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Spotlight on Design (14) General Industry (11)

Water Load Determination Approach in Two wheeler Exhaust System

  • Bosch Limited - Ranjana Kumari Meena
  • Robert Bosch GmbH - Konrad Meister, Andrea Krusch, Christopher Holzknecht
  • Technical Paper
  • 2018-32-0075
To be published on 2018-10-30 by SAE International in United States
Future emission norms in India (BS6) necessitates the 2 wheeler industry to work towards emission optimization measures. Engine operation at stoichiometric Air-Fuel Ratio (AFR) would result in a good performance, durability and least emissions. To keep the AFR close to stoichiometric condition, an Oxygen sensor is placed in the exhaust system, which detects if air-fuel mixture is rich (λ<1) or lean (λ>1) and provides feedback to fuel injection system for suitable fuel control. O2 sensor has a ceramic element, which needs to be heated to a working temperature for its functioning. The ceramic element would break (thermal shock) if water in liquid form comes in contact with it when the element is hot. To counter this, oxygen sensor is fully heated only when all the water in the exhaust system is evaporated, which results in delayed closed loop control. It's a challenge to control the HC emissions during first 100 seconds of engine start, as the catalyst is not functioning during this duration. Also, the system runs in open loop for first 50 seconds, as the lambda sensor is not functioning. Hence, determining the amount of water present in exhaust and having a protective layer for lambda sensor against water would enable early start of sensor functioning. The present paper explains an approach to determine the maximum water droplet size and water flow rate using a special Bosch Liquid sensor mounted in the exhaust pipe. Test cases are defined at various engine and exhaust gas temperatures to determine an appropriate set up and methodology for measurement on a 2Wheeler. The test cases are repeated on various 2wheelers available in the Indian market and influence of different exhaust configurations, mounting location of the Lambda sensor are analysed. The information of water droplet size and water flow rate are driving factors for the design and application of lambda sensor. With thermal shock protection over lambda sensor a full heater voltage can be applied to sensor even before all the water has evaporated in the exhaust system. An early sensor readiness results in a quick closed loop control of the fuel mixture thus reducing emissions.

Study of leak in small engines

  • TVS Motor Co., Ltd. - TL Balasubramanian
  • Technical Paper
  • 2018-32-0038
To be published on 2018-10-30 by SAE International in United States
Complete engine leak testing is generally followed to conform quality of manufacturing and assembly of different parts which otherwise create failures related to overall performance, fluid leak, gas leak and emissions etc. Light weighting of engines and downsizing is a generally accepted and followed theme towards the future emission norms which influences the part design complexity. Objective of the study is to investigate the significant parameters related to leak in cylinder head system and countermeasures to reduce the same when designing the small compact engines. In this study a systematic approach has been followed for arriving the leak rate specifications to qualify the products. In the design and manufacturing of small engines, features like compact combustion chamber with constraints of clamping bolts layout, gasket design, compact crank case layout and lower wall thickness of major casting parts are used to achieve weight and cost targets. During the development of one of such new engine, cylinder head leak rate at the valve – seat interface observed was significantly higher compared to existing production engines. Cause and effect analysis was prepared for the various leaks and valve interface leak has been focused further to bring it under acceptance level. Failure modes causing leak were experimentally evaluated under simulated conditions. Finite elemental analysis was done to understand the cylinder head distortion levels and compared with the bench mark models. Based on the force transfer mechanism from bolt clamping force to the cylinder head, solution was proposed to reduce distortions and leak rate. Volume effect on the pressure drop leak test was studied theoretically and validated experimentally to arrive at the optimum leak rate specification for the new engine. Improvements which reduced valve seat distortion helped in reducing leak significantly and an optimum leak specification arrived for the new engine. Parameters influencing leak in new engine is studied experimentally in sub-system and engine level. Countermeasure was proposed to reduce distortion and leak, improve sealing; process improvements to achieve consistency are studied experimentally and suggested. Combination of design improvements and process improvements helped in achieving the acceptable leak rates which helped to meet the engine quality, cost and weight targets.

Design, Analysis and Optimization of SI Engine Intake Manifold for FSAE

  • Mechanical Engineering, NIT Jamshedpur - Sanath Himasekhar Konthala
  • National Institute of Tech. Jamshedpur - Sanjay S
  • Show More
  • Technical Paper
  • 2018-32-0073
To be published on 2018-10-30 by SAE International in United States
Fluid dynamics of intake system plays a key role in deciding the performance of an engine. This dynamics is different for fuel injected and carburetted engine and varies according to type of engine, number of cylinders, temperature at inlet, valve timing, valve angle and other factors. Careful design of the intake manifold enables to manipulate the performance characteristics of the engine to the desired level. The present work deals with the analysis of the flow within the intake manifold in steady state and analyze the results to evaluate and improve the ability of the intake port to convey air to the cylinder with the highest possible mass flow rate. Enhanced mass air intake increases the breathability of the engine which in turn increases the volumetric efficiency of the engine. Optimising air flow performance during intake process is the main objective of this work. The performance of the engine can be improved by optimized design of intake manifold. In the process of optimizing the flow for improving engine performance, computational fluid dynamics (CFD) simulation plays a very important role. This paper will discuss the 3-D simulation of intake manifold of KTM Duke 390cc engine. Steady state analysis has been done using ANSYS FLUENT. The intake manifold of the above engine has certain engine power restrictions (imposed by Formula SAE rule book) and there is a 20mm restrictor present between the throttle body and engine cylinder. To achieve stagnation of air, plenum is used. Runner connects the plenum with engine and is tuned at certain rpm to optimize engine performance. As KTM 390 Duke engine was used for the competition, all analysis was done on three parts – Restrictor, Plenum and Runner. Optimized design of intake manifold would achieve pressure inside the engine cylinder slightly greater than atmospheric (at the start of compression stroke) even with above mentioned restrictions.

Ion Current Comparison in Small, Fast Running Gasoline Engines for non-Automotive Applications

  • Graz University of Technology - Riccardo Basso, Gabriel Gruber, Pascal Piecha, Hans-Juergen Schacht, Stephan Schmidt
  • ANDREAS STIHL AG & Co. KG - Martin Arenz
  • Technical Paper
  • 2018-32-0077
To be published on 2018-10-30 by SAE International in United States
Small engines for non-automotive applications include 2-stroke and 4-stroke gasoline engine concepts which have a reduced number of sensors due to cost and packaging constraints. In order to cope with future emission regulations, more sophisticated engine control and monitoring becomes mandatory. Therefore a cost-effective way has to be found to gain maximum information from the existing sensors and actuators. Due to an increasing bio-fuel share in the market, the detection of bio-fuel content is necessary to guarantee a stable combustion by adapting the injection and ignition control strategy. Meaningful information about the combustion can be retrieved from combustion chamber ion current measurements. This paper proposes a general overview of combustion process monitoring in different engines concepts by measuring the ion current during combustion. Actually, the ion current measurement technique is not yet established in the automotive sector due to the presence of other more accurate and less signal analysis intense sensors as the oxygen and knock sensor. But in small non-automotive applications the ion current could be beneficial for a dynamic control of the engine, due to its cost-efficient measurement hardware solution. During the research both two and four stroke engines are tested in different operational points and fuel blends resulting in a wide general knowledge of the measuring principle and signal properties. Furthermore, a correlation study between signal properties and engine’s parameters is given in order to extract a stable control variable suitable for the computational power of such engine’s ECUs.

Influence of Autoignition and Behavior of Pressure Wave on Knocking Intensity by using Multipoint Pressure Measurement and In-cylinder Visualization of the End-gas

  • Nihon University - Takahiro YAMASHITA, Shuhei Takahata, HIROKI KUDO, Takuya Izako, Takahiro Ishikawa, Masanori Saito, Mitsuaki Tanabe, Akira Iijima
  • Technical Paper
  • 2018-32-0001
To be published on 2018-10-30 by SAE International in United States
In this study, the effect of autoignition behavior of unburned region on pressure wave formation and knock intensity were investigated. In the experiment, a single-cylinder gasoline engine capable of high-speed observation of the end gas was used. Visualization in the combustion chamber and light absorption spectroscopic measurement of the end gas were carried out, and the autoignition behavior of the unburned portion and the reaction history before autoignition were analyzed. By analyzing the multi-point pressure histories, the process of autoignition and pressure wave growth was analyzed. As a result, it was found that knocking intensity increases by autoignition and pressure wave interaction each other.

CFD analysis of a port fuel injection IC engine to study air-fuel mixture preparation and its impact on hydrocarbon emission and mixture homogeneity in combustion chamber

  • TVS Motor Co Ltd - Manish Garg
  • Technical Paper
  • 2018-32-0005
To be published on 2018-10-30 by SAE International in United States
At part load conditions, effective utilization of fuel is critical for drivability of an IC engine driven automobile, with minimum emissions and fuel consumption. It becomes cardinal to study the mixture preparation in engines to understand the Injection strategy that helps in achieving the prime objectives of lower emission and reliable operation. To add to the complexity of the problem being studied, the injection phenomenon is rapid, turbulent, multi-phase, two-way coupled (where the continuous phase affects the droplets and vice versa) and involves turbulence length scales and time scales, few orders of magnitude lower compared to the characteristic length in the turbulence integral scale. A methodology is developed in Star-CD and ES-ICE to simulate the mixture preparation in Port Fuel Injection (PFI) engines. High quality mixture preparation which is essential for combustion stability and lower emissions is aimed at part load conditions which constitute the majority of driving cycle. This methodology is helpful to understand and solve the injection timing development issues and in improving the combustion stability and lowering the emissions. The fuel injection parameters have been studied in detail both experimentally and numerically in a specialized spray chamber. The fuel injection parameters are correlated to the source of injection to obtain similar fit of droplet distribution profile obtained experimentally. The parameters like - injection timing, injection location and injection pressure can be efficiently optimized through this methodology for efficient mixture formation. Extensive studies have been done on different injection timing in order to reduce the wall film thickness and fuel short circuit losses and to increase the overall evaporation rate of fuel droplets by increasing the residence time. Two injection timing strategies namely - open valve injection and closed valve injection have been analyzed to understand the effect of fuel short circuit losses and its impact on HC (hydro-carbon) emissions. It is observed that, open valve injection has lower short circuit losses compared to closed valve injection which, is experimentally verified and thus has a great significance in reducing the HC emissions. However, open valve injection comparatively affects the in-cylinder charge homogeneity and standard deviation of equivalence ratio. This paper also discusses on the strategies that have been undertaken to achieve best-in-cylinder homogeneity with an adverse effect on increased fuel film thickness on the port walls. Efforts are made to optimize the injection timing and location for best mixture formation in production automotive vehicles and in extending the methodology for the corresponding emission prediction. Being a computationally intensive problem with an additional complexity of movingmesh opens an opportunity for parallel performance study. Parallel performance study shows that, the methodology proposed above uses a Message Passing Interface (MPI) and shows a good scale up for 2-16 cores above which, it saturates. Multi-cycle analysis is carried out to understand the variation in Air-Fuel ratio homogeneity and Coefficient of variation of Indicated Mean Effective Pressure (IMEP)which provides a fundamental vista on the transient behavior of the spray dynamics.

On the effect of the injector position on fuel-air mixture preparation in a two-stroke GDI engine

  • Università degli Studi di Firenze - Francesco Balduzzi, Luca Romani, Andrea Tanganelli, Simone Bigalli, Giovanni Ferrara
  • Technical Paper
  • 2018-32-0040
To be published on 2018-10-30 by SAE International in United States
Modern injection systems are characterized by low cost, light weight and diversified components based on a mature technology. In addition, the constant growth of computational resources allows an in-depth understanding and control of the injection process. In this scenario, increasing interest is presently being paid to understand if an application of such technologies to small two stroke engines could lead to a return to popularity in place of the more widespread use of the four stroke engine. Indeed, the possibility of achieving a drastic reduction of both specific fuel consumption and pollutant emissions would completely reverse the future prospect of the two stroke engine. The authors in previous studies developed a low pressure direct injection (LPDI) system for a 300 cm3 two stroke engine that was ensuring a performance consistent with a standard four stroke engine of similar size. The main drawbacks of the system were the large time required for delivering the fuel and the incomplete vaporization in some working conditions, due to the large size of the injected droplets. In this study, the use of a single high pressure injector with an operating pressure of 100 bar was analyzed. An optimization study was carried out in order to identify the best injector configuration for the GDI system. The results of the preliminary 3 D CFD study are here reported. The effect of the injector positioning and injection timing on the spray vaporization, mixture homogenization and fuel short-circuit was evaluated at different engine operating points. The results will show that also in case of a high pressure injection the best performance can be obtained when a suitable interaction between the liquid jet of fuel and the flow of scavenging air is ensured, as well as with the appropriate choice of the injection timing.

Influence of ethanol and 2-butanol blended fuels on combustion and emissions in a small displacement two stroke engine

  • Graz University of Technology - Stephan Jandl, Stephan Schmidt, Pascal Piecha, Hans-Juergen Schacht
  • Technical Paper
  • 2018-32-0044
To be published on 2018-10-30 by SAE International in United States
Small displacement two-stroke engines are cheap and low-maintenance propulsion systems and commonly used in scooters, recreation vehicles and handheld power-tools. The restriction of emission legislation and the increasing environmental awareness of end users as well as decreasing energy resources cause a rethinking in the development of propulsion systems and fuels in these fields. Despite recent improvements of electric powertrains, two stroke engines are the unchallenged propulsion system in high performance handheld power tools at the moment. The reasons are the extraordinary high power to weight ratio of two-stroke engines, the high energy density of liquid fuels and the reliability of the product with respect to extreme ambient conditions. Nevertheless, further improvements on emissions and fuel consumption of small displacement two-stroke engines have to be realized. This research is focused on the use of alternative renewable fuels, so called biofuels, like ethanol and 2-butanol in small displacement two-stroke engines. The different physical and chemical properties of ethanol and 2-butanol can have a positive impact on the combustion process and emission composition and are a possibility to contribute future engine requirements. Beside advantages in combustion and emission behavior, liquid biofuels also have an advantageous CO2 lifecycle in comparison to conventional gasoline. To point out the characteristics of different alcohol gasoline blends the ignition timing and the air to fuel equivalence ratio has been modified in a wide range. The results are focused on knock and pre-ignition behavior, fail ignition, combustion stability and emissions under rich and lean operation. On this basis, it is possible to find out the boundary conditions for an alcohol fuel use in small displacement two-stroke engines and serving as basis for future combustion process developments with respect to decreasing emissions and fuel consumption.

Study of a charged engine for motorbike application

  • Porsche Engineering Services GmbH - Vincenzo Bevilacqua, Giovanni Corvaglia, Klaus Fuoss, Matthias Penzel
  • Technical Paper
  • 2018-32-0079
To be published on 2018-10-30 by SAE International in United States
Legislation bodies are increasingly pushing vehicles manufacturers all over the world towards the reduction of emissions and fuel consumption of new developed vehicles. These strict requirements applied to motorbikes manufacturers present them with a big challenge, since the efficiency improvement must be achieved without affecting the performance, in terms of torque and power first, and throttle response and drivability, which are significantly important to a motorbike owner. In order to meet the stringent consumption targets, in the recent years, the strategy of “downsizing” has become widespread in the automotive field. The reduction of engine displacement together with the adoption of turbocharging allows shifting the engine operating points in an area of higher efficiency with obvious advantages in terms of fuel consumption. At the beginning of 1980, many motorbike manufacturers attempted to apply the turbocharging technology to their motorbikes, with the aim of reducing the engines displacement and increasing the specific performance. The success of this attempt was limited because at that time the technology was not mature enough and the consequent poor throttle response and low reliability limited acceptance from customers. The technology is nowadays at an advanced stage and modern electronic control systems are so highly-developed and effective in managing high power outputs, that an application of turbocharging to motorbike engines could be meaningful. Nevertheless some important challenges must be faced: packaging, weight and cost, customer acceptance. The objective of this work is to provide a detailed analysis about the feasibility of the application of a supercharged engine to a motorbike: in a first stage, several engine architectures (In-line, V-configuration, Boxer) and charging concepts (centrifugal or volumetric compressor, with mechanical or fluid-dynamic connection to the engine) have been analyzed from the point of view of packaging and in terms of cost and weight. In a second part, a V4 engine architecture has been selected and optimized for a patrol motorcycle application. This kind of employment leads to specific requirements for the engine: high maneuverability especially at low engine speeds and part load conditions, smooth torque curve over the speed range, high maximum power target and an impressive exhaust sound. These performance requirements have been analyzed via 1D gas-exchange simulations and a charging strategy together with optimized intake manifold, exhaust manifold and valve timing has been found out. Finally, the conceptual investigation of the base engine design has been carried out with the development target of lowest possible weight and size. Several concepts of cylinder head, crankcase and valve train, type of lubrication and cooling systems, type and position of the gearbox have been investigated.

Study of Knocking Intensity Determinant by High-speed Observation of the End-gas Autoignition using Optically Accessible Engine

  • Nihon University - Takahiro Ishikawa, Shuhei Takahata, Hiroki KUDO, Takahiro YAMASHITA, Takuya Izako
  • Honda R&D Co Ltd - Hibiki Koga
  • Show More
  • Technical Paper
  • 2018-32-0003
To be published on 2018-10-30 by SAE International in United States
The purpose of this study was to investigate how autoignition leads to the occurrence of pressure oscillations. That was done on the basis of in-cylinder visualization and analysis of flame images captured with a high-speed camera using an optically accessible engine, in-cylinder pressure measurement and measurement of light emission from formaldehyde (HCHO). The results revealed that knocking intensity tended to be stronger with a faster localized growth speed of autoignition. An investigation was also made of the effect of exhaust gas recirculation (EGR) as a means of reducing knocking intensity. The results showed that the application of EGR advanced the ignition timing, thereby reducing knocking intensity under the conditions where knocking occurred.