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The present communication reports on processing and interpreting velocity measurements in the wake of a cooling fan. Velocity data are typically phase averaged to create statistics that would be observed in a rotating frame of reference. The difference between any given instantaneous measurement and the phase mean value is often referred to as the fluctuating component of velocity. These deviations can be caused by a variety of mechanisms (blade vibration for example) and do not necessarily represent “turbulence”. A different approach using an eigenfunction decomposition of the data is used on a sample data set to help distinguish between cycle-to-cycle variations and turbulence.

Rapid compression machines can be used to measure a fuel’s ignition delay time and develop an understanding of its resistance to autoignition. Continuing developments in engine design demand higher octane fuels that are resistant to autoignition. Substituted phenols are members of the aromatic hydrocarbon family, and aromatics like toluene are often added to pump-grade gasoline to increase the fuel octane number. Previous numerical and experimental studies have found that substituted phenols included at additive levels in gasoline surrogates, such as the toluene reference fuel in this study, may have a lengthening effect on the ignition delay time of the base fuel they are added to.

Autoignition delay times of two full blend gasoline fuels (high and low RON) were explored in a rapid compression machine. CO2 dilution by mass was introduced at 0%, 15%, and 30% levels with the O2:N2 mole ratio fixed at 1:3.76. This dilution strategy is used to represent exhaust gas recirculation (EGR) substitution in spark ignition (SI) engines by using CO2 as a surrogate for major EGR constituents(N2, CO2, H2O). Experiments were conducted over the temperature range of 650K-900K and at 10 bar and 20 bar compressed pressure conditions for equivalence ratios of (Φ =) 0.6-1.3. The full blend fuels were admitted directly into the combustion chamber for mixture preparation using the direct test chamber (DTC) approach. CO2 addition retarded the autoignition times for the fuels studied here. The retarding effect of the CO2 dilution was more pronounced in the NTC region when compared to the lower and higher temperature range.

Iso-Octane (2,2,4-trimethlypentane) is an important gasoline primary reference fuel (PRF) surrogate. Auto ignition of iso-octane was examined using a rapid compression machine (RCM) with iso-octane, air and carbon dioxide (CO2) mixtures. Experiments were conducted over a temperature range of 650K-900K at 20bar and 10 bar compressed conditions for equivalence ratios (Φ =) 0.6, 0.8, 1.0 and 1.3. CO2 dilution by mass was introduced at 0%, 15% and 30% levels with the O2:N2 mole ratio fixed at 1:3.76 emulating the exhaust gas recirculation (EGR) substitution in spark ignition (SI) engines. In this study the direct test chamber (DTC) approach is used for introducing iso-octane directly into the RCM test chamber via a direct injector. The results using this approach are compared with other RCM data available in the literature at undiluted Φ = 1.0 and 20 bar compressed pressure and show good agreement.

A direct-injection and spark-ignition single-cylinder engine with optical access to the cylinder was used for the combustion visualization study. Gasoline and ethanol-gasoline blended fuels were used in this investigation. Experiments were conducted to investigate the effects of fuel injection pressure, injection timing and the number of injections on the in-cylinder combustion process. Two types of direct fuel injectors were used; (i) high-pressure production injector with fuel pressures of 5 and 10 MPa, and (ii) low-pressure production-intent injector with fuel pressure of 3 MPa. Experiments were performed at 1500 rpm engine speed with partial load. In-cylinder pressure signals were recorded for the combustion analyses and synchronized with the high-speed combustion imaging recording. Visualization results show that the flame growth is faster with the increment of fuel injection pressure.

To obtain the maximum output power and fuel economy from an internal combustion engine, it is often necessary to detect engine knock and operate the engine at its knock limit. This paper presents the ability to detect knock using in-cylinder ionization signals on a large displacement, air-cooled, “V” twin motorcycle engine over the engine operational map. The knock detection ability of three different sensors is compared: production knock (accelerometer) sensor, in-cylinder pressure sensor, and ionization sensor. The test data shows that the ionization sensor is able to detect knock better than the production knock sensor when there is high mechanical noise present in the engine.

Since its implementation, exhaust gas recirculation has proven to be a reliable technique to control NOx emissions by lowering combustion temperature. Dilution with exhaust gas recirculation, whether in internal combustion engines or sequential-staged gas turbine combustors, affects flame reactivity and stability, which are related to the heat release rate and engine power. Another way to control emissions is to use hydrogen as a carbon-free alternative fuel, which is considered a milestone in the energy-decarbonization journey. However, the high reactivity of hydrogen is one of its hurdles and understanding this effect on laminar burning velocity is important. Flame propagation and burning velocity control the mixture reactivity and exothermicity and are related to abnormal combustion phenomena, such as flashback and knock. Therefore, understanding the effect of exhaust gas addition on the laminar burning velocity of hydrogen/air mixtures is imperative for engine design.

Spherically expanding flames are employed to measure the laminar flame speed of premixed iso-octane/air mixtures at elevated temperatures through both experiments and numerical simulations. Iso-octane (2,2,4-trimethlypentane) is an important gasoline primary reference fuel (PRF). While most studies on laminar burning velocity of iso-octane focus on low temperatures (less than 400 K), the experiments here were conducted in an optically accessible constant volume combustion chamber between 373 K-473 K, at a pressure of 1 bar, and from ϕ=0.8 to ϕ=1.6. The effect of diluent is investigated through the addition of 15% CO2 dilution in order to simulate the effect of exhaust gas recirculation. The decreased reactivity with diluent addition reduces mixture reactivity, which can reduce the propensity for knock in spark ignition engines. All laminar flame speeds were calculated using the constant pressure method enabled via schlieren visualization of the spherically propagating flame front.

A three-dimensional piston ring model has been developed using finite element method with eight-node hexahedral elements. The model predicts the piston ring conformability with the cylinder wall as well as the separation gap between the interfaces if existing in the radial direction. In addition to the radial interaction between the ring front face and the cylinder wall, the model also predicts the contact between the ring and groove sides in the axial direction. This means, the ring axial lift, ring twist, contact forces with the groove sides along the circumferential direction are all calculated simultaneously with the radial conformability prediction. The ring/groove side contact can be found for scraper ring at static condition, which is widely used as the second compression ring in a ring pack. Thermal load is believed having significant influence on the ring pack performance.

Numerical simulations of lean Methanol combustion in a four-stroke internal combustion engine were conducted on a high-compression ratio engine. The engine had a removable integral injector ignition source insert that allowed changing the head dome volume, and the location of the spark plug relative to the fuel injector. It had two intake valves and two exhaust ports. The intake ports were designed so the airflow into the engine exhibited no tumble or swirl motions in the cylinder. Three different engine configurations were considered: One configuration had a flat head and piston, and the other two had a hemispherical combustion chamber in the cylinder head and a hemispherical bowl in the piston, with different volumes. The relative equivalence ratio (Lambda), injection timing and ignition timing were varied to determine the operating range for each configuration. Lambda (λ) values from 1.5 to 2.75 were considered.

A numerical study on the combustion of Methanol in a directly injected (DI) engine was conducted. The study considers the effect of the bowl-in-piston (BIP) geometry, swirl ratio (SR), and relative equivalence ratio (λ), on flame propagation and burn rate of Methanol in a 4-stroke engine. Ignition-assist in this engine was accomplished by a spark plug system. Numerical simulations of two different BIP geometries were considered. Combustion characteristics of Methanol under swirl and no-swirl conditions were investigated. In addition, the amount of injected fuel was varied in order to determine the effect of stoichiometry on combustion. Only the compression and expansion strokes were simulated. The results show that fuel-air mixing, combustion, and flame propagation was significantly enhanced when swirl was turned on. This resulted in a higher peak pressure in the cylinder, and more heat loss through the cylinder walls.

As the variable nozzle turbine(VNT) becomes an important element in engine fuel economy and engine performance, improvement of turbine efficiency over wide operation range is the main focus of research efforts for both academia and industry in the past decades. It is well known that in a VNT, the nozzle endwall clearance has a big impact on the turbine efficiency, especially at small nozzle open positions. However, the clearance at hub and shroud wall sides may contribute differently to the turbine efficiency penalty. When the total height of nozzle clearance is fixed, varying distribution of nozzle endwall clearance at the hub and shroud sides may possibly generate different patterns of clearance leakage flow at nozzle exit that has different interaction with and impact on the main flow when it enters the inducer.

A multicomponent droplet evaporation model which discretizes the one-dimensional mass and temperature profiles inside a droplet with a finite volume method has been developed and implemented into a large-eddy simulation (LES) model for spray simulations. The LES and multicomponent models were used along with the KH-RT secondary droplet breakup model to simulate realistic fuel sprays in a closed vessel. The effect of various spray and ambient gas parameters on the liquid penetration length of different single component and multicomponent fuels was investigated. The numerical results indicate that the spray penetration length decreases non-linearly with increasing gas temperature or pressure and is less sensitive to changes in ambient gas conditions at higher temperatures or pressures. The spray models and LES were found to predict the experimental results for n-hexadecane and two multicomponent surrogate diesel fuels reasonably well.

Piston temperature plays a major role in determining details of fuel spray vaporization, fuel film deposition and the resulting combustion in direct-injection engines. Due to different heat transfer properties that occur in optical and all-metal engines, it becomes an inevitable requirement to verify the piston temperatures in both engine configurations before carrying out optical engine studies. A novel Spot Infrared-based Temperature (SIR-T) technique was developed to measure the piston window temperature in an optical engine. Chromium spots of 200 nm thickness were vacuum-arc deposited at different locations on a sapphire window. An infrared (IR) camera was used to record the intensity of radiation emitted by the deposited spots. From a set of calibration experiments, a relation was established between the IR camera measurements of these spots and the surface temperature measured by a thermocouple.

The fluid motion inside the engine cylinder is transient, three-dimensional and highly turbulent. It is also well known that cycle-to-cycle flow variations have a considerable influence on cycle-to-cycle combustion variations. Laser-based diagnostic techniques, for example, particle image velocimetry (PIV) or molecular tagging velocimetry, can be used to measure two or three components of the velocity field simultaneously at multiple locations over a plane. The use of proper orthogonal decomposition (POD) allows quantification of cycle-to-cycle flow variations, as demonstrated using PIV data [1]. In the present work, POD is used to explore the cycle-to-cycle flow variations utilizing molecular tagging velocimetry data. The instantaneous velocity fields were obtained over a swirl measurement plane when engine was operated at 1500 rpm and 2500 rpm.

Elastohydrodynamic lubrication, piston dynamics and friction are important characteristics determining the performance and efficiency of an internal combustion engine. This paper presents a finite element analysis on a production piston of a gasoline engine performed using commercial software, the COSMOSDesignStar, and a comprehensive cylinder-kit simulation software, the CASE, to demonstrate the advantages of using a reduced, parameterized model analysis in the assessment of piston design characteristics. The full piston model is parameterized according to the CASE specifications. The two are analyzed and compared in the COSMOSDesignStar, considering thermal and mechanical loads. The region of interest is the skirt area on the thrust and anti-thrust sides of the piston.

An auxiliary fueled prechamber ignition system can be used in an IC engine environment to provide lean limit extension with minimal cyclic variability and low emissions. Geometry and distribution of the prechamber orifices form an important criterion for performance of these systems since they are responsible for transferring and distributing the ignition energy into the main chamber charge. Combustion performance of nozzles with a single jet, dual diverging jets and dual converging jets for a methane fueled prechamber ignition system is evaluated and compared in a rapid compression machine (RCM). Upon entering the main chamber, the dual diverging jets penetrate the main chamber in opposite directions creating two jet tips, while the dual converging jets, after exiting the orifices, converge into a single location within the main chamber. Both these configurations minimize jet-wall impingement compared to the single jet.

The sole purpose of combustion in a piston engine is to generate pressure in order to push the piston and produce work. Pressure diagnostics provides means to deduce data on the execution of the exothermic process of combustion in an engine cylinder from a measured pressure profile. Its task is that of an inverse problem: evaluation of the mechanism of a system from its measured output. The dynamic properties of the closed system in a piston engine are expressed in terms of a dynamic stage - the transition between the processes of compression and expansion. All the phenomena taking place in its course were analyzed in the predecessor of this paper, SAE 2002-01-0998. Here, on one hand, its concept is restricted to the purely dynamic effects, while on the other, the transformation of system components, taking place in the course of the exothermic chemical reaction to raise pressure, are taken into account by the exothermic stage.

Camless Variable Valve Actuation (VVA) technologies have been known for improving fuel economy, reducing emissions, and enhancing engine performance. VVA can be divided into electro-magnetic, electro-hydraulic, and electro-pneumatic actuation. A family of camless VVA designs (called LGD-VVA or Gongda-VVA) has been presented in an earlier SAE publication (SAE 2007-01-1295) that consists of a two-spring actuation, a bypass passage, and an electrohydraulic latch-release mechanism. The two-spring pendulum system is used to provide efficient conversion between the moving mass kinetic energy and the spring potential energy for reduced energy consumption and to be more robust to the operational temperature than the conventional electrohydraulic actuation; and the electrohydraulic mechanism is intended for latch-release function, energy compensation and seating velocity control.

The need for increased fuel efficiency in conventional automobiles has motivated the design of lightweight, single passenger, super mileage vehicles. Typical low budget super mileage vehicles are capable of attaining 1000 to 1500 miles per gallon of gasoline. The present work discusses unique features of a high mileage vehicle designed and constructed by a research coterie at Michigan State University. More significant contributions of the coterie include an electronic engine and vehicle control system, a vehicle operation optimization analysis, and a computerized method of designing cam lobes based on flow mach numbers. These subjects are considered along with several customary design problems.