Between Wind And Waves
Gas-Turbine Engines For Wingships
V.S.Gagai
(Chief Designer Aviamotor Enterprise, Merited Machine-Builder, Tatar Republic)
During the last decades, Russian aircraft and ship
designers headed by R.Ye.Alekseyev, have developed and
manufactured a unique design of wingships. The prime example is
the ORLYONOK which is capable of flying at a speed of 350-400km/h
and can operate in sea states with up to 1.5m wave height. The
LUN wingship is capable of a speed of 500km/h and is seaworthy
in conditions up to 2.5m wave height.
Both of these wingships are powered by aircraft
gas-turbine engines produced under the guidance of General
Designer N.D.Kuznetsov, and have been operated on civil aircraft
for many years.
The conversion of the NK-8-4K and NK-87 engines used in
these designs was carried out by a group of engineers from the
Design and Production State Enterprise Aviamotor. The NK-8-4K
and the NK-87 are manufactured at the Kazan Engine-Building
Production Association while the NK-12MK, also used in wing ship
construction, is manufactured by the Samara Engine-Building
Production Association.
The family of NK engines where selected for this unique
operation based on their high reliability, moderate gas-dynamic
parameters and high economy in the third-generation engine
class.
The conversion process involved adoption of a number of
solutions, both design and technological, to provide a high
degree of reliability when working close to water. This process
included:
- protection of main units and components against the
corrosive effect of sea water;
- reinforcement of hull units to sustain increased vibration
overloads when taking off from a rough surface;
- development of an effective system for flushing the engine
blading section to restore the dynamic parameters of a salinated
engine and to protect this from unseparated air which would tend
to find its way in to the inlet;
- special protection of engine air intakes against
birdstrikes (an expected problem when wingships operate in the
offshore zone);
- development of a monitoring system including on-board
computers to allow the workload of the crew to be reduced;
- developing a system of tests for simulating the maximum
degree of engine loading in sea water.
To allow manufacture of the NK-8-4K and NK-87 engines the
Kazan Engine-Building Production Association and Aviamotor have
considerably re-equipped their production process, including:
- re-equipping existing the large-size casting section for
high-strength corrosion-resistant aluminium alloy;
- improving the section responsible for applying special heat-
and corrosion-resistant multicomponent coatings to turbine
blades;
- development of a special stand for multi-component loading
of hull parts, simulating vibration overloads with the wingship
taking off from a rough sea;
- development and production of special test equipment to
simulate engine operating conditions in water and flight
conditions on a stand;
- reduction of the cost of a converted engine - where the
production process envisaged a reduction in labour in
re-equipping rigging used in the manufacture of engine units and
parts.
In conformity with both Russian and international
certification requirements the wingships engines have been
subjected to comprehensive testing to cover all best and worst
case scenarios in different operating conditions, as provided
for in the widely recognised Seaworthiness Regulations and the
ship safety code.
In addition, the experience accumulated in the process of
developing and manufacturing converted engines, and also a study
of international experiences in the use of aircraft gasturbine
engines in multi-purpose displacement-type ships, has provided a
solid reasoning and logic for adopting the NK family of engines
as power plants for marine craft.
It is also of interest that screw propellers can be driven
by free turbines that are also produced at Kazan and Samara for
use at gas-pumping stations.
Adoption of such a system allows:
- drastic reductions in the cost of design and operation of
ships' power plants;
- significant reduction in weight and overall dimensions of
marine engines and reduction gears owing to the use of light
aircraft planetary reduction gears.
Given below is a list and specifications of engines in
current use and those being developed for wingships and
conventional displacement-type ships.
======================================================================================================
THE NK FAMILY OF GAS TURBINE ENGINES
FOR WINGSHIPS
======================================================================================================
TYPE APPLICATION BASE THRUST/ GAS I Specific Fuel Consumption I COMMISSIONED
ENGINE POWER TEMP ~K I---------- sfc -------------I
tf MW I kg/kgt-h I kg/MW I
----------------------------------------------------------+------------+---------------+--------------
IN OPERATION
----------------------------------------------------------+------------+---------------+--------------
NK-12M CRUISE NK-12 11MW 1263 I I 0.277 I 1970
NK-87 CRUISE/ NK-86 13tf 1280 I 0.54 I I 1984
BOOSTER I I I
NK-8-4K BOOSTER NK-8-4 10.5tf 1260 I 0.58 I I 1970
------------------------------------------------------------------------------------------------------
IN DEVELOPMENT
----------------------------------------------------------+------------+------------------------------
NK-93K CRUISE NK-93 19tf 1660 I 0.2 I I 1998
NK-44K CRUISE NK-44 40tf 1580 I 0.325 I I 1997
NK-26K CRUISE NK-12MA 11.25MW 1330 I I 0.266 I 1996
======================================================================================================
|
======================================================================================================
SHIP PROPULSION
------------------------------------------------------------------------------------------------------
TYPE APPLICATION BASE THRUST/ PROPELLER Specific Fue Efficiency COMMISSIONED
ENGINE POWER RPM Consumption
sfc
tf MW kg/kW kg/kp-h
------------------------------------------------------------------------------------------------------
NK-38K CRUISE NK-93 16 22 5300 0.228 0.163 38 1996
NK-36K CRUISE NK-321 25 34 5000 0.242 0.178 36.4 1995
NK-37-1K CRUISE NK-321 30 42 3000 0.232 0.171 37.3 1996
NK-14K CRUISE NK-12 08 11 8000 0.262 0.193 32 1995
NK-16K BOOSTER NK-8-2Y 16 22 5300 0.310 0.228 29 1994
======================================================================================================
|
Conclusions
As a result of extensive work in the application of the NK
family to a new range of maritime roles NK-8-4K engines have
been supplied for the ORLYONOK wingship and the NK-87 engines
have been supplied for the LUN wingship.
Experimental operation of the engines on wingships has
confirmed the design and concept behind our work in this field.
Following their "proof of principle" further efforts covering
operational reliability are to be explored.
An analysis of the wingships' power-toweight ratio has
shown that the considerable difference in the requisite thrust
during the take-off and cruising make it expedient to use two
types of engines - booster and cruise.
Our own analysis had made it possible to draw up specific
requirements for cruise and booster engines with a view to
attaining the optimum operational and economy characteristics
required for this type of craft.
The experience and expertise that is available at the Kazan
Engine-Building Production Association and the Design and
Production State Enterprise Aviamotor in converting aircraft
engines for operation in maritime conditions is now fully
recognised. This fact is recorded through the planned and actual
development of a number of engines for wingships and
conventional displacement-type ships that have been proposed
jointly with the Joint Research and Production Enterprise Trud.
from "MILITARY TECHNOLOGY, Special Issue", 1994
|
