Fluid pressure can be open channel flow or closed passage. Open channel flow is hydrostatic, and closed passage can be hydrostatic or hydrodynamic. Brake and power steering systems use fluid pressure to increase force applied by the driver. Power steering systems use pressurized fluid to make steering easier, while brake systems use fluid pressure to activate slave cylinders at each wheel. Air and leaks can cause these systems to fail.
The two general types of fluid pressure are known as open channel flow and closed passage. Fluids in open conditions, such as air in the atmosphere or water in the ocean, are called hydrostatic. Closed-pass fluids can be either hydrostatic or hydrodynamic, and these are the conditions used to perform various types of automotive work. Two common areas that fluid pressure can be used in are brake and power steering systems. Both systems use fluid pressure to increase the force applied by the driver to steer or stop the vehicle.
Hydrostatic pressure exists in any fluid that is not moving. Open bodies, such as the oceans and atmosphere, are generally referred to as hydrostatic, although localized motions exist within these fluids. In closed systems, such as brake and power steering lines, fluids can be static or dynamic. At rest, these systems are considered hydrostatic. When the power steering pump is running or the brake master cylinder is engaged, they are governed by fluid dynamics.
Some cars use what is known as manual steering. The driver provides all the power needed to turn the wheels in these systems, so it can be very difficult to steer the vehicle. Power steering systems use pressurized fluid to do much of the work for the driver, which can make a vehicle much easier to turn. These systems consist of a pump, a rack and pinion unit or steering gearbox, and lines running between them. The pump is usually driven by the engine via the crankshaft pulley, although some vehicles use cam-driven pumps or other configurations.
After passing through a power steering pump, the fluid is sent through a pressure line to a steering gear. Valves within the gear are used to direct pressurized flow within the unit, resulting in easier handwheel turning. The fluid then returns to the pump through a low pressure line and is subsequently recirculated.
Brake systems that use fluid pressure operate in a slightly different way. These are based on a system of lines and cylinders sealed from the outside environment. When the driver steps on the brake pedal, the master cylinder creates fluid pressure within the lines. This fluid pressure activates the slave cylinders located at each wheel.
If air is allowed into one of these systems, it will not work properly because air and brake fluid compress differently. The system can also fail if a leak develops because fluid pressure requires a closed conduit to build up. It is also possible for a brake caliper, the slave cylinder on drum brakes, to get stuck. In this case, the brake caliper pressure may not be released until the system is manually opened by loosening a bleed screw.
Protect your devices with Threat Protection by NordVPN
