Combustion Feedback Research Articles

Experimental study of emission characteristics for fully premixed combustion of dimethyl ether and hydrogen based on flame ions

The detection of flame ion current is a promising approach in fully premixed combustion. However, how to control the excess air coefficient (α) by ion current still needs an effective method. For this reason, the application of natural gas (12T), hydrogen-doped 12T (12T-H) and dimethyl ether (DME) in fully premixed combustion is experimentally studied in this paper. The emission characteristics of NOx, CO and CO2 from fully premixed condensing gas boilers (FPCGB) were analyzed. The detection voltage generated by the flame ion current is used to monitor the NOx emissions of different gas types. A novel combustion control method based on flame ion current is proposed. The results show that hydrogen addition can reduce NOx, CO and CO2 emissions of 12T. The highest NOx emission is observed at a hydrogen volume ratio (HVR) of 15 % in the experiment. The detection voltage gradually decreases with increasing HVR. The CO2 of DME is always lower than 12T. When α exceeds 1.21, 1.31 and 1.12, respectively, DME exhibits higher values in NOx, CO and detection voltage compared to that of 12T. In addition, two combustion characteristic values are identified and proposed for combustion feedback control. The peak voltage (Up) can be used as a parameter to identify the type of gas. The emission voltage (Ue) can be used to determine whether the NOx emission concentration exceeds the 40 ppm threshold.

CLOSED-LOOP COMBUSTION CONTROL IN PPCI ENGINE

Low-temperature combustion (LTC) is a method which describes extremely low NOx and soot concentrations in an internal combustion engine. Absolutely, the element that mainly affects to mixture fuel-air premixed and combustion in PPCI engines is chemical kinetics. In PPCI combustion, the pressure, and temperature of the mixture inside the cylinder influence the duration of combustion. This study describes closed-loop combustion control in PPCI engines. Initially, control variables are necessary for this method. Secondly, it considers the combustion feedback sensors and control drives burn. The final section presents the PPCI closed-loop combustion control method.

Nonlinear Estimation of Variables for Heat Release Calculation Using a Gradient Method

Advanced combustion such as the partially premixed combustion (PPC) is characterized by high energy efficiency. However, they are sensitive to the inlet condition and injection of a combustion engine. Therefore, it is essential to use combustion feedback. The accuracy of the feedback variables, derived from the cylinder pressure signal, is crucial for effective combustion feedback control. This paper proposes a nonlinear least-squares regression method to estimate the pressure offsets and variable polytropic exponent in heat release calculation automatically. The combustion feedback variables derived from the auto-tuned heat-release rate were applied to a heavy-duty compression ignition (CI) engine burning with gasoline fuel.

Indicated Torque Estimation of Gasoline Direct Injection Engine via Optimized Model-Based Observer

The indicated torque (TQin) is regarded as a key variable for both control and diagnostics of the combustion of gasoline engines. Due to the limitation in available sensors, the TQin, however, cannot be measured directly. In this paper, a real-time TQin estimation approach is presented, based on the instantaneous crankshaft rotational speed (ω) signal. A physics-based control-oriented model ω is developed for a four-cylinder gasoline direct engine, which takes account the load torque, friction torque and the indicated torque. The proposed observer are validated both in simulation and experiments at steady-state operating and during transients. Results show that deviation between the observed value and the actual value is within 4%. The optimized model based observer shows greater potential in engine combustion feedback control.

In-cycle combustion feedback control for abnormal combustion based on digital ion current signal

For better stability of ion current employed for in-cycle combustion diagnosis and feedback control, this research develops a digital post-processing unit for in-cylinder ion current signals. Based on the processed digital ion current signal, abnormal combustion in gasoline direct injection engine is successfully detected, and the in-cycle remedy feedback control is achieved as well. Both re-ignition and re-injection are utilized for misfiring remedy, and only re-injection is employed for knocking inhibition. The accuracy of misfiring diagnosis is achieved no less than 94%, and the re-injection combined with re-ignition operation is shown to be feasible for misfiring remedy as well. The accuracy of knocking diagnosis is around 85% (knocking rate = 20%). The re-injection under the pre-knocking condition is shown to be effective for knocking inhibition.

Closed-Loop Combustion Noise Limit Control for Modern Diesel Combustion Modes

Current and future requirements in diesel engines to meet the legislative emission standards have already led to the use of advanced combustion control and feedback mechanisms such as cylinder pressure-based combustion control. The wealthy information in a cylinder pressure signal can also be used to extract the combustion noise (CN) information from a combustion event. Toward this objective, this paper presents different methods of pressure-based CN estimation and control. Specifically, a novel stochastic CN limit control has been proposed and integrated into an overall closed-loop combustion control management system. The effectiveness of the presented methods has been demonstrated in experiments using a diesel engine running with advanced combustion modes.

Influence of MFB50 control on emission dispersions according to engine parameter changes for passenger diesel engines

Combustion phase variations in diesel engines due to production tolerance, engine aging, and different combustion conditions cause performance deterioration of fuel economy, torque, and emissions. Therefore, the combustion phase should be controlled by feedback information. A well-known method to control the combustion phase is mass fraction burnt 50% (MFB50) control using in-cylinder pressure. MFB50 control can retain performance through combustion phase compensation despite production tolerance, engine aging, and different combustion conditions. However, MFB50 can compensate only for variations caused by combustion phase changes; therefore, further study is required to supplement the limitation of MFB50 control. In this study, to analyze the effect of MFB50 control on combustion, MFB50 is controlled by adjusting the main injection timing using in-cylinder pressure at 1500 rpm and a BMEP of four bar according to engine parameter changes. The parameters are fuel rail pressure, boost pressure, mass air flow, swirl valve open, main injection quantity, pilot injection timing, and quantity. While the engine parameters were changing, the influence of MFB50 control on the combustion and emissions was analyzed to establish improvement points for combustion feedback control. Our experiments demonstrated that MFB50 control reduced NOx dispersions but at the cost of increasing PM dispersions. Therefore, to improve MFB50 control, a control algorithm that can handle PM emission dispersion needs to be considered.

Zero-dimensional modeling of NOx formation with least squares interpolation

Physical models of NO x formation are becoming more and more interesting in the area of combustion feedback control. The fact that cylinder pressure sensors are made available on the market enables fast and accurate calculations of heat release, which is an essential part of every physical NO x formation model. This article describes such a zero-dimensional model for a diesel engine using crank angle–resolved cylinder pressure to determine heat release. The model also incorporates the thermal effect of exhaust gas recirculation that is proven to have a major effect on NO x formation rates. The reaction mechanisms used to describe NO x formation rates are given by the well-known Zeldovich mechanism. The model output results given in this article show an average deviation of about 12.0% from acquired measured NO x data. The least squares interpolation approach indicates a negligible difference from the original model with an average deviation of 1.2% in 25 measurement points.

Diesel pressure departure ratio algorithm for combustion feedback and control

The pursuit for higher efficiency and ultra-low exhaust emissions from diesel engines requires the combustion process to be precisely controlled so as to minimize departures from the intended engine operation. The combustion control system must be able to perform corrective actions on a cycle-by-cycle basis, with a robust feedback on the combustion process. The combustion phasing, commonly represented by the crank angle of 50% heat release and derived from the measured cylinder pressure data, shows a strong correlation to the efficiency and the engine-out nitrogen oxide emissions. To accurately estimate the combustion phasing from the derived heat-release rate, the authors previously introduced and experimentally validated a computationally efficient diesel pressure departure ratio algorithm, against selected cases of boost, engine load and exhaust gas recirculation. In this work, the formulation of the pressure departure ratio algorithm is presented in detail along with its implementation to enable combustion control during both transient and steady-state engine operations. Engine tests demonstrate that the algorithm was effective in stabilizing the combustion process on a cycle-by-cycle basis for a range of engine speeds, load and exhaust gas recirculation, which included conventional and low-temperature diesel combustion modes.

Feedback Combustion Control Using Chemi-Ionization Probe in Supersonic Flow of Combustion Products

DOI: 10.2514/1.43809 The results of the present work demonstrate feasibility of feedback combustion control using a chemi-ionization current sensor placed in a supersonic flow of combustion products. Operated in the saturation regime, the ionization sensor (Thomson probe) removes nearly all electrons from the flow and therefore acts as a global chemi-ionization detector. The results show that a relation between the equivalence ratio in the combustor and the chemi-ionization current in the M 3 flow can be used to maintain the equivalence ratio at the desired value. The experiments have shown that using different target values of the chemi-ionization current in the feedback control program enforces transition from near-stoichiometric to fuel-lean and from fuel-lean to near-stoichiometric conditions in the combustor. The experiments have also demonstrated that the feedback control system can counter external perturbations, which either increase or decrease the equivalence ratio in the combustor and bring the fuel–oxidizer mixture composition back to the specified values. The combustion feedback control system based on a Thomson chemi-ionization probe is simple and straightforward and can be easily adapted for practical applications.

Use of in-cylinder pressure measurement and the response surface method for combustion feedback control in a diesel engine

An engine control algorithm was designed and implemented on a heavy-duty diesel engine. The goal was to develop a control system that could adjust split injection parameters to accommodate changes in operating parameters such as fuel and ambient air conditions, and mechanical wear during engine operation. An in-cylinder pressure transducer was chosen for the closed-loop feedback signal to be used in conjunction with the control algorithm. The control algorithm incorporated a version of the response surface method (RSM) to adjust the fuel injection parameters and to locate the optimum settings. Optimizations of double injections at 821 r/min and 25 per cent load and 0, 15, and 30 per cent exhaust gas recirculation (EGR) were first performed using a combination of the genetic algorithm (GA) and the RSM to provide baseline cylinder pressure data and to develop control criteria. These optima were then used to calibrate the control system by providing target values for the RSM control algorithm. Tests were conducted using a heat release estimate to control heat release phasing and magnitude. The control algorithm was able to adjust the timing of the first and second injections, as well as the amount of fuel injected in each pulse to phase combustion properly.