Dual-fuel Compression Ignition Engine Research Articles

Modeling and Control of Combustion Phasing in Dual-Fuel Compression Ignition Engines

Dual-fuel engines can achieve high efficiencies and low emissions but also can encounter high cylinder-to-cylinder variations on multicylinder engines. In order to avoid these variations, they require a more complex method for combustion phasing control such as model-based control. Since the combustion process in these engines is complex, typical models of the system are complex as well and there is a need for simpler, computationally efficient, control-oriented models of the dual-fuel combustion process. In this paper, a mean-value combustion phasing model is designed and calibrated, and two control strategies are proposed. Combustion phasing is predicted using a knock integral model (KIM), burn duration (BD) model, and a Wiebe function, and this model is used in both an adaptive closed loop controller and an open loop controller. These two control methodologies are tested and compared in simulations. Both control strategies are able to reach steady-state in five cycles after a transient and have steady-state errors in CA50 that are less than ±0.1 CA deg (CAD) with the adaptive control strategy and less than ±1.5 CAD with the model-based feedforward control method.

Effect of diesel fuel injection parameters on performances and efficiency of a turbocharged dual-fuel compression ignition engine operating on propane

The paper presents results of investigation on a turbocharged dual-fuel engine operating on propane. The obtained results are presented in form of adjustment characteristics of the injection timing of diesel fuel pilot dose for a few chosen values of the boost pressure as well as injection timing of the main dose. The principal objective of this research was to observe the effect of diesel fuel injection parameters on thermal, mechanical and overall efficiencies of the investigated engine. Diesel fuel was delivered divided in two doses. Both, ratio between the doses and their injection timing were varied. Injection timing of the first dose varied in a broad range and depended on the boost pressure. Injection timing of the second dose varied in a narrower range, mainly due to considerable changes in the combustion process. The investigation were carried out for three values of the first dose preserving, at the same time, a constant energy quantity delivered with diesel fuel. The energy share of propane at each measuring point was equal to ca. 70%. The investigation were carried out for three values of the boost pressure, i.e. 200, 400 and 600 [mbar] but also for the naturally aspirated version. The obtained results answered a number of questions regarding the strategy of selection of diesel fuel injection parameters taking into consideration engine performances as well as thermal, mechanical and overall efficiencies at a high share of the gaseous fuel.

Combustion characteristics of biomethane–diesel dual-fueled CI engine with exhaust gas recirculation

ABSTRACTIn this investigation biomethane and diesel fuel were used in a compression ignition (CI) engine with a dual fuel mode of operation. Biomethane is induced along with the intake air stream while diesel fuel is injected in a conventional way. Experiments were carried out on an exhaust gas recirculation (EGR)-equipped CI engine (single cylinder, four stroke, water cooled). The main goal of this investigation is to study the combustion characteristics of a biomethane–diesel fuel combination in dual fuel mode of a CI engine. The EGR system is also used in the dual fuel mode of operation to determine its effects. Cylinder pressure, rate of pressure rise, and heat release are the combustion parameters examined. Experimental results showed that all combustion parameters give lower values in the dual-fuel mode of operation compared to straight diesel operation. EGR again reduces the values of combustion parameters in dual-fuel mode.

Effects of charge preheating on the performance of a biogas-diesel dual fuel CI engine

This study explores the viability of preheating the intake charge as a means to enhance the performance of a compression ignition (CI) engine operated on biogas and diesel in dual fuel mode. Biogas is the primary fuel, which is mixed with air in the intake, preheated and inducted into the engine. This mixture is compressed and subsequently ignited by means of pilot diesel injection within the cylinder. The influence of charge temperature and biogas flow rate on brake thermal efficiency, volumetric efficiency, diesel fuel consumption, diesel equivalent brake specific fuel consumption, exhaust gas temperature and overall equivalence ratio are investigated under two speeds and various loads. Charge preheating, low biogas flow rates and high speed operation are observed to enhance brake thermal efficiency. Methane enrichment is effective in improving thermal efficiency at low biogas flow rates. While charge preheating and increasing the biogas flow rate reduce diesel fuel consumption, volumetric efficiency is lowered. Displacement of air by biogas increases the overall equivalence ratio and exhaust gas temperature. Low speed mode is characterised by reduced diesel fuel consumption and high volumetric efficiency. Under low speed operation, biogas can provide more than 90% of the total energy release.

Performance and Emission Characteristics Analysis of Dual Fuel Compression Ignition Engine Using Natural Gas and Diesel

The demand for higher output efficiencies, greater specific power output, increased reliability, and ever reduced emissions has been rising. One promising alternative is the use of a gaseous fuel as partial supplement to liquid fuel. In this study, the effects of diesel-natural gas substitution ratios on the engine performance parameters like brake specific fuel consumption (BSFC), and gaseous emissions of nitrogen oxides (NOX), hydrocarbons (HC), carbon monoxide (CO) and carbon dioxide (CO2) were investigated for natural gas-diesel fuel operation and then compared with the original diesel operation. The engine was modeled with GT-Power computational simulation tool. The diesel fuel was injected into the cylinder while natural gas was injected in to air-intake pipe then compressed together with air. The simulation was carried out at constant engine speed of 1800rpm for four different natural gas fractions (15%, 25%, and 50% and 75%). NOX and CO2 emissions decreased sharply by more than 45% and 50% respectively in dual-fuel mode when compared to only diesel fuel mode. However an increase was observed in CO and HC emissions in dual fuel mode. The results also indicated that higher BSFC and lower brake thermal efficiency (BTE) in dual fuel mode when compared to those of the corresponding diesel engine.

Experimental exploration of the impact of compression ratio on the characteristics of a biogas fueled dual fuel compression ignition engine

The influence of compression ratio on the characteristics of combustion, emission and performance in a dual fuelled CI engine using bio gas as the pilot fuel have been explored. The experiments were executed at four different CRs, viz. 16.5, 17, 17.5 and 18 under four distinct load settings of engine, viz. 25%, 50%, 75% and 100% respectively. The results from the investigation manifested an overall superior characteristics of combustion, emissions and performance at CR = 18 as compared to the other values. In contrast to the diesel only approach, the dual fuel approach resulted in superior improvement in NO x emissions for all the load settings.

A study of hydrogen fuel impact on compression ignition engine performance

In this paper, a dual-fuel compression ignition engine test bench is presented. In hydrogen-diesel fuel co-combustion conditions, the engine parameters are determined – performance: effective torque, effective power and mean effective pressure; fuel economy: fuel consumption and specific fuel consumption; toxicity: carbon monoxide, carbon dioxide, nitrogen oxides, hydrocarbons, and smoke emissions (opacity). The impact of hydrogen-diesel fuel mass ratio on the performance, toxicity and economy of the engine is studied by obtaining a series of hydrogen-diesel fuel ratio variation characteristics at constant engine speed and load. Improvement of the economical parameters of the engine and reduction of carbon dioxide concentration in exhaust gases is detected under operation with hydrogen gas fuel. Significant reduction of the exhaust gases opacity is observed. It is not clear what the impact of the quantity of hydrogen, injected in the engine, on the concentration of nitrogen oxides in the exhaust gases is.

Improvement in high load ethanol-diesel dual-fuel combustion by Miller cycle and charge air cooling

At high load, dual-fuel compression ignition engines often rely on exhaust gas recirculation (EGR) to avoid excessive in-cylinder pressure rise rates caused by the autoignition of the premixed fuel. This can adversely affect the net indicated efficiency depending on the resulting fuel/air equivalence ratio and pressure differential across the cylinder used to drive the requested amounts of EGR. In this work, advanced combustion control strategies have been experimentally investigated to improve ethanol-diesel dual-fuel operation at a high engine load of 1.8 MPa net indicated mean effective pressure. Miller cycle and charge air cooling have been explored to reduce the in-cylinder gas temperature and help control the ethanol autoignition process, potentially minimising the EGR requirements and increasing net indicated efficiency. Experiments were carried out on a single-cylinder heavy-duty engine equipped with a high pressure common rail diesel injection, an ethanol port fuel injection, and a variable valve actuation system on the intake camshaft. Exhaust emissions and net indicated efficiency were measured and discussed for different ethanol energy fractions. Early autoignition of the premixed ethanol fuel at the baseline intake valve lift profile resulted in high levels of pressure rise rate, which limited the ethanol energy fraction to 0.26. The application of a Miller cycle strategy via late intake valve closing events effectively delayed the ethanol autoignition process. The reduction of the intake manifold air temperature via an air-to-water charge air cooler also suppressed the early ignition of ethanol. Both approaches allowed for a substantial improvement in terms of the maximum ethanol energy fraction, which was increased to 0.79 without EGR. Moreover, high load dual-fuel operations with Miller cycle and charge air cooling attained higher net indicated efficiency and lower nitrogen oxides emissions than conventional diesel combustion. These improvements can help generate a viable business case of dual-fuel combustion as a technology for future compression ignition engines.

Effect of the boost pressure on basic operating parameters, exhaust emissions and combustion parameters in a dual-fuel compression ignition engine

The dual-fuel engine enables application of various fuels. One of such fuels is propane or its mixture with butane (LPG). Application of such fuels results in reduction of engine operation costs. The paper presents effect of application of such fuel in a turbocharged dualfuel engine on basic operating parameters, exhaust emissions and basic combustion parameters. Test results in the form of load characteristics for various boost ratios obtained for dual-fuel engine were compared to corresponding results obtained for conventional engine operating on diesel fuel only. The obtained results indicate that it is possible a dual-fuel operation with the propane energy share of 70% for maximum engine loads.

Dual Fuel Combustion of N-heptane/methanol-air-EGR Mixtures

Numerical simulations are performed to study the combustion processes of n-heptane and methanol/air/EGR under high-temperature and high-pressure conditions relevant to a dual-fuel compression-ignition engine. Detailed chemical kinetic mechanism and transport properties are considered in the simulation. The simulations are carried out by performing three-dimensional (3D) direct numerical simulation (DNS) in a cuboid constant volume enclosure and two-dimensional (2D) DNS in a constant volume domain corresponding to the 3D domain. The results reveal three combustion modes involved in dual fuel engines, the ignition of the n-heptane jet, the propagation of thin reaction fronts in the methanol/air/EGR mixture, and finally the onset of ignition of the entire mixture. In dual-fuel combustion under high initial temperature conditions (1000K or higher) the three different combustion modes occur rather quickly with two distinct peaks of heat release corresponding to the two ignition modes. At low temperatures (800K or lower) the ignition delay time of the mixture is longer and more complete mixing is achieved before the onset of a single ignition of the n-heptane/methanol mixture.

Hydroxyl radicals as an indicator of knocking combustion in the dual-fuel compression-ignition engine

The occurrence of knocking combustion is one of the basic problems of dual-fuel compression-ignition engines supplied with diesel oil and gaseous fuel. In order to detect this phenomenon and evaluate its intensity, several methods are commonly used, including the analysis of pressure of working medium in the combustion chamber of the engine or vibrations of certain engine components. This paper discusses the concept of using mass fraction of hydroxyl radicals as the indicator of the occurrence of knocking combustion. Current knowledge on the conditions of hydroxyl radical formation in the engine combustion chamber has been systematized and the results of research on this subject have been presented. Theoretical considerations are illustrated by exemplary results of simulation studies of the combustion process in a dual-fuel compression-ignition engine supplied with diesel oil and methane. The conclusions drawn may be -useful for the development of dual-fuel engine control systems.

Wpływ umieszczenia wtryskiwacza gazu na wskaźniki procesu spalania i emisję NOx dwupaliwowego silnika o zapłonie samoczynnym

The use of alternative energy sources for internal combustion (IC) engines is being raised. The most promising fuel in such application is natural gas in gaseous state, which mainly consists methane. It is mainly being used as an engine fuel for both monofuel and dual fuel configuration. Many investigations confirmed the benefits of application of dual fuel compression ignition engine fuelled with natural gas. The aim of this paper is analysis of engine operation parameters and emissions for two different locations of gas injector in the inlet duct. The operation parameters and NOx emission from this research are presented and compared for different natural gas shares in total energy delivered to the cylinder with fuel. The parameters are compared to monofuel operated engine. Keywords: dual fuel engine, compressed natural gas, injector, performance

Hydrogen-Rich Gas for Clean Combustion in a Dual-Fuel Compression Ignition Engine

Hydrogen-Rich Gas for Clean Combustion in a Dual-Fuel Compression Ignition Engine

Validation of a zero-dimensional and 2-phase combustion model for dual-fuel compression ignition engine simulation

Increasing demands for the reduction of exhaust emissions and the pursuit to re-duce the use of fossil fuels require the search for new fuelling technologies in combustion engines. One of the most promising technologies is the multi-fuel compression ignition engine concept, in which a small dose of liquid fuel injected directly into the cylinder acts as the ignition inhibitor of the gaseous fuel. Achieving the optimum combustion process in such an engine requires the application of advanced control algorithms which require mathematical modelling support. In response to the growing demand for new simulation tools, a 0-D model of a dual-fuel engine was proposed and validated. The validation was performed in a broad range of engine operating points, including various speeds and load condition, as well as different natural gas/diesel blend ratios. It was demonstrated that the average model calculation error within the entire cycle did not exceed 6.2%, and was comparable to the measurement results cycle to cycle variations. The maximum model calculation error in a single point of a cycle was 15% for one of the complex (multipoint injection) cases. In other cases, it did not exceed 11%.

Numerical modelling of soot formation and oxidation using phenomenological soot modelling approach in a dual-fueled compression ignition engine

Modelling soot formation and oxidation in diesel engines has been a long-standing challenge. In this study, soot particle characteristics in terms of particle dynamics, particle size and number density were modelled by integrating a multi-step phenomenological soot model into the KIVA-CHEMKIN CFD code for compression ignition engine combustion simulations. This semi-detailed soot model is dedicated to solving rate equations using sub-models to account for precursor formation, soot particle inception and coagulation as well as soot surface growth and oxidation. Soot growth and oxidation is inherently derived from the concentration of certain species found in the chemical reaction mechanism used, namely H, O2, C2H2 and the nucleating polycyclic aromatic hydrocarbon (PAH). Acetylene is taken as the core precursor species in nucleating PAH, soot inception as well as acetylene-assisted soot surface growth. The integrated multi-step phenomenological soot model has been validated under gasoline and diesel dual-fuel engine conditions.The predicted histograms of soot particle number along with size distribution contribute towards the understanding of dominant factors that affect soot formation. The factors affecting soot particle under varying engine loads and fuel conditions were extensively investigated. Generally, the predicted soot particle size was larger for heavy-sooting conditions as compared to low-sooting conditions. For port-injected gasoline-dominated combustion, there is less soot being discharged. This might be attributed to two reasons. First, a more homogenous mixture is realized with less diesel fuel, thus effectively reducing the formation of soot precursors. The other reason is the intensive heat release which enhances the depletion of soot precursors, thereby impeding the growth of soot particles in terms of size and mass.

Assessment of the effect of gaseous fuel delivery mode on thermal efficiency and fuel losses during the valve overlap period in a dual-fuel compression ignition engine

The paper describes the effect of dual fuelling of single cylinder AVL test CI engine with the use of two ways of gas delivery to the engine manifold. The engine was fuelled diesel oil and propane. For all the tests, gas consumption was maintained at the same level. In the first mode the gas was delivered by injector located under inlet valve. In the second method, there was used a mixer fitted to the intake manifold. The paper compares the results of thermal efficiency and emissions of propane in the exhaust for both fuelling modes. Research clearly show how important it is to synchronize the injector opening time of the intake stroke. This is especially important for supercharged engines in which there is a valve overlap.

Combustion and Exhaust Emissions Characteristics of a Dual-Fuel Compression Ignition Engine Operated with Diesel Fuel and Liquefied Petroleum Gas

AbstractThe paper reports on the utilization of liquefied petroleum gas (LPG) as a primary fuel with diesel as an ignition pilot fuel in a direct injection diesel engine. A detailed account on brake-specific fuel consumption (BSFC), exhaust emissions, and combustion characteristic parameters in a wide range of engine load conditions with different LPG substitution ratios (SR) has been presented. From the results it was observed that, at low engine loads, the peak cylinder pressure, pressure rise rate, and heat release rate decreased with the increase of LPG SR, and at high engine loads, these parameters of dual fuel with a LPG SR of 25% were highest. The ignition delay period increased with the increase of LPG SR, and the combustion duration also increased with the increase of LPG SR at low engine loads, but firstly increased and then decreased at high engine loads. At each engine load, there existed a LPG SR at which the BSFC was lowest. The BSFC of dual fuel was higher than that of diesel fuel at low en...

Numerical investigation of the impact of gas composition on the combustion process in a dual-fuel compression-ignition engine

This study discusses the model of operation of a dual-fuel compression-ignition engine, powered by gaseous fuel with an initial dose of diesel fuel as the ignition inhibitor. The study used a zero-dimensional multiphase mathematical model of a dual-fuel engine to simulate the impact of enhancing Natural Gas (NG) with other gases on the combustion process. The model simulated the thermodynamic parameters of the gas mixture in the cylinder of a dual-fuel (NG/Diesel), turbocharged, four cylinder CRDI (Common-Rail Direct Injection) engine. The tests discussed herein were conducted for steady state engine operation, for partial load and constant consumption of gaseous fuel. In the discussed tests, carbon dioxide and higher hydrocarbons (ethane and propane) were used as additions to NG.It has been shown that a change of gas composition has a significant impact on the combustion process and parameters of operation of a dual-fuel engine. The combustion of gas additives largely determines the combustion of both the main component of gaseous fuel and the initial dose of diesel fuel. The addition of higher hydrocarbons to methane can improve engine performance by as much as 6% with additions of higher carbon amounting to 20% of total fuel volume. Also, it has been shown that changes of gas composition significantly impact the ignition delay of the initial diesel dose.

Effects of Octane Number of Gasoline Fuel on Ignition and Combustion Processes in a Dual-Fuel Compression Ignition Engine

Effects of Octane Number of Gasoline Fuel on Ignition and Combustion Processes in a Dual-Fuel Compression Ignition Engine

Effect of Fuel Pilot Dose Parameters on Efficiency of Dual-Fuel Compression Ignition Engines Fuelled with Biogas

Increasing the share of renewable electrical energy in the overall energy balance is one of the major challenges of humanity. It is primarily connected with global warming and increasing environmental pollution. One of the ways to counteract this problem is to promote the importance of renewable fuels, including gaseous fuels which are relatively low in carbon.This paper presents the effects of selected parameters of a pilot dose of diesel fuel on the efficiency of a dual-fuel compression ignition engine. The dose of gaseous fuel powering the engine was a mixture of methane and carbon dioxide in varying proportions.