Amit Shrestha

Detection of Combustion Resonance Using an Ion Current Sensor in Diesel Engines

This paper discusses the use of an ion current sensor to detect combustion resonance in a heavy duty direct injection diesel engine. A modified glow plug is used to measure the ion current in addition to its main function in warming up the combustion chamber. A comparison is made between the combustion resonance determined from the signals of an ion current sensor, a cylinder pressure transducer and an engine vibration sensor. Experiments are conducted on a four cylinder, turbo-charged 4.5L diesel engine to determine the potential of using the ion current sensor to detect combustion resonance under different injection pressures and exhaust gas recirculation rates. It is concluded that the ion current signal can be used to determine the timing, amplitude, frequency and duration of the resonance. The sensor output has the potential to be used as a feedback signal to the ECU (Electronic Control Unit) to minimize engine vibration and noise.Copyright

An Investigation on Sensitivity of Ignition Delay and Activation Energy in Diesel Combustion

The auto-ignition process plays a major role in the combustion, performance, fuel economy and emission in diesel engines. The auto-ignition quality of different fuels has been rated by its cetane number (CN) determined in the CFR engine, according to ASTM D613. More recently, the Ignition Quality Tester (IQT), a constant volume vessel, has been used to determine the derived cetane number (DCN) to avoid the elaborate, time consuming and costly engine tests, according to ASTM D6890. The ignition delay period in these two standard tests and many investigations has been considered to be the time period between start of injection (SOI) and start of combustion (SOC). The ignition delay (ID) values determined in different investigations can vary due to differences in instrumentation and definitions. This paper examines the different definitions and the parameters that effect ID period. In addition the activation energy dependence on the ID definition is investigated. Furthermore, results of an experimental investigation in a single-cylinder research diesel engine will be presented while the charge density is kept constant during the ID period. The global activation energy is determined and its sensitivity to the charge temperature is examined.Copyright

Detection of combustion resonance using an ion current sensor in diesel engines

This paper discusses the use of an ion current sensor to detect combustion resonance in a heavy duty direct injection diesel engine. A modified glow plug is used to measure the ion current in addition to its main function in warming up the combustion chamber. A comparison is made between the combustion resonance determined from the signals of an ion current sensor, a cylinder pressure transducer and an engine vibration sensor. Experiments are conducted on a four cylinder, turbo-charged 4.5L diesel engine to determine the potential of using the ion current sensor to detect combustion resonance under different injection pressures and exhaust gas recirculation rates. It is concluded that the ion current signal can be used to determine the timing, amplitude, frequency and duration of the resonance. The sensor output has the potential to be used as a feedback signal to the ECU (Electronic Control Unit) to minimize engine vibration and noise.Copyright

Experimental Validation and Combustion Modeling of a JP-8 Surrogate in a Single Cylinder Diesel Engine

Abstract : Experimental Validation: At the test conditions analyzed, the two-component S2 surrogate fairly reproduced the following characteristics of the target JP-8: -Ignition delays -Pressure, RHR, mass-averaged gas temperature -Engine-out emissions (CO, HC, NOX), with an exception of the absolute PM values. 3D CFD Simulation: -The simulation results were in fairly good agreement with the experimental data for the surrogate. The two-component S2 surrogate could be a reasonable choice for its use in further investigations on the target JP-8.

Computational Analysis of a Diesel Engine Autoignition, Combustion, and Emissions Using Injection Rate Shapes

Injection rate shaping is a method used to control the instantaneous mass flow rate of the fuel during an injection event. The rate at which the fuel is delivered affects the composition of the combustible mixture and its distribution in the combustion chamber, thereby has an impact on the combustion process in the diesel engine. This paper investigates the effects of five different types of injection rate shapes on diesel engine autoignition, combustion, and engine-out emission trends using a three-dimensional computational simulation approach. For this purpose, an n-heptane fuel model is utilized. Initially, a tophat rate-shape, characterized by the constant mass flow rate of the fuel, is assumed to represent the actual injection profile of an actual engine. Then, in order to develop sufficient confidence in the simulation predictions, this assumption together with the calibrated CFD models are validated by reproducing the cylinder gas pressure, the rate of heat release, and engine-out emissions trends for two sets of engine operating conditions. Later, using all the rate shapes the investigation is conducted for one test point considering two different cases of fuel injection: Case 1 - same SOI and duration of injection (DOI), and Case 2 - same combustion phasing and DOI.The results obtained from the computational analysis show that the injection rate shape affects the autoignition, combustion, and emissions of a diesel engine. It is observed that the rate shapes, characterized by high injection rates at the beginning of the injection event, enhance the formation of negative temperature coefficient (NTC) regime. Therefore, the mole fractions of different species are determined during the NTC regime in order to examine the processes relevant to the formation of the NTC regimes for these rate shapes. Further, for the same SOI and DOI case, significant differences in the ignition delays between each rate shapes are observed. The maximum deviation of the ignition delay from the reference tophat is found to be 37%. Furthermore, the paper highlights the differences in the cylinder gas pressure, gas temperature, and rate of heat release due to different fuel delivery rates of different rate shapes. Finally, the comparison of the engine-out emissions for different rate shapes for both the cases of injection are presented and discussed in detail.Copyright