Emissions and In-Cylinder Combustion Characteristics of Fischer-Tropsch and Conventional Diesel Fuels in a Modern CI Engine

Derived from natural gas, coal, and even biomass Fischer-Tropsch (F-T) diesel fuels have a number of very desirable properties. The potential for emissions reduction with F-T diesel fuels in laboratory engine tests and on-road vehicle tests is well documented. While a number of chemical and physical characteristics of F-T fuels have been attributed to the observed reduction in emissions, the actual effects of both the fuel properties and in-cylinder combustion characteristics in modern diesel engines are still not well understood. In this study a 2002, six-cylinder, 5.9 liter, Cummins ISB 300 diesel engine, outfitted with an in-cylinder pressure transducer. was subjected to a subset of the Euro III 13-mode test cycle under steady-state operating conditions. Emissions and in-cylinder pressure measurements were conducted for neat F-T diesel, low sulfur diesel (LSD), ultra-low sulfur diesel (ULSD), and a blend of FT/LSD. In addition, a detailed chemical analysis of the fuels was carried out. The differences in the measured combustion characteristics and fuel properties were compared to the emissions variations between the fuels studied, and an explanation for the observed emissions behavior of the fuels was developed.

Wear Model for Piston Ring and Cylinder Bore System

A new wear model for piston ring and cylinder bore system has been developed to predict wear process with high accuracy and efficiency. It will save time and cost compared with experimental investigations. Surfaces of ring and bore were divided into small domains and assigned to corresponding elements in two-dimensional matrix. Fast Fourier Transform (FFT) and Conjugate Gradient Method (CGM) were applied to obtain pressure distribution on the computing domain. The pressure and film thickness distribution were provided by a previously developed ring/bore lubrication module. By changing the wear coefficients of the ring and bore with accumulated cycles, wear was calculated point by point in the matrix. Ring and bore surface profiles were modified when wear occurred. The results of ring and bore wear after 1 cycle, 10 cycles and 2 hours at 3600 rpm were calculated. They coincided well with the general tendency of wear in a ring and bore system.

Prediction of Heat Flow and Temperature for Pistons With Improved Cooling Methods

This study deals with the prediction of the heat flow and temperature of an IC engine piston having different types of cooling methods. This decade has seen a very significant increase in the load rating of the internal combustion engines. There is a marked shift in the current engines from the conventional NA (Naturally Aspirated) engines. The presence of turbo chargers and super chargers has improved the power output by more than two times. The engines develop a pressure upto 180 bar and release very high heat energy. This has resulted in a piston crown temperature to the tune of 350 Deg. Centigrade. The increase in temperature will have a very serious effect on the lubricating oil, as at elevated temperature oil will have greatly reduced viscosity. Therefore, it is essential to bring the temperature down by having a proper cooling arrangement for the piston system. Two design options of cooling the piston are studied in this paper. In the first option piston is cooled by forcing a jet of oil towards the under-crown portion of the piston. The second option is having a cavity popularly known as cooling gallery, through which the jet of oil is allowed to circulate. The predictive study is carried out by using Finite Element Analysis Techniques. The numerical results obtained for the two options are compared with the base line configuration and the effects of the modifications are discussed in detail. In addition transient thermal analysis is done to predict the transient thermal hoop stress developed in the piston bowl. Since transient hoop stress is the main cause for fatigue failure of the piston bowl, a parametric study is carried out to study the effect of cooling methods on thermal hoop stress.

Friction Force Measurements Using the Instantaneous IMEP Method and Comparison With RINGPAK Simulations

Even though many researchers have measured the piston/ring assembly friction force over the last several decades, accurate measurement of the piston/ring assembly friction force is a still challenging problem. The floating liner method is not widely used, in spite of its accuracy, due to the substantial modifications required to the engine. On the other extreme, bench tests of the piston/ring assembly cannot completely simulate the real firing condition although bench tests are rapid, consistent, and cost effective. In this study, friction forces of the piston/ring assembly were measured using the instantaneous IMEP method and compared with modeling results using Ricardo’s RINGPAK software. In this research, a flexible flat cable was used to connect the connecting rod strain gage signal to the analysis system instead of using a grasshopper linkage. Therefore, the piston/ring assembly friction force was measured with the minimum change to the engine hardware.

Equilibrium Thermodynamics of Combustion by Means of Genetic Algorithms

In order to carry out an accurate heat release analysis, it is necessary to solve a non linear set of chemical equilibrium equations to calculate concentrations of the species present in cylinder gases during the combustion process. So, the thermodynamics properties of the mixture can be evaluated. The present paper deals with the study of the thermodynamics of combustion using a genetic approach. A genetic algorithm was used to solve the set of non linear equations. The goal of this method is the possibility of solving the equations set in a wide range of pressure, temperature and equivalence ratio combinations, where more traditional methods are often found to fail.

Prediction of Peak Cylinder Pressure Variations Over Varying Inlet Air Condition of Compression-Ignition Engine

Peak cylinder pressure of a compression-ignition engine can be affected by engine inlet air condition such as its temperature and pressure. The variation of peak cylinder pressure due to varying inlet air temperature and pressure is analytically studied in this paper. An analytical model is developed and thus the variations of peak cylinder pressure can be predicted along with inlet air temperature or pressure varying. It is indicated that cylinder compression ratio (CR) and intake air boost ratio (pm0/pi0) play significant roles in affecting the variation of peak cylinder pressure over inlet air temperature and pressure, and the pressure variation is proportional to CRk and pm0/pi0. The predicted results are compared to those from engine experiments, and show a close agreement. The prediction also includes the investigation of the variation in peak cylinder pressure due to varying the cylinder TDC volume. Results from the analytical studies are presented and show that the change in pmax versus a change in the volume is also affected by compression ratio. This indicates that for a certain change in the clearance volume, a higher compression-ratio configuration would produce a greater change in pmax than a lower compression-ratio would with the rest of the engine design parameters remaining unchanged.

A Study on the Calculation of Heat Release Rate to Compensate the Error Due to Single Zone Assumption in Diesel Engine

Accurate heat release analysis based on the cylinder pressure trace is important for evaluating combustion process of diesel engines. However, traditional single-zone heat release models (SZM) have significant limitations due mainly to their simplified assumptions of uniform charge and homogeneity while neglecting local temperature distribution inside cylinder during combustion process. In this study, a heat release analysis based on single-zone model has been evaluated by comparison with computational analysis result using Fire-code, which is based on multi-dimensional model (MDM). The limitations of the single-zone assumption have been estimated. To overcome these limitations, an improved model that includes the effects of spatial non-uniformity has been applied. From this improved single-zone heat release model (Improved-SZM), two effective values of specific heats ratios, denoted by γV and γH in this study, have been introduced. These values are formulated as the function of charge temperature changing rate and overall equivalence ratio by matching the results of the single-zone analysis to those of computational analysis using Fire-code about medium speed marine diesel engine. Also, it is applied that each equation of γV and γH has respectively different slopes according to several meaningful regions such as the start of injection, the end of injection, the maximum cylinder temperature, and the exhaust valve open. This calculation method based on improved single-zone model gives a good agreement with Fire-code results over the whole range of operating conditions.

Optical Investigation of HCCI Two-Stage Ignition Using Multiple Injection of Synthetic Fuels

Different synthetic fuels have been investigated within a variety of optical experiments at a rapid compression machine using diverse optical set-ups. The experiments have been carried out to determine the fuel requirements for good homogenisation and a controlled ignition and heat release for HCCI combustion. A directly actuated piezo injection system, which allows a flexible multiple injection strategy has been used to inject the fuel at different times during the compression stroke. Mie-scatter and Schlieren optics have been applied to investigate the different behaviour of the synthetic fuels concerning evaporation and mixture formation. The auto ignition behaviour of the different fuels has been investigated using an intensified relay optics and combustion chamber probes utilising the two-colour-method and a photo multiplier analysis systems. A multiple injection strategy and a 13 hole injection nozzle for HCCI operation mode with diesel-like fuels have been designed and optimised using CFD simulation prior to the experimental work. The experimental results using synthetic fuels will then be used to verify advanced 3D CFD models for multi component fuels and their behaviour concerning mixture formation and HCCI two-stage ignition.

Evaluation of Biodiesel Blends in a Single-Cylinder Medium-Speed Diesel Engine

Biodiesel blends were prepared by mixing low sulphur #2 diesel and biodiesel of two origins (canola and frying oil) at two different concentrations (5% and 20%). They were tested in a single-cylinder four-stroke medium-speed diesel engine under three engine modes representing idle, about 50% power and full load conditions. Engine performance and emissions data obtained with the blends were compared to that of engine running with the #2 diesel. Results indicated that the 5% blends could maintain engine power and fuel economy. Frying oil based B5 provided more significant reductions on CO, THC and PM emissions and increments on NOx emissions as compared with that of the canola B5 fuel. The 20% blends reduce engine CO, PM and smoke emissions, but increase NOx emissions by up to approximately 8%. Engine cylinder pressure and injection pressure data was also collected to provide additional information for evaluation of fuel economy and emissions benefits of using the blends.

On Moore’s Law and Its Application to SI Engine Technology

Moore’s law relates how the integration of semiconductors has progressed in time. This research shows that the exponential trend shown in the electronics manufacturing industry can have applications elsewhere. This study shows that the internal combustion engine followed the same trend for over 70 years. Though not the most used engine variable, engine power density shows the same trends for engines as transistor density does for microchips. This now mature technology has ended its period of rapid growth. However the present day engine trends can show how Moore’s law can be extended to include the slower growth of long established technologies. Because exponential growth cannot go on forever, the extension Moore’s law requires that the logistic function be used. The new function also allows one to predict a theoretical value for maximum power density.