Decoupling of consecutive gasoline controlled auto-ignition combustion cycles by field programmable gate array based real-time cylinder pressure analysis

Abstract

Gasoline Controlled Auto Ignition (GCAI) combustion offers high potential for CO 2 emission reduction, but faces challenges regarding combustion stability and high sensitivity to changing boundary conditions. 1 Combustion chamber recirculation allows a wide operation range, but results in a strong coupling of consecutive cycles 2 due to residuals that are transferred to the subsequent combustion cycle. The cycle coupling leads to phases of unstable operation with reduced efficiency and increased emission levels. 3 State of the art control algorithms use data-driven models of GCAI combustion to achieve cycle-to-cycle control of the process 4 or use offline calibration and optimization. 5 A closed-loop control is proposed and implemented on a rapid control prototyping ECU. The control algorithm continuously calculates the current residual fuel in the combustion chamber. The heat release is observed and compared with the theoretical heat release of the injected fuel mass. The rate of unburned fuel mass transferred to the subsequent cycle is calculated offline by a detailed gas exchange model. Based on this information, the control algorithm adapts the injected fuel quantity for each cycle individually using an inverse injector model. In this article, a concept for decoupling consecutive cycles is presented to reduce the deviations of the indicated mean effective pressure (IMEP) and thus the heat release. Unstable sequences are analyzed in the time domain, and unburned residuals are identified as a strong correlating factor for consecutive cycles. Using real-time cylinder pressure analysis based on a field programmable gate array (FPGA) enables the online calculation of unburned residual fuel. Based on this calculation, the injection of each cycle can be adapted individually to decouple consecutive cycles and avoid unstable operation. The results of the control algorithm and the stabilization of the GCAI combustion are validated using a single cylinder research engine and compared to steady state operation.

Autoregressive modeling of cycle-to-cycle correlations in homogeneous charge compression ignition combustion

“…23,24 The potential of FPGA-based real-time analysis for decoupling of consecutive cycles has been identified. 25,26 The bifurcative behavior could successfully be demonstrated on a cycle-to-cycle basis. 27 This approach was extended by applying extreme learning machines by Vaughan.…”

Development and experimental validation of a real-time capable field programmable gate array–based gas exchange model for negative valve overlap

“…30 The calculation of heat release in real time has also been achieved in less than 0.02 CA at 1200 r/min on an FPGA, which can be used for HCCI combustion control. 31 An FPGA controller has been used to control the amount of injected fuel to prevent an overshoot of indicated mean effective pressure (IMEP) resulting from unburned fuel from the previous cycle 32 and it is proposed that a real-time calculation of exhaust gas fraction would improve the accuracy of the transferred fuel mass and allow for a better prediction of the fuel transferred from one cycle to the next. An FPGA has been used to calculate the real-time combustion metrics, CA50 and IMEP, which are then used for closed-loop control.…”

Symposium for combustion control 2017 and 2018 special issue

“…Their work focused on closing the control loop by using ultra-fast field-programmable gate arrays (FPGAs) within a combustion cycle. 10,13 This extended the in-cycle control approach presented in the contribution of Liu et al 14 Another very important aspect of control development always lies on the process simulation. The contribution of Franken et al 9 presented a stochastic reactor model with tabulated chemistry.…”

“…The intrinsic nonlinear behavior of the engine process was investigated by Nuss et al, 4 Sowman et al 3 and Ritter et al 12 by applying model predictive control approaches for the examples of selective catalytic reduction (SCR) aftertreatment and gasoline-controlled autoignition. Also, Gordon et al 10 and Wick et al 13 have investigated new control approaches for the homogeneous charge compression ignition (HCCI) process. Their work focused on closing the control loop by using ultra-fast field-programmable gate arrays (FPGAs) within a combustion cycle.…”