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This paper describes a numerical model developed to predict the elastohydrodynamic (coupled solid-fluid) response of unit injector fuel systems. These systems consist of a concentric barrel and plunger with a small annular clearance. During operation (axial movement of the plunger), highly non-uniform pressure and clearance fields are developed which are strongly coupled with each other. The model simultaneously solves for the transient response of the fluid film pressure distribution and three different structural deformation components in a two-dimensional (axial-circumferential) domain. These structural components are the transverse bending of the plunger, radial expansion of the barrel, and radial growth of the plunger from a Poisson effect. The fluid film pressure distribution is governed by the transient Reynold's equation (i.e. lubrication theory) and the structural deformation components are governed by linear elastic theory.

Diesel engine manufacturers have been asking for new, innovative, flexible fuel injection systems in order to meet future diesel engine emission requirements throughout the world and improve engine performance. Engineers at Caterpillar have listened to these requests and developed a fuel system concept to meet their needs. This new fuel system is called the Next Generation Electronic Unit Injector (NGEUI). The new concept is adaptable to mechanically actuated electronic unit injector, hydraulic electronic unit injector, electronic unit pump, and pump/line/nozzle systems. Features of the new fuel system are listed below: 1. Fully controllable injection pressure independent of engine speed and load 2. Injection pressure capability to 207 MPa (30,000 psi) 3. Reduced drive train torsional excitation and improved hydraulic efficiency 4.