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An experimental investigation was conducted to characterize the combustion of a pure monopropellant isopropyl nitrate (IPN). Quartz tubes of 3, 5, 7.5, and 9 mm inner diameter were utilized to create the strands of varying dimensions. The experiments were conducted in a quiescent atmosphere of air and the ambient pressure was varied from atmospheric pressure to 40 bar in steps of 5 bar. Ignition of the IPN strands was achieved by using a heated 60 μm Nichrome wire dipped in the liquid. The dependence of the linear burning rate of pure IPN on ambient pressure as well as the strand diameter was elucidated. The temperatures in the flame zone and liquid phase were measured by K-type thermocouples of 250 and 75 μm diameters respectively. The ambient pressure variation was investigated for strand diameter of 5 mm, while the tube diameter variation was studied at 1, 10, 20 and 40 bar pressure. The linear burning rate of pure IPN strands of 5 mm diameter was found to exhibit staged behavior where a steep rise in burning rate with pressure was observed after an initial decreasing trend. The linear burning rate was found to reduce with increasing tube diameter. The effect of IPN monopropellant flame was prominently observed only for pressures higher than 10 bar.

An experimental investigation was conducted to characterize the strand combustion of pure isopropyl nitrate (IPN) blended with a known de-sensitizer dibutyl sebacate (DBS). The blend was prepared with 75% IPN mixed with 25% DBS by weight so as to mimic the composition of Otto fuel II. Quartz tubes of 3, 5, 7.5, and 9 mm in diameters were utilized to create the strands of various diameters. The experiments were conducted in a quiescent atmosphere of air and the ambient pressure was varied from 5 to 40 bar in steps of 5 bar. Ignition of the strands was achieved by using a heated 60 μm Nichrome wire dipped in the liquid. The dependence of the linear burning rate of IPN-DBS blends on ambient pressure as well as the strand diameter was elucidated. The temperatures in the flame zone were measured with K-type thermocouples of 250 μm diameter. The ambient pressure variation was investigated for a strand diameter of 5 mm while, the tube diameter variation was studied at 5 and 40 bar pressure. The linear burning rate of IPN-DBS blends in 5 mm diameter tube was found to rise with pressure. The gas phase temperature above the tip of the tube was measured using 250 μm K-type thermocouple. The burning rate of IPN-DBS blends was found to be lower than that of pure IPN as well as Otto fuel II.

Experimental investigation of spray combustion of the monopropellant nitromethane (NM) assisted by a hot surface is presented. Spray combustion of NM was studied in a constant volume combustion chamber fitted with glow plugs within the chamber pressure range of 1 to 5 bar. The sprays were produced by injecting approximately 0.1 ml of the propellant through a commercial gasoline injector. Ignition was achieved by using two glow plugs placed in a horizontally opposed manner at a distance of 70 mm from the nozzle tip within the chamber. The pressure rise within the chamber was used to elucidate the ignition and combustion processes. The ignition delays were found to be in the order of milliseconds, with high heat release rates accompanying the combustion phenomena. The maximum differential pressures reached during combustion were found to increase with chamber pressure up to 3 bar, and decrease thereafter. The rate of pressure rise achieved after combustion were also found to be dependent on the initial chamber pressures. FTIR spectrometry of the combustion products yielded further insight into the reactions.