Naeim A. Henein

A new approach to evaluate instantaneous friction and its components in internal combustion engines

A new approach has been developed at Wayne State University to determine the instantaneous friction and its components in internal combustion engines. The method is based on the fact that the instantaneous cylinder gas forces and the instantaneous frictional, inertia and load forces cause the instantaneous variation in the flywheel angular velocity. The instantaneous total friction forces have been computed for a single diesel engine, under idling conditions. A breakdown of the friction into its components and a formulation for each component has been made. By applying linear regression, correlations between the individual components of the friction losses and the different parameters have been developed. The components are classified into two categories: piston assembly losses and crankcase assembly losses. The correlations have been applied to a multi-cylinder and a single cylinder diesel engine to compute frictional losses under operating and motoring conditions. The computed results have been found to be in a fairly good agreement with the experimental results. The correlations were also applied to the gasoline engine and compared with published experimental results in the literature.

CYCLE-BY-CYCLE ANALYSIS OF HC EMISSIONS DURING COLD START OF GASOLINE ENGINES

A cycle-by-cycle analysis of HC emissions from each cylinder of a four-stroke V-6, 3.3 L production engine was made during cold start. The HC emissions were measured in the exhaust port using a high frequency flame ionization detector (FID). The effect of the initial startup position of the piston and valves in the cycle on combustion and HC emissions from each cylinder was examined. The mass of fuel injected, burned and emitted was calculated for each cycle. The equivalence ratio of the charge in the firing cycles was determined. The analysis covered the first 120 cycles and included the effect of engine transients on HC emissions.

Engine Fault Analysis: Part II---Parameter Estimation Approach

The general fault analysis problem can be divided into two parts: fault detection and diagnosis (location). Fourier series, autocorrelation, and other techniques have been used for fault detection. However, these approaches cannot be utilized for locating the faults. In this paper a methodology is presented to locate faulty cylinder(s). The procedure involves the development of a mathematical model of the engine dynamics. This model takes into consideration the cylinder gas pressure, engine inertia, and load. The resultant torque is computed by using parameter estimation techniques. The parameter estimation technique employed can determine time-varying parameters without prior knowledge of the structure of the parameter. In the problem at hand, this is an important requirement. The resultant torque is the net of the cylinder gas torque and the frictional torque. The model and the estimation procedure have been verified by performing tests on a single-cylinder engine. A discriminant function has been defined to classify the performance of each cylinder. Our results indicate that the amplitude of the resultant torque can be used to identify the faulty cylinder(s). We have verified this approach by tests and studies on a six-cylinder engine. In our experiments we have studied cases involving one or two faulty cylinders.

Effect of Biodiesel (B-20) on Performance and Emissions in a Single Cylinder HSDI Diesel Engine

The focus of this study is to determine the effect of using B-20 (a blend of 20% soybean methyl ester biodiesel and 80% ultra low sulfur diesel fuel) on the combustion process, performance and exhaust emissions in a High Speed Direct Injection (HSDI) diesel engine equipped with a common rail injection system. The engine was operated under simulated turbocharged conditions with 3-bar indicated mean effective pressure and 1500 rpm engine speed. The experiments covered a wide range of injection pressures and EGR rates. The rate of heat release trace has been analyzed in details to determine the effect of the properties of biodiesel on auto ignition and combustion processes and their impact on engine out emissions. The results and the conclusions are supported by a statistical analysis of data that provides a quantitative significance of the effects of the two fuels on engine out emissions.

Parametric Characterization of High-Pressure Diesel Fuel Injection Systems

The focus of the study described herein is the characterization of the high-pressure hydraulic electronic unit injector (HEUI) and of the electronic unit injector (EUI) diesel injection systems. The characterization items include injection pressure, injection rate, injector response time, needle lift, start up injection transient, and dynamic discharge coefficient of the nozzles. Macroscopic and microscopic spray visualizations were also performed. The effects of injection conditions and nozzle configurations on injection characteristics were reviewed. Nozzle sac pressure was measured to correlate with the upstream injection pressure. A LabVIEW data acquisition and controls system was implemented to operate the injection systems and to acquire and analyze data. For an HEUI system, based on the results of the study, it can be concluded that common-rail pressure and length of the injection rate-shaping pipe determine the injection pressure, while the pressure rising rate and injection duration determine the peak injection pressure; it was also found that the nozzle flow area, common-rail pressure, and the length of the rate-shaping pipe are the dominating parameters that control the injection rate, and the rate shape is affected mainly by common-rail pressure, especially the pressure rising rate and length of the rate-shaping pipe. Both injection pressure and ambient pressure affected the spray tip penetration significantly. The penetration increased corresponding to the increase of injection pressure or decrease of ambient pressure. The variation of spray penetration depends on the type of injection system, nozzle configuration, and ambient pressure. The large penetration variation observed on the HEUI sprays could be caused by eccentricity of the VCO (valve-covered-orifices) nozzle. The variation of the mini-sac nozzle was 50% less than that of the VCO nozzle. The near-field spray behavior was shown to be highly transient and strongly depended on injector design, nozzle configuration, needle lift and oscillation, and injection pressure.

The frequency analysis of the crankshaft's speed variation: A reliable tool for diesel engine diagnosis

The speed variation of the crankshaft may be easily and accurately measured using a shaft encoder and counting the pulses of the internal clock of the data acquisition system. If the crankshaft would be a rigid body, the variation of its angular speed could be directly correlated to the total gas-pressure torque. Actually, the variation of the crankshafts speed has a complex nature being influenced by the torsional stiffness of the cranks, the mass moments of inertia of the reciprocating masses and the average speed and load of the engine. Analyzing only the lower harmonic orders of the speed variation spectrum can filter out the distortions produced by the dynamic response of the crankshaft. The information carried by these harmonic orders permits to establish correlations between measurements and the average gas pressure torque of the engine, and to detect malfunctions and identify faulty cylinders.

Simulation of a Single Cylinder Diesel Engine Under Cold Start Conditions Using Simulink

A nonlinear dynamic model is developed in this study to simulate the overall performance of a naturally aspirated, single cylinder, four-stroke, direct injection diesel engine under cold start and fully warmed-up conditions. The model considers the filling and emptying processes of the cylinder, blowby, intake, and exhaust manifolds. A single zone combustion model is implemented and the heat transfer in the cylinder, intake, and exhaust manifolds are accounted for. Moreover, the derivations include the dynamics of the crank-slider mechanism and employ an empirical model to estimate the instantaneous frictional losses in different engine components. The formulation is coded in modular form whereby each module, which represents a single process in the engine, is introduced as a single block in an overall Simulink engine model. The numerical accuracy of the Simulink model is verified by comparing its results to those generated by integrating the engine formulation using IMSL stiff integration routines. The engine model is validated by the close match between the predicted and measured cylinder gas pressure and engine instantaneous speed under motoring, steady-state, and transient cold siart operating conditions.

Investigation of Physical and Chemical Delay Periods of Different Fuels in the Ignition Quality Tester

Abstract : This paper investigates the physical and chemical ignition delay (ID) periods in the constant volume combustion chamber of the Ignition Quality Tester (IQT). IQT was used to determine the Derived Cetane Number (DCN) according to ASTM D6890-10a standards. The fuels tested were ultra low sulfur diesel (ULSD), jet propellant-8 (JP-8), two synthetic fuels of Sasol IPK and F-T SPK (S-8). A comparison was made between the DCN and cetane number (CN) determined according to ASTM-D613 standards. Tests were conducted under steady state conditions at a constant pressure of 21 bar, and various air temperatures ranging from 778 K to 848 K. The rate of heat release (RHR) was calculated from the measured pressure trace and a detailed analysis of the RHR trace was made particularly for the autoignition process. Tests were conducted to determine the physical and chemical delay periods by comparing results obtained from two tests. In the first test, the fuel was injected into air according to ASTM standards. In the second test, the fuel was injected into nitrogen. The point at which the two resultant pressure traces separated was considered to be the end of the physical delay period. The effects of the charge temperature on the total ID as defined in ASTM D6890-10a standards, as well as on the physical and chemical delays were determined. It was noticed that the physical delay represented a significant part of the total ID over all the air temperatures covered in this investigation. Arrhenius plots were developed to determine the apparent activation energy for each fuel using different IDs. The first was based on the total ID measured according to ASTM standards. The second was the chemical delay determined in this investigation. The activation energy calculated from the total ID showed higher values for lower CN fuels except Sasol IPK.

Diesel starting: a mathematical model

A mathematical model is developed to study the transient behavior of a four-stroke, single cylinder naturally-aspirated, DI diesel engine during cranking and starting. The model simulates the full thermodynamic cycle of the engine and includes detailed sub-models for the intake and exhaust gas flow processes, autoignition combustion, heat transfer, mechanical friction, blowby, and engine dynamics. The model considers the period of time from starter on until the engine reaches the idle speed

A Model for Wear and Friction in Cylinder Liners and Piston Rings

Abstract A one-dimensional elstohydrodynamic mixed lubrication wear and friction model is developed. The model can predict the effects of surface roughness, asperity contact, temperature-pressure-viscosity on wear, lubrication, and friction of the piston rings and cylinder liner. Wear is predicted based on the surface asperity contact pressure. The cylinder bore wear and the ring pack friction during an engine break-in are simulated and compared with the experimental results. The influence of cylinder wall temperature and surface roughness on friction and wear is investigated. The ring pack friction due to oil viscous shearing and asperity contact is found to reach its minimum at a certain oil temperature.