Kuznetsov NK-12



The Kuznetsov NK-12 is a Soviet turboprop engine of the 1950s, designed by the Kuznetsov design bureau. It drives two large four-bladed (eight blades per engine) contra-rotating propellers, 5.6 m (18 ft 4.5 in) in diameter, and 6.2 m (20 ft 4.1 in) in the NK-12MA and NK-12MV. It is the most powerful turboprop engine to enter service.

Design and development
The design that eventually became the NK-12 turboprop was developed after World War II by a team of Russian scientists and deported German engineers under Ferdinand Brandner, who had worked for Junkers previously; the design bureau was headed by chief engineer Nikolai D. Kuznetsov. Thus, the NK-12 design evolved from late-war German turboprop studies. This started with the postwar development of the wartime Jumo 022 turboprop design that developed 6000 eshp in a 3000 kg (6,600 lb) engine. The effort continued with a 5000 ehp engine that weighed in at 1700 kg (3,740 lb), completed by 1947. The evolution to the TV-12 12000 Ehp engine required extensive use of new Soviet-developed alloys and was completed in 1951.

The NK-12M developed 8,948 kW (12,000 ehp), uprated in the NK-12MV to 11,033 kW (14,795 ehp) and reaching 11,185 kW (15,000 ehp) in the NK-12MA. The NK-12 remains the most powerful turboprop engine to enter service although the Progress D-27 and Europrop TP400 have come close to this (in 1982 and 2005 respectively). Another engine of similar size, the Pratt & Whitney T57 with 15,000 shp and 5,000 lb jet thrust, ran 3,100 hours before being cancelled in 1957. The NK-12 powers the Tupolev Tu-95 bomber and its derivatives such as the Tu-142 maritime patrol aircraft and the Tupolev Tu-114 airliner (with NK-12MV), which still holds the title of the world's fastest propeller-driven aircraft despite being retired from service in 1991. It also powered the Antonov An-22 Antei (with NK-12MA), the world's largest aircraft at the time, and several types of amphibious assault craft, such as the A-90 Orlyonok "Ekranoplan".

The engine has a 14-stage axial-flow compressor, producing compression ratios between 9:1 and 13:1 depending on altitude, with variable inlet guide vanes and blow-off valves for engine operability. The combustion system used is a cannular-type: each flame tube is centrally mounted on a downstream injector that ends in an annular secondary region. The contra-rotating propellers and compressor are driven by the five-stage axial turbine. Mass flow is 65 kg (143 lb) per second.

Applications

 * A-90 Orlyonok
 * Antonov An-22
 * Tupolev Tu-95
 * Tupolev Tu-114
 * Tupolev Tu-116
 * Tupolev Tu-126
 * Tupolev Tu-142