Abstract
The common rail pressure has a direct influence on the working stability of Opposed-Piston Two-Stroke (OP2S) diesel engines, especially on performance indexes such as power, economy and emissions. Meanwhile, the rail pressure overshoot phenomenon occurs frequently due to the operating characteristics of OP2S diesel engines, which could lead to serious consequences. In order to solve the rail pressure overshoot problem of OP2S diesel engines, a nonlinear concerted algorithm adding a speed state feedback was investigated. First, the nonlinear Linear Parameter Varying (LPV) model was utilized to describe the coupling relationship between the engine speed and the rail pressure. The Linear Quadratic Regulator (LQR) optimal control algorithm was applied to design the controller by the feedback of speed and rail pressure. Second, cooperating with the switching characteristics of injectors, the co-simulation of MATLAB/Simulink and GT-Power was utilized to verify the validity of the control algorithm and analyze workspaces for both normal and special sections. Finally, bench test results showed that the accuracy of the rail pressure control was in the range of ±1 MPa, in the condition of sudden 600 r/min speed increases. In addition, the fuel mass was reduced 76.3% compared with the maximum fuel supply quantity and the rail pressure fluctuation was less than 20 MPa. The algorithm could also be appropriate for other types of common rail system thanks to its universality.
Highlights
The Opposed-Piston Two-Stroke (OP2S) diesel engine concept, which has been developed for more than a century, came to being in the end of 19th century
With the evolution of new materials, new techniques and internal combustion engine electronic control technology, many corporations including FEV, Advanced Propulsion Technologies (APT), EcoMotors and Achates Power have launched research on OP2S engines and obtained satisfactory results [3,4,5], people have come to focus on this high power density two-stroke diesel engine format once again [6,7]
A common rail system mathematical model addressing the control strategy and a nonlinear Linear Parameter Varying (LPV) model used to reflect the coupling relationship between the engine condition and the rail pressure were established, which aimed at the problem that rail pressure might suddenly increase because of a sudden change of engine speed in an OP2S diesel engine
Summary
The Opposed-Piston Two-Stroke (OP2S) diesel engine concept, which has been developed for more than a century, came to being in the end of 19th century. In order to meet the air-fuel mixture accuracy requirements under the impact of engine speed and load, the injection quantity must be measured precisely under the control of injection pressure and timing. Catania et al [25] came up with a simple lumped parameter model of system vibration phenomena through a phenomenological analysis They put forward a referenced simplified model aiming at one-time fluctuation effect, based on which the fuel quantity could be amended. A common rail system mathematical model addressing the control strategy and a nonlinear Linear Parameter Varying (LPV) model used to reflect the coupling relationship between the engine condition and the rail pressure were established, which aimed at the problem that rail pressure might suddenly increase because of a sudden change of engine speed in an OP2S diesel engine. This turned out to achieve a wide stability margin and good consistency
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