Browse Topic: Two stroke engines

Items (1,881)

4/7/2021

This recommended practice is applicable to reciprocating engines powering unmanned aerial vehicles (UAV) having rated power values less than 22.4 kW, and which are not to be used for human transport.

E-39 Unmanned Aircraft Propulsion Committee

7.0.101 - A New Image De-hazing Method for Safety Critical ADAS Applications

SAE-PP-002772/4/2021

Driver safety and Advanced Driver Assistance Systems (ADAS) is gaining lot of importance these days. In some countries, there are strict regulations in place which mandate the use of certain ADAS features in automobiles. However, as the need for these safety critical systems increases, the challenges associated also increase. These challenges can arise due to technology, human factors or due to nature. In countries like India, where one can expect different weather conditions with changing geography, the associated challenges are mainly due to the natural factors like haze, fog, rain and smoke. This poses a challenging problem in terms of visibility for the drivers as well as in vision based ADAS; thereby, leading to many fatal road accidents. In this paper, a novel pre-processing technique, which addresses the interesting problem of enhancing the perceptual visibility of an image that is degraded by atmospheric haze, is proposed. The solution to this problem is presented by combining model (Beer Lambert model) based and non-model based technique of haze removal. The combined hybrid model picks the best haze free image from the series of non-hazy outputs, that are derived based on multiple scattering coefficients of the input hazy image. The idea here is to restore the true color of an image that is affected by the atmospheric haze. In comparison with the state of the art methods that are available in literature, the proposed method is shown to be capable of recovering better haze-free images both in terms of visual perception and quantitative evaluation. The proposed method promises better perceptual understandings and visibility restoration for vision based ADAS under hazy driving conditions.

Lname, Fname

6.0.116 - Development of 6 Years Old Child Virtual Model by Automatic Scaling

SAE-PP-002712/4/2021

Traffic accidents cause one of the highest numbers of severe injuries in the whole population. The numbers of deaths or seriously injured citizens prove that traffic accidents and their consequences are still a serious problem to be solved. A lot of effort is devoted to both passive and active safety systems development. The transportation standards usually define safety requirements by regulations (e.g. ECE-R94, 96/79/EC and ECE-R95, 96/27/EC in Europe) with specific dummies for children to be used. The dummies include hardware sensors for monitoring accelerations, loads and other signals and each dummy is developed for a specific scenario, but there are limitations of these dummies, such as only a specific age or calibration just for a specific test. Taking into account that the consequence of a traffic accident is highly influenced by the stature of the body, virtual human body models, including those for children, start to play a significant role because they can be scaled or even personalized towards a particular population or even a particular person. The paper contributes to the field of vehicle safety technology concerning child restraint systems development, assessment and optimization with a virtual numerical approach. The goal of the paper is to exploit the previously developed scaling algorithm to create a virtual model of a six-year-old (6YO) child and to compare its response to the virtual dummy used for child safety in order to propose an automatic scaling process for a population-based vehicle safety assessment. The automatic scaling algorithm developing virtual human body models for a given age and gender is used to create the virtual 6YO child model. The algorithm scales body dimensions and particular segments' mass and the flexibility of the body is driven by flexindex and stiffness scaling. The performance of the automatically developed virtual 6YO child model was tested in frontal and lateral directions. The frontal response was tested with a standard sled test simulation using the standardized AAMA pulse in the frontal direction. The lateral response was tested with a side barrier impact test. The results of both tests were compared to the validated virtual Q6 Child Dummy FE model. The paper shows good performance of the automatic scaling process for developing 6YO virtual model for safety assessment. The automatically developed 6YO child model corresponds well from both the anthropological point of view and performance point of view to the existing validated dummy model.

Mutagaana, Festo

6.0.101 - Piston Sealing System Structure Design for Automobile's Lightweight Auto-Transmission

SAE-PP-002572/4/2021

Current automobile's auto-transmission has problems of defects and cost reduction because of welding process and very complicated assembly process due to individualized transmission piston and sealing components. Also, size and heavy weight of transmission piston components are the source of low mileage because they are made of aluminum, steel material. In this study, therefore, we perform structure design for piston sealing system which integrates piston and sealing material for automobile's lightweight auto-transmission. Also performed stress analysis through finite element analysis to secure required suitable strength when internal pressure is applied after assemble.

Mutagaana, Festo

Near-TDC flow field analysis in a high-tumble production SI engine using endoscopic high-speed Particle Image Velocimetry (eHS-PIV)

SAE-PP-002512/3/2021

The latest generation spark-ignition (SI) engines implement high tumble flow design to achieve unprecedented high brake thermal efficiency of over 40%, which will continue to play an important role in both conventional and electrified future vehicles. To maximise the potential of high-tumble SI engines, there is a clear need for in-cylinder flow and flame analysis conducted timely in a realistic environment. For the first time, this study meets this need by performing innovative endoscopic imaging of flow fields and flame inside the cylinder of a selected production engine using a particle image velocimetry (PIV) laser and high-speed camera system operated at 35 kHz. Through this timeresolved, two-dimensional measurement of the realistic in-cylinder phenomenon, many new findings have been achieved. Regarding the tumble vortex, its centre is seen more shifted to the exhaust valve side, which is related to an asymmetric, “surging” flow structure formed during the upward motion of the piston in the compression stroke. When the piston approaches towards the top dead centre, the tumble centre is not clearly defined anymore, but a new lateral exhaust-to-intake flow forms as the surging flow bounces back off the exhaust valve side of the pent-roof. This wallguided “bounce-back” flow does not form when the intake valve closure is retarded for the realisation of Atkinson Cycle and thus the surging flow is reduced and peaks at later timing. The new in-cylinder flow structures observed from the high-tumble engine directly impact the flame development. From the high-speed natural combustion luminosity imaging performed using the same camera endoscope, the flame centroid is found to shift towards the intake valve side, which is consistent with the bounce-back flow direction at the advanced intake valve closure timing.

Anthony, Lindsay

2.0.101 - Experimental Study of cooling of Continuously Variable Transmission (CVT) in Scooter

SAE-PP-002102/1/2021

The continuously variable transmission (CVT), which was conceptualized more than 500 years ago, is just now beginning to replace traditional transmissions in some automobiles. It is mostly used in scooter transmission. Engine power is transmitted to wheel through belt drive between two pulleys. The diameter of belt contact with pulley can change continuously and hence provide infinite gear ratios between driver and driven shafts. This technology leads to a smoother ride of vehicle. Heat is generated inside CVT due to friction between drive belt and clutch pulley. Amount of heat generated is even more due to clutch slippage during acceleration and deceleration. This will affect the service life of CVT components such as front movable drive (FMD), clutch pulley, clutch outer, and belt. In scooters generally, air cooling is preferred over liquid cooling. Cooling is achieved by incorporating centrifugal fan inside CVT housing. For better durability/service life, the degree of heat generated at CVT components should be minimal. The objective of this work is to identify the parameters causing change in temperature of CVT components and to evaluate its surface temperature in accordance with changed parameters. With reference to this, experiments were conducted with requisite design modification inside CVT housing, which enhances cooling effect. Amongst, variables determining air flow rate, are studied and their effect on temperature inside CVT housing is observed experimentally. Keeping the previous variables unaltered, further design modifications related to air flow pattern are done and cumulative effect of all variables is observed. Experiments were performed on an 110cc scooter engine by following customer driving pattern on chassis dynamometer. Results showed that design modifications intended for better cooling effect, has brought down temperature at CVT components. So, desired cooling effect is observed inside CVT housing imparting better service life of CVT components.

Mutagaana, Festo

Review of Additive Manufacturing for Internal Combustion Engine Components

03-13-05-0039

9/9/2020

With highway vehicles using over 20% of the total energy consumption in the United States, making strides in improving their fuel economy will positively influence the nation’s environmental impact. One methodology to accomplish this outcome is by reducing vehicle weight. In this regard, since the internal combustion (IC) engine is a major contributor to the mass of an automobile, it is an ideal area to target. Prior efforts in this area include using alternative materials (e.g., aluminum or magnesium) to decrease weight. Here, additive manufacturing (AM) is an appealing option due to its freedom from typical manufacturing constraints and the ability to produce highly optimized designs using nonconventional powertrain materials (e.g., titanium). The use of AM has the potential to increase reliability, improve performance, decrease production cost, and possibly minimize the number of parts. Since metal-based AM is a relatively new area of manufacturing for IC engines, its use has been largely limited to research, motorsport, and luxury vehicle activities. Given its potential, this effort provides a review and summary of AM work completed in this field including design optimization, prototyping, tooling and indirect manufacturing, part production, and remanufacturing and repair for IC engine components.

Gray, Jamee, Depcik, Christopher

Downsized-Boosted Gasoline Engine with Exhaust Compound and Dilute Advanced Combustion

2020-01-07954/14/2020

This article presents experimental results obtained with a disruptive engine platform, designed to maximize the engine efficiency through a synergetic implementation of downsizing, high compression-ratio, and importantly exhaust-heat energy recovery in conjunction with advanced lean/dilute low-temperature type combustion. The engine architecture is a supercharged high-power output, 1.1-liter engine with two-firing cylinders and a high compression ratio of 13.5: 1. The integrated exhaust heat recovery system is an additional, larger displacement, non-fueled cylinder into which the exhaust gas from the two firing cylinders is alternately transferred to be further expanded. The main goal of this work is to implement in this engine, advanced lean/dilute low-temperature combustion for low-NOx and high efficiency operation, and to address the transition between the different operating modes. Those include well-mixed charge compression-ignition at low-load, and a mixed-mode combustion at higher loads, before transitioning to boosted homogenous and stochiometric spark-ignited combustion. Here, the mixed-mode combustion strategy is composed of a deflagration of a stratified mixture created by a late direct injection, then triggering a controlled autoignition of the surrounding gas, improving the robustness of lean/dilute combustion. The paper describes the key features of the engine and details regarding the combustion and multi-mode valve strategies. The experiments were performed under steady-state operation at 2000 rpm, from 1 to 11 bar IMEPn and naturally aspirated conditions. The engine demonstrated great efficiency gains compared to a conventional naturally-aspirated and downsized-boosted spark-ignited engines. The piston-compounding exhaust-heat recovery system contributes to up to 10% of the total efficiency improvement, while lean/dilute advanced combustion increases the fuel economy by up to 38% compared to a naturally aspirated engine, and up to 22%, compared to a downsized-boosted engine. NOx emissions target was met using high-levels of internal and external dilution in mixed-mode combustion operation, as well as by optimizing the injection and ignition strategy. Finally, the analysis shows that a seamless transition between the different valving strategies is achievable in support of robust transient operation.

Dernotte, Jeremie, Najt, Paul M., Durrett, Russell P.

The Use of Piezoelectric Washers for Feedback Combustion Control

2020-01-11464/14/2020

The use of piezoelectric cylinder pressure sensors is very popular during engine testing, but cylinder pressure information is becoming mandatory also in several on-board applications, where Low Temperature Combustion (LTC) approaches require a feedback control of combustion, due to poor combustion stability and the risk of knock or misfire. Several manufacturers showed the capability to develop solutions for cylinder pressure sensing in on-board automotive and aeronautical applications, and some of them have been patented. The most straight-forward approach seems the application of a piezo-electric washer as a replacement of the original part equipping the spark plug; the injector could also be used to transfer the cylinder pressure information to the piezoelectric quartz, in diesel or Gasoline Direct Injections (GDI) engines. The paper describes the features of signals acquired using piezoelectric washers, discussing possible applications, highlighting the factors which impact the sensors accuracy, and proposing algorithms to compensate potential errors in the evaluation of combustion metrics. The sensors have been first tested on a press, then in two different gasoline engines: a naturally aspirated V12 and a turbocharged 2 cylinders with Variable Valve Lift system (VVL). Signals have been compared to those obtained with lab-grade cylinder pressure sensors, with particular attention to peak pressure, combustion phase and knock intensity. The main issue affecting the accuracy of cylinder pressure measurement using the piezoelectric spark plug washer is the effect of temperature variations both on the force transmitted by the thread to the washer and piezoelectricity properties.

Corti, Enrico, Abbondanza, Marco, Ponti, Fabrizio, Raggini, Lorenzo

Optical Characterization of the Combustion Process inside a Large-Bore Dual-Fuel Two-Stroke Marine Engine by Using Multiple High-Speed Cameras

2020-01-07884/14/2020

Dual-fuel engines for marine propulsion are gaining in importance due to operational and environmental benefits. Here the combustion in a dual-fuel marine engine operating on diesel and natural gas, is studied using a multiple high-speed camera arrangement. By recording the natural flame emission from three different directions the flame position inside the engine cylinder can be spatially mapped and tracked in time. Through space carving a rough estimate of the three-dimensional (3D) flame contour can be obtained. From this contour, properties like flame length and height, as well as ignition locations can be extracted. The multi-camera imaging is applied to a dual-fuel marine two-stroke engine, with a bore diameter of 0.5 m and a stroke of 2.2 m. Both liquid and gaseous fuels are directly injected at high pressure, using separate injection systems. Optical access is obtained using borescope inserts, resulting in a minimum disturbance to the cylinder geometry. In this type of engine, with fuel injection from positions at the rim of the cylinder, the flame morphology becomes asymmetric. The optical spatial mapping and tracking method is demonstrated to be well suited for the study of such an asymmetric combustion system. Spatial mapping and tracking of flame position is applied to both engine operating modes; normal diesel operation and dual-fuel operation with diesel pilot ignition of the gas. Similarities and differences between diesel and gas flame shape and development can thus be visualised directly. The effects of changing charge density, gas injection pressure and injection nozzle geometry on the flame geometry and development are also studied.

Hult, Johan, Matamis, Alexios, Baudoin, Eric, Mayer, Stefan, Richter, Mattias

Pre-design Investigation of Resonant Frequency Effects on Gas Exchange Efficiencies of a One-kW Natural-Gas Linear Engine Alternator

2020-01-04884/14/2020

Performance of a natural gas two-stroke engine incorporated in a 1-kW free-piston oscillating Linear Engine Alternator (LEA) - a household electricity generator - was investigated under different resonant frequencies for pre-design phase purposes. To increase the robustness, power density, and thermal efficiencies, the crank mechanism in free-piston LEA is omitted and all moving parts of the generator operate at a fixed resonant frequency. Flexure springs are the main source of the LEA’s stiffness and the mass-spring dynamics dominates the engine’s speed. The trade-off between the engine’s performance, mass-spring system limits, and power and efficiency targets versus the LEA speed is very crucial and demands a careful investigation specifically at the concept design stages to find the optimum design parameters and operating conditions. CFD modeling was performed to analyze the effects of resonant frequency on the engine’s gas exchange behavior. To take combustion effects into account, a semi-empirical method was employed to obtain the initial and boundary conditions during the gas exchange from experiments and imported into CFD simulation. The numerical results of the gas exchange were validated at the engine speed of 5400 RPM with the experimental results. The semi-empirical method eliminated the complicated combustion simulation and significantly reduced the computational time and well-matched with experiments within 1 % error. Results showed enhanced trapping efficiency of 7.1% per 1000 RPM, and reduced scavenging efficiencies of 5.5% per 1000 RPM as speed engine’s speed increased. Comparison of the trapping and scavenging efficiencies showed an improved fuel/power efficiency equal to about 1.45 % per each 15 Hz increase in the LEA resonant frequency.

Zamani Meymian, Nima, Darzi, Mahdi, Johnson, Derek, Famouri, Parviz

Initial Investigations into the Benefits and Challenges of Eliminating Port Overlap in Wankel Rotary Engines

2020-01-02804/14/2020

The Wankel rotary engine historically found limited success in automotive applications due in part to poor combustion efficiency and challenges around emissions. This is despite its significant advantages in terms of power density, compactness, vibrationless operation, and reduced parts count in relation to the 4-stroke reciprocating engine, which is now-dominant in the automotive market. A large part of the reason for the poor fuel economy and high hydrocarbon emissions of the Wankel engine is that there is a very significant amount of overlap when the ports are opened and/or closed by the rotor apices (so-called peripheral ports). This paper investigates the benefits of zero overlap from a production engine with this characteristic and the effect of configuring a peripherally-ported Wankel engine in such a manner. As discussed in the paper, arranging this condition for peripherally-ported engines unfortunately reduces the trapped compression and/or expansion ratios significantly, such that when naturally-aspirated operation is simulated, a large reduction in performance ensues. In order to demonstrate the potential of zero port overlap in Wankel engines with respect to emissions, a 2007 model year Mazda RX-8 was rebuilt, run-in, degreened, and tested on a chassis dynamometer. As standard, the engine in this vehicle is configured with no port overlap through the adoption of side intake and exhaust ports. This testing was performed in order to see subjectively how successful such an approach could be in controlling emissions. The vehicle easily met Euro 5 limits for all criteria emissions and was even better in terms of hydrocarbon emissions versus Euro 6 on the WLTP cycle, giving the lie to the belief that a Wankel engine can no longer meet current automotive emissions targets. The analytical work reported here studies the result of eliminating overlap on the performance of a peripherally-ported single-rotor Wankel engine using a 1-D model. This was implemented and correlated to the in-production Advanced Innovative Engineering (UK) Ltd 225CS engine used in the UK government-funded ADAPT project. The initial port study focused on advancing and retarding the exhaust and intake port respectively to achieve zero port overlap and then sweeping their zero-overlap positions together around the trochoid housing. The best location for the ports was then identified; this was essentially an “Otto” timing set, with broadly equal compression and expansion ratios. Notwithstanding this, potential performance was found to be severely curtailed, as was to be expected given the marked reduction in trapped compression and/or expansion ratios necessary due to peripheral porting. Countermeasures to this reduction are discussed. Those that will be studied later in the project will be reported in a later publication.

Turner, James, Turner, Matthew, Vorraro, Giovanni, Thomas, Toby

Measurement of Fuel Distribution in a Small PFI Spark-Ignition Engine Using Tracer PLIF

2020-01-0786

4/14/2020

The distribution of fuel-air mixture inside the engine cylinder strongly influences the combustion process. Planar laser-induced fluorescence (PLIF) is commonly used for fuel distribution measurement, however, it is mostly reported on moderate- to large-sized engines. In the present work, PLIF is applied to measure the fuel distribution inside the cylinder of a small, four-stroke, port-fuel-injection (PFI), spark-ignition engine with displacement volume of 110 cm3. Iso-octane was used as the base fuel, and 3-pentanone (15% by volume) was added as a fluorescent tracer in the base fuel. The effect of equivalence ratio, considering ϕ = 1.2, 1.0, and 0.8, on in-cylinder fuel distribution was studied with low throttle opening of 25% at 1200 rpm. PLIF images were recorded at different crank angle degrees during both intake and compression strokes over a swirl measurement plane located at the TDC position. It was found that the fuel stratification was present from intake to even late compression. Also, no significant change in fuel distribution patterns was noted at different crank angle degrees for a given operating condition. Instantaneous PLIF images of the fuel distribution at 330 CAD during compression also showed a considerable variation from one cycle to the next. As expected, the fluorescence signal intensity was increased with the increase in equivalence ratio. Results also showed that the fuel distribution was much more noticeable near the diametrically opposite location to the spark plug on the tested engine, and continued to exist till late compression (i.e. 330 CAD).

Garg, Shubham, Mittal, Mayank, Sahu, Srikrishna, Lakshminarasimhan, V

Waste Heat Recovery System Thermal Management

J3173_202002 (Current)2/24/2020

Waste heat recovery (WHR) systems are used in vehicles and machines powered by internal combustion (IC) engines to capture unused/waste heat and utilize it thereby reducing fuel consumption and emissions by improving efficiency. This information report is a survey of the waste heat recovery methods that include the use of heat exchangers.

Cooling Systems Standards Committee

Intermittent Injection for a Two-Stroke Direct Injection Engine

2019-32-05241/24/2020

Cycle-to-cycle variation is one of the main factors for high fuel consumption and emissions of a two-stroke engine during the low-load and low-speed running. The increase of residual gas ratio due to the lower delivered amount of fresh scavenging air leads to a lower flame front speed and, therefore, to a slow combustion or even misfiring. The consequence is a very high level of unburnt hydrocarbons, since a large amount of fuel does not take part in the combustion process. The use of a direct injection system allows a more flexible management of the injection of fuel over subsequent engine cycles. Under a low-load condition, the low request in terms of brake mean effective pressure (BMEP) can be achieved by performing a load control based on an intermittent injection, thus reducing the need for intake throttling and avoiding the loss of fresh fuel resulting from cycles without combustion. In more detail, the supply of fuel to the combustion chamber can be skipped for one or more cycles, thus performing a number of consecutive scavenging cycles with only fresh air. As a result, the fresh air is less diluted by the residual gas and the combustion efficiency increases. This paper presents the results of a preliminary experimental activity on the use of an intermittent injection strategy with a Low Pressure Direct Injection (LPDI) system. In more detail, the effect of skipping one cycle - thus operating the two-stroke engine in a four-stroke-like mode - was investigated at part load conditions by considering four BMEP levels (i.e. from 1.0 bar to 2.5 bar). The benefits of such strategy were evaluated at the test bench and compared with the performance of the standard operation mode. In particular, the cycle-to-cycle variation was drastically reduced and the combustion misfire was avoided with the intermittent injection, thus leading to a strong reduction of both hydrocarbon emissions and brake specific fuel consumption.

Balduzzi, Francesco, Romani, Luca, Bosi, Lorenzo, Ferrara, Giovanni

Sensor Fusion Concept for Improved Rotational Speed Measurement in Small Engines

2019-32-05191/24/2020

Future developments for small engines, e.g. engines for handheld working tools, like chain saws require the integration of ECU-systems for engine control. For small engines often only a rotational speed senor is available. The application of additional engine sensors is in many cases unwanted, e.g. due to cost aspects and additional wiring. The lack of sensor data requires tailored control strategies and signal processing techniques to infer information about the engine from the sensor data. E.g. for rotational speed sensors the Δω method has been proposed, where the load is estimated from the temporal variation of the rotational speed. This approach requires a rotational speed sensor with sufficient angular resolution. In this paper we present a simulation study for a sensor fusion concept to improve the temporal resolution of engine speed measurements for low cost engines by means of an additional vibration sensor. The rotational sensor of the engine is assumed to have insufficient resolution to determine variations of the rotational speed over an engine revolution. However, variations of the rotational speed of the engine also cause vibrations of the engine chassis. A vibration sensor can be used to pick up the vibration signal with high temporal resolution. As the transfer function between the variation of the rotational speed and the sensor readings is only approximately known, a sensor fusion concept for the rotational speed sensor and the acceleration sensor has to be applied, which combines the different measurements, while simultaneously estimating the unknown transfer function. We will use an extended Kalman filter for the data fusion and an autoregressive-model for the unknown transfer function.

Neumayer, Markus, Bretterklieber, Thomas, Suppan, Thomas

Replacement of a 50cc Two-stroke Engine with an Electric Powertrain

2019-32-06231/24/2020

As global regulations look to create a dramatic reduction in CO2 emission and other forms of pollution, companies with products that rely on engine technology must be ready to take on the electrification challenge. Applications that remain using two-stroke engine technology continue to exist due to their very high power density requirements. However, their history of higher pollution compared to four-stroke engines makes them a target to be regulated out of existence. Such high power two-stroke applications include high performance off-road motorcycles. In this type of product, electrification can solve not only pollution challenges but market challenges, such as ridership and public perception. By addressing the core problems presented by the two-stroke engine and turning challenges into opportunity, a strong attraction is created to convert a two-stroke engine motorcycle to an electric vehicle. With Automotive electric vehicle technology paving the way, the basis for cost effective electric motorcycle powertrain is explored for a 50cc off-road motorcycle application. The 50cc engine and motorcycle represent a special product where size, performance, and cost have a high sensitivity. The 50cc product also represents an area of great opportunity for the product as it is connected to the youth riding segment that establishes the future of motorcycle riding. With both strong opportunity and strong challenges, the electrification solution for a 50cc application provides broad justification for mass market adoption across the motorcycle industry. Challenges will be presented towards a OEM level product where design change is to be minimized without compromising performance. Various challenges include system design, packaging, supply chain, product lifecycle, competition readiness, safety, and cost. Opportunities will be discussed in the context of how the electrified powertrain can create a better product for the rider and solve challenges to enable the next generation of motorcycling. These opportunities include manufacturing advantages, environmental harmony, and new features.

Beeker, Jesse

Study on Robust Fuel Performance with Differing Fuel Types in a 2-Stroke CAI Combustion Engine

2019-32-0573

1/24/2020

This study sought to achieve robust combustion with the differing fuel types and levels of fuel quality that are present in various areas of the world. The tests used the 2-stroke controlled auto ignition (CAI) engine from our earlier report [1], which was proven to have potential as an efficient, clean engine for diesel fuel. This study verified whether efficient, clean CAI combustion of gasoline fuel could be achieved with the same basic structure and engine system. Diesel and gasoline have very different volatility, viscosity and ignition characteristics, all of which significantly affect combustion in an engine. It is particularly necessary in CAI combustion to adjust the ignition timing according to the fuel used, as the difference in auto-ignition temperature from gasoline and diesel affects the CAI ignition timing. This issue was addressed by conducting experiments with a test engine to determine how the ignition timing is affected by the equivalent ratio, compression ratio and in-cylinder flow, and the ideal solution was verified. The results indicated that the ignition timing for CAI combustion can be effectively adjusted by changing the shape of the scavenging port to alter the in-cylinder flow. Computational fluid dynamics (CFD) analysis confirmed that the change in the scavenging port shape increased the in-cylinder flow velocity and the turbulence kinetic energy at the compression end. This indicates that the in-cylinder flow during the compression stroke affects the ignition timing for CAI combustion. The results produced by this study also indicated that equivalent thermal efficiency and emission levels can be achieved for both diesel and gasoline by setting an appropriate equivalent ratio, compression ratio, in-cylinder flow and exhaust valve lift profile for each type of fuel. In conclusion, this study confirmed that 2-stroke CAI is a combustion process with extremely robust fuel performance and the potential to be suitable for various fuel types with significantly different properties.

Kurata, Mashu, Okubo, Masami, Yamada, Yoshikazu, Kitano, Sho

Identifying the limitations of the Hot Tube test as a predictor of lubricant performance in small engine applications

2019-32-05101/24/2020

The Hot Tube Test is a bench test commonly used by OEMs, Oil Marketers and Lubricant Additive manufacturers within the Small Engines industry. The test uses a glass tube heated in an aluminum block to gauge the degree of lacquer formation when a lubricant is subjected to high temperatures. This test was first published by engineers at Komatsu Ltd. (hence KHT) in 1984 to predict lubricant effects on diesel engine scuffing in response to a field issue where bulldozers were suffering from piston scuffing failures [1]. Nearly 35 years after its development the KHT is still widely used to screen lubricant performance in motorcycle, power tool and recreational marine applications as a predictor of high-temperature piston cleanliness - a far cry from the original intended performance predictor of the test. In this paper we set out to highlight the shortcomings of the KHT as well as to identify areas where it may still be a useful screening tool as it pertains to motorcycle applications.

Hanthorn, Jason, Schmiesing, Jessica

Calcium in Oil Effects on Pre-ignition of Two-stroke Engine

2019-32-05791/24/2020

Investigations of the influence of calcium on pre-ignition in a two-stroke engine have shown that the lower the calcium concentration, the lower the frequency of pre-ignition. Pre-ignition problems can occur in small, air-cooled, two-stroke engines such as a chainsaw. In contrast, in a supercharged automobile engine, it has been reported that calcium, which is a detergent component in engine oil, causes low-speed pre-ignition. The oil for two-stroke engines also contains calcium and is mixed with the fuel and lubricated before being supplied to the combustion chamber. This makes, two-stroke engines more likely to be affected by oil components. Based on this, we investigated the influence of calcium on pre-ignition of a two-stroke engine. First, we investigated driving conditions in which pre-ignition is likely to occur, such as warming up the engine. Under this condition, oil with calcium concentrations ranging from 0 ppm to 1,500 ppm were tested at a mixing ratio of 2%. The results show that the lower the calcium concentration, the lower the incidence rate of pre-ignition. Which could also occur at 0 ppm. The incidence rate was 4.6% at 1,500 ppm and 2.3% at 0 ppm.

Eto, Kuniyoshi, Kihara, Masaki

Effect of Two-point Ignition on Knocking in Spark-assisted HCCI Combustion using an Optically Accessible Engine

2019-32-05621/24/2020

This study investigated the effect of the ignition positions in a two-point ignition system on homogeneous charge compression ignition (HCCI) combustion. Focus was put on controlling the ignition timing, and changes in combustion behavior due to the ignition positions were observed on the basis of in-cylinder combustion visualization and pressure analysis. Experimental results showed that misfire occurred under a condition where the temperature rise time was short and combustion became unstable. In contrast, combustion was stable under a condition where the rise time was sufficiently long and autoignition developed along the cylinder wall. As a result, knocking intensity was reduced by stable combustion.

Yoshida, Kojiro, Furusho, Takuma, Abe, Yosuke, Iimura, Masaya, Imai, Takafumi, Hoshi, Kazutoshi, Iijima, Akira

Development of a Novel Hybrid-Piston for Application in High Performance Two-Stroke Engines

2019-32-05081/24/2020

The current development trends for high performance two-stroke engines have been identified in raising combustion pressures and therefore higher cylinder temperatures [1] [2]. Thus, the requirements on piston assembly are increased in such a way that pistons based on aluminium-silicon alloys – as most commonly used in high performance two-stroke engines - reach their application limit. A suitable solution has been shown by research work such as that conducted by Mahle König, by using a piston consisting of different materials. With this approach, the higher stressed piston crown consists of steel, while the lower stressed piston skirt is made out from aluminium. Previous basic examinations showed the high potential of the hybrid piston concept in terms of pressure and temperature increase, while also showing the need for a temperature-stable and pressure-tight joint between crown and skirt. This paper will focus on the development of two novel hybrid-piston concepts, where the piston crown and the piston skirt are connected in different ways. The first hybrid concept presented uses the piston pin in order to realize a plugconnection between piston crown and piston skirt (a conjunction hereafter known as plug-connection). A second approach is a material joint between piston crown and piston skirt, with the result that the two parts are integrally joined to one another (a conjunction hereafter known as multimaterial joint). During the predevelopment phase the design and dimensioning of the hybrid concepts were carried out with reference to mechanical and thermal operation loads, as well as joining aspects. A specific joining concept using a bimetal transition joint was created, along with the development of a special adapted laser beam welding procedure. The multi-material joint properties were further verified by FEM simulations as well as by mechanical and thermal tests. Finally, hybrid-piston prototypes were produced in time for first bench tests. In this paper the design concept of the hybrid piston and the joining technology will be presented, along with the results of FEM simulations and material testing.

Bechter, Christian, Jahn, Axel, Zimmermann, Frieder, Stamm, Uwe, Herb, Thomas

Feasibility Study of the Fuel Magnetizer in Flex-Fuel Cars

2019-36-0238

1/13/2020

The topic of energy efficiency is currently a subject widely debated in industrial sectors because of its high relevance due to the finite life time of fossil fuels and the need for reduction in consumption and consequently the emissions of gases and the environmental impact. The objective of this work was to evaluate the performance of fuel magnetizers, a product marketed that, according to suppliers, guarantees an improvement in combustion efficiency, representing a saving of 10% to 22% of fuel. For the analysis of the efficiency of the magnetizer, consumption tests were carried out on engine test bench with and without the use of the product in idling speed, 2000 rpm and 2700 rpm. The conclusions obtained showed that the use of magnetizers did not achieve a satisfactory result in the efficiency of internal combustion engines, a possible factor responsible is the high content of ethanol in Brazilian gasoline.

Amorim, Pablo A., De N. Mattos, Luiz F., Almeida, Everton L. P., Pellacani, Gustavo C., Marques, Luiz A. M. M.

Chemical kinetic mechanisms for HCCI combustion of wet ethanol with exhaust gas recirculation

2019-36-02931/13/2020

This work compares the accuracy of in-cylinder pressure and apparent heat release rate (AHRR) diagrams to the experimental data and the use of different chemical kinetics models applied to the GT-Power® software. The engine computational model is based on a naturally aspirated diesel engine with three cylinders, one of them modified to operate with hydrous ethanol with port fuel injection and HCCI combustion achieved with hot exhaust gas recirculation (EGR) of the Diesel cylinders. Operating points chosen to perform the comparison to experimental tests were 1800 rpm, 300 kPa of indicated mean effective pressure and fuels with 10% and 20% of water-in-ethanol by volume. The kinetic mechanisms for ethanol oxidation evaluated were the detailed NUI Galway and a Skeletal model based on it. With either model, cylinder pressure diagrams were not very different from the experimental values. The detailed mechanism was, on average, 9 times slower to process each case than the Skeletal mechanism. The quality of data obtained with the Skeletal mechanism and its lower computational cost makes it a good solution for a quick analysis. However, when greater reliability is required, it is recommended to use the detailed NUI Galway kinetic mechanism, since it provides a better fit to the experimental data, with a more complete analysis of the chemical species involved in ethanol oxidation.

Herzer, Filipe A., Fagundez, Jean L. S., Martins, Mario E. S., Salau, Nina P. G.

Investigation on Knock Resistance with Turbulent Jet Ignition at Different Engine Load in an Optical Engine

2019-01-215112/19/2019

This research was focused on the effect of pre-chamber ignition and compared the knock limit of normal spark ignition in the main chamber and pre-chamber jet ignition combustion in a spark ignition gasoline engine. Experiments were conducted in a single-cylinder engine with optical access. Engine was operated with stoichiometric air/fuel mixtures at 1200 rev/min and different inlet pressures of 1, 1.2, and 1.4 bar. No auxiliary fuel was injected into the pre-chamber when jet-ignition mode was used. The results show that significant knock limit extension can be realized with use of a pre-chamber ignition unit. The main differences in engine performance, heat release and combustion, knock resistance and flame propagation were compared between the pre-chamber ignition and conventional spark ignition in the main chamber by in-cylinder pressure measurements and high-speed flame chemiluminescence imaging. Pre-chamber ignition is capable of extending the knock limit over conventional spark ignition combustion due to the burn rate enhancement. Pre-chamber ignition lowered the CoV of IMEP. For instance, at inlet pressure 1.2 bar and common spark timing 18 °CA bTDC, CoV of IMEP with pre-chamber ignition was only around 2%, whereas normal SI reached almost 4.5%. At inlet pressure 1.0 bar, IMEP is lower with jet ignition comparing with normal SI but at elevated inlet pressures of 1.2 bar and 1.4bar pre-chamber ignition always produces higher IMEPs. The knock intensity increased as the inlet air pressure increased and spark timing advanced. The high speed combustion images show that incomplete combustion of ignition jets was present during the knocking combustion cycle.

Bureshaid, Khalifa, Shimura, Ray, Zhao, Hua, Feng, Dengquan, Bunce, Mike

Experimental study of cylinder oil stripping behavior at the scavenge port of a low-speed two-stroke engine

2019-01-233512/19/2019

The stripping of cylinder oil at the scavenging ports of low-speed two-stroke marine engines is one of the main sources of floating oil droplets existing in cylinders. The combustion of these oil droplets is one of the major reasons of PM emissions and pre-ignition for dual-fuel engines. In order to investigate the stripping behavior, a prototype model and a test bench were set up to carry out the experiment of cylinder oil stripping behavior and single droplet deformation under different conditions. Meanwhile, a CFD model was established to analyze the actual scavenging flow field, and the verification results were obtained: in the case of excessive lubrication, a considerable amount of cylinder oil remains on the upper surface of the scavenge ports. Such cylinder oil can be blown into the cylinder when the ports are opened. Then the oil droplets floating in the cylinder or attaching to the exhaust valve form potential spontaneous combustion points, which leads to the worsening of PM emissions and the threat of pre-ignition, the most harmful abnormal combustion for Otto-cycle dual-fuel engines.

Pan, Min, Feng, Liyan, Gong, Zhen, Yu, Zhengran, Sun, Hongjie, Wang, Zixin, Yan, Peng

A Study of Injection Directions on Improvement of Engine Performance and NOx Emission in A Low-speed Marine Engine

2019-01-232212/19/2019

A computational fluid dynamics (CFD) simulation model for a two-stroke low-speed marine engine has been established in CONVERGE software, to study the impact of different injection directions on fuel consumption and emissions of the engine. The goal of this research was to investigate injection angles in horizontal and vertical directions respectively. According to the simulation results, “trade-off” relationship was found in both directions between fuel consumption and NOx emission. Based on these results, 8° and -16° were considered as optimal injection angles in horizontal and vertical directions. With the optimized injection angles, lower NOx emission can be achieved with a little penalty on fuel consumption.

Sun, Qian, Ji, Wenxia, Huang, Zhen, Zhu*, Lei

Analysis on flow motion and combustion process in pre-chamber and main chamber for low-speed two-stroke dual-fuel engine

2019-01-217512/19/2019

ABSTRACT Low-speed two-stroke dual-fuel engines has been paid more attention due to the energy efficiency design index and Tier III emissions limitations issued by International Marine Organization. Although the dual-fuel engines have strong merits on emissions reduction, which can reach the IMO Tier III without aftertreatment, the power output is much lower than that of diesel engines. Therefore, the dual-fuel engine is also needed to improve continuously. However, the mixing and combustion processes in the engine have not been fully understood. In this study, a 3D-CFD model of the dual-fuel engine was established using CONVERGE to explore the mixing and combustion processes. Locally embedding fine grids are considered at scavenging ports, natural gas injection ports, pre-chamber. The model was validated by experimental in-cylinder pressure. Then, the flow motion, mixing of natural gas and air, flow in pre-chamber, torch and combustion in main-chamber were analyzed based on swirl variation, flow velocity distribution, equivalence ratio distribution and torch propagation.

Liu, Long, Wu, Yue, Xiong, Qian, Liu, Teng

OH, soot and temperature distributions of wall-impinging diesel fuel spray under different wall temperatures

2019-01-218412/19/2019

OH, soot and temperature distributions of wall-impinging diesel fuel spray were investigated in a high-temperature high-pressure constant volume combustion vessel. The ambient temperature (Ta) was set as 773 K, and the wall temperature (Tw) was set as 523 K, 673 K, 773 K, respectively. Three different injection pressures (Pi) of 60 MPa, 100 MPa, 160 MPa, and the ambient pressures (Pa) of 4 MPa were applied. The OH spatial distributions of wall-impinging spray were measured by the method of OH chemiluminescence imaging. Two-color pyrometry was applied to evaluate the spatial distributions of KL factor and flame temperature of wall-impinging spray. The results reveal that, OH chemiluminescence is observed in the region near the impingement point firstly. The regions of high OH chemiluminescence intensity and high KL factor appear in the location near the wall surface along the whole combustion process. As the wall temperature increases, the appearance time of the OH moves up, the intensity and area of OH chemiluminescence increase. Besides, KL factor and the average flame temperature, the soot formation and oxidation rates also increase when the wall temperature increases. As the injection pressure increases, the intensity of OH chemiluminescence decreases. It can be concluded that the change of the wall temperature affects the spatial distributions of OH, KL factor and flame temperature of wall-impinging spray.

Feng, Lei, Wang, Yu, Chen, Beiling, Geng, Chao, Yi, Wentao, Cui, Yanqing, Liu, Haifeng, Zheng, Zunqing, Wang, Hu, Yao, Mingfa

Effects of Engine Operating Condition and Fuel Property on Pre-Ignition Phenomenon in a Highly Boosted Premixed Natural Gas Engine

2019-01-215412/19/2019

The stochastic pre-ignition phenomenon plays a vital role to limit the further increasing BMEP for natural gas engines. In this study, the pre-ignition propensities were examined in a highly boosted premixed natural gas engine by various engine loads and air/fuel ratios, as well as different methane number (MN) altered by hydrogen addition. A proper pre-ignition evaluation method was proposed referring to intake temperature. Moreover, the limits of in-cylinder temperature and pressure for the onset of pre-ignition were estimated. The results show that both higher IMEP and richer mixture conditions readily lead to pre-ignition. The significant increases of pre-ignition frequency and heavy-knocking pre-ignition cycle present with lowering MN.

Chen, Run, Kuboyama, Tatsuya, Moriyoshi, Yasuo, Yasueda, Shinji, Doyen, Valerie, Martin, Jean-Baptiste

Modelling for Collective Effect of Muffler Geometric Modifications and Blended Microalgae Fuel Use on Exhaust Performance of a Four-Stroke Diesel Engine: A Computational Fluid Dynamics Approach

2019-28-237711/21/2019

Engine performance significantly depends on the effective exhaust of the combustion gases from the muffler. With stricter BSVI norms more efficient measures have to be adopted to reduce the levels of emissions from the exhaust to the atmosphere. Muffler along with reducing the engine noise is intended to control the back pressure as well. Back pressure change has a significant effect on muffler temperature distribution which affects the NOx emission from the exhaust. Many research communications have been made to reduce the exhaust emissions like HC, CO and CO2 from the exhaust by using different generation biofuels as an alternative fuel, yet they have confronted challenges in controlling the NOx content from the exhaust. This work presents the combined effect of Muffler geometry modifications and blended microalgal fuel on exhaust performance with an aim to reduce NOx emission form a four-stroke engine. In this exertion, the computational fluid dynamics model is developed to analyze the effect of muffler geometry modification on vital exhaust parameters of an engine. The engine is powered with a blend of chlorella microalgae and diesel. The engine used for testing is a four-stroke diesel, water-cooled, SOHC engine. The muffler geometry such as Chambered Elliptic (CE), and Turbo Elliptic (TE) are designed for study. The reference for designing the mufflers in CREO was published literature and company product blueprints. The combined effect of muffler geometry modification and blended microalgal fuel use on back pressure, chamber temperature, pressure and velocity distribution are deliberated. The result shows that the chambered elliptic muffler using B5 (5% Algal fuel) developed significantly less exhaust temperature, whereas the gas density is more in case of turbo elliptic muffler using B20 (20% Algal fuel). Finally, the velocity is slightly higher in the case of Turbo Elliptic (TE) muffler using B20 blend. Significant decrease in back pressure was noted for B20 blended fuel in case of TE over CE. The exhaust temperature was notably reduced in all B5 blends for all muffler’s geometries created. The work also aims to explore the effect on NOx emissions by analyzing the use of the combined effect of microalgae fuel and muffler geometry modifications on exhaust parameters by controlling the back pressure in the muffler. Almost no research is reported in this [1] field of work for microalgal fuels which is the objective of this work.

Kanchan, Sumit, Choudhary, Rajesh, Brahmaiah, Chavagani, Qayoom, Shahid

Feasibility of Multiple Piston Motion Control Approaches in a Free Piston Engine Generator

2019-01-259910/22/2019

The control and design optimization of a Free Piston Engine Generator (FPEG) has been found to be difficult as each independent variable changes the piston dynamics with respect to time. These dynamics, in turn, alter the generator and engine response to other governing variables. As a result, the FPEG system requires an energy balance control algorithm such that the cumulative energy delivered by the engine is equal to the cumulative energy taken by the generator for stable operation. The main objective of this control algorithm is to match the power generated by the engine to the power demanded by the generator. In a conventional crankshaft engine, this energy balance control is similar to the use of a governor and a flywheel to control the rotational speed. In general, if the generator consumes more energy in a cycle than the engine provides, the system moves towards a stall. If the generator consumes less energy, then the effective stroke, compression ratio and maximum translator velocity must rise steadily from cycle-to-cycle until the heat transfer losses stop the increase. Moreover, when stiff springs are added to the FPEG system, the dynamics becomes more sinusoidal and more consistent with increasing spring stiffness. To understand the behavior of proposed control and cycle-to-cycle variations, a comprehensive FPEG numerical model with a 1 kW target electric power was developed in MATLAB®/Simulink. An FPEG system corresponding to that numerical model has been operated in the laboratory. This MATLAB®/Simulink numerical model has been used to examine the sensitivity of FPEG dynamics and performance parameters to the changes in design and operating inputs. A difficulty during the modeling is associated with the cycle-to-cycle energy balance, and this difficulty is also reflected in the real-world FPEG control. Therefore, the authors have devised a control strategy similar to the real world intended control methodology. In this numerical model, two different feedback control methodologies were implemented and investigated. These control methodologies were applied to regulate the generator load with selected control or input variables, namely peak pressure, mid-stroke piston velocity, trapped compression ratio and dead center set points. The controllers with optimized coefficients demonstrated the feasibility of energy balance management during the transient operation. Based on the simulation results, the controllers with compression ratio, peak pressure and dead center clearance set points as control variables demonstrated stable FPEG operation whereas the mid-stroke velocity failed to achieve the steady-state operation due to deviation in the piston dynamics. The simulation results from this study will be used as the pathway for improving and optimizing the experimental FPEG design.

Bade, Mehar, Clark, Nigel, Famouri, Parviz, Guggilapu, PriyaankaDevi

Features of Mathematical Modeling in the Problems of Determining the Power of a Turbocharged Engine According to the Characteristics of the Turbocharger

03-13-01-000110/8/2019

The features of modeling the working process of a turbocharged two stroke marine diesel engine (MDE) in order to reveal the relationship between the engine power and the operation modes of a turbocharger (TC) are discussed in the article. Based on the results of modeling, a model was obtained for the dependence of the power of the MDE on the parameters of the TC operation. As a basic parameter of the TC operation, the TC speed was chosen. The scavenging air temperature is selected as an additional parameter. The article describes the structure of a diagnostic system that allows recording the operating modes of a TC in a noncontact method. The research for vibroacoustic fields of the G70-883kW marine engine was carried out by the author on ship “SEMINOLE,” in the process of research a noncontact vibroacoustic method was used to determine the TC speed. An analysis of the obtained experimental results demonstrates that the use of the averaged model of the dependence of the engine power on the TC speed for one engine family could lead to an error of 5-10%. The article shows that the results of experimental studies to determine the performance of a TC at various modes of operation of a MDE. The use of experimental data in the verification of simulation results has made it possible to reduce the error in determining the power of a MDE by 5-10%. The described method for estimating the power of a MDE based on the TC rotor speed and scavenging air temperature without using expensive piezoelectric type pressure sensors is an alternative method for estimating engine power.

Golovan, Andrii, Gritsuk, Igor, Popeliuk, Vadym, Sherstyuk, Olga, Honcharuk, Iryna, Symonenko, Roman, Saravas, Viktoriya, Volodarets, Mykyta, Ahieiev, Maksym, Pohorletskyi, Dmytro, Khudiakov, Igor

Validation and Analysis of Heat Losses Prediction Using Conjugate Heat Transfer Simulation for an Internal Combustion Engine

2019-24-00919/9/2019

New technologies are required to improve engine thermal efficiency. For this it is necessary to use all the tools available nowadays, in particular computational tools, which allow testing the viability of different solutions at reduced cost. In addition, numerical simulations often provide more detailed information than experimental tests. Such is the case for the study of the heat transfer through the walls of an engine. Conjugate Heat Transfer (CHT) simulations permit precise calculations of the heat transfer from gas to walls throughout the whole engine cycle, and thus it is possible to know such details as the instantaneous heat losses and wall temperature distribution on the walls, which no experiment can give. Nevertheless, it is important to validate CHT calculations, either with some experimental measurements or with some other reliable tool, such as 0D-1D modelling known to work well. The proposed work is based on the CHT simulation of the heat transfer to the walls of an engine piston during an entire cycle to determine the parameters that permit obtaining good results. This will be ascertained by comparison with the results of a lumped model previously validated for many applications. Another objective of this work is also to determine if it is significant to take into account the spatial and temporal variations of the wall temperature for the prediction of the heat losses during the engine cycle, as generally a mean and constant wall temperature (isothermal walls) is assumed for CFD combustion calculations.

Broatch, Alberto, Margot, Xandra, Garcia-Tiscar, Jorge, Escalona, Johan

Optical Investigation of Mixture Formation in a Small Bore DISI Engine by Laser Induced Exciplex Fluorescence (LIEF)

2019-24-01339/9/2019

Legislative and customer demands in terms of fuel consumption and emissions are an enormous challenge for the development of modern combustion engines. Downsizing in combination with turbocharging and direct injection is one way to increase efficiency and therefore meet the requirements. This results in a reduction of the displacement and thus the bore diameter. The emerging trends towards long-stroke engine design and hybridization make the use of small bore diameters in future gasoline engines a realistic scenario. The application of direct injection with small cylinder dimensions increases the probability of the interaction of liquid fuel with the cylinder walls, which may result in disadvantages concerning especially particulate emissions. This leads to the question which bore diameter is feasible without drawbacks concerning emissions as a result of wall wetting. In the previous project “GDI Boundary Bore” the feasibility of an SI engine with direct injection and small bore diameter (60 mm) was shown by the analysis of two different cylinder head concepts (3V and 4V). For the acquirement of deeper understanding of the mixture formation in such engines the laser induced exciplex fluorescence (LIEF) was applied on a transparent engine in a follow up project for the simultaneous visualization of the vapor and liquid phase. The optical investigation on the transparent single cylinder engine included various operating points with variation of the start of injection. Within the scope of the investigations on the 3V concept, it was possible to determine why a charge movement flap increasingly loses its influence with early injection. The optical investigations on the 4V concept showed that a 7-hole injector with a lower penetration depth has disadvantages compared to a 6-hole injector. Furthermore, it was possible to determine why a charge movement flap can have a negative effect on mixture formation, contrary to common opinion.

Pauls, Alexander, Eilts, Peter

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

A Review of Spark-Assisted Compression Ignition (SACI) Research in the Context of Realizing Production Control Strategies

2019-24-00279/9/2019

This paper seeks to identify key input parameters needed to achieve a production-viable control strategy for spark-assisted compression ignition (SACI) engines. SACI is a combustion strategy that uses a spark plug to initiate a deflagration flame that generates sufficient ignition energy to trigger autoignition in the remaining charge. The flame propagation phase limits the rate of cylinder pressure rise, while autoignition rapidly completes combustion. High dilution within the autoignited charge is generally required to maintain reaction rates feasible for production. However, this high dilution may not be reliably ignited by the spark plug. These competing constraints demand novel mixture preparation strategies for SACI to be feasible in production. SACI with charge stratification has demonstrated sufficiently stable flame propagation to reliably trigger autoignition across much of the engine operating map. A key controls challenge of SACI is the two regimes of combustion are near several constraints that may be competing. This work summarizes key findings from decades of research that can help enable production control strategies for SACI engines. A summary and analysis of the broad research of SACI is included, along with an examination of the relevant factors that must be considered while developing a control strategy. Additionally, a discussion of how production-intent SACI designs extend or innovate upon previous decades of research is included. Key control actuators and design parameters are synthesized along with their sensitivity on several SACI combustion metrics.

Robertson, Dennis, Prucka, Robert

Experimental Studies of Gasoline Auxiliary Fueled Turbulent Jet Igniter at Different Speeds in Single Cylinder Engine

2019-24-01059/9/2019

Turbulent Jet Ignition (TJI) is a pre-chamber ignition system for an otherwise standard gasoline spark ignition engine. TJI works by injecting chemically active turbulent jets to initiate combustion in a premixed fuel/air mixture. The main advantage of TJI is its ability to ignite and burn, completely, very lean fuel/air mixtures in the main chamber charge. This occurs with a very fast burn rate due to the widely distributed ignition sites that consume the main charge rapidly. Rapid combustion of lean mixtures leads to lower exhaust emissions due to more complete combustion at a lower temperature. For this research, the effectiveness of the Mahle TJI system on combustion stability, lean limit and emissions in a single cylinder spark engine fueled with gasoline at different speeds was investigated. The combustion and heat release process was analyzed and the exhaust emissions were measured. The results show that the effect of the Mahle TJI system on the lean-burn limit and exhaust emissions varied with engine speeds. The lean limit was extended by increasing the engine speed, to λ = 1.71 with 1,200 rpm, followed by λ = 1.69 with 1,000 rpm and then, λ = 1.51 with 800 rpm. NOx emissions were significantly reduced with increased engine speed under stable combustion conditions, because at higher speeds it was possible to increase the lean limit and offer a lower combustion temperature.

Bureshaid, Khalifa Isa, Feng, Dengquan, Bunce, Michael, Zhao, Hua

Experimental Studies on Liquid Phase LPG Direct Injection on a Two-Stroke SI Engine

03-12-03-0023

5/31/2019

Directly injecting fuel in two-stroke spark-ignition (2S-SI) engines will significantly reduce fuel short-circuiting losses. The liquid phase liquefied petroleum gas (LPG) DI (LLDI) mode has not been studied on 2S-SI engines even though this fuel is widely used for transportation. In this experimental work a 2S-SI gasoline-powered engine used on three-wheelers was modified to operate in LLDI mode with an electronic engine controller. The influences of injection pressure (IP), end of injection (EOI) timing, location of the spark plug, and type of injector on performance, combustion, and emissions were studied at different operating conditions. EOI close to bottom dead center with the spark plug located near the exhaust port was the most suitable for the LLDI mode which significantly enhanced the fuel trapping efficiency and improved the thermal efficiency. At 70% throttle condition the brake thermal efficiency increased from 19% to 25.6% and there was an 87% reduction in hydrocarbon (HC) emission compared to liquid phase LPG manifold injection. The use of multi-hole injector extended the maximum power output due to better in-cylinder mixture formation, whereas the single-hole injector extended the lean operating limit. LLDI has potential to improve the performance of small two-stroke engines significantly.

Dube, Adwitiya, Vivekanand, M., Ramesh, A.

The Application of Controlled Auto-Ignition Gasoline Engines -The Challenges and Solutions

2019-01-09494/2/2019

Controlled Auto-Ignition (CAI) combustion, also known as Homogeneous Charge Compression Ignition (HCCI), has the potential to simultaneously reduce the fuel consumption and nitrogen oxides emissions of gasoline engines. However, narrow operating region in loads and speeds is one of the challenges for the commercial application of CAI combustion to gasoline engines. Therefore, the extension of loads and speeds is an important prerequisite for the commercial application of CAI combustion. The effect of intake charge boosting, charge stratification and spark-assisted ignition on the operating range in CAI mode was reviewed. Stratified flame ignited (SFI) hybrid combustion is one form to achieve CAI combustion under the conditions of highly diluted mixture caused by the flame in the stratified mixture with the help of spark plug. CAI combustion in two-stroke gasoline engine can be used to enhance the torque of a four-stroke gasoline engine with the same displacement at the same indicated mean effective pressure. Poppet-valved two-stroke gasoline engines with normal valve lift and variable valve timing device, and uniflow two-stroke engine with gas exchange process completed by intake ports on the bottom of cylinder wall and overhead exhaust poppet valves are promising to achieve CAI combustion in a wide operating range. Hence, CAI combustion in two-stroke gasoline engines is a feasible solution for its commercial application to vehicles.

Fu, Xue-Qing, He, Bang-Quan, Zhao, Hua, Zhang, Yan, Li, Yufeng, Bai, Honglin

Sensitivity Analysis and Control Methodology for Linear Engine Alternator

2019-01-02304/2/2019

Linear engine alternator (LEA) design optimization traditionally has been difficult because each independent variable alters the motion with respect to time, and therefore alters the engine and alternator response to other governing variables. An analogy is drawn to a conventional engine with a very light flywheel, where the rotational speed effectively is not constant. However, when springs are used in conjunction with an LEA, the motion becomes more consistent and more sinusoidal with increasing spring stiffness. This avoids some attractive features, such as variable compression ratio HCCI operation, but aids in reducing cycle-to-cycle variation for conventional combustion modes. To understand the cycle-to-cycle variations, we have developed a comprehensive model of an LEA with a 1kW target power in MATLAB®/Simulink, and an LEA corresponding to that model has been operated in the laboratory. This MATLAB®/Simulink numerical model has been used to examine the sensitivity of the LEA dynamics and performance parameters to changes in the design and operating inputs. The sensitivity analysis provides insight into the pathway for improving and optimizing the design, as well as an assessment of the effects of modeling assumptions on the reliability of predictions. A difficulty during the modeling is associated with the cycle-to-cycle energy balance for the LEA, and it is clear that this difficulty is reflected in real-world LEA control. If the alternator consumes more energy in a cycle than the engine provides, the system moves towards a stall. If the alternator consumes less energy, then the stroke, compression ratio and maximum translator velocity must rise steadily from cycle-to-cycle until efficiency losses curb the increase. The authors have recognized that the control of this energy balance in the model affects sensitivity analysis and must, therefore, mimic the real world intended control methodology. To understand the LEA behavior further, a control methodology was developed based on the basic feedback control systems in order to monitor the compression ratio of the single cylinder LEA system from cycle-to-cycle, with a view of keeping compression ratio substantially constant. Initially, the LEA system behavior was analyzed with and without the external controller, mainly to highlight the importance and need for an external control methodology. Further, two different control strategies were implemented and investigated. Finally, the cycle-to-cycle variations were studied as spring stiffness increased, by introducing combustion stochastics. With the proposed controller strategies and the addition of stiff springs, the cycle-to-cycle variations were reduced, and the LEA system operated steadily.

Bade, Mehar, Clark, Nigel, Famouri, Parviz, Guggilapu, PriyaankaDevi, Darzi, Mahdi, Johnson, Derek

Mixing-Limited Combustion of Alcohol Fuels in a Diesel Engine

2019-01-0552

4/2/2019

Diesel-fueled, heavy-duty engines are critical to global economies, but unfortunately they are currently coupled to the rising price and challenging emissions of Diesel fuel. Public awareness and increasingly stringent emissions standards have made Diesel OEMs consider possible alternatives to Diesel, including electrification, fuel cells, and spark ignition. While these technologies will likely find success in certain market segments, there are still many applications that will continue to require the performance and liquid-fueled simplicity of Diesel-style engines. Three-way catalysis represents a possible low-cost and highly-effective pathway to reducing Diesel emissions, but that aftertreatment system has typically been incompatible with Diesel operation due to the prohibitively high levels of soot formation at the required stoichiometric fuel-air ratios. This paper explores a possible method of integrating three-way catalysis with Diesel-style engine operation. The proposed concept utilizes a high-temperature combustion system-enabled by a combination of thermal insulation, reduced turbocharger aftercooling, and exhaust gas retention-to combust low-cetane “sootless” fuels like ethanol, methanol, and natural gas in a traditional Diesel-style combustion mode (i.e. mixing-limited diffusive combustion, rather than HCCI-like strategies). The proposed concept has demonstrated the ability to meet EPA 2010 soot emissions limits without a particulate filter, while also maintaining a stoichiometric exhaust composition that is compatible with three-way catalysis. Further, the proposed concept can meet, and even exceed, baseline Diesel engine efficiency by combining the high compression ratio Diesel engine design with reduced heat transfer losses. Finally, use of mixing-limited, Diesel-style combustion drastically simplifies combustion phasing, and limits rate of rise. These early results motivate additional work on this concept, further optimizing components for high-temperature operation on alcohol fuels, and integrating the results into a commercial multi-cylinder engine demonstration.