Sustainable Development Goals

An introduction to heat transfer

Biodiesel is a renewable transportation fuel consisting of fatty acid methyl esters (FAME), generally produced by transesterification of vegetable oils and animal fats. In this review, the fatty acid (FA) profiles of 12 common biodiesel feedstocks were summarized. Considerable compositional variability exists across the range of feedstocks. For example, coconut, palm and tallow contain high amounts of saturated FA; while corn, rapeseed, safflower, soy, and sunflower are dominated by unsaturated FA. Much less information is available regarding the FA profiles of algal lipids that could serve as biodiesel feedstocks. However, some algal species contain considerably higher levels of poly-unsaturated FA than is typically found in vegetable oils. Differences in chemical and physical properties among biodiesel fuels can be explained largely by the fuels’ FA profiles. Two features that are especially influential are the size distribution and the degree of unsaturation within the FA structures. For the 12 biodiesel types reviewed here, it was shown that several fuel properties – including viscosity, specific gravity, cetane number, iodine value, and low temperature performance metrics – are highly correlated with the average unsaturation of the FAME profiles. Due to opposing effects of certain FAME structural features, it is not possible to define a single composition that is optimum with respect to all important fuel properties. However, to ensure satisfactory in-use performance with respect to low temperature operability and oxidative stability, biodiesel should contain relatively low concentrations of both long-chain saturated FAME and poly-unsaturated FAME.

Review of biodiesel composition, properties, and specifications

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Occupational Outlook Handbook

Review of the effects of biodiesel on NOx emissions

Oxides of nitrogen emissions from biodiesel-fuelled diesel engines

This work studies the complex interactions resulting from the application and control of Exhaust Gas Recirculation (EGR) on a production heavy-duty diesel engine system, and its effectiveness in reducing NOx emissions. The coupling between EGR, the Variable Geometry Turbocharger (VGT) and the EGR cooler critically affects boost pressure, air/fuel ratio (A/F), combustion efficiency and pumping work. It is shown that EGR provides an effective means for reducing flame temperatures and NOx emissions, particularly under low A/F ratio conditions. However, engine thermal efficiency tends to decrease with EGR as a result of decreasing indicated work and increasing pumping work. Combustion deterioration is predominant at higher load, low speed and low boost conditions, due to a significant decrease of A/F ratio with increasing EGR. For conditions allowing the VGT to maintain high enough boost and hence A/F ratio, efficiency losses with increased EGR are largely attributed to increased pumping work. Finally, the total system heat rejection increases significantly due to EGR cooling.

The Impact of Exhaust Gas Recirculation on Performance and Emissions of a Heavy-Duty Diesel Engine

This study theoretically proposes and experimentally demonstrates the simultaneous reductions of exhaust nitric oxide (NO) and soot via the attainment of premixed compression ignition (PCI) combustion in a modern compression ignition direct injection (CIDI) engine. The key features leading to PCI combustion are a well-mixed fuel–air mixture, following a long ignition delay period, which burns at relatively low temperature. It is shown that simultaneous reductions in exhaust NO and soot concentrations are possible with the implementation of PCI combustion. At very low combustion temperatures, soot formation mechanisms decrease substantially so that both NO and soot formation have very little dependence on local equivalence ratios. As a result, it becomes possible to increase the global equivalence ratio above stoichiometric, and produce rich products of combustion for regeneration of certain diesel aftertreatment systems.

The attainment of premixed compression ignition low-temperature combustion in a compression ignition direct injection engine

Lean premixed compression ignition low-temperature combustion promises to simultaneously reduce NO x and PM emissions while suffering a moderate penalty in fuel consumption. Similarly, opportunities exist to develop rich combustion strategies which can provide the necessary exhaust constituents for aggressive regeneration of a lean NO x trap (LNT). The current work highlights the development of lean and rich premixed compression ignition combustion strategies. It is shown that the lean premixed compression ignition combustion strategy successfully operates with low NO x and smoke, at the expense of a 5% increase in fuel consumption over conventional diesel operation. The rich premixed compression ignition combustion strategy similarly operates with low NO x and smoke, and produces enough CO (up to 5% by volume in exhaust) for aggressive regeneration of an LNT. INTRODUCTION In his lecture given to the Society of Cassell on June 16, 1897, Rudolph Diesel stipulated as a third condition of his rational heat motor that fuel must be introduced gradually so as to maintain an isothermal combustion process [1]. Hence, from the early days of diesel engine development, it appeared that diffusion burn combustion would dominate. Nevertheless, this developmental road progressively changed direction as awareness of vehicle emissions and their impact on the atmosphere surfaced [2]. As researchers learned more about diesel engine combustion, it became increasingly clear that the diffusion burn portion was largely responsible for its soot emission [3]. Therefore, the desire to overturn Diesel’s condition of isothermal combustion developed, and attention shifted to premixed combustion modes [4]. Today, the development of combustion strategies resembling homogenous charge compression ignition strategies is vigorously pursued. The promise of simultaneously reduced NO

Lean and rich premixed compression ignition combustion in a light-duty diesel engine

Simultaneous reduction of nitric oxides (NOx) and particulate matter (PM) emissions is possible in a diesel engine by employing a Partially Premixed Compression Ignition (PPCI) strategy. PPCI combustion is attainable with advanced injection timings and heavy exhaust gas recirculation rates. However, over-advanced injection timing can result in the fuel spray missing the combustion bowl, thus dramatically elevating PM emissions. The present study investigates whether the use of narrow spray cone angle injector nozzles can extend the limits of early injection timings, allowing for PPCI combustion realization. It is shown that a low flow rate, 60-degree spray cone angle injector nozzle, along with optimized EGR rate and split injection strategy, can reduce engine-out NOx by 82% and PM by 39%, at the expense of a modest increase (4.5%) in fuel consumption. This PPCI strategy has the potential for meeting upcoming stringent fuel specific NOx emission levels of less than 1 g/kg-fuel and fuel specific PM levels less than 0.25 g/kg-fuel.

Evaluation of a Narrow Spray Cone Angle, Advanced Injection Timing Strategy to Achieve Partially Premixed Compression Ignition Combustion in a Diesel Engine

Timothy J. Jacobs

Papers

Oxides of nitrogen emissions from biodiesel-fuelled diesel engines

The Impact of Exhaust Gas Recirculation on Performance and Emissions of a Heavy-Duty Diesel Engine

The attainment of premixed compression ignition low-temperature combustion in a compression ignition direct injection engine

Lean and rich premixed compression ignition combustion in a light-duty diesel engine

Evaluation of a Narrow Spray Cone Angle, Advanced Injection Timing Strategy to Achieve Partially Premixed Compression Ignition Combustion in a Diesel Engine