Heat engine Greg Pahl’s book gives a good overview of historical account of diesel engine development
Submitted for patent in 1894 Engine exploded and almost killed Rudolf First successful diesel engine operation in 1897 Patent awarded in 1898
Take care with some newer glow plugs not to touch the ceramic electrode, Oil residue may can premature damage Don’t test new CDI 2.8l glow plugs with 12 volts- they are 7 volts
Bosch injection pump & Yanmar injection pumps An Injection Pump is the device that pumps fuel into the cylinders of a diesel engine or less typically, a gasoline engine. Traditionally, the pump is driven indirectly from the crankshaft by gears, ch ains or a toothed belt (often the timing belt ) that also drives the crankshaft on overhead-cam engines (OHC). It rotates at half crankshaft speed in a conventional four-stroke engine. Its timing is such that the fuel is injected only very slightly before top dead-centre of that cylinder's compression stroke. It is also common for the pump belt on gasoline engines to be driven directly from the camshaft. Because of the need for positive injection into a very high-pressure environment, the pump develops great pressure - typically 15,000 PSI or more on newer systems. This is a good reason to take great care when working on diesel systems; escaping fuel at this sort of pressure can easily penetrate skin and clothes, and be injected into body tissues with serious consequences. Earlier diesel pumps used an in-line layout with a series of cam-operated injection cylinders in a line, rather like a miniature inline engine. The pistons have a constant stroke volume, and injection volume (ie, throttling) is controlled by rotating the cylinders against a cut-off port that aligns with a helical slot in the cylinder. When all the cylinders are rotated at once, they simultaneously vary their injection volume to produce more or less power from the engine. Inline pumps still find favour on large multi-cylinder engines such as those on trucks, construction plant, static engines and agricultural vehicles. For use on cars and light trucks, the rotary pump or distributor pump was developed. It uses a single injection cylinder driven from an axial cam plate, which injects into the individual fuel lines via a rotary distribution valve. Later incarnations such as the Bosch VE pump vary the injection t iming with crank speed to allow greater power at high crank speeds, and smoother, more economical running at slower revs. Some VE variants have a pressure-based system that allows the injection volume to increase over normal to allow a turbocharger or supercharger equipped e ngine to dev elop more power under boost conditions. All injection pumps incorporate a governor to cut fuel supply if the crank speed endangers the en gine - t he heavy moving parts of diesel engines do not tolerate overspeeding well, and catastrophic damage can occur if they are over-revved. Mechanical pumps are gradually being phased out in order to comply with international emissions directives, and to increase performance and economy. Alternatives include common rail diesel systems and unit direct injection systems. These all ow for higher pres sures to be developed, and for much finer control of injection volumes compared to mechanical systems.
2.8L Jeep Liberty 24,000 PSI Multi pilot fuel injection- 1 or 2 before main injection
VGTC- low speeds, movable vanes expand for additional air boost High speeds, vanes retract to limit boost
EGR cooler on 2.8L jeep liberty
Prime indicator of Diesel fuel quality * Ability to auto-ignite * Inverse of gasoline’s octane More saturates - increases cetane # soy (48-52) yellow grease (60-75)
Measured by viscometer * Motor oil analogy* Low viscosity can affect leak down on inj pump plungers -> power loss Higher viscosity can affect insuff. Fuel supply -> power loss
8.4% power loss- JVG, Biodiesel Handbook
Overview of the Diesel Engine Operation National Biodiesel Board Technician Outreach Program
Rudolf Diesel developed the idea for the diesel engine and obtained the German patent for it in 1892.
His goal was to create an engine with high efficiency .
Gasoline engines had been invented in 1876 and, especially at that time, were not very efficient
Both the gasoline and diesel engine utilize the process of internal combustion for power
The diesel engine: first patented in 1892 The Diesel engine was initially Intended to run on coal dust. Rudolph Diesel (1858 – 1913) Diesel demonstrated his engine at the Exhibition Fair in Paris, France in 1898. This engine was fueled by peanut oil - the "original" biodiesel.
The first Diesel race car placed 13 th in the Indianapolis 500 because it never stopped to refuel…
The American public looked to diesel fuel which was more efficient and economical and they began buying diesel-powered automobiles. Diesel vehicle popularity In the 70s due to Oil crisis This surge of diesel sales in American ended in the 1980's.
Intake stroke : intake valve opens while the piston moves down from its highest position in the cylinder to its lowest position, drawing air into the cylinder in the process.
Compression stroke: intake valve closes and the piston moves back up the cylinder.
This compresses the air & therefore heats it to a high temperature, typically in excess of 1000°F (540°C).
Near the end of the compression stroke, fuel is injected into the cylinder. After a short delay, the fuel ignites spontaneously, a process called auto ignition .
Combustion stroke: The hot gases produced by the combustion of the fuel further increase the pressure in the cylinder, forcing the piston down
Exhaust stroke: exhaust valve opens when the piston is again near its lowest position, so that as the piston once more moves to its highest position, most of the burned gases are forced out of the cylinder.
This is defined as the ratio of the volume of the cylinder at the beginning of the compression stroke (when the piston is at BDC) to the volume of the cylinder at the end of the compression stroke (when the piston is at TDC).
The higher the compression ratio, the higher the air temperature in the cylinder at the end of the compression stroke.
Higher compression ratios, to a point, lead to higher thermal efficiencies and better fuel economies .
Diesel engines need high compression ratios to generate the high temperatures required for fuel auto ignition.
In contrast, gasoline engines use lower compression ratios in order to avoid fuel auto ignition, which manifests itself as engine knock or pinging sound
Common spark ignition compression ratio: 8:1 to 12:1
A lower-cost injection pump used with pump-line-nozzle systems.
The pump has a central plunger system (usually consisting of two opposing plungers) that provides fuel to every cylinder during the required injection period.
A plate located near the top of the pump rotates, opening an appropriate orifice at the right time for distribution to each cylinder’s injection nozzle through a separate line.
It is usually used with automotive or agricultural engines that have lower performance and durability requirements than the heavy-duty truck diesels.
A diesel fuel injection system employing a common pressure accumulator, called the rail, which is mounted along the engine block. The rail is fed by a high pressure fuel delivery pump. The injectors, which are fed from the common rail, are activated by solenoid valves. The solenoid valves and the fuel pump are all electronically controlled. Also known as CRD, Common Rail Diesel Technology Common Rail Injection
Common Rail Diesel Injection pressures are much higher: 24,000- 36,000 PSI In the common rail injection system the injection pressure is independent from engine speed and load. Therefore, the injection parameters can be freely controlled. Usually a pilot injection is introduced, which allows for reductions in engine noise and NOx emissions. This system operates at 27,500 psi (1900 BAR). The injectors use a needle-and-seat-type valve to control fuel flow, and fuel pressure is fed to both the top and bottom of the needle valve. By bleeding some of the pressure off the top, the pressure on the bottom will push the needle off its seat and fuel will flow through the nozzle holes.
These converters often reach 90% effectiveness, virtually eliminating diesel odor and helping to reduce visible particulates ( soot ), however they are incapable of reducing NO x as chemical reactions always occur in the simplest possible way, and the existing O 2 in the exhaust gas stream would react first.
To reduce NO x on a compression ignition engine use : selective catalytic reduction (SCR) and NOx (NO x ) traps (or NOx Adsorbers ).
One of the most important properties of a diesel fuel is its readiness to auto-ignite at the temperatures and pressures present in the cylinder when the fuel is injected.
The cetane number is the standard measure of this property.
Cetane – (ASTM D613) is tested by adjusting the fuel/air ratio and the compression ratio in a single cylinder, indirect injection diesel engine to produce a standard ignition delay (the period between the start of fuel injection and the start of combustion).
ASTM D6751 Biodiesel spec. has a minimum cetane number of 47
Cetane improvers are fuel additives that are designed to readily decompose to give precursors to combustion and thus enhance the rate at which auto-ignition occurs.
Typical compounds used are alkyl nitrates, ether nitrates, dinitrates of polyethylene glycols, and certain peroxides. Due to low cost and ease of handling, alkyl nitrates are the most widely used cetane improvers.