Pulsejet engine dynamics in vertical motion using momentum conservation

TL;DR

This paper models pulsejet engine dynamics during vertical motion using momentum conservation, predicting terminal speed, conditions for non-return, and comparing with turbojet and octopus models, aimed at students in mechanics and aerospace.

Contribution

It introduces a novel analysis of pulsejet dynamics in vertical motion, including conditions for terminal speed and return to start, with comparisons to other engine models.

Findings

Existence of a terminal speed depending on pulse frequency.

Engine does not return to start under certain conditions.

Return cycles are independent of exhaust velocity and gravity for specific pulse frequencies.

Abstract

The momentum conservation law is applied to analyse the dynamics of pulsejet engine in vertical motion in a uniform gravitational field in the absence of friction. The model predicts existence of a terminal speed given frequency of the short pulses. The conditions that the engine does not return to the starting position are identified. The number of short periodic pulses after which the engine returns to the starting position is found to be independent of the exhaust velocity and gravitational field intensity for certain frequency of the pulses. The pulsejet engine and turbojet engine aircraft models of dynamics are compared. Also the octopus dynamics is modelled. The paper is addressed to intermediate undergraduate students of classical mechanics and aerospace engineering.