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A combustion bomb has been developed which allows simulation of diesel combustion without the need to heat the bomb to high temperatures. Simulation of the compression stroke is achieved by burning a lean precharge composed of acetylene, oxygen and nitrogen. By controlling the initial partial pressures of these constituents it is possible to burn them to a state with an oxygen concentration, temperature and pressure representative of conditions in a diesel engine at the start of fuel injection. Diesel fuel injected into these gases autoignites and burns in a manner typical of combustion in diesel engines. This paper describes the design and operation of such a bomb. Experimental results are presented to illustrate its salient features. Particular attention is devoted to various means of obtaining optical access to the flow and the advantages offered over rapid compression machines or heated bombs.

A fuel injection meter and controller has been developed which (1) measures the instantaneous injection rate and the total mass of fuel injected, and (2) controls the mass of fuel injected and injection pressure. The injection rate is computed from instantaneous measurements of the velocity of a pumping plunger and the pressure of fuel injection. A mathematical model of the meter and controller was developed to futher the understanding of various design and operating parameters on the injection rate. Compressibility of the fuel is accounted for. Good agreement is realized between numerically computed injection pressure and rate histories with corresponding experimental results.

A turbulent entrainment model for the turbulent combustion process in spark-ignition engines is described. The model uses the basic quantities of turbulent flow; i.e. the integral length scale, micro length scale, and turbulent intensity. The characteristic reaction time for a large eddy τ is calculated using the characteristic reaction time τc for the microscale, λ/S ℓ, where S ℓ is the laminar flame speed and propagation of ignition sites within a coherent turbulent structure. τ is related to the flame kernel development time and shows similar trends to the ignition delay time. The combustion model is demonstrated by calculations showing the typical trend behavior of combustion duration with equivalence ratio, exhaust gas recirculation, spark timing and engine speed.

This paper provides an overview of spark-ignition engine unburned hydrocarbon emissions mechanisms, and then uses this framework to relate measured engine-out hydrocarbon emission levels to the processes within the engine from which they result. Typically, spark-ignition engine-out HC levels are 1.5 to 2 percent of the gasoline fuel flow into the engine; about half this amount is unburned fuel and half is partially reacted fuel components. The different mechanisms by which hydrocarbons in the gasoline escape burning during the normal engine combustion process are described and approximately quantified. The in-cylinder oxidation of these HC during the expansion and exhaust processes, the fraction which exit the cylinder, and the fraction oxidized in the exhaust port and manifold are also estimated.

The flow and combustion processes of a three-valve, stratified charge engine with small prechamber are examined for exhaust emissions. The exhaust emissions from a single-cylinder version of this engine are shown to depend on the internal flow processes as well as mixture supply stoichiometry. A theoretically-based simulation model of the engine flow and combustion processes is described. Model predictions are compared with time-resolved prechamber air-fuel ratio measurements made during intake and compression strokes. These comparisons are used to illustrate and describe the complex flow phenomena which take place in this engine. The combustion process is then examined with the aid of calculations using the simulation model. The complexity of the combustion process is illustrated by showing that, in addition to burned gas temperatures, the cylinder and prechamber burned gas air-fuel ratios change with time.

Today's diesel PM reduction systems are mainly based on catalyzed particulate filter(CPF) systems. However, most of their reaction kinetics remain unresolved. Among others, the soot oxidation rate over catalyst is particularly important in the evaluation of the performance of the catalysts and the efficient control of CPF regeneration. This study, therefore, investigated the oxidation rate of carbon black (Printex-U) over various Pt supported catalysts using a flow reactor setup simulating diesel exhaust conditions. Compared to non-catalyzed soot oxidation, the oxidation rate of carbon black over Pt catalysts was to an extent shifted towards low temperatures. This activity enhancement of soot oxidation over a catalyst can be attributed principally to NO to NO2 conversion because NO2 oxidizes soot with much lower activation energy (Ea=60kJ/mol) than O2 (Ea=177kJ/mol).

Particles have been collected from a direct injection diesel engine at varying dilution ratios and air temperatures for four different operating conditions. Particulate samples have been introduced into a mass spectrometer ion source with a direct insertion probe thus dispensing with the extraction processes typically used in chemical characterization. The sample is volatized and then chemically ionized using isobutane. Typical mass spectra are presented for each operating condition. The samples analyzed have a mean molecular weight of 195 amu with a standard deviation of approximately 100 amu. Application of tandem mass spectrometry for species identification is illustrated. Both negative and positive chemical ionization are employed to identify carboxylic acids in the particulate. Several types of ms-ms scans are shown to have utility in this study, including scans which provide molecular weight profiles for compounds having common functional groups.

Spark-ignition engine knock was characterized in terms of when during the engine cycle and combustion process knock occurred and its magnitude or intensity. Cylinder pressure data from a large number of successive individual cycles were generated from a single-cylinder engine of hemispherical chamber design over a range of operating conditions where knock occurred in some or all of these cycles. Mean values and distributions of following parameters were quantified: knock occurrence crank angle, knock intensity, combustion rate and the end-gas thermodynamic state. These parameters were determined from the cylinder pressure data on an individual cycle basis using a mass-burn-rate analysis. The effects of engine operating variables on these parameters were studied, and correlations between these parameters were examined.

Diesel engines are the most commonly used power plant of freight and public transportations in the world. Also, the newly developed injection system, Common Rail system, increases the demands for both light and heavy duty diesel vehicles. On the other hand, stringent emission regulations are being proposed with growing concern on NOx and PM emissions from diesel engines. Future emission regulations require advanced emission control technologies, such as EGR and SCR. Exhaust gas recirculation (EGR) is a commonly used technique to reduce NOx emission. In this paper, a model-based investigation was conducted to compare the effect of high pressure loop (HPL) EGR and low pressure loop (LPL) EGR system on NOx level and BSFC of a heavy-duty diesel engine. A WAVE model was created to simulate EURO 3 engine and each component of the engine was modeled using CATIA and WaveMesher.

NO2 is an effective soot oxidizer operating at lower temperatures than O2. The effect of pure NO2 on soot oxidation was evaluated and compared with the gas treated by plasma, which initially consisted of NO, O2, and hydrocarbons. The cutout of a commercial DPF was used and the pressure difference across the DPF was monitored for an hour. The concentration of NO/NO2, CO, CO2 at the outlet of the DPF was measured as a function of time. CO and CO2 concentration was measured periodically by gas chromatography. The experiment was performed at 230, 250, 300, 350°C. When NO2 only was used as an oxidizing agent, there was a close relationship between the decrease of the pressure difference across the DPF, the CO and CO2 concentration at the outlet of the DPF, and the back conversion of NO2 to NO.

A computer simulation of the four-stroke spark-ignition engine cycle has been developed for studies of the effects of variations in engine design and operating parameters on engine performance, efficiency and NO emissions. The simulation computes the flows into and out of the engine, calculates the changes in thermodynamic properties and composition of the unburned and burned gas mixtures within the cylinder through the engine cycle due to work, heat and mass transfers, and follows the kinetics of NO formation and decomposition in the burned gas. The combustion process is specified as an input to the program through use of a normalized rate of mass burning profile. From this information, the simulation computes engine power, fuel consumption and NO emissions. Predictions made with the simulation have been compared with data from a single-cylinder CFR engine over a range of equivalence ratios, spark-timings and compression ratios.

Instantaneous opacity measurements have been made for gases in the exhaust port and one meter downstream. The results obtained showed the opacity to be time independent, of negligible variation from cycle to cycle except near the smoke limit and an order of magnitude greater at the port than one meter downstream. Results are compared with gas sampling measurements of the particulates.

In this study, compositions, size distributions and activation energy in oxidation of diesel PM were investigated. Benzene (C6H6) was mixed to diesel fuel as a promoter of PM formation, and further, ferrocene (Fe(C5H5)2) was added as a promoter for oxidation processes during in-cylinder combustion and after-treatment. The effect of those additions on the PM characteristics was discussed on the basis of measured results such as SOF and dry-soot ratio in PM, primary and aggregate particle size distributions of PM, activation energy of PM oxidation, and PM components with elemental analysis. As a result, it was shown that ferrocene had special effect on the PM size distribution and the activation energy.

For gasoline engine, thermal efficiency can be improved by using lean burn. However, combustion instability occurs when gasoline engine is operated on lean condition. Hydrogen has features that can be used for improving combustion stability of gasoline engine. In this paper, an experimental study of hydrogen effect on lean limit was carried out using a four-cylinder 2.0L turbo gasoline direct injection engine. The engine torque was fixed at 110Nm on 1600RPM, 2000RPM and 2400RPM. The results showed that lean limit was extended and brake thermal efficiency was improved by hydrogen addition. Especially, at lower engine speed, the large improvement of lean limit was achieved. However, improvement of brake thermal efficiency was achieved at high speed. HC and CO2 emissions were decreased and NO emissions increased with hydrogen addition. CO emissions were slightly reduced with hydrogen addition.

Effect of various hydrocarbons on the plasma DeNOx process in simulated diesel engine operating conditions is investigated experimentally and theoretically. This paper shows the results of an extensive series of experiments on the NOx conversion effect of various hydrocarbons (methane, ethene, propene, propane) in the plasma. The effects of energy density, temperature, and the initial concentrations of hydrocarbon and oxygen are discussed and the results for each hydrocarbon are compared with one another. The energy required to convert one NO molecule is measured 13.8eV, 16.1eV, 23.2eV, 45.6eV for propene, ethene, propane, methane, respectively when energy density of 25.4J/L is delivered to the mixture of 10% O2, base N2 with 440ppm NO and 500ppm hydrocarbon at 473K, while it is 143.2eV without hydrocarbon. The best NOx conversion effect of propene among the mentioned hydrocarbons is due to the highest reaction rates of propene with O and OH.

LDA measurements of the flow in a motored engine near TDC of compression have been obtained, along with burnrate data in a firing engine having a near-central spark plug location. Results are reported for two different intake ports and four intake valve lifts varying from 25% to 100% of full lift. Opposite trends of swirl vs valve lift were found for the two ports, and the rms velocity fluctuation was found to be relatively insensitive to changes in valve lift. Regression analysis of the burn duration data was conducted, with swirl ratio and rms as independent variables. The analysis indicated that burn duration decreases with an increase in swirl ratio and/or rms velocity fluctuation. In light of the experimental findings, a new conceptual model is proposed regarding the effect of valve lift on the dissipation of turbulent velocity via changes in the length scale.

CARS temperature measurements were carried out both in a constant volume combustion chamber and in a spark-ignition engine. The CARS temperature measurement under engine-like condition was validated by comparing the unburned gas temperatures for premixed propane-air flame in a constant volume combustion chamber obtained by CARS with predicted temperatures of 2-zone flame propagation simulation model. There was good agreement between the predicted temperatures and the mean values of 10 CARS measurements. The standard deviation of 10 measurements at each measuring timing was about ±40 K. End-gas temperatures were measured by CARS technique in a conventional 4-cylinder DOHC spark-ignition engine with the engine motoring and firing. The measured motoring temperature matched well with the adiabatic core temperature calculated from the measured cylinder pressure. The engine was fueled with primary reference fuel (PRF80) of 80% iso-octane and 20% n-heptane by volume.

The high concentration of particulate matter (PM) in diesel exhaust gas causes significant soot deposition on the wall of EGR cooler, and reduces the heat transfer performance of the EGR cooler and the reduction rate of NOx. The deposition of PM tends to be occurred more severely with "heavy wet PM," which is more frequently at the LTC (low temperature combustion) engine. The objective of this work is to evaluate the effects of soluble organic fraction (SOF) on deposit characteristics of the EGR cooler. To measure reliable mean particle concentration values and surrogate SOFs, the soot generator with SOF vaporizer was used. As for two surrogate SOFs, n-dodecane and diesel lube oil, deposit mass increased when they were injected. Especially from the experiment results, it was found that the lube oil effect was more significant than the n-dodecane effect and lube oil also had a stronger effect on reduction of thermal conductivity by filling pores in deposits.

Characteristics of soot oxidation were investigated with a carbon black (Printex-U). A flow reactor system which can simulate the condition of diesel particulate filter and diesel exhaust gas (1 bar, O2 0 ∼ 10%, NO2 200 ∼ 900ppm) was designed and used with the temperature programmed oxidation (TPO) and constant temperature oxidation (CTO) techniques. The temperature increase rate was 5°C/min for TPO experiments. From the experiments, the apparent activation energy for carbon oxidation with nitrogen dioxide was determined as 60 ± 3 kJ/mol with the first order of carbon in the range of 10∼90% oxidation and the temperature range of 250∼500°C. This value was exceedingly lower than the activation energy of oxygen oxidation which was 177 ± 1 kJ/mol. When oxygen exists with nitrogen dioxide, the reaction rate increased with the concentration of oxygen. Its rate of increase was faster for low oxygen concentration and slower for high concentration.

Plasma-catalyst (Ag, Au/Al2O3) systems were applied to NOx reduction in a model lean-burn engine exhaust gas. Also, DeNOx test of real diesel exhaust gas was performed by plasma-Ag/Al2O3 system. In the case of model exhaust gas, the catalytic activity for NOx reduction was enhanced by the assistance of plasma in the wide temperature range. The NOx conversion efficiency of plasma-Ag/Al2O3 was 40∼90% under the condition of C3 H6 3200ppm (C1/NOx = 5.96) and 10% O2 over the temperature range of 250∼400°C. The plasma-Au/Al2 O3 system showed remarkable low temperature NOx reduction activity at 100∼250°C. The real engine full flow test was performed for 70% of the full load and at engine speed of 1500rpm. NOx removal of 46% from the diesel exhaust gas was achieved by the plasma-Ag/Al2O3 catalyst system at 364°C(C1/NOx = 6). In the case of higher C1/NOx = 10, the NOx conversion increased up to 73% at 381°C. Also, DeNOx engine tests were performed for full load of 1500, 2000 and 2500rpm.