Optimization and control of feed and transfer pumps

A new low pressure fuel system implementation for Scania’s trucks is being investigated. The main challenge consists in exchanging the mechanical pump with electrical pumps. The electrical pumps must then be controlled to supply exactly the demanded amount of fuel at the required pressure. System redundancy allows a lot of degrees of freedom influencing the final performance. This thesis studies the factors influencing system’s performance to design a controller that enhances its behavior. The physical basis of the elements in the system are investigated and stated with that purpose. The system is analyzed and the output pressure and tank level are controlled by a LQG regulator giving successful results in reference tracking. Integral action is included for disturbance rejection and the states are estimated to overcome quantifications and noise from the signals. The disturbance rejection performance is improved by extending the regulator with a Smith Predictor for time delay compensation and including information about the engine mass-flow demand. The control actions are minimized by the tuning of the controller in order to extend component’s life. The controller includes different modes for when an external action should be input e.g., when a diagnosis test must be run. The optimization of free set-points is discussed and holistic criteria from experience is set. The result is that the system endurance is enhanced by running only two pumps when one does not provide higher efficiency. Results show that different pumps should be chosen in the final design for an improvement of the global efficiency. Future work will consist in implementing the resulting controller in the real system built with actuators selected accordingly to the optimization results

Design and Optimization of In-Cycle Closed-Loop Combustion Control with Multiple Injections

With the increasing demand of transportation, biofuels play a fundamental role in the transition to sustainable powertrains. For the increased uncertainty of biofuel combustion properties, advanced combustion control systems have the potential to operate the engine with high flexibility while maintaining a high efficiency and robustness. For that purpose, this thesis investigates the analysis, design, implementation, and application of closed-loop Diesel combustion control algorithms. By fast in-cylinder pressure measurements, the combustion evolution can be monitored to adjust a multi-pulse fuel injection within the same cycle. This is referred to as in-cycle closed-loop combustion control.The design of the controller is based on the experimental characterization of the combustion dynamics by the heat release analysis, improved by the proposed cylinder volume deviation model. The pilot combustion, its robustness and dynamics, and its effects on the main injection were analyzed. The pilot burnt mass significantly affects the main combustion timing and heat release shape, which determines the engine efficiency and emissions. By the feedback of a pilot mass virtual sensor, these variations can be compensated by the closed-loop feedback control of the main injection. Predictive models are introduced to overcome the limitations imposed by the intrinsic delay between the control action (fuel injection) and output measurements (pressure increase). High prediction accuracy is possible by the on-line model adaptation, where a reduced multi-cylinder method is proposed to reduce their complexity. The predictive control strategy permits to reduce the stochastic cyclic variations of the controlled combustion metrics. In-cycle controllability of the combustion requires simultaneous observability of the pilot combustion and control authority of the main injection. The imposition of this restriction may decrease the indicated efficiency and increase the operational constraints violation compared to open-loop operation. This is especially significant for pilot misfire. For in-cycle detection of pilot misfire, stochastic and deterministic methods were investigated. The on-line pilot misfire diagnosis was feedback for its compensation by a second pilot injection. High flexibility on the combustion control strategy was achieved by a modular design of the controller. A finite-state machine was investigated for the synchronization of the feedback signals (measurements and model-based predictions), active controller and output action. The experimental results showed an increased tracking error performance and shorter transients, regardless of operating conditions and fuel used.To increase the indicated efficiency, direct and indirect optimization methods for the combustion control were investigated. An in-cycle controller to reach the maximum indicated efficiency increased it by +0.42%unit. The indirect method took advantage of the reduced cyclic variations to optimize the indicated efficiency under constraints on hardware and emission limits. By including the probability and in-cycle compensation of pilot misfire, the optimization of the set-point reference of CA50 increased the indicated efficiency by +0.6unit at mid loads, compared to open-loop operation.Tools to evaluate the total cost of the system were provided by the quantification of the hardware requirements for each of the controller modules

Optimizacion and control of feed-and transfer-pumps

Proyecto confidencial (Riunet)Jorques Moreno, C. (2014). Optimizacion and control of feed-and transfer-pumps. http://hdl.handle.net/10251/43847.Archivo delegad

Bayesian Method for Fuel Mass Estimation of Short Pilot Injections based on its Misfire Probability

A fuel mass estimation method for short pilot diesel injections is proposed and analyzed in this article. Previous studies showed that the pilot misfire ratio was more strongly correlated with the fuel mass than the on-time. This characteristic is exploited for the fuel mass estimation in a region where it is otherwise challenging to get good estimation accuracy due to the low signal-to-noise ratio, such as by rail pressure measurements or in-cylinder pressure for heat release estimation. The suggested method uses a Bayesian approach where the calibrated injectors, the pilot misfire ratio and the misfire detection are stochastically modelled. The effect of the different model parameters and dispersion on the estimator properties are analyzed. Experimental results in a Scania D13 Diesel engine confirm the improvement in the pilot mass estimation, for the regions within the transition from full misfire to full combustion. In this region, a 60% reduction in the estimation error was obtained, from 0.66mg to 0.27mg standard deviation

In-Cycle Closed-Loop Combustion Control with Pilot-Main Injections for Maximum Indicated Efficiency

An in-cycle closed-loop combustion controller is proposed in this paper. The controller uses a pilot-main injection scheme where the cycle-individual properties of the pilot combustion are estimated by in-cylinder pressure measurements, and used to predict their effect on the heat release shape of the main combustion. The prediction is used to obtain the optimal main SOI that gives the Maximum Reachable Indicated Efficiency (MRE). The optimal law was linearised to obtain a linear controller that adjusts the main SOI and main duration to obtain the MRE given the conditions of each cycle. The controller was implemented in an FPGA and tested on a Scania D13 Diesel engine. The results show that the main SOI control improves the indicated efficiency. However, the linear controller application is limited due to the non-linear behaviour of the system, which is dependent on the fuel type

Stochastic Set-Point Optimization for In-Cycle Closed-Loop Combustion Control Operation

The constrained indicated efficiency optimization of the set-point reference for in-cycle closed-loop combustion regulators is investigated in this article. Closed-loop combustion control is able to reduce the stochastic cyclic variations of the combustion by the adjustment of multiple-injections, a pilot and main injection in this work. The set-point is determined by the demand on engine load, burned pilot mass reference and combustion timing. Two strategies were investigated, the regulation of the start of combustion (SOC) and the center of combustion (CA50).The novel approach taken in this investigation consists of including the effect of the controlled variables on the combustion dispersion, instead of using mean-value models, and solve the stochastic optimization problem. A stochastic heat release model is developed for simulation and calibrated with extensive data from a Scania D13 six-cylinder engine. A Monte Carlo approach is taken for the simulations. The set-point optimization is based on the stochastic simulation of the heat release shape, including operational constraints on the maximum pressure, maximum pressure rise rate, maximum and minimum exhaust temperature.By exploiting the reduction of the cyclic variations, the indicated efficiency can be increased by up to +1.8%unit at low loads and +0.6%unit at medium loads, compared to open-loop operation. The greatest advantage resulted by the regulation of CA50 under demanding maximum pressure rise rate constraints. By considering the risk of pilot misfire, the indicated efficiency can be increased additionally by +0.3%unit. The benefits of the in-cycle closed-loop combustion control reduces as the engine load increases, due to the lower sensitivity to combustion variations. Future work can use the same approach to include other constraints such as NOx, additional fuel injections and regulators

FPGA Implementation of In-Cycle Closed-Loop Combustion Control Methods

This paper investigates the FPGA resources for the implementation of in-cycle closed-loop combustion control algorithms. Closed-loop combustion control obtains feedback from fast in-cylinder pressure measurements for accurate and reliable information about the combustion progress, synchronized with the flywheel encoder. In-cycle combustion control requires accurate and fast computations for their real-time execution. A compromise between accuracy and computation complexity must be selected for an effective combustion control. The requirements on the signal processing (evaluation rate and digital resolution) are investigated. A common practice for the combustion supervision is to monitor the heat release rate. For its calculation, different methods for the computation of the cylinder volume and heat capacity ratio are compared. Combustion feedback requires of virtual sensors for the misfire detection, burnt fuel mass and pressure prediction. Different alternatives proposed in the literature are compared based on their accuracy and implementation requirements. In-cycle closed-loop combustion controllers were previously investigated by the authors. A National Instruments Xilinx Virtex-5 platform was used as a case study for the quantification of the total necessary resources. The resources for the implementation of the different modules and control strategies are studied to determine the hardware requirements. The results show that the total number of slices is the main limiting factor on the consumed FPGA resources. The quantification of the required hardware provides guidance on how to select an FPGA to implement the different in-cycle combustion control alternatives. This permits to evaluate the total cost of the system as a trade-off between the increased efficiency by the closed-loop combustion control and the cost for its implementation

In-Cycle Closed-Loop Combustion Controllability with Pilot-Main Injections

In-cycle closed-loop combustion control has been proved to reduce cycle-to-cycle variations on emissions and indicated thermal efficiency. In this paper, the in-cycle closed-loop combustion con-trollability achieved by a pilot-main fuel injection scheme is investigated. The controllability is studied by means of the maximum reachable indicated thermal efficiency (MRE). A combustion model is used for the heat release optimisation. The pilot model parameters were modified to simulate the dis-turbances of the pilot combustion. The MRE is the result of optimizing the heat release, constrained to a constant load, with a disturbed pilot injection and adjusting the main start of injection (SOI) and its duration. The nominal indicated thermal efficiency was optimized at the central operating condi-tions.The results showed that the most influential variable in the indicated thermal efficiency was the dis-turbances in the pilot mass. 79% of the efficiency variability can be explained by the actual injected pilot mass. The second and third most significant variables were the variances in the combustion effi-ciency and either of both, the start of vaporisation or the start of combustion (depending on the vari-ables interaction). The disturbances in the pilot combustion resulted in a reduction down to -0.8%unit net indicated thermal efficiency compared to the nominal maximum indicated thermal efficiency.The results confirmed that by adjusting the main SOI, the indicated thermal efficiency can be im-proved in 86% of the total cases with an average change about +0.1%unit in net indicated thermal effi-ciency. The maximum improvement was +1%unit net indicated thermal efficiency for pilot masses larg-er than the nominal point, with longer ignition delay and increased combustion efficiency. The pilot in-jection is observable 1CAD after its start of combustion, which limits the controllability of the main SOI. In 86.2% of the considered cases, the main SOI was controllable in-cycle. When the main SOI was constrained to the controllable window, the reduction in indicated thermal efficiency was negligi-ble compared to the maximum indicated thermal efficiency achievable by in-cycle closed-loop com-bustion control

Predictive In-Cycle Closed-Loop Combustion Control with Pilot-Main Injections

This paper studies the use of predictive in-cycle close-loop combustion control to reduce the stochastic cyclic variations of diesel combustion. The combustion metrics that fully define the pressure trace with a pilot-main injection i.e. pilot and main start of combustion, burned pilot mass, and engine load are used as the set-point reference. These metrics are in-cycle predicted by calibrated models as functions of the current cylinder state, estimated by in-cylinder pressure measurements. The proposed approach uses four individual controllers for the set-point error minimization, which respectively regulate the injection’s timing and duration of the pilot-main injection. The controllers are implemented in a FPGA and tested in a Scania D13 engine. The steady-state error reduction, disturbance rejection and transient response are discussed. The results confirm the error reduction in both, cycle-to-cycle and cylinder-to-cylinder variations. The error dispersion, measured by the 95% confidence interval, was reduced between 25% and 75% for all the controlled parameters. By on-line adaptation, the controllers are robust against model uncertainties and fuel types

Influence of Small Pilot on Main Injection in a Heavy-Duty Diesel Engine

Factors influencing the effect of pilot-injection on main-injection combustion were investigated using heat release analysis in a heavy-duty diesel engine fuelled with standard diesel fuel, and included the effect of those factors on engine performance and emissions.Combinations of pilot injection parameters i.e. pilot start of injection, pilot mass, pilot-main injection separation, and rail pressure were studied for various operating conditions and combustion phases.It was concluded that the effect of pilot-injection combustion on main injection can be studied based on the phase of pilot combustion at the start of main injection. Four cases were identified: a) main injection during the mixing phase of pilot injection; b) main injection during the premixed phase of pilot combustion; c) main injection during the diffusive phase of pilot combustion and d) main injection after pilot combustion was completed.The effect of pilot injection was illustrated by the conceptual model of interaction modes. This approach has the advantage that the effect of each mode on the main injection is independent of the pilot injection parameters. For combustion control stability and convergence reasons, it is important to consider the transition between the four different interaction modes in regard to variances in the chamber conditions, pilot injected mass and pilot injection combustion