HYDROSTATIC LOCK

Hydrolock (a shorthand notation for hydrostatic lock) is an abnormal condition of any device which is designed to compress a gas by mechanically restraining it; most commonly the reciprocating internal combustion engine, the case this article refers to unless otherwise noted. Hydrolock occurs when a volume of liquid greater than the volume of the cylinder at its minimum (end of the piston's stroke) enters the cylinder. Since most common liquids are incompressible the piston cannot complete its travel; either the engine must stop rotating or a mechanical failure must occur.

 

Bend Connecting Rod due to Hydrolock

 

Symptoms and damage :-

If an engine hydrolocks while at speed, a mechanical failure is likely. Common damage modes include bent or broken connecting rods, a fractured head, a fractured block, crankcase damage, damaged bearings, or any combination of these. Forces absorbed by other interconnected components may cause additional damage. Physical damage to metal parts can manifest as a "crashing" or "screeching" sound and usually requires replacement of the engine or a substantial rebuild of its major components.

If an internal combustion engine hydrolocks while idling or under low power conditions, the engine may stop suddenly with no immediate damage. In this case the engine can often be purged by unscrewing the spark plugs or injectors and spinning the engine to expel the liquid from the combustion chambers and then restarted. Depending on how the liquid was introduced to the engine, it possibly can be restarted and dried out with normal combustion heat, or it may require more work, such as flushing out corrupted operating fluids and replacing damaged gaskets.

If a cylinder fills with liquid while the engine is turned off, the engine will refuse to turn when a starting cycle is attempted. Since the starter mechanism's torque is normally much lower than the engine's operating torque and momentum this will usually not damage the engine but may burn out the starter. The engine can be drained as above and restarted. If a corrosive substance such as water has been in the engine long enough to cause rusting, more extensive repairs will be required.

Amounts of water significant enough to cause hydrolock tend to upset the air/fuel mixture in gasoline engines. If water is introduced slowly enough, this effect can cut power and speed in an engine to a point that when hydrolock actually occurs it does not cause catastrophic engine damage.

 

Automotive

Hydrolock most commonly occurs in automobiles when driving through floods, either where the water is above the level of the air intake or the vehicle's speed is excessive, creating a tall bow wave. A vehicle fitted with a cold air intake mounted low on the vehicle will be especially vulnerable to hydrolocking when being driven through standing water or heavy precipitation. Engine coolant entering the cylinders through various means (such as a blown head gasket) is another common cause. Excessive fuel entering (flooding) one or more cylinders in liquid form due to or other abnormal operating conditions can also cause hydrolock.

 

DRDO - NISHANT

 The DRDO Nishant is an Unmanned Aerial Vehicle (UAV) developed by India's ADE (Aeronautical Development Establishment) a branch of DRDO for the Indian Armed Forces. The Nishant UAV is primarily tasked with intelligence gathering over enemy territory and also for reconnaissance, training, surveillance, target designation, artillery fire correction, damage assessment, ELINT and SIGINT. The UAV has an endurance of 4 h 30 min. Nishant has completed development phase and user trials. 

DRDO - NISHANT

 

 

The 380 kg (840 lb) Nishant UAV requires rail-launching from a hydro-pneumatic launcher and recovered by a Parachute System. Launches at a velocity of 45 m/s are carried out in 0.6 second with 100 kW power and subsequent launches can be carried out in intervals of 20 minutes. The Mobile Hydro-Pneumatic Launcher (MHPL) system mounted on a Tatra truck weighs 14,000 kg (31,000 lb) and boasts of a life cycle of 1000 launches before requiring overhaul. Nishant is one of the few UAVs in the world in its weight-class capable of being catapult-launched and recovered by using parachute, thus eliminating the need for a runway as in case of conventional take-off and landing with wheels.

On 3rd Feb 2011 Nishant UAV has successfully completed confirmatory trials conducted by the Indian Army at Pokhran ,Rajasthan.

 

Features

• Day/night capability training vehicle

• Battlefield reconnaissance & surveillance,

• Target tracking and localization

• Artillery fire correction

• All terrain mobility

• Target designation (using integral laser target designator)

• Endurance: 4 h 30 min

Ground support systems

• Mobile hydropneumatic launcher (MHPL)

• Ground control station (GCS)

• Antenna vehicle/Ground Data Terminal(GDT)

• Avionics preparation vehicle(APV)

• Mechanical maintenance vehicle

• UAV transportation vehicle

• Power supply vehicle

General characteristics

• Crew: None

• Payload: 45 kg

• Length: 4.63 m (15.2 ft)

• Wingspan: 6.57 m (21.6 ft)

• Empty weight: 380 kg (840 lb)

• Powerplant: 1 × RE-2-21-P or RE-4-37-P

Performance:

• Maximum speed: 185 km/h

• Cruise speed: 125 km/h to 150 km/h

• Range: 160 km (100 mi)

• Service ceiling: 3,600 m (up to 11,800 ft)

Launch & recovery

• Launch: Mobile hydropneumatic launcher (MHPL) system

• Recovery: Parachute + landing bags

DRDO DRONES- AURA(Autonomous Unmanned Research Aircraft)

AURA

The AURA will be a stealth UCAV, capable of releasing missiles, bombs and precision-guided munitions. The programme is in its project definition stage. The design is in line with what former DRDO chief controller for Aeronautics said in 2007, that India's combat drone would be a stealthy flying-wing concept aircraft with internal weapons and a turbofan engine.The UCAV's design is similar to Northrop Grumman's B-2 Spirit.The ADA describes the AURA as a "self-defending high-speed reconnaissance UAV with weapon firing capability". The first images released as part of a presentation shows the UAV as having a stealth design.The AURA will cruise at medium altitude and will be capable of carrying two or more guided strike weapons with on-board sensors for targeting and weapon guidance. The flight control system and data link packages of Aura (unmanned combat aerial vehicle) will be designed and developed jointly by ADA and Defense Electronic Application Laboratory. DRDO's Chief Controller, R&D (aeronautics), Dr Prahlada said, "Capable of flying at altitudes of 30,000 feet and weighing less than 15 tonnes, the UCAVs will have rail-launching for the missiles, bombs and PGMs (precision-guided munitions) they will carry.". The DRDO is going to use a Kaveri engine to power this unmanned vehicle. The AURA will be approximtely 15 tonnes aircraft with a range of 300+ km.

AURA (Autonomous Unmanned Research Aircraft)
Role	Unmanned Stealth Bomber
Manufacturer	DRDO
Designer	DRDO
First flight	2015
Introduction	2019-2020
Status	Under Development
Primary user	Indian Air Force Indian Navy

STIRLING ENGINE

A Stirling engine is a heat engine operating by cyclic compression and expansion of air or other gas, the working fluid, at different temperature levels such that there is a net conversion of heat energy to mechanical work.Or more specifically, a closed-cycle regenerative heat engine with a permanently gaseous working fluid, where closed-cycle is defined as a thermodynamic system in which the working fluid is permanently contained within the system, and regenerative describes the use of a specific type of internal heat exchanger and thermal store, known as the regenerator. It is the inclusion of a regenerator that differentiates the Stirling engine from other closed cycle hot air engines. Originally conceived in 1816 as an industrial prime mover to rival the steam engine, its practical use was largely confined to low-power domestic applications for over a century. The Stirling engine is noted for its high efficiency compared to steam engines,quiet operation, and the ease with which it can use almost any heat source. This compatibility with alternative and renewable energy sources has become increasingly significant as the price of conventional fuels rises, and also in light of concerns such as peak oil and climate change. This engine is currently exciting interest as the core component of micro combined heat and power (CHP) units, in which it is more efficient and safer than a comparable steam engine.

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