The Critical Spontaneous Combustion Condition Research Of Pure Component Fuel On Sequence Auto-ignition

Based on serious challenges of energy and environmental issues in the internal combustion engine industry, the idea of "Reaction Controlled Homogeneous-Charge Sequence Auto-Ignition Combustion Mode" has been proposed. And the key premise to realize the new combustion mode is to confirm the difference of critical volume concentration and critical spontaneous combustion temperature of each component. So this research developed a CVCB(constant volume combustion bomb) test platform through which the condition such as pressure, mixture composition can be controlled accurately to study critical spontaneous combustion temperature of pure fuel in different fuel volume concentration and air volume concentration.The CVCB test platform mainly includes the following systems:1.The CVCB body. It is composed of the upper cover board, the intermediate chamber and the bottom cover board. It meets the maximum explosion pressure of 18 MPa. Its combustion chamber which has 132 mm diameter and 83 mm height is cylindrical.2.The air intake system and exhaust system. They are mainly to realize the accurate control of the amount of air into the CVCB body and to discharge the exhaust gas through the design, selection and connection of the key parts such as gas source, pipeline, valve and pressure gauge.3.The fuel supply system. At first the fuel for the test is input to the gas-liquid separation pressure adjusting box, and then the required high pressure are built by using high pressure nitrogen in the pressure adjusting box. In order to provide the needed stable high pressure for the injector, the high pressure oil rail and pressure adjusting box are linked to make the same pressure.4.The temperature control system. It is based on heating power of theoretical calculation to complete the selection of each part of temperature control system. The heating power of the heating pipe can be changed by adjusting the voltage regulator. And the heating circle have the function of auxiliary heating and heat preservation.5.Data acquisition system. The pressure in the CVCB changes into electric charge signal through the cylinder pressure sensor and then converts into analog voltage signal through charge amplifier. The temperature converts into contact potential through temperature sensor and then changes into analog voltage signal through the temperature transmitter. After that, by using data acquisition card the analog voltage signals which are corresponding to the temperature and pressure are collected synchronously and are converted into the digital signals which can be processed by computer. At last the signals are displayed and stored by the Lab VIEW software.6.Fuel injection control system. The square wave pulse which is output by the electronic control unit(ECU) are enlarged by driving circuit to control the opening and closing of fuel valve, which uses Code Warrior software to compile and then downloads to Freescale microcontroller to realize fuel injection control. By using USB-CAN riser card, the communication function of Lab VIEW software of PC and microcontroller can be achieved.By using the CVCB test platform, the research gains the distribution of steady-state temperature field inside the CVCB under the condition of different heating power and air volume concentration. For the region of 25 to 44 mm radius in the radial direction, 30 to 55 mm height in axial direction, the temperature reached the peak and the limit temperature difference of this region is not beyond 50℃. Above all, the temperature sensor probe can be put in the position of 42 mm height and 44 mm radius to determine the critical spontaneous combustion temperature. In the debugging operating point of intake air amount 6412.17 mg and n-butanol injection amount 572 mg, the combustion process is analyzed and by calculating the combustion efficiency is 42.82%. And the test platform is evaluated and considered how to improve. Accordingly, some critical spontaneous combustion temperature data are measured in different fuel volume concentration and air volume concentration. According to the experimental results, When fuel injection amount has doubled and intake air amount is constant, the critical spontaneous combustion temperature drops by 9.73 percent. While intake air amount increases by 1.3 times and fuel injection amount is constant, the critical spontaneous combustion temperature increases by 5.39%. When either fuel volume concentration or the air volume concentration changes, the critical spontaneous combustion temperature has the downward trend to the increasing direction of the mixture concentration. At the same time, the critical spontaneous combustion temperature is affected by fuel volume concentration is more sensitive than air volume concentration.In conclusion, the mixture gas of n-butanol and air has the corresponding critical spontaneous combustion temperature in a certain fuel volume concentration and air volume concentration. Through the subsequent plentiful experiments calibration the MAP graph of each pure component fuel’s critical spontaneous combustion temperature which are determined by the air volume concentration and fuel volume concentration can be drawn. This can be used to estimate whether the sequence auto-ignition of the mixture gas with various pure component fuels can be realized as well as to obtain the effective way to trigger reliable sequence auto-ignition through inputting energy.