Hydrolock (short notation for hydrostatic lock ) is an abnormal condition of any device designed to compress gas by mechanically resisting; most common internal combustion reciprocating engine, the case of this article refers to unless otherwise stated. Hydrolock occurs when the liquid volume is greater than the volume of the cylinder at the minimum (the end of the piston stroke) enters the cylinder. Because the fluid is almost incompressible the piston can not complete its journey; either the engine must stop spinning or a mechanical failure should occur.
Video Hydrolock
Symptoms and breakdown
If the engine hydrolock is at speed, mechanical failure may occur. Common damage modes include bent or broken ridge rid, cracked crank, cracked head, cracked block, crank case damage, defective bearing, or a combination of both. Forces absorbed by other interconnected components may cause additional damage. Physical damage to metal parts may manifest as "bumping" or "shrill" sound and usually requires substantial engine replacement or reconditioning of the main components.
If the internal combustion engine hydrollock when in idle state or in low power conditions, the machine can stop suddenly without direct damage. In this case the machine can often be cleaned by releasing spark plugs or injectors and rotating the engine to remove the liquid from the combustion chamber and then restart. Depending on how the liquid is introduced to the engine, it may be restarted and dried by normal combustion heat, or may require more work, such as discharging a malfunctioning liquid and replacing a defective gasket.
If the cylinder fills with liquid when the engine is turned off, the machine will refuse to turn when the initial cycle is attempted. Since the torque starter mechanism is usually much lower than the engine operating torque, this usually does not damage the engine but can burn the starter. The machine can be dried as above and restarted. If a corrosive substance such as water has been in the machine long enough to cause rusting, a wider improvement will be required.
A significant amount of water causes the hydrolock to interfere with the mixture of air/fuel in the gasoline engine. If water is introduced slow enough, this effect can cut power and speed in the machine to the point that when the hydrolock actually happens it does not cause catastrophic engine damage.
Maps Hydrolock
Causes and special cases
Automotive
Hydrolocks are most common in cars when driving through floods, either where water is above the level of air intake or excessive vehicle speed, creating high arc waves. A vehicle equipped with low air intake mounted on the vehicle will be very susceptible to hydrolocking when pushed through puddles or heavy rains. The engine coolant that enters the cylinder through various means (such as exploding gaskets) is another common cause. Excessive fuel enters (flooding) one or more cylinders in liquid form due to abnormal operating conditions can also cause hydrolock.
Marine
Small boats with outboard engines and PWC tend to swallow water just because they run in and around it. During the rollover, or when the wave washes over the plane, the engine can be hydrolocked, although severe damage is rare due to special air intakes and low rotary inertia of small marine engines. Marine ship engines have different vulnerabilities because often the cooling water mixes with the exhaust gases in the header to calm the engine. A rusty exhaust header or an old starter rotation period can cause water to accumulate in the drain until it returns through the exhaust manifold and fills the cylinder.
Diesel engine
Diesel engines are more susceptible to hydrolock than gasoline engines. Due to the higher compression ratio, the diesel engine has a much smaller volume of combustion chamber, requiring far less fluid than hydrolock. Diesel engines also tend to have higher torque, spinning inertia, and a starter motor that is stronger than a gasoline engine. The result is that diesel engines are more likely to suffer major damage.
Radial and reverse engine
Hydrolock is common on radial and reverse engine (cylinder pointing down) when the machine sits for a long time. Engine oil seeps down the gravity into the cylinder through various means (via ring, valve guides, etc.) and can fill the cylinder with enough oil to hydrolyze it. The seepage effect can be observed by the usual blue-and-white smoke seen when the radial machine is run. To prevent engine damage, this is a universal practice for ground crew or pilots to check hydrolock during aircraft pre-flight inspections, usually by hand crank for multiple turns to ensure normal crankshaft cycles through all cylinders.
Steam engine
Hydraulic locks can occur in steam engines because the steam condenses back into the water. In most steam engine designs there should be a small moment at the end of the piston's return when all the valves are closed and compressing the remaining vapors. Water can be introduced from the boiler or in a cold machine, the steam will condense into water on the cold wall of the cylinder and potentially hydrolock the engine. It is as destructive as in internal combustion engines and in the case of steam locomotives can be very dangerous because the damaged connecting rods can pierce the furnace/boiler and cause a steam explosion. Steam engines (with the exception of small models and toy engines) are always equipped with cylinder drain cylinders that are opened to allow excess water and steam to escape during heating.
References
Source of the article : Wikipedia
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