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Viewing 1 to 30 of 87
Technical Paper
2012-04-16
Chandrasekharan Jayakumar, Ziliang Zheng, Umashankar Joshi, Walter Bryzik, Naeim Henein, Eric Sattler
This paper investigates the effect of boost pressure and intake temperature on the auto-ignition of fuels with a wide range of properties. The fuels used in this investigation are ULSD (CN 45), FT-SPK (CN 61) and two blends of JP-8 (with CN 25 and 49). Detailed analysis of in-cylinder pressure and rate of heat release traces are made to correlate the effect of intake pressure and injection strategy on the events immediately following start of injection leading to combustion. A CFD model is applied to track the effect of intake pressure and injection strategy on the formation of different chemical species and study their role and contribution in the auto-ignition reactions. Results from a previous investigation on the effect of intake temperature on auto-ignition of these fuels are compared with the results of this investigation.
Technical Paper
2012-04-01
Tamer Badawy, Naeim Henein, Walter Bryzik
Signals indicative of in-cylinder combustion have been under investigation for the control of diesel engines to meet stringent emission standards and other production targets in performance and fuel economy. This paper presents the results of an investigation on the use of the ion current signal for the close loop control of a heavy duty four cylinder turbocharged diesel engine equipped with a common rail injection system. A correlation is developed between the start of ion current signal (SIC) and the location of the peak of premixed combustion (LPPC) in the rate of heat release trace. Based on this correlation, a PID closed loop controller is developed to adjust the injection timing for proper combustion phasing under steady and transient engine operating conditions.
Technical Paper
2011-04-12
Mufaddel Dahodwala, Vinay Nagaraju, Kaushik Acharya, Walter Bryzik, Naeim Henein
The use of biodiesel and its blends with ultra low sulfur diesel (ULSD) is gaining significant importance due to its ability to burn in conventional diesel engines with minor modifications. However the chemical and physical properties of biodiesel are different compared to the conventional ULSD. These differences directly impact the injection, spray formation, auto ignition and combustion processes which in turn affect the engine-out emissions. To understand the effect of fueling with B-20, tests were conducted on a single cylinder 0.42L direct injection research diesel engine. The engine is equipped with a common rail injection system, variable EGR and swirl control systems and was operated at a constant engine speed of 1500 rpm and 3 bar IMEP to simulated turbocharged conditions. Injection timing and duration were adjusted with B-20 at different locations of peak premixed combustions (LPPC) and two different swirl ratios to achieve 3 bar IMEP. ULSD was then injected using the same injection strategy as developed for B-20.
Technical Paper
2010-04-12
Anubhav Sinha, Chandrasekharan J., Jagdish Nargunde, Walter Bryzik, Kaushik Acharya, Naeim Henein
The effect of biodiesel on the Particulate emissions is gaining significant attention particularly with the drive for the use of alternative fuels. The particulate matter (PM), especially having a diameter less than 50 nm called the Nanoparticles or Nucleation mode particles (NMPs), has been raising concerns about its effect on human health. To better understand the effect of biodiesel and its blends on particulate emissions, steady state tests were conducted on a small-bore single-cylinder high-speed direct-injection research diesel engine. The engine was fueled with Ultra-Low Sulfur Diesel (ULSD or B-00), a blend of 20% soy-derived biodiesel and 80% ULSD on volumetric basis (B-20), B-40, B-60, B-80 and 100% soy-derived biodiesel (B-100), equipped with a common rail injection system, EGR and swirl control systems at a load of 5 bar IMEP and constant engine speed of 1500 rpm. The exhaust sampling was done using a Dekati Fine Particle Sampler (FPS) and the exhaust was diluted to a ratio of 35(±2): 1 and the dilution temperature was maintained around 200°C(±10).
Technical Paper
2010-04-12
Jagdish Nargunde, Chandrasekharan Jayakumar, Anubhav Sinha, Kaushik Acharya, Walter Bryzik, Naeim Henein
JP-8 is an aviation turbine engine fuel recently introduced for use in military ground vehicle applications and generators which are mostly powered by diesel engines. Many of these engines are designed and developed for commercial use and need to be adapted for military applications. This requires more understanding of the auto- ignition and combustion characteristics of JP-8 under different engine operating conditions. This paper presents the results of a comparative analysis of an engine operation using JP-8 and ultra low sulfur diesel fuel (ULSD). Experiments were conducted on 0.42 liter single cylinder, high speed direct injection (HSDI) diesel engine equipped with a common rail injection system. The results indicate that the distillation properties of fuel have an effect on its vaporization rate. JP-8 evaporated faster and had shorter ignition delay as compared to ULSD. The fuel economy with JP-8 was better than ULSD. The gaseous emission components such as unburned Hydrocarbons (HC), Carbon monoxide (CO) reduced with JP-8 suggesting improved combustion quality.
Technical Paper
2010-04-12
Naeim A. Henein, Walter Bryzik, Ahmed Abdel-Rehim, Ashish Gupta
Ion current sensors have been considered for the feedback electronic control of gasoline and diesel engines and for onboard vehicles powered by both engines, while operating on their conventional cycles or on the HCCI mode. The characteristics of the ion current signal depend on the progression of the combustion process and the properties of the combustion products in each engine. There are large differences in the properties of the combustible mixture, ignition process and combustion in both engines, when they operate on their conventional cycles. In SI engines, the charge is homogeneous with an equivalence ratio close to unity, ignition is initiated by an electric spark and combustion is through a flame propagating from the spark plug into the rest of the charge. In diesel engines, the charge is heterogeneous with equivalence ratios that vary from zero to infinity, gas pressures are much higher than the pressures in gasoline engines, autoignition starts the combustion process in a premixed charge followed by combustion controlled by mixing and diffusion processes.
Technical Paper
2009-11-02
Marcis Jansons, Kan Zha, Radu Florea, Dinu Taraza, Naeim Henein, Walter Bryzik
Fuel wall impingement commonly occurs in small-bore diesel engines. Particularly during engine starting, when wall temperatures are low, the evaporation rate of fuel film remaining from previous cycles plays a significant role in the autoignition process that is not fully understood. Pre-injection chemiluminescence (PIC), resulting from low-temperature oxidation of evaporating fuel film and residual gases, was measured over 3200 μsec intervals at the end of the compression strokes, but prior to fuel injection during a series of starting sequences in an optical diesel engine. These experiments were conducted to determine the effect of this parameter on combustion phasing and were conducted at initial engine temperatures of 30, 40, 50 and 60°C, at swirl ratios of 2.0 and 4.5 at 1000 RPM. PIC was determined to increase and be highly correlated with combustion phasing during initial cycles of the starting sequence. This suggests that under starting conditions, combustion phasing is determined by wall film evaporation rates and residual concentrations rather than the fuel injection event.
Technical Paper
2009-04-20
Kaushik Acharya, Mufaddel Dahodwala, Walter Bryzik, Naeim Henein, Nathan Sova
The effects of different blends of Soybean Methyl Ester (biodiesel) and ultra low sulfur diesel (ULSD) fuel: B-00 (ULSD), B-20, B-40, B-60, B-80 and B-100 (biodiesel); on autoignition, combustion, performance, and engine out emissions of different species including particulate matter (PM) in the exhaust, were investigated in a single-cylinder, high speed direct injection (HSDI) diesel engine equipped with a common rail injection system. The engine was operated at 1500 rpm under simulated turbocharged conditions at 5 bar IMEP load with varied injection pressures at a medium swirl of 3.77 w ithout EGR. Analysis of test results was done to determine the role of biodiesel percentage in the fuel blend on the basic thermodynamic and combustion processes under fuel injection pressures ranging from 600 bar to 1200 bar. The effects of increasing the biodiesel percentage in the fuel blend on autoignition, rate of heat release, fuel economy and emission of total unburned hydrocarbon (THC), oxides of nitrogen (NOx), carbon monoxide (CO) and particulate matter (PM) are determined.
Technical Paper
2009-04-20
Marcis Jansons, Radu Florea, Kan Zha, Fadi Estefanous, Elena Florea, Dinu Taraza, Walter Bryzik, Naeim Henein, Laura Hoogterp
Ultraviolet chemiluminescence has been observed in a diesel engine cyclinder during compression, but prior to fuel injection under engine starting conditions. During a portion of the warm-up sequence, the intensity of this emission exhibits a strong correlation to the phasing of the subsequent combustion. Engine exhaust measurements taken from a continuously misfiring, motored engine confirm the generation of formaldehyde (HCHO) in such processes. Fractions of this compound are expected to be recycled as residual to participate in the following combustion cycle. Spectral measurements taken during the compression period prior to fuel injection match the features of Emeleus' cool flame HCHO bands that have been observed during low temperature heat release reactions occurring in lean HCCI combustion. That the signal from the OH* bands is weak implies a buildup of HCHO during compression. To investigate the combined effects of wall temperature, equivalence ratio and HCHO concentration on combustion phasing, a two-zone CFD-kinetics model was employed utilizing the second version of the Lawrence Livermore National Laboratory detailed n-heptane mechanism [1,2].
Technical Paper
2008-04-14
Radu Florea, Dinu Taraza, Naeim A. Henein, Walter Bryzik
EGR is a proven technology used to reduce NOx formation in both compression and spark ignition engines by reducing the combustion temperature. In order to further increase its efficiency the recirculated gases are subjected to cooling. However, this leads to a higher load on the cooling system of the engine, thus requiring a larger radiator. In the case of turbocharged engines the large variations of the pressures, especially in the exhaust manifold, produce a highly pulsating EGR flow leading to non-steady-state heat transfer in the cooler. The current research presents a method of determining the pulsating flow field and the instantaneous heat transfer in the EGR heat exchanger. The processes are simulated using the CFD code FIRE (AVL) and the results are subjected to validation by comparison with the experimental data obtained on a 2.5 liter, four cylinder, common rail and turbocharged diesel engine.
Technical Paper
2008-04-14
Krishna C. Natti, Naeim A. Henein, Yusuf Poonawala, Walter Bryzik
Several mechanisms are discussed to understand the particulate matter (PM) characterization in a high speed, direct injection, single cylinder diesel engine using low sulfur diesel fuel. This includes their formation, size distribution and number density. Experiments were conducted over a wide range of injection pressures, EGR rates, injection timings and swirl ratios, therefore covering both conventional and low temperature combustion regimes. A micro dilution tunnel was used to immediately dilute a small part of the exhaust gases by hot air. A Scanning Mobility Particle Sizer (SMPS) was used to measure the particulate size distribution and number density. Particulate mass was measured with a Tapered Element Oscillating Microbalance (TEOM). Analysis was made of the root cause of PM characterization and their relationship with the combustion process under different operating conditions. PM increased with an increase in EGR in conventional combustion regime and decreased with increase in EGR under the Low Temperature Combustion (LTC) regime.
Technical Paper
2008-04-14
Marcis Jansons, Amandeep Brar, Fadi Estefanous, Radu Florea, Dinu Taraza, Naeim Henein, Walter Bryzik
This paper presents an experimental investigation conducted to determine the parameters that control the behavior of autoignition in a small-bore, single-cylinder, optically-accessible diesel engine. Depending on operating conditions, three types of autoignition are observed: a single ignition, a two-stage process where a low temperature heat release (LTHR) or cool flame precedes the main premixed combustion, and a two-stage process where the LTHR or cool flame is separated from the main heat release by an apparent negative temperature coefficient (NTC) region. Experiments were conducted using commercial grade low-sulfur diesel fuel with a common-rail injection system. An intensified CCD camera was used for ultraviolet imaging and spectroscopy of chemiluminescent autoignition reactions under various operating conditions including fuel injection pressures, engine temperatures and equivalence ratios. The chemiluminescent spectra were measured to confirm the presence of excited-state formaldehyde, (HCHO*), CH* and OH*, the spatial distribution of which were subsequently observed during the ignition period by filtered imaging.
Technical Paper
2007-04-16
Krishna C. Natti, Anamitra Bhattacharyya, Aditya Kastury, Naeim A. Henein, Walter Bryzik
Several mechanisms are discussed to understand the formation of both regulated and unregulated emissions in a high speed, direct injection, single cylinder diesel engine using low sulphur diesel fuel. Experiments were conducted over a wide range of injection pressures, EGR rates, injection timings and swirl ratios. The regulated emissions were measured by the standard emission equipment. Unregulated emissions such as aldehydes and ketones were measured by high pressure liquid chromatography and hydrocarbon speciation by gas chromatography. Particulate mass was measured with a Tapered Element Oscillating Microbalance (TEOM). Analysis was made of the sources of different emission species and their relationship with the combustion process under the different operating conditions. Special attention is given to the low temperature combustion (LTC) regime which is known to reduce both NOx and soot. However the HC, CO and unregulated emissions increased at a higher rate.
Technical Paper
2007-04-16
Lurun Zhong, Steve Gruenewald, Naeim A. Henein, Walter Bryzik
One of the most challenging problems in diesel engines is to reduce unburned HC emissions that appear as (white smoke) during cold starting. In this paper the research is carried out on a 4-cylinder diesel engine with a common rail fuel injection system, which is able to deliver multiple injections during cold start. The causes of combustion failure at lower temperature limits are investigated theoretically by considering the rate of heat release. The results of this clearly indicate that in addition to low cranking engine speed, heat transfer and blow-by losses at lower ambient temperatures, fuel injection events would contribute to the failure of combustion. Also, combustion failure takes place when the compression temperature is lower than some critical value. Based on these results, split-main injection strategy was applied during engine cold starting and validated by experiments in a cold room at lower ambient temperatures.
Technical Paper
2007-04-16
Philipe Saad, Lloyd Kamo, Milad Mekari, Walter Bryzik, Victor Wong, Nicolas Dmitrichenko, Rudolf Mnatsakanov
This paper presents tribological modeling, experimental work, and validation of tribology parameters of a single cylinder turbocharged diesel engine run at various loads, speeds, intake boost pressures, and cylinder liner temperatures. Analysis were made on piston rings and liner materials, rings mechanical and thermal loads, contact pressure between rings and liner, and lubricant conditions. The engine tribology parameters were measured, and used to validate the engine tribology models. These tribology parameters are: oil film thickness, coefficient of friction between rings and liner, friction force, friction power, friction torque, shear rate, shear stress and wear of the sliding surfaces. In order to measure the oil film thickness between rings and liner, a single cylinder AVL turbocharged diesel engine was instrumented to accept the difference in voltage drop method between rings, oil film, and liner. The oil film thickness was measured between top piston ring, second piston ring and oil ring along the engine stroke from the bottom reversal to top reversal.
Technical Paper
2007-04-16
Dorsaf Saad, Philipe Saad, Lloyd Kamo, Milad Mekari, Walter Bryzik, Ernest Schwarz, John Tasdemir
Thermal barrier coatings (TBC) are perceived as enabling technology to increase low heat rejection (LHR) diesel engine performance and improve its longevity. The state of the art of thermal barrier coating is the plasma spray zirconia. In addition, other material systems have been investigated for the next generation of thermal barrier coatings. The purpose of this TBC program is to focus on developing binder systems with low thermal conductivity materials to improve the coating durability under high load and temperature cyclical conditions encountered in the real engine. Research and development (R&D) and analysis were conducted on aluminum alloy piston for high output turbocharged diesel engine coated with TBC.
Technical Paper
2007-04-16
Dinu Taraza, Naeim A. Henein, Radu Ceausu, Walter Bryzik
The simulation of I.C. Engines operation, especially during transients, requires a fairly accurate estimation of the internal mechanical losses of the engine. The paper presents generic friction models for the main friction components of the engine (piston-ring-liner assembly, bearings and valve train), considering geometry of the engine parts and peculiarities of the corresponding lubrication processes. Separate models for the mechanical losses introduced by the injection system, oil and water pumps are also developed. All models are implemented as SIMULINK modules in a complex engine simulation code developed in SIMULINK and capable to simulate both steady state and transient operating conditions. Validation is achieved by comparison with measurements made on a four cylinder, common rail diesel engine, on a test bench capable to run controlled transients.
Technical Paper
2007-04-16
Dongying Jiang, Yuanyuan Liu, Chang Qi, Zheng-Dong Ma, Basavaraju B. Raju, Walter Bryzik
An advanced design methodology is developed for innovative composite structure concepts which can be used in the Army's future ground vehicle systems to protect vehicle and occupants against various explosives. The multi-level and multi-scenario blast simulation and design system integrates three major technologies: a newly developed landmine-soil-composite interaction model; an advanced design methodology, called Function-Oriented Material Design (FOMD); and a novel patent-pending composite material concept, called BTR (Biomimetic Tendon-Reinforced) material. Example results include numerical simulation of a BTR composite under a blast event. The developed blast simulation and design system will enable the prediction, design, and prototyping of blast-protective composite structures for a wide range of damage scenarios in various blast events.
Technical Paper
2007-04-16
Lloyd Kamo, Philipe Saad, Dorsaf Saad, Walter Bryzik, Milad H. Mekari
Abstract Adiabatics, Inc., with the support of the U.S. Army Tank Automotive Research & Development Engineering Center (TARDEC) has developed a low cost, durable ceramic composite cylinder bore coating for diesel engines operating under severe conditions. This bore coating is a ceramic composite consisting primarily of Iron Oxide, Iron Titanate and Partially Stabilized Zirconia. It is applied by unique chemical thermal bonding technology developed at Adiabatics, Inc. and is referred to as Low Temperature Iron Titanate (LTIT). This coating has been tested against a wide range of cylinder bore treatments ranging from hard chrome plate to hard Nickel Silicon Carbide (NikaSil) and found to provide a superior sliding wear surface. It is superior because it is compatible against most common piston ring materials and coatings. As compared to other liner treatments, it displays superior running in or break in performance of the ring against the cylinder liner and yields significantly better wear rates under high wear extreme loading engine operating conditions.
Technical Paper
2007-04-16
Lurun Zhong, Naeim A. Henein, Walter Bryzik
A new tool has been used to arrive at appropriate split injection strategy for reducing the cranking period during the cold start of a multi-cylinder engine at decreasing ambient temperatures. The concept behind this tool is that the combination of different injection parameters that produce the highest IMEP should be able to improve the cold startability of the diesel engine. In this work the following injection parameters were considered: 1) injection timing, 2) split injection fraction, 3) dwell time and 4) total fuel mass injected per cycle. A commercial engine cyclic simulation code has been modified for diesel engine cycle simulation at lower ambient temperatures. The code was used to develop IMEP control maps. The maps were used to identify the parameters that would give the best IMEP. The strategies that have been identified have been validated experimentally in a multi-cylinder diesel engine equipped with a common rail fuel injection system. The simulation-based strategy proved to be very effective in improving cold start of the diesel engine at ambient temperature as low as -10°C.
Technical Paper
2006-04-03
Naeim A. Henein, I. P. Singh, Walter Bryzik
Advanced diesel engines developed for the commercial market need to be adapted to the military requirements by OPERAS (Optimizing the injection pressure P, the Exhaust gas recirculation E, injection events Retard and/or Advance and the swirl ratio S). The different after treatment devices, already used or expected to be applied to diesel engines, require feed gases of appropriate properties for their efficient operation. To produce these gases some OPERAS are needed to control the diesel combustion process. Since military vehicles do not need the after treatment devices, the OPERAS of the commercial engines should be modified to meet the military requirements for high power density, better fuel economy, reduction of parasitic losses caused by the cooled EGR system, and reduction of invisible black and white smoke in the field. The data for this paper were obtained from an experimental investigation conducted on a single cylinder diesel engine equipped with a common rail injection system, under different loads and speeds, covering a wide range of operating variables. 2-D and 3-D trade-off maps are developed to identity the OPERAS for the commercial engines, considering the type of the after treatment device used.
Technical Paper
2006-04-03
N. A. Henein, A. Bhattacharyya, J. Schipper, A. Kastury, Walter Bryzik
The fuel injection pressure and the swirl motion have a great impact on combustion in small bore HSDI diesel engines running on the conventional or advanced combustion concepts. This paper examines the effects of injection pressure and the swirl motion on engine-out emissions over a wide range of EGR rates. Experiments were conducted on a single cylinder, 4-valve, direct injection diesel engine equipped with a common rail injection system. The pressures and temperatures in the inlet and exhaust surge tanks were adjusted to simulate turbocharged engine conditions. The load and speed of the engine were typical to highway cruising operation of a light duty vehicle. The experiments covered a wide range of injection pressures, swirl ratios and injection timings. Engine-out emission measurements included hydrocarbons, carbon monoxide, smoke (in Bosch Smoke Units, BSU) and NOx. Exhaust Gas Recirculation (EGR) rates were varied to cover the engine operation from the conventional to the low temperature combustion regime, up to the misfiring point.
Technical Paper
2003-03-03
Lloyd Kamo, Philipe Saad, Rudolf Mnatsakanov, Walter Bryzik, Milad Mekari
Abstract Adiabatics, Inc. with the support of the U.S. Army Tank Automotive & Armaments Command has examined the feasibility of using Diamond Like Carbon (DLC) films and Iron Titanate (Fe2TiO5 or IT) for sliding contact surfaces in Low Heat Rejection (LHR) diesel engines. DLCs have long been a popular candidate for use in sliding contact tribo-surfaces where a perceived reduction of friction losses will result in increased engine efficiency [1]. There exists a broad range of technologies for applying DLC films. This paper examines several types of these technologies and their future application to automotive internal combustion engines. Our work focuses upon DLC use for LHR military diesel engines where operating temperatures and pressures are higher than conventional diesel engines. However, a direct transfer of this technology to automotive diesel or gasoline engines exists for these thin films. The work presented in this paper examines laboratory phenomena between different types of DLC films [2], and also their suitability for use in the internal combustion engine.
Technical Paper
2003-03-03
Mircea Teodorescu, Dinu Taraza, Naeim A. Henein, Walter Bryzik
The paper analyses the particularities of the lubricating conditions at the contact between the cam and a flat tappet in the valve train of an internal combustion engine and develops a method for the calculation of the friction force. The existing lubrication models show the predominance of the entraining speed and oil viscosity on the thickness of the oil film entrapped between cam and tappet, predicting a very small value (less than 0.1 μm) of the oil film thickness (OFT). The oil viscosity increases exponentially with pressure in the Hertzian contact, determining non-Newtonian behavior of the oil in the contact zone. Using the model developed by Greenwood and Tripp [11] for the contact of two rough surfaces and the Eyring model [2] for the oil it is shown that non-Newtonian behavior of the oil prevails and that the OFT plays a secondary role on the friction force. The simplified friction model developed according to these assumptions is experimentally validated by measurements made on a single cylinder diesel engine.
Technical Paper
2003-03-03
Inderpal Singh, Lurun Zhong, Ming-Chai Lai, Naeim A. Henein, Walter Bryzik
The combustion and emission characteristics of a high speed, small-bore, direct injection, single cylinder, diesel engine are investigated using two different nozzles, a 430-VCO (0.171mm) and a 320 Mini sac (0.131mm). The experiments were conducted at conditions that represent a key point in the operation of a diesel engine in an electric hybrid vehicle (1500 rpm and light load condition). The experiments covered fuel injection pressures ranging from 400 to 1000 bar and EGR ratios ranging from 0 to 50%. The effects of nozzle hole geometry on the ignition delay (ID), apparent rate of energy release (ARER, ARHR), NOx, Bosch smoke unit (BSU), CO and hydrocarbons are investigated. The results show that the 430 VCO produced longer ignition delays and cool flames of longer durations and higher intensities than its counterpart, the 320 mini sac nozzle, under all the operating conditions At zero EGR, the analysis of the data for the two nozzles showed the dependence of NOx on the premixed combustion fraction, and the dependence of smoke on the mixing controlled and diffusion controlled combustion fraction.
Technical Paper
2003-03-03
Hengqing Liu, N.A. Henein, Walter Bryzik
Diesel engine cold-start problems include long cranking periods, hesitation and white smoke emissions. A better understanding of these problems is essential to improve diesel engine cold-start. In this study computer simulation model is developed for the steady state and transient cold starting processes in a single-cylinder naturally aspirated direct injection diesel engine. The model is verified experimentally and utilized to determine the key parameters that affect the cranking period and combustion instability after the engine starts. The behavior of the fuel spray before and after it impinges on the combustion chamber walls was analyzed in each cycle during the cold-start operation. The analysis indicated that the accumulated fuel in combustion chamber has a major impact on engine cold starting through increasing engine compression pressure and temperature and increasing fuel vapor concentration in the combustion chamber during the ignition delay period. An “Autoignition Index” (AI) is introduced to determine the diesel engine first firing cycle.
Technical Paper
2002-03-04
Mircea Teodorescu, Dinu Taraza, Naeim A. Henein, Walter Bryzik
The paper analyses the friction in the valve train of an internal combustion engine trying to separate the contribution of the different components to the total friction losses in the valve train. The measurements are performed on a running engine in order to avoid extraneous factors introduced by simulating rigs. The experimental engine is instrumented with strain gauge bridges on the rocker arm, the push rod and the camshaft to measure forces and moments acting on these components. Original techniques are developed to isolate and determine the friction forces between the valve stem and its guide, the friction force in the rocker arm bearing and the combined friction between cam/tappet and tappet/bore. It was found that the friction in the rocker arm bearing never reaches hydrodynamic conditions and that the friction coefficient between cam and tappet reduces with an increase in the engine speed.
Technical Paper
2002-03-04
Peter Schihl, John Tasdemir, Ernest Schwarz, Walter Bryzik
A zero-dimensional heat release model has been formulated for small bore, automotive-type, direct injection diesel engines and compared with high-speed data acquired from a prototype single-cylinder engine. This comparison included a significant portion of the full-load torque curve and various light-loads with variable speed, injection timing sweeps, and injection pressures. In general, the agreement between the predicted net heat release rate profiles and the experimentally, indirectly-determined profiles was acceptable from a mean cylinder pressure point-of-view while employing a single constant for the turbulent mixing dissipation rate. The proposed model also revealed that moderate swirl rates included in this study had little impact on the gross fuel burning rate profile especially at higher load conditions.
Technical Paper
2002-03-04
Bogdan Nitu, Inderpal Singh, Lurun Zhong, Kamal Badreshany, Naeim A. Henein, Walter Bryzik
Abstract In view of the new regulations for diesel engine emissions, EGR is used to reduce the NOx emissions. Diluting the charge with EGR affects the autoignition, combustion as well as the regulated and unregulated emissions of diesel engines, under different operating conditions. This paper presents the results of an investigation on the effect of EGR on the global activation energy and order of the autoignition reactions, premixed and mixing-controlled combustion fractions, the regulated (unburned hydrocarbons, NOx, CO and particulates), aldehydes, CO2 and HC speciation. The experiments were conducted on two different direct injection, four-stroke-cycle, single-cylinder diesel engines over a wide range of operating conditions and EGR ratios.
Technical Paper
2001-05-07
Pai-Hsiu Lu, Joong-Sub Han, Ming-Chia Lai, Naein A. Henein, Walter Bryzik
An experimental setup using rapid compression machine to provide excellent optical access to visualize simulated high-speed small-bore direct injection diesel engine combustion processes is described. Typical combustion visualization results of diesel spray combustion under different EGR, swirl, and injection pressure and nozzle conditions are presented. Different swirl intensities are achieved using an air nozzle with variable orientations and a check valve to connect the compression chamber and the combustion chamber. Different EGR ratios are achieved by pre-injection of diesel fuel prior to the main observation sequence. Clear visualization of the high-pressure fuel injection, ignition, combustion and spray/wall/swirl interactions is obtained. The injection system is a high-pressure common-rail system with either a VCO or a mini-sac nozzle. High-speed movies up to 35,000 frame-per-second are taken using a framing drum camera to record the combustion events. Combustion luminosity was used to qualify the combustion and sooting processes.
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