Presentation on theme: "PISTON ENGINES Part 4 Piston Engine Operations (Oil and Fuel Pumps)"— Presentation transcript:
PISTON ENGINES Part 4 Piston Engine Operations (Oil and Fuel Pumps)
Introduction Oil Systems Lubrication is used between 2 sliding surfaces to overcoming friction, and therefore prevent or reduce component wear. The properties demanded from a lubricant vary considerably with the particular application. Lubricant for a bicycle is not suitable for a steam engine; a lubricating oil for any engine should be of a suitable viscosity for maximum loads and also retain this viscosity over the full range of engine temperature.
Engine Block SUMP Oil Systems The ‘Wet Sump’ System Common to most vehicles Filter Pump Oil is stored in the sump and pulled out, through a strainer, by a pump. The oil then passes through a filter to ensure it is clean etc. It then passes into the engine, returning excess oil to the sump.
Engine Block SUMP Oil Systems Filter Pump High Performance/Rally vehicles and Aircraft Tank The ‘Dry Sump’ System Oil is stored in a separate tank, but still pulled by pump through a strainer, and passed through a filter into the engine, returning excess oil to the sump.
Engine Block SUMP Oil Systems Filter Pump High Performance/Rally vehicles and Aircraft Tank Scavenge Pump The ‘Dry Sump’ System But the oil is then taken out of the sump by a scavenge pump & returned to the tank, hence the name ‘Dry Sump’ This gives protection against oil loss in cars; and helps maintain correct levels of lubrication in aircraft.
Oil flowing from the pump is passed through the filter, and then forced along internal passageways to the areas needing lubrication. The oil lubricates the ball and roller bearings, gear teeth, piston rings, cylinder walls and other moving parts, then drains to the sump. Let’s take a closer look here. Oil Distribution Sump (Oil Tank) Pump Filter
The illustration shows the main bearing locations for: - Crankshaft support bearings. Conrod to crankshaft bearings (big-ends) for each piston. The gudgeon pins. In addition (not illustrated) are other bearings required to provide smooth running of other components such as the cam shaft, water pump drive shaft, oil pump drive shaft etc. Let’s take a closer look here. Oil Distribution Bearing Lubrication Flywheel Front Support Bearing Rear Support Bearings SupportBearings GudgeonPin Crankshaft Con Rod A 4 CYLINDER ENGINE CRANKSHAFT 1 234
Con Rod Big End Oil Distribution Bearing Lubrication Crankshaft Shell Bearings The illustration shows a cross sectional view of a plain bearing. The plain bearings are made up of two distinct halves, called ‘shell’ bearings, and the big-ends are fixed to prevent rotation in the conrod.
Con Rod Big End Oil Splash Oil Distribution Bearing Lubrication Crankshaft Oil Distribution Groove Internal Oil Feed Lubricating Oil Film Shell Bearings The oil is fed into distribution grooves cut in the shells, spreading an even thin film of oil between the bearing and crankshaft surfaces. Excess oil is then returned to the sump.
Maintaining oil pressure is critical. In most cars a simple indicator light is illuminated. In performance cars and aircraft, a gauge is usual to display actual pressure. To prevent mechanical damage regular servicing is necessary. Oil specification is found in vehicle Owner Handbooks and Service Manuals, and aircraft Maintenance Manuals. Engine life in vehicles is monitored as miles travelled, while in aircraft it is as hours or cycles flown. Front Support Bearing Rear Support Bearings SupportBearings GudgeonPin Con Rod Oil Distribution Bearing Lubrication
Oil Pumps Internal Gear Type Pump Rotating Parts Driving Gear Pump Body This pump consists of two gears, one inside the other. The smaller centre gear is the driving gear, powered by the engine. The larger outer gear (‘idler’ gear) is driven by the inner gear via the meshing of the gear teeth or ‘lobes’. Pump Assembly (end plate removed) Driven Gear
Oil Pumps Internal Gear Type Pump Pump Assembly (end plate removed) Rotating Parts Driving Gear Driven Gear Pump Body Yellow = Inlet Flow Red = Outlet Flow ‘Kidney’ Ports The inlet and outlet ports are a known as kidney ports. Fluid is pulled in and forced out through these ports. As the gears rotate, fluid is pulled in and forced out. Kidney Ports
Fuel Pumps Where are the fuel tanks in most aircraft ? Aircraft fuel tanks are formed by the structure of the wing. Fuel can be transferred from tank to tank to help balance the aircraft in flight. This allows trimming the aircraft efficiently without using aerodynamic forces which cause drag.
The filler connection is usually underneath the wing and is a self sealing device to prevent spillage. It is also hidden away behind an access hatch to maintain aerodynamic smoothness. Fuel level is measured via a level sensor and indicated on the flight deck by the fuel gauge. The tank is filled from either a vehicle born bowser or underground storage tanks, as with vehicle filling stations. Tank E F 1/2 FUEL Fuel Pumps Tank Cavity Filler Cap Filler Neck Fuel Level Sensor Cockpit Fuel Gauge But to get the fuel to the engines, some form of pump is needed. Fuel Pump
Mechanical Diaphragm Pump One-way Inlet Valve Diaphragm One-way Outlet Valve Driving Cam This is a Positive Displacement pump, which means when the pump stops, flow is prevented. This pump consists of a flexible diaphragm, which is moved up by spring force and down by an engine driven cam, and two one-way valves. Spring
Solenoid Diaphragm Pump One-way Inlet Valve One-way Outlet Valve Diaphragm Solenoid Windings Magnetic Plate Switch Mechanism Another Positive Displacement pump. Consisting of a flexible diaphragm, moved up and down by an electro-magnetic force. In this pump, the piston is moved up and down by a magnetic field generated by the electrically powered coil underneath.
Fuel Pumps The Gear Type Pump ‘SPUR’ GEARS BODY The Gear Type Pump is the most favoured pump design, because it consists of just a few easy to produce working parts. Intermeshing straight cut spur gears rotating in a close fitting body.
FLOW OUT Fuel Pumps The Gear Type Pump ‘SPUR’ GEARS Flow Controller As the gears rotate the fluid is carried between the gear teeth. A control valve is set to limit the absolute pressure in the system, (around 450 psi) to protect against system damage.
FLOW OUT Fuel Pumps The Gear Type Pump ‘SPUR’ GEARS Pump flow restriction in the controller causes pressure to increase Flow Controller Without the flow controller, the pump would provide a flow, but at no pressure. Pressure is only achieved because the flow control system works on flow restrictions which causes the pressure to rise.
Carburettor Air Filter Fuel is pumped to the carburettor (which we will examine later). The carburettor controls the mixing of air and atomized fuel, but the air must be filtered to prevent any damage or blockage in the fuel system or engine. Tank E F 1/2 FUEL Fuel Pump Air Filter Inlet Exhaust We will look at this area
Air Filter A paper based element bonded into a rubberized material, is concertinaed to get the greatest surface area. Air with contaminants passes through the filter, which catches the contaminants and leaves the air cleaner. Filtration rate is in Microns (1 micron = 0.000,001 metre). So a 30 micron filter stops particles of 30 microns or more. Filter of corrugated paper Air and Dirt Dirt trapped by filter Clean Air
Check of Understanding Where would a Dry Sump Oil System be most commonly used? Only in High Performance/Rally vehicles Most vehicles Only in Aircraft High Performance/Rally vehicles and Aircraft
What differentiates a Dry Sump system from a Wet Sump system? A Scavenger Pump A Diaphragm Pump A Positive Displacement Pump An Internal Gear Type Pump Check of Understanding
Bearings in a crankshaft are made up of two distinct parts. What are these called? Ball Bearings Dry Bearings Shell Bearings Roller Bearings Check of Understanding
Where would you find the oil specifications for an aircraft? The aircraft log The service manual The operating manual The maintenance manual Check of Understanding
Within an internal gear-type pump there are two gears. Which one is driven by the engine? The Driven Gear The Idler Gear The Outer Gear The Driving Gear Check of Understanding
Which of these pumps has a flexible diaphragm moved up and down by an electro-magnetic force? A Solenoid Diaphragm Pump A Gear Type Pump A Scavenger Pump A Mechanical Diaphragm Pump Check of Understanding
Which is the most favoured type of pump design? Meshing Gear Pump Solenoid Diaphragm Pump Mechanical Diaphragm Pump Gear Type Pump Check of Understanding
Without the flow controller in a gear-type pump, What flow would the pump supply? No flow at all A flow at no pressure A flow at high pressure A flow at low pressure Check of Understanding
What is a Micron? Check of Understanding of a metre 1100,000 11,000, ,000 11,000