Cold Idle Research Articles

Cold idle vs hot idle: Gaseous and particulate emissions using a third-generation oxygenated biofuel

Engine idling is a significant contributor to vehicle emissions, however, it is often unaccounted for. Presented in this study is a comprehensive analysis of gaseous and particulate emissions during cold idle compared to hot idle operations. Fuels used in this study were B20 (20 %) and B10 (10 %) (%v/v) blends of di-octyl phthalate (a third-generation microalgae-based biofuel) and ultra-low sulphur diesel (B00), used as a reference fuel. Compared to cold idle operation, hydrocarbon (HC) emissions during hot idle showed marginal variation (±10 %) using blended fuels, and a significant increase (+55 %) using B00. Compared to cold idle operation, hot idle showed increased oxides of nitrogen (NOx) emissions, using all fuels (with a more significant increase shown using B00). During cold idle, particle concentrations (PNT) were 50–65 % higher using the blended fuels, compared to B00; however, during hot idle, the (PNT) using the blended fuels were one order of magnitude lower than B00. During cold idle operation, the average particle count mean diameter (CMD) in the Lower Aitken and Aitken modes was 5–10 % and 20–30 % higher using blended fuels, compared to B00, respectively. Higher CMD with the blended fuels during the cold idle operation caused a higher percentage increase in the particle mass (PMT), compared to B00. Sub-23 particles (<23 nm) were observed during cold and hot idle operations, using all fuels.

Performance and emission of a converted bio-fuel motorcycle engine in cold condition: A case study

ABSTRACT This paper presents a study on the performance and emission characteristics of a currently used motorcycle fueled with either gasoline or ethanol at cold starting and idling condition. The engine’s fuel system was modified by extending the injection pulse width to allow it to operate with pure ethanol or gasoline. The ethanol-fueled engine required three to four cranking times to achieve success starting at an ambient temperature between 15°C and 20°C. In cold idling conditions, the ethanol-fueled engine operated at a high coefficient of variation of speed (COVspeed) of 1.20% to 2.49% at an ambient temperature of 17°C, while a COV speed of 0.92% of the gasoline-fueled engine was observed. However, with the aid of the electric-based heating system (EHS), the ethanol-fueled engine performance was enhanced significantly as the COV speed was 0.95% at 15°C, 0.85% at 17°C, and 0.73% at 20°C in idling condition and achieved successful starting at the first time of cranking after 30 s of pre-heating. During the warm-up stage, a significant fluctuation of emission was observed with different test cases. However, with the heating system, the engine enhanced completed combustion quicker as incomplete combustion products of HC and CO were reduced rapidly in idling compared to gasoline and ethanol-fueled engine. NOx emissions increased with the aid of the heating system but were still lower compared to the gasoline-fueled engine during idling condition.

Numerical Optimization of Spray-Guided Spark Assistance for Cold Idle Operation in a Heavy-Duty Gasoline Compression Ignition Engine

This article describes the results of a response surface model (RSM)-based numerical optimization campaign for spray-guided spark assistance at cold operations in a heavy-duty gasoline compression ignition (GCI) engine. On the basis of an earlier work on spark-assisted GCI cold combustion, a space-filling design of experiments (DoE) method was first undertaken to investigate a multitude of hardware design variables and engine operating parameters. The main design variables included the number of injector nozzles, fuel split quantities and injection timings, and spark timing. The objective variables were engine combustion efficiency (ŋc), maximum pressure rise rate (MPRR), and engine-out nitrogen oxide (NOx) emissions. A total of 150 design candidates were automatically generated using the Sobol sequence method provided by the commercial software package, CAESES. Then, closed-cycle computational fluid dynamic (CFD) spark-assisted GCI simulations under cold idling operations were performed. The outcomes from the CFD-DoE design campaign were utilized to construct high-fidelity RSMs that allowed for further design optimization of the spark plug- and fuel injector-related design variables, along with fuel injection strategy parameters. A merit function with respect to objective variables was formulated with an appropriate weight assignment on each objective variable. Finally, the best design candidate was identified from the RSM-based optimization process and further validated in the CFD analysis. The best design candidate showed the potential to significantly improve combustion efficiency (ŋc &gt; 90%) over the baseline at cold idle while satisfying MPRR and NOx emissions constraints (MPRR &lt; 5 bar/CAD and NOx &lt; 4.5 g/kWh).

The initiation and development of combustion under cold idling conditions using a glow plug in diesel engines

Factors determining the success or failure of combustion initiation using a glow plug have been investigated through experimental work on a single cylinder, common rail diesel engine with a geometric compression ratio of 15.5, and a quiescent combustion bomb with optical access. A glow plug was required to avoid engine misfires when bulk gas temperature at the start of injection was less than 413 °C. The distance between the glow plug and the spray edge, the glow plug temperature, and the bulk gas temperature were important factors in meeting two requirements for successful ignition: a minimum local temperature of 413 °C and a minimum air/fuel vapour equivalence ratio of 0.15–0.35.

Characterization of particulate matter emitted from transit buses fueled with B20 in idle modes

Characterization of particulate matter (PM) of public transit buses in idle modes has been conducted to identify PM specification and to determine the effect of biodiesel properties on the emissions. Two different sets of transit buses that were running on B20 (20% biodiesel and 80% ultra-low sulfur diesel or ULSD in volume percent) were selected. For both hot and cold idle tests, a substantial reduction in total particulate matter (TPM) was observed compared to the TPM from ULSD. The maximum PM concentrations under hot and cold idling conditions were 2.77 and 5.59μg/m3, respectively, while ULSD showed 247.49 and 218.27μg/m3 under the same conditions. In elemental analyses, fifteen elements were observed in the PM emissions obtained from the buses (77–85wt% of total emissions). The major elements were calcium (Ca), sodium (Na), and iron (Fe) in PM samples. Positive matrix factorization (PMF) method was used for source apportionment analysis, and as a result, four factors were identified as the possible sources. Organic carbon to elemental carbon ratio (OC/EC) analyses showed that more OC was emitted in cold idling (>80%) than hot idling (>65%). Furthermore, the OC/EC ratio was found to be greater for the new buses with post treatment facilities (9.57–13.37) than for the old buses without them (1.85–4.55), which indicates the shift of the ratio between organic carbon and elemental carbon in the emissions as an engine ages.

Quantification of aldehydes emissions from alternative and renewable aviation fuels using a gas turbine engine

In this research three renewable aviation fuel blends including two HEFA (Hydrotreated Ester and Fatty Acid) blends and one FAE (Fatty Acids Ethyl Ester) blend with conventional Jet A-1 along with a GTL (Gas To Liquid) fuel have been tested for their aldehydes emissions on a small gas turbine engine. Three strong ozone formation precursors: formaldehyde, acetaldehyde and acrolein were measured in the exhaust at different operational modes and compared to neat Jet A-1. The aim is to assess the impact of renewable and alternative aviation fuels on aldehydes emissions from aircraft gas turbine engines so as to provide informed knowledge for the future deployment of new fuels in aviation. The results show that formaldehyde was a major aldehyde species emitted with a fraction of around 60% of total measured aldehydes emissions for all fuels. Acrolein was the second major emitted aldehyde species with a fraction of ∼30%. Acetaldehyde emissions were very low for all the fuels and below the detention limit of the instrument. The formaldehyde emissions at cold idle were up to two to threefold higher than that at full power. The fractions of formaldehyde were 6–10% and 20% of total hydrocarbon emissions in ppm at idle and full power respectively and doubled on a g kg−1-fuel basis.

Carbon speciation of exhaust particulate matter of public transit buses running on alternative fuels

This paper examines the change from ultra-low sulfur diesel (ULSD) to biodiesel (BD) in different idling mode with respect to organic carbon (OC) and elemental carbon (EC) for public transit buses in Toledo, Ohio. The carbon source profile for both alternative fuels for eight carbon fractions was developed through real time experiments. The average OC and EC concentrations in biodiesel fueled bus were 109.53 and 12.06μg/m3. The average OC and EC concentrations in ULSD fueled bus were 91.78 and 19.54μg/m3. By comparison, it is clear that the ULSD fueled bus emits more elemental carbon and less organic carbon than the BD fueled bus. The OC/EC ratio was 9.82 for the BD fueled bus and 5.66 for the ULSD fueled bus. The carbonaceous fraction (CF) was 0.87 for the BD fueled bus and 0.88 for the ULSD fueled bus. The CF was 0.90 for hot idling and 0.86 for cold idling. OC1, OC2, and EC2 accounted for about 24.8%, 32.5%, and 47.2% of the Total Carbon (TC), respectively. Correlation analysis was also carried out for identifying the main fractions of OC and EC. The results indicated that the use of BD instead of ULSD is environmentally sustainable based on the above chemistry approach.

Particulate emissions from tailpipe during idling of public transit buses fueled with alternative fuels

Engine exhaust in public transit buses has been associated with health effects. This pilot study examines the toxic nature of these engine exhausts under different idling conditions. The emission tests on public buses were performed with two different fuels: the ultra low sulfur diesel (ULSD: Bus 536) and 20% Biodiesel (BD) mixed with ULSD (B20: Bus 506). Particulate matter (PM) was collected from the tailpipe emissions and then analyzed for elements and polycyclic aromatic hydrocarbons (PAH). Cold and hot‐idle‐engine testing was conducted. The results of the PM emission analysis showed that the PM mean value of emission is dependent on the engine operation conditions and fuel type. The PM emissions in cold idling were lower than the hot idling condition. However, the absence of 16‐EPA PAH in the samples suggests that the tested public buses are using clean fuel. It was found that lubricant oil, PM ash content, and storage tanks were the major sources of elemental concentrations in the PM. However, heavy metals are primary reasons in catalyzing the oxidation reactions that results in reduced PM and PAH emissions. © 2012 American Institute of Chemical Engineers Environ Prog, 32: 1134–1142, 2013

Investigating the Effects of Multiple Pilot Injections on Stability at Cold Idle for a Dl Diesel Engine

Investigating the Effects of Multiple Pilot Injections on Stability at Cold Idle for a Dl Diesel Engine