The Application of Piezoceramic Actuation to Direct Fuel Injection

With increasing demands to reduce emissions from internal combustion engines, engine manufacturers are forced to seek out new technology. One such technology employed primarily in the diesel and two-stroke engine community is direct-injection (DI). Direct injection has shown promising results in reduction of CO and NOx for both two- and four-stroke engines. While having been used for several years in the diesel industry, direct injection has been scrutinized for an inability to meet future requirements to reduce particulate matter emissions. Direct injection has also came under fire for complicating fuel delivery systems, thus making it cost prohibitive for small utility engine manufacturers. Recent research shows that the application of piezo-driven actuators has a positive effect on soot formation reduction for diesel engines and as this paper will distinguish, has the ability to simplify direct injection fuel delivery systems in general. The potential for emissions reduction and improved engine performance by use of direct injection is well documented in the literature. The current debate centers around the most efficient way to produce direct injection without having a negative effect on system complexity, cost, and performance. This work investigates the use of the newly emerging piezoceramic actuation technology to accomplish such goals.

Piezoceramic actuation has become an area of increased interest in the past ten years. Having been used for many years as sensors in such applications as pressure transducers and smoke detectors, piezoceramics are now being investigated as prime movers in fuel injectors. In an effort to aid the engineering community, this paper will conduct a comprehensive review of several piezoceramic actuators and discuss the current state of the art. An existing direct-injector used on an outboard two-stroke engine is used as the benchmark in this study. The system parameters are determined experimentally and used to select the appropriate piezoceramic actuator architecture. A proof of concept device will be constructed to determine the feasibility of designing direct-injectors using piezoceramics. The experimental results will show that the piezoceramic actuator can successfully deliver the force and stroke required. The results will also show the limitations imposed on the actuation system when use of mechanical advantage is incorporated into the design.