View source for Engineering:Water injection (engine)

{{Short description|Means of cooling parts of an engine to allow more power}}

In [[Earth:Internal combustion engine|internal combustion engine]]s, '''water injection''', also known as '''anti-detonant injection''' (ADI), can spray [[Chemistry:Water|water]] into the incoming air or fuel-air mixture, or directly into the [[Engineering:Combustion chamber|combustion chamber]] to cool certain parts of the induction system where "hot points" could produce premature ignition. In jet engines — particularly early turbojets or engines in which it is not practical or desirable to have an [[Engineering:Afterburner|afterburner]] — water injection may be used to increase engine [[Thrust|thrust]], particularly at low-altitudes and at takeoff.

Water injection was used historically to increase the power output of military aviation engines for short durations, such as during aerial combat or [[Engineering:Takeoff|takeoff]]. However it has also been used in motor sports and notably in drag racing. In [[Physics:Otto cycle|Otto cycle]] engines, the cooling effect of water injection also enables greater [[Engineering:Compression ratio|compression ratio]]s by reducing [[Engineering:Engine knocking|engine knocking]] (detonation). Alternatively, this reduction in engine knocking in Otto cycle engines means that some applications gain significant performance when water injection is used in conjunction with a [[Engineering:Supercharger|supercharger]], [[Engineering:Turbocharger|turbocharger]], or modifications such as aggressive [[Ignition timing|ignition timing]].

Depending on the engine, improvements in power and [[Physics:Fuel efficiency|fuel efficiency]] can also be obtained solely by injecting water.<ref name=wilson>{{cite thesis |url=http://digital.lib.uidaho.edu/cdm/ref/collection/IR/id/11 |last1=Wilson |first1=J. Parley |title=Effects of Water Injection and Increased Compression Ratio in a Gasoline Spark Ignition Engine |publisher=University of Idaho |date=February 2011}}</ref> Water injection may also be used to reduce [[Earth:NOx|NOx]] or [[Chemistry:Carbon monoxide|carbon monoxide]] emissions.<ref name="wilson" />

==Composition of fluid==
Many water injection systems use a mixture of water and [[Chemistry:Ethanol|alcohol]] (often close to 50/50), with trace amounts of water-soluble oil. The water provides the primary cooling effect due to its great [[Physics:Density|density]] and high heat absorption properties. The alcohol is combustible, and also serves as an [[Chemistry:Antifreeze|antifreeze]] for the water. The main purpose of the oil is to prevent [[Chemistry:Corrosion|corrosion]] of water injection and fuel system components.{{sfn|Kroes|Wild|1995|page=143}} 


==Use in aircraft==
[[File:Boeing KC-135 J57 wet takeoff.jpg|thumb|250px|A "wet" takeoff of a [[Engineering:Boeing KC-135 Stratotanker|KC-135]] with J57 engines]]

Water injection has been used in both reciprocating and turbine aircraft engines. 

In a [[Engineering:Reciprocating engine|reciprocating engine]], the use of water injection, also called anti-detonation injection or ADI, is used to prevent [[Engineering:Engine knocking|engine knocking]] also known as "detonation".<ref name=":1">{{Cite book |title=A&P Powerplant Textbook |publisher=Jeppeson Company |year=2011 |isbn=978-0884873389 |edition=3rd}}</ref> Commonly found on large radial engines with [[Engineering:Pressure carburetor|pressure carburetor]]s, it is a mixture of water and alcohol injected into the carburetor at high power settings. When using a rich mixture, the engine runs cooler, but cannot reach maximum power, and a leaner mixture means detonation is likely. With the use of ADI, the injected water and alcohol (which is mixed with the water to prevent it from becoming ice) absorbs the excess heat to prevent detonation while still allowing for a leaner and more powerful mixture.<ref name=":1" />

When used in a turbine engine, the effects are similar, except that normally preventing detonation is not the primary goal. Water is normally injected either at the compressor inlet or in the diffuser just before the combustion chambers. Adding water increases the mass being accelerated out of the engine, increasing thrust and it also serves to cool the turbines. Since temperature is normally the limiting factor in turbine engine performance at low altitudes, the cooling effect lets the engine run at higher RPM with more fuel injected and more thrust created without overheating.{{sfn|Kroes|Wild|1995|pages=285-286}}

Prior to the widespread adoption of [[Engineering:Afterburner|afterburning engines]], some first-generation jet fighters used water injection to provide a moderate boost in performance. For example, the late-model variant of the Lockheed F-80 Shooting Star, the F-80C, used water injection on its [[Engineering:Allison J33|Allison J33-A-35]] engine. Water injection increased thrust from {{cvt|4600|to|5400|lbf|kN|order=flip|1}}, a 17% thrust increase (at sea level).<ref>{{cite book |title=Turbofan and Turbojet Engines: Database Handbook |last=Roux |first=Élodie |url={{google book|id=_5vA_5XK33sC|page=213|plain-url=yes}} |year=2007 |page=213 |isbn=9782952938013}}</ref>

Early versions of the [[Engineering:Boeing 707|Boeing 707]] fitted with Pratt & Whitney JT3C turbojets used water injection for extra takeoff power, as did [[Engineering:Boeing 747|Boeing 747]]-100 and 200 aircraft fitted with Pratt & Whitney JT9D-3AW and -7AW turbofans;<ref>{{cite journal |last1=Daggett |first1=D. L. |last2=Ortanderl |first2=S. |last3=Eames |first3=D. |last4=Berton |first4=J. J. |last5=Snyder |first5=C. A. |title=Revisiting Water Injection for Commercial Aircraft |journal=SAE Mobilus |location=US |date=November 2, 2004 |doi=10.4271/2004-01-3108}}</ref> this system was not included in later versions fitted with more powerful engines. The [[Engineering:BAC One-Eleven|BAC One-Eleven]] airliner also used water injection for its [[Engineering:Rolls-Royce Spey|Rolls-Royce Spey]] [[Engineering:Turbofan|turbofan]] engines. Filling the tanks with jet fuel instead of water led to the Paninternational Flight 112 crash.<ref name="bac111 crash">{{ASN accident|id=19710906-0|title=Paninternational crash near Hamburg-Fuhlsbüttel}}</ref>

In 1978, Olympic Airways Flight 411 had to abort and return to its take-off airport due to a failure of the water injection system or its processes.<ref>{{Cite news |date=2020-12-27 |title=Ολυμπιακή Αεροπορία πτήση 411: Οταν κατα την απογείωση το ΑΕΡΟΠΛΑΝΟ εξυσε τις πολυκατοικίες στον Αλιμο |trans-title=Olympic Aviation flight 411: When during the take-off the PLANE scraped the apartment buildings in Alimos |language=el |url=https://www.koolnews.gr/to-aeroplano-exyse-tis-polykatikies/ |access-date=2022-02-17}}</ref>

==Use in automobiles==
A limited number of road vehicles with forced induction engines from manufacturers such as [[Company:Chrysler|Chrysler]] have included water injection. The [[Engineering:Oldsmobile Cutlass#1962|1962 Oldsmobile Jetfire]] was delivered with the Turbo Jetfire engine.<ref>{{cite web |url=http://www.442.com/oldsfaq/ofjet.htm |title=Jetfire |work=Oldsmobile Mail List Server Community |archive-url=https://web.archive.org/web/19990225151327/http://www.442.com/oldsfaq/ofjet.htm |archive-date=1999-02-25}}</ref> 

In 2015 [[Company:BMW|BMW]] has introduced a version of their high performance [[Engineering:BMW M4|M4]] coupe, the M4 GTS, that combines water injection with intercooling. The car was featured in the 2015 MotoGP season as the official safety car for the series and was released for the commercial market in 2016.<ref>{{cite web |url=https://www.bmw-m.com/en/topics/magazine-article-pool/5-litres-of-water-for-500-horses.html |title=New BMW M water injection system |work=BMW M Power |publisher=BMW |date=October 7, 2015 |access-date=November 14, 2021}}</ref> As per [[Company:BMW|BMW]] example, current engine developments featuring water injection seem to concentrate on the effect of “Performance Improvement”. But  by the mid 2020s, engine development will shift focus also on improved fuel consumption, due to the pressure on {{CO2}} emissions reduction and related regulations.<ref>{{cite journal |url={{google book|id=6XtxDwAAQBAJ|page=146|plainurl=yes}} |title=Leistungssteigerung von Ottomotoren durch verschiedene Wassereinspritzungskonzepte |last1=Durst |first1=B. |last2=Unterweger |first2=G. |last3=Reulein |first3=C. |last4=Ruppert |first4=C. |last5=Linse |first5=D |last6=Kerkn |first6=W. |journal=MTZ-Fachtagung Ladungswechsel im Verbrennungsmotor |language=German |location=Germany |year=2015}}</ref><ref name=":0">PAUER, T.; FROHNMAIER, M.; WALTHER, J.; SCHENK, P.; HETTINGER, A.; KAMPMANN, S., 2016. "Optimierung von Ottomotoren durch Wassereinspritzung." In: ''37. Internationales Wiener Motorensymposium.''</ref>

Bosch, which co-developed the technology with [[Company:BMW|BMW]], offers a water injection system named WaterBoost for other manufacturers. The company claims up to 5% increase in engine performance, up to 4% decrease in {{CO2}} emissions and up to 13% improvement in fuel economy.<ref>[http://www.bosch-mobility-solutions.com/en/powertrain-electrified-mobility/water-injection/ Bosch WaterBoost - Bosch Mobility Solutions]</ref> Similar results were reported in "Water Injection - High Power and High Efficiency combined"<ref>THEWES, M.; BAUMGARTEN, H.; SCHARF, J.; BIRMES, G.; BALAZS, A. et. alt., 2016 "Water Injection - High Power and High Efficiency combined" In: ''25. Aachener Kolloquium Fahrzeug- und Motorentechnik''</ref> 

Water Injection and cooled [[Chemistry:Exhaust gas recirculation|exhaust gas recirculation (EGR)]] could be seen as competitive technologies: it has been demonstrated that at medium load a 40-50 % Water-to-Fuel Ratio (WFR) with Port Water Injection (PWI) has the same effect as an EGR-rate of 10%, which is seen as relatively limited even for petrol engines.<ref>CONWAY, Graham, 2019. "Injection of Alternative Fluids for Knock Mitigation." In: SAE, ''International Powertrains, Fuels and Lubricants Meeting''. San Antonio, Texas, January 22–24, 2019.</ref>
  
=== On-Board Water Generation ===

Surveys asking customers about their willingness to regularly fill up an additional operating fluid have demonstrated that the acceptance level is limited.<ref name=":0" /> Therefore, the need for refilling is considered as one of the main barrier for the mass adoption of Water Injection. A key enabler is the development of on-board water generation system to run in close loop system, especially in order to guarantee consistent low level of emissions (engine {{CO2}} emissions will be raised if the water supply is exhausted). Three major sources can be investigated:
* Harvesting air humidity from ambient (e.g. by A/C condensate)
* Surface Water (e.g. rain water collected from vehicle body)
* Exhaust Gas Condensate
The first two variants are highly dependent on weather ambient conditions with sufficiently high humidity levels or driver habits (no A/C operation wanted). Consequently, an adequate supply of water cannot be ensured. In contrast, condensing of water vapour formed during the combustion of gasoline is a reliable source of water: there is approximately a volume of 1L of water vapour in exhaust per each liter of gasoline fuel consumed. 
In October 2019, Hanon Systems together with FEV presented an [[Engineering:Audi TT|Audi TT]] Sport demonstrator equipped with water injection operating as a closed system thanks to a Hanon Systems "Water Harvesting System".<ref>{{cite conference |title=Exhaust Gas Condensate as an Enabler for Self-Contained Water Injection Systems |first1=Guillaume |last1=Hébert |first2=Jiří |last2=Bazala |first3=Oliver |last3=Fischer |first4=Jürgen |last4=Nothbaum |first5=Matthias |last5=Thewes |first6=Tobias |last6=Voßhall |first7=Peter |last7=Diehl |conference=28th Aachen Colloquium Automobile and Engine Technology |year=2019}}</ref>

==Use in diesel==
A 2016 study combined water injection with [[Chemistry:Exhaust gas recirculation|exhaust gas recirculation]]. Water was injected into the exhaust manifold of a diesel engine and, by opening the exhaust valve during the induction stroke, the injected water and some of the exhaust gas was drawn back into the cylinder. The effect was an 85% reduction in [[Earth:NOx|NOx]] emissions, but at the cost of increased soot emissions.<ref>{{cite journal |doi=10.1016/j.egypro.2016.10.162 |title=Effect of Water Injection into Exhaust Manifold on Diesel Engine Combustion and Emissions |journal=Energy Procedia |volume=100 |pages=178–187 |year=2016 |last1=Nour |first1=M |last2=Kosaka |first2=H |last3=Abdel-Rahman |first3=Ali K |last4=Bady |first4=M |doi-access=free }}</ref>

==See also==
* [[Engineering:Six-stroke engine#Crower six-stroke engine|Crower six stroke]]

==References==
{{reflist}}

==Further reading==
* {{Cite web | first1=David L. |last1=Daggett | first2=Lars |last2=Fucke |first3=Robert C. |last3= Hendricks | first4=David J.H. |last4= Eames |date=2010 |title=Water Injection on Commercial Aircraft to Reduce Airport Nitrogen Oxides |url=https://ntrs.nasa.gov/api/citations/20100015629/downloads/20100015629.pdf |website=NASA}}
* {{Cite journal |last=Daggett |first=David L. |last2=Ortanderl |first2=Silvio |last3=Eames |first3=David |last4=Snyder |first4=Chris |last5=Berton |first5=Jeff |date=2004 |title=Water Injection: Disruptive Technology to Reduce Airplane Emissions and Maintenance Costs |url=https://www.jstor.org/stable/44738026 |journal=SAE Transactions |volume=113 |pages=1547–1556 |issn=0096-736X}}
* {{cite magazine | first1=Bill | last1=Gunston | title=Boosting Gas Turbines | magazine=Flight | date=1952  |url=https://www.flightglobal.com/pdfarchive/view/1952/1952%20-%200092.html| archive-url=https://web.archive.org/web/20180927204402/https://www.flightglobal.com/pdfarchive/view/1952/1952%20-%200092.html | archive-date=2018-09-27 }}
* {{cite web |last1=Heinicke | first1=Orville H.| last2=Vandeman | first2=Jack E. |title=Effect of Water-Alcohol Injection and Maximum Economy Spark Advance on Knock-Limited Performance and Fuel Economy of a Large Air-Cooled Cylinder | work=NACA Wartime Memorandum Report E5H12 | publisher=NASA | url=https://ntrs.nasa.gov/citations/19930093596 | date=August 1945 }}
* {{cite book |last=Kroes |first=M |last2=Wild |first2=T |title=Aircraft Powerplants |edition=7th |page=143 |publisher=Glencoe |year=1995}}
* {{cite journal |last1=Rowe |first1=M. R. |last2=Ladd |first2=G. T. |title=Water Injection for Aircraft Engines |journal=SAE Transactions |date=1946 |volume=54 |pages=26–37, 44 |url=http://www.jstor.org/stable/44548241 |url-access=subscription |access-date=12 October 2021}}

==External links==
* {{Cite AV media |url=https://www.youtube.com/watch?v=r4WauAEUGnU |title=Water Injection at Aircraft Engines |date=March 12, 2021 |last=Aircraft Technicians |type=Video | via=YouTube}}

[[Category:Engine technology]]
[[Category:Aircraft engines|Water Injection]]

{{Sourceattribution|Water injection (engine)}}