06 Jan What Are Piezo Diesel Injectors and How Do They Work?
Why do we need Piezo Diesel Injectors?
Alongside economic growth and societal progress, society today rightfully places greater emphasis on environmental sustainability. Due to concerns regarding diesel engine emissions, Piezo Diesel Injectors have been developed to address this issue. Regulations involving diesel engine emissions have become increasingly stringent, yet customers’ demands for quieter engines with improved power output has led the world’s leading firms in fuel injection technologies to invest in extensive research and development. In order to meet customer demands while remaining compliant and ahead of regulatory pressures, Piezo Diesel Injectors were developed to reduce emissions by making the combustion of fuel within the cylinder more efficient. Such technological progress leads a new phase with possibilities of improved performance and reduced emissions through precisely timed and metered injections of fuel during the diesel combustion process.
What is the Piezoelectric effect?
Piezoelectric injector technology makes use of the Piezoelectric effect and thus the injector is named as such. The phenomenon of the Piezoelectric effect was discovered in 1880 by Pierre Curie (yes, the Nobel Prize winner and husband of Marie Curie!) and his brother Jacques. Piezoelectric technology, while relatively unknown to many people, is actually the secret to many of the conveniences in our day-to-day lives, as its widespread use includes that in cell phones, earbuds, ultrasound imaging, and of course, diesel fuel injectors! Certain crystals contain this unique property and are said to be “piezoelectric” – when mechanical stress is exerted along certain crystal axes, an electrical charge is generated on the crystal surface. This electrical polarisation occurs due to the shifting positive and negative ions in the crystal, and an electrical field forms between the ends of the crystal. Similarly, there is an “inverse piezoelectric effect”, where an electrical voltage applied to the end faces of the crystal can cause the crystal to expand or contract. Utilizing these noted characteristics of piezoelectric crystals, piezo crystals thus found its use as a critical component in the Piezoelectric injector. With their ability to expand rapidly when in contact with an electrical charge, Piezoelectric crystals serve as efficient actuators in diesel fuel injectors. This technology acts up to five times faster than a standard injector and operates in a frictionless motion, thereby resulting in precise fuel measurements and allowing for multiple injections per combustion cycle.
How do Piezo Diesel Injectors work?
The key to the functioning of modern common rail technology is the Piezoelectric injector. In Piezo diesel injectors, Piezo crystals alter their structures in less than thousandths of a second by slightly expanding when an electrical voltage is applied. Hundreds of Piezo wafers, which are stacked over one another in an injector, will expand, and when they do, a linear movement occurs and transmits directly to an injector needle without any mechanical link between them.
As Piezo diesel injectors are used in common rail injection systems, high-pressured fuel is continuously delivered to the tip of the injector, where you can find a needle preventing fuel from being injected. Pressurized fuel is also sent to the top of this needle, the force from which keeps the needle closed. When energized, the Piezo crystal will open a valve above the needle. This allows the pressurized fuel at the top of the needle to return to the tank through the return line. With no pressure holding the needle closed, the fuel injects into the combustion chambers. The actuator is later de-energized, closing the valve, which then causes the build-up of high-pressured fuel which forces the needle to close again.
What are the benefits of Piezo Injectors?
As a Piezo injector performs faster, it can carry out more injections per cylinder stroke and allows for higher fuel system pressures. This improves the atomisation of the diesel, giving improved spray momentum and greater accuracy. Furthermore, the technology allows for greater flexibility with regard to the start of injection and the relevant time interval between individual injection events. In addition, the new piezo injectors developed are found to be smaller in size and lower in weight compared to the traditional injectors. With the use of Piezo Fuel Injectors, we can benefit from improved combustion control, less fuel consumption, reduced noise, improved engine performance, and a considerable reduction in emissions.