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The noise radiated from the tail pipe plays an important role in the total noise emitted for small two stroke engines. In this paper, an engine cycle and exhaust system model for a commercial 50 c.c., crankcase-scavenged type, single cylinder two stroke engine was developed to determine the noise emitted from the exhaust pipe. In modeling the engine cycle, a zero dimensional thermodynamic model was used to represent the compression and the expansion process in cylinder, and a two zone quasi dimensional model was used to represent the combustion process. As for the scavenging process, the perfect mixing model was used. In modeling the gas dynamics in the intake and the exhaust system, an unsteady one dimensional model was used, and the characteristic line method was employed to solve the partial differential equations.

Multidimensional calculations and laser Doppler anemometry measurements are presented of the air flow in a research diesel engine motored at 900 rpm with a compression ratio of ∼8.5. The engine comprised the cylinder head of a Ford 2.5L high speed direct-injection diesel mounted on a single cylinder Fetter engine modified to provide optical access for LDA measurements in a toroidal piston-bowl. The accuracy of the predictions is assessed against ensemble-averaged velocity data and found to be sufficient to allow better understanding of the flow in production engine geometries under realistic operating conditions.

Minimizing heat-transfer (HT) losses is important for both improving engine efficiency and increasing exhaust energy for turbocharging and exhaust aftertreatment management, but engine combustion system design to minimize these losses is hindered by significant uncertainties in prediction. Empirical HT correlations such as the popular Woschni model have been developed and various attempts at improving predictions have been proposed since the 1960s, but due to variations in facilities and techniques among various studies, comparison and assessment of modelling approaches among multiple combustion modes is not straightforward. In this work, simultaneous cylinder-wall temperature and OH* chemiluminescence high-speed video are all recorded in a single heavy-duty optical engine operated under multiple combustion modes. OH* chemiluminescence images provide additional insights for identifying the causes of near-wall heat flux changes.

To observe the effect of engine applications on small engine design, bending and torsional stresses of a crankshaft were measured dynamically under various load conditions. A dynamometer and a generator were selected as the load sources, because these two devices can provide different load patterns respectively. As the results, the peak bending stresses at the crankshaft pin fillets of a dynamometer set engine were about 40∼60% larger than those of a generator set engine. Conversely, the peak torsional stress at a crankshaft journal of the dynamometer set engine was about 25% smaller than that of the generator set engine. To investigate the reasons of these differences. additional measurements and FEM calculations were carried out. Finally we found that the stiffness of the crankshaft support had a great influence on the value of the peak bending stress and the torsional stress was affected by the installation angle between the engine TDC and the rotor of the generator.

The residual gas in SI engines is one of important factors on emission and performance such as combustion stability. With high residual gas fractions, flame speed and maximum combustion temperature are decreased and there are deeply related with combustion stability, especially at Idle and NOx emission at relatively high engine load. Therefore, there is a need to characterize the residual gas fraction as a function of the engine operating parameters. A model for predicting the residual gas fraction has been formulated in this paper. The model accounts for the contribution due to the back flow of exhaust gas to the cylinder during valve overlap and it includes in-cylinder pressure prediction model during valve overlap. The model is derived from the one dimension flow process during overlap period and a simple ideal cycle model.

The battery efficiency is strongly affected by the operating temperature, granting the best performance in a limited range. Great attention is given to the design and the testing of materials for the battery heat dissipation. In the present study, the thermal behavior of a Li-polymer cell, which is part of a battery pack for electric vehicles, is investigated. The cell is provided with different coatings of carbon, graphene, and silicone, used in turn, to dissipate the heat generated during the operation in natural convection. The coating is placed only on one side of the battery while the other one is inspected via thermal imaging. Optical diagnostics in the infrared band are used to evaluate the bi-dimensional distribution of the battery surface temperature and the effect of the coatings. Different operating conditions are tested by varying the current demand.

The computational fluid dynamics codes, which help to predict the behaviour of combusting gas in reciprocating engines, need, as boundary conditions for the momentum and energy equations, to approximate wall frictions and heat transfer between gas and walls. The purpose of this work is to outline the physical parameters which affect the heat transfer in spark ignited engines, and then to validate a multidimensional model which takes these parameters into account. In an experimental study, measurements were made on a test-engine instrumented with fast-response surface heat flux gages. Each gage was made of a steel cylinder, containing two thermocouples. A laser doppler velocimeter was used to analyze the influence of fluid dynamics on heat transfer. Up to ten data inputs could be simultaneously recorded at each crank — angle, including the heat flux at four locations of the combustion chamber, two velocity components and the cylinder pressure.

A combined experimental and analytical approach was followed in this work to study stress distributions and causes of failure in diesel cylinder heads under steady-state and transient operation. Experimental studies were conducted first to measure temperatures, heat fluxes and stresses under a series of steady-state operating conditions. Furthermore, by placing high temperature strain gages within the thermal penetration depth of the cylinder head, the effect of thermal shock loading under rapid transients was studied. A comparison of our steady-state and transient measurements suggests that the steady-state temperature gradients and the level of temperatures are the primary causes of thermal fatigue in cast-iron cylinder heads. Subsequently, a finite element analysis was conducted to predict the detailed steady-state temperature and stress distributions within the cylinder head. A comparison of the predicted steady-state temperatures and stresses compared well with our measurements.

Laser Doppler velocimeter results are presented for the mean velocity and turbulence intensity measured in a motored research engine. The compression of complex bulk motions created during induction produces turbulence as the piston approaches top dead center. The turbulence field is shown to be isotropic but nonhomogeneous. A zero-dimensional computer simulation based on an averaged k-ϵ model is shown to adequately predict the decay of turbulence at a point in the flow after the production phase is completed. Cylinder pressure measurements were recorded for homogeneous stoichiometric combustion for a range of engine speeds and ignition locations. A two-zone (burned and unburned gases) thermodynamic model accurately predicts the measured pressure histories when the turbulence results determined from the motored tests are used to establish initial conditions for the combustion model.

High intensity discharge lights (HID) are the innovation step that is now beginning to penetrate in all car classes. Investigating drivers, all results show that the benefits are visible to them and positively accepted. The quantification of the improvements has yet been insufficiently examined. In this article some of the aspects will be highlighted.

Nowadays, acoustic comfort is an important consideration in the design and operation of airplanes. In this context, an alternative approach, Statistical Energy Analysis (SEA) allows the study of energy diffusion in vibro-acoustic systems in mid and high frequency regions. This present study aims to describe the vibro-acoustic characterization of a structure similar to an aircraft fuselage. Several SEA models were considered to compare the analytical formulations found in the literature with measurement data. Two classes of the panels were investigated: simple and ribbed-stiffened. In this regard, the revised model for computing the coupling loss factors was evaluated and the results gave a good agreement with measured data.

Automotive electric and electronic devices are commonly tested with standard pulses at the battery lines according to ISO 7637-Part 1 and 2. As these pulses do not cover all disturbances that occur in modern passenger cars, each OEM defines its own additional test-pulses which makes it difficult for component suppliers to satisfy all existing requirements. The paper shows a comparison between measurement and simulation such as slow “ignition on” pulses of a modern passenger car. Additionally, the ability of the computing model to calculate the propagation of fast transients and characteristic pulses of currently used electric and electronic devices is demonstrated. This data can be used for the definition of new test-pulses.

For the present study, an ultraviolet light absorption diagnostic was used to measure O3 concentration during the compression stroke of a rapid compression machine and an optically-accessible research engine. Charge oxygen concentration, initial temperature, and equivalence ratio were varied; neat iso-octane was used for fueled experiments. Measurements were compared to single-zone chemical kinetic simulation results. Rapid thermally induced O3 decomposition was observed near top dead center. Ozone decomposition advanced when the charge temperature was increased, oxygen concentration was reduced, or fuel was added. While the model well-captures the experimental trends, for unfueled conditions the temporal prediction of O3 decomposition is generally too far retarded.

The idea of making a measurement with an energy conversion device called a transducer is presented. Types of transducers are discussed and their important characteristics are defined and discussed. Several examples are presented to illustrate how transducer characteristics and equations of operation are evaluated. Finally, the generalized measurement problem is presented and discussed in terms of obtaining valid data in order that the concept of making measurements can be treated as a science rather than as an art.

An understanding of exhaust processes, especially during unsteady engine operation, greatly assists in achieving emission goals. Conventional~i.e., integral~measurement systems only provide lump-sum, final values at the end of a given interval, or instantaneous rate values during steady-state operation. The paper presents a system for measuring instantaneous emission values during unsteady engine operation. The system is designed for installation in commercial vehicles, it is resistant to vibration, and it does not affect fuel consumption. The equipment includes infrared CO analyzers with transistorized sensors, rather than gas-filled receptor chambers which are sensitive to vibration. Mass flow rates of inlet combustion air rather than exhaust are measured, due to temperature fluctuations of exhaust. The produced electric signals are amplified, corrected, and filtered before they are processed to provide read-out emission values.

When using "green" hydrogen, fuel cell technology plays a key role in emission-free mobility. A powertrain based on fuel cells (FC) shows its advantages over battery-electric powertrains when the requirement profile primarily demands high performance over a longer period of time, high flexible availability and short refueling times. In addition, FC achieves higher effi-ciencies than the combustion of hydrogen in a gas engine, meaning that the chemical energy is used more efficiently than with established combustion engines. When using FC technology, numerous companies in Baden-Württemberg can contribute their specific expertise from the traditional automotive construction and supplier business. This includes auxiliary units in the air (cathode) and hydrogen (anode) path, such as the air compressor, the H2 recycling pump, humidifier, cooling system, power electronics, valve and pressure tank technology as well as components of the fuel cell stack itself.

The effect of rear splitter plates and base cavities on the near wake behind a ground vehicle body above a moving ground plane were studied. Static pressure taps on the base of the body were used to measure both the mean and fluctuating pressures acting on the model base. Hot wire anemometry and flow visualization were used to study the effect of splitter plates and cavities on the near wake velocity field. The effects of varying ground clearance and of the moving ground on the base pressure were also studied. It was determined that some splitter plate configurations affect the base pressure distribution by forming a low pressure vortex on one side of the plate with high pressure fluctuations and altering the flow on the opposite side of the plate to raise the mean pressure. The suction region could be eliminated by moving the splitter plate to the model edge to form a side of a cavity. A full four sided cavity was able to increase the overall base pressure by 11% on the model.

The research reported on here is concerned with the subject of air flow and temperature buildup in a pneumatic tire. Its ultimate objectives are to understand the basic mechanisms by which energy delivered to the tire is converted to heat, and to quantify the contribution to rolling resistance that is made by this energy-conversion path. Direct measurement of the heat-transfer rate is very difficult, because the tire surface undergoes such large deformations. The approach being taken here is to make measurements of the velocity distributions, and to relate these to the heat-transfer rate by numerical modeling of the flow field. This paper contains experimental results for the velocity distributions. The numerical modeling effort is not yet complete; however, a crude estimate of the heat-transfer rate can be made on the basis of the measured mass flow rates.

The focus of this research effort was to develop a technique to measure the cyclic variability of the mass injected by fuel injectors. Successful implementation of the measurement technique introduced in this paper can be used to evaluate injectors and improve their designs. More consistent and precise fuel injectors have the potential to improve fuel efficiency, engine performance, and reduce emissions. The experiments for this study were conducted at the Michigan State University Automotive Research Experiment Station. The setup consists of a fuel supply vessel pressurized by compressed nitrogen, a Dantec laser Doppler anemometry (LDA) system to measure the centerline velocity of fuel, a quartz tube for optical access, and a Cosworth IC 5460 to control the injector. The detector on the LDA system is capable of resolving Doppler bursts as short as 6μs, depending on the level of seeding, thus giving a detailed time/velocity profile.

Measurement of oil film thickness between piston rings and cylinder liner was conducted on a single cylinder version of a Cummins L-10 diesel engine using a laser induced fluorescence technique. The oil was illuminated with blue laser light (λ=442 nm) that causes the oil to fluoresce at a longer characteristic wavelength (λ=500 nm). This fluorescent light intensity is proportional to oil film thickness. A single fiber (50 μm core) was used to carry the laser light to the oil and to return the fluorescent light back to a photomultiplier tube. The paper presents results of oil film thickness measured under motored engine conditions for varying engine speeds, intake boost pressures and cylinder liner temperatures. The following conclusions were drawn from the experimental data. Oil film thickness increases with engine speed showing hydrodynamic lubrication. An increase in liner temperature decreases oil film thickness.