Effects of impingement and shear upon the ignition of hypergolic rocket bipropellants

John Funk, Purdue University

Abstract

Despite the large amount of work into propellant atomization and mixing, little information exists on the relationship between atomization, mixing, and hypergolic ignition. Treated as a transient phenomenon, the mixing and atomization processes that enhance or inhibit hypergolic ignition have been overlooked in an effort to enhance steady state performance. While the steady state mixing and atomization of propellants is crucial to the performance of rocket engines used for long duration firings, the transient hypergolic ignition event may be crucial for missions utilizing numerous short duration (tens of milliseconds) burn durations. Given the renewed interest in hypergolic propellants, and the missions being required of them, an examination into the injection properties that control hypergolic reaction is required. Impinging and shear injectors were developed to examine the injection parameters that affect hypergolic reaction time. A model single element impinging injector was utilized to examine the effects of jet diameter, impingement velocity, and impingement angle on non-combusting, yet chemically reactive, test species. Impinging element tests have shown that greater impingement angles and impingement velocities minimize reaction time, but not necessarily reaction distance, for all injector styles examined. Shear tests, utilizing combusting propellants, showed a general decrease with increasing shear velocities until a blow-apart regime was reached. In addition, a transition region from velocities until a blow-apart regime was reached. In addition, a transition region from laminar diffusion gradients to turbulent mixing was observed where ignition time was seen to increase, before again decreasing with increased shear velocities. A similar region was also observed in the impingement testing.

Degree

Ph.D.

Advisors

Rusek, Purdue University.

Subject Area

Aerospace materials

COinS