Experimental Characterization of Hydrocarbons and Nitrogen Oxides Production in a Heavy-Duty Diesel–Natural Gas Reactivity-Controlled Compression Ignition Engine

Reactivity-Controlled Compression Ignition (RCCI) combustion is considered one of the most promising Low-Temperature Combustion (LTC) concepts aimed at reducing greenhouse gases for the transportation and power generation sectors. Due to the spontaneous combustion of a lean, nearly homogeneous mixture of air and low-reactivity fuel (LRF), ignited through the direct injection of a small quantity of high-reactivity fuel (HRF), RCCI (dual-fuel) shows higher efficiency and lower pollutants compared to conventional diesel combustion (CDC) if run at very advanced injection timing. Even though a HRF is used, the use of advanced injection timing leads to high ignition delays, compared to CDC, and generates high cycle-to-cycle variability, limited operating range, and high pressure rise rates at high loads. This work presents an experimental analysis performed on a heavy-duty single-cylinder compression ignited engine in dual-fuel diesel-natural gas mode. The objective of the present work is to investigate and highlight the correlations between combustion behavior and pollutant emissions, especially unburned hydrocarbons (HC) and oxides of nitrogen (NOx). Based on the analysis of crank-resolved pollutants measurements performed through fast FID and fast NOx systems under different engine operating conditions, two correlations were found demonstrating a good accordance between pollutant production and combustion behavior: Net Cyclic Hydrocarbon emission-cyclic IMEP variations (R-2 = 0.86), and Cyclic NOx-maximum value of the Rate of Heat Released (R-2 = 0.82)

Experiments on the influence of intake conditions on local instantaneous heat flux in reciprocating internal combustion engines

[EN] The present study tries to be a contribution for the development of more precise theoretical models for predicting the dissipation of heat through the combustion chamber walls of reciprocating (internal combustion) IC engines. A fast response thermocouple was embedded in the combustion chamber of a single cylinder engine to measure instantaneous wall temperatures. The heat flux was obtained by solving the one-dimensional transient energy equation with transient boundary conditions using the Fast Fourier Transform. The engine was tested under different operating conditions to evaluate the sensitivity of the measurement procedure to variations of three relevant combustion parameters: injection pressure, air temperature and oxygen concentration at the intake. The local heat flux obtained was compared with other relevant parameters that characterize the thermal behaviour of engines, showing, in most of the cases, correlation among them. The results showed that the instantaneous heat flux through the walls and hence the local wall temperatures are strongly affected by the ignition delay and the start of combustion. © 2010 Elsevier Ltd.Desantes, J.; Torregrosa, AJ.; Broatch, A.; Olmeda González, PC. (2011). Experiments on the influence of intake conditions on local instantaneous heat flux in reciprocating internal combustion engines. Energy. 36(1):60-69. doi:10.1016/j.energy.2010.11.011S606936

Methane and carbon monoxide emissions from asphalt pavement: Measurements and estimates of their importance to global budgets

We measured emissions of methane from asphalt surfaces used in pavement for roadways. Maximum emissions were 22 mg/m2/yr for 1- to 4-week-old pavement during maximum sunlight intensity. Emissions were much smaller at low sunlight intensity and dropped off to negligible amounts at night. Smaller emissions were observed for asphalt pavement of 2.5 to 3 years approximate age under similar conditions. Companion measurements of carbon monoxide emissions resulted in maximum emissions of about 2.6 mg/m2/hr for 1-wk-old pavement. These findings indicate that emissions of CH4 and CO are a function of both sunlight and temperature. Based on our results, methane emissions from asphalt pavement cannot be a significant source of atmospheric methane. -from Author

Combustion and heat transfer studies in a spark ignition engine.

This study utilized time-resolved heat-flux measurements, heat-release analysis and high-speed flame photography to investigate experimentally the combustion and heat-transfer characteristics of an optically accessible single-cylinder engine. The engine had a pent-roof shaped combustion chamber with two intake and two exhaust valves. The primary variable examined was the intake-flow configuration which was varied by means of shrouded intake valves. The experimental data gathered was used to assess the applicability of a thermal boundary-layer based heat-transfer model. The model is significant in that it is not based on a $Nu \sim Re$ correlation of the heat transfer in steady incompressible pipe flow as most heat-transfer models used in quasi-dimensional engine simulations. The measured local heat-flux histories on the combustion side of the head were found to have significant spatial variations, which are believed to be caused by spatial nonuniformities in combustion and the flow field. The introduction of swirl or tumbling motion to the intake charge accelerated early flame development and increased peak combustion rate. These augmentations consequently caused higher local surface temperatures and increased steady-state as well as local peak heat fluxes. The presence of large cycle-to-cycle variations in the measured local heat-flux histories necessitated evaluating the heat-transfer model with information from individual cycle calculations. The model in its original formulation was able to accurately predict the heat transfer if convective effects were negligible. After the model was modified to account for these effects, the model showed good agreement with measurements made at a location exposed to a strong convective influence. The model gave significantly improved heat-transfer predictions over the currently available correlations tested, but the additional accuracy comes with added computing cost and increased implementation complexity.Ph.D.Applied SciencesMechanical engineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/128441/2/9013991.pd

Spark ignition engine simulation models

http://deepblue.lib.umich.edu/bitstream/2027.42/3754/5/bab9014.0001.001.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/3754/4/bab9014.0001.001.tx

Alternative Fillers for the Production of Bituminous Mixtures: A Screening Investigation on Waste Powders

There has been a significant increase in the demand for using recycled materials in construction because of the lack and limitation of available natural resources. A number of industrial and domestic waste products are being used in the replacement of traditional materials for road construction, and many studies have been carried out in recent years on the use of different recycled materials in substitution of conventional fillers in Asphalt Concretes (AC). The aim of this laboratory research is to analyze the physical characteristics of three different recycled fillers and compare them with those of a traditional limestone filler. The alternative fillers presented in this paper are: a waste bleaching clay that comes from two consecutive stages in the industrial process for decolouring vegetable oils and producing biogas (Ud filler), a dried mud waste from a tungsten mine (MW filler) and a recycled glass powder (Gl filler). Results show significant differences between the fillers, and, in particular, Rigden Voids (RV) seem to have the largest potential influence on the rheology of ACs