The effect of transient operation on diesel particulate emission

One adult male inhales about 10.8 m3 of air per day. Therefore, achieving good air quality is a global concern from a health point of view. As one of the most prevalent toxic pollution sources are emissions from diesel fleets, researchers have been introducing various approaches to reduce the exhaust emission, such as introducing new fuels and engine modifications (Ristovski, 2012). Most of the current research has focused on emission reduction methods in steady-state operating modes; however, the daily driving schedule of automotive and truck vehicles is inherently unsteady. Moreover, the most critical conditions encountered by engines are met during transient operations. Despite the increased complexity, results from tests involving transient operation are more closely related to reality than steady-state testing, in most cases (Giakoumis, 2012). Generally, transient operation could refer to operating conditions that are not steady-state, such as: free acceleration, load changes, cold start and driving cycles. For example, cold start emissions from a heavy duty vehicle reported to be 15 times higher than their steady-state values (Giakoumis, 2012). This study intends to show the effect of transient operation on exhaust particulate emission by adapting the stall test, as outlined in MDG29, Guideline for the management of diesel engine pollutants in underground environments in New South Wales-Australia (MDG29, 2008), to a repeatable engine testbed drive cycle. For this implementation, the stall test is designed to be performed on three speeds, (1500, 2000 and 2400) with a similar pattern. At each speed the engine is on idle for 20 s, then accelerated from idle to full load (100% throttle) as quickly as possible and held there for a defined period at which point the throttle is return to 0%. Each point is repeated three times with 20 s of idle between each test. To ensure integrity between the tests, there is 50 s of idle between the unique tests (varying period at full load). The full load time are defined as 5, 10, 20, 30, 40, 50 and 60 s. In this experimental study a heavy-duty, six cylinder, turbo-charged, after-cooled diesel engine with a common rail injection system is used. Engine load and speed are controlled by an electronically water brake dynamometer. DMS500 MkII Fast Particle Analyzer utilised to measure diesel particulate matter. The results show that the amount of emission depends on the duration of full load operation. Figure 2 shows the average particulate mass of three repeats under different durations of full load at 2000 RPM on the stall test. It shows that by increasing the duration of full load operation from 5 s to 60 s, the measured diesel particulate emission reduces significantly by 40 %. This work was supported by Biofuel Engine Research Facility (BERF), Queensland University of Technology. Giakoumis, E. G., Rakopoulos, C. D., Dimaratos, A. M., & Rakopoulos, D. C. (2012). Exhaust emissions of diesel engines operating under transient conditions with biodiesel fuel blends. Progress in Energy and Combustion Science, 38(5), 691-715. MDG29. (2008). Guideline for the management of diesel engine pollutants in underground environments. New South Wales Mine Safety Operations Division. Ristovski, Z. D., Miljevic, B., Surawski, N. C., Morawska, L., Fong, K. M., Goh, F., & Yang, I. A. (2012). Respiratory health effects of diesel particulate matter. Respirology, 17(2), 201-212

Particulate number emissions during cold-start with diesel and biofuels: A special focus on particle size distribution

The share of biofuels in the transportation sector is increasing. Previous studies revealed that the use of biofuels decreases the size of particles (which is linked to an increase in particulate toxicity). Current emission regulations do not consider small particles (sub-23 nm); however, there is a focus in future emissions regulations on small particles. These and the fact that within cold-start emissions are higher than during the warmed-up operation highlight the importance of a research that studies particulate matter emissions during cold-start. This research investigates the influence of biofuel on PN and PM concentration, size distribution, median diameter and cumulative share at different size ranges (including sub-23 nm and nucleation mode) during cold-start and warm-up operations using diesel and 10, 15 and 20% mixture (coconut biofuel blended with diesel). During cold-start, between 19 and 29% of total PN and less than 0.8% of total PM were related to the nucleation mode (sub-50 nm). Out of that, the share of sub-23 nm was up to 9% for PN while less than 0.02% for PM. By using biofuel, PN increased between 27 and 57% at cold-start; while, the increase was between 4 and 19% during hot-operation. The median diameter also decreased at cold-start and the nucleation mode particles (including sub-23 nm particles) significantly increased. This is an important observation because using biofuel can have a more adverse impact within cold-start period which is inevitable in most vehicles’ daily driving schedules.<br/

Experimental Investigation of Diesel Engine Performance, Combustion and Emissions Using a Novel Series of Dioctyl Phthalate (DOP) Biofuels Derived from Microalgae

Physico-chemical properties of microalgae biodiesel depend on the microalgae species and oil extraction method. Dioctyl phthalate (DOP) is a clear, colourless and viscous liquid as a plasticizer. It is used in the processing of polyvinyl chloride (PVC) resin and polymers. A new potential biofuel, hydrothermally liquefied microalgae bio-oil can contain nearly 11% (by mass) of DOP. This study investigated the feasibility of using up to 20% DOP blended in 80% diesel fuel (v/v) in an existing diesel engine, and assessed the performance and exhaust emissions. Despite reasonable differences in density, viscosity, surface tension, and boiling point, blends of DOP and diesel fuel were found to be entirely miscible and no separation was observed at any stage during prolonged miscibility tests. The engine test study found a slight decrease in peak cylinder pressure, brake, and indicated mean effective pressure, indicated power, brake power, and indicated and brake thermal efficiency with DOP blended fuels, where the specific fuel consumption increased. This is due to the presence of 16.4% oxygen in neat DOP, responsible for the relatively lower heating value, compared to that of diesel. The emission tests revealed a slight increase in nitrogen oxides (NOx) and carbon monoxide (CO) emissions from DOP blended fuels. However, particulate matter (PM) emissions were lower from DOP blended fuels, although some inconsistency in particle number (PN) was present among different engine loads

Presentation and Evaluation of a New Graduate Unit of Study in Engineering Product Development

Engineering education has a key role to play in equipping engineers with the design skills that they need to contribute to national competitiveness. Product design has been described as &ldquo;the convergence point for engineering and design thinking and practices&rdquo;, and courses in which students design, build, and test a product are becoming increasingly popular. A sound understanding of product development and the implications associated with developing a product have been strongly linked to sustainability outcomes. This paper presents an evaluation of a new Master level engineering unit offered at Deakin University in product development technology. The unit allowed the students an opportunity to engage with the entire product development cycle from the initial idea to prototyping and testing through strategic assessment, which drove the unit content and student learning. Within this, students were also afforded an opportunity to explore resource usage and subsequent minimisation. Student evaluation surveys over two successive years found that students were responsive to this type of learning and appreciated the opportunity to do hands-on work. Improved student effort and engagement indicate that the students likely had better learning outcomes, as compared to traditionally taught units

Presentation and evaluation of a new graduate unit of study in engineering product development

Engineering education has a key role to play in equipping engineers with the design skills that they need to contribute to national competitiveness. Product design has been described as &ldquo;the convergence point for engineering and design thinking and practices&rdquo;, and courses in which students design, build, and test a product are becoming increasingly popular. A sound understanding of product development and the implications associated with developing a product have been strongly linked to sustainability outcomes. This paper presents an evaluation of a new Master level engineering unit offered at Deakin University in product development technology. The unit allowed the students an opportunity to engage with the entire product development cycle from the initial idea to prototyping and testing through strategic assessment, which drove the unit content and student learning. Within this, students were also afforded an opportunity to explore resource usage and subsequent minimisation. Student evaluation surveys over two successive years found that students were responsive to this type of learning and appreciated the opportunity to do hands-on work. Improved student effort and engagement indicate that the students likely had better learning outcomes, as compared to traditionally taught units

A preliminary study modelling NO emission by subset selection using a genetic algorithm and in-cylinder parameters

Introduced in this paper is the application of a genetic algorithm to perform subset selection to reduce the number of input parameters into a time history dependent model for the estimation of NO emission. For this work, a bespoke cycle, denoted as a sweep test, was utilised to provide the data for training the model. Input parameters into this model are in-cylinder parameters: indicated mean effective pressure, engine speed, peak pressure, peak pressure timing and the maximum rate of pressure rise, in addition to: intake air flowrate, instantaneous fuel consumption and boost pressure. Shown was that these input parameters allowed a high correlation between the estimated NO emission and the measured NO emission on the NRTC. A key advantage of subset selection is in being able to interpret the model itself to gain a physical understanding of what input parameters influence NO emission. A significant outcome from this work was in identifying that, for the engine under investigation, a time history of 8.5 s is needed to accurately estimate NO emission.</p

Investigation of diesel engine combustion instability using a dynamical systems approach

This study investigates the combustion instability of a compression ignition engine using dynamical system analysis in the form of a recurrence plot approach. In-cylinder combustion chamber pressure and crank angle are obtained from a six-cylinder, turbocharged diesel engine with a common-rail direct fuel injection system using a piezoelectric transducer and encoder, respectively. The common-rail system keeps the fuel pressure at a constant rate, which helps to minimise the effect of fuel pressure in this study. Constant speed and 4 loads are investigated. The engine emission and operation can be influenced by combustion instabilities and inter-cycle variability. Previous studies reported that ambient temperature, fuel pressure and injection timing, residual gases and fuel properties significantly alter the combustion instability. This study focus on the effect of biodiesel on this phenomena. Considering the CI engine as a dynamical system, the dynamic state of the combustion can indicate its stability. Typically, peak pressure, heat-release rate and indicated mean effective pressure in a range of consecutive cycles are utilised to represent the variability of combustion. The recurrence plot of these data is used to visually study the characteristics of combustion dynamics. Additionally, the recurrence quantitative analysis is used to present the characteristic dynamics of the system. The study finds that the combustion instability is higher for biodiesel compared with diesel, owing to the fuel properties. The results aid in developing our understanding of the complexity of biodiesel combustion in a modern engine and help to advance the combustion control strategy in order to improve the performance of biodiesel fuelled engines

Analysis of cycle-to-cycle variations in a common-rail compression ignition engine fuelled with diesel and biodiesel fuels

Using wavelet and fractal theories, cycle-to-cycle variations (CCVs) in a common-rail compression ignition (CI) engine have been investigated at engine loads of 25% and 50%, biodiesel blend level was from 0% to 100%. Wavelet power spectrums and singularity spectra were calculated to identify the dominant oscillatory combustion modes and multifractal complexity. Reaction paths and component consumption sensitivity of n-heptane and methyl decanoate were studied to reveal the effect of biodiesel blend level on the combustion process of diesel fuel. Results reveal that the effect of biodiesel blend level on the CCVs is more significant at a low load, even when biodiesel blend level increases to 20%, the coefficients of variation decreases from 3.99% to 1.57%. The CCVs exhibit multiscale dynamics for all tested cases, and persistent high-frequency oscillations appear around a 16-cycle period persisting over the entire or several hundred of the engine cycles. As the biodiesel blend level increases, the periodic bands with the highest power were interrupted and combined with lower-frequency and high-frequency intermittent fluctuations. However, for the higher load, the dynamics of CCVs are mainly displayed in an intermittent fashion. The larger broadness of singularity spectra at higher engine loads suggests a higher degree of multifractality. For all of the tested cases, the dynamics of the CCVs behave like antipersistent walks. As a oxygenated fuel, biofuel substitution leads to increase of c7h15-1 concentration and radicals such as OH, O and H2O2, which are beneficial to decrease ignition delay and accelerate the chemical reaction rate of diesel fuel, and therefore inhibit the CCVs.</p

Development of a reduced multi-component combustion mechanism for a diesel/natural gas dual fuel engine by cross-reaction analysis

In this paper, a four-component reduced mechanism (methane, n-dodecane, methylcyclohexane and toluene) with 150 species and 847 reactions was proposed for predicting the combustion characteristics and emissions from natural gas-diesel dual fuel engines. Equivalence ratio (ϕ) from 0.5 to 2.0, pressure (P) from 30 to 90 bar, temperature (T) from 500 to 1700 K and ϕ from 0.5 to 2.0, P from 1 to 10 bar, T from 298 to 550 K were set as the reaction conditions for two reaction models respectively. The detailed mechanisms were reduced using the directed relation graphs (DRG), directed relation graphs with error propagation (DRGEP) and full species sensitivity analysis (FSSA) methods. The validation of the reduced mechanism was performed based on the ignition delay and the laminar flame speed data available in the literature. Then the effects of cross-reactions on the oxidation of diesel were further studied, associated with the reaction flux, concentration and sensitivity analysis. Finally, the reduced mechanisms were verified at a reactivity controlled compression ignition (RCCI) combustion mode at 25% and 75% loads, the maximum validation error is 3.3%. It was found that the effects of cross-reactions on ignition were more pronounced in medium and low temperatures. Ignition was also enhanced by an increase in the equivalence ratio, but was not found to be sensitive to pressure. Under lower temperatures, adding cross-reactions can better reveal the formation of diesel intermediates. However, at higher temperatures, the addition of cross-reactions did not significantly increase the reaction speeds of the intermediate products.</p