Cold Start Conditions Research Articles

Development and Application of a Virtual NOx Sensor for Robust Heavy Duty Diesel Engine Emission Control

To meet future emission targets, it becomes increasingly important to optimize the synergy between engine and aftertreatment system. By using an integrated control approach minimal fluid (fuel and DEF) consumption is targeted within the constraints of emission legislation during real-world operation. In such concept, the on-line availability of engine-out NOx emission is crucial. Here, the use of a Virtual NOx sensor can be of great added-value. Virtual sensing enables more direct and robust emission control allowing, for example, engine-out NOx determination during conditions in which the hardware sensor is not available, such as cold start conditions. Furthermore, with use of the virtual sensor, the engine control strategy can be directly based on NOx emission data, resulting in reduced response time and improved transient emission control. This paper presents the development and on-line implementation of a Virtual NOx sensor, using in-cylinder pressure as main input. The development steps from off-line modelling, calibration and validation towards real-time on-line implementation and validation will be presented in great detail. The Virtual NOx sensor is validated on a state-of-the-art EURO-VI Heavy Duty Diesel Engine. Steady-state validation results show that the performance of the Virtual NOx sensor is similar to the physical NOx sensor. Transient load ramp tests and frequency response function evaluation both show improved transient response from the Virtual NOx sensor. Furthermore, the Virtual NOx sensor is successfully applied as substitute for the physical NOx sensor as input to the air path controller over a transient cycle. These validation results demonstrate the application of the Virtual NOx sensor for engine control and show the potential for improved transient emission control.

Quantitative and Atomic-Scale View of CO-Induced Pt Nanoparticle Surface Reconstruction at Saturation Coverage via DFT Calculations Coupled with in Situ TEM and IR.

Atomic-scale insights into how supported metal nanoparticles catalyze chemical reactions are critical for the optimization of chemical conversion processes. It is well-known that different geometric configurations of surface atoms on supported metal nanoparticles have different catalytic reactivity and that the adsorption of reactive species can cause reconstruction of metal surfaces. Thus, characterizing metallic surface structures under reaction conditions at atomic scale is critical for understanding reactivity. Elucidation of such insights on high surface area oxide supported metal nanoparticles has been limited by less than atomic resolution typically achieved by environmental transmission electron microscopy (TEM) when operated under realistic conditions and a lack of correlated experimental measurements providing quantitative information about the distribution of exposed surface atoms under relevant reaction conditions. We overcome these limitations by correlating density functional theory predictions of adsorbate-induced surface reconstruction visually with atom-resolved imaging by in situ TEM and quantitatively with sample-averaged measurements of surface atom configurations by in situ infrared spectroscopy all at identical saturation adsorbate coverage. This is demonstrated for platinum (Pt) nanoparticle surface reconstruction induced by CO adsorption at saturation coverage and elevated (>400 K) temperature, which is relevant for the CO oxidation reaction under cold-start conditions in the catalytic convertor. Through our correlated approach, it is observed that the truncated octahedron shape adopted by bare Pt nanoparticles undergoes a reversible, facet selective reconstruction due to saturation CO coverage, where {100} facets roughen into vicinal stepped high Miller index facets, while {111} facets remain intact.

Improvement of diesel combustion with multiple injections at cold condition in a constant volume combustion chamber

A series of diesel spray combustion tests was carried out in a constant volume combustion chamber (CVCC) to investigate the effect of multiple injection strategies on cold startability. The experiments were performed under a simulated low temperature cold start condition. In-chamber pressure analysis and high speed flame imaging were conducted to compare the effectiveness of each injection strategy on cold startability. Spray targeting visualization was also performed to examine the wall impingement of injected fuel. The diesel fuel was injected into the CVCC with an injection pressure of 35MPa. Multiple injection strategies with different amounts of pilot injection quantities were applied to improve the diesel combustion under simulated cold start ambient condition. The flame imaging and in-chamber pressure results showed that the multiple injection strategy provided better cold startability than the single injection condition. According to the pilot injection quantity, the peak of the flame luminosity and in-chamber pressure were gradually increased with larger pilot injection quantity cases. The peak of the variation rate of the in-chamber pressure with a multiple injection strategy was approximately 2 times higher than that of the single injection case. In terms of spray targeting imaging, the results indicated that the fuel impingement and flow to the piston crevice volume were increased with a larger amount of pilot2 injection. Therefore, the increment of the pilot1 injection quantity rather than the pilot2 injection quantity was suggested not only to improve cold startability, but also to reduce unburned hydrocarbon emissions under a cold start condition in a real engine.

Acoustic power delivery to pipeline monitoring wireless sensors

The use of energy harvesting for powering wireless sensors is made more challenging in most applications by the requirement for customization to each specific application environment because of specificities of the available energy form, such as precise location, direction and motion frequency, as well as the temporal variation and unpredictability of the energy source. Wireless power transfer from dedicated sources can overcome these difficulties, and in this work, the use of targeted ultrasonic power transfer as a possible method for remote powering of sensor nodes is investigated. A powering system for pipeline monitoring sensors is described and studied experimentally, with a pair of identical, non-inertial piezoelectric transducers used at the transmitter and receiver. Power transmission of 18mW (Root-Mean-Square) through 1m of a118mm diameter cast iron pipe, with 8mm wall thickness is demonstrated. By analysis of the delay between transmission and reception, including reflections from the pipeline edges, a transmission speed of 1000m/s is observed, corresponding to the phase velocity of the L(0,1) axial and F(1,1) radial modes of the pipe structure. A reduction of power delivery with water-filling is observed, yet over 4mW of delivered power through a fully-filled pipe is demonstrated. The transmitted power and voltage levels exceed the requirements for efficient power management, including rectification at cold-starting conditions, and for the operation of low-power sensor nodes. The proposed powering technique may allow the implementation of energy autonomous wireless sensor systems for monitoring industrial and network pipeline infrastructure.

Design and evaluation of the thermal capability to secure a working time of cryogenic explosion-proof camera in LNG carrier tank

With an increase in the usage of LNG, there is a heightened interest about its safety aspects regarding the explosion of LNG carrier tank. The need for a cryogenic explosion-proof camera has increased. The camera has to work in cryogenic environment (below −160 °C) in LNG carrier. This study conducted design and heat transfer analysis of cryogenic camera to secure working time in limitation of heat source. The design with gap width of double pane windows was conducted based on simple vertical cavity model to insulate from cryogenic environment. The optimal gap width was 12.5 mm. For effective analysis considering convection within the camera, equivalent thermal conductivity method was adopted with ABAQUS. The working time of the camera predicted was over 10 h at warm-start condition. In cold-start condition, it required about 5 h of pre-warming time to work. The results of analysis were compared with the ones of the actual cryogenic test.

A new FFT acquisition scheme based on partial matched filter in GNSS receivers for harsh environments

FFT acquisition scheme based on partial matched filter is an important search method in GNSS receivers, which can scan the code phase and Doppler frequency by parallel search scheme. However, the detection probability reduces due to the coherent combing loss and scalloping loss. To solve this problem, we propose a new FFT acquisition method based on Partial Matched Filter (PMF-FFT) in GNSS receiver, in which, the IF signal is divided and central frequency is shifted before the matched filters, and the FFT results are combined to search the Doppler frequency. The performance of the scheme is analyzed by amplitude response of the system. Both analysis and simulation results show that the new scheme has a larger acquisition range without adding the FFT points, which is quite appropriate for dynamic and weak signal environments. We also do a comparison based on the collected data test, showing that the PMF-FFT scheme outperforms the other three methods generally used in the GNSS receivers. Moreover, we apply an FPGA&DSP hardware receiver to verify the practicability and superiority of our method, which turns out our method can extremely reduce the acquisition time in a cold start condition, compared to the serial scheme.

Density, viscosity and specific heat capacity of diesel blends with rapeseed and soybean oil methyl ester

By 2020, the EU aims to have 10% of the transport fuel of every EU countries come from renewable sources such as biofuels. Fuel suppliers are also required to reduce the greenhouse gas intensity of the EU fuel mix by 6% in comparison to 2010. The thermophysical properties of biofuels are, therefore, required for the efficient design of every step in their production, distribution, and utilization. Despite of these needs, high pressure thermodynamical characterization of biofuels is not still exhaustive. Next generation injection systems work with pressure up to 300 MPa, but available measurements are limited to 200 MPa. Measurements extrapolation generally are not recommended at these pressure because it can hide freezing phenomena here documented at temperature of (20 and 30) °C. In this work, density and viscosity of pure and blended FAME (SME and RME) biofuels have been measured up to 300 MPa. Since the scope of the work is both to investigate cold start conditions found in engines and the thermal behaviour of fuels in tanks of cars, petrol station and dispenser, the temperature interval is limited to (0–60) °C. In particular, it has been observed a partial freezing even for temperature up to 30 °C. Density and viscosity values were obtained by direct experimental measurements, while heat capacities have been calculated using density and speed of sound results previously obtained. At ambient pressure conditions, the uncertainty in density measurements was between 0.005% and 0.01% (k=2) and for viscosity measurements the uncertainty was between 0.2% and 1.3% (k=2). At elevated pressures the uncertainty in density measurements was 0.08% (k=2), while for viscosity and heat capacity it was 2% (k=2).

Impact of the Zeolite Structure and Acidity on the Adsorption of Unburnt Hydrocarbons Relevant to Cold Start Conditions

Adsorption behavior of commercial zeolites were investigated for the trapping of a hydrocarbon mixture (propene, toluene and decane) mimicking Diesel cold start exhausts under dry conditions. The studied commercial zeolites, in most cases under protonated form, (with Si/Al ratio in the range 2–15) present different structures: FAU, *BEA, MOR, MFI, FER, and LTA. Textural and structural characterizations were carried out using N2 adsorption at −196 °C and X-ray diffraction. In situ FTIR spectroscopy of adsorbed pyridine was used to probe quantitatively the acid sites. The methodology used in this study consisted of an adsorption phase at 35 °C followed by temperature-programmed desorption (TPD) under He at 10 °C/min, and three different adsorption mechanisms were highlighted according to the pore size and the host framework. MOR and MFI structures appear to be the less selective for any type of hydrocarbon and are thus the most suitable for cold start applications. Except for these types of zeolites present...

Characterizing particulate matter emissions from GDI and PFI vehicles under transient and cold start conditions

Ultrafine particle emissions from Gasoline Direct Injection (GDI) and Port Fuel Injection (PFI) vehicles under the New European Driving Cycle (NEDC) were measured by using the Differential Mobility Spectrometer 500 (DMS 500) for size distribution information and Transmission Electronic Microscopy (TEM) for morphological analysis. The first phase of the ECE 15 cycle (representing the urban driving condition) within the NEDC was examined to evaluate the cold start effect on particulate matter (PM) emissions. Even though the ECE 15 cycle1 only occupies 1/6th of the time of the NEDC, the cold start emissions accounted for more than 50% of the total particle number for GDI vehicles and approximately 70% for PFI vehicles. Further analysis in terms of the Count Medium Diameter (CMD) of the PM emissions is also discussed. A linear regression method was adopted to analyze the correlation between PM emissions and vehicle parameters. For GDI vehicles, acceleration demonstrated a strong correlation with PM emissions, particularly under warm start conditions. The effects of the after treatment device Three Way Catalyst (TWC) on PM emissions was also investigated.

Electrically heated 3D-macro cellular SiC structures for ignition and combustion application

The paper describes different aspects of porous combustion reactor operation especially at cold start conditions. Under cold start conditions it is necessary to increase the internal energy of the combustion reactor, to accumulate enough energy inside its solid phase and to reach at least the ignition temperature on the reactors inner surface. The most practicable method to preheat a cold porous reactor is to use its surface as a flame holder and to apply free flame combustion as a heat source for the preheating process. This paper presents a new electrically heated ignition element, which gets integrated in a three dimensional macro-cellular SiSiC reactor structure. For the development of the ignition element it was assumed, that the element is made of the same material as the combustion reactor itself and is fully integrated within the three-dimensional macro-cellular structure of the combustion reactor. Additive manufacturing like three-dimensional (3D) printing permits the production of regular SiSiC structures with constant strut thickness and a defined current flow path. To get a controlled temperature distribution on the ignition element it is necessary to control the current density distribution in the three-dimensional macro-cellular reactor structure. The ignition element used is designed to be an electrical resistance in an electric current system, converting flowing current into heat with the goal to get the highest temperature in the ignition region (glow plug). First experiments show that the ignition element integrated in a combustion reactor exhibits high dynamics and can be heated to the temperatures much above 1000°C in a very short time (approx. 800ms) for current of I=150A.

Experimental Analysis of Telescopic Catalytic Converter in a Petrol Engine to Reduce Cold Start Emission

Control of harmful emissions during cold start of the engine has become a challenging task over the years due to the ever increasing stringent emission norms. Positioning of the catalytic converter closer to the exhaust manifold is an efficient way of achieving rapid light-off temperature. On the other hand, the resulting higher thermal loading under high-load engine operation may substantially cause thermal degradation and accelerate catalyst ageing. The objective of the present work is to reduce the light-off time of the catalyst and at the same time to reduce the thermal degradation and ageing of the catalyst to the minimum possible extent. In the present work two innovative approaches namely Parallel Catalytic Converter System (PCCS) and Telescopic Catalytic Converter System (TCCS) have been adopted to reduce the light-off time of the catalyst. The tests were conducted on a 4 cylinder Spark Ignition Engine under cold start condition. It was established that considerable reduction in the light-off time was achieved by using TCCS. Further reduction in the light-off time was achieved by using pre catalysts (40%vol. & 20%vol.) and hot air injection. It has been found that 13% reduction in CO light-off time was achieved with pre-catalyst (40%vol.), 50% reduction with pre-catalyst (20%vol.) and 66% reduction with hot air injector system, when compared to TCCS. Also 14% reduction in HC light-off time was achieved with pre-catalyst (40%vol.), 43% reduction with pre-catalyst (20%vol.) and 63% reduction with hot air injection system, when compared to TCCS. It was also established that light-off time of TCCS can be brought down to 10 seconds using hot air injection.

Experimental study on primary breakup of diesel spray under cold start conditions

Studies on primary breakup of diesel spray under room temperature (25°C) and low temperature (−2°C), were carried out by mass flow rate measurement and microscopic imaging. It was shown that under low injection pressure and low temperature, raised viscosity and surface tension caused slower penetration and poorer breakup. Under high injection pressure, higher chances of mushroom formation under low temperature due to higher viscosity surprisingly leaded to quicker penetration but still poorer dispersion during the initial spray stage. Low temperature retarded the start of atomization as the needle rose. The end of injection showed a large amount of compact liquid fuel with little dispersion, which was deteriorated by low temperature. In addition, a new equation including the influences of ambient gas on breakup, was proposed to quantify the spray stability, allowing quantitative analysis of the effects of temperature and ambient gas.

Combustion and Sooting Behavior of Spark-Ignited Ethanol–Isooctane Sprays under Stratified Charge Conditions

A spray combustion investigation within an optically accessible high-temperature/high-pressure chamber with ignition was conducted to study soot formation of ethanol blended fuels at cold start conditions. The fuels ethanol, isooctane, and its blends E85 (85 vol% of ethanol in isooctane) and E20 were studied at different temperatures under direct injection spark ignition engine stratified charge conditions. A high-speed camera in combination with an image stereoscope was used in order to visualize the combustion in two different wavelength regions simultaneously to distinguish between premixed and sooting combustion. Additionally, a spectroscopic setup was applied for detailed flame emission analysis on high time-resolved scale. Furthermore, a spray formation investigation was carried out in order to evaluate the fuel evaporation process. The study reveals that depending on the operation conditions either the chemical or the physical processes dominate the combustion and sooting behavior. At low ambient t...

A Nonlinear Model Predictive Controller With Multiagent Online Optimizer for Automotive Cold-Start Hydrocarbon Emission Reduction

In this paper, a nonlinear model predictive controller (NMPC) with a multiagent heuristic optimizer, which is called dynamic particle swarm optimization (DPSO), is proposed to reduce the cold-start hydrocarbon (HC) emission of an automotive spark-ignited engine. In general, the cold-start HC emission reduction has been proven to be a very challenging control problem that has attracted increasing attention from the automotive research community. The main contribution of this paper lies in the implementation of a model-based predictive control scheme that uses a discrete nonlinear control-oriented model for calculating the control commands. In the first part of the experiments, the developed control-oriented model is validated with some data obtained through experiments. Then, by applying the controller to different cold-starting conditions, the values of exhaust gas temperature $T_{\mathrm{exh}}$ and engine-out HC emissions are controlled to reduce the cumulative tailpipe emissions $\text{HC}_{\mathrm{cum}}$ . To ascertain the veracity of the proposed control scheme, the same problem is solved using Pontryagin's minimum principle. The conducted simulations indicate the applicability of DPSO as an effective solver at the heart of the NMPC. Moreover, the results of model-in-the-loop simulation and hardware-in-the-loop testing demonstrate the acceptable performance of the proposed control scheme for real-time applications, which is based on the NMPC method for the considered problem.

Near-nozzle microscopic characterization of diesel spray under cold start conditions with split injection strategy

Near-nozzle microscopic characteristics of diesel spray under room temperature (25°C) and low temperature (−2°C) were investigated by microscopic imaging technique. The primary breakup of winter diesel (WD) and rapeseed methyl ester (RME) sprays were investigated with single and split injection strategies. It was shown that increased viscosity and surface tension under low temperature lead to much poorer dispersion. Under low injection pressure with split injection strategy, the first split injection was unexpectedly severely affected by both temperature and dwell, with significant breakup characteristic differences when dwell varied. By contrast, the second split under low injection pressure tended to be affected only by temperature rather by dwell. High injection pressure considerably alleviated the breakup characteristic difference of the first split injection caused by temperature and dwell although the effects of fuel properties were still seen, leading to better fuel dispersion and more predictable spray characteristics. In addition, RME with higher viscosity and surface tension consistently presented much poorer dispersion quality compared with WD even under high injection pressure where the influence of fuel properties may be insignificant.

Effect of Soot on N2O Formation Over Pt Based Diesel Oxidation Catalyst Supported on Microporous TiO2

The N2O formation over the diesel oxidation catalyst supported on microporous TiO2 has been investigated in the presence of the soot to simulate cold start or regeneration condition. The platinum (Pt) catalyst entrapped in micropore was resulted in the increase of the catalytic activity compared to the Pt catalyst supported on alumina. Also, it was shown that the presence of the soot with the oxidation catalyst enhanced the N2O formation.

A thermal mixed lubrication model to study the textured ring/liner conjunction

In this paper, a semi-deterministic analytic thermal solution is presented for the rough textured ring/liner conjunction. The energy equation is employed to reveal more detailed information about the tribological performance of the textured surfaces in terms of the thermal effects and the viscosity change. The effects of surface texturing under the cold and warm engine conditions are studied over a wide range of engine speeds. It is shown that the thermal effects play a crucial role in hydrodynamic lubrication, particularly under the cold start condition. Including the thermal effects in the numerical simulation can ensure the accurate predictions.

Development of a novel cooking stove based on catalytic hydrogen combustion

A hydrogen based cooking stove was developed and tested in respect to efficiency, functionality and hydrogen safety. Therefore the developed novel combustion unit technology is based on the catalytic oxidation of hydrogen on a platinum coated highly porous reticulated silicon carbide foam ceramics. Compared to other works [1], premixing of hydrogen and air is avoided, thus providing the basis for safe and reliable operation. With this catalytic combustion technology, no initial hydrogen ignition is required, implying a high application security. Separate air and hydrogen supplies make regulation of temperature and power efficient, simple and save.Catalytic hydrogen oxidation is performed already at room temperature; whereby at high hydrogen load, a small hydrogen slip is detected under cold start conditions, nevertheless in operation this becomes negligible. In order to overcome this issue, a hydrogen flow regulation, based on the hydrogen combustion temperature, was introduced.A heat exchanger is integrated into the exhaust line, in order to recover heat for the incoming air, required for the catalytic combustion. This leads to a stove efficiency of up to 80%, measured according to the DIN EN 30-2-1: 2005–08 test standard and greatly exceeds the postulated standard minimum efficiency of 35%. For comfortable and save use, the combustion unit is mounted under a glass ceramic coverage, as common for conventional electrical stoves.

Investigation of Cold Starting and Combustion Mode Switching as Methods to Improve Low Load RCCI Operation

Reactivity controlled compression ignition (RCCI) is an engine combustion strategy that utilizes in-cylinder fuel blending to produce low NOx and particulate matter (PM) emissions while maintaining high thermal efficiency. The current study investigates RCCI and conventional diesel combustion (CDC) operation in a light-duty multicylinder engine (MCE) using a transient capable engine test cell. The main focus of the work uses engine experiments to investigate methods which can improve low load RCCI operation. The first set of experiments investigated RCCI operation during cold start conditions. The next set of tests investigated combustion mode switching between RCCI and CDC. During the cold start tests, RCCI performance and emissions were measured over a range of engine coolant temperatures (ECTs) from 48 °C to 85 °C. A combination of open- and closed-loop controls enabled RCCI to operate at a 1500 rpm, 1 bar BMEP operating point over this range of coolant temperatures. At a similar operating condition, i.e., 1500 rpm, 2 bar BMEP, the engine was instantaneously switched between CDC and RCCI combustion using the same open- and closed-loop controls as the cold start testing. During the mode switch tests, emissions and performance were measured with high-speed sampling equipment. The tests revealed that it was possible to operate RCCI down to 48 °C with simple open- and closed-loop controls with emissions and efficiency similar to the warm steady-state values. Next, the mode switching tests were successful in switching combustion modes with minimal deviations in emissions and performance in either mode at steady state.

The problem of cold starts: A closer look at mobile source emissions levels

While the phenomenon of excess vehicle emissions from cold-start conditions is well known, the magnitude and duration of this phenomenon is often unclear due to the complex chemical processes involved and uncertainty in the literature on this subject. This paper synthesizes key findings regarding the influence of ambient and engine temperatures on light-duty vehicle (LDV) emissions. Existing literature, as well as analytical tools like the U.S. Environmental Protection Agency’s Motor Vehicle Emission Simulator (MOVES), indicate that while total vehicle emissions have dropped significantly in recent years, those associated with cold starts can still constitute up to 80% for some pollutant species. Starting emissions are consistently found to make up a high proportion of total transportation-related methane (CH4), nitrous oxide (N2O), and volatile organic compounds (VOCs). After 3–4min of vehicle operation, both the engine coolant and the catalytic converter have generally warmed, and emissions are significantly lower. This effect lasts roughly 45min after the engine is shut off, though the cooling rate depends greatly on the emission species and ambient temperature. Electrically (pre-)heated catalysts, using the bigger batteries available on hybrid drivetrains and plug-in vehicles, may be the most cost-effective technology to bring down a sizable share of mobile source emissions. Trip chaining (to keep engines warm) and shifting to non-motorized modes for shorter trips, where the cold start can dominate emissions, are also valuable tactics.