Cold Start Of Diesel Engines Research Articles

Experimental study on the cerium oxide nanoparticles doped in diesel fuel improving the cold start performance of diesel engines at high-altitude and low-temperature environments

CeO2 nanoparticles are effective fuel additives that enhance fuel spray, atomization, and combustion characteristics due to their high catalytic activity and excellent thermal properties. When added to fuel, CeO2 nanoparticles significantly improve in-cylinder combustion, and engine performance, and reduce pollutant emissions under normal engine operating conditions. Diesel engines encounter persistent challenges during cold starts at low temperatures and high altitudes. However, there is limited research on the effects of CeO2 nanoparticles on ignition and combustion at low temperatures and cold start performance. This study aims to evaluate the impact of CeO2 nanoparticles doping in diesel fuel on the cold start performance of diesel engines in high-altitude and low-temperature environments. Diesel fuel doped with CeO2 nanoparticles at various concentrations was prepared using magnetic stirring and ultrasonication. The cold start performance of the test engine was assessed in an environmental chamber. This work investigated and evaluated the improvements of CeO2 nanoparticles on cold start performance from three perspectives: general low-temperature conditions, high-altitude environments, and extreme low-temperature scenarios with diethyl ether premixing. Experimental results indicate that incorporating CeO2 nanoparticles expanded the critical temperature required for a successful cold start from 0 °C to −5 °C. At high altitudes, the addition of CeO2 nanoparticles effectively increased the proportion of efficient combustion, evidenced by single peak and parent peak patterns during cold starts. CeO2 nanoparticles facilitated the transition from low-temperature to high-temperature reactions, promoting fuel ignition during the first injection cycle and reducing speed fluctuations during cold starts with diethyl ether premixing at −40 °C. Furthermore, adding CeO2 nanoparticles prevented detonation and rapid pressure surges during cold starts. Overall, doping diesel fuel with CeO2 nanoparticles proves to be an effective method for enhancing cold start performance in diesel engines. This study offers a novel approach for improving diesel engine cold start performance in high-altitude and low-temperature conditions.

A comprehensive investigation of injection strategies for improving diesel engine combustion under cold start development

Starting at cold temperatures ranging from -30°C to 0°C has been a concern for all diesel engines, especially for future diesel engines that need to meet tighter carbon emission standards. Combustion instability and increasing smoke emissions are rising concerns during the cold start of diesel engines. Cold ambient conditions cause long cranking periods or complete misfire events in diesel engines; therefore, they produce a large proportion of pollutants within the cylinder due to incomplete combustion. In this study, a comprehensive investigation of multiple injection strategies was conducted under cold-start conditions to identify an optimal injection strategy that improves diesel combustion stability, cold-startup performance, and decreases white smoke emissions at cold ambient temperatures. This study found that cold start-up performance can be improved by eliminating misfire and lowering time to clean up white smoke with a three-injection strategy (two pilots and one main injection, simply named Pilot-Pilot-Main).

Experimental investigation of atomization characteristics at low temperature environments during diesel engine cold start

Exploring the atomization characteristics of fuel in low-temperature environments is crucial for improving the cold start performance of diesel engines. In this work, based on LIEF-PIV laser testing technology, a diesel engine cold start fuel atomization experimental system was built, which could simulate the internal environment of a diesel engine's cylinder during cold start. The concentration and velocity distributions of free-jet spray and wall-impinging spray at low temperature were measured experimentally. The results showed that the decrease in ambient temperature had a significant impact on the rate of evaporation of fuel droplets, which was mainly reflected in two aspects: the total evaporation of the fuel and the uniformity of the distribution of vapor phase. The decrease in fuel temperature led to a decrease in the conversion efficiency of vapor/liquid phases of the fuel. When the fuel temperature was −20 °C, the distribution range of vapor equivalence ratio near the wall area was 0.11–0.59, which is significantly lower than the other two conditions. In addition, the increase in environmental pressure resulted in a certain decrease in the maximum flow velocity and turbulent flow energy of the mixture, with an average decrease of 0.32 m/s in the maximum flow velocity at the three fuel temperatures of 0 °C, −20 °C, and −40 °C.

Effect of injection pressure on low-temperature fuel atomization characteristics of diesel engines under cold start conditions

Exploring the atomization characteristics and spray impingement characteristics of low-temperature fuel under different injection pressures has important practical significance for improving the cold start performance of diesel engines. In this study, based on LIEF-PIV combined laser testing technology, a fuel atomization experimental system for diesel engine cold start was established. The concentration and velocity fields of low-temperature fuel with the temperature from 20 to - 40 ℃ were experimentally analyzed within the injection pressures of 40-80MPa. The results showed that the increase of injection pressure increased the initial kinetic energy of the diesel droplets, whereas the concentration gradient of spray decreased significantly. Meanwhile, the mixing effect of spray and ambient gas increased. When the fuel temperature decreased from 0 ℃ to - 20 ℃, the values of the average equivalence ratio in the near-wall region decreased from 0.52 to 0.21. The change of injection pressure had an obvious effect on the macro morphology of wall-impinging spray and the flow characteristics of the fuel/air mixture. When the injection pressure increased from 40MPa to 80MPa, the difference of maximum turbulent kinetic energy among various temperatures increased from 0.66 m2/s2 to 0.90 m2/s2.

Co3O4 as an efficient passive NOx adsorber for emission control during cold-start of diesel engines

The Co3O4 nanoparticles, dominated by a catalytically active (110) lattice plane, were synthesized as a low-temperature NOx adsorbent to control the cold start emissions from vehicles. These nanoparticles boast a substantial quantity of active chemisorbed oxygen and lattice oxygen, which exhibited a NOx uptake capacity commensurate with Pd/SSZ-13 at 100 °C. The primary NOx release temperature falls within a temperature range of 200-350 °C, making it perfectly suitable for diesel engines. The characterization results demonstrate that chemisorbed oxygen facilitate nitro/nitrites intermediates formation, contributing to the NOx storage at 100 °C, while the nitrites begin to decompose within the 150-200 ºC range. Fortunately, lattice oxygen likely becomes involved in the activation of nitrites into more stable nitrate within this particular temperature range. The concurrent processes of nitrites decomposition and its conversion to nitrates results in a minimal NOx release between the temperatures of 150–200 °C. The nitrate formed via lattice oxygen mainly induces the NOx to be released as NO2 within a temperature range of 200–350 °C, which is advantageous in enhancing the NOx activity of downstream NH3-SCR catalysts, by boosting the fast SCR reaction pathway. Thanks to its low cost, considerable NOx absorption capacity, and optimal release temperature, Co3O4 demonstrates potential as an effective material for PNA applications.

Energy-based cold-start strategies for diesel engines at extreme low temperature

The cold start of diesel engines at extreme low temperatures is currently one of the most critical problems in the field of transportation. An experiment on the cold start was conducted in a controlled environment, and a one-dimensional simulation model was built to study diesel engine cold start performance based on energy analysis. The cyclic energy loss of cold start failure and success cases, ramp-up-speed period characteristic of diesel engine were studied by using special low temperature diesel and adopting two pilots and one main injection control strategy at −43 ℃. The numerical calculation and analysis results show that when the exhaust energy is high and the heat transfer loss energy is very low, there may be a misfire cycle in the cylinder. The increase in the pilot injection 1 mass, main injection mass, pilot injection 1 timing, and main injection timing within certain limits can significantly increase the fuel vapor fraction during the ramp-up-speed period (maximum of 66.67%). The speed of ramp-up-speed period and idle steady phase faster obviously, the maximum increase is 300 r/min (30%). The fuel vapor fraction increases as the pilot injection 2 mass increases during the ramp-up-speed period but slows down the speed of ramp-up and idle phase, with a maximum decrease of 300 r/min (23.07%).

Experimental study on improving cold start performance of diesel engines at extremely low ambient temperatures with diethyl ether

How to achieve a fast and reliable cold start of diesel engines at extremely low temperatures is a significant and longstanding problem. In this study, a precise amount of diethyl ether was premixed in the intake to facilitate the starting at extremely low ambient temperatures down to −40 °C. The study investigated the effects of diesel fuel injection strategies, diethyl ether concentration, and ambient temperature on the cold-start performance. Additionally, an analysis was conducted on energy consumption and heat loss during the cold start period. The test engine could start quickly and steadily when diethyl ether was premixed in the intake. This was achieved by optimizing the diesel injection quantity to 60% of the original quantity and retarding the injection timing from 6 oCA BTDC to 2 oCA BTDC. The engine exhibited reliable starting at −40 °C when 2.0% v/v diethyl ether was premixed. However, excessive direct injection of diesel had an adverse effect on fuel ignition at such extremely low temperatures. Moreover, the electricity consumption was much lower with diethyl ether premixed in the intake than that with an electric intake heater, greatly reducing the requirements for starting batteries during the cold start under extremely low-temperature conditions.

Hazardous particles during diesel engine cold-start and warm-up: Characterisation of particulate mass and number under the impact of biofuel and lubricating oil

The increasing share of using biofuels in vehicles (mandated by current regulations) leads to a reduction in particle size, resulting in increased particle toxicity. However, existing regulations disregarded small particles (sub-23 nm) that are more toxic. This impact is more significant during vehicle cold-start operation, which is an inevitable frequent daily driving norm where after-treatment systems prove ineffective. This study investigates the impact of biofuel and lubricating oil (as a source of nanoparticles) on the concentration, size distribution, median diameter of PN and PM, and their proportion at size ranges within accumulation and nucleation modes during four phases of cold-start and warm-up engine operation (diesel-trucks/busses application). The fuels used were 10% and 15% biofuel and with the addition of 5% lubricating oil to the fuel. Results show that as the engine warms up, PN for all the fuels increases and the size of particles decreases. PN concentration with a fully warmed-up engine was up to 132% higher than the cold-start. Sub-23 nm particles accounted for a significant proportion of PN (9%) but a smaller proportion of PM (0.1%). The fuel blend with 5% lubricating oil showed a significant increase in PN concentration and a decrease in particle size during cold-start.

Computational Investigations of Spray Atomization and Evaporation Under Cold-Start Conditions of a Diesel Engine

Abstract Unburnt hydrocarbon emissions and combustion instability are severe issues in diesel engines during cold starting. This simulation study aims to provide insights for improving the cold-start issues of diesel engines. Computational analysis of the diesel spray and evolution of plumes from a 7-hole injector was done in a constant volume quiescent spray chamber for analyzing the effect of fuel temperature. This study was based on a comprehensive numerical analysis using CONVERGE computational fluid dynamics (CFD) software, where an Eulerian–Lagrangian approach was adopted in a large eddy simulation (LES) framework. Diesel engine-like cold-start conditions were replicated by reducing the fuel temperatures to 250 K to simulate freezing conditions outside. This computational study compares fuel sprays at 250 K with 312 K into a relatively colder ambient temperature of 626 K vis-a-vis high-temperature diesel engine-like ambient conditions with ambient temperature to 961 K to investigate the degree of spray characteristics improvements due to increased fuel temperature. The predicted liquid spray penetration obtained by simulations agreed well with the experimental data for fuel temperatures injected into the ambient at cold (626 K) and hot (961 K) engine-like ambient conditions. The available empirical relations justify the simulation results of this study. Results showed that fuel and ambient temperatures significantly affected the spray atomization and evaporation characteristics. A higher reduction in liquid penetration length was found with increasing fuel temperature at hot ambient conditions. Increasing ambient temperature also improved the evaporation characteristics of the spray droplets. Vapor formation for the same increase in fuel temperature was higher at hot ambient temperature than the cold. Fuel temperature had a major role in the spray atomization process, whereas the ambient temperature affected the spray evaporation process. However, fuel and ambient temperatures had only a minor effect on the distribution of total kinetic energy (TKE). Among all test conditions, a fuel temperature of 312 K sprayed in hot ambient conditions showed superior fuel spray atomization and evaporation. Hence, to tackle the cold-start of diesel engines, measures taken to increase the fuel and ambient temperatures simultaneously proved to be useful.

Study on the First-Firing-Cycle combustion characteristics of high-altitude and low-temperature environments during diesel engine cold start

Cold-start performance is one of the main problems that affects the reliability of diesel engines in high-altitude and cold areas. The First-Firing-Cycle (FFC) is the most important cycle during the cold-start process, which apparently affects the cold-start performance. An environmental simulation storehouse and a 3D simulation model were used to study the spray and combustion of FFC in the start-up phase, which temperature varied from −20℃ to 10℃ and altitudes varied from 0 m to 4000 m. A skeleton mechanism using n-dodecane with 117 species and 649 reactions was proposed. Because of the cold temperature and low air density in the plateau area, the cold-start performance was worse and more difficult to reach idle conditions. Verified by experiments and simulations, the spray and combustion characteristics of FFC during the start-up phase were affected by the altitude and ambient temperature obviously. When the altitude increased or the ambient temperature decreased, the atomization and combustion were insufficient, which ultimately produced less power. The control parameters of the Electronic control unit (ECU) should consider the altitude to obtain better cold-start performance in the future.

SELECTION AND JUSTIFICATION OF THE MATHEMATICAL 6 FACTORS EXPERIMENT PLAN IN THE STUDY OF ICE STARTING QUALITIES

The practical significance of the application of multivariate regression analysis in engineering practice as a necessary step towards improving and optimizing complex systems and processes is presented. The goal and investigation tasks have been actualized to optimize the start-up process of a high-speed subcompact diesel engine. Preparation of the plural factors experiment features of diesel start-up process based on regression analysis and the theory of mathematical design of experiment are presented. Qualitative optimizing parameters of the diesel engine cold start are determined: instantaneous acceleration of the crankshaft dn / dτ at the time of crankshaft cranking by an external energy source close to the time spent on starting the engine with optimal parameters of the starting system and starting energy consumed during the crankshaft cranking by an external energy source. Six main factors influence on certain parameters of the diesel engine start quality have been investigated. The regression equation for assessing the quality of the start-up process is substantiated. The form of regression equation is a full quadratic polynomial for the reproduction of the investigated functions, based on the previous study of some used in the study individual factors influence. The analysis of proposals for rational plan selection of a six-factor experiment to find the coefficients of the second-degree regression polynomial is carried out. The substantiation of the decision regarding the choice of the plan is given. Selection was based on the requirements of the investigation test bench and the conditions for study organizing. Main impact had the predecessors experience of similar investigation and the statistical criteria for different plans of experiment comparison used in mathematical theory of design of experiments. The points of the plan have been defined on a multidimensional cube due to the need to vary on three levels with a uniform step of all 6 factors that were identified as influential. Under the conditions of the available laboratory test bench, the current values of the factors of equivalent cold start temperature, crankshaft-cranking speed and maximum temperature of the glow plugs have a variance of the installation at different points of the plan, and the nature of the factors on energy consumption is unknown in advance. As a rational experimental design for organizing the current study, the Box-Wilson orthogonal central compositional plan was chosen, built by adding plan points on the axes of the factorial space to the full-factorial plan of the lowest order, while maintaining the requirement of orthogonality and symmetry of the plan.

Effects of vortex tube on exhaust emissions during cold start of diesel engines

This study investigates the emissions of a 6-cylinder direct injection (DI) diesel engine with vortex tube for cold start conditions. Four ambient temperatures: 5 °C, −3 °C, 0 °C and 4C were considered. The compressed air required to operate the vortex tube was supplied from compressed air cylinders from pneumatic brake system components located in heavy vehicles. The air from the compressed air tanks entered the vortex tube and the vortex emerged from the tube as hot and cold air. The hot air from the vortex tube was mixed with the intake air in the intake manifold to make the intake air hotter. Emissions analysis was conducted for carbon monoxide (CO), hydrocarbons (HC), nitrogen oxides (NOx), and particulate matter (PM). Exhaust emission characteristics for the engine with vortex tube and without vortex tube were obtained and the results were compared with each other. The cold starting performance and fuel consumption of the diesel engine could be improved by using vortex tubes. The use of the vortex tube increased the intake air temperature, which decreased durations of engine starting–cranking, cranking–idling, and idling–stabling and reduced the fuel consumption. CO and PM emissions decreased, but HC and NOx emissions increased by using vortex tube.

A numerical investigation of injection pressure effects on wall-impinging ignition at low-temperatures for heavy-duty diesel engine

The effect of injection pressure on impinging ignition at low temperatures is not systematic or even confusing. This work is to reveal the impinging ignition mechanism by the numerical method to further improve the success rate and thermal efficiency at cold-start conditions in a diesel engine. In which, n-dodecane was used as the diesel surrogate, and the intermediate reaction radicals, equivalence ratio, and temperature were studied to analyze chemical reaction processes and local burn conditions. The simulation well represents the experiments. The results show that increasing injection pressure with the same mass leads to a faster fuel spreading and makes the mixture region wider and leaner for the impinging spray simulations, and the spray-wall impingement can instantly change the direction of the fuel movement and make fuel more dispersed. Under low-temperature cold-wall conditions, the physical ignition conditions are gradually destroyed due to the diffusion during longer ignition delay and finally result in misfire at higher injection pressure. In the misfire case, there is a generation of CH2O, but no obvious generation of OH. It proves that the low-temperature reactions occurred but transition into high-temperature reaction was stopped even the local temperature has reached the decomposition threshold (1000 K) of H2O2. However, lengthening injection duration can guarantee the success of ignition at higher injection pressures. It indicates that concentration is a key parameter for triggering the high-temperature reaction, and which can be made up by extending the injection duration. This research proves and explains why the lower injection pressure is helpful to the combustion in the cold start process from the mechanism level, and also has important implications for the design of fuel injection strategy in diesel engine cold start.

The Optical Investigation on Initial Flame Developing Characteristics of Diesel Jet under Cold Start Conditions

ABSTRACT Cold start ability is essential for heavy duty vehicles equipped diesel engine operating in cold regions. However, it is the diesel jet’s initial flame developing characteristics that determines whether it is able to start success. Thus, it is investigated on a constant volume chamber by optical diagnostics technologies. In order to simulate cold start conditions, there are four conditions varied during experiments including injection pressure (40~160 MPa), ambient temperature (707 K~827 K), ambient density (9.1~22.6 kg/m3), and fuel temperature (343 K~283 K). It is found that under low ambient temperatures flame starts as blue color then turning to yellow to realize high-rate heat release. And, a bimodal phenomenon on flame intensity is found during ignition process which can be used as transition indicator between two flames. With the reduction of the ambient temperature and density, the ignition delay and ignition position increase and finally misfired. At the low ambient temperature of 723 K, increasing injection pressure is unconducive to stabilize initial flame, which means that the higher injection pressure might not helpful for cold start. Moreover, the ignition delay decreased from 1.7 to 1.1 ms when fuel temperature increased from 283 to 343 K at the ambient temperature of 808 K, which indicates fuel heating is a promising way to improve diesel engine cold start.

Ignition-Characteristic Research of the Diesel Fuel in Combustion Vessel Simulated Diesel Engine Cold Start Condition

AbstractThe initial ignition characteristic of fuel spray in a diesel engine is of great significance in the cold start problem. In this paper, the constant volume combustion vessel was applied to ...

Features of cold start of 6ЧН 13/11 engine and after start warming-up of engine and transmission unit of T-150K tractor

The article analyzes the features of diesel engine cold start in conditions of low ambient temperature. A method for estimation of fuel combustion incompleteness in period of after start warming-up has been developed. Particular method estimating the efficiency of burned fuel heat utilization is proposed. Reliability of the proposed methods has been confirmed experimentally. The article outlines the ways of improving the efficiency and reliability of machines’ performance by means of reducing the warming-up time of engine and transmission unit in after start period.

Improvement of the Forced Diesel Engines Cold Starting Characteristics by Oil Injection into the Cylinder

One way to improve the cold starting characteristics is to reduce the operating loss of air mass at the compression stroke using oil injection into the combustion chamber. The article presents the results of theoretical and experimental investigation of oil injection in diesel cylinder at the cold start modes. A mathematical model of the working process in the combustion chamber is developed. The methodological basis of the synthesis engine cycle at crankshaft rotation with compressed air on the starting conditions is the system of mass and energy balances differential equations. The model takes into account the futures of engine start with compressed air and air leakage through the gap between piston and cylinder. The mathematical model allows calculating non-stationary regimes and processes. The mathematical model was implemented as a program in Matlab/Simulink environment. The experimental studies of diesel engine cold start have been conducted in the “climate” chamber. The experiment confirmed the correctness of the mathematical model. The study made recommendations to improve the starting characteristics of the forced diesel engine with oil injection into combustion chamber. The equation, based on the analysis of experimental data, allows assessing the impact of the oil mass, injected in the cylinders, and other factors on the maximum air compression pressure and temperature in the combustion chamber. Using of oil injection system can be recommended as a means to improve the forced diesel engine with cylinder diameter 150mm starting characteristics.

Experimental Research of Forced Diesel Engine with Oil Temperature Control System in Cold Ambient Conditions

The article presents the results of experimental investigation of oil temperature control system as means of forced diesel engine (cylinder diameter – 150mm) cold start characteristics improvement. The effect of operating conditions and oil temperature control system design on the thermal state and the cold start characteristics of the diesel engine was determined experimentally (in “climate” chamber). It is proved, that the application of this system and coolant heater with the recommended design parameters and operating modes, ensures the diesel compliance with the requirements of normative and technical documentation, and allows increasing oil temperature in the main oil line (without coolant heating) by -10...23°C, in the crankcase – by 5...10°C, the average temperature of the diesel engine – by 7...8°C, before the start, providing a guaranteed engine start at ambient temperatures of -25°C within 5...8.5minutes, at -50°C – within 21...28min. The impact of the diesel engine start with coolant heater and oil temperature control system on the wear of engine parts is analyzed. It was established experimentally, that the main power and fuel consumption parameters of the engine meet the technical requirements. The condition of the engine parts friction surfaces, to which oil is supplied under pressure (crankshaft and camshaft, oil pump, etc.), is normal. This confirms the satisfactory condition of these parts lubrication in the cold start-up process.

Evaluation of Diesel Engine Cold-Start Performance: Definition of a Grading System To Assess the Impact of Fuel

The objective of this study is first to develop and validate a scientific methodology for the evaluation of diesel engine cold-start performance and then to use this methodology to assess the impac...

Opposing effects of recirculated gases during cranking on cold start of diesel engines

The effect of recirculating engine-out gases into the intake manifold on the cold start of direct-injection diesel engines is investigated. Two types of recirculation are examined. The first is low-pressure recirculation of engine-out gases into the intake manifold where their rate is controlled by a gas recirculation (GR) valve installed between the exhaust and intake manifold. The second is high-pressure recirculation by restricting the flow of the engine-out gases using a butterfly (BF) valve, installed in the exhaust system after the turbocharger to increase the back pressure and the rate of recirculated gases. Since there is no combustion during cranking, these gases contain evaporated hydrocarbons and partial oxidation products, mostly formaldehyde (HCHO). Experimental investigations on a four-cylinder direct-injection diesel engine indicated that high rates of cranking gas recirculation (CGR) increase the ignition delay and lengthen the cranking period. Since higher concentrations of hydrocarbons (HC) are expected to enhance the autoignition process, it is suspected that the recirculated HCHO would have an opposite effect. These opposing effects are investigated using the ChemKin diesel cycle simulation model. The model results demonstrated the effect of HCHO on slowing the autoignition and combustion reactions.