Showing papers on "Carbureted compression ignition model engine published in 2014"

Comparison of Low Temperature Combustion Strategies for Advanced Compression Ignition Engines with a Focus on Controllability

Abstract: In the present study, various low temperature combustion strategies were investigated using single cylinder engine experiments. The combustion strategies that were investigated premix the majority of the fuel and do not require exhaust gas recirculation (EGR) to achieve ultra-low NOx and soot emissions for low- to mid-load engine operation. These types of advanced compression ignition combustion strategies have been shown to have challenges with combustion phasing control. The focus of the study was to compare engine performance and emissions, combustion sensitivity to intake conditions, and the ability to control any observed sensitivity through the fuel injection strategy. Even though these are steady state engine experiments, this will demonstrate a given combustion strategies controllability on a cycle-to-cycle basis. The combustion strategies that were investigated are fully premixed dual-fuel homogeneous charge compression ignition (HCCI), dual-fuel reactivity controlled compression ignition (RCCI),...

Development of a Gasoline Direct Injection Compression Ignition (GDCI) Engine

Abstract: In previous work, Gasoline Direct Injection Compression Ignition (GDCI) has demonstrated good potential for high fuel efficiency, low NOx, and low PM over the speed-load range using RON91 gasoline. In the current work, a four-cylinder, 1.8L engine was designed and built based on extensive simulations and single-cylinder engine tests. The engine features a pent roof combustion chamber, central-mounted injector, 15:1 compression ratio, and zero swirl and squish. A new piston was developed and matched with the injection system. The fuel injection, valvetrain, and boost systems were key technology enablers. Engine dynamometer tests were conducted at idle, part-load, and full-load operating conditions. For all operating conditions, the engine was operated with partially premixed compression ignition without mode switching or diffusion controlled combustion. At idle and low load, rebreathing of hot exhaust gases provided stable combustion with NOx and PM emissions below targets of 0.2g/kWh and FSN 0.1, respectively. The coefficient of variation of IMEP was less than 3 percent and the exhaust temperature at turbocharger inlet was greater than 250 C. BSFC of 280 g/kWh was measured at 2000 rpm-2bar BMEP. At medium-to-higher loads, rebreathing was not used and cooled EGR provided NOx, PM, and combustion noise below targets. MAP was reduced to minimize boost parasitics. At full load operating conditions, near stoichiometric mixtures were used with up to 45 percent EGR. Maximum BMEP was about 20 bar at 3000 rpm. For all operating conditions, injection quantities and timings were used to control mixture stratificaton and combustion phasing. Transient co-simulations of the engine system were conducted to develop control strategies for boost, EGR, and intake air temperature control. Preliminary transient tests on a real engine with high rate of load increase demonstrated potential for very good control. Cold start simulations were also conducted using an intake air heating strategy. Preliminary cold start tests on a real engine at room temperature demonstrated potential for very good cold starting. More work is needed to calibrate the engine over the full operating map and to further develop the engine control system. CITATION: Sellnau, M., Foster, M., Hoyer, K., Moore, W. et al., \"Development of a Gasoline Direct Injection Compression Ignition (GDCI) Engine,\" SAE Int. J. Engines 7(2):2014, doi:10.4271/2014-01-1300. 2014-01-1300 Published 04/01/2014 Copyright © 2014 SAE International doi:10.4271/2014-01-1300 saeeng.saejournals.org developed with significant improvements. Delphi [23, 24, 25, 26, 27] reported single-cylinder and multi-cylinder engine test results with various injectors using single, double, and triple injection strategies. Engine tests have also been performed using naphtha fuels on both modified spark-ignited engines [28] and modified diesel engines [29]. Naphtha has significantly lower octane number (RON 70 to 84) and significantly lower processing cost compared to current market gasoline. This work has shown compatibility of the PPCI combustion process with lower octane fuels in a longer term perspective. PPCI has demonstrated very good potential for very high fuel efficiency with low engine-out NOx and PM emissions using a range of gasoline-like fuels. However, towards a production solution, significant issues remain. Due to the lower exhaust enthalpy of low temperature engines using PPCI, it is difficult to produce intake boost with acceptable boost system parasitics. A practical powertrain system with robust PPCI combustion is needed, including injection, valvetrain, boost, and exhaust subsystems. The engine must also meet vehicle packaging requirements under hood and satisfy cold start and transient response requirements. As part of a US Department of Energy funded program, Delphi has been developing a multi-cylinder engine concept for PPCI combustion with current US market gasoline (RON91). The engine has four cylinders with a 1.8L displacement and was designed based on extensive simulations and single-cylinder engine tests. A multiple-late-injection (MLI) strategy with GDi-like injection pressures was selected without use of a premixed charge. The absence of classic knock and preignition limits in this process enabled a higher compression ratio of 15. The engine operates “full time” [25] over the entire operating map with partially premixed compression ignition. No combustion mode switching, diffusion controlled combustion, or spark plugs were used. Delphi uses the term Gasoline Direction Injection Compression Ignition (GDCI) in reference to this combustion process. One program objective was to build a practical GDCI engine that achieves diesel-like fuel efficiency using current market gasoline (RON91) with engine-out NOx and PM emissions below that needed for NOx or PM aftertreatment. Table 1 lists initial targets for engine testing and development. Combustion noise level (CNL) limits are shown in Figure 1. Other program objectives include demonstration of good transient load response and room temperature cold starts. In the current work, analysis and simulation tools were used to design and fabricate a new multi-cylinder GDCI engine. Design tools were used to package the powertrain in a D-class vehicle. Engine dynamometer tests were conducted over a range of operating conditions and included preliminary calibration mapping. With this data, a competitive assessment of brake specific fuel consumption (BSFC) was performed using published data for gasoline, diesel, and hybrid vehicle engines. Finally, aggressive transients with high rate of load increase were simulated and then tested on the real engine. Cold starts at various ambient temperatures were also simulated and tested on the real engine. Table 1. Preliminary Targets for Engine Testing. Figure 1. Combustion Noise Level (CNL) Limits used for Testing. GDCI CONCEPT AND INJECTION STRATEGY The GDCI engine concept combines the best of diesel and spark-ignited engine technology. Like diesel engines, the compression ratio is high, there is no intake throttling, and the mixture is lean for improved ratio of specific heats. GDCI uses a new low-temperature combustion process for partiallypremixed compression-ignition. Multiple-late-injections of gasoline (RON91) vaporize and mix very quickly at low injection pressure typical of direct injected gasoline engines. Low combustion temperatures combined with low mixture motion and reduced chamber surface area result in reduced heat losses. A schematic of the GDCI combustion chamber concept is shown in Figure 2. The engine features a shallow pent roof combustion chamber, central-mounted injector, and 15:1 compression ratio. A quiescent, open chamber design was chosen to support injection-controlled mixture stratification. Swirl, tumble, and squish were minimized since excessive mixture motion may destroy mixture stratification created during the injection process. The piston and bowl shape were matched with the injection system and spray characteristics. The bowl is a symmetrical shape and was centered on the cylinder and injector axes. The GDCI injection strategy is central to the overall GDCI concept and is depicted in the Phi-T (equivalence ratiotemperature) diagram shown in Figure 3. The color contours in Figure 3 show simulated CO emissions concentration. The injection process involves one, two, or three injections during Sellnau et al / SAE Int. J. Engines / Volume 7, Issue 2 (July 2014)

A Multicomponent Blend as a Diesel Fuel Surrogate for Compression Ignition Engine Applications

Abstract: A mixture of n-dodecane and m-xylene is investigated as a diesel fuel surrogate for compression ignition engine applications. Compared to neat n-dodecane, this binary mixture is more representative of diesel fuel because it contains an alkyl-benzene which represents an important chemical class present in diesel fuels. A detailed multi-component mechanism for n-dodecane and m-xylene was developed by combining a previously developed n-dodecane mechanism with a recently developed mechanism for xylenes. The xylene mechanism is shown to reproduce experimental ignition data from a rapid compression machine and shock tube, speciation data from the jet stirred reactor and flame speed data. This combined mechanism was validated by comparing predictions from the model with experimental data for ignition in shock tubes and for reactivity in a flow reactor. The combined mechanism, consisting of 2885 species and 11754 reactions, was reduced to a skeletal mechanism consisting 163 species and 887 reactions for 3D diesel engine simulations. The mechanism reduction was performed using directed relation graph (DRG) with expert knowledge (DRG-X) and DRG-aided sensitivity analysis (DRGASA) at a fixed fuel composition of 77% of n-dodecane and 23% m-xylene by volume. The sample space for the reduction covered pressure of 1 – 80 bar, equivalence ratiomore » of 0.5 – 2.0, and initial temperature of 700 – 1600 K for ignition. The skeletal mechanism was compared with the detailed mechanism for ignition and flow reactor predictions. Finally, the skeletal mechanism was validated against a spray flame dataset under diesel engine conditions documented on the Engine Combustion Network (ECN) website. These multi-dimensional simulations were performed using a Representative Interactive Flame (RIF) turbulent combustion model. Encouraging results were obtained compared to the experiments with regards to the predictions of ignition delay and lift-off length at different ambient temperatures.« less

Effects of compression ratio, swirl augmentation techniques and ethanol addition on the combustion of CNG-biodiesel in a dual-fuel engine

Abstract: The diminishing resources and continuously increasing cost of petroleum in association with their alarming pollution levels from diesel engines has led to an interest in finding alternative fuels to diesel. Emission control and engine efficiency are two of the most important parameters in current engine design. The impending introduction of emission standards such as Euro IV and Euro V has forced research towards developing new technologies for combating engine emissions. This paper examines the effects of compression ratio, swirl augmentation techniques and ethanol addition on the combustion of compressed natural gas (CNG) blended with Honge oil methyl esters (HOME) in a dual fuel engine. The present results show that the combustion of HOME and 15% ethanol blend with CNG induction in a dual-fuel engine operated in optimized parameters at an injection timing of 27° Before Top Dead Centre and a compression ratio of 17.5 resulted in acceptable combustion emissions and improved brake thermal efficiencies. Th...

Combustion and Emissions Characteristics of Valeric Biofuels in a Compression Ignition Engine

Abstract: New-generation biofuels are mainly produced from nonfood crops or waste. Although second-generation ethanol is one of the main options, valeric esters can also be produced from lignocellulose through levulinic acid. However, only few experimental results are available to characterize their combustion behavior. Using a traditional compression ignition (CI) engine converted to monocylinder operation, the engine performances and emissions of butyl and pentyl valerate (BV and PenV, respectively) were investigated. This paper analyses the experimental results for blends of 20%vol of esters in diesel fuel, taking diesel fuel as the reference fuel. The BV and PenV have a smaller cetane number and consequently the ignition delay of the blends is slightly longer. However, engine performances and emissions are not significantly modified by adding 20%vol of esters to diesel fuel. The BV and PenV then represent very good alternative biofuels for CI engines.

Performance Analysis of the Vehicle Diesel Engine-ORC Combined System Based on a Screw Expander

Abstract: To achieve energy saving and emission reduction for vehicle diesel engines, the organic Rankine cycle (ORC) was employed to recover waste heat from vehicle diesel engines, R245fa was used as ORC working fluid, and the resulting vehicle diesel engine-ORC combined system was presented. The variation law of engine exhaust energy rate under various operating conditions was obtained, and the running performances of the screw expander were introduced. Based on thermodynamic models and theoretical calculations, the running performance of the vehicle diesel engine-ORC combined system was analyzed under various engine operating condition scenarios. Four evaluation indexes were defined: engine thermal efficiency increasing ratio (ETEIR), waste heat recovery efficiency (WHRE), brake specific fuel consumption (BSFC) of the combined system, and improvement ratio of BSFC (IRBSFC). Results showed that when the diesel engine speed is 2200 r/min and diesel engine torque is 1200 N·m, the power output of the combined system reaches its maximum of approximately 308.6 kW, which is 28.6 kW higher than that of the diesel engine. ETEIR, WHRE, and IRBSFC all reach their maxima at 10.25%, 9.90%, and 9.30%, respectively. Compared with that of the diesel engine, the BSFC of the combined system is obviously improved under various engine operating conditions.