BULLETIN OF DEFENCE RESEARCH ANDDEVELOPMENT ORGANISATION

ISSN : 0971-4413

Technology Vol. 17 No. 6 December 2009

Technology

OTARY ENGINE is an emerging t e c h n o l o g y a n d o n l y f e w R

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-to-weight 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 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.

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

Development of Rotor

In this IssueRotatry Engine for UAVs

84 mm LWL System

Sanjeevani

DRDO Test FacilitiesScramjet Combustor Facility

Shock Test Facility

ROTARY ENGINE FOR UAVsROTARY ENGINE FOR UAVs

Maiden flight trials of rotary engine (inset) on Nishant UAV

Technology

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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 wire-cut electro discharge machining (EDM), and computer numerical control (CNC) vertical milling was used for cutting grooves for seals and generating combustion chamber recess.

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.

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 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 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.

Eccentric shaft transmits the torque developed from the combustion force. It drives various accessories like

Development of Housings

Development of Eccentric Shaft

Machining of combustion chamber

Patterns and cores

Non-drive and drive side housings

Dies for housing. Central housing (right)

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.

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

Development of Gear Train

oshaft speed ratio; 120 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.

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.

Development of Ignition System

Eccentric shaft

Eccentric shaft f ixtures

Stationary gear Rotor gear

Rotor housing and eccentric shaft assembly

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Technology

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.

Capacitive discharge ignition system Rotary engine on thrust cradle test rig

Salient Features

Displacement : 324 cc

Type : Single rotor Wankel engine

Idle speed : 2700–2900 rpm

Cooling : Water cooled housings and air cooled rotor

Power output : 55 bhp at 8000 rpm

Compression ratio : 9.2:1

Specific fuel consumption : 250 gm/bhp hr

Lubrication system : Total loss type forced lubrication4

RDO's Armament Research and Development DEstablishment (ARDE), Pune, has successfully developed 84 mm Lightweight Launcher (LWL). This is an effective antitank infantry weapon which is man-portable, 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, 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.

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.

Calibre : 84 mm

MassLauncher : 10 + 5 kgCarrier : 3.5 kg

Length of launcher : 1065 mm

Sub-systems

Technical Specifications

84 mm lightweight launcher

Firing positions clockwise from right top: Kneeling; prone; and standing

84 mm LIGHTWEIGHT LAUNCHER SYSTEM84 mm LIGHTWEIGHT LAUNCHER SYSTEM

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Technology

Muzzle velocity : 290 m/s for HEAT

Armour penetration : > 400 mm on RHA

Type of ammunitionIndigenous : HEAT, HE, illuminating, TPT and 9 mm sub-calibreEx-import : HEAT-RAP, HEDP, SMK

Effective firing rangeHEAT : 400 mHE : 1000 mIlluminating : 2100 mHEAT-RAP : 700 M

Crew : Two

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

Reduced fatigue

Enhanced mobility

Enhanced ammunition carrying capacity

Improved combat efficiency

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

Technological Achievements

Advantages

Carrier case and system for 84 mm lightweight launcher

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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 AA type batteries)

Continuous operating life 8 h

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SANJEEVANI THE LIFE DETECTING DEVICESANJEEVANI THE LIFE DETECTING DEVICE

Technology

While measuring shock acceleration of equipment, it is more often required to record its shape to further determine the required a c c e l e r a t i o n p a r a m e t e r s b y 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 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.

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.

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.

Testing Range

Shock Test Mode

Specifications

Corset Side Platform Side

Length : 4-12 m Length : 1.5 m (max)

Diameter : 0.4-0.9 m Diameter : 1.5 m (max)

Mass : 2 ton (max)

Mass : 10 ton (max) Height : 2 m (max)

Shock test facility

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Shock Parameters

Data Acquisition and Analysis

Hardware

Software

LMS SCADAS-based data acquisition systemHigh-speed data acquisitionTuned to meet specific requirements of shock measurementHigh-speed camera

Host workstation with high-speed processorStrain gauge amplifier moduleSignal conditioning module32-channel IPC/voltage input module4-channel analog output module25–10, 000 g accelerometer range0.1–4, 000 kN force sensor range

Integrated with LMS test lab software

FFT with resolution of 6, 400 lines

Mass (kg) Shock acceleration range Mass (kg) Shock acceleration range

10, 000 4 g (min) at 72 ms 2, 000 3 g (min) at 65 ms30 g (max) at 17 ms 38 g (max) at 14 ms

5, 000 4 g (min) at 63 ms 1, 000 5 g (min) at 62 ms36 g (max) at 20 ms 43 g (max) at 16 ms

2, 500 5 g (min) at 53 ms 500 5 g (min) at 60 ms40 g (max) at 24 ms 40 g (max) at 16 ms

Corset side Platform side

Shock input position

Buffer Mass

Pulse Shaper

Striker

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Technology

Statistical analysis2-D/3-D graphsReal-time zoomFast automatic report

Peak acceleration valueTotal rise time of shock accelerationShock pulse duration and wave formImpact force

Tests for shock resistance and shock stability of equipment are used in the following fields:Automobiles: For suspension system, and motion start and stopAerospace: For stage separation, arrest landing, and landing gearDefence: For shock absorber testing, missile stage separation, and catapult launchMachinery structure and engineering instruments: For shock worthiness test, shock mount, and packaging test

Measured Parameter

ApplicationsLMS SCADAS-based data acquisition system

Printed & published by Director, DESIDOC, on behalf of DRDO

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esVdkWQ gkml] fnYyh Dr AL Moorthy, Director, DESIDOC, Metcalfe House, Delhi

Dr BR Gandhe, Director of Armaments, DRDO

Director of Materials, DRDO

Shri R Shankar, Director of CV&E, DRDO Bhavan, New Delhi

Director of Naval Research & Development

DRDO

Shri Ranjit Elias, SO to SA to RM, DRDO Bhavan, New Delhi

Coordinator

Members

Bhavan, New Delhi

Dr Sudarshan Kumar, Bhavan, New Delhi

Cmde PK Mishra,

Bhavan, New Delhi

Editorial Committee

Technology Focus focuses on the technological developments in the Organisation, covering the products, processes and technologies.