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Showing papers in "SAE International journal of engines in 2009"






Journal ArticleDOI
TL;DR: This paper considers the future development of gasoline engine downsizing in the short to medium term and the various technologies that can be applied to further increase the efficiency of operation and uses analysis tools and engine test results to show the benefits achievable.
Abstract: In order to achieve the required future CO 2 reduction targets significant further development of both gasoline and diesel engines is required. One of the main methods to achieve this with the gasoline engine in the short to medium term is through the application of engine downsizing, which has resulted in numerous downsized engines already being brought to production. It is, however, considered that there is still significant further CO 2 reduction potential through continued development of this technology. This paper considers the future development of gasoline engine downsizing in the short to medium term and the various technologies that can be applied to further increase the efficiency of operation. As such this paper covers, among other areas, fundamental engine layout and design, alternative boosting systems, methods of increasing part load efficiency and vehicle modelling, and uses analysis tools and engine test results to show the benefits achievable.

192 citations


Proceedings ArticleDOI
TL;DR: In this paper, the authors compared the performance of a single-cylinder light-duty compression ignition engine on four different fuels of different octane numbers, in the gasoline boiling range, compared to running on a diesel fuel.
Abstract: Previous work has showed that it may be advantageous to use fuels of lower cetane numbers compared to today’s diesel fuels in compression ignition engines The benefits come from the longer ignition delays that these fuels have There is more time available for the fuel and air to mix before combustion starts which is favourable for achieving low emissions of NOx and smoke though premixing usually leads to higher emissions of CO and unburned hydrocarbons In the present work, operation of a single-cylinder lightduty compression ignition engine on four different fuels of different octane numbers, in the gasoline boiling range, is compared to running on a diesel fuel The gasoline fuels have research octane numbers (RON) of 91, 84, 78, and 72 These are compared at a low load/low speed condition (4 bar IMEP / 1200 rpm) in SOI sweeps as well as at a higher load and speeds (10 bar IMEP / 2000 and 3000 rpm) in EGR sweeps There is a NOx advantage for the 91 RON and 84 RON fuels at the lower load At the higher load, NOx levels can be reduced by increasing EGR for all gasolines while maintaining much lower smoke levels compared to the diesel In the conditions studied, the optimum RON range might be between 75 and 85

184 citations


Journal ArticleDOI
TL;DR: In this article, the effects of fuel properties on the performance and emissions of an engine running in partially premixed combustion mode were investigated using nine test fuels developed in the gasoline boiling point range.
Abstract: The effects of fuel properties on the performance and emissions of an engine running in partially premixed combustion mode were investigated using nine test fuels developed in the gasoline boiling point range. The fuels covered a broad range of ignition quality and fuel chemistry.The fuels were characterized by performing a load sweep between 1 and 12 bar gross IMEP at 1000 and 1300 rpm. A heavy duty single cylinder engine from Scania was used for the experiments; the piston was not modified thus resulting in the standard compression ratio of 18:1.In order to properly run gasoline type of fuels in partially premixed combustion mode, an advanced combustion concept was developed. The concept involved using a lot of EGR, very high boost and an advanced injection strategy previously developed by the authors.By applying this concept all the fuels showed gross indicated efficiencies higher than 50% with a peak of 57% at 8 bar IMEP. NOx were mostly below 0.40 g/kWh only in few operative points 0.50 g/kWh was reached. At high load the soot levels were mostly a function of the octane number; with RON higher than 95 it was possible to be below 0.5 FSN while for the more reactive fuels a peak value of 3 FSN was reached at 13 bar IMEP.The pressure rise rate reached a peak of 19 bar/CAD with fuels which had a RON above 95, when the octane number decreased below 90 the pressure rise rate was always below 14 bar/CAD. (Less)

168 citations




Proceedings ArticleDOI
TL;DR: In this paper, the authors compared strengths and weaknesses of different options for performing optical diagnostics on HD diesel sprays and described practical experiences with the design and operation of a constant volume test cell over a period of more than five years.
Abstract: This paper first compares strengths and weaknesses of different options for performing optical diagnostics on HD diesel sprays. Then, practical experiences are described with the design and operation of a constant volume test cell over a period of more than five years. In this test rig, pre-combustion of a lean gas mixture is used to generate realistic gas mixture conditions prior to fuel injection. Spray growth, vaporization are studied using Schlieren and Mie scattering experiments. The Schlieren set-up is also used for registration of light emitted by the combustion process; this can also provide information on ignition delay and on soot lift-off length. The paper further describes difficulties encountered with image processing and suggests methods on how to deal with them. Results are presented that illustrate the wide range of capabilities of this test-rig when combined with high speed video registration, in particular its potential for studying issues related to vaporizing fuel spray dynamics.

95 citations



Journal ArticleDOI
TL;DR: In this paper, the effects of fuel stratification by means of multiple injections as well as the sensitivity of auto-ignition and burn rate to intake pressure and temperature are presented.
Abstract: The objective of this study was to examine the operating characteristics of a light duty multi cylinder compression ignition engine with regular gasoline fuel at low engine speed and load. The effects of fuel stratification by means of multiple injections as well as the sensitivity of auto-ignition and burn rate to intake pressure and temperature are presented. The measurements used in this study included gaseous emissions, filter smoke opacity and in-cylinder indicated information. It was found that stable, low emission operation was possible with raised intake manifold pressure and temperature, and that fuel stratification can lead to an increase in stability and a reduced reliance on increased temperature and pressure. It was also found that the auto-ignition delay sensitivity of gasoline to intake temperature and pressure was low within the operating window considered in this study. Nevertheless, the requirement for an increase of pressure, temperature and stratification in order to achieve auto-ignition time scales small enough for combustion in the engine was clear, using pump gasoline. Copyright © 2009 SAE International.

Journal ArticleDOI
TL;DR: In this article, the authors describe the development of a 3 cylinder 1.2l technology demonstrator engine from MAHLE and demonstrate production ready technologies that enable low CO2 emissions via downsizing by 50%.
Abstract: This paper describes the initial development of a 3 cylinder 1.2l technology demonstrator engine from MAHLE. The purpose of this highly turbocharged direct injection engine is to demonstrate productionready technologies that enable low CO2 emissions via downsizing by 50%. Downsizing is one of the most proven paths to CO2 emission reduction. By using careful design, a 2.4 l engine can be replaced by a 1.2l engine that has superior torque at all speeds and on-road fuel consumption benefits of 25 30%. A two-stage turbocharging system has been developed for the engine to enable good transient response and the high torque levels at all engine speeds demanded by a downsizing approach. Several options were tested and the final system exceeds the 30bar peak BMEP target with stoichiometric fuelling. Indeed, lambda = 1.0 fuelling is maintained over the majority of the full-load line and the 144kW peak power requirement is fulfilled at only 6000 rpm. Test data are presented for both steady state and transient performance as well as vehicle fuel economy simulation results. Discussions on combustion system development and emissions performance status are included.










Journal ArticleDOI
TL;DR: In this paper, the authors focus on the effects of random pre-ignition on low-end torque of a supercharged gasoline engine and show that this violent phenomenon which emits a sharp metallic noise is unacceptable even on modern super-charged gasoline engines.
Abstract: Recent developments on highly downsized spark ignition engines have been focused on knocking behaviour improvement and the most advanced technologies combination can face up to 2.5 MPa IMEP while maintaining acceptable fuel consumption. Unfortunately, knocking is not the only limit that strongly downsized engines have to confront. The improvement of low-end torque is limited by another abnormal combustion which appears as a random pre-ignition. This violent phenomenon which emits a sharp metallic noise is unacceptable even on modern supercharged gasoline engines because of the great pressure rise that it causes in the cylinder (up to 20 MPa).



Journal ArticleDOI
TL;DR: In this paper, a series hydraulic hybrid concept (SHHV) was explored as a potential pathway to an ultra-efficient city vehicle, and the simulation study focused on the SHHV supervisory control development, to address the challenge of the low storage capacity of the accumulator.
Abstract: A series hydraulic hybrid concept (SHHV) has been explored as a potential pathway to an ultra-efficient city vehicle. Intended markets would be congested metropolitan areas, particularly in developing countries. The target fuel economy was ~100 mpg or 2.4 l/100km in city driving. Such an ambitious target requires multiple measures, i.e. low mass, favorable aerodynamics and ultra-efficient powertrain. The series hydraulic hybrid powertrain has been designed and analyzed for the selected light and aerodynamic platform with the expectation that (i) series configuration will maximize opportunities for regeneration and optimization of engine operation, (ii) inherent high power density of hydraulic propulsion and storage components will yield small, lowcost components, and (iii) high efficiency and high power limits for accumulator charging/discharging will enable very effective regeneration. The simulation study focused on the SHHV supervisory control development, to address the challenge of the low storage capacity of the accumulator. Two approaches were pursued, i.e. the thermostatic SOC control, and Stochastic Dynamic Programming for horizon optimization. The stochastic dynamic programming was setup using a set of naturalistic driving schedules, recorded in normal traffic. The analysis included additional degree of freedom, as the engine power demand was split into two variables, namely engine torque and speed. The results represent a significant departure from the conventional wisdom of operating the engine near its “sweet spot” and indicate what is preferred from the system stand-point. Predicted fuel economy over the EPA city schedule is ~93 mpg with engine idling, and ~110 mpg with engine shutdowns.


Journal ArticleDOI
TL;DR: In this article, a sequential coupling approach of 3D CFD with a Stochastic Reactor Model (SRM) is used to simulate the PCCI engine and the results show that the fuel rich pockets in the late injection timing are desirable for triggering auto-ignition and advancing the combustion phasing.
Abstract: Premixed Charge Compression Ignition (PCCI), a Low Temperature Combustion (LTC) strategy for diesel engines is of increasing interest due to its potential to simultaneously reduce soot and NOx emissions. However, the influence of mixture preparation on combustion phasing and heat release rate in LTC is not fully understood. In the present study, the influence of injection timing on mixture preparation, combustion and emissions in PCCI mode is investigated by experimental and computational methods. A sequential coupling approach of 3D CFD with a Stochastic Reactor Model (SRM) is used to simulate the PCCI engine. The SRM accounts for detailed chemical kinetics, convective heat transfer and turbulent micro-mixing. In this integrated approach, the temperature-equivalence ratio statistics obtained using KIVA 3V are mapped onto the stochastic particle ensemble used in the SRM. The coupling method proved to be advantageous in terms of computational expense and emission prediction capability, as compared with direct coupling of CFD and chemical kinetics. The results show that the fuel rich pockets in the late injection timing are desirable for triggering auto-ignition and advancing the combustion phasing. Furthermore, the model is utilised to study the impact of combustion chamber design (open bowl, vertical side wall bowl and re-entry bowl) on PCCI combustion and emissions. The piston bowl geometry was observed to influence the in-cylinder mixing and the pollutant formation for the conditions studied. INTRODUCTION Low Temperature Combustion (LTC) modes such as Homogeneous or Premixed Charge Compression Ignition (HCCI/PCCI) are receiving increased attention due to their potential for simultaneously reducing soot and NOx emissions from Direct Injection (DI) diesel engines. PCCI mode involves premixed combustion of a highly diluted or lean mixture and the combustion process is primarily controlled by the chemical kinetics. Thus, the control of ignition timing and burning rate in PCCI combustion is fundamentally more challenging than in a conventional compression ignition DI diesel engine governed mainly by physical processes such as fuel-air mixing. Furthermore, for the cases where the airfuel charge is often not purely homogeneous, the influence of fuel-air mixing on combustion also needs to be taken into account. In addition to experimental studies, a variety of computational modelling approaches based on multidimensional computational fluid dynamics (CFD) have also been applied to investigate early direct injection PCCI combustion. The detailed chemical kinetics and the flow description in PCCI mode are relatively decoupled, when compared to conventional diesel combustion. This fact has been exploited by sequential solvers based on CFD and multi-zone combustion models [1-3]. In a multi-zone approach, the computational cells having similar temperature and composition histories are grouped into a relatively small number of zones (~10). The chemical kinetics solver is applied to each zone, assumed as a well stirred reactor. Flowers et al. [2] modified the multi-zone model to This is Computational Modelling Group's latest version of the paper. For the published version please refer to http://www.sae.org/technical/papers/2009-01-1102

Journal ArticleDOI
TL;DR: In this article, the authors investigated the effect of injection parameters on liquid-phase diesel spray penetration after the end-of-injection (EOI) in a constant-volume chamber over a range of ambient and injector conditions typical of a diesel engine.
Abstract: Diesel injection parameters effect on liquid-phase diesel spray penetration after the end-of-injection (EOI) is investigated in a constant-volume chamber over a range of ambient and injector conditions typical of a diesel engine. Our past work showed that the maximum liquid penetration length of a diesel spray may recede towards the injector after EOI at some conditions. Analysis employing a transient jet entrainment model showed that increased fuel-ambient mixing occurs during the fuel-injection-rate ramp-down as increased ambient-entrainment rates progress downstream (i.e. the entrainment wave), permitting complete fuel vaporization at distances closer to the injector than the quasi-steady liquid length. To clarify the liquid-length recession process, in this study we report Mie-scatter imaging results near EOI over a range of injection pressure, nozzle size, fuel type, and rate-of-injection shape. We then use a transient jet entrainment model for detailed analysis. Results show that an increased injection pressure correlates well with increasing liquid length recession due to an increased entrainment wave speed. Likewise, an increased nozzle size, with higher jet momentum and faster entrainment wave, enhances the liquid length recession. A low-density, high-volatility fuel does not decrease the strength of the entrainment wave; however, it decreases the steady liquid length causing the entrainmentmore » wave to reach the liquid spray tip earlier, which ultimately results in faster liquid length recession. A slow ramp down in injection rate causes a weaker entrainment wave so that the liquid length recession occurs even prior to injector close.« less

Journal ArticleDOI
TL;DR: In this article, a multi-zone, direct-injection (DI) diesel combustion model, the so-called RK-model, has been developed and implemented in a full cycle simulation of a turbocharged engine.
Abstract: A multi-zone, direct-injection (DI) diesel combustion model, the so-called RK-model, has been developed and implemented in a full cycle simulation of a turbocharged engine. The combustion model takes into account: • transient evolution of fuel sprays, • interaction of sprays with swirl and walls, • evolution of near-wall flow formed after spray-wall impingement depending on impingement angle and local swirl velocity, • interaction of Near-Wall Flows (NWF) formed by adjacent sprays, • influence of temperatures of gas and walls in the zones on evaporation rate. In the model the fuel spray is split into a number of specific zones with different evaporation conditions including zone on the cylinder liner and on the cylinder head. The piston bowl is assumed to be a body of revolution with arbitrary shape. The combustion model supports central and non-central injector as well as the side injection system. NOx formation model uses Detail Kinetic Mechanism (199 reactions with 33 species). Soot formation model is phenomenological. The general equation for prediction of ignition delay period was derived as for conventional engines as for engines with PCCI where pilot injection timing achieved 130 CA deg. before TDC. The model has been validated by experimental data obtained from high-speed, mediumspeed and low-speed engines over the whole operating range; a good agreement has been achieved without recalibration of the model for different operating modes. General equations for prediction of spray tip penetration, spray angle and ignition delay for low temperature combustion and high temperature combustion were derived and validated with the published data obtained for different diesels including diesels with multiple injection system and injection timing varied from very early up to after the TDC. To make a computational optimization of multiple injection strategy possible, the full cycle thermodynamic engine simulation software DIESEL-RK has been supplied with library of nonlinear optimization procedures.