7 of 67
Fuel injector flower
Fuel Injector Flower
By Nicholaos Demas
The nozzle of the fuel injector in a car sprays gasoline through tiny holes, designed to make as fine a mist as possible so that the fuel burns better. Researchers at Argonne, attempting to make the engine even more efficient, reduced the size of the holes to less than the size of a single human hair. This is a nozzle with eight holes—polished from the tip down to reveal a flower-like pattern—seen under a microscope. The yellow area is the iron nozzle, the black areas are epoxy used to hold the nozzle, and the petals are the nickel-phosphorous material used to reduce the size of the holes.
The gas pedal in your car is connected to a valve that regulates how much air enters the engine. So the gas pedal is really the air pedal.
When you step on the gas pedal, the throttle valve opens up more, letting in more air. The computer that controls all of the electronic components on your car engine "sees" the throttle valve open and increases the fuel rate in anticipation of more air entering the engine. It is important to increase the fuel rate as soon as the throttle valve opens; otherwise, when the gas pedal is first pressed, there may be a hesitation as some air reaches the cylinders without enough fuel in it. Sensors monitor the mass of air entering the engine, as well as the amount of oxygen in the exhaust. The computer uses this information to fine-tune the fuel delivery so that the air-to-fuel ratio is just right.
A fuel injector is basically an electronically controlled valve. When the injector is supplied with -pressurized fuel it opens, allowing the pressurized fuel to squirt out through a nozzle. The nozzle of the fuel injector is designed to atomize the fuel to make as fine a mist as possible so that it can burn easily. There are different nozzle designs varying from single-hole to multi-hole and are typically made from a ferrous material. The size of the holes of a nozzle is critical for fuel atomization.
A common method used to make the holes is a process called wire electrical discharge machining during which a thin metal wire removes material from the nozzle.
After this process, we subjected the nozzle to an electroless Nickel plating process in order to reduce the size of the holes made by wire electrical discharge machining. Due to the size of the holes (less than 100 micrometers), in order to examine the plated layer’s uniformity and adhesion a microscope is necessary. The nozzle was mounted onto epoxy, mechanically polished and microscope images at various stages during the polishing process are taken. Due to precise vertical orientation and polishing to the specific height corresponding to this image a flower-like pattern was created.
The main area is ferrous, the black areas are epoxy and the petals are the nickel-phosphorus layer of the EN plating process.
Argonne National Laboratory.