Jin-Lu Yu

A new pre-combustion AC plasma jet igniter has been designed. The pre-combustion plasma jet igniter can widen the ignition envelope for the aeroengine and reduce the power consumption of the igniter. To fully exploit the ignition efficiency of the plasma jet, experimental studies concerning the operational parameters and the discharge and arc motion characteristics have been performed. The results showed that three discharge modes were formed in the new igniter, namely, the Intermittent Breakdown Mode (IBM), the Stable Breakdown Mode (SBM) and the Stable-Intermittent Breakdown mode (S-IBM), the three different discharge modes corresponding to different arc shapes and movement processes. Moreover, the addition of kerosene readily changed the discharge state from the SBM to the IBM. The discharge state and discharge power of the igniter were affected by the working parameters. The discharge power increased with increase of the output voltage of the regulator, and an increase in the air supply affected the discharge power when the output voltage of the regulator was varied. After the addition of kerosene, the discharge power of the igniter was reduced to a certain extent, the maximum reduction being up to 47.7%.

In order to study the stability of gliding arc plasma discharge under mal-conditions, an experimental system for studying the high air pressure alternating current rotating gliding arc discharge is built. The discharge characteristics, arc motion characteristics and spectral characteristics of rotating gliding arc discharge are analyzed under high pressure experimentally. Experimental results show that the voltage, current and energy increase in the gliding arc discharge with the increase of air pressure. As the air pressure rises to 0.52 MPa, the discharge energy increases from 84.74 to 147.13 J. With the increase of gas pressure, the breakdown frequency of the arc does not change monotonically, but reaches a maximum value of 26.55 kHz at 0.2 MPa, while the emission spectral intensity increases. The “arc channel mutation” occurs in the process of arc motion under high pressure. The electron excitation temperature in the process of gliding arc discharge is calculated by the two-line method, and the electron excitation temperature of gliding arc discharge is 0.8153 eV at an atmosphere pressure. The electron excitation temperature rises with the increase of air pressure. The excitation temperature increases to 5.3165 eV at an air pressure of 0.4 MPa.

Plasma ignition technology is the research frontier in the field of energy and power. In this paper, a novel type of plasma jet igniter called pre-combustion plasma jet igniter is designed and the experimental results show that it has great potential in strengthening jet stiffness, improving ignition energy, decreasing ignition energy consumption and reducing igniter ablation. The value S called jet stiffness is defined for the first time to reflect the stiffness characteristics of the plasma jet. And the effects of jet gas flow rate, fuel-air ratio and input current on the jet stiffness are investigated experimentally. The experimental results show that the stiffness of the pre-combustion plasma jet is significantly stronger than that of the air plasma jet. When the total jet gas flow rate is increased from 16 L/min to 40 L/min, the stiffness of the air plasma jet and the pre-combustion plasma jet are increased by 73.3 % and 27.2 % respectively. When the current value reaches 30 A, the jet stiffness is increased by about 70 % compared to the input current of 20 A.

At present, aero-engines face a major need to widen the ignition envelope. In order to provide a technical support to expand the high altitude ignition envelope of aero-engines, in this article we propose a novel ignition technology, i.e., “pre-combustion plasma jet ignition technology”. In this paper, we also design a pre-combustion plasma jet igniter. Its discharge characteristics, jet characteristics, and ignition effects are studied. The results show that increasing the equivalent ratio of jet gas can enhance the discharge stability and increase the duty cycle. At the same time, it can reduce working power and energy consumption. The increase of equivalent ratio in jet gas can enhance the length and ignition area of plasma jet. In the process of ignition, the pre-combustion plasma jet igniter has obvious advantages, suchn as shortening the ignition delay time and enlarging the ignition boundary. When the airflow velocity is 39.11 m/s and the inlet air temperature is 80 °C, compared with the spark igniter and the air plasma jet igniter, the pre-combustion plasma jet igniter has an ignition boundary that is expanded by 319.8% and 55.7% respectively.

In recent past, the plasma-assisted ignition has been explored for applications on a variety of engines. The plasma ignition has been shown to possess special advantages such as reducing the ignition delay time, improving the reliability, and reducing the NOx emissions. By using a plasma jet ignition experimental system, the plasma jet ignition of argon-discharge arc has been investigated. Owing to the characteristics of high temperature, the mixture can be easily ignited by the plasma jet. Through the propane–air mixture ignition experiments, the ignition limits of the plasma jet and spark ignition are investigated. The results show that the plasma jet ignition could extend the ignition limits of propane–air mixture obviously. The ignition limit extends with the increase in the air flow rates. The average ignition limit (the gap between rich and lean limit) of spark ignition and plasma jet ignition are 2.34 and 2.57, respectively. The average ignition limit of the propane–air mixture extends by 9.8%. The plasma jet ignition limit extends with increasing arc current, and the degree of extending plasma jet ignition limit increases with increasing air flow rates. The average ignition limits of 5.7 A and 20.3 A are 2.57 and 2.79, respectively. The average ignition limit of the propane–air mixture extends by 8.5%. The plasma jet ignition limit extends with increasing argon flow rates. The average ignition limits of 200 L/h and 250 L/h are 2.79 and 3.08, respectively. The average ignition limit of the propane–air mixture extends by 10.4%.

Based on nonequilibrium plasma dynamics of air discharge, the dynamic model of two-dimensional plasma is established by combining the plasma dynamic model, chemical reaction equations and Navier-Stokes equations. The discharge process of disk-shape plasma igniter is simulated. The process of discharge stream formation is obtained, which results from by electrons’ movement and aggregation. At

To study the chemical effect of direct current arc plasma igniter, the emission spectrum of plasma jet was measured, and the active particles produced by the interaction of plasma jet with atmospheric air were analyzed. The NO and CO volume fractions were measured quantificationally by smoke analyzer at the 8cm downstream the plasma igniter exit, and the changing law between arc current and NO, CO volume fractions was obtained. The results show that the plasma jet interacting with atmospheric air produced active particles (H, O, N), charged particles (O2 +, N2+), and excited particles (N2 (A3), N2 (B3), N2 (C3), N2 (a1), O2 (a1), O2 (b1)). The NO and CO volume fractions increased with rising of are current and feedstock argon flow rate.