Browse Topic: Hydrogen engines

Items (325)

Evaluation of Trajectory Based Combustion Control for Electrical Free Piston Engine

2020-01-11494/14/2020

Previously, the authors have proposed a novel strategy called trajectory based combustion control for the free piston engine (FPE) where the shape of the piston trajectory between top and bottom dead centers is used as a control input to modulate the chemical kinetics of the fuel-air mixture inside the combustion chamber. It has been shown that in case of a hydraulic free piston engine (HFPE), using active motion control, the piston inside the combustion chamber can be forced to track any desired trajectory, despite the absence of a crankshaft, providing reliable starting and stable operation. This allows the use of optimized piston trajectory for every operating point which minimizes fuel consumption and emissions. In this work, this concept is extended to an electrical free piston engine (EFPE) as a modular power source. A dynamic model of a linear electrical free piston engine unit has been developed which consists of a single phase linear generator driven by a single cylinder engine. The linear generator unit not only provides the required electromagnetic force to ensure precise trajectory tracking for the piston in the combustion chamber, but also efficiently extracts the combustion energy to charge the battery. The concept has been experimentally validated in a hardware-in-loop setup. The combustion data corresponding to a predetermined piston trajectory is obtained from a controlled trajectory rapid compression and expansion machine (CT-RCEM) and the dynamic model is used to evaluate the electrical output corresponding to the combustion data.

Nahin, Minal, Tripathi, Abhinav, Sun, Zongxuan

Attainment of High Thermal Efficiency and Near-zero Emissions by Optimizing Injected Spray Configuration in Direct Injection Hydrogen Engines

2019-01-230612/19/2019

The authors have previously proposed a plume ignition and combustion concept (i.e., PCC combustion), in which a hydrogen fuel is directly injected to the combustion chamber in the latter half of compression stroke and forms a richer mixture plume. By combusting the plume, both cooling losses and NOx formation are reduced. In this study, thermal efficiency was substantially improved and NOx formation was reduced with PCC combustion by optimizing such characteristics as direction and diameter of the jets in combination with combustion of lean mixture. Output power declined due to the lean mixture, however, was recovered by supercharging while keeping NOx emissions at the same level. Thermal efficiency was further improved by slightly re-optimizing the jet conditions. The results showed that the hydrogen engine can attain near-zero emissions of NOx reduced to the single-digit ppm level with high thermal efficiency close to 50 percent and can thus be truly called a near-zero emission engine.

Oikawa, Masakuni, Takagi, Yasuo, Mihara, Yuji, Kawahara, Nobuyuki, Tomita, Eiji, Naitoh, Ken

Wall Heat Transfer Modeling Based on the Energy Equation For Zero Dimensional Engine Simulation

2019-01-231312/19/2019

ABSTRACT It was important for predicting wall heat flux to apply wall heat transfer model by taking into account of the behavior of turbulent kinetic energy and density change in wall boundary layer. Although energy equation base wall heat transfer model satisfied above requirements, local physical amounts such as turbulent kinetic energy in near wall region should be applied. In this study, in order to predict wall heat transfer by zero dimensional analysis, how to express wall heat transfer by using mean physical amounts in engine combustion chamber was considered by experimental and numerical approaches.

Harada, Yuji, Uchida, Kenji, Yamashita, Hiroyuki

Development of Dedicated Lubricant for Hydrogen Fuelled Spark Ignition Engine

2019-28-251111/21/2019

Hydrocarbon based fossil fuels are being used as the main energy resource, burning of which produces carbon dioxide (CO2) and other emissions harmful to environment. Moreover, CO2 is considered as the main contributor to global warming or greenhouse effect. These are the main drivers behind the ongoing research & development in the area of alternative energy sources. Among various alternatives, Hydrogen is identified as the most promising alternative fuel. Hydrogen is the cleanest fuel having some of the most attractive features such as various methods of production from renewable energy (solar, wind, biomass etc.), from fossil fuels etc. H2 as a fuel can be used in various applications such as spark ignition engine, fuel cells etc. Hydrogen has low ignition energy and ensures easy ignition of the ultra-lean mixture with air. The flame speed of hydrogen is about five times higher than methane and gasoline which allows hydrogen fuelled IC engines to have relatively reduced cyclic variations than that of with methane and gasoline. High flame speed also helps to make the combustion closer to constant volume which enhances the thermal efficiency of hydrogen fuelled IC engine. High octane of hydrogen makes it suitable as a fuel for Spark ignition (SI) engines. Since the hydrogen combustion in spark ignition engine generates water which can interfere with the lubricant performance, different lubricant is to be developed for this purpose. In this background, the present work is aimed at the development of dedicated lubricant for hydrogen fuelled SI engine. This paper presents the various parameters required for evaluating different lubricants for hydrogen fuelled genset. Existing CNG genset has been converted into hydrogen genset. State of the art electrical load bank panel system having PLC based automation with data logging provision for accurate measurement of testing parameters is used. It is suitable to apply desirable load in a balanced manner for adequate genset loading with minimised fluctuations. Three different lubricants were evaluated with respect to emissions such as CO, HC, NOx, Particulates, fuel consumption, BSFC etc. at different loads. Loads were increased in the interval of 1kW/step upto 10 kW. Lubricants were selected based on different chemistry, composition and ash content required for hydrogen fuelled SI engine. CO, HC, particulate emissions of varying diameter are observed even in carbon-less fuel vehicle due to the combustion of lube oil in engine. This effect of lube oil was studied in detail to determine the intensity of emissions produced in the engine since hydrogen has a very less particulate emission. The life of lubricant was established as it is prone to blow-by having high moisture content.

Singh, Sauhard, Bathla, Verinder Kumar, Mathai, Reji, Subramanian, K A

Oxy-Fuel HCCI Combustion in a CFR Engine with Carbon Dioxide as a Thermal Buffer

2019-24-01199/9/2019

Global warming and the increasingly stringent emission regulations call for alternative combustion techniques to reduce CO2 emissions. Oxy-fuel combustion is one of those techniques since the combustion products are easily separated by condensing the water and storing CO2. A problem associated with the burning of fuel using pure oxygen as an oxidant is that it results in high adiabatic flame temperature. This high flame temperature is decreased by introducing a thermal buffer to the system. A thermal buffer in this context is any gas that does not participate in combustion but at the same time absorbs some of the released heat and thus decreases the temperature of the medium. Many experiments have been conducted to study oxy-fuel combustion in ICE using noble gases as thermal buffers. However, those experiments focused on using hydrogen as a fuel to avoid any build-up of CO2 in the system. On the contrary, the work presented in this paper investigates using CO2 as a thermal buffer for oxy-fuel combustion in HCCI engines. Experiments were performed on a standard Waukesha variable compression ratio cooperative fuel research CFR engine, modified to run in HCCI mode. Emissions were measured using an AVL SESAM-i60 FTIR spectrometer. As expected, results showed that the CO2 mixture degraded engine efficiency. The relatively lower engine temperature also decreased NOx emissions, simultaneously increasing CO and unburned hydrocarbon (UHC) emissions.

Mohammed, Abdulrahman, MASURIER, JEAN-BAPTISTE, Elkhazraji, Ali, Johansson, Bengt, Mohammed, Abdulrahman, MASURIER, JEAN-BAPTISTE, Elkhazraji, Ali, Johansson, Bengt

Back-Pressure and Fuel Type Effects on Exhaust Gas Oxygen Sensor Readings for a Single Cylinder Spark Ignition Engine Running on Gasoline and Ethanol

2019-24-00469/9/2019

Application of more and more complex control strategies in spark ignition (SI) engines is required for ensuring high conversion efficiency and effective emissions reduction. Closed loop fuel injection is being implemented on an ever wider scale in small size SI units that generally feature single cylinder architecture. For such systems the readings from the exhaust gas oxygen sensor are essential for controlling air-fuel ratio and indirectly combustion. The present study looked at the influence of pressure oscillations on the values given by the sensor, for different equivalence ratio settings in wide open throttle conditions for an experimental SI unit. As expected, the readings were found to be influenced by pressure oscillations in the exhaust line during lean operation, while with stoichiometric and rich fueling the effects were minimal. Fuel type was also found to be an important aspect. Gasoline was compared to ethanol, and the latter underlined the effect of combustion efficiency on how the sensor readings need to be interpreted. Quasi-dimensional simulation using the GT-Power software was also used to provide further insight into the correlation between combustion phenomena and read air-fuel ratio. Following the combined experimental and numerical approach, the bases were put for defining an algorithm capable of compensating the effects of pressure oscillations without the need for an additional sensor.

Irimescu, Adrian

Modelling and Numerical Simulation of Dual Fuel Lean Flames Using Local Burning Velocity and Critical Chemical Timescale

03-12-04-00257/2/2019

Addition of hydrogen to hydrocarbons in premixed turbulent combustion is of technological interest due to their increased reactivity, flame stability and extended lean extinction limits. However, such flames are a challenge to reaction modelling, especially as the strong preferential diffusion effects modify the physical processes, which are of importance even for highly turbulent high-pressure conditions. In the present work, Reynolds-averaged Navier-Stokes (RANS) modelling is carried out to investigate pressure and hydrogen content on methane/hydrogen/air flames. For this purpose, four different subclosures, used in conjunction with an algebraic reaction model, are compared with two independent sets of experimental data: (1) Orléans data consists of pressures up to 9 bar, with addition of hydrogen content by up to 20% in hydrogen/methane mixture, for moderate turbulence intensities. 2) The Paul Scherrer Institute data includes same fuels with higher volume proportion of hydrogen (40%), at much higher turbulent intensities at 5 bar. The first model Model I is based solely on the increased reactivity of the hydrogen/methane mixture under laminar conditions. It shows that the increase of unstretched laminar burning velocity (S L0) is not sufficient to describe the increased reactivity in turbulent situations. This non-corroboration proves the importance of preferential diffusion effects in highly turbulent flames. Models II and III are formulated based on the localized increase in S L0, local burning velocity which is a strong function of local curvature and flow strain. Model II overpredicts the reactivity for higher pressures. Model III accurately predicts for nearly all studied flame conditions. Model IV is based on the leading point concept (LPC) that the leading part of the turbulent flame brush is more important than the rear part of premixed flame with the Lewis number less than unity. This model in its present formulation underpredicts the average reaction rate compared with experiments.

Muppala, Siva, Vendra, C. Madhav Rao, Aluri, Naresh K.

High Power-Density, High Efficiency, Mechanically Assisted, Turbocharged Direct-Injection Jet-Ignition Engines for Unmanned Aerial Vehicles

01-12-01-00025/2/2019

More than a decade ago, we proposed combined use of direct injection (DI) and jet ignition (JI) to produce high efficiency, high power-density, positive-ignition (PI), lean burn stratified, internal combustion engines (ICEs). Adopting this concept, the latest FIA (Fédération Internationale de l’Automobile) F1 engines, which are electrically assisted, turbocharged, directly injected, jet ignited, gasoline engines and work lean stratified in a highly boosted environment, have delivered peak power fuel conversion efficiencies well above 46%, with specific power densities more than 340 kW/liter. The concept, further evolved, is here presented for unmanned aerial vehicle (UAV) applications. Results of simulations for a new DI JI ICE with rotary valve, being super-turbocharged and having gasoline or methanol as working fuel, show the opportunity to achieve even larger power densities, up to 430 kW/liter, while delivering a near-constant torque and, consequently, a nearly linear power curve over a wide range of speeds.

Boretti, Alberto

Investigation of Oil Sources in the Combustion Chamber of Direct Injection Gasoline Engines

2018-01-18119/10/2018

To reduce hydrocarbon and particle emissions as well as irregular combustion phenomena, the identification and quantification of possible oil sources in the combustion chamber of the direct injection gasoline engine are of main interest. The aim of this research activity is to fundamentally investigate the formation of locally increased lubricating oil concentration in the combustion chamber. For this purpose, the oil sources are considered separately from each other and divided into two groups - piston/compression ring and lubricating film on the liner. The associated oil emissions and their influence on the engine combustion process are the core of the investigations.

Gohl, Marcus, Matz, Gerhard, Preuss, Ann-Christin, Pischinger, Stefan, Günther, Marco, Ebert, Thomas

Super-Turbocharging the Gasoline Engine

2018-28-00077/9/2018

In this paper, the concept of super-turbocharging is applied, in simulation, to a four-cylinder direct injection jet ignition gasoline engine. Turbocharging improves the power density of internal combustion engines, both the compression ignition and the spark ignition. However, a standalone turbocharger suffers from transient and steady state performance and efficiency degradation where the energy to turbine is either smaller or larger than what would be needed to optimize the engine operation in a specific point. Hence a concept is proposed to use a super-turbocharger, where the turbocharger shaft is connected to the crankshaft through a continuously variable transmission (CVT) and a gears pair. Energy is drawn from the crankshaft or delivered to the crankshaft to better work in every operating point. The concept was originally proposed for a diesel engine. Here it is applied to a gasoline engine. Results of simulations of engine performance are presented and discussed, prompting a conclusion that super-turbocharging would be suitable solution for gasoline engines, in terms of energy recovery, efficiency, boosting performance at low speed, and reducing the turbo lag.

Boretti, Alberto

Influence of Combustion Efficiency on the Operation of Spark Ignition Engines Fueled with Methane and Hydrogen Investigated in a Quasi-Dimensional Simulation Framework

2018-37-00125/30/2018

Within the context of widening application of numerical simulations for shortening engine development times, the present work covers the issue of quasi-dimensional simulation of spark ignition engines. Multi-fuel operation was the main goal of the study, with the analysis of methane and its blends with hydrogen; gasoline was also considered as a reference case. Data recorded on two engines with practically the same geometry, was used for calibrating the model. The first power unit was of commercial derivation for small applications, while the second one featured optical accessibility through the piston crown. The relative difference between the two engines allowed the top-land region crevice to be identified as the major contributor to overall combustion evolution, especially during its late stages. Using an in-cylinder pressure based method, compression ratio and blow-by losses were determined, and differences between fuel types were recognized in the sense of oxygen utilization rates. Then, the effects of the latter parameter were investigated with regard to model calibration. It was found that the entrainment coefficient was practically insensitive to combustion efficiency, while the characteristic length was closely linked to its modification. An important decrease was observed in the characteristic length when oxidation completeness was lower. Hydrogen addition to methane was found to improve combustion efficiency, most likely linked to its higher reactivity. These results emphasize the importance of incorporating fuel effects in quasi-dimensional simulation and given insight into how specific properties could be integrated for correct interpretation of results.

Irimescu, Adrian, Catapano, Francesco, Di Iorio, Silvana, Sementa, Paolo

Real-Time Measurement of the Piston Ring Gap Positions and Their Effect on Exhaust Engine Oil Emission

2018-01-50065/5/2018

Measurement techniques for piston ring rotation, engine oil emission and blow by have been implemented on a single-cylinder petrol engine. A novel method of analysis allows continuous and fast real-time identification of the piston ring rotation of the two compression rings, while the mass-spectrometric analysis of the exhaust gas delivers the cylinder oil emission instantly and with a high temporal resolution. Only minor modifications to the piston rings were made for the insertion of the γ-emitters, the rings rotate freely around the circumference of the piston. The idea of this setup is that through online observation at the test bench, instant feedback of the measured variables is available, making it possible to purposefully select and compare measurement points. The high time resolution of the measurement methods enables the analysis of dynamic effects. In this article, the measurement setup and evaluation method is described. Results monitoring the ring gap positions and the exhaust engine oil emission are discussed together with results of blow-by measurements for different speeds and loads. With the production piston assembly, only minor rotational movement of piston rings was apparent at stationary operation. Measurement results of the dynamic effects are discussed.

Uhlig, Benedict Paul, Kirner, Claus, Preuss, Ann-Christin, Wachtmeister, Georg

Hydrogen Fueled ICE, Successfully Overcoming Challenges through High Pressure Direct Injection Technologies: 40 Years of Japanese Hydrogen ICE Research and Development

2018-01-11454/3/2018

After some 40 years of practical research and testing in Japan, the technology for a high pressure direct injection hydrogen internal combustion engine (ICE) with near-zero emissions free from CO2 was successfully developed by the author. Four fundamental challenges to make a hydrogen car a competitive alternative to both electric and traditional fossil fuel vehicles were successfully met. (1) Hydrogen’s lack of lubrication destroys the sealing surface of the injector nozzle. (2) Injectors must be of very small size to be installed onto the engine head where the four valves are located on each cylinder. (3) Multi-injection requires high dynamic response. (4) Liquid hydrogen tank’s internal pump would fail when bringing liquid hydrogen (LH2) to the required high pressure levels due to frictional heat. Technology solutions by this author to these challenges result in a hydrogen internal combustion engine vehicle, delivering high specific power, and brake thermal efficiency of 40% or higher, using direct injection of hydrogen fuel. The hydrogen ICE solution using high pressure LH2 pumps, hydraulically-operated common-rail-type small gaseous hydrogen (GH2) injectors with no leakage of hydrogen gas, and a cryogenic LH2 fuel tank are detailed. Engine test performance and emission data running a 4-cylinder with a total stroke volume of 4.7-liter, 4-stroke and hybrid spark-ignition engine with diesel common-rail type injectors are presented. The advantages of an ICE over fuel cell and electric vehicle are explained. A five year plan for a development-to-production schedule of a vehicle with the high pressure direct injection hydrogen ICE is presented.

Yamane, Kimitaka

Influence of Engine Speed and Injection Phasing on Lean Combustion for Different Dilution Rates in an Optically Accessible Wall-Guided Spark Ignition Engine

2018-01-14214/3/2018

Alternative combustion control in the form of lean operation offers significant advantages such as high efficiency and “clean” fuel oxidation. Maximum dilution rates are limited by increasing instability that can ultimately lead to partial burning or even misfires. A compromise needs to be reached between high tumble-turbulence levels that “speed-up” combustion and the inherent stochastic nature of this fluid motion. The present study is focused on gaining improved insight into combustion characteristics through thermodynamic analysis and flame imaging, in a wall-guided direct injection spark ignition engine with optical accessibility. Engine speed values were investigated in the range of 1000 to 2000 rpm, with commercial gasoline fueling, in wide open throttle conditions; mixture strength ranged from stoichiometric, down to the equivalence ratios that allowed acceptable cycle-by-cycle variations; and all cases featured spark timing close to the point of maximum brake torque. The effect of injection phasing was also scrutinized, with three different settings of start of injection during the intake stroke. For the “leanest” cases, fuel delivery timing exerted a significant influence on combustion stability; overall performance was comparable for all three settings. These results were further detailed with the evaluation of macro- and micro-characteristics of the flame front, as well as flame intensity that was correlated to the evolution of bulk oxidation and locally rich regions caused by fuel impingement. Natural flame emission spectroscopy revealed that indeed, the nature of the two flame types was related to “normally,” premixed combustion-related propagating fronts in the first case, while for the latter, “soot production” was the driving mechanism. The experimental results were also correlated to simulations of characteristic length within the reaction zone, using a quasi-dimensional approach. Both types of data confirmed a reduction of the characteristic length at high dilution rates, in line with results obtained on burner flames at high pressure.

Irimescu, Adrian, Merola, Simona, Martinez, Santiago

Experimental and Numerical Study on Combustion Characteristics of Hydrogen-Argon Jet in a Hot Vitiated Co-flow

2018-01-11394/3/2018

This paper presents a study of the Hydrogen/Argon lifted flames in a hot vitiated co-flow. The effects of the dilution of argon in central fuel, the volume fraction of argon in the central fuel, co-flow temperature and the velocity of the central jet on the flame lift-off length were studied, and the numerical simulation with PDF model were analyzed as well. The results could provide theoretical supports for the research of the hydrogen fueled argon cycle engine which is a potential way not only to increase the indicated thermal efficiency of internal combustion engine but also realize the zero emission. The result shows that at the same boundary condition the central jet of H2+Ar has a lower lift-off length than the central jet of H2+N2. By the numerical simulation, the jet flame of H2+Ar has a higher maximum temperature and maximum OH concentration. It indicated that the dilution of argon could promote the combustion reaction.

Gong, Yinchun, Zhan, Yu, Deng, Jun, Wu, Zhijun

Instantaneous Surface Temperature Measurement in Internal Combustion Engine Using Newly Developed Coaxial Type Thin-Film Temperature Sensor

2017-32-011311/5/2017

In order to establish standard method to evaluate cooling loss in combustion chamber of internal combustion engines based on measurement of instantaneous heat flux / wall temperature with higher response and accuracy than previously reported coaxial type thin-film temperature sensor by applying thin film fabrication technology based on PVD method (Physical Vapor Deposition method) which improved to realize higher responsiveness than the conventional sensor was developed by the authors, and it was confirmed that the sensor has sufficient durability in conditions in which the hydrogen jet and flame directly contacts surface of the sensor by thin-film material change. The influence of the improvement on the measurement accuracy was verified by numerical analysis including thermoproperty evaluation. In this report, the configuration of measurement system that can measure minute voltage from the sensor with low noise and high response is reported. Furthermore, in addition to the thermoelectromotive force calibration, an instantaneous responsiveness evaluation device (laser calibration device) that can evaluate the responsiveness of instantaneous heat flux of the sensor was developed and evaluated.

Ishii, Daijiro, Saito, Hiromi, Mihara, Yuji, Takagi, Yasuo

Effect of Hydrogen Volume Ratio on the Combustion Characteristics of CNG-Diesel Dual-Fuel Engine

2017-01-227010/8/2017

CNG-diesel dual fuel combustion mode has been regarded as a practical operation strategy because it not only can remain high thermal efficiency but also make full use of an alternative fuel, natural gas. However, it is suffering from misfire and high HC emissions under cold start and low load conditions. As known, hydrogen has high flammability. Thus, a certain proportion of hydrogen can be added in the natural gas (named HCNG) to improve combustion performance. In this work, the effect of hydrogen volume ratio on combustion characteristics was investigated on an optically accessible single-cylinder CNG-diesel engine using a Phantom v7.3 color camera. HCNG was compressed into the tank under different hydrogen volume ratios varied from 0% to 30%, while the energy substitution rate of` HCNG remained at 70%. The results show that with the increase of hydrogen volume ratios, the peak of in-cylinder pressure and heat release increase significantly, and the crank angles corresponding to the maximum pressure, maximum heat release rate, and cumulative heat release rates of 5%, 20% and 50% advance. With the increase of hydrogen volume ratios, the ignition delay, from main injection timing to initial flame timing, decreases while the number of yellow ignition spots and the yellow ignition area increase. The HCNG has two ways to combustion, which are flame propagation and compression ignition. Based on the flame images, the combustion process can be divided into five phases: (1) ignition delay phase, (2) diesel premixed combustion phase, (3) diesel mixing controlled combustion phase, (4) HCNG premixed combustion phase, (5) remaining diesel mixing controlled combustion phase. Hydrogen has more notable effect on the early combustion than the late phase.

Liu, Fushui, Kang, Yue, Wu, Han, Lee, Chia-Fon, Li, Yikai

Cyclic Variations of Argon Power Cycle Engine with Fuel of Hydrogen

2017-01-240910/8/2017

The work of this paper aimed at investigating the cyclic variations of argon power cycle engine with fuel of hydrogen at lean burn operating conditions. The engine had been modified based on a 0.402 L, single-cylinder diesel engine into spark ignition engine with a port fuel injection system. The influencing factors on the cyclic variations, such as ignition timing, engine speed and compression ratio, were tested in this study. In all tests, the throttle opened at 0%, and the excess oxygen coefficient was maintained at 2.3. The results showed that as the ignition timing retards, CoVPmax and CoV(dp/dφ)max of argon power cycle engine increased, while CoVIMEP decreased firstly and increased afterward. And there is an ignition timing to make the lowest CoVIMEP, which is not consistent with MBT. Under the condition of 900 rpm and MBT, when compression ratio increases from 5.6 to 6.9, both CoVIMEP and CoV(dp/dφ)max of argon power cycle engine were found to decrease, while CoVPmax was found to increase. The engine was also operated with Air-H2 mixtures and a compression ratio of 6.9 for comparison with the condition of argon cycle. For low speed and low load, it was found that Ar-O2-H2 mixtures result in higher IMEP, Pmax and (dp/dφ)max. The significant reduction in CoVIMEP, CoVPmax and CoV(dp/dφ)max indicated that better combustion stability could be achieved when running with Ar-O2-H2 mixtures. Moreover, for operation with Ar-O2-H2 mixtures, there was a very strong correlation between Pmax and its corresponding crank angle; and the absolute value of the correlation coefficient between the two was up to 0.926.

Zhang, Erbao, Gong, Yinchun, Deng, Jun, Hu, Zongjie, Jiang, Chuanqian, Wu, Zhijun, Li, Liguang

Effect of the Pre-Chamber Orifice Geometry on Ignition and Flame Propagation with a Natural Gas Spark Plug

2017-01-233810/8/2017

Natural gas is one of the promising alternative fuels due to the low cost, worldwide availability, high knock resistance and low carbon content. Ignition quality is a key factor influencing the combustion performance in natural gas engines. In this study, the effect of pre-chamber geometry on the ignition process and flame propagation was studied under varied initial mixture temperatures and equivalence ratios. The pre-chambers with orifices in different shapes (circular and slit) were investigated. Schlieren method was adopted to acquire the flame propagation. The results show that under the same cross-section area, the slit pre-chamber can accelerate the flame propagation in the early stages. In the most of the cases, the penetration length of the flame jet and flame area development are higher in the early stages of combustion.

Akhtar, Muhammad Saqib, Sun, Shuaishuai, Ma, Xiao, Shen, Yitao, Shuai, Shi-Jin, Wang, Zhi

Reduced Convective Combustion Chamber Wall Heat Transfer Losses of Hydrogen-Fueled Engines by Vortex-Stratified Combustion - Part 1: Background and Optical Engine Observations

2017-01-928610/5/2017

A vortex-stratified combustion process for hydrogen-fueled reciprocating internal combustion engines is introduced to increase the thermal efficiency by reducing the convective heat transfer losses to the surrounding walls during combustion. The process imposes a highly ordered rotational field upon the charge in a separate, transverse, cylindrically shaped combustion chamber by means of channels that connect with the main chamber enclosed by the engine cylinder and piston. Gaseous hydrogen is injected directly during the compression stroke, while air enters into the combustion chamber tangentially and preferentially along the circumference due to the Coandă effect. The two streams entrain one another and develop into a vigorous vortex by virtue of the chamber and channel geometries. As mixing proceeds, the fuel is confined radially from the combination of finite-time diffusion being outpaced by the replenishment of pure air at the periphery, and the centripetal field formed by the rotating flow acting on the different density gas mixture. Combustion takes place with a flame propagation that initially follows the rotation of the bulk flow, and then curls radially inward toward the center. This work investigates the process in a fired, optically accessible 2-stroke hydrogen-fueled direct-injected engine tested at up to 5000 RPM. This paper, the first of two parts, explains the theoretical background; presents the schlieren observations; results of zero-dimensional cylinder pressure indication; and apparent heat release measurements comparing two combustion chamber designs - one that actualizes a homogeneous mixture without specific charge motion directionality, and another with the here-introduced vortex-stratified approach.

Oh, David, Brouillette, Martin, Plante, Jean-Sebastien

Reduced Convective Combustion Chamber Wall Heat Transfer Losses of Hydrogen-Fueled Engines by Vortex-Stratified Combustion - Part 2: Numerical Analyses

2017-01-928710/5/2017

In this second of two parts, the fundamentals of convective wall heat transfer losses are elucidated in the context of the desired objective toward its reduction in a direct-injected, hydrogen-fueled internal combustion engine. A comparative, transient 2D CFD analysis evaluated at 4500 RPM between a combustion chamber design representing current practice and the here-introduced “vortex-stratified combustion” process finds an approximately 50% reduction in the peak convective flux with the latter. The simulation results show that reduced heat flux of the vortex approach is driven by the combination of two effects: The first is finite-time diffusive mixing getting outpaced by the replenishment of pure air being introduced preferentially along the circumference of the combustion chamber due to the Coandă effect; this results in a distinct radial charge stratification during mixture preparation in the compression stroke, with a fuel-concentrated center and essentially pure air at the periphery. The second effect is the forced-segregation of different density reactants during the course of the combustion process caused by large body forces that result from the gravitational acceleration of the rapidly rotating charge, thereby constraining the combustible mixture and the flame to some distance from the walls. Evidence for this is observed by hot, low-density hydrogen being forced to remain near the center and cooler, heavier oxygen being inhibited from migrating from the outer periphery to react with the aforementioned hydrogen, and the distinct curvature of the radial gas temperature profile at a substantially greater distance from the wall than the thermal boundary layer thickness.

Oh, David, Brouillette, Martin, Plante, Jean-Sebastien

On the Entrainment Velocity and Characteristic Length Scales Used for Quasi-Dimensional Turbulent Combustion Modeling in Spark Ignition Engines

2017-24-00029/4/2017

Quasi-dimensional modeling is used on a wide scale in engine development, given its potential for saving time and resources compared to experimental investigations. Often it is preferred to more complex CFD codes that are much more computationally intensive. Accuracy is one major issue of quasi-dimensional simulations and for this reason sub-models are continuously developed for improving predictive capabilities. This study considers the use of equivalent fluid velocity and characteristic length scales for simulating the processes of fresh charge entrainment and oxidation behind the flame front. Rather than dividing combustion into three different phases (i.e. laminar kernel, turbulent flame propagation and oxidation near the walls), the concept of turbulent heat and mass transfer is imposed throughout the entire process. Within this framework, the calibration of the two coefficients for fresh charge entrainment and oxidation behind the flame front was investigated, based on in-cylinder pressure and flame imaging recorded in a spark ignition (SI) engine fueled with gasoline, ethanol, methane and hydrogen. After the procedure of identifying the pairs of coefficients that ensured good accuracy during flame propagation, a more detailed analysis was performed with respect to the three combustion phases. These findings constitute the basis for developing mass transfer sub-models that ensure improved accuracy for multi-fuel operation of SI engines.

Irimescu, Adrian, Di Iorio, Silvana, Merola, Simona, Sementa, Paolo, Vaglieco, Bianca Maria

Numerical Study of the Potential of a Variable Compression Ratio Concept Applied to a Downsized Turbocharged VVA Spark Ignition Engine

2017-24-00159/4/2017

Nowadays different technical solutions have been proposed to improve the performance of internal combustion engines, especially in terms of Brake Specific Fuel Consumption (BSFC). Its reduction of course contributes to comply with the CO2 emissions legislation for vehicle homologation. Concerning the spark ignition engines, the downsizing coupled to turbocharging demonstrated a proper effectiveness to improve the BSFC at part load. On the other hand, at high load, the above solution highly penalizes the fuel consumption mainly because of knock onset, that obliges to degrade the combustion phasing and/or enrich the air/fuel mixture. A promising technique to cope with the above drawbacks consists in the Variable Compression Ratio (VCR) concept. An optimal Compression Ratio (CR) selection, in fact, allows for further improvements of the thermodynamic efficiency at part load, while at high load, it permits to mitigate knock propensity, resulting in more optimized combustions. Of course, the VCR implementation involves increased costs and mechanical complexity, which can be only accepted if actual and relevant efficiency benefits are achieved. In this work, the potential advantages of VCR technique are numerically investigated with reference to a small turbocharged SI engine. First, a 1D model of the tested engine is implemented in GT-Power™ framework and is integrated with “in-house developed” sub-models for the description of in-cylinder phenomena. The engine model with the standard CR, selected by the manufacturer, is validated against the experimental data over the complete range of speed and load levels. In a second stage, an engine calibration strategy is proposed, aiming to automatically identify, for each operating point, the optimal spark timing, throttle valve opening, intake valve strategy, air-to-fuel ratio and turbocharger setting, complying with proper limitations on allowable levels of boost pressure, in-cylinder peak pressure, turbine inlet temperature, and knock intensity. This effort is hence considered to numerically reproduce the actual engine calibration process, resulting in a realistic prediction of the performance maps, at various CRs. The calibration strategy, allowing to select the CR realizing the minimum BSFC for each operating condition, also defines a complete map of the VCR engine. Fixed and variable CR strategies, with two or multiple CR stages, are finally compared in terms of CO2 emission over a WLTP driving cycle, with reference to a segment A vehicle, denoting interesting advantages for VCR solution.

Teodosio, Luigi, De Bellis, Vincenzo, Bozza, Fabio, Tufano, Daniela

The Future of the Internal Combustion Engine After “Diesel-Gate”

2017-28-19337/10/2017

The paper captures the recent events in relation with the Volkswagen (VW) Emissions Scandal and addresses the impact of this event on the future of power train development. The paper analyses the impact on the perspectives of the internal combustion engine, the battery based electric car and the hydrogen based technology. The operation of the United States Environmental Protection Agency (EPA), VW and the United States prosecutor, sparked by the action of the International Council on Clean Transportation (ICCT) is forcing the Original Equipment Manufacturers (OEM) towards everything but rationale immediate transition to the battery based electric mobility. This transition voids the value of any improvement of the internal combustion engine (ICE), especially in the lean burn, compression ignition (CI) technology, and of a better hybridization of powertrains, both options that have much better short term perspectives than the battery based electric car. This transition similarly narrows the future perspectives of the hydrogen internal combustion engine (H2-ICE) or the hydrogen fuel cell (H2-FC) electric mobility, solutions equally competitive vs. the battery based electric car. As the further development of the diesel emission scandals may determine the premature end of not only the diesel, but of the internal combustion engine, without any realistic replacement, the paper rings the alarm bell for the transport industry that must engage more deeply into the discussion of the future of transportation.

Boretti, Alberto

Future Challenges for Engine Manufacturers in View of Future Emissions Legislation

2017-01-19235/10/2017

Countries around the world are expected to continue to adopt more stringent emissions standards for heavy-duty markets for both oxides of nitrogen (NOx) and greenhouse gases (GHG). While there is uncertainty about the timing and extent of these regulations, it is clear that significant reductions will be required to address urban air pollution and climate change concerns. The rate and pace of technology evolution and how it will affect the energy pathways for commercial transportation and industrial use are dependent on multiple variables such as national energy and environmental policies and public-private partnerships. Although it adds complexity, the engine system has great potential to evolve as it continues to be highly integrated into the super system for which it is producing power. This paper examines the potential opportunities and challenges for engine manufacturers to continue to be the supplier of power to vehicles and equipment of the future.

Eckerle, Wayne, Sujan, Vivek, Salemme, Gary

Correlation between Simulated Volume Fraction Burned Using a Quasi-Dimensional Model and Flame Area Measured in an Optically Accessible SI Engine

2017-01-05453/28/2017

Multi-fuel operation is one of the main topics of investigative research in the field of internal combustion engines. Spark ignition (SI) power units are relatively easily adaptable to alternative liquid-as well as gaseous-fuels, with mixture preparation being the main modification required. Numerical simulations are used on an ever wider scale in engine research in order to reduce costs associated with experimental investigations. In this sense, quasi-dimensional models provide acceptable accuracy with reduced computational efforts. Within this context, the present study puts under scrutiny the assumption of spherical flame propagation and how calibration of a two-zone combustion simulation is affected when changing fuel type. A quasi-dimensional model was calibrated based on measured in-cylinder pressure, and numerical results related to the two-zone volumes were compared to recorded flame imaging. Gasoline, ethanol, methane and hydrogen were used as fuels and the aforementioned comparison was performed for each case. In order to identify the influence of specific properties, intake pressure, air-fuel ratio and spark timing were kept constant for al fuel types. Overall the spherical flame assumption was found to ensure acceptable results and the correlation between turbulence intensity and flame propagation emphasized the importance of proper description of localized scales at which chemical reactions occur behind the flame front.

Irimescu, Adrian, Di Iorio, Silvana, Merola, Simona Silvia, Sementa, Paolo, Vaglieco, Bianca Maria

Calculations and Test Measurements of In-Cylinder Combustion Velocity of Hydrogen - Air Mixtures Considering the Effect of Flame Instability

2017-01-07803/28/2017

The combustion characteristics of hydrogen-air mixtures have significance significant impact on the performance and control of hydrogen-fueled internal combustion engines and the combustion velocity is an important parameter in characterizing the combustion characteristics of the mixture. A four-cylinder hydrogen internal combustion engine was used to study hydrogen combustion; the combustion characteristics of a hydrogen mixture were experimentally studied in a constant-volume incendiary bomb, and the turbulent premixed combustion characteristics of hydrogen were calculated and analyzed. Turbulent hydrogen combustion comes under the folded laminar flame model. The turbulent combustion velocity in lean hydrogen combustion is related not only to the turbulent velocity and the laminar burning velocity, but also to the additional turbulence term caused by the instability of the flame. The formula to calculate turbulent combustion velocity considering instability is proposed and verified by experiments. This formula can be used to calculate the combustion velocity under the boundary conditions of the hydrogen internal combustion engine, which is instrumental for hydrogen internal combustion engine design and optimization.

Wu, Dongwei, Sun, Baigang, Luo, Qinghe, Wang, Xi, Ge, Yunshan

Experimental and Numerical Study of the Water Injection to Improve the Fuel Economy of a Small Size Turbocharged SI Engine

2017-01-05403/28/2017

In this work, a promising technique, consisting of a liquid Water Injection (WI) at the intake ports, is investigated to overcome over-fueling and delayed combustions typical of downsized boosted engines, operating at high loads. In a first stage, experimental tests are carried out in a spark-ignition twin-cylinder turbocharged engine at a fixed rotational speed and medium-high loads. In particular, a spark timing and a water-to-fuel ratio sweep are both specified, to analyze the WI capability in increasing the knock-limited spark advance. In a second stage, the considered engine is schematized in a 1D framework. The model, developed in the GT-Power™ environment, includes user defined procedures for the description of combustion and knock phenomena. Computed results are compared with collected data for all the considered operating conditions, in terms of average performance parameters, in-cylinder pressure cycles, burn rate profiles, and knock propensity, as well. Finally, the validated model is applied to investigate the full potential of water injection in reducing the knock tendency and improving the fuel economy in a wide load range. The numerical results highlight that WI technique involves significant Brake Specific Fuel Consumption (BSFC) advantages, especially at the medium-high loads. These benefits are limited by the maximum allowable levels for the in-cylinder pressure, while additional advantages are obtained in terms of reduced turbine inlet temperature, turbocharger speed, and boost pressure. The developed numerical procedure, based on validated combustion and knock sub-models, is able to take into account the complex interactions among different parameters, which affect the engine behavior. It is hence believed to realistically forecast the WI-related BSFC advantages and constraints, induced by thermo-mechanical stresses. Simultaneously, it underlines the need of a partial engine redesign to fully exploit WI potential.

De Bellis, Vincenzo, Bozza, Fabio, Teodosio, Luigi, Valentino, Gerardo

A General Selection Method for the Compressor of the Hydrogen Internal Combustion Engine with Turbocharger

2017-01-10253/28/2017

Hydrogen is a promising energy carrier because it is characterized by a fast combustion velocity, a wide range of sources, and clean combustion products. A hydrogen internal combustion engine (H2ICE) with a turbocharger has been used to solve the contradiction of power density and control NOx. However, the selection of a H2ICE compressor with a turbocharger is very different from traditional engines because of gas fuel. Hydrogen as a gas fuel has the same volume as its cylinder and thus increases pressure and reduces the mass flow rate of air in cylinder for a port fuel injection-H2ICE (PFI-H2ICE). In this study, a general method involving a H2ICE with a turbocharger is proposed by considering the effect of hydrogen on cylinders. Using this method, we can calculate the turbocharged pressure ratio and mass flow rate of air based on the target power and general parameters. This method also provides a series of intake temperatures of air before calculation to improve accuracy. The calculated compressor outlet temperatures are compared with the theoretical temperatures to obtain accurate data. A fit compressor is selected for a 2.3 L H2ICE and the engine is tested at different engine speed and throttle openings to validate the correctness of this method. The error is below 5% when the experimental turbocharging pressure ratio and mass flow rate of air are compared with the calculated results, and this error is acceptable. Therefore, this method can be used as a basis for the designing and selection of H2ICE compressors.

Luo, Qinghe, Sun, Baigang, Wang, Xi

Unsteady Three-Dimensional Computations of the Penetration Length and Mixing Process of Various Single High-Speed Gas Jets for Engines

2017-01-08173/28/2017

For various densities of gas jets including very light hydrogen and relatively heavy ones, the penetration length and diffusion process of a single high-speed gas fuel jet injected into air are computed by performing a large eddy simulation (LES) with fewer arbitrary constants applied for the unsteady three-dimensional compressible Navier-Stokes equation. In contrast, traditional ensemble models such as the Reynolds-averaged Navier-Stokes (RANS) equation have several arbitrary constants for fitting purposes. The cubic-interpolated pseudo-particle (CIP) method is employed for discretizing the nonlinear terms. Computations of single-component nitrogen and hydrogen jets were done under initial conditions of a fuel tank pressure of gas fuel = 10 MPa and back pressure of air = 3.5 MPa, i.e., the pressure level inside the combustion chamber after piston compression in the engine. An important point of the present study is to obtain clear evidence for Hamamoto’s experimental data that the penetration length of a light hydrogen gas jet of low density is nearly the same as that of relatively heavy gas jets such as nitrogen or carbon dioxide. It is confirmed that the computed penetration lengths of hydrogen and nitrogen gas jets injected into air are nearly the same, although hydrogen has very small inertia due to its low density. It is also stressed that computational results agree fairly well with Hamamoto’s empirical data on penetration lengths and diffusion area in the direction normal to the jet axis. Moreover, computations based on the present LES also clarify a physical mechanism underlying combustion instability in engine experiments conducted by Takagi et al., although the RANS is relatively difficult to reveal instability of unsteady flow field.

Konagaya, Remi, Naitoh, Ken, TSURU, Kohta, Takagi, Yasuo, Mihara, Yuji

The Impact of a Combustion Chamber Optimization on the Mixture Formation and Combustion in a CNG-DI Engine in Stratified Operation

2017-01-07793/28/2017

A previous study by the authors has shown an efficiency benefit of up to Δηi = 10 % for stratified operation of a high pressure natural gas direct injection (DI) spark ignition (SI) engine compared to the homogeneous stoichiometric operation with port fuel injection (PFI). While best efficiencies appeared at extremely lean operation at λ = 3.2, minimum HC emissions were found at λ = 2. The increasing HC emissions and narrow ignition time frames in the extremely lean stratified operation have given the need for a detailed analysis. To further investigate the mixture formation and flame propagation und these conditions, an optically accessible single-cylinder engine was used. The mixture formation and the flame luminosity have been investigated in two perpendicular planes inside the combustion chamber. By quantifying the equivalence ratio using the laser-induced fluorescence (LIF) technique a correlation between the presence of an ignitable mixture at the spark plug and the indicated start of combustion (SOC) was shown [1]. Through the investigation of the flame luminosity, the main reason for incomplete combustion and the according emissions was revealed. With this cause-and-effect comprehension, the combustion chamber has been modified to enforce an improved charge stratification. A geometric modification of the piston head ensures deflecting the ignitable mixture to the spark plug and prevents the injection from reaching the inner cylinder wall and crevices. Optical investigations were used to develop a design that improves mixture formation.

Friedrich, Wolfgang, Grzeszik, Roman, Lauschke, Philipp, Zelenov, Vadim, Wensing, Michael

Experimental Analysis of Four Cylinder 4-Stroke Gasoline Engine Using Hydrogen Fractions for Performance and Emission Parameters

2017-26-00631/10/2017

Hydrogen’s combustion properties made it as a gifted fuel and energy carrier to combat the current scenario of depletion of the fossil fuels and crisis of environmental pollution problems. Its superior thermo physical properties and least toxic emissions are favorable to use it in an internal combustion (IC) engine as an alternative fuel. This paper describes an experimental analysis of performance and emission parameters for a four cylinder, four stroke SI engine by supplementing hydrogen fraction with gasoline. Tests were carried out by using hydrogen fraction from 0-10% in step of 2% by volume. Study revealed an improvement in brake power, efficiency and brake specific energy consumption up to 8% hydrogen fractions in comparison with gasoline operation while volumetric efficiency decreased for all hydrogen fractions. Carbon monoxide (CO), Hydrocarbons (HC) emissions were reduced and Nitrogen oxides (NOx) was slightly increased for all hydrogen fractions than gasoline.

Chitragar, Parashuram R, Shivaprasad, K V, Kumar, G N

Influence of Injector Location on Part-Load Performance Characteristics of Natural Gas Direct-Injection in a Spark Ignition Engine

2016-01-236410/17/2016

Interest in natural gas as an alternative fuel source to petroleum fuels for light-duty vehicle applications has increased due to its domestic availability and stable price compared to gasoline. With its higher hydrogen-to-carbon ratio, natural gas has the potential to reduce engine out carbon dioxide emissions, which has shown to be a strong greenhouse gas contributor. For part-load conditions, the lower flame speeds of natural gas can lead to an increased duration in the inflammation process with traditional port-injection. Direct-injection of natural gas can increase in-cylinder turbulence and has the potential to reduce problems typically associated with port-injection of natural gas, such as lower flame speeds and poor dilution tolerance. A study was designed and executed to investigate the effects of direct-injection of natural gas at part-load conditions. Steady-state tests were performed on a single-cylinder research engine representative of current gasoline direct-injection engines. Tests were performed with direct-injection in the central and side location. The start of injection was varied under stoichiometric conditions in order to study the effects on the mixture formation process. In addition, exhaust gas recirculation was introduced at select conditions in order to investigate the dilution tolerance. Relevant combustion metrics were then analyzed for each scenario. Experimental results suggest that regardless of the injector location, varying the start of injection has a strong impact on the mixture formation process. Delaying the start of injection from 300 to 120°CA BTDC can reduce the early flame development process by nearly 15°CA. While injecting into the cylinder after the intake valves have closed has shown to produce the fastest combustion process, this does not necessarily lead to the highest efficiency, due to increases in pumping and wall heat losses. When comparing the two injection configurations, the side location shows the best performance in terms of combustion metrics and efficiencies. For both systems, part-load dilution tolerance is affected by the injection timing, due to the induced turbulence from the gaseous injection event. CFD simulation results have shown that there is a fundamental difference in how the two injection locations affect the mixture formation process. Delayed injection timing increases the turbulence level in the cylinder at the time of the spark, but reduces the available time for proper mixing. Side injection delivers a gaseous jet that interacts more effectively with the intake induced flow field, and this improves the engine performance in terms of efficiency.

Sevik, James, Pamminger, Michael, Wallner, Thomas, Scarcelli, Riccardo, Boyer, Brad, Wooldridge, Steven, Hall, Carrie, Miers, Scott

Computations and Experiments for Clarifying Compression Level and Stability of Colliding Pulsed Supermulti-Jets in a Piston-Less Single-Point Autoignition Engine

2016-01-233110/17/2016

In recent years, a new type of engine (Fugine) based on the colliding of pulsed supermulti-jets was proposed by us, which indicates the potential for attaining very high thermal efficiencies and also less combustion noise. A prototype engine with eight nozzles for injecting octagonal pulsed supermulti-jets, which was developed with a low-cost gasoline injector and a double piston system, showed high thermal efficiency comparable to that of diesel engines and also less combustion noise comparable to that of traditional spark-ignition gasoline engines. Another type of prototype piston-less engine having fourteen bioctagonal nozzles was also developed and test results confirmed the occurrence of combustion, albeit it was unstable. In this work, time histories of pressure were measured in the combustion chamber of the piston-less prototype engine under a cold flow condition without combustion in order to examine the compression level obtained with the colliding supermulti-jets. Pressure was measured with a piezoelectric sensor. Unsteady three-dimensional computations were also performed and compared with the experimental pressures. The results showed a relatively high pressure level at the cylinder center and low pressure at the walls, which provided evidence of silent autoignition. Moreover, the reason why combustion was unstable in the prototype piston-less engine was also clarified. The data obtained have led to a new technique for improving combustion stability at engine start.

Naitoh, Ken, Tsuchiya, Jumpei, Ikoma, Daiki, Nakai, Takuya, Oyanagi, Susumu, Kanase, Takuto, Okamoto, Takuma, Tanaka, Yoshiaki, Ayukawa, Ken, Konagaya, Remi

High Thermal Efficiency Obtained with a Single-Point Autoignition Gasoline Engine Prototype Having Pulsed Supermulti-Jets Colliding in an Asymmetric Double Piston Unit

2016-01-233610/17/2016

A single-point autoignition gasoline engine (Fugine) proposed by us previously has a strongly asymmetric double piston unit without poppet valves, in which pulsed multi-jets injected from eight suction nozzles collide around the combustion chamber center. Combustion experiments conducted on this engine at a low operating speed of 2000 rpm using gasoline as the test fuel under lean burn conditions showed both high thermal efficiency comparable to that of diesel engines and silent combustion comparable to that of conventional spark-ignition gasoline engines. This gasoline engine was tested with a weak level of point compression generated by negative pressure of about 0.04 MPa and also at an additional mechanical homogeneous compression ratio of about 8:1 without throttle valves. After single-point autoignition, turbulent flame propagation may occur at the later stage of heat release. Loss of work necessary for generating negative pressure is relatively small because the period for negative pressure is relatively short and also because dissipation is less than the loss due to throttle valves. It is stressed that this prototype engine employs a low-cost gasoline injector for port injection, which results in an almost homogeneous charge of fuel vapor. Because of port injection, the gasoline injector injects fuel at lower pressures than in a direct-injection engine, so it is less expensive. Thus, homogeneous vapor fuel and autoignition will produce lower levels of NOx and soot. Moreover, some interesting experimental data on spark-assisted autoignition of gasoline were obtained, which suggest more stable combustion can be achieved by optimizing the autoignition timing.

Naitoh, Ken, Ohara, Soichi, Onuma, Yuichi, Kojima, Kentaro, Hasegawa, Kenya, Shirai, Tomoya

Fundamental Combustion Experiments of a Piston-Less Single-Point Autoignition Gasoline Engine Based on Compression Due to Colliding of Pulsed Supermulti-Jets

2016-01-233710/17/2016

Computational and theoretical analyses for a new type of engine (Fugine), which was proposed by us based on the colliding of pulsed supermulti-jets, indicate a potential for very high thermal efficiencies and also less combustion noise. Three types of prototype engines were developed. One of them has a low-cost gasoline injector installed in the suction port and a double piston system in which eight octagonal supermulti-jets are injected and collide. Combustion experiments conducted on the prototype gasoline engine show high thermal efficiency comparable to that of diesel engines and less combustion noise comparable to that of traditional spark-ignition gasoline engines. This paper presents some combustion experiments of one of the other piston-less prototype engines having bi-octagonal pulsed multi-jets injected from fourteen nozzles. The purpose of this study was to make clear the level of compressive combustion obtained with the pulsed supermulti-jets and air-insulation effect as basic data for application to automobiles, aircraft, and rockets. A torch system for stabilizing the onset of combustion was important in this study because the engine has no pistons and no homogeneous compression at engine start. By developing and employing the torch system, combustion experiments were performed using the colliding of pulsed supermulti-jets. As a result, very strong combustion light was obtained in nine continual cycles, although start of combustion was not still reliable. Therefore, experiments were carried out with a higher oxygen concentration. As a result, more reliable start of combustion with a higher pressure increase and nearly complete air insulation effect were obtained.

Naitoh, Ken, Ayukawa, Ken, Ikoma, Daiki, Nakai, Takuya, Oyanagi, Susumu, Kanase, Takuto, Tsuchiya, Jumpei

Computations and Experiments of Single-Point Autoignition Gasoline Engine with Colliding Pulsed Supermulti-Jets, Single Piston and Rotary Valve

2016-01-233410/17/2016

A new engine concept (Fugine) based on colliding pulsed supermulti-jets was proposed in recent years, which is expected to provide high thermal efficiencies over 50% and less combustion noise. Theoretical analyses indicate a high potential for thermal efficiency over 60%. Three types of prototype engines have been developed. The first prototype engine based only on the colliding of pulsed supermulti-jets with fourteen nozzles has no piston compression, while the second type equipped with a low-cost gasoline injector in the suction port has a double piston system and eight jet nozzles. Combustion experiments conducted on the second prototype gasoline engine show high thermal efficiency similar to that of traditional diesel engines and lower combustion noise comparable to that of traditional spark-ignition gasoline engines. This paper presents the third prototype engine: a single-piston engine having a rotary valve, which induces strong point compression produced by twenty-four pulsed multi-jets injected from suction nozzles. Negative pressure generated by expansion due to piston motion under a closed rotary valve condition results in strong jets going to the cylinder center. This third engine has no compression due to piston motion. Unsteady three-dimensional computations for this engine including spray calculations of liquid gasoline, subsonic and supersonic turbulent flows, and combustion phenomena show the potential for very high combustion efficiency over 95%. Based on the result, combustion experiments of the engine were started. The colliding of the pulsed supermulti-jets causes combustion to occur.

Yamagishi, Kan, Onuma, Yuichi, Ohara, Soichi, Hasegawa, Kenya, Kojima, Kentaro, Shirai, Tomoya, Kihara, Takahiro, Tsuru, Kota, Naitoh, Ken

Simulation of the Effect of Initial Temperature and Fuel Injection Pressure on Hydrogen Combustion Characteristics in Argon-Oxygen Compression Ignition Engine

2016-01-222710/17/2016

Hydrogen fuel is a potential energy source for vehicles in the future. The emission of this fuel complies with the stringent policies issued by the International Energy Agency (IEA). Researchers have nominated the hydrogen compression ignition engine in an argon atmosphere as one of the ways to enhance power output and volumetric efficiency in the midst of pre-ignition and knock problems. Since this type of research is still in the initial stage, numerical studies have become the best method for researchers to obtain data on hydrogen fuel combustion in an argon-oxygen atmosphere. The purpose of this study was to validate the simulation results with the experimental data, investigate the combustion characteristics of hydrogen fuel in an argon-oxygen atmosphere, and to study the effects of the initial temperature and injection pressure on the combustion process. In this research, CONVERGE CFD software was used for the simulation process. When the ambient temperature increased, there was a decrease in the pressure but an increase in the heat release rate. On the other hand, when the injection pressure was increased, the in-cylinder pressure and the heat release rate decreased slightly.

Hafiz, Nik Muhammad, Mansor, Mohd Radzi Abu, Wan Mahmood, Wan Mohd Faizal, Shioji, Masahiro

Comparative Study of Unregulated Emissions on a Heavy Duty CNG Engine using CNG & Hydrogen Blended CNG as Fuels

2016-01-80909/27/2016

One of the most promising solutions to address the twin problems of transport related pollution and energy security is to use alternative fuels. Compressed Natural gas (CNG) has been widely used in India to address the menace of pollution from commercial vehicles in cities like Delhi. Hydrogen blended compressed natural gas (HCNG) as a fuel has potential for further reducing harmful emissions and greenhouse gases. Enriching hydrogen in CNG improves combustion characteristic of CNG and reduces carbonyl emissions. Due to growing concerns over un-regulated emissions and their effect on human health, it is imperative to estimate un-regulated emissions from such alternatives for assessing overall impact of such fuels. Presently world over, emission legislations mainly addresses pollutants like CO, HC, NOx, CH4, NH3, PM etc. Relatively higher quantity in exhaust qualifies these pollutants to be monitored and controlled. But as the consumption of alternative fuels becomes comparable to that of the liquid fuels, other unregulated emissions like Methanol (CH3OH), Ethanol (C2H5OH), Formaldehyde (HCHO), Acetaldehyde (CH3CHO), Formic Acid (HCOOH), Acetic Acid (CH3COOH), Propene (C3H8), Ethylene (C2H4), Ethyne (C2H2) Benzene (C6H6), 1,3-Butadiene (1,3-C4H6), Toluene (C7H8), Butene (C4H8) etc. become significant. This paper presents the study of unregulated emissions on a heavy duty six cylinder engine used in the transport buses with CNG and HCNG as fuels. A transient engine dynamometer set up was used along with Fourier Transform Infrared Spectroscopy Gas Analyzer (FTIR) for measuring unregulated emissions. It was observed from the test results that regulated emissions like CO, NO, HC and PM are considerably reduced with HCNG fuel. Also, unregulated emissions like Formic Acid (HCOOH), Propane (C3H8), Ethylene (C2H4), Ethyne (C2H2), Benzene (C6H6), 1,3-Butadiene (1,3-C4H6), Toluene (C7H8) and Butene (C4H8) are significantly reduced with HCNG fuel. Whereas, there is slight increase in Methanol (CH3OH), Ethanol (C2H5OH), Formaldehyde (HCHO) and Acetaldehyde (CH3CHO) with HCNG. It can be inferred from the study that HCNG has reduced significant amount of unregulated emissions and it is the most promising fuel for transport sector in future. Beside this it is also observed that with HCNG Fuel, there is increase in NH3 and NO2 which create favorable condition for effective working of exhaust after treatment device like selective catalytic reduction (SCR) for Euro VI compliant vehicles.

Singh, Sauhard, Mishra, Sumit, Mathai, Reji, Sehgal, A K, Suresh, R

E-KERS Energy Management Crucial to Improved Fuel Economy

2016-01-19479/18/2016

The operation of a conventional passenger car is characterised by increasing or maintaining the kinetic energy, when accelerating or cruising the vehicle, and reducing the kinetic energy by using the brakes. While the energy taken by the friction brakes to slow the vehicle is dissipated into heat, the introduction of Kinetic Energy Recovery Systems (KERS) has permitted the recovery of part of the braking energy. This reduces the amount of energy needed from the internal combustion engine (ICE). The contribution reviews the latest developments in electric KERS (E-KERS), with emphasis to round trip efficiency wheels to wheels and electrification of the powertrain. The contribution considers the opportunity to connect the E-KERS traction battery to other electric machines, such as an electrically assisted turbocharger (E-TC) connected to a motor/generator unit, or an electric water pump (EWP), to further optimise the vehicle operation. The electrically assisted TC permits a reduced turbo-lag and the recovery of the extra energy at the TC turbine. The EWP permits to reduce the inertia of the cooling system precisely operated for a faster warm-up and better steady state conditions. The vehicle energy management permitted by the E-KERS and the electrification is concluded to represent a fundamental step to improve the fuel economy of today’s passenger cars.

Boretti, Albert, Al-Zubaidy, Sarim

Impact of EGR Quality on the Total Inert Dilution Ratio

2016-01-07134/5/2016

A series of tests were performed on a gasoline powered engine with a Dedicated EGR® (D-EGR®) system. The results showed that changes in engine performance, including improvements in burn rates and stability and changes in emissions levels could not be adequately accounted for solely due to the presence of reformate in the EGR stream. In an effort to adequately characterize the engine's behavior, a new parameter was developed, the Total Inert Dilution Ratio (TIDR), which accounts for the changes in the EGR quality as inert gases are replaced by reactive species such as CO and H2. By calculating the TIDR and using this factor, rather than the reformation ratio or EGR rate, the results of the testing and sources of combustion improvement in the engine can be segregated into improvements due to the presence of reformate, such as initial kernel formation periods and unburned hydrocarbon emissions, and improvements due to the reduction in the total inert dilution levels, such as the emissions of the oxides of nitrogen and the fully turbulent combustion period.

Alger, Terrence, Gukelberger, Raphael, Gingrich, Jess

Plasma Assisted Ignition Effects on a DISI Engine Fueled with Gasoline and Butanol under Lean Conditions and with EGR

2016-01-07104/5/2016

Considering the generalized diversification of the energy mix, the use of alcohols as gasoline replacement is proposed as a viable option. Also, alternative control strategies for spark ignition engines (SI) such as lean operation and exhaust gas recirculation (EGR) are used on an ever wider scale for improving fuel economy and reducing the environmental impact of automotive engines. In order to increase the stability of these operating points, alternative ignition systems are currently investigated. Within this context, the present work deals about the use of plasma assisted ignition (PAI) in a direct injection (DI) SI engine under lean conditions and cooled EGR, with gasoline and n-butanol fueling. The PAI system was tested in an optically accessible single-cylinder DISI engine equipped with the head of a commercial turbocharged power unit with similar geometrical specifications (bore, stroke, compression ratio). All experiments were performed at 2000 rpm and 100 bar injection pressure. Optical accessibility through the piston crown allowed the application of two different techniques, UV-visible 2D chemiluminescence and natural emission spectroscopy. The first one gave information on the flame morphology and the second investigative method ensured insight into the specific processes related to the active chemical species. With the alternative ignition system, an increase in engine stability was obtained and the effects of butanol were related to its different chemical properties compared to gasoline. The differences among in-cylinder pressure data were correlated to the characteristics of flame shape and displacement, especially during the first stages of kernel formation and propagation.

Irimescu, Adrian, Merola, Simona Silvia, Tornatore, Cinzia, Valentino, Gerardo, Grimaldi, Alberto, Carugati, Eugenio, Silva, Stefano

Numerical and Experimental Studies on Mixture Formation with an Outward-Opening Nozzle in a SI Engine with CNG-DI

2016-01-08014/5/2016

CNG direct injection is a promising technology to promote the acceptance of natural gas engines. Among the beneficial properties of CNG, like reduced pollutants and CO2 emissions, the direct injection contributes to a higher volumetric efficiency and thus to a better driveability, one of the most limiting drawbacks of today’s CNG vehicles. But such a combustion concept increases the demands on the injection system and mixture formation. Among other things it requires a much higher flow rate at low injection pressure. This can be only provided by an outward-opening nozzle due to its large cross-section. Nevertheless its hollow cone jet with a specific propagation behavior leads to an adverse fuel-air distribution especially at higher loads under scavenging conditions. This paper covers numerical and experimental analysis of CNG direct injection to understand its mixture formation. For this purpose experimental investigations were carried out by the Robert Bosch GmbH using a two-cylinder SI engine at a high load operating point with high scavenging degree. To understand the mixture phenomena the test-bench activities were supported by numerical simulations with the 3D-CFD-tool QuickSim at the FKFS. The experiments included various injection timings and valve overlaps. Additionally, the tests were performed with two different nozzle concepts (outward- and inward-opening injector) to identify the influence of the jet shape on the fuel-air distribution. The simulations also contained these parameters and particularly considered the jet development and flow field in the combustion chamber and the intake port. The test-bench investigations revealed a close dependence of the mixture formation on the injection timing and jet characteristic during scavenging operation. The associated numerical studies resulted in a good agreement with the engine performance and led to a conclusive interpretation of the observed phenomena.

Seboldt, Dimitri, Lejsek, David, Wentsch, Marlene, Chiodi, Marco, Bargende, Michael

Experimental Analysis of Retarding the Spark Timing in a Hydrogen Enriched Gasoline and Alcohol Blend Powered Spark Ignition Engine

2016-01-12774/5/2016

Gasoline has been the major fuel in transportation, its good calorific value and high volatility have made it suitable for use in different injection methods. The drastic increase in use of carbon based fuels has led to increase in harmful emissions, thus resulting in implementation of stricter emissions norms. These harmful emissions include carbon monoxide and NOx. To meet the new norms and reduce the harmful emissions, better techniques have to be implemented to achieve better combustion of gasoline and reduce the amount of carbon monoxide in the exhaust. One such way of doing this is by enriching gasoline with hydrogen. Due to its low activation energy and high calorific value, the high energy released from hydrogen can be used to achieve complete combustion of gasoline fuel. However, there are certain drawbacks to the use of hydrogen in spark ignition engine, knocking and overheating of engine parts being the major problems. The paper deals with the problems caused when hydrogen is used in spark ignition engine, this is done by varying the spark timing around the TDC and studying the effect on power output and emissions. The spark is varied through an external controlling unit. Concentration of CO decreases and an increase of NOx is observed by the enrichment, torque and NOx emissions are increased while an increase of CO concentration is observed by retarding the spark.

Alam, Monis, Jaiswal, Ashish, Agarwal, Jatin, Yadav, Ketan, Kumar, Naveen

Optimisation of Expansion Ratio of an Advanced Compressed Air Engine Kit

2016-01-12834/5/2016

Worldwide, research is going on numerous types of engines that practice green and alternative energy such as natural gas engines, hydrogen engines, and electric engines. One of the possible alternatives is the air powered car. Air is abundantly available and can be effortlessly compressed to higher pressure at a very low cost. After the successful development of Compressed Air Engines, engineers shifted their focus in making this technology cost effective and feasible. This led to advancement in the field of pneumatics that is advanced Compressed Air Engine Kit (used for conversion of a small-two stroke SI engine to Compressed Air Engine) where its frugality and compatibility is kept at high priority. This research is in continuation with our previous project of development of an advanced Compressed Air Engine kit and optimisation of injection angle and injector nozzle area for maximum performance. Compressed Air Engine Kit demonstrated significant imperative results in performance testing which fuelled the need for optimizing various parameters such as injection angle, injection pressure and injector nozzle area. Most of the optimization was piloted on Injection parameters which provided substantial merits such as low cost and easy modifications with same amount of input energy required hence increasing efficiency. This paper explains another injection parameter optimization, which is Expansion ratio (Final volume / Initial volume). A number important and performance analysis were performed in order to pinpoint maximum torque and power generated which eventually leads to optimized Expansion ratio. Valuable data from previous studies and testing on above mentioned intake and injection parameters are considered in account, and testing and performance analysis is conducted after rectifying changes on injection angle and injector area. This study leads to optimization injection parameters simultaneously, which aids in eliminating power and energy losses building it more productive and efficient.

Kumar, Akshay, Gupta, Ashraya, Kamra, Ketan

Experimental Evaluation of a Prototype Free Piston Engine - Linear Alternator (FPLA) System

2016-01-06774/5/2016

This paper describes the experimental evaluation of a prototype free piston engine - linear alternator (FPLA) system developed at Sandia National Laboratories. The opposed piston design was developed to investigate its potential for use in hybrid electric vehicles (HEVs). The system is mechanically simple with two-stroke uniflow scavenging for gas exchange and timed port fuel injection for fuel delivery, i.e. no complex valving. Electrical power is extracted from piston motion through linear alternators which also provide a means for passive piston synchronization through electromagnetic coupling. In an HEV application, this electrical power would be used to charge the batteries. The engine-alternator system was designed, assembled and operated over a 2-year period at Sandia National Laboratories in Livermore, CA. This report primarily contains a description of the asbuilt system, modifications to the system to enable better performance, and experimental results from start-up, motoring, and hydrogen combustion tests. Passive synchronization of the pistons was successfully demonstrated through continuous motoring tests. However, operation was limited to less than a minute by the somewhat weak restoring force of the passive synchronization. Low equivalence ratio HCCI combustion with hydrogen was successfully demonstrated. Hydrogen/air mixtures with phi = 0.04 to 0.25 were compression ignited with compression ratios ranging from 20:1 up to 70:1. Net indicated thermal efficiencies between 50% and 55% were common with some results as high as 60%.

Johnson, Terry A., Leick, Michael T., Moses, Ronald W.

SI Engine with Direct Injection of Methanol Reforming Products - First Experimental Results

2015-32-071211/17/2015

In this paper we describe conversion of the gen-set gasoline-fed carburetor single-cylinder SI engine to the direct-injection version operating with the gaseous hydrogen-rich methanol reforming products, and present the first experimental results. It was found that engine feeding by methanol steam reforming products has a great potential of pollutant emissions mitigation as compared with gasoline. NOx concentrations in the exhaust gas were reduced by a factor of 7 as a result of the lean combustion and lowering in-cylinder temperatures. Particle mass emissions were mitigated to zero-impact levels. Harmful emissions of the target pollutants THC, CO and the GHG gas CO2 were reduced by a factor of 6, 25 and 1.5, respectively. The achieved efficiency improvement of the engine fed by the directly injected methanol reformate calculated for primary liquid methanol consumption was found to be in the range of 20-70% (depending on the operating mode) as compared with the carburetor-fed gasoline. Higher values of the improvement were observed at lower engine loads. The in-cylinder maximal pressure and the value of pressure-rise rate were higher under the reformate feeding by 75% and 37%, respectively at the same ignition timing.

Tartakovsky, Leonid, Amiel, Ran, Baibikov, V., Fleischman, R., Gutman, M., Poran, A., Veinblat, M.

Development of a Dedicated Hydrogen Port Injection Kit for Small Engines

2015-01-28819/29/2015

The danger posed by climate change and the striving for securities of energy supply are issues high on the political agenda these days. Governments are putting strategic plans in motion to decrease primary energy use, take carbon out of fuels and facilitate modal shifts. Man's energy requirements are touching astronomical heights. The natural resources of the Earth can no longer cope with it as their rate of consumption far outruns their rate of regeneration. The automotive sector is without a doubt a chief contributor to this mayhem as fossil fuel resources are fast depleting. The harmful emissions from vehicles using these fuels are destroying our forests and contaminating our water bodies and even the air that we breathe. The need of the hour is to look not only for new alternative energy resources but also clean energy resources. Hydrogen is expected to be one of the most important fuels in the near future to meet the stringent emission norms. The use of the hydrogen as fuel in the internal combustion engine represents an alternative use to replace the hydrocarbons fuels, which produce polluting gases such as carbon monoxide (CO), hydro carbon (HC) during combustion. Developing countries like India in particular are pushing for research and development of Hydrogen fuelled internal combustion engines (H2ICEs), powering two- and three-wheeler as well as passenger cars and buses to decrease local pollution at an affordable cost. This article offers a comprehensive overview of developing a dedicated hydrogen port injection kit to run a conventional 170 cc SI Engine on Hydrogen only. The comprehensive assessment was done to investigate the effects of hydrogen fuel compositions variation on brake thermal efficiency (BTE), brake specific fuel consumption (BSFC), Exhaust gas temperature, Unburned Hydrocarbon emission (UHC), Carbon monoxide Emission (CO), Oxides of nitrogen emission (NOx) and Smoke opacity. Also, the measures taken to prevent knocking and ensure smooth running of hydrogen engine have been discussed.

Gupta, Dhruv, Kumar, Vasu, Roy, Soumya, Kumar, Naveen

CAD/CFD/CAE Modelling of Wankel Engines for UAV

2015-01-24669/15/2015

The Wankel engine for Unmanned Aerial Vehicle (UAV) applications delivers advantages vs. piston engines of simplicity, smoothness, compactness and high power-to-weight ratio. The use of computational fluid dynamic (CFD) and computer aided engineering (CAE) tools may permit to address the major downfalls of these engines, namely the slow and incomplete combustion due to the low temperatures and the rotating combustion chambers. The paper proposes the results of CAD/CFD/CAE modelling of a Wankel engine featuring tangential jet ignition to produce faster and more complete combustion.

Boretti, Alberto

Two Stroke Direct Injection Jet Ignition Engines for Unmanned Aerial Vehicles

2015-01-24249/15/2015

Unmanned Aerial Vehicles (UAV) require simple and reliable engines of high power to weight ratio. Wankel and two stroke engines offer many advantages over four stroke engines. A two stroke engines featuring crank case scavenging, precise oiling, direct injection and jet ignition is analyzed here by using CAD, CFD and CAE tools. Results of simulations of engine performances are shown in details. The CFD analysis is used to study fuel injection, mixing and combustion. The CAE model then returns the engine performances over the full range of loads and speeds with the combustion parameters given as an input. The use of asymmetric rather than symmetric port timing and supercharging scavenging is finally suggested as the best avenue to further improve power density and fuel conversion efficiency.

Boretti, Alberto, Jiang, Shuheng

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