Kuznetsov NK-93

The Kuznetsov NK-93 was a civilian aircraft engine, a hybrid between a turbofan and a turboprop known as a propfan. The engine was also unique in having a separate duct around the contra-rotating propellers, as most other propfans are unducted. Once described in a respected aviation encyclopedia as "potentially the most fuel-efficient aircraft jet engine ever to be tested,"[4] the NK-93 was targeted for derivatives of Soviet/Russian airliners such as the Ilyushin Il-96, Tupolev Tu-204, and Tupolev Tu-330.[2] Five in-flight engine tests were conducted on the NK-93 from December 2006[5] to December 2008.[6][7][8][9]

NK-93
NK-93 engine
Type	Propfan
National origin	Soviet Union
Manufacturer	Kuznetsov Design Bureau
First run	1989[1]
Number built	11[2]
Program cost	US$900 million (US$100 million more to complete program) as of 2001[3]
Developed from	Kuznetsov NK-92[2]

Development

The NK-93 engine was developed beginning in the late 1980s,[7] although the design of the engine was allegedly envisioned as early as 1968.[6] Many of the design features were adopted from the Kuznetsov NK-92, the military complement to the NK-93.[2] The core of the NK-93 was to form the foundation of a family of direct-drive turbofans and geared propfans, ranging from 11,000 to 22,000 kilograms-force (24,000 to 49,000 pounds-force; 110 to 220 kilonewtons) in thrust.[10] It was the last major project of Kuznetsov Design Bureau founder Nikolai Dmitriyevich Kuznetsov.[11]

The NK-93 was originally scheduled for flight testing in late 1993/early 1994[12] and certification in 1997 so that it could be used on the Ilyushin Il-96M and Tupolev Tu-204M.[13] By May 1994, seven full-size versions of the engine had been built, with five of them close to the production configuration.[14] Due to the breakup of the Soviet Union, though, the schedule was repeatedly delayed because of severe funding shortages[15] and other issues. However, by October 2001, a tenth NK-93 engine neared completion, out of a total of 15 planned engine prototypes.[4]

The engine finally underwent flight testing on an Ilyushin Il-76LL testbed aircraft beginning on December 29, 2006, with a second flight occurring on May 3, 2007. A total of 50 flight test hours were planned.[2] Testing was suspended again in June 2007 because of funding troubles.[16] Airborne testing did not restart until October 2008,[17] with flights on October 2[18] and 6.[19] Another test flight occurred on December 15, 2008,[6] but the NK-93 was removed from the testbed by May 14, 2009.[5]

A Central Institute of Aviation Motors (CIAM) director later enumerated reasons for ending NK-93 development, such as concerns about the compressor and turbine that went unaddressed, and the difference in fuel efficiency at the NK-93's design cruise speed of Mach 0.75 versus desired airliner speeds of Mach 0.8-0.82.[20] Nevertheless, the status of the NK-93 remains controversial. Supporters of the NK-93 claim that the amount of money needed to certify the engine is minuscule compared to the development costs of competing new Russian engines, which they regard as still inferior to the older NK-93.[21]

In April 2014, Kuznetsov announced that it would resume work on the NK-93 engine.[22]

Foreign interest

The advanced nature of the engine attracted the attention of airframers and engine manufacturers in other countries. By 1992, the NK-93 was already drawing interest from the Japanese aviation industry.[1] Investors from South Korea were among the groups discussing investment in the NK-93 at the 2001 MAKS air show.[3] In 2004, Airbus and the Kuznetsov Design Bureau studied the feasibility of using the engine to power Airbus commercial aircraft.[23] German engine maker MTU Aero Engines purchased a Kuznetsov report on the noise characteristics of the NK-93 engine for 600,000 Deutsche marks.[24] When the NK-93 was displayed on the Il-76LL demonstrator at the 2007 MAKS air show, Chinese aircraft manufacturers reportedly made a "tempting offer" to buy all of the NK-93's blueprints and documentation.[25] In October 2013, the European Commission gave a three-and-a-half year grant to study the Innovative Counter rOtating fan system for high Bypass Ratio Aircraft engine (COBRA). COBRA was a European Union-Russia cooperative program to study an ultra-high bypass ratio (UHBR) counter-rotating turbofan (CRTF) that was similar to the NK-93. Participating organizations included Kuznetsov, CIAM, Russian propeller manufacturer Aerosila, French engine maker Safran (Snecma), the French aerospace laboratory (ONERA), and the German Aerospace Center (DLR).[26]

Design

The NK-93 has a core that was developed from the NK-110, an unducted Kuznetsov propfan that was never built.[7] Its Aerosila SV-92 contra-rotating propellers are 114 inches (2,900 mm) in diameter, have eight blades on the front propeller, and have ten blades on the back propeller. The engine has a rated thrust of 18,000 kgf (39,700 lbf; 177 kN),[27] a maximum thrust of 20,000 kgf (45,000 lbf; 200 kN), a cruise SFC of 0.49 kg/kgf-thrust/hr, and a takeoff SFC of 0.234 kg/kgf-thrust/hr. 13 percent of the thrust is produced directly by the gas generator, while the rest of the thrust is produced through the turning of the ducted fans.[7] The front and back fans are both variable pitch propellers; by 1993, the coaxial fans could combine to produce 85 percent of the desired 4,000 kgf (8,800 lbf; 39 kN) maximum reverse thrust,[28] and by 1995, the reverse thrust capability was 3,800 kgf (8,300 lbf; 37 kN). The engine has a bypass ratio of 17 and is designed around a 22,000 kW (30,000 hp) planetary gearbox with seven satellites.[7]

Applications

The Kuznetsov NK-93 ducted propfan mounted on an Ilyushin Il-76LL testbed aircraft at the MAKS 2007 air show.

• Antonov An-70 (proposed twin-engine version)[29]
• Antonov An-124 (proposed re-engine)[30]
• Ilyushin Il-76LL (testbed)[5]
• Ilyushin Il-96[31]
• Sukhoi KR-860[32]
• Tupolev Tu-154M3[33]
• Tupolev Tu-204
• Tupolev Tu-330

Specifications

General characteristics

• Type: 3-shaft ducted propfan, with the 8-blade front fan absorbing 40% of the power and the 10-blade back fan absorbing 60% of the power[6]
• Length: 5.972 m (19.59 ft; 597.2 cm; 235.1 in)[34]
• Width:
• Height:
• Propeller diameter: 2.9 m (9.5 ft; 290 cm; 110 in)[2]
• Diameter:
• Dry weight: 3,650 kg (8,050 lb)[35]
• Propeller weight: 1,000 kg (2,200 lb)[27]

Components

• Compressor: 7-stage axial low-pressure compressor; 8-stage high-pressure compressor[2]
• Combustors: annular[2]
• Turbine: 1-stage high-pressure turbine, 1-stage low-pressure turbine[2]

Performance

• Maximum thrust: 18,000 kgf (40,000 lbf; 180 kN)[2]
• Overall pressure ratio: 37[36]
• Bypass ratio: 16.6[36]
• Air mass flow: 976 kg/s (2,150 lb/s)[7]
• Turbine inlet temperature: 1,700 °C (3,090 °F)[7]
• Specific fuel consumption: Takeoff: 6.6 g/(kN⋅s) (0.234 lb/(lbf⋅h));[7] Cruise: 14 g/(kN⋅s) (0.49 lb/(lbf⋅h)) at Mach 0.75, 14.7 g/(kN⋅s) (0.520 lb/(lbf⋅h)) at Mach 0.8[37]
• Power-to-weight ratio:

See also

• Europrop TP400
• Kuznetsov NK-12

Related development

• Geared turbofan
• Propfan

Comparable engines

• General Electric GE36
• IAE SuperFan
• Kuznetsov NK-92
• Pratt & Whitney/Allison 578-DX
• Progress D-27 / Progress D-627
• Progress D-236
• Rolls-Royce RB3011

Related lists

• List of aircraft engines

References

1. Moxon, Julian (April 22–28, 1992). "Engines of recovery: Aero-engine manufacturers in the Commonwealth of Independent States must head off competition from the West while restructuring to compete in a market economy" (PDF). News Analysis. Flight International. Vol. 141 no. 4315. p. 19. ISSN 0015-3710.
2. "NK-93 kicks off flight trials". Industry – In Brief. Take-off: Russia's National Aerospace Magazine. June 2007. p. 20. Lay summary.
3. Karnazov, Vladimir (July 31, 2001). "MAKS 2001 - Moscow on show". Flight International. Moscow, Russia. ISSN 0015-3710.
4. "Kuznetsov NK-93 (Russian Federation)". Jane's aero-engines. Aero-engines - Propfan. Jane's Information Group. November 27, 2011. Archived from the original on March 14, 2012.
5. Drozdov, Sergey (2013). "С.В. Дроздов. Авиационный "спецназовец" Ил-76" [Aviation 'commando' Il-76]. Kryl'ia Rodiny (in Russian). No. 3. pp. 39–45. ISSN 0130-2701. Archived (PDF) from the original on August 27, 2018. Retrieved July 25, 2019 – via Ilyushin Aviation Complex.
6. About the revolutionary NK-93 jet engine (Documentary) (English subtitles) (in Russian) – via YouTube.
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13. Lenorovitz, Jeffrey (March 30, 1992). "Samara engineers plan flight tests for counter-rotating shrouded propfan". Reshaping Russia's Propulsion Industry. Aviation Week & Space Technology. Vol. 136 no. 13. Samara, Russia. pp. 57–58. ISSN 0005-2175.
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18. Volkov, Evgeny (October 2, 2008). "PhotoID: 58476; Type: IL-76LL; Onboard: 76492". RussianPlanes.net (in Russian).
19. "Испытание нового самарского авиационного двигателя НК-93" [Testing the new Samara aircraft engine NK-93]. TV Samara (in Russian). October 6, 2008. Archived from the original on October 16, 2008.
20. Kozlov, Dmitry (April 14, 2012). "Каждое новое поколение авиадвигателей требует увеличения затрат на НИР" [Each new generation of aircraft engines requires an increase in research costs]. AviaPort.ru (in Russian). Moscow, Russia. Archived from the original on May 30, 2012.
21. Falichev, Oleg (October 16, 2018). "Тормозной путь НК-93: Российский двигатель пятого поколения, о чем только мечтают на Западе, объявлен устаревшим" [NK-93 stopping distance: Russian engine of the fifth generation, which only dream in the West, declared obsolete]. Voyenno-promyshlennyy kur'yer (Military Industrial Courier) (in Russian). 40 (753).
22. "Russian air forces to take delivery of 10 upgraded Tu-160 bombers". Russian Aviation. June 18, 2014.
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24. Tetekin, Vyacheslav; Donkovtsev, Nikolay; Kulakov, Anatoly; Korovin, Boris; Fedorchenko, Dmitry (March 26, 2013). "НК-93 – затянувшийся проект: Как демонстратор передовых технологий не пошел в серию" [NK-93 - a protracted project: As a demonstrator of advanced technology did not go into a series]. Voyenno-promyshlennyy kur'yer (Military Industrial Courier) (in Russian).
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26. "Project overview - context and challenges". COBRA Project. Retrieved July 26, 2019.
27. "Propfans: Thrust class > 10000 kgf: Technical characteristics". Aerosila. Archived from the original on October 15, 2017.
28. "Trud's NK-93 reaches better than 45,000 lbst. --- Propfan seen making its first flight next year". Special Focus. Aerospace Propulsion. Vol. 4 no. 20. McGraw-Hill. September 30, 1993. p. 3. ISSN 1050-5245 – via Factiva.
29. "Ilyushin arrives, but Antonov...who knows". Flight Daily News. June 16, 1997. ISSN 0015-3710.
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32. "World airliners: Part 2" (PDF). Flight International. Vol. 160 no. 4796. September 4–10, 2001. p. 72. ISSN 0015-3710.
33. Drozdov, Sergey Valerievich (2019). "МЕЖДУ Як-42Д И "СУПЕРДЖЕТОМ" (работы в Российской Федерации по созданию самолетов и вертолетов гражданского и двойного назначения в 1992-2011 гг.)" [Between Yak-42D and "SuperJet" (work in the Russian Federation on the development of civil and dual-use airplanes and helicopters in 1992-2011)] (PDF). Kryl'ia Rodiny (Wings of the Motherland) (in Russian). No. 5–6. pp. 106–118. ISSN 0130-2701. Archived (PDF) from the original on July 15, 2019. Alt URL
34. "NK-93" (PDF). Ulyanovsk Higher Aviation School of Civil Aviation (in Russian). 2005. pp. 49–50.
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