Author: Pai-Hsiu LuPublisher:
ISBN:
Category :
Languages : en
Pages : 190
Book Description
Experimental Simulation of the Small Bore Diesel Engine by Using an Optically Accessible Rapid Compression Machine
Author: Pai-Hsiu LuMixing and Combustion Studies in an Optically-accessible Small-bore High-speed Direct-injection Diesel Engine
Author: William Sean MathewsPublisher:
ISBN:
Category :
Languages : en
Pages : 364
Book Description
Diesel Engine Cold-Starting Studies: Optically Accessible Engine Experiments and Modeling
Author: Publisher:
ISBN:
Category :
Languages : en
Pages : 0
Book Description
An experimental and numerical study was carried out to simulate the diesel spray breakup, vaporization, ignition, and combustion during cold starting conditions. This report summarizes the optical diagnostics and multi-dimensional computation results for two single-cylinder optically accessible engines. The results showed that optically accessible engines provide very useful information for studying the diesel cold starting conditions, which also provide a critical test for diesel combustion models. The pre-ignition chemistry showed great sensitivity to the compressed air temperature. KIVA with a modified shell model responds accordingly to the change of inlet air temperatures and fuel injection parameters. However, other submodels do not have enough sensitivity to simulate the starting of diesel engine without careful validation and further improvements. A method to compute the ignition delay in engines from data obtained in constant volume vessels was also developed. The method accounts for the effect of variations in charge pressure and temperature on the formation of the chain carriers from the combustible mixture during the ID period. A comparison is made between the computed ID and data obtained in a LABECO research engine under different ambient temperatures ranging from +200 to - 100 C.
Modeling the Autoignition, Blow-by, and Pollutant Formation in a Small Bore High Speed Direct Injection Optically Accessible Diesel Engine
Author: Jia Xi ZhaoAn Investigation of Phase-change Effects During Rapid Compression Machine Experiments
Author: Colin BanyonPublisher:
ISBN:
Category : Combustion engineering
Languages : en
Pages :
Book Description
Rapid compression machines (RCMs) are well characterized laboratory scale devices capable of achieving internal combustion (IC) engine relevant thermodynamic environments. These machines are often used to collect ignition delay times as targets for gas-phase chemical kinetic fuel autoigntion models. Modern RCMs utilize creviced piston(s) to improve charge homogeneity and allow for an adequate validation of detailed chemistry mechanisms against experiments using computationally efficient, homogeneous reactor models (HRMs). Conventionally, experiments are preformed by introducing a premixed gas of fuel + oxidizer + diluent into the machine, which is compressed volumetrically via a piston. Experiments investigating low-vapor pressure fuels (e.g. diesels, biodiesels, jet fuels, etc.) and surrogates can be conducted by preheating both the charge as well as the machine. This method of fuel loading can lead to pretest fuel pyrolysis as well as machine seal degradation. Under some conditions loading a fuel aerosol of finely atomized liquid droplets in an oxidizer + diluent bath gas (i.e. wet compression) has been suggested to extend the capabilities of RCM experiments to involatile fuels. This work investigates phase-change effects during RCM experiments, especially for aerosol-fueling conditions, while the methodology can be applied to gas-phase fuel experiments where fuel condensation can occur at the compressed conditions within the boundary layer region. To facilitate this study a reduced-order, physics-based model is used. This work highlights important machine-scale influences not investigated in previous work, and provides additional detail concerning an aerosol RCM{u2019}s capabilities and limitations. A transient formulation is developed for the multi-phase transport within the RCM reaction chamber as well as the flow to the piston crevice region during both the compression and delay periods. The goal of this work is threefold. First, an a priori knowledge of the stratification present under various conditions can help determine an optimum machine geometry so that discrepancies between experimental data sets and 0D kinetics simulations are minimized for involatile fuels. Second, the model is computationally tractable to prescribe heat loss rates to an HRM during simulations of experiments so that physical effects can be incorporated into simulations using detailed chemistry. Finally, heat loss rates that are prescribed to the HRM are only a function of machine geometry, and are independent of ad hoc and empirically derived fits that vary between facilities. Thus a more adequate comparison of data between RCM facilities and with existing literature can be made.
Development of a Rapid Compression-expansion Machine to Simulate Combustion in Diesel Engines
Author: Takeyuki KamimotoPublisher:
ISBN:
Category : Diesel motor
Languages : en
Pages : 6
Book Description
Low-temperature Combustion in a Small-bore High-speed Direct Injection Optically Accessible Diesel Engine
Author: Tiegang FangPublisher:
ISBN: 9780549095378
Category : Automobiles
Languages : en
Pages : 448
Book Description
Small-bore High Speed Direct-Injection (HSDI) diesel engines are becoming attractive candidates for light duty vehicles. However, exhaust emissions must be significantly reduced to meet the increasingly restrictive emission standards.
Modeling and Experimental Investigation of Methylcyclohexane Ignition in a Rapid Compression Machine
Author: W. J. PitzA Rapid Compression Machine with the Novel Concept of Crevice Containment
Author: Anil BhariPublisher:
ISBN:
Category : Internal combustion engines
Languages : en
Pages : 76
Book Description
Rapid Compression Machines (RCMs) typically incorporate creviced pistons to suppress the formation of the roll-up vortex. The use of a creviced piston, however, can enhance other multi-dimensional effects inside the RCM due to the crevice zone being at a lower temperature than the main reaction chamber. In this work, such undesirable effects of the creviced piston are first highlighted through computational fluid dynamics simulations of n-heptane ignition in an RCM. Specifically, the results show that in an RCM with a creviced piston, additional mass flow takes place from the main combustion chamber to the crevice zone during the first-stage ignition. This phenomenon is not captured by the conventional zero-dimensional modeling approaches. Consequently, a novel approach of 'crevice containment' is introduced and evaluated. According to this approach, in order to avoid the undesirable effects of the creviced piston, the crevice zone is separated from the main reaction chamber at the end of compression. The computational results with this novel approach show significant improvement in the fidelity of the zero-dimensional modeling in terms of predicting the overall ignition delay and pressure rise in the first-stage ignition. In addition, this approach also offers other advantages, namely a reduction in the rate of post-compression pressure drop and improved data during species sampling experiments. An RCM is subsequently designed and successfully fabricated with the feature of 'crevice containment' for the purpose of chemical kinetics studies at elevated pressures and temperatures. Characterization experiments for the newly built RCM show that the operation of the RCM is free from any vibrations, allows fast compression (22 ms), compressed pressures up to 100 bar and the experimental data obtained is highly reproducible. Using this facility, autoignition investigations are conducted for Hydrogen at a pressure of 50 bar. The experiments are modeled using the kinetic mechanism of O'Conaire et al. (2004). Results showed that the mechanism of O'Conaire et al. agree very well with the experimental data.
Paper
Author: Publisher:
ISBN:
Category : Mechanical engineering
Languages : en
Pages : 584
Book Description