of 26000 feet (7,924.8 m).
Measurement of boost pressure
The British measured boost pressure as lbf/in² (or psi). The normal atmospheric pressure at sea level is 14.7 psi, so a reading of +6 means that 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 1 lbf/in2 or 1 lbf/in2, and a standard atmosphere is 101.325 kPa =29.92 inHg =14.70 lbf/in². In early Merlin engines the maximum manifold (boost) pressure was +18. This was increased in later models.
| Inches of mercury (inHg) absolute pressure |
Pounds per square inch of boost gauge pressure |
| 80 inHg= |
| 67 inHg= |
| 61 inHg= |
| 46 inHg= |
| 44.5 inHg= |
Post-war use
In the United States many war surplusMilitary surplus
Military surplus are goods, usually matériel, that are sold or otherwise disposed of when no longer needed by the military. Entrepreneurs often buy these goods and resell them at surplus stores. Military surplus rarely includes weapons or munitions, though they are occasionally found in such stores...
engines and airframes were sold relatively cheaply – two of the most popular items were P-51 Mustang
P-51 Mustang
The North American Aviation P-51 Mustang was an American long-range, single-seat fighter and fighter-bomber used during World War II, the Korean War and in several other conflicts...
s and Packard V-1650 Merlin engines, several of which were "souped up" and modified for air racing in the Bendix Trophy
Bendix trophy
The Bendix Trophy is a U.S. aeronautical racing trophy. The transcontinental, point-to-point race, sponsored by industrialist Vincent Bendix founder of Bendix Corporation, began in 1931 as part of the National Air Races. Initial prize money for the winners was $15,000...
, the Cleveland Air Races
National Air Races
The National Air Races were a series of pylon and cross-country races that took place in the United States from 1920 to 1949. The science of aviation, and the speed and reliability of aircraft and engines grew rapidly during this period; the National Air Races were both a proving ground and...
and the Thompson Trophy
Thompson trophy
The Thompson Trophy race was one of the National Air Races of the heyday of early airplane racing in the 1930s. Established in 1929, the last race was held in 1961. The race was long with pylons marking the turns, and emphasized low altitude flying and maneuverability at high speeds...
.
Work continues on increasing the power output of the Merlin for the Unlimited Class racers at the Reno Air Races
Reno Air Races
The Reno Air Races, also known as the National Championship Air Races, take place each September at the Reno Stead Airport a few miles north of Reno, Nevada, USA...
. Innovations, such as the use of Allison V-1710 connecting rods and the replacement of the intercooler with ADI (Anti-Detonate Injection) (50% Distilled Water and 50%) Methanol, have allowed great increases in power output. Many of the fastest Unlimited racers are pushing their Merlins to manifold pressures as high as 145 inHg to obtain the 3,800 horsepower it takes to get a Mustang to go 490 mph.
Variants
- V-1650-1: 1390 hp; Based on Merlin 28, used in P-40 Kittyhawk and Curtiss XP-60Curtiss P-60The Curtiss P-60 was a 1940s United States single-engine single-place, low-wing monoplane fighter aircraft developed by the Curtiss-Wright company as a successor to their P-40. It went through a lengthy series of prototype versions, eventually evolving into a design that bore little resemblance to...
fighters - V-1650-3: 1280 hp; Based on Merlin 63.
- V-1650-5: 1400 hp; Experimental.
- V-1650-7: 1315 hp; Similar to Merlin 66.
- V-1650-9: 1380 hp; Water methanol injection.
- V-1650-9A: 1380 hp;
- V-1650-11: 1380 hp; Modified fuel system.
- V-1650-21: 1380 hp; Opposite rotation for P-82 Twin Mustang
- V-1650-23:
- V-1650-25:
Applications
- Avro LancasterAvro LancasterThe Avro Lancaster is a British four-engined Second World War heavy bomber made initially by Avro for the Royal Air Force . It first saw active service in 1942, and together with the Handley Page Halifax it was one of the main heavy bombers of the RAF, the RCAF, and squadrons from other...
- Bell XP-63P-63 KingcobraThe Bell P-63 Kingcobra was a United States fighter aircraft developed in World War II from the Bell P-39 Airacobra in an attempt to correct that aircraft's deficiencies...
- Curtiss P-60Curtiss P-60The Curtiss P-60 was a 1940s United States single-engine single-place, low-wing monoplane fighter aircraft developed by the Curtiss-Wright company as a successor to their P-40. It went through a lengthy series of prototype versions, eventually evolving into a design that bore little resemblance to...
- de Havilland MosquitoDe Havilland MosquitoThe de Havilland DH.98 Mosquito was a British multi-role combat aircraft that served during the Second World War and the postwar era. It was known affectionately as the "Mossie" to its crews and was also nicknamed "The Wooden Wonder"...
- North American XP-78
- P-40F/L KittyhawkCurtiss P-40The Curtiss P-40 Warhawk was an American single-engine, single-seat, all-metal fighter and ground attack aircraft that first flew in 1938. The P-40 design was a modification of the previous Curtiss P-36 Hawk which reduced development time and enabled a rapid entry into production and operational...
- P-51 MustangP-51 MustangThe North American Aviation P-51 Mustang was an American long-range, single-seat fighter and fighter-bomber used during World War II, the Korean War and in several other conflicts...
- F-82 Twin MustangF-82 Twin MustangThe North American F-82 Twin Mustang was the last American piston-engine fighter ordered into production by the United States Air Force. Based on the P-51 Mustang, the F-82 was originally designed as a long-range escort fighter in World War II; however, the war ended well before the first...