Combustion Phase Indicator Research Articles

Mutual information of cylinder pressure and combustion phase estimation in spark ignition engines

For the study of internal combustion engines, combustion control is an important method to achieve high efficiency and low emissions. Currently, in-cylinder pressure sensor-based closed-loop control strategies have become the preferred solution. However, their productional application in automotive industries is limited due to the cost of intensive pressure acquisition for a whole cycle and the calculation load of combustion phase indicators. This paper proposes a method of combustion phase estimation for spark ignition (SI) engines. In this method, the combustion phase is estimated only based on pressure measurements at several crank angles. Information entropy and mutual information are introduced to analyze the feasibility and accuracy of the combustion phase estimation, which shows that the pressure measurements at selected points contain most of the information for the estimation. As a result, only pressure measurements at 3 points and ELM estimation models are required to obtain the combustion phase, instead of intensive data acquisition and calculation.

Closed-loop combustion phase control for multiple combustion modes by multiple injections in a compression ignition engine fueled by gasoline-diesel mixture

Partially premixed combustion with low octane fuel aims to reduce NOx and soot emission simultaneously without fuel consumption penalty. Cylinder pressure based combustion phase control is an essential technology for partially premixed combustion. A novel closed-loop combustion phase control strategy for multiple combustion modes is proposed in the current study. The combustion modes are classified into three basic categories based on injection patterns and heat release stages: (1) with only one heat release stage; (2) with two separated heat release stages; (3) with two overlapped heat release stages. Crank angle when 50% fuel is consumed (CA50) is chosen as the combustion phase indicator for the first case. Start of combustion (SOC) of each heat release stage is the combustion phase indicator for the second case. Both SOC and CA50 are the combustion phase indicators for the third case. Each combustion phase is closed-loop controlled by a proportional–integral (PI) controller with the timing adjustments of the corresponding injection. The control strategy is verified under different operating conditions in a 1.9 L light duty diesel engine fueled by gasoline-diesel mixture (volumetric 70% gasoline, 30% diesel). The experimental results show that the control strategy is able to control the combustion phase, reduce cylinder to cylinder variations as well as cycle to cycle variations under the operating conditions with exhaust gas circulation (EGR) rates of 10% and 15%.

Thermochemical Properties of PM2.5 as Indicator of Combustion Phase of Fires

Past studies suggest that certain properties of fire emitted particulate matter (PM) relate to the combustion phase (flaming, smoldering) of biomass burning, but to date there has been little consideration of such properties for use as combustion phase indicators. We studied the thermochemical properties of PM2.5 emitted from experimental and prescribed fires using multi-element scanning thermal analysis (MESTA). Resulting thermograms show that the carbon from PM2.5 generally can be grouped into three temperature categories: low (peak ~180 °C), medium (peak between 180–420 °C), and high (peak > 420 °C) temperature carbons. PM2.5 from smoldering phase combustion is composed of much more low-temperature carbon (fraction of total carbon = 0.342 ± 0.067, n = 9) than PM2.5 from the flaming phase (fraction of total carbon = 0.065 ± 0.018, n = 9). The fraction of low-temperature carbon of the PM2.5 correlates well with modified combustion efficiency (MCE; r2 = 0.76). Therefore, this MESTA thermogram method can potentially be used as a combustion phase indicator solely based on the property of PM2.5. Since the MESTA thermogram of PM2.5 can be determined independently of MCE, we have a second parameter to describe the combustion condition of a fire, which may refine our understanding of fire behavior and improve the accuracy of emission factor determinations. This PM2.5 indicator should be useful for discerning differential diffusion between PM2.5 and gases and providing insight into the impact of PM emission on atmospheric environment and the public health.

An On-Board Calibration Scheme for Map-Based Combustion Phase Control of Spark-Ignition Engines

To improve the transient-state combustion phase control performance and adapt to the shift of engine dynamics, this paper presents an on-board calibration scheme to control the combustion phase of spark-ignition (SI) engines. First, taking a crank angle of 50% of the mass fraction burnt (CA50) as the combustion phase indicator, the relationship between CA50 and SA is studied, and the influences of two other important factors, engine speed and load, are regarded, as the parameters need calibration or update. Second, a bilinear interpolation algorithm is employed to depict the polynomial influence function of speed and load on CA50, which is also used for the CA50 control later. Then, the on-board calibration issue is converted to a parameters identification problem, and a stochastic gradient descent algorithm is utilized to identify model parameters by iterative updates, which reduces computational complexity and the use of memory space for the embedded control system. Finally, the proposed strategy is verified on a gasoline SI engine and is applied to the combustion phase control in the feedforward channel, which can significantly improve the performance at a transient-state operating condition.

Cylinder pressure sensor‐based real‐time combustion phase control approach for SI engines

As one of most effective factors affecting the economy and emissions of internal combustion engines, the combustion phase can maximize performance by tracking its optimum reference. In this study, the combustion phase indicator CA50 is employed for the combustion control of spark‐ignited (SI) engines with the application of a cylinder pressure sensor. In order to suppress the influence of cylinder pressure variation on CA50 measurement, a moving average method is used to stabilize CA50 calculation, and based on measured CA50, a linear autoregressive model is obtained by identification, which depicts the relationship between spark advance and combustion phase. Then, a closed‐loop controller is synthesized for CA50 regulation, including both feedforward and feedback channels. Finally, the proposed strategy is validated by experiments on an SI engine. © 2016 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

On-line statistical combustion phase optimization and control of SI gasoline engines

This paper focuses on analysis and control of the ignition timing of spark ignition (SI) engines to maximize fuel efficiency, in which the optimal reference of combustion phase and moving average based control strategy are discussed. To extract the fuel efficiency information from combustion, in-cylinder pressure sensor is available to calculate combustion phase and indicated mean effective pressure (IMEP). Then, employing CA50 as combustion phase indicator, statistical gradient descent method is utilized to seek the CA50 set point that ensures the maximum indicated fuel conversion efficiency (IFCE) and satisfies the probability constraint of incorrect adjustment with least cycles. Since the combustion suffers from cyclic variation, moving average based feedback control approach on the evaluation of consecutive in-cylinder pressure traces, is designed to track CA50 set point by adjusting spark advance. Finally, the experiments on a 6-cylinder 3.5-l SI gasoline engine validate the performance of the proposed strategies.

Experimental comparisons of hypothesis test and moving average based combustion phase controllers

For engine control, combustion phase is the most effective and direct parameter to improve fuel efficiency. In this paper, the statistical control strategy based on hypothesis test criterion is discussed. Taking location of peak pressure (LPP) as combustion phase indicator, the statistical model of LPP is first proposed, and then the controller design method is discussed on the basis of both Z and T tests. For comparison, moving average based control strategy is also presented and implemented in this study. The experiments on a spark ignition gasoline engine at various operating conditions show that the hypothesis test based controller is able to regulate LPP close to set point while maintaining the rapid transient response, and the variance of LPP is also well constrained.

A statistical combustion phase control approach of SI engines

In order to maximize the performance of internal combustion engine, combustion phase is usually controlled to track its desired reference. However, suffering from the cyclic variability of combustion, it is difficulty but meaningful to control mean of combustion phase and constrain its variance. As a combustion phase indicator, the location of peak pressure (LPP) is utilized for real-time combustion phase control in this research. The purpose of the proposed method is to ensure the mean of LPP statistically tracks its reference and constrains the standard deviation of LPP distribution. To achieve this, LPP is first calculated based on the cylinder pressure sensor, and its characteristics are analyzed at the steady-state operating condition, then the distribution of LPP is examined online using hypothesis test criterion. On the basis of the presented statistical algorithm, current mean of LPP is applied in the feedback channel for designing spark advance adjustment law, and the stability of closed-loop system is theoretically ensured according to a steady statistical model. Finally, the proposed strategy is verified on a spark ignition gasoline engine.

REMOVED: Experimental investigation of impacts of engine hardware, operating parameters and combustion performance on particulate emissions in a DISI engine

With increasing concern over ultrafine Particulate Matter (PM) emissions from Direct Injection Spark Ignition (DISI) engines and ever tightening emissions legislation, substantial research work is required to obtain a better understanding of influence of advanced engine technologies on particulate formation and oxidation. In this work, experimental investigation of engine-out particulate emissions were carried out on a single cylinder spray-guided DISI engine. With regard to effects of engine hardware on PM emissions; impacts of fuel spray angle, fuel flow rate and intake valves’ lift and camshaft phasing were examined over a wide start of injection sweep window. Injector tests highlighted a complex relation between injector characteristics and engine operating parameters with PM emissions as a result of fuel impingement and poor mixture preparation. Valvetrain tests indicated some benefits from engine throttling by valve lift and intake camshaft phasing in particulate number concentration reduction at low load. This was associated with increased intake flow turbulence and improved mixture preparation. Number-weighted particle size distribution was also affected by intake valve modes at low load. Nevertheless, at high load, impacts of variable valve lift and camshaft phasing on particulate number concentration and size distribution became negligible. Furthermore, combustion phase indicators were studied in order to probe impacts of combustion performance on PM emissions. While no satisfactory correlation of initial flame development with PM emissions was identified; shorter rapid-burning angles were observed with lower particulate number concentrations.

Combustion Phase Control of SI Gasoline Engines Using Hypothesis Test

In order to maximize the performance of internal combustion engines, combustion phase is usually controlled to track its optimal setpoint. In this paper, as one of combustion phase indicators, location of peak pressure (LPP) is employed for combustion phase control. In the statistic point of view, hypothesis test is utilized to check the distribution of LPP, then a decision block is designed based on the statistics of LPP. Using the mean of LPP calculated by the presented hypothesis test algorithm, a simple steady model based controller is synthesized, which regards spark advance as system input. Finally, the proposed strategy is verified by the experiment test on a spark ignition gasoline engine.

Spark Ignition Feedback Control by Means of Combustion Phase Indicators on Steady and Transient Operation

In order to reduce fuel cost and CO2 emissions, modern spark ignition (SI) engines need to lower as much as possible fuel consumption. A crucial factor for efficiency improvement is represented by the combustion phase, which in an SI engine is controlled acting on the spark advance. This fundamental engine parameter is currently controlled in an open-loop by means of maps stored in the electronic control unit (ECU) memory: such kind of control, however, does not allow running the engine always at its best performance, since optimal combustion phase depends on many variables, like ambient conditions, fuel quality, engine aging, and wear, etc. A better choice would be represented by a closed-loop spark timing control, which may be pursued by means of combustion phase indicators, i.e., parameters mostly derived from in-cylinder pressure analysis that assume fixed reference values when the combustion phase is optimal. As documented in literature (Pestana, 1989, “Engine Control Methods Using Combustion Pressure Feedback,” SAE Paper No. 890758; BERU Pressure Sensor Glow Plug (PSG) for Diesel Engines, http://beru.federalmogul.com; Sensata CPOS SERIES—Cylinder Pressure Only Sensors, http://www.sensata.com/download/cpos.pdf; Malaczynski et al., 2013, “Ion-Sense-Based Real-Time Combustion Sensing for Closed-Loop Engine Control,” SAE Int. J. Eng., 6(1), pp. 267–277; Yoshihisa et al., 1988, “MBT Control Through Individual Cylinder Pressure Detection,” SAE Paper 881779; Powell, 1993, “Engine Control Using Cylinder Pressure: Past, Present, and Future,” J. Dyn. Syst., Meas. Control, 115, pp. 343–350; Muller et al., 2000, “Combustion Pressure Based Engine Management System,” SAE Paper 2000-01-0928; Yoon et al., 2000, “Closed-Loop Control of Spark Advance and Air-Fuel Ratio in SI Engines Using Cylinder Pressure,” SAE Paper 2000-01-0933; Eriksson, 1999, “Spark Advance Modeling and Control,” Dissertation N° 580, Linkoping Studies in Science and Technology, Linköping, Sweden; Samir et al., 2011, “Neural Networks and Fuzzy Logic-Based Spark Advance Control of SI Engines,” Expert Syst. Appl., 38, pp. 6916–6925; Cook et al., 1947, “Spark-Timing Control Based on Correlation of Maximum-Economy Spark Timing, Flame-Front Travel, and Cylinder Pressure Rise,” NACA Technical Note 1217; Bargende, 1995, “Most Optimal Location of 50% Mass Fraction Burned and Automatic Knock Detection,” MTZ, 10(56), pp. 632–638.), the use of combustion phase indicators allows the determination of the best spark advance, apart from any variable or boundary condition. The implementation of a feedback spark timing control, based on the use of these combustion phase indicators, would ensure the minimum fuel consumption in every possible condition. Despite the presence of many literature references on the use combustion phase indicators, there is no evidence of any experimental comparison on the performance obtainable, in terms of both control accuracy and transient response, by the use of such indicators in a spark timing feedback control. The author, hence, carried out a proper experimental campaign comparing the performances of a proportional-integral spark timing control based on the use of five different in-cylinder pressure derived indicators. The experiments were carried out on a bench test, equipped with a series production four cylinder spark ignition engine and an eddy current dynamometer, using two data acquisition (DAQ) systems for data acquisition and spark timing control. Pressure sampling was performed by means of a flush mounted piezoelectric pressure transducer with the resolution of one crank angle degree. The feedback control was compared to the conventional map based control in terms of response time, control stability, and control accuracy in three different kinds of tests: steady-state, step response, and transient operation. All the combustion phase indicators proved to be suitable for proportional-integral feedback spark advance control, allowing fast and reliable control even in transient operations.

Real-Time Combustion Phase Detection Using Central Normalized Difference Pressure in CRDI Diesel Engines

To develop eco-friendly diesel engines, accurate combustion phase control is important due to its significant effects on harmful emissions and fuel efficiency. In order to accurately control the combustion phase, the detection of the combustion phase should precede control system design. Currently, combustion phase detection is done by the location of 50% mass fraction burned (MFB50), because of its close correlation with emissions and fuel efficiency. However, this method is not easily implemented in real-time applications because the calculation of MFB50 requires a large amount of in-cylinder pressure data and an excessive computational load. For this reason, a combustion phase indicator with a simple algorithm is required for real-time combustion control. In this study, we propose a new combustion phase indicator, called the “Central normalized difference pressures (CNDP).” The CNDP indicates the center of the two crank angles where the normalized difference pressure between firing pressure and motoring pressure (NDP) reaches 90% of the maximum value before peak (NDPbp90), and 70% of the maximum value after peak (NDPap70). The NDPbp90 and NDPap70 are highly correlated with MFB50 and the correlation is enhanced as the center between the two points obtained. The CNDP is represented by a fixed quadratic polynomial with MFB50 that robust to changes in various engine operating conditions such as engine speed, main injection timing, injected fuel quantity, fuel-rail pressure, exhaust gas recirculation (EGR) rate and boost pressure. Furthermore, in performance evaluation, the CNDP requires remarkably fewer in-cylinder pressure data samples, calculation steps and less computation time compared to MFB50. These results show great potential for the CNDP to be a substitute for the MFB50 since the proposed combustion phase detection algorithm can be used effectively for real-time combustion phase detection and control.

A Comparison Between Combustion Phase Indicators for Optimal Spark Timing

The closed-loop control of internal combustion engine spark timing may be accomplished by means of a combustion phase indicator, i.e., a parameter, derived from in-cylinder pressure analysis, whose variation is mainly referable to combustion phase shift and assumes a fixed reference value under optimal spark timing operation. The aim of the present work is a comparison between different combustion phase indicators, focusing on the performance attainable by a feedback spark timing control, which uses the indicator as pilot variable. An extensive experimental investigation has been carried out, verifying the relationship between indicators’ optimal values and the main engine running parameters: engine speed, load, and mixture strength. Moreover, assessment on the effect of the most common pressure measurement problems (which are mainly related to pressure referencing, sampling resolution, top dead center determination, and cycle-by-cycle variations) on the indicators’ values and on the performance attainable by the spark timing control is included. The results of the comparison point out two indicators as the most suitable: the location of pressure peak and the location of maximum heat release rate. The latter, not available in literature, has been introduced by the author as an alternative to the 50% of mass fraction burned.