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In an automotive suspension, a shock absorber plays a significant role to enhance the vehicle performances, particularly ride comfort and road holding. Because of its important influences on the overall vehicle performances, the understanding of its physical characteristics is essential. Thus, this paper develops a mathematical model of twin-tube shock absorber that is widely used in modern production cars. The model is derived based on a rational polynomial formulation. This formulation generally represents the flow behaviors of fluid across a restriction. Further, simulation results are compared to those obtained from experiments to determine the model accuracy. The result comparison illustrates that the model is able to describe the behavior of shock absorber with slight discrepancies.

In a state-of-the-art lean-burn spark ignition engine, a strong in-cylinder flow field with enhanced turbulence intensity is formed, and understanding the wall heat transfer mechanism of such a complex flow is required. The flow velocity and temperature profiles inside the wall boundary layer are strongly related to the heat transfer mechanism. In this study, two-dimensional three-component (2D3C) velocity distribution near the piston top surface was measured during the compression stroke in a strong tumble flow using a rapid compression and expansion machine (RCEM) and a stereoscopic micro-PIV system. The bore, stroke, compression ratio, and compression time were 75 mm, 128 mm, 15, and 30 ms (equivalent to 1000 rpm), respectively.

In order to investigate the mechanism of heat transfer on the chamber wall of direct-injection diesel engines, 2-D temperature imaging and heat flux measurement in the flame impinging region on the chamber wall were conducted using laser-induced phosphorescence technique. The temperature of the chamber wall surface was measured by the calibrated intensity variation of the 355nm-excited laser-induced phosphorescence from an electrophoretically deposited thin layer of La2O2S:Eu phosphor on a quartz glass plate placed in a rapid compression and expansion machine (RCEM). Instantaneous 2-D images of wall temperature at different timings after start of injection and time-resolved (10kHz) heat flux near the flame impinging region were obtained for combusting and non-combusting diesel sprays with impinging distance of 23.4mm at different injection pressures (80 and 120MPa).

In this study, the combustion characteristics of diesel flame achieved in a rapid compression and expansion machine (RCEM) at various patterns of oxygen distribution in the chamber are investigated in order to clarify the effect of heterogeneity of oxygen distribution in diesel engines induced by EGR on the soot and NOx emissions. To make the heterogeneous distribution of oxygen in a combustion chamber, the mixtures with different oxygen concentrations are injected through the each different port located on the cylinder wall. Results indicate that the amount of oxygen entrained into the spray upstream the luminous flame region affects the NO emission from diesel flame strongly.

This paper presents the polytopic modeling method and state variable observer design approach for semi-active suspension with changeable damping and variant stiffness elements. And such semi-active suspension system is suitable to be modeled as a dynamic polytopic system where the extreme vertices of damping and stiffness values are taken as the convex vertices of polytope. Thus, a dynamic polytopic model is the convex synthesis with all the vertex system dynamics and linear system theory can be applied to the system at each vertex. Herein, the conventional Kalman filter theory is utilized to design the observer for each vertex system, then the polytopic observer is formulated by a convex synthesis. The proposed observer design approach is testified by numerical study and vehicle test.

As an important class of nonlinear system, polytopic bilinear system is investigated. Combined with the properties of convex polytope, the nonlinear control for polytopic bilinear system is formulated by synthesizing nonlinear H∞ controller which is designed for polytopic bilinear system at vertices. For a semi-active suspension system with controllable damping and variant stiffness elements, it is easily modeled as a polytopic bilinear system model. In this case, the desired nonlinear control properties are pursued in making effective use of the changeable damping property while the variant stiffness is taken as the affine parameter of polytopic model. Therefore, polytopic bilinear system model could be reduced to a feasible problem by polytopic convex decomposition. Then the control problem of bilinear system model is to find a solution of nonlinear H∞ control.

The relation between the characteristics of a non-evaporating spray and those of a corresponding frame achieved in a rapid compression machine was investigated experimentally. The fuel injection pressure was changed in a range of 55 to 260 MPa and the other injection parameters such as orifice diameter and injection duration were changed systematically. The characteristics of the non-evaporating spray such as the Sauter mean diameter and the mean excess air ratio of the spray were measured by an image analysis technique. The time required for a pressure rise due to combustion was taken as an index to characterize the flame. It was concluded that the mean excess air ratio of a spray is the major factor which controls the burning rate and that the high injection pressure is effective in shortening the combustion duration and reducing soot formation.

In order to investigate the combustion phenomena in a combustion chamber of the diesel engine at transient operations, the simultaneous measurements of temperatures of flame and wall surface in a combustion chamber were conducted. The new technique for simultaneous measurements of flame temperature and wall surface was developed. Laser-Induced phosphorescence was used for the measurement of wall surface temperature which was coupled with the flame temperature measurement by a two-color pyrometry. The NOx and soot emissions were also measured simultaneously in transient operations. The relation between the temporal changes of emissions and temperatures of flame and surface wall are discussed. The results show that the temporal change of NOx emission during transient operation is similar to that of the average gas temperature in a chamber. On the other hand, the temporal change of soot emission is similar to neither that of flame temperature nor that of average gas temperature.

To understand further the mixing process between the injected fuel and air in the combustion chamber of a diesel engine, the turbulent mixing process in a one-phase, two-dimensional transient jet was theoretically studied using the discrete vortex simulation. First, the simulation model was evaluated by comparisons between calculated and experimental data on two-dimensional turbulent jets. Second, the trajectories of the injected fluid elements marked with different colors were graphically demonstrated. Also the process of entrainment of the surrounding fluid into the jet was visually presented using colored tracers.

Local heat flux from the flame to the combustion chamber wall, q̇, was measured the wall surfaces of a rapid compression-expansion machine which can simulate diesel combustion. Temperature of the flame zone, T1, was calculated by a thermodynamic two-zone model using measured values of cylinder pressure and flame volume. A local heat transfer coefficient was proposed which is defined as q̇/(T1-Tw). Experiments showed that the local heat transfer coefficient depends slightly on the temperature difference, T1-Tw, but depends significantly on the velocity of the flame which contacts the wall surface.

Air-entrainment characteristics of non-evaporating sprays and flames were measured by means of high-speed photography including ordinary shadowgraphy of sprays, back diffused light illumination photography and laser shadow photography of flames. Effects of injection pressure and nozzle orifice diameter on air-entrainment characteristics were investigated parametrically. The amount of air entrained into a flame was calculated by a two-zone thermodynamic model with data obtained from the photographs and the pressure measurement in the combustion chamber. The air-entrainment characteristics of flames were compared with those of the corresponding sprays. It showed that immediately after the start of ignition, the air entrainment into a flame increased more rapidly as compared with the corresponding spray and then, with the development of diffusion combustion, the air entrainment gradually approached that of the spray.

A new method to determine simultaneously the temperature and the fuel vapor concentration inside an evaporating spray was described by using a laser-induced fluorescence technique. A TMPD doped base fuel composed of C12H26: 22%, C13H28: 54% and C14H30: 30% was injected into the combustion chamber of a rapid compression machine which is filled with a high temperature and high pressure nitrogen. The laser sheet was used for incident light, which was reflected by a prism located inside the combustion chamber and propagated through the center of an evaporating spray. The laser induced fluorescence intensity was imaged by a high speed-gated intensifier from a direction perpendicular to the incident light. The results shows that mixtures with high equivalence ratio are observed in the central region, while low equivalence ratio mixtures are observed in the periphery of the spray. It is also observed that the temperature of richest mixture is 50 K as low as the surrounding gas temperature.

A rapid compression-expansion machine was developed, which can simulate intake, compression, expansion and exhaust strokes in a single Diesel cycle by an electrically controlled and hydraulically actuated driving system. The whole system which is composed of a hydraulic actuator, fuel injector and a valve driving device, is sequentially controlled by a micro-computer. The machine features; 1) accurate control of piston position at TDC, 2) no effect of lubricant on HC emission due to the use of dry piston rings; 3) independent control of local wall temperature; and 4) high power output to drive heavy piston at high frequency. The single cycle operation permits Diesel combustion experiments under a wide range of operating conditions and easy access of optical diagnostics with minimized amount of test fuel. The performance test showed that the machine can drive a DI Diesel type piston with a 100 mm bore at a maximum frequency of 16.7 Hz at a maximum compression pressure of 15 MPa.

In an attempt to achieve lean combustion in Diesel engines which has a potential for simultaneous reduction in no and soot, the authors developed a micro-hole nozzle which has orifices with a diameter as small as 0.06 mm. Combustion tests were carried out using a rapid compression-expansion machine which has a DI Diesel type combustion chamber equipped with the micro-hole nozzle. A comparison with the result of a conventional nozzle experiment revealed that the ignition delay was shortened by 30 %, and in spite of that, both peaks of initial premixed combustion and diffusion combustion increased significantly. The combustion in the case of the micro-hole nozzle experiment was accompanied with a decrease in soot emission, whereas an increase in NO emission.

The local heat fluxes from impinging combusting and evaporating diesel sprays to the wall of a square combustion chamber were measured in a rapid compression machine. It was revealed that the ratio of local heat flux between the combusting and evaporating spray, q̇c/q̇e, is of the same order of magnitude as (Tc-Tw)/(Te-Tw) and its values estimated by a two-zone model agree roughly with the measured ones. The time-mean local heat flux during the spray impingement was found to be approximately proportional to the 0.8th power of the injection velocity and the heat-transfer phenomenon depends largely on whether the ignition starts before or after the impingement.

A one-dimensional numerical calculation has been performed on a new reciprocating heat engine proposed on the basis of super-adiabatic combustion in porous media. The system consists of two pistons and a thin porous medium in a cylinder; one being a displacer piston and the other a power piston. These create reciprocating motions with a phase relation angle. By means of the reciprocating flow system, the residual combustion gas enthalpy is effectively regenerated to induce enthalpy increase in the mixture through the porous medium. Due to heat recirculation, the thermal efficiency reaches to 58% under the condition of the compression ratio of 2.3.

A diesel spray and flame in a quiescent atmosphere were realized without interference with combustion chamber walls in a newly constructed rapid compression machine. High speed shadow photography and pressure measurement were employed to obtain data for calculating the amount of air entrainment into the the flame and spray. From a comparison of air entrainment between the flame and spray, it turned out that when ignition delay becomes longer air entrainment into flames is promoted by the thermal expansion of multi-points ignition sources in the central region of the spray.

The concentrations of soot, NO and the other combustion products were measured by incylinder gas sampling in a DI diesel engine. The effects of injection timing, swirl ratio, and combustion chamber geometry on the formation and emission processes of soot and NO were studied. The following results were obtained: (1) Soot is promptly formed in the flame during the early combustion period where the equivalence ratio in the flame is high over 1.0. Thereafter almost all the formed soot is swiftly burnd up by oxidation during the middle combustion period. This process mainly determines the exhaust soot concentration. (2) NO is formed in the flame during the early and middle combustion period where the flame temperature is high over 2000 K. The highest NO concentration is observed at the flame tip swept by the air swirl. Though the concentration of the formed NO decreases by dilusion it nearly constant during the later combustion period.

A rapid compression-expansion machine which can simulate the combustion processes in diesel engines is developed. The configuration of the combustion chamber is a 100 mm bore and a 90 mm stroke, and the compression ratio is 15. The piston is driven by an electro-hydraulic system with a thrust of 90 kN and the maximum frequency of 20 Hz. The whole system composed of a hydraulic actuator, a fuel injection system, and a valve driving unit is sequentially controlled by a computer. The reproducibility of the stop position of the piston at the end of compression is achieved with an accuracy of ±0.1 mm by employing a hydraulic-mechanical brake mechanism. The experiment shows that the combustion in the expansion stroke is achieved, and that the combustion characteristics such as the rate of heat release and indicated output as well as the exhaust emission can be measured.

The increasing of global energy demand and stringent pollution regulations have promoted research on alternative fuels. In Thailand, ethanol, can be produced from many sources of national agriculture products as renewable fuel, which was strongly promoted by government due to its many merits for use in transportation field. In this study, combustion characteristics of ethanol-gasoline blend (20%, 85%, and 100%) as well as pure gasoline (E0) were investigated by using a swirl-generated constant volume combustion chamber. Flame propagations of different fuel blends were observed by high speed Schlieren photography technique while pressure history data were recorded for detailed combustion analysis. Combustion behavior, combustion duration and rate of pressure rise of all tested fuels were investigated in various swirl intensities and equivalence ratios. In addition, effect of swirl intensities and ethanol concentration on lean misfire limit were also discussed.