Cylinder Pressure Data Research Articles

Convex Identification of Minimal Function Bases for Cylinder Pressure by Using Pressure Values as Basis Weights

Estimating cylinder individual pressures using flywheel angular measurements is difficult, foremost because several input signals must be estimated from one single measurement signal. Since the pressures cannot vary arbitrary, estimation can still be possible, but it leaves little room for robustness. To take most use of data and models, it is suggested here to parameterize pressures using a function basis. For a general physics-based engine model, it is shown how the information content in the angular measurement is limited, implying that only a few parameters per cylinder can be estimated. If small deviations in the combustion are to be identified, a very parameter efficient basis is, therefore, needed. By showing that the basis can be chosen such that its weights are pressures at distinct angles, a convex optimization problem to determine optimal basis functions is derived. The method is applied to extensive cylinder pressure data for a six-cylinder diesel engine in a case study with induced combustion faults. The result is that only three to four free parameters per cylinder are needed to achieve a close fit, and a provided analysis suggests that this may enable the design of robust estimators.

Flame transport in a heavy-duty diesel engine

A heavy-duty diesel engine has been constructed to provide full optical access to the piston bowl with a window forming the bottom of the “optical” piston. The engine is operated up to 1400 rpm, with peak firing pressure of up to 160 bar and IMEP levels of up to 20 bar. Fuel injection is accomplished with a common rail system and an externally driven high-pressure pump. Data were taken for cylinder pressure with synchronous recording of diesel flame ignition and combustion by means of a high-speed camera. The task of the project summarized in this paper was to evaluate flame and cylinder pressure data gained in this engine at part load and high-load operation. The focus of data evaluation was on identifying main flame transport mechanisms and relating them to simultaneously recorded rates of heat release.

Comparative Exergy Analysis of Fuel Additives Containing Oxygen and HC based in a Spark-Ignition (SI) engine

The effects of fuel additives have been investigated based on the second law (exergy analysis) of thermodynamic in an SI engine. Exergy terms such as the total cylinder exergy, exergy transfers via heat transfer and work, fuel chemical exergy and irreversibility were computed for closed part of the engine cycle. Additionally, the exergy distributions, the brake power, brake specific fuel consumption (BSFC), first (energy) and second law (exergy) efficiencies were determined. The experimental data, especially the measured cylinder pressure data, were used to calculate the exergy terms with a home-made code. Test results showed that when compared with gasoline operation, the peak cylinder pressure for M10, E10, and S10 was increased by 18.65%, 12.75% and 15.52%, respectively, and also shifted towards to TDC. In addition, the energy and exergy efficiency decreased with the addition of methanol, ethanol, and solketal. The maximum reduction in the exergy efficiency occurred for the S10, and this reduction was determined as about an 8.42%. The results also revealed that the gasoline blends containing a 10% methanol, ethanol, and solketal were an unfavorable choice from the second-law perspective, due to the reduction in the exergy.

Comparative study of the simulation ability of various recent hydrogen combustion mechanisms in HCCI engines using stochastic reactor model

Hydrogen is a clean potential alternative fuel for internal combustion engines and completely eliminates the carbon based engine emissions (CO, CO2 and unburned hydrocarbons). Homogenous charge compression ignition (HCCI) is a low temperature combustion mode with higher thermal efficiency and ultralow NOx emission. Hydrogen HCCI engine can combine potential benefit of fuel and combustion characteristics. In HCCI engine, combustion is governed by the chemical kinetics of the oxidation reactions. In-order to find a suitable reaction mechanism to numerically predict the combustion characteristics of hydrogen HCCI engine, 15 recent hydrogen combustion mechanisms are compared and analyzed. All mechanisms were simulated using a stochastic reactor model (SRM) to evaluate the combustion parameters for HCCI engine. Simulations were performed by varying inlet temperature (400–440 K), intake pressure (1.0–3.0 bar), engine speed (1000–3000 rpm) and relative air-fuel ratio (λ = 2 to 8) for all the mechanisms. Ignition delay predicted from different mechanism was compared with experimental data and ignition delay was also compared at engine like condition using all the test mechanisms. Error in prediction of different combustion parameters such as start of combustion (CA10), maximum cylinder pressure (Pmax) and maximum heat release rate (HRRmax) were evaluated using different hydrogen combustion mechanisms. It was found that a recently developed hydrogen mechanism (Maurya-2017) shows the closet resemblance with the experimental cylinder pressure data. The Oconaire-2004 mechanism was able to accurately predict the characteristics of hydrogen HCCI combustion. It was also found that NUIG-NGM-2010 and CRECK-2014 mechanisms were able to estimate the HCCI combustion characteristics under higher combustion temperature.

A phenomenological combustion analysis of a dual-fuel natural-gas diesel engine

Energy security concerns and an abundant supply of natural gas in the USA provide the impetus for engine designers to consider alternative gaseous fuels in the existing engines. The dual-fuel natural-gas diesel engine concept is attractive because of the minimal design changes, the ability to preserve a high compression ratio of the baseline diesel, and the lack of range anxiety. However, the increased complexity of a dual-fuel engine poses challenges, including the knock limit at a high load, the combustion instability at a low load, and the transient response of an engine with directly injected diesel fuel and port fuel injection of compressed natural gas upstream of the intake manifold. Predictive simulations of the complete engine system are an invaluable tool for investigations of these conditions and development of dual-fuel control strategies. This paper presents the development of a phenomenological combustion model of a heavy-duty dual-fuel engine, aided by insights from experimental data. Heat release analysis is carried out first, using the cylinder pressure data acquired with both diesel-only and dual-fuel (diesel and natural gas) combustion over a wide operating range. A diesel injection timing correlation based on the injector solenoid valve pulse widths is developed, enabling the diesel fuel start of injection to be detected without extra sensors on the fuel injection cam. The experimental heat release trends are obtained with a hybrid triple-Wiebe function for both diesel-only operation and dual-fuel operation. The ignition delay period of dual-fuel operation is examined and estimated with a predictive correlation using the concept of a pseudo-diesel equivalence ratio. A four-stage combustion mechanism is discussed, and it is shown that a triple-Wiebe function has the ability to represent all stages of dual-fuel combustion. This creates a critical building block for modeling a heavy-duty dual-fuel turbocharged engine system.

Estimation of optimum number of cycles for combustion analysis using measured in-cylinder pressure signal in conventional CI engine

Abstract Analysis of measured in-cylinder pressure data provides various parameters that characterize engine combustion process. Advanced engine control technologies use cylinder pressure based combustion parameters for closed loop control. Four step signal processing (i) absolute pressure correction, (ii) crank angle position referencing, (iii) cycle averaging and (iv) filtering is typically applied to get sufficiently accurate cylinder pressure data for an engine cycle. This paper focuses on cycle averaging and filtering of in-cylinder pressure signal from a conventional compression ignition (CI) engine. Experiments are conducted at different engine load and compression ratios at 1500 rpm. The in-cylinder pressure trace of 2500 consecutive engine cycles is recorded and analyzed. Effect of in-cylinder pressure signal noise and cyclic variation on combustion analysis is investigated. A method based on standard deviation of pressure and pressure rise rate is used to find sufficient minimum number of engine cycles to be recorded for averaging to get reasonably accurate pressure data independent of cyclic variability.

Effect of Butanol Blends on Nano Particle Emissions from a Stationary Conventional Diesel Engine

In this study, combustion characteristics and nano-size soot particle emissions from a stationary conventional diesel engine have been experimentally investigated using butanol/diesel blends. Experiments were conducted on a single cylinder stationary diesel engine at a constant speed of 1500 rpm for neat diesel and butanol/diesel blends (i.e., 10%, 20% and 30% butanol on volume basis) at different engine loads. Piezoelectric pressure transducer installed in the engine combustion chamber was used for measuring cylinder pressure data. In-cylinder pressure data for 2000 consecutive engine cycles was recorded and averaged data was used for the analysis of combustion characteristics. Butanol/diesel blends show higher rate of heat release in comparison to neat diesel and heat release rate increases with butanol percentage in the blend. Opacity meter and exhaust particle sizer were used for analyzing smoke opacity, size and mass distributions of soot particles respectively at different engine operating conditions. Soot particle distribution from 5 nm to 1000 nm was recorded at each test condition. Results show that total particle concentration decreases with an increase in engine operating loads. It was found that butanol/diesel blends have lower total particulate concentration and the surface area.

Determining the Initial In-Cylinder Gas State Based on Semi-Physical Models

Two methodologies are presented for modeling the initial in-cylinder gas state prior to the combustion. The first method is based on measured in-cylinder pressure data and allows the cylinder individual calculation of the gas mass and temperature. A physical equation for the online calculation of the polytropic exponent during the compression stroke is derived in order to receive accurate absolute pressure data from piezo based in-cylinder pressure sensors. In order to model the in-cylinder temperature an additional semi physical model is proposed to account for the heat input during the intake stroke. From the first methodology a second semi-physical model for the average in-cylinder gas mass and temperature is derived which will only need cylinder pressure data for the calibration process of the experimental model.

Determining burning duration in SI engines

In the present work a simple technique for determining the burning duration in SI engines has been presented. This method is based on entropy calculation during the burning process of engine. This method has been tested successfully by means of pressure–crank angle data obtained from CFR engine at different operating conditions and then it has been applied on XU7 engine. The comparison between theoretical and experimental data shows the acceptable accuracy of the method. Since the presented method utilizes cylinder pressure and volume data versus crank angle, low computational costs, acceptable accuracy and the ease of use are its advantages and it can be a powerful replacement for expensive laboratory measurement devices such as ion gaskets or optical flame detectors.

Stability-Guaranteed Force-Sensorless Contact Force/Motion Control of Heavy-Duty Hydraulic Manipulators

In this paper, a force-sensorless high-performance contact force/motion control approach is proposed for multiple-degree-of-freedom hydraulic manipulators. A rigorous stability proof for an entire hydraulic manipulator performing contact tasks is provided for the first time. The controller design for the manipulator is based on the recently introduced virtual decomposition control approach. As a significant novelty, the end-effector contact force is directly estimated from the manipulator's cylinder pressure data, which provides a practical solution for heavy-duty contact force control without engaging fragile force/torque sensors. In the experiments, the proposed controller achieved a force control accuracy of 4.1% at a desired contact force of 8000 N while in motion. This can be considered a significant result due to the hydraulic actuators’ highly nonlinear behaviors, the coupled mechanical linkage dynamics, and the complex interaction dynamics between the manipulator and the environment.

Real-time start of a combustion detection algorithm using initial heat release for direct injection diesel engines

The start of combustion (SOC) in a compression ignition engine may not be consistent due to the engine operating conditions of each engine cycle. This is true even if fuel is injected at a consistent time. Variable factors include humidity, temperature, fuel quality, exhaust gas recirculation (EGR) rate, and boost pressure. These variations in SOC cause an increase in harmful emissions as well as deterioration of engine performance; therefore, SOC has to be detected and controlled. In this study, we present a simplified heat release (HR) equation to detect SOC for real-time closed-loop combustion control in a compression ignition engine. The proposed method extracts SOC using an initial heat release (IHR) equation that is a modified heat release equation. The detected SOC using IHR reveals a close correlation with one percent of heat release at various engine operating conditions such as main injection timing, injected fuel quantity, fuel-rail pressure, and EGR rate changes. In addition, the SOC detected from the proposed method shows great potential for real-time applications as it reduces of the amount of cylinder pressure data by 50.2% and computational load by 55.2%. Finally, SOC was well controlled in real-time with the estimated SOC despite engine operating condition changes.

Combustion characteristics of lemongrass (Cymbopogon flexuosus) oil in a partial premixed charge compression ignition engine

Indeed, the development of alternate fuels for use in internal combustion engines has traditionally been an evolutionary process in which fuel-related problems are met and critical fuel properties are identified and their specific limits defined to resolve the problem. In this regard, this research outlines a vision of lemongrass oil combustion characteristics. In a nut-shell, the combustion phenomena of lemongrass oil were investigated at engine speed of 1500rpm and compression ratio of 17.5 in a 4-stroke cycle compression ignition engine. Furthermore, the engine tests were conducted with partial premixed charge compression ignition-direct injection (PCCI-DI) dual fuel system to profoundly address the combustion phenomena. Analysis of cylinder pressure data and heat-release analysis of neat and premixed lemongrass oil were demonstrated in-detail and compared with conventional diesel. The experimental outcomes disclosed that successful ignition and energy release trends can be obtained from a compression ignition engine fueled with lemongrass oil.

THE HEAT TRANSFER COEFFICIENT CALCULATION IN THE ICE CYLINDER BASED ON IN-CYLINDER PRESSURE DATA

In this paper the calculations algorithm of heat-transfer coefficient in the combustion chamber of the internal combustion engine is presented. Developed algorithm is based on the in cylinder pressure data. The proposed algorithm can be helpful to determine the average values of heat-transfer coefficient from working medium to the combustion chamber walls (crown of a cylinder head, cylinder walls and piston head) during combustion process. The calculation method includes modified one zone heat release model in combustion chamber of SI engine. Proposed method consists in closing the energy balance equation by the coefficient which expresses the heat losses to the walls of the combustion chamber. The average value of the heat losses during combustion process is calculated by two steps. Firstly, the integration of the energy balance equation (without specifying the heat losses) leads to designation of the so-called net value of heat released in cylinder. In the next step the amount of the total energy supplied to the cylinder is determined taking into account the chemical energy of the supplied fuel. The difference between the supplied value of chemical energy and heat released net value allows to determine the heat losses average value. In last stage, the heat flow equation leads to calculate the mean value of heat transfer coefficient during combustion process.

Determination of specific heat ratio and error analysis for engine heat release calculations

The burnt fraction f of Wiebe equation has been shown to be dependent only on the newly defined parameter ‘combustion burn factor (Ci)’; and the benefits of expressing heat release rate with respect to Ci have been presented. The errors associated with the determination of apparent heat release rate (Ahrr) and the cumulative heat release (Cum.Hrr) from the measured cylinder pressure data and the assumed specific heat ratio (γ) was determined and compared. The γ affected the calculated Ahrr more than the cylinder pressure. Overestimation of γ resulted in an underestimation of the peak value of the Ahrr and vice versa, this occurred without any shift in the combustion phasing. A new methodology has been proposed to determine the instantaneously and mean value of γ for a given combustion. This new methodology has been applied to determine γ for a wide range of engine operating conditions and for different fuels.

Engine Noise Synthesis Based on Cylinder Pressure Data

Engine Noise Synthesis Based on Cylinder Pressure Data

Real-time combustion parameter estimation algorithm for light-duty diesel engines using in-cylinder pressure measurement

This paper proposes a real-time estimation algorithm of combustion parameters for the location of 50% of mass fraction burnt (MFB50), and indicated mean effective pressure (IMEP). The proposed estimation algorithm uses the difference pressure only instead of the in-cylinder pressure for calculation of the combustion parameters. Since the difference pressure is the pressure that is generated only by the combustion, it occurs between the start of combustion (SOC) and the end of combustion (EOC); this allows the proposed algorithm to estimate the combustion parameters with fewer cylinder pressure data samples and low computational load compared with the conventional method. The proposed algorithm estimates the IMEP with a result acquired during the MFB50 calculation and that can significantly reduce the computational load required to calculate the combustion parameters. Consequently, the proposed estimation algorithm requires only 51% of the execution time to calculate the combustion parameters compared to the conventional method. The proposed estimation algorithm is validated with an engine experiment under 131 operating conditions that showed high linear correlation with the original combustion parameters. In-cylinder pressure based combustion control using the estimated combustion parameters is introduced as a case study and the proposed estimation algorithm validated its significant potential for real-time applications.

Effect of the diesel injection timing and the pilot quantity on the combustion characteristics and the fine-particle emissions in a micro-diesel pilot-ignited natural-gas engine

Natural gas is a potential alternative to conventional liquid fuels for utilization in automotive internal combustion engines. Its utilization can significantly reduce the levels of nitrogen oxide and particulate matter emissions from dual-fuel diesel/natural-gas engines. However, this reduction in the particulate matter emissions may induce an increase in the quantity of particles of smaller size, which are harmful to human health. The engine parameters, namely the diesel injection timing and the pilot quantity directly, affect the homogeneity of the fuel–air mixture, the spatial distribution of initial ignition centres and the quantity of initial ignition centres. In this paper, the effects of these two engine parameters on the combustion and the particle emission characteristics of micro-diesel pilot-ignited natural-gas fuel are investigated. The combustion parameters were calculated from the cylinder pressure data. An electrical low-pressure impactor was employed to measure the particle number concentration and particle size distribution. Experimental results indicate that the ignition delay period is prolonged and the particle number concentration progressively increases with advance of the injection timing, while the particle mass concentration undergoes a steady decrease and then a rapid increase. On the other hand, increasing the pilot diesel quantity can shorten the ignition delay period and enhance the burning rate. Meanwhile, the particle mass concentration increases evidently but the particle number concentration decreases unexpectedly. It should be noted that the total number of fine particles is sensitive to advancing injection and decreasing pilot mass, especially above the 20° crank angle before top dead centre injection timing and below the basic pilot mass.

Effects of using vortex tubes on events during cold start of a direct injection diesel engine

Vortex tubes use a compressed gas flow and separate it into low and high temperature regions without using any moving mechanical parts. Cold and hot exhaust flows of vortex tubes can be used for different purposes. In this study, a vortex tube was used to improve the cold start performance of a six cylinders, four stroke and direct injection diesel engine of a truck. To increase the engine intake air temperature, hot exhaust of vortex tube was introduced to the engine intake manifold. Pressured air was supplied to the vortex tube from the air tank of the compressed-air brake system of the truck. Variation in the cold starting events was observed by both in cylinder pressure data and revolution of engine crank shaft. Experiments were started when the ambient air and engine cooling fluid temperatures were at 0 °C, which is a critical temperature for cold-starting diesel engines. Experimental results showed that the cold starting performance of the engine can be successfully improved by using vortex tubes. Durations of engine starting-cranking, cranking-idling, and idling-stabling were decreased due to the increase in the intake air temperature.

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.

Simulation on Combustion Characteristics and External Characteristics of the Linear Engine System

A simulation model of the linear engine system is built in this paper. The cylinder pressure data obtained through engine experiments is used to validate the accuracy of the simulation model. Based on the model, the combustion characteristics and external characteristics of the linear engine system were studied. And the maximization model is used to find an optimum operating region of the linear engine. The results show that, as the air fuel ratio(AFR) decreases under a steady engine speed, both the cylinder pressure and brake power increase first and then decrease, reaching their peak value when the AFR is 12. Under this AFR, the maximum brake power is 16.83kW at 6500rpm. Meanwhile, the fuel economy and the power performance reach the optimum combination within 5200rpm and 6500rpm.