PISTON ENGINES

1. PISTON ENGINES Part 4 Piston Engine Operations (Oil and Fuel Pumps)

2. 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.

3. Oil Systems The ‘Wet Sump’ System Engine Block Pump Filter Common to most vehicles 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. SUMP

4. Oil Systems Tank The ‘Dry Sump’ System Engine Block Pump Filter High Performance/Rally vehicles and Aircraft 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. SUMP

5. Oil Systems Tank Scavenge Pump The ‘Dry Sump’ System Engine Block Pump Filter High Performance/Rally vehicles and Aircraft But the oil is then taken out of the sump by a scavenge pump & returned to the tank, hence the name ‘Dry Sump’ SUMP This gives protection against oil loss in cars; and helps maintain correct levels of lubrication in aircraft.

6. Oil Distribution Sump (Oil Tank) Filter Pump 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.

7. Oil Distribution Crankshaft Rear Support Bearings Flywheel Support Bearings Front Support Bearing Gudgeon Pin Con Rod Bearing Lubrication 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. 3 2 4 1 A 4 CYLINDER ENGINE CRANKSHAFT

8. Oil Distribution Crankshaft Bearing Lubrication 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 Shell Bearings

9. Oil Distribution Oil Splash Oil Splash Oil Distribution Groove Crankshaft Internal Oil Feed Oil Splash Oil Splash Bearing Lubrication 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. Con Rod Big End Lubricating Oil Film Shell Bearings

10. Oil Distribution Rear Support Bearings Support Bearings Front Support Bearing Gudgeon Pin Con Rod Bearing Lubrication 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. 3 2 4 1

11. Oil Pumps Pump Body Driven Gear Driving Gear Internal Gear Type Pump 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) Rotating Parts

12. Oil Pumps ‘Kidney’ Ports Pump Body Driven Gear Driving Gear Internal Gear Type Pump 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. Pump Assembly (end plate removed) Yellow = Inlet Flow Red = Outlet Flow Rotating Parts Kidney Ports

13. 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.

14. Cockpit Fuel Gauge Filler Cap Filler Neck E F Fuel Level Sensor Tank Cavity Fuel Pumps 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. FUEL 1/2 But to get the fuel to the engines, some form of pump is needed. Tank Fuel Pump

15. One-way Inlet Valve One-way Outlet Valve Diaphragm Spring Driving Cam Mechanical Diaphragm Pump 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.

16. One-way Inlet Valve One-way Outlet Valve Magnetic Plate Diaphragm Solenoid Windings Switch Mechanism Solenoid Diaphragm Pump 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.

17. BODY ‘SPUR’ GEARS Fuel Pumps The Gear Type Pump 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.

18. ‘SPUR’ GEARS Flow Controller FLOW OUT Fuel Pumps The Gear Type Pump 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.

19. ‘SPUR’ GEARS Flow Controller FLOW OUT Fuel Pumps The Gear Type Pump Pump flow restriction in the controller causes pressure to increase 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.

20. Air Filter Carburettor E F Fuel Pump 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. Exhaust Inlet FUEL We will look at this area 1/2 Tank

21. Air Filter Filter of corrugated paper Dirt trapped by filter 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. Clean Air Air and Dirt

22. Check of Understanding Where would a Dry Sump Oil System be most commonly used? Most vehicles High Performance/Rally vehicles and Aircraft Only in Aircraft Only in High Performance/Rally vehicles

23. Check of Understanding What differentiates a Dry Sump system from a Wet Sump system? A Diaphragm Pump An Internal Gear Type Pump A Positive Displacement Pump A Scavenger Pump

24. Check of Understanding Bearings in a crankshaft are made up of two distinct parts. What are these called? Dry Bearings Roller Bearings Shell Bearings Ball Bearings

25. Check of Understanding Where would you find the oil specifications for an aircraft? The service manual The maintenance manual The operating manual The aircraft log

26. Check of Understanding Within an internal gear-type pump there are two gears. Which one is driven by the engine? The Idler Gear The Driving Gear The Outer Gear The Driven Gear

27. Check of Understanding Which of these pumps has a flexible diaphragm moved up and down by an electro-magnetic force? A Gear Type Pump A Mechanical Diaphragm Pump A Scavenger Pump A Solenoid Diaphragm Pump

28. Check of Understanding Which is the most favoured type of pump design? Solenoid Diaphragm Pump Gear Type Pump Mechanical Diaphragm Pump Meshing Gear Pump

29. Check of Understanding Without the flow controller in a gear-type pump, What flow would the pump supply? A flow at no pressure A flow at low pressure A flow at high pressure No flow at all

30. Check of Understanding What is a Micron? 1 of a metre 1,000,000 1 of a metre 100,000 1 of a metre 10,000 1 of a metre 1,000

31. PISTON ENGINES End of Presentation