Dual ignition 1 Dual ignition Dual ignition A Hirth 2702 twin-cylinder, two-stroke aircraft engine. Equipped with dual ignition, the photo shows the two spark plugs per cylinder. Dual Ignition is a system for spark-ignition engines, whereby critical ignition components, such as spark plugs and magnetos, are duplicated. Dual ignition is most commonly employed on aero engines, [1][2] and is sometimes found on cars and motorcycles. Dual ignition provides two advantages: redundancy in the event of in-flight failure of one ignition system; and more efficient burning of the fuel-air mixture within the combustion chamber. [1][2] In aircraft, redundancy is the prime consideration, but in other vehicles combustive efficiency is the target. Design A dual ignition system will typically provide that each cylinder has twin spark plugs, and that the engine will have at least two ignition circuits, such as duplicate magnetos or ignition coils. [3] A 160 hp Gnome 9N Monosoupape with dual ignition provision. The provision of dual ignition in aero-engines is a safety feature to allow an aircraft to continue flying and land safely after an ignition system failure. Operation of aero engines on one magneto (rather than both) typically results in an rpm drop of around 75 rpm. [2] Its existence on aviation powerplants dates back to the World War I years, when such famous engines as the Hispano-Suiza 8 and Mercedes D.III, and even rotary engines as the later Gnome Monosoupape model 9N 160 hp versions featured twin spark plugs per cylinder. While true dual ignition uses completely separate and redundant systems, some certified engines, such as the Lycoming O-320-H2AD use a single engine magneto drive-shaft turning two separate magnetos. Whilst saving weight, this creates a single point of failure that could cause both ignition systems to cease working. [2] The Hewland AE75, an inline 3-cylinder aero-engine created for the ARV Super2, had three ignition circuits, one for each cylinder. If just one of the three circuits failed, all three cylinders still received sparks, and even if two circuits were to fail, the remaining circuit would keep the engine running on two cylinders. [4] Another form of partial dual ignition that has been used on amateur-built aircraft uses a single spark plug, but duplicates the coil and pick-up for better redundancy than traditional single ignition. [] Dual ignition promotes engine efficiency by initiating twin flame fronts, giving faster and more complete burning and thereby increasing power. [] Although a dual ignition system is a very effective method of achieving optimum
Transcript
Dual ignition 1
Dual ignition
Dual ignition
A Hirth 2702 twin-cylinder, two-stroke aircraft engine. Equipped with dual ignition, the photo shows the two spark plugs per cylinder.
Dual Ignition is a system for spark-ignition engines, whereby critical ignition components, such as spark plugs andmagnetos, are duplicated. Dual ignition is most commonly employed on aero engines,[1][2] and is sometimes foundon cars and motorcycles.Dual ignition provides two advantages: redundancy in the event of in-flight failure of one ignition system; and moreefficient burning of the fuel-air mixture within the combustion chamber.[1][2] In aircraft, redundancy is the primeconsideration, but in other vehicles combustive efficiency is the target.
DesignA dual ignition system will typically provide that each cylinder has twin spark plugs, and that the engine will have atleast two ignition circuits, such as duplicate magnetos or ignition coils.[3]
A 160 hp Gnome 9N Monosoupape with dualignition provision.
The provision of dual ignition in aero-engines is a safety feature toallow an aircraft to continue flying and land safely after an ignitionsystem failure. Operation of aero engines on one magneto (rather thanboth) typically results in an rpm drop of around 75 rpm.[2] Its existenceon aviation powerplants dates back to the World War I years, whensuch famous engines as the Hispano-Suiza 8 and Mercedes D.III, andeven rotary engines as the later Gnome Monosoupape model 9N160 hp versions featured twin spark plugs per cylinder.
While true dual ignition uses completely separate and redundantsystems, some certified engines, such as the Lycoming O-320-H2ADuse a single engine magneto drive-shaft turning two separate magnetos.Whilst saving weight, this creates a single point of failure that couldcause both ignition systems to cease working.[2]
The Hewland AE75, an inline 3-cylinder aero-engine created for the ARV Super2, had three ignition circuits, one foreach cylinder. If just one of the three circuits failed, all three cylinders still received sparks, and even if two circuitswere to fail, the remaining circuit would keep the engine running on two cylinders.[4]
Another form of partial dual ignition that has been used on amateur-built aircraft uses a single spark plug, butduplicates the coil and pick-up for better redundancy than traditional single ignition.[]
Dual ignition promotes engine efficiency by initiating twin flame fronts, giving faster and more complete burning and thereby increasing power.[] Although a dual ignition system is a very effective method of achieving optimum
combustion and better fuel consumption, it remains rare in cars and motorcycles because of difficulties in siting thesecond plug. Alfa Romeo Twin Spark cars (eponymously) use dual ignition, as do Honda cars with the i-DSI seriesengines.[5] In 1980 Nissan installed twin sparkplugs on the Nissan NAPS-Z engine, with Ford introducing it on the1989 Ford Ranger and 1991 Ford Mustang four-cylinder models. Mercedes Benz utilizes 2 spark plugs per cylinderon certain models.[citation needed] Some motorcycles, such as the Honda VT500 and the Honda NT400 Bros, alsoemploy dual ignition.[6] The Ducati Multistrada has been modified for 2012 to have "twin-plug cylinder heads forsmoother, more efficient combustion", the change contributing to a 5% increase in torque and a 10% improvement infuel consumption.[7] The 2012 Bajaj Pulsar 200 NS has three spark plugs per cylinder.[8]
Wankel engines have such an elongated combustion chamber that even non-aero wankel engines may adopt dualignition to promote better combustion, in some cases like the Mazda 787B racing car even triple ignition[citation
needed]. The MidWest AE series Wankel aero-engine has twin plugs per chamber, but these are placed side-by-side,not sequentially, so their main purpose is to give redundancy rather than improved combustion.[9]
References[1] Crane, Dale: Dictionary of Aeronautical Terms, third edition, page 177. Aviation Supplies & Academics, 1997. ISBN 1-56027-287-2[2] Aviation Publishers Co. Limited, From the Ground Up, (27th revised edition), page 67, ISBN 0-9690054-9-0[4][4] ARV Super2 Handbook[5] Intelligent-Dual Sequential Ignition (iDSI) - The Honda iDSI (http:/ / honda. co. nz/ technology/ engine/ idsi/ )[6] Honda - NT 400 L Bros MKll (NC25) PGM Ignition 90-92 (http:/ / www. motorbikespecs. net/ index. dyn?flag=2& model_id=3611136&
make=Honda)[7] Kevin Ash in Daily Telegraph, page M18, "Motoring Section", Saturday 29 September 2102[9][9] MidWest Engines Ltd AE1100R Rotary Engine Manual
