Towards Model-Based Control of RCCI-CDF Mode-Switching in Dual Fuel Engines
The operation of a dual fuel combustion engine using combustion mode-switching offers the benefit of higher thermal efficiency compared to single-mode operation. For various fuel combinations, the engine research community has shown that running dual fuel engines in Reactivity Controlled Compression Ignition (RCCI) mode, is a feasible way to further improve thermal efficiency compared to Conventional Dual Fuel (CDF) operation of the same engine. In RCCI combustion, also ultra-low engine-out NOx and soot emissions have been reported. Depending on available hardware, however, stable RCCI combustion is limited to a certain load range and operating conditions. Therefore, mode-switching is a promising way to implement RCCI in practice on short term. In this paper, a model-based development approach for a dual fuel mode-switching controller is presented. Simulation results demonstrate the potential of this controller for a heavyduty engine running on natural gas and diesel. An existing control-oriented engine model is extended with a new CDF model to simulate both CDF and RCCI operation. This model shows good agreement with experimental data. As a first step towards model-based control development, this extended model is used for system analysis to understand the switching behavior and to design a coordinated air-fuel path controller. This closed-loop controller combines static decoupling with next-cycle CA50-IMEP-Blend Ratio control. For a modeswitching sequence in a low load operating point, the closedloop controlled engine demonstrates stable behavior and good reference tracking. The paper concludes with an outlook on necessary steps to bring model-based control strategies for dual fuel mode-switching in a multi-cylinder engine on the road.
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Heavy duty engines
Dual fuel engines
2018 SAE World Congress Experience, WCX 2018. 10 April 2018 through 12 April 2018
SAE Technical Papers