Roger Krieger, GM R&D Center

Diesel Fuel If you have ever compared diesel fuel and gasoline, you know that they are different.gasoline They certainly smell different. Diesel fuel is heavier and oilier. Diesel fuel evaporates much more slowly than gasoline -- its boiling point is actually higher than the boiling point of water. You will often hear diesel fuel referred to as "diesel oil" because it is so oily.

Diesel fuel evaporates more slowly because it is heavier. It contains more carbon atoms in longer chains than gasoline does (gasoline is typically C9H20, while diesel fuel is typically C14H30). It takes less refining to create diesel fuel, which is why it is generally cheaper than gasoline.refining

DIESEL FUEL Diesel fuel must meet an entirely different set of standards than gasoline. The fuel in a diesel engine is not ignited with a spark, but is ignited by the heat generated by high compression. All diesel fuel must be clean, be able to flow at low temperatures, and be of the proper cetane rating. Cleanliness. Low-temperature fluidity. Cetane number.

Diesel Fuel Characteristics Cetane number Measure of relative ease to initiate combustion Higher number: easier to ignite Octane number for gas: opposite Higher number: less tendency to ignite

Cetane Number Ignition quality measure Affects: cold starting, warm-up, combustion roughness, acceleration, and exhaust smoke density Cetane number is based on the ignition characteristics of two hydrocarbons: Cetane - short delay period and ignites readily (100) Alphamethylnaphthalene (AMN) - long delay period and poor ignition quality (0) It is the percentage by volume of normal cetane in a blend with AMN PC engines require a minimum cetane no. of 35 DI engines require a minimum cetane no. of 40

Cetane Number High cetane number indicates good ignition quality (short delay period) Low cetane number indicates poor ignition quality (long delay period) PC engines require a minimum cetane # of 35 DI engines require a minimum cetane # of 40 Cetane improver additive can improve ignition quality and reduce white smoke during start up

FUEL CYCLE

Fuel Injection In CI Engines Delay Period Rapid Combustion - knock Diffusion Combustion - smoke Cylinder Pressure

Fuel Injection In CI Engines Less air means less fuel required Fuel injection system has to compensate for air density to minimize smoke output 7% decrease in air density per 1000m altitude

FUEL FILTERS The fuel filtration and water separation needs of today's new generation diesel fuel systems demand extremely high efficiency, flexibility, multiple functions and ease of use with no risk of fuel spills or contaminated parts. Stan dyne's patented Fuel Manager® range of Available for light, medium and heavy duty trucks; and agricultural, industrial, construction and marine applications, there is a Fuel Manager

The FM10 Series is designed for diesel engines with a fuel flow rate up to 50 US gallons/hr (190 liters/hr). Typical engines range from 10 to 200 HP The FM100 Series is designed for diesel engines with a fuel flow rate up to 80 US gallons/hr (300 liters/hr). Typical engines range from 50 to 350 HP.

The FM1000 Series is designed for diesel engines with a fuel flow rate up to 180 US gallons/hr (680 liters/hr). Typical engines range from 200 to

Types of filters

Fuel pump  The ‘traditional’ style of injection pump is the in- line pump. They have been used for many  decades and are still commonly found on agricultural and stationary diesels, and very many older  model diesel road vehicles still employ them, including the Toyota Landcruiser 2H diesel.. They  are typically capable of generating injection nozzle pressures up to about 750 bar in light road  vehicles – towards the lower end of the range that is required these days.

 They have a separate pump plunger for each  cylinder of the engine, so a 4 cylinder engine  has a four plunger pump, a 6 cylinder engine  has a six plunger pump, etc. The pump is run at  half engine crankshaft speed and has a central  shaft with four/six etc. cam lobes attached. So,  each plunger is operated by it’s cam once every  two crankshaft revolutions, coinciding of course  with the power stroke of its engine cylinder.  Each plunger has a spiral groove or helix  machined on it’s side and cut through to the top  of the plunger. When operated, the plunger is  pushed up by its cam lobe. At a certain point  the spiral groove will line up with a spill port on  the side of the plunger cylinder and the rest of  the fuel is ‘spilled’.

 Because the groove is a spiral shape, the point in the plunger stroke when it uncovers the spill port  will vary as the plunger is rotated a few degrees either way. This adjusts the spill point and hence,  the volume of its fuel charge to the engine cylinder.

 So that all engine cylinders receive the same sized fuel charge, all of the plungers are rotated  together. This is achieved by each plunger having gear teeth machined to it’s circumference which  are engaged by a common gear rack which runs through the pump body. As the rack moves back  and forth, all four (or six or more) plungers are rotated together. The extremes of travel of the  pump rack control the minimum and maximum fuel charge quantities the pump is capable of

PRE SUPPLY PUMP The electric fuel pump comprises of: 1.Electric Motor 2.Roller-Cell Pump 3.Non Return Valve

 The roller cell is driven by an electric motor.  Its rotor is mounted eccentrically and provided with slots in which movable rollers are free to travel. PRE SUPPLY PUMP

The rollers are forced against the base plate by rotation and by fuel pressure. The fuel is transported to the outlet openings on the pump’s pressure side. PRE SUPPLY PUMP

 Gear type fuel pump ï The drive gear wheel is driven by the engine. ï Delivery quantity is directly proportional to engine speed. ï Shut off is by means of an electromagnet.. PRE SUPPLY PUMP variants

High- pressure pump ë The pump plunger moves downwards ë The inlet valve opens ë The fuel is drawn in to the pumping element chamber(suction stroke)

ë At BDC, the inlet valve closes ë The fuel in the chamber can be compressed by the upward moving plunger. High- pressure pump

High- pressure accumulator (Rail) Store fuel Prevent pressure fluctuations

Rail is a forged-steel tube. ID is approx.. 10mm Length is between 280 and 600mm The volume must be “ as small as possible, as large as necessary” High- pressure accumulator (Rail)

Pressure-control valve (DRV)  Responsible for maintaining the pressure in the rail at a constant level.

The injector on a diesel engine is its most complex component and has been the subject of a great deal of experimentation -- in any particular engine it may be located in a variety of places. The injector has to be able to withstand the temperature and pressure inside the cylinder and still deliver the fuel in a fine mist. Fuel Injector

Getting the mist circulated in the cylinder so that it is evenly distributed is also a problem, so some diesel engines employ special induction valves, pre-combustion chambers or other devices to swirl the air in the combustion chamber or otherwise improve the ignition and combustion process.

CI Engine Combustion Chambers  Two types:  Indirect (divided chamber) injection - into a pre-combustion chamber

CI Engine Combustion Chambers  Two types:  Direct injection - into cylinder

Combustion Chamber Comparison  Indirect  Good  Excellent mixing, turbulence characteristics  Can burn lower quality fuel  Lower injection pressure  Less pronounced knock

Combustion Chamber Comparison  Indirect  Bad  Very high temperature/pressure in injection chamber  Higher emissions, especially NO x  Harder to start - glow plugs  Less efficient

Combustion Chamber Comparison  Direct  Bad  Pressure rise can be great, knock  High injection pressure, high quality fuel

Combustion Chamber Comparison  Direct  Good  Lower specific fuel consumption - 20%  Lower emissions  Bigger valves, higher volumetric efficiency

Direct Injection  Air-fuel mixing important  Controlled by:  Use of swirl-inducing designs  Intake port geometry  Piston cap geometry  Injection system design  High pressure  Many nozzle holes  Positioning Bad: high-tech injection system Good: Higher volumetric efficiency

DIESEL ENGINES Indirect and Direct Injection FIGURE 4-4 A direct injection diesel engine injects the fuel directly into the combustion chamber. Many designs do not use a glow plug.

DIESEL ENGINES Indirect and Direct Injection  In an indirect injection (abbreviated IDI) diesel engine, fuel is injected into a small prechamber, which is connected to the cylinder by a narrow opening.  The initial combustion takes place in this prechamber.  This has the effect of slowing the rate of combustion, which tends to reduce noise. FIGURE 4-3 An indirect injection diesel engine uses a prechamber and a glow plug.

DIESEL ENGINES Diesel Fuel Ignition  Ignition occurs in a diesel engine by injecting fuel into the air charge, which has been heated by compression to a temperature greater than the ignition point of the fuel or about 1,000°F (538°C).

Roger Krieger, GM R&D Center Fuel Injection Systems Electronic distributor pump Electronic unit injector (EUI) High-pressure common rail

Electronic Distributor Pump

Roger Krieger, GM R&D Center Electronic Unit Injector (EUI)

High-Pressure Common Rail High-Pressure Pump ECU Fuel Return to Tank Common Rail Injectors Spill Control Valve