ROTARY ENGINE FOR UAVs

Technology
ISSN : 0971-4413
BULLETIN OF DEFENCE RESEARCH AND
DEVELOPMENT ORGANISATION
Vol. 17 No. 6 December 2009
ROTARY ENGINE FOR UAVs
R
OTARY ENGINE is an emerging
technology and only few
countries in the world have the
capability of developing the rotary
engines. Rotary engines are being
used mainly for the aerial or special
applications like racing cars where the
power-to-weight ratio is very critical.
These engines have high power-toweight ratio, compact design, less
vibration, less balancing problem, etc.
Many unmanned air vehicles (UAVs)
are also equipped with rotary engines
having certain advantages over the
conventional reciprocating engines.
Vehicles Research and Development
Maiden flight trials of rotary engine (inset) on Nishant UAV
Establishment (VRDE)—a premier lab of Defence Research and Development Organisation (DRDO)—and National Aerospace
Laboratories (NAL), Bengaluru, have jointly designed and developed an indigenous rotary engine for application in UAVs. Some
of the important and critical technologies established for the engine are: Rotor,
housings, eccentric shaft, gear train, ignition system, and lubrication system.
In this Issue
Rotatry Engine for UAVs
84 mm LWL System
Sanjeevani
DRDO Test Facilities
Scramjet Combustor Facility
Shock Test Facility
Development of Rotor
Rotor performs the function of piston of a reciprocating engine. It directly
transmits the pressure of the combustion gases to the eccentric shaft as a turning
moment. Rotor should withstand high temperature generated due to
combustion. The design of rotor satisfying all the requirements was a challenge
overcome by using best available tools and techniques.
Rotor profile was generated by complex parametric equations. Recess
volume, needed to have a particular shape to perform best combustion
characteristics, was provided on the flanks to obtain the required compression
Technology
ratio. Special fixtures have been developed for the
manufacturing of rotor. Profile of the rotor (central
triangular portion) was cut on the cast block using wirecut electro discharge machining (EDM), and computer
numerical control (CNC) vertical milling was used for
cutting grooves for seals and generating combustion
chamber recess.
Development of Housings
The rotary engine comprises three types of
housings, i.e., drive side housing, non-drive side
housing, and central housing. The drive side housing is
located at propeller side, non-drive side housing at
opposite end, and central housing (in which rotor
rotates) is located centrally.
Machining of combustion chamber
Housings are provided with internal paths for liquid
and air cooling. The side housings are liquid cooled by
the circumferential flow of water and ethylene glycol
mixture, whereas central housing has both liquid and air
cooling paths. Housings were manufactured by gravity
Dies for housing. Central housing (right)
die casting for which various patterns, cores, and dies
were designed to manufacture typical cooling paths.
Central housing is the same as cylinder of the
reciprocating engine. The internal geometry of this
housing is an epitrochoidal curve. The coordinates of
the epitrochoidal curve were obtained from the
standard equation and corresponding profile was
prepared on solid model. Epitrochoidal profile was cut
on wire-cut EDM machine leaving a scope for 120
micron of coating and grinding over epitrochoidal
Patterns and cores
portion. Nickel–silicon carbide composite coating, also
known as Nicasil coating, was done over the bore of the
trochoid because of its exceptional wear-resistance and
low-friction properties. It also provides greater oil
retention than chromium or steel.
Development of Eccentric Shaft
2
Eccentric shaft transmits the torque developed from
the combustion force. It drives various accessories like
Non-drive and drive side housings
Stationary gear
Rotor gear
Eccentric shaft
Eccentric shaft fixtures
blower, water pump, and lubrication pump of the
engine. The eccentric shaft carries balance
weights—one at the front side and another at the rear
side. The shaft is subject to torsional shear stress due to
torque transmission, bending stress due to weight of
mountings, and belt tensions to blower and water
pump.
VRDE has manufactured eccentric shaft
using
special fixtures with desired accuracy.
Development of Gear Train
The rotary engine is equipped with a synchronising
gear pair for controlling the orbital motions of the rotor.
The synchronising gear pair comprises an internal gear
(rotor gear) and an external pinion (stationary gear). The
stationary gear and rotor gear are designed for a gear
ratio of 2:3. The rotor gear is an integral part of the rotor
and is fitted in the rotor by shrink fit. Stationary gear is
fixed at drive side housing.
The rotor gear meshes with the stationary pinion to
enable the rotor to follow the trochoidal path in central
housing and maintains the required 1: 3 rotor-to-output
Rotor housing and eccentric shaft assembly
shaft speed ratio; 120o of rotor rotation means one
complete revolution of the output shaft. Stationary
pinion comprises a flange and an internal mating gear.
Gear shaping is therefore the most suitable method for
manufacturing a gear.
Development of Ignition System
The capacitive discharge ignition system has been
used for supplying full voltage output at high engine
speeds instead of two spark plugs which fire
simultaneously. Besides, two spark plugs increase
redundancy in the air vehicle. The capacitive discharge
ignition system also has an ability to supply full voltage
output at low engine speed. The engine has a very fast
voltage rise, which reduces energy lost in shunt
resistances, which makes it possible to operate plugs in
fouling condition also. In addition, there are no breakers
or rubbing blocks that require adjustment because of
wear.
3
Technology
Rotary engine on thrust cradle test rig
Capacitive discharge ignition system
Status
Two prototype engines have been ground tested as per testing agencies guidelines. Engines developed 55 hp at
8000 rpm on dynamometer and 93 kgf thrust with a flight propeller at 7400 rpm, which is comparable with
corresponding imported engine on thrust cradle. During this development process, critical technologies for the
development of various components were established in the country. Ground testing, i.e., testing on thrust cradle and
dynamometer has also been completed successfully.
First ever-successful test-flight of an indigenous Rotary Engine powering indigenous UAV Nishant was carried out
at Kolar, near Bengaluru, on 31 March 2009.
Salient Features
4
Type
:
Single rotor Wankel engine
Power output
:
55 bhp at 8000 rpm
Displacement
:
324 cc
Compression ratio
:
9.2:1
Idle speed
:
2700–2900 rpm
Specific fuel consumption
:
250 gm/bhp hr
Cooling
:
Water cooled housings and air cooled rotor
Lubrication system
:
Total loss type forced lubrication
84 mm LIGHTWEIGHT LAUNCHER SYSTEM
D
RDO's Armament Research and Development
Establishment (ARDE), Pune, has successfully
developed 84 mm Lightweight Launcher (LWL). This is an
effective antitank infantry weapon which is manportable, shoulder-fired, and works on recoilless (RL)
principle. Its lightweight, approximately 50 per cent that
of 84 mm RL Mk II, will enhance the mobility, the
ammunition carrying capacity, and the combat efficiency
of the troops. Barrel of the weapon has been designed
and developed indigenously with hybrid composite
technology. Manufacturing technology of the launcher
system has also been established for the first time in the
country. The launcher can be used from standing,
84 mm lightweight launcher
kneeling/seating, and prone positions by the crew of two,
and will especially be effective in high altitude warfare.
Mount brackets, furniture items, and carrier system of the
launcher have been designed and developed using the
advanced lightweight engineering materials technology.
The ultrasonic and acoustic emission non-destructive
evaluation (NDE) techniques have also been established
to check the structural integrity of the launcher system.
Sub-systems
The 84 mm lightweight launcher comprises the
barrel assembly, carrier case, and carrier system. The
barrel assembly comprises composite gun barrel, firing
mechanism, shoulder pad, ventury, bipod, telescopic day
and night sight front, and firing grips, etc. The carrier case
assembly is meant to hose the weapon and the fitment
items during transportation. It also protects the weapon
from moisture, rain, UV radiation, and humidity.
Technical Specifications
Calibre
:
84 mm
Launcher
:
10 + 5 kg
Carrier
:
3.5 kg
Length of launcher
:
1065 mm
Mass
Firing positions clockwise from right top: Kneeling; prone;
and standing
5
Technology
Carrier case and system for 84 mm lightweight launcher
Muzzle velocity
:
290 m/s for HEAT
Armour penetration
:
> 400 mm on RHA
Sustain rate of fire
:
6-8 rounds/min
Sighting system
:
Telescopic day sight, passive night sight, flare sight, and open sight
Training device
:
9 mm sub-calibre
Type of ammunition
Indigenous
:
HEAT, HE, illuminating, TPT and 9 mm sub-calibre
Ex-import
:
HEAT-RAP, HEDP, SMK
HEAT
:
400 m
HE
:
1000 m
Illuminating
:
2100 m
:
:
700 M
Two
Effective firing range
HEAT-RAP
Crew
Technological Achievements
Hybrid composite technology developed for gun barrel application
Mount brackets, furniture items, carrier system, etc., designed using advanced lightweight engineering materials
Ultrasonic and acoustic emission NDE techniques developed for structural health monitoring of gun barrel
Advantages
Reduced fatigue
Enhanced mobility
Enhanced ammunition carrying capacity
6
Improved combat efficiency
SANJEEVANI THE LIFE DETECTING DEVICE
anjeevani is a civilian spin-off of the naval technology being developed by DRDO's Naval Physical and
Oceanographic Laboratory, Kochi. Sanjeevani is used for detecting live human beings trapped under debris of
collapsed buildings, mines or landsides. It can be used in all emergency rescue operations of such nature. The low-level
acoustic or sound signals, which are indicative of life, generated by victims by hitting, tapping, scratching or moaning
can be detected by the device. It is very effective in detecting sounds through air or through the brick walls even when
the source of sound is a few meter away. Sanjeevani can even detect the sound signals in situations where the distance
between the source of sound and the sound detector in the equipment is flooded with water.
Sanjeevani has three sub-systems, viz., an electronic assembly, a probe assembly, and a headphone set. The device
is very elegant, lightweight and portable, and can be operated by a single person. The operator can also speak to the
victim, if required, through a microphone attached to the headset.
The electronic assembly of Sanjeevani has been fitted on a waist belt. The probe assembly consists of an acoustic
sensor, probe head, telescopic tube, and a plastic handle. The headphone consists of two earphones, a bracket that
rests on the head and, a phone jack with cable for connection to the electronic assembly. The probe head can be used in
air, water, mud and even in sand or loose soil, but at a reduced efficiency. Probe is a hand-held device comprising a
sensor and a preamplifier. The probe tube, whose length can be varied from one metre to two metre, is telescopic in
nature. The output of the sensor is taken through a special cable that passes through a PVC tube and is given as input to
the electronics module—a very small and compact unit mounted on a nylon waist belt while in operation. Models with
flexible probes have also been designed for use in different situations.
Amplifier output
:
250 mw (max)
Power supply
:
6V DC (4 AA type batteries)
Continuous operating life
:
8h
Technology
While measuring shock acceleration
of equipment, it is more often
required to record its shape to
further determine the required
acceleration parameters by
processing of data. The most usable
of these are:
Peak acceleration value
Total rise time of shock
Pulse duration
A shock testing machine is a
mechanical device that applies a
mechanical shock to the equipment
under test. Shock Test Facility at
Shock test facility
DRDO is a sophisticated engineering
installation intended to carry out testing of various objects for their resistance to shock. It is a two-sided horizontal
pendulum type stand designated to test objects for their resistance to single powerful shock and for special purpose
testing.
Testing Range
The facility operates on the deceleration principle. Kinetic energy accumulated by the body in the course of
preliminary speed up is damped during collision with a fixed barrier, thus inducing the resulting test loading. The shock
parameters can be varied by changing the drop height of the stand and the rubber thickness of the pulse shaper.
Shock Test Mode
While selecting the shock test mode, the full scale environmental shock is substituted by one or several pulses of
simple shape such that the shock spectrum of these pulses overlaps the spectrum of a more complicated
environmental shock throughout the frequency band under consideration.
Specifications
Corset Side
10
Platform Side
Length
:
4-12 m
Length
:
1.5 m (max)
Diameter
:
0.4-0.9 m
Diameter
:
1.5 m (max)
Mass
:
10 ton (max)
Height
:
2 m (max)
Mass
:
2 ton (max)
Corset side
Platform side
Shock Parameters
Mass (kg)
Shock acceleration range
Mass (kg)
Shock acceleration range
10, 000
4 g (min) at 72 ms
30 g (max) at 17 ms
2, 000
3 g (min) at 65 ms
38 g (max) at 14 ms
5, 000
4 g (min) at 63 ms
36 g (max) at 20 ms
1, 000
5 g (min) at 62 ms
43 g (max) at 16 ms
2, 500
5 g (min) at 53 ms
40 g (max) at 24 ms
500
5 g (min) at 60 ms
40 g (max) at 16 ms
Data Acquisition and Analysis
LMS SCADAS-based data acquisition system
High-speed data acquisition
Tuned to meet specific requirements of shock measurement
High-speed camera
Hardware
Host workstation with high-speed processor
Strain gauge amplifier module
Signal conditioning module
32-channel IPC/voltage input module
4-channel analog output module
25–10, 000 g accelerometer range
0.1–4, 000 kN force sensor range
Software
Striker
Pulse Shaper
Buffer Mass
Integrated with LMS test lab software
FFT with resolution of 6, 400 lines
Shock input position
11
Technology
Statistical analysis
2-D/3-D graphs
Real-time zoom
Fast automatic report
Measured Parameter
Peak acceleration value
Total rise time of shock acceleration
Shock pulse duration and wave form
Impact force
Applications
Tests for shock resistance and shock stability of equipment
are used in the following fields:
LMS SCADAS-based data acquisition system
Automobiles: For suspension system, and motion start and stop
Aerospace: For stage separation, arrest landing, and landing gear
Defence: For shock absorber testing, missile stage separation, and catapult launch
Machinery structure and engineering instruments: For shock worthiness test, shock mount, and packaging
test
Technology Focus focuses on the technological developments in the Organisation, covering the products, processes and technologies.
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Editorial Committee
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Coordinator
Dr AL Moorthy, Director, DESIDOC, Metcalfe House, Delhi
Members
Dr BR Gandhe, Director of Armaments, DRDO Bhavan, New Delhi
Dr Sudarshan Kumar, Director of Materials, DRDO Bhavan, New Delhi
Shri R Shankar, Director of CV&E, DRDO Bhavan, New Delhi
Cmde PK Mishra, Director of Naval Research & Development
DRDO Bhavan, New Delhi
Shri Ranjit Elias, SO to SA to RM, DRDO Bhavan, New Delhi
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Editor-in-Chief
AL Moorthy
Assoc. Editor-in-Chief
Shashi Tyagi
Editors
B Nityanand
Manoj Kumar
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Printing
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Distribution
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Printed & published by Director, DESIDOC, on behalf of DRDO