Slide Bearing Types for Combustion Engines Designed for Upcoming Emission Regulations

Intelligent handling of our limited energy resources and the demand to reduce emissions are today the main drivers for developing efficient combustion engines. Therefore slide bearings and also other parts of the powertrain are facing major challenges caused by: Significantly increased operating pressure, temperature and sliding speed as well as the use of new lubricants and fuels. Furthermore, a ban of hazardous elements (e.g. lead, cadmium) in the applied materials is looming. With respect to above mentioned facts, the mechanical and tribological boundary conditions for bearings in future engines are subjected to change immensely. These changes can only be met by new lining materials and bearing types. From the standpoint of strength, the main critical factors are the soft phases — mainly tin and lead — added to both aluminum and copper based bearing alloys to obtain the necessary tribological behavior. Soft phases are limited in their temperature stability and in addition, lead is an environmental critical element and is restricted. For upcoming engine generations even novel aluminum-tin alloys will reach their performance limits and the classical leaded-bronze material as basis for tri-metal and sputter coatings can no longer cope with the life-time expectations. In addition, corrosion issues will come up due to new oil additives in truck and high speed engines. The present paper proposes, for the application in high speed and truck engines, new slide bearing types with appropriate characteristics and the desired performance required by engine designers: A high strength, thermally stable aluminum alloy with excellent mechanical properties by using re-crystallization inhibition mechanisms; a series of new solutions on the basis of a lead-free bronze linings having brilliant thermo-mechanical process capabilities resulting in high strength properties. Adequate tribological behavior is gained by combination of the new lining alloys with different surface layers. Fundamental working principles, development work and first application results of the new bearing types are presented in relation to existing solutions.

Intake-Air Oxygen-Enrichment of Diesel Engines as a Power Enhancement Method and Implications on Pollutant Emissions

Increasing the in-cylinder oxygen availability of diesel engines is an effective method to improve combustion efficiency and to reduce particulate emissions. Past work on oxygen-enrichment of the intake air, revealed a large decrease of ignition delay, a remarkable decrease of soot emissions as well as reduction of CO and unburned hydrocarbon (HC) emissions while, brake specific fuel consumption (bsfc) remained unaffected or even improved. Moreover, experiments conducted in the past by authors revealed that oxygen-enrichment of the intake air (from 21% to 25% oxygen mole fraction) under high fuelling rates resulted to an increase of brake power output by 10%. However, a considerable increase of NOx emissions was recorded. This manuscript, presents the results of a theoretical investigation that examines the effect of oxygen enrichment of intake air, up to 30%v/v, on the local combustion characteristics, soot and NO concentrations under the following two in-cylinder mixing conditions: (1) lean in-cylinder average fuel/oxygen equivalence ratio (constant fuelling rate) and (2) constant in-cylinder average fuel/oxygen equivalence ratio (increased fuelling rate). A phenomenological engine simulation model is used to shed light into the influence of the oxygen content of combustion air on the distribution of combustion parameters, soot and nitric oxide inside the fuel jet, in all cases considered. Simulations were made for a naturally aspirated single-cylinder DI diesel engine “Lister LV1” at 2500 rpm and at various engine loads. The outcome of this theoretical investigation was contrasted with published experimental findings.

Effects of B20 on Emissions and the Performance of a Diesel Particulate Filter in a Light-Duty Diesel Engine

This paper compares 20% bio-diesel (B20-choice white grease) fuel with baseline ultra low sulfur diesel (ULSD) fuel on the emissions and performance of a diesel oxidation catalyst (DOC) and diesel particulate filter (DPF) coupled to a light-duty 4-cylinder 2.8-liter common-rail DI diesel engine. The present paper focuses on the comparison of the fuel effects on loading and active regeneration of the DPF between B20 and ULSD. B20, in general, produces less soot and has lower regeneration temperature compared to soot loaded with ULSD. NO2 concentrations before the DPF were found to be 6% higher with B20, indicating more availability of NO2 to oxidize the soot. Exhaust speciation of the NO2 availability indicates that the slight increase in NOx from B20 is not the dominant cause for the lower temperature regeneration and faster regeneration rate but the reactivity of the soot that is in the DPF. Formaldehyde concentrations are found to be higher with B20 during regeneration due to increased oxygen concentrations in the exhaust stream. Finally the oil dilution effect due to post injection to actively regenerate the DPF is also investigated using a prototype oil sensor and FTIR instrumentation. Utilizing an active regeneration strategy accentuates the possibility of fuel oil dilution of the engine oil. The onboard viscosity oil sensor used was in good agreement with the viscosity bench test and FTIR analysis and provided oil viscosity measurement over the course of the project. Operation with B20 shows significant fuel dilution and needs to be monitored to prevent engine deterioration.

A Study on the Applicability of Straight Vegetable Oils to Medium Speed Diesel Engines

Straight vegetable oil (SVO) fuels such as palm oil, animal fat oil and waste vegetable oil were tested as fuels in a single-cylinder diesel engine to evaluate applicability to medium-speed diesel engines. Fuel-related properties of the SVO were assessed and compared with conventional marine diesel fuel oil (MDO). The total acid number (TAN) of the SVO fuels changed during a short interval in a drying oven which heated the SVO fuels to 170 degrees Celsius for several weeks. The SVO have not gone rancid any further after reaching limit. And the TAN of the SVO fuels was not related to corrosion of the parts. The SVO fuels needed to be heated to an appropriate temperature to use as fuel of the engine since the SVO fuels are more viscous than conventional diesel fuels. Both the injection period and the injection pressure increased due to low heating values of the SVO fuels. By the same token, fuel oil consumption increased over 10%. The overall exhaust emissions were lower with the SVO fuels, but NOx emission was as much as MDO at the higher loads.

Modifications to Quasi-Dimensional Burning Model of Spark Ignition Engines

The way in which position of spark plug affects combustion in a spark ignition engine can be analyzed by using two-zone burning model. The purpose of this paper is to extract correlations to simulate the geometric interaction between the propagating flame and the general cylindrical combustion chamber. Eight different cases were recognized. Appropriate equations to calculate the flame area (Af), the burned and the unburned volume (Vb & Vu) and the heat transfer areas related to the burned and unburned regions were derived and presented for each case using Taylor expansion in order to replace numerical solution with trigonometric algebraic functions.

Predicting Mixing Rates in Multiple Injection CRDI Engines

The possibility of multiple-injection in Common Rail Direct Injection (CRDI) engine allows achieving improved combination of oxides of nitrogen (NOx) and smoke emissions. In CRDI engines, the turbulent kinetic energy due to high pressure fuel injection is primarily responsible for fuel air mixing and hence the in-cylinder mixture formation. The air fuel mixing characteristics in the case of multiple-injection are quite different from that of single injection schedule. In this work a zero-dimensional model is proposed for mixing rate calculations with multiple-injection scheduling. The model considers generation and dissipation of in-cylinder turbulence through processes namely fuel injection, air swirl and combustion. The model constants are fine tuned with respect to the data available in existing literature. The model predictions are validated with the available data for the cylinder pressure and heat release rate histories on known single and multiple-injection schedules. These comparisons show good agreement to establish the role of mixing rate variations with multiple-injection. A single set of constants were found to match the cylinder pressure and heat release rate histories for single and multiple-injection from different sources in the literature. Further, the mixing rate and peak temperature predictions of the model are found to relate with the possible effect of specific injection scheduling on emission reductions reported in CRDI engine investigations.

Application of an Experimental EGR System to a Medium Speed EMD Marine Engine

This paper focuses on quantifying emission reductions associated with various on-engine technologies applied to Electro-Motive Diesel two-cycle diesel engines, which are very popular in marine and locomotive applications in North America. This paper investigates the benefits of using exhaust gas recirculation (EGR), separate circuit aftercooler, and retarded injection timing on a EMD 12-645E7 marine engine. The EGR system alone provided up to a 32.9% reduction in brake specific Nitrogen Oxides (NOx) emissions while demonstrating less than one percent increase in cycle brake specific fuel consumption (BSFC). The brake specific particulate matter emissions increased somewhat, but at a modest rate based on the amount of NOx emission reduction. When the enhanced aftercooler system was combined with the addition of EGR, there was a 31.9% reduction in NOx and essentially no change to the BSFC when compared to the baseline test. The minimum manifold air temperature (MAT) was limited due to the size of the standard EMD aftercooler heat exchanger that is fitted on the engine. No efforts to modify the turbocharger to improve the turbo match to take advantage of the lower manifold air temperatures and the corresponding lower exhaust energy. Once 4° static injection timing retard was introduced, along with the EGR and the minimum MAT, a maximum NOx reduction of 49% was realized with only a 1.1% increase over the baseline BSFC.

Predicted Qualitative Effects of Alternate Liquid Fuels on Heavy-Duty Compression-Ignition Engines

It is always desirable for a heavy-duty compression-ignition engine, such as a diesel engine, to possess a capability of using alternate liquid fuels without significant hardware modification to the engine baseline. Because fuel properties vary between various types of liquid fuels, it is important to understand the impact and effects of the fuel properties on engine operating and output parameters. This paper intends and attempts to achieve that understanding and to predict the qualitative effects by studying analytically and qualitatively how a heavy-duty compression-ignition engine would respond to the variation of fuel properties. The fuel properties considered in this paper mainly include the fuel density, compressibility, heating value, viscosity, cetane number, and distillation temperature range. The qualitative direct and end effects of the fuel properties on engine bulk fuel injection, in-cylinder combustion, and outputs are analyzed and predicted. Understanding these effects can be useful in analyzing and designing a compression-ignition engine for using alternate liquid fuels.

Simulation of Instantaneous Heat Transfer in Spark Ignition Internal Combustion Engines: Unsteady Thermal Boundary Layer Modelling

Simulation of internal combustion engine heat transfer using low-dimensional thermodynamic modelling often relies on quasi-steady heat transfer correlations. However, unsteady thermal boundary layer modelling could make a useful contribution because of the inherent unsteadiness of the internal combustion engine environment. Previous formulations of the unsteady energy equations for internal combustion engine thermal boundary layer modelling appear to imply that it is necessary to adopt the restrictive assumption that isentropic processes occur in the gas external to the thermal boundary layer. Such restrictions are not required and we have investigated if unsteady modelling can improve the simulation of crank-resolved heat transfer. A modest degree of success is reported for the present modelling which relies on a constant effective turbulent thermal conductivity. Improvement in the unsteady thermal boundary layer simulations is expected in future when the temporal and spatial variation in effective turbulent conductivity is correctly modelled.

Design of a Flow Reactor for Testing Multi-Brick Catalyst Systems Using Rapid Exhaust Gas Composition Switches

In recent years, diesel exhaust gas aftertreatment has become a core combustion engine research subject because of both increasingly stringent emission regulations and incentives toward more fuel-efficient propulsion systems. Lean NOX traps (LNT) and selective catalytic reduction (SCR) catalysts represent two viable pathways for the challenging part of exhaust gas aftertreatment of lean burn engines: NOX abatement. It has been found that the combination of LNT and SCR catalysts can yield synergistic effects. Switches in the operation mode of the engine, temporarily enriching the mixture, are required to regenerate the LNT catalyst and produce ammonia for the SCR. This paper describes the design of a catalyst flow reactor that allows studying multi-brick catalyst systems using rapid exhaust gas composition switches and its initial validation. The flow reactor was designed primarily to study the potential of combining different aftertreatment components. It can accommodate two sample bricks at a time in two tube furnaces, which allows for independent temperature control. Moreover, the flow reactor allows for very flexible control of the composition and flow rate of the synthetic exhaust, which is blended using mass flow controllers. By using a two-branch design, very fast switches between two exhaust gas streams, as seen during the regeneration process of a LNT catalyst, are possible. The flow reactor utilizes a variety of gas analyzers, including a 5-Hz FTIR spectrometer, an emissions bench for oxygen and THC, a hydrogen mass spectrometer, and gas chromatographs for HC speciation. An in-house control program allows for data recording, flow reactor control, and highly flexible automation. Additionally, the hardware and software incorporate features to ensure safe testing. The design also has provisions for engine exhaust sampling.