Reduction In HC Emissions Research Articles

Jatropha oil methyl ester as diesel engine fuel - an experimental investigation

The use of jatropha oil as a fuel for diesel engines is gaining more interest. Biodiesel is defined as a transesterified alternative fuel obtained from vegetable oils or animal fats having properties comparable to those of diesel. In the present investigation a methyl ester derived from jatropha oil (JOME) was considered as fuel. This paper presents a comparative study on the use of JOME and its blends of 20 and 50% on a volume basis with standard diesel as a source of fuel for a compression ignition engine. The engine tests were carried out at 0%, 25%, 50%, 75% and 100% load using a single-cylinder, fourstroke, constant speed diesel engine to study the performance, emission and combustion characteristics of these fuels. The results showed a 21% reduction in smoke, 17.9% reduction in HC emissions and 16% reduction in CO emissions for 20% JOME, with a 3.8% increase in NOx emission at full load. JOME and its blends showed a slight decrease in thermal efficiency and increase in the specific fuel consumption but at an acceptable level. There was a 2.8% decrease in brake thermal efficiency for the 20% JOME blend at full load. Among the blends, 20% JOME showed better results compared to 50% JOME and can be used as an alternative fuel in DI diesel engines.

A robust time delay auto-regressive exogenous fuzzy inference system for real-time estimation of catalyst temperature over engines coldstart operation: a multiobjective implementation scenario

In the current investigation, the authors propose an intelligent real-time system to dynamically simulate the catalyst temperature in automotive engines over the coldstart period. In general, the behavior of an engine during the first few minutes of its operation, namely the coldstart period, is highly transient and nonlinear. However, it is important to the engineers of automotive industry to develop advanced simulation techniques capable of capturing the engine system’s behavior during coldstart periods. The main motivation behind such a fact emanates in the pursuit of making successful strides towards decreasing the amount of unburned hydrocarbon emissions (HCs) of the engine. Catalytic convertors play a pivotal role in reducing the amount of this emitted pollutant. Therefore, here, the authors develop a knowledge based intelligent identification system, based on the integration of a low-level fuzzy identification machine (FIM) identifier and a hyper-level multiobjective optimizer, to monitor the catalyst temperature over the coldstart period for a given automotive engine system. In the current investigation, the authors propose the use of synchronous self-learning Pareto strategy for the multi-objective optimization of the architecture of FIM. To suit the intelligent scheme for online applications, the authors capture the required database using the concept of nonlinear auto-regressive exogenous systems. The developed intelligent approach can be used as a real-time soft sensor to observe the state of the catalytic convertor and send the required data to the coldstart controller. To ensure the efficacy of the resulting time delay FIM framework, it is used for capturing the catalyst temperature in three different experimental conditions. Through a comparative numerical study, it is demonstrated that the proposed soft sensor can be efficiently used for real-time estimations of the catalyst temperature. Besides, the results let us make sure that intelligent approaches have an aptitude to be effectively used as real-time observers instead of expensive commercial sensors. Generally, the results of the current investigation substantiates the authenticity of advanced computational approaches for coping with the considered identification problem, to help resolving one of the challenging issues in the field of automotive engineering, that is, the coldstart HC emission reduction.

Effect of fuel metering on combustion and emissions of a PFI gasoline engine during fast startup under an HEV-like mode

In this paper, the transient conditions during fast startup are investigated to develop a fuel metering strategy under HEV-like mode. The fuel mixture preparation and its effects on the combustion are analyzed in detail. Specifically, the combustion in the first cycle is characterized under both conventional low-speed cranking startup and HEV-like fast startup modes. The test results show that the enhancement of cranking speed has marginal effects on mixture preparation in the first cycle. However, it prolongs the combustion duration and reduces HC emissions. The sensitivity of the fuel metering is evaluated for the initial cycles. The combustion in the 3rd ~ 5th cycles during startup is found to be fairly sensitive to the fuel metering due to the effects of transient fuel film vaporization. The fuel metering in the first cycle has the most significant effect on the combustion and emissions during fast startup. Optimized fuel metering in the first cycle shows effective reduction of HC emissions during fast startup process.

Evolution of unburnt hydrocarbons under “cold-start” conditions from adsorption/desorption to conversion: On the screening of zeolitic materials

The general purpose of this work is to examine the relative ability of some well-selected zeolitic materials for the reduction of HC emissions generated within the Diesel “cold-start” period, i.e. when the work temperature of the Diesel Oxidation Catalyst (DOC) has not been reached. More peculiarly, this study is focused on the chemical, textural and structural parameters of zeolites influent on the elimination, namely by adsorption, of unburnt HC (propene, toluene and decane) in presence of potential inhibitors (H2O, CO, NO). Simulated “cold-start” conditions consisted in the rapid heating of the pre-treated zeolite sorbent/catalyst under the whole gas mixture from 35 to 530°C. The quantity of trapped HC and those converted to COx by oxidation were measured in function of the temperature, as well as the amount of NOx converted by the HC-SCR reaction. The interpretation of the HC emission profiles in close relation with the porous and acidic (through FTIR of adsorbed pyridine) properties of the corresponding zeolites allowed to gain insight onto the relative contributions of the pore topology, the pore size and the acid strength. For some selected zeolites, several consecutive cold-start cycles were performed in order to assess their stability.

Effective utilisation of butanol along with gasoline in a spark ignition engine through a dual injection system

In spark ignition engines fuelled by alcohol gasoline blends, the proportion of the two fuels has to be varied according to the operating condition. Further high amounts of alcohol cannot be blended with gasoline because the two phases can separate under certain conditions. In this work a dual injection system, wherein n-butanol and gasoline can be injected separately in any ratio has been employed in a spark ignition engine. The objective is to determine the most suitable amounts of n-butanol and gasoline to be used at different operating conditions of a four stroke spark ignition engine when these fuels are simultaneously injected into the intake manifold using this dual injection system. Experiments are conducted at different fuel ratios and throttle positions at an equivalence ratio of 1. The system results in good vaporization of the fuels even at low load conditions because the fuel jets are aligned to hit different portions of the intake valve. Results indicate that with proper selection of the fuel ratio significant reduction in HC emissions can be achieved as compared to operation on neat gasoline. Up to 60% of n-butanol could be used at 15% throttle while up to 80% could be used at 25% throttle. These proportions are higher than what have been achieved by pre-blending these fuels. The possibility of using high amounts of n-butanol reduced the tendency to knock. Hence, with the dual injection system n-butanol can be effectively used along with gasoline.

Load characteristics of a spark-ignited ethanol engine with DME enrichment

Alternative fuels have become the new energy for future life. Compared with others, Dimethyl ether (DME) is regarded as one of the most promising choices for future internal combustion (IC) engines. Due to some negative properties of ethanol, spark-ignited (SI) ethanol engines always encounter some barriers such as the high fuel consumption, low power output, and difficulty in cold start. In order to deal with the above problems, the SI ethanol engine is enriched with DME aiming at improving the overall performance.Under the engine speed of 1400rpm, three DME volume fractions of 0–2% and various intake manifold absolute pressures from 43.4kPa to 81.0kPa, the influence of DME addition on the performance of SI engines at the stoichiometric air/fuel ratio were experimentally investigated in this paper. The intake and exhaust manifolds were modified to ensure the injection of ethanol and DME as well as collect the exhaust emissions.The results indicate that, DME addition avails increasing the engine indicated thermal efficiency by about 15%. And DME addition benefits reducing the combustion duration due to the elevated flame speed of mixtures, especially at mid-to-high loads. Besides, the DME blending is also capable of reducing HC emissions under the test conditions. The HC emissions of the DME/ethanol engine are decreased by 35%, compared with those of the original ethanol fueled engine. Thus, under the tested operating conditions, DME enhancement can be used to enhance the fuel economy and reduce parts of the exhaust emissions for SI ethanol engines.

Effects of Secondary Air Injection During Cold Start of SI Engines

The paucity of exhaust oxygen during cold start of automobile SI engines limits the extent of exothermic chemical reactions in the exhaust port, manifold, and catalyst. The injection of air into the exhaust system therefore could be an effective way to utilize additional thermal and chemical energy available in the exhaust gas. This study investigates the thermal and chemical processes associated with secondary air injection (SAI) inside the exhaust system in order to fully exploit the simultaneous benefits of reducing converter-in emissions and improving catalyst lightoff performance during cold start. An experimental study was performed to develop a more fundamental understanding of the effects of SAI on exhaust gas emissions and catalyst light-off characteristics during cold start of a modern SI engine. The effects of several design and operating parameters such as spark retardation, fuel enrichment, secondary air flow rate and air injection location were investigated to understand the mixing, heat loss, and thermal and catalytic oxidation processes associated with SAI. Timeresolved HC, CO and CO2 concentrations were tracked from the cylinder exit to the catalytic converter outlet and converted to mass flow rates by applying an instantaneous exhaust mass flow rate model. A phenomenological model of exhaust heat transfer combined with the gas composition analysis was also developed to define the thermal and chemical energy state of the exhaust gas with SAI. The study found that significant emissions reduction can be achieved with SAI by the thermal oxidation process prior to the catalyst, which results in enhancing the chemical process inside the catalyst by faster catalyst light-off. The engine operation, with a relative air/fuel ratio 20% rich of stoichiometric and 100% secondary air, yielded the fastest catalyst light-off (4.2 sec). The SAI system reduced HC emissions by 46% to 88% and CO emissions by 37% to 93% compared with the normal operating conditions. The analysis showed that the post-catalyst HC emissions levels were optimized with secondary air flow rates corresponding to an overall exhaust lambda of 1.3. Thesis Supervisor: John B. Heywood Title: Professor of Mechanical Engineering

Experimental studies on low pressure semi-direct fuel injection in a two stroke spark ignition engine

In this work a two-stroke scooter engine was modified to work with semi-direct injection of gasoline at a pressure of 8 bar from an injector in the cylinder barrel pointed toward the cylinder head. The influence of injection timing, injection pressure, spark plug location and air-fuel ratio, on performance, emissions and combustion characteristics has been investigated. In addition, a comparison has been made with manifold injection of gasoline on the same engine at a given speed and various outputs. A significant reduction in HC emissions and fuel consumption with no adverse effects on NOx emissions and combustion stability was observed. A small drop in power and increase in CO emission were observed disadvantages of the new injection system. Injection timing was found to be the most important factor and a balance between reduction in shortcircuited fuel by late injection, and time for mixture preparation by advancing the injection, was found to be essential.

A study of the performance, emission and combustion characteristics of a compression ignition engine using methyl ester of paradise oil–eucalyptus oil blends

The significance of this study is the complete replacement of diesel fuel with bio-fuels. For this purpose; bio-fuels, namely, methyl ester of paradise oil and eucalyptus oil were chosen and used as fuel in the form of blends. Various proportions of paradise oil and eucalyptus oil are prepared on a volume basis and used as fuels in a single cylinder, four-stroke DI diesel engine, to study the performance and emission characteristics of these fuels. In the present investigation a methyl ester derived from paradise oil is considered as an ignition improver. The results show a 49% reduction in smoke, 34.5% reduction in HC emissions and a 37% reduction in CO emissions for the Me50–Eu50 blend with a 2.7% increase in NO x emission at full load. There was a 2.4% increase in brake thermal efficiency for the Me50–Eu50 blend at full load. The combustion characteristics of Me50–Eu50 blend are comparable with those of diesel.

Effect of hot exhaust gas recirculation on the performance and emissions of an advanced injection low pilot-ignited natural gas engine

The development of the advanced injection low pilot-ignited natural gas (ALPING) combustion concept that employs very small diesel pilots (1–5 per cent by energy) to compression ignite a premixed natural gas-air mixture to achieve very low NO x (0.2 g/kWh) and high efficiencies (about 41 per cent) has been described in a previous work. However, at part loads the ALPING combustion mode suffers from higher HC emissions (mostly unburned methane) and poor engine stability. To resolve this problem, tests were carried out employing various levels of hot EGR (0–26 per cent) at different loads on a single-cylinder research engine at a constant speed of 1700 r/min. Experimental results compared with baseline ALPING mode (0 per cent EGR) for quarter load operation are presented in the current paper. The results show that, at 60° BTDC injection timing, the application of hot EGR reduced HC emissions by up to 70 per cent without any significant NO x emissions penalty. The fuel conversion efficiencies were improved by 8 percentage points, while COVi.m.e.p. and CO emissions decreased 20 percentage points and 40 per cent, respectively. To identify the upper limits of hot EGR substitution, engine knock tests, which were conducted to identify audible knock limits, are also presented for a representative case (half load). The progress made by this project better positions ALPING combustion as a potentially viable approach to meet the regulatory and economic challenges of the future.

Sub-ambient cold-start emissions reduction using SwRI® PO x catalyst technology

This paper describes the application of SwRI’s cold-start PO x catalyst technology to reduce cold-start hydrocarbon emissions from a US Tier 2 vehicle at −7 °C. A reduction in −7 °C (20 °F) cold-start hydrocarbons will help US Tier 2 vehicles meet the proposed EPA NMOG standards. Improvements in cold temperature hydrocarbon emissions would also be beneficial in many parts of Europe during the winter months. In this work, a total hydrocarbon reduction of 19% was realized at 24 °C, in line with previous results, but only up to 3% at −7 °C. Insufficient oxygen in the engine-out exhaust gas at −7 °C was determined to be the reason why the PO x catalyst failed to significantly reduce HC emissions. Addition of supplemental oxygen to the exhaust during the cold-start, to simulate an adjustment in the engine calibration to less rich operation, resulted in a total hydrocarbon reduction of 18% with the PO x catalysts in place, but no benefit when the PO x catalysts were removed. Hence, the PO x catalyst approach can be used to good effect, even under sub-ambient cold-start conditions.

Estimation of Turkish road transport emissions

Using the COPERT III program, an inventory of Turkish road transport emissions was calculated and the contributions of road transport to global and local air pollutant emissions were examined for the year 2004. It was observed that passenger cars are the main source of CO, HC, and Pb emissions while heavy duty vehicles are mainly responsible for NO x , particulate matter (PM), and SO 2 emissions. Taking the emissions for the year 2004 as the baseline, a parametric study was conducted to determine the emission reduction potentials of different road transport strategies. The results indicated that the following road transport strategies; fleet renewal, promotion of public transportation, and faster urban traffic speed are very effective strategies for reducing regulated emissions and fuel consumption (FC) from a technical point of view. It was also noted that replacement of two-stroke motorcycles with four-stroke motorcycles is as effective as fleet renewal in reducing HC emissions.

Emission control options for power two wheelers in Europe

This paper quantifies the emission contribution of motorcycles and mopeds in Europe, in the period 1999–2012. Projections show that these vehicles will emit more than 7% and 20% of total road transport CO and HC, respectively, by the year 2012, if no additional regulatory measures are taken. In contrast, they will continue to be negligible NO x (0.7%) and CO 2 (<1%) emitters, while their particulate matter (PM) emission contribution is expected to decline to below 1% in the future. The relative importance of their emissions, however, increases in urban environments, especially in southern European countries, which host large fleets of small two wheelers. Hence, further regulatory measures are being considered which include durability requirements for the emission controls, in-use compliance and roadworthiness procedures, on-board diagnostics, control of evaporation emissions, PM specific measures and new steps for emission standards. The study quantifies the environmental benefits and the costs associated with each measure, and calculates cost-effectiveness figures which may be used to evaluate each policy option. Results show that for the reduction of HC emissions, both evaporation control and roadworthiness tests are cost-effective while a further tightening of the emission standards for mopeds will bring the largest benefit. Additionally, on-board diagnosis for motorcycles is found to be an expensive measure with questionable effectiveness, while the replacement of mineral with synthetic lubricants would bring clear benefits with respect to PM of 2-stroke engines.

Improvement of Stratified Combustion by a Large Amount of Hot EGR (Reduction of Unburned Hydrocarbons)

Unburned hydrocarbons from a direct injection stratified charge engine were greatly reduced by a large amount of hot EGR. A hydraulically controlled variable valve system was used to realize the hot EGR. Almost all the amount of required EGR gas for the NOx reduction was supplied directly from the previous cycle through the exhaust or inlet valves. Two kinds of recirculation were examined in this test. The first was the recirculation through the exhaust valves, which opened additionally during the suction stroke. Another was the recirculation through the inlet valves. The exhaust gas was pushed back to the port during the exhaust stroke through the additionally opened inlet valves and re-induced in the next cycle. Although both methods have the same ability to reduce HC emissions, required EGR was less in the latter method.

Adsorber System to Reduce HC Exhaust from Gasoline Engine. 1st Report. Adsorption and Desorption Characteristics with Si/2 Al Ratio, H2O and HC Species.

Exhaust gas temperatures of automotive gasoline engines are not high enough for catalysts to activate under cold start conditions and unburned hydrocarbons are abundantly emitted to the atmosphere without being oxidized. This study was conducted to develop an aftertreatment system to reduce HC emissions using zeolite to store HC at low temperatures. Model gas tests, to examine the adsorption and desorption characteristics of zeolites, were performed using C3H6 and C7H8 as typical HC species in the exhaust gas. From the FTP vehicle test, it was found that H2O molecules in the exhaust gas suppress HC adsorption, and zeolites with high Si/2 Al ratios are effective to store HC, but tend to desorb HC readily. These results showed good agreement with predictions derived from model gas test.

Characteristics of Quenching Crevice Widths in Combustion Chamber of a Spark Ignition Engine.

Exhaust HC emissions from spark ignition engines are still creating a major environmental problem. It is difficult to reduce HC emissions during engine warm-up because the catalysts cannot work well at low temperatures. The source of unburned HCs from engines is thought to be crevices in the combustion chamber, oil layer and deposits on the cylinder wall surfaces. Quenching crevice widths in the combustion chamber were measured under various engine operating conditions with an ion probe that could detect flame arrival. Then, an experimental equation of quenching crevice width was estimated as a function of cylinder pressure and cylinder wall temperature. Schlieren photographs of a combustion chamber with a lubricant-free piston were also taken to monitor the flow of gas of unburned HCs emitted from the piston crevice during the expansion and exhaust processes.