Determination of a most representative cycle from cylinder pressure ensembles via statistical method using distribution skewness

In internal combustion engine research, cylinder pressure measurements provide valuable information about the underlying thermodynamic and combustion processes, and are typically collected in ensembles of several 100 traces. Although in some particular fields of combustion research all traces are analyzed, in most cases only one trace is studied because analyzing all the traces is impractical due to the large number of collected samples. Instead, an ensemble-averaged pressure trace is commonly calculated and used for analysis. However, this pressure trace is highly smoothed and dynamic information is lost during the averaging process. With the average trace, pressure rise rates are lower and pressure oscillations such as the ones resulting from combustion knock are lost. In this work, a statistical method was developed to determine the “most representative cycle,” which is the cycle from the ensemble that has the pressure trace most representative of the engine operating condition. Eleven characteristic parameters are computed from each pressure trace and probabilistic distributions are obtained for each of the parameters using all the traces in the ensemble. Finally, the most representative cycle is selected by means of a cost function minimization. The benefits of this method are illustrated using experimental data from four very different engine platforms, under four different combustion modes and over a range of operating conditions.

Machine Learning Integration with Combustion Physics to Develop a Composite Predictive Model for Reactivity Controlled Compression Ignition Engine

Phasing of combustion metrics close to the optimum values across operation range is necessary to avail benefits of reactivity controlled compression ignition (RCCI) engines. Parameters like start of combustion occurrence crank angle (θsoc), occurrence of burn rate fraction reaching 50% (θ50), mean effective pressure from indicator diagram (IMEP) etc. are described as combustion metrics. These metrics act as markers for macroscopic state of combustion. Control of these metrics in RCCI engine is relatively complex due to the nature of ignition. As direct combustion control is challenging, alternative methods like combustion physics derived models are a subject of research interest. In this work, a composite predictive model was proposed by integrating trained random forest (RF) machine learning and artificial neural networks (ANN) to combustion physics derived modified Livengood-Wu integral, parametrized double-Wiebe function, autoignition front propagation speed based correlations and residual gas fraction model. The RF machine learning established a correlative relationship between physics based model coefficients and engine operating condition. The ANN developed a similar correlation between residual gas fraction parameters and engine operating condition. The composite model was deployed for the predictions of θsoc, θ50 and IMEP as RCCI engine combustion metrics. Experimental validation showed an error standard deviation (θ68.3,err) of 0.67 °CA, 1.19°CA, 0.223 bar and symmetric mean absolute percentage error of 6.92%, 7.87% and 4.01% for the predictions of θsoc, θ50 and IMEP respectively on cycle to cycle basis. Wide range applicability, lesser experiments for model calibration, low computational costs and utility for control applications were the benefits of the proposed predictive model.

Evaluation Methods of Motor-and-Tractor Diesel Engines Operating Conditions

При выборе метода оценки условий эксплуатации автотракторных дизельных двигателей необходимо учитывать, среди прочих факторов, наиболее часто используемые фазы движения конкретного автомобиля, от которых зависит режим работы двигателя. В статье предложены критерии качественной оценки условий эксплуатации для различных транспортных средств. Для оценки «тяжести» условий эксплуатации тракторов при выполнении различных сельскохозяйственных работ (пахота, боронование, посев и др.) целесообразно учитывать средний эксплуатационный расход топлива. В этом случае указанный параметр определяется отношением общего расхода топлива в литрах к общему времени выполнения трактором конкретной работы в часах. Для автобусов, работающих на маршрутах «Ярославль – центры муниципальных образований», как и для аналогичных перевозок в других регионах нашей страны, рассматриваемый параметр малоинформативен. Здесь для оценки их условий эксплуатации имеет смысл использовать коэффициент КS – количество остановок, приходящееся на один километр маршрута. Для автопредприятий, осуществляющих перевозки пассажиров по указанным маршрутам, рекомендуется проводить плановую ротацию автобусов по маршрутам согласно составленному графику, что позволит усреднить показатели надёжности узлов и агрегатов автобусов (неисправности и отказы) до их капитального ремонта. When choosing a method for assessing the operating conditions of diesel motor engines, it is necessary to take into account, among other factors, the most commonly used phases of movement of a particular vehicle on which engine operating condition depends. The article proposes criteria for the qualitative assessment of operating conditions for various vehicles. It is advisable to take into account the average operational fuel consumption in order to assess the "heaviness" of tractor operation conditions when doing various agricultural works (plowing, harrowing, sowing, etc.). In this case, specified parameter is determined by the ratio of the total fuel consumption in liters to the total tractor time of the particular operation in hours. For buses operating on the routes "Yaroslavl – centers of municipalities", as for similar transportation in other regions of our country, the parameter under consideration is not informative. Here, to evaluate their operating conditions, it makes sense to use the KS coefficient – the number of stops per kilometer of the route. For automobile companies carrying out passenger transportation along the indicated routes, it is recommended to carry out a planned rotation of buses along the routes according to the made up schedule, which will allow averaging the individual reliability of bus assemblies (faults and failures) before their general overhaul.

Control-Oriented Modeling of Cycle-to-Cycle Combustion Variability at the Misfire Limit in SI Engines

A control-oriented model is presented that can capture the prior-cycle correlation of combustion cycles during conditions with high levels of exhaust gas recirculation (EGR). Combustion events are modeled in discrete time and the dynamic evolution is captured by the residual air, fuel, and inert gas trapped in the combustion chamber. The mathematical formulation of the model is presented together with the calibration procedure to emulate a particular engine operating condition. A cycle-to-cycle system identification methodology is described which allows regressing model parameters from experimental data. Simulations are presented and compared to real engine measurements to show the modeling potential for analysis and control of combustion events.

Energy Savings From Electrification of Cooling System

The cooling system is essential for creating suitable ambient for optimal performance of the engine and a healthy operating temperature to achieve high efficiency. Reaching the desired engine operating condition earlier will not only improve the life span of the engine but also improve the fuel efficiency and reduce environmental pollution. In conventional cooling systems, where the pump is always mechanically connected to the crankshaft, the optimum cooling efficiency of the engine is limited. In fact, the coolant circulates in the engine even when cooling is not desired, and this leads to extended engine warm-up time. Decoupling the pump from the crankshaft and driving the pump with electric motor, the cooling process can be controlled efficiently. The pump is then used only when required. A simple Pulse Width Modulation (PWM) controller with variable duty cycle has been adopted to impose the forced convention flow using a pump. The result of the simulation of the electrically driven pump reported here has been obtained for New European Drive Cycle (NEDC) and shows the possibility of saving about 3% of fuel during the homologation cycle compared to mechanically coupled pump. In addition, the engine operating temperature can be reached seven minutes (7mins) earlier in idling condition, corresponding to about 46.5% fuel saving with respect to the conventional cooling system.

F100-PW-229 Engine Fault Detection Based on Real Time Data

Gas turbine engines exhibit very high maintenance costs. Moreover, in the case of aero applications an in-flight engine incidence, shall, by all means, be avoided, a condition that drives total maintenance costs even higher. A measure in favor of balancing these costs is to monitor continuously the variation of engine performance data recorded during flight, establish methods to deduce useful information regarding the engine “health” status and, as a result, take appropriate actions to maintain a good engine operating condition. The current work presents such a method tailored on the “F100-PW-229” engine that is operated by the ellenic Air Force as the propulsion system of the “F-16 block 52M” aircraft [3]. CEDATS and MS Excel were the computational tools used for the current engine performance study. CEDATS is a software developed for the engine users. It provides basic data trend monitoring functions and engine fault warnings. It is well known that there is always space for improvement for such health monitoring tools since there are cases where engine operating faults are not captured. Within the frame of the current work, a data post – processing method on the engine performance data time series was applied using MS Excel, in order to raise early warnings of an uncaptured compressor operating fault.

Research on the Status of Lubricating Oil Transport in Piston Skirt-Cylinder Liner of Engine

The status of the lubricating oil transport in the piston skirt-cylinder liner has important influence on the lubrication of piston assembly frictional pair, the consumption of lubricating oil, the emission, and the performance degradation of lubrication oil. In this paper, based on the model of piston secondary motion, fluid lubrication and lubricating oil flow, the status of the lubricating oil transport between the piston skirt and the cylinder liner on different engine operating condition is calculated, and the quantity of lubricating oil retained on the surface of cylinder liner is mainly analyzed when the piston skirt moves from the top dead center to the bottom dead center. The results show that the variation of the quantity of retained lubricating oil is almost same in the corresponding stroke on different engine operating condition; the quantity of retained lubricating oil is dissimilar at different moment and is equal in principle at the piston top and bottom dead center. The quantity of lubricating oil retention is dissimilar at different moment in the intake stroke or expansion stroke, but the quantity of lubricating oil retention is equal in principle at the top and bottom dead center on different engine operating condition. When the engine is on the same load condition, as the engine rotational speed increasing, the quantity of retained lubricating oil is decreased in the whole intake stroke and the middle and later parts of expansion stroke, but the quantity of retained lubricating oil is increased in the front part of expansion stroke. When the engine is on the same rotational speed condition, the quantity of retained lubricating oil increases with the increasing engine load in the front part of expansion stroke, it does not vary with the engine load in principle in the middle and later part of expansion stroke, the variation that the quantity of retained lubricating oil varies with the engine load is dissimilar in the intake stroke on different engine rotational speed condition.

On-line mixing and emission characteristics of diesel engine with dimethyl ether injected into fuel pipeline

This article presents a new on-line dimethyl ether/diesel mixing method, researches its blend characteristics, and also validates combustion and emission effects on a light-duty direct injection engine. This new blend concept is that dimethyl ether is injected into the fuel pipeline to mix with local diesel as the injector stops injection, and this mixing method has some advantages, such as utilization of the original fuel system to mix dimethyl ether with diesel intensively, flexibility on adjustable mixing ratio varying with the engine operating condition, and so on. A device was designed to separate dimethyl ether from the blends, and its mixing ratios and injection quantity per cycle were also measured on a fuel pump bench. The results show that compared with the injected diesel, the percentages of dimethyl ether injected into fuel pipeline are 13.04, 9.74, 8.55, and 7.82% by mass as the fuel pump speeds increase, while dimethyl ether injected into fuel pipeline are 45.46, 35.53, 31.45, and 28.29% of wasting dimethyl ether. The power outputs of engine fueled with the blends are slight higher than those of neat diesel at low speeds, while at high speeds, its power outputs are a little lower. Smoke emissions of the blends are lower about 30% than that of neat diesel fuel at medium and high loads with hardly any penalty on smoke and NOx emissions at light loads. The NOx and HC emissions of the blends are slight lower than that of neat diesel fuel at all loads.