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Isobaric Combustion at a Low Compression Ratio

King Abdullah University of Science & Technology-Aibolat Dyuisenakhmetov, Harsh Goyal, Moez Ben Houidi, Rafig Babayev, Bengt Johansson
Saudi Aramco-Jihad Badra
  • Technical Paper
  • 2020-01-0797
To be published on 2020-04-14 by SAE International in United States
In a previous study, it was shown that isobaric combustion cycle, achieved by multiple injection strategy, is more favorable than conventional diesel cycle for the double compression expansion engine (DCEE) concept. In spite of lower effective expansion ratio, the indicated efficiencies of isobaric cycles were approximately equal to those of a conventional diesel cycle. Isobaric cycles had lower heat transfer losses and higher exhaust losses which are advantageous for DCEE since additional exhaust energy can be converted into useful work in the expander. In this study, the performance of low-pressure isobaric combustion (IsoL) and high-pressure isobaric combustion (IsoH) in terms of gross indicated efficiency, energy flow distribution and engine-out emissions is compared to the conventional diesel combustion (CDC) but at a relatively lower compression ratio of 11.5. The experiments are conducted in a Volvo D13C500 single-cylinder heavy-duty engine using standard EU diesel fuel. The current study consists of two sets of experiments. In the first set, the effect of exhaust gas recirculation (EGR) is studied at different combustion modes using the same air-fuel ratio obtained…
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Effect of Pre-Chamber Enrichment on Lean Burn Pre-Chamber Spark Ignition Combustion Concept with a Narrow-Throat Geometry

King Abdullah University of Science & Technology-Ponnya Hlaing, Manuel Echeverri Marquez, Eshan Singh, Fahad Almatrafi, Moez Ben Houidi, Bengt Johansson
Saudi Aramco-Emre Cenker
  • Technical Paper
  • 2020-01-0825
To be published on 2020-04-14 by SAE International in United States
Pre-chamber spark ignition (PCSI) combustion is an emerging lean-burn combustion mode capable of extending the lean operation limit of an engine. The favorable characteristic of short combustion duration at the lean condition of PCSI results in high efficiencies compared to conventional spark ignition combustion. Since the engine operation is typically lean, PCSI can significantly reduce engine-out NOx emissions while maintaining short combustion durations. In this study, experiments were conducted on a heavy-duty engine at lean conditions at mid to low load. Two major studies were performed. In the first study, the total fuel energy input to the engine was fixed while the intake pressure was varied, resulting in varying the global excess air ratio. In the second study, the intake pressure was fixed while the amount of fuel was changed to alter the global excess air ratio. At each global excess air ratio, the fuel injection to the pre-chamber was varied parametrically to assess the effect of pre-chamber enrichment on engine operating characteristics. Multi-chamber heat release analysis was performed to present the pre-chamber and main…
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Optical Diagnostics of Isooctane and n-Heptane Isobaric Combustion

King Abdullah University of Science & Technology-Abdullah S. Al Ramadan, Gustav Nyrenstedt, Moez Ben Houidi, Bengt Johansson
  • Technical Paper
  • 2020-01-1126
To be published on 2020-04-14 by SAE International in United States
Isobaric combustion has demonstrated a great potential to reach high thermodynamic efficiency in the advanced Double Compression Expansion Engine (DCEE) concept. It appears as one of few viable choices for applications with high-pressure combustion. At these conditions, releasing heat at a constant pressure minimizes the peak in-cylinder pressure and, hence, mitigates excessive mechanical stress on the engine. This study focuses on the effect of fuels on the multiple-injection isobaric combustion. A single-cylinder heavy-duty engine was utilized to test and compare the isobaric combustion with pure isooctane and n-heptane fuels. The engine was equipped with an optical piston to allow a bottom-view of the combustion chamber. The interactions of multiple injections and the combustion behavior were studied using high-speed acquisition of chemiluminescence. The examined isobaric cases have a peak pressure of 70 bar. For cases with high soot luminosity, a short band-pass filter was used to avoid image saturation. Fuels with short ignition delay time such as n-heptane are usually used for isobaric applications as they offer good controllability of injections. However, the study herein demonstrates…
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Isobaric Combustion for High Efficiency in an Optical Diesel Engine

King Abdullah University of Science & Technology-Gustav Nyrenstedt, Abdullah Al Ramadan, Qinglong Tang, Moez Ben Houidi, Bengt Johansson
Saudi Aramco-Jihad Badra, Emre Cenker
  • Technical Paper
  • 2020-01-0301
To be published on 2020-04-14 by SAE International in United States
Isobaric combustion has been proven a promising strategy for high efficiency as well as low nitrogen oxides emissions, particularly in heavy-duty Diesel engines. Previous single-cylinder research engine experiments have, however, shown high soot levels when operating isobaric combustion. The combustion itself and the emissions formation with this combustion mode are not well understood due to the complexity of multiple injections strategy. Therefore, experiments with an equivalent heavy-duty Diesel optical engine were performed in this study. Three different cases were compared, an isochoric heat release case and two isobaric heat release cases. One of the isobaric cases was boosted to reach the maximum in-cylinder pressure of the isochoric one. The second isobaric case kept the same boost levels as the isochoric case. Results showed that in the isobaric cases, liquid fuel was injected into burning gases. This resulted in shorter ignition delays and thus a poor mixing level. The lack of fuel/air mixing was clearly the main contributor to the high soot emissions observed in isobaric combustion. The lower heat losses of the isobaric strategy were…
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Optical Study on the Fuel Spray Characteristics of the Four-Consecutive-Injections Strategy Used in High-Pressure Isobaric Combustion

King Abdullah University of Science & Technology-Qinglong Tang, Ramgopal Sampath, Priybrat Sharma, Gustav Nyrenstedt, Abdullah Al Ramadan, Moez Ben Houidi, Bengt Johansson, Gaetano Magnotti
Saudi Aramco-Jihad Badra
  • Technical Paper
  • 2020-01-1129
To be published on 2020-04-14 by SAE International in United States
High-pressure isobaric combustion used in the double compression expansion engine (DCEE) concept was proposed to obtain higher engine brake thermal efficiency than the conventional diesel engine. Experiments on the metal engines showed that four consecutive injections delivered by a single injector can achieve isobaric combustion. Improved understanding of the detailed fuel-air mixing with multiple consecutive injections is needed to optimize the isobaric combustion and reduce engine emissions. In this study, we explored the fuel spray characteristics of the four-consecutive-injections strategy using high-speed imaging with background illumination and fuel-tracer planar laser-induced fluorescence (PLIF) imaging in a heavy-duty optical engine under non-reactive conditions. Toluene of 2% by volume was added to the n-heptane and served as the tracer. The fourth harmonic of a 10 Hz Nd:YAG laser was applied for the excitation of toluene. The PLIF image distortion caused by the side window curvature and the optical piston was mitigated using a correction lens and corrected with a grid mapping technique. The effects of hydraulic delay and injection dwell on the in-cylinder liquid-phase fuel penetration and vapor-phase…
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In Situ Injection Rate Measurement to Study Single and Split Injections in a Heavy-Duty Diesel Engine

King Abdullah University of Science & Te-Bassam S. E. Aljohani, Moez Ben Houidi, Rafig Babayev, Khalid Aljohani, Bengt Johansson
Published 2019-09-09 by SAE International in United States
The split injection strategy holds a potential for high pressure combustion engines. One advantage of such strategy is the capability to control the heat release rate, which also implies the use of multiple split-injections with relatively short dwell intervals. Most injection rate measurement techniques require installment of the injector on a dedicated test rig. However, these techniques fail to accurately reproduce real-engine operating conditions. Using the spray impingement method, this paper investigates the injection rate of a high flow-rate solenoid injector while being operated on the engine. The aim is to have an experimental configuration as similar as possible to the real engine in terms of the acoustics and the fuel temperature within the injection system. The assumption of spray force proportional to the spray momentum is used here to measure the injection rate. The spray momentum is measured while the injector is mounted on the Volvo D13 engine and connected to the in-series fuel rail and pump. A high-natural-frequency piezoelectric pressure transducer is mounted perpendicularly at 4 mm from one of the nozzle holes.…
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A Study of Lean Burn Pre-Chamber Concept in a Heavy Duty Engine

King Abdullah Univ of Science & Tech-Ponnya Hlaing, Manuel Echeverri Marquez, Vijai Shankar Bhavani Shankar, Moez Ben Houidi, Bengt Johansson
Saudi Aramco-Emre Cenker
Published 2019-09-09 by SAE International in United States
Due to stringent emission standards, the demand for higher efficiency engines has been unprecedentedly high in recent years. Among several existing combustion modes, pre-chamber spark ignition (PCSI) emerges to be a potential candidate for high-efficiency engines. Research on the pre-chamber concept exhibit higher indicated efficiency through lean limit extension while maintaining the combustion stability. In this study, a unique pre-chamber geometry was tested in a single-cylinder heavy-duty engine at low load lean conditions. The geometry features a narrow throat, which was designed to be packaged inside a commercial diesel injector pocket. The pre-chamber was fueled with methane while the main chamber was supplied with an ethanol/air mixture. The ‘avalanche activated combustion’ or L.A.G. process was explored which relies on enriched pre-chamber combustion to generate radicals which, upon being discharged into the main combustion chamber, will trigger ignition sites distributed in the combustion chamber, thus achieving fast combustion. The ability of PCSI concept to enhance the lean limit with progressive enrichment in the pre-chamber was demonstrated. In addition, passive pre-chamber concept, where no additional fuel was…
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Compression Ratio and Intake Air Temperature Effect on the Fuel Flexibility of Compression Ignition Engine

King Abdullah Univ of Science & Tech.-Abdullah S. AlRamadan, Moez Ben Houidi, Bassam S. E. Aljohani, Hassan Eid, Bengt Johansson
Published 2019-09-09 by SAE International in United States
The effect of compression ratio (CR) and intake air temperature on the combustion characteristics of fuels with different octane ratings were investigated on a single-cylinder heavy duty engine. The study focused on Primary Reference Fuels (PRFs) and commercial grade diesel with octane numbers ranging from 0 to 100. The engine was configured at a CR of 11.5:1, which is lower than typical heavy-duty compression ignition CI engines. This aims to compare the fuels’ burning regime with recently reported measurements at CR17:1. Experiments were performed at different intake air temperatures of 20 to 80 °C and net indicated mean effective pressure (IMEPNet) of 5 to 20 bar. The injection rates have been characterized to determine the hydraulic delay of the injector and thus define the actual ignition delay time. At low loads, diesel-like fuels were found to burn in partially premixed combustion (PPC) mode whereas high octane fuels did not ignite. At high loads, fuels combustion becomes diffusion driven regardless of their RON or MON values. The effect of intake air temperature on the combustion characteristics…
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Isobaric Combustion: A Potential Path to High Efficiency, in Combination with the Double Compression Expansion Engine (DCEE) Concept

King Abdullah University of Science & Technology-Rafig Babayev, Moez Ben Houidi, Bengt Johansson
Volvo Global Truck Tech Powertrain Engineering-Arne Andersson
Published 2019-01-15 by SAE International in United States
The efficiency of an internal combustion engine is highly dependent on the peak pressure at which the engine operates. A new compound engine concept, the double compression expansion engine (DCEE), utilizes a two-stage compression and expansion cycle to reach ultrahigh efficiencies. This engine takes advantage of its high-integrity structure, which is adapted to high pressures, and the peak motored pressure reaches up to 300 bar. However, this makes the use of conventional combustion cycles, such as the Seiliger-Sabathe (mixed) or Otto (isochoric) cycles, not feasible as they involve a further pressure rise due to combustion. This study investigates the concept of isobaric combustion at relatively high peak pressures and compares this concept with traditional diesel combustion cycles in terms of efficiency and emissions. Multiple consecutive injections through a single injector are used for controlling the heat release rate profile to achieve isobaric heat addition. In this study, the intake pressure is varied to enable a comparison between the isobaric cases with different peak pressures, up to 150 bar, and the mixed cycle cases. Tests are…
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